JPH01175775A - Photo-driven mos semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the efficiency of photosensitivity of a photo-sensitive section, to shorten the charging time of the gate capacitance of a MOS FET and to produce a photo-driven MOS FET which may respond at a high speed, by a structure wherein a plurality of photodetectors are laminated on the main surface of a MOS semiconductor device through insulating films, respectively, in a multilayer. CONSTITUTION:Photodetectors 2 are laminated on the main surface of a MOS semiconductor device 1, and the MOS semiconductor device 1 is driven by utilizing the photoelectromotive force which is generated by the photodetectors 2. In such a photo- driven MOS semiconductor device, the plurality of photodetectors 2 are laminated on the main surface of the MOS semiconductor device 1 through insulating films 19, respectively, in a multilayer. For example, after an n<-> type epitaxial layer 4 is grown on an n<+> type substrate 3, a p<-> type well diffusion layer 5 is formed. Subsequently, a gate oxide film 7 is formed on the epitaxial layer 4, and a gate electrode 8 is then formed thereon. Further, an n<+> type diffusion layer 6 is formed, and thereby a vertical MOS FET is completed. Next, after an SiO2 film 14 is deposited on the surface of the epitaxial layer 4 over which the gate electrode 8 is formed, two layers of photodiode sections 2 are formed in a laminated construction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light-driven MOS field effect transistor, and more particularly to the structure of a light-driven MO3 field effect transistor that improves the light receiving efficiency of a light receiving section. .

[Prior Art] An optical coupler device, which is an optical coupling device that converts an electrical signal into an optical signal and transmits it, is a device that can be used in a wide range of applications, such as solid-state relays, non-contact switches, non-contact variable resistors, etc. It is used in An optical coupler device is composed of a light emitting element that converts an electrical signal into an optical signal and emits light, and a light receiving element that receives the light emitted from the light emitting element and converts it into an electrical signal. There are various combinations of the light-emitting element and the light-receiving element, and the optimum combination for the use of the optical coupler device is constructed.

In recent years, photodiodes and MO8 type FETs (M
etal-Oxide Sem1 conductor
There is an optically driven MO9FET which is composed of a type field effect transistor (hereinafter referred to as MO8FET).

A conventional optically driven MO8FET structure is shown in FIGS. 6 and 7. FIG. 6 shows a plan view of the optically driven MO3FET, and FIG. 7 shows a cross-sectional view taken along the cutting line ■--■ in FIG. Hereinafter, the explanation will be made using FIG. 6 and FIG. 7 together. Conventional optically driven MOS FE
T is a 5OI (Si
It has a 1Lcon on In5ulator) structure.

First, the MOS FET section 1 includes an n-type epitaxial layer 4 grown on an n-type substrate 3, a p-type well diffusion layer 5 formed in the n''-type epitaxial layer 4, and a p-type well diffusion layer 5 formed in the n''' type epitaxial layer 4. It is composed of an n++ source diffusion layer 6 formed in the well diffusion layer 5, a gate insulating layer 7 formed on the n- type epitaxial layer 4, and a gate electrode 8 and a source electrode 9 formed thereon. Ru.

Further, the photodiode section 2 is formed by depositing an insulating film 10 on the surface of the MOS FET, and further forming a p-type silicon single crystal layer 11 and an n+ type scattering layer 12 thereon.
Configure the junction. Finally, a protective film 13 is formed on the surface.

Furthermore, this optically driven MO8FET is arranged on a plurality of MOS FETs and MOSFETs as shown in FIG.
The photodiode sections 2 are connected in series in each column to increase the output voltage, and one end of the photodiode section 2 is connected to the MO3FET section 1. It is connected to the gate electrode 8, and the other end is grounded.

This optically driven MOS FET operates as follows.

That is, when light enters the photodiode section 2, a photovoltaic force is generated at the pn junction. This photovoltaic force is M
The MOS FET is operated by introducing it into the OS FET and applying a voltage to the gate electrode of the MOS FET.

