JPS61152065A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To prevent the erroneous operation due to the incident ray from other than a specific direction by making the directivity against the incident ray from the specific direction shaper. CONSTITUTION:A light emitting diode 1 and a photo sensing part 5 are fixed, a rotary slit plate 3 is rotated synchronously with the rotation of a detected object and the light irradiated on the photo sensing part from the light emitting diode 1 through a slit 4 is moved to the same direction with the rotating direction of the rotary slit late 3. A photo diode which detected the light irradiated from the light emitting diode 1 through the slit 4 is made conductive, a current flows through the resistance connected to the photo diode and the photo diode from a power source Vcc, he cathode terminal of the photo doide is made an L level by the voltage drop of the resistance and an L level signal is applied to the inversion input terminal of the AND circuit connected to the cathode terminal. The AND circuit inverts the applied L level signal to an H level signal and generates a photo sensing signal. In this way, especially sharp directivity against the incident ray from a specific direction is make.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a semiconductor light-receiving element, and more particularly to a semiconductor light-receiving element with improved directivity for incident light from a specific direction.

[Technical background and problems of the invention]

Due to recent advances in semiconductor technology, so-called line image sensors, in which the light-receiving section has a plurality of semiconductor light-receiving elements arranged in a straight line, are becoming popular, and their application fields are quite wide, and they are being put into practical use in various fields. 'There is.

Incidentally, in order for the line image sensor to perform accurate measurements, it is necessary for each of the plurality of semiconductor light receiving elements constituting the light receiving section to reliably detect the presence or absence of light from a predetermined direction. However, each light-receiving element of the line image sensor is generally formed in a substantially planar shape on a substrate, and is not configured to have particular directivity with respect to light from a specific direction. External light that causes noise such as light easily enters, and the S/N is lower than before.
Measures against such extraneous light have been desperately needed from the viewpoint of improving the ratio.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to sharpen the directivity of light incident from a specific direction and prevent malfunctions caused by light incident from a direction other than the specific direction. The purpose is to provide devices.

[Summary of the invention]

In order to achieve the above object, the present invention provides at least two or more light receiving means capable of receiving incident light from a specific direction and having mutually different angles of light receiving surfaces, and when all of the light receiving means are in a light receiving state. The gist of the present invention is to include a detection processing means for outputting a light reception signal.

(Example of the invention) Hereinafter, the present invention will be explained in detail using the drawings.

1 and 2 show an example in which the semiconductor light-receiving element according to the present invention is applied to a rotation sensor, and FIG. 1 is a sectional view schematically showing a light transmitting section and a light receiving section of the rotation sensor, FIG. 2 is a plan view of the light receiving section shown in FIG. 1.

In FIG. 1, 1 is a light emitting diode, 3 is a rotating slit plate that rotates in synchronization with the object to be detected, the rotation of which is to be detected;
Reference numeral 4 denotes a slit provided on this rotary slit plate, and 5 denotes a light-receiving section arranged with the rotary slit plate 3 interposed between the light emitting diode 1 and the light emitting diode 1.

The light emitting diode 1 is connected to the light receiving section 5 via the rotating slit plate 3.
supply light to. The rotating slit plate 3 has slits 4 continuously cut at a predetermined pitch, and during rotation, transmits and blocks light from the light emitting diode 1 from being supplied to the light receiving section 5.

The light receiving section 5 is formed by a bipolar process described later, and includes a light receiving detecting section 7 that detects the light from the light emitting diode 1 that has passed through the slit 4 and converts the detected light into an electrical signal.
For example, five photodiodes 8 to 7e are arranged in a line, and two photodiodes, for example, are formed in each of the light receiving and detecting parts 7a to 7e. That is, the light reception detection section 7a includes photodiodes 9a and 9b, the light reception detection section 7b includes photodiodes 9c and 9d, the light reception detection section 7C includes photodiodes 9e and 9f, the light reception detection section 7d includes photodiodes 9Q and 9h, and the light reception detection section 7e. Photodiodes 9i and 9j are formed in . The photodiodes 9a to 9j are placed in V-shaped grooves dug into the surfaces of substantially rectangular n-epitaxial layers 158 to 15j formed on the P-type silicon substrate 11, so that the photodiodes 9a to 9j face each other at an angle of, for example, 54.7°. By forming it at an angle, the inclined surface having a rectangular surface serves as a light-receiving surface for light incident from above.

