JPH04320917A - Semiconductor optical rotation angle sensor - Google Patents

Abstract

PURPOSE:To detect a rotational angle precisely with a simple construction. CONSTITUTION:A semiconductor optical rotation angle sensor is equipped with a ring-shaped light-sensing element 12 which is formed of a semiconductor and made to generate a photocurrent by application of light 14 and with an electrode element which is provided inside the light-sensing element 12 and takes out the photocurrent 13 from this light-sensing element 12. Between these light-sensing element 12 and electrode element 13, a resistance element 11 so constructed as to show different resistance values according to the position of application of the light 14 is provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical rotation angle sensor that detects a rotation angle based on the photoelectric effect of a semiconductor.

0002

[Prior Art] FIG. 16 is a diagram showing an example of a conventional semiconductor optical rotation angle sensor (Y.Z.Xing, Senso
rs and Actuators, 7 (1985
) pp. 153-166). In the figure, 1 is an n-type silicon substrate, 2 is a p-type diffusion layer formed in a ring shape on this substrate 1, and this diffusion layer 2 is doped with impurities so that the diffusion layer 2 itself has a certain degree of resistance. The concentration is set, and the depth is such that it is easy to obtain a photocurrent against light irradiated from the outside. Reference numeral 3 designates electrode portions made of fine wires of Al (aluminum), which are formed at four locations across the diffusion layer 2 in its radial direction. For example, 4 is H
This is a light beam consisting of an e-Ne laser beam, and is irradiated toward the diffusion layer 2 from a light source (not shown). This light beam 4 rotates on the diffusion layer 2 in a circular orbit as shown by the broken line in FIG. 16, depending on the rotation angle to be detected. Note that the n-type substrate 1 is grounded, and the electrode portion 3 is biased to the same negative potential.

Next, the operation of this semiconductor optical rotation angle sensor will be explained. When a light beam 4 is irradiated from a light source (not shown) to a position corresponding to the rotation angle to be detected, electron-hole pairs are generated in the n-type substrate 1 in the portion irradiated with the light beam 4, and the p-type diffusion layer A photocurrent (holes excited by light) flows through 2. This photocurrent is shunted to the two electrode parts 3 closest to the position irradiated with the light beam 4 and taken out to the outside. Here, since the p-type diffusion layer 2 is resistive, the photocurrent is divided into the two electrode parts 3 with a current value depending on the position irradiated with the luminous flux 4. Therefore, since the current value obtained from each electrode part 3 changes in a certain relationship depending on the position of the luminous flux 4, based on this output current, the position of the luminous flux 4,
As a result, the rotation angle can be detected.

FIG. 17 shows the irradiation position (rotation angle φ) of the light beam 4.
FIG. 4 is a diagram showing actually measured values of the relationship between the current and the current taken out from each electrode part 3 (i=1 to 4). Since the irradiation position of the luminous flux 4 is uniquely determined from the electrode part 3 where the current is detected and the current of the electrode part 3, the irradiation position of the luminous flux 4 can be determined by using all the current values of the four electrode parts 3. It can be understood.

The semiconductor optical rotation angle sensor shown in FIG.
One-dimensional PSD (Position
It is considered to be equivalent to forming a PSD in an arc shape and arranging four PSDs.

[0006]

However, the conventional semiconductor optical rotation angle sensor has a structure in which the p-type diffusion layer 2 is divided into four parts by the electrode parts 3 and the photocurrent is taken out from these electrode parts 3. Since there are a large number of electrode sections 3 and the current taken out from the electrode sections 3 does not directly represent the rotation angle, an arithmetic circuit is required to calculate the rotation angle, and detection can be done by passing through this arithmetic circuit. There is a problem in that there is a possibility that an error may occur in the rotation angle obtained. Furthermore, since the electrode section 3 is configured to cross the p-type diffusion layer 2, if the light beam 4 is irradiated around the electrode section 3, a predetermined photocurrent may not be obtained, which may cause an error in the output. There was also a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor optical rotation angle sensor that has a simple configuration but can detect rotation angles with high accuracy.

