CN104062746B - Catadioptric immersion projection optical system with large numerical aperture - Google Patents

本发明涉及一种大数值孔径的折反射浸没投影光学系统。本发明中大数值孔径的折反射浸没投影光学系统由多个透镜和四个反射镜组成。从物面到像面依次可分为四个镜组。其中，第一透镜组具有正光焦度，且相对于其他镜组沿径向有一定距离偏移，有利于压缩后续光路，从而减小后续光路中透镜和反射镜的口径。本发明中的投影光学系统数值孔径大、像差小。相对于其他投影物镜，其最大优势在于达到较大数据孔径的同时，系统中透镜和反射镜的口径较小，从而降低对光学材料的尺寸要求，减小制造成本，降低镜片的加工、检测难度。

The invention relates to a large numerical aperture catadioptric immersion projection optical system. The catadioptric immersion projection optical system with large numerical aperture in the present invention is composed of multiple lenses and four mirrors. From the object plane to the image plane, it can be divided into four mirror groups. Wherein, the first lens group has a positive refractive power, and has a certain radial offset relative to other lens groups, which is beneficial to compressing the subsequent optical path, thereby reducing the aperture of the lens and the mirror in the subsequent optical path. The projection optical system in the present invention has large numerical aperture and small aberration. Compared with other projection objectives, its biggest advantage is that while achieving a larger data aperture, the lenses and mirrors in the system have smaller apertures, thereby reducing the size requirements for optical materials, reducing manufacturing costs, and reducing the difficulty of lens processing and inspection .

一种大数值孔径的折反射浸没投影光学系统A Catadioptric Immersion Projection Optical System with Large Numerical Aperture

技术领域technical field

本发明涉及一种工作于紫外波段的投影光学系统，特别涉及一种大数值孔径(数值孔径可达1.35)的折反射浸没投影光学系统。The invention relates to a projection optical system working in the ultraviolet band, in particular to a catadioptric immersion projection optical system with a large numerical aperture (the numerical aperture can reach 1.35).

背景技术Background technique

光学光刻是现代超大规模集成电路的最主要生产方法。随着需要的发展，光学投影光刻技术是目前大规模低成本生产大规模集成电路的最有效方法，该技术生产效率高，技术成熟稳定，广泛应用于平板显示、半导体照明等半导体产业。随着超大规模集成电路(VLSI)的发展，其集成度越来越高，其关键尺寸也变得越来越小，现在主流电子产品关键尺寸都在28nm，正向22nm大规模低成本化发展。这对光刻机曝光系统的光学性能提出了更高的要求。Optical lithography is the most dominant production method of modern VLSI. With the development of needs, optical projection lithography is currently the most effective method for large-scale and low-cost production of large-scale integrated circuits. This technology has high production efficiency, mature and stable technology, and is widely used in semiconductor industries such as flat panel display and semiconductor lighting. With the development of very large scale integration (VLSI), its integration level is getting higher and higher, and its key dimensions are becoming smaller and smaller. Now the key dimensions of mainstream electronic products are all at 28nm, and they are developing towards 22nm large-scale and low-cost. . This puts higher requirements on the optical performance of the exposure system of the lithography machine.

要减小电子产品的关键尺寸，只有两种途径。一种是减小波长，使用波长更短的紫外光；另一个途径就是增加光刻投影物镜的像方数值孔径。现阶段主要是使用193nm的ArF紫外光。在波长不变的情况下，为了减小电子产品的关键尺寸，只有增加光刻投影物镜的像方数值孔径。对于干式曝光，光刻投影物镜的像方数值孔径在达到0.93后，已无法继续增加。为了增加像方数值孔径，只有增加投影物镜最后一面透镜材料在使用波长的折射率或增加最后一面与像面之间的折射率。相对更换透镜材料，在投影物镜最后一片透镜与像面间充入折射率较高的液体，则是一种相对容易实现且成本较低的方法。To reduce the critical size of electronic products, there are only two ways. One is to reduce the wavelength and use ultraviolet light with a shorter wavelength; the other is to increase the image-side numerical aperture of the lithography projection objective. At this stage, 193nm ArF ultraviolet light is mainly used. In the case of constant wavelength, in order to reduce the critical size of electronic products, only increase the image-side numerical aperture of the lithography projection objective lens. For dry exposure, the image-side numerical aperture of the lithography projection objective lens cannot continue to increase after reaching 0.93. In order to increase the numerical aperture of the image side, only increase the refractive index of the last lens material of the projection objective lens at the wavelength used or increase the refractive index between the last surface and the image plane. Compared with changing the lens material, it is a relatively easy and low-cost method to fill the gap between the last lens of the projection objective lens and the image plane with a liquid with a high refractive index.

