JPS63121810A - Projection lens system - Google Patents

Abstract

PURPOSE:To improve the compensation of various aberrations including a chromatic aberration by using SiO2 for one negative lens group among plural lens groups which constitute a projection lens system used for light having specific wavelength, and making other lens groups of materials which are larger in Abbe number than SiO2. CONSTITUTION:The projection lens system used for the light within a wavelength range of 150-300nm is constituted by using SiO2 for one negative lens group among the plural lens groups constituting the lens system and making other lens groups of materials which are larger in Abbe number than SiO2. The projection lens system has three lens groups and is constituted as a reduction system which have 1 and lens group II with negative refracting power at the lens center part and the 1st and the 3rd lens groups I and II having positive refracting power on both sides, and the aberrations are compensated excellently by setting conditional expressions. Consequently, the chromatic aberration is easily compensated and other various aberrations are also compensated excellently, so that the chromatic aberration and five Seidel aberrations are compensated with good balance.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a projection lens system used when manufacturing integrated circuits such as ICs and LSIs using a projection exposure apparatus, and particularly relates to a projection lens system for manufacturing integrated circuits such as ICs and LSIs using a projection exposure apparatus. The present invention relates to a projection lens system that is effective when printing an integrated circuit pattern onto a silicon wafer or the like using a light source that emits an emission spectrum close to .

(Prior Art) Very high resolution has been required of projection lens systems for printing patterns of integrated circuits such as ICs and LSIs onto silicon wafers using projection exposure apparatuses.

Generally, the shorter the wavelength used, the better the resolution of the projected image by the projection lens system, so a light source that emits as short a wavelength as possible has been used. For example, currently, projection exposure apparatuses often use light with a wavelength of 436 nm or 365 nm from a mercury lamp. In order to obtain a high resolving power, a projection lens system is required to have an optical system that can completely correct aberrations and obtain a resolving power close to the theoretical limit value. In particular, in order to print a pattern, aberrations are corrected so that resolving power up to the theoretical limit can be obtained over the entire screen, not just at the center of the screen. For example, in the manufacture of integrated circuits, a projection lens system is used in which distortion among optical speaking aberrations is almost completely corrected because the process of printing the integrated circuit pattern is performed multiple times.

The wavelength of the mercury lamp used in projection exposure equipment is 365 nm.
When using light with a small wavelength width centered on the i-line of the Fraunhofer lines, 4 to 5 f, which has good transmittance on the short wavelength side, is used to completely correct chromatic aberration! Similar glass materials are needed.

Also, for these glass materials, the error between the design values such as refractive index 1 dispersion and the actual values, and the variation in various values within the same glass material, are due to photographic lenses, plate-making lenses, and TV lenses.

The requirements are more than one order of magnitude stricter than other general optical systems such as.

This is because various aberrations such as chromatic aberration must be corrected in units of a fraction of a wavelength by utilizing the slight difference in refractive index and dispersion of the glass materials that constitute the projection lens system.

Further, as a projection lens system, it is preferable to use an optical system that is as bright as possible, but the transmittance of glass materials on the short wavelength side is low, and since a large number of lenses are used, it is generally difficult to obtain high transmittance.

For example, in a projection lens system intended for a wavelength of 436 nm and a projection lens system intended for a wavelength of 365 nm, the transmittance of the latter is approximately 1/3 to 1/6 of the transmittance of the former.

For this reason, projection exposure apparatuses that target short wavelengths use reflection systems or projection lens systems that use a new type of glass that has good transmittance on the short wavelength side.

Glass materials that can be used for the projection lens system include S
There are i 02 , CaF2, MgF2, etc.

The applicant had previously developed a high-performance projection lens system using only 5io2 of this type of material in Japanese Patent Application Laid-Open No. 60-140310.
This was disclosed in the No. 1 bulletin, etc.

The projection lens system disclosed in Japanese Patent Application Laid-Open No. 60-140310 is used when the wavelength width of the used light beam is extremely narrowed by means such as injection locking using an excimer laser. Therefore, in the projection lens system disclosed in the above-mentioned publication, no consideration is given to chromatic aberration in design.

