CN103759657A - Two-freedom heterodyne grating interferometer displacement measuring system based on optical octave method - Google Patents
Two-freedom heterodyne grating interferometer displacement measuring system based on optical octave method Download PDFInfo
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Abstract
A two-freedom heterodyne grating interferometer displacement measuring system based on the optical octave method comprises a two-frequency laser, a grating interferometer, a measuring grating and a photovoltaic conversion unit. The grating interferometer comprises a polarization splitting prism, a reference grating and a refraction element. On the basis of optical grating diffraction, optical Doppler and the optical beat frequency principle, the measuring system realizes displacement measurement. Laser of the double-frequency laser enters the grating interferometer and the measuring grating, and then two paths of optical signals are output to the photovoltaic conversion unit. When the interferometer and the measuring grating are in two-freedom linear relative motion, the system can output two linear displacements. The measuring system realizes optical octave through the second diffraction principle, improves resolution, can realize sub-nanometer and even higher resolution, and can measure two linear displacements at the same time. The two-freedom heterodyne grating interferometer displacement measuring system has the advantages of being insensitive to environments, high in measuring precision, small in size, light in weight and the like, and can improve the performance of a workpiece table when used as a lithography machine ultra-precise workpiece table displacement measuring system.
Description
Technical field
The present invention relates to a kind of two degrees of freedom heterodyne grating interferometer displacement measurement system based on optics times journey method, particularly a kind of two degrees of freedom heterodyne grating interferometer measuring system for photo-etching machine work-piece platform displacement measurement.
Background technology
Optical grating measuring system is widely used in numerous electromechanical equipments as the typical displacement transducer of one.The measuring principle of optical grating measuring system is mainly based on Moire fringe principle and diffraction interference principle.Optical grating measuring system based on Moire fringe principle becomes the first-selection of numerous electromechanical equipment displacement measurements as many merits such as a kind of full-fledged displacement transducer are long with its range finding, cost is low, be easy to debug, but precision, conventionally in micron dimension, is common in general industry application.
Litho machine in semiconductor manufacturing equipment is the key equipment in semiconductor chip fabrication.Ultraprecise work stage is the kernel subsystems of litho machine, for carrying mask plate and silicon chip, completes high speed ultraprecise step-scan campaign.Ultraprecise work stage becomes the most representative type systematic in ultraprecise kinematic system with movement characteristics such as its high speed, high acceleration, large stroke, ultraprecise, multiple degrees of freedoms.For realizing above-mentioned motion, ultraprecise work stage adopts two-frequency laser interferometer measuring system to measure the displacement of ultraprecise work stage multiple degrees of freedom conventionally.But improving constantly along with motion index such as measuring accuracy, measuring distance, measuring speeds, two-frequency laser interferometer is with the series of problems that environmental sensitivity, measuring speed are difficult to improve, large, expensive, the measurement target work stage poor dynamic of taking up room etc. exists, thereby is difficult to meet higher measurement demand.
For the problems referred to above, each major company in ultra precise measurement field and research institution have launched a series of research in the world, and research mainly concentrates on the optical grating measuring system based on diffraction interference principle, and achievement in research all has exposure in many patent papers.
