JPH06196726A - Light receiving element, and displacement detector equipped with this light receiving device - Google Patents

Abstract

PURPOSE:To obtain a small light receiving element having a simple structure by forming a light receiving section on a lattice pattern using a lithography technique so as to integrate the light receiving element and the lattice pattern into a single body. CONSTITUTION:A section 50 has the same constitution as a conventional silicon photo-diode, and a p-n junction is made by laminating an n-type layer 52 and a p-type layer 53, in this order, on a cathode electrode 51 of the section 50. An SiO2 film 54 for protecting purpose is formed on the p-type layer 53. A film 55 made of a transparent material, such as SiO2 or the like, is formed on the SiO2 film 54, and a photoresist is applied over the film 55. A lattice pattern is written on the photoresist, and the photoresist is exposed to light. Only the photoresist remaining on unnecessary portions is removed by etching to form gratings 56 on the transparent film 55. Accordingly, when an anode electrode 57 is formed by removing a part of the SiO2 film on the p-type layer 53, the lattice pattern is formed together with a light receiving section of a light receiving element in an integrated fashion, and hence it is possible to constitute a small simple light receiving element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for optically detecting displacement (movement amount, rotation amount, speed, acceleration) of an object, specifically, an encoder, a speed sensor, an acceleration sensor, and the like.
The present invention relates to a light receiving element used for these sensors.

[0002]

2. Description of the Related Art An optical displacement sensor, such as an optical encoder, which irradiates an object with light to obtain the displacement of the object with high accuracy.
Laser Doppler speedometer, laser interferometer, etc.
It is widely used in the fields of machine tools, office automation equipment, robots, precision manufacturing equipment, etc.

Some of such displacement sensors illuminate a scale attached to an object to be inspected so that the phase of light and dark is changed in accordance with the movement of the scale produced by a beam from the scale. The changing striped pattern is projected on the grid pattern of another scale, and the grid pattern of the index scale concerned is projected.
A beam forming a striped pattern that has passed through the sensor is received by a light receiving element placed relatively far from the index scale and converted into an electric signal indicating the displacement of the object to be inspected.

[0004]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
The resolution can be increased by reducing the grid pitch of the scale attached to the object and the pitch of the grid pattern of the index scale, but the pitch of the grid pattern of the index scale can be increased. In order to efficiently direct the beam passing through the lattice pattern to the light receiving element when the value is reduced, it is unavoidable to dispose a condensing means such as a lens between the index scale and the light receiving element. There is a problem that the configuration becomes complicated and large.

[0005]

The light receiving element of the present invention is a light receiving element which generates an electrical signal in response to a beam incident on the light receiving portion, wherein the light receiving portion is formed by a lithography technique. By having the light emitting element, the light receiving element and the grating pattern are integrated to solve the above problems.

Further, the displacement detecting apparatus of the present invention is an apparatus for detecting a relative displacement of an object to be detected with respect to a light receiving element based on a phase change of a striped pattern formed by a beam from the object to be inspected. The light receiving element is provided with a light receiving section having a lattice pattern, and the light receiving section is configured to output an electric signal in response to the beam forming the striped pattern. They are integrated to solve the above problems.

In a preferred embodiment of the present invention, the lattice pattern is made of a resist material, the lattice pattern is made of a wiring pattern, and the lattice pattern covers a semiconductor layer. What is formed on the grid pattern
And the grating pattern is formed by at least one of the P layer and the N layer of the semiconductor layer. Each grating pattern is formed by lithography. It can be created by the technology and is disclosed in the examples below.

[0008]

1 is a schematic view showing an embodiment of a light receiving element of the present invention. The bottom view of FIG. 1 is a- in the top view of FIG.
It is sectional drawing which combined the a'section and the bb 'section, and plotted it. In FIG. 1, a portion indicated by reference numeral 50 has the same configuration as that of a normal silicon photodiode.
A N-layer 52 and a P-layer 53 are sequentially stacked on the cathode electrode 51 at the lower end of to form a PN junction. Also, P
A SiO ₂ film 54 is formed on the layer 53 for protection.

In this embodiment, on the SiO ₂ film 54, further, Si
The film 55 made of a light-transmitting material such as O _{2 is} formed by a film forming technique such as spin coating, and the light-transmitting (material) film 55 is formed.
After applying a photoresist on the surface, it is exposed through a mask on which a lattice pattern is drawn, or the lattice pattern is drawn and exposed by an electron beam or laser light, and hydrogen fluoride or the like is used. By removing only the unnecessary portion of the resist by etching, the residual resist itself forms a grid 56 on the light transmissive film 55.
(Diffraction grating) is formed. On the other hand, SiO ₂ above the P layer 53
A part of the film 54 is removed by photoetching, and the anode electrode 57 is formed of aluminum or the like. Further, as shown in the top view, the anode electrodes are formed for two channels to form two light receiving portions, and a pair of gratings whose phases are shifted from each other are formed on the corresponding light receiving portions, so that the phases are mutually offset from the element. It is configured to be able to output different pairs of signals.

