JPH0423324A - Manufacture of soi substrate - Google Patents

Abstract

PURPOSE:To obtain a pasted SOI substrate whose irregularity in a thickness is extremely small and which is provided with a thin element substrate by a method wherein the mirror-polished face of a second Si wafer is pasted on a first Si wafer having a uniform thickness, the second Si wafer is ground to form a thin film of the second Si wafer, an oxide film is formed on the thin film, a third Si wafer is pasted and, after that, the third Si wafer is stripped off and removed. CONSTITUTION:The following are prepared: a first Si wafer 1 whose irregularity TTV in a thickness inside the wafer face is 0.5mum or lower; and a second Si wafer 2 whose surface has been mirror-polished. The mirror-surface of the Si wafer 2 is pasted on the Si wafer 1 in such a way that it is not stripped off during a grinding process of the Si wafer 2 and adjusted to a strength so as to be stripped off when it is stripped off finally. In addition, the Si wafer 2 is ground from a face opposite to the pasted face; and the Si wafer 2 is worked to be a thin film 3 having a thickness of 0.7mum. Then, the thin film 3 is oxidized at a low temperature; and an oxide film 4 is formed. An Si wafer 5 is used as a third Si wafer; it is pasted on the oxide film 4; and after that, the Si wafer 1 is stripped off from the pasted face of the Si wafer 2 (the thin film). Thereby, it is possible to obtain an SOI substrate which uses the Si wafer 5 as a support substrate and which uses the thin film 3 as an element substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Summary) The present invention relates to a method of manufacturing a Sol substrate, particularly a method of manufacturing a laminated SOI substrate, and aims to provide a laminated SOI substrate having an element substrate with a small and uniform thickness.

After bonding the mirror-polished surface of the second Si wafer to the first Si wafer having a uniform thickness, the second Si wafer is
A step of grinding the i-wafer to form a thin film of a second Si wafer, a step of oxidizing the thin film to form an oxide film on the surface of the thin film, and a step of bonding a third Si wafer to the oxide film. , and a step of peeling off and removing the first Si wafer.

In addition, after bonding the mirror-polished surface of the second Si wafer to the first Si wafer having a uniform thickness, the second Si wafer is ground to form one layer of the second Si wafer. and a step of laminating the surface of a third Si wafer having an oxide film formed on one surface on the thin film, and then peeling off and removing the first 34 wafers. .

[Industrial application field]

The present invention relates to a method for manufacturing a Sol substrate, and particularly to a method for manufacturing a bonded Sol substrate.

Sol substrates are superior to bulk substrates in terms of element characteristics and isolation between elements, and among them, bonded SOI substrates that take advantage of bulk crystallinity are attracting attention. Furthermore, in recent years, SO2 substrates having a uniform Si active layer with an in-plane thickness variation of 0.5 μm or less have been attracting attention.

[Conventional technology].

FIGS. 3(a) to 3(c) are cross-sectional views for explaining the conventional process of manufacturing a bonded Sol substrate.

First, a first Si wafer 1 with an oxide film 1a formed on two surfaces, and a second Si wafer 1 with an oxide tPiJ2a formed on the third surface.
The oxide films of i-wafer 2 are faced to each other (Fig. 3 (
a)).

A first Si wafer 1 and a second Si wafer 2 are pasted together, and the bonding between them is completed by annealing. The oxide film 1a and the oxide film 2a form an oxide film 4 (FIG. 3(b))
reference).

The first Si wafer 1 is ground and polished to form a thin film 3 (see FIG. 3(c)).

In this way, the thin film 3 is formed into an element substrate (active layer).

A Sol substrate using the second Si wafer 2 as a support substrate is obtained.

FIGS. 4(a) to 4(c) are sectional views for explaining conventional problems.

First, the first Si wafer 1 and the second Si wafer 2 have variations in thickness, as schematically shown in FIG. 4(a).

When the first Si wafer 1 and the second Si wafer 2 are bonded together and the first Si wafer 1 is ground to become a thin film,
Corresponding to variations in the thickness of the second Si wafer 2, variations in the thickness of the thin film 3 also occur. At this time, variations in thickness due to the habits of the grinding machine are also added. There is a damaged layer 1b on the surface of the thin film 3 due to the grinding process (see Fig. 4(b)).
)).

