JPH0992802A - SOI substrate and manufacturing method thereof - Google Patents

Abstract

(57) Abstract: An SOI substrate that can be put into a bulk IC production process and a manufacturing method thereof are provided. A second substrate (5) is attached to an inner surface (1a) of a first substrate (1) via a silicon oxide film (4), and an outer surface (5c) of the second substrate (5) is roughened (5).
a. [Effect] Since the outer surface 5c of the second substrate 5 is roughened, the separation can be done smoothly when vacuum suction is performed.

Description

Detailed Description of the Invention

[0001]

The present invention relates to SOI (Silic).
More specifically, the present invention relates to an SOI substrate formed by adhering a substrate, which is one type of semiconductor device, and a method for manufacturing the SOI substrate.

[0002]

2. Description of the Related Art Conventionally, a semiconductor device forming an IC is provided with an element region forming the IC on a substrate, a groove is formed to separate the element regions, and SiO is formed therein.
₂ (silicon oxide) is embedded. Hereinafter, this type of IC will be referred to as a bulk type IC. However, in this type of IC, it is said that SiO ₂ exists only between the element regions and is bonded to the substrate on the lower side, so that complete separation is not possible. There was a problem.

Recently, in place of this type of bulk type IC, SOI
Type IC has appeared. According to this SOI type IC, isolation between elements becomes complete, soft error and CMOS
It is known that it is possible to suppress latch-up peculiar to transistors. Therefore, 500
CM with an SOI structure with a Si active layer thickness of about nm
OS. Research has been conducted on high speed and high reliability of LSI.

More recently, an SOI surface Si layer of 100n has been formed.
If the condition is set so that the entire Si active layer is depleted by controlling the impurity concentration of the channel to be relatively low to about m, the short channel effect is suppressed and the current drive capability of the MOS transistor is improved. It has been found that even better performance can be obtained.

In recent years, as a method of forming this SOI layer, S
IMOX (Separation by Implant)
The ed Oxgen) method and the wafer bonding method are being put to practical use. However, each of these two methods has merits and demerits at the present time, and the SIMOX method uses SOI.
Although the uniformity of the film thickness is excellent, the flatness of the buried oxide film interface is poor and the reliability of the transistor remains a problem. On the other hand, the SOI substrate prepared by the wafer bonding method has good characteristics at the buried oxide film interface, but there is a problem in the film thickness uniformity especially in the case of a thin Si film thickness. Here, the process steps for producing an SOI substrate by the wafer bonding method are performed by the following flow.

This flow will be described with reference to FIGS. First, the first substrate 1 made of silicon
A photoresist pattern 2 is formed thereon by a lithography method, and reactive ion etching (RIE) is performed (see FIG. 4A). Then, the resist film is stripped by dipping in a stripping solution or by plasma ashing (FIG. 4).
(B)). As a result, the concave portion 3 is formed on the first substrate 1.

Then, a CVD (Chemica)
A silicon oxide (SiO ₂ ) film 4 is deposited by the 1 Vapor Deposition method (see FIG. 4C). At this time, the silicon oxide film 4 deposited on the concave portion 3 becomes the stopper portion 3a used in a later step. Then
The surface of the silicon oxide film 4 is flattened and polished (FIG. 4D).
reference).

Next, a support substrate (second substrate) 5 made of silicon and having both surfaces mirror-finished and having a small thickness unevenness is attached to the surface of the silicon oxide film 4 by heating (FIG. 5 (e)). reference).

Next, the lower surface of the first substrate 1 is ground to a thickness of about one wafer (FIG. 5).
(See (f)). Then, the lower surface of the first substrate 1 is polished. The polishing is performed up to the surface of the stopper portion 3a of the silicon oxide film 4 having high hardness, so that many SOI regions 6 are formed on the lower surface of the first substrate 1 (see FIG. 5G).

An SOI substrate is manufactured by the bonding method according to the processing steps described above. In the grinding and polishing steps performed in this processing step, the reference surface for processing is one surface of the support substrate 5, and the surface thereof is used. Is a mirror surface, so L
The following problems occur in the subsequent steps for forming SI.

When the SOI substrate is transported in the atmosphere, the SO
When the back surface of the I substrate is held by a vacuum chuck, it becomes difficult to separate it. That is, the mirror surface of the wafer and the vacuum chuck come into close contact with each other, making it difficult for air to flow in after the vacuum is cut off, resulting in a transfer error.

Further, in the case of an apparatus in which the temperature of the SOI substrate is adsorbed on a susceptor or the like and is controlled by heat conduction from there, the temperature of the SOI substrate differs depending on the state of the back surface of the SOI substrate even if the temperature of the susceptor is the same. It will be. Therefore, even if the optimum process condition is given to the back surface of a normal bulk substrate, it does not apply to a mirror-finished SOI substrate.

[0013]

Therefore, an object of the present invention is to prevent troubles in carrying and heating even in a manufacturing line in which adjustments and conditions are set in the existing bulk substrate.
An OI substrate and a manufacturing method thereof.

[0014]

In order to solve such a problem, an SOI substrate according to the invention of claim 1 is formed by adhering a second substrate to a first substrate through a silicon oxide film. The outer surface of the second substrate of the substrate is made rough so that it can be easily separated after being gripped by a vacuum chuck or the like.

An SOI substrate according to a second aspect of the present invention has the structure of the SOI substrate according to the first aspect, in which the outer surface of the second substrate is formed by roughening, and is gripped by a vacuum chuck or the like. It was easy to separate after doing.

