CN104613865A - Grating interferometer with high subdivision and high density - Google Patents

Abstract

The invention discloses a grating interferometer with high subdivision and high density. The grating interferometer comprises a diffraction grating with high density which does a relative movement, a linear polarization light source, a polarization beam splitter, a first high fineness prism, a second high fineness prism, a first reflector, a second reflector, a first quarter-wave plate, a second quarter-wave plate, a polarization phase-shifting interference photoelectric detection unit or a double frequency heterodyne interference photoelectric detection unit, a data acquisition and processing unit and a control unit. According to the grating interferometer provided by the invention, the grating interferometer with high density can be designed to be negative primary high diffraction optical efficiency; furthermore, the multiple repeated diffraction between a reflecting surface of the prism and a raster compartment with high density can be realized by adopting the high fineness prisms, and finally the auto-collimation retroreflection of collimation planes of the prisms can be realized and then the repeated diffraction on the raster compartment can be realized, so as to enable the grating interferometer to obtain the high subdivision effect, and improve the optical resolution of the grating interferometer effectively.

Description

High segmentation high dencity grating interferometer

Technical field

The present invention relates to optical gauge, particularly a kind of high segmentation high dencity grating interferometer.

Background technology

Grating interferometer is the nucleus module of high precision optical grating ruler measurement system (pitch is generally less than 10 microns), determines its precision and resolution.High precision optical grating ruler measurement system is by grating scale body, sectional fixture, form based on the read head of grating interferometer and signal controller and display, and its function carries out the measurement of high precision displacement amount.Be widely used in the fields such as machine tooling control, processing of wafers and cutting, integrated circuit (IC) etching equipment, semiconductor detection, robot system, Aero-Space, scientific research, military affairs.

High precision optical grating ruler measurement system is not only one of modern most basic robotization amount instrument, and is modern processing and produces and one of the important guarantee means of high precision, high-quality in scientific research.Especially the field such as 20nm/14nm integrated circuit (IC) etching equipment, nanometer/sub-nano science research, Aero-Space, scientific research, military affairs, proposes the demand of more high precision and resolution to high precision optical grating ruler measurement system.

For high-precision laser interferometer, the optical grating ruler measurement system based on grating interferometer has the insensitive advantage of environment.Its electronic fine-grained resolution has reached micromicron magnitude.But in practical application, the synthetic resolution of optical grating ruler measurement system is determined jointly by grating interferometer optical resolution and electronic fine-grained resolution; Grating interferometer optical resolution determines the validity of electronic fine-grained resolution.Therefore, improving grating interferometer optical resolution is the basic place of improving optical grating ruler measurement systemic resolution further.

Canon proposes patent, the American I BM such as US5038032, US5146085, US4912320 and proposes patent US5442172, U.S. ZYGO has also applied for the grating interferometer patent of many novelties, as US8300233B2, US0194824A1, US0114061A1, to obtain more high precision and resolution.Germany's Heidenhain, Sony are also proposed high-resolution optical grating ruler measurement system.But with above-mentioned be the technical scheme of representative, grating interferometer optical fine number is generally 2 or 4.Many employings are high electronic fine-grained, as 12bit, 14bit; Further high bit is electronic fine-grained to be easy to realize, but is limited to grating interferometer optics 4 and segments resolution, meaningless.Therefore, improve grating interferometer optical fine number further and grating interferometer optical resolution and even optical grating ruler measurement overall system resolution are improved for reality, there is important value.

Summary of the invention

The object of the invention is to overcome above-mentioned prior art not enough, propose a kind of high segmentation high dencity grating interferometer: first high dencity grating is designed to negative one-level height diffraction light efficiency; And then the repeatedly diffraction repeatedly adopting high segmentation prism to realize between prismatic reflection face and high dencity grating, and finally in the retroeflection of prism collimation plane autocollimation and again diffraction repeatedly between high dencity grating, thus make grating interferometer obtain high segmentation effect, effectively improve grating interferometer optical resolution.