Next, the damaged layer 1b is removed by mechanochemical polishing, and the surface roughness caused by the grinding is also removed to make the surface smooth. However, at this time, the amount removed within the wafer surface is not necessarily uniform, and further variations are added to the thickness of the thin film 3 (FIG. 4(C)).

[Problem to be solved by the invention]

Therefore, in the conventional bonded SOI substrate, the thickness variations of the second Si wafer 2 serving as the supporting substrate, the thickness variations caused by grinding, and the thickness variations due to mechanochemical polishing are added, and the element substrate ( The variation in the thickness of the thin layer 11!3 which becomes the active layer becomes large.

In view of the above problems, the present invention provides a manufacturing method for realizing a laminated S○1 substrate having extremely small variation in thickness and having a thin element substrate (active layer).

[Means to solve the problem]

Figures 1 (a) to (e) and Figures 2 (a) to (e) are
FIG. 3 is a cross-sectional view for explaining the steps of uninvented Example I and Example H, respectively.

The above problem is solved by the first Si wafer 1 having a uniform thickness.
A step of bonding the mirror-polished surface of the second Si wafer 2 to the substrate, and then grinding the second Si wafer 2 to form a copy 3 of the second Si wafer, and oxidizing the thin film 3. , an SOI substrate comprising the steps of forming an oxide film 4 on the surface of the thin film 3, and bonding a third Si wafer 5 to the oxide film 4, and then peeling off and removing the first Si wafer 1. The problem is solved by the manufacturing method.

In addition, a second Si wafer 1 having a uniform thickness is
After bonding the mirror-polished surfaces of the 31 wafers 2 together, a step of grinding the second Si wafer 2 to form a second Si wafer 3 and forming an oxide film 4 on one surface of the thin film 3 is performed. The problem is solved by a method for manufacturing an SOI substrate, which includes a step of bonding the surfaces of the third Si wafer 5 formed and then peeling off and removing the first Si wafer 1.

[Effect]

In the present invention, since the first Si wafer 1 has a uniform thickness, the second Si wafer 2, which will become an element substrate in the future,
Even if the thickness is not uniform, it is
When bonded to Si wafer 1 and ground to make a thin film,
Since the thin film 3 is formed using the first Si wafer 1 as a reference, the thickness of the thin film 3 is uniform.

If the same grinding machine is used for grinding the first Si wafer 1 to a uniform thickness and grinding the second Si wafer 2 to form a thin film, S
Since the i-wafer 2 is similarly affected by the grinder, variations in thickness due to the habit of the grinder do not appear.

Furthermore, if the thin film 3 is attached to the surface of the third Si wafer 5 and then the first Si wafer 1 is peeled off and removed,
Since the bonding surface of the second Si wafer 2 is a mirror-polished surface, there is no need for mechanochemical polishing that would cause variations in thickness.

[Example] FIGS. 1(a) to 1(e) are cross-sectional views for explaining the steps of Example (2), and the following description will be made with reference to these figures.

Refer to Fig. 1(a) In-plane thickness variation T T V (Total T
thickness variation) is 2 to 4 μm
A commercially available 6-inch Si wafer of about
．． A first Si wafer 1 with a thickness of 5 μm or less is prepared.

Furthermore, a second Si wafer 2 is prepared by mirror polishing the surface of a commercially available 6-inch Si wafer.

The mirror surface of the second Si wafer 2 is bonded to the first Si wafer 1. The bonding will not come off in the next grinding process of the second Si wafer 2.The bonding strength is adjusted so that it will peel off when it is finally removed.In other words, the surface roughness of the bonding surface of the Si wafer and the bonding temperature The bonding strength was adjusted to approximately 25 kg/cm.

Refer to FIG. 1(b) Using the high-precision surface grinding device used to prepare the first Si wafer 1, the second Si wafer 2 is ground from the surface opposite to the bonding surface, and the second Si wafer 2 is 2 with a thickness of 0.7μ
It was processed into a thin film 3 of m. The TTV is the combination of the first Si wafer 1 and the thin film 3.

The TTV of the thin film 3 was 0.1 μm.

The thin film 3 referred to in FIG. 1(c) was oxidized at low temperature to form an oxide film 4 with a thickness of 0.1 μm on the 2 surface.

