TW201426205A - Catadioptric projection objective with pupil mirror, projection exposure apparatus and projection exposure method - Google Patents

Abstract

A catadioptric projection objective for imaging a pattern from an object field arranged in an object surface of the projection objective onto an image field arranged in an image surface of the projection objective has a first objective part configured to image the pattern from the object surface into a first intermediate image, and having a first pupil surface, a second objective part configured to image the first intermediate image into a second intermediate image, and having a second pupil surface optically conjugate to the first pupil surface, and a third objective part configured to image the second intermediate image into the image surface, and having a third pupil surface optically conjugate to the first and second pupil surface. A pupil mirror having a reflective pupil mirror surface positioned at or close to one of the first, second and third pupil surface. A pupil mirror manipulator operatively connected to the pupil mirror and configured to vary the shape of the reflective surface of the pupil mirror allows for dynamically correcting imaging aberrations originating from lens heating, compaction and other radiation induced imaging aberrations occurring during operation of the projection objective.

Description

Reflective refractive projection objective lens with pupil mirror, projection exposure device, and projection exposure method

The invention relates to a catadioptric projection objective for imaging an object field disposed in an object surface of the projection objective on an image field disposed in an image plane of the projection objective.

Reflectively reflective projection objectives, for example, are used in projection exposure systems, particularly wafer scanners or wafer steppers, for the fabrication of semiconductor devices and other micro devices, and are used in The pattern on the projection mask or grating is such that it has an easily sensitized coating and has a high resolution in a small range.

In order to create a finer architecture, it is generally sought to improve the numerical aperture (NA) of the image end of the projection objective, as well as to apply shorter wavelengths, especially ultraviolet light having a wavelength shorter than 260 nanometers (nm). However, very few materials, especially synthetic crystals and crystalline fluorides, are sufficiently transparent in the wavelength section to make optical components. Since the Abbe numbers of such materials for making optical components are typically too close together, it is difficult to provide a pure refractive system to achieve a sufficiently good color correction (corrected chromatic aberration).

In optical lithography, high resolution and good correction states can be achieved via relatively large and substantially planar image planes. Currently considered One of the most difficult requirements to achieve in optical design is a flat image, especially if this is a total reflection design. Provides a flat image that requires refraction of the lens's refractive index, and thus leads to a stronger lens, longer system length, greater system glass quality, and greater higher-order aberrations due to stronger lens curvature .

Concave mirrors are sometimes used to help solve color correction and flat field problems. The concave mirror has a positive refractive index, like a positive lens, but has a negative Petzval curvature. Moreover, the concave mirror does not cause color problems. Thus, a catadioptric system incorporating refractive and reflective elements, in particular a lens and at least one concave mirror, is primarily used to set the previously mentioned high resolution projection objective. Unfortunately, concave mirrors are difficult to integrate into optical designs because they reflect radiation from a certain direction back along the same path. There is a need for an intelligent design to integrate concave mirrors without causing structural problems or problems caused by beam vignetting or pupil obscuration.

Due to the increased demand for the efficiency of lithography processes, there is currently a tendency to increase the intensity of the light source. Also, gradually shorter wavelengths are also used. Specific illumination settings are utilized to optimize imaging conditions for a variety of different pattern types. Thus, the various properties of the optical material in the projection system that are produced over time are observed, which significantly affects the imaging quality of the exposure system. The lens group and other transparent optical elements are heated (lens heating) due to the gradual increase in absorption during operation, which constantly affects the imaging characteristics. Moreover, long-term (semi-steady-state) effects (such as compaction effects) caused by changes in the refractive index induced by radiation are observed.

The applicant's U.S. Patent Application Serial No. 2004/0144915 A1 describes a solution to the problem caused by the absorption of heat caused by absorption in a catadioptric projection objective lens having a physical beam splitter. The application discloses a foldable catadioptric projection objective designed as a single imaging system (with no intermediate image), and one of the concave mirrors is disposed on the braided surface. Physical beam splitter with beam-selective physical beam splitter surface (beam A splitter is provided to separate the radiation from the object field in the axial direction toward the concave mirror and the radiation reflected from the concave mirror to the image plane. The concave mirror is composed of a deformed mirror, and the shape of the concave mirror surface can be controlled by a light mirror operator, which compensates for some of the dependence of the optical performance change caused by the radiation when operating the projection objective. Time-varying imaging aberrations. The light mirror operator has a simple structure and is mounted on the back side of the concave mirror without affecting the optical path. The deformed pupil mirror is designed to compensate for the following situations, such as astigmatism, cubic beam splitter, and rectangular phase retardation plate heating due to absorption, resulting in two-fold or four Four-fold wavefront deformation, as well as compaction effects.

It is an object of the present invention to provide a catadioptric projection objective suitable for use in the vacuum ultraviolet range, having potential energy to provide a very high image side numerical aperture, and long term stability performance can be maintained.

Another object of the present invention is to provide a projection objective and an exposure device assembly to be operated with illumination settings having stable operating conditions including non-conventional off-axis illumination, such as bipolar or quadrupole illumination.

Another object of the present invention is to provide a catadioptric projection objective that provides stable optical performance for immersion lithography etching.

Another object of the present invention is to provide a catadioptric projection objective for lithographic etching applications, which can be fabricated at a low cost to a wavelength of 193 nm, and which is in dry lithography or immersion lithography. Stable optical performance under a variety of lighting conditions.

In order to solve the above object of the present invention, according to an aspect, a catadioptric projection objective lens is provided for imaging a pattern from an object field to an image field, the object field being disposed on one of the projection objective lenses In the plane, the image field is disposed in an image plane of the projection objective, and the catadioptric projection objective comprises: a first objective lens component for imaging the pattern from the object surface as a first intermediate image, and the first objective lens component has a first pupil surface; and a second objective lens component for imaging the first intermediate image a second intermediate image, the second objective lens member having a second pupil surface optically conjugated to the first pupil plane; and a third objective lens component for imaging the second intermediate image on the image plane And the third objective lens member has a third pupil plane optically conjugate with the first pupil plane and the second pupil plane; a pupil mirror having a reflective pupil mirror surface located at or near One of the first pupil plane, the second pupil plane and the third pupil plane; and a stop mirror operator operatively coupled to the aperture mirror for modifying the surface of the aperture mirror shape.

In projection systems, various changes in optical material characteristics due to time variations and radiation are mentioned at the very beginning of this application, resulting in characteristic imaging aberrations that are difficult to compensate with conventional operators; The main factor of the difference is the invariant factor for the aspheric aberration. In more detail, the on-axis astigmatism (AIDA) and the quadruple radial symmetry error (four wavy) constants in the field can be observed. Assuming that the pupil mirror has a pupil mirror surface and an operation device having a shape that can change the reflection surface of the pupil mirror, the aberration can be compensated, and thus, substantially one of the aberrations can be obtained from the image plane. Even if a large disturbance to the shape of the wavefront is generated in the projection objective, such interference is based on lens heating or compression. Correcting the shape of the surface of the reflected light mirror can be corrected so that negative interference due to lens heating or the like can be cancelled by the pupil mirror. Since the pupil mirror is close to or located on the pupil surface of the projection objective, the deformation or change in the shape of any reflective surface has substantially the same effect on all field points, wherein substantial field invariant correction can be obtained.

A catadioptric projection objective with two real intermediate images can be designed to obtain a high image side numerical aperture in the image field, which is large enough to do It is used for lithography and does not cause vignetting problems. Further, when the off-axis object field and the image end system are used, in a system having a high image side numerical aperture, 瞳 shielding can be avoided. The projection objective has exactly three consecutive objective components, as well as two intermediate images. Each of the first objective lens component to the third objective lens component is an imaging system that achieves two consecutive Fourier transforms (2f-system) and that there are no redundant objective lenses. When just two intermediate images are provided, a large number of free angles are provided in the optical system, which can be manufactured in a size and complexity. The numerical aperture on the large image side of the image end is useful as a lithography.

While a pupil mirror may have a substantially flat reflective surface, in most embodiments, the pupil mirror is designed as an optical component having optical intensity. In some embodiments, the pupil mirror is a concave mirror.

At least one intermediate image formed between the object surface and the pupil mirror is useful. It can provide radiation appropriately before being reflected on the pupil mirror. When at least one imaging subsystem (objective component) is placed between the object surface and the pupil mirror, the radiation that is incident on the pupil mirror can be effectively prepared to optimize the correction performance of the pupil mirror.

In some embodiments, the aperture mirror is disposed in the second objective lens component and is located adjacent to the second side of the surface. One or more lenses may additionally be provided in the second objective lens component to form a catadioptric second objective lens component. Alternatively, the second objective lens component can be purely reflective.

In some embodiments, the first objective lens component that forms the first intermediate image is purely refractive, in other words, contains only one or more lenses, and no imaging mirror. Optionally, or additionally, the third objective component forming the final image on the image surface of the second intermediate image is a pure refractive objective component.

The tandem system sequentially includes a first refractive objective component (R), a second reflective refractive (or reflective) objective component (C), and a third refractive objective component (R); this tandem system may be referred to as "RCR" type system.

In some embodiments, the first objective lens component is a catadioptric objective lens The component, the second objective component is catadioptric or reflective, and includes a pupil mirror; the third objective component is a refractive objective component. These systems may be referred to as "C-C-R" type systems.

The optical elements of the projection objective can be arranged in a variety of different ways.

Some embodiments are designed as "folded" catadioptric projection objectives having an optical axis that is cut by at least two non-flat axis sections by a mirror (bending mirror). In general, a curved mirror can have a flat reflective surface, that is, no optical intensity.

Some embodiments include a first bending mirror configured to bend radiation from the object toward the pupil mirror, or to bend radiation from the pupil mirror toward the image plane, such that the radiation is The opposite direction is geometrically formed between the first bending mirror and the aperture mirror through at least two passes of the region. Providing at least one curved mirror makes it easier to set the aperture mirror close to or on the pupil plane without excessively limiting the usable numerical aperture by the size of the aperture mirror.

A second bending mirror having an angle of 90° with the first bending mirror may be provided, such that the object plane and the image plane are parallel to each other. The second curved mirror can be configured to directly receive radiation reflected from the aperture mirror or can be configured to receive radiation reflected from the first curved mirror.

In some embodiments, the first bending mirror is configured to bend radiation from the object face toward the pupil mirror, and the second weight mirror is configured to direct radiation from the aperture mirror toward the image The direction of the face is bent. The folding geometry can set the blocks on the optical axis to be substantially coaxial, the blocks being defined by the optical elements of the first objective component and the third objective component, that is, accurate coaxial or only some The lateral displacement of the micro, this displacement is very small with respect to the conventional lens diameter. According to this general folding geometry, examples of projection objectives are disclosed, for example, in WO 2004/019128 A2, or WO 2005/111689 A. The disclosure of such documents is incorporated herein by reference.

In other embodiments, the first bending mirror is disposed on the aperture mirror The optically downstream position is bent toward the second bending mirror by the radiation reflected by the pupil mirror, and the second bending mirror is arranged to direct radiation from the first bending mirror toward the image plane Bend. In these types of embodiments, the optical axis defined by the concave aperture mirror can be coaxial with the optical axis block defined by the first objective lens component. The large lateral displacement between the object surface and the image plane can generally be obtained, which is larger than the conventional lens straight mirror. Objective lenses of this type generally comprise two lens barrel structures arranged parallel to one another. Representative examples are disclosed, for example, in U.S. Patent No. 6,995,833 B2. The disclosure of the above documents is incorporated herein by reference.

