JPH0360007A - Clad sio substrate - Google Patents

Abstract

PURPOSE:To prevent peeling of silicon at the side where an element is formed by setting the thickness of an oxide film to be formed on a silicon wafer, at the side where the element is formed, less than the thickness of the silicon wafer at the side where the element is formed. CONSTITUTION:A silicon wafer 10 at the side where an element is formed is subjected to steam oxidation, and oxide films 11a and 11b are formed on the surfaces. What is more, the thickness of the oxide films 11a and 11b is set less than the thickness of the silicon wafer 10a at the side where an element is formed after filming.

Description

[Detailed Description of the Invention] [Summary] Silicon wafers with an oxide film formed on their surfaces are stacked and bonded together, and then the silicon wafer bar on the element forming side is converted to Si, so-called bonded 5ot (Siticon on
1 nsulatar >Regarding the substrate, when the thickness of the silicon wafer on the element formation side is set to WAss of less than 1 μm, the purpose of preventing the peeling of the silicon on the element formation side and its oxide film is to form on the silicon wafer on the element formation side. The thickness of the oxide film formed is less than the thickness of the silicon wafer on the element formation side.

[Industrial application field]

The present invention relates to a so-called bonded SOI substrate in which silicon wafers having an oxide film formed on their surfaces are stacked and bonded together, and then the silicon wafer on the element forming side is thinned.

The bonded Sol substrate is made by laminating a silicon wafer on the element forming side and a silicon wafer on the support substrate side with an oxide film such as silicon oxide (S!Oz) interposed therebetween. In particular, this method improves the crystallinity of the silicon. Since it can be used as is, a high-performance SOI substrate can be obtained. For substrates with such a Sol structure, thinner silicon wafers on the element formation side are advantageous in terms of integration degree and operation speed. Since the back surface (i.e., the interface between the silicon wafer on the element formation side and the oxide film) also becomes part of the electrically active element region, the interface characteristics between the silicon wafer on the element formation side and the oxide film are important. It is important to have a structure that allows the silicon wafer on the forming side and the oxide film to be reliably held on the silicon wafer on the receiving substrate side without peeling off from the adhesive surface. As shown in Figure 3, a silicon wafer 1 on the element formation side and a silicon wafer 2 on the supporting substrate side
The structure is such that the two are overlapped with each other with an oxide film 3 interposed therebetween.

In this case, when the oxide film 3 is formed by thermally oxidizing the silicon wafer 2 on the support substrate side, the upper surface 3a of the oxide film 3 becomes an adhesive interface (which causes leakage current), so the silicon wafer 2 on the element formation side Although it is not possible to obtain good characteristics with an ultra-thin film type (thickness of the silicon wafer 1 on the element formation side less than 1 μm) in which the back surface (3a) of the silicon wafer 1 is used as the active element region, thermal oxidation of the silicon wafer 1 on the element formation side In this case, the lower surface 3b of the oxide film 3 becomes the adhesive interface, so leakage current does not become a problem in the super 11111 type described above in which the back surface 3a of the silicon wafer 1 on the element forming side is used as the active element region. .

Therefore, conventional ultra-thin film type lamination t! In sOI substrate wafers, oxide films are formed only on the element formation side silicon wafer, or on both the element formation side silicon wafer and the support substrate side silicon wafer, in order to obtain good interface characteristics.

In this case, in the conventional ultra-thin film type bonded SOI substrate wafer, the oxide film thickness is generally 0.5 .mu.-, and this thickness is determined regardless of the thickness of the silicon wafer 1 on the element forming side.

[Problem to be solved by the invention]

In general, silicon oxide (Si 02 ) and silicon have thermal expansion coefficients that differ by more than an order of magnitude, so when the film is made thinner, the balance between the oxide film and the silicon wafer is disrupted, causing stress in the silicon wafer that tends to deform it. This stress becomes stronger as the oxide film becomes thicker and the silicon wafer becomes thinner. Since the direction of this stress is opposite to the direction of the silicon wafer bonding interface 3b in FIG. There was a problem in that the silicon wafer 1 on the side of the element formation had a strong tendency to peel off from the adhesive interface 3b with the silicon wafer 2 on the support substrate side, especially in the case of an ultra-thin film type with a thickness of less than 1 μm (this phenomenon (This phenomenon did not occur in the case of a Sol substrate in which the thickness of the silicon wafer on the element formation side was 1 μm or more).

An object of the present invention is to provide a bonded Sol substrate that can prevent peeling of the silicon on the element formation side when the thickness of the silicon wafer on the element formation side is made into an ultra-thin film of less than 1a haze.

[Means to solve the problem]

FIG. 1 shows a diagram of the principle of the present invention. In the same figure, 20 is the thickness 1
Element formation side silicon wafer with a thin film of less than μm, 2
1 is a supporting substrate side silicon wafer, 22 is an oxide film provided between these, and the oxide film 22 is an oxide film formed at least on the surface of the element forming side silicon wafer 20.