对于大数值孔径光学系统而言，由于存在很大的匹兹瓦场曲，这将导致光学系统的像面弯曲严重，而对于曝光半导体硅片而言，获得平场像是很重要的。为了获得平场像，其中一个解决的方法就是将投影光学系统设计为折反射式投影光学系统，这个折反射投影光学系统里包含折射元件和反射元件，由于凹面反射镜具有类似于正透镜光焦度但却有负透镜场曲，利于矫正场曲。因此，折反射投影光学系统中由于有一个或多个凹面反射镜。从而能很好地校正系统场曲。为了结构上的需要，凹面反射镜一般成对出现，即系统中的反射镜数量为偶数。For large numerical aperture optical systems, due to the large Petzval field curvature, this will lead to severe curvature of the image plane of the optical system, and for exposing semiconductor silicon wafers, it is very important to obtain a flat field image. In order to obtain a flat-field image, one of the solutions is to design the projection optical system as a catadioptric projection optical system. This catadioptric projection optical system contains refractive elements and reflective elements. Since the concave mirror has an optical focal point similar to that of a positive lens But it has negative lens field curvature, which is beneficial to correct field curvature. Therefore, there are one or more concave mirrors in the catadioptric projection optical system. Therefore, the field curvature of the system can be well corrected. For structural needs, concave mirrors generally appear in pairs, that is, the number of mirrors in the system is an even number.

随着投影物镜像方数值孔径的增大，光学系统中透镜和反射镜的口径也急剧增大，这对光学材料的尺寸提出更高要求，给生产、加工大口径高质量的光学元件带来严重困难。同时也对检测提出更高要求。With the increase of the numerical aperture of the projected object mirror, the aperture of the lens and mirror in the optical system also increases sharply, which puts forward higher requirements for the size of the optical material, and brings great challenges to the production and processing of large-diameter and high-quality optical components. serious difficulty. At the same time, it also puts forward higher requirements for detection.

本发明中涉及的投影光学系统在很好地实现系统的大数值孔径的同时，很好地解决了由系统的大数值孔径带来的像面弯曲和光学元件尺寸过大的问题。另外，与纯折射系统相比，本发明中的系统更好地解决了由大数值孔径带来的元件尺寸过大的问题。当投影物镜像方数值孔径达到1.35时，光学元件的最大尺寸大约在300mm，甚至更大。在本专利中涉及的投影物镜在像方数值孔径达到1.35时，光学元件的尺寸都控制在240mm以内。光学元件的口径减小20％。The projection optical system involved in the present invention well realizes the large numerical aperture of the system, and at the same time well solves the problems of image plane curvature and excessive size of optical elements caused by the large numerical aperture of the system. In addition, the system of the present invention better solves the problem of oversized elements caused by large numerical apertures than pure refractive systems. When the numerical aperture of the projection object mirror reaches 1.35, the maximum size of the optical element is about 300mm, or even larger. When the projection objective lens involved in this patent has an image-side numerical aperture of 1.35, the size of the optical elements is controlled within 240mm. Optics are 20% smaller in aperture.

本发明的特点在于在实现系统大数值孔径、且保证了系统极高的成像质量和紧凑的系统结构的同时，有效地减小了投影物镜中光学元件的口径，从而减小制造成本，降低元件的加工和检测的难度。The feature of the present invention is that while realizing the large numerical aperture of the system and ensuring the extremely high imaging quality and compact system structure of the system, the aperture of the optical elements in the projection objective lens is effectively reduced, thereby reducing the manufacturing cost and reducing the cost of components. Difficulty in processing and testing.

发明内容Contents of the invention

本发明要解决的技术问题是提供一种大数值孔径的折反射浸没投影光学系统，提高曝光分辨率，减小系统尺寸。本发明提出了适用于深紫外光波长照明且数值孔径达到1.35的浸没投影光学系统，该光学系统结构紧凑、视场大、成像质量好，且具有较小的尺寸和较少的材料消耗。The technical problem to be solved by the present invention is to provide a catadioptric immersion projection optical system with large numerical aperture, improve exposure resolution and reduce system size. The invention proposes an immersion projection optical system suitable for deep ultraviolet light wavelength illumination and having a numerical aperture of 1.35. The optical system has a compact structure, a large field of view, good imaging quality, a small size and less material consumption.

