CN108286943A - Displacement measurement optical system applied to lithography system workbench - Google Patents
Displacement measurement optical system applied to lithography system workbench Download PDFInfo
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- CN108286943A CN108286943A CN201810035524.2A CN201810035524A CN108286943A CN 108286943 A CN108286943 A CN 108286943A CN 201810035524 A CN201810035524 A CN 201810035524A CN 108286943 A CN108286943 A CN 108286943A
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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
- G01B11/022—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by means of tv-camera scanning
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Abstract
The invention discloses a kind of displacement measurement optical systems applied to lithography system workbench, first difference frequency interference device is used to generate the difference frequency coherent light that centre wavelength is first wave long value, emit two frequency content light to the first speculum and the second speculum respectively, and receives after two-beam returns and converge the interference light to be formed；Second difference frequency interference device is used to generate the difference frequency coherent light that centre wavelength is second wave length value, emits two frequency content light to the first speculum and the second speculum respectively, and receives after two-beam returns and converge the interference light to be formed；First reflector position is fixed, and the second speculum can calculate the displacement for eliminating the second speculum after environmental factor disturbs according to the interference image that two difference frequency interference devices record with movable workbench, signal processing apparatus.This displacement measurement optical system is based on Through Optical Interference Spectra using two kinds of optical source wavelength light and realizes displacement measurement, and the influence of environmental factor is compensated in entire displacement region, measurement accuracy can be improved compared with the prior art.
Description
Technical field
The present invention relates to field of optical measuring technologies, are surveyed more particularly to a kind of displacement applied to lithography system workbench
Measure optical system.
Background technology
Currently, the nano level long stroke two-dimentional work bench applied in a lithography system, to its displacement measurement using more
Be that pattern displacement measurement and difference frequency laser interferometer displacement measure, but in long stroke displacement measurement, it is desirable that grating line number is high,
Length is big, and such grating scribes difficulty, there are the contradiction that Measurement Resolution and range cannot be taken into account, and measurement accuracy and grating
Precision of scribing there is direct relationship, light grate processing technology to be affected.In comparison, the position based on difference frequency laser interference
The distinguishing features such as there is shift measurement high-resolution, high-precision, height to test the speed, long stroke and multichannel, it may be said that be nano level
The optimal selection of long stroke two-dimentional work bench displacement measurement.
However, laser interferometer displacement measuring system is high to environmental condition requirement, environmental factor has measurement in measurement process
Considerable influence.In the prior art, temperature in use sensor, baroceptor, humidity sensor detect in measuring environment
Relevant parameter, calculate refractive index and wavelength value in conjunction with these environmental parameters, then the signal parallel measured with system is input to
In signal processing system, air refraction compensation is carried out, measurement accuracy can effectively improve by the compensation method.However due to
The limitation of measuring instrument and method for long stroke and is that can not accurately detect entire displacement field for the workbench moved
The environmental parameter in domain cannot achieve the accurate compensation of effect on environment.
Invention content
In consideration of it, the present invention provides a kind of displacement measurement optical system applied to lithography system workbench, for measuring
The displacement of workbench is based on Through Optical Interference Spectra using two kinds of optical source wavelength light and realizes displacement measurement, the influence of environmental factor is mended
It repays in entire displacement region, measurement accuracy can be improved.
To achieve the above object, the present invention provides the following technical solutions：
A kind of displacement measurement optical system applied to lithography system workbench, including the first difference frequency interference device, second
Difference frequency interference device, the first speculum, the second speculum and signal processing apparatus；
The position of first speculum is fixed, and second speculum is connect with workbench, can be with movable workbench；
The first difference frequency interference device is used to generate the difference frequency coherent light that centre wavelength is first wave long value, respectively to institute
It states the first speculum and second speculum emits two frequency content light, and receive after two-beam returns and converge the interference to be formed
Light；
The second difference frequency interference device is used to generate the difference frequency coherent light that centre wavelength is second wave length value, respectively to institute
It states the first speculum and second speculum emits two frequency content light, and receive after two-beam returns and converge the interference to be formed
Light；
The signal processing apparatus be used for the interference image that is recorded according to the first difference frequency interference device be calculated with
First light path displacement of first wave long value description, the interference image recorded according to the second difference frequency interference device are calculated
With the second light path displacement that second wave length value describes, and eliminated according to the first light path displacement and the second light path displacement calculation
The displacement of second speculum of environmental factor disturbance.
Optionally, further include third speculum；
The third speculum is fixed in exposure system；
The first difference frequency interference device is additionally operable to respectively into first speculum and third speculum transmitting
Two frequency content light of a length of first wave long value of cardiac wave, wherein to the third speculum launch with to second speculum
The identical frequency of transmitting receives after two-beam returns at light splitting and converges the interference light to be formed；
The second difference frequency interference device is additionally operable to respectively into first speculum and third speculum transmitting
Two frequency content light of a length of second wave length value of cardiac wave, wherein launching to the third speculum and emitting to described second instead
The identical frequency of mirror is penetrated into light splitting, and receives after two-beam returns and converges the interference light to be formed；
The signal processing apparatus is additionally operable to be calculated according to the interference image that the first difference frequency interference device records
With the third light path displacement that first wave long value describes, the interference image recorded according to the second difference frequency interference device calculates
To the 4th light path displacement described with second wave length value, and according to the actual displacement of the third speculum, the third light
Journey displacement and the 4th light path displacement calculate and eliminate environmental factor disturbance, light source stability disturbance and the exposure
Displacement of the system due to thermally expanding second speculum for generating disturbance.
