JPH0547743A - Vapor growth method - Google Patents

Abstract

PURPOSE:To increase a ratio of thicknesses of a grown film to a monitoring film by specifying a surface temperature of a semiconductor substrate, and specifying a volumetric ratio of oxygen gas of reaction gas to be supplied to silane. CONSTITUTION:A p<+> type diffused layer 4 is selectively formed on a surface of a semiconductor substrate 1, and a CVD film 2 is formed on the substrate 1 by a normal pressure hot CVD. In the CVD, oxygen gas O2 and silane SiH4 are supplied as reactive gases, and a volumetric ratio of the gas O2 of the reaction gas to be supplied to the silane SiH4 is set to 8 or less. And, the substrate is so heated that the surface temperature becomes 400 deg.C or higher. Thus, the thickness of the grown film can be set to a value near the thickness of a monitoring film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase epitaxy method, and more particularly to a vapor phase epitaxy method capable of making a thickness of a grown film substantially equal to a monitor thickness.

[0002]

_2. Description of the Related Art The growth of an oxide film by atmospheric pressure thermal CVD using oxygen gas O ₂ and silane SiH ₄ as reaction gases is
Generally, at a temperature of about 395 ° C., oxygen gas O _{2 as} a reaction gas
And the ratio of silane SiH ₄ to 10 to 20: 1.

[0003]

By the way, according to the conventional atmospheric pressure thermal CVD method described above, the growth rate of the CVD film is very strongly influenced by the surface temperature of the semiconductor substrate, and the actual growth film thickness and The difference from the monitor film thickness is large, so CV
It was difficult to make the film thickness of the D film as desired. Figure 3
(A) and (B) are sectional views showing a semiconductor substrate in the case of a conventional atmospheric thermal CVD method, (A) shows a case where the semiconductor substrate is warped so that its upper surface is convexly curved, B)
Shows the case where the semiconductor substrate is warped such that its upper surface is concavely curved. In the case shown in FIG. 3A, since the central portion of the semiconductor substrate 1 is floating from the support base 3, the substrate surface temperature is higher in the peripheral portion than in the central portion. Therefore, the CVD film 2
Of the CVD film 2 is faster in the peripheral portion than in the central portion, and naturally the CVD film 2 is thicker in the peripheral portion than in the central portion.

On the contrary, in the case shown in FIG. 3B, since the peripheral portion of the semiconductor substrate 1 is floated from the support base 3, the film thickness of the CVD film 2 is opposite to that in the case shown in FIG. 3A. In addition, the peripheral portion becomes thinner than the central portion. As shown in FIGS. 3 (A) and 3 (B)
Have shown that the substrate surface temperature is greatly affected by the growth rate of the CVD film by the conventional vapor phase growth method. Further, according to the conventional atmospheric pressure thermal CVD described above, it is difficult to form a CVD film on the surface of the semiconductor substrate where plasma damage or contamination exists, or on the surface of the p ⁺ -type diffusion layer.
There is a problem that the film becomes thin. FIG. 4 is a sectional view showing this.

In FIG. 1, reference numeral 4 denotes a p ⁺ type diffusion layer selectively formed on the surface of the semiconductor substrate 1, and the p ⁺ type diffusion layer 4 of the CVD film 2 formed on the semiconductor substrate 1 is shown. The film thickness t2 in the upper portion is also the film thickness t in other portions.
It is considerably smaller than 1. As a specific example, the temperature is 395 ° C., the supply reaction gas is silane SiH ₄ 42 cc, oxygen gas O ₂ 750ce, and the growth rate is 750 Å / min. When the CVD film 2 is formed, p of the CVD film 2
The film thickness t1 except for the ⁺ type diffusion layers 4 and 4 is 30.
If there is 00 angstrom, p of the CVD film 2
The film thickness t2 on the ⁺ type diffusion layers 4 and 4 was only 2100 angstroms. The thickness t1 of the CVD film is not constant due to the warp of the semiconductor substrate 1. However, if there is no warp, the film thickness t1 becomes a substantially monitor film thickness. Therefore, the ratio of the film thickness t2 on the p ⁺ type diffusion layers 4 and 4 of the CVD film 2 to the monitor film thickness t1 is only about 70%. We would like this ratio to be at least 90%, but this was not the case in the past.

