WO2016000496A1 - 一种基于平面光栅的硅片台大行程运动测量系统 - Google Patents

一种基于平面光栅的硅片台大行程运动测量系统 Download PDF

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WO2016000496A1
WO2016000496A1 PCT/CN2015/079237 CN2015079237W WO2016000496A1 WO 2016000496 A1 WO2016000496 A1 WO 2016000496A1 CN 2015079237 W CN2015079237 W CN 2015079237W WO 2016000496 A1 WO2016000496 A1 WO 2016000496A1
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bench
wafer
wafer stage
grating
plane
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PCT/CN2015/079237
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French (fr)
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朱煜
张鸣
刘峰
成荣
杨开明
支凡
张利
赵彦坡
胡清平
田丽
徐登峰
尹文生
穆海华
张金
陈安林
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清华大学
北京华卓精科科技有限公司
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Publication of WO2016000496A1 publication Critical patent/WO2016000496A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/04—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving

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  • the invention relates to a six-degree-of-freedom large-stroke motion measuring system for a silicon wafer table, in particular to a high-precision measuring scheme for large-stroke plane motion, which is mainly used in semiconductor processing manufacturing and testing equipment, and belongs to the field of ultra-precision measuring technology.
  • a wafer stage is used to carry a silicon wafer for step scan motion.
  • the productivity and precision of the lithography machine determine the high speed, high acceleration, large stroke and ultra-precise motion characteristics of the wafer stage.
  • the measurement of the plane motion of the silicon wafer mainly adopts optical measurement method, inductance measurement method and capacitance measurement method.
  • the optical measurement method is relatively mature in ultra-precision measurement, and is a widely used displacement measurement method at present.
  • a measurement method based on a laser interferometer is often used. According to the number of degrees of freedom required to measure, the laser interferometer measurement system with the corresponding number of axes is configured, or the redundant interferometer number is used to reduce the difficulty of solving and improve the measurement accuracy by using the redundant measurement method.
  • the redundant interferometer number is used to reduce the difficulty of solving and improve the measurement accuracy by using the redundant measurement method.
  • a long mirror and a 45° mirror are required on the wafer stage (see US Pat. No. 7,355,719 B2). This arrangement will greatly increase the volume and weight of the wafer stage, which in turn leads to a series of problems such as reduced dynamic performance of the wafer stage, increased energy consumption, and severe heat generation.
  • the optical path increases as the motion stroke increases, and the laser is susceptible to environmental influences.
  • strict environmental control is required, which brings great challenges to the design and control of the lithography machine system.
  • 8,665,455 B2 uses a plurality of readheads arranged in a one-dimensional array, and four plane one-dimensional arrays are orthogonally arranged to measure the motion of the wafer stage in a large stroke plane.
  • the grating is arranged on the upper surface of the wafer stage.
  • the readheads are arranged in an array above the wafer stage.
  • the movement of the wafer stage in this solution is limited by the arrangement of the readheads, that is, when the grating on the wafer stage is below the array of readhead arrays arranged orthogonally, the measurement system can operate normally.
  • the invention aims to provide a large-stroke motion measuring system of a silicon wafer table based on a plane grating, which is used for realizing high-precision measurement of a large stroke plane motion of a silicon wafer table, and has the characteristics of short measuring optical path and small environmental impact.
  • a planar grating-based wafer stage motion measuring system comprising a silicon wafer stage, a silicon stage stage, a plane grating and a readhead, wherein the planar grating is mounted on the bottom surface of the wafer stage Measuring surface facing the wafer table;
  • the readhead adopts a plurality of readheads arranged in a two-dimensional array on the wafer stage, and distributed in the moving area of the wafer stage and near the upper surface of the wafer stage.
  • a gap is reserved between the readhead and the planar grating; each readhead simultaneously measures the displacement in both directions of the wafer stage, ie the x and z directions or the y and z directions; measurements in each row of the two dimensional array