Optionally, further include optical frames：
The light exit direction of the first difference frequency interference device and the light exit direction of the second difference frequency interference device are hung down
Directly, the optical frames is located at the outgoing beam intersection of the first difference frequency interference device and the second difference frequency interference device,
For penetrating the light that centre wavelength is first wave long value, the light reflection that centre wavelength is second wave length value is gone out.
Optionally, the first difference frequency interference device includes：
First light source, for generating the difference frequency coherent light that centre wavelength is first wave long value；
Two frequency content light of the first polarization splitting prism, the difference frequency coherent light for generating first light source are incident respectively
To the first speculum and the second speculum, and will be converged by the light of the first speculum and the return of the second speculum；
First optical receiver is connected with the signal processing apparatus, is passed by first polarization splitting prism for receiving
That broadcasts converges interference light；
The second difference frequency interference device includes：
Second light source, for generating the difference frequency coherent light that centre wavelength is second wave length value；
Two frequency content light of the second polarization splitting prism, the difference frequency coherent light for generating second light source are incident respectively
To the first speculum and the second speculum, and will be converged by the light of the first speculum and the return of the second speculum；
Second optical receiver is connected with the signal processing apparatus, is passed by second polarization splitting prism for receiving
That broadcasts converges interference light.
Optionally, in light path and described between the first difference frequency interference device and first speculum
Between one difference frequency interference device and second speculum quarter-wave plate is both provided in light path；
It is dry in light path and in second difference frequency between the second difference frequency interference device and first speculum
It relates to and is both provided with quarter-wave plate in light path between device and second speculum.
Optionally, the first difference frequency interference device includes：
First light source, for generating the difference frequency coherent light that centre wavelength is first wave long value；
First spectroscope is arranged between the first light source and the first polarization splitting prism in light path, and being used for will be described
First light source sends out light and is divided into the parallel two-beam in the direction of propagation, is incident on first polarization splitting prism；
First polarization splitting prism, for two frequency content light of incident a branch of difference frequency coherent light are incident respectively
To the first speculum and the second speculum, and it will be converged by the first speculum and the second speculum return light, by the another of incidence
Two frequency content light of beam difference frequency coherent light are incident on the first speculum and third speculum respectively, and will by the first speculum and
Third speculum return light is converged；
First optical receiver is connected with the signal processing apparatus, is passed by first polarization splitting prism for receiving
Interference light broadcasting, being converged by the first speculum return light and the second speculum return light；
Third optical receiver is connected with the signal processing apparatus, is passed by first polarization splitting prism for receiving
Interference light broadcasting, being converged by the first speculum return light and the third speculum return light；
The second difference frequency interference device includes：
Second light source, for generating the difference frequency coherent light that centre wavelength is second wave length value；
Second spectroscope is arranged between the second light source and the second polarization splitting prism in light path, and being used for will be described
Second light source sends out light and is divided into the parallel two-beam in the direction of propagation, is incident on second polarization splitting prism；
Second polarization splitting prism, for two frequency content light of incident a branch of difference frequency coherent light are incident respectively
To the first speculum and the second speculum, and it will be converged by the first speculum and the second speculum return light, by the another of incidence
Two frequency content light of beam difference frequency coherent light are incident on the first speculum and third speculum respectively, and will be returned by the first speculum
Light echo and third speculum return light are converged；
Second optical receiver is connected with the signal processing apparatus, is passed by second polarization splitting prism for receiving
Interference light broadcasting, being converged by the first speculum return light and the second speculum return light；
4th optical receiver is connected with the signal processing apparatus, is passed by second polarization splitting prism for receiving
Interference light broadcasting, being converged by the first speculum return light and the third speculum return light.
Optionally, between the first difference frequency interference device and first speculum in light path, it is poor described first
It is reflected in light path and in the first difference frequency interference device and the third between frequency interference device and second speculum
Quarter-wave plate is both provided between mirror in light path；
Interfere dress in light path, in second difference frequency between the second difference frequency interference device and first speculum
It sets between second speculum in light path and the light between the second difference frequency interference device and the third speculum
Road is both provided with quarter-wave plate.
Optionally, light source include lasing light emitter, acousto-optic modulator, the first spectroscope, the second spectroscope, speculum, two/
One wave plate and polarization spectroscope；
The lasing light emitter is for sending out laser；
The acousto-optic modulator is incident on first spectroscope for laser to be divided into the unchanged light all the way of frequency, and
The another way light for generating frequency displacement is incident on second spectroscope；
Second spectroscope, the speculum are set gradually along light path, and the speculum is by light reflection to described two points
One of wave plate, after be incident on the polarization spectroscope；
First spectroscope, the polarization spectroscope are set gradually along light path, are reflected by second spectroscope
Frequency displacement light is incident on first spectroscope, is transmitted through first spectroscope；
The non-darkening of frequency reflected by first spectroscope converges with the frequency displacement light transmitted by first spectroscope
It closes, as with reference to light, the light exported by the polarization spectroscope is as measurement light.
Optionally, the first wave long value belongs to red spectral band, and the second wave length value belongs to blue wave band.
Optionally, it is provided in light path between second speculum and the third speculum and difference frequency interference device
For the temperature sensor of measuring temperature, and the humidity sensor for measuring humidity.
As shown from the above technical solution, the displacement measurement optical system provided by the present invention applied to lithography system workbench
System, including the first difference frequency interference device, the second difference frequency interference device, the first speculum, the second speculum and signal processing apparatus.