However, when the light beam emitted from a short wavelength light source such as an excimer laser has a certain wavelength width, for example, about 0.5 nm, correction of chromatic aberration is an essential problem in order to obtain high resolution. Therefore, as a projection lens system applied to a device using an excimer laser or the like as a light source, there is a demand for a high-performance lens system that corrects chromatic aberration at least in the inn width from the reference wavelength.

(Summary of the Invention) In view of the above-mentioned problems, an object of the present invention is to
It is an object of the present invention to provide a high-performance projection lens system that satisfactorily corrects various aberrations including chromatic aberration in a device using a light source having an emission spectrum distribution with a wavelength width in the range of approximately 300 nm.

In order to achieve the above object, a projection lens system according to the present invention is a projection lens system used with light within a wavelength range of approximately 150 to 300 nm, and includes a plurality of lens groups constituting the lens system. At least one negative lens group of Si
It is characterized in that it is made of O2, and the other lens groups are made of a material with a larger Atsube number than the above-mentioned S i 02.

Further features of the invention are illustrated in detail in the Examples below.

(Example) Fig. 1 is a sectional view showing an example of the projection lens system according to the present invention.In the figure, I, II, and III are lens groups arranged in order from the object side, and I is CaF2 II is a positive second lens group made of SiO2, and II is a positive third lens group made of CaF2.

Further, II and 12 indicate the front group and the rear group when the Luns group (2) is divided into two groups. In addition, the symbols Di and R in the figure
i (i=1.2, 3...) indicates the radius of curvature of each refractive surface constituting this projection lens system, the axial air spacing between each refractive surface, or the axial wall thickness, as described below. This corresponds to the lens data in the numerical example.

The projection lens system of this embodiment has three lens groups: two lens groups TI with negative refractive power at the center of the lens, and first lens groups TI with positive refractive power on both sides thereof. By constructing a reduction system in which the third lens groups I and 11 are arranged and setting the following conditional expressions (1) and (2), good aberration correction is achieved.

0.8≦l f 1/ f 2 1≦3.8...
(1) 1.1≦lf+/fsl≦4 (2)
Conditions (1) and (2) are conditions for properly correcting field curvature by appropriately setting the refractive power of each lens group, which is one of the basics of lens performance.If the lower limit is exceeded, the Petzval sum If the upper limit value is exceeded, the field curvature will be overcorrected, making it difficult to satisfactorily correct aberrations over the entire screen.

Furthermore, in this projection lens system, in order to achieve good aberration correction, the lens group I is composed of two lens groups 11 and 12 having negative and positive refractive powers in order from the object side, and the lens group is constituted by a lens having at least one each of a biconvex lens I2+ whose both lens surfaces are convex and a lens I22 having a positive refractive power, and the focal length of the lens group I2 is f12. The second lens group is configured to have a meniscus-shaped lens with a negative refractive power with convex surfaces facing the object side and the image plane side, and the condition is satisfied when the focal length of the second lens group is f2. is satisfied.

The lens 122 has a reduction magnification of 1/3 to 1/3 of the projection lens system.
In order to properly correct aberrations, it is preferable to use a meniscus lens with a convex surface facing the object side when the reduction ratio is about 1/7, and to use a biconvex lens when the reduction ratio is about 1/7 to 1712.

In order to maintain good imaging performance as a projection lens system over the entire screen, in addition to the field curvature conditions, coma aberration must be corrected to almost τ over the entire screen, and spherical aberration,
Off-axis halo aberrations must be corrected. In order to achieve this, it is necessary not only to satisfy the above conditions (1) and (2), but also to form a meniscus-shaped lens with negative refractive power, with the object side and image side of the second lens group I+ facing convex surfaces, respectively, as in this projection lens system. Preferably, it is composed of a lens.