[0008]

[Means for Solving the Problems] To explain in conjunction with FIGS. 1 and 12 showing embodiments, the semiconductor optical rotation angle sensor according to claim 1 has a ring made of a semiconductor that generates a photocurrent when irradiated with light 14. a shaped light receiving section 12; an electrode section 13 provided inside the light receiving section 12 for taking out the photocurrent 13 from the light receiving section 12; and an electrode section 13 provided between the light receiving section 12 and the electrode section 13, The resistor section 11 is configured such that its resistance value varies depending on the irradiation position. Further, in the semiconductor optical rotation angle sensor according to the second aspect, the resistor section 11 is configured to move the light receiving section 12 depending on the irradiation position of the light 14.
The distance between the electrode section 13 and the electrode section 13 is configured to vary. Further, in the semiconductor optical rotation angle sensor according to the third aspect, the resistor section 11 is located between the center of the light receiving section 12 and the electrode section 13.
It is configured such that the center of the Furthermore, in the semiconductor optical rotation angle sensor according to claim 4, the resistor section is arranged on a semiconductor substrate 40 in which the carrier mobility in the plane direction has directional dependence.
It is made up of.

[0009]

[Operation] -Claim 1- When the light receiving section 12 is irradiated with the light 14, a photocurrent is generated in the light receiving section 12, and this photocurrent is taken out from the electrode section 13 via the resistor section 11. The resistance section 11 is connected to the light 14
Since the resistance value is different depending on the irradiation position of the light 14, the voltage drop across the resistor 11 changes depending on the irradiation position of the light 14. -Claim 2- The resistor section 1 is configured such that the distance between the light receiving section 12 and the electrode section 13 changes depending on the irradiation position of the light 14. The voltage drop varies. -Claim 3- The resistor section 11 is configured such that the center of the light receiving section 12 and the center of the electrode section 13 are different from each other, so that the light 1
The voltage drop across the resistor section 11 changes depending on the irradiation position. -Claim 4- Since the resistor section is constituted by the semiconductor substrate 40 in which carrier mobility in the plane direction has direction dependence, the current value changes depending on the direction in which the photocurrent flows.

[0010] In the section of means and effects for solving the above-mentioned problems that explains the structure of the present invention, figures of embodiments are used to make the present invention easier to understand. It is not limited to.

[0011]

【Example】

-First Embodiment- FIG. 1 is a plan view showing a first embodiment of a semiconductor optical rotation angle sensor according to the present invention, and FIG. 2 is a sectional view taken along line AA' in FIG.

In these figures, 10 is a p-type silicon substrate, and 11 is a resistive n-type diffusion layer formed in a circular shape on the surface of this p-type substrate 10. In FIG. Outside this n-type diffusion layer 11, a ring-shaped n-type diffusion layer 12 having low impurity concentration and high resistance is formed. Further, inside the n-type diffusion layer 11, a low-resistance n+-type diffusion layer 13 with a high impurity concentration is formed in a circular shape at a position eccentric from the center thereof. Reference numeral 14 denotes a light beam composed of, for example, a He-Ne laser beam, which is irradiated toward the n-type diffusion layer 12 from a light source (not shown). This luminous flux 14 is generated depending on the rotation angle to be detected.
As shown by the broken line in FIG. 1, it rotates and moves in a circular orbit on the n-type diffusion layer 12. Reference numeral 15 denotes an n+ type electrode portion formed on the surface of the n− type diffusion layer 12, and this electrode portion 15 is formed at a position out of the trajectory of the light beam 14.

The p-type substrate 10 is grounded via an electrode (not shown), and the n+ type diffusion layer 13 is biased to a positive voltage VDD. A voltmeter 16 is interposed between the n+ type diffusion layer 13 and the n+ type electrode section 15.