Wherein, the difference frequency coherent light that centre wavelength is first wave long value is generated by the first difference frequency interference device, by two frequencies
Emit respectively to the first speculum and the second speculum at light splitting, and receives after two-beam returns and converge the interference light to be formed；By
Second difference frequency interference device generate centre wavelength be second wave length value difference frequency coherent light, by two frequency content light emit respectively to
First speculum and the second speculum, and receive after two-beam returns and converge the interference light to be formed.The position of first speculum is solid
Fixed, as with reference to mirror, the second speculum is connect with workbench, can be with movable workbench.Signal processing apparatus is according to the first difference frequency
The the first light path displacement described with first wave long value is calculated in the interference image of interference device record, dry according to the second difference frequency
The the second light path displacement described with second wave length value is calculated in the interference image for relating to device record, and according to the first light path position
Shifting amount and the second light path displacement calculation go out to eliminate the displacement of the second speculum of environmental factor disturbance, the i.e. displacement of workbench.
Displacement measurement optical system of the present invention utilizes the relevant light measurement displacement of the difference frequency of two kinds of different wave lengths, according to two kinds of waves
The light path displacement calculation that long flash ranging obtains obtains displacement, and the influence by environmental factor to displacement measurement is compensated in entire displacement region
In, measurement accuracy is improved compared with the prior art.
Description of the drawings
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technology description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
Obtain other attached drawings according to these attached drawings.
Fig. 1 is a kind of showing for displacement measurement optical system applied to lithography system workbench provided in an embodiment of the present invention
It is intended to；
Fig. 2 is a kind of displacement measurement optical system applied to lithography system workbench that further embodiment of this invention provides
Schematic diagram；
Fig. 3 is a kind of displacement measurement optical system applied to lithography system workbench that further embodiment of this invention provides
Schematic diagram；
Fig. 4 is a kind of displacement measurement optical system applied to lithography system workbench that further embodiment of this invention provides
Schematic diagram；
Fig. 5 is a kind of schematic diagram of light source provided in an embodiment of the present invention.
Specific implementation mode
In order to make those skilled in the art more fully understand the technical solution in the present invention, below in conjunction with of the invention real
The attached drawing in example is applied, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described implementation
Example is only a part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, this field is common
The every other embodiment that technical staff is obtained without making creative work, should all belong to protection of the present invention
Range.
Referring to FIG. 1, a kind of displacement measurement optics applied to lithography system workbench that one embodiment of the invention provides
System, including the first difference frequency interference device 10, the second difference frequency interference device 11, the first speculum 12, the second speculum 13 and letter
Number processing unit 14.
Wherein, the position of the first speculum 12 is fixed, and the setting of the second speculum 13 on the table, connects with workbench
It connects, it can be with movable workbench, using the first speculum 12 as mirror is referred to, using the second speculum 13 as measurement mirror.
First difference frequency interference device 10 is used to generate the difference frequency coherent light that centre wavelength is first wave long value, respectively to described
First speculum 12 and second speculum 13 emit two frequency content light, and receive converge after two-beam returns to be formed it is dry
Relate to light.Wherein, two frequency content light are coherent light.
The second difference frequency interference device 11 be used for generate centre wavelength be second wave length value difference frequency coherent light, respectively to
First speculum 12 and second speculum 13 emit two frequency content light, and receive after two-beam returns and converge to be formed
Interference light.Wherein, two frequency content light are coherent light.
The interference image that the signal processing apparatus 14 is used to be recorded according to the first difference frequency interference device 10 calculates
To the first light path displacement described with first wave long value, the interference image meter recorded according to the second difference frequency interference device 11
Calculation obtains the second light path displacement described with second wave length value, and according to the first light path displacement and the second light path displacement gauge
Calculate the displacement for the second speculum 13 for eliminating environmental factor disturbance, the i.e. displacement of workbench.
The measuring principle of this displacement measurement optical system is：If it is assumed that the difference frequency phase that the first difference frequency interference device 10 generates
The centre wavelength of dry light is λ1, the centre wavelength for the difference frequency coherent light that the second difference frequency interference device 11 generates is λ2, in optical system
Measuring arm (i.e. interfere between the second speculum 13 and the first difference frequency interference device 10 by light path, the second speculum 13 and the second difference frequency
Light path between device 11) in corresponding air refraction be respectively nλ1m、nλ2m.Then measured by the first difference frequency interference device 10
First light path displacement Lλ1m, the second light path displacement L for being measured by the second difference frequency interference device 11λ2mIt is expressed as：
Lλ1m=nλ1mL, Lλ2m=nλ2mL； (1)
Wherein L indicates the actual displacement amount (i.e. the displacement of the second speculum 13) of measuring arm.
The geometrical length L that measuring arm can be then derived by according to above formula is：
Wherein, K (λi)、g(λi) (i=1 or 2) be wavelength XiFunction, pwmIndicate vapor pressure in measuring arm.
As can be seen that calculating the displacement for measuring wall, wherein temperature, pressure and CO according to calculating formula (2)2These environment of concentration
Factor has eliminated the disturbing influence for measuring displacement, and the influence of only remaining vapor pressure is not eliminated, and vapor pressure
Influence it is small and compensation can be measured by temperature and moisture sensors.Therefore the present embodiment works applied to lithography system
The displacement measurement optical system of platform is based on Through Optical Interference Spectra using two kinds of wavelength lights and realizes displacement measurement, by some environmental factors
Disturbing influence compensate in entire displacement region.The precision of displacement measurement can be improved.