本发明采用的技术方案为：一种大数值孔径的折反射浸没投影光学系统，所述大数值孔径投影光学系统沿其光轴方向包括第一透镜组G1、第二反射透射镜组G2、第三反射镜组G3和第四透镜组G4。本发明中的大数值孔径折反射浸没投影物镜的第一透镜组G1具有正光焦度，第二反射透射镜组G2具有负光焦度，第三透镜组G3具有正光焦度，第四透镜组G4具有正光焦度，所述大数值孔径的投影光学系统包含了二十四片透镜和四片反射镜，且包含多个非球面。The technical solution adopted in the present invention is: a large numerical aperture catadioptric immersion projection optical system, the large numerical aperture projection optical system includes a first lens group G1, a second reflective and transmissive lens group G2, a second lens group G2 along the optical axis direction Three mirror groups G3 and a fourth lens group G4. The first lens group G1 of the large numerical aperture catadioptric immersion projection objective lens in the present invention has positive refractive power, the second reflection-transmission lens group G2 has negative refractive power, the third lens group G3 has positive refractive power, and the fourth lens group G4 has positive refractive power, and the projection optical system with large numerical aperture includes twenty-four lenses and four mirrors, and includes multiple aspherical surfaces.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第一透镜组G1包含四个透镜，其中第一片透镜为平行平板1，第二片透镜为双凸透镜2，第三片透镜为正弯月透镜3，第四片透镜为正弯月透镜4。The first lens group G1 of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention comprises four lenses, wherein the first lens is a parallel plate 1, the second lens is a biconvex lens 2, and the third lens is Positive meniscus lens 3, the fourth lens is positive meniscus lens 4.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第一透镜组G1中的双凸透镜2、正弯月透镜3、正弯月透镜4透镜沿垂直于系统光轴的方向具有偏离。The biconvex lens 2, positive meniscus lens 3, and positive meniscus lens 4 in the first lens group G1 of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention have deviations along the direction perpendicular to the optical axis of the system.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第二反射透射镜组G2、第三透镜组G3、第四透镜组G4沿垂直于系统光轴方向没有偏离。The second reflective-transmissive mirror group G2, the third lens group G3, and the fourth lens group G4 of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention do not deviate along the direction perpendicular to the optical axis of the system.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第二反射透射镜组G2包含六片透镜和四个反射镜。其中第五片为凹反射镜5，第六片为凹反射镜6，第七片为双凸透镜7，第八片为正弯月透镜8，第九片为正弯月透镜9，第十片为正弯月透镜10，第十一片为凹反射镜11，第十二片为正弯月透镜12，第十三片为凹反射镜13，第十四片为正弯月透镜14。The second reflection-transmission mirror group G2 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention includes six lenses and four reflection mirrors. Among them, the fifth piece is a concave reflector 5, the sixth piece is a concave reflector 6, the seventh piece is a biconvex lens 7, the eighth piece is a positive meniscus lens 8, the ninth piece is a positive meniscus lens 9, and the tenth piece It is a positive meniscus lens 10, the eleventh is a concave reflector 11, the twelfth is a positive meniscus lens 12, the thirteenth is a concave reflector 13, and the fourteenth is a positive meniscus lens 14.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第二反射透射镜组G2中的第五片凹反射镜5、第六片凹反射镜6、第九片正弯月透镜9第一面、第十片正弯月透镜10第一面、第十一片凹反射镜11、第十二片正弯月透镜12第一面、第十三片凹反射镜13、第十四片正弯月透镜14第一面为非球面。The fifth concave reflector 5, the sixth concave reflector 6, and the ninth positive meniscus lens 9 in the second reflective-transmissive mirror group G2 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention One side, the first surface of the tenth positive meniscus lens 10, the eleventh concave reflector 11, the first surface of the twelfth positive meniscus lens 12, the thirteenth concave reflector 13, the fourteenth The first surface of the positive meniscus lens 14 is aspherical.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第三透镜组G3包含九片透镜。其中第十五片为双凸透镜15，第十六片为负弯月透镜16，第十七片为负弯月透镜17，第十八片为正弯月透镜18，第十九片为正弯月透镜19，第二十片为负透镜20，第二十一片为双凸透镜21，第二十二片为正弯月透镜22，第二十三片为双凸透镜23。The third lens group G3 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention includes nine lenses. Among them, the fifteenth piece is a biconvex lens 15, the sixteenth piece is a negative meniscus lens 16, the seventeenth piece is a negative meniscus lens 17, the eighteenth piece is a positive meniscus lens 18, and the nineteenth piece is a positive meniscus lens. Moon lens 19, the twentieth sheet is a negative lens 20, the twenty-first sheet is a biconvex lens 21, the twenty-second sheet is a positive meniscus lens 22, and the twenty-third sheet is a biconvex lens 23.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第三透镜组G3中的第十五片双凸透镜15的第二面、第十六片负弯月透镜16的第二面、第十七片负弯月透镜17的第二面、第十九片正弯月透镜19的第一面、第二十片负透镜20的第一面、第二十一片双凸透镜21的第一面、第二十三片双凸透镜23的第一面为非球面。The second surface of the fifteenth biconvex lens 15, the second surface of the sixteenth negative meniscus lens 16, the second surface of the sixteenth negative meniscus lens 16, The second surface of the seventeenth negative meniscus lens 17, the first surface of the nineteenth positive meniscus lens 19, the first surface of the twentieth negative lens 20, the first surface of the twenty-first biconvex lens 21 Surface, the first surface of the twenty-third lenticular lens 23 is an aspheric surface.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第四透镜组G4包含五片透镜。其中第二十五片为正弯月透镜25，第二十六片为正弯月透镜26，第二十七片为正弯月透镜27，第二十八片为正弯月透镜28，第二十九片为正弯月透镜29。The fourth lens group G4 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention includes five lenses. Wherein the twenty-fifth piece is a positive meniscus lens 25, the twenty-sixth piece is a positive meniscus lens 26, the twenty-seventh piece is a positive meniscus lens 27, the twenty-eighth piece is a positive meniscus lens 28, and the twenty-eighth piece is a positive meniscus lens 28. Twenty-nine are positive meniscus lenses 29.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第四透镜组G4中的第二十五片正弯月透镜25的第二面、第二十七片正弯月透镜27的第二面、第二十八片正弯月透镜28的第二面为非球面。The second surface of the twenty-fifth positive meniscus lens 25 and the first surface of the twenty-seventh positive meniscus lens 27 in the fourth lens group G4 of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention The second surface of the two-sided, twenty-eighth positive meniscus lens 28 is an aspheric surface.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的最后一面与像面之间的介质是高折射率液体，包括但不限于去离子水。The medium between the last surface and the image plane of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention is a high refractive index liquid, including but not limited to deionized water.

