JP2003243277A - Reflection type reduction projection optical system, aligner and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type reduction projection optical system of a five-mirror system balancing resolution and throughput by applicable to an EUV lithography system, and to provide an aligner and a device manufacturing method. <P>SOLUTION: In the reflection type reduction projection optical system, five mirrors are arranged to basically form a co-axial system, in the order from a body side to an image side, a first concave mirror (M1), a second convex mirror (M2), a third concave mirror (M3), a fourth convex mirror (M4) and a fifth concave mirror (M5) to reflect light in this order. An intermediate image is formed in between the third mirror (M3) and the fourth mirror (M4), and the position of the optical axis of the third mirror (M3) is spatially located between the first mirror (M1) and the second mirror (M2). Moreover, the aperture stop is spatially arranged on the optical axis between the first mirror (M1) and the third mirror (M3). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an exposure apparatus, and more particularly to ultraviolet light and extreme ultraviolet (EUV).
The present invention relates to a reflection-type reduction projection optical system for projecting and exposing an object to be processed, such as a single crystal substrate for a semiconductor wafer or a glass substrate for a liquid crystal display (LCD), by using emultraviolet light, an exposure apparatus, and a device manufacturing method.

[0002]

2. Description of the Related Art Due to recent demands for miniaturization and thinning of electronic devices, there is an increasing demand for miniaturization of semiconductor elements mounted on the electronic devices. A projection exposure apparatus, which is a typical exposure apparatus for manufacturing semiconductors, includes a projection optical system that projects and exposes a pattern drawn on a mask or a reticle (which is used interchangeably in this application) onto a wafer. In order to improve resolution, the well-known Rayleigh equation is used to shorten the wavelength of the exposure light source and the numerical aperture (NA) of the projection optical system.
Is effective. Therefore, due to the shortening of the wavelength of the exposure light source, in recent years, F ₂ excimer laser (wavelength of about 157 nm), ultraviolet light and EUV have been put into practical use as the exposure light source.

However, as the wavelength of light is shortened, the glass material through which light is transmitted is limited, so that it is difficult to use many refracting elements, that is, lenses, and the projection optical system includes reflecting elements, that is, mirrors. Will be advantageous. Furthermore, when the exposure light becomes ultraviolet light or EUV light, there is no usable glass material, and it becomes impossible to include a lens in the projection optical system. Therefore, a projection optical system has been proposed in which the projection optical system is composed of only a mirror (for example, a multilayer mirror).

[0004]

However, the conventional reflection-type projection optical system has a problem that it is not possible to achieve a well-balanced exposure performance such as resolution and throughput, and it is not possible to provide a high-quality device. More specifically, assuming that the reflectance of one multilayer film mirror is, for example, 67%, a reflective projection optical system composed of four mirrors (hereinafter also referred to as a four-mirror system) is generally used. It is possible to obtain a reflectance of about 20%, but NA
Can be achieved only up to about 0.1, so improvement in resolution cannot be expected. On the other hand, a reflection type projection optical system composed of 6 mirrors (hereinafter sometimes referred to as 6 mirror system)
Then, although the NA can be increased to about 0.15 or more, the resolution can be improved, but since the reflectance is about 9% in total, the throughput is reduced.

Therefore, a reflection type projection optical system (hereinafter also referred to as a five-mirror system) composed of five mirrors in which the resolution and the throughput are well balanced has been proposed as an intermediate number. There is. An example of this type of five-mirror system is disclosed in Japanese Patent Publication No. 2000-269132.
US Pat. No. 6,072,852, US Pat. No. 6,19
No. 9,991.

Published Patent No. 2000, 269132,
NA 0.15, 1/4 times, slit width 1.7 mm and 2
mm examples are disclosed. However, it is considered that the NA is still insufficient in this embodiment when considering the high resolution of the device in the future.