The concentration of the p-type substrate 10 and the concentration and depth of the n-type diffusion layer 12 are set such that a photocurrent can be easily obtained by the light beam 14. In addition, the n+ type diffusion layer 13
may be formed at any position other than the center of the n-type diffusion layer 11, but if the rotation angle is 0° or 90°,
If the position of the light beam 14 irradiated when taking the reference rotation angles such as 180°, 180°, and 270° is on the same diameter as the center position of the n+ type diffusion layer 13, the rotation angle described later It is preferable that the peak value of the output voltage for detection coincides with the reference rotation angle position. In this embodiment, as shown in FIG. 1, the position of the light beam 14 irradiated when the rotation angle is 0° and the center position of the n+ type diffusion layer 13 are set so that they are on the same diameter. ing.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2. When a light beam 14 is irradiated from a light source (not shown) to a position corresponding to the rotation angle to be detected,
Electron-hole pairs are generated in the n-type diffusion layer 12 in the portion irradiated with this light beam 14. Here, in this embodiment, the p-type substrate 10 is grounded, and the n+ type diffusion layer 13 is connected to the positive voltage VDD.
Therefore, a reverse bias voltage is applied between the pn junction between the n-type diffusion layer 12 and the p-type substrate 10. Therefore, the electrons photoexcited by the light beam 14 are n-
Holes flow into the type diffusion layer 12 and into the p-type substrate 10 . Thereafter, electrons generated by photoexcitation flow through the n-type diffusion layer 11 to the n + -type diffusion layer 13 and are taken out to the outside. At this time, since the n-type diffusion layer 11 is resistive, a voltage drop occurs between the n+ diffusion layer 13 and the n+ electrode part 15 due to the flow of photocurrent, and this voltage drop is measured by the voltmeter 16. Ru.

Here, in this embodiment, the n+ type diffusion layer 13
are a circular n-type diffusion layer 11 and a ring-shaped n-diffusion layer 1.
It is not formed at the center of 2, but is formed at a position eccentric from the center. Therefore, the luminous flux 1 when detecting the rotation angle
The distance between the irradiation position 4 and the n+ diffusion layer 13 changes depending on the irradiation position of the light beam 14, and the resistance value of the n-type diffusion layer 11 with respect to the photocurrent also changes. Therefore, depending on the irradiation position of the light beam 14 (rotation angle to be detected), the n+ diffusion layer 13 and n
+ The amount of voltage drop between the electrode section 15 also changes, and the voltmeter 16
The indicated amount also changes. Conversely, measure this voltage drop using voltmeter 1.
By measuring at 6, the rotation angle can be detected. FIG. 4 shows an example of the relationship between the output voltage and rotation angle of the semiconductor optical rotation angle sensor shown in FIGS. 1 and 2.

FIG. 3 is a circuit diagram showing an equivalent circuit of the semiconductor optical rotation angle sensor shown in FIGS. 1 and 2. 17 is a photodiode made up of a p-type substrate 10 and an n-type diffusion layer 12; 18 is a variable resistor made up of an n-type diffusion layer 11; when the photodiode 17 is irradiated with light, the photodiode 17 The configuration is such that a voltage drop across the variable resistor 18 that occurs when the variable resistor 18 becomes conductive is measured by a voltmeter 16. Since the resistance value of the variable resistor 18 changes depending on the irradiation position of the light beam 14, the irradiation position of the light beam 14, that is, the rotation angle can be detected from the voltage drop value measured by the voltmeter 16.

The rotation angle can be detected by the procedure described above. Here, the semiconductor optical rotation angle sensor of this embodiment requires only three terminals in total including the ground terminal,
It has the advantage that it has fewer terminals and can have a simpler configuration than conventional sensors. In addition, since the voltage drop value between the n+ type diffusion layer 13 and the n+ type electrode section 15 directly corresponds to the rotation angle to be detected, there is no need for a conventional calculation circuit for calculating the rotation angle. The overall configuration including the detection device can be made simple and inexpensive, and there is no risk of errors caused by the arithmetic circuit. Furthermore, the light receiving section n-
Since the electrode does not cross over the diffusion layer 12 and there is no place where the rotation angle cannot be detected unlike in the conventional method, there is an advantage that the rotation angle can be detected without error.

-Modification of First Embodiment- FIG. 5 is an equivalent circuit diagram showing a modification of the first embodiment of the semiconductor optical rotation angle sensor according to the present invention. In the illustrated example, an ammeter 19 is connected in series to the variable resistor 18 formed of the n-type diffusion layer 11, and the value of the current flowing through the n-type diffusion layer 11 is measured. Then, using the divider 20, the output Vout from the voltmeter 16 is divided into the output Iou from the ammeter 19.
The sensor output is divided by t.

According to the above configuration, it is possible to compensate for the fluctuation (error) of the photocurrent depending on the change in the amount of light of the luminous flux 14 with the current value, and it is possible to eliminate the dependence of the sensor output on the amount of irradiated light. can. Moreover, it has the advantage that it can be realized with a simple configuration simply by adding the divider 20.