本发明中涉及的大数值孔径的折反射浸没投影光学系统的第三透镜组G3与第四透镜组G4之间设置系统孔径光阑24。A system aperture stop 24 is provided between the third lens group G3 and the fourth lens group G4 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention.

本发明中涉及的大数值孔径的折反射浸没投影光学系统为双远心系统。The catadioptric immersion projection optical system with large numerical aperture involved in the present invention is a double telecentric system.

本发明中涉及的大数值孔径的折反射浸没投影光学系统适用于深紫外照明光源，包括但不限于波长为157nm、193.3nm或248nm的光源。The catadioptric immersion projection optical system with large numerical aperture involved in the present invention is suitable for deep ultraviolet illumination light sources, including but not limited to light sources with a wavelength of 157nm, 193.3nm or 248nm.

本发明与现有技术相比有以下优势：Compared with the prior art, the present invention has the following advantages:

1.本发明中涉及的大数值孔径的折反射浸没投影光学系统的第一透镜组G1、第二反射透射镜组G2、第三透镜组G3和第四透镜组G4的光焦度分别为正、负、正和正，这种结构能很好的校正系统像差。1. The refractive powers of the first lens group G1, the second reflective-transmissive lens group G2, the third lens group G3 and the fourth lens group G4 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention are respectively positive , negative, positive and positive, this structure can correct system aberration very well.

2.本发明中涉及的大数值孔径的折反射浸没投影光学系统的第一透射镜组G1的第一片透镜为平行平板1，可以在使用过程中按需要进行更换。2. The first lens of the first transmission lens group G1 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention is a parallel plate 1, which can be replaced as needed during use.

3.本发明中涉及的大数值孔径的折反射浸没投影光学系统的第一反射镜组G1具有正光焦度，且沿垂直于光轴方向具有一定偏离。可以压缩光路，减小后续光学元件的尺寸。3. The first mirror group G1 of the large numerical aperture catadioptric immersion projection optical system involved in the present invention has a positive power and a certain deviation along the direction perpendicular to the optical axis. The optical path can be compressed to reduce the size of subsequent optical components.

4.本发明中涉及的大数值孔径的折反射浸没投影光学系统的第二反射透射镜组G2包含四个凹面反射镜，有得于校正系统场曲，提高成像质量。4. The second reflection-transmission mirror group G2 of the catadioptric immersion projection optical system with a large numerical aperture involved in the present invention includes four concave mirrors, which can correct the field curvature of the system and improve the imaging quality.

5.本发明中涉及的大数值孔径的折反射浸没投影光学系统的第二反射透射镜组G2包含四个凹面反射镜可以折叠系统光路，使得系统结构紧凑。5. The second reflection-transmission mirror group G2 of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention includes four concave mirrors that can fold the optical path of the system, making the system compact.

6.本发明中涉及的大数值孔径的折反射浸没投影光学系统的17个非球面是凹面，只有1个非球面凸面，有得于降低加工和检测难度。6. The 17 aspheric surfaces of the large numerical aperture catadioptric immersion projection optical system involved in the present invention are concave, and only 1 aspherical surface is convex, which can reduce the difficulty of processing and testing.

7.本发明中涉及的大数值孔径的折反射浸没投影光学系统为双远心系统，物方和像方都是远心光路。因此，可以相对降低物面(掩模面)和像面30(硅片面)的位置误差。即使其实际位置相对于设计位置有较小偏差时，也不会造成投影物镜光学性能的显著降低。7. The catadioptric immersion projection optical system with large numerical aperture involved in the present invention is a double-telecentric system, and both object space and image space are telecentric light paths. Therefore, the position error between the object plane (mask plane) and the image plane 30 (silicon wafer plane) can be relatively reduced. Even if there is a small deviation between the actual position and the design position, it will not cause significant reduction in the optical performance of the projection objective lens.

