JPH0473844B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a projection lens used when manufacturing integrated circuits such as ICs and LSIs using a projection exposure apparatus, and in particular, the present invention relates to a projection lens used when manufacturing integrated circuits such as ICs and LSIs using a projection exposure apparatus, and in particular, the present invention relates to a projection lens used when manufacturing integrated circuits such as ICs and LSIs using a projection exposure apparatus. This invention relates to a projection lens that is effective when printing circuit patterns onto silicon wafers and the like. Conventionally, extremely high resolution has been required of projection lenses used to print patterns of integrated circuits such as ICs and LSIs onto silicon wafers using projection exposure equipment. Generally, the shorter the wavelength used, the better the resolution of the image projected by the projection lens, so a light source that emits as short a wavelength as possible is used.
For example, the current wavelength of mercury lamps is 436nm or 365nm.
This light is often used in projection exposure equipment. In order to obtain high resolving power, a projection lens is required to have an optical system that can completely correct aberrations and obtain resolving power close to the theoretical limit value. In particular, in order to print a pattern, aberrations are corrected so that resolving power close 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, the process of printing the integrated circuit pattern is performed multiple times, so a projection lens whose distortion among various optical aberrations is almost completely corrected is used. An object of the present invention is to provide a high-performance projection lens for a projection exposure apparatus using a light source having a relatively narrow emission spectrum distribution within a wavelength range of about 150 nm to 400 nm. In particular, the present invention aims to provide a projection lens that exhibits a unique effect when the wavelength width is narrowed by means such as injection locking using an excimer laser whose main emission spectrum is 248.5 nm. . The main feature of the projection lens for achieving the object of the present invention is that it has three lens groups, first, second, and third lens groups, each having positive, negative, and positive refractive powers in order from the object side. The first lens group has negative refractive power.
It has two lens groups, a -1 lens group and a 1-2 lens group with positive refractive power, and the 1-1 lens group has at least two lenses with negative refractive power and whose object-side surfaces are concave. lenses L ₁₁₁ and L ₁₁₂ , and the first-second lens
The lens group includes a lens L ₁₂₁ whose both lens surfaces are convex, and a lens L ₁₂₂ whose object side surface is convex and has a positive refractive power.
The second lens group includes a meniscus-shaped lens L ₂₁ with a negative refractive power with a convex surface facing the object side, a lens L ₂₂ with a concave surface 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 includes a meniscus-shaped lens _{L 31} with a positive refractive power with a convex surface facing the image side, a lens L ₃₂ with both lens surfaces convex, and at least two objects-side lenses. The lens L ₃₃ has a positive refractive power and has a convex surface facing toward the object side, and at least one meniscus-shaped lens L ₃₄ has a positive refractive power and has a convex surface on the object side. The present invention achieves a projection lens that satisfactorily corrects aberrations by employing the above-described configuration. Particularly good imaging performance was obtained within the range of projection magnification of 1/10 and shooting angle of view of 10 x 10 mm. Next, each component of the present invention will be explained in detail. The 1-1 lens group includes at least two lenses L ₁₁₁ , L ₁₁₂ with negative refractive power whose image side image is concave, preferably a meniscus-shaped lens L with negative refractive power with a convex surface facing the object side. ₁₁₁ and L ₁₁₂ , it is possible to satisfactorily correct distortion over the entire screen and print the mask pattern without distortion. By appropriately distributing the negative refractive power of the 1-1st lens group to the two lenses L ₁₁₁ and L ₁₁₂ , the angle of view is widened, the printing range is expanded, and the throughput is improved. The 1st-2nd lens group is a lens with both lens surfaces convex.
By configuring the lens L ₁₂₁ and the lens L ₁₂₂ with positive refractive power, inward coma aberration and halo aberration occurring in the 1-1st lens group are corrected, and high resolution is achieved. The second lens group consists of a meniscus-shaped lens L ₂₁ with negative refractive power with its convex surface facing the object side, a lens L 22 with concave surfaces on both lens surfaces, and a meniscus-shaped lens L ₂₂ with negative refractive power with its convex surface facing the image plane side. By configuring the lens L ₂₃ , negative spherical aberration occurring in the first and second lens groups and sagittal flare from the center to the periphery of the screen are corrected. In particular, the lens L ₂₂ corrects negative spherical aberration and halo aberration occurring in the first and second lens groups, and the lenses L ₂₁ and L ₂₃ correct sagittal flare at the periphery of the screen. If the second lens group is configured as described above, the light flux above the principal ray of the off-axis rays will be overcorrected, causing extroverted coma aberration. Therefore, the third lens group includes a meniscus-shaped lens L ₃₁ with positive refractive power with its convex surface facing the image plane side, a lens L ₃₂ with both lens surfaces convex, and at least two meniscus-shaped lenses L with positive refractive power. ₃₃ and L ₃₄ , the extroverted coma aberration generated in the second lens group and the field curvature and distortion from the center to the periphery of the screen are corrected in a well-balanced manner. In the present invention, it is preferable that the following conditions are further satisfied. The focal lengths of the first, second, and third lens groups are f ₁ , f ₂ , and f _{3 ,} respectively, and the focal lengths of the 1-1 lens group and the 1-2 lens group are f ₁₁ , f , respectively. ₁₂
When the focal length of the lens L ₁₁₁ is f ₁₁₁ , 1.9<|f ₁ /f ₂ |<3.7 ...(1) 0.8<|f ₂ /f ₃ |<1.2 ...(2) 1.1<| It is to satisfy the following conditions: f ₁₁ /f ₁₂ |＜2.3 ...(3) 1.4＜f ₁₁₁ /f ₁₁ <2.2 ...(4) Conditions (1) and (2) are necessary to properly correct the screen curvature of the entire screen by appropriately setting the refractive power of each lens group, which is one of the basics of lens performance. If the sum becomes large, the image plane will be under-corrected, and if the upper limit is exceeded, the field curvature will be over-corrected, making it difficult to satisfactorily correct the aberrations of the entire screen. Condition (3) is the first condition under the refractive power arrangement of conditions (1) and (2).
This is to correct distortion aberration by the -1 lens group, correct introverted coma aberration and halo aberration by the 1-2 lens group, and reduce the field curvature of the entire screen to achieve high resolution. If the lower limit of condition (3) is exceeded, the field curvature will be under-corrected, and if the upper limit is exceeded, the field curvature will be over-corrected. Condition (4) is for appropriately setting the share of the negative refractive power for the object-side lens L ₁₁₁ of the 1-1 lens group having negative refractive power, and for satisfactorily correcting distortion. When the lower limit of condition (4) is exceeded, distortion becomes under-corrected, and when the upper limit is exceeded, distortion becomes over-corrected. In the present invention, the lens L ₁₂₂ may have both lens surfaces convex or may have a meniscus shape with the convex surface facing the object side. In the present invention, if the 1-1st lens group 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, and the occurrence of comatic aberration will be reduced. This is also preferable because it has less influence on other aberrations. By dividing lens L ₃₃ and lens ₃₄ of the third lens group into three or more lenses to reduce the burden on the refractive power of each lens, it is possible to better correct coma aberration and image curvature over the entire screen. Higher resolution can be achieved. In the numerical examples described later, since the wavelength range used is very narrow, a case is shown in which a single glass is used.However, depending on the wavelength width used, multiple glasses such as _CaF2 ,
It goes without saying that it may be composed of MgF ₂ or the like. As described above, according to the present invention, a high-performance projection lens with high resolution can be achieved in a projection exposure apparatus. Next, various numerical values of numerical examples 1 to 5 of the present invention are shown. In the numerical example, R _i is the i-th i in order from the object side.
The radius of curvature of the ith lens surface, D _i is the thickness and air gap of the ith lens in order from the object side, and N _i is the refractive index of the glass of the ith lens in order from the object side. The glass material SIO ₂ is fused silica and has a refractive index of 1.521130 at a wavelength of 248.5 nm. The numerical example has a projection magnification of 1/10, NA-0.35, and a screen range of 10×10. Further, Table 1 shows the relationship between each of the above-mentioned conditional expressions and various numerical values in the numerical examples. Numerical example 1