In this way, in this projection lens system, correction of spherical aberration is mainly performed by appropriately setting the radius of curvature of the lens surface of the second lens group II. At this time, comatic aberration is corrected at the same time as spherical aberration, but in order to do so, the second lens group TI
It is preferable that the lens be composed of at least two meniscus-shaped lenses having negative refractive power. One is to have a lens shape with a convex surface facing the object side, and the other is to have a lens shape with a convex surface facing the image plane. This means that the entire lens system is composed of, for example, three lens groups, positive, negative, and positive, and the second lens group compensates for the insufficient correction of spherical aberrations that occur in the remaining lens groups, the first and third lens groups. This is to provide a correcting effect. In the present projection lens system, the second lens group II further includes at least two lenses.
By arranging the two meniscus-shaped lenses with negative refractive power as described above, coma aberration is corrected, that is, a balance is achieved between the light flux portion above and the light flux portion below the off-axis principal ray. In other words, the lower beam part is formed by a meniscus lens placed on the object side with its convex surface facing the object side, and the upper beam part is formed by a negative meniscus lens placed on the image side with its convex surface facing the image plane. It is possible to correct the aberrations of the off-axis light beam in a well-balanced manner, and it has become possible to perform good correction of the off-axis coma aberration. Furthermore, since the chief ray of the off-axis beam passes near the optical axis of the second lens group I+, the configuration (shape) of the second lens group IT itself does not have much influence on distortion and astigmatism, and the condition (1 ), (2) allows the second lens group TI to satisfactorily correct spherical aberration and coma aberration. In particular, comatic aberration can be corrected by appropriately arranging the aforementioned negative meniscus lens. Further, it is preferable to satisfy condition (3) in order to satisfactorily correct meridional and sagittal halos off-axis. In this projection lens system, when the combined refractive power of the meniscus-shaped lens and the biconvex lens of the object-side lens group ■ is strong compared to the refractive power of the second lens group I+, spherical aberration occurs. When correcting comatic aberration, high-order Herot aberration occurs in the lens group I, and correction over the entire screen is difficult by using a slight difference in refractive index or using glass materials with a high refractive index and a low refractive index. If all aberrations are corrected, higher-order aberrations will occur, making it difficult to perform good correction.

Conditions (1), (2), and (3) were to satisfy the imaging performance (resolution, contrast ratio) required for a projection lens for printing integrated circuits, but there were also additional requirements for a projection lens. Distortion is an important performance condition.

In the manufacturing of ICs and LSIs, the printing process is performed many times, so alignment must be performed for each process, and in order to achieve accurate alignment for each exposure device, it is necessary to suppress the distortion of the projection lens system to almost zero. There must be.

Therefore, the projection lens system of this embodiment is composed of three lens groups with positive, negative, and positive refractive powers, and the third lens group is further comprised of two lenses with negative and positive refractive powers in order from the object side. Group I
I, I2. The lens group II and I2 each have a focal length of fIl+f+2, which is the focal length of the lens group fl.

In this projection lens system, especially when used as a reduction system, the lens group I has two negative and positive refractive powers when viewed from the object side.
Two lens groups 1. ．． For I2, distortion is mainly corrected by the lens group 11.

In particular, it is preferable for lens group I to be composed of at least two menicus-shaped lenses having negative refractive power and having convex surfaces facing the object side in order to satisfactorily correct distortion.

It is further preferable to configure the lens group 11 with three or more lenses, since the sharing of refractive power will be reduced and the effects of other aberrations will be reduced.

In addition, by making lens group I2 positive refractive power and configuring it with at least two or more lenses having positive refractive power, the position through which the off-axis principal light image passes is near the optical axis, thereby reducing distortion and astigmatism. It also corrects off-axis coma and halo well.

If the upper limit of conditional expression (4) exceeds the lower limit of conditional expression (5), a large amount of positive distortion will occur, which is undesirable. If it exceeds this, positive distortion will occur and other aberrations will also increase, which is not preferable.

