JPH11274089A - Manufacture of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the decline in boron density near the surface of a semiconductor crystalline substrate at the growing of a silicon thin film on the boron- doped semiconductor crystalline substrate, by growing the silicon thin film after forming a boron thin film on the boron-doped semiconductor crystalline substrate. SOLUTION: Since a silicon semiconductor crystalline substrate 1 including boron as a dopant is formed on its surface with a natural oxide film 2, in order to completely remove the natural oxide film 2, the substrate is heat-treated in a hydrogen gas atmosphere. During the heat treatment, boron segregates on the surface of the substrate, and then a boron thin film 4 of about one monolayer thickness is formed on the surface of the substrate. Next, the substrate is heat-treated in a hydrogen gas atmosphere to completely remove the boron thin film 4. After that, while the silicon semiconductor crystalline substrate 1 is being heated, for example, to 1,000 deg.C, trichlorosilane is supplied together with hydrogen to grow a silicon crystalline thin film 3 on the silicon semiconductor crystalline substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a silicon thin film on a semiconductor single crystal substrate doped with boron.

[0002]

2. Description of the Related Art Boron has been conventionally used as a dopant for manufacturing a p-type semiconductor single crystal substrate. It is well known that a silicon source gas is supplied onto a semiconductor single crystal substrate which has been doped with boron and adjusted to a desired resistivity, and a silicon thin film is grown on the semiconductor single crystal substrate by vapor phase growth. ing. Specifically, for example, a silicon semiconductor single crystal substrate was heated to a desired temperature such as 1000 ° C. in a reaction vessel, and trichlorosilane (SiHCl ₃ ) gas was diluted as a silicon raw material in a diluent gas such as hydrogen gas. A gas is supplied into the reaction vessel to grow a silicon single crystal thin film on the silicon semiconductor single crystal substrate.

On the surface of a silicon semiconductor single crystal substrate, natural oxide films, organic substances, fine particles, etc. (hereinafter collectively referred to as "natural oxide films, etc.") are generated and adhered. It must be removed before the growth step. As a removing method, a method of heating the semiconductor single crystal substrate to 1000 ° C. or more in an atmosphere such as a hydrogen gas is used. That is, as shown in FIG. 5, a semiconductor single crystal substrate 1 (FIG. 5A) having a native oxide film 2 or the like on its surface is heated to 1000 ° C. or more in a hydrogen gas atmosphere to thereby remove the native oxide film 2 or the like. (FIG. 5 (b)), and then trichlorosilane (Si
HCl ₃ ) is diluted in hydrogen gas and supplied to grow a silicon single crystal thin film 3 on the semiconductor single crystal substrate 1 (FIG. 5C).

[0004]

When the semiconductor single crystal substrate 1 is heated to a temperature of 1000 ° C. or more to remove the natural oxide film 2 or the like, the semiconductor single crystal substrate 1 is removed during the heat treatment.
Of the boron contained in the semiconductor single crystal diffuses into the gas phase by outward diffusion and vaporization. As a result, the dopant concentration in the vicinity of the surface of the semiconductor single crystal substrate 1 decreases, as shown in FIG. As described above, there has been a problem that the density profile is not flat.

Accordingly, an object of the present invention is to provide a method for preventing a decrease in the boron concentration near the surface of a semiconductor single crystal substrate when a silicon thin film is grown on the semiconductor single crystal substrate doped with boron.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors have conducted researches based on the results of basic experiments, and as a result, have reached the following invention.

The invention described in claim 1 of the present application provides a method for manufacturing a thin film, comprising forming a boron thin film on a boron-doped semiconductor single crystal substrate and then growing a silicon thin film.

According to a second aspect of the present invention, there is provided a method of manufacturing a thin film according to the first aspect, wherein a silicon thin film is grown after removing the formed boron thin film.

According to a third aspect of the present invention, there is provided a method of manufacturing a thin film according to the first aspect, wherein a silicon thin film is grown on the formed boron thin film, and further subjected to a heat treatment.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the boron doped in the semiconductor single crystal substrate is segregated on the substrate surface to form a boron thin film. And a method for producing a thin film characterized by the following.

According to a fifth aspect of the present invention, there is provided a thin film forming method according to any one of the first to third aspects, wherein a diborane gas is supplied onto the semiconductor single crystal substrate to form a boron thin film. A manufacturing method is provided.

According to a sixth aspect of the present invention, there is provided a method for producing a thin film according to the fourth aspect, wherein the heating temperature for segregating boron is 700 ° C. or more and 980 ° C. or less.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a thin film according to the second aspect, wherein the silicon thin film is grown after removing the boron thin film and inwardly diffusing boron. .

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the semiconductor single crystal substrate is a silicon semiconductor single crystal substrate, and the silicon thin film is a silicon single crystal thin film. There is provided a method for manufacturing a silicon thin film.