  • the reading heads in the x direction and the z direction are spaced apart from the reading heads measuring the y direction and the z direction, and the reading heads of the adjacent two rows are arranged or staggered; when the wafer stage moves in a plane
  • the planar grating covers at least three readheads.
  • the planar grating is formed by one piece or by using a plurality of two-dimensional plane gratings.
  • the invention Compared with the prior art, the invention has the following advantages and outstanding effects: the measuring system adopts a two-dimensional read head array and a plane grating, and realizes the silicon wafer by arranging a plurality of read heads in the moving region of the silicon wafer stage Measurement of the movement of the National Taiwan University.
  • the two-dimensional readhead array reduces the limit on the motion area of the moving table.
  • the planar grating is mounted on the moving platform to avoid cable interference.
  • the measurement system provided by the invention has a shorter optical path and less error caused by environmental changes.
  • FIG. 1 is a schematic diagram of a planar grating-based silicon wafer stage large-stroke motion measuring system provided by the invention.
  • Figures 2a, 2b and 2c show the composition of the planar grating, respectively.
  • Figures 3a, 3b show two versions of the readhead array, respectively.
  • FIG. 1 is a schematic diagram of a planar grating-based wafer stage large stroke motion measurement system provided by the present invention.
  • the motion system includes a wafer stage 4 and a wafer stage 1 .
  • the silicon wafer stage 4 uses a coreless planar motor as a driving element, and adopts air floating or magnetic floating to realize a wide range of planar motion.
  • the planar grating 3 is mounted on the lower surface of the wafer stage 4, and the measuring surface faces the wafer stage fixing table 1, and can be mounted by screwing or bonding. A gap is also left between the planar grating 3 and the wafer stage 1 to avoid damage to the grating during operation.
  • the readhead 2 is mounted on the wafer stage 1 and close to the upper surface of the stage to shorten the measurement path and reduce the influence of environmental changes on the measurement accuracy.
  • a plurality of readheads are arranged within the range of the wafer stage, and the plurality of readheads are mounted in an array.
  • Each readhead measures the linear displacement of the wafer stage 4 in both directions, i.e., the x and z directions, or the y and z directions.
  • the number of readheads 2 below the plane of measurement of the planar grating 3 is at least three at any time, and the six-degree-of-freedom displacement of the wafer stage is calculated.
  • the sensors used at different positions are also different. The different sensors switch according to the position, and the reading head under the wafer stage 4 feeds back the position information, and the reading head outside the wafer stage does not work.
  • Figures 2a, 2b and 2c show the composition of the planar grating in the present invention. Since each readhead can only measure motion with two degrees of freedom, multiple readheads need to be used simultaneously for six-degree-of-freedom measurements.
  • the readheads 2 are arranged in an array, so the size of the planar grating is required to cover at least three readheads. Therefore the invention
  • the first composition of the midplane grating 3 consists of a large planar grating, as shown in Fig. 2(a).
  • large-scale gratings are difficult to manufacture and costly, it is possible to use multiple small-plane gratings to form a large-plane grating for measurement.
  • two splicing methods are given.
  • the first mode is a tight splicing mode, that is, there is no gap between every two adjacent gratings, as shown in FIG. 2(b); the second mode is a gap splicing manner.
  • this splicing method there is a certain gap between adjacent planar gratings, as shown in FIG. 2(c), the size of the required single-block planar grating is further reduced, which is advantageous for reducing the cost.
  • Figures 3a and 3b show the form of the readhead array in the measurement system of the present invention, respectively.
  • the wafer stage 4 performs a wide range of planar motion above the wafer stage 1 to ensure motion measurement over the entire motion range.
  • the present invention provides a plurality of readheads 2 throughout the motion area.
  • the plurality of readheads are arranged in a two-dimensional array, and the readheads measuring the x-direction and the z-direction in each row of the two-dimensional array are spaced apart from the readheads measuring the y-direction and the z-direction.
  • the reading heads of two adjacent rows are arranged in alignment, as shown in Fig. 3(a), or arranged in a staggered manner, as shown in Fig. 3(b).