American documentation literature US7, 102, 729B2(is day on August 4th, 2005 openly), US7, 483, 120B2(is day on November 15th, 2007 openly), US7, , 940, 392B2(is day on Dec 24th, 2009 openly), open day on Dec 23rd, 2010 of publication number US2010/0321665A1() a kind of plane grating measuring system and arrangement that is applied to Ultra-precision Stages of Lithography disclosed, this measuring system mainly utilizes the plane grating of one dimension or two dimension to coordinate the large travel displacement of read head measuring workpieces platform level, vertical direction displacement measurement adopts the sensors such as current vortex or interferometer, but the application restric-tion work stage measuring accuracy of multiple sensors.American documentation literature US7,864, open day on January 4th, 2011 of 336B2() a kind of grating interferometer measuring system that is applied to Ultra-precision Stages of Lithography disclosed, this system utilizes the Littrow condition optical grating reflection of two read heads to realize displacement measurement, but the components and parts that need are many, volume is large, and owing to resolving by the result of two read heads, has limited measuring accuracy.Open day on October 20th, 2011 of american documentation literature publication number US2011/0255096A1() a kind of optical grating measuring system that is applied to Ultra-precision Stages of Lithography disclosed, this measuring system also adopts one dimension or two-dimensional grating to coordinate specific read head to realize displacement measurement, can carry out level to measuring with vertical deviation simultaneously, but complex structure; American documentation literature publication number US2011/0096334A1(is day on April 28th, 2011 openly) a kind of heterodyne ineterferometer is disclosed, in this interferometer, adopt grating as target mirror, but this interferometer only can be realized one-dimensional measurement.Japanese scholars GAOWEI has proposed a kind of single-frequency two-dimensional grating measuring system of utilizing diffraction interference principle in research paper " Design and construction of a two-degree-of-freedom linear encoder for nanometric measurement of stage position and straightness.Precision Engineering34 (2010) 145-155 ", this optical grating measuring system can realize simultaneously horizontal and vertical to displacement measurement, but owing to adopting single-frequency laser, measuring-signal is easily disturbed, and precision is difficult to guarantee.November 09 2012 Chinese patent literature application number 201210449244.9(applying date) and November 09 2012 201210448734.7(applying date) a kind of heterodyne grating interferometer measuring system disclosed respectively, in read head structure in two kinds of interferometer measuring systems, all adopted quarter-wave plate for changing the polarization state of light beam, optical texture complexity, the imperfection of optical element will cause measuring error simultaneously.In addition, Chinese patent literature publication number CN103307986A(open day on 09 18th, 2013) and CN103322927A(open day on 09 18th, 2013) a kind of heterodyne grating interferometer measuring system disclosed respectively, the light path design that has all adopted optics two to segment in read head structure in two kinds of interferometer measuring systems, causes the deficiency that resolution is low.
Summary of the invention
Consider the limitation of technique scheme, the object of the invention is to seek one and utilize optical beat principle, and can realize the heterodyne grating interferometer measuring system of optics times journey; When can realize two Linear-free degree displacements, measure, and systematic survey light path is short, environmental sensitivity is low, measuring-signal is easy to process; This grating interferometer measuring system also will have the advantages such as simple for structure, volume is little, quality is light, be easy to install, convenient application simultaneously.Adopt this measuring system as ultraprecise work stage displacement measuring device, can effectively reduce the deficiency of laser interferometer measurement system in the application of ultraprecise work stage, make Ultra-precision Stages of Lithography performance boost.This two degrees of freedom heterodyne grating interferometer displacement measurement system also can be applicable to the precision measurement of the work stage multiple degrees of freedom displacement of precision machine tool, three coordinate measuring machine, semiconductor detection etc.
Technical scheme of the present invention is as follows:
Two degrees of freedom heterodyne grating interferometer displacement measurement system based on optics times journey method, comprises two-frequency laser, grating interferometer, measurement grating and photoelectric conversion unit; Grating interferometer comprises polarization splitting prism, with reference to grating, first fold optical element and the second dioptric element, described first fold optical element is comprised of two parallel right angle optical prisms of placing and is placed in polarization splitting prism and with reference between grating, it is characterized in that: the second dioptric element adopts two symmetrical dioptric elements of placing, and be placed in polarization splitting prism and measure between grating, utilize this dioptric element to complete re-diffraction and realize optics times journey; Two-frequency laser outgoing double frequency cross polarization laser is divided into reflected light and transmitted light after coupling fiber is incident to polarization splitting prism; Described reflected light is incident to reference to producing two bundle diffraction reflection reference lighies after grating, two bundle reference lighies form the parallel reference light of two bundles through two right angle optical prism post deflections of first fold optical element respectively, and the parallel reference light retroeflection of two bundles forms two bundle reflection reference lighies to polarization splitting prism; Described transmitted light is beaten on measurement grating after being incident to and measuring grating for the first time, produce two bundle diffraction reflections and measure light, two bundle diffraction reflections are measured light and after the second dioptric element reflection, are formed the emergent light of measuring parallel light with diffraction reflection respectively, two bundle emergent light retroeflection for the second time form two bundle horizontal survey light to diffraction reflection after measuring grating, and two bundle horizontal survey light retroeflection form two bundle transmission measurement light to polarization splitting prism; A branch of coincidence in a branch of and two bundle transmission measurement light in two bundle reflection reference lighies forms a drive test amount light signal, another Shu Chonghe in another road in two bundle reflection reference lighies and two bundle transmission measurement light forms another drive test amount light signal, two-way measure light signal respectively through Optical Fiber Transmission to Signal Processing Element, form therein two-way and measure electric signal processing; Two-frequency laser is also exported a branch of reference electrical signal to measuring-signal photoelectric conversion unit simultaneously; When measurement grating does the linear movement of horizontal direction and two degree of freedom of vertical direction with respect to grating interferometer, photoelectric conversion unit will be exported two degrees of freedom linear displacement.
