JP2006120899A - Projection optical system, projection optical system adjustment method, projection exposure apparatus, projection exposure method, and projection exposure apparatus adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection capable of obtaining a pattern image having a desired line width over an entire effective imaging region without being substantially affected by scattered light caused by, for example, surface roughness of a refracting surface or a reflecting surface. Optical system.
A projection optical system of the present invention for forming an image of a first surface (M) on a second surface (W) is disposed at a predetermined position in an optical path between the first surface and the second surface. A diffusing surface having a required diffusivity distribution for making the distribution of flare light reaching the effective imaging region on the second surface a predetermined distribution. The diffusing surface is formed on the reflecting surface of the planar reflecting mirror (M0) disposed at a predetermined position substantially away from the pupil position of the projection optical system.
[Selection] Figure 2

Description

  The present invention relates to a projection optical system, a projection optical system adjustment method, a projection exposure apparatus, a projection exposure method, and a projection exposure apparatus adjustment method. More particularly, the present invention relates to adjustment of flare light in a projection optical system mounted on an exposure apparatus for manufacturing a microdevice such as a semiconductor element, an imaging element, a liquid crystal display element, and a thin film magnetic head in a lithography process.

2. Description of the Related Art Conventionally, in an exposure apparatus used for manufacturing a semiconductor element or the like, a circuit pattern formed on a mask (reticle) is projected and transferred onto a photosensitive substrate (for example, a wafer) via a projection optical system. A resist is coated on the photosensitive substrate, and the resist is exposed by projection exposure through the projection optical system, and a resist pattern corresponding to the mask pattern is obtained. Here, the resolving power W of the exposure apparatus depends on the wavelength λ of the exposure light and the numerical aperture NA of the projection optical system, and is expressed by the following equation (a).
W = k · λ / NA (k: constant) (a)

  Therefore, in order to improve the resolving power of the exposure apparatus, it is necessary to shorten the wavelength λ of the exposure light and increase the numerical aperture NA of the projection optical system. In general, it is difficult to increase the numerical aperture NA of the projection optical system to a predetermined value or more from the viewpoint of optical design, and therefore it is necessary to shorten the wavelength of the exposure light. Therefore, as a next-generation exposure method (exposure apparatus) for semiconductor patterning, an EUVL (Extreme UltraViolet Lithography) technique has been attracting attention.

  In the EUVL exposure apparatus, EUV (Extreme UltraViolet) light having a wavelength of about 5 to 20 nm as compared with a conventional exposure method using a KrF excimer laser light having a wavelength of 248 nm or an ArF excimer laser light having a wavelength of 193 nm. Is used. When EUV light is used as the exposure light, there is no optically transmissive optical material that can be used. For this reason, an EUVL exposure apparatus inevitably uses a reflective mask and a reflective projection optical system.

  In recent years, in the projection optical system of an exposure apparatus that uses KrF excimer laser light (wavelength λ = 248 nm) or ArF excimer laser light (wavelength λ = 193 nm) as exposure light, the surface roughness of the refractive surface of the lens and the optical for forming the lens The influence of scattered light generated due to fluctuations in the internal refractive index of the material is a problem. In an EUVL exposure apparatus that uses EUV light as exposure light, since the projection optical system is a reflection optical system that does not include a lens as described above, the generation of scattered light due to fluctuations in the internal refractive index of the lens does not occur. The influence of the scattered light caused by the surface roughness of the reflecting surface of the mirror becomes a problem.

  In particular, even with the same surface roughness, the effect of scattered light due to the surface roughness of the reflecting surface is greater than the surface roughness of the refracting surface, and the scattered light is inversely proportional to the square of the wavelength of the light used. Therefore, the problem of the influence of scattered light is expected to become more serious in the EUVL exposure apparatus. The scattered light thus generated reaches the effective imaging region of the projection optical system as so-called flare light.

  In the case of an exposure apparatus, it becomes difficult to obtain a printing pattern having a desired line width over the entire exposure area due to the influence of the distribution of flare light reaching the exposure area (effective imaging area). Also, different amounts of flare light are generated depending on the pattern density of the mask pattern, and the distribution of flare light reaching the effective image formation area of the projection optical system changes, making it difficult to control the line width of the printing pattern. .

  Also, in exposure equipment, the surface of the lens refracting surface and the reflecting surface of the reflecting mirror usually change over time, and the surface shape itself changes, or the surface characteristics change due to foreign matter adhering to the surface. To do. Also in this case, the amount of scattered light generated increases or decreases due to changes in the refractive surface of the lens or the surface of the reflecting surface of the reflecting mirror over time, and the distribution of flare light that reaches the effective imaging region of the projection optical system changes. Therefore, it becomes difficult to control the line width of the printing pattern.

  The present invention has been made in view of the above-described problems. For example, the present invention covers the entire effective imaging region without being substantially affected by scattered light caused by the surface roughness of the refracting surface and the reflecting surface. An object of the present invention is to provide a projection optical system capable of obtaining a pattern image having a desired line width and an adjustment method thereof.

