Two-degree-of-freedom heterodyne grating interferometer displacement measurement system

Abstract

A two-degree-of-freedom heterodyne grating interferometer displacement measurement system comprises a double-frequency laser device, a grating interferometer, a measuring grating, a receiver and a signal processing unit, wherein the grating interferometer comprises a lateral displacement beam splitter prism, a polarization splitter prism, a referencing grating and a retraction component, and the measurement system achieves displacement measurement based on grating diffraction, an optical Doppler effect and an optical beat frequency principle. Laser of the double-frequency laser device is emitted to the grating interferometer and the measuring grating, and then optical signals are output to the receiver and then to the signal processing unit. When the grating interferometer and the measuring grating do two-degree-of-freedom linear relative motion, the system can output two pieces of linear displacement. According to the two-degree-of-freedom heterodyne grating interferometer displacement measurement system, a secondary diffraction principle is adopted to achieve four optical subdivisions, the sub-nanometer and even higher resolution ratio can be achieved, and the two pieces of the linear displacement can be measured simultaneously. The two-degree-of-freedom heterodyne grating interferometer displacement measurement system has the advantages of being insensitive to environment, high in measurement precision, light and the like, and is capable of improving the comprehensive performance of the workpiece table serving as a position measurement system for a photoetching machine ultraprecise workpiece table,.

Description

technical field [0001] The invention relates to a grating measurement system for realizing optical four subdivision, in particular to a two-degree-of-freedom heterodyne grating interferometer measurement system. Background technique [0002] As a typical displacement sensor, the grating measurement system is widely used in many electromechanical equipment. The measurement principle of the grating measurement system is mainly based on the Moiré fringe principle and the diffraction interference principle. As a well-developed displacement sensor, the grating measurement system based on the Moiré fringe principle has become the first choice for displacement measurement of many electromechanical equipment due to its long measuring range, low cost, and easy installation and adjustment, but the accuracy is usually on the order of microns, which is common for general industrial applications. [0003] The lithography machine in semiconductor manufacturing equipment is the key equip...

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Netherlands ASML company US patent US7,102,729B2 (disclosure date August 4, 2005), US7,483,120B2 (disclosure date November 15, 2007), US7,940,392B2 (disclosure date December 24, 2009) , Publication No. US2010 / 0321665A1 (public date: December 23, 2010) discloses a planar grating measurement system and layout scheme applied to ultra-precision workpiece tables of lithography machines. The measurement system mainly uses a one-dimensional or two-dimensional plane The grating cooperates with the reading head to measure the horizontal large-stroke displacement of the workpiece table, and height sensors such as eddy currents or interferometers are used to measure the displacement in the height direction, but the application of various sensors limits the measurement accuracy of the workpiece table

U.S. Patent Publication No. US2011 / 0255096A1 (published on October 20, 2011) of ZYGO Corporation of the United States discloses a grating measurement system applied to ultra-precision workpiece tables of lithography machines. The measurement system also uses one-dimensional or two-dimensional gratings to cooperate with A specific reading head realizes displacement measurement, which can simultaneously measure horizontal and vertical displacements, but the structure is complicated; Japanese CANON company US Patent Publication No. US2011 / 0096334A1 (publication date April 28, 2011) discloses a heterodyne interferometry In this interferometer, a grating is used as the objective mirror, but the interferometer can only realize one-dimensional measurement

In the research paper "Design and construction of a two-degree-of-freedom linear encoder for nanometric measurement of stage position and straightness. Precision Engineering 34 (2010) 145-155", Japanese scholar GAOWEI proposed a single encoder using the principle of diffraction interference. Frequency two-dimensional grating measurement system, which can realize horizontal and vertical displacement measurement at the same time, but due to the use of single-frequency laser, the measurement signal is susceptible to interference, and the accuracy is difficult to guarantee

In addition, Chinese Patent Literature Publication Nos. CN103307986A (disclosure date: September 18, 2013) and CN103322927A (disclosure date: September 18, 2013) respectively disclose a heterodyne grating interferometer measurement system. The optical two-division optical path design is adopted in the structure of the reading head, resulting in low resolution, and the reference signal also needs a grating, which increases the cost

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