JPH0682072B2 - Position detection semiconductor device - Google Patents

Description

The present invention relates to a position detecting semiconductor device capable of outputting information on the incident position of light or a particle beam as a current or the like.

[Conventional technology]

Conventionally, as a technique in such a field, for example, JP-A-59-
There was one shown in the 17288 publication. In the first conventional example, first, a pair of position signal electrodes are provided on both ends of an n-type rectangular semiconductor substrate. Then, 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 them, and a plurality of p-type basic conductive layers are formed so as to extend from the basic conductive layer to the incident surface. A branched conductive layer is formed.

According to the first 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 and can be set with high accuracy, and therefore the detection sensitivity can be improved.

On the other hand, as an example of dividing the area for position detection into multiple areas, “Application example of PSD in improving the accuracy of distance detection”
(RIKEN Symposium 8th "Non-contact measurement and image processing")
13 to 20, October 15, 1987) and "RORS-based optical stylus for three-dimensional measurement" (pages 21 to 32 of the above document) and the like are known. According to the second conventional example, a plurality of position signal electrodes are provided at a predetermined interval on the light receiving surface on the semiconductor substrate, whereby the light receiving surface is divided into a plurality of light receiving areas.

According to the first and second conventional examples described above, in order to actually detect the incident position of light, it is necessary to perform predetermined signal processing on the obtained signal photocurrent. Specifically, when the signal photocurrents from the pair of position signal electrodes are I _A and I _B , an amplifier circuit for amplifying them and (I _A + I B
Addition circuit and for performing analog operation _{B), (I A} -
Subtraction circuit for performing analog operations I _{B) or, (I} A -I
_{B) / (I A + I} B) division circuit for performing analog operations are required. This is also shown in the RIKEN symposium literature mentioned above.

[Problems to be Solved by the Invention]

However, according to the above-mentioned first conventional example, there is a drawback that the position resolution is likely to deteriorate.

This is because only one pair of position signal electrodes are provided at both ends of the basic conductive layer. That is, when the signal currents I _A and I _B from these position signal electrodes are smaller than the noises from the analog operation circuit for analog operation and the position detecting semiconductor device itself, the position signals obtained from the analog operation circuit are obtained. The position resolution at the output is reduced.

Such deterioration of the position resolution can be considerably improved by dividing the light receiving surface into a plurality of light receiving areas by a plurality of position signal electrodes as in the second conventional example. However, in the second conventional example, since the position signal electrode that does not transmit light is formed on the light receiving surface, if the incident light hits this position, the sensitivity is lowered. In particular, when the spot of incident light is sufficiently small in relation to the position signal electrode, the sensitivity is significantly reduced when the spot is located on the electrode,
Only unstable output was obtained.

Therefore, an object of the present invention is to provide a semiconductor device for position detection, which is capable of increasing the position resolution and also making the detection sensitivity high and stable.

[Means for Solving the Problems]

The position detecting semiconductor device according to the present invention is a semiconductor substrate of one conductivity type, and the light to be detected is formed on one surface of the semiconductor substrate and is formed along the incident surface. A basic conductive layer having a resistance enough to divide the current into a resistance, a plurality of branched conductive layers formed so as to extend from the basic conductive layer to the incident surface, a fixed interval or a required position resolution. It is characterized in that it is provided with three or more position signal electrodes formed on the semiconductor substrate and connected to the basic conductive layer at predetermined intervals set by the above. Further, a plurality of branched electric layers and impurities of opposite electric type may be included.

Further, in the position detecting semiconductor device according to the present invention, a selection circuit for selecting two position signal electrodes connected to each of the three or more position signal electrodes and extracting the signal photocurrent is formed on the semiconductor substrate. It may be that.

In addition, a conductive shield film may be formed on the semiconductor substrate to cover the core conductive electrode via an insulating film and shield the core conductive layer from the influence of the charges of the surface protective layer.

[Action]

According to the configuration of the present invention, a plurality of backbone conductive layers are provided on the light-receiving surface of the semiconductor substrate without a position extraction electrode that blocks incident light and connected to the branched conductive layer formed on the light-receiving surface. The light-receiving surface is apparently divided into a plurality of light-receiving areas.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 of the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

The detailed configuration of the apparatus of the embodiment of the present invention will be described with reference to the plan view of FIG. 1 and the sectional view taken along the line AA.

For example, on the surface of a semiconductor substrate 1 made of n-type silicon having a side length of 1 to 50 mm, a basic conductive layer 3 in which p-type impurities are implanted to about 1 × 10 ¹³ to 10 ¹⁴ cm ⁻² is 0.5 to 1.0 μm. Is formed to a depth of about 5 μm, and the branched conductive layer 4 is 5 μm by the same process.
It is formed at a pitch of about 0.5 to 1 μm in depth.
Ohmic contact regions 6a, 6 in which p-type impurities are implanted at about 1 × 10 ¹⁸ to 10 ¹⁹ cm ^-2 between both ends of the incident surface and between them.
b, 6t _{1 to} 6t _n are formed, and these are the above-mentioned basic conductive layers 3
Connected with. On top of these, for example, thermally oxidized SiO ₂
Is formed on the ohmic contact regions 6a, 6b, 6t _{1 to} 6t _n , and the position signal electrodes 2a, 2b, 2t _{1 to} 2t _{n made of} , for example, aluminum are formed through the openings of the insulating film 7 on the ohmic contact regions 6a, 6b, 6t _{1 to} 6t _n.
Ohmic contact with is taken.