A negative mirror group including at least one negative mirror may be disposed before a reflective end of the concave aperture mirror and in a secondary pass region such that the radiation passes through the negative mirror twice in the reverse direction. The negative mirror group can be placed adjacent to the concave aperture mirror near the pupil region, and the region near the pupil is characterized by an imaged edge beam height (MRH) greater than the primary beam height (CRH). Preferably, the edge beam height is at least twice as large as the main beam height in the negative mirror group, or even at least five to ten times larger. A negative lens group located in a region with a large edge beam height can effectively provide chromatic aberration correction, especially for correcting axial chromatic aberration. Since the axial chromatic aberration of the thin lens is proportional to the square of the height of the edge beam, the edge beam height is at the position of the lens. (And, proportional to the intensity of the refraction and the dissipation of the lens). Addition thereto is that the projected radiation passes through the negative mirror twice in the opposite direction, and the negative mirror group is located directly adjacent to the concave mirror, so that the chromatic aberration overcorrecting effect of the negative mirror group can be utilized twice. The negative mirror group can comprise a single negative mirror or at least two negative mirrors.

In some embodiments, all of the optical elements in the projection objective are arranged along a straight optical axis. This type of optical system can be referred to as an "inline system."

From an optical point of view, an in-line system is preferred because optical problems such as polarity effects due to the use of planar folding mirrors can be avoided. In addition, from a manufacturing point of view, the in-line system can be designed such that conventional mounting techniques for optical components can be utilized, thus improving the mechanical stability of the projection objective. Using a double mirror, such as two or four or six mirrors, can make imaging Image bounce will occur.

The optical component of the in-line system can include a mirror assembly having an object end mirror inlet for receiving radiation from the object surface and having an end mirror assembly outlet for exiting the mirror assembly from the image surface Radiation is emitted, wherein the mirror assembly includes at least one aperture mirror.

When an on-axis field is desired (the object field and the image field are centered on the optical axis), the mirror group may be composed of a pair of concave mirrors, the concave mirrors comprising facing concave reflecting surfaces, and the transparent portions (such as holes or holes) Manufactured by a mirror surface located near the optical axis that allows radiation to pass through the mirror. A concave mirror can be placed optically near the surface of the pupil. At least one concave mirror can be provided with a pupil mirror operator to form a deformable aperture mirror. A system having two intermediate images, an on-axis field, and a shadow mask is disclosed in U.S. Patent No. 6,600,608, the disclosure of which is incorporated herein by reference.

For imaging without obscuration, the off-axis field (image field and object field are completely outside the optical axis) can be used.

In-line systems generally have only a very small installation space for the mirror. In addition, the size of the mirror on the surface of the pupil is limited to the ability of the large image side numerical aperture to image a rectangular or arched "effective image field" of a reasonable size. This corresponds to the relatively low "effective light spread" (effective geometric flux) of the object field, that is, the distance between the innermost field point of the imaging without vignetting and the outer edge of the effective misfield is small. Under these conditions, the size of the "design object", that is, the field where the projection objective can be sufficiently corrected, can become relatively large, assuming that an "effective image field" having a rectangular or arch shape and a reasonable size is desired. If the size of the design object is increased, the size and number of optical components will increase significantly. Generally, it is desirable to keep the design object as small as possible. (The effective object field, the effective light spread of the design object field, and the detailed definition of the relationship between the two can be found in the International Patent Application No. WO 2005/098506 A1, the disclosure of which is incorporated herein by reference.

In view of the above considerations, the lens set includes: a first lens for receiving Radiation from the entrance of the lens group to a first reflective area; second lens for receiving radiation from the first lens to a second reflective area; and third lens for receiving radiation reflected from the second lens And a fourth lens for receiving radiation reflected from the third lens and for reflecting the radiation to the lens assembly outlet; wherein at least two of the lenses are concave mirrors having a The surface is rotationally symmetric about the optical axis.

Even if the image side numerical aperture is increased, the inclusion of at least four mirrors in the lens group limits the size of the pupil mirror, so that vignetting control is more easily achieved. Preferably, exactly four mirrors are provided. All mirrors in the mirror group can be concave mirrors.

Although it is possible to use the second lens (geometrically closer to the object surface) as the pupil mirror, it is useful if the third lens is constructed as a pupil mirror. The third lens, in general, is geometrically spaced from the object surface at the image end of the mirror so as to provide a geometrical space to properly direct the radiation toward the third lens. Additionally, optically up to the third lens, and the optical elements comprising the first and second lenses can be used to shape and prepare the radiation beam for the pupil. For example, the correction state and the main beam height can be affected if necessary.

Preferably, the mirror of the mirror is arranged such that the radiation from the entrance of the mirror passes through the plane of the mirror at least five times, the plane of the mirror being defined transverse to the optical axis and geometrically placed between the entrance of the mirror and Between the exits of the mirror group, before the radiation is emitted from the exit of the mirror group. A plurality of at least four reflections can thus be obtained, and in the space of axial compression, this space is defined between the mirror set entrance and the mirror set exit.

The front lens group can be disposed between the object surface and the entrance of the lens group, so that the spatial distribution of the radiation of the object surface can be converted into the angular distribution of the radiation desired at the entrance of the lens group, and the incident angle can be adjusted. This radiation enters the mirror and illuminates the first lens. The design of the front lens group can be selected such that the radiation entering the entrance of the lens group has a desired cross-sectional shape, allowing the radiation beam to pass through the entrance of the lens group without touching the edge of the adjacent mirror, thus avoiding the beam. gosh. The front lens group can be designed as a Fourier lens Group, that is, a single optical element that can achieve a single Fourier transform or an optical set that includes at least two optical elements, or a singular continuous Fourier transform between the front end focus plane and the back end focus plane. In a preferred embodiment, the Fourier lens group forming the front lens group can be set to substantially image the entrance of the projection objective at the entrance of the lens assembly such that a pupil plane is at or near the entrance of the lens assembly. There may also be embodiments without a front lens group.

A system of refracting in-line with a mirror of a four-sided mirror is disclosed in the applicant's International Patent Application No. WO 2005/098505 A1, the disclosure of which is incorporated herein by reference. Some embodiments include a light pupil mirror and are related to the present invention with appropriate adjustments.

In some embodiments, the first objective lens component (forming an intermediate image down to the pupil mirror) is designed to magnify the imaging system with magnification |β|>1 such that the first intermediate image system formed is larger than the effective object field. Preferably, the condition of |β| > 1.5 is maintained. The magnified intermediate image can be utilized to obtain a large primary beam angle CRA _PM located downstream of the pupil. Considering that in the optical imaging system, the output of the main beam angle CRA of the parallel axis and the 瞳 size are constant (Lagrangian invariant), the main beam angle at the pupil plane corresponds to a small 瞳, that is, Corresponds to the small beam diameter of the beam at the pupil plane.

In some embodiments, the aperture mirror is disposed between a first lens upstream of the aperture mirror and a second lens downstream of the aperture mirror, and one of the primary beam heights of the object plane is CRH _O The primary beam height of one of the first lenses is CRH ₁ , and the primary beam height of one of the second lenses is CRH ₂ , wherein the conditions of CRH ₁ >CRH _O and CRH ₂ >CRH _O are satisfied. . Preferably, at least one of the conditions of CRH ₁ >1.5*CRH _O and CRH ₂ >CRH _O is satisfied. In other words, the main beam height of the mirror that immediately goes up and down to the pupil mirror is greater than the object height. The mirrors optically up or down to the pupil mirror have a ratio of at least one of the primary beam heights to the primary beam height CRH _O of the object plane of at least 1.5, or at least 2.0, or at least 2.5. In these cases, a small beam diameter is obtained in the pupil mirror, which allows for a small-sized pupil lens.

In some embodiments, an optical element disposed between the object surface and the pupil mirror is configured to provide a maximum primary beam angle CRA _MAX > 25° to the aperture mirror. In some embodiments, a maximum primary beam angle greater than 30° or greater than 35° or even greater than 40° is possible. A small flaw can give the pupil mirror a small diameter. This directs the radiation through the pupil mirror even if the projection beam has a large aperture. Therefore, the large main beam angle on the pupil mirror makes it easier to obtain a high image side numerical aperture in a system of reflection and refraction lines.

The optical aperture mirror free diameter D _PM that is optically used can be particularly small. In some embodiments, the optical mirror is the optical element having the smallest diameter throughout the projection objective. The pupil diameter D _PM can be 50% less, or 40% or 30% less than the maximum free diameter of the optical elements in the projection objective.

The projection objective may have an aperture stop to allow adjustment to the diameter of the desired aperture, wherein the aperture aperture has a maximum aperture diameter that is at least twice as large as the pupil diameter _DPM .

The deformation of the pupil mirror surface is used to influence the correction, which is substantially the same for all field points (also known as field invariant correction). Special emphasis should be placed on the corrected state of the projected beam incident on the pupil mirror. Preferably, the projection beam of the pupil mirror follows the following conditions: | CRH _i |/D ₀ <0.1 (1)

0.9=<D _i /D ₀ =<1.1 (2)

Wherein | CRH _i | is the value of the main beam height of one of the main beams in the object field i of the surface of the pupil mirror; D ₀ is the number of beam heights at one edge of the pupil mirror surface is worth two And D _i =| HRRU _i -HRRL _i | is a field point i on the surface of the pupil mirror, and one of the pupil directions of one of the pupil entrances in the projection objective lens, wherein the HRRU _i is The edge beam height of an upper edge beam, and the HRRL _i is the edge beam height of the lower edge beam, corresponding to the field point i.

The primary beam is the beam that travels from the outermost field point to the center of the entrance. Assuming that the above conditions (1) and (2) are satisfied, the image of the entrance is very close to or located in the pupil mirror, which responds to the deformation of the pupil mirror to obtain a field-constant correction.

Certain embodiments of the axial compression design may require that the aperture mirrors and other mirrors having the same direction of reflection be geometrically placed close to each other. In some embodiments, this problem can be solved by providing a pair of mirrors. The pair of mirrors comprises two concave mirrors having mirror surfaces of the same curved surface, the same curved surface being provided on a common substrate, one of the two concave mirrors being the light pupil mirror having a reflective light mirror surface. It is set to be deformable by the pupil mirror operator, and the other concave mirror has a refractive surface separate from the pupil mirror surface. This mirror combination can be provided in the same configuration, which makes the setting of the pupil mirror easier.

In some embodiments, the pupil mirror is disposed at or near one of the pupil surfaces, and one or more transparent optical elements are disposed at or near at least one optically conjugated pupil surface. In general, the position at or near the surface of the pupil refers to the position at which the edge beam height MRH is greater than the main beam height CRH such that the beam height ratio RHR = MRH / CRH > 1. The deformation caused by absorption, as well as the change in the refractive index (close to the conjugated pupil surface) caused in the lens element, can cause wavefront aberrations, which can be compensated by appropriately morphing the light-mirror surface. For example, if a polar illumination setting, such as bipolar or quadrupole illumination, is used, a non-homogeneous radiation load having a double or quadruple radial symmetry, respectively, can bring the transparent optical element close to the pupil surface. The wavefront deformation caused by the double or quadruple radial symmetry can be at least partially compensated by the deformation of the surface of the corresponding pupil mirror, which is transmitted through the radial symmetry of the double or quadruple to deform the aperture Mirror surface.