This projection lens system uses SiO□ for each lens constituting the second lens group II, and the first and third lens groups I, I
By using CaF2 in each lens constituting II, the chromatic aberration of the entire lens system is corrected well. SiO2
The Abbe number (νd) of CaF2 is 67.9, and the Abbe number (ud) of CaF2 is 95.1, and SiO2 has a larger dispersion than CaF2. Therefore, in this projection lens system, the second lens group II, which has negative power, is made of Si, which has a small Atsube number.
O2 is applied to the first and third lens groups 1 and 3, which have positive power, and CaF2, which has a large Atsube number, is applied to control chromatic aberration occurring in each lens group, and spherical aberration, coma aberration, and image Surface curvature, astigmatism.

In addition to correcting distortion, it is now possible to correct chromatic aberration as well.

Particularly, in the projection lens system of the present invention, the lens system is composed of three or more lens groups, and one of the plurality of lens groups is mainly used as a negative lens group such as the second lens group in the above embodiment. When the lens group is used to correct spherical aberration, by using at least a 5in2 lens group, chromatic aberration and other aberrations can be corrected in a well-balanced manner.

Therefore, although it depends on the configuration and arrangement of the lens group, when this type of lens group is introduced into a projection lens system, it is preferable to use S i O2 in this lens group in terms of aberration correction. or,
In the above embodiment, the negative second lens group is composed of a deformed glass type lens group, but it is not limited to the glass type or deformed glass type, but can take various lens configurations such as a normal triplet type or a deformed triplet type. . Furthermore, the projection lens system of the above embodiment has three lenses, positive, negative, and positive, from the object side.
The structure of the lens group,
The power arrangement is also not limited to the above embodiment.

As for the negative lens group to which 5in2 is applied, it is preferable that the inner lining of the negative lens group constituting the projection lens system is also a lens group with a large power, and the power of this negative lens group is equal to that of the entire lens group ( It is even more preferable to configure the lens system so that the neutral (including positive and negative) is also large. because,
This is because with this configuration, the effect of chromatic aberration correction using SiO2 in the negative lens group becomes even more remarkable.

Further, in the above embodiment, CaF2 was used as a material having a larger Abbe number than 5102, but MgF2 may be used instead of CaF2.

Furthermore, as in the numerical examples described later, the front group I of the Luns group ■
SiO2 may be used instead of CaF2 for I (negative refractive power).

FIG. 2 is a sectional view showing another embodiment of the projection lens system according to the present invention. All the symbols in the figure indicate the same lens groups and parameters as in FIG. 1, so their explanation will be omitted here.

The projection lens system of this embodiment also includes, in order from the object side, a lens group T made of CaF2, and a second lens group II made of SiO2.
, CaF2. Also, the Luns group ■ has a negative front group I, a positive rear group I,
The lens group (1) has at least two lenses with negative refractive power whose object side surfaces are concave, and the lens group (2) has a lens with both lens surfaces convex. It has a positive refractive power lens whose object side surface is convex. The second lens group IT includes a meniscus-shaped lens with a negative refractive power with a convex surface facing the object side, a lens with concave surfaces on both lens surfaces, and a meniscus-shaped lens with a negative refractive power with a convex surface facing the image plane side. The third lens group 11T includes a meniscus-shaped lens with a positive refractive power with a convex surface facing the image side, a lens with both lens surfaces convex, and at least two positive lenses with a convex surface facing the object side. It has a lens L34 having a refractive power and at least one meniscus-shaped lens L34 having a positive refractive power and having a convex object-side surface.

By adopting this configuration, the present projection lens system achieves a projection lens system in which aberrations are well corrected. Particularly good imaging performance is obtained within the range of a projection magnification of 1/10 and a shooting angle of view of 1010×10.

Next, each component of the present invention will be explained in detail.

Distortion can be suppressed over the entire screen by configuring the lens group with at least two lenses with negative refractive power and concave image sides, preferably menicus-shaped lenses with negative refractive power and with the convex surface facing the object side. This makes it possible to print the mask pattern without distortion by making good corrections. By appropriately sharing the negative refractive power of the lens group 11 between two lenses, the angle of view is widened, the printing range is expanded, and the throughput is improved.