  Further, in the present invention, a pattern image having a desired line width can be obtained over the entire effective imaging region without being substantially affected by scattered light caused by, for example, the surface roughness of the refracting surface or the reflecting surface. It is an object of the present invention to provide an exposure apparatus and an exposure method capable of faithfully projecting and exposing a fine mask pattern by using a projection optical system capable of performing the exposure.

In order to solve the above problems, in the first embodiment of the present invention, in the projection optical system for forming the image of the first surface on the second surface,
A required diffusivity distribution for making a predetermined distribution of flare light that is arranged at a predetermined position in an optical path between the first surface and the second surface and reaches an effective imaging region on the second surface. A projection optical system is provided that includes a diffusing surface.

In the second aspect of the present invention, in the adjustment method of the projection optical system for forming the image of the first surface on the second surface,
A flare measurement step of measuring the distribution of flare light reaching the effective imaging area on the second surface;
A preparation step of preparing a diffusion surface having a required diffusivity distribution for adjusting the distribution of flare light reaching the effective imaging region on the second surface based on the measurement result of the flare measurement step;
And a diffusion surface arranging step of arranging a diffusion surface having the required diffusivity distribution at a predetermined position in an optical path between the first surface and the second surface.

  According to a third aspect of the present invention, there is provided a projection optical system characterized by being adjusted by the adjustment method of the second aspect.

In the fourth embodiment of the present invention, in a projection exposure apparatus that projects and exposes a predetermined pattern on a photosensitive substrate,
A projection optical system of the first form or the third form for projecting the image of the predetermined pattern set on the first surface onto the photosensitive substrate set on the second surface is provided. A projection exposure apparatus is provided.

In a fifth aspect of the present invention, in a projection exposure method for projecting and exposing a predetermined pattern on a photosensitive substrate,
Including an exposure step of projecting an image of the predetermined pattern set on the first surface onto a photosensitive substrate set on the second surface via the projection optical system of the first or third mode. A characteristic projection exposure method is provided.

In a sixth aspect of the present invention, in the adjustment method for a plurality of projection exposure apparatuses that project and expose a predetermined pattern on a photosensitive substrate,
A first flare measurement step of measuring a first distribution of flare light reaching an image plane of a specific one of the plurality of projection exposure apparatuses;
A second flare measurement step of measuring a second distribution of flare light reaching the image plane of another projection exposure apparatus different from the specific one projection exposure apparatus among the plurality of projection exposure apparatuses;
A preparation step of preparing a diffusion surface having a required diffusivity distribution for adjusting the second distribution of the flare light based on the measurement results of the first flare measurement step and the second flare measurement step;
A diffusing surface disposing step of disposing a diffusing surface having the required diffusivity distribution at a predetermined position in an optical path between the first surface and the second surface of the another projection exposure apparatus. An adjustment method is provided.

In a seventh aspect of the present invention, in the adjustment method for a plurality of projection exposure apparatuses for projecting and exposing a predetermined pattern on a photosensitive substrate,
A first flare measurement step of measuring a first distribution of flare light reaching an image plane of a specific one of the plurality of projection exposure apparatuses;
A second flare measurement step of measuring a second distribution of flare light reaching the image plane of another projection exposure apparatus different from the specific one projection exposure apparatus among the plurality of projection exposure apparatuses;
Based on the measurement results of the first flare measurement step and the second flare measurement step, it is arranged at a predetermined position in the optical path between the first surface and the second surface in the another projection exposure apparatus. And an adjusting step for adjusting a diffusing surface having a required diffusivity distribution.

  The projection optical system according to the present invention includes a diffusing surface having a required diffusivity distribution for making a predetermined distribution of flare light that is disposed at a predetermined position in the optical path and reaches an effective imaging region on the image surface. Yes. Therefore, for example, even if the scattered light generated due to the surface roughness of the refracting surface or the reflective surface forms a flare light distribution in the effective imaging region, the effect of the scattered light intentionally generated on the diffusion surface Thus, the influence of the scattered light caused by the surface roughness is compensated, and for example, a substantially uniform flare light distribution is formed over the entire effective imaging region.

  Thus, in the present invention, a pattern image having a desired line width can be obtained over the entire effective imaging region without being substantially affected by scattered light caused by, for example, the surface roughness of the refracting surface or the reflecting surface. Can be realized. Therefore, in the exposure apparatus and exposure method of the present invention, a desired line width can be obtained over the entire effective imaging region without being substantially affected by scattered light caused by, for example, the surface roughness of the refracting surface or reflecting surface. By using a projection optical system capable of obtaining a pattern image, a fine mask pattern can be accurately projected and exposed, and as a result, a high-precision and good device can be manufactured.

  Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. In the present embodiment, the present invention is applied to an EUVL exposure apparatus having a reflection type projection optical system. In FIG. 1, the Z axis along the normal direction of the wafer W, which is a photosensitive substrate, the Y axis in the direction parallel to the plane of FIG. 1 in the plane of the wafer W, and the plane of the wafer W in FIG. The X axis is set in the direction perpendicular to the paper surface.