Further include light referring to FIG. 1, to carry out light path design and each optical element layout in the present embodiment optical system
Mirror 15 is learned, for guiding the difference frequency coherent light emitted by the first difference frequency interference device 10 and the second difference frequency interference device 11 to propagate to
First speculum 12, the second speculum 13.
Refering to what is shown in Fig. 1, in the specific implementation, light exit direction and the second difference frequency of the first difference frequency interference device 10 are interfered
The light exit direction of device 11 is vertical, and optical frames 15 is located at going out for the first difference frequency interference device 10 and the second difference frequency interference device 11
Irradiating light beam intersection, it is for penetrating the light that centre wavelength is first wave long value, centre wavelength is anti-for the light of second wave length value
It projects, realizes guiding light propagation.
Specifically, dichroscope can be used in optical frames 15, this dichroscope makes centre wavelength be first wave long value λ1Light
It transmits, it is second wave length value λ to make centre wavelength2Light reflection go out.The light exit direction of first difference frequency interference device 10 and the
The light exit direction of two difference frequency interference devices 11 is vertical, and optical frames 15 to be arranged in angle of 45 degrees with outgoing light direction.
Referring to FIG. 2, the first difference frequency interference device 10 specifically includes in the present embodiment：
First light source 100, for generating the difference frequency coherent light that centre wavelength is first wave long value；
First polarization splitting prism 101, the two frequency content light point of the difference frequency coherent light for generating first light source 100
It is not incident on the first speculum 12 and the second speculum 13, and the light returned by the first speculum 12 and the second speculum 13 is converged
It closes；
First optical receiver 102, is connected with the signal processing apparatus 14, for receiving by the first polarization spectro rib
What mirror 101 propagated out converges interference light.
Second difference frequency interference device 11 specifically includes：
Second light source 110, for generating the difference frequency coherent light that centre wavelength is second wave length value；
Second polarization splitting prism 111, the two frequency content light point of the difference frequency coherent light for generating second light source 100
It is not incident on the first speculum 12 and the second speculum 13, and the light returned by the first speculum 12 and the second speculum 13 is converged
It closes；
Second optical receiver 112 is connected with the signal processing apparatus 14, for receiving by the second polarization spectro rib
What mirror 111 propagated out converges interference light.
In addition, between the first difference frequency interference device 10 and the first speculum 12 in light path, in the first difference frequency interference device
10 and second are both provided with quarter-wave plate 16 in light path between speculum 13；It is anti-in the second difference frequency interference device 11 and first
It penetrates between mirror 12 and is both provided with a quarter in light path in light path, between the second difference frequency interference device 11 and the second speculum 13
Wave plate 16.
In first difference frequency interference device 10, it is first wave long value λ that first light source 100, which generates centre wavelength,1Difference frequency it is relevant
Light, including two frequency contents, wherein a frequency content light λ1mAs light is measured, another frequency content light, which is used as, refers to light λ1r, two
Frequency content light is relevant, parallel, polarization state orthogonal.Wherein, frequency content light λ1cIt is guided through the first polarization splitting prism 101
It is incident on the first speculum 12, backtracking after reflection, wherein passing through quarter-wave plate 16 twice, its polarization state is made to rotate
90 degree, light is transmitted out back to 101 diagonal plane of the first polarization splitting prism；Frequency content light λ1mThrough the first polarization splitting prism
101 are directed into and are mapped to the second speculum 13, backtracking after reflection, wherein passing through quarter-wave plate 16 twice, polarize shape
State is rotated by 90 °, and light is reflected back to 101 diagonal plane of the first polarization splitting prism；The two-way light of return converges to form interference
Light is received by the first optical receiver 102.
In second difference frequency interference device 11, it is second wave length value λ that second light source 110, which generates centre wavelength,2Difference frequency it is relevant
Light, including two frequency contents, wherein a frequency content light λ2mAs light is measured, another frequency content light, which is used as, refers to light λ2r, two
Frequency content light is relevant, parallel, polarization state orthogonal.Wherein, frequency content light λ2cIt is guided through the second polarization splitting prism 111
It is incident on the first speculum 12, backtracking after reflection, wherein passing through quarter-wave plate 16 twice, its polarization state is made to rotate
90 degree, light is transmitted out back to 111 diagonal plane of the second polarization splitting prism；Frequency content light λ2mThrough the second polarization splitting prism
111 are directed into and are mapped to the second speculum 13, backtracking after reflection, wherein passing through quarter-wave plate 16 twice, polarize shape
State is rotated by 90 °, and light is reflected back to 111 diagonal plane of the second polarization splitting prism；The two-way light of return converges to form interference
Light is received by the second optical receiver 112.
In the displacement measurement optical system applied to lithography system workbench of above-described embodiment description, using double Light Source Methods
Influence of the Natural environment factors to measurement is successfully eliminated, but is at the same time exaggerated light path displacement measurement value uncertainty pair
The influence of measurement, it is this to influence mainly caused by the unstability of optical source wavelength.In addition, for lithography system, carved
Lose object setting on the table, the level that is etched by this displacement measurement optical system measuring worktable displacement is moved, to control
Photoetching position.However, when exposure system is subjected to displacement due to thermally expanding, exposure system occurs inclined relative to operating position
It moves, and the displacement measurement optical system that above-described embodiment provides is measured just for operating position, can not capture exposure system
It unites due to the offset of the factors such as thermal expansion disturbance generation, photoetching position and the deviation of ideal position can be caused.In consideration of it, of the invention
Another embodiment provides a kind of displacement measurement optical system applied to lithography system workbench, using compensator arm to measuring arm light
The influence of journey displacement measurement value uncertainty compensates, specially while being measured to measuring arm geometrical length,
The geometrical length of compensator arm is measured, to obtain unstability of the measuring arm light path displacement measurement value due to optical source wavelength
The offset progress error compensation that caused uncertainty and exposure system are generated due to the disturbance of the factors such as thermal expansion.
