A kind of plane grating interferometer displacement measurement system
Technical field
The utility model is related to a kind of plane grating interferometer displacement measurement systems, more particularly to a kind of to be used for litho machine work
The plane grating interferometer displacement measurement system of part platform displacement measurement.
Background technology
Optical grating measuring system is widely used in numerous electromechanical equipments as a kind of typical displacement sensor.Grating measuring system
The measuring principle of system is based primarily upon Moire fringe principle and diffraction interference principle.Optical grating measuring system based on Moire fringe principle
As a kind of displacement sensor of mature with its ranging it is long, it is at low cost, be easy to many merits such as adjustment as numerous electromechanics
The first choice of equipment displacement measurement, but precision is common in general industry application usually in micron dimension.
Litho machine in semiconductor manufacturing equipment is the key equipment in semiconductor chip fabrication.Ultra-precision table system is light
Quarter machine kernel subsystems, complete high speed ultraprecise step-scan campaign for carrying mask plate and silicon chip.Ultra-precision table system
Become in ultraprecise kinematic system with the movement characteristics such as its high speed, high acceleration, big stroke, ultraprecise, multiple degrees of freedom and most represented
A kind of system of property.To realize above-mentioned movement, ultra-precision table system generally use two-frequency laser interferometer measuring system measures super
Precision workpiece stage multiple degrees of freedom displacement.However as constantly carrying for the motion index such as measurement accuracy, measurement distance, measuring speed
Height, two-frequency laser interferometer is difficult to improve with environmental sensitivity, measuring speed, occupied space is big, it is expensive, measure target work
A series of problems existing for part platform poor dynamic etc., so as to be difficult to meet higher measurement demand.
In view of the above-mentioned problems, each major company in ultra precise measurement field and research institution expand a series of grind in the world
Study carefully, research focuses primarily upon the optical grating measuring system based on diffraction interference principle, and achievement in research has in many patent papers
It discloses.
U.S. Patent Publication Document US2011/0255096 A1 (publication date on October 20th, 2011) disclose a kind of answer
For the optical grating measuring system of Ultra-precision Stages of Lithography, which reads using the cooperation of one-dimensional or two-dimensional grating is specific
Several realization displacement measurements, can be carried out at the same time horizontal direction and vertical deviation measures, but complicated;U.S. Patent Publication Document number
US2011/0096334 A1 (publication date on April 28th, 2011) disclose a kind of heterodyne ineterferometer, and grating is used in the interferometer
As target mirror, but the interferometer is only capable of realizing one-dimensional measurement.U.S. Patent Publication Document US2013/0114087 Al are (public
Open on May 2013 day 9) disclose a kind of interferometer measuration system applied to Ultra-precision Stages of Lithography, the measuring system
In a manner that a grating interferometer and a laser interferometer combine, but program structure is excessively complicated, optical path length, for
Integration of compact difficulty is big.U.S. Patent Publication Document US2016/0102999 AL (publication date on April 12nd, 2016) are open
A kind of optical grating measuring system applied to Ultra-precision Stages of Lithography, the measuring system are coordinated using one-dimensional or two-dimensional grating
Reading head realizes displacement measurement, but it is mixed polarization easily occur using two-frequency laser and the coaxial biography light of double frequency for interferometer structure
Folded phenomenon, measurement error are big.Japanese scholars GAOWEI is in research paper " Design and construction of a two-
degree-of-freedom linear encoder for nanometric measurement of stage position
A kind of utilization diffraction is proposed in 34 (2010) 145-155 " of and straightness.Precision Engineering to do
Relate to the single-frequency two-dimensional grating measuring system of principle, the optical grating measuring system can be achieved at the same time it is horizontal and vertical to displacement measurement,
But due to using single-frequency laser, measuring signal is easily disturbed, and precision is difficult to ensure that.Chinese patent literature application number
201210449244.9 (November 09 2012 applying date) and 201210448734.7 (November 09 2012 applying date) point
It does not disclose a kind of heterodyne grating interferometer measuring system, is employed in the reading header structure in two kinds of interferometer measuring systems
Quarter-wave plate is for changing the polarization state of light beam, and optical texture is complicated, while the imperfection of optical element will cause to survey
Measure error.
