WO2015051587A1 - 极紫外光刻机中匹配多个物镜的照明系统调整与设计方法 - Google Patents

极紫外光刻机中匹配多个物镜的照明系统调整与设计方法 Download PDF

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WO2015051587A1
WO2015051587A1 PCT/CN2014/000658 CN2014000658W WO2015051587A1 WO 2015051587 A1 WO2015051587 A1 WO 2015051587A1 CN 2014000658 W CN2014000658 W CN 2014000658W WO 2015051587 A1 WO2015051587 A1 WO 2015051587A1
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Prior art keywords
compound eye
aperture
lighting system
lithography machine
relay mirror
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PCT/CN2014/000658
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English (en)
French (fr)
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李艳秋
梅秋丽
刘菲
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北京理工大学
李艳秋
梅秋丽
刘菲
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Publication of WO2015051587A1 publication Critical patent/WO2015051587A1/zh

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70058—Mask illumination systems
    • G03F7/70141—Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
    • G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
    • G03F7/705—Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions

Definitions

  • the present invention relates to an illumination system adjustment and design method for matching a plurality of objective lenses in an EUV lithography machine, and belongs to the technical field of lithography illumination design.
  • EUVL Extreme ultraviolet lithography
  • the core component of the projection lithography machine is the projection exposure optical system, the most important components of which are the illumination system and the projection objective system.
  • the main function of the lighting system is to provide uniform illumination of the mask surface, control the exposure dose and achieve an off-axis illumination mode.
  • the illumination system is essential to improve the performance of the entire lithography machine. Therefore, designing the illumination system is an important part of completing the entire projection exposure system.
  • the illumination system in the industrial projection lithography machine is usually composed of a light source, a condensing mirror, a double-row compound eye, a relay mirror group, and the like.
  • the object of the present invention is to provide an illumination system adjustment and design method for matching multiple objective lenses in an EUV lithography machine, by which the illumination system is adjusted so that the illumination system can be a series of projection objective lenses having the same exposure field of view. Provides the required illumination to greatly reduce the manufacturing cost of the EUV lithography machine.
  • An illumination system adjustment and design method for matching multiple objective lenses in an extreme ultraviolet lithography machine the illumination system applicable to the method comprises a light source, a condensing mirror, a compound eye, a complex eye, and a relay lens group; and defining a relay lens group
  • the first relay mirror through which the medium light source emits light is the relay mirror A, and the second relay mirror that passes through is the relay mirror B; the specific steps of the method are:
  • Step 101 An aperture stop is disposed on the curved image surface of the illumination system, and the size of the aperture stop is the same as the size of the curved image surface;
  • Step 102 Taking a ray point of the exit point of the illumination system as an object point, and separately calculating an aperture angle of the exiting ray of the relay mirror A on the meridional plane and the sagittal plane;
  • Step 103 Acquire relevant parameters of a projection objective lens in a current extreme ultraviolet lithography machine, wherein the related parameters include a size of an arc image surface, a principal ray incident angle on the curved image surface, and a numerical aperture on the curved image surface; 104. Calculate the kneading surface according to the relevant parameters, and take out the center point of the kneading surface as the object point for ray tracing;
  • Step 105 Adjust the tilt angle of the relay mirror A to compensate for the change of the magnification of the field of view compound eye caused by the subsequent adjustment of the illumination system; adjust the tilt angle of the relay mirror B to compensate the center of the arc beam The change in the angle during the propagation due to subsequent adjustments; Step 106, adjusting the position of the relay mirror A, so that the aperture angles of the exiting beams of the relay mirror A in the illumination system on the meridional plane and the solitary plane are equal to the aperture angles calculated in step 102, respectively;
  • Step 107 Adjust the position of the relay mirror B so that the exit pupil is imaged on the central compound eye of the pupil complex eye after passing through the relay mirror B and the relay mirror A, and simultaneously satisfy the following two conditions: First, the pupil The center of the spot on the central compound eye of the compound eye coincides with the center of the complex eye, and second, the spot incident on the central compound eye of the complex eye of the complex eye can be reflected by the complex eye to the compound eye of the field of view;
  • Step 108 Adjusting the tilt angle of the center complex eye element on the complex eye of the pupil and the compound eye of the field of view, so that the beam can be reflected by the central compound eye of the compound eye of the field after passing through the center complex eye of the complex eye, and the central compound eye of the complex eye of the field of view The reflected beam is incident on the position of the light source after being vertically incident on the condensing mirror;
  • Step 109 Determine whether the image plane of the current illumination system is close to the orphan image plane obtained in step 103. If yes, calculate the coordinates and the tilt angle of each compound eye in the compound eye of the field of view and the complex eye of the pupil, and according to the calculated coordinates and The tilt angle adjusts each compound eye to complete the adjustment of the illumination system. If not, steps 105 through 108 are repeated in sequence until the requirements are met.