In the present invention, the thickness of the oxide film 22 formed on the element forming side silicon wafer 20 is formed to be less than the thickness of the element forming side silicon wafer 20.

[Effect]

Oxide film 22 formed on the silicon layer 1c 20 on the element formation side
is less than the thickness of the element forming side silicon wafer 20, so the thickness of the element forming side silicon wafer 20 is 1 μm.
Even in the case of ultra-thin film type devices, the stress generated in silicon wafers due to the difference in thermal expansion coefficients between silicon and silicon oxide can be significantly reduced compared to conventional devices. As a result, the thickness of the silicon wafer 20 on the element forming side is 1 μm.
Even in the ultra-thin film type, the element formation side silicon wafer 20 and the oxide film 22 are the supporting substrate side silicon wafer 21.
It will not peel off from the adhesive interface 21a.

〔Example〕

FIG. 2 shows a process diagram for manufacturing an embodiment of the present invention.

In this example, a silicon wafer 10 on the element forming side after thinning is used.
The thickness of a is 0.5 μm, and the film thickness distribution within the wafer plane is ±0.
．． This is a case where a 2 μm bonded SOI substrate is manufactured.

As shown in Fig. 2<A), the silicon wafer 1 on the element formation side
0 was steam oxidized at an oxidation temperature of 1000°C for 9M for 20 minutes, and an oxide film 11a with a thickness of 0.1 μm was formed on the surface.
, 11b. The thickness of the oxide films 11a and 11b may be less than the thickness of the element forming side silicon wafer 10a after thinning, and is not limited to the above thickness. Next, see Figure 2 (
As shown in B), the support substrate side silicon wafer 12 is steam oxidized at an oxidation temperature of 1100° C. and an oxidation time of 120 minutes to form an oxide film 13a with a thickness of 1 μm on its surface.

13b is formed.

Next, as shown in FIG. 2C, the silicon wafer 10 on the element forming side and the silicon wafer 12 on the supporting substrate side are placed one on top of the other and bonded together by heat treatment at 1100° C. for 120 minutes. Next, the silicon wafer 10 on the element forming side is thinned to a thickness of 3 μm using a grinding machine (broken line in FIG. 2(C)).
After that, as shown in FIG. 2(D), the substrate is thinned to a thickness of 0.5±0.2 μm using a polishing device, thereby completing the bonded Sol substrate of the present invention.

In this way, in the present invention, the element forming side silicon wafer 1
I! of the oxide film 11b formed on 0a! ! The thickness is less than the film thickness of the element forming side silicon wafer 10a (in this example, 115
) Therefore, even if the thickness of the silicon wafer 10a on the element forming side is reduced to less than 1 μm, the stress generated in the silicon wafer due to the difference in thermal expansion coefficient between silicon oxide and silicon can be significantly reduced compared to the conventional example. Therefore, the element forming side silicon wafer 10a and the oxidation 1! llb is the adhesive interface with the silicon wafer 12 on the supporting substrate side (1 of the oxide film 13a)
It will not peel off from the surface.

In the above embodiment, the surface oxide film was formed on both the silicon wafer on the element forming side and the silicon wafer on the support substrate side, but the present invention is not limited to this.
It may be formed only on the silicon wafer on the element formation side, and in short, it is sufficient if the surface oxide film is formed on at least the six element formation side silicon wafers.

〔Effect of the invention〕

As explained above, according to the present invention, the thickness of the oxide film formed on the silicon wafer on the element formation side is less than the thickness of the silicon wafer on the element formation side, so that the thickness of the silicon wafer on the element formation side is 1μ. Even with the ultra-thin film type, the stress generated on the silicon wafer on the element forming side is significantly smaller than that of conventional types, and therefore the silicon wafer on the element forming side and the oxide film peel off from the adhesive interface with the supporting substrate side silicon wafer. This can be prevented.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a process diagram for manufacturing an embodiment of the present invention, and FIG. 3 is a configuration diagram of a conventional example. In the figure, 10 is a silicon wafer on the element formation side, 108.20 is a thinned silicon wafer on the element formation side, 11a, 11b, 13a, 13b, 22 is an oxide film, 12
．． Reference numeral 21 indicates a silicon wafer on the support substrate side.

Claims (1)

[Claims] The oxide film (22) provided between the thinned element forming side silicon wafer (20) and the supporting substrate side silicon wafer (21) is at least
0), which is an oxide film formed on the surface of the element forming side silicon wafer (20) in a bonded SOI substrate in which the thickness of the element forming side silicon wafer (20) is determined to be less than 1 μm. The thickness of the oxide film formed on the silicon wafer (20) on the element forming side is
Laminated S characterized by being formed to a thickness less than
OI board.