JPS61280655A - Semiconductor integrated circuit with incorporated photosensor - Google Patents

Abstract

PURPOSE:To facilitate the expansion of a depletion layer and thereby to increase the detection output level of a photosensor, by using as the photosensor a P-N junction of low impurity concentration which is formed by a layer with implanted ions and a semiconductor substrate of a one conductivity type. CONSTITUTION:A photosensor is formed of a P-N junction which is formed by a layer 5 with implanted ions and a substrate 1. The impurity concentration of the layer 5 with implanted ions is set to be 10<11-13>cm<-2>, substantially the same with the impurity concentration of the semiconductor substrate 1, which is low owing to its structure, and therefore a junction approximate to a P-I-N structure having low impurity concentration is obtained. This photosensor is employed with a resistor 9 for detection and a DC power source 10 connected between a cathode contact region 8 and the substrate 1, and it forms an equivalent circuit shown in the figure. When infrared rays are applied to the photosensor, a generation combination current is generated therein, causing a fall of voltage in the resistor 9. This fall of voltage is amplified by an amplifier 11, so as to obtain an output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION B) Industrial Application Field The present invention relates to a semiconductor integrated circuit incorporating a photosensor, and particularly to an improvement of a photosensor incorporated in a semiconductor integrated circuit having a plurality of island regions.

(b) Conventional technology A semiconductor integrated circuit incorporating a conventional 7-point sensor is disclosed, for example, in Japanese Patent Application Laid-Open No. 59-96765 (I(01L27./1
4) is shown at ℃.

In Figure 4, 0υ is a P-type semiconductor substrate, 0υ is an N-type epitaxial layer grown on a silicon substrate, and (c)
is a P-type isolation region, (F) is a P-type anode region diffused on the surface of the epitaxial layer, (E) is an N+-type cathode region, and the area between the anode region (F) and cathode region (C) is Using the PN junction as a photodiode
there was.

P→ Problems to be Solved by the Invention When a photodiode, especially an infrared detection photodiode, is formed from a PN junction with a low impurity concentration, the depletion layer can expand more easily and the detection output level can be increased.

However, such a photodiode has an anode region 124)
Since the (NPN) transistor is formed by pace diffusion and the cathode region (c) is formed by emitter diffusion, the PN junction forming the photodiode has a high impurity concentration.

For this reason, the photodiode incorporated in the semiconductor integrated circuit has the disadvantage that its detection output level cannot be increased.

2) Means to Solve the Problems The present invention has been made in view of these drawbacks, and has greatly improved the drawbacks of the conventional method by providing an ion-implanted layer (5) with a low impurity concentration on the surface of the semiconductor substrate (1). This realizes a semiconductor integrated circuit with a built-in photosensor.

(E) Effect According to the present invention, since the impurity concentration of the PN junction constituting the photosensor can be reduced by the ion implantation layer (5),
The depletion layer can be easily expanded, and the detection output level of the photosensor can be increased.

(F) Embodiment An embodiment of a semiconductor integrated circuit incorporating a photosensor according to the present invention will be described in detail with reference to FIGS. 1 to 3.

As shown in FIG. 1, the semiconductor integrated circuit according to the present invention includes a P type silicon semiconductor substrate (1), an N- type epitaxial layer (2) grown on a substrate +11, and a P+ type isolation region (3). ), an island region (4) surrounded by the substrate (1) and the isolation region (3), and an N''" type ion implantation layer ( 5) and the board (
1), and a cathode region (6) formed by the ion implantation layer (5) and the island region (4).
7) and an N-type cathode contact region (8) provided on the surface of the island region (4).

Such a photosensor consists of an ion-implanted layer (5) and a substrate (1).
) is formed by a PN junction. The impurity concentration of the ion implantation layer (5) is 1011-IscrIL'ffi
is set to the same level as the semiconductor substrate (1), and the semiconductor substrate (
Since the impurity concentration in 1) is structurally low, a junction close to a P-I-N structure with a low impurity concentration can be obtained.