  • the present invention adjusts the illumination system so that it can provide a desired illumination for a series of projection objective systems having the same exposure field of view; therefore, after the EUV lithography machine replaces the projection objective, the adjustment method is based on the present invention.
  • the illumination system is adjusted so that an illumination system matching the projection objective system can be obtained without replacing the corresponding illumination system, thereby greatly reducing the design cost of the EUV lithography machine.
  • DRAWINGS 1 is a schematic view showing the structure of an optical system in an extreme ultraviolet lithography machine.
  • FIG. 2 is a flow chart of a method for adjusting and designing the present invention.
  • Figure 3 is a schematic view of the curved image of the illumination system.
  • FIG. 4 is a schematic structural view of a condensing mirror. detailed description
  • the present invention provides an illumination system adjustment and design method for a plurality of objective lenses for an EUV lithography machine, so that the adjusted illumination system can provide a required illumination for a series of projection objective lenses having the same exposure field of view.
  • the illumination system includes a light source, a condensing mirror, a field of view compound eye, a pupil compound eye, a relay lens group composed of two quadric surfaces, and defines a first relay mirror through which the light source exiting the relay lens group passes.
  • Mirror A, the second relay mirror that passes through is relay mirror B, as shown in Figure 1.
  • the coordinate system 0-XYZ is established, which is the center of the concentric circle of the orphan image plane in the initial illumination system as the coordinate origin ⁇ , and the vector formed by the center point of the pupil plane to the origin of the coordinate is used.
  • the direction is the positive direction of the ⁇ axis, and the direction of the vector formed by the center point of the orphan image plane to the origin of the coordinate is taken as the positive direction of the ⁇ axis, and the positive direction of the X axis is determined by the "right hand rule";
  • the calculations are all performed in the coordinate system; as shown in Fig. 2, the specific process of the adjustment method of the present invention is as follows:
  • Step 101 Design an aperture stop on the curved image surface of the illumination system, and make the size of the aperture stop the same as the size of the curved image surface.
  • the light beam emitted by the light source converges on the curved image surface and then enters the exit pupil surface during the actual working process, when the method is implemented as the object surface, the light exits from the exit surface. All light must also converge at the orphan image before it can enter the subsequent system.
  • the correctness of the design of the reverse design (the basis of the adjustment method in the present invention is the reverse design).
  • the area corresponding to the curved image surface corresponds to an aperture stop, and the size of the aperture is the same as the size of the above area.
  • Step 102 Perform ray tracing by using the exit surface as the object surface, that is, take out the center point of the ⁇ surface as the object point for ray tracing, and calculate the aperture angle of the exiting ray of the relay mirror A on the meridional plane and the sagittal plane respectively.
  • ray tracing is a common technical means for optical design, which can be implemented in the optical design software zemax or code V.
  • Step 103 Obtain relevant parameters of the projection objective lens in the current extreme ultraviolet lithography machine, and use the same as a design index of the illumination system, and the related parameters include the size of the isolated image plane, the incident angle of the chief ray on the orphan image plane, and the arc. The numerical aperture on the image plane.
  • the projection objective lens to which the present invention is applied has the same exposure pupil field, the arcuate image plane sizes of the respective projection objective lenses are the same.
  • the illumination system In the following steps, a series of adjustments are made to the illumination system such that the distance from the exit center of the illumination system to the origin of the coordinate system is equal to the center of the two concentric circles constituting the curved object surface of the objective lens system to the entrance center of the objective lens system.
  • the exit size of the illumination system should be the same as the entrance size of the objective system.
  • Step 104 Calculate the kneading surface according to the relevant parameter, and take out the center point of the kneading surface as the object point for ray tracing.
  • the calculation of the kneading surface based on the relevant parameters in this step is a prior art, and therefore will not be described in detail in the present invention.