By constructing the lens group with a lens with convex surfaces on both surfaces and a lens with positive refractive power, the introverted coma and halo aberrations that occur in the first lens group are corrected and high resolution is achieved. .

The second lens group TI is composed of a meniscus-shaped lens with a negative refractive power with a convex surface facing the object side, a lens with concave surfaces on both lens surfaces, and a meniscus-shaped lens with a negative refractive power with a convex surface facing the image plane side. By doing so, negative spherical aberration occurring in lens group (2) and sagittal flare from the center to the periphery of the screen are corrected. In particular, the lens located at the center corrects negative spherical aberration and halo aberration occurring in the lens group 2, and the object-side lens and image-side lens correct sagittal flare at the periphery of the screen.

If the second lens group 11 is configured as described above, the light flux above the principal ray of the off-axis rays will be overcorrected, causing outward coma aberration.

Therefore, in this projection lens system, the third lens group II+ is composed of a meniscus-shaped lens with positive refractive power with its convex surface facing the image plane side, a lens with both lens surfaces convex, and at least two meniscus-shaped lenses with positive refractive power. By constructing the lens, the extroverted coma aberration generated in the second lens group I+, the curvature of field from the center to the periphery of the screen, and distortion are collectively corrected in a well-balanced manner.

The projection lens system of this example further satisfies the following conditions (1) to (
By satisfying 4), good aberration correction is achieved.

That is, the above-mentioned No. 1. second and third lens group I;

Let the focal lengths of n and nr be fl and F2 + F3, respectively.
, the focal lengths of the lens group I+ and the lens group 2 are each f lI+ f+2, and the focal length of the object side lens of the lens group 11 is f Il+, then 1
．． 9<l f+ /f21<3.7...(1)0,
8 < l f 2 / f s l < 1, 2・
...(2) 1.1<lf mouth/f12+<2.3...(
3) 1.4<f+++ /f++<2.2... (
4) Satisfy the following conditions.

Conditions (1) and (2) are necessary to properly correct the field curvature of the entire screen by appropriately setting the refractive power of each lens group, which is one of the basics of lens performance. The Petzval sum becomes large and the image plane becomes under-corrected.
If the upper limit is exceeded, the field curvature will be overcorrected, making it difficult to satisfactorily correct the aberrations of the entire screen.

Condition (3) is based on the lens group 1. under the refractive power arrangement of conditions (1) and (2). This is to correct distortion aberration by the lens group I2, correct introverted coma aberration and halo aberration by the lens group I2, and reduce field curvature of the entire screen to achieve high resolution. If the lower limit of condition (3) is exceeded, the curvature of field will be under-corrected, and if the upper limit is exceeded, the curvature of field will be over-corrected.

Condition (4) is for properly setting the distribution of the negative refractive power to the object-side lens of the lens group 11 having negative refractive power, so as to satisfactorily correct distortion.

If the lower limit of condition (4) is exceeded, the distortion will be under-corrected, and if the upper limit is exceeded, the distortion will be over-corrected.

In the present invention, both lens surfaces of the image-side lens of the lens group I2 may be convex, or may have a meniscus shape with the convex surface facing the object side.

In this embodiment, lens group 1. If it is composed of three or more meniscus-shaped lenses with negative refractive power with convex surfaces facing the object side, the sharing of refractive power between each lens will be reduced, reducing the occurrence of coma aberration and affecting other aberrations. It is preferable because it has less

Furthermore, if the third and fourth lenses counted from the object side of the third lens group III are divided into three or more lenses to reduce the burden on the refractive power of each lens, coma aberration and images can be reduced over the entire screen. Surface curvature can be corrected even better, and higher resolution can be achieved.

