JPS62124754A - Manufacture of dielectric isolation substrate - Google Patents

Abstract

PURPOSE:To reduce generation of warpage due to the difference of the thermal expansion coefficients of a polycrystalline layer and a semiconductor single crystal wafer by laminating at least three layers of polycrystalline layers, among which oxide films are held, onto an insulating film and using the polycrystalline layers as a laminate and polishing and removing the laminate to form a supporter layer consisting of the polycrystalline layer composed of two layers. CONSTITUTION:Polycrystalline layers hold oxide films among them and are shaped in a laminate A', in which at least three layers are laminated, at the time of cooling immediately after the formation of the polycrystalline layers onto an insulating film 4 in which there is the possibility of the generation of the largest warpage. Accordingly, the generation of warpage at the step can be reduced remarkably. Since the laminate A' has large thickness, handling at the time of a polishing process is also facilitated, too.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] This invention relates to dielectric layer separation (Dielectric layer separation).
(olation: DI) relates to a method of manufacturing a substrate.

[Background technology]

“Recently, insulating layer-separated substrates have come to be used as substrates for semiconductor integrated circuits.The most common structure of such insulating layer-separated substrates is as shown in FIG. A plurality of single-crystal island-like regions (hereinafter referred to as "separated islands") la... surrounded by
It is supported on 0. The isolated island 1a...
These are used as element forming regions, and as many isolation islands as the required number of elements are formed on one substrate. Since each isolation island 1a... is completely electrically isolated by an insulating layer, compared to the isolation of each element by a conventional P-N junction,
It achieves much higher voltage resistance, lower parasitic capacitance, and higher soft error tolerance. Furthermore, there is no possibility that parasitic elements or latch amplifiers will occur.

The insulating component M substrate as described above is generally formed by the following steps.

First, a wafer made of single crystal silicon or the like is prepared, and grooves are formed at desired positions on the surface of the wafer so as to surround the elements to be formed.

Next, the entire surface of this wafer on the side where the grooves are formed is covered with an insulating film such as a silicon oxide film, and further, polysilicon or the like is deposited thereon to form a support layer.

Then, the wafer is polished and removed from the back surface, the grooves are exposed on the back surface, and the wafer is divided into the separation islands to obtain an insulating layer separated substrate.

In the above-mentioned insulating layer-separated substrate, the biggest problem is the difference in the materials of the wafer and the support layer, especially the following two problems caused by the difference in the thermal expansion coefficient of each material.
It is a point.

(2) During the manufacturing process, when the support layer is formed, warpage occurs in which the support layer side is concave and the wafer side is convex.

As mentioned above, this warpage is caused by the difference in thermal expansion coefficient between the wafer and the support layer, and when the support layer formed at high temperature is cooled to near room temperature, This occurs because the shrinkage is greater than the wafer.

If this warpage occurs, the entire surface of the wafer cannot be uniformly polished during the next step of polishing the wafer, and the isolated islands cannot be uniformly formed.

Further, such an insulating layer separated substrate has a thickness of about 30 mm.
Since it is extremely thin, measuring approximately 0 m, it is difficult to handle it during each of the steps described above.

■ After forming the insulating layer separation substrate, epitaxial crystal growth,
When elements are formed on isolation islands through processes such as thermal diffusion, aluminum wiring formation, and passivation film formation, the warpage described in (2) above may be further expanded due to the accompanying heating (thermal history), etc. will cause warping in the opposite direction.

Such warpage not only makes it difficult to perform mask alignment in one photolithography process, but also may cause trouble in automatic conveyance systems and the like in various semiconductor manufacturing devices.

[Purpose of the invention]

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an insulating layer-separated substrate that is easy to handle and less likely to cause warping.