In this embodiment, since the grating pattern is formed in the light receiving portion of the light receiving element and both are integrated, the light receiving element is simple and small.

By utilizing the semiconductor device manufacturing process as described above, it becomes easy to integrally form the light receiving portion and the grating pattern, and the positional relationship between the grating 56 and the light receiving portion (or the light receiving element) is extremely reduced. Can be suppressed with high accuracy.

Further, by using the present light receiving element, the displacement sensor can be easily assembled and miniaturized.

When it is desired to sufficiently secure the function of the grating 56 as a diffraction grating, the distance between the grating 56 and the P layer 53 which is the light receiving surface is set to be sufficiently larger than the wavelength of light incident on the light receiving element (working wavelength). I'll do it.

The present light receiving element has a grating 56 on a light transmitting film 55.
However, the grating 56 may be formed directly on the SiO ₂ film 54 without forming the light transmitting film 55.

The light receiving element is made of a photoresist to form a grating 5.
6 is configured, the present invention is not limited to this configuration.

FIG. 2 is a schematic view showing another embodiment of the light receiving element of the present invention. As shown in the drawing, the aluminum wiring pattern used for the anode electrode 57 constitutes a (diffraction) grating. Further, the aluminum wiring is the anode electrode 53 as shown in FIG.
It may be connected to the cathode electrode 53, or may be separated from the anode electrode 53 and connected externally to the cathode electrode, circuit ground, or the like.

FIG. 3 is also a schematic view showing another embodiment of the light receiving element of the present invention, and FIG. 3 exemplifies an element having only a grating and one set of light receiving portions. In FIG. 3, a portion 50 is a normal silicon photodiode, which is the same as the embodiment of FIGS. The light receiving element is the same as the element of FIG.
5 is omitted and a (diffraction) grating made of an aluminum wiring pattern used for the anode electrode 57 is directly formed on the SiO ₂ film 54.

FIG. 4 is also a schematic view showing another embodiment of the light receiving element of the present invention, and FIG. 4 also illustrates an element having only a grating and one set of light receiving portions. In this light receiving element, the shape of the P layer 53 of the embodiment of FIG. 3 is changed, and the P layer is not formed in the portion where the aluminum wiring forming the grid shields light, but the P layer is formed in the grid shape. , The junction capacitance of the PN junction is suppressed small, and the response of the element is increased.

FIG. 5 is also a schematic view showing another embodiment of the present invention, and FIG. 5 also exemplifies an element having only one set of the grating and the light receiving portion. In FIG. 5, a portion 50 is a normal silicon photodiode, which is the same as the embodiment shown in FIGS.
In this light receiving element, a light transmissive film 55 formed by spin coating of SiO ₂ is formed on a SiO ₂ film 54 of a portion 50 corresponding to a normal silicon photodiode, and a part of the light transmissive film 55 is formed. Is partially removed by photoetching to form a phase (diffraction) grating.

FIG. 6 is also a schematic diagram showing another embodiment of the present invention, and FIG. 6 also illustrates an element having only one set of grating and light receiving section. 6, the same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals as those in FIGS. In this light receiving element, the shape itself of the P layer 53, which is the light receiving portion of the portion 50 corresponding to a normal silicon photodiode, is formed into a lattice shape.

FIG. 7 is also a schematic view showing another embodiment of the present invention, and FIG. 7 also illustrates an element having only one set of a grating and a light receiving portion. In order to make the drawing easy to understand, the anode electrode 57 (including the aluminum wiring portion) is transparently displayed only in FIG. 7, and the cross-sectional views in the middle and bottom of FIG. 7 are the top views of FIG. 7, respectively. 2 shows an aa 'cross section and a bb' of FIG. This light receiving element is a light receiving surface of the element of FIG. 6 in which the aluminum wiring is provided on a portion of the P layer which does not form a lattice to shield light.

The number of light receiving portions with a grating formed on one chip is not limited to one or two as in the above embodiment, and three or more light receiving portions with a grating for outputting signals having mutually different phases. May be configured on the same chip.

It is also possible to form a small number of light receiving portions with a grid on one chip and take out a plurality of chips as one light receiving element when slicing the chips from the wafer.

