JPH06188198A - Epitaxial growth method - Google Patents

Abstract

PURPOSE:To provide an epitaxial growing method that allows film forming for out-dope prevention with ease, without special process and facility, and also allows forming of the out-dope prevention film and epitaxial growing in the same furnace continuously. CONSTITUTION:A susceptor 2 of an epitaxial growth device is provided with a polysilicon film 3 in advance, and a semiconductor wafer 4 is placed an it, then under hydrogen atmasphere of high temperature, a part of the palycilicon film 3 is stuck to at least the rear side of the semiconductor wafer, as a film far preventing out-dope. Then, with the conventional method, a semiconductor crystal layer 9 is epitaxial-grown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epitaxial growth method for growing a semiconductor crystal layer on a semiconductor wafer. More specifically, the present invention relates to an epitaxial growth method for growing a high-resistance semiconductor crystal layer on a low-resistivity semiconductor wafer that is heavily doped with impurities.

[0002]

2. Description of the Related Art Conventionally, when a single crystal semiconductor crystal layer is epitaxially grown on the surface of a semiconductor wafer, a susceptor on which the semiconductor wafer is placed is placed in a growth furnace, and a growth gas and a dopant gas as an impurity are used together with a carrier gas. A semiconductor single crystal layer is grown on a semiconductor wafer by introducing it into a growth furnace and reacting it at a high temperature.

In this case, when, for example, a semiconductor crystal layer having a low resistivity of several hundreds of times or more of resistivity is epitaxially grown on the surface of a semiconductor wafer having a high concentration of impurities and a low resistivity, the semiconductor wafer has a high temperature during the epitaxial growth. Impurity out-doping into the growth furnace and the gas mixes with the growth gas to grow, and during semiconductor layer epitaxial growth, auto-doping occurs where impurities directly diffuse from the semiconductor wafer to the growth layer, causing the impurity concentration in the epitaxial growth layer. Is difficult to grow constantly.

In order to prevent out-doping of impurities, a single-layer or multi-layer out-doping prevention film such as an oxide film, a nitride film or a polysilicon film is previously formed on the back surface of a semiconductor wafer before the epitaxial growth. By forming it, diffusion from the semiconductor wafer to the semiconductor crystal layer epitaxially grown via the inside of the growth furnace is prevented.

[0005]

However, in order to form the above outdoping prevention film only on the back surface of the semiconductor wafer and not on the front surface of the semiconductor wafer on which epitaxial growth is performed, the After forming a protective film such as an oxide film, a nitride film or a polysilicon film on both surfaces, the protective film attached to the surface of the semiconductor wafer must be removed. Therefore, a plurality of processes that are not continuous with the epitaxial growth process for performing these processes and dedicated equipment are required, which leads to an increase in manufacturing cost.

According to the present invention, such a problem is solved and a film for preventing out-doping is easily formed without requiring a wafer processing step in advance, and furthermore, the formation of the out-doping preventing film and the epitaxial growth are continuously performed. It is an object of the present invention to provide an epitaxial growth method that can be performed.

[0007]

The epitaxial growth method of the present invention is an epitaxial growth method in which a semiconductor crystal layer is grown on the surface of a semiconductor wafer having a low resistivity, and (a) a susceptor on which a semiconductor wafer having a low resistivity is mounted. A polysilicon film is provided at the place where the semiconductor wafer is placed, and (b) the semiconductor wafer is placed on the susceptor and one of the polysilicon films is provided on at least the back surface of the semiconductor wafer under a high-temperature hydrogen gas atmosphere. And (c) continuously introducing a growth gas to epitaxially grow a semiconductor crystal layer on the surface of the semiconductor wafer.

[0008]

According to the present invention, a polysilicon film is provided in advance on a susceptor of an epitaxial growth apparatus, a semiconductor wafer is placed thereon, and the polysilicon film is formed on the back surface of the semiconductor wafer in a high-temperature hydrogen gas atmosphere. By depositing a part of the above, it is possible to easily and selectively form an outdoping prevention film on the back surface of the semiconductor wafer or the like inside the epitaxial growth apparatus. Moreover, after forming the film, the growth gas can be continuously introduced to perform epitaxial growth.

Although the susceptor of the epitaxial growth apparatus is coated with high-purity silicon carbide,
In use, a polysilicon film of about 20 μm is attached for epitaxial growth. This is used as a protective film when etching with hydrogen chloride gas, and is formed for the purpose of extending the life of the susceptor and suppressing the scattering of fine particles of silicon carbide. Therefore, the thickness of the polysilicon film is also small, and a polysilicon film for outdoping has not been provided on the back surface of the semiconductor wafer before the epitaxial growth.

[0010]

The present invention will be described below with reference to the drawings. FIG. 1 is an explanatory sectional view showing an example of an epitaxial growth apparatus, FIG. 2 is an enlarged sectional view of an essential part of a susceptor on which a semiconductor wafer is mounted, and FIG. 3 is a graph showing a processing temperature change in the epitaxial growth method of the present invention.

First, a polysilicon film 3 is formed on the susceptor 2 of the epitaxial growth apparatus 1 shown in FIGS. As a method of forming the polysilicon film 3, for example, by introducing trichlorosilane gas and hydrogen gas, 1100 to 1150 ° C.,
The film is formed to a film thickness of 50 to 100 μm by the CVD method for processing for about 60 minutes.

Next, on the susceptor 2, the impurity concentration is high and the specific resistance is small, for example, the specific resistance is 1/1000 to 5 /.
A semiconductor wafer 4 of 1000 Ω · cm is placed. A pocket 5 which is a recess for holding the semiconductor wafer 4 is usually provided on the susceptor 2. By inserting the semiconductor wafer 4 into the pocket 5, the pocket 5 is provided substantially at the center of the surface of the susceptor 2. The gas introduction pipe 6 can be arranged at substantially the same distance. The inner diameter of the pocket 5 of the semiconductor wafer 4 is formed to be substantially the same as the outer diameter of the semiconductor wafer 4 so as not to hinder the flow of the reaction gas.