  Referring to FIG. 1, the exposure apparatus of this embodiment includes, for example, a laser plasma light source 1 as a light source for supplying exposure light. The light emitted from the light source 1 enters the illumination optical system 3 via the wavelength selection filter 2. Here, the wavelength selection filter 2 has a characteristic of selectively transmitting only EUV light (X-ray) having a predetermined wavelength (for example, 13.5 nm) from light supplied from the light source 1 and blocking transmission of other wavelength light. Have.

  The EUV light transmitted through the wavelength selection filter 2 illuminates a reflective mask M on which a pattern to be transferred is formed via an illumination optical system 3 composed of a plurality of reflecting mirrors. The mask M is held by a mask stage MS that can move along the Y direction so that the pattern surface extends along a surface slightly inclined with respect to the XY plane. The movement of the mask stage MS is configured to be measured by a laser interferometer (not shown). Thus, on the mask M, for example, an arcuate illumination area (view field area) symmetrical with respect to the Y axis is formed.

  The light from the illuminated pattern on the mask M forms an image of the mask pattern on the wafer W, which is a photosensitive substrate, via the reflective projection optical system PL. That is, on the wafer W, an arcuate still exposure region (effective imaging region) symmetrical with respect to the Y axis is formed so as to correspond to the arcuate illumination region on the mask M. The wafer W is held by a wafer stage WS that can move two-dimensionally along the X and Y directions so that the exposure surface extends along the XY plane.

  The movement of the wafer stage WS is configured to be measured by a laser interferometer (not shown) as in the mask stage MS. Thus, the scan exposure (scan exposure) is performed while moving the mask stage MS and the wafer stage WS along the Y direction, that is, while relatively moving the mask M and the wafer W along the Y direction with respect to the projection optical system PL. As a result, the pattern of the mask M is transferred to one shot area (exposure area) on the wafer W.

  Here, the length in the X direction of one shot area coincides with the length in the X direction of the arc-shaped still exposure area, and the length in the Y direction depends on the moving distance of the wafer W. When the projection magnification (transfer magnification) of the projection optical system PL is 1/4, synchronous scanning is performed with the moving speed of the wafer stage WS set to 1/4 of the moving speed of the mask stage MS. The pattern of the mask M is sequentially transferred to each shot area of the wafer W by repeating scanning exposure while moving the wafer stage WS two-dimensionally along the X direction and the Y direction.

  FIG. 2 is a diagram schematically showing the configuration of the projection optical system according to the present embodiment. Referring to FIG. 2, the projection optical system PL of the present embodiment includes a first reflective imaging optical system G1 for forming an intermediate image of the mask M pattern, and an intermediate image of the mask pattern (pattern of the mask M). In the optical path between the mask M and the first reflective imaging optical system G1 and the second reflective imaging optical system G2 for forming the second secondary image) on the wafer W. It is comprised by the plane reflective mirror M0.

  The first reflective imaging optical system G1 is composed of four reflecting mirrors M1 to M4, and the second reflective imaging optical system G2 is composed of two reflecting mirrors M5 and M6. The projection optical system PL is a telecentric optical system on the wafer side (image side), and an aperture stop (not shown) is arranged in the optical path from the first reflecting mirror M1 to the second reflecting mirror M2. The configuration and operation of the plane reflecting mirror M0 will be described later.

  As described above, for example, the scattered light generated due to the surface roughness of the reflecting surfaces of the reflecting mirrors M1 to M6 is the flare light (unnecessary light other than the original imaging light beam), and effective imaging of the projection optical system PL. The mask pattern having a desired line width may not be formed over the entire exposure region on the wafer W due to the influence of the flare light distribution. However, this problem can be solved to some extent by a technique called OPC (Optica1 proximity effect correction).

  Originally, OPC is a method of feeding back information on the change in the line width of the printing pattern due to the diffraction effect of light to the manufacture of the mask (reticle). In short, the mask at a place where the printing pattern is likely to be thicker than the desired line width. This is a technique of obtaining a printing pattern having a desired line width as a result of forming the pattern narrowly. This OPC method can be applied as it is even when a printing pattern having a desired line width is not formed due to the influence of the distribution of flare light reaching the exposure area (effective imaging area). It is possible to manufacture an OPC application mask that can obtain a width printing pattern to some extent.

  However, although the OPC application mask manufactured in this way is used for a plurality of exposure apparatuses, the amount of flare light generated differs between apparatuses, and the distribution of flare light reaching the exposure area differs between apparatuses. It is common. As a result, the variation in the amount of flare light generated between the devices, and the variation in the distribution of flare light between the devices, directly leads to the variation in the line width of the printing pattern between the devices.

