WO2002077692A1 - Optical system manufacturing method and exposure device having an optical system manufactured by the manufacturing method - Google Patents

Abstract

An optical system manufacturing method capable of manufacturing, for example, a projection optical system having an extremely low aberration of a wave aberration of 10 mλ, even if the lenses have a more or less refractive index distribution or a planar shape error. The method comprises a refractive index distribution measuring step (S11) of measuring a refractive index distribution in an optical material for forming a lens a planar shape measuring step (S13) of measuring the surface shape of the lens, and a correction film forming step (S14) of determining the optical error (or the wavefront error) of the lens on the basis of the measurement result at the refractive index distribution measuring step and the measurement result of the planar shape measuring step and forming a thin film (antireflection film) having a predetermined thickness distribution with respect to the surface of the lens, on the basis of the calculatetion results.

Description

 Description: MANUFACTURING METHOD OF OPTICAL SYSTEM AND EXPOSURE APPARATUS HAVING OPTICAL SYSTEM MANUFACTURED BY THE MANUFACTURING METHOD

 The present invention relates to a method for manufacturing an optical system and an exposure apparatus including the optical system manufactured by the method. In particular, the present invention relates to a method for manufacturing a projection optical system used in an exposure apparatus for manufacturing a micro device such as a semiconductor device, an imaging device, a liquid crystal display device, and a thin film magnetic head in one lithography process. . Background art

 In the manufacture of LSI, a semiconductor exposure apparatus using ultraviolet light as a light source is used in a lithography process for forming a circuit pattern. This type of semiconductor exposure apparatus incorporates a projection optical system for transferring a pattern on a mask to a resist on a wafer, and the projection optical system is required to reduce aberrations to the utmost. The degree of integration of LSIs has increased at twice the rate in three years, but with the improvement in the resolution of exposure equipment (and projection optics) and resists, processing can be performed at a speed that meets the demand for high integration of LSIs. Miniaturization is realized.

 However, in recent years, the speed of improving the resolution performance of the exposure apparatus and the resist is lower than the speed of miniaturization of the LSI, so that there is no room for the resolution. As a result, the LSI pattern is formed under conditions close to the limit of resolution performance. For example, the parameter called the k1 factor was about 0.8 ten years ago, but now it is about 0.6, and in the future, development will be made on the assumption of about 0.4. I have. In such a situation, the line width and shape of the circuit pattern tend to vary due to the aberration of the projection optical system. Therefore, it is essential to keep the aberration of the projection optical system within a certain range in order to suppress variations in circuit characteristics well and to maintain good LSI quality.

Generally, a projection optical system mounted on an exposure apparatus has at least 20 lenses (lens required). The aberration of the projection optical system is suppressed to a predetermined value or less at the stage of optical design. However, individual lenses actually manufactured have characteristics that deviate from the design values due to manufacturing errors. For example, even if we try to obtain synthetic quartz with a uniform refractive index as the optical material (lens material) that forms the individual lenses, there is a limit to the uniformity of the refractive index of the optical materials that are actually available. The refractive index non-uniformity (refractive index distribution) is one of the factors that eventually deteriorate the aberration of the projection optical system. In the polishing process of the lens surface, polishing is repeated while measuring the surface shape as needed with an interferometer.However, in order to economically manufacture the projection optical system, a processing error that affects the aberration to some extent remains. I have no choice. That is, an error in the surface shape of the lens is one of the factors that cause aberration in the projection optical system.

 Furthermore, in the adjustment step of optically adjusting the projection optical system assembled using a large number of lenses so as to minimize aberrations, the adjustment of the distance between the lenses by moving the lenses along the optical axis, By adjusting the eccentricity by shifting (moving) or tilting (tilting) the lens perpendicularly to the optical axis, the projection optical system is brought to the minimum aberration state. Further, in order to further reduce the aberration of the projection optical system, the influence of the rotationally asymmetric error of the lens is reduced by rotating the lens around the optical axis. However, even in the interval adjustment, the eccentricity adjustment, and the rotation adjustment, an error remains in the setting (amount of movement of the lens, a shift amount, a tilt amount, a rotation angle, and the like), and the setting error is also a cause of aberration in the projection optical system. Become one.

 In general, in a projection optical system composed of a large number of lenses, the transmitted portion of the light beam differs for each lens, and the phase advance and delay of the wavefront received when passing through a large number of lenses are randomly overlapped. The effects of lens wavefront errors are not cumulative. Therefore, for example, when manufacturing a projection optical system having a wavefront aberration of about πππλ (λ: wavelength of exposure light) using 25 lenses, the wavefront error (wavefront Is about 2 mA. In this case, since there is a refractive index distribution in the lens, the allowable surface shape error (wavefront error) on one surface of the lens is about 0.5 to 1πιλ.

The wavelength λ of the exposure light is 248 nm, and the refractive index of the optical material forming the lens is Assuming 1.6, a wavefront error of about 0.5 to 1πιλ corresponds to a shape error of 0.25 to 0.5 nm along the traveling direction of the light beam. Even with the current state-of-the-art polishing technology, it is impossible to process lenses with a diameter of 200 mm or more with such an error. It is about. As described above, in the conventional method for manufacturing a projection optical system, a projection optical system having an extremely low wavefront aberration of 1Οπιλ or less due to the influence of the refractive index distribution of the lens and the surface shape error of the lens. I couldn't do that. Disclosure of the invention

 The present invention has been made in view of the above-described problems, and even if individual lenses have a certain degree of refractive index distribution or surface shape error, for example, projection optics having an extremely low wavefront aberration of 10 mA or less. It is an object of the present invention to provide a method for producing an optical system capable of producing a system.

 Another object of the present invention is to provide an exposure apparatus including a projection optical system having an extremely low aberration of, for example, 1 O mA or less in terms of wavefront aberration, and capable of performing good exposure under high resolution. And

 Further, the present invention uses an exposure apparatus having a projection optical system having an extremely low wavefront aberration of 1ιπιλ or less, for example, to manufacture a good microdevice under a high resolution and good exposure condition. It is an object of the present invention to provide a method for manufacturing a micro device that can perform the method.

 In order to solve the above problems, in a first invention of the present invention, in a method of manufacturing an optical system having at least one lens,

 A refractive index distribution measuring step of measuring a refractive index distribution in the optical material forming the at least one lens;

 A surface shape measurement step of measuring a surface shape of the at least one lens; and an optical error of the at least one lens based on a measurement result of the refractive index distribution measurement step and a measurement result of the surface shape measurement step. The calculation process to be determined;

The surface of the at least one lens is determined based on a calculation result of the calculation step. And forming a correction film for forming a thin film having a predetermined thickness distribution.

 According to a second aspect of the present invention, in the method for manufacturing an optical system having a plurality of lenses, an assembling step of assembling the optical system using the plurality of lenses;

 An aberration measuring step of measuring an aberration of the optical system assembled in the assembling step; and at least one of the plurality of lenses based on a measurement result of the aberration measuring step.

A method of correcting the thickness of a thin film formed on the surface of one lens.

 In a third aspect of the present invention, in the method for manufacturing an optical system having a plurality of lenses, an assembling step of assembling the optical system using the plurality of lenses;

 A first aberration measurement step of measuring aberration of the optical system assembled in the assembly step,

 A lens adjustment step of adjusting at least one lens in the optical system based on the measurement result of the first aberration measurement step;

 A second aberration measurement step for measuring the aberration of the optical system adjusted in the lens adjustment step;

 A film thickness correction step of correcting a thickness distribution of a thin film formed on a surface of at least one of the plurality of lenses based on a measurement result of the second aberration measurement step. An optical system manufacturing method is provided.

 According to a fourth aspect of the present invention, there is provided an illumination optical system for illuminating a mask on which a predetermined pattern is formed,

 An exposure apparatus, comprising: an optical system manufactured by the manufacturing method according to any one of the first to third inventions for projecting the pattern image of the mask onto a photosensitive substrate.

 In a fifth aspect of the present invention, an exposure step of exposing the pattern of the mask to a photosensitive substrate using the exposure apparatus of the fourth aspect of the invention,

And a developing step of developing the photosensitive substrate exposed in the exposing step. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1A is a first diagram illustrating the basic principle of the present invention.

 FIG. 1B is a second diagram illustrating the basic principle of the present invention.

 FIG. 2 is a diagram schematically illustrating a relationship between a thickness distribution of a thin film and correction of a wavefront error.

 FIG. 3 is a diagram schematically showing a configuration of an exposure apparatus having a projection optical system manufactured by a manufacturing method according to each embodiment of the present invention.

 FIG. 4 is a flowchart showing a manufacturing flow of the manufacturing method according to the first embodiment of the present invention.

 FIG. 5 is a diagram schematically showing a configuration of an interferometer device for measuring an absolute value and a refractive index distribution of a refractive index of a block glass material on which each lens is to be formed.

 FIG. 6 is a diagram schematically showing a configuration of an interferometer device for measuring a surface shape error of each lens.

In Figure 7 Figure, _c 8 FIG Furochiya an bets antireflection film formation step in the first embodiment, illustrating a first method for imparting a predetermined thickness distribution at the time of forming the antireflection film is there.