- Another modification of the first embodiment - FIG. 6 is a sectional view showing another modification of the first embodiment of the semiconductor optical rotation angle sensor according to the present invention. In the illustrated example, a ring-shaped p-type diffusion layer 21 is formed inside a resistive n-type diffusion layer 11,
The p-type diffusion layer 21 is configured to be irradiated with a light beam 14. The depth of the p-type diffusion layer 21 is the same as that of the n-type diffusion layer 11.
The p-n junction is formed at the bottom of the p-type diffusion layer 21, similar to the example shown in FIGS. 1 and 2. Further, the n+ type electrode section 15 is formed on the surface of the n type diffusion layer 11. Note that the other configurations are the same as those shown in FIGS. 1 and 2, so the description thereof will be omitted.

In the above structure, the p-type diffusion layer 2
When the light beam 14 is irradiated onto a position corresponding to the rotation angle to be detected on the p-type diffusion layer 21 and the n-type diffusion layer 11,
Since the n-junction is reverse biased, the electrons excited by this light beam 14 are transferred from the p-type diffusion layer 21 to the n-type diffusion layer 11.
It flows into the n+ type diffusion layer 13 and is taken out to the outside. In the illustrated example as well, the n+ type diffusion layer 13 is formed at an eccentric position, so the resistance value of the n type diffusion layer 11 to the photocurrent changes depending on the irradiation position of the light beam 14, and the voltage drop amount also changes accordingly. Change. Therefore, from the amount of voltage drop measured by the voltmeter 16, the irradiation position of the luminous flux 14 and, by extension, the rotation angle can be detected.

Therefore, the example shown in FIG. 6 can also provide the same effects as the examples shown in FIGS. 1 and 2. In particular, according to the example shown in FIG.
1 can be formed shallowly, sensitivity to light on the short wavelength side is increased, and an excellent effect can be obtained in that detection accuracy and S/N ratio can be improved.

That is, when the light receiving section is formed of the n-type diffusion layer 12 as shown in FIGS. 1 and 2, the p-type substrate 10
A depletion layer generated at the pn junction due to the bias voltage applied between the two ends of the depletion layer extends longer toward the n-type diffusion layer 12, which has a lower impurity concentration. If this depletion layer reaches the substrate surface, no electrons will be generated by photoexcitation, so
It is necessary to make the depth of the n-type diffusion layer 12 greater than the width of the depletion layer determined by the bias voltage. Note that it is possible to suppress the width of the depletion layer by increasing the impurity concentration of the diffusion layer 12, but if the impurity concentration is high, the change in voltage drop due to a change in the irradiation position of the luminous flux 14 becomes small. The impurity concentration of layer 12 cannot be made too high.

On the other hand, when the light-receiving section is formed of a p-type diffusion layer 21 as shown in FIG. Since the p-type diffusion layer 21 does not become small, the impurity concentration of the p-type diffusion layer 21 can be increased. Therefore, even if a reverse bias voltage is applied to the pn junction formed by the p-type diffusion layer 21 and the n-type diffusion layer 12, the depletion layer will not extend long toward the p-type diffusion layer 21 side (that is, toward the substrate surface side). Therefore, this p-type diffusion layer 21 can be formed thinly.

If the p-type diffusion layer 21 becomes thinner, the location where the pn junction is formed will also be located closer to the substrate surface. Here, the shorter the wavelength of light, the more electron-hole pairs are excited near the substrate surface, so the pn junction is closer to the substrate surface, that is, the electron-hole pairs are excited by light with a shorter wavelength. If it is easily located, the sensitivity to light on the shorter wavelength side will increase, and the detection accuracy and S/N ratio will improve. Therefore, there is a great advantage in forming the light receiving section with the p-type diffusion layer 21 as shown in FIG. In particular, when considering the case where the light source of the light beam 14 is composed of a semiconductor diode or the like, the high sensitivity on the short wavelength side is an excellent advantage.

In the above embodiment, the n+ type diffusion layer 13 was formed at a position eccentric from the center of the n- type diffusion layer 12, but as shown in FIG. The intersection of the short axis and the long axis is the n-type diffusion layer 12.
Even if it is formed so as to coincide with the center of , the same effect as in the embodiment can be obtained. Naturally, the n-type diffusion layer 11 and the n-type
The shape of the + type diffusion layer 13 is not limited to this, and any shape can be selected as long as the resistance value of the n type diffusion layer 11 differs depending on the irradiation position of the light beam 14. Further, in the embodiment, the sensor is constructed using the p-type substrate 10, but the sensor may be constructed using the n-type substrate. In this case, the conductivity type of each diffusion layer etc. may be reversed, and the bias voltage VDD may also be set to a negative voltage.