Referring to FIG. 3, in the present embodiment displacement measurement optical system, including the first difference frequency interference device 20, the second difference frequency
Interference device 21, the first speculum 22, the second speculum 23, third speculum 27 and signal processing apparatus 24.
Wherein, the position of first speculum 22 is fixed, and second speculum 23 is arranged on the table, with work
Platform connects, can be with movable workbench, and the object that is etched is arranged on the table, and third speculum 27 is fixed in exposure system, with
First speculum 12 is as mirror is referred to, using the second speculum 13 as measurement mirror, the reality of third speculum 27 in measurement process
Known to displacement.
First difference frequency interference device 20 is used to generate the difference frequency coherent light that centre wavelength is first wave long value, respectively to first
Speculum 22 and the second speculum 23 emit two frequency content light, and receive after two-beam returns and converge the interference light to be formed；Also
Respectively to the two frequency content light that the first speculum 22 and 27 emission center wavelength of third speculum are first wave long value,
The middle identical frequency launched to the third speculum 27 and emitted to the second speculum 23 receives two-beam and returns at light splitting
Converge the interference light to be formed after returning.Wherein, it is phase that centre wavelength, which is two frequency content light of the difference frequency coherent light of first wave long value,
Dry light.
The second difference frequency interference device 21 be used for generate centre wavelength be second wave length value difference frequency coherent light, respectively to
First speculum 22 and second speculum 23 emit two frequency content light, and receive after two-beam returns and converge to be formed
Interference light；It is additionally operable to be respectively second wave length to first speculum 22 and 27 emission center wavelength of third speculum
Two frequency content light of value, wherein launching to the third speculum 27 and emitting to the same frequency of second speculum 23
Rate receives after two-beam returns at light splitting and converges the interference light to be formed.Wherein, centre wavelength is the difference frequency phase of second wave length value
Two frequency content light of dry light are coherent light.
The interference image that the signal processing apparatus 24 is used to be recorded according to the first difference frequency interference device 20 calculates
To the first light path displacement described with first wave long value, the interference image meter recorded according to the second difference frequency interference device 21
Calculation obtains the second light path displacement described with second wave length value.
The signal processing apparatus 24 is additionally operable to be calculated according to the interference image that the first difference frequency interference device 20 records
With the third light path displacement that first wave long value describes, calculated according to the interference image of the second difference frequency interference device 21 record
The 4th light path displacement described with second wave length value is obtained, wherein third light path displacement and the 4th light path displacement is described
The light path displacement of third speculum 27,
The signal processing apparatus 24 according to the actual displacement of the third speculum 27, the third light path displacement and
The 4th light path displacement calculates and eliminates environmental factor disturbance, light source stability disturbance and the exposure system due to heat
Expansion generates the displacement of second speculum 23 of disturbance..
The measuring principle of upper displacement measurement optical system is：According to measuring arm, light path displacement measurement value uncertainty
ΔLλ1m、ΔLλ1mIt is expressed as：
Wherein elaser1、elaser2The fluctuating error of first light source and second light source is indicated respectively.
Influence of the light path displacement measurement value uncertainty to measurement be：
Compensator arm is constituted with light path between third speculum 27 and difference frequency interference device, the third light path displacement measured
Measure Sλ1cWith the 4th light path displacement Sλ2c, light path displacement measurement value uncertainty Δ Sλ1c、ΔSλ2cIt is expressed as：
ΔSλ1c=nλ1cS-Sλ1c=Sλ1c·elaser1； (6)
ΔSλ2c=nλ2cS-Sλ2c=Sλ2c·elaser2； (7)
Wherein, nλ1c、nλ2cIndicate two wavelength lights compensator arm (i.e. third speculum 27 and the first difference frequency interference device 20 it
Between light path between light path, the second speculum 23 and the second difference frequency interference device 21) in corresponding air refraction, S indicates compensation
The actual displacement amount (i.e. the displacement of third speculum 27) of arm.
Can obtain light beats error by above formula is：
Aggregative formula (1), formula (5), formula (8) and formula (9), the measuring arm displacement measurement after compensation are：
Further, according to Edlen formula, the refractive index of compensator arm is expressed as：
nλic- 1=K (λi)·D(tc,pc,xc)-pwc·g(λi), i=0or1。 (11)
Wherein, tc、pc、xcAnd pwcThe temperature of expression compensator arm air, pressure, CO respectively2Concentration and vapor pressure.It will
Formula (11) brings formula (10) into, and is approximated as follows：
Formula (10) is rewritten as：
Further, compensator arm being constituted with light path between third speculum 27 and difference frequency interference device, actual displacement amount is S,
The third speculum 27 is fixed in exposure system, when exposure system is subjected to displacement Δ S due to thermally expanding, measuring arm displacement
Measured value is Lc=LmS/(Sm+ Δ S), the third mirror displacements carry out error compensation to second mirror displacements
Meanwhile exposure system can also be compensated due to thermally expanding the displacement occurred.