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

一种基于平面光栅的硅片台大行程运动测量系统，包含平面光栅（3）与读数头（2）阵列，平面光栅（3）安装在硅片台动台（4）下表面，读数头（2）阵列安装在硅片台定台（1）上；每个读数头（2）能够测量硅片台动台（4）两个方向位移，任意时刻平面光栅（3）下方覆盖三个及三个以上的读数头（2）；当硅片台动台（4）进行大行程平面运动时，通过读数头（2）之间的切换，能够实现硅片台动台（4）的位移测量。采用二维高精度平面光栅（3）作为测量元件，在硅片台运动区域内布置多个读数头（2），满足了硅片台大行程运动的测量需求；读数头（2）与平面光栅（3）之间测量光路短，环境变化引起的误差较小，同时将平面光栅（3）布置在硅片台动台（4）上，避免了测量系统对硅片台运动产生线缆扰动。

Description

一种基于平面光栅的硅片台大行程运动测量系统 技术领域
本发明涉及硅片台六自由度大行程运动测量系统，尤其涉及一种大行程平面运动的高精密测量方案，主要应用于半导体加工制造和检测设备中，属于超精密测量技术领域。
背景技术
在光刻机系统中，硅片台用于承载硅片进行步进扫描运动。光刻机的产率和套刻精度决定了硅片台高速、高加速度、大行程与超精密的运动特点。目前硅片台平面运动的测量主要采用光学测量法、电感测量法和电容测量法等，光学测量法在超精密测量中相对较为成熟，是目前应用较为广泛的位移测量方法。
在光刻机硅片台运动测量中，往往采用基于激光干涉仪的测量方法。根据所需测量的自由度的数目，配置相应轴数的激光干涉仪测量系统，或者利用冗余测量的方法，采用多余自由度轴数的激光干涉仪，降低解算难度，并提高测量精度。为实现提高测量范围，满足硅片台大行程运动的应用需求，硅片台上需要安装长反射镜及45°反射镜(参见美国专利US7,355,719 B2)。这种布置方案将会大大增加硅片台体积与重量，进而导致硅片台动态性能降低、能耗增大、发热严重等一系列问题。同时，利用激光进行测量时，光路随着运动行程增大而增长，且激光易受环境影响。为保证高精度测量，需要进行严格的环境控制，给光刻机系统的设计、控制带来极大的挑战。
针对上述问题，世界上超精密测量领域的各大公司与研究机构展开了一系列研究，主要集中于基于衍射干涉原理的光栅测量系统。例如在美国专利US 7,289,212 B2中，采用两块长条形光栅配合三个读数头实现对掩模台的运动测量，但是该方案中只能实现一个方向的大行程测量，并且当掩模台运动范围超出上述三个读数头布置区域后，该测量方案失效。美国专利US8,665,455 B2采用多个读数头按照一维阵列进行布置，并通过四个一维阵列正交布置实现对硅片台大行程平面运动的测量，方案中光栅布置在硅片台上表面，读数头以阵列形式布置在硅片台上方。但是该方案中的硅片台运动行程受限于读数头的布置方式，即当硅片台上的光栅处于正交布置的读数头阵列下方时，测量系统才能正常工作。
发明内容
本发明旨在提供一种基于平面光栅的硅片台大行程运动测量系统，用以实现硅片台大行程平面运动的高精密测量，具有测量光路短、受环境影响小等特点。
本发明的技术方案如下：
一种基于平面光栅的硅片台运动测量系统，含有硅片台定台、硅片台动台、平面光栅和读数头，其特征在于：所述的平面光栅安装在硅片台动台底面，测量面朝向硅片台定台；所 述的读数头采用多个，多个读数头成二维阵列布置在硅片台定台上，并分布安装在硅片台动台的运动区域内，且靠近硅片台定台的上表面，读数头与平面光栅之间保留间隙；每个读数头同时测量硅片台动台两个方向上的位移，即x方向和z方向或者y方向和z方向；二维阵列的每行中的测量x方向和z方向的读数头与测量y方向和z方向的读数头间隔布置，相邻两行的读数头之间对齐布置或者错列布置；当所述的硅片台动台进行平面运动时，任意时刻下平面光栅覆盖至少三个读数头。
上述技术方案中，所述的平面光栅采用一块，或者采用多块二维平面光栅拼接而成。
本发明与现有技术相比，具有以下优点及突出性效果：该测量系统采用二维读数头阵列与平面光栅，通过在硅片台动台运动区域内布置多个读数头，实现对硅片台大行程运动的测量。二维读数头阵列减少了对动台运动区域的限制。同时，平面光栅安装在动台上，避免了线缆干扰。与采用激光干涉仪的测量方案相比，本发明提供的测量系统光路更短，环境变化引起的误差较小。
附图说明
图1为发明提供的一种基于平面光栅的硅片台大行程运动测量系统的示意图。
图2a、2b和2c分别表示出平面光栅的组成方式。
图3a、3b分别表示出读数头阵列的两种形式。
图中：1－硅片台定台；2－读数头；3－平面光栅；4－硅片台动台。
具体实施方式
下面结合附图对本发明的原理、结构和具体实施方式做进一步的说明。
图1给出了本发明提供的一种基于平面光栅的硅片台大行程运动测量系统的示意图。运动系统含有硅片台动台4与硅片台定台1。硅片台动台4利用无铁芯平面电机作为驱动元件，采用气浮或者磁浮实现大范围平面运动。平面光栅3安装在硅片台动台4下表面，测量面朝向硅片台定台1，可以采用螺钉连接、粘接的方式安装。平面光栅3与硅片台定台1之间也保留间隙，避免工作时损坏光栅。读数头2安装在硅片台定台1之上，且靠近定台上表面，缩短测量光路，降低环境变化对测量精度的影响。在硅片台运动范围内，布置多个读数头，多个读数头成阵列安装。每个读数头测量硅片台动台4两个方向的线性位移，即x方向和z向，或者y方向和z方向。为实现六自由度运动测量，任意时刻处于平面光栅3测量面下方的读数头2的数量至少为三个，进而解算出硅片台动台六自由度位移。硅片台动台4进行大行程运动时，在不同的位置上使用的传感器也不同。不同传感器根据位置进行切换，处于硅片台动台4下方的读数头反馈位置信息，处于硅片台动台之外的读数头不工作。
图2a、图2b和图2c表示出本发明中平面光栅的组成方式。由于每个读数头只能测量两个自由度的运动，因此在进行六自由度测量时，需要同时使用多个读数头。而读数头2成阵列布置，因此对平面光栅的尺寸有一定的要求，使其能够至少覆盖3个读数头。因此本发明 中平面光栅3的第一种组成方式为由一大块平面光栅组成，如图2(a)所示。但是，考虑到大型光栅制作难度较大，且成本较高，因此可以采用多块小平面光栅拼接成一块大平面光栅进行测量。本发明中给出了两种拼接方式，第一种方式为紧密拼接方式，即每两个相邻光栅之间不存在间隙，如图2(b)所示；第二种方式为间隙拼接方式，此种拼接方式中，相邻平面光栅之间存在一定的间隙，如图2(c)所示，进一步减小了所需的单块平面光栅的尺寸，有利于降低成本。
图3a和图3b分别表示出本发明的测量系统中读数头阵列形式。硅片台动台4在硅片台定台1上方进行大范围平面运动，为保证在整个运动行程内都能实现运动测量，本发明在整个运动区域内布置了多个读数头2。多个读数头成二维阵列布置，二维阵列中每行中的测量x方向和z方向的读数头与测量y方向和z方向的读数头间隔布置。除此之外，相邻两行的读数头之间对齐布置，如图3(a)所示，或者错列布置，如图3(b)所示。

