JP2002208549A - Exposure apparatus adjustment method and micro device manufacturing method - Google Patents

Abstract

(57) Abstract: A method of adjusting an exposure apparatus that satisfactorily corrects deterioration of imaging performance of a projection optical system caused by a change in physical properties of an optical member due to irradiation of a pulse laser beam. A method of adjusting an exposure apparatus including a projection optical system (PL) for forming a pattern image of a reticle (R) illuminated by a pulsed laser beam on a photosensitive substrate (W). The number of pulses of the laser light and the optical characteristics of the projection optical system are measured, and at least one of a refractive index change and a volume change of at least one optical member in the projection optical system is calculated. In order to correct the deterioration of the imaging performance of the projection optical system caused by the irradiation of the laser light onto the projection optical system, the rotation amount of at least one optical member in the projection optical system is calculated. Rotating and adjusting at least one optical member in the projection optical system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for adjusting an exposure apparatus and a method for manufacturing a micro device. More specifically, the present invention relates to adjustment of a projection optical system suitable for 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 by a photolithography process.

[0002]

2. Description of the Related Art In a photolithography process for manufacturing a semiconductor device or the like, a pattern on a photomask or a reticle (hereinafter collectively referred to as a "reticle") is formed on a photosensitive substrate such as a wafer through a projection optical system. An exposure apparatus for exposing upward is used. In this type of exposure apparatus, the wavelength of exposure light is shortened in response to integration of chip patterns such as semiconductor elements. Currently, as a light source,
The mainstream is shifting from a KrF excimer laser that supplies light having a wavelength of 248 nm to an ArF excimer laser that supplies light having a wavelength of 193 nm.

Incidentally, an optical material having a sufficient transmittance in the ultraviolet wavelength region of 250 nm or less, ie, 250 nm
Quartz (synthetic quartz) and fluorite are known as optical materials that can be used in an exposure apparatus that uses the following exposure light. Here, when comparing quartz and fluorite, quartz has a higher refractive index than fluorite. Also, quartz is cheaper and easier to mass-produce than fluorite. Furthermore, quartz is harder and easier to handle than fluorite. As a result, quartz is used much more frequently than fluorite, and is an essential optical material for forming a projection optical system.

On the other hand, in an exposure apparatus, it is required to transfer a larger reticle pattern to each exposure area (each shot area) on a wafer in order to cope with an increase in the size of a chip pattern of a semiconductor element or the like. Therefore, while the reticle pattern in the rectangular illumination area is projected onto the wafer via the projection optical system, the reticle pattern is projected onto each shot area on the wafer while the reticle and the wafer are synchronously scanned with respect to the projection optical system. The so-called step-and-scan method, in which exposure is performed sequentially, has become mainstream.

In a step-and-scan type exposure apparatus, that is, a scanning exposure type exposure apparatus, a wafer is scanned with respect to a slit-like (elongated rectangular) effective exposure area substantially inscribed in an effective exposure field of a projection optical system. While performing exposure. Therefore, when setting the slit-like effective exposure area, the circular effective exposure field of the projection optical system can be used to the maximum. Further, the length of the transfer pattern to each shot area along the scanning direction can be set longer than the diameter of the effective exposure field.
As a result, in a scanning exposure type exposure apparatus, a large area reticle pattern can be transferred onto a wafer in a favorable aberration state.

Further, by rotating a pair of optical members (that is, a pair of anamorphic lenses) provided in the projection optical system and having an anamorphic optical surface relatively, two straight lines orthogonal to each other on the wafer surface. A method for correcting aberrations symmetric with respect to has been proposed. Specifically, in Japanese Patent Application Laid-Open No. 7-183190, a plurality of lenses having a toric surface are provided in a projection optical system, and rotationally asymmetric aberrations caused by absorption of heat generated by use of the projection optical system are eliminated. A correction technique is disclosed.

[0007]

However, in quartz, the internal atomic arrangement changes slightly due to the accumulation of the irradiated pulsed laser energy (number of pulses and illuminance), whereby the optical refractive index and the volume ( It is known that the density (and thus the density) slightly changes. Among these, the phenomenon that the refractive index increases and the volume decreases (density increases) due to laser irradiation has been known as radiation compaction (hereinafter simply referred to as "compaction") (J. Opt. Soc. Am. B vol.14, P1606-1615, Borrelli e
t. al., Optics Letters Dec-1996D.C. Allan et.al.
See).

Recently, when a relatively small amount of laser is irradiated as in a projection optical system mounted on an exposure apparatus, the phenomenon that the refractive index decreases and the volume increases (density decreases) is a rare phenomenon. Also known as rarefaction (Micro-lithography Conference, Santa Clara
Mar. 2000). The amount of change in refractive index and volume due to laser irradiation also depends on the characteristics (properties) of the individual quartz samples, but considering the illuminance used in the projection optical system, at most 10 ^{− with} respect to the original value. ^This is on the order of ^six times, and is generally not large.

However, this value cannot be ignored in an optical system such as a projection optical system that requires very high optical performance. That is, when the refractive index change and the density (volume) change of this degree occur in the optical member constituting the projection optical system, the outer shape of the optical member changes, and the refractive index distribution in the optical member becomes uneven. become. As a result, when performing exposure using the projection optical system, there is a disadvantage that various aberrations occur depending on the position of the optical member made of quartz.

In particular, in a scanning exposure type exposure apparatus,
Since laser irradiation is performed on a rectangular illumination area on the reticle, a rotationally asymmetric illuminance distribution is formed on most of the optical members in the projection optical system from the reticle to the wafer. As a result, the change in refractive index and the change in density occurring in the optical member made of quartz also become rotationally asymmetric, and the resulting aberration also becomes rotationally asymmetric.

In this case, it is impossible to correct this kind of rotationally asymmetric aberration with a conventional adjusting mechanism that changes the distance between the optical members. In a single optical axis projection optical system in which the effective exposure area is set around the optical axis,
Both the illuminance distribution and the change in physical properties (change in refractive index and change in volume) of the optical member are kept substantially symmetric with respect to two axes orthogonal to each other in a plane perpendicular to the optical axis. Therefore, even in an adjustment mechanism that performs eccentric shift (movement in the direction orthogonal to the optical axis) or eccentric tilt (inclination with respect to the optical axis) of the optical member, one of two axes orthogonal to each other in a plane perpendicular to the optical axis. Since the symmetry is maintained only with respect to the axis, it is impossible to correct the rotationally asymmetric aberration described above.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to satisfactorily correct the deterioration of the imaging performance of a projection optical system caused by a change in physical properties of an optical member due to irradiation of a pulse laser beam. It is an object of the present invention to provide a method of adjusting an exposure apparatus which can be performed. Further, there is provided a microdevice manufacturing method capable of manufacturing a good microdevice using an exposure apparatus in which deterioration of the imaging performance of a projection optical system caused by irradiation with a pulsed laser beam has been well corrected. The purpose is to:

[0013]

According to a first aspect of the present invention, there is provided a projection optical system for forming a pattern image of a reticle illuminated by a pulsed laser beam on a photosensitive substrate. A measuring step of measuring the number of pulses of the laser beam and optical characteristics of the projection optical system, and at least one optical member in the projection optical system based on a measurement result of the measurement step. A first calculation step of calculating at least one of a change in refractive index and a change in volume with respect to the projection optical system, and to correct deterioration of the imaging performance of the projection optical system caused by irradiation of the projection optical system with the laser light. A second calculating step of calculating a rotation amount of at least one optical member in the projection optical system based on a calculation result of the first calculating step; Based on the extent of the calculation result, to provide a method of adjusting an exposure apparatus which comprises a rotary adjustment step of adjusting by rotating at least one optical element in the projection optical system.

