JPS5845191B2 - photo diode array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Photodiode arrays are used in photocopy transmission and the like to improve the reading speed.

In other words, a large number of photodiodes are arranged in a row (2,
The original image is moved perpendicular to the direction in which it is arranged, and signals are extracted from each diode in parallel.To obtain the resolution necessary for reading newspapers, three to five photodiodes are arranged in a width of one square. There is a need to.

Furthermore, when forming multiple photodiodes on the same semiconductor substrate, it is necessary to provide an interval of about 20 μm between each photodiode due to the diffusion length of excited carriers.
One photodiode has a dog size of about 180 μm x 180 μm.

Moreover, since the original picture is generally A4 or B4 in size, the total length of the photodiode array is 200 to 2601 fL.
However, since a single-crystal semiconductor substrate such as silicon is a disk with a diameter of about 50 mm, if this is cut into strips and used, a photodiode array is formed on each of the strips. It is necessary to connect the strip-shaped substrates in a straight line.

However, if the edges of a strip-shaped semiconductor substrate are cut, polished, and butted, there will be a gap of 100% between them due to the accuracy of mechanical processing.
It is unavoidable that a gap on the order of μm will occur.

Since this gap is much larger than the 20 μm gap between photodiodes formed on the same substrate, the resolution decreases at the joint between the substrates.

Therefore, conventionally, at the joint of the substrates, another photodiode is placed at a position away from the photodiode array on the substrate, and a certain delay is given to the output, so that the output of the photodiodes on the connected substrates is A device was used to send out the same.

However, the structure of the photodiode array is complicated, making it complicated to manufacture (this requires a delay circuit, etc., so the circuit configuration is also complicated, and there are disadvantages such as not being able to obtain sufficient resolution due to errors in delay time). Ta.

The present invention therefore provides a photodiode array that does not have these drawbacks.

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a vertical sectional view thereof, and FIG. 3 is an enlarged view of a part of FIG. 1.

In this way, the band-shaped silicon single crystal substrates 2 and 3 are adhered to the base 1 with an epoxy adhesive, and the adhesive 4 is also applied to the joint where the ends of the substrates 2 and 3 are butted together. .

The substrates 2 and 3 are, for example, n-type conductive semiconductors, and a p-type impurity diffusion layer 5 is formed on their surfaces, and both sides are removed by etching, leaving a strip in the center, and a 20 μm thick layer is formed on the remaining strip. Insert the width of 180
A square photodiode 6.6 having a size of μm×180 μm is formed.

That is, photodiodes 6. are placed on the strip-shaped substrates 2 and 3.
6... are arranged in a line with a density of 5 pieces per space.

Further, a metal electrode pad 7 is provided on the diffusion layer 5 of each diode, and metal terminal layers 9, 9 are provided on -L of the insulator layer 8 attached to both sides of the photodiode row.
For example, a gold wire 10.10 with a diameter of 25μ is formed.
. . . to connect each electrode pad 7 and terminal layer 9, respectively.

Therefore, when the boards 2 and 3 are grounded, the terminal layers 9, 9...
The output of each photodiode 6.6 can be obtained from .

The semiconductor substrates 2 and 3 described above have their ends connected to diodes 6.
6... are cut at an angle a of, for example, 45 degrees with respect to the arrangement direction, and the cut end surfaces are butted.

In this case, from the viewpoint of mechanical finishing accuracy of the end face,
A gap of about 100 μm must be provided between the abutted end faces.

When the end surfaces c and d of the substrates 2 and 3 are placed opposite each other with a predetermined gap, the diode rows of the substrate 2 and the diode rows of the substrate 3 are continuously arranged at a predetermined pitch, forming a series of diode arrays. This is how you configure it.

In other words, the figure shows that the diodes 6□ and 63 at the ends of the substrates 2 and 3 are cut into triangular shapes and combined to form one photodiode.In such a case, the two diodes mentioned above are connected to one terminal layer by connecting them with a gold wire 10.

However, if only a portion of the diodes at the ends of substrates 2 and 3 are removed, as shown by the chain lines in Figure 3, this is not necessary and each can be connected to a different terminal layer as an independent diode. do.

As in the above embodiments, the present invention provides an edge portion of a strip-shaped semiconductor substrate,
It is cut diagonally and butted together.

Therefore, in the embodiment described, the photodiodes 62 and 63 at the ends of the substrates 2 and 3 overlap by a distance e in the running direction perpendicular to the diode array.

In other words, since there is no gap at all between the connecting parts of the substrates 2 and 3, there is no drawback that the resolution in this part is degraded.Furthermore, since all the photodiodes are arranged substantially in a straight line, the delay circuit is not required. Therefore, there is no need to compensate for differences in signal generation times, and the structure of the photodiode array is simple, making it easy to manufacture.

In addition, in the case of the above embodiment, one) first
・The light-receiving area of the diode is reduced to about one-third.

However, when converting an original image into a black and white binary signal, such as when copying and transmitting data, the output of the photodiode is added to a slicer to obtain mark and space signals, so by setting the slice level relatively low, etc. will not cause any problems.

[Brief explanation of the drawing]

FIG. 1 is a plan view of this sensible embodiment, FIG. 2 is a vertical sectional view of the photodiode array of FIG. 1, and FIG. 3 is an enlarged view of a part of FIG. 1. In the figure, 1 is a base, 2 and 3 are silicon single crystal semiconductor substrates, 4 is an adhesive, 5 is an impurity diffusion layer, 6 is a photodiode, 7 is an electrode pad, 8 is an insulator layer, and 9 is a metal terminal. Layer 10 is gold wire.

Claims (1)

[Claims] 1. The ends of a plurality of strip-shaped semiconductor substrates each having a plurality of photodiodes formed in a row are cut diagonally in the direction in which the photodiodes are arranged.
A photodiode array characterized in that a desired length is obtained by butting and connecting the ends of each semiconductor substrate.