JPS62213117A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent cracks from being generated when a compound semiconductor layer is made to grow thickly and directly on a Si substrate, by performing selective growth of the compound semiconductor layer on an exposed regions not covered with a mask layer on the Si substrate on which the mask layer made of the insulating film are partially formed. CONSTITUTION:A GaAs layer 25 grows partially on a Si substrate 11 by making the GaAs layer 25 or the like grow as a compound semiconductor layer only on the region which is not covered with a mask layer 23. Therefore, strain caused by difference between thermal expansion coefficiency of the Si substrate 11 and that of the GaAs layer 25 becomes smaller than the strain in the GaAs layer growing over the whole surface of the Si substrate. Hence, cracks are prevented from being generated and a bend of the wafer becomes extremely small, capable of manufacturing the semiconductor element with good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a compound semiconductor device on a Si substrate.

(Conventional technology) S
Attempts have been made to grow a compound semiconductor layer such as GaAs on which a device that emits light or operates at high speed is produced on an i-substrate, and to manufacture a semiconductor device by taking advantage of the characteristics of both Si and compound semiconductors.

For this purpose, molecular beam epitaxial growth (MBE)
Alternatively, there is a method in which a GaAs layer is grown on the entire surface of an St substrate by a metal organic chemical vapor deposition method (MOCVD method) and then the device is manufactured.

For example, the method for growing this GaAs layer is described in the literature (Journal on Crystal Growth).
al of (:rystal Growth),
68 [13 (1984) P, 21-26). This document describes GaAs on a Si substrate.
Reports have been made on methods for direct crystal growth of layers and on the quality of crystals obtained by this method. According to this method, first, the Si substrate is coated at a low temperature (40°C).
A GaAs layer grown to a thin thickness at a temperature of 0 to 600°C);
A GaAs layer and GaAj! are formed on this GaAs layer. A buffer layer consisting of alternately laminated As layers is grown, and then a GaAs layer is grown on this buffer layer, and by using this method, it can be used to fabricate both electronic devices and optical devices. A suitable crystal was obtained.

In addition, there is another method for directly growing a GaAs layer on a Si substrate, as described below (Nikkan Kogyo Shimbun (September 25, 1985)).

First, a Si substrate is heat-treated at a temperature of about 900°C in a mixed gas atmosphere of arsine and hydrogen, and then a GaAs layer is formed on the entire surface of the Si substrate at a temperature of 400 to 450°C.
We will grow the film to a level where there are no people. Next, by growing a GaAs layer on this thin GaAs layer at a temperature of 700 to 850°C, EPD (Etch
Pit Density) is small (electron mobility is 520
A large GaAs crystal layer of 0 cm2/V-see was obtained.

FIGS. 2(A) and 2(CB) are manufacturing process diagrams schematically showing a conventional method for manufacturing semiconductor devices.

First, a GaAs layer 13 is grown on the entire surface of the Si substrate 11 by the method described above (FIG. 2(A)). Next, unnecessary portions of this GaAs layer 13 are removed using photoetching technology, and Ga necessary for forming a semiconductor element is removed.
The As layer region 13a is left (FIG. 2(B)). Then, a desired semiconductor element was fabricated in the remaining GaAs layer region 13a or in the region including the Si substrate. In FIG. 2(B), I5 is a Si3N film, for example, provided for the purpose of electrically or optically isolating the elements.
An insulating layer consisting of four films, etc. is shown.

(Problems to be Solved by the Invention) However, according to research conducted by the applicant, in the conventional manufacturing method in which a GaAs layer is grown all over the Si substrate, as the thickness of the GaAs layer increases, the Si These strains increase due to the difference in thermal expansion coefficient between the substrate and the GaAs layer, and as a result, as long as the GaAs layer is thin, the wafer consisting of the Si substrate and the GaAs layer warps depending on the thickness. It has been found that there is a problem in that when the thickness of the GaAs layer exceeds a certain level, cracks occur in the GaAs layer.

In fact, for example, 2 inches (1 inch is about 2.54 cm)
When a GaAs layer is grown on the entire surface of a Si substrate to a thickness of approximately 4 μm, the wafer warpage will be several tens of μm.Furthermore, when grown to a thickness thicker than 4 μm, this GaAs
Cracks form in the layer.