Next, numerical examples 1 to 4 of the present invention will be shown. Numerical Example 1~
4, Ri is the radius of curvature of the i-th surface counting from the object side, and Di is the axial air gap or axial thickness between the i-th and i+1-th surfaces counting from the object side. It shows the thickness. Further, the glass material 5102 is fused silica, and C and F2 are fluorite, each having a wavelength of 248.5 nm.

The O refractive index at 248.48 nm and 248.52 nm is shown in the attached table.

Numerical Example 1.2 has a projection magnification of 115. This is a projection lens system having a lens configuration shown in the cross-sectional view of FIG. 1, with NA=0.3 and a screen range of 14×14 mm. Numerical Example 1 is a lens system in which S and O2 are applied only to the second lens group II, and Numerical Example 2 is a lens system in which S and O2 are applied only to the second lens group II.
This is a lens system in which 5102 is applied to the second lens group II.

Numerical Examples 3 and 4 have a projection magnification of 1/10. NA=0.3.
This is a projection lens system having a lens configuration shown in the cross-sectional view of FIG. 2 in the case of a screen area of 1010×10. Numerical Example 3 is a lens system in which S, O, is applied only to the second lens group II, and Numerical Example 4 is a lens system in which S, O, is applied only to the second lens group II.
This is a lens system in which 5I02 is applied to the second lens group II.

Figures 3' (A) and (B) are diagrams showing the effect of chromatic aberration correction of this projection lens system.
It shows the longitudinal chromatic aberration of light of nm, 24B, and 52nm.

FIG. 3(A) shows the chromatic aberration in the projection lens system shown in the cross-sectional view of FIG. The broken line (B) represents the aberration in the lens system of Numerical Example 1, and the lens system of Numerical Example 2.

Similarly, FIG. 3(B) shows the chromatic aberration in the projection lens system shown in the cross-sectional view of FIG. (C
) indicates the lens system of Numerical Example 3, and the broken line (D) indicates the lens system of Numerical Example 4 Numerical Example 1 RD Glass material 1 553.028 8.00000 CAF22 2
72.352 6.85000 3 183.526 8.00000 CAF24 1
33.45260.00000 5 170.1B124.00000 CAF26-3
71.635 1.00000 7 98.41520.00000 CAF28 37
1.31930.00000 9 73.58520.0000O5IO21050,
64450,00000 11-67,42812,0000O5IO21219
5,91070,00000 13-50,17320,000005IO214-6
7,43910,00000 15-484,68918,00000CAF216-
120.170 1.0000017 284.339
16.50000 CAF218-228.209 1
．． 0000019 138.70118.50000
CAF2201074,'414 1.0000021
86.30920.00000 CAF222 10
7.066 Numerical Example 2 RD Glass Material 1 533.972 8.0000O5IO22279
,0046,85000 3180,1038,0000O5IO24134,0
2660,00000 5171,96024,00000CAF26-358
．． 140 1.00000 7 98.04320.00000 CAF28 37
2.70230.00000 9 73.32320.0000O5IO21050,
69150,00000 11-67,26912,0000O5IO21219
5,28170,00000 13-50,14420,0000O5IO214-6
7,51610,00000 15-487,26718,00000CAF216-
120.039 1.0000017 285.441
16.50000 CAF218-228.041 1
．． 0000019 139.02018.50000
CAF2201069.527 1.0000021
86.41720.00000 CAF222 107
．． 134 Numerical Example 3 RD Glass Material 1 376.369 8.00000 CaF22 9
7.603 6.85000 3 451.294 8.00000 CaF24 1
17.24260.00000 5 230.93424.00000 CaF22-1
35.702 1.00000 7 147.98720.00000 CaF28-1
301.77130.000009 62.96920
．． 0000O5IO21046,37155,0000
0 11-84,75712,000005IO21295
,21730,00000 13-35,81320,0000O5IO214-5
1,0191,00000 15-930,95318,00000CaF216
-85.314 1.0000017 254.125
16.50000 CaF218-201.518 1
．． 0000019 111.18918.50000
CaF2201259.281 1.0000021
64.36020.00000 CaF222 122
．． 094 Numerical Example 4 RD Glass Material 1 376.553 8.0000O5102299,
1786,85000 3439,0288,0000O5IO24117,9
4360,00000 5247,49524,00000CaF22-132
．． 735 1.00000 7 146.59220.00000 CaF28-7
30.54330.00000 9 62.55320.0000O5IO21047,
00355,00000 11-83,82112,0000O5IO21210
0,92130,00000 13-36,07620,0000O5IO214-5
1,5121,00000 15-833,39018,00000CaF216
-86.251 1.0000017 258.918
16.50000 CaF218-200.521 1
．． 0000019, 112.17018.50000
CaF2201328.516 1.0000021
64.56120.00000 CaF222 12
1.644 As can be seen from Figures 3 (A) and (B), this projection lens system can correct chromatic aberration better than the conventional lens system configured with only a single glass material. is possible. Here, the effect of chromatic aberration correction in the present projection lens system is shown using axial chromatic aberration, but off-axis chromatic aberration is also corrected just as well as on-axis.