[Problems to be Solved by the Invention] Normally, since there is a capacitance at the gate of the MOS FET described above, the MOS FET remains closed until the gate capacitance is charged.
ET is not driven. On the other hand, conventional optically driven MOS FE
The photodiode portion of T is made of its silicon single crystal layer 11.
Since the silicon single crystal layer 11 is formed by tenth annealing, the thickness of the silicon single crystal layer 11 can only be formed to be about 1 to 2 μm. For this reason, the light receiving efficiency of the photodiode is low and the photovoltaic force is small. Therefore, this photovoltaic force causes MO
When charging the gate capacitance of SFET, the charging time becomes long. As a result, the response speed of the optically driven MO3FET is determined by the charging time of the gate capacitance of the MOS FET, which poses a problem that hinders high-speed response.

Therefore, the present invention improves the light receiving efficiency of the light receiving part of the optically driven MO8FET, shortens the charging time of the gate capacitance of the MOS FET, and provides an optically driven MOS FET capable of high-speed response.
The purpose is to provide ET.

[Means for Solving the Problems] The optically driven MOS type semiconductor device according to the present invention has a light receiving element stacked on the main surface of the MOS type semiconductor device, and uses the photovoltaic force generated by the light receiving element to drive the MOS type semiconductor device. The present invention is an optically driven MOS type semiconductor device for driving a semiconductor device, and is characterized in that a plurality of the light receiving elements are stacked in multiple layers on the main surface of the MOS type semiconductor device, each with an insulating film interposed therebetween.

[Function] The optically driven MOS type semiconductor device according to the present invention has a light-receiving portion made up of a plurality of light-receiving elements each laminated in multiple layers with an insulating film interposed therebetween. For this reason, compared to conventional optically driven MOS type semiconductor devices, the light receiving efficiency in the same light receiving area becomes higher, and as a result, the photovoltaic force generated from these light receiving elements also becomes higher. Therefore, it is possible to shorten the charging time of the gate of a MOS type semiconductor device that utilizes the photovoltaic force generated by this light receiving element. [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 to 3 show optically driven MOS according to the present invention.
A structural diagram of an FET is shown. Fig. 1 shows its plan view, Fig. 2 shows a cross-sectional view taken along the cutting line ■-H in Fig. 1, and Fig. 3 shows a cross-sectional view taken along the cutting line ■-■. A cross-sectional view taken from the direction shown in FIG.

The optically driven MO3FET according to the present invention has a plurality of photodiode parts 21 on the surface of the MO5FET part 1 via an insulating film.
This embodiment is characterized by a structure (Sol structure) formed by stacking two photodiode sections 2. Hereinafter, the structure of the optically driven MO8FET according to this embodiment will be explained according to its manufacturing process. Figures 4A, 4B, 4C, 5A, 5B, and 5C are optical drive MOs, respectively.
4A to 4C are cross-sectional views showing the manufacturing process of S FET, and FIGS. 4A to 4C are along the cutting line ■-■ in the plan view of FIG.
5A to 5C.
The figure also shows a view seen from the direction along the cutting line ■-■. Furthermore, Figures 4A and 5A, Figures 4B and 5
Figure B, Figure 4C and Figure 5C each show the same process.

First, the structure of the MOS FET section 1 will be explained according to its manufacturing process. As shown in FIGS. 4A and 5A, n+
After growing the n-epitaxial layer 4 on the type substrate 3,
A p-type well diffusion layer 5 is formed by diffusing p-type impurities. Next, a gate oxide film 7 is formed on the n-type epitaxial layer 4, and after polysilicon is deposited thereon, a gate electrode 8 is formed by photoetching.

Furthermore, an n-type impurity is diffused into the p-well diffusion layer 5 using the gate electrode 8 and a resist patterned by photoetching as a mask to form an 01-type diffusion layer 6 to form a vertical MO3FET.

Next, the structure of the photodiode section 2 will be explained according to its manufacturing process. As shown in Figures 4B and 5B,
After depositing 5 in 2 H 14 on the surface of the n-type epitaxial layer 4 on which the gate electrode 8 is formed, the SiO 2 film 14 is etched back. And this 5i
After forming a seed portion 15 by opening a window in a part of the 02 film 14, an n-type polysilicon layer 16 is deposited. and,
Laser annealing is applied to this p-type polysilicon layer 16 to make the region where a photodiode is to be formed into a single crystal.
A single crystal layer 17 is formed.