By the way, when a semiconductor device is manufactured using a thin GaAs layer, such as an FET (field effect transistor), the above-mentioned wafer warpage is small, so it does not pose a problem in device manufacturing. .

However, when manufacturing a device that requires a GaAs layer that is somewhat thick, the warping of the wafer caused by the above-mentioned causes reduces the accuracy of mask alignment or exposure dose in the photoetching process, which leads to ,
The manufacturing yield of semiconductor devices decreases. Furthermore, when manufacturing a compound semiconductor laser device on a Si substrate, for example, the thickness of the GaAs layer needs to be about 101 μm (details will be described later), and cracks occur at a thickness of about 4 μm. It is not possible to manufacture the device if the process ends.

An object of the present invention is to solve the above-mentioned problems, to obtain a desired semiconductor device even if a compound semiconductor layer is directly grown to a large thickness on a Si substrate, and to manufacture the semiconductor device with a high yield. The goal is to provide a method that can be used.

(Means for Solving the Problems) In order to achieve this object, according to the present invention, when manufacturing a semiconductor element by growing a compound semiconductor layer on a Si substrate, for example, an insulating film is grown on the Si substrate. The present invention is characterized in that it includes the steps of partially forming a mask layer consisting of the following: and selectively growing a compound semiconductor layer in exposed regions of the Si substrate not covered by the mask layer.

This selective growth can be performed, for example, by MOCVD, MBE using gas as a raw material, or the like.

(Function) According to the method for manufacturing a semiconductor device of the present invention, for example, a GaAs layer as a compound semiconductor layer grows only in the region of the Si substrate that is not covered by the mask layer. Therefore,
The GaAs layer will grow partially on the Si substrate, and therefore, the strain caused by the difference in thermal expansion coefficient between the Si substrate and the GaAs layer will be caused by G on the entire surface of the Si substrate.
The strain is smaller than that when an aAs layer is grown.

Therefore, a compound semiconductor layer can be grown thicker than before on a Si substrate without warping the wafer or cracking the GaAs layer.

(Example) Hereinafter, an example of the method for manufacturing a semiconductor device of the present invention will be described with reference to FIGS. 1(A) to 1(C). Note that these figures show cross sections of wafers at major steps in the manufacturing process, but they are only shown schematically to the extent that this invention can be understood. The relationship is not limited to the illustrated example. Further, in these figures, the same components are designated by the same reference numerals.

In FIG. 1(A), 11 indicates a Si (silicon) substrate. First, the surface of the Si substrate 11 is cleaned with a cleaning solution containing a 1:1 mixture of sulfuric acid and hydrogen peroxide. Next, the surface of this Si substrate II is slightly etched with hydrofluoric acid to clean the surface. Next, this Si substrate 1 is processed by plasma CVD method or thermal CVD method.
An insulating film 21 made of, for example, a Si3N4 film for forming a mask layer is formed on the surface of the substrate 1 to a thickness of about 2000 mm (FIG. 1(A)).

Next, this insulating film 21 is removed in a predetermined shape, for example, in a stripe shape, using photolithography and hydrofluoric acid to form a mask layer 23 made up of the remaining portion of the insulating film 21 on the Si substrate 11. (Figure 1 (B)). Although FIG. 1B is a cross-sectional view focusing on a part of the Si substrate 11, a part of the Si substrate II is also exposed at a plurality of predetermined locations of the insulating film 21 in an area not shown. Each stripe-shaped window is formed.

Next, by MOCVD method, a compound semiconductor layer such as GaA is formed on the Si substrate 11 including this mask layer 23.
Perform crystal growth of s. When performing this crystal growth, if the growth conditions are such that the pressure in the growth layer is 100 Torr and the molar ratio of the raw materials is 20, for example, I[1/V, GaAs will grow on the mask layer 23. without any
GaAs grows selectively only in the exposed regions of the Si substrate 11 that are not covered by the mask layer 23 (see FIG.
)).

Therefore, in this embodiment, striped GaAs layers 25 are scattered in island shapes at a plurality of predetermined locations on the Si substrate 11.

Further, although not shown, desired electronic devices and optical devices can be formed in the GaAs layer 25 region or in both regions of the GaAs layer 25 region and the Si substrate 11 region to obtain a semiconductor element.

