JPH06204555A - Semiconductor device for detecting position of incidence - Google Patents

Abstract

PURPOSE:To furnish a semiconductor device for detecting a position of incidence which can output information on the position of incidence of light or a particle beam as a current or the like. CONSTITUTION:Seven conductive layers 31 to 37 are formed on a semiconductor substrate 1. These conductive layers 31 to 37 have the same concentration of impurities of the same conductivity type respectively and the thicknesses thereof are thinned gradually toward the inside. Therefore the respective resistances between the opposite ends of the conductive layers 31 to 37 are equal to one another. Holes generated by incidence of a spot light flow into the conductive layers 31 to 37 of a P type and divided to position signal electrodes 2a and 2b in the resistance ratio corresponding to the angle of a point of inflow. Accordingly, it is possible to detect information on a rotational angle precisely, and a device thus constituted can be applied to an angle detector, a small-sized rotary encoder, etc., which are small in size and have a high resolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device for detecting an incident position, which can output information about the incident position of light or particle beam as a current or the like.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field,
For example, there is one disclosed in JP-A-59-17288. In this conventional example, first, a pair of position signal electrodes are provided on both ends of an n-type rectangular semiconductor substrate. And
A p-type basic conductive layer having a uniform cross-sectional area and a uniform impurity concentration is formed in the center of the incident surface between these, and a plurality of p-type branched branches are formed so as to extend from the basic conductive layer to the incident surface. A conductive layer is formed.

According to this conventional example, the charges generated on the incident surface by the incidence of light or particle beam are collected by the branched conductive layer and resistance-divided by the basic conductive layer. Here, since the basic conductive layer is formed thin, its resistance value is sufficiently high,
It can be set with high accuracy, and thus the detection sensitivity can be improved.

As another sensitive semiconductor device in such a field, there is one disclosed in JP-A-59-127883. In this conventional example, first, a stable high resistance layer can be easily formed by forming the resistance layer in a stripe shape on the surface of the semiconductor substrate. Since the depletion layer spreads in the gaps between the stripes, the carriers generated by the absorption of light in the gaps between the stripes can be used as a drift current without being recombined, and thus the sensitivity can be improved. .

[0005]

However, the conventional examples disclosed in JP-A-59-17288 and JP-A-59-127883 cannot be used for a rotation angle detector or a rotary encoder. A conventional rotary encoder or the like uses a rotating disk having slits formed along its circumference, and detects light passing through the slits with a pair of a light emitting element and a light receiving element. For this reason, it is difficult to miniaturize the device, and due to the dimensional limit of slit formation, the resolution remains within a fixed range.

Therefore, an object of the present invention is to provide a semiconductor device for detecting an incident position which can be applied to a small angle detector having a high resolution and a small rotary encoder.

[0007]

An incident position detecting semiconductor device according to the present invention comprises a semiconductor substrate of one conductivity type and one of hole-electron pairs excited by incidence of light or a particle beam. The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at both ends of the incident surface of the semiconductor substrate for collecting the other of the hole-electron pairs, and the pair of position signal electrodes are connected with high resistance. A plurality of parallel conductive layers formed along the circumference of a circle of a predetermined radius centered on a predetermined point on the semiconductor substrate, the resistance value between the respective ends of the plurality of conductive layers, It is characterized by being equal.

[0008]

According to the present invention, carriers generated by the incidence of light or particle beams flow into the conductive layer and are resistance-divided according to the ratio of the length of the conductive layer to the position detection electrode. Therefore, it becomes possible to accurately detect the information about the rotation angle.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to facilitate understanding of the present invention, an example of the principle common to the present invention will be described with reference to FIGS. 1 to 5 of the accompanying drawings, and then the present invention will be described with reference to FIG. An example will be described. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a plan view of a semiconductor device for detecting an incident position according to an example having the same principle. As shown in the figure, a pair of position signal electrodes 2a and 2b are provided at both ends of the donut-shaped incident surface on the front surface side of the semiconductor substrate 1, and the core conductive layer 3 is provided at the outer ends of the incident surface between them. Are formed. The basic conductive layer 3 extends along the circumference of a circle centered on the point P in the figure. The branched conductive layers 4 are formed in the radial direction so as to extend from the basic conductive layer 3 in the direction of the incident surface, and the branched conductive layers 4 are arranged at equal angular intervals.