8.本发明中涉及的大数值孔径的折反射浸没投影光学系统中的像方数值孔径达到1.35。8. The image-side numerical aperture of the large numerical aperture catadioptric immersion projection optical system involved in the present invention reaches 1.35.

9.本发明中涉及的大数值孔径的折反射浸没投影光学系统中的光学元件都具有较小的口径，且光学元件的最大口径不大于240mm。9. The optical elements in the large numerical aperture catadioptric immersion projection optical system involved in the present invention all have small apertures, and the maximum aperture of the optical elements is not greater than 240 mm.

附图说明Description of drawings

图1为本发明的大数值孔径的折反射浸没投影光学系统的示意图。FIG. 1 is a schematic diagram of a large numerical aperture catadioptric immersion projection optical system of the present invention.

图2为本发明的大数值孔径的折反射浸没投影光学系统的视场设置示意图。图中用斜线标示出的矩形为系统视场。FIG. 2 is a schematic diagram of the field of view setting of the large numerical aperture catadioptric immersion projection optical system of the present invention. The rectangle marked with oblique lines in the figure is the field of view of the system.

图3为本发明的大数值孔径的折反射浸没投影光学系统在全场范围内光学调制传递函数；图中的英文MTF意思为调制传递函数；图中的英文DIFFRACTION LIMT意思为衍射极限；DEFOCUSING意思为离焦。图中的字母T意思为子午面内的调制度；图中的英文R意思为弧矢面内的调制度，图中的英文FIELD意思为视场；图中的英文Mar意思是三月。Fig. 3 is the optical modulation transfer function of the catadioptric immersion projection optical system with large numerical aperture of the present invention in the whole field; the English MTF in the figure means the modulation transfer function; the English DIFFRACTION LIMT in the figure means the diffraction limit; DEFOCUSING means is out of focus. The letter T in the picture means the modulation degree in the meridian plane; the English R in the picture means the modulation degree in the sagittal plane, and the English FIELD in the picture means the field of view; the English Mar in the picture means March.

图4为本发明的大数值孔径的折反射浸没投影光学系统在像散和畸变像差曲线。图中FOCUS意思为聚焦点；图中MILLIMETERS意思为毫米；图中DISTORTION意思为相对畸变。Fig. 4 is a curve of astigmatism and distortion aberration of the catadioptric immersion projection optical system with large numerical aperture of the present invention. FOCUS in the figure means focal point; MILLIMETERS in the figure means millimeter; DISTORTION in the figure means relative distortion.

标号说明：1－第一平行平板、2－双凸透镜、3－正弯月透镜、4－正弯月透镜、5－凹反射镜、6－凹反射镜、7－双凸透镜、8－正弯月透镜、9－正弯月透镜、10－正弯月透镜、11－凹反射镜、12－正弯月透镜、13－凹反射镜、14－正弯月透镜、15－双凸透镜、16－负弯月透镜、17－负弯月透镜、18－正弯月透镜、19－正弯月透镜、20－负透镜、21－双凸透镜、22－正弯月透镜、23－双凸透镜、24－孔径光阑、25－正弯月透镜、26－正弯月透镜、27－正弯月透镜、28－正弯月透镜、29－正弯月透镜、30－像面。标号9’和标号9”所标示的透镜与标号9所标示的透镜是同一片透镜。标号10’所标示的透镜与标号10所标示的透镜是同一片透镜。标号12’所标示的透镜与标号12所标示的透镜是同一片透镜。Explanation of symbols: 1-first parallel plate, 2-biconvex lens, 3-positive meniscus lens, 4-positive meniscus lens, 5-concave reflector, 6-concave reflector, 7-biconvex lens, 8-positive curve Moon lens, 9-positive meniscus lens, 10-positive meniscus lens, 11-concave mirror, 12-positive meniscus lens, 13-concave mirror, 14-positive meniscus lens, 15-biconvex lens, 16- Negative meniscus lens, 17-negative meniscus lens, 18-positive meniscus lens, 19-positive meniscus lens, 20-negative lens, 21-biconvex lens, 22-positive meniscus lens, 23-biconvex lens, 24- Aperture stop, 25-positive meniscus lens, 26-positive meniscus lens, 27-positive meniscus lens, 28-positive meniscus lens, 29-positive meniscus lens, 30-image surface. The lens indicated by the numeral 9' and the numeral 9 "is the same lens as the lens indicated by the numeral 9. The lens indicated by the numeral 10' is the same lens as the lens indicated by the numeral 10. The lens indicated by the numeral 12' is the same as the lens indicated by the numeral 9. The lenses indicated by reference number 12 are the same lens.