Technical solution of the present invention is as follows:

A kind of high segmentation high dencity grating interferometer, comprise: the high density diffraction grating of relative motion, linear polarization light source, polarization beam apparatus, first high segmentation prism, second high segmentation prism, first catoptron, second catoptron, first quarter-wave plate, second quarter-wave plate, data acquisition and processing (DAP) and control module and interference photoelectric detection unit, its feature is, described linear polarization light source sends light beam and is divided into the P light of transmission and the S light of reflection through polarization beam apparatus, described P light is successively through the first described quarter-wave plate, first catoptron incides described relative motion diffraction grating, described S light is successively through the second described quarter-wave plate, second catoptron incides described relative motion diffraction grating, by the first high segmentation prism, the second high segmentation prism, incident beam is 2N time-1 order diffraction (N is the unidirectional number of times of diffraction repeatedly on diffraction grating) on the diffraction grating, produce positive and negative 2N times of doppler optical frequency displacement respectively, and then realize 4N times of optical fine.Two bundle-1 order diffraction light after this relative motion diffraction grating 2N diffraction are after the described first high segmentation prism and the second high segmentation prism transmission and reflection, the former road of autocollimation returns again, the linearly polarized light orthogonal with former polarization state is converted to respectively through the first described quarter-wave plate and the second quarter-wave plate, again incide described interference photoelectric detection unit through polarization beam apparatus, the output terminal of this interference photoelectric detection unit is connected with the input end of described data acquisition and processing (DAP) and control module.

Described first high segmentation prism and the second high segmentation prism include at least one reflecting surface, transmission plane that an adjacent collimation plane is relative with one; Described height segmentation prismatic reflection face and collimation plane angle α, height segment prismatic reflection face and transmission plane included angle, the high angle α segmenting prism transmission face and high density diffraction grating plane ₃meet following relation:

$\mathrm{\α}=\mathrm{\π}-\frac{\arcsin (n_0/n_1\·\sin (\mathrm{\β}-{\mathrm{\α}}_3))-\arcsin (n_0/n_1\·\sin (\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))-{\mathrm{\α}}_3))}{2}---\left(1\right)$

$\mathrm{\φ}=\frac{\arcsin (n_0/n_1\·\sin (\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))-{\mathrm{\α}}_3))+\arcsin (n_0/n_1\·\sin (\mathrm{\β}-{\mathrm{\α}}_3))}{2}---\left(2\right)$

Wherein, n ₀for air refraction, n ₁high segmentation Refractive Index of Glass Prism, λ is optical source wavelength, and β is incident beam and high density diffraction grating normal angle, and d is the pitch of high density diffraction grating, α ₃>=0.

Described first high segmentation prism and the second high segmentation prism include at least one reflecting surface collimation plane adjacent with; Described height segmentation prismatic reflection face and collimation plane angle α meet following relation:

$\mathrm{\α}=\mathrm{\π}-\frac{\mathrm{\β}-\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))}{2}$

Wherein, n ₀for air refraction, n ₁high segmentation Refractive Index of Glass Prism, λ is optical source wavelength, and β is incident beam and high density diffraction grating normal angle, and d is the pitch of high density diffraction grating.

Described linear polarization light source is light emitting diode, laser diode, the light source of solid or gas lamp; The laser instrument of single-frequency or the laser instrument of double frequency cross polarization.

Described interference photoelectric detection unit is that polarization phase-shifting interferes photoelectric detection unit or double frequency difference interference photoelectric detection unit.

Described polarization phase-shifting interferes photoelectric detection unit to comprise the 3rd quarter-wave plate, non-polarizing beamsplitter, the first polarization beam apparatus, the second polarization beam apparatus locating cross polarization 45 degree placement, the first detector, the second detector, the 3rd detector and the 4th detector.

Described double frequency difference interference photoelectric detection unit comprises non-polarizing beamsplitter, is in the first detector of the first analyzer of orthogonal double frequency linearly polarized light 45 degree placement and correspondence, is in the second analyzer of orthogonal double frequency linearly polarized light 45 degree placement and the second detector of correspondence, described linear polarization light source sends light beam and is divided into two bundles through described non-polarizing beamsplitter, polarization beam apparatus described in a branch of warp is divided into the P light of transmission and the S light of reflection, and another beam enters the first described analyzer.

Described data acquisition and processing (DAP) and control module are by data collecting card and motion control card and industrial computer forms or be made up of the circuit board at least with collection and computing function.

In such scheme, diffraction grating can also be transmission-type; When transmission-type uses, place completely reflecting mirror diffraction light one side, and by-1 order diffraction light oppositely with former incident angle of light incident transmission type diffraction grating, the first and second high segmentation prism parameters are constant.