The compensation capabilities provided by the manipulators located in the pupil mirrors are particularly useful in certain optical systems that use certain optical materials that are particularly sensitive to thermal effects caused by uneven absorption. For example, it may be necessary to make some or all of the lenses from fused alumina (synthetic quartz glass). Fused silica can be of high optical quality and large enough in both mass and size to produce large lenses, such as projection objectives requiring high NA lithographic etching. Further, processing fused alumina to obtain a high quality optical surface is a technique that has been achieved. In addition, fused alumina, in fact, still has no absorption for wavelengths as low as about 190 nm. Therefore, a large amount of fused alumina may be required as a lens of the objective lens. On the other hand, the characteristic heat conduction of fused alumina is less than the characteristic heat conduction of calcium fluoride (CaF ₂ ) and other basic fluoride crystal materials, and such fluorides are used at shorter wavelengths, such as 157 nm. It is due to the very low absorption even at these short wavelengths. Since the characteristic heat conduction of calcium fluoride (CaF ₂ ) is greater than the characteristic heat conduction of fused alumina, the negative effect of uneven heating of the projection beam in calcium fluoride is less than that of fused alumina, based on materials with relatively high characteristic heat conduction. The local temperature caused by uneven heating can reach equilibrium faster and more efficiently. Therefore, the system made of such materials is less susceptible to the problems caused by the heating of the uneven lens. A pupil mirror that can be manipulated to compensate for lens heating effects allows the use of, for example, fused alumina, even at or near the surface of the conjugate aperture, where the problem of uneven lens heating is very likely to occur when in certain lighting conditions Under, or under the use of a certain pattern architecture.

In some embodiments, the optical element at or near the optically conjugated pupil surface is made of an optical material having characteristic heat conduction, the characteristic heat conduction of which is less than the characteristic heat conduction of the calcium fluoride. For example, an optical element located at or near the surface of the conjugate aperture can be made of fused alumina.

In some embodiments, at least 90% of the lenses in the projection objective are made of fused alumina. In some embodiments, all of the lenses are made of fused alumina.

It is possible in embodiments to have, for example, an image side numerical aperture NA >= 0.6, which can be used in lithography etching to achieve a small size in lithographic etch exposure fabrication. There may also be embodiments with NA >=0.7. Certain embodiments The medium catadioptric projection objective has an image side numerical aperture NA >= 0.8, or even NA >= 0.9, which is close to the theoretical limit on the dry system, that is, the projection is suitable for imaging aberration and is used for the projection of the dry process. The objective lens, wherein the image space between the exit surface of the projection objective and the image plane is filled with a gas having a refractive index close to 1.

In other embodiments, the catadioptric projection objective is designed as an immersion objective, adapted to a wet process associated with imaging differences, the image space between the exit surface of the projection objective and the image surface being filled with a refractive index Immersion medium much larger than 1. For example, the refractive index may be 1.3 or greater, or 1.4 or greater, or 1.5 or greater. The projection objective has an image side numerical aperture NA > 1.0, when the projection objective is used in an immersion medium having a refractive index n _I > 1.3, such as NA >=1.1 or NA >=1.2 or NA >=1.3. Alternatively, the projection objective can have an image side numerical aperture NA < 1.0 when used in an immersion medium.

In general, the image side numerical aperture NA is limited by the refractive index of the surrounding medium in the imaging space. In immersion lithography, the theoretically feasible image side numerical aperture NA is limited by the refractive index of the immersion medium. The immersion medium can be a liquid (liquid immersion, wet process) or a solid (solid immersion).

In practice, the aperture should not be arbitrarily close to the refractive index of the final medium, and finally the medium is the medium closest to the image; it is because the angle of advancement becomes large relative to the optical axis. As far as experience is concerned, at the image end, the image side numerical aperture NA can reach 95% of the refractive index of the final medium. In the case of immersion lithography at 193 nm, in the case of water (n _H2O = 1.43) as the immersion medium, the corresponding numerical aperture NA = 1.35.

Some embodiments are set to allow numerical aperture NA to NA = 1.35 or higher along the image side. In some embodiments at least one optical component is a high coefficient optical component made of a material having a high coefficient and a refractive index n >= 1.6 at the operating wavelength. This refractive index may be about 1.7 or more, or 1.8 or more, or even 1.9 or more in the operating wavelength. Operating wavelength It can be deep ultraviolet (DUV) below 260 nm, such as 248 nm or 193 nm.

The projection objective has the last optical element closest to the image plane. Finally, the exit end of the optical element is immediately adjacent to the image plane, which exit surface forms the exit surface of the projection objective. The exit surface can be a flat or curved surface, such as a recess. In some embodiments, the final optical component is made, at least in part, of a material having a high coefficient and having a refractive index n > 1.6 at the operating wavelength. For example, the final optical element as a whole may be a plano-convex lens having a spherical or aspheric curved entrance surface with a flat exit surface immediately adjacent to the image surface.

The high coefficient material can be, for example, alumina (Al ₂ O ₃ ), which can be used as a high coefficient material with operating wavelengths as low as 193 nm. In some embodiments, the high coefficient material is aluminum telluride garnet (LuAG) having a refractive index n = 2.14 at 193 nm. The high coefficient material may be barium fluoride (BaF ₂ ), lithium fluoride (LiF), and barium lithium fluoride (BaLiF ₃ ). An immersion liquid having a higher refractive index than water can be used, for example, an additive in which water is doped to increase the coefficient, or a cyclohexane having nI = 1.65 at 193 nm. In some embodiments, at λ = 193 nm, the image side numerical aperture NA > 1.4 and NA > 1.5 can be obtained, for example, NA = 1.55. The use of a high coefficient of material in a catadioptric projection objective as an immersion lithography is disclosed, for example, in the applicant's U.S. Patent Application Serial No. 11/151,465. The above disclosure is incorporated herein by reference.

The catadioptric projection objective provided by the invention has an appropriate size for immersion lithography, particularly with an image side numerical aperture NA > The imaging features of the projection objective can be dynamically adjusted during the life cycle of the projection objective by adjusting the shape of the reflective pupil mirror surface. When some conditions relating to the corrected state of the projected beam to the pupil mirror are observed, a correction effect (field invariant correction) that is substantially constant (slightly or no change) throughout the field can be obtained. In immersion systems, these characteristics can be used to compensate for imaging errors caused by changes in the optical properties of the immersion liquid that are produced over time, for example, which can be caused by changes in temperature. For example, the field constant contribution to the spherical error due to the immersion layer temperature drift can be compensated, and the immersion layer is substantially in the wafer. Heart image.

The use of compensation is independent of the type of projection objective (eg, with or without intermediate images, in-line or folded projection objectives).

According to another aspect, the present invention is directed to a method of fabricating a semiconductor device and other microdevices, the reflective refraction projection objective of the device comprising: a reticle providing a pre-engraved pattern on an image surface of the projection objective; Having a predetermined wavelength of ultraviolet radiation illuminating the reticle; immersing the immersion layer formed by the immersion liquid having a refractive index much larger than 1 between the exit surface of the projection objective and the substrate, the substrate having the substrate surface substantially disposed on the image surface of the projection objective; Projecting an image of the pattern onto the light-sensitive substrate through the immersion layer; and adjusting an imaging feature of the projection objective by changing a surface shape of the aperture mirror, the aperture mirror having a light aperture at or near the projection objective The surface of the mirror is reflected.

The adjusting step is performed in at least one exposure of the substrate, and in the exchange of the substrates, and in the exchange of different masks, and is located at a position where the projection objective is used, or in replacing different illumination settings Among them.

It can be observed that the lens heating effect can be specifically judged if a small coherent illumination setting is used, such as bipolar or quadrupole illumination. Under these conditions, a transparent optical element, such as being placed at or near the pupil surface, may suffer from a heterogeneous radiation loading of the space, resulting in maximizing localized radiation intensity, as well as localized heating in the region of maximum diffraction of imaging. This can result in characteristic deformation of the lens elements as well as variations in refractive index, for example, double or quadruple radial symmetry in accordance with bipolar or quadrupole illumination. These deformations and variations in the refractive index may sequentially cause corresponding wavefront deformations to deteriorate imaging performance.

The solution to the above problem is a method for manufacturing a semiconductor device or other kinds of micro devices, and the reflective refraction projection objective lens used by the devices includes: placing a photomask having a predetermined pattern on the object surface of the projection objective; Ultraviolet radiation of a predetermined wavelength illuminates the reticle, which utilizes illumination settings provided by the illumination system; adjusts the illumination to provide off-axis illumination settings at the pupil plane of the illumination system and at least optically conjugated pupil planes, Having the intensity of the region outside the optical axis greater than the intensity of the light near the optical axis; adjusting the imaging features of the projection objective to change the surface shape of the aperture mirror by adjusting the off-axis illumination setting Thus, the wavefront aberrations caused by the spatially heterogeneous radiation load are at least partially compensated by the optical components located at or near one of the pupil faces of the projection objective .

In general, the illumination settings can be set according to the pattern provided by the reticle or other patterning device. A change in illumination settings can be achieved by replacing a first reticle having a certain architecture with a second reticle having another architecture. In exposure methods with multiple exposures, two or more different illumination settings, optionally including off-axis illumination settings, can be used to illuminate one of the successive exposure steps. Off-axis illumination settings can be polar illumination settings, such as bipolar or quad-polar illumination.

Some of the errors caused by changes in the characteristics of the immersion layer and changes in the characteristics of the projection objective may be dynamic in a relatively short period of time, which may be provided with this imaging error (or other characteristic that may affect imaging errors). Such optical characteristics associated with variables occurring over time, including such optical characteristics of the immersion layer as a function of time, and changes resulting from the use of polar illumination settings, off-axis illumination settings; The detector is detected, and the sensing signal generated by the detector indicates that the time is generated over time When the change is made, the change of the shape of the surface of the aperture mirror caused by the aperture mirror operator is driven to respond to the sensing signal, so that the deformation of the surface shape of the aperture mirror can effectively compensate at least part of the time-dependent generation. change. The frog mirror operator is thus integrated into the control loop for immediate imaging error control. In particular, the pupil mirror operator can be driven such that the field invariant error contribution caused by the change in the refractive index of the immersion liquid is at least partially compensated. A more stable process of immersion lithography can be obtained.

For example, using an interferometer or other suitable direct measurement system, imaging errors can be detected directly. It is also possible to use an indirect method. For example, if a immersion liquid is used, the temperature sensor is supplied to monitor the temperature of the immersion liquid forming the immersion layer, and the variation of the refractive index due to the temperature change can be based on the measurement of the look-up table. It is acquired by experience and dynamically compensated by operating the aperture mirror.

Alternatively, or additionally, a feed control operation can be utilized to obtain the desired pupil mirror shape. For example, the control unit can receive a signal indicating the type of polar illumination used by the illumination system, and the control unit can provide an appropriate control signal to the pupil mirror operator based on the lookup table to deform the surface of the pupil mirror. The wavefront deformation caused by the heating of the lens due to local heterogeneous absorption can be at least partially compensated, and such lenses are located at or near the pupil surface of the projection objective.

The foregoing and other features are not only apparent in the scope of the claims but also in the description and the drawings, wherein the individual features can be used individually or in combination as an embodiment of the invention or in other fields, and The patentable and advantageous embodiments may be represented separately.