US Pat. No. 6,072,852 discloses NA
Examples of 0.18, 1/4 times, and slit width of 1.5 mm are disclosed. However, in the optical system of the design example of this publication, the distance between the object point and the image point on the opposite sides of the optical axis in the direction orthogonal to the optical axis of the optical system is about 260 mm. Therefore, in the case of an EUV lithography system using a 300 mm silicon wafer and a 6-inch reticle, the mask stage and the wafer stage mechanically interfere with each other, which makes it difficult to realize the apparatus.

US Pat. No. 6,199,991 discloses NA
0.20, 1/4 times, slit width 1.5mm and 1m
However, although the NA is relatively large, it is considered that the slit width is still insufficient for increasing the throughput.

Therefore, the present invention can be applied to an EUV lithography system using a 300 mm silicon wafer and a 6-inch reticle, and a five-mirror system reflection type reduction projection optical system, an exposure apparatus, and a system in which resolution and throughput are well balanced. It is an exemplary object to provide a device manufacturing method.

[0010]

In order to achieve the above object, a reflection type reduction projection optical system according to one aspect of the present invention comprises:
In order from the object side to the image side, a concave first mirror (M1), a convex second mirror (M2), a concave third mirror (M3), a convex fourth mirror (M4),
Five concave mirrors (M5) are arranged in order to reflect light in order so as to basically form a coaxial system, and the third mirror (M3) and the fourth mirror (M4) are arranged.
An intermediate image is formed at an intermediate position between the first mirror (M1) and the second mirror (M2), and the aperture stop is spatially positioned. It is arranged on the optical axis between the first mirror (M1) and the third mirror (M3). Such a reflection-type reduction projection optical system uses a five-mirror system, and it is possible to widen the space between the object point and the image point while increasing the NA and the slit width to balance the resolution and the throughput. In addition,
At least one of the five mirrors is preferably an aspherical mirror. The five mirrors are multilayer film mirrors that reflect EUV light and can efficiently reflect light having a wavelength of 20 nm or less.

An exposure apparatus according to another aspect of the present invention is the above-mentioned projection optical system, a stage for holding the mask so as to position the pattern of the mask on the object plane, and a photosensitive layer on the image plane. A stage for holding the substrate so as to position it, and an illumination optical system for illuminating the mask with EUV light corresponding to the arc-shaped visual field of the projection optical system,
And means for synchronously scanning the respective stages while illuminating the mask with the EUV light. According to such an exposure apparatus, it is possible to perform excellent exposure while having the reflection-type reduction projection optical system described above as a part of the constituent elements and increasing the NA and the slit width to balance the resolution and the throughput. .

According to still another aspect of the present invention, there is provided a device manufacturing method, which comprises projecting and exposing the substrate using the above-mentioned exposure apparatus, and performing a predetermined process on the projection-exposed object. Have. The claims of the device manufacturing method having the same operation as the above-described operation of the exposure apparatus extend to the devices themselves which are intermediate and final products. Further, such a device is, for example, an LSI
And semiconductor chips such as VLSI, CCD, LCD, magnetic sensor, thin film magnetic head, etc.

Other objects and further features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A reflective reduction projection optical system 100 and an exposure apparatus 200 according to one aspect of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a schematic cross-sectional view showing a cross section of the reflection type reduction projection optical system 100 and its optical path. 2 and 3 are schematic cross-sectional views showing cross sections and optical paths of reflection type reduction projection optical systems 100a and 100b showing another form of the reflection type reduction projection optical system 100, respectively. In the following description, the reflection-type reduction projection optical system 100 is a general term for the reflection-type reduction projection optical systems 100a and 100b unless otherwise specified.

The reflection type reduction projection optical system 100 is an object plane MS.
The pattern on the mask surface (for example, the mask surface) is transferred to the image surface W (for example,
An optical system for reducing and projecting onto a target object surface such as a substrate). The five mirrors M1 to M5 are arranged in the order of reflecting light from the object plane MS as shown in FIGS. Concave mirror) M1, mirror (convex mirror) M2, mirror (concave mirror) M3, mirror (convex mirror) M4, mirror (concave mirror) M
5 are arranged.