Compared with prior art, technique effect of the present invention:

Adopt and high dencity grating is designed to negative one-level height diffraction light efficiency; And then the repeatedly diffraction repeatedly adopting high segmentation prism to realize between prismatic reflection face and high dencity grating, and final in the retroeflection of prism collimation plane autocollimation and again diffraction repeatedly between high dencity grating.Incident beam is 2N time-1 order diffraction (N is the unidirectional number of times of diffraction repeatedly on diffraction grating) on the diffraction grating, produces positive and negative 2N times of doppler optical frequency displacement respectively, and then realize 4N times of optical fine.If N=10, then can realize the optical fine of 40 times.Thus make grating interferometer obtain high segmentation effect, greatly effectively improve grating interferometer optical resolution.

Accompanying drawing explanation

Fig. 1 is the enforcement illustration of the height segmentation high dencity grating interferometer adopting double frequency difference interference photoelectric detection unit.

Fig. 2 is the enforcement illustration adopting polarization phase-shifting to interfere the height segmentation high dencity grating interferometer of photoelectric detection unit.

Fig. 3 is the fundamental diagram of high segmentation prism.

Fig. 4 is the another kind of fundamental diagram of high segmentation prism.

Fig. 5 is the fundamental diagram of integral type height segmentation prism.

Fig. 6 is the fundamental diagram of the height segmentation prism simplified.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the invention will be further described, but should not limit the scope of the invention with this.

1, embodiment 1.As Fig. 1.

Laser instrument 8 sends orthogonal double frequency linearly polarized light, two-beam is divided equally into through non-polarizing beamsplitter 10, a branch of double frequency difference interference photoelectric detection unit entered in empty frame, interference signal is formed by after the first analyzer 11 of placing with orthogonal double frequency linearly polarized light 45 degree, and received, as the reference signal of double frequency difference interference art by the first detector 12; Another bundle is divided into the P light of transmission and the S light of reflection by polarization beam apparatus 9, is transformed to circularly polarized light respectively by the first quarter-wave plate 6 and the second quarter-wave plate 7, then by the first catoptron 2 and the incident diffraction grating 1 of the second catoptron 3.First high segmentation prism 4 and the second high segmentation prism 5 on one side is separately entered respectively by two bundle-1 grade after diffraction grating 1 diffraction, the former road of autocollimation returns again, the linearly polarized light orthogonal with former polarization state is transformed to through the first quarter-wave plate 6 and the second quarter-wave plate 7, the double frequency difference interference photoelectric detection unit in empty frame is again jointly entered through polarization beam apparatus 9, interference signal is formed by after the second analyzer 14 of placing with orthogonal double frequency linearly polarized light 45 degree, and received, as the measuring-signal of double frequency difference interference art by the second detector 13; Above-mentioned reference signal and measuring-signal can obtain the transversal displacement amount of diffraction grating 1 via data acquisition and processing (DAP) and control module 15 process.

First high segmentation prism 4 and the second height segment the principle of work of prism 5 as Fig. 3, below only for the first high segmentation prism 4.

Incident beam 30 after grating 1 diffraction ,-1 order diffraction light beam by the first high segmentation prism 4 transmission plane 33 through, then reflected transmission plane 33 by the reflecting surface 32 of the first high segmentation prism 4, and parallel with incident beam 30.So repeatedly repeatedly, until finally a branch of-1 order diffraction light beam be overlap with incident beam 30 but the contrary light beam 31 in direction in the collimation plane 34 autocollimation retroeflection of the first high segmentation prism 4.Correlation parameter is as follows:

$\mathrm{\α}=\mathrm{\π}-\frac{\arcsin (n_0/n_1\·\sin (\mathrm{\β}-{\mathrm{\α}}_3))-\arcsin (n_0/n_1\·\sin (\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))-{\mathrm{\α}}_3))}{2}---\left(1\right)$

$\mathrm{\φ}=\frac{\arcsin (n_0/n_1\·\sin (\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))-{\mathrm{\α}}_3))+\arcsin (n_0/n_1\·\sin (\mathrm{\β}-{\mathrm{\α}}_3))}{2}---\left(2\right)$

Wherein, n ₀for air refraction, n1 are Refractive Index of Glass Prism, θ is angle of diffraction, and λ is wavelength, α ₃for prism transmission face 33 and the angle of diffraction grating 1 plane.

Incident beam 30 and diffraction grating 1 incident angle are β, and diffraction grating 1 pitch is d, and the reflecting surface 32 of the first high segmentation prism 4 meets (1) formula with collimation plane 34 angle α.The reflecting surface 32 of the first high segmentation prism 4 meets (2) formula with transmission plane 33 included angle.