100‧‧‧Reflective projection objective

500‧‧‧Inline projection objective

600, 1000‧‧‧projection objective

AS‧‧‧ aperture diaphragm

CR‧‧‧ main beam

CRA‧‧‧main beam angle

CRA _PM ‧‧‧Glass mirror PM main beam angle

CRH _O ‧‧‧The main beam height of the object surface

CRH _M ‧‧‧Main beam height on the mirror

CON‧‧‧Compression Department

D ₀ ‧‧‧ twice the edge beam height value of one of the light mirror surfaces

D _i ‧‧‧ Field i is one of the diameters of the image meridian direction at the entrance of the pupil

D _PM ‧‧‧Optical diameter

ES‧‧‧Light exit surface

FP‧‧‧Flexible part

FPO‧‧‧ points on the optical axis

IMI1‧‧‧ first intermediate image

IMI 2‧‧‧ second intermediate image

IF‧‧‧like field

IS‧‧‧Like

IM‧‧‧Immersion medium

ILL‧‧‧Lighting system

IR‧‧‧ off-axis lighting area

LG1‧‧‧first lens group

LG2‧‧‧second lens group

LG3‧‧‧third lens group

LG4‧‧‧Fourth lens group

MGI‧‧ ‧ mirror entrance

MGO‧‧‧ lens group export

MG‧‧‧Mirror

M1‧‧‧ first lens

M2‧‧‧ second lens

M3‧‧‧ third lens

M4‧‧‧Fourth lens

MGP‧‧‧ mirror plane

MR‧‧‧ edge light

OA‧‧‧ optical axis

OF‧‧‧物场

OS‧‧‧face

OP1‧‧‧First objective part

OP2‧‧‧Second objective parts

OP3‧‧‧third objective lens unit

P1‧‧‧ first light face

P2‧‧‧Second light surface

P3‧‧‧The third optical plane

PCL‧‧‧ Plano-convex lens

PO‧‧‧Projection Objective

PS‧‧‧Light surface

PM‧‧‧Light Mirror

PMM‧‧‧Light Mirror Operator

PMCU‧‧‧Light Mirror Control Unit

RA1‧‧‧reflection area

RA3‧‧‧reflection area

RP‧‧‧hard part

RRL‧‧‧Bottom beam

RRU‧‧‧Upper edge beam

RD‧‧‧ accommodating device

RS‧‧‧Grating table

SENS1‧‧‧first sensor

SENS2‧‧‧Second sensor

SS‧‧‧ substrate surface

W‧‧‧ device

WS‧‧‧ wafer table

Figure 1 is a lens portion of an in-line reflective refractive dry objective lens used for lithography etching in the first embodiment, having a deformable concave aperture mirror at NA = 0.93; 2 is a schematic view showing an axial portion of an in-line reflective refraction projection objective, which is similar to the embodiment of FIG. 1. FIG. 3 is an enlarged view of a region of the mirror group in the embodiment of FIG. On the substrate, which comprises a concave mirror group forming an adaptive pupil mirror and an off-axis illumination mirror; FIG. 4 is a schematic diagram showing a correction state of the projection beam affecting the pupil mirror; FIG. 5 is a second embodiment. The lens portion of the in-line reflective refraction projection objective used for immersion lithography utilizes a rectangular effective object field at NA = 1.2; Figure 6 shows the immersion lithography in the third embodiment. The lens portion of the catadioptric projection objective lens utilizes an arched effective object field at NA=1.55; FIGS. 7 and 8 are schematic views of the axial portion of the in-line reflective refraction projection objective lens having four faces. a mirror group comprising one or two (Fig. 8) pupil mirrors; and Fig. 9 is a scanning projection exposure system for lithography etching having an illumination system designed to produce a crack shaped illumination field, And a refraction projection having four concave mirrors and one of which includes a deformable aperture mirror Objective lens; Figure 10 shows the lens portion of the in-line reflective refraction projection objective, which is suitable for dry lithography, using an arched effective object field at NA = 0.75; and Figure 11 shows a folded refraction projection An embodiment of the lens portion of the objective lens, which is suitable for immersion lithography, utilizes an effective object field of a rectangle at NA = 1.25.

In the following description of the preferred embodiment, the related object is A reticle having a layer pattern of one of the integrated circuits, or other pattern, such as a grating pattern. The image of the object is projected onto the wafer, which is used as a substrate for coating a layer of photoresist, although other types of substrates are also suitable, such as components or gratings of liquid crystal displays.

The following describes an embodiment having a plurality of mirrors. Unless otherwise stated, the mirrors will be labeled in the order in which they are reflected on the mirror. In other words, the number of the mirror represents the position of the mirror on the optical path of the radiation, not the geometric position.

In different embodiments, appropriate, identical or similar features or feature sets represent similar reference definitions.

The tables are provided for the design shown in the drawings, and the tables are labeled with the same reference numerals as the drawings.

In some of the embodiments described below, the surface curvature of all of the curved mirrors has a common axis of symmetry, expressed as the mirror set axis. The mirror group is axially overlapped with the optical axis OA of the projection objective. An axially symmetric optical system, also referred to as a coaxial system or a linear system, is provided in this manner. The object surface and the image plane are parallel. Even reflections will occur. The effective use of the object field and the image field is off-axis, for example, completely outside the optical axis. All systems have a circular ring that surrounds the optical axis and can therefore be used as a projection objective for photolithography.

In other embodiments, the optical axis is folded into a plurality of shaft segments that are inclined at an angle to each other.

1 shows a lens area of a catadioptric projection objective lens 100 of a first embodiment, the catadioptric projection objective lens 100 being designed to project an image of a pattern placed on a mask of a flat object surface OS (object surface) on a smaller scale. The flat image surface IS (image surface), for example a ratio of 4:1, creates two real intermediate images IMI1 and IMI2. The off-axis effective object field OF placed outside the optical axis OA is thus projected onto the off-axis image field IF. Figure 2 illustrates a simplified representation of a deformation of a projection objective of the type of Figure 1.

In Figs. 1 and 2, the path of the main beam CR of the outer field point in the off-axis object field is indicated by a thick line to facilitate the follow-up of the beam path of the projected beam. For the purposes of this application, the term "primary beam" means the beam that travels from the outermost field point of the object field OF that is effectively used (farth from the optical axis) to the center of the entrance pupil. Due to the rotationally symmetric system, the primary beam may be selected from the equivalent field point of the meridional plane, as shown by the graphical representation for the purposes of the demonstration. Substantially at the end of the object field is a telecentric projection objective, the main beam emitted from the object plane is parallel to the optical axis, or a very small angle to the optical axis. The imaging process is further characterized by trajectory or marginal rays. Here, "marginal rays" are used as a beam of light traveling from the axis of the object object point (the field point on the optical axis) to the edge of the aperture stop. The vignetting caused by the effective off-axis object field is used, so that the side light may not constitute an image. The imaging process is further characterized by the orbit of "rim rays". The "edge ray" is here taken as a beam that travels from the off-axis object field point (the point of the field at a distance from the optical axis) to the edge of the aperture stop. The term "upper edge ray" refers to the edge ray whose direction of travel is such that the distance between the ray and the optical axis is gradually increased, that is, the light is away from the optical axis near the object plane. Conversely, the term "lower edge ray" refers to the edge ray that causes the direction of travel of the ray to gradually shorten the distance between the ray and the optical axis, that is, the ray travels toward the optical axis near the object plane. The primary and side and edge beams are selected as the optical features of the projection objective (see also Figure 4 for an illustration). The angle between the selected beam and the optical axis at a certain axis point is represented as "main beam angle", "edge light angle", and the like. The radius distance between the selected beam and the optical axis at a certain axis point is represented as "main beam height", "edge light height", and the like.

The projection objective 100 may be an optical element divided into five groups, arranged along a straight (unfolded) optical coaxial OA, that is, the first lens group LG1 is adjacent to the object surface and has a positive refractive power. , the mirror group MG is adjacent to the first lens group LG1 and has an overall positive intensity; The second lens group LG2 of the incident intensity is next to the mirror group MG, the third lens group LG3 is adjacent to the second lens group LG2, and has a negative refractive power; and, the fourth lens group LG4 of the third lens group LG3 has Forward refraction intensity. The lens groups LG1 to LG4 are purely refracting, and the mirror group MG is purely reflective (only reflective surfaces).

The first lens group LG1 (also the front lens group) is designed to image the telecentric incident pupil of the projection objective with a strong positive intensity on the first pupil plane P1, so that the first lens group LG1 is similar to Fourier ( The action of the Fourier lens group completes a single Fourier transform. This Fourier transform results in a relatively large main beam angle CRA _p1 which is at an angle of 28 degrees to the first pupil plane P1. Therefore, the pupil diameter on the first pupil plane is relatively small.

The radiation generated from the first pupil plane P1 is incident on the first lens M1, the first lens M1 is non-spherical, and the object end is a concave mirror surface; and the radiation optics sequentially forms the first intermediate image IMI1 and There is a distance between the first lenses M1. Thereafter, the radiation is reflected by the second lens M2 designed as a non-spherical concave mirror, and is reflected at an oblique angle to the third lens M3 having the reflecting surface including the optical axis OA. The concave mirror surface of the third lens is located on the second pupil plane P2, and the main beam intersects the optical axis on the second pupil plane P2, thereby forming the pupil mirror PM. Since a very large main beam angle CRA _pm ~42 degrees is formed on the second pupil plane, a small second aperture (Lagrange invariant) is obtained. The radiation having a large main beam angle and reflected from the third lens M3 (the pupil mirror PM) can be measured, and when it is reflected on the concave mirror surface of the aspherical image end of the fourth lens M4, the fourth lens M4 has The optical intensity is designed to polymerize the radiation beam and immediately travel down the second intermediate image IMI2 and a distance from the fourth lens M4.

It is possible to adjust the optical design so that the mirror does not have an aspherical shape but a spherical shape. For example, the second lens M2 and the fourth lens M4 may be implemented with a spherical mirror. Further, it is also possible to construct the second lens M2 with different mirrors having different surface features (surface shapes). And the fourth lens M4, and/or different mirrors having different surface features (surface shapes) to construct the first lens M1 and the third lens M3. In this case, at least one of the separate mirrors may be implemented as a spherical mirror rather than an aspherical mirror.

Obviously, the main beam height at the object surface OS (also referred to as the object height) is much smaller than the main beam height at the second lens M2, which immediately travels up to the pupil mirror M3; and it is also much smaller than in the fourth The main beam height of lens M4, which immediately travels down to the pupil mirror. In a preferred embodiment, the ratio of the main beam height CRH _O on the object plane to the main beam height CRH _M on the mirror (which immediately goes up and down to the pupil plane) is substantially greater than 1, such as greater than 2 or Greater than 2.5. In the embodiment of Figure 1, the ratio of mirrors M2 and M4 is approximately 2.7.

The mirror group entrance MGI radiating close to the first aperture P1 enters the mirror group, and approaches the second intermediate image, that is, the mirror group exit MGO of the near scene. The mirror group plane MGP arranged perpendicular to the optical axis and placed between the apexes of the first lens and the second lens is passed five times before the beam exits the lens group exit of the mirror group. Therefore, four reflections are obtained in the axial small space defined between the entrance of the lens group and the exit of the lens group.

The second intermediate image IMI2, which is enlarged with respect to the effective object field OF, is imaged to the image plane IS by a purely refractive objective lens component (also referred to as a rear lens group), and the purely refractive objective lens component includes a second lens group LG2, a third lens group LG3, and the fourth lens group LG4. The compressed portion of the projected beam, which is indicated as a partial minimum beam diameter, is formed in the region of the negative lens of the third lens group LG3. The second lens group LG2 has a positive refracted light intensity and substantially serves as a field mirror for imaging the pupil exit of the fourth lens M4 closer to the mirror group. This allowed lens is designed to have a relatively small optically adjustable diameter over an overall short axial length. The third lens group LG3 has a negative refractive power and thus constitutes a "waist" of the compression portion or the beam diameter. This negative lens group can increase the numerical aperture after the second intermediate image IMI2. The third lens group LG3 and the portion after the fourth lens group LG4 together form an opposite telecentric system, the fourth through The portion after the mirror group LG refers to the portion between the third lens group LG3 and the third pupil plane P3; the remote system has a small axial length, regardless of the minimum diameter required for the second intermediate image IMI The system aperture of the small numerical aperture.

