JP7446068B2 - Exposure apparatus and article manufacturing method - Google Patents

Description

The present invention relates to an exposure apparatus and a method of manufacturing an article.

With the miniaturization of semiconductor devices, exposure apparatuses used in lithography processes, which are semiconductor device manufacturing processes, are required to have even higher resolution. In order to achieve high resolution, it is necessary to shorten the wavelength of exposure light, increase the numerical aperture (NA) of the projection optical system (higher NA), and furthermore, use modified illumination (annular illumination, dipole illumination, quadruple illumination, etc.). (e.g. polar illumination) is effective.

On the other hand, as device structures have become multilayered in recent years, exposure apparatuses are required to have high overlay accuracy. Patent Document 1 discloses a double slit configuration in which a light shielding section 103 and a light shielding section 105 are arranged before and after a masking unit 104, which is a conjugate surface of the illuminated surface (FIG. 1). This double slit configuration is effective for improving overlay accuracy.

Further, Patent Document 1 also discloses disposing a light shielding section 401 or a filter 402 to alleviate the asymmetry of the cumulative effective light source distribution caused by the double slit configuration (FIGS. 12 and 14).

Japanese Patent Application Publication No. 2010-73835

However, when a light shielding section or a filter is disposed to alleviate the asymmetry of the integrated effective light source distribution caused by the double slit configuration, the image plane illuminance decreases. A decrease in image plane illuminance is undesirable because it leads to a decrease in throughput.

The present invention provides, for example, an exposure apparatus that is advantageous in achieving both correction performance for the illuminance distribution on the image plane of an illumination optical system and suppression of a decrease in image plane illuminance.

According to one aspect of the present invention, there is provided an exposure apparatus that scans and exposes a substrate, and includes an illumination optical system that illuminates an illuminated surface of an original with light from a light source, and the illumination optical system includes light from a light source. a diffractive optical element disposed on the optical path leading to the illuminated surface; a first light shielding portion disposed at a position defocused from the conjugate plane of the illuminated surface toward the light source; and the conjugate of the illuminated surface. a second light-shielding portion disposed at a defocused position from the surface toward the illuminated surface , and the diffractive optical element is arranged on a Fourier transform surface that is optically in a Fourier transform relationship with the diffractive optical element. There is provided an exposure apparatus, characterized in that the exposure apparatus forms a light intensity distribution that reduces asymmetry in the cumulative effective light source distribution caused by the first light shielding part and the second light shielding part .

According to the present invention, for example, it is possible to provide an exposure apparatus that is advantageous in achieving both correction performance of the illuminance distribution on the image plane of the illumination optical system and suppression of a decrease in the image plane illuminance.

FIG. 1 is a schematic cross-sectional view showing the configuration of an exposure apparatus in an embodiment. FIG. 3 is a diagram illustrating an integrated effective light source. FIG. 3 is a diagram illustrating an integrated effective light source. The figure which shows the structure of a light shielding part. FIG. 3 is a diagram illustrating the design of a diffractive optical element in an embodiment. A graph showing the asymmetry of the integrated effective light source for each σ value. A graph showing the difference in line width between vertical and horizontal patterns for each σ value.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the claimed invention. Although a plurality of features are described in the embodiments, not all of these features are essential to the invention, and the plurality of features may be arbitrarily combined. Furthermore, in the accompanying drawings, the same or similar components are designated by the same reference numerals, and redundant description will be omitted.

<First embodiment>
FIG. 1 is a schematic cross-sectional view showing the configuration of an exposure apparatus in an embodiment. This exposure apparatus is a scanning type exposure apparatus that exposes a pattern of an original (mask) onto a substrate using a step-and-scan method. In the step-and-scan method, one shot of exposure is performed while the original and the substrate are driven (scanned) relative to each other, and after one shot of exposure is completed, the substrate is moved in steps to move to the next shot area. be exposed.