具体实施方式detailed description

下面结合附图和具体实施方式对本发明作进一步详细描述。The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

图1为大数值孔径的折反射浸没投影光学系统示意图，共使用了二十四片透镜和四片反射镜，从光束入射方向依次包括第一透镜组G1、第二反射透射镜组G2、第三反射镜组G3和第四透镜组G4。第一透镜组G1具有正光焦度；第二反射透射镜组G2具有负光焦度；第三透镜组G3具有正光焦度；第四透镜组G4具有正光焦度。像面33为硅片面。Figure 1 is a schematic diagram of a catadioptric immersion projection optical system with a large numerical aperture. A total of twenty-four lenses and four mirrors are used. From the incident direction of the light beam, it includes the first lens group G1, the second reflective and transmissive mirror group G2, and the second lens group G2. Three mirror groups G3 and a fourth lens group G4. The first lens group G1 has a positive refractive power; the second reflective lens group G2 has a negative refractive power; the third lens group G3 has a positive refractive power; the fourth lens group G4 has a positive refractive power. The image plane 33 is a silicon wafer plane.

本发明所包含的第一透镜组G1沿垂直于光轴方向具有一定偏离量。第二反射透射镜组G2、第三透镜组G3和第四透镜组G4中二十个透镜和四个反射镜共轴(系统光轴)，即沿垂直于光轴方向没有偏离。The first lens group G1 included in the present invention has a certain amount of deviation along the direction perpendicular to the optical axis. The twenty lenses and four mirrors in the second reflective-transmissive lens group G2, the third lens group G3 and the fourth lens group G4 are coaxial (system optical axis), that is, there is no deviation along the direction perpendicular to the optical axis.

本发明所包含的第一透镜组G1包含四个透镜，第一片为平行平板1，第二片透镜为双凸透镜2，第三片透镜为正弯月透镜3，第四片透镜为正弯月透镜4。The first lens group G1 included in the present invention includes four lenses, the first lens is a parallel plate 1, the second lens is a biconvex lens 2, the third lens is a positive meniscus lens 3, and the fourth lens is a positive curve Moon lens 4.

本发明所包含的第一透镜组G1的第一片透镜为平行平板1，作为整个投影物镜的保护玻璃和密封窗口，可以在使用过程中按需要进行更换。The first lens of the first lens group G1 included in the present invention is a parallel plate 1, which serves as the protective glass and sealing window of the entire projection objective lens, and can be replaced as required during use.

本发明所包含的第一透镜组G1具有正光焦度，且沿垂直于光轴方向具有一定偏离量。其主要作用在于将物面上的物点发射的光线压缩，如图1中所示，将图1中各视场点的上光线向下折转，将图1中各视场点的下光线向上折转，从而减小后续光路中光学元件的口径。The first lens group G1 included in the present invention has positive refractive power and has a certain amount of deviation along a direction perpendicular to the optical axis. Its main function is to compress the light rays emitted by the object points on the object surface. As shown in Figure 1, the upper light rays of each field of view point in Fold upwards, thereby reducing the aperture of the optical elements in the subsequent optical path.

本发明所包含的第二反射透射镜组G2包含六片透镜和四个反射镜，它们分别是：第五片为凹反射镜5，第六片为凹反射镜6，第七片为双凸透镜7，第八片为正弯月透镜8，第九片为正弯月透镜9，第十片为正弯月透镜10，第十一片为凹反射镜11，第十二片为正弯月透镜12，第十三片为凹反射镜13，第十四片正弯月透镜14。其中第五片反射镜5和第十三片反射镜13只使用反射镜的中上部分，第六片反射镜6和第十一片反射镜11，只使用反射镜的中下部分。The second reflection-transmission mirror group G2 included in the present invention includes six lenses and four reflectors, which are respectively: the fifth is a concave reflector 5, the sixth is a concave reflector 6, and the seventh is a double-convex lens 7. The eighth piece is a positive meniscus lens 8, the ninth piece is a positive meniscus lens 9, the tenth piece is a positive meniscus lens 10, the eleventh piece is a concave mirror 11, and the twelfth piece is a positive meniscus lens Lenses 12, the thirteenth piece is a concave mirror 13, and the fourteenth piece is a positive meniscus lens 14. Wherein the fifth reflector 5 and the thirteenth reflector 13 only use the middle and upper part of the reflector, and the sixth reflector 6 and the eleventh reflector 11 only use the middle and lower part of the reflector.

本发明所包含的第二反射透射镜组G2的第五片凹反射镜5、第六片凹反射镜6和第七片双凸透镜7主要作用是将从第一透镜组出射的光线成实像于第七片双凸透镜7和第八片正弯月透镜8之间的空气间隔中，并防止中间像面“落入”透镜内部。第八片正弯月透镜8、第九片正弯月透镜9、第十片正弯月透镜10、第十一反凹反射镜11、第十二片正弯月透镜12、第十三片凹反射镜13和第十四片正弯月透镜14主要作用在于一次实像面成像于第十四片正弯月透镜14与第十五片双凸透镜15之间的空气间隔中，并防止中间像面“落入”透镜内部。第二反射透射镜组G2具有负光焦度，且包含多个凹面反射镜，对于校正像差，尤其是场曲具有很大作用。The main functions of the fifth concave reflector 5, the sixth concave reflector 6 and the seventh double-convex lens 7 of the second reflective-transmissive mirror group G2 included in the present invention are to form a real image on the light rays emitted from the first lens group. The air space between the seventh double-convex lens 7 and the eighth positive meniscus lens 8 prevents the intermediate image plane from "falling into" the interior of the lens. The eighth positive meniscus lens 8, the ninth positive meniscus lens 9, the tenth positive meniscus lens 10, the eleventh anti-concave mirror 11, the twelfth positive meniscus lens 12, the thirteenth The concave mirror 13 and the fourteenth positive meniscus lens 14 are mainly used to form a real image plane in the air space between the fourteenth positive meniscus lens 14 and the fifteenth double-convex lens 15, and to prevent the intermediate image The facets "fall into" the interior of the lens. The second reflection-transmission lens group G2 has a negative refractive power and includes a plurality of concave mirrors, which have a great effect on correcting aberrations, especially curvature of field.