In another description, the optical element of the projection objective 100 constitutes a first imaging objective component comprising a lens of the first lens group LG1 and a first lens M1 for imaging the pattern of the object field region of the reticle in the first middle The image IMI1; constitutes a second imaging objective component, comprising a pupil mirror PM for imaging the first intermediate image to the second intermediate image IMI2; and forming a third imaging objective component for imaging the second intermediate image to the image plane IS. The first objective lens component is catadioptric (having six lenses in the first lens group LG and one concave mirror M1), the second objective lens component is purely reflective (catoptric) and composed of concave mirrors M2, M3 and M4 And, the third objective lens component consisting of LG2, LG3, and LG4 is pure refraction. The refraction of the first objective lens component (β = 2.1) defines the size of the first intermediate image IMI1, and the interaction with the second lens M2 can be defined as the correction state of the projection beam of the pupil mirror. The absolute value of the main beam height of the mirror M2 that immediately travels up to the pupil mirror, and the absolute value of the main beam height of the mirror M4 that immediately travels down to the pupil mirror, is much larger than the main beam on the object plane Height, and this conditional type is preferred for a light-shield mirror with a small aperture. The large beam angle of the small aperture on the pupil mirror can be measured by the fourth lens M4 to form a beam for polymerization to the second intermediate image and the refractive lens groups LG2, LG3 and LG4 toward the image end. This portion (rear lens group) is preferably used to control imaging aberrations and to provide a large image side numerical aperture NA = 0.93.

The purely reflective (catoptric) mirror MG system provides over-correction of the Pazval sum to counteract the reaction of the forward refractive power of the lens. For this purpose, the mirror group MG includes a first concave mirror M1 placed on a side opposite to the optical axis of the object field OF, a second concave mirror M2 placed on the same side of the optical axis, and a third concave mirror M3 Placed on the optical axis as the pupil mirror PM, and the fourth concave mirror M4 is placed on one side of the object field. The mirror group inlet MGE is formed between the mutually facing edges of the concave mirrors M2 and M4, and is located at the object field end of the mirror group, and is geometrically close to the first pupil plane P1. The mirror set inlet MGE may be formed by drilling holes in the concave mirrors M2 and M4 having a common substrate or drilling holes thereon. The mirror group exit MGO is located outside the optical axis OA, adjacent to the edge of the pupil mirror M3, on the opposite side of the first concave mirror M1. As explained in more detail below with respect to Figure 3, the pupil mirror M3 and the first concave mirror M1 may be formed on the same substrate to form a pair of mirrors, although separate substrates may be used (see Figure 2).

The projection objective 100 is designed as a dry objective for operation at a wavelength λ = 193 nm and a numerical aperture = 0.93 at the image end. The size of the rectangular effective object field OF is 26 nm * 5.5 mm. The radius of the image field (half the diameter) y' = 18 mm. The specifications are summarized in Table 1. The leftmost row lists the refraction, reflection, or other marked surface; the second row lists the radius r (in mm) of the surface on which it is located, and the third row lists the distance d between the surface and the bottom. For the distance of the surface, this parameter is indicated as the "thickness" of the optical component; the fourth row is used as the material for the optical component, and the fifth row indicates the refractive index of the material. The sixth row lists the optically usable and clear radius (expressed in mm) of the optical component. In the table, the radius r=0 represents a plane (with a radius of infinity).

Some of the surfaces in Table 1 are non-spherical surfaces. Table 1A lists the corresponding data for these non-spherical surfaces. The maximum distance between the arcs (sagitta) or the rise height p(h) of the shape of these surfaces is taken as a function of height h, which can be calculated by the following equation: p (h)=[((1/r)h ² )/(1+SQRT(1-(1+K)(1/r) ² h ² ))]+C1*h ⁴ +C2*h ⁶ +. ..., where the inverse of the radius 1/r is the surface curvature at the surface apex, and the height h is the distance from one of the points on the surface to the optical axis. The maximum distance (sagitta) or rise height p(h) between the arcs of the string thus represents the distance from the surface apex to that point, which is measured along the Z-axis, that is, along the optical axis. The constants K, C1, C2, etc. are listed in Table 1A.

The projection objective 100 of Figure 1 is a catadioptric in-line system that is optimized for the requirements of at least two phase conflicts. First, the benefits of in-line construction (no folding mirrors, solid adhesion techniques, etc.) can be obtained from a large image side numerical aperture while still maintaining a small object field design. As stated above, the vignetting control system is the key. Second, by deforming the surface shape of the pupil mirror surface, a pupil mirror is provided to facilitate dynamic or static control of the imaging characteristics. Since the pupil mirror is placed on the optical axis, the pupil mirror can form an obstacle to the projected beam, making vignetting control more difficult. Third, careful control of the state of the projection beam correction of the pupil mirror is found to be necessary if the target imaging aberration control that would be affected as a substantial constant throughout the field is required. The above requirements are noted here by the solution shown by the example of projection objective 100 (see also Figures 3 and 4).

Since the projected beam should be directed through the mirror designed in the line without vignetting, the size of the critical area associated with vignetting should be kept as small as possible. In the example, it corresponds to some requirements such that the pupil of the projected beam, that is, where the projected beam meets at the pupil surface, is kept as small as possible in the area of the mirror. According to the Lagrange invariant, this requirement is converted to provide a particularly large primary beam incident angle at the location of the 瞳, at or near the mirror. The large forward intensity of the first mirror group LG1 (Fourier mirror group or front lens group) that significantly bends the main beam CR toward the optical axis provides a small size of the first pupil plane P1, which thus allows a small mirror group entrance MG1 And extending the reflection regions of the mirrors M2 and M4 that are very close to the optical axis. In combination with the positive intensities of the concave lenses M1 and M2, the main beam angle at the pupil mirror PM is further increased to CRAPM ≒ 42°, resulting in a small beam diameter at the second pupil plane P2 where the pupil lens PM is located. When the light mirror PM (= M3) reflection area RA3 The small size can be maintained, and the vignetting control between the fourth lens M4 and the image plane can be simplified, and it is possible to separate the reflection area RA1 of the used first lens M1 and the reflection area RA3 of the pupil mirror M3. In other words, the paths of the projection beams to the reflections of the mirrors M1 and M3 do not overlap. This is one of the necessary conditions for using the aperture mirror PM as a dynamically adjustable operator to dynamically influence the imaging characteristics of the projection objective.

Further, the focus is on the correction state of the projection beam of the pupil mirror PM, that is, the second pupil plane P2. An optimization condition is related to causing a field-invariant correction for imaging aberrations to be obtained if the secondary apertures corresponding to different field points in the object field have the same size and shape and are completely complementary to each other in the pupil surface. overlapping. Assuming that this condition is met, local variations in the reflection characteristics of the pupil mirror, such as deformation of the mirror surface, will produce similar effects for all beams from different field points, thus producing a field-invariant effect in the image plane. On the other hand, if the secondary apertures of different field points do not overlap on the pupil plane, the local variation of the reflection characteristics of the pupil mirror will have different effects on the beams from different field points, thus producing corrections in the field. The effect changes.

These conditions in Fig. 4 are represented by the following rays; the edge ray MR from the field point FPO on the optical axis OA, and the partial beam representing the off-axis field point FP1, that is, the main beam CR, the upper edge beam RRU and the lower Edge beam RRL. In the above-mentioned ideal example (the light beams in all the field points of the pupil plane have completely overlapping sub-apertures), the main beam CR should be interlaced with the optical axis at the position of the refractive surface of the pupil mirror PM. The deviation from the ideal condition will be described by the parameter CRH _i of the beam height of the main beam (distance from the radius of the optical axis), and the main beam is incident on the optical system at the outermost field point FP1 of the pupil mirror PM. The lateral displacement is small compared to the height D ₀ representing the double edge beam MR. Further, the pupil mirror PM of the objective lens at the field point FP1 (indicated by the parameter D _i ), the meridian diameter of the image of the pupil entrance should ideally correspond to the diameter D ₀ or, in other words, the ratio of D _i to D ₀ . D _i /D ₀ should be equal to or close to 1. The following values can be obtained from the embodiment shown in Figure 1: |CRH _i |/D ₀ =0.03, and D _i /D ₀ =0.991. In essence, the same conditions can be applied to the sagittal section between strings. In general, the condition | CRH _i | / D ₀ <0.1 and 0.9 ≦ D _i / D ₀ ≦ 1.1 should be observed, if the shape of the mirror surface of the operator must be corrected in all field points on the image field Essentially a constant effect.

Figure 3 shows an enlarged detail of the mirror of Figure 1 to emphasize the details of the performance conditions around the pupil PM. From the viewpoint of construction, it is shown here that the first lens M1 and the third lens M3 constitute a pair of concave lens groups, and are formed on a common substrate. The substrate has a thick and mechanically rigid portion to provide a concave surface with a reflective layer to form the first lens M1. Formed integrally with the hard portion RP is a relatively thin and resilient portion FP which is provided with a refractive coating for the pupil mirror PM. The back surface of the elastic portion FP on the mirror substrate forms a notch. A plurality of flip-flops (indicated by arrows) of the pupil mirror operator PMM are located within the recess and are coupled to the back of the resilient portion FP. The trigger is controlled by the pupil mirror control unit PMCU, which can be integrated as part of the central control unit of the projection exposure device. The light mirror operator control unit is coupled to receive a signal representative of the surface of the pupil mirror to be deformed. The light mirror operator and the corresponding control unit can be substantially designed as disclosed in U.S. Patent Application Serial No. 2004/0144915. Corresponding disclosures are incorporated herein by reference. The architecture of any suitable aperture mirror operator may be used instead, for example, using a motor-type trigger, such as a piezoelectric element, a reaction-hydraulic change trigger, an electrical/magnetic trigger. These triggers may be used to deform the continuity (unbroken) light frog mirror surface. The pupil mirror operator may also contain one or more heating elements or cooling elements that affect the local temperature variation of the mirror such that the surface of the pupil mirror to be formed is deformed. A resistive heater or Peltier element can be used for the above purposes. The aperture mirror can also be designed as a polygon mirror array with a plurality of single micromirrors that are relatively movable between the corresponding drive signals. Suitable polygon mirror arrays are disclosed, for example, in US patents Application 2006/0039669. The aperture mirror may be designed in accordance with some principles, such as the International Publication No. WO 2003/093903, the disclosure of which is incorporated herein by reference.

From an optical point of view, it is worth noting that the reflective area RA1 (in bold) of the utilized first lens M1 does not overlap the reflective area RA3 corresponding to the pupil mirror M3. This property can change the shape of the surface of the pupil mirror without affecting the reflection generated by the first lens M1. Moreover, the design is optimized to be related to the caustics of the projected beam, which is the refractive area of the concave mirror and the lens, in particular the first lens of the second lens group LG2, which is in the second intermediate image. Immediately, the light travels down to the exit of the mirror. The above is accomplished by providing an intermediate image located at a relatively distant distance from the optical surfaces of the mirrors and the first lens of the second lens group LG2, the intermediate image being substantially for astigmatism and coma ( Corrected by coma). Avoiding caustics on optical surfaces that are refracted or reflected helps to avoid large localized radiation densities and simplifies selective aberration control. Further, avoiding caustics on the surface makes the quality of the specification easier to achieve.