Utility model content
In view of the limitation of above-mentioned technical proposal, the purpose of this utility model is to provide a kind of plane grating interferometer displacement
Measuring system makes it not only have many advantages, such as high certainty of measurement, simple in structure and integrated convenient for minimizing, but also can realize that Asia is received
The even higher resolution ratio of rice and precision, and two linear displacements can be measured simultaneously, and then can lifting workpieces platform comprehensive performance.
The technical solution of the utility model is as follows:
A kind of plane grating interferometer displacement measurement system, including single-frequency laser, beam splitter, grating interferometer, plane
Grating, acousto-optic modulator, receiver, electronic signal process component, fiber coupler and frequency synthesizer;It is characterized in that;Light
Grating interferometer include polarization spectroscope, dioptric element, the first right-angle prism, the second right-angle prism and third right-angle prism, four points
One of wave plate;Wherein the first right-angle prism is located at polarization spectroscope top, and the second right-angle prism and third right-angle prism simultaneously discharge
It puts in the bottom end of polarization spectroscope;The single-frequency laser of single-frequency laser outgoing is after beam splitter is divided, respectively by being closed by frequency
The acousto-optic modulator for supply source of growing up to be a useful person is modulated, respectively after two beam splitters are divided, wherein two beam laser are through fiber coupler
After being interfered, receiver is input to as compensation axis signal, electric signal all the way is formed after processing and is input to electronic signal process
Component;Another two beams laser is then incident to polarization spectroscope light splitting afterwards, and two beam reflected lights are reference light, and two beam transmitted lights is measure
Light;
Two beam measures light and is incident to planar light after quarter-wave plate and dioptric element with Littrow angle for the first time
Grid are incident to polarization spectroscope second after reflection through dioptric element and quarter-wave plate, and two beams measure light difference after reflection
By the second right-angle prism and third right-angle prism, after retroeflection to polarization spectroscope, then secondary reflection through dioptric element and four/
Plane grating is incident to Littrow angle again after one wave plate, it is incident after dioptric element and quarter-wave plate again after reflection
To polarization spectroscope, two beams measure light exiting parallel after transmission;
The two beams reference light after the first right-angle prism retroeflection to polarization spectroscope, after reflection two beam reference lights it is parallel go out
It penetrates;
Wherein a branch of reference light and a branch of measurement interference of light form interference light signal all the way, another beam reference light and another beam
It measures the interference of light and forms another way interference light signal, two-way interference light signal is transmitted to receiver through optical fiber respectively and carries out processing point
Not Xing Cheng two-way measure electric signal, two-way measures electric signal and is input to electronic signal process component and is handled;
In above-mentioned technical proposal, using two-dimentional reflection-type grating, the dioptric element uses to be cut the plane grating
Face is that the refracting telescope of isosceles trapezoid, second right-angle prism and third right-angle prism are arranged using parallel side-by-side.
Another technical solution of the utility model is:The dioptric element using two speculum groups into.
Another technical solution of the utility model is:The dioptric element uses lens.
The utility model has the following advantages and high-lighting technique effect:The measuring system utilizes single-frequency laser and optical fiber
Separation passes light, and interferometer employs special structure, therefore inhibits polarization aliasing error, improves measurement accuracy;It is dry
Interferometer can realize large-scale outer corner measurement, and it is symmetrical to realize light path after using right-angle prism;Plane grating is using two dimension
Reflection-type grating realizes the two degrees of freedom measurement of system and Z-direction motion-insensitive using Littrow structure;Interferometer structure uses
Optical device is few, simple in structure, integrated convenient for minimizing.
Description of the drawings
Fig. 1 is a kind of plane grating interferometer displacement measurement system schematic diagram of the utility model.
Fig. 2 is the utility model grating interferometer index path.
Fig. 3 is the utility model grating interferometer two-way reference light index path.