The detailed structure of the apparatus of the above example will be described with reference to the plan view of FIG. 2 and the sectional view taken along the line AA. For example, a semiconductor substrate 1 made of n-type silicon with each side of 1 to 50 mm
A ring-shaped main conductive layer 3 in which a p-type impurity is implanted at a ^{concentration of} about 1 × 10 ¹³ to 10 ¹⁴ cm ⁻³ is formed on the surface side of, and a branched conductive layer 4 of about 5 μm is formed in the same step. The pitch is formed to a depth of about 0.5 to 1 μm. Ohmic contact regions 6a and 6b, in which p-type impurities are implanted to about 1 × 10 ¹⁸ to 10 ¹⁹ cm ⁻³ , are formed at both ends of the incident surface, and these are connected to the above-mentioned basic conductive layer 3. On top of these, an insulating film 7 made of, for example, thermally oxidized SiO _{2 is} formed.
Is formed, and ohmic contact is made with the position signal electrodes 2a and 2b made of, for example, aluminum through the openings of the insulating film 7 on the ohmic contact regions 6a and 6b.

A surface protective layer 8 made of, for example, an epoxy resin is applied and formed on these, and a wire (not shown) is provided with a wire (not shown) through the opening (not shown).
Bonded to a and 2b. On the back surface side of the semiconductor substrate 1, an ohmic contact layer 10 containing, for example, about 1 × 10 ¹⁹ to 10 ²⁰ cm ⁻³ of n-type impurities is formed.
A back electrode 11 is provided in ohmic contact with this surface.

Next, the operation of the apparatus of the above example will be described.
For example, when an infrared spot is incident from the front surface side, it passes through the surface protective layer 8 and the insulating film 7 and reaches the incident surface of the semiconductor substrate 1. As a result, the semiconductor substrate 1
When a hole pair is generated, the electron is in ohmic contact layer 1
0 and the back electrode 11 side, and the holes flow into the p-type branched conductive layer 4. Then, the photocurrent due to the holes flows through the branch conductive layer 4 into the basic conductive layer 3 and is divided by the resistance ratio according to the ratio of the distance (angle) from the inflow point to the position signal electrodes 2a and 2b. It Therefore, this semiconductor substrate 1
If a spot light is made incident on this incident surface by attaching the to the object to be measured, a signal according to the rotation angle is generated by the position signal electrodes 2a, 2
It will be obtained from b.

Next, a modification of FIG. 1 will be described with reference to FIG. FIG. 1A shows an example in which the size of the semiconductor substrate 1 is halved so that an angle of 180 ° can be detected. With this configuration, the device can be installed on the object to be measured that does not rotate 180 ° or more, and thus can be used for an inclination sensor or the like.

FIG. 1B shows an example in which the branch conductive layer 4 is not provided in a portion where spot light does not hit. By doing so, the total area of the pn junction formed by the semiconductor substrate 1, the backbone conductive layer 3 and the branched conductive layer 4 can be reduced, so that the leak current can be suppressed and the sensitivity can be improved. Further, since the pn junction capacitance is reduced, it is suitable for high speed and high frequency detection.

Next, another modification of FIG. 1 will be described with reference to FIGS. FIG. 4 is a plan view of FIG.
FIG. 3 is an enlarged view and a cross-sectional view taken along line BB and CC.
As shown in the figure, the basic conductive layer 3 is provided at the outer end of the incident surface, and the shield films 5a and 5b are provided integrally therewith on the position signal electrodes 2a and 2b. The shield films 5a and 5b need to have conductivity, and are separated at the central portion. The effective incident area where the branched conductive layer 4 is formed is only in the left half of the incident surface, and spot light is not incident on the other invalid incident areas. Therefore, in this example, the semiconductor substrate 1 in the invalid incident region
A p-type carrier trapping layer 20a is formed on the above, and a light shielding film 21b made of, for example, aluminum is further formed thereon. On the other hand, the carrier trapping layer 20a and the light-shielding film 21a are also formed outside the basic conductive layer 3, and the carrier trapping layer 20a and the carrier trapping layer 20b are the contact electrodes 2.
The semiconductor substrate 1 is short-circuited by 2a and 22b.

FIG. 5A shows the position signal electrodes 2a and 2 of FIG.
It is an enlarged plan view of the vicinity of b, and the same figure (b), (c) is a BB line and CC sectional view, respectively. As shown, the shield films 5a and 5b and the carrier trapping layers 20a and 20b
And the light shielding films 21a and 21b are laminated with the insulating film 7 interposed therebetween. Then, the semiconductor substrate 1 and the carrier trapping layers 20a and 20b are short-circuited by the contact electrodes 22a and 22b through the opening of the insulating film 7. Further, a surface protection layer 8 made of epoxy resin or the like is provided on the uppermost part.
Are stacked.

Next, the operation of the above modification will be described. The holes generated by the spot light incident on the effective incident area are
It is collected by the branched conductive layer 4 and flows into the basic conductive layer 3. Therefore, the photocurrent is divided by the resistance ratio according to the angle of the inflow point.