The embodiment of Figure 1 can be adjusted to increase the selectivity of operating image quality over a relatively short period of time. For example, the projection objective can include at least one additional mirror whose mirror surface can be operated by an associated operator attached to the mirror. In view of the fact that the operable aperture mirror is generally placed where the edge beam height MRH exceeds the main beam height CRH, the additional mirror described above can be optically placed closer to the scene, especially at the beam height. The ratio MRH/CRH is less than 1 or even less than 0.5. An adaptive mirror that is optically located near the scene (with a mirror that can be changed by the operator) can be used to correct field subordinate aberrations. As a modification of the first embodiment, the first lens M1 or the mirror group MG optically placed close to the adjacent scene (intermediate image IMI1) is provided by providing a field mirror operator similar to the construction and operation of the above-described diaphragm operator. May be designed as an adaptive mirror. Since both the pupil mirror M3 and the field mirror M1 may be shaped The triggers designed for the field mirror operator and the pupil mirror operator can be connected to each other for easy construction on the same substrate. As an alternative, or in addition, at least one of the second lens M2 and the fourth lens M4, which are optically close to the scene, can be designed as a mirror having a mirror surface that can be adjusted or changed by the operator. Both the mirrors M2 and M4 are formed on the same substrate, and a common trigger mechanism can be applied to this example.

The second embodiment shown in FIG. 5 is an in-line projection objective 500 having a general layout relating to FIGS. 1 and 2, relating to the type and order of the optical element groups (lens group, lens group), and the whole. The trajectory of the projected beam in the system. Please refer to the corresponding description. The elements and group of elements have similar features as indicated by the same referenced definition in the previous embodiments. The specifications for this design are in Table 5 and Table 5A.

The projection objective 500 is designed as an immersion objective lens at λ=193 nm, and has an image side numerical aperture NA=1.2 when used in combination with a high coefficient immersion liquid I, such as pure water, between the exit surface of the projection objective and the image plane. Between IS. This design is optimized for a rectangular effective image field. This image field does not have image vignetting and the field size is 26*5.5mm ² .

In the embodiment shown in Fig. 1, the catadioptric first objective member of the first lens M1 comprising the mirror set MG creates a first intermediate image IMI1 located in the space between the mirror and the mirror in the mirror. The second, third and fourth lenses M1 to M4 of the mirror set MG form a second, reflective imaging subsystem to form a second intermediate image IMI2 from the first intermediate image. The lens groups LG2, LG3, and LG4 constitute a third, refracting objective lens component for re-imaging the second intermediate image IMI2 on the image plane IS at a lower magnification (ratio of magnification ratio β = -0.125). It is obvious that the maximum lens diameter in the image waist portion between the compression portion CON and the image plane IS is improved relative to the system of the lower numerical aperture in FIG. 1, wherein the image waist close is located close to the first The aperture stop of the three-gloss plane P3 is AS. Invariably, the optical diameter D _{PM of the} pupil mirror PM (third lens M3) remains relatively small, guiding the projection beam through the mirror without vignetting. The size of the small aperture mirror is composed of a strong positive intensity of the first lens group LG1 (as a Fourier lens group for forming the first pupil of P1) and a forward intensity of the mirrors M1 and M2. The main beam angle CRA _PM ≒ 45° is obtained in the light mirror. In other words, the main beam angle of the pupil mirror is further increased with increasing NA, wherein the gradually increasing NA maintains a small pupil size according to the Lagrangian invariant.

The pupil mirror operator PMM is provided to deform the pupil mirror reflecting surface to be changed, as described in connection with FIG.

Figure 6 shows a third embodiment of the projection objective 600 designed to be immersed in lithography at λ = 193 nm, with an image side numerical aperture NA = 1.55 in a ring field of 26 * 5.5 mm ² when used in combination with high coefficients. The immersion liquid has a refractive index n ₁ = 1.65. The optical element closest to the scene IS is a plano-convex lens PCL made of yttrium-aluminum garnet having a refractive index n = 2.14 at λ = 193 nm. The immersion liquid system is a cyclohexan having a coefficient n1 = 1.65. The specifications are as described in Table 6 and Table 6A. In this example, a very high numerical aperture is shown in an in-line system with a pupil PM (mirror M3) on the optical axis. The aperture stop AS adjacent to the image-side third pupil plane P3 is placed in a region having a strong converged beam between the region of the maximum beam diameter and the image plane IS in the fourth lens group LG4. Although, with respect to the embodiment shown in FIG. 1, the image side numerical aperture increases sharply, the size of the pupil mirror PM remains moderate, and the system is partially attributed to the large main beam angle on the second pupil plane P2. CRA _PM ≒ 36°. Moreover, vignetting control is more easily achieved by an arched effective object field OF (ring field).

In all of the embodiments described above, an in-line reflective refractive objective having an axially compressed mirror set that provides four reflections is used, and a third lens is placed in the position of the crucible for use as a pupil mirror (if needed, It can be operated). It is considered advantageous to obtain a high main beam angle CRA _{PM at} the position of the pupil mirror by optically moving up to at least two reflections of the concave lens to the pupil mirror, such a small size crucible and a small aperture mirror Can be achieved. A small-sized aperture mirror, therefore, allows a high-aperture projection beam to be directed through a compression mirror in a relatively small object field with a substantial effective object field without vignetting.

8 and 9 show an alternative embodiment of a projection objective in a spectroscopic line having an axially compressed mirror that provides four reflections and providing at least one aperture mirror, which may be used It is a dynamically controllable correction element to control aberrations.

In the embodiment shown in FIGS. 1 to 6 as described above, the position of the mirror group entrance MGI is close to the pupil plane P1 (first pupil plane), whereas the mirror group exit MGO is optically close to the second intermediate image IMI2. The position is located in a region separated from the optical axis OA. The pupil mirror is provided with a third reflection in the mirror.

In the embodiment of Fig. 7, the mirror set MG is arranged such that the mirror set entrance MGI is located outside the optical axis OA, and the optical is close to the object plane OS, for example, optically close to the scene. There are no lenses or groups of lenses between the object face and the mirror set entrance MGI, however, one or more lenses may be provided here. The first convex mirror M1 forms a first optical element and polymerizes the radiation toward the second lens M2, which is a pupil mirror located on the optical axis OA. The third lens M3 polymerizes the radiation to form a first intermediate image IMI1 that is located within the catadioptric recess of the mirror. The catadioptric secondary system includes a fourth lens M4 that directs the radiation beam through the mirror exit MGO at the second pupil face P2. The second intermediate image IMI2 is formed outside the mirror group and between the forward lens groups (indicated by arrows with arrows pointing outward). The refracting third objective lens component re-images the second intermediate image onto the image plane. In this embodiment, the mirrors in the mirror are utilized substantially in reverse order as compared to the previous embodiments. This design requires that the effective object field be placed away from the optical axis, which increases the diameter of the designed object field, so that it is more difficult to project a relatively large object field of high numerical aperture without vignetting.

As with the embodiment illustrated in Figure 8, both the mirror inlet MGI and the mirror outlet MGO are placed optically near the image plane (i.e., optically away from the pupil plane) and outside of the optical axis OA. The refractive element placed upstream of the entrance of the mirror group radiates radiation toward the first lens M1, which is the first aperture mirror PM1. The second aperture M4 is formed as a second aperture mirror PM2 after the second lens M2 and the third lens M3 are reflected at the position of the fourth lens M4. The first intermediate image IMI1 is formed between the second and third refractions, and the second intermediate image IMI2 is formed at a position where the fourth reflection goes downward, so that the intermediate images are placed on the surface of the mirror and the mirror. Among the spaces defined by curvature. The second intermediate image IMI2 is imaged again on the image plane by the subsequent refractive lens group. Regardless of the first lens M1 or the fourth lens M4 or both, the first and fourth lenses may be designed as an adaptive mirror to dynamically compensate for imaging errors in the system by operating the shape of the pupil mirror surface. According to the height of the object, it is difficult to obtain a large main beam angle on the first aperture mirror PM1 and the second aperture mirror PM2. Thus, as the numerical aperture of the image side increases, the size of the aperture mirror will have Significant increase. This effect may limit the ability to transmit large geometric fluxes without vignetting. Also, a relatively large lens is required to immediately travel down to the mirror to capture the diverging beam exiting the mirror exit MGO. Such a system preferably has a relatively large reduction ratio, for example, 4:1 instead of 4:1, due to the numerical aperture of the object end relative to a system having a smaller magnitude reduction ratio (eg 4:1) The height of the object field can be reduced.

Figure 9 illustrates a lithographic projection exposure system as a wafer scanner WS that is provided as a step-by-step scanning mode using immersion lithography to fabricate large-sized integrated semiconductor components. The projection exposure system includes a quasi-molecular laser L that acts as a light source and has an operating wavelength of 193 nm. Other operating wavelengths, such as 157 nm or 248 nm, may also be used. The descending illumination system ILL generates a large, sharply bound, homogeneous illumination illumination field in its light exit surface ES, which is disposed at a position offset from the optical axis of the projection objective PO and adapted The telecentric condition of the downward reflection refraction projection objective lens PO. The lighting system ILL has a device for selecting a lighting mode, in which case the lighting system ILL can be changed between conventional on-axis illumination with off-axis illumination and off-axis illumination, especially ring illumination (light in the illumination system) The surface of the crucible has a circular illumination area) and bipolar or quadrupole illumination.

The device disposed in the downward direction of the illumination system is a reticle stage RS for supporting and operating the reticle M by placing the reticle in an illumination system conforming to the object surface OS. The light exit surface ES, and in this plane, the reticle can be moved to scan in the scanning direction (Y-phase); the scanning direction is perpendicular to the optical axis OA, and the optical axis OA is located in the illumination system and the projection objective The same direction (that is, the Z direction).

The size and shape of the illumination field IF provided by the illumination system determines the size and shape of the effective object field OF of the projection objective. The projection objective is actually used as a pattern image of the projection mask on the image surface of the projection objective. The illumination field IF having a slit shape has a height A parallel to the scanning direction, and has a width B>A in the vertical direction of the scanning direction, and the illumination field IF may be rectangular (as shown) or Arched (ring field).

The reduced projection objective OP is telecentric at the object end and the image end, and is designed to image a pattern image provided by a photomask having a reduction ratio of 4:1 on the wafer W coated with the photoresist layer. Other reduction ratios, such as 5:1 or 8:1, are also possible. The wafer W as a photosensitive substrate is disposed such that the planar substrate surface SS coated with the photoresist layer substantially coincides with the planar image plane IS of the projection objective. The wafer-supporting device WS (wafer stage) includes a scan driver for moving the wafer in synchronization with the mask M and in parallel. The device WS further includes an operator for moving the wafer in the Z direction parallel to the optical axis OA and in the X direction and the Y direction perpendicular to the optical axis. A tilting device is integrated therewith, the tilting device having at least one tilting axis that vertically circumscribes the optical axis.

The device WS for supporting the wafer W is constructed as an immersion micro Shadow. This device includes a receiving device RD that is movable by the scan driver and has a flat recess at the bottom to accommodate the wafer W. A peripheral edge forms a flat, open-ended, and containment reservoir that prevents liquid from escaping, which contains liquid immersion medium IM, which can be directed into the receptacle and can be directed to the receptacle by a device not shown. The height of the edge is designed such that the filled immersion medium can completely cover the surface SS of the water W, and the end region of the exit surface of the projection objective lens PO can be immersed in the immersion liquid, if the objective lens exit and the operating distance of the wafer surface are correctly set .

The projection objective lens PO has a plano-convex lens PCL as the last optical element closest to the image plane IS, and the plane exit surface of the lens is the last optical surface of the projection objective lens PO. During operation of the projection exposure system, the exit surface of the final optical element is completely submerged in the immersion liquid IM and is wetted. In this example, an ultrapure water system having a refractive index n _I ≒ 1.437 (193 nm) was used as the immersion liquid.