Fig. 4 measures light index path all the way for the utility model grating interferometer.
Fig. 5 measures light index path for the utility model grating interferometer another way.
Fig. 6 is the first grating interferometer internal structure schematic diagram of the utility model.
Fig. 7 is second of grating interferometer internal structure schematic diagram of the utility model.
Fig. 8 is the third grating interferometer internal structure schematic diagram of the utility model.
In figure, 1-single-frequency laser, the beam splitters of 2a-first, the beam splitters of 2b-second;2c-third beam splitter;3-light
Grating interferometer, 4-plane grating, 5a-first sound-optic modulator, 5b-second sound-optic modulator;6-receiver;7-electronics
Signal Processing Element;31-polarization spectroscope, 32-dioptric element;32a-refracting telescope;32b-speculum;32c-lens;
33-the first right-angle prism;34-the second right-angle prism;35-third right-angle prism;36-quarter-wave plate.
Specific embodiment
The structure of the utility model, principle and specific embodiment are described in further detail below in conjunction with the accompanying drawings.
It please refers to Fig.1, which includes single-frequency laser 1, beam splitter, grating interference
Instrument 3, plane grating 4, acousto-optic modulator, receiver 6 and electronic signal process component 7, plane grating 4 are two-dimentional reflection type optical
Grid.
It please refers to Fig.2, the grating interferometer 3 includes polarization spectroscope 31, dioptric element 32, the first right-angle prism
33rd, the second right-angle prism 34 and third right-angle prism 35, quarter-wave plate 36, dioptric element 32, wherein the first right-angle prism
33 are located at polarization spectroscope top, and the second right-angle prism 34 is placed side by side on the bottom of polarization spectroscope with third right-angle prism 35
End.
It please refers to Fig.1, Fig. 2, the single-frequency laser that single-frequency laser 1 is emitted passes through respectively after the first beam splitter 2a light splitting
After being modulated by the first sound-optic modulator 5a and second sound-optic modulator 5b of 9 supply source of frequency synthesizer, respectively through second point
Beam device 2b and third beam splitter 2c are divided, wherein, the beam of laser and third beam splitter 2c separated through the second beam splitter 2b
The beam of laser separated is input to receiver 6 after fiber coupler 8 is interfered, as compensation axis signal, is formed after processing
Electric signal is input to electronic signal process component 7 all the way;Other two beams laser is then incident to 31 light splitting afterwards of polarization spectroscope, two beams
Reflected light is reference light, and two beam transmitted lights is measure light;
It please refers to Fig.2, Fig. 3, two beams reference light retroeflection after the first right-angle prism 33 to polarization spectroscope 31, is reflected
Two beam reference light exiting parallel afterwards.
It please refers to Fig.2, Fig. 4, Fig. 5, two beam measures light first time after quarter-wave plate 36 and dioptric element 32
Plane grating 4 is incident to Littrow angle, polarization is incident to through dioptric element 32 and quarter-wave plate 36 second after reflection
Spectroscope 31, two beams measure light respectively by the second right-angle prism 34 and third right-angle prism 35, retroeflection to polarization point after reflection
Light microscopic 31, then plane grating 4 is incident to Littrow angle again after dioptric element 32 and quarter-wave plate 36 after secondary reflection,
Polarization spectroscope 31 is incident to after dioptric element 32 and quarter-wave plate 36 again after reflection, two beams measure light and put down after transmission
Row outgoing.
Wherein a branch of reference light and a branch of measurement interference of light form interference light signal all the way, another beam reference light and another beam
It measures the interference of light and forms another way interference light signal, two-way interference light signal is transmitted to receiver 6 through optical fiber respectively and is handled
It is respectively formed two-way and measures electric signal, two-way measurement electric signal is input to electronic signal process component 7 and is handled.