In the above embodiment, the n- type diffusion layer 12 and the p-type diffusion layer 21 constitute the light receiving section, the n+ type diffusion layer 13 constitutes the electrode section, and the n-type diffusion layer 11 constitutes the resistance section. It consists of

-Second Embodiment- FIG. 8 is a plan view showing a second embodiment of the semiconductor optical rotation angle sensor according to the present invention, and FIG. 9 is a sectional view taken along line A-A' in FIG. .

In these figures, 30 is a high resistance p-type substrate with low impurity concentration, and 31 is this p-type substrate 30.
This is a resistive n-type diffusion layer formed in a circular shape on the surface. On the outside of this n-type diffusion layer 30, at a predetermined distance from the outer periphery of this diffusion layer 30, a low-resistance n +
The type diffusion layer 32 is formed in a ring shape. The region between the n-type diffusion layer 31 and the n+-type diffusion layer 32 is a p--type substrate region 35. Further, inside the n-type diffusion layer 31, a low-resistance n+-type diffusion layer 33 with a high impurity concentration is formed in a circular shape at a position eccentric from the center thereof. 34
is a light beam irradiated toward the p-type substrate region 35 from a light source (not shown). This light beam 34 rotates in a circular orbit on the p-type substrate region 35, as shown by the broken line in FIG. 8, depending on the rotation angle to be detected. Furthermore, this p-
The width of the mold substrate region 35 is set to be equal to or less than the spot diameter of the light beam 34.

A negative voltage -VS is applied to the p-substrate 30 via an electrode (not shown), and the n+-type diffusion layer 3
3 is applied with a positive voltage VDD via an ammeter 36. Further, the n+ type diffusion layer 32 is grounded.

Next, the operation of this embodiment will be explained with reference to FIGS. 8 and 9. In the sensor of this embodiment, since the positive voltage VDD is applied to the n+ type diffusion layer 33, the pn junction between the n type diffusion layer 31 and the p- type substrate region 35 is in a reverse bias state. . Therefore, the luminous flux 34
In a state in which the p-type substrate region 35 is not irradiated, conduction from the n-type diffusion layer 31 to the p-type substrate region 35 is cut off. Similarly, the n+ type diffusion layer 32 is grounded, and the p- substrate 30 (p- substrate region 35
), a negative voltage -VS is applied to this n+
The pn junction between the type diffusion layer 32 and the p-type substrate region 35 is also in a reverse bias state. Therefore, when the light beam 34 is not irradiated, the n+ type diffusion layer 32 to the p− type substrate region 35
The conduction to is also cut off.

In this state, when a light beam 34 is irradiated from a light source (not shown) to a position corresponding to the rotation angle to be detected, electron-hole pairs are created in the p-substrate region 35 in the portion irradiated with this light beam 34. occurs. Due to the generation of electron-hole pairs due to photoexcitation, the resistance of the p- substrate region 35 in the portion irradiated with the light beam 34 decreases, and the n-type diffusion layer 31 and the n+-type diffusion layer 32 become electrically conductive. As a result, a positive voltage VD
A current flows from the n+ type diffusion layer 33 biased to D to the n+ type diffusion layer 32 through the p- type substrate region 35 in the portion irradiated with the light beam 34, and the value of this current is measured by the ammeter 36.

Here, in this embodiment, the n+ type diffusion layer 33
is not formed at the center of the circular n-type diffusion layer 31 and the ring-shaped n+ type diffusion layer 32, but is formed at a position eccentric from the center. Therefore, the distance between the irradiation position of the light beam 34 and the n+ type diffusion layer 33 when detecting the rotation angle changes depending on the irradiation position of the light beam 34, and the resistance value of the n-type diffusion layer 31 with respect to the current also changes. Therefore, the value of the current flowing from the n+ diffusion layer 33 to the n+ diffusion layer 32 changes depending on the irradiation position of the light beam 34 (rotation angle to be detected), and the current value flowing from the n+ diffusion layer 33 to the n+ diffusion layer 32 changes.
The indicated amount also changes. Conversely, by measuring this current value with the ammeter 36, the rotation angle can be detected. FIG. 11 shows an example of the relationship between the output current and rotation angle of the semiconductor optical rotation angle sensor shown in FIGS. 8 and 9.