A temperature sensor SENS is provided to monitor the temperature of the immersion liquid IM during operation of the projection exposure system. For this purpose, one of the sensing elements in response to the temperature change is placed close to the exit surface of the projection objective PO to monitor the temperature of the immersion layer that is radiated while exposed. The temperature sensor is coupled to a central control unit of the exposure system that includes a pupil mirror control unit PMCU for controlling the shape of the pupil mirror reflective surface of the projection objective PO, using a pupil mirror operator PMM (eg, compared to a map) 3). The pupil mirror control unit PMCU comprises a digital memory comprising a lookup table for converting the temperature signal provided by the temperature sensor to a value which is the refractive index of the immersion liquid for the immersion layer. The temperature of the immersion layer changes during exposure, possibly for the following reasons: by absorbing the radiation intensity of the projected beam (increased temperature), or because the new immersion liquid flows into the space between the exit surface of the projection objective and the wafer (temperature increases or Reduce), and the refractive index of the immersion layer fluctuates. These may cause the field to change and cause spherical aberration, which affects the formation of images on the wafer. The fluctuations in the operational characteristics of these telecentric projection systems at the image end are compensated by adjusting the aperture mirror The shape of the reflection, such that the corresponding amount of spherical aberration is transmitted to the pupil mirror to compensate for the effect of the immersion layer on the spherical aberration. With this control loop, a stable immersion lithography process can be achieved.

The pupil mirror control unit PMCU is still set to receive the signal of the illumination system ILL, which represents the illumination setting used in the exposure, and the control unit PMCU contains a control routine that allows adjustment of the pupil mirror surface, corresponding to the selection Lighting settings. For example, the reticle pattern projected onto the wafer essentially includes parallel lines that travel in the same direction, and a bipolar set DIP (see illustration) can be used to increase resolution and depth of focus. For this purpose, the adjustable optical element in the illumination system is adjusted to obtain an intensity distribution at the pupil surface PS of the illumination system ILL, characterized by a region IR having two locally concentrated illuminations, two having a large light intensity The region is located opposite the opposite position outside the optical axis OA, and the intensity of the light on the optical axis is small or even zero. A similar heterogeneous intensity distribution is obtained in the pupil plane of the projection objective, which is optically paired with the pupil plane of the illumination system. Therefore, the lenses of the first or third pupil surfaces P1, P3 respectively adjacent to or at the above-mentioned projection objective lens may be subjected to different qualitative radiation loads in the space, which are characterized by two opposite regions in the opposite direction of the optical axis. "Hot zone", which may cause local lens heating due to absorption, causing deformation of the characteristic lens and variation of refractive index, which causes characteristic deformation of the waveform, which is characterized by substantially radial symmetry to both sides of the optical axis.

Proper operation of the pupil mirror surface can be used to compensate for these effects by providing a suitable deformation on the pupil mirror surface that is radially symmetric about both sides of the optical axis in the correct direction.

If the illumination setting is changed to obtain, for example, general illumination (rotational symmetry to the optical axis) or quadrupole illumination (radial symmetry to the four sides of the optical axis, please see the right hand thumbnail QUAD in the figure, with four off-axis Illumination area IR), and the light mirror operating unit will provide a corresponding signal to the pupil mirror operator to According to the shape of the surface of the diaphragm.

An illumination system that selectively provides an off-axis illumination mode as described above is described in, for example, U.S. Patent No. 6,252,647 B1, or in the U.S. Patent Application Serial No. US 2006/005026 A1, which is incorporated herein by reference. The disclosure is incorporated herein by reference. The adaptation of the illumination setting optics can be used in an immersion system, such as the embodiments described above, or can also be used in a dry system, that is, a system using a dry objective of NA < 1.

In other embodiments (not shown), the optical mirror operator control signal provided to deform the reflective surface of the pupil mirror is an empirical or operational value from a control parameter stored in the pupil mirror control unit. . In these embodiments, direct or indirect measurement of the imaging characteristics of the projection system is not necessary.

Further, a catadioptric projection objective having a concave pupil mirror and a control system for controlling the shape of the reflective surface of the pupil mirror will be described in detail below with reference to FIGS. 10 and 11.

Figure 10 illustrates that the catadioptric projection objective 1000 is designed to nominally operate at a wavelength of λ = 193 nm. The layout of the projection objective of this example, relating to the number, shape and position of the lenses, and other optical components are taken from the projection objective shown in Fig. 4, and in the second embodiment of the European patent EP 1 069 448 B1 (Table 2 ) is discussed. The disclosure of the above references is incorporated herein by reference. The projection objective system is suitable for "dry lithography", and has a space filled with gas between the exit surface of the projection objective and the image plane. In the arched off-axis image field with a reduction ratio of 6:1 (|β| = 1/6), the numerical aperture NA = 0.75 of the image end can be obtained. Other embodiments may have different magnification ratios, such as |β|=1/5 or |β|=1/4, or |β|=1 (unit magnification).

The projection objective 1000 can be set to project an image of the reticle pattern set on the plane object plane OS (object plane) onto the plane image plane IS (image plane) when the same real intermediate image IMI is produced. First reflective refractive mirror component OP1 It is designed to image the pattern from the object surface to the intermediate image IMI. The purely reflective second objective lens component OP2 images the intermediate image directly onto the image plane (ie, without further intermediate images). Two conjugated pupil surfaces P1 and P2 are formed where the CR intersects at the optical axis OA. The first pupil surface P1 is formed on the first objective lens member, and the second pupil surface is formed on the second objective lens member OP2. When the first objective lens part OP1 has only a moderate reduction effect, the main reduction is due to the contribution of the second refractive objective lens part OP2. All of the optical elements are arranged along a single, straight optical axis OA such that the object plane OS and the image plane IS are arranged in parallel. The exit of the projection objective is substantially annular. The first concave mirror M1 is placed at a position relatively close to the first pupil plane P1, thus forming the pupil mirror PM.

The first objective lens part OP1 has a forward lens group LG1 formed by two positive meniscus lenses, and a negative lens group LG2 formed by a single double concave negative mirror, having a first reflecting surface facing the object surface The concave mirror M1 immediately travels down to the negative lens group LG2, and has a second concave mirror M2 facing the first concave mirror and the image surface. The second objective lens part OP2 has a forward lens group LG3 composed of a single forward lens, and a negative lens group LG4 composed of a single double concave negative mirror, and between the second pupil plane P2 and the image plane Five forward lenses and two negative mirror positive lens groups LG5. A variable aperture stop AS that allows adjustment of the image side numerical aperture NA used is placed between the second pupil face and the fourth and fifth lens groups.

The radiation from the object plane is polymerized toward the first concave mirror M1 by the forward first lens group LG1 and is reflected by the first concave mirror to the second concave mirror M2, which polymerizes the radiation to form a first intermediate image. The radiation directed toward and reflected from the first concave mirror M1 passes through the negative mirror group LG2 twice in the opposite direction. Both the reflecting surface of the first concave mirror M1 and the negative mirror group LG2 are optically located very close to the second pupil plane P2, and the position is that the section of the radiation beam is only slightly different from the ring shape, and This position is where the edge beam height is at least 4 to 5 times greater than the main beam height. Quite close to the light The concave mirror M1 and the negative mirror group LG2, which are coaxial with the radiation and passed through twice, support the correction of the chromatic aberration, in particular the correction of the axial chromatic aberration, in the manner of "Schupmann achromatic". The second objective lens part OP2 re-images the intermediate image IMI1 to form a final image in the image plane IS.

The pupil mirror operator PMM mounted behind the pupil mirror PM (M1) is set to change the shape of the aspherical reflective surface of the pupil mirror by a suitable trigger (not shown). The design of a typical pupil mirror operator may be the same or different than the diaphragm operator described in FIG. The trigger is controlled by the pupil mirror control unit PMCU, which may be integrated into the central control unit of the projection exposure unit. The pupil mirror control unit is configured to generate a control signal such that the trigger of the pupil mirror operator can adjust the shape of the pupil mirror surface such that the desired shape can be achieved.

The pupil mirror control unit PMCU is connected to the first sensor SENS1 and the second sensor SENS2. The first sensor SENS1 is integrated into a measurement system, such as an interferometer, to detect the imaging quality of the projection objective in operation, and to provide a signal indicative of the measurement of the optical performance. For example, the first sensor SENS1 can be set to detect wavefront aberrations incident on the wavefront of the image plane. An example of a wavefront measurement system suitable for this purpose can be found in, for example, U.S. Patent Application Serial No. US 2002/0001088 A1, the disclosure of which is incorporated herein by reference. The second sensor SENS2 is set to obtain a signal indicative of the current state of the aperture stop, as may be obtained, for example, from the image side numerical aperture NA currently used in the process. Alternatively, or additionally, the second sensor can be provided to obtain a signal indicative of the intensity or intensity distribution of the pupil plane, or to indicate the wavefront features of the scene in the pupil plane and/or at the projection objective. Signal.

In embodiments with more intermediate imaging, such as two intermediate imaging and/or in a folding system, similar control circuitry can be provided.

FIG. 11 shows a catadioptric projection objective 1100. The projection objective system is designed to nominally operate at a wavelength of λ = 193 nm. Projection objective lens of this example The layout, the number, shape and position of the lenses, and other optical components are taken from the projection objective shown in Figure 9, and in the fifth embodiment of the international patent application WO 2004/019128 A2 (Table 9 and 10) Being discussed. The disclosure of the above references is incorporated herein by reference. In a rectangular off-axis image field having a reduction ratio of 4:1 and a size of 26 mm * 4 mm, an image side numerical aperture NA = 1.25 can be obtained.

The projection objective lens 1100 is designed to project an image of a pattern of a mask (gate) provided on a plane object plane OS (object plane) onto a plane image surface IS (image plane) of a smaller size, for example, 4:1, when Two identical and realistic intermediate images IMI1, IMI2 are generated. The rectangular effective object field OF and the image field IF are off-axis, that is, completely outside the optical axis OA. The first refractive objective lens part OP1 is designed to image the pattern of the object surface on the first intermediate image IMI1. The catadioptric second objective lens part OP2 images the first intermediate image IMI1 at a magnification close to 1: (-1) to the second intermediate image IMI2. The refracted third objective lens part OP3 images the second intermediate image IMI2 at a large reduction ratio on the image plane IS.

Three mutually conjugated pupil planes P1, P2, and P3 are formed at positions where the main beam CR intersects the optical axis. The first pupil plane P1 is formed on the first objective lens member between the object surface and the first intermediate image; the second pupil plane P2 is formed on the second objective lens component, and is interposed between the first and second intermediate images. And a third pupil plane P3 is formed on the third objective lens member between the second intermediate image and the image plane IS.

The second objective lens part OP2 includes a single concave mirror CM on the second pupil plane P2, thus forming the pupil mirror PM. The first plane folding mirror FM1 is disposed at a position optically close to the first intermediate image IMI1 and sandwiched by the optical axis OA by 45°, such that the first plane folding mirror FM1 reflects the direction from the object surface to the conventional concave mirror CM. The second heavy mirror FM2 has a plane mirror surface and is arranged at an angle on the right side of the first folding mirror FM1 to refract the radiation from the concave mirror CM (the optical mirror M) to advance the image surface, and the image plane is parallel to the object surface. fold The overlay mirrors FM1, FM2 are respectively located optically adjacent to the intermediate image.

The projection objective has 27 lenses, including two negative meniscus lenses, which immediately form a negative mirror before the concave mirror CM, and it is radiated twice, once from the first folding mirror FM1 toward the concave mirror, once from the concave mirror Second heavy mirror. a combination of a concave mirror that is optically close to the pupil plane and a negative mirror group that includes at least one negative mirror and is located before the concave mirror reflecting surface (in the region where the radiation can pass twice and the direction through which the negative mirror passes twice) It is called "Schupmann achromat". This lens group has a considerable contribution to chromatic aberration correction, especially axial chromatic aberration correction.