Further, as shown in FIGS. 4C and 5C, the polysilicon layer 1 other than the p-type crystal layer 17 of the photodiode is
6 is removed by etching, and an n+ diffusion layer 18 is formed on the surface of the p-type wheel crystal layer 17 by ion implantation, thereby forming a pn junction of the photodiode. Thereafter, a protective film 19 of 5i02 is formed on the surface of the photodiode, and source and gate electrodes and contact holes for the photodiode are formed by photoetching. Then, a high melting point metal or polysilicon is deposited to form the source electrode 2.
0. Contact wiring section 21 between p-type nest crystal layer 17 and n+ diffusion layer 18 of photodiode connected in series, and n+ diffusion layer 18 of photodiode and MOS FET
A contact wiring portion 22 with the gate electrode 8 is formed.

Through the above steps, the formation of the first layer photodiode is completed. Next, a second layer photodiode is formed on this first layer photodiode using the same process as that used for forming the first layer. Through these steps, an optically driven MOS FET is formed in which two layers of photodiodes are stacked on a MOS FET with a Sol structure as shown in FIGS. 1 to 3.

In addition, the position of the seed part 15 mentioned above should just be provided at the optimal position with respect to a laser annealing technique.

Further, for example, the seed portion for forming the second layer photodiode does not necessarily have to be connected to the substrate.

Since the optically driven MO3FET according to this embodiment has photodiodes stacked in two layers, the light receiving efficiency is increased and the generated photovoltaic force is increased. Therefore, the charging time of the gate electrode of the MOS FET using this photovoltaic force can be shortened.

In this embodiment, a case has been described in which two layers of photodiodes are stacked on a MOS FET, but a structure may also be adopted in which multiple layers of photodiodes are stacked to increase the light receiving efficiency.

Furthermore, although this embodiment has been described using a vertically structured MOS FET, a horizontal MOS FET may also be used.

[Effects of the Invention] The optically driven MOS type semiconductor device according to the present invention has a structure in which a light receiving element for driving an MO8 type semiconductor device is laminated in multiple layers on the MO8 type semiconductor device with an insulating film interposed therebetween. . Therefore, it is possible to realize a light-driven MO8 type semiconductor device in which the light receiving efficiency of the light receiving element is high and the response speed of the MO5 type semiconductor device is fast.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an optically driven MOSFET according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the cutting line ■-■ in FIG. 1, and FIG. 3 is a cross-sectional view taken along the cutting line in FIG. A cross-sectional view seen from the direction ■-■ is shown. FIGS. 4A, 4B, and 4C are cross-sectional views showing the cross-sectional structure of the optically driven MO8FET shown in FIG. 2 in the order of manufacturing steps, and FIGS. 5A, 5B, and 5C are FIG. 4 is a cross-sectional view showing the cross-sectional structure shown in FIG. 3 in the order of its manufacturing steps. 4A and 5A, 4B and 5.
Figures B, 4C and 5C each show the same manufacturing process. FIG. 6 is a plan view of a conventional optically driven MO8FET,
FIG. 7 shows a cross-sectional view taken from the direction of section line (■--) in FIG. 6. In the figure, 1 is a MOS FET section, 2 is a photodiode section, 6 is an n+ source diffusion layer, 7 is a gate insulating layer,
8 is a gate electrode, 14 is a 5LO2 film, 17 is a p-type nested crystal layer, 18 is an n+ type scattering layer 20 is a source electrode, 21.2
2 indicates a contact wiring section. In the figures, the same reference numerals indicate the same or corresponding parts. Figure 4A Figure 4B Figure 5A

Claims (1)

[Scope of Claims] A light-driven MOS type semiconductor device in which a light receiving element is stacked on a main surface of the MOS type semiconductor device, and the MOS type semiconductor device is driven using a photovoltaic force generated by the light receiving element, comprising: 1. A light-driven MOS type semiconductor device, characterized in that a plurality of the light receiving elements are laminated in multiple layers on a main surface of the type semiconductor device, each with an insulating film interposed therebetween.