JPS6057716B2 - semiconductor optical position detector - Google Patents

Description

[Detailed Description of the Invention] A semiconductor optical position detector is a device that outputs a current corresponding to the incident point on the light receiving surface from a plurality of electrodes when a point of light is incident on an arbitrary point on the light receiving surface. It is.

For example, to explain a semiconductor optical position detector whose plan view is shown in FIG. 1 and a cross-sectional view taken along line A-A in FIG. )
, 2 is a p conductivity type layer (hereinafter p conductivity type layer) formed on one surface of the wafer.
3 is an n* layer for providing an electrode, and 4 and 5 are electrodes connected to the p layer, which extend parallel to each other and perpendicular to the plane of the paper.

6 is an electrode connected to the n* layer 3, and 7 is a light receiving surface.

For convenience of explanation, an electrode 4 is placed on the light receiving surface 7 in FIG.
, the origin is the center of the square with 5 as the two sides 0) 2 with no electrode
Define the coordinates of the X axis parallel to the side and the Y axis parallel to the electrode.

Then, a reverse bias voltage is applied in advance from electrodes 4 and 5 and electrode 3 to the p1n junction. When point-like light enters an arbitrary point Q (not shown) on the light-receiving surface 7, a photocurrent flows.
The current is divided into respective currents in inverse proportion to the resistance and the resistance of the p layer 2 between the point Q and the electrode 5. The position of point Q is known from the ratio of this current. Therefore, when the distance between point Q and each electrode 4 and 5 is proportional to the resistance, the distance between electrodes 4 and 5 is 2L)
If the X coordinate of point Q (!) is set as X, then 1, -2 (
1-[) (1) Emitted from the electrode 5.

Therefore, since the coordinates of Q are , the position coordinates can be determined from the difference in output current.

However, when the lengths of the electrodes 4 and 5 are finite, even if the specific resistance and layer thickness of the p-layer 2 are uniform, 14,I, deviates from the linearity of equations (1) and (2). , and the current also depends on the Y coordinate. That is, the difference 13 in the output current is not proportional to the position coordinate X and also depends on the Y coordinate. From this phenomenon, when a point of light moves on a light-receiving surface on a straight line with a constant X, and the output signal obtained is drawn on a recorder, a curve is reproduced. This deviation from linearity and the dependence of the Y coordinate can be seen, for example, in one-position sensitive light detectors with high linearity (IEE Journal of Solid State Circuits, No. 13).
Vol. 3, No. 3, pp. 392-399), the ratio ρ2/ρ1 of the specific resistance ρ1 of the p-layer in a square part with the electrodes 4 and 5 as two sides and the specific resistance ρ2 of the p-type layer surrounding the part is described. It has been shown that it can be obtained as a function, but in short, ρ2/ρ1 is 20~
It is stated that if it is 30 or more, it can be ignored. Therefore, conventionally, as shown in FIGS. 8 and 9, the peripheries 8 and 9 of the square portion near the p-n junction formed by the p layer 2 and the n layer 1 are removed by chemical etching. This was achieved by making the resistance of the surrounding area virtually infinite.

However, after chemical etching, this semiconductor optical position detector
The p-n junction is exposed, and the current flowing through the electrodes 4 and 5 due to the leakage current flowing through the exposed portion is the leakage current J, and 14, 15, and 14-15 are linear. deviate from

Moreover, there is no effective means to protect this p-n junction.
The present invention is a semiconductor optical position detector that eliminates the above-mentioned drawbacks.

An embodiment of the present invention will be explained using a semiconductor optical position detector shown in a plan view in FIG. 4 and a sectional view taken along line B--B in FIG.

That is, the square portion 13 on the first surface of the n-type semiconductor wafer
A p-layer 12 is formed on the p-layer 12, and this portion is used as a light-receiving surface. A high concentration p+ region 1 is formed along two opposing sides of the square 13 of the p layer.
4, 15 are formed, and metal electrodes 17, 1 are formed on the surface of the p+ region.
8 is provided as an output electrode, a transparent insulating layer 16 of at least p-n junction is formed on the first surface excluding the electrode, an n+ layer is formed on the second surface, and an electrode 20 is formed on a part of the n+ layer. is provided. Note that the remainder of the n-type semiconductor wafer is the Na layer 11.
Therefore, the two sides 21 and 22 of the square 13 of the p layer 12 that do not have electrodes
Since a p-n junction is formed, the photocurrent is on the side 21.
, 22 to the outer n region.