  • Step 105 Adjust the tilt angle of the relay mirror A to compensate for the change of the magnification of the field of view compound eye caused by the subsequent adjustment of the illumination system; adjust the tilt angle of the relay mirror B, and fine-tune the Y coordinate of the relay mirror A Z coordinate, used to compensate for the central angle of the orphan beam due to the follow-up Adjustments made to change.
  • Step 106 Adjust the position of the relay mirror A (ie, adjust the Y coordinate and the Z coordinate of the relay mirror A) to simultaneously control the aperture angle of the outgoing beam of the relay mirror A in the illumination system on the meridional plane and the sagittal plane. , respectively, equal to the aperture angle of the outgoing beam of the relay mirror A calculated in step 102 on the meridional plane and the sagittal plane.
  • Step 2 ( ⁇ 7, adjust the position of the relay mirror B (that is, adjust the Y coordinate and the Z coordinate of the relay mirror B) to ensure that the center of the exit pupil is imaged at the center of the pupil complex eye after passing through the relay mirror B and the relay mirror A.
  • Step 108 Adjusting the tilt angle of the pair of central compound eye elements on the compound eye of the pupil and the compound eye of the field of view, so that the beam can be reflected by the center compound eye of the compound eye of the field through the center complex eye of the complex eye, and the center of the compound eye through the field of view
  • the beam reflected by the compound eye element is incident on the light source and is concentrated at the position of the light source.
  • Step 209 Using optical design software modeling to determine whether the image plane of the current illumination system is close to the curved image plane obtained in step 103. If it is satisfied, the coordinates and the tilt angle of each compound eye in the compound eye of the pupil and the compound eye of the field of view can be calculated by ray tracing, etc., thereby completing the adjustment of the illumination system matched with the objective lens system, wherein the coordinates of the compound eye element are calculated.
  • the illuminance in the arc image area determined in step 103 accounts for more than 80% of the total illuminance of the entire image surface, and secondly, The illumination non-uniformity in the arc image area determined in step 103 is less than or equal to 5%.
  • Table 1 shows the design specifications of three sets of lighting systems that match different projection objectives.
  • the first set is used as the design indicator for the initial lighting system, and the other two sets are designed according to the present invention.
  • the laser plasma source is used in all three systems.
  • the parameters of the light source condenser are calculated according to the data provided by the EUV light source manufacturer Cymer.
  • the structure is shown in Figure 4.
  • the size of the orphan planes is the same in all objective systems.
  • the structure is shown in Figure 3. However, the incident angle of the principal ray and the numerical aperture of the object are different in each objective system.
  • the parameters for entering are also different.
  • the incident angle of the chief ray on the curved object surface in the EUV lithography objective system usually varies between 4.9° and 6°
  • the current numerical aperture of the EUV lithography objective lens is typically 0.0625, 0.075 and 0.0825.
  • the incident angles of the chief ray on the curved image planes of the system ⁇ , system 2 and system 3 are set to 5.52°, 4.9° and 6°, respectively, and the image numerical apertures are set to 0.0625, 0.075, 0.0825.
  • Three sets of illumination systems are designed according to the method of the present invention.
  • the amount of change of the relay lens group parameters in the other two sets of illumination systems is shown in Table 2.
  • #1 represents the relay mirror 1
  • #2 represents the relay mirror 2
  • AY, ⁇ , ⁇ " respectively represent the Y coordinate, Z coordinate, and ⁇ tilt of the corresponding relay mirror.
  • the amount of change in angle is shown in Table 2.
  • Three sets of lighting systems can be implemented A variety of off-axis illumination modes, such as two-pole, four-pole and ring, are now simple and clear. The performance of the three systems is evaluated by taking two-pole illumination as an example.