According to a preferred aspect of the first invention, the first calculating step includes the step of irradiating a laser beam having a wavelength of 250 nm or less with a change in refractive index of an optical member whose physical property changes in at least one of a refractive index and a density. At least one of the volume changes is calculated. Further, the second calculating step calculates a relative rotation amount of a pair of anamorphic optical members provided in the projection optical system and having an anamorphic optical surface, and the rotation adjusting step includes: It is preferable to rotate at least one of them to adjust. Further, the second calculating step calculates a rotation amount of at least one optical block provided in the projection optical system and including a plurality of the optical members, and the rotation adjusting step includes rotating the at least one optical block. It is preferable to adjust it.

According to a second aspect of the present invention, there is provided a method for adjusting an exposure apparatus having a projection optical system for forming a pattern image of a reticle illuminated by a pulsed laser beam on a photosensitive substrate. And a measuring step of measuring optical characteristics of the projection optical system, and at least one of the projection optical system based on a measurement result of the measurement step.
A calculating step of calculating at least one of a refractive index change and a volume change of one optical member, and correcting a deterioration of an imaging performance of the projection optical system caused by the irradiation of the laser light to the projection optical system. A selecting step of selecting at least one optical member to be replaced in the projection optical system based on a calculation result of the calculating step; and an exchange in the projection optical system based on a result of the selecting step. A replacement adjustment step of replacing at least one optical member to be replaced with another optical member and adjusting the optical member.

According to a preferred aspect of the second invention, the first calculating step includes the step of irradiating a laser beam having a wavelength of 250 nm or less with a change in the refractive index of an optical member whose physical property changes in at least one of the refractive index and the density. At least one of the volume changes is calculated. In the selecting step, at least one optical block provided in the projection optical system and including a plurality of the optical members is selected as an optical block to be replaced, and the replacement adjusting step includes selecting the at least one optical element. It is preferable to adjust the block by replacing it with another optical block.

According to a third aspect of the present invention, there is provided an exposure step of exposing the pattern of the reticle onto the photosensitive substrate using an exposure apparatus adjusted by the adjustment method of the first or second aspect, and And a developing step of developing the exposed photosensitive substrate.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, compaction is a phenomenon in which atoms are rearranged in quartz due to deep ultraviolet light and physical properties of quartz are changed. There are various theories about the detailed physical phenomena, and they are not clearly understood. However, the relational expressions for the refractive index change and the volume change (density change) due to pulsed laser irradiation have been measured experimentally in many papers and are considered to be reliable. Note that each constant in the equation varies depending on experiments, samples, and hypotheses, but using any value does not significantly affect the simulation described below. ing.

In general, the relationship between laser irradiation and change in refractive index is expressed by the following equation (1). Δn / n = κ ₁ (N · I ² ) ^α (1) where n is the refractive index of the substance and Δn is the amount of change in the refractive index. Therefore, Δn / n is the refractive index change rate. In the present invention, the refractive index of quartz with respect to the wavelength of ArF excimer laser light (193 nm) is n = 1.560.
326 is set. Κ ₁ is a proportionality constant, which is set to 2.3 × 10 ⁻¹¹ in the present invention. Further, N is the number of pulses (cumulative pulses) of laser irradiation, and I is the illuminance (mJ / cm ² / pulse) per pulse. Α is a power coefficient, and in the present invention, α is 0.6.
Is set.

The relationship between the change in the refractive index and the change in the density is
It is considered to be expressed by the Lorentz-Lorentz relational expression. The Lorentz-Lorentz expression is differentiated and expressed by the following expression (2). Δn = {(n ² −1) (n ² +2) / 6n} (1 + Ω) (Δρ / ρ) (2) where Ω is a constant depending on the substance, and Ω = −0 in the case of quartz. .15. Ρ is the density of the substance, and Δρ is the density change. Therefore,
Δρ / ρ is the density change rate.

The relationship between the change in density and the change in volume is naturally expressed by the following equation (3). ΔV / V = −Δρ / ρ (3) where V is the volume of the substance, and ΔV is the amount of change in the volume. Therefore, ΔV / V is the volume change rate.

By substituting n = 1.560326 into the above equation (2), the following equation (4) is obtained. Δn = 0.577623 (Δρ / ρ) (4)

Referring to equations (1) and (4), the following equation (5) is obtained. ΔV / V = −6.213 × 10 ⁻¹¹ (N · I ² ) ^0.6 (5)

In order to simulate the influence of a change in the physical properties of a quartz lens (a lens made of quartz) due to compaction on the imaging performance of the projection optical system, reference is made to these relational expressions (1) to (5) and an optical evaluation is made. What is necessary is just to calculate by combining software and the finite element method software of an elastic body. As described above, in the case of laser irradiation with low illuminance such that it is used in an exposure apparatus, a rare faction phenomenon in which the refractive index of quartz decreases and the volume increases (density decreases) has recently been reported. However, the details have not been fully elucidated yet.

However, even in the case where this rare-faction phenomenon occurs, the calculation can be performed by combining the optical evaluation software and the finite element method software for the elastic body as in the case of the compaction, and the analysis method is exactly the same. Therefore, it can be considered similarly to compaction.
Furthermore, if calculation is performed for compaction, if a rare faction occurs, simply reverse the sign of the calculation result and apply a predetermined constant, and immediately predict the calculation result for the rare faction. And no need to recalculate. Therefore, in the present invention, only a simulation in the case of compaction will be described as an example.

FIG. 1 is a flowchart schematically showing a simulation procedure according to the present invention. Hereinafter, the simulation procedure according to the present invention will be outlined with reference to FIG. First, in the present invention, the illuminance distribution on each surface of each quartz lens is calculated (S11). Specifically, an average illumination condition is assumed, and the illuminance I and the number of irradiation pulses (the number of accumulated pulses) N on the photosensitive substrate in one pulse are measured. Then, based on the assumed average illumination conditions and the measured illuminance I, calculate what illuminance distribution the exposure light through the reticle forms on each surface of each quartz lens in the middle. This calculation is possible by combining the functions of ordinary optical evaluation software.

Next, the initial volume change rate of each finite element of each quartz lens is calculated (S12). Specifically, the data of each quartz lens is taken into finite element analysis software, and each quartz lens is divided into an appropriate number of finite elements. The initial volume change rate ΔV / V of each finite element is calculated by substituting the measured irradiation pulse number N and illuminance I into the above-described relational expression (5). Here, the initial volume change rate is defined assuming that each finite element constituting one quartz lens is spatially independent of each other, and that the volume change is not affected by the adjacent finite element at all. Is the rate of change in volume.

Next, the final volume change rate of each finite element of each quartz lens is calculated (S13). As described above, the volume change rate calculated in step S12 assumes that each finite element is spatially independent, but in practice, each finite element dynamically acts as an elastic body with each other. Matching. Therefore, the actual volume change rate of each finite element in consideration of the influence of the adjacent finite element, that is, the final volume change rate is obtained by, for example, calculating the initial volume change rate calculated in step S12 using the initial temperature distribution. And equivalent replacement (analogy)
Then, it is obtained by conducting a heat conduction analysis of the elastic body. Of course, other calculation methods are also possible, and an appropriate calculation method may be determined according to the function of the finite element analysis software.

Further, a change in the refractive index of each finite element of each quartz lens is calculated (S14). Specifically, step S13
The refractive index change Δn of each finite element is calculated based on the final volume change rate of each finite element calculated in the above and the above-mentioned relational expressions (2) and (3).

Finally, the wavefront aberration of the projection optical system is calculated (S15). Specifically, the data of the volume change rate calculated in step S13 and the data of the refractive index change calculated in step S14 are taken into the optical evaluation software as the data of the surface change and the data of the refractive index distribution, The wavefront aberration of the projection optical system is calculated, and the deterioration of the imaging performance of the projection optical system is evaluated.

