JPH06105163B2 - Semiconductor image position detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor image position detecting element (hereinafter, referred to as “PSD”) for detecting the position of a bright spot image, and more particularly, to a single basic resistor. The present invention relates to a structure of a PSD having a conductor having a conductor extending in a light-sensing portion in a branch shape.

(Prior Art) In order to improve the image position detection accuracy by PSD, it is necessary to manufacture the dividing resistors accurately and stably. When this is formed as a resistance layer, it is not easy to obtain a uniform and predetermined resistance value. In order to avoid this difficulty, the dividing resistors are formed as a concentrated type in a predetermined narrow area stably and accurately,
A PSD having a structure in which this is used as a basic resistance and a conductive portion is extended from the basic resistance to the light-sensing portion in the shape of a comb tooth has been proposed. the 4th
Figure a is a conceptual diagram showing the structure of a conventional one-dimensional PSD. The dividing resistance is concentrated on the side portion of the photosensitive section D to form a basic resistance R, and the conductive extension portion t is extended from the basic resistance R to the photosensitive section D in the shape of a comb tooth. The photocurrent i generated in the conductive part of the teeth of the comb flows into the basic resistance R from the root of the teeth, propagates through the basic resistance R, and the bias layer C and the output terminals T _A , T _B
More detected. That is, if the bright spot image is at the center position, currents of the same magnitude flow in opposite directions along the basic weather R toward the output terminals T _A and T _B , respectively, and the difference between the two currents becomes zero. It indicates that the bright spot image is at the center position, and when the bright spot image is offset from the center position to one side, the difference between the two currents is positive and negative and has a magnitude corresponding to that position. Give instructions.

(Problems to be Solved by the Invention) In this conventional comb-shaped PSD, it is possible to manufacture the detecting portion extremely stably and accurately because the dividing resistors are concentrated in a predetermined narrow area and configured as a basic resistor. As the size of the half-plane bright spot image becomes smaller, the following problems occur.

If the size of the bright spot image is at least several times larger than the distance between the comb teeth, the sum of the detection currents and the image position detection signal are wavy depending on the distance between the comb teeth due to the movement of the bright spot image position. Will fluctuate. Figure 5 shows a conventional one-dimensional PSD
This is an example of a detection position signal obtained by actually measuring a bright spot image with a small size (to a distance between comb teeth).

If the width of the conductive extension of the teeth of the comb is widened in an attempt to solve this problem, the uniformity of the resistance value of the basic resistance is disturbed, and the position cannot be accurately determined.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, the width of the conductive extension formed in the light-sensing portion is made as wide as possible, and the width of the portion to be joined to the core resistance is made wider. The branches and leaves are made as narrow as possible. Furthermore, by widening the width of the conductive extension, the wavy fluctuation of the image position detection signal due to the movement of the bright spot image is reduced, and by narrowing the width of the part connected to the main resistance, the resistance value of the main resistance is made uniform. It avoids disturbing the sex at its connection. Further, in order to further reduce the wavy fluctuation of the image position detection signal, if one area of the adjacent conductive extension portions occupied by the images moving in the direction orthogonal to the extension direction of the conductive extension portions arranged in parallel decreases, the area of the other increases. The shape of the complementary conductive extension is as follows.

(Function) By making the width of the conductive extension portion in the light-sensing portion as wide as possible, the fluctuation of the detected photocurrent value is reduced even when the size of the bright spot image is reduced. Further, by making the width of the portion where the conductive extension portion is connected to the basic resistance as narrow as possible, the degree of disturbing the uniformity of the basic resistance value at the connection point becomes small.

Further, by making the shapes of the adjacent conductive extensions complementary to the occupied area of the moving bright spot image, the bright spot movement and the detected current value have a linear relationship.

(Examples) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the structure of a one-dimensional PSD constructed according to the present invention. The width of the conductive extension portion t provided on the photosensitive portion D of the semiconductor substrate is widened, and the width of the portion t ′ coupled to the basic resistance R is narrowed. As shown in the cross-sectional view of FIG. 1b, the photocurrent i flows between the conductive extension t and the bias layer C in the bright spot image portion at a current density corresponding to the luminance I. This current flows into the position where it is connected by the conductive portion t'having a narrow width of the basic resistance (in the case where the polarities are opposite, it flows out to that position).

