JP2002081962A - Rotary angle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical rotary angle detector having an encoder scale including high resolution and accuracy. SOLUTION: A lattice pattern formed on the encoder scale and a shaft hole are etched by using the same photomasks or photomasks accurately locatable with each other in combination with a photolithography used to manufacture a semiconductor integrated circuit and the like and an etching method using an ion or a plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects an operating rotation angle or rotation speed of a rotation mechanism to control the rotation mechanism.
The present invention relates to an optical rotation angle detection device generally called a rotary encoder that converts an electric signal into an electric signal.

[0002]

2. Description of the Related Art FIG. 9 shows a rotation angle detecting device according to the prior art, and FIG. 10 shows an encoder scale according to the prior art. An optical rotation angle detection device generally called a rotary encoder includes a rotating disk type encoder scale 203 coupled to a rotation shaft 222, and an encoder
It comprises a detection head section having a pair of light emitting element 201 and light receiving element 202 for detecting rotation of the scale. The rotation detecting device shown in FIG. 9 includes a light emitting element 201 and a light receiving element 202 on one side of an encoder scale.
And a type called reflection type using reflected light from the scale surface.

On the encoder scale 203, a radial grating pattern 218 (grating pattern) for detecting a rotation angle is drawn in a slit shape. In the conventional encoder scale, a lattice pattern is formed by using a thin metal plate and forming slit grooves directly in the metal plate by an etching method. However, in this method, a very thin metal plate of, for example, 0.2 mm or less cannot be used for the encoder scale in order to maintain a necessary strength. And by this,
It has been difficult to form a fine grid pattern for obtaining higher resolution.

For this reason, in recent years, in order to produce an encoder scale with higher resolution, a metal thin film is deposited on the surface of a smooth glass disk, and a lattice pattern is formed on the metal thin film by photolithography. In addition, a lattice pattern is formed on the surface of a silicon wafer (silicon substrate) by a photolithography method. This is a method in which a metal thin film having a thickness of about 1 μm or less is formed on a smooth glass substrate, and the metal thin film is processed by a photolithography technique and an etching technique to form a fine lattice pattern. According to this method, a fine grid pattern having a line width of several μm or less can be formed. For example, even in a small-diameter encoder scale having a diameter of 50 mm or less, high-resolution performance of about tens of thousands of pulses can be realized. .

As the light emitting element 201 for detecting the rotation of the encoder scale, a light emitting diode or a semiconductor laser is mainly used. As the light receiving element 202, a photodiode or a phototransistor is mainly used.
The light emitting element 201 and the light receiving element 202 are arranged in parallel so that the light emitted from the light emitting element 201 is reflected by the lattice pattern 218 of the metal thin film 217 formed on the surface of the encoder scale 203 and reaches the light receiving element 202. Need to be deployed. Therefore, as shown in the drawing, the light emitting element 201 and the light receiving element 202 are fixed and supported using the detection head frame 231 such as a resin molded member. The detection head unit frame 231
Is fixed by a mounting plate 233.

[0006]

In such a conventional optical rotation angle detecting device, the rotary shaft is simply inserted into and fixed to the shaft hole of the encoder scale. In particular, the center of the encoder scale and the center of the rotary shaft are fixed. Each member did not have a function for precisely aligning the axes. Therefore, it is difficult to precisely match the center of the shaft hole of the encoder scale with the center of the lattice pattern due to the problem of accuracy due to machining, and even if the encoder scale 203 is manufactured with high resolution, the rotation angle is not In some cases, an error occurs in the signal of the detection device.

[0007] It is difficult to form a hole in the encoder scale for passing the rotary shaft with high accuracy by aligning the center position with the center. Even if the work was carefully performed using a processing machine, an error of about 100 μm was inevitable. Therefore, in a state where the rotating shaft is assembled, only an encoder scale with low accuracy can be obtained as a result.

In order to prevent this, play is provided by increasing the diameter of the shaft hole 234 of the encoder scale 203 with respect to the diameter of the rotary shaft 222, and the encoder scale 203 is attached to the shaft flange 237 during assembly. And rotate encoder scale 203 to form grid pattern 2
After adjusting the position while observing the sample 18 with a microscope or the like, a method of fixing the fixing screw 236 and the fixing ring 238 using the scale fixing hole 235 may be used. However, since the method is not suitable for mass production, the production cost is increased, and it cannot be used for an inexpensive consumer device.

