JPH03136346A - Manufacture of soi substrate - Google Patents

Abstract

PURPOSE:To enable an SOI substrate in even thickness of an Si layer not exceeding 1mum to be formed by a method wherein an element formation substrate and an oxide film are etched away from openings of a mask formed on the element formation substrate junctioned with a holding substrate through the oxide film while exposed parts are thermal-oxidized to form insulating films for element isolation to leave element isolation regions by grinding process. CONSTITUTION:A holding substrate (Si) 1 and an element formation substrate (Si) 3 are junctioned with each other through an oxide film (SiO2) 2. The substrate 3 is thinned by grinding process to form an element formation Si layer 8. When a mask 4 having openings 5 in the substrate 3 is formed while the substrate 3 and an oxide film 2 are etched away from the openings 5 to expose the holding substrate 1 for thermal-oxodizing the exposed parts, insulating films 6 for element isolation are formed and the surfaces of the films 6 jut out of the surface of the oxide film 2 but the level differences in respective openings 5 between the surfaces of the insulating film 6 and the surface of the oxide film 2 are equal to each other. When the substrate 3 is ground at much higher grinding rate than that of the insulating film 6, the grinding process can be almost stopped as soon as the insulating films 6 appear so that element formation regions 7 in even thickness isolated from the insulating films 6 may be formed.

Description

[Detailed description of the invention] 〔overview〕 .

The present invention relates to a method of manufacturing an SOI substrate, particularly a method of manufacturing a bonded SOI substrate.

S with an extremely thin and uniform device formation area
The purpose is to provide OI substrates.

a step of bonding a support substrate and an element formation substrate via an oxide film, and forming a mask having an opening on the element formation substrate,
A step of etching and removing the element formation substrate and the oxide film through the opening to expose the supporting substrate; and a step of thermally oxidizing the exposed portion so that the upper surface thereof protrudes above the upper surface of the oxide film. A method for manufacturing a Sol substrate, including a step of forming a film, and a step of polishing the element formation substrate to the same height as the element isolation insulating film, leaving an element formation region separated by the element isolation insulating film. Configure.

[Industrial application field]

The present invention is based on SOI (Silicon on Insu)
The present invention relates to a method of manufacturing a bonded SOI substrate, and particularly to a method of manufacturing a bonded SOI substrate.

Sol substrates are superior to bulk substrates in terms of element characteristics and isolation between elements, and among them, SO2 substrates made of bonding technology that take advantage of bulk crystallinity are attracting attention.

The bonded SOI substrate has the possibility of obtaining an ultra-thin film SOI substrate in which the thickness of the Si layer that forms the element formation area is less than lam, but it is difficult to obtain an element formation area that is thin and has a uniform thickness. Reliable technology for formation has not yet been established.

[Conventional technology]

FIGS. 2(a) to 2(c) are cross-sectional views showing an example of the process of manufacturing a bonded SOI substrate as Conventional Example I.

The oxide films of a Si wafer 1 having an oxide film 11 formed on its surface and a Si wafer 3 having an oxide film 31 formed on its surface are butted against each other and overlapped (FIG. 2(a)).

The oxide films are bonded together by heating to form oxide film 2 (second
Figure (b)).

Using the Si wafer 1 as a supporting substrate and the Si wafer 3 as an element forming substrate, the Si wafer 3 is polished to become a thin film and an element forming Si layer 8 is formed (FIG. 2(C)).

By the way, it is usually extremely difficult to reduce the variation in the thickness of Si wafers, which are used as supporting substrates and element forming substrates, to 1 μm or less depending on the location. It is virtually impossible to form an element-forming Si layer with a thickness of 1 μm or less and with a uniform thickness.

FIGS. 3(a) to 3(d) are cross-sectional views showing another example of the process of making a bonded Sol substrate as conventional example (2).

First, an oxide film 31 is placed on a Si wafer 3 that will become an element formation substrate.
and LOCOS (Local oxidation
of 5ilicon) 32 (Fig. 3(a)
)).