Therefore, the present embodiment is applied to the displacement measurement optical system of lithography system workbench, passes through double light source measurement methods
Influence of the environmental factor to interferometer measurement is eliminated, and light path displacement measurement value uncertainty is influenced to carry out by compensator arm
Compensation, compensates for optical source wavelength fluctuation and exposure system thermally expands caused measurement error.It is greatly improved displacement measurement
Precision is applied in lithography system, is greatly improved the precision of long stroke two-dimentional work bench displacement measurement, helps to improve photoetching
Lithographic accuracy in system.
Further include optical frames 25 to carry out light path design and each optical element layout, for guiding by the in the present embodiment
It is anti-that one difference frequency interference device 20 and the difference frequency coherent light of the second difference frequency interference device 21 transmitting propagate to the first speculum 22, second
Penetrate mirror 23 and third speculum 27.
Fig. 3 is can refer to, in the specific implementation, light exit direction and the interference of the second difference frequency of the first difference frequency interference device 20 fill
Set 21 light exit direction it is vertical, optical frames 25 is located at the outgoing of the first difference frequency interference device 20 and the second difference frequency interference device 21
At beam intersection, for penetrating the light that centre wavelength is first wave long value, by the light reflection that centre wavelength is second wave length value
Go out, realizes guiding light propagation.
Specifically, dichroscope can be used in optical frames 25, this dichroscope makes centre wavelength be first wave long value λ1Light
It transmits, it is second wave length value λ to make centre wavelength2Light reflection go out.The light exit direction of first difference frequency interference device 20 and the
The light exit direction of two difference frequency interference devices 21 is vertical, and optical frames 25 to be arranged in angle of 45 degrees with outgoing light direction.
Fig. 4 is can refer to, the first difference frequency interference device 20 includes in the present embodiment：
First light source 200, for generating the difference frequency coherent light that centre wavelength is first wave long value；
First spectroscope 203 is arranged between the first light source 200 and the first polarization splitting prism 201 in light path, uses
It is divided into the parallel two-beam in the direction of propagation in the first light source 200 is sent out light, is incident on first polarization splitting prism
201；
First polarization splitting prism 201, for two frequency content light of incident a branch of difference frequency coherent light are incident respectively
It to the first speculum 22 and the second speculum 23, and will be converged by the first speculum 22 and 23 return light of the second speculum, will be entered
Two frequency content light of another beam difference frequency coherent light penetrated are incident on the first speculum 22 and third speculum 27 respectively, and will be by
First speculum 22 and 27 return light of third speculum are converged；
First optical receiver 202, is connected with the signal processing apparatus 24, for receiving by the second polarization spectro rib
Interference light that mirror 201 propagates out, being converged by 22 return light of the first speculum and 23 return light of the second speculum；
Third optical receiver 204.It is connected with the signal processing apparatus 24, for receiving by the first polarization spectro rib
Interference light that mirror 201 propagates out, being converged by 22 return light of the first speculum and 27 return light of third speculum.
Second difference frequency interference device 21 includes：
Second light source 210, for generating the difference frequency coherent light that centre wavelength is second wave length value；
Second spectroscope 213 is arranged between the second light source 210 and the second polarization splitting prism 211 in light path, uses
It is divided into the parallel two-beam in the direction of propagation in the second light source 210 is sent out light, is incident on the second polarization splitting prism 211；
Second polarization splitting prism 211, for two frequency content light of incident a branch of difference frequency coherent light are incident respectively
It to the first speculum 22 and the second speculum 23, and will be converged by the first speculum 22 and 23 return light of the second speculum, will be entered
Two frequency content light of another beam difference frequency coherent light penetrated are incident on the first speculum 22 and third speculum 27 respectively, and will be by
First speculum, 22 return light and 27 return light of third speculum are converged；
Second optical receiver 212, is connected with the signal processing apparatus 24, for receiving by the second polarization spectro rib
Interference light that mirror 211 propagates out, being converged by 22 return light of the first speculum and 23 return light of the second speculum；
4th optical receiver 214 is connected with the signal processing apparatus 24, for receiving by the second polarization spectro rib
Interference light that mirror 211 propagates out, being converged by 22 return light of the first speculum and 27 return light of third speculum.
In addition, between the first difference frequency interference device 20 and the first speculum 22 in light path, in the first difference frequency interference device
20 and second in light path between speculum 23, the light path between the first difference frequency interference device 20 and the third speculum 27
On be both provided with quarter-wave plate 26.
Between the second difference frequency interference device 21 and the first speculum 22 in light path, in the second difference frequency interference device 21 and
It is all provided in light path in light path, between the first difference frequency interference device 21 and the third speculum 27 between two-mirror 23
It is equipped with quarter-wave plate 26.
In first difference frequency interference device 20, it is first wave long value λ that first light source 200, which generates centre wavelength,1Difference frequency it is relevant
Light, including two frequency contents, wherein a frequency content light λ1mAs light is measured, another frequency content light, which is used as, refers to light λ1r, two
Frequency content light is relevant, parallel, polarization state orthogonal.Each frequency content light is divided into horizontal infection by the first spectroscope 203
Two beams are incident on the first polarization splitting prism 201.
In second difference frequency interference device 21, it is second wave length value λ that second light source 210, which generates centre wavelength,2Difference frequency it is relevant
Light, including two frequency contents, wherein a frequency content light λ2mAs light is measured, another frequency content light, which is used as, refers to light λ2r, two
Frequency content light is relevant, parallel, polarization state orthogonal.Each frequency content light is divided into horizontal infection by the second spectroscope 213
Two beams are incident on the first polarization splitting prism 211.