Claims (2)

  1. 一种基于平面光栅的硅片台运动测量系统，含有硅片台定台(1)、硅片台动台(4)、平面光栅(3)和读数头(2)，其特征在于：所述的平面光栅(3)安装在硅片台动台(4)底面，测量面朝向硅片台定台(1)；所述的读数头(2)采用多个，多个读数头(2)成二维阵列布置在硅片台定台(1)上，并分布安装在硅片台动台(4)的运动区域内，且靠近硅片台定台(1)的上表面，读数头(2)与平面光栅(3)之间保留间隙；每个读数头(2)同时测量硅片台动台(4)两个方向上的位移，即x方向和z方向或者y方向和z方向；二维阵列的每行中的测量x方向和z方向的读数头与测量y方向和z方向的读数头间隔布置，相邻两行的读数头之间对齐布置或者错列布置；当所述的硅片台动台(4)进行平面运动时，任意时刻下平面光栅(3)覆盖至少三个读数头(2)。
  2. 如权利要求1所述的一种基于平面光栅的硅片台运动测量系统，其特征在于：所述的平面光栅(3)采用一块，或者采用多块二维平面光栅拼接而成。
PCT/CN2015/079237 2014-06-30 2015-05-19 一种基于平面光栅的硅片台大行程运动测量系统 WO2016000496A1 (zh)

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