[Disclosure of the invention]

In order to achieve the above object, the present invention forms isolation grooves on the surface of a semiconductor single crystal wafer, covers the entire surface with an insulating film, and then forms a support layer thereon. , polishing the single crystal side until the bottom of the groove is exposed, forming an insulating component M on the support layer to form a semiconductor single crystal island region electrically isolated by the insulating film;
A method for manufacturing a substrate, in which, in making the support layer, a polycrystalline layer and an oxide film are alternately formed in this order on the insulating film, and at least three of the polycrystalline layers are laminated;
The gist of the present invention is a method for producing an insulating layer-separated substrate, which is then reversely polished and removed from above to leave at least two polycrystalline layers, which serve as the support layer.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to the accompanying drawings. In addition, in this example,
Although single crystal silicon is used as the isolation island, polysilicon is used as the polycrystalline layer, and SiO2 is used as the insulating film and the oxide film, it is of course possible to use other compound semiconductor materials.

First, regarding one embodiment of the method for manufacturing an insulating layer-separated substrate according to the present invention, FIG.
) to (f) and FIG. 2 fat to (C).

Prepare a single-crystal silicon Ueno\1 that will become a separation island [Figure 1 (a)].

Next, grooves 2 are formed at desired positions on the surface of the wafer 1 so as to surround the elements to be formed. The method of forming such a2... is not particularly limited, but for example, KO
Groove 2 is etched using an alkaline etching solution containing H etc. as the main component.
There is a method of etching. This method takes advantage of the fact that the etching rate of this alkaline etching solution for <111> plane single crystal silicon is extremely slow compared to the etching rate for <100> plane single crystal silicon (anisotropy). When a part of the wafer 1 of monocrystalline silicon with a 〉 plane is etched with this alkaline etching solution, a V-shaped groove 2 consisting of a 〈111〉 plane that makes a 54° angle with this 〈100〉 plane is automatically formed. It is formed in At this time, the same material (SiO2) as the insulating film to be formed in the next step is used as an etching mask.
It is more preferable to use the mask 3 because it can be used as a part of the insulating film and there is no need to remove the mask 3 before sending it to the next process. By the above operations, a groove having a depth of about 70 Ilrn, for example, can be formed [FIG. 1(b)].

A silicon oxide film 4, which is an insulating film, is formed over the entire surface of the wafer 1 on the side where the groove 2 is formed. Although the method for forming the silicon oxide film 4 is not particularly limited, it is preferable, for example, to form such a silicon oxide film by thermally oxidizing the surface of the wafer 1 by pyrogenic oxidation or the like. This is because such a pyroxidation method requires simple operations, processes, manufacturing equipment, etc., and the silicon oxide film 4 formed has excellent physical properties [Figure 1 (C)]. .

A polysilicon layer 5, which is a polycrystalline layer, is formed on the silicon oxide film 4 by a method such as epitaxial growth.

The growth conditions for the polysilicon layer 5 are not limited to these, but for example, when a reaction furnace normally used for epitaxial growth is used, the growth condition is 1.3 to 1.4 μm.
The growth may be performed at a growth rate of about 1/min. The gas t+ that can be used for growth can be the one used for normal epitaxial growth [1st
Figure (d)].

A silicon oxide film 6 which is an oxide film is formed on the surface of the polysilicon layer 5.
form. As a method for forming the silicon oxide film 6, it is preferable to use, for example, a pyrogenic oxidation method for the same reason as the silicon oxide film 4 [FIG. 1(e)].

The above operations are alternately repeated on the silicon oxide film 6 to form a polysilicon layer 7 [FIG. 1(f)], a silicon oxide film 8 [FIG. 2(al)], and a polysilicon layer 9 [FIG. 2(al)].
Figure (b)] ... are formed alternately, and at least three polysilicon layers with a silicon oxide film sandwiched therebetween are laminated on the silicon oxide film 4, which is an insulating film, to form a laminate A. ′ is obtained.

The wafer 1 is polished and removed from the opposite side until the wafer 1 is separated into a plurality of separation islands 1a by the grooves 2 [FIG. 2(C)].

After that, the laminate A' is polished from the upper layer,
This is then removed, leaving at least two polysilicon layers, which will be referred to as support layer A. At this time, it is preferable that the support layer A is substantially vertically symmetrical in its thickness direction. That is, as shown in the figure, when there are two polysilicon layers, two polysilicon layers 5
．． 7 preferably have approximately the same thickness. As a result, the silicon oxide film 6 can be located approximately at the center of the support layer A in its thickness direction. It can also prevent warping. The ratio of the thicknesses of the two polysilicon layers 5.7 is also not particularly limited, but is between 10 and 7:1.
It is preferably within the range of 0 [Fig. 3]. .