In other words, the same effect as in the case where the resistivity ρ2 outside the square 13 described above becomes substantially infinite can be obtained. In addition, since the pn junction appearing on the first surface is protected by the transparent insulating layer 16, no leakage current occurs in this portion.
As a result, the device of the present invention uses the center of the light-receiving surface as the "origin",
If the x-axis is parallel to the two sides 21 and 22 without electrodes, and the Y-axis is parallel to the electrodes, when a point of light is incident on point Q (X, y) on the light receiving surface, each electrode 17 and 18 is transmitted, and an incident position coordinate signal proportional to the X coordinate and unaffected by the Y coordinate is obtained.

Another conventional example of a semiconductor optical position detector is to form a p layer on the first surface of an n-type semiconductor wafer, provide an electrode on the p layer, form an n+ layer on the second surface, and provide a pair of electrodes on the n+ layer. There is a device in which parallel electrodes are provided, and when point-like light is incident, the incident position can be determined by the ratio of the photocurrents that are shunted to the two electrodes of the n+ layer according to the point of incidence.

An embodiment of the present invention applied to such a conventional example will be explained with reference to the sectional view of FIG. 6.

That is, a p layer 32 is formed on the first surface of an n-type semiconductor wafer to provide an electrode 33, and an n+ layer 3 is formed on a square portion on the second surface.
4, the resistivity of the n+ layer 34 is several tenths of the resistivity of the wafer, and electrodes 3 parallel to two opposing sides of the square are formed.
5 and 36, an incident position signal proportional to the X coordinate and unaffected by the Y coordinate can be obtained.

Note that the remaining portion of the n-type semiconductor wafer becomes an n-type layer 31. Further, other conventional examples of two-dimensional semiconductor optical position detectors include n
A p layer is formed on the first surface of a type semiconductor wafer, an n+ layer is formed on the second surface, a pair of electrodes parallel to the first surface are provided, and a pair of electrodes parallel to the above electrodes are provided on the second surface at right angles. By providing a square with a pair of parallel electrodes on the first surface, the x-coordinate signal is transmitted from the electrode on the first surface, and the Y-coordinate signal is transmitted from the electrode on the second surface.
Some obtain coordinate signals.

An embodiment of the present invention applied to such a two-dimensional semiconductor optical position detector will be described with reference to FIGS. 7, 8, and 9.

Figure 7 is a plan view, Figure 8 is a sectional view taken along line CC in Figure 6, and Figure 9 is a cross-sectional view taken along line C-C in Figure 9.
The figure is a sectional view taken along the line DD in FIG. 6. A p-layer 42 is formed on a square 50 portion of the first surface of the n-type semiconductor wafer to serve as a light-receiving surface.

P+ regions 43 and 44 with high impurity concentration are formed along two sides 51 and 52 of square 50 of the p layer 42, and metal electrodes 46 and 47 are provided on the surfaces of the p+ regions to serve as output electrodes. Furthermore, an insulating layer 4 is formed on at least the exposed part of the p-n junction surface on the first surface.
form 5. A square 50 of the p layer 42 on the first surface on the second surface.
An n+ layer 48 is formed at exactly the same position, and further n+ layers 61 and 62 are formed along the two sides 53 and 54 of the square 50 on which no electrodes are provided in the p layer 42 on the first surface of the n+ layer 48. , metal electrodes 63 and 64 are provided on the expanded portion.

The specific resistance of the n+ layer needs to be several tenths or less of the specific resistance of the n-type semiconductor wafer. If a reverse bias voltage is applied in advance to the p-n junction surface from each electrode of this two-dimensional semiconductor optical position detector, when a point of light is incident on an arbitrary point Q on the light receiving surface, the point QO) A photocurrent is generated at the p-n junction, and current flows through the p-layer and n-layer.

The current flowing through the p-layer is divided in inverse proportion to the resistance between point Q and electrode 46 and the resistance between point Q and electrode 47. Similarly, the current flowing through the n-layer is divided in inverse proportion to the resistance between point Q and electrode 63 and the resistance between point Q and electrode 64. Then, the current flowing through the p layer is caused by the p-n junction surface at the side 53 of the square 50,
The current flowing through the n-layer without flowing beyond the square 54 hardly flows beyond the sides 51 and 52 of the square 50 due to the large resistivity of the outer n-layer. Therefore square 5
0 is the origin, and the x-axis is parallel to side 53 and the Y-axis is parallel to side 51. When a point of light is incident on point Q (X, y) on the light receiving surface, the electrode on the first surface Since the current is sent from the electrode 46 to the electrode 52, and from the electrode 63 to the electrode 64 on the second surface, by taking the difference in the output currents, a two-dimensional signal of an accurate incident position can be obtained.

The above explanation is based on the p layer 12 (first example), the n+ layer 34 (second example),
Example), the case where the p layer 42 and the n+ layer 48 (third example) are square has been described, but the present invention is completely applicable even if they are rectangular.