In technique scheme, the second described dioptric element is comprised of two right-angle reflecting prism, and light is realized refractive power by its right-angle side reflection.Or the second described dioptric element is comprised of two retroreflection prisms, light is realized refractive power by the reflection of its inner three reflectings surface.
Two degrees of freedom heterodyne grating interferometer displacement measurement system based on optics times journey method provided by the present invention has the following advantages and high-lighting effect: this measuring system adopts re-diffraction principle to realize optics times journey, it is even higher that resolution and precision can reach sub-nanometer, and measure when can realize two Linear-free degree displacements; This measuring system optical path is short, environmental sensitivity is low, measuring-signal is easy to process, also have simultaneously simple for structure, volume is little, quality is light, be easy to install, facilitate the advantage such as application.Be applied to the displacement measurement of Ultra-precision Stages of Lithography, contrast laser interferometer measurement system, on the basis that meets measurement demand, can effectively reduce work stage volume, quality, greatly improve the dynamic property of work stage, work stage overall performance is comprehensively improved.This two degrees of freedom heterodyne grating interferometer displacement measurement system also can be applicable in the precision measurement of work stage multiple degrees of freedom displacement of precision machine tool, three coordinate measuring machine, semiconductor detection etc.
Accompanying drawing explanation
Fig. 1 is a kind of heterodyne grating interferometer displacement measurement system schematic diagram of the present invention.
Fig. 2 is the first grating interferometer inner structure schematic diagram of the present invention.
Fig. 3 is the second grating interferometer inner structure schematic diagram of the present invention.
In figure, 1-two-frequency laser, 2-grating interferometer, 3-measurement grating, 4-photoelectric conversion unit; 21-polarization splitting prism, 22-with reference to grating, 23-right angle optical prism, 24a-right-angle reflecting prism, 24b-retroreflection prism.
Embodiment
Below in conjunction with accompanying drawing, structure of the present invention, principle and embodiment are described in further detail.
Please refer to Fig. 1, Fig. 1 is a kind of heterodyne grating interferometer displacement measurement system schematic diagram of the present invention.As shown in Figure 1, this two degrees of freedom heterodyne grating interferometer displacement measurement system comprises two-frequency laser 1, grating interferometer 2, measures grating 3, measuring-signal photoelectric conversion unit 4, and measuring grating 3 is one dimension reflection-type grating.
Please refer to Fig. 2, Fig. 2 is the first grating interferometer inner structure schematic diagram of the present invention.Described grating interferometer 2 comprises polarization splitting prism 21, with reference to grating 22, first fold optical element 23, the second dioptric element 24a, with reference to grating 22, it is one dimension reflection-type grating, first fold optical element is comprised of two parallel right angle optical prisms 23 of placing, and the second dioptric element is comprised of two symmetrical right-angle reflecting prism 24a that place.
In conjunction with Fig. 1, Fig. 2, set forth measuring system principle, described two-frequency laser 1 outgoing double frequency cross polarization laser light splitting after coupling fiber is incident to polarization splitting prism 21, reflected light is reference light, transmitted light is for measuring light.