FIGS. 2a to 2d are examples of theoretically calculated changes in the image position detection value when the width of the conductive extension portion t in the light sensing portion is changed. dx indicates the deviation of the detected image position from the theoretical value. The larger the width of the conductive extension t in the light sensitive section, the smaller the fluctuation of the image position detection value.

From this fact, in the conventional comb structure shown in FIG. 4, the detected photocurrent value fluctuates significantly due to the movement of the bright spots, whereas in the case where the width of the conductive extension portion in the photosensitive portion according to the present invention is wide. It will be appreciated that the variability will be small.

However, if the width of the conductive extension is widened in the configuration shown in FIG. 4, the rate at which the current flowing through the basic resistance flows into the conductive extension increases at the point where it joins with the basic resistance R, and The resistance value of the resistor is disturbed at that point,
This causes an image position detection error. This obstruction can be avoided according to the invention by making the width of the electrically conductive extension where it joins the basic resistance as narrow as possible.

In order to further improve the linearity of the image position detection, as shown in FIGS. 3a, 3b, and 3c, the area of one of the adjacent conductive extension portions occupied by the image moving in the direction orthogonal to the extension direction of the parallel conductive extension portions. It is preferred that the parallel conductive extensions have complementary shapes so that as the other decreases, the other area increases (see Figures 6a, b and 7a, b).

Although the configuration of the present invention has been described with respect to the one-dimensional PSD, the two-dimensional PSD may be configured by arranging the same configuration on the lower surface of the semiconductor substrate in an orthogonal relationship with the configuration of the upper surface of the semiconductor substrate instead of the bias layer.

(Effect) According to the present invention, it is possible to avoid the fluctuation of the detected photocurrent value when the bright spot image is small, and further, the complementary shape arrangement of the parallel conductive extension portions causes a difference between the detected current and the bright spot movement. Linearity is realized.

[Brief description of drawings]

FIG. 1a is a conceptual diagram of the structure of the PSD of the present invention, and FIG. 1b is a sectional view thereof. FIGS. 2a, 2b, 2c, and 2d show changes in the deviation of the image position detection characteristic from the ideal characteristic when the width of the conductive extension portion of the light sensitive portion is changed. FIGS. 3a, 3b, and 3c show examples of the shape of the conductive extension portion in the light sensing portion of the present invention. FIG. 4a is a conceptual diagram of the structure of a conventional PSD having a comb structure, and FIG. 4b is a sectional view thereof. Figure 5 shows the image position detection characteristics (measured values) obtained when the bright spot image was made small in the conventional PSD with a comb structure.
An example is shown. FIG. 6a is a functional explanatory diagram of the extension part having a complementary shape, and FIG. 6b shows its current distribution. FIG. 7a is a functional explanatory view of another extension portion having a complementary shape, and FIG. 7b shows its current distribution. T _A , T _B …… Output terminal, R …… Basic resistance t …… Conduction extension, C …… Bias layer I …… Bright spot image illuminance distribution, i …… Photocurrent dx …… Ideal detection image position Deviation from the value

Claims (3)

[Claims] 1. A plurality of wide parallel conductive extensions extending to a light sensitive area on one surface of a semiconductor substrate, a basic resistance extending away from the conductive extensions in a direction orthogonal to an extension direction of the conductive extensions, A narrow connecting conductive portion that connects each of the parallel conductive extensions to the basic resistor, output terminals connected to both ends of the basic resistor, and a conductor layer provided on the other surface of the semiconductor substrate are provided. A semiconductor image position detecting element characterized by the above. 2. A conductive layer on the other side of the semiconductor substrate, a plurality of wide parallel conductive extensions extending to a light sensitive area on the other side of the semiconductor substrate, and extending the conductive extension apart from the conductive extensions. A basic resistance extending in a direction orthogonal to the direction, a narrow conductive connecting portion that connects each of the parallel conductive extension portions to the basic resistance, and an output terminal connected to both ends of the basic resistance. 2. The semiconductor image position detecting element according to claim 1, wherein the parallel conductive extension and the basic resistance on the other surface are arranged in an orthogonal relationship with the parallel conductive extension and the basic resistance on the one surface of the semiconductor substrate. 3. A parallel conductive extension having a complementary shape such that when the area of one of the adjacent conductive extensions occupied by an image moving in a direction orthogonal to the extension direction of the parallel conductive extension decreases, the area of the other increases. The semiconductor image position detecting element according to claim 1 or 2, which the portion has.