After adopting the first high segmentation prism 4 and the second high segmentation prism 5, incident beam is 2N time-1 order diffraction (N is the unidirectional number of times of diffraction repeatedly on diffraction grating 1) on diffraction grating 1, produce positive and negative 2N times of doppler optical frequency displacement respectively, and then realize 4N times of optical fine.If N=10, then can realize the optical fine of 40 times.Be 2000 lines per millimeter gratings for pitch, be designed to negative one-level height diffraction light efficiency, as being greater than 90%, if N=10, so still can effectively detect its interference signal, then can obtain the optical cycle signal of 12.5nm.Be aided with 1024 grades electronic fine-grained, then can realize the high resolving power of about 12.2pm.

Fig. 4 is the another kind of working method schematic diagram of the first high segmentation prism 4 or the second high segmentation prism 5.Incident ray comparatively Fig. 3, away from diffraction grating 1, segments the incident diffraction grating 1 in top of prism 5 from the first high segmentation prism 4 or the second height.

High segmentation prism 4 and 5 can be designed to integral type height segmentation prism further, as shown in Figure 5.Fig. 5 is that Fig. 3 and Fig. 4 works as α ₃special case when=0 °.

$\mathrm{\α}=\mathrm{\π}-\frac{\arcsin (n_0/n_1\·\sin \left(\mathrm{\β}\right))-\arcsin (n_0/n_1\·\sin \left(\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))\right))}{2}$

$\mathrm{\φ}=\frac{\arcsin (n_0/n_1\·\sin \left(\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))\right))+\arcsin (n_0/n_1\·\sin \left(\mathrm{\β}\right))}{2}$

Parameter is consistent with above-mentioned.

In Fig. 5, the sequence number of the right band single quotation marks is the symmetric body of left side sequence number.

First high segmentation prism 4 and the second high segmentation prism 5 can be reduced to the reflecting surface collimation plane adjacent with, are directly processed into or bond to form, as Fig. 5.By that analogy, the first high segmentation prism 4 and the second high segmentation prism 5 can be designed to the same symmetrical structure of integral type further.Two faces meet following relation:

$\mathrm{\α}=\mathrm{\π}-\frac{\mathrm{\β}-\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))}{2}$

Parameter is consistent with above-mentioned.

2, embodiment 2.As Fig. 2.

Laser instrument 8 sends linearly polarized light, is divided into the P light of transmission and the S light of reflection, is transformed to circularly polarized light respectively by quarter-wave plate 6 and 7 through polarization beam apparatus 9, then by the first catoptron 2 and the incident diffraction grating 1 of the second catoptron 3.First high segmentation prism 4 and the second high segmentation prism 5 on one side is separately entered respectively by two bundle-1 grade after diffraction grating 1 diffraction, the former road of autocollimation returns again, the linearly polarized light orthogonal with former polarization state is transformed to through the first quarter-wave plate 6 and the second quarter-wave plate 7, again through polarization beam apparatus 9 enter in dotted line frame by the 3rd quarter-wave plate 16, non-polarizing beamsplitter 17, first polarization beam apparatus 18, second polarization beam apparatus 22 (45 degree rotate placement) and the first detector 19, second detector 20, 3rd detector 21, the polarization phase-shifting that 4th detector 23 forms interferes photoelectric detection unit, form the detectable signal of four tunnel phase shift 90 °.And then the transversal displacement amount that can obtain diffraction grating 1 is processed by data acquisition and processing (DAP) and control module 15.

In described scheme, data acquisition and processing (DAP) and control module 15 are by data collecting card and motion control card and industrial computer forms or be made up of the circuit board at least with collection and computing function.

In described scheme, diffraction grating 1 can also be transmission-type; When transmission-type uses, place completely reflecting mirror-1 order diffraction light one side, and by-1 order diffraction light oppositely with former incident angle of light incident transmission type diffraction grating, the first segmentation prism 4 and the second high segmentation prism 5 parameter constant.

Claims (9)

1. one kind high segmentation high dencity grating interferometer, comprise: the high density diffraction grating (1) of relative motion, linear polarization light source (8), polarization beam apparatus (9), first high segmentation prism (4), second high segmentation prism (5), first catoptron (2), second catoptron (3), first quarter-wave plate (6), second quarter-wave plate (7), data acquisition and processing (DAP) and control module (15) and interfere photoelectric detection unit, it is characterized in that, described linear polarization light source (8) sends light beam and is divided into the P light of transmission and the S light of reflection through polarization beam apparatus (9), described P light is successively through described the first quarter-wave plate (6), first catoptron (2) incides described relative motion diffraction grating (1), described S light is successively through described the second quarter-wave plate (7), second catoptron (3) incides described relative motion diffraction grating (1), respectively via after the first high segmentation prism (4) and the second high segmentation prism (5) transmittance and reflectance, upper unidirectional N the diffraction of two bundle-1 each comfortable diffraction grating of order diffraction light beams (1), unidirectional N the diffraction in the former road of autocollimation returns again, the linearly polarized light orthogonal with former polarization state is converted to respectively through described the first quarter-wave plate (6) and the second quarter-wave plate (7), again incide described interference photoelectric detection unit through polarization beam apparatus (9), the output terminal of this interference photoelectric detection unit is connected with the input end of described data acquisition and processing (DAP) and control module (15).