 FIG. 9 is a diagram schematically showing a configuration of an ion beam processing apparatus used in a second method for correcting the thickness distribution of the once formed antireflection film to a predetermined thickness distribution. FIG. 10 is a diagram showing the relationship between the film thickness correction amount of the antireflection film used for light having a wavelength of 248 nm, the shift of the wavefront (change of the wavefront), and the reflectance.

 FIG. 11 is a diagram schematically showing the configuration of a Fizeau interferometer type wavefront aberration measuring instrument for measuring the wavefront aberration of a projection optical system using a KrF excimer laser light source. FIG. 12 is a diagram schematically showing a configuration of a PDI type wavefront aberration measuring instrument for measuring a wavefront aberration of a projection optical system using an ArF excimer laser light source.

 FIG. 13 is a diagram schematically showing an internal configuration of a projection optical system configured to be capable of adjusting an interval and an eccentricity.

FIG. 14 shows one of the plurality of partial lens barrels in the projection optical system shown in FIG. FIG. 3 is a top view showing a configuration of a split lens barrel.

 FIG. 15 is a diagram schematically showing a configuration of a lens center thickness measuring device using a Michelson interferometer.

 Fig. 16 shows the relationship between the intensity of the interference light incident on the light-receiving element and the position of the reflection mirror when a light source that supplies light is sufficiently smaller than the distance to be measured (lens center thickness). It is a figure showing a relation.

 FIG. 17 is a flowchart showing a production flow of the production method according to the second embodiment of the present invention.

 FIG. 18 is a flowchart showing a manufacturing flow of a method for manufacturing a projection optical system according to the third embodiment of the present invention.

 FIG. 19 is a flowchart of a method for obtaining a semiconductor device as a micro device.

 FIG. 20 is a flowchart of a method for obtaining a liquid crystal display element as a micro device. BEST MODE FOR CARRYING OUT THE INVENTION

 FIG. 1A and FIG. 1B are diagrams for explaining the basic principle of the present invention. First, as shown in Fig. 1A, the case where the surface 2 of the actually manufactured lens 1 is deviated from the ideal design surface (best fit surface) 3 by d along the traveling direction of the light beam 11 is assumed. Think. In this case, the light transmitted through the lens 1 is caused by an error in the surface shape of the lens 1, that is, by a shift d between the design ideal surface 3 and the actual surface 2 along the light beam traveling direction. A wavefront error (a shift between the wavefront obtained through the ideal lens and the wavefront obtained through the actual lens along the light beam traveling direction) occurs in the wavefront.

In the present invention, a thin film (for example, an antireflection film) having a predetermined thickness distribution is formed in order to correct a wavefront error (wavefront deviation) generated due to a surface shape error of the lens 1. Specifically, as shown in Fig. 1B, when a thin film composed of the lower layer 4 and the upper layer 5 is formed on the surface 2 of the lens 1, for example, the lower layer 4 is rotationally symmetric with respect to the optical axis according to the design. The outermost upper layer 5 according to the present invention. Accordingly, a predetermined thickness distribution considering the surface shape error is given. In FIG. 1B, the solid line 5a indicates the surface of the upper layer 5 formed according to the present invention, and the broken line 5b indicates the designed surface of the upper layer 5 (that is, the designed surface).

 In the present invention, in order to correct the wavefront error generated due to the surface shape error of the lens 1, the surface 5 a of the upper layer 5 of the thin film is moved from the design surface 5 b by e only along the traveling direction of the light beam 11. It is formed shifted. Here, assuming that the refractive index of the optical material forming the lens 1 for the light beam 11 is n 1 and the refractive index of the material forming the upper layer 5 for the light beam 11 is n 2, the correction amount e is e 2 (n 1 / n 2) expressed as d. Thus, even if there is a surface shape error in the actually manufactured lens 1, by forming a thin film (4, 5) having a predetermined thickness distribution on the surface 2 of the lens 1, the surface shape of the lens 1 is obtained. Wavefront errors caused by shape errors (eg, random or rotationally asymmetric wavefront errors) can be corrected.

 FIG. 2 is a diagram schematically illustrating a relationship between a thickness distribution of a thin film and correction of a wavefront error. In FIG. 2, a lower layer 8 having a uniform film thickness is formed on the surface of a lens 7, and upper layers 9 and 10 having different film thicknesses are formed thereon. In general, the number of layers forming an antireflection film as a thin film is often about 1 to 5 layers. When the antireflection film is formed as a single layer, the lower layer 8 shown in FIG. 2 does not exist. Here, the light beam 12 incident on the region of the upper layer 9 of the thin film and the light beam 13 incident on the region of the upper layer 10 of the thin film are converted into light beams 14 and 15 via the lens 7.

In FIG. 2, since the upper layers 9 and 10 of the thin film have different thicknesses by f, that is, since the predetermined thickness distribution is given to the thin film, the light flux passing through the upper layer 9 of the thin film is A wavefront shift (phase difference) can be imparted to the light flux passing through the layer 10. On the other hand, when there is a difference in surface shape error between the region corresponding to the upper layer 9 of the thin film and the region corresponding to the upper layer 10 on the surface of the lens 7, the wavefront between the light beams passing through these two regions is A shift, that is, a phase difference occurs. Therefore, if the difference in the surface shape error between the two regions is d, the difference between the film thicknesses of the upper layers 9 and 10 is set to f = e. The wavefront error can be corrected by the difference in thin film thickness between the two regions. In other words, by giving a predetermined thickness distribution to the thin film formed on the surface of the lens, it is possible to correct the wavefront error caused by the surface shape error of the lens. In order to correct the wavefront error caused by the surface shape error of the lens, a predetermined thickness distribution may be given to the thin film formed on the surface on the entrance side of the lens, or the surface on the exit side of the lens may be provided. A predetermined thickness distribution may be given to the formed thin film. Further, if necessary, a predetermined thickness distribution can be imparted to both the thin film formed on the entrance surface of the lens and the thin film formed on the exit surface of the lens. When the thin film includes a multilayer film, it is preferable to add a correction amount of 15% or less of the thickness of the outermost layer of the multilayer film.

 Even when there is no error in the lens surface shape, transmission through the lens is caused by the refractive index distribution (non-uniform refractive index, for example, rotationally asymmetric or random refractive index distribution) of the optical material forming the lens. Light has a wavefront error. In this case, as in the case of the correction of the wavefront error caused by the surface shape error, by giving a predetermined thickness distribution to the thin film, the wavefront error caused by the refractive index distribution (for example, random or rotation) Asymmetric wavefront aberration) can also be corrected. However, while the refractive index distribution of the optical material occurs inside the lens, the phase correction based on the thickness distribution of the thin film is performed on the lens surface, so strictly speaking, the wavefront error caused by the refractive index distribution is completely eliminated. In some cases, the correction cannot be completed and some correction error remains.

 In a typical method for manufacturing an optical system according to the present invention, a refractive index distribution of an optical material forming a lens is measured, and a surface shape of the lens is measured. Then, based on the measurement result of the refractive index distribution and the measurement result of the surface shape, a wavefront error generated via the lens is calculated as an optical error of the lens. Further, based on the calculation result of the wavefront error, the thickness distribution of the thin film to be formed on the surface of the lens to correct the wavefront error is calculated. Thus, a thin film having a predetermined thickness distribution with respect to the lens surface is formed based on the calculation result of the thickness distribution.

Alternatively, in another typical method for manufacturing an optical system according to the present invention, after assembling the optical system using a plurality of lenses, the aberration of the assembled optical system is measured. Then, the lens in the optical system is adjusted based on the measurement result. In addition, lens adjusted optics Measure the system aberrations. Prior to assembling the optical system, the refractive index distribution of each optical material forming each of the plurality of lenses and the surface shape of each of the plurality of lenses are measured. In this way, the thickness distribution of the thin film formed on the surface of the lens is corrected based on the measurement result regarding the aberration of the lens-adjusted optical system and the measurement result regarding the refractive index distribution and the surface shape of the lens.

 As described above, in the method of manufacturing an optical system according to the present invention, by forming a thin film having a predetermined thickness distribution on the surface of a lens, or by forming the thin film distribution formed on the surface of the lens, By correcting, even if there is a certain degree of refractive index distribution or surface shape error in each lens, as described later, it is necessary to manufacture an optical system with extremely low aberration of 1 た と え ば πιλ or less due to wavefront aberration, for example. Can be. Therefore, for example, the exposure apparatus of the present invention including an optical system having an extremely low wavefront aberration of 1Οπιλ or less as a projection optical system can perform favorable exposure with high resolution. Furthermore, for example, in the method for manufacturing a micro-portal device of the present invention using an exposure apparatus having a projection optical system having an extremely low aberration of 1Οπιλ or less in terms of wavefront difference, high resolution and favorable exposure conditions are obtained. A good microphone opening device can be manufactured.

 An embodiment of the present invention will be described with reference to the accompanying drawings.