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a diagram schematically showing a configuration of the exposure apparatus according to the present embodiment. In FIG. 2, the Z axis is set in parallel with the optical axis AX of the projection optical system PL, the Y axis is set in parallel with the plane of FIG. 2 in the plane perpendicular to the optical axis AX, and the X axis is set perpendicular to the plane of FIG. ing. The illustrated exposure apparatus includes an ArF excimer laser light source (oscillation center wavelength: 193.306 nm) as the light source 1 for supplying illumination light in the ultraviolet region.

The light emitted from the light source 1 illuminates a reticle (mask) R on which a predetermined pattern is formed via a first illumination optical system 2a and a second illumination optical system 2b. The illumination optical system 2 (2a and 2b) includes an optical integrator (an internal reflection type rod member, a fly-eye lens, and a microlens array) that forms a secondary light source having a predetermined shape and size based on light from the light source 1. , A diffractive optical element, etc.), a field stop that defines an illumination area on the reticle R, and an imaging optical system that projects an image of the field stop onto the reticle R.

The reticle R is a reticle holder (not shown).
Are held on reticle stage RST in parallel to the XY plane. A pattern to be transferred is formed on the reticle R, and a rectangular pattern area having a long side along the X direction and a short side along the Y direction in the entire pattern area is illuminated. The reticle stage RST can be moved two-dimensionally along the reticle plane (ie, XY plane) by the action of a drive system (not shown), and its position coordinates are measured by an interferometer RIF using a reticle moving mirror RM. And the position is controlled.

The light from the pattern formed on reticle R forms a reticle pattern image on wafer W as a photosensitive substrate via projection optical system PL. The wafer W is placed on a wafer stage WST via a wafer holder (not shown).
Above, it is held parallel to the XY plane. And
On the wafer W, a pattern is formed on a rectangular exposure area having a long side along the X direction and a short side along the Y direction so as to correspond optically to the rectangular illumination area on the reticle R. An image is formed. Wafer stage WST can be moved two-dimensionally along the wafer surface (ie, XY plane) by the action of a drive system (not shown), and its position coordinates are measured by interferometer WIF using wafer moving mirror WM. In addition, the position is controlled.

FIG. 3 is a diagram showing a positional relationship between a rectangular effective exposure area formed on a wafer in this embodiment and an effective exposure field of the projection optical system. As shown in FIG. 3, in the present embodiment, a radius Y0 around the optical axis AX is set.
In a circular effective exposure field (image field) IF having (corresponding to the maximum image height), a rectangular effective exposure area ER is set around the optical axis AX. Here, the length in the X direction of the effective exposure area ER is LX, and the length in the Y direction is LY. Therefore, on the reticle R, a rectangular illumination area having a size and a shape corresponding to the rectangular effective exposure area ER centered on the optical axis AX is formed.

As described above, the illumination area on the reticle R and the effective exposure area ER on the wafer W are rectangular with short sides along the Y direction. Therefore, while controlling the position of the reticle R and the wafer W using the drive system and the interferometers (RIF, WIF), the reticle stage along the short side direction of the rectangular effective exposure region ER and the illumination region, that is, the Y direction. RST and wafer stage WST
And thus the reticle R and the wafer W are synchronously moved (scanned), so that the wafer W has a width equal to the long side of the effective exposure area ER and the scanning amount (movement amount) of the wafer W The reticle pattern is scan-exposed to an area having a length corresponding to.

The exposure apparatus shown in FIG.
An integrator sensor 3 for detecting the integrated light amount in the inside and an illuminance sensor 4 for monitoring the light amount on the wafer W are provided. Although not shown, an internal sensor for detecting light energy from the light source 1 is provided inside the excimer laser light source 1. In this way, the number of pulses of the excimer laser light (the number of accumulated pulses up to the time of measurement) N is counted based on the output of the integrator sensor 3.
The illuminance I on the wafer W in one pulse is determined by the output of an internal sensor built in the excimer laser light source 1, the output of the integrator sensor 3 in the illumination optical system 2, and the illuminance provided at the height position of the wafer W. It is measured based on the output of the sensor 4 and the like.

FIG. 4 is a diagram showing a lens configuration of a projection optical system according to this embodiment. As shown in FIG. 4, the projection optical system PL includes, in order from the object side (reticle side), a first partial optical system G1, an aperture stop AS arranged at the entrance pupil position of the projection optical system PL, and a second partial optical system G1. And an optical system G2.

The first partial optical system G1 includes, in order from the reticle side, a biconcave lens L11, a biconvex lens L12, a biconvex lens L13, a biconvex lens L14, a negative meniscus lens L15 having a convex surface facing the reticle side, Convex lens L1
6, a biconcave lens L17, a biconcave lens L18, a biconcave lens L19, a positive meniscus lens L110 having a concave surface facing the reticle side, a negative meniscus lens L111 having a concave surface facing the reticle side, and a concave surface facing the reticle side. Positive meniscus lens L112, biconvex lens L113,
Biconvex lens L114, positive meniscus lens L115 with convex surface facing reticle side, negative meniscus lens L116 with convex surface facing reticle side, negative meniscus lens L117 with convex surface facing reticle side, and biconcave lens L11
8, a biconcave lens L119, and a biconvex lens L120.

The second partial optical system G2 includes, in order from the reticle side, a positive meniscus lens L21 having a concave surface facing the reticle side, a biconvex lens L22, a negative meniscus lens L23 having a concave surface facing the reticle side, and a reticle. A positive meniscus lens L24 having a convex surface facing the reticle side; a positive meniscus lens L25 having a convex surface facing the reticle side; a positive meniscus lens L26 having a convex surface facing the reticle side; and a negative meniscus lens L27 having a convex surface facing the reticle side. , A positive meniscus lens L28 having a convex surface facing the reticle side, and a positive meniscus lens L29 having a convex surface facing the reticle side. The positive meniscus lens L115, the biconvex lens L120, the biconvex lens L22, the positive meniscus lens L25, and the positive meniscus lens L26 are formed of fluorite. Other lenses are made of quartz.

The following Table (1) lists values of specifications of the projection optical system according to the present embodiment. In the main specifications of Table (1), λ is the central wavelength of the exposure light, β is the projection magnification, NA is the image-side (wafer-side) numerical aperture, and Y0 is the radius of the image circle IF on the wafer W, ie, The maximum image height LX is the dimension (long side dimension) of the effective exposure area ER along the X direction.
LY represents a dimension (short side dimension) of the effective exposure region ER along the Y direction.

Further, in the optical member specifications in Table (1),
The surface number of the first column is the order of the surface from the reticle side, r of the second column is the radius of curvature (mm) of each surface, and d of the third column is the axial spacing of each surface, that is, the surface spacing (mm). To the fourth
In column n0, the refractive index for the center wavelength of 193.306 nm, and in the fifth column, n + is 193.306 nm + 0.
The refractive index for 56 pm = 193.306656 nm is
N- in the sixth column is 193.306 nm-0.56 pm
= 193.33054 nm, and φ in the seventh column indicates the effective diameter (radius: mm).