As described above, in the insulating layer separation substrate formed according to the present invention, as shown in FIG. (oxide film) sandwiched between Tahori silicon layer (polycrystalline N
) 5 and a polysilicon layer (polycrystalline layer) 7 . In this way, the support layer A is formed of at least two polysilicon layers with a silicon oxide film sandwiched between them. This is because the thermal expansion coefficient of the entire support layer A can be adjusted by combining it with a small silicon oxide film. And by this,
It is possible to balance the thermal expansion coefficients of both the support layer A and the wafer 1 or the isolation islands 1a made from it. Although the reason is not well understood, this effect is enhanced when the oxide film 6 is formed by pyrogenic oxidation. Further, if the support layer A is made to be substantially vertically symmetrical in the thickness direction as in this embodiment, the coefficient of thermal expansion within the support layer A will remain constant. For this reason, heating is required during the formation of the support layer A, the formation of elements, etc.

In each process, the risk of warpage occurring due to the difference in thermal expansion coefficient between the two as described above is significantly reduced. Furthermore, in the present invention, at the time of cooling immediately after the formation of the polycrystalline layer on the insulating film 4, where the greatest warpage is likely to occur, the polycrystalline layer is stacked with at least three layers with an oxide film sandwiched therebetween. Since it is a laminate A′,
The occurrence of warping at this stage can be significantly reduced. Moreover, since this laminate A' has a large thickness, it is easy to handle during the polishing process. When forming each layer as described above, first, epitaxial growth is performed in a reactor to form the first polysilicon layer 5, and then the first polysilicon layer 5 is transferred to a thermal oxidation furnace and grown by pyrogenic oxidation or the like. A silicon oxide film 6 is formed and then returned to the original reactor to form a second polysilicon layer 7.
At least 3
A stack of layers A' can be formed. As described above, since the formation of each layer can use the equipment normally used in that process, no special equipment is required.

Although the insulating layer-separated substrate of the present invention has been described so far based only on the embodiments shown in the figures, the structure of the present invention is not limited to the embodiments shown in the figures. For example, in the above embodiment, the plate 2 was formed by so-called anisotropic etching using an alkaline etching solution, but it can also be formed by physical polishing or other methods. In addition, the method for removing the wafer 1 is not limited to physical polishing, but may also be chemical polishing such as etching. The method for forming each layer is not limited to the above embodiments, and may be formed by different methods. For example, the silicon oxide film, which is the insulating film 4 and the oxide film 6, can be formed by a method other than thermal oxidation. However, these oxide films are preferably formed by thermal oxidation such as pyrogenic oxidation method for the reasons mentioned above. The same applies to other parts, and they can be formed by methods other than those shown in the examples, but the method of the examples has the advantage that conventional equipment can be used as is. ,
It is more preferable. Furthermore, in the above embodiment, single crystal silicon is used as the single crystal wafer serving as the isolation island, polysilicon is used as the polycrystalline layer, and 5i02 is used as the insulating film and oxide film. Other compound semiconductor materials can also be used.

In short, at least three
Other configurations are not limited as long as the polycrystalline layer of the layer is formed and then polished to form a support layer consisting of at least two polycrystalline layers.

Next, examples of the present invention will be described together with comparative examples.

(Example 1) A silicon wafer [diameter 76 mm (3 inches), thickness 400 μm] was used as a single crystal wafer to serve as the isolation island.
In addition, Fig. 1 ta) to (f) and Fig. 2 (al
, (A three-layer laminate A' (total thickness 450 pm) was formed by the steps shown in BL. At this time, the thickness of each layer was as follows: the first polysilicon layer = 10Q pm, the second polysilicon layer = 10Q pm,
Polysilicon layer = 2001rm, third polysilicon layer: 150- After that, this was polished and removed from both sides, and on one side there was a layer separated from wafer 1. Remote island 1a/
An insulating layer-separated substrate as shown in FIG. 3 was obtained, having a thickness of about 300 mm and having a support layer A made of two polysilicon layers on the other side.