  Therefore, this embodiment is not a technique for suppressing the absolute amount of scattered light generated due to, for example, the surface roughness of the refracting surface or the reflecting surface, but conversely, the scattered light is intentionally generated to cause flare between devices. A technique is adopted that suppresses variations in the line width of the baking pattern between devices by suppressing variations in the light distribution. Specifically, in this embodiment, a diffusing surface having a required diffusivity distribution for making the distribution of flare light reaching the effective imaging region (still exposure region in the exposure apparatus) a predetermined distribution is a predetermined in the projection optical system. Place in position. Then, scattered light is intentionally generated by the action of the diffusing surface to suppress the variation in flare light distribution between devices, and hence the variation in the line width of the baking pattern between devices.

  In addition, as described above, the amount of scattered light generated increases or decreases due to changes in the surface of the refracting surface or reflecting surface over time, and the distribution of flare light reaching the effective imaging area of the projection optical system changes over time. There are things to do. Here, in order to stably obtain a printing pattern having a desired line width using the same mask, the amount of scattered light, that is, the amount of flare light is returned to the initial state, and as a result, the exposure area (effective imaging area) is restored. It is necessary to return the distribution of the flare light reaching the initial state. Also in this case, by changing the diffusivity distribution of the diffusing surface arranged at a predetermined position in the projection optical system, the flare light distribution reaching the exposure area can be returned to the initial state in a timely manner, and the printing pattern with the desired line width can be stabilized. Can get to.

  In addition, as described above, scattered light is generated due to the surface roughness of the refracting surface and the reflecting surface in the projection optical system, and due to the influence of the flare light distribution reaching the exposure region (effective imaging region), The line width of the printing pattern varies depending on the position in the exposure area, and it may not be possible to obtain a printing pattern having a desired line width locally in the exposure area. Also in this case, the scattered light is intentionally generated by the action of the diffusing surface arranged at a predetermined position in the projection optical system, and the distribution of flare light reaching the exposure region is set to a predetermined distribution, for example, a uniform distribution. A printing pattern having a desired line width can be obtained over the entire exposure region.

  In the present embodiment, the required diffusivity distribution on the reflecting surface of the plane reflecting mirror M0 arranged in the vicinity of the mask M in the optical path between the mask M and the first reflective imaging optical system G1 according to the above-described method. The distribution of flare light reaching the still exposure region (effective imaging region) on the wafer W by the action of this diffusion surface is changed to a predetermined distribution, for example, over the entire arc-shaped still exposure region. The distribution is almost uniform. Here, “diffusivity” means the degree of diffusion, that is, the degree of generation of scattered light.

  That is, in the projection optical system PL of the present embodiment, even if the scattered light generated due to, for example, the surface roughness of the reflecting surfaces of the reflecting mirrors M1 to M6 forms a flare light distribution in the still exposure region, The influence of the scattered light caused by the surface roughness is compensated by the action of the scattered light intentionally generated on the diffusing surface of the reflecting mirror M0, and a substantially uniform flare light distribution is formed over the entire still exposure region. Is done. As a result, in the projection optical system PL of the present embodiment, the entire exposure area is desired without being substantially affected by the scattered light caused by the surface roughness of the reflecting surfaces of the reflecting mirrors M1 to M6, for example. A line width printing pattern (mask pattern image) can be obtained.

  Further, in the exposure apparatus of the present embodiment, a pattern image having a desired line width over the entire effective imaging region without being substantially affected by scattered light due to, for example, the surface roughness of the refracting surface or the reflecting surface. A fine mask pattern can be faithfully projected and exposed using the projection optical system PL capable of obtaining the above. In particular, since the exposure apparatus of the present embodiment uses EUV light as the exposure light, the pattern of the mask M can be formed on the wafer W with high resolution (high resolution) and faithfully.

  As described above, a different amount of flare light is generated depending on the pattern density of the mask pattern, and the distribution of flare light reaching the effective image formation region of the projection optical system PL, that is, the still exposure region, changes. In addition, as described above, the amount of generated scattered light increases or decreases due to changes in the surface of the refracting surface or reflecting surface over time, and the distribution of flare light reaching the effective imaging region of the projection optical system PL, that is, the still exposure region Changes. As a result, it becomes difficult to control the line width of the pattern printed on the exposure region due to the change in flare light distribution over time.

  In this case, it is preferable to configure the diffusing surface so that the distribution of flare light in the exposure region can be adjusted. Specifically, a diffusing surface having a different diffusivity distribution depending on the position is formed on the reflecting surface of the planar reflecting mirror M0, and the planar reflecting mirror M0 is formed in a predetermined direction (on the virtual extension surface of the reflecting surface of the planar reflecting mirror M0). The flare light distribution in the exposure region can be adjusted by moving along the predetermined direction. Further, the flare light distribution in the exposure region can be obtained by replacing the plane reflecting mirror M0 on which the diffusing surface having a certain diffusivity distribution is formed with another plane reflecting mirror on which a diffusing surface having a different diffusivity distribution is formed. Can be adjusted.