 FIG. 3 is a diagram schematically showing a configuration of an exposure apparatus having a projection optical system manufactured by a manufacturing method according to each embodiment of the present invention. In FIG. 3, the Ζ axis is parallel to the optical axis Α の of the projection optical system, the Υ axis is parallel to the plane of FIG. 3 in a plane perpendicular to the optical axis Α 、, and the Ζ axis is the optical axis Χ Χ. The X axis is set perpendicular to the plane of the paper in Fig. 3 in a vertical plane.

The exposure apparatus shown in FIG. 3 includes, for example, a KrF excimer laser light source (wavelength: 248 nm) as a light source 21 for supplying illumination light (exposure light). The light emitted from the light source 21 illuminates a mask (reticle) 23 on which a predetermined pattern is formed, via an illumination optical system 22. The mask 23 is held in parallel with the XY plane on a mask stage 25 via a mask holder 24. The mask stage 25 can be moved along the mask plane (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are determined by a mask interferometer (not shown). It is configured to be measured and controlled in position.

 The light from the pattern formed on the mask 23 forms a mask pattern image on a wafer 27 as a photosensitive substrate via a projection system 26. The wafer 27 is held in parallel with the XY plane on a wafer stage 29 via a wafer table (wafer holder) 28. The wafer stage 29 can be moved along the wafer surface (that is, the XY plane) by the action of a drive system (not shown), and its position coordinates are measured by a wafer interferometer (not shown) and position control is performed. It is configured to be. In this manner, by performing batch exposure or scan exposure while controlling the wafer 27 two-dimensionally in a plane (XY plane) orthogonal to the optical axis AX of the projection optical system 26, each wafer 27 can be exposed. The pattern of the mask 23 is sequentially exposed on the exposure area.

 FIG. 4 is a flowchart showing a manufacturing flow of the manufacturing method according to the first embodiment of the present invention. In the manufacturing method of the first embodiment, after manufacturing a block glass material (blanks) on which each lens is to be formed, the absolute value of the refractive index and the refractive index distribution of the manufactured block glass material are measured, for example, as shown in FIG. The measurement is performed using a measuring device (S11). In FIG. 5, a block glass material 103 as a test object is set at a predetermined position in a sample case 102 filled with oil 101. Then, light emitted from the interferometer unit 105 controlled by the control system 104 enters a Fizeau flat (Fizeau plane) 106 supported on a Fizeau stage 106a.

Here, the light reflected by the Fizeau flat 106 becomes reference light, and returns to the interferometer unit 105. On the other hand, the light transmitted through the Fizeau flat 106 becomes measurement light, and enters the test object 103 in the sample case 102. The light transmitted through the test object 103 is reflected by the reflection plane 107 and returns to the interferometer unit 105 via the test object 103 and the Fizeau flat 106. Thus, the wavefront aberration due to the refractive index distribution of each block glass material 103 as an optical material is measured based on the phase shift between the reference light and the measurement light returned to the interferometer unit 105. The details of the measurement of the refractive index homogeneity by an interferometer can be referred to, for example, JP-A-8-55505. Next, in the manufacturing method according to the first embodiment, each lens that constitutes the projection optical system 26 is manufactured using a block glass material that is ground as necessary from a block glass material whose refractive index distribution has been measured. That is, the surface of each lens is polished with a design value as a target according to a known polishing process (S12). In the polishing process, polishing is repeated while measuring the error in the surface shape of each lens with an interferometer to bring the surface shape of each lens closer to the target surface shape (best-fit spherical shape). Thus, when the surface shape error of each lens falls within a predetermined range, the surface shape error of each lens is measured using, for example, a more precise interferometer device shown in FIG. 6 (S13).

 In FIG. 6, light emitted from the interferometer unit 112 controlled by the control system 111 enters the Fizeau lens 113 supported on the Fizeau stage 113a. Here, the light reflected by the reference surface (Fizeau surface) of the Fizeau lens 113 becomes reference light, and returns to the interferometer unit 112. In FIG. 6, the Fizeau lens 1 13 is shown as a single lens, but the actual Fizeau lens is composed of a plurality of lenses (lens groups). On the other hand, the light transmitted through the Fizeau lens 113 becomes measurement light, and is incident on the optical surface of the lens 114 to be measured.

 The measurement light reflected by the test optical surface of the test lens 1 14 returns to the interferometer unit 1 12 via the Fizeau lens 1 13. In this way, based on the phase shift between the reference light and the measurement light returned to the interferometer unit 112, the wavefront aberration of the test optical surface of the test lens 114 with respect to the reference surface and, consequently, the test lens 1 The error of the surface shape (deviation from the best-fit small spherical surface in the design) in 14 is measured. For details on the measurement of the lens surface shape error using an interferometer, see, for example, US Pat. No. 5,561,525, US Pat. No. 5,563,706, and Reference can be made to Japanese Patent Publication No. 0—1 5 4 6 5 7. Here, reference is made to U.S. Pat. No. 5,561,525, U.S. Pat. No. 5,563,706, and Japanese Patent Application Laid-Open No. H10-156457. Invite.

Next, in the manufacturing method of the first embodiment, an antireflection film having a predetermined thickness distribution is formed on each lens whose surface shape error has been measured (S14). FIG. 7 is a flowchart of an antireflection film forming step in the first embodiment. In the anti-reflection film forming process As shown in FIG. 7, the refractive index distribution information of the optical material obtained in the refractive index distribution measurement step S11 and the surface shape of each lens obtained in the surface shape error measurement step S13, as shown in FIG. The wavefront error generated in each lens is calculated based on the shape error information (S111). Then, based on the wavefront error generation amount obtained in the wavefront error process S111, the thickness distribution of the antireflection film required to correct the generation of the wavefront error is calculated (S112). . In this way, based on the thickness distribution of the antireflection film obtained in the thickness distribution calculating step S112, an antireflection film having a predetermined thickness distribution is formed on the surface of each lens (S113) ). Thus, in the prior art, an antireflection film having a thickness distribution that is rotationally symmetric with respect to the optical axis designed independently of the refractive index distribution information and the surface shape error information is formed. And forming an antireflection film having a predetermined thickness distribution calculated based on the surface shape error information.

Hereinafter, a method of forming an antireflection film having a predetermined thickness distribution on the surface of each lens will be described. There are two methods for providing a predetermined thickness distribution to the antireflection film. In the first method, a predetermined thickness distribution is provided from the beginning when the antireflection film is formed in consideration of the refractive index distribution information and the surface shape error information. On the other hand, in the second method, an antireflection film having a designed thickness distribution is formed without considering the refractive index distribution information and the surface shape error information. Then, the thickness distribution of the formed antireflection film is corrected to a predetermined thickness distribution in consideration of the refractive index distribution information and the surface shape error information. The second method can be realized by, for example, ion beam processing. FIG. 8 is a view for explaining a first method for providing a predetermined thickness distribution when forming an anti-reflection film. In FIG. 8, a case is considered in which an antireflection film having a thickness distribution as represented by contour lines 52 and 53 is formed on the surface of a lens having an outer shape indicated by reference numeral 51. Here, the thickness of the anti-reflection film in the area indicated by the contour line 53 is the largest, and the thickness correction minimum unit is smaller than the thickness of the anti-reflection film in the area indicated by the contour line 52 (excluding the area indicated by the contour line 53). It is larger by the amount △. The thickness of the anti-reflection coating in the area indicated by the contour line 52 (excluding the area indicated by the contour line 53) is the thickness of the anti-reflection coating in other areas (excluding the area indicated by the contour lines 53 and 52). It is larger than the thickness by the thickness correction minimum unit amount Δ. In this case, in the process of forming the outermost layer of the anti-reflection film (for example, the upper layer having a thickness of 40 nm), when forming the final thickness of 2 mm, the shape shown by the contour line 52 is the same. A mask having an opening with a shape is positioned immediately before the lens surface, and a film thickness Δ is formed through the mask by an evaporation method or a sputtering method. Next, a mask having an opening having the same shape as the shape shown by the contour line 53 is positioned immediately before the lens surface, and a film thickness Δ is formed through this mask. Here, assuming that the thickness correction minimum unit amount Δ is, for example, 1 nm, the minimum unit of the wavefront error that can be corrected for light having a wavelength of 248 nm is about 2 ιηλ.

 FIG. 9 is a diagram schematically showing a configuration of an ion beam processing apparatus used in a second method for correcting the thickness distribution of the once formed antireflection film to a predetermined thickness distribution. The ion beam processing apparatus shown in FIG. 9 has a stage 42 that can move two-dimensionally while holding the processing lens 41, and a surface (strictly speaking, an antireflection film surface) of the processing lens 41. Ion beam processing device main body 4 4 for irradiating ion beam 4 3 for film thickness processing, drive system 45 for moving stage 42 two-dimensionally, movement of stage 42 and main body of ion beam processing device 4 It has a control system 46 for controlling the energy of the ion beam 43 irradiated from 4, and an input system 47 for inputting information on the film thickness processing of the processing lens 41.

 Then, based on the information on the film thickness processing of the processing lens 41 from the input system 47, the control system 46 receives the energy of the ion beam 43 irradiated from the ion beam processing device main body 44 and the energy of the stage 42. By controlling the movement, the thickness distribution of the antireflection film formed on the surface of the processing lens 41 is corrected to a predetermined thickness distribution by so-called ion beam application. As described above, in the case of ion beam processing, local correction of the film thickness can be performed without using a mask. When the antireflection film is irradiated with an ion beam of a rare gas as an ion beam at low energy, a minute amount of film thickness processing can be performed with high accuracy.