In the above embodiments, to make two-way optical path there is identical measuring environment, optical frames to use two-way Look mirror,
Reference light, measurement light and compensation light that difference frequency interference device exports are closed into beam respectively, to ensure its total light path.
Further, it is arranged in light path between second speculum and the third speculum and difference frequency interference device
It is useful for the temperature sensor of measuring temperature, and the humidity sensor for measuring humidity.Pass through temperature sensor and humidity
Temperature, the humidity that sensor detection measures light light path and compensates in light path change, to compensation water vapor pressure to light velocity measurement
Influence.
In the above embodiments, referring to FIG. 5, light source includes lasing light emitter 30, acousto-optic modulator 31, the first spectroscope
32, the second spectroscope 33, speculum 34, half wave plate 35 and polarization spectroscope 36；
The lasing light emitter 30 is for sending out laser；
The acousto-optic modulator 31 is incident on first spectroscope 32 for laser to be divided into the unchanged light all the way of frequency,
And the another way light of generation frequency displacement is incident on second spectroscope 33；
Second spectroscope 33, the speculum 34 are set gradually along light path, and the speculum 34 is by light reflection to institute
State half wave plate 35, after be incident on the polarization spectroscope 36；
First spectroscope 32, the polarization spectroscope 36 are set gradually along light path, anti-by second spectroscope 33
The frequency displacement light of injection is incident on first spectroscope 32, is transmitted through first spectroscope 32；
The non-darkening of frequency reflected by first spectroscope 32 and the frequency displacement transmitted by first spectroscope 32
Light converges, and as with reference to light, the light exported by the polarization spectroscope 36 is as measurement light.
In a specific embodiment, the first wave long value belongs to red spectral band, and the second wave length value belongs to blue light
Wave band.
Specifically, first wave long value is 0.6328 μm, two frequency content light of generation have 3MHz frequency displacements.Specifically it can be used
Agilent5517C lasers.
The light source of second light source using the above structure, the horizontal polarization light for being 0.4131 μm by lasing light emitter output wavelength, can
Light source used in exposure system is chosen, the unchanged measurement light λ of frequency is formed through acousto-optic modulator2mWith the reference that frequency shift amount is 20MHz
Light λ2r。
In specific the present embodiment, Fig. 2 and Fig. 4 can refer to, polarization splitting prism is by that cross section is parallelogram
One prism and the second prism that cross section is right-angled trapezium splice, the first side of first prism and second prism
Inclined-plane is bonded.First prism one side opposite with first side is reflecting surface.
A kind of displacement measurement optical system applied to lithography system workbench provided by the present invention is carried out above
It is discussed in detail.Principle and implementation of the present invention are described for specific case used herein, above example
Illustrate the method and its core concept for being merely used to help understand the present invention.It should be pointed out that for the common skill of the art
, without departing from the principle of the present invention, can be with several improvements and modifications are made to the present invention for art personnel, these change
It is also fallen within the protection scope of the claims of the present invention into modification.
Claims (10)
1. a kind of displacement measurement optical system applied to lithography system workbench, which is characterized in that interfere including the first difference frequency
Device, the second difference frequency interference device, the first speculum, the second speculum and signal processing apparatus；
The position of first speculum is fixed, and second speculum is connect with workbench, can be with movable workbench；
The first difference frequency interference device is used to generate the difference frequency coherent light that centre wavelength is first wave long value, respectively to described the
One speculum and second speculum emit two frequency content light, and receive after two-beam returns and converge the interference light to be formed；
The second difference frequency interference device is used to generate the difference frequency coherent light that centre wavelength is second wave length value, respectively to described the
One speculum and second speculum emit two frequency content light, and receive after two-beam returns and converge the interference light to be formed；
The interference image that the signal processing apparatus is used to be recorded according to the first difference frequency interference device is calculated with first
First light path displacement of wavelength value description, the interference image recorded according to the second difference frequency interference device are calculated with the
Second light path displacement of two wavelength values description, and environment is eliminated according to the first light path displacement and the second light path displacement calculation
The displacement of second speculum of factor disturbance.
2. the displacement measurement optical system according to claim 1 applied to lithography system workbench, which is characterized in that also
Including third speculum；
The third speculum is fixed in exposure system；
The first difference frequency interference device is additionally operable to respectively to first speculum and the third speculum launching centre wave
Two frequency content light of a length of first wave long value emit wherein launching to the third speculum with to second speculum
Identical frequency at light splitting, and receive two-beam return after converge the interference light to be formed；
The second difference frequency interference device is additionally operable to respectively to first speculum and the third speculum launching centre wave
Two frequency content light of a length of second wave length value, wherein launching to the third speculum and emitting to second speculum
Identical frequency at light splitting, and receive two-beam return after converge the interference light to be formed；
The signal processing apparatus is additionally operable to be calculated with according to the interference image that the first difference frequency interference device records
One wavelength value description third light path displacement, according to the second difference frequency interference device record interference image be calculated with
4th light path displacement of second wave length value description, and according to the actual displacement of the third speculum, third light path position
Shifting amount and the 4th light path displacement calculate and eliminate environmental factor disturbance, light source stability disturbance and the exposure system
Due to thermally expanding the displacement for second speculum for generating disturbance.
3. the displacement measurement optical system according to claim 1 or 2 applied to lithography system workbench, feature exists
In further including optical frames：
The light exit direction of the first difference frequency interference device is vertical with the light exit direction of the second difference frequency interference device, institute
The outgoing beam intersection that optical frames is located at the first difference frequency interference device and the second difference frequency interference device is stated, being used for will
Centre wavelength is that the light of first wave long value penetrates, and the light reflection that centre wavelength is second wave length value is gone out.
