JPH0812330B2 - Projection lens - Google Patents

Description

TECHNICAL FIELD The present invention relates to a projection lens used for printing a required fine pattern on a photoresist-coated light-sensitive material in the field of photolithography, and particularly to a projection lens. The present invention relates to a projection lens suitable for printing with light including g-line (436 nm), h-line (405 nm) and i-line (365 nm).

<< Prior Art >> As a projection lens used for this type of printing, for example, an ultra-precision projection lens that is conventionally used in an ultra-precision reduction printing apparatus called a stepper, and a plate-making enlargement lens used for reduction copying are used. is there.

<< Problems to be Solved by the Invention >> In the case of a stepper lens, the above-mentioned conventional ultra-precision projection lens has, for example, g-line in the near-ultraviolet region of g-line, h-line, and i-line in order to obtain high resolution. Since the various aberrations are corrected with high precision only, there are the following problems.

I. Although the photosensitive wavelength range of photoresist extends to i-line,
In the above-mentioned conventional example, for example, only the g-line is taken into consideration, so that it can be used only with a single bright line, so that the illuminance is low, the time required for exposure is long, and the printing efficiency is inevitably reduced.

B. The effective screen size is small.

On the other hand, the conventional plate-making enlargement lens is a plate-making lens in consideration of the visible light region, so that the effective screen size is large and various aberrations in the visible light region are corrected with high accuracy. There are such difficulties.

C. It has low transmittance in the near-ultraviolet region and low resolution.

The present invention has been made in view of such circumstances, and an object of the present invention is to solve the above-mentioned problems (1) to (3).

<< Means for Solving the Problems >> The present invention is configured as follows to solve the above problems.

That is, the first lens group and the second lens group are arranged in order from the object side, and the first lens group sequentially has a positive meniscus lens having a convex surface facing the object side and a convex surface having a small radius of curvature facing the object side. The second lens group is composed of a positive lens and a negative lens, and the second lens group is a projection lens composed of a positive meniscus lens having a convex surface directed toward the image plane side, a biconcave lens, and a biconvex lens. Refractive index for i-line
Let n _g , n _h , and n _i be the variance values ν _h = (n _h −1) / (n _i −
n _g ), the positive lens of each lens group satisfies 1.67 <n _h <1.69 48 <ν _h <50, and the negative lens of each lens group satisfies 1.56 <n _h <1.61 30 <ν _h <36, and It is characterized by being made of a glass material having an internal transmittance for i-line (when the thickness is 10 mm) of 90% or more.

<Function> In correcting various aberrations such as coma and curvature, it is generally desirable that the refractive index of the glass material that constitutes the positive lens is as high as possible, but a high transmittance is also secured for i-line. In this case, the glass material used is limited, and it is generally impossible to use a glass material having a high refractive index.

Therefore, in the present invention, by selecting a glass material that meets the above conditions, the g rays (435.83 nm), h rays (404.66 nm), and i rays (365.01 nm), which are the main rays within the photosensitive wavelength range of the photoresist, are selected. The transmittance is improved. Further, by adopting the above configuration, the projection lens according to the present invention has a large effective screen size, high resolving power, and overall transmittance.

<< Examples >> Hereinafter, examples of the projection lens according to the present invention will be described with reference to a lens data table (Tables 1 and 2), an arrangement configuration diagram of the lenses (FIGS. 1 and 3), and diagrams showing various aberrations (No. 1). 2 and FIG. 4).

F in each lens data table is the focal length for the h line, Y
Is the maximum image height, F is the effective F number, m is the reference magnification, and T is the internal transmittance (thickness) of the glass material forming each lens element.
Indicates when the 10mm), r, d, n , ν corresponds to each code in Figure 1, n _g, n _h, n _i respectively g-line, h-line, i-line,
The refractive index, ν _h, is the dispersion value defined by the following equation.