  In this way, for example, according to a change in the pattern density of the mask M used, the plane reflecting mirror M0 having a diffusing surface with a different diffusivity distribution depending on the position is moved in a predetermined direction, or the planar reflecting mirror M0 is moved to another diffusivity distribution. By replacing with a plane reflecting mirror having a diffusing surface, the distribution of flare light in the exposure region can be adjusted, and the line width of the pattern printed on the exposure region can be controlled. In addition, the planar reflecting mirror M0 having a diffusing surface with a diffusivity distribution that varies depending on the position is moved in a predetermined direction in accordance with the temporal change of the surface of the refracting surface or the reflecting surface, By replacing with a plane reflecting mirror having a diffusing surface, the distribution of flare light in the exposure region can be adjusted, and the line width of the pattern printed on the exposure region can be controlled.

  At this time, for example, the type of the mask M to be used may be discriminated, and the plane reflecting mirror M0 having a diffusing surface having a diffusivity distribution with a different diffusivity depending on the position may be moved in a predetermined direction according to the discrimination result. Also, a plurality of types of planar reflectors having a diffusivity distribution that provides a predetermined distribution of flare light when the mask M is set are prepared according to the type of the mask M, and A plane reflecting mirror having a diffusivity distribution corresponding to the mask M may be set in the optical path according to the type discrimination result.

  Further, as described above, the same mask M is used for a plurality of exposure apparatuses, but the amount of flare light generated differs between apparatuses, and the distribution of flare light reaching the exposure area differs between apparatuses. Due to the variation in the distribution of flare light between them, the line width of the printing pattern also varies between apparatuses. In this case, for example, a diffusing surface is arranged in the optical path of the projection optical system of each exposure apparatus, and the scattered light is intentionally generated by the action of the diffusing surface arranged at a predetermined position in each projection optical system. Adjustment is made so that the distribution of flare light reaching the region does not vary substantially between devices. Specifically, by adjusting the distribution of flare light reaching each exposure area to the same uniform distribution by the action of the diffusing surface in each projection optical system, the line width of the printing pattern does not vary between apparatuses. A printing pattern having a desired line width can be obtained over the entire exposure region.

  In the above-described embodiment, the diffusion surface is disposed in the vicinity of the mask M in the optical path between the mask M and the first reflective imaging optical system G1. However, the present invention is not limited to this, and is substantially from, for example, the pupil position of the projection optical system PL (for example, the position where the aperture stop is disposed in the optical path from the first reflecting mirror M1 to the second reflecting mirror M2 or the vicinity thereof). A similar effect can be obtained by disposing the diffusion surface at an appropriate position apart from each other. By the way, if the diffusing surface is arranged at or near the pupil position of the projection optical system PL, the flare light distribution in the effective imaging region is adjusted almost uniformly regardless of the position. The amount of flare light at the position cannot be adjusted independently.

  In the embodiment described above, the diffusing surface is formed on the planar reflecting surface of the planar reflecting mirror M0. However, the present invention is not limited to this, and the curved reflecting surface of the concave reflecting mirror or convex reflecting mirror having an imaging function is not limited thereto. A diffusing surface can also be formed on the reflecting surface. In this case, flare measurement is performed after assembling the projection optical system once, and a diffusion surface is formed on one or a plurality of reflection surfaces based on the flare measurement result. Here, as a method for forming the diffusion surface, for example, a physical processing method by grinding or polishing can be applied. For the reflective surface of the projection optical system for EUV light as in the above-described embodiment, a method of forming a multilayer film again after peeling the multilayer film forming the reflective surface and processing the substrate is adopted. Then, since the man-hours are large and time-consuming, the following method may be applied.

  The first method is a method in which energy is locally applied to the multilayer film forming the reflection surface by using EB (electron beam), laser, or the like to contract the multilayer film. In the second method, a layer made of a material (such as resin) that shrinks when heated is formed between the substrate and the multilayer film, and is heated locally using an EB (electron beam), laser, or the like. It is a technique to do. In the third method, a layer made of a soft material that is plastically deformed is formed between the substrate and the multilayer film, and the die is deformed by pressing the mold locally or entirely from the surface (pressing method). It is. In the third method, a method of heating using a material that becomes soft by heating may be used in combination.

  The fourth method is a method of additionally forming a multilayer film or a single layer film locally on the multilayer film on the reflection surface. Here, since the scattered light generated varies depending on the pattern and surface roughness of the additionally formed film, the pattern and surface roughness of the additionally formed film are set so that desired scattered light is generated. In addition, as a method of locally forming a multilayer film or a single layer film locally, an evaporation source (in the case of vacuum deposition) or a target (in the case of sputtering) of a film forming apparatus and a reflection surface to be additionally formed are used. Further, a method of providing a mask for setting the diffusion direction angle of the evaporated particles from the evaporation source or the diffusion atoms or molecules from the target within a desired range can be considered.

  However, if a diffusing surface is formed on a curved surface having a strong power, aberrations are likely to occur secondarily when the diffusing surface is moved or exchanged. It is preferable to form a diffusion surface on a planar reflection surface. When aberration occurs during movement or exchange of the diffusing surface, it is possible to correct the aberration by adjusting the position and posture of the concave reflecting mirror or convex reflecting mirror in the projection optical system, for example. Alternatively, the aberration can be corrected by applying stress to the concave reflecting mirror or the convex reflecting mirror.