[0043]

(Main Specifications) λ = 193.306 nm β = − ／ NA = 0.68 Y0 = 13.1 mm LX = 25 mm LY = 8 mm (Optical member specifications) Surface number r d n0 n + n− φ Optical member (reticle surface) 66.162 1 -367.754 14.217 1.560326 1.560325 1.560327 65.5 (L11) 2 253.076 25.089 72.5 3 420.051 28.056 1.560326 1.560325 1.560327 84.0 (L12) 4 -392.653 1.000 84.0 5 1007.299 25.948 1.560326 1.560325 1.560327 88.0 (L13) 6 343.807 1.000 88.0 7 311.267 26.246 1.560326 1.560325 1.560327 89.0 (L14) 8 -1400.000 1.000 89.0 9 157.459 23.000 1.560326 1.560325 1.560327 83.5 (L15) 10 116.402 30.731 74.5 11 546.080 26.087 1.560326 1.560325 1.560327 73.0 (L16) 122.179 17.000 1.560326 1.560325 1.560327 69.0 (L17) 14 143.035 23.017 60.0 15 -220.246 18.050 1.560326 1.560325 1.560327 59.5 (L18) 16 235.901 25.938 63.5 17 -122.420 16.000 1.560326 1.560325 1.56 0327 61.5 (L19) 18 970.000 14.557 75.5 19 -304.434 23.449 1.560326 1.560325 1.560327 75.5 (L110) 20 -162.839 10.070 82.0 21 -129.805 24.650 1.560326 1.560325 1.560327 82.5 (L111) 22 -177.511 1.000 97.5 23 -538.404 38.931 1.560326 1.560325 1.5603 L112) 24 -192.482 1.000 112.5 25 1793.041 36.647 1.560326 1.560325 1.560327 125.0 (L113) 26 -412.867 1.000 125.0 27 446.034 35.081 1.560326 1.560325 1.560327 126.5 (L114) 28 -2797.707 1.000 126.5 29 198.481 46.284 1.501455 1.501454 1.501455 119.0 (1151) 116.0 31 195.568 25.602 1.560326 1.560325 1.560327 106.0 (L116) 32 139.874 15.219 91.5 33 209.108 19.052 1.560326 1.560325 1.560327 91.0 (L117) 34 132.321 41.343 81.0 35 -280.949 18.000 1.560326 1.560325 1.560327 80.5 (L118) 36 334.482 34.603 21. 1.560327 80.5 (L119) 38 1243.197 1.003 94.5 39 962.439 45.911 1.501455 1.501454 1.501455 97.5 (L120) 40 -194.157 32.8 83 97.5 41 ∞ 30.000 104.0 (AS) 42 -2946.077 28.888 1.560326 1.560325 1.560327 114.0 (L21) 43 -411.107 1.000 114.0 44 309.494 54.314 1.501455 1.501454 1.501455 120.0 (L22) 45 -489.467 9.157 120.0 46 -333.069 25.000 1.560326 1.560325 1.560327 12 ) 47 -665.018 1.225 120.5 48 290.408 36.784 1.560326 1.560325 1.560327 118.0 (L24) 49 2707.107 1.000 114.5 50 164.070 41.449 1.501455 1.501454 1.501455 104.0 (L25) 51 432.975 1.000 104.0 52 136.275 37.320 1.501455 1.501454 1.501455 85.5 525.5825.55 21.221 1.560326 1.560325 1.560327 73.5 (L27) 55 77.652 6.342 53.0 56 88.563 39.020 1.560326 1.560325 1.560327 53.0 (L28) 57 362.173 2.696 40.0 58 383.182 25.000 1.560326 1.560325 1.560327 38.0 (L29) 59 ∞ 13.230 27.5 (Wafer surface)

FIG. 5 is a diagram showing spherical aberration, astigmatism, and distortion of the projection optical system in the present embodiment. FIG. 6 is a diagram illustrating coma aberration in a tangential plane and coma aberration in a sagittal plane of the projection optical system according to the present embodiment. In each aberration diagram, NA indicates the image-side numerical aperture, and Y indicates the image height. As is clear from the aberration diagrams, in the projection optical system according to the present embodiment, various aberrations are satisfactorily corrected, and excellent optical performance is secured.

FIG. 7 is a diagram showing the wavefront aberration of the projection optical system according to the present embodiment by contour lines in units of 0.01λ. As shown in FIG. 7, RMS (root means square) of the wavefront aberration at the center point CE (coincident with the optical axis AX: see FIG. 3) of the effective exposure area ER of the projection optical system PL.
The value is 0.005λ. Further, the RMS value of the wavefront aberration at each of the peripheral points UC, CR, and UR (see FIG. 3) of the effective exposure area ER of the projection optical system PL is 0.0
05λ, 0.008λ and 0.009λ. As described above, it can be seen that the RMS value of the wavefront aberration is corrected to 0.01λ or less over the entire effective exposure area ER of the projection optical system PL.

As described above, in the exposure operation of the present embodiment, by repeating the irradiation of the pulse laser light onto the projection optical system PL many times, phenomena such as compaction and rare faction occur, and the quartz lens Changes in refractive index and density. As a result, the imaging performance (wavefront aberration) of the projection optical system PL deteriorates with the change in the physical properties of the quartz lens. Therefore, in the present embodiment, by performing the following first adjustment method or second adjustment method, the imaging performance of the projection optical system PL deteriorates due to a change in the physical properties of the optical member due to the irradiation of the pulse laser beam. Is corrected.

FIG. 8 is a flowchart schematically showing an adjustment flow of the first adjustment method in the present embodiment. Referring to FIG. 8, in the first adjustment method, the number N of irradiation pulses of laser light and the illuminance I on the wafer W for one pulse are measured (S21). Here, the number of irradiation pulses (the number of accumulated pulses up to the time of measurement) N is determined by the illumination optical system 2 as described above.
Is measured based on the output of the integrator sensor 3 as a detector for detecting the integrated light quantity. The illuminance I as an optical characteristic of the projection optical system PL is measured based on an output of an internal sensor of the excimer laser light source 1, an output of the integrator sensor 3, an output of the illuminance sensor 4, and the like.

Next, based on the measurement result of the measurement step S21, that is, the illuminance I on the wafer W, the illuminance distribution (energy distribution) on the optical surface of each quartz lens (each quartz optical member) constituting the projection optical system PL. Is calculated according to the simulation procedure S11 described with reference to FIG. 1 (S2
2). As described above, in an optical member made of an optical material other than quartz (fluorite in this embodiment), physical properties do not change due to compaction or rare faction. It is not necessary to determine the illuminance distribution on the member.

Next, based on the measurement result of the measurement step S21, that is, the number N of irradiation pulses, and the calculation result of the calculation step S22, that is, the illuminance distribution on the optical surface of each quartz lens, the volume change and the refractive index change of each quartz lens are obtained. Is calculated according to the simulation procedures S12 to S14 described with reference to FIG. 1 (S23). In addition, the wavefront aberration of the projection optical system PL is calculated based on the calculation result of the calculation step S23, that is, the volume change and the refractive index change of each quartz lens (S24). Then, it is determined whether or not the wavefront aberration calculated in the calculation step S24 can be permitted (S2).
5).

In the determining step S25, the calculating step S24
If it is determined that the wavefront aberration calculated in (1) can be tolerated (YES in the figure), the first adjustment method is terminated,
The operation proceeds to the exposure operation. On the other hand, in the determination step S25,
When it is determined that the wavefront aberration calculated in the calculation step S24 cannot be tolerated (NO in the figure), the first adjustment method is continued, and the process proceeds to the adjustment amount calculation step S26. In the adjustment amount calculation step S26, a required rotation amount of the quartz lens to be rotated and adjusted is calculated based on the calculation result of the calculation step S23, that is, the volume change and the refractive index change of each quartz lens.

Finally, based on the calculation result of the adjustment amount calculation step S26, the quartz lens to be rotationally adjusted is adjusted by rotating the quartz lens about its optical axis by a required angle (S27). Thus, in the first adjustment method, the wavefront aberration of the projection optical system PL deteriorates due to the physical property change (change in refractive index and density) of each quartz lens caused by irradiation of the projection optical system PL with the pulsed laser beam ( As a result, deterioration of the imaging performance) can be satisfactorily corrected.

FIG. 9 is a flowchart schematically showing an adjustment flow of the second adjustment method in this embodiment. Referring to FIG. 9, in the second adjustment method, similarly to the first adjustment method, the number N of irradiation pulses of laser light and the illuminance I on the wafer W for one pulse are measured (S31). Next, based on the measurement result of the measurement step S31, that is, the illuminance I on the wafer W, the illuminance distribution on the optical surface of each quartz lens constituting the projection optical system PL is simulated by the simulation procedure S1.
1 (S32).