ν _h = (n _h −1) / (n _i −n _g ) On the other hand, the diagrams showing aberrations (FIGS. 2 and 4) are shown in Example 1.
It corresponds to Example 2, and includes three types of graphs A, B, and C showing spherical aberration, astigmatism, and distortion. In the graph of spherical aberration A, the horizontal axis represents the aberration amount and the vertical axis represents the effective F number, and spherical aberration curves g, h, and i are shown by the g-line, h-line, and i-line, respectively. In the graph B showing astigmatism, S is the sagittal image plane and M is
Is a graph C showing the meridional image plane and showing distortion.
Both show aberrations for the h line.

Example 1 Table 1 shows the lens data of this example, FIG. 1 shows the configuration diagram of the lens, and FIG. 2 shows the aberration diagram.

In this embodiment, the first lens group G ₁ has a positive meniscus lens L ₁ having a convex surface directed toward the object side in order, a positive lens L ₂ having a convex surface with a small radius of curvature directed toward the object side, and a negative lens Lens L ₃
And the second lens group G ₂ is composed of a positive meniscus lens L ₄ having a convex surface sequentially facing the image plane side, a biconcave lens L ₅ and a biconvex lens L _6, and g line, h line as a whole, The combination of convex and concave-concave and convex-concave is arranged and arranged so that the i-line is achromatic. With this configuration, the reference magnification m =
Corrects various aberrations at −0.5.

Example 2 Table 2 shows the lens data of this example, FIG. 3 is a diagram showing the arrangement of lenses, and FIG. 4 is an aberration diagram.

In this embodiment, the first lens group G ₁ has a positive meniscus lens L ₁ whose convex surface is sequentially directed toward the object side, a plano-convex lens L ₂ whose convex surface with a small radius of curvature is directed toward the object side, and a plano-concave lens L 1. ₃
And the second lens group G ₂ is composed of a positive meniscus lens L ₄ having a convex surface sequentially facing the image plane side, a biconcave lens L ₅ and a biconvex lens L _6, and g line, h line, i The lines are arranged and arranged in a combination of convex-concave-concave-concave to form achromatic lines. With this configuration, the reference magnification m = −
Corrects various aberrations at 0.5.

<< Effects of the Invention >> As is apparent from the above description, since the projection lens according to the present invention is configured as described above, the following effects are achieved.

I. The positive lens and the negative lens forming each lens group are g
Since it is made of a glass material that takes into consideration the transmittance of the H-line, the H-line, and the i-line, the G-line, the H-line, and the i-line can be used at the same time, and the light transmittance in the photosensitive wavelength range of the photoresist is significantly improved. Therefore, the baking time can be shortened.

B. You can increase the effective screen size.

C. Various aberrations are improved and the image quality can be improved.

[Brief description of drawings]

FIGS. 1 and 3 are arrangement diagrams of lenses showing Embodiments 1 and 2 according to the present invention, and FIGS. 2 and 4 are aberrations of lenses corresponding to Embodiments 1 and 2, respectively. It is a figure. G ₁ ... 1st lens group, G ₂ ... 2nd lens group, n _g・ n _h・ n _i
... Refractive index for g-line, h-line and i-line, v _h ...
… Dispersion value.

Claims (1)

[Claims] 1. A first lens group and a second lens group are arranged in order from the object side, and the first lens group has a positive meniscus lens whose convex surface faces the object side and a convex surface having a small radius of curvature toward the object side. The second lens group is a projection lens composed of a positive meniscus lens having a convex surface directed toward the image plane side, a biconcave lens, and a biconvex lens, and a g-line of a glass material, Refractive indices for h-line and i-line are n _g ,
When n _h and n _i and the dispersion value is ν _h = (n _h −1) / (n _i −n _g ), the positive lens of each lens group is 1.67 <n _h <1.69 48 <ν _h <50. The negative lens of each lens group is made of a glass material satisfying 1.56 <n _h <1.61 30 <ν _h <36 and having an internal transmittance (when the thickness is 10 mm) of 90% or more for i-line. Projection lens.