FIG. 10 is a circuit diagram showing an equivalent circuit of the semiconductor optical rotation angle sensor shown in FIGS. 8 and 9. 37 is p
- a photoswitch constituted by a substrate region 35, 38;
is a variable resistor composed of an n-type diffusion layer 31, and when the photoswitch 37 is irradiated with light and becomes conductive, the current flowing through the variable resistor 38 is measured by an ammeter 36. It has become. Since the resistance value of the variable resistor 38 changes depending on the irradiation position of the light beam 34, the irradiation position of the light beam 34, that is, the rotation angle can be detected from the current value measured by the ammeter 36.

Therefore, according to this embodiment, the above-mentioned first
Effects similar to those of the embodiment can be obtained. In particular, in this embodiment, the p-substrate region 35 is changed from a non-conductive state to a conductive state by irradiation with the luminous flux 34, so that the amount of light of the irradiated luminous flux 34 changes the p-substrate region 35 into a conductive state. The sensor output is not affected by changes in the light amount as long as it exceeds a certain threshold. That is, the sensor of this embodiment has the advantage that there is no dependence on the amount of irradiated light.

In the above embodiment, the n+ type diffusion layer 33 was formed at a position eccentric from the center of the n+ type diffusion layer 32, but as in FIG. 7, the n+ type diffusion layer 33 was formed in an elliptical shape. Even if the intersection of the short axis and the long axis is formed to coincide with the center of the n+ type diffusion layer 32, the same effect as in the embodiment can be obtained. Naturally, the shapes of the n-type diffusion layer 31 and the n+ type diffusion layer 33 are not limited to these, and any shape can be selected as long as the resistance value of the n-type diffusion layer 31 differs depending on the irradiation position of the light beam 34. In addition, in the example, p-
Although the sensor was constructed using the type substrate 30, the sensor may also be constructed using an n-type substrate. In this case, the conductivity type of each diffusion layer etc. may be reversed, and the applied voltage may also be reversed in positive and negative directions.

Furthermore, if the ammeter 36 is configured to measure the current value by the voltage drop across the n-type diffused resistor formed in the same process as the n-type diffused layer 31, temperature compensation can be performed at the same time. Can be done. That is, the temperature dependence of the resistance of the n-type diffused layer 31 can be canceled using the n-type diffused resistor formed by the same process.

In the above embodiment, the n+ type diffusion layer 33 constitutes an electrode section, the p- type substrate region 35 constitutes a light receiving section, and the n type diffusion layer 11 constitutes a resistor section.

-Third Embodiment- FIG. 12 is a plan view showing a third embodiment of the semiconductor optical rotation angle sensor according to the present invention, and FIG. 13 is a sectional view taken along line AA' in FIG.

In these figures, reference numeral 40 denotes a highly resistive n-type silicon substrate with low impurity concentration, and the surface orientation of this n-type substrate 40 is (110). 41 is a gate electrode made of polysilicon or the like formed in a ring shape on an n-type substrate 40; 42 is this gate electrode 4;
This is a gate oxide film made of SiO2 or the like formed between the n-type substrate 1 and the n-type substrate 40. A low resistance p + type source region 43 and a resistive p type drain region 44 with high impurity concentration are formed on the surface of the n − type substrate 40 corresponding to the inner and outer peripheral portions of the gate electrode 41, respectively. There is. This p+ type source region 43 is also formed in a ring shape, and an n+ type contact region 45 is formed inside the ring shape. 46 is a source electrode in contact with the p+ type source region 43. From the above, a ring-shaped MOSFE is placed on the n-type substrate 40.
T47 is formed.

A low resistance p + -type diffusion layer 48 with high impurity concentration is formed outside the p-type drain region 44 at a predetermined distance from the drain region 44 . The region between the p type drain region 44 and the p + type diffusion layer 48 is an n − type substrate region 49 .

Reference numeral 50 denotes a light beam irradiated toward the n-type substrate region 49 from a light source (not shown). This luminous flux 50
rotates in a circular orbit on the n-type substrate region 49, as shown by the broken line in FIG. 12, depending on the rotation angle to be detected. Note that the width of this n-type substrate region 49 is set to be equal to or less than the spot diameter of the light beam 50.