Further, in the reflection type reduction projection optical system 100, it is preferable that the five mirrors M1 to M5 are axially symmetrical with respect to a common optical axis from the viewpoint that a large ring-shaped image plane area can be taken as described later. . However, when the image plane size is relatively small, decentering may be performed to improve aberration.

Furthermore, the sum of Petzval terms of the five mirrors M1 to M5 is zero or near zero in order to flatten the image plane of the optical system. In other words, in order to correct the field curvature, the sum of the refracting powers (powers) of the respective surfaces of the five mirrors M1 to M5 (that is, when the radius of curvature of each mirror is r ₁ to r ₅ is 1 / r ₁ −1 / r ₂ + 1 / r
_{3 -1 / r 4 + 1 /} r 5) is set to zero or near zero.

In order to satisfy the above-mentioned conditions and satisfactorily correct each aberration, the centers of curvature of the mirrors M1 to M5 of this embodiment are on the same side of each surface. That is, when the design data of the optical system is displayed, the signs of the radii of curvature of the five mirrors are all the same.

In the five-mirror system, the object plane MS and the image plane W are often on the same side of the optical system, and when the reflection type reduction projection optical system 100 is incorporated in the EUV lithography system, the mask of the exposure apparatus 200 is used. Both the MS and wafer W stages cause mechanical interference. Therefore, in the reflection type reduction projection optical system 100, it is required to configure five mirror systems so that the object height and the image height are largely separated from the optical axis. Generally, these large object heights (image heights) are required. It is difficult to realize. Therefore, in the present embodiment,
A large object height (image height) is achieved by constructing the five mirrors M1 to M5 using aspherical mirrors having a relatively large radius of curvature.

In this embodiment, at least one mirror surface of at least one of the five mirrors M1 to M5 has an aspherical surface shape, and the aspherical surface shape is represented by the following equation for displaying a general aspherical surface. It

[0021]

[Equation 1]

Here, Z is the coordinate in the optical axis direction, c is the curvature (the reciprocal of the radius of curvature r), h is the height from the optical axis, k is the conic coefficient, and A, B, C, D, E, and F. , G, H, J ...
4th, 6th, 8th, 10th, 12th, 14th, 1
6th order, 18th order, 20th order ...

It is also a feature of this embodiment that an intermediate image is formed midway (between the mirror M3 and the mirror M4), which enables more well-balanced and excellent aberration correction. By arranging the mirror M3 spatially between the mirrors M1 and M2, the diameter of the mirror M3 can be made relatively small, and a compact optical system can be realized.

The surface of each mirror is provided with a multilayer film that reflects EUV light. Light having a wavelength of 20 nm or less can be efficiently reflected.

Further, an aperture stop STO is arranged on the optical path midway from M1 to M2 and spatially on the optical axis between M1 and M3. The diameter of the aperture stop may be fixed or variable.

In the case of being variable, the NA of the optical system can be changed by changing the diameter of the aperture stop STO.

A mask on which a pattern is drawn is arranged on the object plane. As this mask, in addition to a reflective mask provided with a multilayer film that reflects EUV light, a transmissive mask (for example, a die-cutting mask) is used. Can also be used.

[0028]

EXAMPLES Reflective reduction projection optical systems 100 to 10 will be described below.
The result of the illumination experiment using 0b will be described. Figure 1
3 to 3, MS is a mask arranged at the object plane position, W is a wafer placed at the image plane position, STO is an aperture stop, and AX is an optical axis. Reflective reduction projection optical system 1
00 to 100b, E near the wavelength of 13.4 nm
The mask MS is illuminated by an illumination system (not shown) that emits UV light, and the reflected light from the mask MS is sequentially reflected by the first mirror M1 (concave mirror), the second mirror M2 (convex mirror), and the third mirror M3 (concave mirror). , The fourth mirror M4 (convex mirror) and the fifth mirror M5 (concave mirror), and a reduced image of the mask pattern is formed on the wafer W placed at the image plane position.