Next, the susceptor 2 is attached to the quartz bell jar 7.
It is disposed inside, and while introducing hydrogen gas from the gas introduction pipe 6 at a flow rate of 180 slm, the temperature is raised from the ambient temperature to 1000 to 1150 ° C. by the heater 8 below the susceptor 2 (see A in FIG. 3).

Next, during about 30 to 60 minutes, the substrate temperature 11
Hold the semiconductor wafer 4 in a hydrogen atmosphere at 50 ° C. (FIG. 3).
B). During this time, the polysilicon film 3 on the susceptor 2
Adhere to the back surface of the semiconductor wafer 4. At this time, the polysilicon film 3 formed on the inner surface of the pocket 5 also adheres to the outer peripheral surface of the semiconductor wafer 4. By this treatment, the back surface of the semiconductor wafer 4 is coated with a polysilicon film having a thickness of 0.1 to 1 μm, and it becomes a film for preventing out-doping from the semiconductor wafer 4.

Next, after lowering the temperature to 1130 ° C., the inside of the quartz bell jar 7 is baked with hydrogen gas, and the impurity gas out-doped into the growth furnace is discharged from the gas discharge port 10 (see C in FIG. 3). ).

Subsequently, epitaxial growth is performed by the conventional method. An example of epitaxial growth will be described with a specific example. First, hydrogen chloride gas and hydrogen gas are introduced into the quartz bell jar 7 at flow rates of 1 to 10 slm and 90 to 180 slm, respectively, to clean the surface of the semiconductor wafer 4 (D in FIG. 3).
reference). After cleaning, purge with hydrogen gas (see E in FIG. 3).
reference).

Next, while maintaining the temperature at 1130 ° C., the semiconductor crystal layer 9 is epitaxially grown on the surface of the semiconductor wafer 4 (see F in FIG. 3). For example, in order to epitaxially grow a silicon crystal layer, trichlorosilane (SiHCl ₃ ) gas as a growth gas and phosphine (PH ₃ ) as a dopant are used together with hydrogen as a carrier gas for hydrogen 180 slm.
, Trichlorosilane 15 g / min, and phosphine 15 sccm are mixed and introduced into the quartz bell jar 7, and a chemical reaction is performed to deposit the high specific resistance of 1 to 5 Ω · cm on the surface of the semiconductor wafer 4. A semiconductor crystal layer 9 which is an n-type silicon crystal layer is epitaxially grown.

During the epitaxial growth, the semiconductor wafer 4 is kept at a high temperature, but since the back surface and the outer peripheral surface of the semiconductor wafer 4 are covered with the polysilicon film 3, the impurity diffusion from the inside of the semiconductor substrate 4 does not occur. Suppressed.
Therefore, variations in impurity concentration due to out-doping can be suppressed, and a semiconductor crystal layer having a required impurity concentration can be formed. After the epitaxial growth, only hydrogen gas as a carrier gas is used to lower the temperature in the furnace.

As a post-process, the polysilicon film 3 attached to the semiconductor wafer 4 is removed by plasma etching of reactive gas or mechanical grinding. Note that the removal is generally performed during the device manufacturing process.

In this embodiment, 0.001 to 0.005 Ω.
Although an example of epitaxially growing a semiconductor crystal layer having a high specific resistance of several hundred times or more on a semiconductor wafer having a low specific resistance of cm has been explained, the specific resistance of the semiconductor wafer is 0.001 to When epitaxially growing a high-concentration impurity semiconductor wafer of 0.005 Ω · cm, a semiconductor crystal layer having a uniform impurity concentration is obtained, and the effect of the present invention is obtained.

Further, in this embodiment, an example of performing epitaxial growth using a susceptor having pockets is shown, but the present invention is not limited to this. For example, a polysilicon film can be formed on the back surface of a semiconductor wafer even when directly mounted on the smooth surface of a susceptor having no pockets, and the effect of the present invention can be sufficiently exhibited.

[0022]

According to the present invention, a film for preventing out-doping can be formed selectively on the back surface of a semiconductor wafer or the like inside an epitaxial growth apparatus, so that impurities inside the semiconductor wafer during epitaxial growth can be easily removed. It is possible to suppress out-doping and form an epitaxial layer having a stable impurity concentration with good reproducibility.

Further, a special process for forming a film and a dedicated facility are not required, and furthermore, the epitaxial growth process can be continuously carried out, so that the manufacturing cost can be remarkably reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of an epitaxial growth apparatus used in an epitaxial growth method.

FIG. 2 is an enlarged sectional view of a main part of a susceptor on which a semiconductor wafer is placed.

FIG. 3 is a graph showing a processing temperature change in the epitaxial growth method of the present invention.

[Explanation of symbols]

 1 Epitaxial Growth Device 2 Susceptor 3 Polysilicon Film 4 Semiconductor Wafer 9 Semiconductor Crystal Layer

Claims (1)

[Claims] 1. An epitaxial growth method for growing a semiconductor crystal layer on a surface of a semiconductor wafer having a low resistivity, comprising: (a) polysilicon on a mounting place of the semiconductor wafer of a susceptor on which the semiconductor wafer having a low resistivity is mounted. A film is provided, (b) the semiconductor wafer is placed on the susceptor, and part of the polysilicon film is attached to at least the back surface of the semiconductor wafer in a high-temperature hydrogen gas atmosphere, and (c) the growth gas is continued. Is introduced to grow a semiconductor crystal layer epitaxially on the surface of the semiconductor wafer.