Next, the protruding portion of LOGO3 is polished to make it flat (FIG. 3(b)).

Next, the surface of the Si wafer I serving as a support substrate on which the oxide film 11 is formed and the surface of the planarized LOGO 3 are butted against each other, overlapped, and bonded by heating (FIG. 2(C)).

Grinding is performed from the side opposite to LOGO 3 of the Si wafer 3 to thin the Si wafer 3, and further polishing is performed using a polishing method in which St is polished but SiO2 is not polished, and LO
Element formation regions 7 separated by GO 332 are formed (FIG. 3(d)).

By the way, in this case as well, for the same reason as the above-mentioned conventional example (2), it is extremely difficult to flatten LOGO3 without exposing Si.

This is because if the LOGO 332 is polished using a normal polishing method, the oxide film 31 will also be polished away, and the thickness of the oxide film 31 is less than 1 μm.

This is because it is usually extremely difficult to completely flatten the LOGO 332 while leaving the oxide film 31 uniformly (see the third example).
(See figure (b)).

Furthermore, since the surface of the polished SiO□ film has large surface roughness, the bonding strength of the bonding is reduced.

After all, polishing the surface of the SiO□ film is not desirable when producing a bonded SOI substrate.

[Problem to be solved by the invention]

“Therefore, it is impossible to make an ultra-thin SO2 substrate with a Si layer thickness of 1 μm or less in the element formation region using the conventional method.

It is extremely difficult.

An object of the present invention is to provide a new method for realizing an ultra-thin Sol substrate in which the thickness of the Si layer in the element formation region is 1 μm or less and is uniform.

[Means to solve the problem]

FIGS. 1(a) to 1(d) are sectional views for explaining the present invention in detail.

The above-mentioned problems include the step of bonding the support substrate 1 and the element formation substrate 3 via the oxide film 2, the formation of a mask 4 having an opening 5 on the element formation substrate 3, and the formation of a mask 4 having an opening 5 through the opening 5. The forming substrate 3 and the oxide film 2 are etched and removed, and the supporting substrate 1 is removed.
a step of thermally oxidizing the exposed portion to form an element isolation insulating film 6 whose upper surface protrudes above the upper surface of the oxide film 2; and a step of polishing the element forming substrate 3 to isolate the element. This problem is solved by a method for manufacturing a Sol substrate, which includes a step of leaving an element formation region 7 that is at the same height as the insulating film 6 and separated by the element isolation insulating film.

[Effect]

In the present invention, first, the supporting substrate 1 and the element forming substrate 3 are bonded with the oxide film 2 interposed therebetween. By forming the supporting substrate 1 and the element forming substrate 3 flat and forming an oxide film on their surfaces, the bonding strength can be increased, and the bonded oxide film 2 is flat and has a uniform thickness. It is formed.

The upper surface of the element isolation insulating film 6 formed on the exposed part of the support substrate l under the opening protrudes above the upper surface of the oxide film 2, but the upper surface of the element isolation insulating film 6 and the upper surface of the oxide film 2 are The difference in height is the same for each aperture.

Next, the element formation substrate 3 is polished to form an element isolation insulating film 6.
In this case, the height is the same as that of .

If a polishing method is used in which the polishing rate for the element formation substrate 2 is much higher than the polishing rate for the element isolation insulating film 6, the polishing will almost stop when the element isolation insulating film 6 appears, and the element isolation insulating film 6 will be removed. Element forming regions 7 of uniform thickness are formed.

〔Example〕

FIGS. 1(a) to 1(d) are cross-sectional views for explaining the present invention in detail, and 1 is a support substrate, and 2 is a Si wafer.
3 is an oxide film, which is a Si film; 3 is an element forming substrate, which is a Si wafer; 4 is a mask; and 5 is an opening.

Reference numeral 6 represents an element isolation insulating film, which is a SiO□ film, 7 represents an element forming region, and 8 represents an element forming Si layer.