As described above, in the conventional method, the center of the grid pattern of the encoder scale does not coincide with the center axis of the rotation axis, and the grid pattern is rotated with its eccentricity. However, if the amount of eccentricity caused by the rotation of the encoder is not smaller than the pitch dimension of the pattern, an error occurs in the signal, and a precise rotation angle detecting device cannot be manufactured.

[0010] In addition, mass production is extremely low in a method in which a skilled operator performs adjustment while rotating an encoder scale at the time of assembling the apparatus.

[0011]

In order to solve the above-mentioned problems, a rotation angle detecting device according to the present invention has a rotating shaft and a shaft hole through which the rotating shaft passes, and a radial pattern is formed. In an optical rotation angle detecting device having a disk-shaped encoder scale and a detection head unit having a pair of a light emitting element and a light receiving element for detecting rotation of the encoder scale, an encoder scale axis is provided. The hole and the radial pattern are formed using the same photomask or a plurality of photomasks having alignment marks that can be positioned with respect to each other.

A photolithography method used in the manufacture of a semiconductor integrated circuit or the like is combined with an etching method using ions or plasma, and a lattice pattern and a shaft hole are made of the same photomask or a photomask capable of accurately positioning each other. By performing the etching process, the radial pattern and the center position of the encoder scale can be accurately matched, and with an encoder scale manufactured by this method, the amount of eccentricity due to the rotation of the scale can be reduced. The rotation angle can be held within the pitch dimension, and a highly accurate rotation angle detection device can be realized.

Further, the rotation angle detecting device according to the present invention comprises:
The encoder scale according to the present invention includes two layers: a first layer mainly composed of a crystalline silicon material, and a second layer mainly composed of a silicon compound such as silicon oxide / silicon nitride or silicon carbide; The relief portion is formed in the first layer, and the shaft hole portion is formed in the second layer.

Further, in the method of manufacturing the rotation angle detecting device according to the present invention, the position of the shaft hole of the encoder scale is formed by a photolithography method using a photomask, and the reactive ion etching method and the ion beam etching method are used. Alternatively, this is processed by a plasma etching method, the relief part larger in diameter than the shaft hole is processed into an encoder scale by a wet etching method, and the radial pattern is formed by an encoder scale by a photolithography method using a photomask. And the shaft hole and the pattern are formed on an encoder scale using the same photomask or a plurality of photomasks having alignment marks that can be positioned with respect to each other. .

Further, in the method of manufacturing a rotation angle detecting device according to the present invention, the first layer mainly composed of a crystalline silicon material and the second layer mainly composed of a silicon compound such as silicon oxide / silicon nitride or silicon carbide are provided. In the second layer of the encoder scale consisting of two layers, the position of the shaft hole is formed in the second layer by photolithography using a photomask, and reactive ion etching, ion beam etching, or plasma etching is performed. This is processed by an etching method, and the first layer is processed into a relief portion having a diameter larger than that of the shaft hole by a wet etching method in which an etching rate for silicon is high and an etching rate for a silicon compound is low. A pattern is formed on the encoder scale by a photolithography method using a photomask, and the shaft hole and the pattern are Photomask or by using a photomask having an alignment mark which can be positioned with respect to each other, characterized in that it is formed on the encoder scale.

The material of the encoder scale has a structure having a silicon layer and a silicon compound layer, and the shaft hole and the grid are formed by using an etching method using ions or plasma capable of finely and precisely processing the silicon compound layer. A pattern forming process is performed, and the silicon layer is processed into a relief portion having a larger diameter than the shaft hole portion by using wet etching with a high etching rate. Alternatively, a relief portion is formed in a crystalline silicon material by an anisotropic etching method in which an etching amount is easily controlled, and then a lattice pattern and a shaft hole portion are formed and processed by a plasma etching method.

The ion and plasma etching method comprises:
Although pattern forming processing can be performed with high accuracy, it is difficult to perform processing that directly penetrates an encoder scale having a thickness of 0.3 mm or more because the etching rate is extremely low. Therefore, first, an escape portion is formed in a silicon material by a wet etching method, and then an accurate pattern is formed by a plasma etching method.

[0018]

FIG. 1 shows an embodiment of a rotation angle detecting device according to the present invention, and FIG. 2 shows an embodiment of an encoder scale according to the present invention.

The encoder scale 101 has a shaft hole 14.
3, and the rotating shaft 122 penetrates the shaft hole 143. Then, the encoder scale 101 and the rotating shaft 1
22 is fixed with a fixing ring 138 and an adhesive 136.