The reflection type reduction projection optical system 100 as the first embodiment has a wavelength λ = 13.4 nm, NA 0.16, reduction magnification ⅕, object height = 75 to 87.5 mm, image height =
It is an arcuate image surface having a width of 2.5 mm of 15 to 17.5 mm.

The reflection type reduction projection optical system 100a as the second embodiment has a wavelength λ = 13.4 nm and NA = 0.2.
0, reduction ratio is 1/5, physical height = 92.5-105m
m, image height = 12.5 to 21 mm, and an arc-shaped image surface having a width of 2.5 mm.

The reflection type reduction projection optical system 100b as the third embodiment has a wavelength λ = 13.4 nm and NA = 0.2.
5, the reduction ratio is 1/5, the height = 100-110mm,
Image height = 20 to 22 mm, 2 mm wide arc-shaped image plane.

As described above, in the reflection type reduction projection optical system 100 of Examples 1 to 3, the NA is increased to 0.16 or more and the slit width is increased to 2 mm or more to balance the resolution and the throughput. ing.

Numerical values (radius of curvature, surface spacing, aspherical coefficient, etc.) of the optical systems of Examples 1, 2, and 3 are shown in Tables 1, 2, and 3, respectively.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

Aberrations which do not include manufacturing error (calculated at several points of image height) of each example are as follows: Example 1: Wavefront aberration = 0.001λrms, Distortion = 1.
6 nm (PV) Example 2: Wavefront aberration = 0.004 λrms, distortion = 3.
5 nm (PV) Example 3: Wavefront aberration = 0.022 λrms, distortion = 1.
9 nm (PV), and diffract at wavelength of 13.4 nm
It is an ion limited optical system.

As described above, the present invention achieves a high NA equivalent to that of a conventional 6-mirror system, a relatively large slit width, and a low aberration in spite of the 5-mirror system, thereby achieving a balance between resolution and throughput. This is a reflective optical system that can be used.

An exposure apparatus 200 to which the reflective reduction projection optical system 100 is applied will be described below with reference to FIG. Figure 4
Is an exposure apparatus 20 having a reflection type reduction projection optical system 100.
It is a schematic block diagram which shows 0. The exposure apparatus 200 is a projection exposure apparatus that performs step-and-scan type exposure using EUV light (for example, wavelength 13.4 nm) as illumination light for exposure. Referring to FIG. 4, the exposure apparatus 20
Reference numeral 0 denotes an illuminating device 210, a mask MS, a reflective reduction projection optical system 100, a plate W, a mask stage 220 on which the mask MS is placed, a wafer stage 230 on which the plate W is placed, and a controller 240. Have. Control unit 2
40 is controllably connected to the illumination device 210, the mask stage 220, and the wafer stage 230.

Although not shown in FIG. 4, since EUV light has a low transmittance to the atmosphere, at least the optical path through which EUV light passes is preferably a vacuum atmosphere. In FIG. 4, X, Y, and Z represent a three-dimensional space, and the normal direction of the XY plane is the Z direction.

The illumination device 100 is a reflection type reduction projection optical system 1.
An illumination device that illuminates the mask MS with arc-shaped EUV light (for example, a wavelength of 13.4 nm) corresponding to the arc-shaped visual field of 00, and includes a light source (not shown) and an illumination optical system.

The mask MS is a reflective or transmissive mask,
A circuit pattern (or image) to be transferred is formed thereon, and is supported and driven by the mask stage 220.
The reflected or diffracted light emitted from the mask MS is reflected by the optical system 10.
It is reflected at 0 and projected on the plate W. The mask MS and the plate W are arranged in an optically conjugate relationship. Since the exposure apparatus 200 is a step-and-scan type exposure apparatus, the mask pattern is reduced and projected onto the plate W by scanning the mask MS and the plate W.