2. height segmentation high dencity grating interferometer according to claim 1, it is characterized in that, the described first high segmentation prism (4) and the second high prism (5) that segments include at least one reflecting surface, transmission plane that an adjacent collimation plane is relative with one; Described height segmentation prismatic reflection face and collimation plane angle α, height segment prismatic reflection face and transmission plane included angle, the high angle α segmenting prism transmission face and high density diffraction grating plane ₃meet following relation:

$\mathrm{\α}=\mathrm{\π}-\frac{\arcsin (n_0/n_1\·\sin (\mathrm{\β}-{\mathrm{\α}}_3))-\arcsin (n_0/n_1\·\sin (\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))-{\mathrm{\α}}_3))}{2}---\left(1\right)$

$\mathrm{\φ}=\frac{\arcsin (n_0/n_1\·\sin (\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))-{\mathrm{\α}}_3))+\arcsin (n_0/n_1\·\sin (\mathrm{\β}-{\mathrm{\α}}_3))}{2}---\left(2\right)$

Wherein, n ₀for air refraction, n ₁for height segmentation Refractive Index of Glass Prism, λ is optical source wavelength, and β is incident beam and high density diffraction grating normal angle, and d is the pitch of high density diffraction grating, α ₃>=0.

3. height segmentation high dencity grating interferometer according to claim 1, is characterized in that, the described first high segmentation prism (4) and the second high segmentation prism (5) include at least one reflecting surface collimation plane adjacent with; Described height segmentation prismatic reflection face and collimation plane angle α meet following relation:

$\mathrm{\α}=\mathrm{\π}-\frac{\mathrm{\β}-\arcsin (\mathrm{\λ}/d-\sin \left(\mathrm{\β}\right))}{2}$

Wherein, n ₀for air refraction, n1 are high segmentation Refractive Index of Glass Prism, λ is optical source wavelength, and β is incident beam and high density diffraction grating normal angle, and d is the pitch of high density diffraction grating (1).

4. height segmentation high dencity grating interferometer according to claim 1, is characterized in that described linear polarization light source is light emitting diode, laser diode, the light source of solid or gas lamp; The laser instrument of single-frequency or the laser instrument of double frequency cross polarization.

5. the height segmentation high dencity grating interferometer according to any one of claim 1-4, is characterized in that described interference photoelectric detection unit is that polarization phase-shifting interferes photoelectric detection unit or double frequency difference interference photoelectric detection unit.

6. height segmentation high dencity grating interferometer according to claim 5, it is characterized in that, described polarization phase-shifting interferes photoelectric detection unit to comprise the 3rd quarter-wave plate (16), non-polarizing beamsplitter (17), the first polarization beam apparatus (18), the second polarization beam apparatus (22) locating cross polarization 45 degree placement, the first detector (19), the second detector (20), the 3rd detector (21) and the 4th detector (23).

7. height segmentation high dencity grating interferometer according to claim 5, it is characterized in that, described double frequency difference interference photoelectric detection unit comprises non-polarizing beamsplitter (10), be in first analyzer (11) of orthogonal double frequency linearly polarized light 45 degree placement and first detector (12) of correspondence, be in second analyzer (14) of orthogonal double frequency linearly polarized light 45 degree placement and second detector (13) of correspondence, described linear polarization light source (8) sends light beam and is divided into two bundles through described non-polarizing beamsplitter (10), polarization beam apparatus (9) described in a branch of warp is divided into the P light of transmission and the S light of reflection, another beam enters described the first analyzer (11).

8. the height segmentation high dencity grating interferometer according to any one of claim 1-4, it is characterized in that, described data acquisition and processing (DAP) and control module are by data collecting card and motion control card and industrial computer forms or be made up of the circuit board at least with collection and computing function.

9. the height segmentation high dencity grating interferometer according to any one of claim 1-4, it is characterized in that, described high density diffraction grating (1) is reflection-type or transmission-type.