The encoder scale 101 is composed of a silicon layer 135 mainly composed of a crystalline silicon material and a silicon compound layer 141 mainly composed of a silicon compound such as silicon oxide / silicon nitride or silicon carbide. The inner diameter of the escape portion 142 of the silicon layer 135 is larger than the outer diameter of the rotating shaft 122, and
41 and the outer diameter of the rotating shaft 122 are:
There is no play, for example, a fitting tolerance. Therefore, the center of the encoder scale 101 and the center of the rotating shaft 122 can be accurately matched, and eccentricity does not occur. The encoder scale 101 is assembled by being inserted into the rotating shaft 122 so as to hit the shaft flange 137.

The shaft hole 143 and the lattice pattern 118
Is formed using the same photomask or a plurality of photomasks having an alignment pattern that can be accurately positioned, so that the pattern is not decentered during the rotation operation, and a rotation angle detection device capable of accurate detection Can be made.

Above and below the encoder 101, a pair of a light emitting element 201 and a light receiving element 202 for detecting rotation of the encoder by a lattice pattern 118 are supported by a detection head frame 231. The detection head unit frame 231 is fixed by a mounting plate 233.

FIG. 3 shows a method of processing the encoder scale according to the embodiment. As a material of the silicon layer of the encoder scale 101, a silicon wafer, which is a crystalline silicon material used in semiconductor manufacturing and the like, was used.

First, as shown in FIG. 3B, a silicon compound layer 14 is formed on a silicon layer (silicon wafer) 135 shown in FIG.
Form one. In the example, a wafer having a thickness of 0.4 mm was used. As a formation method, a silicon oxide film can be formed by a thermal oxidation method; however, by using a CVD method, not only a silicon oxide film but also a silicon nitride film and a silicon carbide film can be formed. In the example, the thickness of the silicon compound layer was 0.1 mm.

Next, as shown in FIG.
An escape portion 142 is formed at 35 by a wet etching method. At this time, since chemical properties are different between silicon and a silicon compound, by selecting an appropriate etching solution,
The etching amount of the silicon compound layer 141 can be reduced.

Further, as shown in FIG. 3D, a shaft hole 143 is formed in the silicon compound layer 141 by an ion etching method or a plasma etching method. At this time, the same photomask 240 having the grid pattern 242 and the shaft hole pattern 243 shown in FIG.
By forming the grid pattern 118 at the same time as the shaft hole 143, the center of the shaft hole 143 and the center of the grid pattern 118 can be accurately matched, and a highly accurate encoder scale can be manufactured. In this embodiment, the pitch dimension of the lattice pattern is 3 μm, but the accuracy of the center position of the shaft hole can be formed within 3 μm, and sufficient accuracy can be obtained.

Also, the lattice pattern 118 can be formed simultaneously with the shaft hole 143 by using the two photomasks shown in FIGS. 8B and 8C. In this case,
Alignment mark 24 on each of two photomasks
1, and by aligning these marks, it becomes possible to make the center of the shaft hole 143 coincide with the center of the lattice pattern 118.

Incidentally, in order to improve the reflectance of the encoder scale, a metal thin film such as gold or aluminum may be formed on the surface of the encoder scale by vapor deposition or the like. FIGS. 4 and 5 show a rotation angle detecting device according to another embodiment and an encoder scale according to the embodiment.

FIG. 4 shows another embodiment of the rotation angle detecting device according to the present invention, and FIG. 5 shows another embodiment of the encoder scale according to the present invention. As in FIG. 1, encoder scale 102 of the rotation angle detecting device in FIG. 4 includes a silicon layer 135 mainly composed of a crystalline silicon material and a silicon And a compound layer 141. Grating pattern 118 formed on the surface of encoder scale 102
Is formed by depositing a thin metal film by photolithography.

Also in this case, as in the above embodiment, the same photomask 240 or a plurality of photomasks having mask alignment marks as shown in FIG. , A highly accurate encoder scale can be manufactured. Since a vapor-deposited metal thin film is used, a finer pattern can be formed, and the resolution of the encoder scale can be improved.

FIG. 6 shows another method of processing the encoder scale. Compared to the embodiment of FIG.
Numeral 8 is formed on the silicon compound layer 141 side which is the back surface of the escape portion 142. As described above, the positional relationship between the lattice pattern 118 and the escape portion 142 can be arbitrary.

FIG. 7 shows another embodiment of the rotation angle detecting device according to the present invention. In FIG. 7, the encoder scale 103 is made using a single crystal silicon material 144 (silicon wafer). In the embodiment, the thickness is 0.5 m
m silicon wafers were used. First, a relief portion 142 is formed in a disk-shaped single-crystal silicon material 144 polished on both sides by an anisotropic etching method. In the anisotropic etching method, since the etching depth can be easily controlled by the etching time, the escape portion 142 having a flat bottom can be formed without penetrating the material. In the embodiment, the depth of the escape portion 142 is set to 0.4 mm.