Further, based on the number N of irradiation pulses measured in the measuring step S31 and the illuminance distribution on the optical surface of each quartz lens calculated in the calculating step S32, a change in volume and a change in refractive index of each quartz lens are calculated. Simulation procedure S12
It is calculated according to S14 (S33). Further, the wavefront aberration of the projection optical system PL is calculated based on the volume change and the refractive index change of each quartz lens calculated in the calculation step S33 (S34). Then, it is determined whether the wavefront aberration calculated in the calculation step S34 can be tolerated (S3).
5).

In the determining step S35, the calculating step S34
If it is determined that the wavefront aberration calculated in (2) can be tolerated (YES in the figure), the second adjustment method is terminated,
The operation proceeds to the exposure operation. On the other hand, in the determination step S35,
When it is determined that the wavefront aberration calculated in the calculation step S34 cannot be tolerated (NO in the figure), the second adjustment method is continued, and the process proceeds to the selection step S36. Selection step S3
In 6, the quartz lens to be replaced is selected based on the calculation result of the calculation step S33, that is, the volume change and the refractive index change of each quartz lens.

Finally, the quartz lens selected in the selecting step S36 is replaced with another quartz lens and adjusted (S37).
Here, it goes without saying that the selected quartz lens and the replacement quartz lens have the same optical characteristics as each other. Thus, in the second adjustment method, similarly to the first adjustment method, the projection optics caused by the physical property change (change in refractive index and density) of each quartz lens caused by irradiation of the projection optical system PL with the pulsed laser light. The deterioration of the wavefront aberration of the system PL (and the deterioration of the imaging performance) can be corrected well.

Hereinafter, in the present embodiment, the effect of the change in the physical properties of the quartz lens due to compaction on the imaging performance of the projection optical system PL will be simulated according to the procedure shown in FIG. 1, and the above-described first and second adjustment methods will be described. Verify the effectiveness of As described above, in a lens made of an optical material other than quartz (fluorite in this embodiment), it is assumed that physical properties do not change due to compaction. As simulation conditions, average illumination conditions, illuminance I on the wafer in one pulse, and the number N of irradiation shots are set as follows.

FIG. 10 shows, as an example of the average illumination condition, a σ value (σ) defined by the ratio of the numerical aperture NAi of the illumination light beam to the reticle to the object-side numerical aperture NAp of the projection optical system PL.
= NAi / NAp) and the illumination intensity. That is, in FIG. 10, the vertical axis indicates the illumination intensity on the wafer W, and the horizontal axis indicates the σ value. In FIG. 10, the illumination intensity when σ = 0 is set to 1, the illumination intensity when σ = 1 is set to 0.25, and the gap is smoothly connected by a Gaussian curve. Note that this average lighting condition is
It does not represent individual lighting conditions for each shot, but shows cumulative lighting conditions.

Also, assuming that the illuminance on the reticle in one pulse is 0.15 (mJ / cm ² / pulse) and the transmittance of the reticle (the ratio of the bright pattern) is 60%, The illuminance I on the wafer at 0.09 (mJ
/ Cm ² / pulse). Further, it is assumed that the number N of irradiation shots is 2.5 × 10 ¹¹ pulses. This corresponds to the number of irradiation shots when 18 hours of exposure is performed every day for 10 years at a laser oscillation frequency of 1 kHz (a typical frequency of the current ArF excimer laser).

FIG. 11 is a view corresponding to FIG. 7, and shows the result of a first simulation affected by compaction in the present embodiment. In the wavefront aberration shown in FIG. 11, components that can be easily corrected by adjusting the lens interval, that is, a focus component (defocus component), a shift component (center image shift), a magnification component, and a tertiary field curvature component The third-order distortion component is corrected in advance. Referring to FIG. 11, it can be seen that the wavefront aberration remaining after the correction by adjusting the lens interval includes many components that are rotationally asymmetric with respect to the optical axis.

FIG. 11 shows numerical values of the residual aberration amount of the distortion (shift X and shift Y) and the residual aberration amount of the field curvature after correction by adjusting the lens interval. However, the value of the residual aberration amount of the field curvature and the residual aberration amount of the distortion are 0 at the center point CE.
The whole is shifted so that it becomes. In an actually manufactured projection optical system, there are various aberration deterioration factors such as an error in a lens surface shape and a lens deformation caused by a mechanical hold (mechanical holding mechanism), so that the actual aberration is further deteriorated.

Whether the aberration state shown in FIG. 11 is within the allowable range depends on the standard required for the projection optical system PL, and cannot be described unconditionally. However, while the residual aberration amount of the field curvature falls within 50 nm or less and the residual aberration amount of the distortion falls within ± 1 nm or less, the maximum wavefront aberration deterioration amount 0.027λ indicating deterioration of the image quality itself. (0.009λ at the peripheral point UR in FIG. 7)
From 0.036λ) is considered to be the most problematic in the sense that pattern creation itself becomes impossible. The average illumination conditions, the illuminance I on the wafer per pulse, and the number N of irradiation pulses actually have various other combinations, and may be calculated each time according to the above-described simulation procedure. .

By the way, referring to the wavefront aberration diagram of FIG. 11, the wavefront aberration amount in the field of the center point CE and the peripheral point UC on the center is considerably larger than the field of the upper right peripheral point UR and the center right peripheral point CR. small. Therefore, in the second simulation, the entire projection optical system PL is rotated by 90 ° about the optical axis AX (around the Z axis).
This is equivalent to the rectangular area shown by the broken line in FIG. 3 becoming a new effective exposure area ER. In this case, it is possible to use the fields A and B that are less affected by compaction. Note that the rotation angle of the projection optical system PL is
-The direction of the right-hand thread with respect to the Z axis is positive. This point is the same in other simulations thereafter.

FIG. 12 shows the result of a second simulation in which the projection optical system is rotated by 90 ° as a whole in the present embodiment. In the wavefront aberration shown in FIG. 12, the rotationally symmetric aberration components within the third order are corrected in advance, as in FIG. In addition, since the residual aberration amount of the field curvature and the residual aberration amount of the distortion after the correction by adjusting the lens interval are very small, the values thereof are not illustrated. This point is the same in other simulations thereafter.

Referring to FIG. 12, the projection optical system PL is rotated by 90 degrees as a whole to obtain a field (effective exposure area E).
R), the amount of wavefront aberration at the peripheral point CR (corresponding to the point B in FIG. 3) and the peripheral point UR (corresponding to the point A in FIG. 3) is reduced, and the maximum amount of wavefront aberration deterioration is 0. 023λ (0.005λ to 0.02 at points CE and UC in FIG. 7)
8λ). As described above, when the projection optical system PL is rotated as a whole, the rotation angle is preferably 90 ° ± 30 ° so that a field (such as points A and B in FIG. 3) that is less affected by compaction can be used. It is. Here, the overall rotation amount of the projection optical system PL is
Optimization can be performed using general functions of optical design software.

Next, a first modification of the present embodiment will be described. The configuration of the projection optical system PL according to the first modification is
The configuration is basically the same as that of the above-described embodiment, but differs from the above-described embodiment in that an anamorphic curvature is given to the reticle-side surface of the lens L119 and the wafer-side surface of the lens L21. . Specifically, as shown in FIG. 13, the direction in which the positive power (refractive power) is strong (shown by a thick solid line in the figure) is Y on the reticle-side surface of the lens L119.
Initially, the direction in which the positive power is strong coincides with the X direction on the wafer side surface of the lens L21.

The anamorphic curvature given to the surface of the lens L119 on the reticle side and the surface of the lens L21 on the wafer side is such that Newton ring fringes in two directions orthogonal to 550 nm wavelength light differ by one. It is set to be. In the initial state in which the direction of strong positive power on the reticle side surface of the lens L119 and the direction of strong positive power on the wafer side surface of the lens L21 are orthogonal, the initial powers cancel each other. ing. The provision of a pair of anamorphic lenses having an anamorphic optical surface is effective for initial adjustment of the projection optical system PL, but is also effective for adjustment of the influence of compaction. Hereinafter, this point will be described.