On the other hand, the shield film 5 made of aluminum, for example, covers the basic conductive layer 3 and is grounded via the wire 9G. The shield film 5 also has a light blocking effect for reducing the influence of ambient light. Then, a surface protective layer 8 made of, for example, an epoxy resin is applied and formed on these, and the wires 9a, 9b, 9t _{1 to} 9t _n , 9G are connected to the position signal electrodes 2a, 2b through the openings (not shown). , 2t _{1 to} 2t _n and the shield film 5 are bonded. An ohmic contact layer 10 containing, for example, about 1 × 10 ¹⁹ to 10 ²⁰ cm ⁻² of n-type impurities is formed on the back surface side of the semiconductor substrate 1, and a back surface electrode is formed on this surface.
11 is provided in ohmic contact.

Next, the operation of the apparatus of the above embodiment 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 transferred to the ohmic contact layer 10
And the back surface electrode 11 side, and holes are p-type branch conductive layer 4
Flow into. Then, the photocurrent due to the holes flows to the core conductive layer 3 through the branch conductive layer 4, and, for example, when the extraction position of the photocurrent is set to the position signal electrodes 2a and 2b, the position from the inflow point of the core conductive layer 3 is set. It is divided by the resistance ratio according to the ratio of the distances to the signal electrodes 2a and 2b.

When the infrared spot exists in the section between the position signal electrodes 2t ₁ and 2t ₂ , the extraction position of the photocurrent flow is set to the position signal electrode.
If 2t ₁ and 2t ₂ are set and the obtained photocurrents are I ₁ and I ₂ , the analog calculation output (I ₁ −I ₂ ) / (I ₁ + I ₂ ) will be the incident position of the infrared spot in the above section. Will correspond. Therefore, the position detection resolution can be improved by increasing the number (n) of position signal electrodes connected to the basic conductive layer 3 and decreasing the length of each section.

Here, since the shield film 5 covering the core conductive layer 3 is provided at the end of the incident surface, the ambient light may be blocked even when aluminum or the like is used as the material of the shield film 5. However, the incident light of the signal component focused on the light receiving surface is not blocked. Therefore, the light receiving sensitivity does not decrease. Further, even when the surface protective layer 8 has an electric charge such as Na ⁺ , the basic conductive layer 3 is shielded by the shield film 5, so that the resistance value does not change. Therefore, the resistance division accuracy of the photocurrent is made with high accuracy, and the detection sensitivity can be improved. If the resistance of the core conductive layer 3 changes due to the presence of the shield film 5, the position detection itself cannot be performed accurately.
It is desirable that the impurity concentration of is about 1 × 10 ¹³ cm ^-2 or more.

FIG. 2 is a block diagram of an analog arithmetic circuit including a position signal electrode selection switch and an A / D converter.

In the figure, the position signal electrode selection circuit SW is provided on the semiconductor substrate of FIG. 1, which is composed of the element switches S _A and S _A1 .
It has S _An , S _B , S _B1 and S _{B1 to} S _Bn . One end of each of the element switches S _A , S _{A1 to} S _An is connected to the position signal electrode 2 respectively.
a, 2t _{1 to} 2t _n , the other ends are short-circuited to each other, and the signal photocurrent I _A is taken out from there. Element switch S
One end of each of _B and S _{B1 to} S _Bn has position signal electrodes 2b and 2t _{1 to} 2t, respectively.
_n and the other ends are short-circuited to each other, from which the signal photocurrent I _B is taken out. Then, the signal light currents I _A , I
_B is a divider 30 via amplifiers B ₁ and B ₂ and subtractors A _{1 and} A _2.
And is A / D converted by the output A / D converter 31.

Next, the operation of the above circuit will be described.

First, the position signal electrodes 2a and 2b are first selected, and the element switches S _A and S _B in the position signal electrode selection circuit SW are turned on,
Set the other element switches to the OFF state. At this time, the obtained photocurrents I _A and I _B are amplified by the amplifiers B ₁ and B ₂ , and the subtractor A 1
The _{1 (I} A -I _B) is calculated by the adder _{A 2 (I A + I B} ) is calculated. The two signals at the analog calculator 30 _{(I A -I B) / (} I A + I B) is calculated, the digital signal _{X D} The output voltage is A / D converter 31
Is converted to.

The digital signal X _D are in correspondence with the position of the infrared spot light incident on the incident surface of the position detection semiconductor device.
Therefore, it is possible to select control position signal electrode selection circuit SW by using a digital signal X _D. In FIG. 2, from the digital signal X _D , the infrared spot light shows the position signal electrodes 2t ₁ and 2t ₂
It is determined that the light is incident on the section of, the element switches S _A1 and S _B1 in the position signal electrode selection circuit SW are turned on, and the other switches are controlled to be turned off.