  Hereinafter, a method for adjusting a projection optical system in a single projection exposure apparatus and a method for adjusting a plurality of projection exposure apparatuses will be briefly described. In an initial adjustment method (more generally, an initial adjustment method in manufacturing the projection optical system) in the production of the projection optical system in the projection exposure apparatus alone, a static exposure region on the wafer W (second surface) Measure flare light distribution reaching (effective imaging area). For the measurement of flare light distribution, for example, the apparatus and method disclosed in Japanese Patent Laid-Open No. 2003-318095 can be referred to.

  Next, based on the measurement result of the flare light distribution, a diffusion surface having a required diffusivity distribution for adjusting the distribution of the flare light reaching the still exposure region on the wafer W to a substantially uniform distribution is prepared. The diffusion surface having the required diffusivity distribution is substantially separated from a predetermined position in the optical path between the mask M (first surface) and the wafer W (second surface), for example, the pupil position of the projection optical system. Place in position. Specifically, in the case of the present embodiment, a planar reflecting mirror M0 on which a diffusing surface having a required diffusivity distribution is formed is manufactured, and the manufactured planar reflecting mirror M0 is used as a mask M and a first reflective imaging optical system G1. Is installed at a predetermined position in the vicinity of the mask M.

  On the other hand, in the adjustment method after manufacturing the projection optical system in the projection exposure apparatus alone (more generally, the adjustment method after manufacturing the projection optical system), for example, according to the change in the pattern density on the mask M used, Alternatively, the distribution of flare light reaching the stationary exposure region on the wafer W is measured in a timely manner in accordance with changes in the surface of the refracting surface or reflecting surface over time. Then, based on the measurement result of the flare light distribution, the plane reflecting mirror M0 having a diffusing surface with a different diffusivity distribution depending on the position is moved in a predetermined direction, or the diffusing surface with another diffusivity distribution is moved to the plane reflecting mirror M0 The flare light distribution in the exposure region is adjusted to be, for example, a substantially uniform distribution by exchanging with a plane reflecting mirror.

  Further, in the initial adjustment method when manufacturing a plurality of projection exposure apparatuses, for example, the apparatus and method disclosed in Japanese Patent Application Laid-Open No. 2003-318095 are used to reach the static exposure region on the wafer W for each projection exposure apparatus. Each distribution of flare light is measured. Next, based on the measurement result of the flare light distribution in each projection exposure apparatus, the required diffusion for adjusting the flare light distribution reaching the stationary exposure region on the wafer W to approach, for example, a substantially uniform standard distribution. A diffusion surface having a degree distribution is prepared. In each projection exposure apparatus, a diffusing surface having a required diffusivity distribution is a predetermined position in the optical path between the mask M (first surface) and the wafer W (second surface), for example, the pupil position of the projection optical system. Are arranged at positions substantially distant from each other. Specifically, in the case of the present embodiment, a planar reflecting mirror M0 on which a diffusing surface having a required diffusivity distribution is formed is manufactured for each projection exposure apparatus, and the manufactured planar reflecting mirror M0 for each projection exposure apparatus is manufactured. Are placed at predetermined positions in the vicinity of the mask M in the optical path between the mask M and the first reflective imaging optical system G1.

  On the other hand, in the adjustment method after manufacture of a plurality of projection exposure apparatuses, each projection exposure is performed according to, for example, a change in pattern density on the mask M to be used, or a change with time in the surface of the refracting surface or reflecting surface. With respect to the apparatus, the distribution of flare light reaching the static exposure region on the wafer W is timely measured. Then, based on the measurement result of the flare light distribution in each projection exposure apparatus, the plane reflecting mirror M0 having a diffusing surface with a diffusivity distribution that varies depending on the position is moved in a predetermined direction, or the plane reflecting mirror M0 is moved to another diffusivity. The flare light distribution in the exposure area of each projection exposure apparatus is adjusted so as to approach, for example, a substantially uniform standard distribution by replacing with a plane reflecting mirror having a diffusing surface with a distribution.

  In the above-described embodiment, the present invention is applied to an EUVL exposure apparatus provided with a reflective projection optical system. However, the present invention is not limited to this, and ArF excimer laser light (wavelength, for example) is used as exposure light. The present invention can also be applied to an exposure apparatus that uses KrF excimer laser light (wavelength λ = 248 nm) and includes a refractive or catadioptric projection optical system. In this case, for example, as shown in FIG. 3, the plane parallel plate P1 on which the diffusing surface having the required diffusivity distribution is formed is positioned substantially away from the pupil position in the optical path of the projection optical system PL, for example, a mask. It is arranged at a predetermined position near M (for example, the position closest to the mask M in the projection optical system PL).