For this insulating layer separated substrate, the amount of warpage was measured for 10 samples immediately after polishing and removing the polysilicon layer and immediately after completing the entire device formation process. The results immediately after the polishing and removal steps are shown in FIG. 5, and the results after the completion of the entire device formation process are shown in FIG. 6, respectively. In this example, the ratio of the thicknesses of the upper and lower polysilicon layers in the support layer A after polishing and removal is indicated by Ll and L in FIG.
2, 10:11≦L, :L, 2≦10, and this support layer A was substantially vertically symmetrical in the thickness direction.

(Example 2) 1st. An insulating layer-separated substrate was obtained in the same manner as in Example 1, except that the thicknesses of the second and third polysilicon layers were all 150 μm.

For this example as well, 9
Measurements were performed on two samples. The results are also shown in FIGS. 5 and 6.

Note that the ratio of the thicknesses of the upper and lower polysilicon layers in this example is L+, Lx, and 10:4≦L, :L.
, ≦10:1.3, and the support layer A in this example was asymmetrical in the thickness direction.

(Comparative example) An insulating layer-separated substrate was prepared in the same manner as in the example except that the support layer was made of only conventional polysilicon, but the warpage was too large and measurements could not be performed. .

From the above results, in Examples 1 and 2, which are the manufacturing method of the insulating layer-separated substrate of the present invention, no large warpage was observed immediately after polishing and removing the polysilicon layer, and from this, compared with the conventional method, It is assumed that there was less warpage during the formation of the polysilicon layer than in the example.

Moreover, from the results shown in FIG. 6, in the manufacturing method of the present invention, the support layer A formed by polishing and removing the polysilicon layer is
It was also found that, as in Example 1, if the layers were made vertically symmetrical in the thickness direction, subsequent warping would be reduced.

〔Effect of the invention〕

The manufacturing method of the insulating layer-separated substrate of the present invention is constructed as described above, and includes laminating at least three polycrystalline layers with an oxide film sandwiched between them on an insulating film to form a laminate, and then Since a support layer consisting of at least two polycrystalline layers is formed by polishing away the It decreases significantly. Moreover, since the laminate is thicker than the support layer, it is easier to handle during polishing.

[Brief explanation of drawings]

FIG. 1(al~([1) and FIG. 2(al~(C1 is an explanatory diagram showing the steps of an embodiment of the manufacturing method of an insulating layer separated substrate according to the present invention, and FIG. FIG. 4 is an explanatory diagram showing an example of the structure of an insulating layer separated substrate, FIG. 4 is an explanatory diagram showing a conventional example, and FIG. The hail graph in Figure 6 is the same (this is a hail graph showing an example of the frequency of the amount of warpage immediately after the completion of all the element formation processes. la, lb, lc...single crystal island region 4...insulating film 5 , 7... Polycrystalline layer 6... Oxide film A...
Support layer agent Patent attorney Takehiko Matsumoto Figure 1 @ Figure 2 (a) (c)

Claims (4)

[Claims] (1) After forming a groove for separation on the surface of a semiconductor single crystal wafer and covering the entire surface with an insulating film, a support layer is formed on it, and the single crystal side is placed in the groove. A method for producing an insulating layer-separated substrate, the method comprising: polishing the substrate until the bottom thereof is exposed to form a semiconductor single crystal island-like region on the support layer, which is electrically insulated and isolated by the insulating film; In manufacturing, a polycrystalline layer and an oxide film are alternately formed in this order on the insulating film, and at least three polycrystalline layers are stacked, and then this is reversely polished and removed from above. A method for producing an insulating layer-separated substrate, characterized in that at least two polycrystalline layers are left behind, and these are used as the support layer. (2) A method for manufacturing an insulating layer-separated substrate according to claim 1, wherein the oxide film is formed by a pyrogenic oxidation method. (3) The insulating layer according to claim 1 or 2, wherein the oxide film is arranged in the polycrystalline layer so that after polishing is completed, the support layer is substantially vertically symmetrical in the thickness direction. Separation substrate manufacturing method. (4) The method for manufacturing an insulating layer separated substrate according to any one of claims 1 to 3, wherein the single crystal island region and the polycrystalline layer are silicon, and the insulating layer and oxide film are SiO_2. .