JPS59154082A - Photosensor - Google Patents

Abstract

PURPOSE:To obtain the titled device which makes an incident light efficiently reach a P-I film interface and can obtain an output signal efficiently by a method wherein a transparent insulation layer having partial defect parts and a layer composed by forming boron doped layers at said parts are provided between a clear electrode and an amorphous Si layer. CONSTITUTION:The partial defect parts 3a-3p are formed by etching the transparent insulation layer 7 by photolithography in lattice form. A boron doped amorphous Si film is adhered over the entire surfaces at these defect parts by a glow discharging method, and thereafter said film is processed by photolithography etching. Thereby, the amount of light reaching the I type layer 4 can be increased by reducing the amount of light absorption due to the boron doped layer. As a result, the pair of electrons-holes generated in the I type layer 4 by the light passing through the insulation layer 7 makes the resistance value of said layer 4 reduce and transfers to the P-I film interface, thus enabling to largely vary the depletion layer width at said interface in suitable manner. Thus, the photosensitivity remarkably improves, therefore high speed photo detection can be performed without necessitating an amplifier of a high gain.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a photosensor suitable for improving the photosensitivity of a PIN photodiode formed of an amorphous silicon semiconductor.

(Prior Art) Conventionally, there has been a photo sensor of this type as shown in FIG. FIG. 1(a) is a vertical sectional view of the main part of the optical sensor, and FIG.
b) is a cross-sectional view taken along the line X-X of FIG. A transparent electrode layer formed by depositing by beam evaporation and then etching in a predetermined pattern, such as ITO (N2).
o3+ Sn 02 ), etc. are used. 3 is a boron (B) doped amorphous silicon layer (P-type layer) formed on the transparent electrode layer 2; 4 is a boron (B)-doped amorphous silicon layer (P-type layer) formed on the transparent insulating substrate 1 and the B-doped amorphous silicon layer (P-type layer); A non-doped amorphous silicon layer (■
(type layer), 5 is a P-doped amorphous silicon layer (N-type layer) formed on the non-doped amorphous silicon layer (■-type layer) 4 in the shape of its upper surface; 6 is the transparent insulating substrate 1; and a metal electrode layer (upper electrode) formed in two stages on the P-doped amorphous silicon layer (N-type layer).

In the case of a conventional optical sensor with the above configuration, in the manufacturing process, first a transparent electrode layer 2 is formed as a lower electrode on a transparent insulating substrate 1 by electron beam evaporation, and then a transparent electrode layer 2 is deposited on the transparent insulating substrate 1 as a lower electrode. Then, a B-doped amorphous silicon layer 3 (P-type layer) is doped with boron (B) 7) as an impurity of about several hundred ppm to a thickness of about several 100A, and
Further, a non-doped amorphous silicon semiconductor layer 4 (I-type layer) is formed on the P-type layer 3, and a layer of several layers is further formed on the I-type layer 4.
An amorphous silicon layer 5 (N-type layer) with a thickness of about several hundred times is deposited by doping with phosphorus (P) as an impurity of about 100 pp, and finally, on the N-type layer 5, All,
By depositing an electrode film made of a metal such as NiCr-Au as the upper electrode 6, a structure of lower electrode (ITO layer) 2-P type layer 3-I type layer 4-N type layer 5-upper electrode 6 is formed. An optical sensor having the following is completed. Note that the P-type layer 3
, the ■-type layer 4 and the N-type layer 5 each use silane (SiH4) as a main component gas, and are formed continuously or separately by a glow discharge method.

Next, the operation will be explained.

As shown by the arrow in FIG. 1(a), this optical sensor changes the PIN layer 3.4 in proportion to the intensity of incident light from the substrate 1 side.
The width of the depletion layer at the outer interface of the PI film formed between the P-type layer 3 and the I-type layer 4 in No. 5 changes, and by applying a reverse bias to this, the change is detected as an output signal. It is something. However, in the conventional technology as described above, the incident light is transmitted to the B-doped amorphous silicon layer (P-type layer) 3.
Since it is absorbed and weakened when passing through the 0B doping layer, the amount of light that reaches the outer interface of the PI film and contributes to the change in the depletion layer width is a very small amount of the incident light. There is a problem in that the output signal of this optical sensor is too weak to be detected. In order to solve these problems, an amplifier with high gain is generally required, but increasing the gain of the amplifier will narrow the frequency band, making high-speed optical detection impossible. There were technical shortcomings.

(Objective of the Invention) The present invention has been made in order to eliminate the above-mentioned drawbacks, and it is an object of the present invention to provide an optical sensor that allows incident light to efficiently reach the outer interface of the PI film and efficiently obtains an output signal. It is an object.

