JPS6214478A - Photo-sensor - Google Patents

Abstract

PURPOSE:To prevent the local concentration of electric field and to obtain a stable output even with feeble light, by providing a planar junction between an impurity semiconductor layer and another impurity semiconductor region having the opposite conductivity, in contact with the side faces of grooves formed in the impurity semiconductor layer. CONSTITUTION:After layers 9 and 10 are buried in a p-type semiconductor substrate 5, an n-type layer 6 is epitaxially grown thereon and is anisotropically etched of form grooves 7 and 8. Then, an oxide film 30 is formed on the sides of the grooves 7 and 8. The grooves 7 and 8 are then filled with polysilicon 31. Openings are provided in prdetermined regions of the n-type epitaxial layer 6, and a p<+> type diffused layer 12 and a p<+> type diffused layer 13 are formed for the p-n junction of an avalanche photodiode and for the base/collector junction of a bipolar transistor, respectively. After an n<+> section 17 of the diode, an n<+> section 18 of the emitter and an n<+> section 119 of the collector are formed simultaneously, wiring is performed. According to this construction, the electric field can be prevented from concentrating locally.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensor, and particularly to a high-density, high-sensitivity photosensor.

[Prior art]

Conventionally, photosensors include photodiodes, phototransosters, avalanche photodiodes, and the like. Among these, avalanche photodiodes utilize the electron multiplication phenomenon caused by collision ionization of carriers in a semiconductor, but when a high voltage is applied to the diode, electric field concentration occurs locally in that area. Surrender occurs and sensing becomes impossible. For this reason, we use a mesa shape or provide a guard ring to prevent electric field concentration due to the shape. Figure 1 shows an avalanche model with a guard ring.
In the cross-sectional view of the photodiode, 1 is an electrode, 2 is a guard ring, and 3 is a p-layer of the diode.

[Problem that the invention seeks to solve]

When applying a high voltage to the conventional photosensor mentioned above,
A structure to prevent electric field concentration, such as a mesa hood or a guard ring, is required, which increases the number of steps and makes miniaturization difficult.Also, the photosensor and semiconductor circuit cannot be configured on one chip, making integration difficult.

[Means for solving problems]

The above problem is that in a photosensor having an impurity semiconductor layer and an impurity semiconductor region of an opposite conductivity type provided in the impurity semiconductor layer, the bonding surface between the impurity semiconductor layer and the impurity semiconductor region is a plane; This is achieved by the photosensor of the present invention, wherein the bonding surface is in contact with the side surface of the groove formed in the impurity semiconductor layer.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the photosensor of the present invention.

FIGS. 2 and 3 are cross-sectional views showing the manufacturing process of the above embodiment.

First, the manufacturing process of the embodiment will be explained using FIGS. 1 to 3.

In FIG. 2, after forming a p-type buried layer 9 and an n-type buried layer 10 on a p-type semiconductor substrate 5, an n-type epitaxial layer 6 is grown. Thereafter, the n-type epitaxial layer 6 is selectively etched using an anisotropic etching means such as reactive ion etching to form grooves 7 and 8. An oxide film or a nitride film is used as an etching mask at this time. In the figure, part A shows an avalanche 7 otodiode part, and part B shows a bipolar transistor part. Grooves 7 and 8 are made deep enough to reach the p+ buried layer 9 that has risen up in the epitaxial layer 6.

Next, as shown in FIG. 3, an oxide film is formed on the side surfaces of the grooves 7 and 8 by an oxidation process. Grooves 7 and 8 are then filled with polysilicon or the like. Then, an oxide film 11 is formed and holes are opened in a predetermined region on the n-type epitaxial layer 6 using a photorenoist process. A p-type impurity, such as zolon, is diffused into this opening to form a p-type diffusion layer 12 of the PN junction of the avalanche 7 photodiode and a p-type diffusion layer 13 of the pace-collector junction of the pi/-2 transistor. .

Then, as shown in FIG. 1, the n+ part 17 of the avalanche photodiode, the n+ part 18 of the emitter, and the n+ part 19 of the collector are formed at the same time, and then wiring is performed. 20 and 21 are electrodes of avalanche photodiodes.

As shown in Fig. 1, the PN junction surface of the avalanche photodiode reaches the side surface of the groove 7, and there is no curved part as in the conventional case. Therefore, local electric field concentration can be prevented and stable optical detection can be achieved. It will have characteristics. Grooves 7 and 8 also act as isolation for avalanche photodiodes and bipolar transistors.

In the step of forming the grooves 7 and 8 of the photosensor of the above embodiment, the side surfaces of the grooves are used as a carrier and a child-shield as disclosed in Japanese Patent Laid-Open No. 59-2362, thereby achieving a large capacity with the same area. It becomes possible to incorporate Kiya Gushita. Also, groove type MO8 as disclosed in Japanese Patent Publication No. 49-28790)
It is also possible to form the /F nnostar at the same time.

〔Effect of the invention〕

As described in detail above, according to the photosensor of the present invention, the semiconductor junction surface is flat, electric field concentration does not occur in a specific location, stable output can be obtained even in the presence of minute light, and special Since there is no need for a structure to prevent electric field concentration, the number of man-hours can be reduced and the device can be made smaller. Furthermore, the provided groove can be used for element isolation or as a capacitor, and since the photosensor and the semiconductor circuit can be constructed on one chip, an integrated circuit can be constructed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the photosensor of the present invention. FIGS. 2 and 3 are cross-sectional views showing the manufacturing process of the above embodiment. FIG. 4 is a sectional view of a conventional photosensor. 5... P type semiconductor substrate, 6... N type epitaxial layer, 7, 8... Groove, 9... P medium buried layer, 10...
- n-type buried layer, 12, 13.・"p-type diffusion layer.

Claims (1)

[Claims] In a photosensor having an impurity semiconductor layer and an impurity semiconductor region of an opposite conductivity type provided in the impurity semiconductor layer, a bonding surface between the impurity semiconductor layer and the impurity semiconductor region is a plane, and the bonding surface is A photosensor characterized in that the photo sensor is in contact with a side surface of a groove formed in the impurity semiconductor layer.