JPS58220468A - Photodetector and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a photodetector having high density and high S/N ratio by forming a transparent conductive film as isolated into many segments on a transparent insulating substrate, and forming a recess at the isolating region between the transparent conductive films on the substrate. CONSTITUTION:A transparent electrode 22 and a resist 23 are superposed on an insulating substrate 21, a part 24 is exposed and removed, and when the electrode 22 is etched, the substrate 21 is partly etched to form a recess 25. When the substrate 1 by this configuration is employed, a light which passes vertically through a hole of a mask 5 reaches directly a transparent electrode 4, oblique incident light 8 is refracted at 9, then refracted at 10 at the recess 6 of the substrate 1, and incident to an amorphous Si 3 or reflected at 11, and the light which is incident to the adjacent electrode 4 is lowered, and S/N ratio is improved. Further, the stray light 12 in the substrate 1 is refracted at 13, 14 in the recess 6 and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film photodetector, and more particularly to a photodetector in which light is incident from a transparent insulating substrate side.

An object of the present invention is to provide a photodetector that is capable of high-density light detection per unit area and that detects light incident from the transparent substrate side with a high signal/noise (S/N) ratio. do.

In recent years, amorphous silicon (hereinafter abbreviated as a-Si) containing hydrogen and halogen elements has been developed because it is easy to control impurities.
Because it has photoconductivity, it is applied to semiconductor devices. Additionally, the development of electronic equipment has created a need for high-density photodetectors. Examples include line sensors for facsimile machines and rotation synchronization sensors for capstan motors for video cameras.

Hereinafter, a conventional high-density photodetector as described above will be described with reference to the drawings.

1 and 2 show cross-sectional views of conventional photodetectors. 1 and 2 have the same function, but the structure is reversed. That is, in FIG. 1, light is incident from the thin film side, and in FIG. 2, light is incident from the substrate side.

1 is a substrate of a photodetector, 2 is a back metal electrode, 3 is a photoconductive thin film such as CdS, 4 is a transparent surface electrode on the light incident side, and 6 is a mask that partially blocks light.

The operation of the photodetector configured as above will be described below.

First, in the case of FIG. 1, a bias is applied between the electrodes 2 and 4, and light is irradiated onto or shielded from the electrodes 4 using a mask 6. When irradiated with light, the resistance of the thin film 3 between the electrodes 2 and 4 decreases, and a current flows due to the Iasumi pressure. In the case of Fig. 2, the substrate 1 must be transparent to the incident light. However, the operation is similar to that shown in Fig. 1.

In the above configuration, if the incident light is not parallel,
When the density of electrode 4 increases, light leaks to adjacent electrodes,
There was a drawback that the S/N ratio decreased. For this reason,
In the case of FIG. 1, a SELFOC lens is inserted between the mask 5 and the electrode 4.

However, SELFOC lenses are very expensive and are not widely used. Furthermore, in the case of Fig. 2, in order to solve the problem of reduced S/N ratio mentioned in Fig. 1, it is necessary to make the substrate 1 thinner, or to increase the refractive index of the substrate 1 on the inner side and reduce it on the surface side. We are making efforts. Making the substrate 1 thinner is not practical because it weakens the strength of the element itself, and changing the refractive index makes the substrate expensive and the manufacturing method of the substrate itself is difficult, so it is not practical for industrialization. is not suitable.

In view of the above, an object of the present invention is to provide a photodetector having the structure shown in FIG. 2 in which the S/N ratio does not decrease even when the density of photodetection increases. That is, the present invention is characterized in that a recess is provided on the transparent insulating substrate in the separation region between the transparent conductive films formed separately on the substrate.

FIG. 3 shows a cross section of a completed photodetector according to an embodiment of the present invention, and FIG. 4 is a partially enlarged view thereof. In this figure, several light incidences are shown for explanation. In addition, the first
The same reference numerals as in Figures 1 to 2 represent the same elements.

Reference numeral 6 indicates four parts formed on the substrate 1 in the separation area of the transparent surface electrode 4. The light 7 is vertically incident through the hole in the mask 6 and reaches the electrode 4 directly.

Light 8 that obliquely enters the hole in the mask 6 is refracted as shown in 9, further refracted by the concave portion 6 of the substrate 1, and either incident on a-8i3 as shown in 1o or reflected as shown in 11.

In this way, the concave portion 6 according to the present invention can reduce the light incident on the adjacent electrode and improve the S/N ratio.

Furthermore, the stray light 12 in the substrate 1 is also absorbed by the concave portion 6.
It can be refracted and removed as shown in 4.

Next, an example of the method for manufacturing a substrate according to the present invention will be described.

FIG. 6 is a cross-sectional view showing the method of manufacturing a photodetector substrate according to the present invention in the order of steps. A transparent electrode 22 is deposited on an insulating substrate 21 that has been cleaned (a).

Next, a resist 23 is applied, and at the same time as the transparent electrode 22 is separated and etched, the substrate 21 is partially etched to form a recess 26. If the insulating substrate 21 is made of glass, for example, hydrofluoric acid may be used, and a normal resist 23 can be used for sufficient masking.

As described above, according to the method of the present invention, when patterning a transparent electrode, it is possible to simultaneously form a recess in a substrate, so there is no need to add any special process. Furthermore, by using such a substrate, it is possible to create microfabricated high-density photodetecting elements, and the S/N
The ratio also improves.

By using the photodetecting element according to the present invention, it is possible to supply components that require high density and a high S/N ratio, such as line sensors for facsimile machines and rotational synchronization sensors for capstan motors for video cameras.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional photodetector. FIG. 3 is a sectional view showing a configuration example of a photodetector according to the present invention, FIG. 4 is an enlarged view of a part thereof, and FIG. 5 is a diagram showing a manufacturing process of a photodetector substrate according to the present invention. 1.21...Insulating substrate, 2...Back electrode, 3...Photoconductive or photovoltaic material, 4,22
... surface electrode, 5 ... light shielding mask,
6, 26... Substrate recess.

Claims (1)

[Scope of Claims] (11) A transparent insulating substrate and a transparent conductive film formed on the substrate separated into several parts, the substrate having a recess in a separation area between the transparent conductive films. A photodetector featuring: 2. Depositing a transparent conductive film on a transparent insulating substrate and selectively removing the transparent conductive film, at the same time partially corroding the substrate to form a recess in the separation area between the transparent conductive films on the substrate. A method for manufacturing a photodetector having a process.