  • the illumination system usually adopts the uniformity U of the integrated illuminance of the orphan image in the scanning direction as the evaluation standard:

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Lenses (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Abstract

一种极紫外光刻机中匹配多个物镜的照明系统调整与设计方法，该方法适用的照明系统包括光源、聚光镜、视场复眼、光阑复眼以及中继镜组；该方法的具体步骤为：在极紫外光刻机更换投影物镜前：利用光线追迹，计算中继镜A的出射光线在子午面和弧矢面上的孔径角；在极紫外光刻机更换投影物镜后：取出瞳面的中心点作为物点进行光线追迹；通过调整中继镜A和中继镜B的倾斜角和位置，以及调整光阑复眼和视场复眼上中心复眼元的倾斜角度，直至当前照明系统的像面与投影物镜对应的弧形像面相近为止。从而通过对照明系统进行调整得到与该投影物镜系统相匹配的照明系统，大大降低了投影式光刻机的设计成本。

Description

极紫外光刻机中匹配多个物镜的照明系统调整与设计方法 技术领域 本发明涉及一种极紫外光刻机中匹配多个物镜的照明系统调整与设计方 法， 属于光刻照明设计技术领域。 说
背景技术 极紫外光刻 （EUVL) 是以波长为 11〜 4nm的 EUV射线为曝光光源的光刻
书
技术， 适用于特征尺寸为 22nm及更小特征尺寸的集成电路的大批量生产。 投影 式光刻机的核心部件是投影曝光光学系统， 该系统最重要的组成部分是照明系 统和投影物镜系统。 照明系统主要功能是为掩模面提供均匀照明、 控制曝光剂 量和实现离轴照明模式。 作为光刻机重要组成部分， 照明系统对提高整个光刻 机性能至关重要， 因此设计好照明系统是完成整个投影曝光系统的重要环节。 产业化投影式光刻机中的照明系统通常由光源、 聚光镜、 双排复眼、 中继 镜組等部分构成。 在针对指定的投影物镜进行照明系统设计的过程中， 需要满 足两个方面的要求： 一是照明系统的出瞳需要与投影物镜的入瞳重合， 二是照 明系统的像面， 亦即照明面， 其尺寸需要与投影物镜的物面相同， 且位置也相 同。 然而， 为了进一步降低特征尺寸， 投影物镜的数值孔径会不断增大， 其相 应的入瞳参数也会发生变化， 这就导致与之匹配的照明系统需要重新设计。 显 然， 使用新的元件会极大的增加制造成本， 重新设计一个全新的照明系统也会 耗费大量的人力和物力。 因此， 有必要研究出一种方法， 利用该方法， 能够在 初始照明系统的基础上， 通过改变元件的位置来获得一套多照明系统 ， 从而为 多个不同的物镜系统提供照明。 发明内容
本发明的目的是提供一种极紫外光刻机中匹配多个物镜的照明系统调整与 设计方法， 利用该方法对照明系统进行调整， 使得照明系统可为一系列具有相 同曝光视场的投影物镜提供符合要求的照明， 从而大大减小极紫外光刻机的制 造成本。
实现本发明的技术方案如下：
一种极紫外光刻机中匹配多个物镜的照明系统调整与设计方法， 该方法适 用的照明系统包括光源、 聚光镜、 枧场复眼、 光阑复眼以及中继镜组； 同时定 义中继镜組中光源出射光线经过的第一片中继镜为中继镜 A , 经过的第二片中 继镜为中继镜 B ; 该方法的具体步骤为：
在极紫外光刻机更换投影物镜前：
步骤 101、 在照明系统的弧形像面上设置孔径光阑， 且使孔径光阑的尺寸与 弧形像面的尺寸相同；
步骤 102、 取照明系统的出瞳面的中心点作为物点进行光线追迹 , 分别计算 中继镜 A的出射光线在子午面和弧矢面上的孔径角；
在极紫外光刻机更换投影物镜后：
步骤 103、 获取当前极紫外光刻机中投影物镜的相关参数， 其中所述相关参 数包括弧形像面的尺寸、 弧形像面上主光线入射角以及弧形像面上的数值孔径； 步骤 104、 才艮据所迷相关参数计算出瞳面， 取出瞳面的中心点作为物点进行 光线追迹；