Further, an insulating layer may be formed on the surface of the n+ layer.

In addition, the above explanation is based on the n-type semiconductor wafer having a second light-receiving surface.
Although the case where the p+ layer is formed along the sides of the light-receiving surface has been described, the present invention applies to the case where the n layer, p+ layer, and n+ layer are formed on the p-type semiconductor wafer, respectively. Examples and P. (This also holds true for a semiconductor optical position detector in which 5n is reversed.Finally, the manufacturing method and materials for the device of the present invention will be briefly described.

For example, it is best to use n-type silicon as the n-type semiconductor wafer.

The transparent insulating layer is a silicon oxide coating layer formed by a thermal oxidation method in which the wafer is placed in a high temperature oxygen atmosphere.

The p-layer and n+ layer can be formed by ion implantation through the silicon oxide overlayer.

The p+ layer can be formed by removing a desired portion of the silicon oxide covering layer by photo-etching and then diffusing impurities.

As described above, the present invention forms a square or rectangular second conductivity type layer on the first surface of a first conductivity type semiconductor wafer, provides electrodes on two opposing sides of the second conductivity type layer, and A semiconductor optical position detector characterized in that an electrode is formed on the second surface, with the center of the square or rectangle as the origin,
When the direction toward the electrode is taken as the X axis, when point-like light is incident on the square or rectangular portion, an X-coordinate position signal with very good linearity can be obtained.

The present invention also provides a semiconductor wafer with a second conductivity type layer formed on the first surface of the semiconductor wafer except for the vicinity of the wafer periphery, an electrode provided on the second conductivity type layer, and a square or a semiconductor optical position detector characterized by forming a rectangular high concentration first conductivity type layer and providing electrodes on two opposing sides of the high concentration first conductivity type layer, the square or rectangular When the center is the origin and the direction toward the electrode is the X axis,
When point-like light is incident on the square portion, an X-coordinate position signal with very good linearity can be obtained.
The present invention also provides a method for forming a square or rectangular second conductivity type layer on the first surface of the first conductivity type semiconductor wafer, providing electrodes on two opposing sides of the second conductivity type layer, and forming a second conductivity type layer on the first surface of the first conductivity type semiconductor wafer. A high concentration first conductivity type layer is formed in the same part as the second conductivity type layer above, and a side opposite to the high concentration first conductivity type layer is different from the side of the electrode provided on the second conductivity type layer. A semiconductor two-dimensional optical position detector characterized in that electrodes are provided on two sides of the square or rectangle. When point-like light is incident on the area, an X, Y coordinate position signal with very good linearity can be obtained.

The device of the present invention can detect not only point-like light but also charged particles such as electrons, ions, and X-rays, and electromagnetic waves.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a semiconductor optical position detector for explaining the principle, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. 3 is a sectional view of a semiconductor optical position detector for explaining a conventional example. Fig. 4 is a plan view for explaining an embodiment of the present invention, and Fig. 5 is Fig. 4B-
6 is a sectional view for explaining the second embodiment of the present invention, FIG. 7 is a plan view for explaining the third embodiment of the present invention, and FIG. 8 is a sectional view for explaining the third embodiment of the present invention. Figure 9 is a sectional view taken along line C-C in Figure 7, Figure 10 is a bottom view of the semiconductor optical position detector shown in Figure 7, and the positions corresponding to Figure 7 have the same reference numerals. is attached.

Claims (1)

[Claims] 1. A square or rectangular second conductivity type layer is formed on the first surface of a first conductivity type semiconductor wafer, a bond is formed around the square or rectangle, and a second conductivity type layer is formed on the first surface of the first conductivity type semiconductor wafer. A semiconductor optical position detector characterized in that electrodes are provided on two opposing sides, and the electrodes are formed on the second surface of the wafer. 2. A second conductivity type layer is formed on the first surface of the first conductivity type semiconductor wafer except for the vicinity of the wafer periphery, an electrode is provided on the second conductivity type layer, and a square or rectangular shape is formed on the second surface of the wafer. A highly concentrated layer of the first conductivity type is formed to form a junction around the square or rectangle, and electrodes are provided on two opposing sides of the highly concentrated layer of the first conductivity type. Semiconductor optical position detector. 3. A square or rectangular second conductivity type layer is formed on the first surface of the first conductivity type semiconductor wafer, and a bond is formed around the square or rectangle, and the opposing second conductivity type layer
An electrode is provided on the side, and a highly concentrated first conductivity type layer is formed in the same area as the second conductivity type layer on the second surface of the wafer to form a junction around the square or rectangle. A semiconductor two-dimensional optical position detector, characterized in that electrodes are provided on two opposing sides of the high concentration first conductivity type layer, which is different from the second conductivity type layer.