a projection lens
A projection objective lens and lens technology, which is applied in the field of lithography, can solve the problems of deterioration of imaging quality, large change of lens surface shape, and change of lens temperature gradient, so as to reduce the change of surface shape and the gradient change of material refractive index Effect
Active Publication Date: 2016-04-20
SHANGHAI MICRO ELECTRONICS EQUIP (GRP) CO LTD
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Problems solved by technology
However, in the process of material selection, this patent does not take into account that materials with high refractive index generally have low energy transmittance, especially for those lenses with small aperture and large thickness, in the process of high-intensity light , the thermal deformation of the lens surface due to the absorption of materials will have a serious impact on the imaging quality of the entire projection objective lens, and then affect the exposure performance of the entire lithography machine
If the energy absorption of the material is too high, it will cause a temperature gradient change inside the lens, which will cause a change in the refractive index of the material, and will directly lead to the deterioration of the imaging quality.
[0005] Patent US6806942 such as figure 1 , 2 As shown, the shaded part in the figure is a high refractive index material. In order to correct the influence of chromatic aberration, a large number of high refractive index materials are used in the structure, especially in the first lens group, the first lens and the third lens are both The second highest refractive index material with lower transmittance is used. Although this material selection corrects the chromatic aberration and obtains a wider spectral range, but because the first group of lenses is the closest to the mask surface, and the lens The aperture is relatively small, and the incident energy is relatively concentrated. Using materials with low transmittance at this position will cause the lens to absorb more energy, and the lens surface changes greatly; in addition, under the condition of scanning a rectangular field of view, the The shape of the light beam on the first group of lenses is approximately rectangular, so that under non-rotational symmetric lighting conditions, the absorption of energy by the lens is also non-rotational symmetric, which will inevitably cause the first film and the second film to be damaged in the long-time exposure process. The three lenses are asymmetrically deformed due to more heat absorption, which seriously affects the image quality of the entire exposure system
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[0027] Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.
[0028] In the present invention, high refractive index materials refer to materials with ni>1.57, including the first material with a refractive index higher than 1.57 and the second material with a refractive index higher than 1.61, wherein the first material has a higher Refractive index and higher transmittance (10mm material transmittance τ10>0.997), so it should be used as the preferred high refractive index material; the second material has a very high refractive index, and its effect of correcting chromatic aberration is better than that of the first The material is better, but due to its relatively low transmittance (τ100.998), especially the first Among the four materials, τ10 can reach more than 0.999, so they are widely used in the projection objective lens system of the present invention.
[0029] The heat effect of the lens is ma...
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Abstract
Provided is a projection object lens. Lenses formed by high-refractive-index materials and lenses formed by low-refractive-index materials are arranged in a distributed mode to form the projection object lens, wherein the high-refractive-index materials are materials with ni greater than 1.57 and comprise the first high-refractive-index materials with the refractive index higher than 1.57 and the second high-refractive-index materials with the refractive index higher than 1.61, the radius-thickness ratio of the lenses made of the second high-refractive-index materials is no less than 4, and the lenses made of the second high-refractive-index materials cannot be located in the lenses close to an object plane and an image plane; the low-refractive-index materials are materials with ni less than 1.57 and comprise the first low-refractive-index materials with the ni less than 1.51 and the second low-refractive-index materials with the ni less than 1.48.
Description
technical field [0001] The invention relates to the field of lithography, in particular to a low thermal effect I-line projection objective lens for a lithography machine. Background technique [0002] In the lithography exposure system, the high-pressure mercury lamp is widely used as a light source except the excimer laser. In exposure systems with medium resolution (>200nm). Compared with the laser light source, the high-pressure mercury lamp has a wider spectral range, and the general spectral range is GHI-line (low-end lithography machine) or I-line (mid-end lithography machine), which requires that the design of the projection objective lens must be compatible with it. match. [0003] High refractive index materials commonly used in projection objectives refer to materials with ni>1.57, including the first material with a refractive index higher than 1.57 and the second material with a refractive index higher than 1.61, wherein the first material has a higher ...
Claims
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IPC IPC(8): G02B13/14G02B1/00G03F7/20
Inventor朱立荣
OwnerSHANGHAI MICRO ELECTRONICS EQUIP (GRP) CO LTD