步骤 105、 调整中继镜 A的倾斜角度， 以补偿照明系统由于后续调整而导致 的对视场复眼放大倍率的改变； 调整中继镜 B 的倾斜角度， 用以补偿弧形光束 所对应的圆心角在传播过程中由于后续调整而发生的改变； 步骤 106、 调整中继镜 A的位置， 使得照明系统中中继镜 A的出射光束在 子午面和孤矢面上的孔径角分别与步骤 102中计算的孔径角相等；
步骤 107、 调整中继镜 B 的位置， 使得出瞳中心经过中继镜 B和中继镜 A 后成像于光阑复眼的中心复眼元上， 且同时满足以下两个条件： 第一、 光阑复 眼的中心复眼元上的光斑中心与该复眼元的中心重合， 第二、 入射至光阑复眼 的中心复眼元上的光斑能被该复眼元反射至视场复眼中；
步骤 108、 调整光阑复眼和视场复眼上中心复眼元的倾斜角度， 使得光束经 过光阑复眼的中心复眼元后能被视场复眼的中心复眼元反射， 且经视场复眼的 中心复眼元反射的光束垂直入射至聚光镜后会聚于光源位置上；
步骤 109、 判断当前照明系统的像面是否满足与步骤 103获得的孤形像面相 近， 若满足， 则计算视场复眼和光阑复眼中各复眼元的坐标和倾斜角度， 并根 据计算的坐标和倾斜角调整各复眼元， 完成照明系统的调整， 若不满足， 则依 次重复步驟 105至 108， 直至满足要求为止。
有益效果
首先， 本发明通过对照明系统进行调整， 使得其可为一系列具有相同曝光 视场的投影物镜系统提供符合要求的照明； 因此在极紫外光刻机更换投影物镜 后， 基于本发明调整方法对照明系统进行调整， 使得在无需更换相应照明系统 的情况下， 可得到与该投影物镜系统相匹配的照明系统， 从而大大降低了极紫 外光刻机的设计成本。
其次， 本发明照明系统的调整方法， 只需要依据投影物镜的相关参数调整 照明系统中元件的位置， 其不采用任何新的元件， 极大的降低了极紫外光刻的 设计和制造成本， 缩短了研发周期。 附图说明 图 1为极紫外光刻机中光学系统的结构示意图。
图 2为本发明调整与设计方法的流程图。
图 3为照明系统弧形像面示意图。
图 4为聚光镜的结构示意图。 具体实施方式
下面结合附图和具体实施方式对本发明进行详细说明。
本发明针对极紫外光刻机提供一种匹配多个物镜的照明系统调整与设计方 法， 使得调整后的照明系统可为一系列具有相同曝光视场的投影物镜提供符合 要求的照明， 该方法适用的照明系统包括光源、 聚光镜、 视场复眼、 光阑复眼、 由两片二次曲面构成的中继镜组， 同时定义中继镜組中光源出射光线经过的第 一片中继镜为中继镜 A， 经过的第二片中继镜为中继镜 B , 如图 1所示。
同时在本实施例中建立坐标系 0- XYZ， 该坐标系以初始照明系统中孤形像 面的同心圓环的圆心作为坐标原点 〇， 以出瞳面中心点到该坐标原点所构成的 矢量的方向作为 Ζ轴的正方向， 以孤形像面的中心点到坐标原点所构成的矢量 的方向作为 Υ轴的正方向， 利用 "右手定则" 确定 X轴的正方向； 以下步驟中 涉及的计算都是在该坐标系下进行； 如图 2 所示， 本发明调整方法的具体过程 如下：
在极紫外光刻机更换投影物镜前：
步骤 101、 在照明系统的弧形像面上设计孔径光阑， 且使孔径光阑的尺寸与 与弧形像面的尺寸相同。
由于照明系统在实际工作过程中， 光源出射的光束是会聚于弧形像面上然 后入射至出瞳面上， 所以， 当出瞳面作为物面来实施本方法时， 从出瞳面出射 的所有光线也必须在孤形像面处会聚以后才能进入到后续系统中， 这样才能保 证逆向设计思想 （本发明中的调整方法的基础就是逆向设计） 的正确性。 由此， 弧形像面对应的区域就相当于一个孔径光阑， 且该光阑的尺寸与上述区域的尺 寸需相同。
步骤 102、 以出瞳面作为物面， 进行光线追迹， 即取出瞳面的中心点作为物 点进行光线追迹， 分别计算中继镜 A的出射光线在子午面和弧矢面上的孔径角。
本步骤中光线追迹为光学设计常用的技术手段，其可在光学设计软件 zemax 或者 code V中实现。
在极紫外光刻机更换投影物镜后：
