JPH03259521A - Manufacture of soi substrate - Google Patents

Abstract

PURPOSE:To obtain a superthin film SOI substrate having an Si active layer of uniform thickness, by a method wherein, after a stuck SOI substrate is formed, trenches wherein widths and intervals are changed are formed to a depth wherein an SiO2 layer is exposed. CONSTITUTION:SiO2 of Si substrate, on which surfaces SiO2 films are formed, are brought into contact with each other and heated, thereby sticking the substrates. A thinly polished Si layer 5a is formed on an Si substrate 3, via an SiO2 layer 4. By patterning the Si layer 5a, narrow trenches 6a-6k of 2mum in width are formed to expose the SiO2 layer, 4 thereby forming Si layers 7a-7d and narrow Si layers 8a-8h. Amine based aqueous solution wherein the Si polishing speed is much higher than the SiO2 polishing speed is used; polishing is performed by using an expanded polyurethane cloth; all Si layers 8a-8h are eliminated and very thin Si layers 9a-9d constituted of the residual Si layers 7a-7d are formed. By this constitution, a superthin film SOI substrate having a very thin Si active layer of uniform thickness can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method of manufacturing an SOI substrate, particularly a method of manufacturing a bonded SOI substrate.

The purpose of this study is to provide a method for forming an SOI tombstone having an ultrathin Si layer of uniform thickness.

A step of grinding one side of a bonded SOI substrate consisting of a 5iOz layer and Si layers above and below the SiO□ layer to form a thin Si layer, and forming a plurality of grooves in the thin Si layer to expose the SiO□ layer. A process of forming an Si layer with a large distance between grooves and a Si layer with a small distance between grooves, and a process of polishing the entire surface using an abrasive that selectively polishes Si with respect to Sing. Then, according to a method for manufacturing an SOI substrate, the Si layer with a small distance between the grooves is removed by polishing to expose the SiO□ layer, and the Si layer with a large distance between the grooves is left to form an extremely thin Si layer. Configure.

[Industrial application field]

The present invention relates to a method for manufacturing an SOI substrate, and more particularly to a method for manufacturing a bonded SOI substrate.

SOI substrates are superior to bulk substrates in terms of element characteristics and isolation between elements, but among them, bonded SOI substrates that take advantage of bulk crystallinity are attracting attention.

FIGS. 3(a) to 3(c) show the manufacturing process of a bonded SOI substrate.

Si substrate 1a with 5iOz film 1b formed on the surface and 5i0 of Si substrate 2a with SiO2 film 2b formed on the surface.
The two membranes are faced to each other (see Figure 3(a)).

The SiO□ films of the Si substrate 1a and the Si substrate 2a are brought into contact and heated and bonded together. The Si substrate on one side becomes a supporting substrate 3, and the Si substrate on the opposite side becomes an element substrate 5 on which a Si active layer will be formed in the future, and a SiO□ layer 4 is formed between them (see FIG. 3(b)).

The element substrate 5 is ground to obtain a thin Si layer 5a (see Fig. 3).
c).

Among such bonded SOI substrates, ultra-thin film SOI substrates in which the Si active layer has a thickness of 0.5 μm or less have attracted attention in recent years. In manufacturing this ultra-thin film SOI substrate, it is necessary to suppress in-plane variations in the thickness of the Si active layer on which elements are formed to less than variations in the thickness of the supporting substrate 3. It is impossible to form a Si active layer using techniques, and it is impossible to form a Si active layer with a uniform thickness.
New techniques are needed to form active layers.

(Prior art) The conventional manufacturing process for producing an ultra-thin SOI substrate is shown in Figure 2 (a).
) to (e). The following description will be made with reference to these figures.

Refer to FIG. 2(a). This figure shows a SiO□ layer 4 on a support substrate 3. A thin S on top of that
A laminated substrate on which an i-layer 5 is formed is shown.

Refer to FIG. 2(b), a groove 6 is formed in the thin Si layer 5 to expose the SiO□ layer 4.

See Figure 2(c) For example, SiO□ is deposited on the entire surface by the CVD method.