As described above, according to the present invention, the GaAs layer 25 is grown individually in only the regions necessary for forming the semiconductor element on the Si substrate 11, and then the semiconductor element is formed. . Therefore, the entire surface of the Si substrate 11 is covered with GaA.
Unlike the case where the S layer is grown, in the case of this invention, the S layer is grown.
The strain caused by the difference in thermal expansion coefficient between the GaAs layer 25 and the Si substrate 11 can be alleviated by the region of the i-substrate I+ where the GaAs 25 layer is not grown.

Incidentally, the position on the Si substrate 11 where the GaAs layer 25 is grown, and the shape and layer thickness of the GaAs layer 25 can be set to any suitable position, shape, and layer thickness depending on the type of semiconductor element. For example, an island-shaped G grown on a Si substrate +1
The width of the aAs layer 25 may be set to the width necessary to constitute one chip. In either case, the GaAs layer 25 is arranged and shaped so as to be suitable for semiconductor manufacturing and to reduce strain caused by the above-mentioned difference in coefficient of thermal expansion. According to the present invention, the arrangement and shape of the GaAs layer 25 can be easily changed by changing the shape of the mask layer 23.

In addition, in the above-mentioned embodiment, the selective growth of the compound semiconductor layer is performed using MO.
Although the invention has been explained using an example using the CVD method, the present invention is not limited to this method. Even in this case, the same effects as in the example can be expected.

In addition, although the above-mentioned embodiment has been explained using an example in which the compound semiconductor layer to be grown on the Si substrate is a GaAs layer, the present invention is not limited to this embodiment. It can be applied to any compound semiconductor that can be used. Examples of such compound semiconductors include InP and Zn5e.
Examples include those of the type.

Further, in the above embodiment, an example was explained in which Si3N4 was used as the mask layer, but this mask layer was, for example, 5 inches thick.
2 or an insulating film such as AIL203.

Furthermore, the method for forming the mask layer described in the above embodiments may be performed using other suitable methods such as sputtering, and the etching method for the mask layer may be performed using other suitable methods such as dry etching. It's okay.

(Effects of the Invention) As is clear from the above description, according to the method for manufacturing a semiconductor element of the present invention, it is possible to reduce the strain caused by the difference in thermal expansion coefficient between the Si substrate and the compound semiconductor layer. . Therefore, when a compound semiconductor layer is grown on a Si substrate to the same thickness as before, no cracks will occur in this layer and the wafer warpage will be extremely small, making mask alignment at various parts of the wafer easier. Exposure can be performed accurately.

Further, according to the method of manufacturing a semiconductor device of the present invention, a compound semiconductor layer thicker than conventional methods can be grown on a Si substrate without causing warping or cracking. Therefore, it is possible to grow a compound semiconductor layer with a thickness of, for example, about 10 μm on a Si substrate, thereby forming a semiconductor device that requires a thick compound semiconductor layer, such as a semiconductor laser device with an internal current confinement structure. It is also possible to do so.

Therefore, even if a compound semiconductor layer is directly grown to a large thickness on a Si substrate, a desired semiconductor element can be obtained, and this semiconductor element can be manufactured with a high yield.

[Brief explanation of drawings]

FIGS. 1(A) to (C) are manufacturing process diagrams for explaining the method of manufacturing a semiconductor device of the present invention, and FIGS. 2(A) and (B)
) is a manufacturing process diagram for explaining a conventional method of manufacturing a semiconductor element. 11・"St (silicon) substrate 21・-insulating film, 23・-mask layer 25-・
- Compound semiconductor layer (GaAs layer). Patent applicant Oki Electric Industry Co., Ltd. lf: sr (silicon) base 2f: #color sample g 2J” mask layer 25: 4taQfl14hnonA ((,aAsA)
This understanding [; Iituru Sen 44 Fists Red Chi's GD, Explanation of Fangzi Figure 1

Claims (1)

[Claims] (1) In manufacturing a semiconductor device by growing a compound semiconductor layer on a Si substrate, there is a step of partially forming a mask layer on the Si substrate, and a step of forming a mask layer on the Si substrate, and a portion of the Si substrate that is not covered by the mask layer. 1. A method for manufacturing a semiconductor device, comprising the step of selectively growing a compound semiconductor layer in an exposed region.