步驟 103、 获取当前极紫外光刻机中投影物镜的相关参数， 并将其作为照明 系统的设计指标， 所迷相关参数包括孤形像面的尺寸、 孤形像面上主光线入射 角以及弧形像面上的数值孔径。
由于本发明所适用的投影物镜具有相同的曝光枧场， 因此各投影物镜的弧 形像面尺寸相同。
以下步骤中通过对照明系统进行一系列调整， 使得照明系统的出瞳中心到 坐标系原点的距离等于物镜系统中构成其弧形物面的两个同心圆的圆心到物镜 系统的入瞳中心的距离， 同时， 照明系统的出瞳尺寸应与该物镜系统的入瞳尺 寸相同。
步骤 104、 根据所述相关参数计算出瞳面， 取出瞳面的中心点作为物点进行 光线追迹。 本步骤中根据相关参数计算出瞳面为现有技术， 因此在本发明中不 对其进行详述。
步骤 105、 调整中继镜 A的倾斜角度， 以补偿照明系统由于后续调整而导致 的对视场复眼放大倍率的改变； 调整中继镜 B 的倾斜角度， 同时微调中继镜 A 的 Y坐标与 Z坐标， 用以补偿孤形光束所对应的圆心角在传播过程中由于后续 调整而发生的改变。
步骤 106、 调整中继镜 A的位置 （即调整中继镜 A的 Y坐标与 Z坐标）， 用 以同时控制该照明系统中中继镜 A的出射光束在子午面和弧矢面上的孔径角， 使其分别等于步骤 102 中计算的中继镜 A的出射光束在子午面和弧矢面上的孔 径角。
步驟 2(Τ7、 调整中继镜 B的位置 （即调整中继镜 B的 Y坐标与 Z坐标）， 保 证出瞳中心经过中继镜 B和中继镜 A后成像于光阑复眼的中心复眼元上， 且满 足以下两个条件： 第一、 光阑复眼的中心复眼元上的光斑中心与该复眼元的中 心重合， 第二、 入射至光阑复眼的中心复眼元上的光束能被该复眼元反射至光 阑复眼中。
步骤 108、 调整光阑复眼和视场复眼上一对中心复眼元的倾斜角度， 使得光 束经过光阑复眼的中心复眼元后能被视场复眼的中心复眼元反射， 且经视场复 眼的中心复眼元反射的光束垂直入射至聚光镜后会聚于光源位置。
步骤 209、 利用光学设计软件建模， 判断当前照明系统的像面是否满足与步 驟 103获得的弧形像面相近。若满足， 则可以通过光线追迹等方法计算光阑复眼 和视场复眼中各复眼元的坐标和倾斜角度， 从而完成与该物镜系统相匹配的照 明系统的调整， 其中， 计算复眼元的坐标和倾斜角度的方法为现有技术 （参见 申请号为： 201210132163.6)， 在此不详细说明， 然后根据计算的坐标和倾斜角调 整各复眼元， 完成照明系统的调整； 若不满足， 则依次重复步骤 105至 108， 直 至完成与该物镜系统相匹配的照明系统的设计为止。
本步骤中所迷相近为满足以下两个条件： 一是在当前照明系统的像面上， 位于步骤 103确定的弧形像面区域内的光照度占整个像面总光照度的 80%以上， 二是位于步驟 103确定的弧形像面区域内的光照非均匀度小于或等于 5%。 本发明的实施实例：
表 1 所示为三套与不同投影物镜相匹配的照明系统的设计指标， 其中第一 套作为初始照明系统的设计指标， 其它两套则依据本发明设计获得。 三套系统 均采用激光等离子体光源， 光源聚光镜的参数依据 EUV光源制造商 Cymer提供 的数据计算获得， 其结构如图 4 所示。 所有物镜系统中孤形物面的尺寸是相同 的， 其结构如图 3 所示， 但每一套物镜系统中弧形物面的主光线入射角以及物 方数值孔径均是不同的， 因此其入瞳参数也各不相同。 由于极紫外光刻物镜系 统中弧形物面上的主光线入射角通常在 4.9° 到 6° 之间变化，且目前 EUV光刻 物镜的物方数值孔径的典型取值为 0.0625、 0.075 以及 0.0825 , 为了表明本方法 的广泛适用性， 系统 ί、 系统 2和系统 3的弧形像面上的主光线入射角分別设置 为 5.52° 、 4.9° 和 6° ， 其像方数值孔径则分別设置为 0.0625、 0.075、 0.0825。
表 1
Figure imgf000009_0001
依据本发明中的方法设计得到三套照明系统， 在初始照明系统的基础上， 其它两套照明系统中中继镜組参数的改变量如表 2所示。 为方便说明， 表 2 中 以 #1代表中继镜 1， 以 #2代表中继镜 2 , AY , ΔΖ ， Δ"分别表示的是所对应 的中继镜的 Y坐标、 Z 坐标以及 α倾斜角度的改变量。 三套照明系统均可以实 现二极、 四极和环形等多种离轴照明模式， 为简洁明了， 现以二极照明为例来 对三套系统的性能进行评价。