The present invention can be implemented by using a photodiode whose material and structure are different from those of the light receiving element of each of the above embodiments, and a phototransistor or CdS is used as a photoelectric converter.
This can be implemented by a cell or the like that outputs an electric signal in response to a beam incident on the light receiving portion.

In the present invention, a chip (wafer) on which a light receiving element is formed may be incorporated with a processing circuit such as a voltage conversion circuit, an amplifier circuit, and / or other various circuits used together with the present light receiving element.

FIG. 8 shows an embodiment of a displacement sensor equipped with the light receiving element of the present invention.

This displacement sensor is provided with light receiving portions 32B1 and 3B with a grid.
Light receiving element 61B including 2B2 and light receiving portion 32C with a grid
Using a light receiving element 61C including 1, 32C2,
The basic structure of each of the light receiving element 61B and the light receiving element 61C is the same as that of the light receiving section shown in FIG. This displacement sensor includes a light receiving element 6 having a light receiving portion with a grating in which a diffraction grating is formed on the light receiving surface.
Since 1B and 61C are used, the light receiving element is accurately assembled and adjusted. Therefore, not only the size is small, but also the displacement detection accuracy is high.

In FIG. 8, the light emitted from the light emitting element 1 such as a semiconductor laser or a light emitting diode is a lens 31A.
After being converted into a parallel light flux by, the light is vertically incident on the diffraction grating 32A. This light beam is transmitted and diffracted by the diffraction grating 32A, and is divided into 0-order diffracted light R ₀ , + 1st-order diffracted light R ₊₁ and −1st-order diffracted light R ₋₁ .
The light beam is divided into a plurality of light beams including one, and the light beam is applied to the diffraction grating 21 formed on the scale attached to the object to be inspected.

Incidentally, the diffraction grating 3 which constitutes this displacement sensor
2A, light receiving portions 61B and 61C and the diffraction grating 2 on the scale
1 has the same pitch of 1.6 μm.

Of the diffracted light emitted from the diffraction grating 32A and applied to the diffraction grating 21, the straight-ahead 0th-order diffracted light R ₀ is reflected and diffracted at the point P1 on the diffraction grating 21 and the + 1st-order diffracted light R _0.
It is also divided into ⁺¹ and −1st order diffracted light R ₀ ^{−1 and the} like, and also undergoes phase modulation. That is, when the scale (diffraction grating 21) moves, the phase of the + 1st order diffracted light R ₀ ⁺¹ shifts by + 2πx / P, and the phase of the −1st order diffracted light R ₀ ⁻¹ shifts by −2πx / P. Here, x is the amount of movement of the diffraction grating 21, and P is the pitch of the diffraction grating 21.

The + 1st order diffracted light R ₀ ⁺¹ is received by the light receiving portion 32B.
1, 32B2 is again transmitted and diffracted by the diffraction grating and divided into 0th-order diffracted light, -1st-order diffracted light and other diffracted light,
The −1st order diffracted light in this is extracted perpendicularly to the lattice plane, and the phase of this wavefront is + 2πx / P. On the other hand, the -1st order diffracted light R ₀ ^-1 is again transmitted and diffracted by the diffraction gratings on the light receiving sections 32C1 and 32C2, and is divided into 0th order diffracted light, + 1st order diffracted light and other diffracted lights. Origami R
₀ ^-1 ₊₁ is extracted perpendicularly to the lattice plane, and the phase of the wavefront at this time is -2πx / P.

In this displacement sensor, the phase relationship of the diffraction grating on the light receiving portion 32C1 is shifted from the diffraction grating on the light receiving portion 32B1 by P / 4, and the + 1st order diffracted light R ₀ ^-1 _{+1 is obtained.}
Of the wavefront of is -2π (P / 4) / P = -π / 2
The difference is -2πx / P−π / 2. Further, the diffraction grating of the light receiving portion 32B2 and the diffraction grating of the light receiving portion 32C2 are
The grating array is shifted by P / 2 with respect to the diffraction grating of the adjacent light receiving portion 32B1 and the diffraction grating of the adjacent light receiving portion 32C1, respectively, and the phase of each wavefront incident on the light receiving surface of each light receiving portion is as follows. It is set.