(Example) Two examples of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 shows a first embodiment of the present invention, in which FIG. 2(a) is a plan view of the optical sensor and FIG. 2(b) is a plan view of the optical sensor.
) is a vertical sectional view taken along Y-Y@.

In the figure, 7 is SiH* and N20, 5iHa and NH3
A transparent insulating layer made of Sin or SiN is formed by depositing a mixed gas containing the main component '5 by a glow discharge method, and this layer is photolithographically etched in a lattice pattern to form partial defects 3a to 3p. do. And these defective parts 3a
3P, a boron B-doped amorphous silicon film is deposited on the entire surface by a glow discharge method, and then processed by photolithography. In this case, a B-doped amorphous silicon layer (P
A mold layer) is selectively formed.

According to the first embodiment of the present invention constructed as described above, the partial defect parts 3a to 3p having the B-doped layer are arranged in a lattice-like arrangement with minute intervals, as shown in FIG. It is possible to increase the amount of light that reaches the mold layer 4 by reducing the amount of light absorbed by the B-doped layer, and as a result, the amount of light that has passed through the transparent insulating layer 7 is reduced to the above-mentioned I type. The electron-hole pairs generated in the layer 4 reduce the resistance value of the mold layer 4, and also move the outer interface of the PI film, causing the P
Since the width of the depletion layer at the outer interface of the I film can be suitably and largely changed, the output signal of the present optical sensor can be made significantly larger than that of the conventional one.

Next, FIG. 3 shows a second embodiment of the present invention, in which FIG. 3(a) is a plan view of the optical sensor, and FIG. It is a two-line vertical cross-sectional view.

In the figure, 8a to 8d are partial defective portions of the transparent insulating layer 7 having a B-doped layer in the form of strips at minute intervals.

According to the second embodiment of the present invention configured as described above, as shown in FIG. It is possible to bring about the same effect as the embodiment. That is, by applying a reverse path of 1° to the PIN structure, the variation in the width of the depletion layer, which changes depending on the intensity of the incident light, can be detected as an output signal to a greater extent than in the conventional case.

Note that the technique of providing a B-doped layer in the partially defective portion of the transparent insulating layer 70 disclosed in the first and second embodiments of the present invention involves removing the excess portion by plasma etching using a CF4+02 (5%) mixed gas. by doing,
B doping ff13a to 3 is easily applied to the partial defect portion.
p, 8a to 8d', and there is no particular problem in manufacturing.

(Effects of the Invention) As described above, according to the present invention, in the PIN structure, B is present between the transparent electrode layer and the non-doped amorphous silicon layer (technical layer), and in the partially defective portion of the transparent insulating layer. The partial formation of a doped amorphous silicon layer (P-type layer) has the advantage of significantly improving photosensitivity, making it possible to perform high-speed photodetection without the need for a high-gain amplifier. Therefore, it has a great practical effect as a high-speed optical sensor, and because it is easy to manufacture, it can be used as a large line sensor.

[Brief explanation of the drawing]

FIG. 1(a) is a vertical cross-sectional view of the main part of a conventional optical sensor,
- Figure 1(b) is a cross-sectional view taken along the line X-X of Figure 1(a), Figure 2(a) is a plan view of the optical sensor according to the first embodiment of the present invention, and Figure Φ) is a plan view of the optical sensor according to the first embodiment of the present invention. 2(a) is a vertical sectional view taken along the Y-Y line, FIG. 3(a) is a plan view of the optical sensor according to the second embodiment of the present invention, and FIG. - It is a Z line longitudinal cross-sectional view. 1... Transparent insulating substrate, 2... Transparent electrode layer (lower electrode), 3... B-doped amorphous silicon layer (P-type layer)
, 3a to 3p, 8a to 8d... Partial defects of the transparent insulating layer on which the B-doped amorphous silicon layer (P-type layer) is formed, 4... Non-doped amorphous silicon layer (N-type layer) layer), 5...P-doped amorphous silicon layer (N-type layer)
, 6... Metal electrode layer (upper electrode), 7... Transparent insulating layer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Eggplant: 1 Figure 2 χ Happy Jχ Figure

Claims (1)

[Claims] A transparent electrode layer and boron (B) formed on the transparent electrode layer.
'L-doped amorphous silicon layer, non-doped amorphous silicon layer formed on the B-doped amorphous silicon layer, and phosphorus CP formed on the amorphous silicon layer.
) A photosensor comprising at least a doped amorphous silicon layer and a metal electrode layer formed on the P-doped amorphous silicon layer; An optical sensor characterized in that a layer comprising a doped layer is provided between the transparent electrode layer and the amorphous silicon layer.