A 5iOz film 10 is formed.

By patterning the SiO□ film 10 using a mask (see FIG. 2(d)), the SiO□ film 10 is left only at the bottom of the groove 6.

Refer to FIG. 2(e).Si is polished but SiO□ is not polished. Polishing is performed using an amine-based aqueous solution, and the height of the thin Si layer 5a is reduced to 5in2.
Reduce until it coincides with the top surface of membrane 10.

In this way, an ultra-thin SOI substrate having a Si active layer with a thickness of 5iOz film 10 is fabricated.

By the way, in this conventional method, the process of forming the 5iOz film 10 on the entire surface and patterning the SiO□ film 10 using a primary mask to leave the SiQ□ film 10 only at the bottom of the groove 6 is complicated. Also, if the mask alignment is misaligned, the remaining 5i (
There was a problem that the h-film 10 protruded from the groove 6.

[Problems to be Solved by the Invention] The present invention has the above-mentioned method in which a 5iOz film 10 is formed on the entire surface and the 5iO2 film 10 is first patterned using a mask to leave the SiO□ film 10 only at the bottom of the groove 6. Super 3yS that does not require any process and has a Si active layer of uniform thickness.
0) The purpose is to provide a method for manufacturing a substrate.

[Means for Solving the Problems] FIGS. 1(a) to 1(d) are cross-sectional views showing the manufacturing process of an embodiment of the present invention.

The above-mentioned problems include a step of grinding one side of a bonded SOI substrate consisting of an SiO□ layer 4 and Si layers above and below the 5tOz layer 4 to form a thin Si layer 5a, and a step of forming a thin Si layer 5a.
a step of forming a plurality of grooves 6a to 6k exposing the 5iOz layer 4, and forming Si layers 7a to 7d with large distances between the grooves and Si layers 8a to 8h with small distances between the grooves;
A step of polishing the entire surface using an abrasive that selectively polishes Si with respect to SiO□, and polishing away the Si layers 8a to 8h with a small distance between the grooves to expose the SiO□ layer. At the same time, the Si layer 7a having a large distance between the grooves
S to form ultra-thin Si layers 9a to 9d, leaving 7d to 7d.
This problem is solved by a method for manufacturing an Ol substrate.

[Effect]

In the present invention, a plurality of grooves 68 to 6k are formed in the thin Sii layer a to expose the SiO□ layer 4, and S
Sii layers a to 8h having a small distance between the grooves are formed with the Sii layers a to 7d. When such a state is polished on the entire surface using a polishing agent that selectively polishes Si with respect to SiO When the polishing rate is higher than 7d, and when the Sii layers a to 8h with the short distance between the grooves are removed by polishing and the exposed area of the SiO2 layer 4 becomes large, the area between the remaining grooves becomes larger. The Sii layers a to 7d, which have a large distance, are hardly polished. This is a phenomenon discovered by the present inventor, and the reason why it happens is that the pressure applied during polishing is greater in a Si layer with a small distance between grooves than in a Si layer with a large distance between grooves, and the polishing agent must be replaced. The polishing rate is large due to the large speed, and even more.

This is believed to be because when the exposed area of the Sing layer becomes larger, the abrasive flows over the exposed Sing layer and is no longer supplied to the remaining Si where the distance between the grooves is large.

The thickness of the remaining Si layer with a large distance between grooves can be changed depending on the pressure during polishing, the area ratio to the Si layer with a small distance between grooves, the width of the grooves, the number of grooves, etc. If the width of the grooves, the number of grooves, and the number of Si layers with small distances between grooves are increased, the thickness of the remaining Si layers with large distances between grooves tends to increase.

Therefore, by selecting the groove width, the number of grooves, and the width and number of the Si layer with a small distance between grooves according to the area and thickness of the Si layer with a large distance between grooves, a single-pole 'FJt S A bonded SOI substrate with an i-layer can be produced.

[Example] FIGS. 1(a) to 1(d) are cross-sectional views showing the manufacturing process of an example for manufacturing an ultra-thin film SOI substrate, and the following description will be made with reference to these figures.