本发明所包含的第三透镜组G3包含九片透镜。其中第十五片为双凸透镜15，第十六片为负弯月透镜16，第十七片为负弯月透镜17，第十八片为正弯月透镜18，第十九片为正弯月透镜19，第二十片为负透镜20，第二十一片为双凸透镜21，第二十二片为正弯月透镜22，第二十三片为双凸透镜23。第三透射镜组G3具有正光焦度，为类双高斯结构。它对于系统像方远心度和其他对称像差(如球差、畸变等)的校正有很大作用。The third lens group G3 included in the present invention includes nine lenses. Among them, the fifteenth piece is a biconvex lens 15, the sixteenth piece is a negative meniscus lens 16, the seventeenth piece is a negative meniscus lens 17, the eighteenth piece is a positive meniscus lens 18, and the nineteenth piece is a positive meniscus lens. Moon lens 19, the twentieth sheet is a negative lens 20, the twenty-first sheet is a biconvex lens 21, the twenty-second sheet is a positive meniscus lens 22, and the twenty-third sheet is a biconvex lens 23. The third transmission lens group G3 has a positive refractive power and is a double-Gaussian structure. It has a great effect on the correction of system image telecentricity and other symmetrical aberrations (such as spherical aberration, distortion, etc.).

本发明所包含的第四透镜组G4包含五片透镜。其中第二十五片为正弯月透镜25，第二十六片为正弯月透镜26，第二十七片为正弯月透镜27，第二十八片为正弯月透镜28，第二十九片为正弯月透镜29。第四透射镜组G4具有正光焦度，将物点最终成像于像面上，并保证系统像方数值孔径达到设计要求。对于系统像方远心度、像差平衡也有一定作用。The fourth lens group G4 included in the present invention includes five lenses. Wherein the twenty-fifth piece is a positive meniscus lens 25, the twenty-sixth piece is a positive meniscus lens 26, the twenty-seventh piece is a positive meniscus lens 27, the twenty-eighth piece is a positive meniscus lens 28, and the twenty-eighth piece is a positive meniscus lens 28. Twenty-nine are positive meniscus lenses 29. The fourth transmission lens group G4 has a positive refractive power, and finally images the object point on the image plane, and ensures that the numerical aperture of the image side of the system meets the design requirements. It also plays a role in system image telecentricity and aberration balance.

本发明所涉及的大数值孔径的折反射浸没投影光学系统的物面为掩膜面位置，像面30为硅片面位置。物面和像面30之间的垂轴放大率为-0.25。负号表示物面与像面30的方向是相反的。The object plane of the catadioptric immersion projection optical system with large numerical aperture involved in the present invention is the position of the mask plane, and the image plane 30 is the position of the silicon wafer plane. The vertical axis magnification between the object plane and the image plane 30 is -0.25. A minus sign indicates that the direction of the object plane and the image plane 30 are opposite.

本发明所涉及的大数值孔径的折反射浸没投影光学系统为双远心系统。所谓双远心系统是指物面上每个点发出的光锥中，其在子午面内的主光线与光轴平行，且该光线在子午面内也以平行于光轴的方向入射到像面上。前述的主光线是指物面上的点发射的经过光阑中心的光线。本发明所涉及的大数值孔径的折反射浸没投影光学系统为双远心系统，可以相对降低物面(掩模面)和像面30(硅片面)的位置误差。即使其实际位置相对于设计位置有较小偏差时，也不会造成投影物镜光学性能的显著降低。The catadioptric immersion projection optical system with large numerical aperture involved in the present invention is a double telecentric system. The so-called bi-telecentric system means that in the light cone emitted by each point on the object surface, the chief ray in the meridian plane is parallel to the optical axis, and the ray is also incident on the image plane in the direction parallel to the optical axis in the meridian plane superior. The aforementioned chief ray refers to the ray emitted by a point on the object surface and passes through the center of the diaphragm. The catadioptric immersion projection optical system with large numerical aperture involved in the present invention is a bi-telecentric system, which can relatively reduce the position errors of the object plane (mask plane) and the image plane 30 (silicon chip plane). Even if there is a small deviation between the actual position and the design position, it will not cause significant reduction in the optical performance of the projection objective lens.