The exposure apparatus includes an illumination optical system that illuminates a reticle 24, which is an original, using the light beam from the light source 1, and a projection optical system 26 that projects the pattern of the reticle 24 onto a substrate 27.

As the light source 1, a mercury lamp with a wavelength of about 365 nm, a KrF excimer laser with a wavelength of about 248 nm, an ArF excimer laser with a wavelength of about 193 nm, etc. can be used.

The illumination optical system includes a routing optical system 2, an exit angle preserving optical element 5, a diffractive optical element 6, a condenser lens 7, and a prism unit 10. The illumination optical system further includes a zoom lens unit 11, an optical integrator 12, an aperture 13, a condenser lens 14, a first light shielding section 18, a second light shielding section 20, a masking unit 19, a condenser lens 21, and a collimator lens 23. have

The routing optical system 2 is provided between the light source 1 and the exit angle preserving optical element 5 and guides the luminous flux from the light source 1 to the exit angle preserving optical element 5. The exit angle preserving optical element 5 is provided on the light source side of the diffractive optical element 6, and guides the light beam from the light source 1 to the diffractive optical element 6 while keeping its divergence angle constant. The exit angle preserving optical element 5 may be constituted by an optical integrator such as a microlens array or a fiber bundle. The exit angle preserving optical element 5 can reduce the influence of output fluctuations of the light source 1 on the pattern distribution formed by the diffractive optical element 6.

The diffractive optical element 6 is arranged on a surface that is conjugate with the reticle 24, which is the illuminated surface (image surface), or on a surface that has a Fourier transform relationship with the pupil plane of the illumination optical system. The diffractive optical element 6 uses a diffraction effect to change the light intensity distribution of the light beam from the light source 1 onto a predetermined plane such as the pupil plane of the illumination optical system, which is a plane conjugate with the pupil plane of the projection optical system 26, or a plane conjugate thereto. to form a desired light intensity distribution. As the diffractive optical element 6, a computer generated hologram (CGH) may be used, which is designed by a computer so that a desired diffraction pattern can be obtained on the diffraction pattern surface. The light source shape formed on the pupil plane of the projection optical system 26 is called an effective light source shape. Note that in this specification, the term "effective light source" refers to the light intensity distribution or the light angular distribution on the illuminated surface and its conjugate surface. The diffractive optical element 6 is provided between the exit angle preserving optical element 5 and the condenser lens 7. The light beam from the exit angle preserving optical element 5 illuminates the diffractive optical element 6, is diffracted by the diffractive optical element 6, and is guided to the condenser lens 7.

In one example, a plurality of diffractive optical elements 6 are provided in the illumination optical system, and each diffractive optical element 6 is attached and mounted in a corresponding one of a plurality of slots of a turret (not shown). The plurality of diffractive optical elements can form different effective light source shapes. Depending on these effective light source shapes, illumination modes are called small σ illumination, large σ illumination, annular illumination, dipole illumination, quadrupole illumination, etc.

The condenser lens 7 is provided between the diffractive optical element 6 and the prism unit 10 and condenses the light beam diffracted by the diffractive optical element 6 to form a diffraction pattern on the Fourier transform surface 9. The distribution of the diffraction pattern is constant.

The Fourier transform surface 9 is a surface that is located between the optical integrator 12 and the diffractive optical element 6 and is in an optical Fourier transform relationship with the diffractive optical element 6. By replacing the diffraction optical element 6 located in the optical path, the shape of the diffraction pattern formed on the Fourier transform surface 9 can be changed.

The prism unit 10 and the zoom lens unit 11 are provided on the light source side with respect to the optical integrator 12 and function as a zoom optical system that expands the light intensity distribution formed on the Fourier transform surface 9. The prism unit 10 can guide the diffraction pattern (light intensity distribution) formed on the Fourier transform surface 9 to the zoom lens unit 11 by adjusting the annular ratio and the like.