FIG. 10 is a diagram showing the relationship between the film thickness correction amount of the antireflection film used for light having a wavelength of 248 nm, the shift of the wavefront (change of the wavefront), and the reflectance. In FIG. 10, the horizontal axis represents the thickness correction amount (n) of the anti-reflection film formed on one surface of the lens. m), the vertical axis on the left shows the wavefront deviation (ηιλ), and the vertical axis on the right shows the reflectance (%). In FIG. 10, the line connecting the square points shows the relationship between the film thickness correction amount and the deviation of the wavefront, and the line connecting the triangle points shows the relationship between the film thickness correction amount and the reflectance. ing. Referring to FIG. 10, it can be seen that if the increase in reflectivity due to the film thickness correction is allowed up to 0.1%, the wavefront error of 1Οπιλ can be corrected. Further, by correcting the film thickness of each of the antireflection films formed on both surfaces of the lens, it is possible to correct even larger wavefront errors.

 Referring to FIG. 4 again, in the manufacturing method of the first embodiment, the projection optical system 26 is assembled using a plurality of lenses on which a reflection preventing film having a predetermined thickness distribution is formed as necessary. S15). Specifically, by holding a plurality of lenses in a predetermined holding frame according to the design, each optical unit is assembled sequentially. Then, the assembled optical units are sequentially dropped into the lens barrel through the upper opening of the lens barrel. At this time, a predetermined washer is interposed between the optical units. In this way, the optical unit first dropped into the lens barrel is supported via a pusher at the protrusion formed at one end of the lens barrel, and all the optical units are accommodated in the lens barrel. The assembly of the projection optical system is completed. For details regarding the assembly of the projection optical system, reference can be made, for example, to Japanese Patent Application Laid-Open No. H10-154657.

Next, in the manufacturing method according to the first embodiment, the wavefront aberration of the actually assembled projection optical system is measured (S16). Specifically, for example, a projection optical system using a KrF excimer laser light source using a Fizeau interferometer type wavefront aberration measuring device disclosed in US Pat. No. 5,898,501 is disclosed. Wavefront aberration can be measured. In this case, as shown in FIG. 11, laser light having substantially the same wavelength as the exposure light (for example, the second harmonic of the Ar laser light) is applied to the Fizeau surfaces of the half prism 60 and Fizenlens 61. The light enters the projection optical system 26 as the test optical system via 6a. At this time, the light reflected by the Fizeau surface 61 a becomes so-called reference light, and reaches the imaging device 62 such as a CCD via the Fizeau lens 61 and the half prism 60. On the other hand, the light transmitted through the Fizeau surface 61 a becomes so-called measurement light, and enters the reflective spherical surface 63 via the projection optical system 26. The measurement light reflected by the reflective spherical surface 63 reaches the CCD 62 via the projection optical system 26, the Fizeau lens 61 and the half prism 60. Thus, the wavefront aberration remaining in the projection optical system 26 is measured based on the interference between the reference light and the measurement light. Similarly, the wavefront aberration of a projection optical system using an ultra-high pressure mercury lamp (eg, i-line) is measured using a Fizeau interferometer type wavefront aberration measuring device disclosed in, for example, US Pat. No. 5,898,501. Can also be measured. Here, U.S. Pat. No. 5,898,501 is incorporated by reference.

 Also, for example, a projection optical system using an ArF excimer laser light source using a so-called PDI (Phase Diffraction Interferometer) type wavefront aberration measuring device disclosed in JP-A-2000-97616. It is also possible to measure the wavefront aberration of the system. Here, JP-A-2000-97616 is incorporated by reference. In this case, as shown in FIG. 12, the illumination light for exposure emitted from the light source 21 (not shown in FIG. 12) and passed through the illumination optical system 22 is moved to the first position which is positioned at the mask setting position. Incident on the pinhole 71 of. The spherical wave formed via the first pinhole 71 is transmitted through the projection optical system 26 as an optical system to be measured, and is incident on a grating (one-dimensional diffraction grating) 72.

 The zero-order diffracted light transmitted through the grating 72 as it is enters a second pinhole (not shown) formed in the mask 73. On the other hand, the first-order diffracted light generated by the diffraction action in the drayring 72 is incident on almost the center of an opening (not shown) formed in the mask 73. The 0th-order diffracted light passing through the second pinhole and the 1st-order diffracted light passing through the opening reach the imaging device 75 such as a CCD via the collimating lens 74. Thus, the spherical wave formed via the second pinhole is used as the reference wavefront, the wavefront of the first-order diffracted light that has passed through the opening is used as the measurement wavefront, and the projection optical system 26 is used based on the interference between the reference wavefront and the measurement wavefront. Is measured.

Next, in the manufacturing method of the first embodiment, it is determined whether or not the wavefront aberration of the projection optical system measured in the aberration measurement step S16 falls within an allowable range (S17). Judgment If it is determined in step S17 that the wavefront aberration of the projection optical system is within the allowable range (YES in FIG. 4), the manufacture of the projection optical system according to the first embodiment ends. On the other hand, if it is determined in the determination step S17 that the wavefront aberration of the projection optical system is not within the allowable range (in the case of NO in FIG. 4), the lens is moved along the optical axis AX and the distance between the lenses is reduced. Adjust the interval to change the angle, and adjust the eccentricity by shifting or tilting the lens perpendicular to the optical axis AX (S18).

 FIG. 13 is a diagram schematically showing an internal configuration of a projection optical system configured to be capable of adjusting an interval and an eccentricity. FIG. 14 is a top view showing the configuration of one of the partial barrels in the projection optical system of FIG. 13 and 14 employ a common XYZ coordinate system corresponding to FIG. As shown in FIG. 13, the lens barrel 30 includes a plurality of split lens barrels 30 a to 301, and is supported by a frame of an exposure apparatus (not shown) via a flange 31. The plurality of split lens barrels 30a to 301 are stacked in the optical axis AX direction. The lenses 2b, 2d, 2e, and 2f supported by the divided lens barrels 30b, 30d, 30e, 30f, and 30g among the plurality of divided lens barrels 30a to 301, respectively. , 2g are movable lenses that can move in the optical axis direction (Z direction) and can be tilted about the XY direction.

 About the configuration of the split lens barrel 30 b, 30 d, 30 e, 30 f, 30 g holding the movable lens 2 b, 2 d, 2 e, 2 f, 2 g, the configuration of the split lens barrel 30 b This will be explained as a representative. The configuration of the other divided lens barrels 30d, 30e, 30f, and 30g is substantially the same as the configuration of the divided lens barrel 30b, and thus the description thereof is omitted. The split lens barrel 3Ob holds an outer ring 37b connected to split lens barrels 30a and 30c located above and below (in the Z direction) the split lens barrel 3Ob, and a movable lens 2b. The lens room 38b is provided. This lens chamber 38b is in the optical axis direction with respect to the outer ring 37b.

It is connected to the outer ring 37b so as to be movable in the (Z direction) and tiltable about the XY direction. Further, the split lens barrel 30b has an actuator 32b attached to the outer ring 37b. As the actuator 32b, for example, a piezoelectric element can be used. For example, the actuary 32b is elastic The lens chamber 38b is driven via a link mechanism as a displacement magnifying mechanism constituted by a hinge. The actuator 32b is attached to three places of the split lens barrel 30b, whereby the three places of the lens chamber 38b move independently in the optical axis direction (Z direction).

 This will be described in more detail with reference to FIG. In FIG. 14, on the periphery of the lens 2, three flange portions 201 to 203 are provided at every azimuth angle of 120 ° in the XY plane. The lens chamber 38 includes clamp portions 381 to 383, which hold three flange portions 201 to 203 of the lens 2. Then, the lens chamber 38 is independently driven along the Z direction by three actuators (not shown) via link mechanisms at the positions of the driving points DP1 to DP3 at every azimuth angle of 120 ° in the XY plane. Driven. Here, if the driving amounts in the Z direction by the three actuators are the same, the lens chamber 38 moves in the Z direction (optical axis direction) with respect to the outer ring 37, and the three actuators are moved together. When the driving amount in the Z direction is different, the lens chamber 38 is inclined with respect to the outer ring 37 about the XY direction. If the driving amount in the Z direction by the three actuators is different, the lens chamber 38 may move in the Z direction (optical axis direction) with respect to the outer ring 37. Returning to FIG. 13, the split lens barrel 3 Ob is attached to the outer ring 37b and includes a drive amount measuring unit 39b composed of, for example, an optical encoder. The driving amount measuring section 39b is arranged in the Z direction (optical axis direction) of the lens chamber 38 with respect to the outer ring 37b at the positions of the three measuring points MP1 to MP3 at azimuth angles of 120 ° shown in FIG. Measure the amount of movement. Therefore, the movement of the lens chamber 38 and, consequently, the movement of the lens 2b can be controlled in a closed loop by the actuator 32b and the drive amount measuring unit 39.

