JPS6131386A - Vapor phase epitaxial growth process - Google Patents

Abstract

PURPOSE:To retard the growth of facet by dipping a single crystal silicon substrate having surface coated partly with an insulative film in an anisotropic etching soln. to execute etching of silicon at the exposed part and executing selective epitaxial growth of silicon. CONSTITUTION:A silicon oxide film 7 is formed on the surface of a silicon wafer 6, and an opening part 8 having an almost perpendicular side wall is formed by reactive ion etching. When the substrate is dipped in an anisotropic etching soln. capable of exposing selectively a (111) face, a (100) face 9 is exposed on the base surface and a (111) face 10 is exposed on the side surface. An epitaxial layer 11 is formed by executing selective epitaxial growth of silicon thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a vapor phase epitaxial growth method for suppressing the formation of facets on sidewalls when performing selective epitaxial growth of silicon.

(Prior art and its problems) Silicon CMO8 (Complementary M
etal -Oxide -Sem1conducto
r) devices have speeds equivalent to bipolar devices and are expected to be able to achieve the ultimate speed/power product in MOS, so the range of applications is currently expanding, and in the near future MO8IC (Integrated C
1rcuit) is expected to become a powerful technology. In order to take advantage of such characteristics of CMO8, it is effective to miniaturize element isolation, and various methods are currently being considered, and one of the most promising methods is selective epitaxial growth.

An example of the selective epitaxial growth method is shown in FIG.

A silicon oxide film 2 of 1 to 2μ is deposited on the silicon wafer 1.
A substrate formed with a thickness of m and with silicon partially exposed by reactive ion etching is used as a substrate for epitaxial growth. In some cases, the wall portion of 9111 is coated with a silicon nitride film 3 or the like. When epitaxial growth is performed on such a substrate using S1H2C1t and HC7 as source gases, no silicon is deposited on the silicon oxide film, and the epitaxial layer 4 is formed only in the exposed silicon region. However, when a (100) substrate is used, for example, the facet 5 is formed near the side wall. Since selective epitaxial growth is a method in which silicon is grown only on the silicon without depositing it on the insulator, we believe that this is because surfaces with low surface energy tend to form near the sidewalls. 0 This is the same situation when using a (111) substrate, etc. o When using a (111) substrate, the surface symmetry is 3-fold symmetry, and jD (100) substrate has 4-fold symmetry. Although there are side walls where facets are visible and side walls where facets are not, essentially the same phenomenon occurs. Considering the (100) and (111) substrates together, the (11)
1) A facet occurs when a surface exists. Although the faces of the facets are not necessarily (111), it is thought that the (111) planes are exposed stepwise in detail.

If there is a facet as shown in Fig. 1, the gate '71
When an L pole is formed and the transistor is operated as an MIS transistor, the following deterioration is observed in the transistor characteristics when the surface is flat.

1) Gate breakdown voltage decreases because the electric field concentrates at the tip of the V-shaped part.

■) The threshold value is different between the flat surface and the facet. In other words, it is considered that transistors with two different threshold values are lined up in parallel. Getting worse.

If miniaturization of devices and isolation regions also means a reduction in gate oxide film thickness, the above two deteriorations will become more pronounced as device dimensions become smaller. This was the cause.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a vapor phase epitaxial growth method that reduces the formation of facets.

(Structure of the Invention) Since the formation of facets is a phenomenon in which the growth rate near the sidewall is smaller than the growth rate in the region away from the sidewall, the required thickness of the grown film can be changed depending on the location. To this end, the present invention employs a method in which the substrate before growth is immersed in an anisotropic etching solution to etch regions away from the sidewalls. In the figure (Al is the same as the substrate for normal selective epitaxial growth), a silicon oxide film 7 with a thickness of 1 to 2 μm is entirely formed on the surface of the silicon wafer 16, and the reaction is performed. The opening 8 with substantially vertical side walls is shown formed by ion etching.

The state after immersing the substrate in this state in an anisotropic etching solution that tends to selectively expose the (111) plane is (bl). When a (ioo) substrate is used, (100) and 9 are displayed on the bottom surface. The (111) plane 10 appears near the side wall.(C
) shows the results of selective epitaxial growth using a substrate of (bl).The surface of the epitaxial layer 11 can be made much flatter than that of a normal selective epitaxial growth film.

FIG. 3 is a graph showing how the level difference on the surface after epitaxial growth changes depending on the amount of etching using an anisotropic etching solution. Hydrazine was used as the anisotropic etching solution. The conditions for selective epitaxial growth are stn, c/2300 as the source gas.
cc/min, HC1!1.317m1n The film thickness of the O epitaxial film, which has a growth temperature of 950°C and a growth pressure of 50 Torr, is ~1 μm plus the etching amount, that is, the etching amount by hydrazine is 10 μm.
In the case of 00X, growth was performed by ~1.1 μm, and the amount of unevenness on one surface was measured. As a result, when the etching amount was less than 1 μm, the surface unevenness was less than 1000×, and compared to the case where no etching was performed, the facet could be reduced to 115 or less. Although selective ejection was carried out using silicon oxide without forming another material, it is also possible to form a silicon nitride film on the side wall in the same manner as shown in Fig. 1 and then carry out the method of the present invention. The etching solution is not limited to hydrazine, but may also be KOH or the like.

(Effects of the Invention) As described above, the method of the present invention solves the problems when applying the selective epitaxial growth method to fine element isolation, especially the problem of facets, which becomes noticeable when aiming for further miniaturization. formation can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the conventional selective epitaxial growth method; FIG. 2 is a schematic cross-sectional view of an embodiment of the present invention; FIG. A diagram showing the relationship between the etching amount and surface unevenness. 1...Silicon wafer, 2...Silicon oxide film,
3...Silicon nitride layer, 4...Epitaxial layer,
5...7 assets, 6...silicon wafer, 7.
...Silicon oxide film, 8...Opening, 9...(10
0) plane, 10... (111) plane, 11... epitaxial layer. Attorney Susumu Douchi Hara 7. ;1st ward, 2nd figure δ 3rd ward

Claims (1)

[Claims] A vapor phase epitaxial growth method characterized by immersing a single crystal silicon substrate whose surface is partially covered with an insulating film in an anisotropic etching solution, etching the exposed silicon, and then performing selective epitaxial growth of silicon.