  In the modification shown in FIG. 3, the diffusing surface may be formed not on the planar refracting surface of the plane parallel plate P1 but on the curved refracting surface of the lens having an imaging function. In this case, flare measurement is performed after assembling the projection optical system once, and a diffusion surface is formed on one or more refractive surfaces based on the flare measurement result. Here, as a method for forming the diffusion surface, for example, a processing method such as grinding, polishing, dry etching, or wet etching can be applied.

  However, as described above, in order to suppress the aberration that occurs when the diffusing surface is moved or exchanged, a diffusing surface is formed on a planar refracting surface having no refractive power or a flat refracting surface having relatively weak refracting power. Is preferred. When aberration occurs during movement or exchange of the diffusing surface, it is possible to correct the aberration by adjusting the position and posture of some lenses in the projection optical system, for example. Alternatively, the aberration can be corrected by slightly changing the wavelength of the exposure light, changing part or all of the atmospheric pressure in the projection optical system, or applying a stress to the lens.

  In the modification shown in FIG. 3, the amount and distribution of flare light generated due to fluctuations in the internal refractive index of the light transmitting member in the refractive or catadioptric projection optical system can also be adjusted. . In the above-described modification, the diffusing surface as the flare source is formed by grinding, polishing, or etching. However, the present invention is not limited to this method. For example, the parallel flat plate P1 as the light transmitting substrate is used as the flare generation source. A first method of directly engraving a phase pattern such as a diffraction grating, a second method of forming a light-transmitting film on a plane parallel plate P1 as a light-transmitting substrate, and processing the film into, for example, a diffraction grating shape, A third method of irradiating ultraviolet light having a lattice-like intensity distribution onto a plane-parallel plate P1 as a light-transmitting substrate and locally changing the refractive index by compaction to make a flare source, atoms such as gallium ( For example, a fourth method in which ions are periodically injected into a plane parallel plate P1 serving as a light-transmitting substrate to locally change the refractive index to obtain a flare source can be used. In the above-described modification, for example, when ArF excimer laser light is used as exposure light, in the third method, it is preferable to use quartz glass as the plane parallel plate P1 as the light-transmitting substrate. Further, the pattern as the flare generation source is not limited to the diffraction grating shape.

  In the exposure apparatus according to the above-described embodiment, the illumination system illuminates the mask (illumination process), and exposes the transfer pattern formed on the mask using the projection optical system onto the photosensitive substrate (exposure process). Microdevices (semiconductor elements, imaging elements, liquid crystal display elements, thin film magnetic heads, etc.) can be manufactured. Refer to the flowchart of FIG. 4 for an example of a technique for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of this embodiment. To explain.

  First, in step 301 of FIG. 4, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the one lot of wafers. Thereafter, in step 303, using the exposure apparatus of the present embodiment, the pattern image on the mask (reticle) is sequentially exposed and transferred to each shot area on the wafer of one lot via the projection optical system. .

  Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer. Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput.

  In the exposure apparatus of the above-described embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate). Hereinafter, an example of the technique at this time will be described with reference to the flowchart of FIG. In FIG. 5, in the pattern forming process 401, a so-called photolithography process is performed in which the mask pattern is transferred and exposed to a photosensitive substrate (such as a glass substrate coated with a resist) using the exposure apparatus of the above-described embodiment. . By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate undergoes steps such as a developing step, an etching step, and a resist stripping step, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming step 402.

  Next, in the color filter forming step 402, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix or three of R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning line direction. Then, after the color filter forming step 402, a cell assembly step 403 is executed. In the cell assembly step 403, a liquid crystal panel (liquid crystal cell) is assembled using the substrate having the predetermined pattern obtained in the pattern formation step 401, the color filter obtained in the color filter formation step 402, and the like.

  In the cell assembly step 403, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern formation step 401 and the color filter obtained in the color filter formation step 402, and a liquid crystal panel (liquid crystal cell) is obtained. ). Thereafter, in a module assembling step 404, components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display element, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput.

  In the EUVL exposure apparatus according to the above-described embodiment, a laser plasma light source is used as a light source for supplying EUV light. However, without being limited thereto, other suitable light sources that supply EUV light, such as synchrotron radiation (SOR) light sources, can also be used.

  In the above-described embodiment and modification, the present invention is applied to the projection optical system of the exposure apparatus. However, the present invention is not limited to this, and the image of the first surface (object surface) is converted to the second surface (image). The present invention can also be applied to a general projection optical system formed on the surface. Note that the present invention can be applied not only to the imaging optical system but also to an illumination optical system for illuminating a surface to be irradiated.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows schematically the structure of the projection optical system concerning this embodiment. It is a figure which shows roughly the structure of the projection optical system concerning the modification of this embodiment. It is a figure which shows the flowchart about an example of the method at the time of obtaining the semiconductor device as a microdevice. It is a figure which shows the flowchart about an example of the method at the time of obtaining the liquid crystal display element as a microdevice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser plasma light source 2 Wavelength selection filter 3 Illumination optical system M Mask MS Mask stage PL Projection optical system W Wafer WS Wafer stage M0 Planar reflecting mirror M1-M6 Reflecting mirror P1 Parallel plane plate