Now, among the divided lens barrels 30a to 301, lenses 2a, 2c, 2 supported by the divided lens barrels 30a, 30c, 30h, 30i, 30j, 30k, 301 h, 2i, 2j, 2k, 21 are fixed lenses. The divided lens barrels 30a, 30c, 30h, 30i, 30j, 30k, which hold these fixed lenses 2a, 2c, 2h, 2i, 2j, 2k, 21 30 Regarding the configuration of 1, the configuration of the split lens barrel 30c The following is a description of the configuration. Note that the configuration of the other divided barrels 30a, 30h, 30i, 30j, 30k, 301 is almost the same as the configuration of the divided barrel 30c. Here, the description is omitted. The split lens barrel 30c includes an outer ring 37c connected to split lens barrels 30b and 30d located above and below (in the Z direction) the split lens barrel 30c, and an outer ring 3c. A lens chamber 38c attached to 7c and holding a lens 2c. In addition, since the actuators are made of high-precision, low-heat, high-rigidity, and high-cleanliness piezoelectric elements, the driving force of these piezoelectric elements is expanded by a link mechanism consisting of a natural hinge. There is an advantage that the piezoelectric element itself can be made compact. It should be noted that the actuating unit 32 may be constituted by a magnetostrictive unit or a fluid pressure unit instead of being constituted by a piezoelectric element. In the above description, the movement adjustment (interval adjustment) for moving the lens along the optical axis AX and the tilt adjustment for tilting the lens with respect to the optical axis AX are limited. It is also possible to perform a shift adjustment for shifting the lens along a direction perpendicular to the lens.

 In the manufacturing method of the first embodiment, the wavefront aberration of the projection optical system whose lens has been adjusted by adjusting the distance or the eccentricity is measured again (S16). Then, it is determined again whether or not the wavefront aberration of the projection optical system measured again in the aberration measurement step S16 falls within an allowable range (S17). If it is determined in the determination step S17 that the wavefront aberration of the projection optical system falls within the allowable range, the production of the projection optical system ends. However, if it is determined in the determination step S 17 that the wavefront aberration of the projection optical system is not within the allowable range, the lens adjustment step S 17 is performed until a determination of YES is obtained in the determination step S 17. 18 and the aberration measurement step S 16 are further repeated.

In the manufacturing method of the first embodiment, it is also possible to manufacture a large number of each lens constituting the projection optical system 26 and assemble the projection optical system by combining lenses selected from the manufactured many lenses. it can. In this case, prior to the assembling step S15, a plurality of lenses that constitute the projection optical system 26 are manufactured (lens manufacturing step). Next, information on the shape of the plurality of manufactured lenses, such as the radius of curvature of the processed surface of each lens and the center thickness of each lens, is measured (lens shape measurement step). Soshi Then, a plurality of lenses to constitute the projection optical system 26 are selected, for example, at random from the plurality of lenses whose lens shapes have been measured (selection step).

 In this way, the optical performance of the virtually assembled projection optical system is predicted and evaluated based on the measurement information on the shapes of the selected plurality of lenses (prediction evaluation step). Then, the selection step and the prediction evaluation step are repeated until the optimum combination of a plurality of lenses that allows the predicted optical performance of the projection optical system is determined (iteration step). As described above, in addition to the refractive index distribution information of the lens and the surface shape error information, the lens is virtually created based on the actual measurement data such as the radius of curvature of the processed surface of each lens and the center thickness of each lens. The projection optical system is predicted and evaluated for the aberration generated by the projection optical system obtained by combining the projection optical system, and the projection optical system is combined with the lens selected based on the prediction evaluation result so that the aberration generated by the virtual projection optical system is relatively small. It is preferable to configure For details of a method of finally selecting a plurality of lenses to constitute a projection optical system from a large number of lenses by this virtual combination, see, for example, Japanese Patent Application Laid-Open No. 2000-249917 and a corresponding US patent application. No. 09Z691, 194 (filed on Oct. 19, 2000) can be referred to. No. 09Z691, 194, filed Oct. 19, 2000, is hereby incorporated by reference.

 Hereinafter, a method of measuring the radius of curvature of the lens processing surface after grinding and polishing will be briefly described. The radius of curvature of the lens processing surface can be measured using a Newton gauge as disclosed in JP-A-5-272944, JP-A-6-129836, and JP-A-6-174451. . In this case, the test surface of the test lens is superimposed on the gauge surface of the Newton gauge (the radius of curvature is known), and the test object is obtained from the number of Newton interference fringes observed under a light source of a constant wavelength based on a predetermined arithmetic expression. Find the radius of curvature of the test surface. Here, JP-A-5-272944, JP-A-6-129836, and JP-A-6-174451 are incorporated by reference.

The radius of curvature of the lens processing surface is disclosed in JP-A-5-340734, JP-A-5-340735, JP-A-5-346315 and the like. In addition, it can be measured by a laser interferometer method. In this case, the alignment of the apparatus is performed based on the interference between the reference gauge surface of the master lens and the reference gauge surface of the interferometer, which is substantially the same as the surface to be measured of the lens to be measured and has a known radius of curvature. In this alignment state, the test lens is installed in place of the master lens, and the difference between the radius of curvature of the test surface with respect to the reference gauge surface by interference measurement, and the absolute value of the radius of curvature of the test surface of the test lens is measured. Ask for. Here, JP-A-5-340734, JP-A-5-340735, and JP-A-5-346315 are incorporated by reference.

 Next, a method of measuring the center thickness of the lens after grinding and polishing will be briefly described. FIG. 15 is a diagram schematically showing a configuration of a lens center thickness measuring device using a Michelson interferometer. In FIG. 15, the distance measuring device as a lens center thickness measuring device includes a light source 121 that emits measuring light of a predetermined wavelength, an optical system 122, and a half mirror 123. I have. The optical system 122 includes a pinhole, a collimator lens, and the like (not shown), and converts the measurement light emitted from the light source 122 into a parallel light beam to be incident on the optical mirror 123. The half mirror 123 has a function of reflecting a part of the incident light beam and transmitting the rest. As a result, a part of the light beam incident from the light source 121 side is reflected to the lens element 124 side to be subjected to the distance measurement, and the remaining light beam is transmitted to the reflection mirror 125 side.

 For the light beam reflected on the lens element 124 side, the surface of the lens element 124 on the half-mirror 123 side and the back surface of the lens element 124 are respectively reflective surfaces 122a and 122. 4 b. The reflection mirror 125 is attached to a moving stage (not shown), and is movable together with the moving stage in the direction of the arrow in FIG. The reflecting mirror 125 reflects the light beam transmitted through the half mirror 123 and returns it to the half mirror 123.

The light beam reflected by the lens element 124 passes through the half mirror 123 as measurement light and enters the light receiving element 126. On the other hand, the light beam reflected by the reflection mirror 125 is reflected by the half mirror 123 as reference light, and reaches the light receiving element 126. The measurement light and the reference light interfere on the light receiving element 126. And the light receiving element 1 2 6 As a result, the interference light is photoelectrically converted and output to the outside as an interference signal.

 Fig. 16 shows the intensity of the interfering light incident on the light receiving element 1 26 when using a light source 1 2 1 that supplies light whose coherence distance is sufficiently smaller than the measurement interval (lens center thickness). FIG. 9 is a diagram showing a relationship with the position of a reflection mirror 125. Here, the measurement light is separated by the half mirror 1 2 3, reflected by the reflection surface 1 2 4 a of the lens element 1 2 4, and the optical path length reaching the half mirror 1 2 3 again is A 1. . The measurement light is separated by the half mirror 123, reflected by the reflecting surface 124b of the lens element 124, and the optical path length reaching the half mirror 123 again is A2. The reference light is separated by the half mirror 123, reflected by the reflecting mirror 125, and the optical path length of the optical path reaching the half mirror 123 again is B.

 The measurement light reflected by the reflecting surfaces 1 24 a and 124 b by the half mirror 123 interferes with the reference light reflected by the reflecting mirror 125 according to the optical path length difference. In other words, each measurement light and the reference light interfere when the optical path lengths Al and A2 are substantially equal to the optical path length B, and an interference light whose intensity changes at this time is obtained. Therefore, if the optical path length B becomes almost equal to the optical path length A 1 by changing the position of the reflection mirror 125, the interference light incident on the light receiving element 126 (interference with the reflection surface 124 a) The intensity of the light changes as shown in the waveform on the left in Fig. 16. On the other hand, when the optical path length B becomes almost equal to the optical path length A 2, the intensity of the interference light (interference light relating to the reflecting surface 124 b) incident on the light receiving element 126 becomes equal to the intensity of the right waveform in FIG. To change.

Until the measurement light and the reference light are separated and combined again by the half-mirror 123, the measurement light and the reference light are incident on a medium with a low refractive index, for example, and a medium with a high refractive index is used. In the case of reflection at the boundary surface with, for example, reflection at the reflecting surface 124a, the phase is inverted by 180 degrees, that is, a so-called phase jump occurs. In this case, the intensity distribution of the interference light is approximately at the center of its amplitude, like the change in the interference light intensity on the reflecting surface 124a relative to the change in the interference light intensity on the reflecting surface 124b in Fig. 16. In contrast, the state is reversed. Then, the center thickness of the lens element 124 is determined based on the interference signal output from the light receiving element 126 corresponding to the intensity distribution of the interference light and the position of the reflecting mirror 125 set on the moving stage. Can be In the above description, non-contact light Although the center thickness of the lens is measured using a scientific measuring instrument, the center thickness of the lens can be measured using, for example, a contact measuring instrument using a measuring needle.

