JPH0472204B2 - - 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, the -1 lens group and the 1-2 lens group with positive refractive power, and the 1-1 lens group has a lens L ₁₁₁ with negative refractive power and a convex surface facing the object side. The first-second lens group includes a meniscus-shaped lens L ₁₁₂ with negative refractive power, and the first-second lens group includes a lens L ₁₂₁ with both lens surfaces convex and at least one meniscus with positive refractive power with the convex surface facing the object side. shaped lens group
L ₁₂₂ , and the second lens group includes a meniscus-shaped lens L ₂₁ with a negative refractive power and a convex surface facing the object side.
and a lens L ₂₂ with a negative refractive power, and a meniscus-shaped lens L ₂₃ with a negative refractive power with a convex surface facing the image side, and the third lens group has a positive refractive lens L 23 with a convex surface facing the image side. A lens L ₃₁ with a power meniscus shape, a lens L ₃₂ with both lens surfaces convex, at least two lenses L ₃₃ with positive refractive power with a convex surface facing the object side, and at least one lens with a convex surface facing the object side. It has a meniscus-shaped lens L ₃₄ with positive refractive power, and when the radii of curvature of the object-side and image-side lens surfaces of the lens L ₂₂ are R _2F and R _2R , respectively, |R _2F |<|R _2R | ...(1) The following condition is satisfied. The present invention achieves a projection lens that satisfactorily corrects aberrations by employing the above-described configuration. Particularly good imaging performance has been achieved within the range of projection magnification of 1/5 and shooting angle of view of 14 x 14 mm. Next, each component of the present invention will be explained in detail. The 1st-1st lens group is composed of a lens L ₁₁₁ with a negative refractive power and a meniscus-shaped lens L ₁₁₂ with a negative refractive power with a convex surface facing the object side, which effectively corrects distortion over the entire screen and masks it. This makes it possible to print patterns 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. Like the lens L ₁₁₂ , the lens L ₁₁₁ can be configured to have a meniscus shape with a convex surface facing the object side, or both lens surfaces can be configured to have concave surfaces to achieve good aberration correction. The 1st-2nd lens group is a lens with both lens surfaces convex.
Composed of L ₁₂₁ and at least one meniscus-shaped lens group L ₁₂₂ with positive refractive power with a convex surface facing the object side, it corrects introverted coma aberration and halo aberration that occur in the 1-1 lens group. We are working on increasing the resolution. The lens group L ₁₂₂ may be composed of one lens or two or more lenses. By using two or more lenses, coma aberration and halo aberration can be better corrected. 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 negative refractive power, and a meniscus-shaped lens with a negative refractive power with a convex surface facing the image side. L ₂₃ corrects negative spherical aberration occurring in the first and second lens groups and sagittal flare from the center to the periphery of the screen. Especially with lens L ₂₂ the first -
Negative spherical aberration and halo aberration occurring in the two lens groups are corrected, and sagittal flare at the periphery of the screen is corrected by lenses _L21 and _L23 . 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. Condition (1) is to strengthen the refractive power of the lens surface on the object side of the lens L ₂₂ compared to the lens surface on the image side, and this improves the spherical aberration near the numerical aperture of 0.3 and the sagittal flare around the screen. It has been corrected. If condition (1) is not met, it becomes difficult to satisfactorily correct spherical aberration and sagittal flare. The lens L ₂₂ may have a lens shape that satisfies condition (1), even if both lens surfaces are concave or a meniscus shape with a convex surface facing the image plane side. In particular, when the lens L ₁₁₁ of the 1-1st lens group is configured as a biconcave lens, it is preferable for the lens L ₂₂ to be configured in a meniscus shape with a convex surface facing the image plane side in terms of aberration correction. 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 ₁ , ₂ and ₃ , respectively, the focal lengths of the 1-1st lens group and the 1-2nd lens group are ₁₁ and ₁₂ , respectively, and the lens L ₁₁₁ The focal length of the lens is ₁₁₁ , and the lens L _{is 111.}
Let the radius of curvature of the lens surface on the object side and image side be respectively
When R _1F and R _1R , 0.85＜｜ _1/2 ｜＜ _2.2 ……(2) 0.75＜｜ _{3/2 ｜} ＜1.4……(3) 1.4＜｜ _11/12 ＜ _2.5 ……(4) 1.2 < ₁₁₁ / ₁₁ <2.1 ...(5) |R _1F | > | R _1R | ...(6) It is to satisfy the following conditions. Conditions (2) and (3) 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. If the Petzval 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 (4) is the first condition under the refractive power arrangement of conditions (2) and (3).
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 (4) is exceeded, the field curvature will be under-corrected, and if the upper limit is exceeded, the field curvature will be over-corrected. Condition (5) is for appropriately setting the share of 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 (5) is exceeded, distortion becomes under-corrected, and when the upper limit is exceeded, distortion becomes over-corrected. Condition (6) is to make the refractive power of the lens surface on the object side of lens L ₁₁₁ weaker than the refractive power of the lens surface on the image side, thereby better correcting the distortion of the entire screen. . If condition (6) is not met, distortion becomes under-corrected, which is not preferable. In the present invention, by dividing lenses L ₃₃ and L ₃₄ of the third lens group into three or more lenses to reduce the burden on the refractive power of each lens, coma aberration and field curvature can be better corrected over the entire screen. As a result, 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 CaF ₂ ,
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, 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 spatial interval 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 is a case where the projection magnification is 1/5, NA=0.3, and the screen range is 14×14. Further, Table 1 shows the relationship between each of the above-mentioned conditional expressions and various numerical values in the numerical examples.

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【table】 [Brief explanation of the drawing]

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 various aberration diagrams. In the figure, , are the first, second, and third lens groups, respectively, and I ₁₁ and I ₁₂ 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 surface.

Claims (1)

[Claims] 1. It has three lens groups: positive, negative, and first, second, and third lens groups with positive refractive power in order from the object side, 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 has a negative lens group L ₁₁₁ with a negative refractive power and a negative lens group with a convex surface facing the object side. The first-second lens group has a meniscus-shaped lens L ₁₁₂ with a refractive power of , and the first-second lens group includes a lens L ₁₂₁ with both lens surfaces convex and at least one meniscus-shaped lens with a positive refractive power with a convex surface facing the object side. Lens group L ₁₂₂
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 negative refractive power, and a negative refractive power with a convex surface facing the image plane side. It has a meniscus shaped lens L ₂₃ ,
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 a lens L with a positive refractive power with a convex surface facing the object side. ₃₃ and at least one meniscus-shaped lens with a positive refractive power whose object-side surface is convex
L ₃₄ , the radius of curvature of the object-side and image-side lens surfaces of the lens L ₂₂ are R _2F and R _2R , respectively, and the focal lengths of the first, second, and third lens groups are respectively
f ₁ , f ₂ , f ₃ , the 1-1st lens group and the 1-1st lens group;
The focal lengths of the two lens groups are f ₁₁ and f ₁₂ respectively, the focal length of the lens L ₁₁₁ is f ₁₁₁ , the radius of curvature of the object-side and image-side lens surfaces of the lens L ₁₁₁ is R _1F , respectively.
When R _1R | R _2F | < | R _2R | 0.85 < | f ₁ / f ₂ | < 2.2 0.75 < | f ₃ / f ₂ | < 1.4 1.4 < | f ₁₁ / f ₁₂ | < 2.5 1.2 < f ₁₁₁ /f ₁₁ <2.1 | R _1F | > | R _1R | A projection lens characterized by satisfying the following condition.