Referring to the above equation (1), it can be seen that the compaction proceeds in proportion to (N · I ² ) ^0.6 . Therefore, (N · I ²⁾ were measured, the projection optical system PL when it exceeds a certain threshold measurements in the first field can be determined that the unusable. This threshold value is calculated based on (N · I ² ) because it is considered that the wavefront aberration deterioration amount does not substantially change if (N · I ² ) is the same even when the above simulation conditions are changed. be able to.

In general, the Marshall standard requires that the wavefront aberration to be resolved is λ / 14λ0.071λ or less. However, recently, the demands on an exposure apparatus have become increasingly severe, and a wavefront aberration of about 0.04λ or less is actually required for an exposure wavelength of 250 nm or less. Considering the wavefront aberration caused by design, the wavefront aberration caused by manufacturing error, and the wavefront aberration caused by heat change during projection exposure, the physical property change of quartz lens due to compaction etc. Is at most 0.016λ.

In the above-described embodiment, the amount of wavefront aberration deterioration caused by compaction before rotating the projection optical system PL as a whole was 0.027λ at the maximum. Here, considering that the wavefront aberration increases by the sum of squares, (0.016 /
0.027) ² × 100 ≒ 35%, so when the compaction has advanced by about 35%, the projection optical system PL becomes unusable in the first field, and further adjustment is required to continue using it. . Referring to equation (1), the amount that govern compaction obtains a value for (N · I ²⁾ of ^0.6, compaction corresponds to the advanced state of about ^{35% (N · I 2)} .

In the above embodiment, the number of irradiation pulses N₁=
2.5 × 10¹¹And the illuminance I on the wafer in one pulse
₁= 0.09 (mJ / cm^Two/ Pulse), so (N₁
・ I ₁ ^Two)^0.6Is represented by the following equation (6). (N₁・ I₁ ^Two)^0.6$ 3.8 x 10^Five (6)

Therefore, the use of the projection optical system PL is continued.
Adjustments are required (NI ^Two)^0.6Is the following expression
(7), and the use of the projection optical system PL is continued.
Adjustments are required (NI^Two) Is the following expression
It is represented by (8). (NI^Two)^0.6= 3.8 × 10^Five× 0.35 (7) (NI^Two) = 3.5 × 10⁸ (8)

Therefore, in the first modification, the number N of irradiation pulses is measured based on the output of the integrator sensor 3. Also, based on the output of the internal sensor built in the excimer laser light source 1, the output of the integrator sensor 3 in the illumination optical system 2, the output of the illuminance sensor 4 provided at the height position of the wafer W, etc. The illuminance I on the wafer W is measured. Then, based on the value of (N · I ^2),
It is determined whether adjustment is necessary to continue using the projection optical system PL.

According to another viewpoint, the illuminance I on the wafer W in one pulse is equal to the value I ₁ = assumed in the above embodiment.
Assuming that it is constant at 0.09 (mJ / cm ² / pulse), the value of N that needs to be adjusted in order to continue using the projection optical system PL is expressed by the following equation (9). N ≒ 4.3 × 10 ¹⁰ (9)

In the above embodiment, the operating time of the exposure apparatus is assumed to be an average of 18 hours per day. However, the operating time may be slightly shorter. In this case, the number N of irradiation pulses assumed in equation (9) and the above embodiment is N =
Comparing with 2.5 × 10 ¹¹ , Expression (9) is satisfied when the use period of the exposure apparatus reaches about two years. That is, when the use period of the exposure apparatus has reached about two years, adjustment for continuing to use the projection optical system PL can be performed.

Alternatively, according to still another viewpoint, the wavefront aberration of the projection optical system PL is periodically measured by a wavefront aberration measuring device or the like, and it is confirmed that the wavefront aberration obtained by the measurement exceeds the standard amount. At this point, adjustment for continuing to use the projection optical system PL can be performed. As a wavefront aberration measuring device, for example, a so-called PDI (Phase Diffraction Interferom) disclosed in Japanese Patent Application Laid-Open No. 2000-97616.
eter: phase diffraction interferometer) type wavefront aberration measuring instrument.

In the first modification, in order to clarify the effectiveness of the adjustment for continuing the use of the projection optical system PL, the adjustment is performed after the compaction has proceeded to the same extent as in the above-described embodiment. Let's do it. However, as described above, actually, the adjustment is performed according to the determination based on any one of the measured value of (N · I ² ), the measured value of the irradiation pulse number N, the usage period, and the actually measured value of the wavefront aberration. Can also be performed.

Here, referring to FIG. 9 showing the result of the first simulation showing the influence of compaction in the above-described embodiment, the peripheral points UC,
It can be seen that even in CR and UR, a low-order astigmatic difference appears considerably large on the screen. To correct such a wavefront aberration, a pair of anamorphic lenses L119 and L21 having an anamorphic optical surface may be relatively rotated about the optical axis. Here, the rotation amount of each of the anamorphic lenses L119 and L21 can be optimized using the eccentric function of the optical design software.

Therefore, in the third simulation, FIG.
As shown in FIG. 4, in the first modified example, the lens L119 is rotated by 47.5 °, and the lens L21 is rotated by 47.5 °.
Rotate by 2.5 °. FIG. 15 shows a result of a third simulation in which the lens L119 is rotated by 47.5 ° and the lens L21 is rotated by 42.5 ° in the first modification. 11 and FIG. 15, a pair of anamorphic lenses L119 and L2
By the operation of 1, the wavefront aberration is considerably corrected at the center point CE and the point CR at the center right, and the wavefront aberration is also improved to some extent at the peripheral point UR.

However, in FIG. 15, there is almost no residual wavefront aberration component appearing uniformly on the screen, and it is not possible to perform better correction only by the action of the pair of anamorphic lenses. Therefore, in the fourth simulation, the lenses other than the pair of lenses L119 and L21 are rotated from the state of the third simulation.
In the first modified example, considering that mechanical constraints are large in rotating the projection optical system PL as a whole, FIG.
As shown in the figure, the projection optical system PL is divided into eight optical blocks B.
It is divided into L1 to BL8.

Referring to FIG. 16, the first optical block B
L1 includes lenses L11 to L15, the second optical block BL2 includes lenses L16 to L111,
The third optical block BL3 includes lenses L112 to L1.
14, the fourth optical block BL4 includes a lens L115
~ Lens L120. The fifth optical block BL5 includes lenses L21 to L22, the sixth optical block BL6 includes lenses L23 to L24, and the seventh optical block BL7 includes lenses L25 to L.
26, and the eighth optical block BL8 includes lenses L27 to
The lens L29 is included.

By the way, referring to the result of the third simulation shown in FIG. 15, since the wavefront aberration appearing uniformly on the screen has been almost corrected, it is considered that there is almost no influence of compaction on the lens near the aperture stop AS. Can be In addition, compaction progresses in proportion to (N · I ² ) ^0.6, and thus greatly depends on the illuminance I on the wafer W in one pulse. From this, it is considered that the effect of compaction appears largely in a lens having a relatively small effective diameter and relatively close to the wafer W. From the above,
It is conceivable that the effect of compaction appears to be greatest for a lens having a relatively small effective diameter between the aperture stop AS and the wafer W.

Therefore, in the fourth simulation, the second simulation
The optical block BL2 is rotated by −35 °, and both the sixth optical block BL6 and the eighth optical block BL8 are rotated by 55 °. FIG. 17 shows the second optical block BL from the state of the third simulation in the first modification.
2 by -35 ° and the sixth optical block BL6
14 shows a result of a fourth simulation in which both the optical block BL8 and the eighth optical block BL8 are rotated by 55 °. FIG.
17 is compared with FIG. 17, the wavefront aberration is slightly deteriorated at the peripheral point UC on the center, but the peripheral point U
The amount of wavefront aberration at R is small. Further, the worst value of the wavefront aberration in the entire field (0.026λ in the UR in the fourth simulation) is the smallest among the four simulations so far.