 As described above, in the manufacturing method of the first embodiment, the refractive index distribution of the optical material forming the lens and the surface shape of the lens are measured, and the wavefront error generated via the lens is calculated based on the measurement result. are doing. Then, the thickness distribution of the antireflection film to be formed on the lens surface in order to correct the calculated wavefront error is calculated. As a result, by forming an anti-reflection film having a predetermined thickness distribution on the surface of the lens based on the calculation result of the thickness distribution, the refractive index distribution and the surface shape error can be reduced to some degree in each lens. Even if present, a projection optical system with extremely low aberration can be manufactured. Specifically, as described above, by setting the minimum unit of the wavefront error that can be corrected for light having a wavelength of 248 nm to 2πιλ or less, for example, the wavefront aberration is 1 1πιλ or less. An extremely low aberration projection optical system can be manufactured.

 In the manufacturing method of the first embodiment, the wavefront error is calculated based on the measurement results of the refractive index distribution and the surface shape error. However, it is also possible to form an antireflection film on the surface of the lens in advance, and actually measure a wavefront error generated through the lens on which the antireflection film is formed. In this case, the thickness distribution of the antireflection film to be formed to correct the wavefront error is calculated based on the measurement results of the refractive index distribution and the surface shape error and the measurement result of the wavefront error.

 Further, in the manufacturing method of the first embodiment, after the aberration measurement step S16, the determination step S17 and the lens adjustment step S18 are provided, but these steps S16 to S18 are omitted. can do. In other words, after the projection optical system assembling step S15, the manufacturing method of the first embodiment can be ended.

FIG. 17 is a flowchart showing a manufacturing method of the method for manufacturing a projection optical system according to the second embodiment of the present invention. In the manufacturing method of the first embodiment, by correcting a wavefront error generated through each lens for each lens, that is, by forming an antireflection film having a predetermined thickness distribution on each lens, the extremely low aberration Manufactures projection optical systems. On the other hand, in the manufacturing method of the second embodiment, the film thickness of the antireflection film formed on some of the lenses in the optical system is adjusted without correcting the wavefront error for each lens. By making corrections, an extremely low aberration projection optical system is manufactured. Hereinafter, the manufacturing method of the second embodiment will be described, focusing on the differences from the manufacturing method of the first embodiment.

 In the manufacturing method of the second embodiment, as in the first embodiment, the absolute value of the refractive index and the refractive index distribution of the block glass material on which each lens is to be formed are measured (S 21). Next, similarly to the first embodiment, in order to manufacture each lens to constitute the projection optical system 26 using the block glass material ground as necessary from the block glass material whose refractive index distribution was measured, The surface of each lens is polished (S22). Further, similarly to the first embodiment, the error of the surface shape of each lens is measured (S23).

 Next, a uniform antireflection film (rotationally symmetric with respect to the optical axis A X) based on the design is formed on each lens whose surface shape error has been measured (S 24). However, in the antireflection film forming step S24, unlike the first embodiment in which an antireflection film having a predetermined thickness distribution is formed in order to correct a wavefront error generated via each lens, An anti-reflection film having a thickness distribution that is rotationally symmetric with respect to the optical axis designed independently of the refractive index distribution information and the surface shape error information is formed on the surface of each lens. Then, the projection optical system 26 is assembled using a plurality of lenses on which the antireflection film is formed (S25). At this time, similarly to the first embodiment, a plurality of lenses to be included in the projection optical system are manufactured, and the projection optical system is assembled based on an optimal combination selected from the manufactured many lenses. Can also.

Thus, similarly to the first embodiment, the wavefront difference of the actually assembled projection optical system is measured (S26). Then, it is determined whether or not the wavefront aberration of the projection optical system measured in the aberration measurement step S26 falls within the allowable range A (S27). If it is determined in the determination step S27 that the wavefront aberration of the projection optical system falls within the allowable range A (in the case of YES in FIG. 17), the process proceeds to a later-described step S29. On the other hand, if it is determined in the determination step S27 that the wavefront aberration of the projection optical system is not within the allowable range A (NO in FIG. 17), the lens is adjusted (S28). However, in the lens adjustment step S28 of the second embodiment, in addition to the interval adjustment and the eccentricity adjustment performed in the first embodiment, rotation adjustment for rotating the lens around the optical axis AX is performed as necessary. In the manufacturing method of the second embodiment, the lens adjustment is performed by adjusting the distance, the eccentricity, and the rotation. The wavefront aberration of the adjusted projection optical system is measured again (S26). Then, it is determined again whether or not the wavefront aberration of the projection optical system measured again in the aberration measurement step S26 is within the allowable range A (S27). If it is determined in the determination step S27 that the wavefront aberration of the projection optical system falls within the allowable range A, the process proceeds to step S29 described later. However, if it is determined in the determination step S27 that the wavefront aberration of the projection optical system is not within the allowable range A, the lens adjustment step S2 is performed until a determination of YES is obtained in the determination step S27. 8 and the aberration measurement step S26 are further repeated.

 Next, in the manufacturing method of the second embodiment, some lenses (one or more lenses) suitable for correcting the wavefront aberration remaining in the projection optical system are taken out of the lens barrel (S 2 9). Then, the thickness distribution of the anti-reflection film formed on the lens taken out of the lens barrel is corrected (S30). That is, in the film thickness correction step S30, in order to correct the wavefront aberration remaining in the projection optical system, the measurement result of the refractive index distribution measurement step S21 and the measurement result of the surface shape measurement step S23 are used. Based on the final measurement result of the aberration measurement step S26 and, the thickness distribution of the antireflection film is corrected using, for example, the above-described ion beam processing. When an optical material having a sufficiently uniform refractive index distribution is used, the influence of the refractive index distribution can be ignored in correcting the thickness distribution.

 Thus, the lens whose thickness distribution of the anti-reflection film has been corrected is incorporated into the lens barrel (S 3 Do, ie, the lens taken out of the lens barrel is returned to the original predetermined position in the lens barrel. The wavefront aberration of the projection optical system incorporating the lens with the corrected film thickness distribution is measured (S32), and the wavefront aberration of the projection optical system measured in the aberration measurement step S32 is within the allowable range B. (S33) Here, the allowable range B in the determining step S33 is an allowable range as a final target value regarding the wavefront aberration of the projection optical system. On the other hand, the allowable range A in the above-described determination step S27 is an intermediate allowable range set for shifting to the above-described step S29, for example, a value twice as large as the final allowable range B. Is set to

In the determination step S33, when it is determined that the wavefront aberration of the projection optical system falls within the allowable range B (YES in FIG. 17), the projection optical system according to the second embodiment is used. The production of the system ends. On the other hand, if it is determined in the determination step S33 that the wavefront aberration of the projection optical system is not within the allowable range B (NO in FIG. 17), the lens is adjusted (S34). Here, unlike the lens adjustment step S28 described above, the lens adjustment step S34 does not include the lens rotation adjustment. This is because the thickness distribution of the antireflection film is generally corrected to be rotationally asymmetric with respect to the optical axis AX in the film thickness correction step S30. That is, in the lens adjustment step S34, similarly to the lens adjustment step S18 of the first embodiment, the adjustment of the distance between the lenses and the adjustment of the eccentricity of the lens are performed. In the manufacturing method of the second embodiment, the wavefront aberration of the projection optical system adjusted by the interval adjustment and the eccentricity adjustment through the lens adjustment step S34 is measured again (S32). Then, it is determined again whether or not the wavefront aberration of the projection optical system measured again in the aberration measuring step S32 falls within the allowable range B (S33). If it is determined in the determination step S33 that the wavefront aberration of the projection optical system falls within the allowable range B, the manufacture of the projection optical system according to the second embodiment ends. However, if it is determined in the determination step S33 that the wavefront aberration of the projection optical system is not within the allowable range B, the lens adjustment step S3 is performed until a determination of YES is obtained in the determination step S33. 4 and the aberration measurement step S32 are further repeated.

 As described above, in the manufacturing method of the second embodiment, after assembling the projection optical system using a plurality of lenses, the wavefront aberration of the assembled projection optical system is measured. Then, the lens in the projection optical system is adjusted based on the measurement result, and the wavefront aberration of the adjusted projection optical system is measured. Prior to assembling the projection optical system, the refractive index distribution and surface shape error were measured. In this manner, in the manufacturing method of the second embodiment, the lens is formed on a part of the lens surface based on the measurement result regarding the wavefront aberration of the projection optical system and the measurement result regarding the refractive index distribution and the surface shape error. Since the thickness distribution of the anti-reflection coating is corrected, even if there is a refractive index distribution or surface shape error in each lens, for example, a projection optical system with extremely low wavefront aberration of 10 m or less can be used. It can be manufactured.