The present invention has been made to solve such a problem, and an object thereof is to increase the ratio of the thickness of the growth film to the monitor thickness.

[0007]

In the vapor phase epitaxy method of the present invention, the surface temperature of a semiconductor substrate is set to 400 ° C. or higher and the volume ratio of oxygen gas O ₂ of a reaction gas to be supplied to silane SiH _{4 is set} to 8 or less. Is characterized by.

[0008]

EXAMPLES The vapor phase growth method of the present invention will be described in detail below with reference to the illustrated examples. FIG. 1 is a sectional view for explaining one embodiment of the vapor phase growth method of the present invention. In the drawings, 1
Are semiconductor substrates 4 and 4 are p ⁺ -type diffusion layers selectively formed on the surface of the semiconductor substrate 1, and a CVD film 2 is formed on the semiconductor substrate 1 by atmospheric pressure thermal CVD.

In this atmospheric pressure thermal CVD, oxygen gas O ₂ and silane SiH ₄ are supplied as reaction gases, and the volume ratio R of the supplied reaction gas of oxygen gas O ₂ to silane SiH ₄ is 8 or less. Then, heating is performed so that the substrate surface temperature becomes 400 ° C. or higher.

As one specific example, the substrate surface temperature is 460 ° C., the oxygen gas O ₂ supply amount is 360 cc, and the silane SiH ₄ supply amount is 45 cc (accordingly, the volume ratio R of the oxygen gas O _{2 to} the silane SiH _{4 is} R). = 8), C
VD film 2 growth rate is 550 Å / min
Therefore, the film thickness t1 on the portions of the CVD film 2 other than the p ⁺ type diffusion layers 4 and 4 (this does not always match the monitor film thickness completely, but if the wafer does not warp, the monitor film thickness is It is thought that they are almost the same.) Is 3000
The film thickness t2 on the p ⁺ -type diffusion layers 4 and 4 is 2800 angstroms, and the monitor film thickness t1 of the CVD film thickness t2 (P) on the p ⁺ -type diffusion layer is angstroms.
The ratio to (T), that is, the P / T ratio was about 93.3%.

FIG. 2 is a diagram showing the relationship between the substrate surface temperature with R as a parameter and the P / T ratio. From this figure, the lower the R and the higher the substrate surface temperature, the higher the P / T ratio. And thus the growth rate of the CVD film,
It is clearly insensitive to substrate surface temperature, substrate surface damage, and impurities. And the P / T ratio is 90%
The above is necessary, and in order to obtain the P / T ratio of 90% or more, the substrate surface temperature is 400 ° C. or more and R is 8 or less.

[0012]

The vapor phase growth method of the present invention is characterized in that the surface temperature of the semiconductor substrate is set to 400 ° C. or higher and the volume ratio of the oxygen gas O ₂ of the reaction gas to the silane SiH _{4 is set} to 8 or less. Therefore, according to the vapor phase epitaxy method of the present invention, as is clear from the above description, the thickness of the grown film can be made close to the monitor thickness.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the vapor phase growth method of the present invention.

FIG. 2 is a relationship diagram of a substrate surface temperature and a ratio of a monitor film thickness to a film thickness of a grown film.

3A and 3B are cross-sectional views showing a problem.

FIG. 4 is a cross-sectional view showing a problem.

[Explanation of symbols]

 1 semiconductor substrate 2 growth film t1 monitor film thickness t2 film thickness of diffusion film on diffusion layer

Claims (1)

[Claims] 1. A vapor phase growth method in which silane SiH ₄ and oxygen gas O ₂ are supplied as a reaction gas to form a vapor phase growth film, the surface temperature of a semiconductor substrate is set to 400 ° C. or higher, and the oxygen gas of the reaction gas is used. Vapor growth method characterized in that the volume ratio of O ₂ to silane SiH ₄ is 8 or less