Claims (22)

In a projection optical system for forming an image of a first surface on a second surface,
A required diffusivity distribution for making a predetermined distribution of flare light that is arranged at a predetermined position in an optical path between the first surface and the second surface and reaches an effective imaging region on the second surface. A projection optical system comprising a diffusing surface having: The projection optical system according to claim 1, wherein the diffusing surface is capable of adjusting a distribution of the flare light. The projection optical system according to claim 2, wherein the diffusing surface has a diffusivity distribution that varies depending on a position. 4. The projection optical system according to claim 2, wherein the diffusing surface is configured to be movable along a predetermined direction. 5. The projection optical system according to claim 2, wherein the diffusing surface is configured to be exchangeable with another diffusing surface having a different diffusivity distribution. 6. The projection optical system according to claim 1, wherein the diffusing surface is disposed at the predetermined position substantially away from a pupil position of the projection optical system. The projection optical system according to claim 1, wherein the diffusing surface is formed as a planar reflecting surface. The projection optical system according to claim 1, wherein the diffusing surface is formed as a planar refracting surface. The projection optical system according to claim 1, wherein the projection optical system is a reflection optical system. In the adjustment method of the projection optical system for forming the image of the first surface on the second surface,
A flare measurement step of measuring the distribution of flare light reaching the effective imaging area on the second surface;
A preparation step of preparing a diffusion surface having a required diffusivity distribution for adjusting the distribution of flare light reaching the effective imaging region on the second surface based on the measurement result of the flare measurement step;
And a diffusing surface arranging step of arranging a diffusing surface having the required diffusivity distribution at a predetermined position in an optical path between the first surface and the second surface. 11. The diffusing surface having the required diffusivity distribution for substantially uniforming the distribution of flare light reaching the effective imaging region on the second surface is prepared in the preparing step. The adjustment method described. The adjustment method according to claim 10 or 11, wherein, in the diffusing surface arranging step, the diffusing surface is arranged at the predetermined position substantially away from the pupil position of the projection optical system. A projection optical system adjusted by the adjustment method according to any one of claims 10 to 12. In a projection exposure apparatus that projects and exposes a predetermined pattern on a photosensitive substrate,
14. The projection according to claim 1, for projecting an image of the predetermined pattern set on the first surface onto a photosensitive substrate set on the second surface. 15. A projection exposure apparatus comprising an optical system. In a projection exposure method of projecting and exposing a predetermined pattern on a photosensitive substrate,
An image of the predetermined pattern set on the first surface via the projection optical system according to any one of claims 1 to 9 and claim 13 on a photosensitive substrate set on the second surface A projection exposure method comprising an exposure step of projecting onto a projection. In a method for adjusting a plurality of projection exposure apparatuses that project and expose a predetermined pattern on a photosensitive substrate,
A first flare measurement step of measuring a first distribution of flare light reaching an image plane of a specific one of the plurality of projection exposure apparatuses;
A second flare measurement step of measuring a second distribution of flare light reaching the image plane of another projection exposure apparatus different from the specific one projection exposure apparatus among the plurality of projection exposure apparatuses;
A preparation step of preparing a diffusion surface having a required diffusivity distribution for adjusting the second distribution of the flare light based on the measurement results of the first flare measurement step and the second flare measurement step;
A diffusing surface disposing step of disposing a diffusing surface having the required diffusivity distribution at a predetermined position in an optical path between the first surface and the second surface of the another projection exposure apparatus. Adjustment method. The adjustment method according to claim 16, wherein the required diffusivity distribution of the diffusing surface is a diffusivity distribution that brings the second distribution of flare light closer to the first distribution of flare light. In a method for adjusting a plurality of projection exposure apparatuses that project and expose a predetermined pattern on a photosensitive substrate,
A first flare measurement step of measuring a first distribution of flare light reaching an image plane of a specific one of the plurality of projection exposure apparatuses;
A second flare measurement step of measuring a second distribution of flare light reaching the image plane of another projection exposure apparatus different from the specific one projection exposure apparatus among the plurality of projection exposure apparatuses;
Based on the measurement results of the first flare measurement step and the second flare measurement step, it is arranged at a predetermined position in the optical path between the first surface and the second surface in the another projection exposure apparatus. And an adjusting step for adjusting a diffusion surface having a required diffusion degree distribution. 19. The adjustment method according to claim 18, wherein, in the adjustment step, the diffusion surface is adjusted so that the second distribution of the flare light approaches the first distribution of the flare light. The adjustment method according to claim 18, wherein the diffusion surface has a diffusivity distribution that varies depending on a position. 21. The adjusting method according to claim 20, wherein the adjusting step includes a moving step of moving and adjusting the diffusion surface along a predetermined direction. The adjustment method according to any one of claims 18 to 21, wherein the adjustment step includes an exchange step of exchanging with another diffusion surface having a diffusivity distribution different from that of the diffusion surface.

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