本发明所包含的第三透镜组G3和第四透镜组G4之间设置系统孔径光阑24。该孔径光阑24可以为可变光阑，以调节系统数值孔径的大小。A system aperture stop 24 is provided between the third lens group G3 and the fourth lens group G4 included in the present invention. The aperture diaphragm 24 can be an iris diaphragm to adjust the numerical aperture of the system.

本发明所涉及的大数值孔径的折反射浸没投影光学系统适用于深紫外照明光源，在波长为193.3nm的光源，具有很好的像质。当然也可以用于波长为248nm和157nm。The catadioptric immersion projection optical system with large numerical aperture involved in the present invention is suitable for deep ultraviolet illumination light source, and has very good image quality in the light source with a wavelength of 193.3nm. Of course, it can also be used for wavelengths of 248nm and 157nm.

表1给出了本发明实施例中的大数值孔径的折反射浸没投影光学系统的基本参数。具体参数请参考表1。Table 1 shows the basic parameters of the catadioptric immersion projection optical system with large numerical aperture in the embodiment of the present invention. Please refer to Table 1 for specific parameters.

表2给出了本发明实施例中的大数值孔径的折反射浸没投影光学系统每片镜片的具体参数。其中，表2中的“表面序号”是沿光线传播方向计数，如第一透镜组G1中仅有的平行平板1的光束入射面为序号S1，光束出射面为序号S2，其它镜面序号以此类推；表2中的“半径”表示该面的曲率半径。其正负断定原则是：以该面顶点作为起点，终点为该面的曲率中心。若连线方向与光线传播方向相同则为正，反之为负。若该面为平面，该面曲率半径为无穷大，具体设置视光学设计软件而定，也可以以一个很大的数值代替，如1E20；表2中的“厚度”给出了相邻两个面在光轴上的距离。其正负判定原则是：以当前面顶点作为起点，下一面顶点作为终点。若连线方向与光线传播方向相同则为正，反之为负。若两个面之间的材料为玻璃，则该厚度表示透镜厚度，若两个面之间的没有材料，则表示两个透镜(或者透镜与反射镜)之间的空气间隔。表2中的“半口径”是投影物镜像方数值孔径为1.35时各个光学元件的半口径值。如果调整数值孔径数值，则光学元件半口径值也会改变。表2中的“材料”为各个透镜的光学材料，缺省处为空气。Table 2 shows the specific parameters of each lens in the large numerical aperture catadioptric immersion projection optical system in the embodiment of the present invention. Among them, the "surface serial number" in Table 2 is counted along the direction of light propagation. For example, the beam incident surface of the only parallel plate 1 in the first lens group G1 is serial number S1, the beam outgoing surface is serial number S2, and the serial numbers of other mirror surfaces are as follows By analogy; "radius" in Table 2 indicates the radius of curvature of the surface. The positive and negative determination principle is: take the vertex of the surface as the starting point, and the end point is the curvature center of the surface. If the connection direction is the same as the light propagation direction, it is positive, otherwise it is negative. If the surface is a plane, the radius of curvature of the surface is infinite. The specific setting depends on the optical design software, and it can also be replaced by a large value, such as 1E20; the "thickness" in Table 2 shows the thickness of two adjacent surfaces. distance on the optical axis. The positive and negative judgment principle is: take the current vertex as the starting point, and the next vertex as the end point. If the connection direction is the same as the light propagation direction, it is positive, otherwise it is negative. If the material between the two surfaces is glass, the thickness represents the lens thickness, and if there is no material between the two surfaces, it represents the air gap between the two lenses (or the lens and the mirror). The "half-aperture" in Table 2 is the semi-aperture value of each optical element when the numerical aperture of the projected object image is 1.35. If you adjust the numerical aperture value, the optic semi-diameter value will also change. "Material" in Table 2 is the optical material of each lens, and the default is air.

表2中的所有长度单位为mm。All lengths in Table 2 are in mm.

表2A为表2的补充，它给出了各个非球面的非球面系数。Table 2A is a supplement to Table 2, which gives the aspheric coefficients of each aspheric surface.

表1投影物镜基本参数Table 1 Basic parameters of projection objective lens

工作波长Working wavelength 193.368nm193.368nm 像方数值孔径image square numerical aperture 1.351.35 放大倍率Magnification -0.25-0.25 像方视场image square field of view 26mm×9mm26mm×9mm 物像距离Object distance 1300mm1300mm 物方工作距object space working distance 31.59mm31.59mm 像方工作距image square working distance 3.1mm3.1mm SIO2折射率SIO2 Refractive Index 1.5602191.560219 浸没液折射率Refractive index of immersion liquid 1.4320401.432040

表2投影物镜具体参数Table 2 Specific parameters of projection objective lens

表2A投影物镜非球面系数Table 2A Projection objective lens aspheric coefficient