Usually there is polarization aliasing in general two-frequency laser interferometer, reason has two-frequency laser is undesirable to cause
Double-frequency laser occur to polarize at light source aliasing and when coaxial light path is used to pass light it is similary it can also happen that polarization is mixed
It is folded.And the plane grating interferometer measuring system has used single-frequency laser 1, and carries out frequency modulation(PFM) with acousto-optic modulator 5, this
Sample avoids to be also easy to produce polarization aliasing at light source, also, the measuring system is detached with optical fiber using two frequency lasers and passes light.
Inside grating interferometer, with reference to figure 3, two beam reference lights are s polarised lights, after the first right-angle prism 33 and polarization spectroscope 31
It is emitted, does not occur polarisation leakage in free space light path;With reference to figure 4 and Fig. 5, two beams measure light respectively through the second right-angle prism 34
After third right-angle prism 35, due to the fevering sodium effect of right-angle prism, when by polarization spectroscope 3, partial polarization can be generated
Leakage, but by analysis, error is in micromicron magnitude caused by the polarisation leakage of the part, it is believed that and the structure effectively inhibits
Polarize aliasing error.In conclusion the plane grating measuring system inhibits polarization aliasing, measurement error is effectively reduced.
Three right-angle prisms are used in interferometer structure, wherein two-way reference light passes through the first right-angle prism 33, two-way
Light is measured respectively by the second right-angle prism 34 and third right-angle prism 35, due to the rear reflection characteristic of right-angle prism, grating
Light path angle caused by corner deviation is changed into light beam separation, therefore increases outer corner measurement range, and realize light path
Symmetrically.
Plane grating 4 makes measurement light anti-from plane grating 4 twice using two-dimentional reflection-type grating using Littrow structure
It penetrates, two degrees of freedom displacement measurement and Z-direction motion-insensitive is realized based on Grating Doppler Effect.
When plane grating 4 relative to grating interferometer 3 do horizontal direction and it is vertical (wherein catenary motion be small movements, fortune
Dynamic ranging from ± 1mm) two degree of freedom linear movement when, electronic signal process component 5 will export two degrees of freedom linear displacement.
The expression formula of two degree-of-freedom motion displacement is x=p* (alpha+beta)/8 π, z=(alpha-beta)/16 π * cos θ, and α, β is at electronic signals in formula
The reading value of card is managed, p is grating constant, and θ is optical grating diffraction angle, takes p=0.833 μm, the measurement point of x, z of grating interferometer
Resolution is respectively 0.415nm, 0.22nm.
Fig. 6 is please referred to, Fig. 6 is the first grating interferometer internal structure schematic diagram of the utility model.As shown in fig. 6, light
Dioptric element in grating interferometer internal structure uses refracting telescope 32a.
Fig. 7 is please referred to, Fig. 7 is second of grating interferometer internal structure schematic diagram of the utility model.As shown in fig. 7, light
Dioptric element in grating interferometer internal structure is formed using two speculum 32b.Comparison is using refracting telescope 32a schemes, the party
Case can eliminate the uneven caused beam error of refracting telescope refractive index, but the installation of speculum occupies the space of bigger.
Fig. 8 is please referred to, Fig. 8 is the third grating interferometer internal structure schematic diagram of the utility model.As shown in figure 8, light
Dioptric element in grating interferometer internal structure realizes light beam deflection using lens 32c, speculum 32b is compared, using lens
32c occupies little space, can make interferometer structure it is compacter, it is succinct, be easily installed.
The measuring system and organization plan provided in the above embodiment can realize the same of two linear DOF displacements
When measure;Inhibit polarization aliasing error simultaneously;Realize large-scale outer corner measurement, and it is symmetrical to realize light path;It realizes
Two degrees of freedom measures and Z-direction motion-insensitive;And interferometer structure is simple, integrated convenient for minimizing.Surpass applied to litho machine
The displacement measurement of precision workpiece stage compares laser interferometer measurement system, on the basis of measurement demand is met, can effectively drop
Low work stage volume, quality greatly improve the dynamic property of work stage, improve work stage overall performance synthesis.The planar light
Grating interferometer displacement measurement system applies also for the work stage of precision machine tool, three coordinate measuring machine, semiconductor detection etc.
In the accurate measurement of multiple degrees of freedom displacement.