32B1: -2πx / P 32B2: -2πx / P-π 32C1: -2πx / P-π / 2 32C2: -2πx / P-3π / 2

On the other hand, the + 1st order diffracted light R ₊₁ from the diffraction grating 32A is reflected and diffracted at the point P2 on the diffraction grating 21 on the scale, and divided into -1st order diffracted light, 0th order diffracted light and other diffracted lights. And undergo phase modulation respectively. Particularly, the phase of the −1st order diffracted light is shifted by −2πx / P and the light receiving unit 32B
1, 32B2, and the −1st order diffracted light is received by the light receiving unit 32.
0-order diffracted light R ₊₁ ^-1 ₀ wavefront phase of the diffraction grating and goes straight in B1,32B2 becomes -2πx / P. Also, the -1st-order diffracted light R _-1 from the diffraction grating 32A is reflected and diffracted at a point P3 on the diffraction grating 21 on the scale, + 1-order diffracted light, 0 order diffraction light R _-1 ⁰ and other diffracted light It is divided and each undergoes phase modulation. Particularly, the phase of the + 1st-order diffracted light is shifted by + 2πx / P and enters the light receiving portions 32C1 and 32C2, and the + 1st-order diffracted light is received by the light receiving portions 32C1 and 32C2.
The phase of the wavefront of the _0th-order diffracted light R ₋₁ ⁺¹ ₀ that has proceeded straight through is + 2πx / P.

The light beam superimposed optical paths from each other by the diffraction gratings of the light-receiving portion 32B1,32B2 R ₊₁ ^-1 ₀ and the light beam R ₀ ⁺¹
_-1 becomes two types of interference light, and the light receiving portions 32B1 and 3B3
The light enters the corresponding light receiving surface of 2B2 and is converted into an electric signal. The interference phases of the interference light incident on the light receiving surfaces of the light receiving units 32B1 and 32B2 are (+ 2πx / P) − (− 2πx / P) = 4πx / P (−2πx / P−π) − (+ 2πx / P), respectively. ) = − 4πx / P−π, and one period of the sine wave signal is generated from the light receiving units 32B1 and 32B2 each time the diffraction grating 21 on the scale moves by ½ pitch. The pitch of the diffraction grating 21 is 1.6μ
Since m, a sine wave signal with a period of 0.8 μm can be obtained. Further, a signal A obtained by inverting the phase of the signal A from the light receiving section 32B1 can be obtained from the light receiving section 32B2.

A light beam R _-1 ⁺¹ ₀ and a light beam R ₀ ^-1 whose optical paths are superposed on each other by the diffraction gratings of the light receiving sections 32C1 and 32C2.
₊₁ becomes two types of interference light, and the light receiving portions 32C1 and 32C3
The light enters the corresponding light receiving surface of 2C2 and is converted into an electric signal. The interference phases of the interference light incident on the light receiving surfaces of the light receiving units 32C1 and 32C2 are (−2πx / P−π / 2) − (+ 2πx / P) = − 4πx / P−π / 2 (−2πx / P−3π / 2) − (+ 2πx / P) = − 4πx / P−3π / 2, and a sine wave signal is output from the light receiving units 32C1 and 32C2 each time the diffraction grating 21 on the scale moves by 1/2 pitch. One cycle is generated. The pitch of the diffraction grating 21 is 1.6
Since it is μm, a sine wave signal having a period of 0.8 μm can be obtained. Further, the signal B from the light receiving portion 32C1 is out of phase with the signal A from the light receiving portion 32B1 by 1/4 cycle,
The signal B from the light receiving portion 32C2 is out of phase with each signal A from the light receiving portion 32B2 by 1/4 cycle.

Since the displacement sensor has the above structure,
With the displacement of the scale (diffraction grating 21), the light receiving element 61
Sine wave signals A (0), B (π / 2), A showing four displacement amounts, which are shifted by 1/4 period from B, 61C.
(Π) and B (3π / 2) are obtained. Using these four sine wave signals, a known signal processing circuit is used to detect the relative displacement of the scale (21) with respect to the light receiving portions (61B, 61C) and the light emitting portions (1, 31A, 32A).

The displacement sensor uses the element shown in FIG. 1 as a light receiving element. However, one of the elements shown in FIGS. May be used for.

Further, the form of the displacement sensor which can be used as it is or by appropriately modifying the light receiving element of FIGS. 1 to 7 is not limited to the linear encoder shown in FIG. 8, but is, for example, a rotary encoder. Applicable to optical speedometer.

FIG. 9 is an embodiment showing an application example of the encoder, and is a system configuration diagram of a drive system using the encoder. An encoder 101 is attached to a drive output portion of a drive means 100 having a drive source such as a motor, an actuator, an engine, or a moving portion of an object to be driven, and a displacement state such as a displacement amount or a displacement speed is set. To detect. The embodiment shown in FIG. 8 is used as this encoder. The detection output of the encoder 101 is fed back to the control means 102, and the control means 102 sets the setting means 103.
The drive signal is transmitted to the drive means 100 so that the state set in 1 is obtained. By constructing such a feedback system, the driving state set by the setting means 103 can be obtained. Such drive systems include office equipment such as typewriters, printers, copy machines, facsimiles, video equipment such as cameras and video equipment, information recording / reproducing equipment, robots, machine tools, manufacturing equipment,
The present invention can be widely applied to transportation devices, and further to general devices having driving means, not limited to these.