Described reference light is incident to reference to the rear formation two of grating 22 and restraints diffraction reflection reference light, two bundle diffraction reflection reference lighies form the parallel reference light of two bundles through two right-angle prism 23a post deflections respectively, and the parallel reference light retroeflection of two bundles is to the rear formation two bundle reflection reference lighies of polarization splitting prism 21.
Described transmitted light is beaten on measurement grating 3 after being incident to and measuring grating 3 for the first time, produce two bundle diffraction reflections and measure light, two bundle diffraction reflections are measured light and after the second dioptric element reflection, are formed the emergent light of measuring parallel light with diffraction reflection respectively, two bundle emergent light retroeflection for the second time form two bundle horizontal survey light to measuring the rear diffraction reflection of grating 3, and transmission measurement light is restrainted in two bundle horizontal survey light retroeflection to the rear formation two of polarization splitting prism 21.
A branch of coincidence in a branch of and two bundle transmission measurement light in two bundle reflection reference lighies forms a drive test amount light signal, another Shu Chonghe in another road in two bundle reflection reference lighies and two bundle transmission measurement light forms another drive test amount light signal, two-way measure light signal respectively through Optical Fiber Transmission to Signal Processing Element 4, form therein two-way and measure electric signal processing; Two-frequency laser 1 is also exported a branch of reference electrical signal to measuring-signal photoelectric conversion unit simultaneously, forms therein two-way and measures electric signal and process;
Two-frequency laser 1 is also exported a branch of reference electrical signal to electronic signal process parts 5 simultaneously; When measuring grating 3, with respect to grating interferometer 2, do level when with the linear movement of vertical (wherein catenary motion is small movements, and range of movement is 1mm) two degree of freedom, electronic signal process parts 5 will be exported two degrees of freedom linear displacement.
The expression formula of two degree-of-freedom motion displacement is x=k
x× (alpha-beta), z=k
z× (alpha+beta), k
x=Λ/8 π, k
z=λ/8(1+cos θ), in formula, α, β are the reading value of electronic signal process card, Λ is grating constant, λ is optical maser wavelength, θ is optical grating diffraction angle, gets Λ=1 μ m, λ=632.8nm, the phase resolution of α, β is 2 π/1024, and the x of heterodyne grating interferometer, the Measurement Resolution of z are respectively 0.25nm, 0.09nm.
Please refer to Fig. 3, Fig. 3 is the second grating interferometer inner structure schematic diagram of the present invention.As shown in Figure 3, the second dioptric element in grating interferometer inner structure is realized beam deflection by two symmetrical retroreflection prism 24b that place, contrast right-angle prism 24a, adopt retroreflection prism 24b, insensitive to incident angle, and structure is little, can make interferometer structure compacter, succinct, be convenient to install.
The measuring system providing in above-mentioned embodiment and organization plan adopt re-diffraction principle to realize optics optics times journey, and it is even higher that resolution and precision can reach sub-nanometer; When can realizing two Linear-free degree displacements, this system measures, and systematic survey light path is short, environmental sensitivity is low, measuring-signal is easy to process, simultaneously this grating interferometer measuring system also have simple for structure, volume is little, quality is light, be easy to install, facilitate the advantage such as application.Be applied to the displacement measurement of Ultra-precision Stages of Lithography, contrast laser interferometer measurement system, on the basis that meets measurement demand, can effectively reduce work stage volume, quality, greatly improve the dynamic property of work stage, work stage overall performance is comprehensively improved.This Three Degree Of Freedom heterodyne grating interferometer displacement measurement system also can be applicable in the precision measurement of work stage multiple degrees of freedom displacement of precision machine tool, three coordinate measuring machine, semiconductor detection etc.