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【table】 [Brief explanation of drawings]

FIG. 1 is a sectional view of a lens according to numerical example 1 of the present invention, and FIGS. 2 to 6 are numerical example 1 of the present invention.
5 is a diagram of various aberrations. In the figure, , are the first, second, and third lens groups, ₁₁ and _I12 are the 1-1 and 1-2 lens groups, respectively, Y is the image height, M is the meridional image surface, and S is the sagittal image. It is a surface.

Claims (1)

[Claims] 1. In order from the object side, there are three lens groups: positive, negative, and first, second, and third lens groups with positive refractive power, and the first lens group has negative refractive power. 1-1
It has two lens groups, a lens group and a 1-2 lens group with positive refractive power, and the 1-1 lens group includes at least two lenses with negative refractive power whose image side surfaces are concave. L ₁₁₁ and L ₁₁₂ , the first-second lens group includes a lens L ₁₂₁ whose both lens surfaces are convex, and a positive refractive power lens L ₁₂₂ whose object side surface is a convex surface, and the second lens The group consists of a meniscus-shaped lens L ₂₁ with a negative refractive power with a convex surface facing the object side, a lens L ₂₂ with concave surfaces on both lens surfaces, and a meniscus-shaped lens L ₂₃ with a negative refractive power with a convex surface facing the image side. and the third
The lens group consists of a meniscus-shaped lens L ₃₁ with a positive refractive power with a convex surface facing the image side, a lens L ₃₂ with convex surfaces on both lens surfaces, a lens L ₃₃ with a positive refractive power with a convex surface facing the object side, and the object. It has at least one meniscus-shaped lens L ₃₄ with a positive refractive power and a convex side surface, and the focal lengths of the first, second, and third lens groups are f ₁ , f ₂ , and f , respectively. ₃ , and the focal lengths of the 1-1st lens group and the 1-2nd lens group are each
When f ₁₁ and f ₁₂ and the focal length of the lens L ₁₁₁ is f ₁₁₁ , 1.9<|f ₁ /f ₂ |<3.7 0.8<|f ₂ /f ₃ |<1.2 1.1<|f ₁₁ /f ₁₂ A projection lens characterized by satisfying the following conditions: |<2.3 1.4<f ₁₁₁ /f ₁₁ <2.2.