[0041]

As described above, according to the present invention, it is possible to provide a simple and small light receiving element in which the grating pattern is integrated with the light receiving portion of the light receiving element. In addition, a compact and highly accurate displacement sensor can be easily realized.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a light receiving element of the present invention.

FIG. 2 is a schematic view showing a second embodiment of the light receiving element of the present invention.

FIG. 3 is a schematic view showing a third embodiment of the light receiving element of the present invention.

FIG. 4 is a schematic view showing a fourth embodiment of the light receiving element of the present invention.

FIG. 5 is a schematic view showing a fifth embodiment of the light receiving element of the present invention.

FIG. 6 is a schematic view showing a sixth embodiment of the light receiving element of the present invention.

FIG. 7 is a schematic view showing a sixth embodiment of the light receiving element of the present invention.

FIG. 8 is a schematic diagram showing a configuration example of a displacement detection device of the present invention.

FIG. 9 is a block diagram showing an example of a drive system including the displacement detection device of the present invention.

[Explanation of symbols]

 1 Light emitting element 2 Mirror 31A, 31B, 31C Lens 32A, 32B, 32C Diffraction grating 4B, 4C Light receiving element 50 Photodiode 51 Cathode electrode 52 N layer 53 P layer 54 Protective film 55 Light transmissive material film 56 Photoresist 57 Anode electrode 61B, 61C Diffraction grating integrated type light receiving element

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Kondo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (18)

[Claims] 1. A light receiving element for generating an electric signal in response to a beam incident on the light receiving portion, wherein the light receiving portion has a lattice pattern formed by a lithography technique. . 2. The light-receiving element according to claim 1, wherein the lattice pattern is made of a resist material. 3. The light-receiving element according to claim 1, wherein the lattice pattern is a wiring pattern. 4. The light-receiving element according to claim 1, wherein the lattice pattern is formed on a light transmitting layer that covers the semiconductor layer. 5. The light-receiving element according to claim 1, wherein the lattice pattern is formed of a light transmission layer covering a semiconductor layer. 6. The light receiving element according to claim 1, wherein the lattice pattern is formed by at least one of a P layer and an N layer of a semiconductor layer. 7. An apparatus for detecting a relative displacement of an object to be detected with respect to a light receiving element based on a phase change of a stripe pattern formed by a beam from the object to be inspected, wherein the light receiving element is formed by a lithography technique. A displacement detecting device comprising a light receiving portion having a formed lattice pattern, and outputting an electric signal in response to the beam forming the striped pattern on the light receiving portion. 8. The displacement detecting device according to claim 7, wherein the lattice pattern is made of a resist material. 9. The displacement detecting device according to claim 7, wherein the lattice pattern is a wiring pattern. 10. The displacement detecting device according to claim 7, wherein the lattice pattern is formed on a light transmitting layer which covers the semiconductor layer. 11. The displacement detecting device according to claim 7, wherein the lattice pattern is formed by a light transmitting layer covering the semiconductor layer. 12. The displacement detecting device according to claim 7, wherein the lattice pattern is formed by at least one of a P layer and an N layer of a semiconductor layer. 13. A light-receiving element for generating an electric signal in response to a beam incident on the light-receiving portion, wherein the light-receiving portion comprises a semiconductor layer and a light-transmitting layer covering the semiconductor layer, and the light-transmitting layer is provided on the light-transmitting layer. A light receiving element characterized in that a lattice pattern is formed on. 14. The light-receiving element according to claim 13, wherein the lattice pattern is made of a resist material. 15. The light receiving element according to claim 13, wherein the lattice pattern is a wiring pattern. 16. A device for detecting a relative displacement of an object to be detected with respect to a light receiving element based on a phase change of a striped pattern formed by a beam from the object to be inspected, wherein the light receiving element is a semiconductor layer and a semiconductor layer. And a grid pattern is formed on the light-transmitting layer, and an electric signal is output in response to the beam forming the striped pattern on the grid pattern. Displacement detection device characterized by the above. 17. The displacement detecting device according to claim 16, wherein the lattice pattern is made of a resist material. 18. The displacement detecting device according to claim 16, wherein the lattice pattern is a wiring pattern.