JPS62108539A - Manufacture of soi-structure semiconductor device - Google Patents

Abstract

PURPOSE:To inhibit the generation of dislocation-defects to an silicon island by forming the single crystal N-type silicon island onto the surface of a P-type silicon substrate, changing low-concentration and high-concentration P-type layers into porous silicon layers through anodizing treatment and converting the layers into porous silicon oxide film layers. CONSTITUTION:A high-concentration P-type layer 12 and a P-type layer 13 in concentration lower than the layer 12 are shaped on the surface side of a P-type silicon substrate 11. An N-type epitaxial layer and a desired single crystal N-type silicon island 14 are formed onto the surface of the substrate 11, and the layers 13 and 12 are turned into porous silicon layers 15, 16 through anodizing treatment. The density of the layer 16 is made comparatively large and the density of the layer 15 small. The layers 15, 16 are changed into porous silicon oxide film layers 17, 18 through thermal oxidation treatment, and the N-type silicon island 14 insulated and isolated by the layers 17, 18 is obtained. Accordingly, the porous silicon layers just under the island 14 have small density, thus inhibiting dislocations and defects generated in the island 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to semiconductor devices, particularly SOI (5ilic
The present invention relates to a method of manufacturing a semiconductor device with an on-on inverter structure.

(Prior Art) FIG. 2 is a process cross-sectional view showing a conventional method for manufacturing an SOI structure semiconductor device as described in IEDM 84 P800-803. In this conventional method, first, a highly-concentrated P-type layer (P middle layer) 2 is formed on the surface side of a P-type silicon substrate 1 by ion implantation or a diffusion method (FIG. 2(a)). Thereafter, a desired N-type silicon island 3 is formed on the P-type silicon substrate 1 by forming an N-type epitaxial layer and using well-known photolithography and etching techniques.
(Fig. 2(b)). Thereafter, the highly concentrated P-type layer 2 is changed into a porous silicon layer 4 by anodization treatment (FIG. 2(c)). Thereafter, by performing thermal oxidation treatment, the porous silicon layer 4 is changed to the porous silicon oxide film layer 5.
As shown in FIG. 2(d), a structure having N-type silicon islands 3 insulated and isolated by a porous silicon oxide film layer 5 is obtained. At this time, a thin thermal oxide film 6 is formed on the surface of the N-type silicon island 3. Note that this insulation separation method is a method that utilizes the difference between the oxidation rate of porous silicon and the oxidation rate of single crystal silicon.

(Problems to be Solved by the Invention) However, in the conventional method described above, since the density of the porous silicon layer 4 obtained is relatively higher than that of the highly concentrated P-type layer 2, the porous silicon layer 4 is oxidized. At times, there is a problem in that dislocations and defects are likely to occur in the silicon island 3, which tends to cause deterioration of device characteristics such as leakage current.

This invention was made in view of the above points, and its purpose is to suppress the occurrence of dislocations and defects in the silicon islands mentioned above,
An object of the present invention is to provide a method for manufacturing an SOI structure semiconductor device that can obtain a silicon island with good crystallinity.

(Means for Solving the Problems) In the present invention, a high concentration P type layer is formed at a predetermined depth on the surface side of a P type silicon substrate, and the high concentration P type layer is formed on the upper surface of the P type silicon substrate.
For the mold layer, a low concentration P type layer is formed, and after forming a single crystal N type silicon island on such a P type silicon substrate, the low concentration/high concentration P type layer is made porous by anodizing. Furthermore, this porous silicon layer is used as a porous silicon oxide film layer.

(Function) According to such a method, since the surface side of the P-type layer to be anodized is a low concentration layer, the density of the porous silicon layer directly under the single-crystal N-type silicon island becomes small.

(Example) An embodiment of the present invention will be described below with reference to FIG.

In Figure 1(a), 11 is a P-type silicon substrate 1)
First, a high concentration P type layer (P intermediate layer) 12 is formed at a predetermined depth on the surface side of this silicon substrate 11 by a known diffusion technique. Then, the high concentration P-type layer 12 (specific resistance 0,008Ω/about 100) is formed at a predetermined depth on the surface side of the silicon substrate 11.
is formed, and a low concentration P-type layer 13 (
A specific resistance of 10 to 12 Ω·crIK) is formed.

Next, a desired single-crystal N-type silicon island 14 is formed on the surface of the P-type silicon substrate 11 by forming an N-type epitaxial layer and using well-known photolithography and etching techniques (FIG. 1(b)). .

Thereafter, the low concentration P type layer 13 and the high concentration P type layer 12 are made into porous silicon layers 15 and 16 by anodization treatment (FIG. 1(c)). At this time, the porous silicon layer 1 generated
The density of 5,16 depends on the concentration of the P-type layer before conversion.

The deep porous silicon layer 16 is a highly doped P-type layer 12.
The density is relatively large because it can be obtained easily. -10,000, N
Porous silicon layer 15 on the surface side directly below the mold silicon island 14
Since υ is obtained as compared to the low concentration P-type layer 13, the density becomes smaller.

Thereafter, a thermal oxidation treatment is performed to form a porous silicon layer 15.
By making 16 into porous silicon oxide film layers 17 and 18 (FIG. 1(d)), the porous silicon oxide film layer 17
, 18 is obtained. At this time, since the porous silicon layer (porous silicon layer 15) directly under the N-type silicon island 14 has a low density, dislocations and defects occurring in the N-type silicon island 14 are suppressed. Also, by this thermal oxidation treatment, the N-type silicon island 14
A thin thermal oxide film 19 is formed on the surface. Note that this insulation separation method is a method that utilizes the difference between the oxidation rate of porous silicon and the oxidation rate of single crystal silicon.

(Effects of the Invention) As detailed above, in the method of the present invention, the P-type layer to be anodized is divided into two layers, a low concentration layer and a high concentration layer, from the surface side.
layer, and when the P-type layer is anodized, the density on the surface side of the porous silicon layer is reduced, so in the process of converting the porous silicon layer into a porous silicon oxide layer, a simple Dislocations and defects occurring in crystalline N-type silicon islands can be suppressed, and an excellent element with low leakage current can be formed. In addition, in the method of the present invention, a high concentration P-type layer exists under the low concentration P-type layer, and since anodization proceeds quickly in the high concentration P-type layer, the P-type layer under the high concentration P-type layer is The mold silicon substrate is in a state where it is hardly chemically formed, that is, a wide silicon island region can be obtained without forming a deep porous silicon layer.

[Brief explanation of drawings]

(Drawings) FIG. 1 is a process sectional view showing an embodiment of the method for manufacturing an SOI structure semiconductor device of the present invention, and FIG. 2 is a process sectional view showing a conventional method. 11...P-type silicon substrate, 12...High concentration P-type layer, 13...Low concentration P-type layer, 14...Single crystal N-type silicon island, 15.16...Porous silicon layer , 17.1
8... Porous silicon oxide film layer.

Claims (1)

[Scope of Claims] (a) A high-concentration P-type layer at a predetermined depth on the surface side of a P-type silicon substrate, and a P-type layer with a lower concentration than the high-concentration P-type layer on the surface above this layer. (b) forming a single-crystal N-type silicon island on the surface of the P-type silicon substrate; (c) after that, the low-concentration/high-concentration P-type layer is made porous by anodizing. 1. A method for manufacturing an SOI structure semiconductor device, comprising the steps of: (d) converting the porous silicon layer into a porous silicon oxide film layer.