In the manufacturing method of the second embodiment, the thickness distribution of the antireflection film is corrected using ion beam processing. However, the film thickness is corrected by another appropriate method such as polishing. I can. However, in ion beam processing, film thickness can be corrected without removing the lens from the holder that holds the lens inside the lens barrel, so productivity is higher than in film thickness correction by polishing, which requires removing the lens from the holder. high. In the manufacturing method according to the second embodiment, the wavefront aberration of the assembled projection optical system is measured, and the thickness of the antireflection film formed on some lenses is corrected based on the measurement result. That is, in the second embodiment, the measurement accuracy of the basic data is higher than in the first embodiment using the measurement data relating to the refractive index distribution and the surface shape error of each lens. It has high accuracy and is effective for adjusting the final residual aberration of the projection optical system to a smaller value. However, in the second embodiment, it is necessary to take out a part of the lens from the lens barrel, correct the film thickness, and then re-integrate the lens into the lens barrel.

 Further, in the manufacturing method of the second embodiment, after the aberration measuring step S26, the determining step

Although 5 27 and the lens adjustment step S 28 are provided, these steps S 27 and S 28 can be omitted. That is, after the aberration measurement step S26, it is also possible to directly move to the lens removal step S29. After the aberration measurement step S32, a judgment step S33 and a lens adjustment step S34 are provided.

5 32 to S 34 can be omitted. That is, the manufacturing method of the second embodiment can be ended after the lens incorporating step S31.

 FIG. 18 is a flowchart showing a manufacturing flow of a method for manufacturing a projection optical system according to the third embodiment of the present invention. The manufacturing method of the third embodiment has a form in which the first embodiment and the second embodiment are partially combined. Hereinafter, the manufacturing method of the third embodiment will be briefly described, focusing on differences from the manufacturing method of the first embodiment and the manufacturing method of the second embodiment.

In the manufacturing method of the third embodiment, as in the first and second embodiments, the absolute value of the refractive index and the refractive index distribution of the block glass material are measured (S41), and the projection optical system 26 is mounted. After the surface of each lens is polished (S42) in order to manufacture each lens to be formed, an error in the surface shape of each lens is measured (S43). Next, similarly to the first embodiment, an antireflection film is formed on each lens whose surface shape error has been measured (S 4 4). That is, in the antireflection film forming step S44, in order to correct a wavefront error generated through each lens, an antireflection film having a predetermined thickness distribution is provided for each lens according to the manufacturing flow shown in FIG. Form a film. When an optical material having a sufficiently uniform refractive index distribution is used, the influence of the refractive index distribution can be neglected when the predetermined thickness distribution is applied.

 Then, the projection optical system 26 is assembled using a plurality of lenses on which the anti-reflection film having a predetermined thickness distribution is formed (S45). At this time, similarly to the first embodiment and the second embodiment, a large number of each lens to constitute the projection optical system is manufactured, and the projection optical system is manufactured based on the optimal combination selected from the manufactured many lenses. Can also be assembled. In this way, similarly to the first and second embodiments, the wavefront aberration of the actually assembled projection optical system is measured (S46). Then, it is determined whether or not the wavefront aberration of the projection optical system measured in the difference measuring step S46 is within the allowable range A (S47).

 If it is determined in the determination step S47 that the wavefront aberration of the projection optical system falls within the allowable range A (in the case of YES in FIG. 18), the process proceeds to the lens removal step S49. On the other hand, if it is determined in the determination step S47 that the wavefront aberration of the projection optical system does not fall within the allowable range A (NO in FIG. 18), the lens is adjusted (S48). However, in the lens adjustment step S48 of the third embodiment, as in the first embodiment, only the interval adjustment and the eccentricity adjustment are performed without performing the rotation adjustment. This is because the thickness distribution applied in the antireflection film forming step S44 is generally rotationally asymmetric with respect to the optical axis AX.

In the manufacturing method according to the third embodiment, the wavefront aberration of the projection optical system whose lens has been adjusted by the interval adjustment and the eccentricity adjustment is measured again (S46). Then, it is determined again whether the wavefront aberration of the projection optical system measured again in the aberration measurement step S46 falls within the allowable range A (S47). If it is determined in the determination step S47 that the wavefront aberration of the projection optical system falls within the allowable range A, the process proceeds to a lens removal step S49. However, if it is determined in the determination step S47 that the wavefront aberration of the projection optical system is not within the allowable range A, a determination of YES is made in the determination step S47. Until is obtained, the lens adjustment step S48 and the aberration measurement step S46 are further repeated.

 Next, in the manufacturing method of the third embodiment, some lenses suitable for correcting the wavefront aberration remaining in the projection optical system are taken out of the lens barrel (S49). Then, the thickness distribution of the anti-reflection film formed on the lens taken out of the lens barrel is corrected (S5).

0). That is, in the film thickness correction step S50, in order to correct the wavefront aberration remaining in the projection optical system, the measurement result of the refractive index distribution measurement step S41 and the measurement result of the surface shape measurement step S43 are used. Based on the final measurement result of the aberration measurement step S6, the thickness distribution of the antireflection film is corrected using, for example, ion beam processing. When an optical material having a sufficiently uniform refractive index distribution is used, the influence of the refractive index distribution can be ignored when correcting the thickness distribution.

 In this way, the lens whose thickness distribution of the anti-reflection film has been corrected is incorporated into the lens barrel (S 5

1) Then, the wavefront aberration of the projection optical system is measured (S52). Then, it is determined whether or not the wavefront aberration of the projection optical system measured in the aberration measurement step S52 falls within the allowable range B (S53). In the determination step S53, when it is determined that the wavefront aberration of the projection optical system falls within the allowable range B (YES in FIG. 18), the production of the projection optical system according to the third embodiment is stopped. finish. On the other hand, when it is determined in the determination step S53 that the wavefront aberration of the projection optical system is not within the allowable range B (in the case of NO in FIG. 18), the adjustment of the lens spacing and the eccentricity of the lens are performed. (S54).

In the manufacturing method according to the third embodiment, the wavefront aberration of the projection optical system adjusted by the distance adjustment and the eccentricity adjustment through the lens adjustment step S54 is measured again (S52). Then, it is determined again whether or not the wavefront aberration of the projection optical system measured again in the aberration measurement step S52 falls within the allowable range B (S53). If it is determined in the determination step S53 that the wavefront aberration of the projection optical system falls within the allowable range B, the manufacture of the projection optical system according to the third embodiment ends. However, if it is determined in the determination step S53 that the wavefront aberration of the projection optical system is not within the allowable range B, the lens adjustment step S53 is performed until a determination of YES is obtained in the determination step S53. 4 and the aberration measurement step S52 are further repeated. As described above, in the manufacturing method of the third embodiment, an antireflection film having a predetermined thickness distribution is formed on the surface of each lens in the same manner as in the first embodiment, and the same as in the second embodiment. First, the thickness distribution of the antireflection film formed on the surface of some lenses is corrected. Therefore, in the manufacturing method of the third embodiment, as in the first and second embodiments, even if there is a certain degree of refractive index distribution or surface shape error in each lens, for example, 1Οπι A projection optical system having an extremely low aberration of λ or less can be manufactured.

 In the exposure apparatus including the projection optical system manufactured by the manufacturing method according to each of the above-described embodiments, the mask (reticle) is illuminated by the illumination system (illumination step), and the transfer formed on the mask using the projection optical system is performed. By exposing a photosensitive pattern to a photosensitive substrate (exposure step), a micro device (semiconductor element, image pickup element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. The flow chart of FIG. 19 shows an example of a method 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 each embodiment. It will be described with reference to FIG.

First, in step 301 of FIG. 19, 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 wafer of the lot. Then, in step 303, using the exposure apparatus of each embodiment, an image of the pattern on the mask is sequentially exposed and transferred to each shot area on the one lot of wafers via the projection optical system. Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, etching is performed on the one lot of wafers using the resist pattern as a mask. A circuit pattern corresponding to the pattern on the mask is formed in each shot area on each wafer. After that, a device such as a semiconductor element is manufactured by forming a circuit pattern of a further upper layer and the like. According to the above-described semiconductor device manufacturing method, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput. In steps 301 to 305, a metal is deposited on the wafer, and a resist is applied on the metal film. Fabric, exposure, development, and etching steps are performed. Prior to these steps, a silicon oxide film is formed on the wafer, and then a resist is applied on the silicon oxide film and exposed. It goes without saying that the respective steps such as development, development and etching may be performed.

 Further, in the exposure apparatus of each embodiment, a liquid crystal display device 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. 20, in a pattern forming step 401, a so-called light beam is used to transfer and expose a mask pattern onto a photosensitive substrate (eg, a glass substrate coated with a resist) using the exposure apparatus of each embodiment. The liquidation process is performed. 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 is subjected to a developing process, an etching process, a resist stripping process, etc., thereby forming a predetermined pattern on the substrate, and then moving to the next color filter forming process 402. .