In the fourth simulation described above, the rotation angle of the predetermined optical block is about 90 ° (for example, 90 ° ± 30 °) or 45 ° at which the influence of compaction of the optical block hardly appears on the field.
Around (eg, 45 ° ± 15 °) or around −45 ° (eg, −45 ° ± 15 °) is preferable. Strictly speaking,
Using the eccentric function of the optical design software, a required rotation angle for optimization can be obtained. Hereinafter, the rotation angle in other simulations may be similarly optimized using the eccentric function of the optical design software.

Next, even if the adjustment in the fourth simulation is performed, the adjusted wavefront aberration does not satisfy the standard because the original wavefront aberration is bad due to a manufacturing error.
Consider a case in which the wavefront aberration worsens by continuing the projection exposure after the adjustment of the simulation. In this case, the effect of adjustment by rotating the lens cannot be expected much. Therefore, it is considered that if only the main lens causing the compaction is replaced, most of the other lenses can be used thereafter.

It is to be noted that the lens replacement time is determined by the projection optical system P.
The wavefront aberration of L can be inspected by the above-mentioned wavefront aberration measuring device or the like, and it can be determined based on whether or not the inspection result satisfies the standard. The lens to be replaced is a lens that is most affected by compaction, that is, a quartz lens whose effective diameter is relatively small and relatively close to the wafer W. Therefore, in the fifth simulation, the sixth optical block BL6 and the eighth optical block BL8 are replaced with other optical blocks from the state of the fourth simulation.
Here, the lens forming the replacement optical block has substantially the same optical characteristics (curvature, refractive index, lens thickness, etc.) as the lens forming the original optical block to be replaced.

FIG. 18 shows a result of a fifth simulation in which the sixth optical block BL6 and the eighth optical block BL8 are exchanged from the state of the fourth simulation in the first modification. 17 and 18, the RMS values of the wavefront aberration at the peripheral points UC and UR are:
It can be seen that it is considerably smaller than in the fourth simulation.

The sixth optical block BL6 and the eighth optical block BL6
The replacement of the optical block BL8 may cause a new aberration. However, even in that case,
By adjusting the distance between the optical blocks or shifting and adjusting the optical blocks along a direction perpendicular to the optical axis, aberrations other than aberrations due to compaction can be removed. Further, in the first modification, since the projection optical system PL is divided into a plurality of optical blocks, rotation and exchange can be performed relatively easily for each optical block, and it goes without saying that it is efficient. Absent.

Next, a second modification of the present embodiment will be described. The configuration of the projection optical system PL according to the second modification example is as follows.
Although the configuration is basically the same as that of the above-described embodiment, FIG.
As shown, the projection optical system PL has eight optical blocks BL.
It is different from the above-described embodiment in that it is divided into 1 to BL8. Also in the second modified example, it is assumed that the compaction has progressed under the same conditions as the above-described embodiment and the first modified example, and the wavefront aberration has deteriorated to the state of the first simulation shown in FIG. In the second modified example, it is assumed that the original wavefront aberration due to a manufacturing error is large and the wavefront aberration cannot be sufficiently corrected even when a pair of anamorphic lenses is introduced.

In this case, the most effective adjustment method is to replace a quartz lens which is also greatly affected by compaction. The quartz lens to be replaced has a relatively small effective diameter as in the case of the third simulation.
It is a lens relatively close to. Therefore, in the sixth simulation, in the second modification, the sixth optical block B
Exchange L6 and the eighth optical block BL8 (see FIG. 16). FIG. 19 shows a sixth modification in which the sixth optical block BL6 and the eighth optical block BL8 are replaced in the second modification.
The result of a simulation is shown. Comparing FIG. 19 with the results of other simulations, it can be seen that the RMS value of the wavefront aberration over the entire field is corrected much better than the results of other simulations.

Next, a third modification of the present embodiment will be described. The configuration of the projection optical system PL according to the third modification example is as follows.
The configuration is exactly the same as the configuration of the above-described first modification. That is,
In the third modified example, similarly to the first modified example, an anamorphic curvature is given to the reticle-side surface of the lens L119 and the wafer-side surface of the lens L21. Specifically, as shown in FIG. 13, on the reticle side surface of the lens L119, the direction in which the positive power is strong coincides with the Y direction, and the lens L2
Initially, the direction of the strong positive power on the wafer-side surface 1 is initially set so as to coincide with the X direction.

The anamorphic curvature given to the surface of the lens L119 on the reticle side and the surface of the lens L21 on the wafer side is such that the stripes of Newton rings in two directions orthogonal to the wavelength of 550 nm are one difference. It is set to be. Then, in the initial state where the direction in which the positive power is strong on the reticle side surface of the lens L119 and the direction in which the positive power is strong on the wafer side surface of the lens L21 are orthogonal to each other, the initial powers cancel each other. is there. In the third modified example, as in the first modified example,
The projection optical system PL is divided into eight optical blocks BL1 to BL8.

In the third modification, even if the adjustment in the sixth simulation is performed, the original wavefront aberration is not good due to a manufacturing error, so that the adjusted wavefront aberration does not satisfy the standard. Consider a case in which the wavefront aberration worsens by continuing the exposure. In this case, the lens may be rotated. Therefore, in the seventh simulation, in the third modification,
The second optical block BL2 is rotated by 90 °. Further, as shown in FIG. 20, the lens L119 is rotated by 31 °, and the lens L21 is rotated by 29 °.

FIG. 21 shows a lens L1 according to the third modification.
19 shows a result of a seventh simulation in which 19 is rotated by 31 ° and the lens L21 is rotated by 29 °. 21 and FIG. 19, the peripheral points UC,
It can be seen that the RMS value of the wavefront aberration is further improved in the UR and CR and also at the center point CE as compared with the sixth simulation.

In the exposure apparatus according to the present embodiment (including the modifications), the reticle is illuminated by the illumination system (illumination step), and the transfer pattern formed on the reticle is projected onto the photosensitive substrate using the projection optical system. By exposing (exposure step), a micro device (semiconductor element, image pickup element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Hereinafter, 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 the present embodiment will be described with reference to the flowchart in FIG. Will be explained.

First, in step 301 of FIG.
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 l lot of wafers. Then, step 30
In 3, using the exposure apparatus of the present embodiment, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of the lot through the projection optical system.
Thereafter, in Step 304, after the photoresist on the wafer of the lot is developed, Step 3
At 05, a circuit pattern corresponding to the pattern on the mask is formed in each shot region on each wafer by performing etching on the wafer of the lot using the resist pattern as a mask. Thereafter, a device such as a semiconductor element is manufactured by forming a circuit pattern of an 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 good throughput.

In the exposure apparatus of the present embodiment, a predetermined pattern (circuit pattern,
By forming an electrode pattern or the like, a liquid crystal display element as a microdevice can be obtained. Hereinafter, an example of the technique at this time will be described with reference to the flowchart in FIG. In FIG. 23, in a pattern forming step 401, a so-called photolithography step of transferring and exposing a pattern of a mask onto a photosensitive substrate (a glass substrate coated with a resist or the like) using the exposure apparatus of the present embodiment 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 various steps such as a developing step, an etching step, and a reticle peeling step, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming step 402.

Next, in the color filter forming step 402, three colors corresponding to R (Red), G (Green), and B (Blue)
Many sets of dots are arranged in a matrix,
Alternatively, a color filter in which a plurality of sets of three stripe filters of R, G, and B are arranged in the horizontal scanning line direction is formed. Then, after the color filter forming step 402, a cell assembling step 403 is performed. In the cell assembly step 403, a liquid crystal panel (liquid crystal cell) is assembled using the substrate having the predetermined pattern obtained in the pattern formation step 401, the color filter obtained in the color filter formation step 402, and the like. In the cell assembling step 403, for example, a 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, and a liquid crystal panel (liquid crystal cell) is formed. ) To manufacture.