Further, the zoom lens unit 11 is provided between the prism unit 10 and the optical integrator 12. The zoom lens unit 11 can guide the diffraction pattern formed on the Fourier transform surface 9 to the optical integrator 12 by adjusting the σ value based on the ratio of the NA of the illumination optical system and the NA of the projection optical system. .

The optical integrator 12 is provided between the zoom lens unit 11 and the condenser lens 14, and forms a large number of secondary light sources according to the diffraction pattern whose annular ratio, aperture angle, and σ value are adjusted. May include a fly's eye lens that guides. However, the fly's eye lens portion of the optical integrator 12 may be composed of an optical pipe, a diffractive optical element, a microlens array, or the like. A diaphragm 13 is provided between the optical integrator 12 and the condenser lens 14.

Condenser lens 14 is provided between optical integrator 12 and reticle 24. Thereby, a large number of light beams guided from the optical integrator 12 can be condensed to illuminate the reticle 24 in a superimposed manner. The condenser lens 14 includes a half mirror 15 , and a portion of the exposure light enters the light amount measuring optical system 16 . The light amount measuring optical system 16 has a sensor 17 that measures the amount of light. Based on the amount of light measured by this sensor 17, the amount of exposure during exposure can be appropriately controlled.

A masking unit 19 is arranged on the conjugate plane of the illuminated surface. Masking unit 19 is arranged to define the illumination range of reticle 24 and is scanned synchronously with reticle stage 25 holding reticle 24 and substrate stage 28 holding substrate 27.

Two light shielding parts are provided at positions defocused from the masking unit 19. Specifically, the first light blocking portion 18 is disposed at either a position defocused from the illuminated surface toward the light source or a position defocused from the conjugate plane of the illuminated surface toward the light source. Further, the second light shielding section 20 is arranged at a position defocused from the conjugate plane of the illuminated surface toward the illuminated surface. In order to reduce the non-uniformity of the illuminance distribution on the illuminated surface, each of the first light shielding part 18 and the second light shielding part 20 may be a variable slit.

The light reflected by the mirror 22 having a predetermined inclination with respect to the light flux from the condenser lens 21 illuminates the reticle 24 via the collimator lens 23. The pattern of the reticle 24 is projected onto the substrate 27 via the projection optical system 26.

Next, referring to FIG. 2, the integrated effective light source will be described. FIG. 2A shows an illumination area 24a of the reticle 24, which is the illuminated surface. FIG. 2B shows the illumination area 19a of the masking unit 19 surface that is in a conjugate relationship with the reticle 24 surface. During exposure, the illumination area 24a is scanned. At this time, the incident angle distribution for illuminating a certain point on the exposure surface is the summation of the incident angle distribution for illuminating each point on the straight line 24b parallel to the scanning direction (y direction) in the illumination area 24a. This is called an integrated effective light source. In other words, the integrated effective light source refers to an integrated incident angle distribution obtained by integrating the incident angle distribution during a period in which a certain point in the illumination area is illuminated by scanning exposure.

Next, with reference to FIG. 3, a description will be given of how the integrated effective light source becomes after scanning when the first light shielding section 18 and the second light shielding section 20 are used. FIG. 3A is an enlarged view of the vicinity of the first light shielding part 18 and the second light shielding part 20. FIG. 3(b) shows the angular distribution of illumination light passing through points A, B, and C on the masking unit 19 surface. The light beam heading from the condenser lens 14 to point A via the optical integrator 12 is emitted parallel to the optical axis 1b, and is not eclipsed by a portion of the first light shielding section 18 and the second light shielding section 20. Therefore, the shape of the effective light source 24a at point A' on the reticle surface is approximately circular.