The mask stage 220 supports the mask MS and is connected to a moving mechanism (not shown). The mask stage 220 can apply any structure known in the art. The moving mechanism (not shown) is composed of a linear motor or the like, and can move the mask MS by driving the mask stage 220 at least in the Y direction while being controlled by the control unit 240. The exposure apparatus 200 scans the mask MS and the plate W in a synchronized state by the control unit 240.

The plate W, which is a wafer in this embodiment, includes a liquid crystal substrate and other objects to be exposed. Photoresist is applied to the plate W. The photoresist coating process includes a pretreatment, an adhesion improver coating treatment, a photoresist coating treatment, and a prebake treatment. Pretreatment includes washing, drying and the like. The adhesion improving agent coating treatment is a surface modification treatment (that is, hydrophobic treatment by applying a surfactant) for enhancing the adhesion between the photoresist and the base, and is performed by HMDS (Hexamethyl-disila).
An organic film such as zane) is coated or steamed. Pre-baking is a baking (baking) process, but it is softer than that after development and removes the solvent.

The wafer stage 230 supports the plate W. The wafer stage 230 uses, for example, a linear motor to move the plate W in the XYZ directions. The mask MS and the plate W are controlled by the controller 240 and are synchronously scanned. The positions of the mask stage 220 and the wafer stage 230 are monitored by, for example, a laser interferometer, and both are driven at a constant speed ratio.

The control unit 240 has a CPU and a memory (not shown), and controls the operation of the exposure apparatus 200. Control unit 24
0 is electrically connected to the illumination device 210, the mask stage 220 (that is, a moving mechanism (not shown) of the mask stage 220), and the wafer stage 230 (that is, a moving mechanism (not shown) of the wafer stage 230). Control unit 240
Means that the distance between the mask MS and the plate W is, for example, about 2
The mask stage 220 and the wafer stage 230 are controlled so as to be 70 mm or more.

In the exposure, the EUV light emitted from the illuminating device 210 illuminates the mask MS and images the mask pattern on the plate surface. In this embodiment, the image plane is an arcuate (ring-shaped) image plane, and the entire surface of the mask is exposed by scanning the mask and the plate at the speed ratio of the reduction magnification ratio.

Next, an embodiment of a device manufacturing method using the exposure apparatus 200 will be described with reference to FIGS. FIG. 5 is a flow chart for explaining the manufacture of devices (semiconductor chips such as IC and LSI, LCDs, CCDs, etc.). Here, manufacturing of a semiconductor chip will be described as an example. In step 1 (circuit design), the device circuit is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured. Step 3
In (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by a lithography technique using the mask and the wafer. Step 5 (assembly) is called a post-step, and is a step of forming a semiconductor chip using the wafer created in step 4, and includes an assembly step (dicing, bonding), a packaging step (chip encapsulation) and the like. . In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device created in step 5 are performed.
Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 6 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. Step 13
In (electrode formation), electrodes are formed on the wafer by vapor deposition or the like. In step 14 (ion implantation), ions are implanted in the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the exposure apparatus 1 exposes the circuit pattern of the mask onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. Step 19
In (resist stripping), the resist that has become unnecessary after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. According to such a manufacturing method, it is possible to manufacture a higher quality device than ever before. In this way, the exposure apparatus 2
A device manufacturing method using 00 as well as the resulting device also constitutes one aspect of the present invention.

This embodiment is basically an optical system consisting of five mirrors. However, in order to arrange the object plane outside the optical system, there is a gap between the first mirror M1 and the object plane (mask MS). Alternatively, an additional plane mirror may be arranged. Further, it is possible to further improve the performance of the optical system by giving the flat mirror a curvature or making it an aspherical surface.

Reflective reduction projection optical system 100 to 100b
Although the magnification of is paraxially 1/5, the magnification in the aberration correction region is a value slightly deviated from the perfect 1/5.
However, by slightly shifting the paraxial magnification from ⅕ times, it is possible to easily achieve complete ⅕ magnification in the aberration correction region. Further, the present invention is not limited to these embodiments, and it is possible to further improve the performance within the scope of the present invention. For example, the present invention can be applied to a reflection type reduction optical system for ultraviolet rays other than EUV such as i-line and excimer laser, and can also be applied to an exposure apparatus for scanning and exposing a large screen. As described above, the present invention is a reflective optical system that can realize a large object height / image height and can achieve diffraction-limited performance at the EUV wavelength. Therefore, it is understood that even when the reflection type reduction projection optical system 100 of the present invention is applied to an EUV lithography system, mechanical interference between both stages can be prevented.