The following description will be made with reference to these figures.

FIG. 1(a) Reference support substrate 1 is a 0.6 m++w Si wafer with a 0.25 μm thick SiO□ film formed on the surface, element forming substrate 3 is a 0.25 μm thick 5iO1 surface. Using Si wafers having a thickness of 0.6 +am on which a film has been formed, they are stacked one on top of the other and bonded together by heating. As a result, there is a Sing with a thickness of 0.5 μm between the support substrate l and the element formation substrate 3.
Membrane 2 becomes interposed.

By grinding the reference element forming substrate 3 shown in FIG. 1(b), the thickness is reduced to 2 μm (
Then, an element-forming Si layer 8 is formed.

A SiN mask 4 having a thickness of 0.1 zm and having an opening 5 having a width of 1.2 μm is formed on the element-forming Si layer 8 .

The element forming Si layer 8 and the SiO□ film 2 are etched and removed through the opening 5 to expose the support substrate l.

Referring to FIG. 1(c), the supporting substrate l is thermally oxidized to form an element isolation insulating film 6 of 5i (h film) in the opening.Thermal oxidation increases the volume by 2, and the element isolation insulating film 6 is directed upward. However, it is thermally oxidized under conditions such that its upper surface is approximately 1 μm above the original surface of the supporting substrate 1. As a result, the upper surface of the element isolation insulating film 6 becomes SiO
□0.5 μm higher than the top surface of the membrane 2.

Referring to FIG. 1(d), the element-forming Si layer 8 is polished using an amine aqueous solution as the polishing agent and a foamed polyurethane pad as the polishing cloth. Amine-based aqueous solution has a polishing rate of Sing for Si.
The polishing rate is more than 10' times higher than that of the standard.

The element forming Si layer 8 is uniformly removed from the surface.
From the moment when the element isolation insulating film 6 appears, it is almost no longer removed. As a result, an element formation region 7 is formed in which the Si layer has a thickness of 0.5 am and has a uniform thickness.

Thus, the device formation region 7. has a uniform thickness of less than lam.
It is possible to fabricate an ultra-thin film Sol substrate with

Note that in order to stop the polishing of St when the element isolation insulating film 6 appears, the width of the opening 5 needs to be 0.5 μm or more. In this example, the width of the opening 5 is 1.2 μm.
Thus, the thickness of the element forming region 7 could be suppressed to 0.5 μm plus or minus 0.02 μm.

〔Effect of the invention〕

As described above, according to the present invention, the device has an element formation region with a uniform thickness of 1 μm or less.

Furthermore, it is possible to provide an SO1 substrate with high bonding strength.

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

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are sectional views for explaining an embodiment. FIGS. 2(a) to 2(c) are sectional views for explaining conventional example I. FIGS. 3(a) to 3(d) are sectional views for explaining conventional example (2). In fig. 1 is a supporting substrate, which is a Si wafer. 2 is an oxide film, which is a SiO□ film. 3 is an element forming substrate, which is a Si wafer. 4 is a mask. 5 is an open hole. 6 is an element isolation insulating film, which is a SiO□ film. 7 is an element forming area. 8 is an element forming St layer. 11 is an oxide film, which is a SiO□ film. 31 is an oxide film, which is a SiO□ film. 32 is LOCO3 cusp s! , Example series 1 Figure 2

Claims (1)

[Claims] A step of bonding a support substrate (1) and an element formation substrate (3) via an oxide film (2), and a mask (5) having an opening (5) on the element formation substrate (2).
4), and the element forming substrate (3) is formed through the opening (5).
The oxide film (2) is etched and removed, and the supporting substrate (2) is removed.
1); and a step of thermally oxidizing the exposed portion to form an element isolation insulating film (6) whose upper surface protrudes above the upper surface of the oxide film (2). The element forming substrate (2) is polished to form the element isolation insulating film (6).
) and leaving an element formation region (7) separated by the element isolation insulating film (6).