On the other hand, a part of the light beam traveling from the condenser lens 14 to point B via the optical integrator 12 is vignetted by the light shielding member 18a of the first light shielding part 18 and the light shielding member 20a of the second light shielding part 20. Therefore, the angular distribution of the effective light source 24b at point B' on the reticle surface becomes asymmetrical with respect to the scanning direction (Y direction) of scanning exposure. The upper part of the effective light source 24b is chipped because it is vignetted by the light shielding member 20a of the second light shielding part 20, and the lower part is chipped because it is vignetted by the light shielding member 18a of the first light shielding part 18. As described above, it can be seen that since there are two light shielding parts, asymmetry occurs in the effective light source 24b with respect to the scanning direction (Y direction) of scanning exposure. Regarding the shape of the effective light source 24c at point C' on the reticle surface, asymmetry occurs in the Y direction in the same way as the light beam heading toward point B.

The integrated effective light source obtained by scanning all the light fluxes passing on a straight line including points A, B, and C in the Y direction is as shown in Fig. 3(c), and asymmetry of the integrated effective light source occurs in the scanning direction. I understand that. Asymmetry in the integrated effective light source can cause problems during exposure. For example, when printing a line-and-space pattern with the same line width in the vertical and horizontal directions, a difference in line width occurs between the vertical pattern and the horizontal pattern, which is undesirable. Therefore, it is necessary to correct the asymmetry.

In the embodiment, the third light shielding part 8 is arranged on the light source side of the Fourier transform surface 9. The third light shielding part 8 is arranged, for example, at a position slightly defocused from the position of the Fourier transform surface 9. In order to correct the integrated effective light source (integrated incident angle distribution), it is possible to use the third light shielding part 8. FIG. 4 shows the configuration of the third light shielding part 8. The third light shielding section 8 is composed of, for example, four light shielding plates, and each of the four light shielding plates can be independently driven in the X direction or the Y direction. For example, in the case of the integrated effective light source shown in Figure 3, the asymmetry of the integrated effective light source is adjusted by driving the two light shielding plates in the direction of closing in the X direction and partially vignetting the light in the X direction. can do. Adjustments may be made by applying a filter instead of the light shielding part.

Conventionally, the distribution of the Fourier transform surface 9 was uniform, but in this embodiment, as shown in FIG. Designed to. The diffractive optical element 6 operates in the scanning direction (Y direction) of scanning exposure and in the non-scanning direction (X It has diffraction properties that reduce the difference between the two directions. Specifically, in the Y direction, by offsetting the distribution of the Fourier transform surface and the asymmetrical effect of the effective light source due to the first light shielding part 18 and the second light shielding part 20, as shown in FIG. 5(b), First, the light intensity distribution in the Y direction of the integrated effective light source is made constant. As a result, the integrated effective light source becomes symmetrical in the X and Y directions. This eliminates the need to apply the third light shielding part 8 to adjust asymmetry. Therefore, there is no reduction in image plane illuminance due to the use of the third light shielding part 8, which is advantageous from the viewpoint of throughput of the exposure apparatus.

<Second embodiment>
The second embodiment is an example in which the zoom lens unit 11 is used with the σ value changed. When the zoom lens unit 11 is driven to change the zoom, the influence of vignetting on the first light shielding part 18 and the second light shielding part 20 changes, and the asymmetry of the integrated effective light source changes. Therefore, when one type of diffractive optical element is used, it is difficult to sufficiently reduce the asymmetry of the integrated effective light source in all zooms. Therefore, in this embodiment, the third light shielding section 8 is also used.

FIG. 6 is a graph showing the relationship between the σ value and the asymmetry of the integrated effective light source when the zoom lens unit 11 is driven. As shown in FIG. 6, in the prior art, there is asymmetry in the integrated effective light source for any σ value. On the other hand, in the present embodiment, the diffractive optical element 6 is configured to have a difference between the scanning direction (Y direction) and the non-scanning direction (X direction) with respect to the integrated effective light source at the center value of the range of σ values that can be changed by the zoom lens unit 11. It is designed to have diffraction characteristics that reduce the difference. As a result, the asymmetry of the integrated effective light source in the driving range of the σ value is reduced compared to the prior art.