The pupil mirror operator PMM is provided behind the concave mirror CM which is free to contact. The light mirror operator includes a trigger (indicated by an arrow) acting on the resilient mirror substrate to continuously change the shape of the reflective surface in response to the control signal of the pupil mirror control unit PMCU connected to the pupil mirror operator PMM. The first sensor SENS1 is operatively coupled to the elastic mirror substrate to sense the state of deformation of the refractive surface in a two-dimensional and high spatial resolution manner. The light mirror control unit is connected to the sensor SENS1 to receive the feedback signal, which represents the actual deformation state of the pupil mirror surface. The pupil mirror operator and corresponding control unit can be designed to be substantially as previously described in relation to FIG. The first sensor SENS1 may be a machine inductance detector to receive the electrical signal obtained by the state of the optical mirror. Alternatively, or in addition, the sensing system for monitoring the concave mirror deformation can be designed in accordance with the principles indicated in U.S. Patent No. 6,784,977 B2. The disclosure of this patent is incorporated herein by reference.

In general, the mirror arrangement formed by the pupil mirror, and the aperture mirror operator used to change or deform the shape of the pupil mirror reflection surface, can be constructed by the methods previously described or by other methods. Examples are found in U.S. Patent No. 5,986,795 or U.S. Patent Application Serial No. US 2006/0018045 A1. The disclosures of these patents are incorporated herein by reference.

The control of the pupil mirror operator used to affect the deformation of the reflective surface of the pupil mirror can be set in various ways, independent of the type of objective (folded or inline) and the number of intermediate images.

In some embodiments, the control system for controlling the mirror operator includes a control circuit configured to receive at least one input signal indicative of at least one condition of the projection objective or another portion of the projection exposure device, and outputting the control signal To the mirror operator, this control signal represents, in response to the input signal, the surface shape of the pupil mirror is adjusted to accommodate the imaging characteristics of the projection objective. The control circuit can be operated in an open loop control manner.

For example, an input signal representative of a lighting setting (eg, bipolar or quadrupole illumination) can be received from the illumination system and processed in the control circuit to generate a control signal such that the trigger of the aperture mirror operator will The reflective surface of the pupil mirror is deformed to obtain a surface deformation having a double or quadruple rotational symmetry, such that at least a portion of the non-homogeneous lens heating that may be generated on the pole of the illumination may be asymmetrical. Mirror surface deformation compensation. Alternatively, or in addition, other input signals may also be generated or processed, for example, input signals representing pattern types (eg, line patterns, hole patterns, and/or patterns with lines in different directions), representative values The input signal of the aperture NA, and/or the input signal representing the number of exposures.

Even higher optical performance stability and better response to interference can be achieved in embodiments that include closed loop controlled projection objective performance. Unlike a simple open loop control, closed loop control facilitates feedback to the control circuitry. In some embodiments, the control circuit includes at least one feedback circuit including at least one first sensor configured to detect a shape of a reflective surface of the pupil mirror or to detect a projection objective characteristic associated with the surface shape The detector is connected to the optical mirror control unit to provide a feedback signal, and the optical mirror control unit is configured to selectively adjust the control signal for controlling the optical mirror operator to respond to the feedback signal. For example, A measurement system for the optical performance of the wavefront measuring device or other measurable projection objective can be used to generate a signal, for example, the signal represents the degree of wavefront difference incident on the image plane and/or the pupil plane. The degree of wavefront difference is characterized by one or more differences, including one or more monochromatic aberrations, such as spherical aberration, coma, astigmatism, curvature of field, and distortion, and/or one or more chromatic aberrations, Contains axial or lateral chromatic aberrations, as well as color variations in monochromatic differences. After the difference exceeds a predetermined threshold, the light mirror control unit may generate a control signal to adjust the surface shape of the aperture mirror, so that the degree of the main difference may be reduced below a critical value, which is generally visible to the user as a certain process. Among the specifications provided. The apparatus for detecting wavefronts in the applicant's US Patent Application No. US 2002/0011088 A1 can be utilized with closed loop control to optimize the surface shape of the pupil mirror.

The surface shape of the pupil mirror or the features of the projection objective directly related to the surface shape can be monitored for a long time or periodically to obtain a feedback signal.

At least one input signal processed in the open control loop or the closed control loop can be obtained from a parameter obtained from the measurement of the projection objective; in other words, the parameter can be directly detected in the system. . It is also possible to obtain one or more input signals from the simulation model, the simulation model can reproduce the projection objective or a part of the projection objective, or reproduce a projection exposure device with a sufficient degree of precision, such meaningful control parameters and The signal can be taken from the simulation model. In this case, the control of the pupil mirror may include aspects of model-based (MBC) control. For this purpose, the pupil mirror control unit may include or be connected to the model data memory, and store model data representing model parameters of the simulation model, wherein the simulation model is a simulation model of the projection objective or the projection exposure device. The control system can obtain at least one input signal from the control circuit to store the model data stored in the model data memory. The projection objective may include one or more second sensors to detect parameters of the actual state of the projection objective to obtain actual observable parameters corresponding to the model parameters of the simulated model.

For example, in the feedback control system shown in FIG. 11, the pupil mirror control unit PMCU includes model data memory MDM storing model data representing model parameters of the projection objective 1100 and/or the simulation model of the projection exposure apparatus. The model data memory MDM may be included in an external device that can be accessed by the optical mirror control unit via the data network. In the above embodiments, the model data memory MDM may have stored one or more of the following data: temperature data, representing the temperature of one or more components; temperature distribution data, representing the spatial temperature of one or more components. Distribution; positional data representing at least one axial position of one or more elements, displacement or tilting of one or more elements; shape data representing the shape of the reflective surface of the pupil mirror; aperture data representing the aperture stop State (the NA being used); setting data, representing the illumination setting; radiation intensity data, representing the intensity of the radiation source; difference data, representative of the spatial distribution of one or more differences in the optical mirror of the projection objective or in the image field The immersion data represents at least one immersion medium characteristic, including indication information indicating whether or not an immersion medium exists; and the pattern data represents information of a certain type of pattern provided by the reticle or other pattern device. The simulation model can be corrected at time intervals using the measured parameters corresponding to the model parameters, and the data of these parameters are stored to maintain a close correlation between the simulation model and the actual operating system.

It may be advantageous to include the operation of controlling the adaptive pupilscope in the model-based control feature, particularly in view of certain problems that may occur with an adaptive pupiltoscope, such as a lens heating effect, which is The dynamic effects produced by certain time constants. Further, the relationship between the radiant energy distribution of the optical system and the corresponding optical efficiency effect is not simple. If a closed loop control circuit is used, the actual optical performance of the projection objective is compared to a theoretical or desired value at a particular time interval, which is typically the user's specification. If there is a difference between the actual value and the desired value, the control circuit can effectively reduce these differences by appropriate operation, which can include operations such as on a pupil. One In general, such closed loop control systems can reflect observed errors and effectively remove or minimize these errors. In general, the integration of all aspects of the model-based control can be used to achieve the control of the optical system being estimated, so that when the simulation model is designed, at least some of the future changes that may occur are taken into account. The control of a forward-looking action can be achieved.

A lithographic projection apparatus as disclosed in US Patent Application No. US 2006/0114437 A1 includes a measurement system for measuring a change in time in a projection system, and an estimation control system based on model parameters Can be used to estimate the difference in projection system over time. In this regard, the concepts herein may be modified to be used to control an adaptive aperture mirror, the disclosure of which is hereby incorporated by reference.

Continuous or intermittent correction of the simulation model can be achieved based on the actual measurement of the characteristics of the modeled system. A feature that is detected or determined on a physical system (eg, a projection objective or an entire exposure device) may include one or more of the following information: temperature of one or more components, spatial temperature distribution of one or more components, or The axial position of more components, the displacement or tilt of one or more components, the shape of the reflective surface of the pupil mirror, the state of the aperture stop (the NA being used), the illumination setting, the intensity of the radiation source, the projection The spatial distribution of one or more differences in the exit or image field of the objective lens, the wavefront of the pupil surface, such as the exit of the pupil, the spatial distribution or intensity distribution of the intensity of the pupil surface, the reticle or other patterning device A type of pattern provided. For example, the pattern information can be obtained from the associated pattern recognition material of the reticle and/or stored in the memory component associated with each reticle, and/or stored in permanent Information on memory components.

The various settings used in the control system to control the deformable mirror can be used in embodiments of the present disclosure, or in other projection exposure systems, for example, independent of the folding geometry and the number of intermediate images. For example, a projection objective with more than two intermediate images is possible. With three The projection objective of the intermediate image is substantially designed in accordance with the applicant's international application WO 2005/040890, the disclosure of which is incorporated herein by reference.

The above described preferred embodiments are described by way of example. The disclosure of the present invention, as well as its advantages, may be understood by those skilled in the art, and it should be understood that various modifications and changes may be made in the structure or method disclosed. Accordingly, the scope of the invention, as well as its equivalents, are intended to cover all such modifications and variations of the scope and spirit of the invention.

100‧‧‧Reflective projection objective

CR‧‧‧ main beam

CON‧‧‧Compression Department

IMI1‧‧‧ first intermediate image

IMI 2‧‧‧ second intermediate image

IF‧‧‧like field

IS‧‧‧1

LG1‧‧‧first lens group

LG2‧‧‧second lens group

LG3‧‧‧third lens group

MG‧‧‧Mirror

M1‧‧‧ first lens

M2‧‧‧ second lens

M3‧‧‧ third lens

M4‧‧‧Fourth lens

MGP‧‧‧ mirror plane

OA‧‧‧ optical axis

OF‧‧‧物场

OS‧‧‧face

P1‧‧‧ first light face

LG4‧‧‧Fourth lens group

MGI‧‧ ‧ mirror entrance

MGO‧‧‧ lens group export

P2‧‧‧Second light surface

P3‧‧‧The third optical plane

PM‧‧‧Light Mirror

Claims (3)

A catadioptric projection objective lens images a pattern from an object field in an image field, the object field being disposed in an object surface of the projection objective, the image field being disposed on an image of the projection objective In the face, the catadioptric projection objective comprises: a first objective lens component for imaging the pattern from the object surface as a first intermediate image, and the first objective lens component has a first pupil face; a second objective lens a component for imaging the first intermediate image as a second intermediate image, and the second objective lens member has a second pupil face optically conjugate with the first pupil face; a pupil mirror having a reflection a surface of the grating mirror located at or near the first pupil plane or the second pupil plane; a first bending mirror configured to bend radiation from the object plane toward the pupil mirror, or The radiation from the pupil mirror is bent toward the image plane, such that the radiation is geometrically formed in the opposite direction through at least two of the secondary passage regions between the first bending mirror and the aperture mirror; Two bending mirrors are disposed at an angle of 90° to the first bending mirror Having the object mirror and the image plane parallel; a stop mirror operator operatively coupled to the aperture mirror for changing the shape of the pupil mirror surface; and a control system configured to receive from the A signal from the illumination system that indicates the illumination setting used in an exposure, and the control system is configured to adjust the aperture mirror surface corresponding to the selected illumination mode. The catadioptric projection objective of claim 1, wherein the illumination system is configured to provide at least one polarity illumination setting, with at least one of a double or a quadruple radial symmetry to the optical axis. And the control system is configured to adjust the pupil mirror surface corresponding to the selected polarity illumination having substantially double or quadruple radial symmetry. A catadioptric projection objective according to claim 1, wherein the control system comprises a pupil mirror control unit configured to control the pupil mirror operator.