JP2590690B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using an SOI substrate, and more particularly to a photodiode.

[0002]

2. Description of the Related Art A conventional photodiode semiconductor device is:
As shown in FIG. 2, an oxide film 22 for insulating and separating each diode element by using polycrystalline silicon 21 as a support.
And has a dielectric isolation structure surrounding the single crystal silicon layer 1. This is because it is necessary to separate each diode element region in order to directly connect the diode elements in series and obtain a high electromotive force. Since this conventional dielectric isolation structure has polycrystalline silicon having a thickness of about 400 μm, there are problems such as an increase in cost and an increase in substrate warpage.

In order to solve these problems, Japanese Patent Application Laid-Open Nos. 3-180070 and 3-136 shown in FIG.
No. 346 using an SOI substrate has been proposed. Here, in order to increase the photocurrent of each photodiode element, it is necessary to increase the total amount of carriers to be optically coupled. This is dealt with by increasing the silicon layer thickness 1 in each photodiode element region. In the dielectric isolation substrate shown in FIG. 2, it is easy to increase the thickness of the silicon layer 1, but the SOI substrate shown in FIG.
When the thickness of the silicon layer 1 is increased, it becomes difficult to form the insulating isolation regions 3 and 4. Therefore, even if the thickness of the silicon layer 1 is reduced, the electromotive force can be increased.
As shown in the figure, the high impurity concentration layer 2 was provided at the interface between the silicon layer 1 and the insulating film 31.

[0004]

In this conventional SOI substrate, since the silicon layer is thin, light is easily transmitted through the insulating film. There was a problem that power efficiency did not increase.

[0005]

The present invention provides a single crystal silicon substrate, a composite insulating film provided on one surface of the single crystal silicon substrate, and a single crystal silicon layer provided on the composite insulating film. And an insulating film provided in contact with the side surface, and a polycrystalline silicon layer filling the space between the insulating films, wherein the composite insulating film has a laminated structure including at least a lower layer, an intermediate layer, and an upper layer. The semiconductor device is characterized in that the upper layer is thicker than the intermediate layer. Also, the present invention
In the above semiconductor device, the composite insulating film is formed of two or more kinds of insulating films of different materials.

[0006]

According to the present invention, a semiconductor device using an SOI substrate includes a silicon layer forming a photodiode, an insulating region separating each diode, a composite insulating film for improving light reflection efficiency, and a silicon layer provided at the bottom of the silicon layer. High-concentration impurity layer, and a silicon substrate serving as a support substrate,
Light energy is received from the surface of the silicon layer, the light energy transmitted through the silicon layer (silicon single crystal region) and absorbed near the PN junction boundary becomes a photocurrent, and the remaining light energy is transmitted and the composite insulating film is transmitted. To reach. The composite insulating film reflects light energy with high efficiency, reaches the PN junction again,
It has a function of being converted into a photocurrent.

[0007]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a semiconductor device according to one embodiment of the present invention. A silicon single crystal region 1 and a high-concentration impurity layer 2 forming a photodiode are formed on a composite insulating film formed of insulating oxide films 6 and 8 and a nitride film 7 on a single crystal substrate 5 serving as a support. Each of the photodiode elements is insulated by the insulating oxide film 4 and the polycrystalline silicon layer 3. A photodiode having an arnode 11 and a cathode 12 is formed on the silicon single crystal region 1, and the photodiodes are connected in series by an aluminum electrode 13. Light energy received from the surface of the silicon single crystal region 1 and transmitted through the silicon layer and absorbed near the PN junction boundary becomes a photocurrent, and the remaining light energy is transmitted and reaches the composite insulating film. I do. The composite insulating film is
The light energy is reflected with high efficiency, reaches the PN junction again, and is converted into a photocurrent.

In the composite insulating film, the material and thickness of the insulating oxide films 6 to 8 are changed so as to adjust the wavelength of incident light in order to efficiently reflect light energy. For example, in the first embodiment, the thickness of the insulating oxide films 6 and 8 is 1.0 μm,
Uses a silicon nitride film of 0.1 μm. In the second embodiment, the insulating oxide films 6 and 8 use 2.0 μm.
Using a polycrystalline silicon film of 0.1 μm. The structure of the second embodiment is the same as that of the first embodiment.

[0009]

As described above, the present invention enhances the reflection efficiency of incident light and reduces the light energy by combining and configuring the insulating separation film by combining materials having different refractive indexes. It can be re-absorbed and the energy conversion efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional semiconductor device having a dielectric isolation substrate.

FIG. 3 is a cross-sectional view of a conventional semiconductor device having an SOI substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single crystal silicon layer 2 High concentration impurity layer 3 Polycrystalline silicon layer 4 Insulating oxide film 5 Single crystal silicon substrate 6 Insulating oxide film 7 Insulating film 8 Insulating oxide film 11 Anode 12 Cathode 13 Aluminum electrode 21 Polycrystalline silicon layer 22 Insulating oxidation Film 31 Insulating oxide film

Claims (2)

(57) [Claims] 1. A single-crystal silicon substrate, a composite insulating film provided on one surface of the single-crystal silicon substrate, and a single-crystal silicon layer provided on the composite insulating film are provided so that side surfaces thereof are in contact with each other. Insulating film, and a polycrystalline silicon layer filling between the insulating films, the composite insulating film has a laminated structure of at least a lower layer, an intermediate layer, an upper layer, the thickness of the lower layer and the upper layer is larger than that of the intermediate layer A semiconductor device characterized by being thick. 2. The semiconductor device according to claim 1, wherein the composite insulating film is composed of two or more different types of insulating films.