[0052]

As described above, according to the present invention, EUV
It is possible to realize a five-mirror reflective optical system having a relatively large NA and a large slit width and a small aberration that can be used for exposure, and it is possible to expose a pattern having a fine line width. Also,
Since the reflection type reduction projection optical system of the present invention can realize a large object height and image height, it is possible to prevent interference between the mask stage and the wafer stage, and provide a high quality device with good exposure performance such as throughput. be able to.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a cross section of a reflection type reduction projection optical system and an optical path thereof as one aspect of the present invention.

FIG. 2 is a schematic cross-sectional view showing a cross section and a light path of a modification of the reflection type reduction projection optical system shown in FIG.

FIG. 3 is a schematic cross-sectional view showing a cross section of still another modification of the reflection-type reduction projection optical system shown in FIG. 1 and its optical path.

FIG. 4 is a schematic configuration diagram showing an exposure apparatus having the reflection-type reduction projection optical system shown in FIG.

FIG. 5 is a flowchart for explaining manufacturing of devices (semiconductor chips such as IC and LSI, LCDs, CCDs, etc.).

FIG. 6 is a detailed flowchart of the wafer process in Step 4 shown in FIG.

[Explanation of symbols]

100 Reflective reduction projection optical system 200 exposure equipment 210 Lighting device 220 mask stage 230 wafer stage 240 control unit M1 first mirror (concave mirror) M2 second mirror (convex mirror) M3 3rd mirror (concave mirror) M4 4th mirror (convex mirror) M5 5th mirror (concave mirror) MS mask (object plane) W wafer (image plane) STO aperture stop Optical axis of AX optical system

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/30 531A F term (reference) 2H087 KA21 TA02 TA06 2H097 AA02 AB09 BA10 CA15 EA01 GB01 LA10 5F046 AA08 BA04 BA05 GA04 GB01 GB02 GB03

Claims (6)

[Claims] 1. A concave first mirror (M1) and a convex second mirror (M) in order from the object side to the image side.
2), concave third mirror (M3), convex fourth
The mirror (M4) and the concave fifth mirror (M5) are arranged in this order such that five mirrors that reflect light are arranged basically in a coaxial system, and the third mirror (M3) and the third mirror (M3) An intermediate image is formed in the middle of the four mirrors (M4), the position of the third mirror in the optical axis direction is spatially between the first mirror (M1) and the second mirror (M2), and the aperture is formed. A reflection-type reduction projection optical system, wherein a stop is spatially arranged on the optical axis between the first mirror (M1) and the third mirror (M3). 2. The catoptric reduction projection optical system according to claim 1, wherein at least one of the five mirrors is an aspherical mirror. 3. The five mirrors are EUV (extr
The reflection-type reduction projection optical system according to claim 1, wherein the reflection-type reduction projection optical system is a multilayer film mirror that reflects emultraviolet light. 4. The reflection type reduction projection optical system according to claim 1, wherein the wavelength of the EUV light is 20 nm or less. 5. The projection optical system according to claim 1, a stage for holding the mask so as to position a mask pattern on the object plane, and a photosensitive layer on the image plane. A stage that holds the substrate to be positioned, an illumination optical system that illuminates the mask with EUV light that corresponds to the arcuate field of the projection optical system, and the stages are synchronized while the mask is illuminated with the EUV light. Exposure apparatus having means for scanning. 6. A device manufacturing method comprising: a step of subjecting the substrate to projection exposure using the exposure apparatus according to claim 5; and a step of performing a predetermined process on the substrate subjected to the projection exposure.