Next, the lattice pattern 118 and the shaft hole were formed on the surface opposite to the surface on which the escape portion 142 was formed. As in the above embodiment, by using the same photomask 240 or a plurality of photomasks having mask alignment marks as shown in FIG. 8, a highly accurate encoder scale can be manufactured. Can be.

[0034]

As described above, according to the present invention, it is possible to produce an encoder scale having high resolution and accuracy, and a high-performance rotation angle detecting device can be realized at relatively low cost. Further, it is not necessary to perform a complicated position adjustment at the time of assembling the apparatus, and mass productivity is greatly improved.

[Brief description of the drawings]

FIG. 1 is an embodiment of a rotation angle detecting device according to the present invention.

FIG. 2 is an embodiment of an encoder scale according to the present invention.

FIG. 3 is an embodiment of a method for processing an encoder scale according to the present invention.

FIG. 4 is another embodiment of the rotation angle detecting device according to the present invention.

FIG. 5 is another embodiment of the encoder scale according to the present invention.

FIG. 6 is another embodiment of the encoder / scale processing method according to the present invention.

FIG. 7 shows another embodiment of the rotation angle detecting device according to the present invention.

FIG. 8 is an embodiment of a photomask according to the present invention.

FIG. 9 shows a rotation angle detection device according to the prior art.

FIG. 10 shows an encoder scale in the prior art.

[Explanation of symbols]

 101 Encoder Scale 102 Encoder Scale 103 Encoder Scale 118 Lattice Pattern 122 Rotating Axis 135 Silicon Layer 136 Adhesive 137 Shaft Flange 138 Fixing Ring 141 Silicon Compound Layer 142 Escape 143 Shaft Hole 144 Monocrystalline Silicon Material 201 Light Emitting Element 202 Light receiving element 203 Encoder scale 217 Metal thin film 218 Lattice pattern 222 Rotating axis 231 Detection head frame 233 Mounting plate 234 Shaft hole 235 Scale fixing hole 236 Fixing screw 237 Shaft flange 238 Fixing ring 240 Photo mask 241 Position Alignment mark 242 Grid pattern 243 Shaft hole pattern

Claims (4)

[Claims] 1. A disk-shaped encoder scale having a rotating shaft, a shaft hole penetrating the rotating shaft, and a relief portion having a diameter larger than the shaft hole, and having a radial pattern formed thereon. And, for detecting the rotation of the encoder scale, a detection head having a pair of light emitting element and light receiving element,
In the optical rotation angle detecting device having the above, the shaft hole and the radial pattern of the encoder scale are formed using the same photomask or a plurality of photomasks having alignment marks that can be positioned with respect to each other. Characteristic rotation angle detection device. 2. The encoder scale has two layers: a first layer mainly composed of a crystalline silicon material; and a second layer mainly composed of a silicon compound such as silicon oxide / silicon nitride or silicon carbide. The rotation angle detection device according to claim 1, wherein the relief portion is formed in a first layer, and the shaft hole portion is formed in a second layer. 3. The position of the shaft hole of the encoder scale is
It is formed by photolithography using a photomask, processed by reactive ion etching, ion beam etching, or plasma etching, and the escape portion larger in diameter than the shaft hole is formed by wet etching. Processing into an encoder scale, a radial pattern is formed on the encoder scale by a photolithography method using a photomask, and the shaft hole portion and the pattern are aligned with the same photomask or relative to each other. A method for manufacturing a rotation angle detection device, wherein the rotation angle detection device is formed on an encoder scale using a plurality of photomasks having marks. 4. A first layer mainly composed of a crystalline silicon material,
A second layer mainly composed of a silicon compound such as silicon oxide / silicon nitride or silicon carbide; and a shaft hole formed by a photolithography method using a photomask on the second layer of the encoder scale composed of two layers. Forming a location and processing it by reactive ion etching, ion beam etching or plasma etching, the first layer having a high etching rate for silicon,
Forming a radial pattern on the encoder scale by a photolithography method using a photomask, processing a relief portion having a diameter larger than that of the shaft hole by a wet etching method having a low etching rate with respect to a silicon compound; The method of manufacturing a rotation angle detecting device, wherein the hole and the pattern are formed on an encoder scale using the same photomask or a plurality of photomasks having alignment marks that can be positioned with respect to each other. .