A positive voltage VDD is applied to the source electrode 46 via an ammeter 51. In addition, the gate electrode 4
1 and p+ type diffusion layer 48 are grounded.

Next, the operation of this embodiment will be explained with reference to FIGS. 12 and 13. When the light flux 50 is not irradiated, a positive voltage VDD is applied to the source electrode 46 and the gate electrode 41 is grounded, so that a p-channel inversion layer 52 is formed directly below the gate oxide film 42. Therefore, the MOSFET 47 as a whole is in the on state, but the drain region 44 is surrounded by the highly resistive n-type substrate 40, and since a current path from the drain region 44 is not secured, the drain region 44 is surrounded by the source region 43. No current flows to drain region 44.

In this state, when a light beam 50 is irradiated from a light source (not shown) to a position corresponding to the rotation angle to be detected, electrons and holes are generated in the n-type substrate region 49 in the portion irradiated with this light beam 50. A pair occurs. Due to the generation of electron-hole pairs due to photoexcitation, the resistance of the n- substrate region 49 in the portion irradiated with the light beam 50 decreases, and the p-type drain region 44 and the p+-type diffusion layer 48 become electrically connected. As a result, from the p+ type source region 43 biased to the positive voltage VDD, the p channel inversion layer 52, the p type drain region 44 and the n
A current flows to the p+ type diffusion layer 48 through the - type substrate region 49, and the value of this current is measured by an ammeter 51.

Here, in this embodiment, MOSFET 47
is formed on an n-type silicon substrate 40 with a plane orientation (110), and the surface mobility μ of carriers (holes) in this silicon substrate 40 differs depending on the crystal direction. Therefore, the resistance value of the p-channel inversion layer 52 directly under the gate electrode 41 has direction dependence. Therefore, the resistance value of the p-channel inversion layer 52 changes depending on the irradiation position of the light beam 50 when detecting the rotation angle, and the resistance value of the p-channel inversion layer 52 changes from the p+ type source region 43 to the p-type drain region 4.
The value of the current flowing to 4 also changes depending on this. Conversely, by measuring this current value with the ammeter 51, the rotation angle can be detected. FIG. 15 shows an example of the relationship between the output current and rotation angle of the semiconductor optical rotation angle sensor shown in FIGS. 12 and 13.

FIG. 14 is a circuit diagram showing an equivalent circuit of the semiconductor optical rotation angle sensor shown in FIGS. 12 and 13. Reference numeral 53 denotes a photoswitch constituted by an n-type substrate region 49, and when this photoswitch 53 is irradiated with light and becomes conductive, the current flowing through the MOSFET 47 is measured by an ammeter 51. . This MOSFET4
Since the channel resistance of 7 changes depending on the irradiation position of the luminous flux 50, the luminous flux 50 is determined from the current value measured by the ammeter 51.
The irradiation position, that is, the rotation angle can be detected.

Therefore, according to this embodiment, the above-mentioned first
Effects similar to those of the embodiment can be obtained. In particular, in this embodiment, as in the second embodiment described above, the n-substrate region 49 is changed from a non-conductive state to a conductive state by irradiation with the luminous flux 50, so that the amount of the irradiated luminous flux 50 is The amount of light need only be sufficient to change the n-substrate region 49 into a conductive state, and as long as it exceeds a certain threshold, changes in the amount of light will not affect the sensor output. That is, the sensor of this embodiment has the advantage that there is no dependence on the amount of irradiated light.

Furthermore, in this embodiment, the p-channel resistance is changed by utilizing the fact that the surface mobility of holes in the silicon substrate 40 with the plane orientation (110) has directional dependence. 1. There is no need to make the sensor shape asymmetrical as in the second embodiment, which is advantageous in terms of design and manufacturing.

[0051] In the above-mentioned embodiment, the surface orientation (11
Although the silicon substrate 40 of No. 0) is used, the present invention is not limited to this, and a semiconductor substrate having another surface orientation in which the surface mobility of carriers (electrons or holes) has direction dependence may be used.

Furthermore, if the ammeter 51 is configured to measure the current value by measuring the voltage drop of the p-channel inversion layer in MOSFETs of the same configuration formed on the n-type substrate 40 by the same process, Temperature compensation can be performed at the same time. That is, the temperature dependence of the resistance of the p-channel inversion layer 52 can be canceled using the p-channel inversion layer formed by the same process.