That is, one photodiode 9a to 9j is formed on each of the slopes of the groove, and a PN junction is formed between the P type silicon substrate 11 and the P+ element isolation region 13 and the n'''' epitaxial layers Illa to 15j. This is what is being accomplished.

For example, when the rotating slit plate 3 is in the position shown in FIG.
The light emitted from the light emitting diode 1 is incident on the photodiodes 9a, 9b, 9i, and 9j, while the light emitted from the light emitting diode 1 is blocked by the rotating slit plate 3, and the light emitted from the light emitting diode 1 is blocked by the photodiodes 9a, 9b, 9i, and 9j. As shown above, since the light-receiving surfaces of the photodiodes 93 to 9j are inclined at an angle of 54.7 degrees, the wraparound light that enters through the slit 4 at an incident angle of about ±35.3" or more is not reflected by the photodiodes 9b and 9i. Therefore, the photodiode 9
Even if reflected light or the like enters the photodiodes 9i, 9j and generates an output signal, the outputs of the photodiodes 9a, 9b are sent to the AND circuit 25a, and the photodiodes 9i, 9j are sent to the AND circuit 25a, as will be described later.
Since the outputs of are connected to the AND circuit 250 and ANDed, the light reception signals from the light reception detection sections 7a and 7e are not output. In other words, each light receiving detection section 7
8 to 7e have a configuration in which a light reception signal indicating detection of light is not output unless light is incident on both of the light receiving surfaces of the two photodiodes constituting each photodiode.

Note that the photodiodes 98 to 9j are formed, for example, through the following steps. That is, a bipolar process is performed to form a layer with a thickness of, for example, 12 mm on a P-type silicon substrate 11.
μm, n″″ epitaxial layer 1 with specific resistance 2ΩcIIl
5a to 15j are grown, and BB is formed on the P-type silicon base bond 11.
P+ element isolation region 13 is formed by depositing r' 3 and embedding and diffusing into the substrate, and POCJL:+ is deposited to form n+ emitter diffusion region 17. Next, 3i3N411 is deposited by low pressure CVD, the portion where the V groove is to be dug is removed, and the field oxide film is etched using this SI3N4 film as a mask. Further, a V-groove is dug using, for example, a 3i etching solution, and a process of contact etching, An evaporation, pattern formation, and pad etching is performed.

FIG. 3 shows an example of a circuit that converts the light detected by the light detection section into a light reception signal.

The cathode terminals of the photodiodes 98 to 9j are connected to the power supply Vcc via the resistors 23a to 23j, respectively, and the cathode terminals of the two photodiodes formed for each light receiving section are connected to the same AND. Connected to the negative input terminal of the circuit. That is, the cathode terminals of the photodiodes 9a and 9b are connected to the AND circuit 25a.
The cathode terminals of the photodiodes 9c and 9d are connected to the AND circuit 25b, the cathode terminals of the photodiodes H2O and 9f are connected to the AND circuit 25c, and the photodiode 9(+) is connected to the AND circuit 25b.

The cathode terminal of photodiode 9h is connected to AND circuit 25d, and the cathode terminal of photodiode 9r and 9j is connected to AND circuit 25e.
are connected to each. Further, the anode terminal of each of the photodiodes 98 to 9J is connected to ground. The AND circuits 25a to 25e take the logical product of the respective output signals of two photodiodes formed in one light reception detection section, and when the two photodiodes detect light, the AND circuits connected to the photodiode A light reception signal is generated by inputting "L" level signals to both inverting input terminals.

FIG. 4 shows an example of a circuit that receives a light reception signal and obtains a rotation direction signal and a rotation pulse signal.