FIG. 7 shows the results obtained by optical image simulation of the line width difference between a vertical pattern and a horizontal pattern when exposed with a conventional integrated effective light source having asymmetricity as shown in FIG. This graph shows that the difference in line width between the vertical pattern and the horizontal pattern is smaller in this embodiment than in the prior art.

When actually using the apparatus, the asymmetry of the integrated effective light source as shown in FIG. 6 is used as a starting point, and the asymmetry is adjusted using the third light shielding part 8 according to the σ used. That is, the third light shielding part 8 is adjusted according to the state of the zoom lens unit (the σ value used). Compared to the conventional example, in this embodiment, where the asymmetry is smaller within the range of the σ value used, the amount by which the asymmetry needs to be adjusted is smaller, so the decrease in image plane illuminance by the amount applied by the third light shielding part 8 is smaller. , which is advantageous in terms of throughput of the exposure apparatus.

<Embodiment of article manufacturing method>
The article manufacturing method according to the embodiment of the present invention is suitable for manufacturing articles such as micro devices such as semiconductor devices and elements having fine structures, for example. The article manufacturing method of the present embodiment includes a step of forming a latent image pattern on a photosensitive agent coated on a substrate using the above exposure device (a step of exposing the substrate), and a step of forming a latent image pattern in this step. and developing the substrate. Additionally, such manufacturing methods include other well-known steps (oxidation, deposition, deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method of this embodiment is advantageous in at least one of article performance, quality, productivity, and production cost compared to conventional methods.

The invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the following claims are hereby appended to disclose the scope of the invention.

DESCRIPTION OF SYMBOLS 1: Light source, 6: Diffractive optical element, 11: Zoom lens unit, 18: First light shielding part, 19: Masking unit, 20: Second light shielding part, 24: Reticle (original), 26: Projection optical system, 27: substrate

Claims (9)

An exposure apparatus that scans and exposes a substrate,
It has an illumination optical system that illuminates the illuminated surface of the original plate with light from a light source,
The illumination optical system includes:
a diffractive optical element disposed on an optical path from the light source to the illuminated surface;
a first light shielding portion disposed at a position defocused from a conjugate plane of the illuminated surface toward the light source;
a second light shielding portion disposed at a position defocused from the conjugate plane of the illuminated surface toward the illuminated surface,
The diffractive optical element reduces asymmetry in the cumulative effective light source distribution caused by the first light shielding part and the second light shielding part on a Fourier transform surface that is optically in a Fourier transform relationship with the diffractive optical element. An exposure apparatus characterized by forming a light intensity distribution . It has a zoom lens unit that changes the σ value,
2. The exposure apparatus according to claim 1, wherein the diffractive optical element has a diffraction characteristic that reduces the asymmetry at a center value of a range of σ values that can be changed by the zoom lens unit. comprising a third light shielding part capable of adjusting the integrated effective light source distribution ,
3. The exposure apparatus according to claim 2, wherein the integrated effective light source distribution is adjusted by the third light shielding section depending on the state of the zoom lens unit. 4. The exposure apparatus according to claim 3, wherein the third light shielding part is disposed at a position defocused from the position of the Fourier transform surface toward the light source. The first light shielding part and the second light shielding part each include a variable slit,
The exposure apparatus according to any one of claims 1 to 4, wherein the variable slit is adjusted so as to reduce the asymmetry . The third light shielding section includes a variable slit,
5. The exposure apparatus according to claim 3, wherein the variable slit is adjusted depending on the state of the zoom lens unit. 7. The exposure apparatus according to claim 1, wherein the diffractive optical element includes a computer -generated hologram designed by a computer so as to obtain a desired diffraction pattern on a diffraction pattern surface . 8. The exposure apparatus according to claim 1, further comprising a masking unit disposed on the conjugate plane and defining an illumination range of the original. A step of exposing a substrate using the exposure apparatus according to any one of claims 1 to 8;
A method for manufacturing an article, comprising the step of developing the exposed substrate, and manufacturing an article from the developed substrate.

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