The SOI substrate according to claim 3 has the structure of the SOI substrate according to claim 1, wherein polysilicon is deposited on the outer surface of the second substrate to roughen the surface.
The separation after gripping with a vacuum chuck was made easy.

According to a fourth aspect of the method of manufacturing an SOI substrate of the present invention, a recess is formed on the inner surface of the first substrate,
A silicon oxide film is deposited on the inner surface, the silicon oxide film is polished, a second substrate is attached to the polished surface of the silicon oxide film, the outer surface of the first substrate is ground, and the second substrate is ground. The outer surface of the straight was roughened, and the outer surface of the first substrate was polished to facilitate separation after gripping with a vacuum chuck or the like.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The structure and operation of an SOI substrate and a method of manufacturing the same according to the present invention will be described below with reference to FIGS.

Embodiment 1 FIG. 1 to FIG. 2 are side sectional views of a wafer along each step of an SOI substrate according to the present invention. First, the first made of silicon
A photoresist pattern 2 is formed on the substrate 1 by a lithography method, and reactive ion etching (RIE) is performed (see FIG. 1A). Then, the resist film is peeled off by dipping in a peeling solution or by plasma ashing (see FIG. 1B), and as a result, the concave portion 3 is formed on the first substrate.

Then, a CVD (Chemica)
A silicon oxide (SiO ₂ ) film 4 is deposited by the 1 Vapor Deposition method (see FIG. 1C). At this time, the silicon oxide film 4 deposited on the concave portion 3 becomes the stopper portion 3a used in a later step. Then
The surface of the silicon oxide film 4 is flattened and polished (FIG. 1D).
reference).

Next, the inner surface 5d of the support substrate (second substrate) 5 made of silicon and having both surfaces mirror-finished and having a small thickness unevenness is attached to the surface of the silicon oxide film 4 by heating (FIG. 2 (e)). Next, the outer surface 1a of the first substrate 1 is ground to a thickness of about one wafer (see FIG. 2 (f)). At this time, S
The OI layer is ground to a thickness of at least 4 μm which causes damage due to grinding throughout the wafer so that the first first substrate 1 remains.

Then, the outer surface 5c of the second substrate 5 is lapped, sandblasted or the like to obtain a surface roughness #.
Roughening is performed to about 1200 (see FIG. 2G).
Next, the outer surface 1a of the first substrate 1 is polished. Polishing is performed up to the surface of the stopper portion 3a of the silicon oxide film 4 having a high hardness to form a large number of SOI regions 6 on the outer surface of the first substrate 1 (FIG. 2).
(See (h)). In this case, since the polishing is performed on the basis of the surface of the wafer, the unevenness of the second substrate 5 has a considerable influence on the in-plane uniformity of the polishing. In order to reduce this effect, polishing may be performed first, and then a protective resist or the like may be applied to the wafer surface, followed by lapping.

Second Embodiment Next, a second embodiment of the SOI substrate and the manufacturing method thereof according to the present invention will be described with reference to FIG. FIG. 3 is a side sectional view of a wafer in each step of the method of manufacturing an SOI substrate. However, since the steps up to the first substrate grinding step (f) are the same as those in the first embodiment, the description thereof will be omitted. In the step of FIG. 3G, a polysilicon film 5b is formed on the outer surface 5c of the support substrate 5 by CVD (Chemical Vapor).
Deposition method or the like is used to deposit about 1.0 μm. This polysilicon film 5b has a rough surface by selecting deposition temperature conditions.

Next, the outer surface 1 of the first substrate
A is polished in the same manner as in Embodiment 1 (see FIG. 3 (h)).

[0025]

As is clear from the above description, according to the SOI substrate of the present invention, one surface thereof is roughened, so that it can be quickly separated when gripped by a vacuum chuck or the like. It can be put into the bulk substrate production line without any special temperature conditions.

[Brief description of drawings]

FIG. 1 is a side sectional view of a wafer in steps (a) to (d) of a method for manufacturing an SOI substrate according to a first embodiment of the present invention.

FIG. 2 is a side sectional view of a wafer in steps (e) to (h) of the method for manufacturing an SOI substrate according to the first embodiment of the present invention.

FIG. 3 is a side sectional view of a wafer in steps (e) to (h) of the method for manufacturing an SOI substrate according to the second embodiment of the present invention.

FIG. 4A to 4A of a conventional method for manufacturing an SOI substrate.
It is a sectional side view of a wafer in a (d) process.

FIG. 5 (e) of a conventional method for manufacturing an SOI substrate
It is a sectional side view of a wafer in a (g) process.

[Explanation of symbols]

 1 First Substrate 1a Outer Side 1b Inner Side 2 Photoresist Pattern 3 Recess 3a Stopper 4 Silicon Oxide Film 5 Supporting Substrate (Second Substrate) 5a Rough Surface 5b Outer Side 5d Inner Side 6 SOI region

Claims (4)

[Claims] 1. An SOI substrate in which an outer surface of a second substrate is a rough surface, which is an SOI substrate having a structure in which a second substrate is attached to a first substrate via a silicon oxide film. 2. The SOI according to claim 1, wherein the outer surface of the second substrate is formed by roughening.
substrate. 3. The SOI substrate according to claim 1, wherein polysilicon is deposited on the outer surface of the second substrate and roughened. 4. A recess is formed on the inner surface of the first substrate, a silicon oxide film is deposited on the inner surface, the silicon oxide film is polished, and a second substrate is formed on the polished surface of the silicon oxide film. A step of laminating a straight surface, grinding the outer surface of the first substrate, roughening the outer surface of the second substrate, and polishing the outer surface of the first substrate; Substrate manufacturing method.