Although the switches of the position signal electrode selection circuit are shown as external circuits in FIG. 2, these element switches S _A , S _{A1 to} S _An and S _{B1 to} S _Bn , S _B are analog switch circuits in the position detecting semiconductor device. It is desirable to integrate and output the signal photocurrent from the position signal electrode in a desired section by a selection signal from the outside.

FIG. 3 shows an embodiment in which the length of each divided section is short on the left side and long on the right side. As shown in the figure, a plurality of branch conductive layers 4 are formed on the light receiving surface of the semiconductor substrate 1 at equal intervals, and the position signal electrodes 2a, 2b, 2t ₁ are formed on the main conductive layer (not shown).
~ 2t ₁₀ is connected. As shown in the figure, by arranging the position signal electrodes 2t _{1 to} 2t ₁₀ in two rows or more in the vertical direction of the figure, the size of the position signal electrodes 2t _{1 to} 2t _n is limited. Without, a narrow position detection section can be created. This is suitable for use when the required resolution differs depending on the incident position.

The present invention is not limited to the above-mentioned embodiments and modified examples, and various modes are possible.

For example, the material concentration of the semiconductor substrate 1 and the like, and the impurity concentrations of the basic conductive layer 3 and the branched conductive layer 4 are not limited to those illustrated. The basic conductive layer 3 can also be realized by depositing polysilicon on the surface of the semiconductor substrate 1 or forming a metal thin film of SnO ₂ or the like. Then, if the branch conductive layer 4 is connected to the basic conductive layer 3 formed of the polysilicon film or the metal thin film, the photocurrent is resistance-divided as in the embodiment. Further, the light receiving surface is not limited to the rectangular shape, and the branched conductive layers are not limited to those provided at equal intervals.

〔The invention's effect〕

As described above in detail, according to the present invention, the core conductive layer connected to the branched conductive layer formed on the light receiving surface is not provided on the light receiving surface of the semiconductor substrate without the position extraction electrode for blocking the incident light. Since the layer is connected to the plurality of position signal electrodes at a predetermined interval, the light receiving surface is apparently divided into a plurality of light receiving areas. Therefore, it is possible to make the position resolution high and the detection sensitivity high and stable.

[Brief description of drawings]

1 is a plan view and a sectional view of a position detecting semiconductor device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a signal processing circuit, and FIG. 3 is a plan view of a modification. 1 ... Semiconductor substrate, 2a, 2b, 2t _{1 to} 2t _n ...... Position signal electrode, 3 ... Basic conductive layer, 4 ... Branched conductive layer, 5 ... Shield film, 6a, 6b, 6t _{1 to} 6t _n ... Ohmic contact region, 7 ... Insulating film, 8 ... Surface protective layer, 9a, 9b, 9t _{1 to} 9t
_n , 9G ... Wire, 10 ... Ohmic contact layer, 11
...... Back electrode, 30 …… Division circuit, 31 …… A / D converter.

Front Page Continuation (72) Inventor Akira Kurahashi 1126, Nomachi, Hamamatsu, Shizuoka Prefecture 1126, Hamamatsu Photonics Co., Ltd. (72) Inventor Hitoshi Tanaka, 1126, Nomachi, Hamamatsu City, Shizuoka Prefecture, Hamamatsu Photonics Co., Ltd. (72) Inventor Masanori Idezawa 2-1, Hirosawa Hirosawa, Wako-shi, Saitama RIKEN

Claims (4)

[Claims] 1. A semiconductor substrate of one conductivity type and a semiconductor substrate which is formed on one surface of the semiconductor substrate and which is formed along an incident surface on which light to be detected is incident and which resists a photocurrent generated by the incident light. A basic electroconductive layer having a resistance that can be divided, a plurality of branched electroconductive layers formed so as to extend from the basic electroconductive layer to the incident surface, and fixed intervals or set according to a required positional resolution. A position detecting semiconductor device, comprising: three or more position signal electrodes formed on the semiconductor substrate, the position signal electrodes being connected to the core conductive layer at predetermined intervals. 2. A semiconductor substrate of one conductivity type and a semiconductor substrate which is formed on one surface of the semiconductor substrate and which is formed along an incident surface on which light to be detected is incident and which resists a photocurrent generated by the incident light. A basic conductive layer having a resistance that can be divided, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to the incident surface, and a constant interval or required position A semiconductor device for position detection, comprising: three or more position signal electrodes formed on the semiconductor substrate and connected to the core conductive layer at predetermined intervals set according to the resolution. 3. The semiconductor substrate is formed with a selection circuit that is connected to each of the three or more position signal electrodes and selects two position signal electrodes for extracting a signal photocurrent. A semiconductor device for position detection according to item 1. 4. A conductive shield film is formed on the semiconductor substrate, the conductive shield film covering the core conductive layer via an insulating film and shielding the core conductive layer from the influence of charges of the surface protective layer. The semiconductor device for position detection and detection according to claim 1.