Referring to FIG. 1(a), Si substrates on which a SiO□ film with a thickness of 0.5 μm has been formed are bonded together, and one side thereof is ground to reduce the thickness to 2 μm. In Fig. 1(a), 3 is a 600 μm thick Si substrate, 4
5a is a SiO□ layer with a thickness of 1 μm, and 5a is a thin Si layer with a thickness of 2 μm.

Refer to FIG. 1(b), a thin Sii layer a is patterned by a normal photolithography process to form a plurality of grooves 6a to 6 with a width of 2 μm.
5102 layer 4 is exposed.

In places where the grooves are widely spaced, Sii layers a to ? dC width 40 μm) is formed. In places where the distance between the grooves is small, Sii layers a to 8h (width 2
μm) is formed.

Referring to FIG. 1(c), polishing was carried out using an amine-based aqueous solution in which the polishing rate of Si is 10' times higher than that of Sing as a polishing agent, and a foamed polyurethane pad as a polishing cloth.

The polishing rates for Sii layers a to 8h with short distances between grooves were higher than the polishing rates for Sii layers a to 7d with long distances between grooves.

Refer to FIG. 1(d) When the polishing is continued and the Sii layers a to 8h with the short distance between the grooves are removed by polishing and the Sing layer 4 underneath is exposed, not only the SiO□ layer 4 is no longer polished.
5iFJ7a to 7d, which had a large remaining distance, were no longer polished. Then, the thickness of the Si layer is 0. l ±0.0
Thirty-one ultrathin layers 9a to 9d of 1 μm were obtained. Ultra thin 31
Layers 9a to 9d had good thickness uniformity.

In this way, an ultra-thin SOI substrate having a very thin (uniform thickness) Si active layer was fabricated.

Note that the thickness of the ultra-thin 31 layers 9a to 9d can be changed depending on the width and number of Si layers with small distances between grooves, and the width and number of grooves. If the width of the Si layer with a large distance between grooves is kept constant and the width of the grooves, the number of grooves, and the number of Si layers with a small distance between grooves are increased, the thickness of the remaining ultra-thin 31 layers 9a to 9d will increase. Become.

〔Effect of the invention〕

As explained above, according to the present invention, the lamination SO
After forming the I-substrate, multiple grooves with different widths and intervals are formed on the Si.
By simply forming and polishing the O□ layer to a depth where it is exposed, an ultra-thin SOI substrate having a Si active layer of uniform thickness can be produced.

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

[Brief explanation of drawings]

FIGS. 1A to 1D are cross-sectional views for explaining the manufacturing process of the embodiment. FIGS. 2(a) to 2(e) are cross-sectional views for explaining the manufacturing process of a conventional example. FIGS. 3(a) to 3(c) are cross-sectional views for explaining the manufacturing process of the bonded SOr substrate. In fig. la and 2a are Si substrates. lb and 2b are SiO□ films. 3, the support substrate 4 is a SiO□ layer. 5 is an element substrate. 5a is a thin Si layer 6. 6a to 6 are grooves. 7a to 7d are Si layers with large distances between grooves. 8a to 8h are Si layers with small distances between grooves. 9a to 9d, the ultra-thin Si layer 10 is a SiO□ film (d) Example c') Fig. 1 (e) Conventional strawberry making process Fig. 2

Claims (1)

[Claims] A step of forming a thin Si layer (5a) by grinding one side of a bonded SOI substrate consisting of a SiO_2 layer (4) and Si layers above and below the SiO_2 layer (4); A plurality of grooves (6a to 6k) exposing the SiO_2 layer (4) are formed in the Si layer (5a), and the Si layer (7a to 7d) with a large distance between grooves and the Si layer (8a) with a small distance between grooves are formed. and a step of polishing the entire surface using an abrasive that selectively polishes Si with respect to SiO_2. The SiO_2 layer is exposed by polishing and removed, and the Si layer (7a to 7d) with a large distance between the grooves is left and an ultra-thin S
SO characterized by forming an i-layer (9a to 9d)
Method for manufacturing an I-board.