In the present invention, since the silicon thin film is grown after the boron thin film is formed on the semiconductor single crystal substrate, the boron is removed from the boron thin film by the heat during the growth of the silicon thin film or the heat treatment before and after it. It can be diffused inward to suppress a decrease in boron concentration near the surface of the semiconductor single crystal substrate.

As a method of forming a boron thin film, there is a method of segregating boron in a semiconductor single crystal substrate on a substrate surface, and a method of supplying a boron source gas such as diborane (B ₂ H ₆ ) to the substrate surface to deposit a boron thin film. There is a way to make it. The method of segregating boron is as follows.
By heating to 0 ° C. or lower, boron added and contained in the semiconductor single crystal substrate segregates on the surface to form a boron thin film.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a process chart showing an example of an embodiment of the present invention. In this example, first, a silicon semiconductor single crystal substrate 1 containing boron as a dopant is prepared. The surface of the silicon semiconductor single crystal substrate 1 is provided with a natural oxide film 2 or the like 2 (FIG. 1A). This silicon semiconductor single crystal substrate 1 is
When heated at 950 ° C. for 1 minute in a hydrogen gas atmosphere, the natural oxide film 2 and the like 2 are completely removed by etching. At this time, since boron atoms have a property of going out of the silicon semiconductor single crystal substrate 1 and collecting on the surface, boron segregates on the substrate surface to form a boron thin film 4 having a thickness of about one monolayer. (FIG. 1 (b)). Next, in a hydrogen gas atmosphere, 110
When the silicon semiconductor single crystal substrate 1 is heated at 0 ° C. for 30 seconds,
Boron is converted into a hydride such as borane (BH ₃ ) or diborane (B ₂ H ₆ ) by the reduction action of hydrogen gas to vaporize and diffuse inward into the silicon semiconductor single crystal substrate 1 (FIG. 1).
(C)), the boron thin film 4 is completely removed (FIG. 1)
(D)). After that, the silicon semiconductor single crystal substrate 1
By supplying trichlorosilane (SiHCl ₃ ) together with hydrogen while heating to ° C., a silicon single crystal thin film 3 is grown on the silicon semiconductor single crystal substrate 1.

The boron segregation phenomenon is known in the field of molecular beam epitaxy using ultra-high vacuum, especially as surface segregation. The main point of the present invention is to use the natural law that this surface segregation occurs even in a hydrogen gas atmosphere even at 1 atm, and apply this to the industrially important surface treatment method of a silicon semiconductor single crystal substrate. It is in.

Boron is an element having a very low vapor pressure and an element having a boiling point exceeding 2500 ° C., so that the silicon semiconductor single crystal substrate 1 is heated to 70 ° C. in a hydrogen gas atmosphere.
When heated in a relatively low temperature range of 0 to 980 ° C., the boron thin film 4 can be stably present on the surface of the silicon semiconductor single crystal substrate 1. At the same time, since the boron thin film 4 serves as a diffusion source of boron into the silicon semiconductor single crystal substrate 1, the concentration distribution of boron atoms near the surface of the silicon semiconductor single crystal substrate 1 after the removal of the boron thin film 4 is: A substantially flat density profile can be maintained.

If the temperature is lower than 700 ° C., no surface segregation occurs or the degree of the surface segregation is very weak, so that the conditions effective for the purpose of the present invention are not formed. When the silicon semiconductor single crystal substrate 1 is heated at a temperature exceeding 980 ° C. in a hydrogen gas atmosphere, the hydrogen gas is
Is reduced to form a hydride such as borane (BH ₃ ) or diborane (B ₂ H ₆ ) having a high vapor pressure, so that the boron thin film 4 is immediately removed.

FIG. 2 shows the above-mentioned process, that is, the silicon semiconductor single crystal substrate 1 doped with boron at 1 × 10 ¹⁸ / cm ³ is kept at 950 ° C. for 1 minute in a hydrogen gas atmosphere.
Next, when it is held at 1100 ° C. for 30 seconds (A),
The concentration profile of the boron concentration in the depth direction of the silicon semiconductor single crystal substrate 1 is compared between the case where the silicon semiconductor single crystal substrate 1 is held at 1100 ° C. for 30 seconds without passing through the 0 ° C. holding process.
In (B), in the vicinity of the very surface of the silicon semiconductor single crystal substrate 1, the concentration of boron as a dopant is remarkably reduced in the range of about 0.1 μm from the substrate surface in the depth direction.
In (A), the boron concentration in the silicon semiconductor single crystal substrate 1 is maintained substantially flat. From this, the effectiveness of the method of the present invention became clear.