On the other hand, electron / hole pairs are also generated in the semiconductor substrate 1 outside the effective incident region due to thermal excitation or the like. However, holes due to this thermal excitation are generated in the carrier trapping layer 2
0a, 20b and contact electrodes 22a, 22
It flows into the semiconductor substrate 1 via b. Then, similarly, the electrons generated by the thermal excitation and the holes that have flowed in are recombined, and as a result, the carriers do not exist. Therefore, so-called thermal noise can be significantly reduced. Further, since the light-shielding films 21a and 21b are provided in regions other than the effective incident region, it is possible to eliminate all light incident on these regions. Therefore, also in this respect, the noise component can be significantly reduced.

Further, since the shield films 5a and 5b are provided on the basic conductive layer 3 with the insulating film 7 interposed therebetween, the influence of the charges contained in the surface protective layer 8 can be eliminated. Specifically, the epoxy resin or the like forming the surface protective layer 8 often contains sodium ions (Na ⁺ ), and the presence of this causes the effective cross-sectional area of the basic conductive layer 3 to vary. This variation of the cross-sectional area becomes more remarkable as the impurity concentration of the basic conductive layer 3 is lowered in order to increase the resistance of the basic conductive layer 3 and improve the detection accuracy. However, in the above example, the conductive shield film 5a,
Since the core conductive layer 3 is shielded by 5b, the above inconvenience does not occur.

Next, an embodiment of the present invention will be described with reference to FIG. Note that the material of the substrate, the concentration of impurities, the material of the electrodes, and the like are the same as those of the above-described example having the same principle as the present invention.

FIG. 6 (a) is a plan view thereof, and FIG. 6 (b) is a sectional view taken along line BB. As illustrated, seven conductive layers 31 to 37 are formed on the semiconductor substrate 1.
These conductive layers 31 to 37 have the same conductivity type impurity concentration and the same concentration, and the thickness thereof gradually decreases toward the inside. Therefore, the resistances between both ends of the conductive layers 31 to 37 are the same.

According to this example, the holes generated by the incident spot light flow into the p-type conductive layers 31 to 37,
Position signal electrodes 2a, 2b with a resistance ratio according to the angle of the inflow point
Is divided into Therefore, it can be used as an angle sensor, an inclination sensor, or the like.

The present invention is not limited to the above, and various modes are possible. For example, the shield film provided via the insulating film may be connected to the semiconductor substrate without being connected to the position signal electrode, or may be connected to an external earth via a separate electrode. Further, the material such as the semiconductor substrate and the impurity concentration of the conductive layer are not limited to those illustrated. Further, the conductive layer is formed by depositing polysilicon on the surface of the semiconductor substrate or SnO ₂
It can also be realized by forming a metal thin film such as.

[0025]

As described above in detail, in the present invention, the carriers generated by the incidence of light or particle beam flow into the conductive layer and the resistance is increased according to the ratio of the length of the conductive layer to the position detection electrode. Since it is divided, it becomes possible to accurately detect information about the rotation angle. Therefore, there is an effect that it can be applied to a small angle detector having a high resolution, a small rotary encoder, and the like.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor device for detecting an incident position according to an example having the same principle as the present invention.

FIG. 2 is an enlarged view and a cross-sectional view of FIG.

FIG. 3 is a plan view of a modified example of FIG.

FIG. 4 is a plan view of another modified example of FIG.

5 is an enlarged view and a sectional view of FIG.

FIG. 6 is a plan view and a sectional view of an embodiment according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2a, 2b ... Position signal electrode, 3 ... Basic conductive layer, 4 ... Branch conductive layer, 5a, 5b ... Shield film, 6
a, 6b ... Ohmic contact region, 7 ... Insulating film, 8
... Surface protective layer, 10 ... Ohmic contact layer, 11 ...
Back electrode, 20a, 20b ... Carrier trapping layer, 21a,
21b ... Shading film, 22a, 22b ... Contact electrode, 3
1-37 ... Conductive layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Inose 1 126-1, Nomachi, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd.

Claims (1)

[Claims] 1. A semiconductor substrate of one conductivity type, an electrode provided on the semiconductor substrate for collecting one of hole-electron pairs excited by incidence of light or particle beam, and an incident surface of the semiconductor substrate. A pair of position signal electrodes provided at both ends of the pair for collecting the other of the hole-electron pairs, and a predetermined point centered on a predetermined point on the semiconductor substrate so as to connect the pair of position signal electrodes with a high resistance. An incident position characterized by comprising a plurality of conductive layers parallel to each other formed along the circumference of a circle of radius, and resistance values between both ends of each of the plurality of conductive layers being equal to each other. Semiconductor device for detection.