4. the displacement measurement optical system according to claim 1 applied to lithography system workbench, which is characterized in that
The first difference frequency interference device includes：
First light source, for generating the difference frequency coherent light that centre wavelength is first wave long value；
Two frequency content light of the first polarization splitting prism, the difference frequency coherent light for generating first light source are incident on respectively
One speculum and the second speculum, and will be converged by the light of the first speculum and the return of the second speculum；
First optical receiver is connected with the signal processing apparatus, is propagated out by first polarization splitting prism for receiving
Converge interference light；
The second difference frequency interference device includes：
Second light source, for generating the difference frequency coherent light that centre wavelength is second wave length value；
Two frequency content light of the second polarization splitting prism, the difference frequency coherent light for generating second light source are incident on respectively
One speculum and the second speculum, and will be converged by the light of the first speculum and the return of the second speculum；
Second optical receiver is connected with the signal processing apparatus, is propagated out by second polarization splitting prism for receiving
Converge interference light.
5. the displacement measurement optical system according to claim 4 applied to lithography system workbench, which is characterized in that
In light path and in the first difference frequency interference device and institute between the first difference frequency interference device and first speculum
It states and is both provided with quarter-wave plate in light path between the second speculum；
Interfere dress in light path and in second difference frequency between the second difference frequency interference device and first speculum
It sets and is both provided with quarter-wave plate in light path between second speculum.
6. the displacement measurement optical system according to claim 2 applied to lithography system workbench, which is characterized in that
The first difference frequency interference device includes：
First light source, for generating the difference frequency coherent light that centre wavelength is first wave long value；
First spectroscope is arranged between the first light source and the first polarization splitting prism in light path, is used for described first
Light source sends out light and is divided into the parallel two-beam in the direction of propagation, is incident on first polarization splitting prism；
First polarization splitting prism, for two frequency content light of incident a branch of difference frequency coherent light to be incident on the respectively
One speculum and the second speculum, and will be converged by the first speculum and the second speculum return light, incident another beam is poor
Two frequency content light of frequency coherent light are incident on the first speculum and third speculum respectively, and will be by the first speculum and third
Speculum return light is converged；
First optical receiver is connected with the signal processing apparatus, is propagated out by first polarization splitting prism for receiving
, the interference light converged by the first speculum return light and the second speculum return light；
Third optical receiver is connected with the signal processing apparatus, is propagated out by first polarization splitting prism for receiving
, the interference light converged by the first speculum return light and the third speculum return light；
The second difference frequency interference device includes：
Second light source, for generating the difference frequency coherent light that centre wavelength is second wave length value；
Second spectroscope is arranged between the second light source and the second polarization splitting prism in light path, is used for described second
Light source sends out light and is divided into the parallel two-beam in the direction of propagation, is incident on second polarization splitting prism；
Second polarization splitting prism, for two frequency content light of incident a branch of difference frequency coherent light to be incident on the respectively
One speculum and the second speculum, and will be converged by the first speculum and the second speculum return light, incident another beam is poor
Two frequency content light of frequency coherent light are incident on the first speculum and third speculum respectively, and will be by the first speculum return light
Converge with third speculum return light；
Second optical receiver is connected with the signal processing apparatus, is propagated out by second polarization splitting prism for receiving
, the interference light converged by the first speculum return light and the second speculum return light；
4th optical receiver is connected with the signal processing apparatus, is propagated out by second polarization splitting prism for receiving
, the interference light converged by the first speculum return light and the third speculum return light.
7. the displacement measurement optical system according to claim 6 applied to lithography system workbench, which is characterized in that
Between the first difference frequency interference device and first speculum in light path, in the first difference frequency interference device and described the
It is respectively provided in light path in light path and between the first difference frequency interference device and the third speculum between two-mirror
There is quarter-wave plate；
Between the second difference frequency interference device and first speculum in light path, the second difference frequency interference device with
Between second speculum in light path and between the second difference frequency interference device and the third speculum in light path
It is both provided with quarter-wave plate.
8. it is applied to the displacement measurement optical system of lithography system workbench according to claim 4-7 any one of them, it is special
Sign is, light source include lasing light emitter, acousto-optic modulator, the first spectroscope, the second spectroscope, speculum, half wave plate and
Polarization spectroscope；
The lasing light emitter is for sending out laser；
The acousto-optic modulator, which is used to laser being divided into the unchanged light all the way of frequency, is incident on first spectroscope, and generates
The another way light of frequency displacement is incident on second spectroscope；
Second spectroscope, the speculum are set gradually along light path, and the speculum is by light reflection to the half
Wave plate, after be incident on the polarization spectroscope；
First spectroscope, the polarization spectroscope are set gradually along light path, the frequency displacement reflected by second spectroscope
Light is incident on first spectroscope, is transmitted through first spectroscope；
The non-darkening of frequency reflected by first spectroscope converges with the frequency displacement light transmitted by first spectroscope, makees
For reference light, the light exported by the polarization spectroscope is as measurement light.
9. the displacement measurement optical system according to claim 1 applied to lithography system workbench, which is characterized in that institute
It states first wave long value and belongs to red spectral band, the second wave length value belongs to blue wave band.
10. the displacement measurement optical system according to claim 1 applied to lithography system workbench, which is characterized in that
It is provided with for measuring temperature in light path between second speculum and the third speculum and difference frequency interference device
Temperature sensor, and the humidity sensor for measuring humidity.
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