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

In the above-described embodiments and modifications,
Although an ArF excimer laser light source is used, the present invention is not limited to this. For example, a KrF excimer laser light source that supplies light having a wavelength of 248 nm, or a 156 nm wavelength light source is used.
The light can also be used other suitable light sources such as F ₂ excimer laser light source which supplies.

In the above embodiments and modifications,
Although the present invention is applied to a refraction type projection optical system,
The present invention is not limited to this, and can be applied to a catadioptric projection optical system.

[0101]

As described above, according to the present invention, the physical property change caused by the irradiation of the projection optical system with the pulse laser light is adjusted by rotating the predetermined optical member around its optical axis by a required angle. It is possible to satisfactorily correct the deterioration of the imaging performance of the projection optical system caused by (change in refractive index and change in density). In addition, by exchanging and adjusting a predetermined optical member, it is possible to satisfactorily correct the deterioration of the imaging performance of the projection optical system caused by a change in physical properties caused by irradiation of the projection optical system with the pulse laser light. it can.

[Brief description of the drawings]

FIG. 1 is a flowchart schematically showing a simulation procedure according to the present invention.

FIG. 2 is a view schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a positional relationship between a rectangular effective exposure area formed on a wafer and an effective exposure field of a projection optical system in the present embodiment.

FIG. 4 is a diagram showing a lens configuration of a projection optical system according to the embodiment.

FIG. 5 is a diagram illustrating spherical aberration, astigmatism, and distortion of the projection optical system according to the present embodiment.

FIG. 6 is a diagram illustrating coma in a tangential plane and coma in a sagittal plane of the projection optical system according to the present embodiment.

FIG. 7 is a diagram illustrating the wavefront aberration of the projection optical system according to the present embodiment by contour lines in units of 0.01λ.

FIG. 8 is a flowchart schematically illustrating an adjustment flow of a first adjustment method according to the embodiment.

FIG. 9 is a flowchart schematically showing an adjustment flow of a second adjustment method in the embodiment.

FIG. 10 shows, as an example of an average illumination condition, a σ value (σ = NAi / NA) defined by a ratio between a numerical aperture NAi of an illumination light beam to a reticle and an object-side numerical aperture NAp of the projection optical system PL.
It is a figure which shows the relationship between p) and illumination intensity.

FIG. 11 is a view corresponding to FIG. 7, and shows a result of a first simulation affected by compaction in the present embodiment.

FIG. 12 shows a projection optical system according to the present embodiment,
The result of the second simulation rotated by 0 ° is shown.

FIG. 13 is a diagram showing a state in which a pair of anamorphic lenses L119 and L21 are initially set so that directions with strong positive power are orthogonal to each other.

FIG. 14 is a diagram showing a lens L119 of the first modification example.
While rotating by 7.5 °, the lens L21 is
It is a figure showing signs that it rotates by 2.5 degrees.

FIG. 15 illustrates a lens L119 of 47.
It is a figure showing the result of the 3rd simulation which rotated 5 degrees and rotated lens L21 by 42.5 degrees.

FIG. 16 is a diagram showing a state in which a projection optical system PL is divided into eight optical blocks BL1 to BL8 in a first modification.

FIG. 17 is a fourth simulation in which the second optical block BL2 is rotated by −35 ° and both the sixth optical block BL6 and the eighth optical block BL8 are rotated by 55 ° from the state of the third simulation in the first modified example. It is a figure which shows the result of.

FIG. 18 is a diagram illustrating a result of a fifth simulation in which the sixth optical block BL6 and the eighth optical block BL8 are exchanged from the state of the fourth simulation in the first modified example.

FIG. 19 shows a sixth optical block BL6 in the second modification.
It is a figure showing the result of the 6th simulation which exchanged the 8th optical block BL8.

FIG. 20 is a diagram illustrating a lens L119 according to a third modification.
It is a figure which shows a mode that rotates the lens L21 by 29 degrees while rotating only by degrees.

FIG. 21 shows a lens L119 of 31 ° in the third modification.
FIG. 21 is a diagram illustrating a result of a seventh simulation in which the lens L21 is rotated by 29 degrees and the lens L21 is rotated by 29 degrees.

FIG. 22 is a flowchart of a method for obtaining a semiconductor device as a micro device.

FIG. 23 is a flowchart of a method for obtaining a liquid crystal display element as a micro device.

[Explanation of symbols]

 Reference Signs List 1 light source 2 illumination optical system 3 integrator sensor 4 illuminance sensor R reticle RST reticle stage PL projection optical system W wafer WST wafer stage

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Claims (8)

[Claims] 1. A method for adjusting an exposure apparatus having a projection optical system for forming a pattern image of a reticle illuminated by a pulsed laser beam on a photosensitive substrate, comprising the steps of: A measurement step of measuring an optical characteristic, and a first calculation step of calculating at least one of a refractive index change and a volume change of at least one optical member in the projection optical system based on a measurement result of the measurement step, In order to correct the deterioration of the imaging performance of the projection optical system caused by the irradiation of the laser light to the projection optical system, based on the calculation result of the first calculation step, A second calculation step of calculating a rotation amount of at least one optical member; and at least one of the projection optical systems in the projection optical system based on a calculation result of the second calculation step. Adjustment method for an exposure apparatus which comprises a rotary adjustment step of adjusting by rotating the faculty member. 2. The method according to claim 1, wherein the first calculating step has a wavelength of 250 nm.
The exposure apparatus according to claim 1, wherein at least one of a change in refractive index and a change in volume of an optical member whose physical property changes at least one of a refractive index and a density by the following laser light irradiation is calculated. Adjustment method. 3. The second calculating step calculates a relative rotation amount of a pair of anamorphic optical members provided in the projection optical system and having an anamorphic optical surface, and the rotation adjusting step includes: 3. The method according to claim 1, wherein at least one of the anamorphic optical members is rotated for adjustment. 4. The second calculating step calculates a rotation amount of at least one optical block provided in the projection optical system and including a plurality of the optical members, and the rotation adjusting step includes the rotation adjusting step. The method according to any one of claims 1 to 3, wherein the adjustment is performed by rotating. 5. A method for adjusting an exposure apparatus having a projection optical system for forming a pattern image of a reticle illuminated by a pulsed laser beam on a photosensitive substrate, the method comprising adjusting the number of pulses of the laser beam and the projection optical system. A measurement step of measuring optical characteristics; a calculation step of calculating at least one of a refractive index change and a volume change of at least one optical member in the projection optical system based on a measurement result of the measurement step; In order to correct the deterioration of the imaging performance of the projection optical system caused by irradiating the projection optical system with light, based on the calculation result of the calculation step, at least the exchange in the projection optical system should be performed. A selecting step of selecting one optical member; and, based on a result of the selecting step, at least one optical member to be replaced in the projection optical system is replaced with another optical member. Adjustment method for an exposure apparatus which comprises an interchangeable adjusting step of adjusting and replace it with a faculty member. 6. The first calculating step, wherein the wavelength is 250 nm
6. The exposure apparatus according to claim 5, wherein at least one of a refractive index change and a volume change of an optical member whose physical property changes at least one of a refractive index and a density by the following laser light irradiation is calculated. Adjustment method. 7. The selecting step selects at least one optical block provided in the projection optical system and including a plurality of the optical members as an optical block to be replaced. 7. The method according to claim 5, wherein one optical block is exchanged with another optical block for adjustment. 8. An exposure step of exposing the pattern of the reticle to the photosensitive substrate using an exposure apparatus adjusted by the adjustment method according to claim 1.
A developing step of developing the photosensitive substrate exposed in the exposing step.