Claims (3)
1. the two degrees of freedom heterodyne grating interferometer displacement measurement system based on optics times journey method, comprises two-frequency laser (1), grating interferometer (2), measures grating (3) and photoelectric conversion unit (4); Grating interferometer (2) comprises polarization splitting prism (21), with reference to grating (22), first fold optical element and the second dioptric element, described first fold optical element is comprised of two parallel right angle optical prisms of placing and is placed in polarization splitting prism (21) and with reference between grating (22), it is characterized in that: the second dioptric element adopts two symmetrical dioptric elements of placing, and be placed in polarization splitting prism (21) and measure between grating (3), utilize this dioptric element to complete re-diffraction and realize optics times journey; Two-frequency laser (1) outgoing double frequency cross polarization laser is divided into reflected light and transmitted light after coupling fiber is incident to polarization splitting prism (21); Described reflected light is incident to reference to producing two bundle diffraction reflection reference lighies after grating (22), two bundle reference lighies form the parallel reference light of two bundles through two right angle optical prism post deflections of first fold optical element respectively, and the parallel reference light retroeflection of two bundles forms two bundle reflection reference lighies to polarization splitting prism (21); Described transmitted light is beaten on measurement grating (3) after being incident to and measuring grating (3) for the first time, produce two bundle diffraction reflections and measure light, two bundle diffraction reflections are measured light and after the second dioptric element reflection, are formed the emergent light of measuring parallel light with diffraction reflection respectively, two restraint emergent light retroeflection for the second time forms two bundle horizontal survey light to measuring the rear diffraction reflection of grating (3), and two bundle horizontal survey light retroeflection are to the rear formation two bundle transmission measurement light of polarization splitting prism (21); A branch of coincidence in a branch of and two bundle transmission measurement light in two bundle reflection reference lighies forms a drive test amount light signal, another Shu Chonghe in another road in two bundle reflection reference lighies and two bundle transmission measurement light forms another drive test amount light signal, two-way measure light signal respectively through Optical Fiber Transmission to Signal Processing Element (4), form therein two-way and measure electric signal processing; Two-frequency laser (1) is also exported a branch of reference electrical signal to measuring-signal photoelectric conversion unit (4) simultaneously; When measurement grating (3) does the linear movement of horizontal direction and two degree of freedom of vertical direction with respect to grating interferometer (2), photoelectric conversion unit (4) will be exported two degrees of freedom linear displacement.
2. the two degrees of freedom heterodyne grating interferometer displacement measurement system based on optics times journey method according to claim 1, it is characterized in that: the second described dioptric element is comprised of two right-angle reflecting prism (24a), light is realized refractive power by its right-angle side reflection.
3. the two degrees of freedom heterodyne grating interferometer displacement measurement system based on optics times journey method according to claim 1, it is characterized in that: the second described dioptric element is comprised of two retroreflection prisms (24b), light is realized refractive power by the reflection of its inner three reflectings surface.
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Cited By (3)
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| CN105823422A (en) * | 2016-03-01 | 2016-08-03 | 清华大学 | Two-degree-of-freedom heterodyne grating interferometer displacement measurement system and method |
| CN106813578A (en) * | 2015-11-30 | 2017-06-09 | 上海微电子装备有限公司 | A kind of two-dimensional grating measuring system |
| WO2020007217A1 (en) * | 2018-07-02 | 2020-01-09 | 清华大学 | Five-degree-of-freedom heterodyne grating interferometry system |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106813578A (en) * | 2015-11-30 | 2017-06-09 | 上海微电子装备有限公司 | A kind of two-dimensional grating measuring system |
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| CN105823422A (en) * | 2016-03-01 | 2016-08-03 | 清华大学 | Two-degree-of-freedom heterodyne grating interferometer displacement measurement system and method |
| CN105823422B (en) * | 2016-03-01 | 2018-08-28 | 清华大学 | A kind of two degrees of freedom heterodyne grating interferometer displacement measurement system and method |
| WO2020007217A1 (en) * | 2018-07-02 | 2020-01-09 | 清华大学 | Five-degree-of-freedom heterodyne grating interferometry system |
| US11703361B2 (en) | 2018-07-02 | 2023-07-18 | Beijing U-Precision Tech Co., Ltd. | Five-degree-of-freedom heterodyne grating interferometry system |
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