表 2
Figure imgf000010_0002
由于极紫外光刻采用的是步进 -扫描的模式， 其照明系统通常采用扫描方向 上孤形像面的积分光照度的均勾度 U来作为评价标准：
Figure imgf000010_0001
E max + E mm . 其中 £ max与 £ min分别表示的是在扫描方向上孤形像面的最大和最小的积分 光照度。 为准确的评价系统的性能， 在三套照明系统设计完成以后， 可以利用 光学软件进行光线追迹。 由于激光等离子体光源的尺寸相对照明系统来说足够 小， 因此可以用点光源来模拟实际光源。 200，000，000条光线从点光源出射， 三套 照明系统的性能如表 2所示。从表中可知， 系统 2和系统 3中元件的移动量相对 整个系统的总长来说较小， 且每一套照明系统在弧形像面上的光照均匀度满足 要求。 结果表明本发明中的方法是有效可行的。
综上所述， 以上仅为本发明的较佳实施例而已， 并非用于限定本发明的保 护范围。 凡在本发明的精神和原则之内， 所作的任何修改、 等同替换、 改进等， 均应包含在本发明的保护范围之内。

Claims

1、 一种极紫外光刻机中匹配多个物镜的照明系统调整与设计方法， 该方法 适用的照明系统包括光源、 聚光镜、 视场复眼、 光阑复眼以及中继镜组； 定义 中继镜组中光源出射光线经过的第一片中继镜为中继镜 A， 经过的第二片中继 镜为中继镜 B ; 其特征在于， 该方法的具体步骤为： 在极紫外光刻机更换投影权物镜前： 步骤 101、 在照明系统的弧形像面上设置孔径光阑， 且使孔径光阑的尺寸与 弧形像面的尺寸相同； 步骤 102、 取照明系统出瞳面的中心点作为物点进行光线追迹， 分别计算中 书
继镜 A的出射光线在子午面和孤矢面上的孔径角； 在极紫外光刻机更换投影物镜后： 步骤 103、 获取当前极紫外光刻机中投影物镜的相关参数， 其中所述相关参 数包括弧形像面的尺寸、 孤形像面上主光线入射角以及弧形像面上的数值孔径； 步骤 104、 根据所述相关参数计算出瞳面， 取出瞳面的中心点作为物点进行 光线追迹； 步骤 105、 调整中继镜 A的倾斜角度， 以补偿照明系统由于后续调整而导致 的对视场复眼放大倍率的改变； 调整中继镜 B 的倾斜角度， 用以补偿弧形光束 所对应的圆心角在传播过程中由于后续调整而发生的改变； 步骤 106、 调整中继镜 A的位置， 使得中继镜 A的出射光束在子午面和弧 矢面上的孔径角分别与步骤 102中计算的孔径角相等； 步骤 107、 调整中继镜 B 的位置， 使得出瞳中心经过中继镜 B和中继镜 A 后成像于光阑复眼的中心复眼元上， 且同时满足以下两个条件： 第一、 光阑复 眼的中心复眼元上的光斑中心与该复眼元的中心重合， 第二、 入射至光阑复眼 的中心复眼元上的光斑能被该复眼元反射至视场复眼中； 步骤 108、 调整光阑复眼和视场复眼上中心复眼元的倾斜角度， 使得光束经 过光阑复眼的中心复眼元后能被视场复眼的中心复眼元反射， 且经视场复眼的 中心复眼元反射的光束垂直入射至聚光镜后会聚于光源位置上；
步骤 109、 判断当前照明系统的像面是否满足与步骤 103获得的弧形像面相 近， 若满足， 则计算视场复眼和光阑复眼中各复眼元的坐标和倾斜角度， 并根 据计算的坐标和倾斜角调整各复眼元， 完成照明系统的调整， 若不满足， 则依 次重复步骤 105至 108， 直至满足要求为止。
2、 根据权利要求 1所述极紫外光刻机中匹配多个物镜的照明系统调整与设 计方法， 其特征在于， 步骤 109中所述相近为满足以下两个条件： 一是在当前照 明系统的像面上，位于步骤 103确定的孤形像面区域内的光照度占整个像面总光 照度的 80%以上， 二是位于步骤 103确定的弧形像面区域内的光照非均匀度小 于或等于 5%。
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