4 to 7 are aberration diagrams showing various aberrations of the projection lens systems of the numerical examples 1 to 4 described above. Figures 4 to 7 show spherical aberration, astigmatism, distortion, and lateral aberration.
In the figure, M indicates aberration at the meridional image plane, and S indicates aberration at the sagittal image plane.

〔Effect of the invention〕

As described above, in the projection lens system according to the present invention, among the plurality of lens groups constituting the lens system, at least one negative lens group is made of SiO2, which has a small Atsbe number, and the remaining lens groups are made of CaF2, which has a small Atsbe number. By applying this, chromatic aberration can be well corrected even when using light with a certain wavelength range emitted from a light source such as an excimer laser that does not perform injection locking, and the lens system has high resolution. . Needless to say, Seidel's five aberrations such as spherical aberration and astigmatism can be well corrected by appropriately setting the configuration of the lens group, the curvature of each refractive surface, and the like.

Therefore, it is extremely effective as a high-performance projection lens system used when projecting and exposing a circuit pattern such as a mask or reticle onto a wafer.

In addition, as shown in the above embodiment, when a lens system is composed of a plurality of lens groups, one of which is composed of a negative lens system, and the lens system mainly corrects spherical aberration and coma aberration. ,
It is preferable to apply 5in2 to at least this lens group. That is, by designing a lens using SiO2 in this lens group and CaF2 or MgF2 in any other lens group, chromatic aberration can be easily corrected, and other aberrations can also be corrected well, and chromatic aberration and Seidel The five aberrations can be corrected in a well-balanced manner.

Furthermore, the lens systems shown in the examples described in this specification do not use laminated lenses. usually,
A bonded lens is well known as a lens system that corrects chromatic aberration by bonding two lenses with different Abbe numbers. However, in lens systems used for light from high-output light sources such as excimer lasers, problems such as peeling of the lens and reduction in transmittance occur, so bonded lenses are used as much as possible. It is preferable not to use it. Therefore, in view of this point, as shown in each of the above-mentioned embodiments, it is possible to obtain further effects for this type of lens system by using non-bonded lenses in the present projection lens system.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a projection lens system according to the present invention. FIG. 2 is a cross-sectional view showing another embodiment of the projection lens system according to the present invention. FIGS. 3(A) and 3(B) are diagrams showing the effect of chromatic aberration correction of the present projection lens system, showing longitudinal chromatic aberration. ing. 4 to 7 are aberration diagrams showing various aberrations of the projection lens systems shown in Numerical Examples 1 to 4. I --------1------1st Runs group rl -11-11--2nd 111------1-
-----Third 〃I, --------------Anterior group I, ------------------------One rear group

Claims (1)

[Claims] A projection lens system used for light within a wavelength range of approximately 150 to 300 nm, in which at least one negative lens group among a plurality of lens groups constituting the lens system is made of Si.
A projection lens system comprising SiO_2 and other lens groups made of a material having a larger Abbe number than the SiO_2.