Referring to FIG. 1(d), a commercially available 6-inch Si wafer is used as the third Si wafer 5, and the oxide film 4 is bonded thereto. At the time of lamination, the temperature was set at 1000°C, and electrostatic force was applied so that the lamination strength was approximately 500 kg/cm2.

Referring to FIG. 1(e), the first Si wafer 1 was peeled off from the bonded surface of the second Si wafer 2 (thin film 3) using a cutter knife. The mirror surface of the exposed thin film 3 was polished by 0.1 μm. The thickness of the thin film 3 was 0.5±0.05 μm.

Thereafter, in order to completely bond the oxide film 4 and the third Si wafer 5, annealing was performed in nitrogen at 1100° C. for 530 minutes.

In this way, a Sol substrate was obtained in which the third Si wafer 5 was used as a supporting substrate and the thin film 3 was used as an element substrate (active layer).

Next, Example H will be described.

FIGS. 2(a) to 2(e) are cross-sectional views for explaining the steps of Example (2).

The process shown in FIG. 2(a) is the same as that shown in FIG. 1(a).

Similar to Example 2 (see FIG. 2(b)), the second Si wafer 2 is ground from the surface opposite to the bonding surface using the high-precision surface grinding device used to prepare the first Si wafer 1. Then, the second Si wafer 2 was processed into a thin film 3 with a thickness of 0.5 μm.

FIG. 2(c) Sanwaki A commercially available 6-inch Si wafer was used as the third Si wafer 5, and an oxide film 4 having a thickness of 0.1 μm was formed on the surface thereof.

Refer to FIG. 2(d), the oxide film 4 and the thin film 3 are pasted together. The bonding strength is approximately 50% by adjusting the bonding temperature and the applied electrostatic force.
0 kg/cm".

See FIG. 2(e). The subsequent steps are the same as in Example I, and the third Si
The wafer 5 is used as a support substrate, and the thickness is 0.5 ± 0.05 μm.
A Sol substrate was obtained using the thin film 3 as the element substrate (active layer).

Note that an oxide film may be formed on the surface of the thin film 3, an oxide film may also be formed on the surface of the third Si wafer 5, these oxide films may be pasted together, and then the first Si wafer 1 may be peeled off.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a laminated Sol substrate in which the element substrate (active layer) is a thin film having a thickness of 1 μm or less and good thickness uniformity.

The present invention greatly contributes to improving the performance and yield of devices using bonded SOI substrates.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are cross-sectional views for explaining the steps of Example I. FIGS. 2(a) to 2(e) are cross-sectional views for explaining the steps of Example 2. FIGS. 3(a) to 3(c) are cross-sectional views for explaining conventional processes. FIGS. 4(a) to 4(c) are sectional views for explaining conventional problems. In fig. 1 is a first Si wafer 1a is a II oxide layer and 1b is a damaged layer. 2, the second Si wafer 2a is an oxide film. 3 is a thin film. 4 is an oxide film. 5 is the third Si wafer (σ) 1.Explain the process of Example 1 84￥U △Approximate concavity diagram (e) Real expiration degree] II's 1/FL 't-S To advance Cross-sectional diagram of Figure 2 (I) N (C) Cross-sectional diagram of Nukiho's L-note begging theory Figure 2

Claims (1)

[Claims] [1] After attaching the mirror-polished surface of the second Si wafer (2) to the first Si wafer (1) having a uniform thickness, the second Si wafer (2) is bonded to the first Si wafer (1) having a uniform thickness. ) to form a thin film (3) of a second Si wafer; oxidizing the thin film (3) to form an oxide film (4) on the surface of the thin film (3); A method for manufacturing an SOI substrate, comprising the steps of laminating a third Si wafer (5) to an oxide film (4) and then peeling off and removing the first Si wafer (1). [2] After bonding the mirror-polished surface of the second Si wafer (2) to the first Si wafer (1) having a uniform thickness, the second Si wafer (2) is ground to form a second Si wafer (2). a step of forming a thin film (3) on the Si wafer of No. 2; and after laminating the surface of a third Si wafer (5) on which an oxide film (4) is formed on the surface of the thin film (3); A method for manufacturing an SOI substrate, comprising a step of peeling off and removing a Si wafer (1).