Note that in the above embodiment, the n-type silicon substrate 40 constitutes a semiconductor substrate, and the n-type substrate region 4
Reference numeral 9 constitutes a light receiving section, and p+ type diffusion layer 48 constitutes an electrode section.

[0054]

[Effects of the Invention] As explained in detail above, according to the present invention, the input/output terminals of the semiconductor optical rotation angle sensor can be reduced to three terminals in total including the ground terminal, and compared to conventional sensors. This has the advantage that the number of terminals is small and the configuration can be simple. In addition, since the voltage drop value or current value between both ends of the resistor directly corresponds to the rotation angle to be detected,
There is no need for an arithmetic circuit for calculating the rotation angle as in the prior art, and the overall configuration including the detection device can be made simple and inexpensive, and there is no fear of errors caused by the arithmetic circuit. Furthermore, since the electrode does not cross over the light-receiving section and there is no place where the rotation angle cannot be detected unlike in the conventional case, there is an advantage that error-free rotation angle detection is possible. In particular, the invention of claim 4 makes use of the fact that the carrier mobility in the plane direction of the semiconductor substrate has directional dependence, so that the sensor shape can be made symmetrical, and the sensor shape can be made symmetrical. It has advantages in design and manufacturing.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of a semiconductor optical rotation angle sensor according to the present invention.

FIG. 2 is a cross-sectional view taken along line AA' in FIG. 1;

FIG. 3 is an equivalent circuit diagram of the sensor shown in FIG. 1.

FIG. 4 is a diagram showing an example of the relationship between the output voltage of the sensor shown in FIG. 1 and the rotation angle.

FIG. 5 is an equivalent circuit diagram showing a modification of the first embodiment of the semiconductor optical rotation angle sensor according to the present invention.

FIG. 6 is a sectional view showing another modification of the first embodiment of the semiconductor optical rotation angle sensor according to the present invention.

FIG. 7 is a sectional view showing another modification of the first embodiment of the semiconductor optical rotation angle sensor according to the present invention.

FIG. 8 is a plan view showing a second embodiment of the semiconductor optical rotation angle sensor according to the present invention.

9 is a cross-sectional view taken along line AA' in FIG. 8;

10 is an equivalent circuit diagram of the sensor shown in FIG. 8. FIG.

FIG. 11 is a diagram showing an example of the relationship between the output current of the sensor shown in FIG. 8 and the rotation angle.

FIG. 12 is a plan view showing a third embodiment of the semiconductor optical rotation angle sensor according to the present invention.

13 is a sectional view taken along line AA' in FIG. 12;

14 is an equivalent circuit diagram of the sensor shown in FIG. 12. FIG.

FIG. 15 is a diagram showing an example of the relationship between the output current of the sensor shown in FIG. 12 and the rotation angle.

FIG. 16 is a plan view showing an example of a conventional semiconductor optical rotation angle sensor.

17 is a diagram showing an example of the output current and rotation angle from each electrode portion of the sensor shown in FIG. 16. FIG.

[Explanation of symbols]

10 p-type silicon substrate 11, 31 N-type diffusion layer 12 N-type diffusion layer 13, 33 N+ type diffusion layer 14, 36, 50 luminous flux 21 p-type diffusion layer 30 p-type silicon substrate 35 p-type substrate region 40 N-type silicon substrate 41 Gate electrode 43 p+ type source region 44 p-type drain region 48 p+ type diffusion layer 49 N-type substrate region 51 p-channel inversion layer

Claims (4)

[Claims] 1. A ring-shaped light receiving section made of a semiconductor that generates a photocurrent when irradiated with light; an electrode section provided inside the light receiving section to take out the photocurrent from the light receiving section; A semiconductor optical rotation angle sensor consisting of a resistor section provided between an electrode section and a resistor section configured to have a resistance value that differs depending on the position of light irradiation. 2. The semiconductor optical rotation angle sensor according to claim 1, wherein the resistor section is configured such that the distance between the light receiving section and the electrode section changes depending on the irradiation position of the light. 3. The semiconductor optical rotation angle sensor according to claim 2, wherein the resistor section is configured such that the center of the light receiving section and the center of the electrode section are different from each other. 4. The semiconductor optical rotation angle sensor according to claim 1, wherein the resistor portion is constituted by a semiconductor substrate in which carrier mobility in a plane direction has direction dependence.