In the figure, the D input terminal of the D-type flip 70 tube circuit 41 is connected to the output of one of the AND circuits, for example, the AND circuit 25a, which is connected to the output of the photodiode formed in each of the adjacent light detection sections. The GK terminal of the D-type flip 70 tube circuit 41 is supplied with a light reception signal output from the other AND circuit, for example, the AND circuit 25b. D type flip-flop circuit 4
When a light reception signal is input to the CK terminal of No. 1, the level of the signal input to the D input terminal, for example, a "L" or "H" level signal, is transferred from the Q output terminal immediately before this light reception signal is input to the GK terminal. Generated as a rotation direction signal. The edge-triggered monostable multi-pipe detector 43 receives a received light signal at its input terminal, and its output terminal is connected to the input terminal of an OR circuit 45, which is triggered by the rising edge of the input received light signal and outputs a one-shot pulse signal to an OR circuit. 45.

The OR circuit 45 takes the logical sum of the one-shot pulse signals output from the respective edge-triggered monostable multivibrators 43, and generates a rotation pulse signal.

Next, the operation of this embodiment will be explained.

When the emitting diode 1 and the light receiving section 5 are fixed and the rotating slit plate 3 rotates in synchronization with the rotation of the object to be detected, the light irradiated from the emitting diode 1 to the light receiving section via the slit 4 is transmitted to the rotating slit plate. Move in the same direction as the rotation direction in step 3. The photodiode that detects the light emitted from the emission diode 1 through the slit 4 becomes conductive, and a current flows from the power supply Vcc to the ground through the resistor connected to the photodiode and the photodiode.
The cathode terminal of the photodiode is at the "L" level due to the voltage drop across the resistor, and an "L" level signal is input to the inverting input terminal of the AND circuit connected to the cathode terminal. “L” level signal “
The H'' level signal is inverted and a light reception signal is generated.

FIG. 5 shows examples of light reception signals (A) to (E) generated by each of the AND circuits 25a to 25e. Each received light signal is inputted by the edge to a monostable multivibrator 43,
This edge trigger monostable multivibrator 43 supplies a one-shot pulse signal to the OR circuit 45 at the same time as it detects the rise of the light reception signal. In the OR circuit 45, each edge receives the one-shot pulse signal output from the monostable multivibrator 43, performs a logical sum, and generates the rotation pulse signal shown in FIG. 5(F). Also D
When the light reception signal is input to the CK terminal of the flip-flop circuit 41, the flip-flop circuit 41 generates a rotation direction signal from its Q output terminal.

Therefore, it is possible to reliably prevent rotational pulse miscounts and rotational direction signal malfunctions due to erroneous detection of reflected light after passing through the slit.

〔Effect of the invention〕

The light receiving portion of the semiconductor light receiving element is provided with at least two or more light receiving means capable of receiving incident light from a specific direction, each of which has a square-shaped light receiving surface, and all of the light receiving means are in a light receiving state. and a detection processing means that outputs a light reception signal when
Since the configuration has particularly sharp directivity with respect to incident light from a specific direction, it is possible to prevent malfunctions due to incident light from directions other than the specific direction, and to improve the S/N ratio.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partial plan view of FIG. 1, and FIG. 3 is a circuit diagram for obtaining a received light signal.
FIG. 4 is a circuit diagram for obtaining a rotation direction signal and a rotation pulse signal, and FIG. 5 is an operation time chart of FIG. 4. (Explanation of symbols representing main parts in the figure) 1... Issuing diode 3... Rotating slit plate 4... Slit 5... Light receiving sections 78 to 7e... Light receiving detection sections 9a to 9j ... Photodiode 258-25e ... AND circuit 41 ... D-type flip 70 tube circuit 43 ... Edge trigger monostable multivibrator 45
...OR circuit Kuno (JOda)

Claims (1)

[Claims] At least two or more light receiving means capable of receiving incident light from a specific direction and having mutually different angles of light receiving surfaces, and a detection processing means for outputting a light reception signal when all of the light receiving means are in a light receiving state. . A semiconductor light-receiving element, characterized in that the semiconductor light-receiving element is configured to have sharp directivity with respect to incident light from the specific direction.