FIG. 3 is a process chart showing another example of the embodiment of the present invention. In this example, a silicon semiconductor single crystal substrate 1 (FIG. 3A) having a natural oxide film or the like 2 on its surface is heated at 950 ° C. for 1 minute in a hydrogen gas atmosphere to segregate boron onto the substrate surface. Boron thin film 4 was formed (FIG. 3B)
Thereafter, by supplying trichlorosilane (SiHCl ₃ ) together with hydrogen to the surface of the silicon semiconductor single crystal substrate 1, the silicon single crystal thin film 3 is formed on the boron thin film 4 at 950 ° C.
Is grown (FIG. 3C). Next, in a hydrogen gas atmosphere,
When heated at 1100 ° C. for 10 seconds, the boron of the boron thin film 4 diffuses into the upper silicon single crystal thin film 3 and also into the silicon semiconductor single crystal substrate 1 (FIG. 3D),
The boron thin film 4 disappears (FIG. 3E).

FIG. 4 is a process chart showing another example of the embodiment of the present invention. In this example, the silicon semiconductor single crystal substrate 1 (FIG. 4A) having a natural oxide film 2 on the surface is heated to 1100 ° C. in a hydrogen gas atmosphere to remove the natural oxide film 2 and the like. 0.001 ppm of diborane (B ₂
H ₆ ) gas is supplied for 10 seconds, and a boron thin film 4 is
Is deposited (FIG. 4B). Then, boron thin film 4
By supplying trichlorosilane (SiHCl ₃ ) together with hydrogen to the surface of the silicon semiconductor single crystal substrate 1 on which is deposited, the silicon thin film 3 is grown on the boron thin film 4 (FIG. 4).
(C)). Next, 10 minutes at 1100 ° C. in a nitrogen gas atmosphere.
When heated for 2 seconds, the boron atoms of the boron thin film 4 diffuse into the upper silicon thin film 3 and the silicon semiconductor single crystal substrate 1
The boron thin film 4 also diffuses inward (FIG. 4D) and disappears (FIG. 4E).

The once formed boron thin film 4 may be removed before the growth of the silicon thin film 3 as in the first embodiment,
Alternatively, as in the second and third embodiments, the silicon thin film 3 may be grown while the boron thin film 4 is left, and the boron thin film 4 may be annihilated by heat during the growth of the silicon thin film 3 or subsequent heat treatment. . However, if the boron thin film 4 may adversely affect the next growth of the silicon thin film 3, it is preferable to remove the boron thin film 3 before growing the silicon thin film 3. As a method for removing the boron thin film 4, for example, there is a method using a plasma treatment or an etching gas in addition to the method of heating to 1000 ° C. or more for a suitable time in a hydrogen gas atmosphere as described above.

The present invention is not limited to the above embodiment. For example, it is obvious that the same concept can be applied to a compound semiconductor single crystal substrate in addition to a silicon semiconductor single crystal substrate. Although the pressure is particularly effective at 1 atm, the same effect has been confirmed at reduced pressure.

[0027]

As described above, according to the present invention, when growing a silicon thin film on a boron-doped semiconductor single crystal substrate, the silicon concentration can be reduced without decreasing the boron concentration near the surface of the semiconductor single crystal substrate. A thin film can be grown.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a silicon thin film growth process of the present invention.

FIG. 2 is a graph showing a concentration distribution of a boron atom concentration in a substrate in a depth direction.

FIG. 3 is a process chart showing another example of the silicon thin film growth process of the present invention.

FIG. 4 is a process chart showing another example of the growth process of the silicon thin film of the present invention.

FIG. 5 is a process chart showing an example of a conventional silicon thin film growth process.

[Explanation of symbols]

 Reference Signs List 1 semiconductor single crystal substrate 2 natural oxide film 3 silicon thin film 4 boron thin film

Claims (8)

[Claims] 1. A method for producing a thin film, comprising: forming a boron thin film on a boron-doped semiconductor single crystal substrate and then growing a silicon thin film. 2. The method according to claim 1, wherein the silicon thin film is grown after removing the formed boron thin film. 3. The method for producing a thin film according to claim 1, wherein a heat treatment is further performed after growing the silicon thin film on the formed boron thin film. 4. The method of manufacturing a thin film according to claim 1, wherein boron doped in the semiconductor single crystal substrate is segregated on the substrate surface to form a boron thin film. Method. 5. A boron thin film is formed by supplying diborane gas onto a semiconductor single crystal substrate.
A method for producing a thin film according to claim 3. 6. A heating temperature at the time of segregating boron is 70.
The temperature is between 0 ° C and 980 ° C.
A method for producing the thin film according to the above. 7. The method according to claim 2, wherein a silicon thin film is grown after the boron thin film is removed and boron is diffused inward at the same time. 8. The silicon according to claim 1, wherein the semiconductor single crystal substrate is a silicon semiconductor single crystal substrate, and the silicon thin film is a silicon single crystal thin film. Manufacturing method of thin film.