This photosensor is used with a detection resistor (9) and a DC power supply α1 connected between the cathode contact region (8) and the substrate (1), and is used at 0.degree. C., and an equivalent circuit diagram shown in FIG. 2 is constructed.

When the photosensor is irradiated with infrared rays, a coupling current is generated in the photosensor, causing a voltage drop across the °C resistor (9).

This voltage drop is amplified by an amplifier aυ to obtain an output signal.

Next, FIG. 3A shows a method for manufacturing a semiconductor integrated circuit according to the present invention.
This will be explained in detail with reference to the third diagram.

First, as shown in FIG. 3A, phosphorus is ion-implanted into the surface of a semiconductor substrate (1) on which a photodiode is to be formed, to form an ion-implanted layer (5) having the same impurity concentration as the semiconductor substrate (11). This ion implantation is carried out at an accelerating voltage of 50~2
00 KeV, )"-su 10"~10"α-2
Do it with

Next, as shown in FIG. 3B, one N-type buried layer is diffused on the surface of the semiconductor substrate (1) that will become the other island region (13), and on the surface of the semiconductor substrate 11 that will become the isolation region (3). is P+
Diffusion is performed under the separation area (3) of the mold.

Next, as shown in FIG. 3C, an N-type epitaxial layer (2) is grown on the surface of the semiconductor substrate (1), and the buried layer C121 and isolation region (3) are diffused into the epitaxial layer (2) as well. .

Further, as shown in the third diagram, after diffusion is performed from the surface of the epitaxial layer (2) onto the P type isolation region (3), a pace region (14) and an emitter region a9 are formed in the other island region CI3.
and the island region forming the photodiode (
4) The cathode contact region (8
) to spread.

As described above in detail, the manufacturing process of the 7-oto sensor of the present invention can be inserted into the manufacturing process of a normal semiconductor integrated circuit, and the 7-oto sensor with an extremely high output can be obtained.

(G) Effects of the Invention According to the present invention, a photosensor is built in by forming a PN junction with a low impurity concentration in a normal semiconductor integrated circuit.
This has the advantage that a photosensor with a high output level in which the depletion layer can easily expand can be easily obtained.

Further, in the present invention, since the impurity concentrations of the semiconductor substrate t1) and the epitaxial layer (2) are not changed, there is an advantage that a high-performance photosensor can be built in while the characteristics of other circuit elements such as transistors remain unchanged.

Furthermore, in the present invention, since the PN junction forming the photosensor is formed deep into the surface of the semiconductor substrate (1), it has the advantage that it reacts only to infrared rays and the S/N ratio is extremely improved.

Finally, it has the advantage that it can be easily introduced into the current manufacturing process of semiconductor integrated circuits, and that semiconductor integrated circuits with built-in photosensors can be mass-produced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating a semiconductor integrated circuit incorporating a photosensor according to the present invention, FIG. 2 is an equivalent circuit diagram of the present invention, and FIGS. 3A to 3 are manufacturing of a semiconductor integrated circuit according to the present invention. A sectional view explaining the method, and FIG. 4 is a sectional view illustrating a conventional photosenser. Explanation of main figure numbers +11 is the semiconductor substrate, (2) is the epitaxial layer, (
3) is an isolation region, (4) is an island region, (5) is an ion implantation layer, (6) is an anode region, and (7) is a cando region. Applicant: Sanyo Electric Co., Ltd. and 1 other agent: Shizuo Sano, patent attorney! J 1 Figure #12 Figure 3 Figure C Figure 3 Figure 4

Claims (1)

[Claims] (1) A semiconductor substrate comprising a semiconductor substrate of one conductivity type, an epitaxial layer of an opposite conductivity type provided on the substrate, and a plurality of island regions formed by separating the epitaxial layers, and a surface of the semiconductor substrate of one of the island regions. A semiconductor integrated device having a built-in photosensor, characterized in that an ion-implanted layer of opposite conductivity type and with a low impurity concentration is provided in the substrate, and a PN junction with a low impurity concentration formed between the ion-implanted layer and the substrate is used as a photosensor. circuit.