 Next, in the color filter forming step 402, a set of three dots corresponding to R (Red), G (Green), and B (B 1 ue) are arranged in a matrix, or , G, B are formed as a color filter in which a set of three stripe filters is arranged in a plurality of horizontal scanning line directions. Then, after the color filter forming step 402, a cell assembling step 403 is executed. In the cell assembling step 403, a liquid crystal panel is formed using the substrate having the predetermined pattern obtained in the pattern forming step 401 and the color filter obtained in the color filter forming step 402. (Liquid crystal cell). In the cell assembling step 403, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern forming step 401 and the color filter obtained in the color filter forming step 402. Then, a liquid crystal panel (liquid crystal cell) is manufactured.

Then, in the module assembling step 404, each part such as an electric circuit and a backlight for performing the display operation of the assembled liquid crystal panel (liquid crystal cell) is attached. Completed as a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display device, a liquid crystal display device having an extremely fine circuit pattern can be obtained with high throughput.

 In each of the embodiments described above, the anti-reflection film having a predetermined thickness distribution is formed on the surface of the lens, or the thickness distribution of the anti-reflection film formed on the surface of the lens is corrected. Produces an extremely low aberration optical system. However, in the present invention, it is possible to manufacture an optical system with extremely low aberration by controlling the thickness distribution of a general thin film formed on the surface of a lens without being limited to the antireflection film. it can.

 In each of the above embodiments, the present invention is applied to a method of manufacturing a projection optical system mounted on an exposure apparatus. However, the present invention is not limited to this. The present invention can also be applied to a method. Industrial applicability

 As described above, in the method of manufacturing an optical system according to the present invention, the thickness distribution of the thin film formed on the surface of the lens is formed by forming a thin film having a predetermined thickness distribution on the surface of the lens. By correcting this, even if there is a certain degree of refractive index distribution or surface shape error in each lens, it is possible to manufacture an optical system having an extremely low difference of, for example, 1 以下 πιλ or less due to wavefront aberration.

 Therefore, for example, the exposure apparatus of the present invention including an optical system having an extremely low wave aberration of 1Οπιλ or less as a projection optical system can perform favorable exposure with high resolution. Furthermore, for example, in the microdevice manufacturing method of the present invention using an exposure apparatus equipped with a projection optical system having an extremely low wavefront aberration of 1ππιλ or less, a high resolution and a good microdevice under favorable exposure conditions are provided. Can be manufactured.

Claims

The scope of the claims 1. In a method for manufacturing an optical system having at least one lens,  A refractive index distribution measuring step of measuring a refractive index distribution in the optical material forming the at least one lens;  A surface shape measurement step of measuring a surface shape of the at least one lens; and an optical error of the at least one lens based on a measurement result of the refractive index distribution measurement step and a measurement result of the surface shape measurement step. The calculation process to be determined;  A correction film forming step of forming a thin film having a predetermined thickness distribution on the surface of the at least one lens based on a calculation result of the calculation step. 2. In the method for manufacturing an optical system according to claim 1,  The calculating step includes a wavefront error calculating step of calculating a wavefront error generated through the at least one lens based on at least the measurement result of the refractive index distribution measuring step and the measurement result of the surface shape measuring step,  A thickness distribution calculating step of calculating a thickness distribution of a thin film to be formed on the surface of at least one lens to correct the wavefront error based on the calculation result of the wavefront error calculating step.  The correction film forming step includes forming a thin film having a predetermined thickness distribution on a surface of the at least one lens based on a calculation result of the thickness distribution calculating step. Production method. 3. The method of manufacturing an optical system according to claim 1 or 2, wherein the correcting film forming step includes: forming a thin film on a surface of the at least one lens; A method of correcting the thickness distribution of the thin film formed in the thin film forming step. 4. In the method for manufacturing an optical system according to any one of claims 1 to 3,  Prior to the calculating step, further comprising: a thin film forming step of forming a thin film on the surface of the at least one lens; and a wavefront error measuring step of measuring a wavefront error generated via the at least one lens,  The calculating step includes correcting the wavefront error based on the measurement result of the refractive index distribution measurement step, the measurement result of the surface shape measurement step, and the measurement result of the wavefront error measurement step. A method for producing an optical system, comprising: calculating a thickness distribution of a thin film to be formed on a surface of a substrate. 5. The method for manufacturing an optical system according to any one of claims 1 to 4, wherein  An assembling step of assembling an optical system using the at least one lens after the correcting film forming step;  An aberration measuring step of measuring the aberration of the optical system assembled in the assembling step; and correcting a thickness distribution of a thin film formed on a surface of the at least one lens based on a measurement result of the aberration measuring step. 2. A method for manufacturing an optical system, comprising: a film thickness correction step. 6. The method of manufacturing an optical system according to any one of claims 1 to 4, wherein  An assembling step of assembling an optical system using the at least one lens after the correcting film forming step;  A first aberration measurement step of measuring aberration of the optical system assembled in the assembly step, A lens adjustment step of adjusting the at least one lens based on a measurement result of the first aberration measurement step; A second aberration measurement step for measuring the aberration of the optical system adjusted in the lens adjustment step;  A second film thickness correcting step of correcting a thickness distribution of a thin film formed on a surface of the at least one lens based on a measurement result of the second aberration measuring step. Method. 7. The method for manufacturing an optical system according to any one of claims 1 to 6, wherein  The thin film includes a multilayer film,  The method of manufacturing an optical system, wherein the correcting film forming step adds a correction amount of 15% or less of a film thickness of an outermost layer of the multilayer film. 8. In a method of manufacturing an optical system having a plurality of lenses,  An assembling step of assembling an optical system using the plurality of lenses,  An aberration measuring step of measuring an aberration of the optical system assembled in the assembling step; and at least one of the plurality of lenses based on a measurement result of the aberration measuring step. A film thickness correcting step of correcting a thickness distribution of a thin film formed on the surface of one lens. 9. In the method for manufacturing an optical system according to claim 8,  A member measuring step of measuring at least one of a refractive index distribution of each optical material forming each of the plurality of lenses and a surface shape of each of the plurality of lenses;  The film thickness correction step includes: calculating a thickness distribution of a thin film formed on a surface of at least one of the plurality of lenses based on a measurement result of the aberration measurement step and a measurement result of the member measurement step. A method for manufacturing an optical system, comprising correcting. 10. In a method of manufacturing an optical system having a plurality of lenses, An assembling step of assembling an optical system using the plurality of lenses,  A first aberration measurement step of measuring aberration of the optical system assembled in the assembly step,  A lens adjustment step of adjusting at least one lens in the optical system based on the measurement result of the first aberration measurement step;  A second aberration measurement step for measuring the aberration of the optical system adjusted in the lens adjustment step;  A film thickness correction step of correcting a thickness distribution of a thin film formed on a surface of at least one of the plurality of lenses based on a measurement result of the second aberration measurement step. Optical system manufacturing method. 11. The method for manufacturing an optical system according to claim 10, wherein:  A member measuring step of measuring at least one of a refractive index distribution of each optical material forming each of the plurality of lenses and a surface shape of each of the plurality of lenses;  The film thickness correction step includes a thickness distribution of a thin film formed on a surface of at least one of the plurality of lenses based on a measurement result of the second aberration measurement step and a measurement result of the member measurement step. A method of manufacturing an optical system, wherein 12. The method for manufacturing an optical system according to claim 10 or 11, wherein the lens adjusting step comprises: moving at least one lens in the optical system along an optical axis of the optical system. A movement adjusting step of moving; a shift adjusting step of shifting at least one lens in the optical system along a direction intersecting with the optical axis; and at least one lens in the optical system with respect to the optical axis. A method for manufacturing an optical system, comprising: at least one of a tilt adjusting step of tilting the lens relative to the optical system and a rotation adjusting step of rotating at least one lens in the optical system around the optical axis. 13. The method of manufacturing an optical system according to any one of claims 8 to 12. In the law,  Prior to the assembling step, a lens manufacturing step of manufacturing a plurality of lenses to constitute the optical system;  A lens shape measuring step of measuring information on the shapes of the plurality of lenses manufactured in the lens manufacturing step;  A selection step of selecting a plurality of lenses that should constitute the optical system from the plurality of lenses measured in the lens shape measurement step;  A prediction evaluation step of predicting and evaluating the optical performance of the optical system based on the measurement information on the shapes of the plurality of lenses selected in the selection step,  The method further includes a repetition step of repeating the selection step and the prediction evaluation step until an optimal combination of a plurality of lenses whose optical performance predicted by the prediction evaluation step is acceptable is determined. A method for producing an optical system, comprising: 1. In the method for manufacturing an optical system according to any one of claims 8 to 13,  The thin film includes a multilayer film,  The method of manufacturing an optical system, wherein the correcting film forming step adds a correction amount of 15% or less of a film thickness of an outermost layer of the multilayer film. 15. An optical system manufactured by the manufacturing method according to any one of claims 1 to 14. 1 6. An illumination optical system for illuminating a mask on which a predetermined pattern is formed,  An optical system manufactured by the manufacturing method according to any one of claims 1 to 14 for projecting a pattern image of the mask onto a photosensitive substrate. An exposure apparatus characterized by the following. 17. The pattern of the mask is formed by using the exposure apparatus according to claim 16. An exposure step of exposing the photosensitive substrate,  A developing step of developing the photosensitive substrate exposed in the exposing step.