JPS60147123A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain clean surface on wafers by a method wherein a semiconductor substrate, having an oxide film on the chemically washed surface, is heat- treated in a vacuum atmosphere of specific partial pressure of gas of silicon steam or silicon compound gas, and the oxide film is evaporated. CONSTITUTION:When the washing process using a bunch of chemical solutions is finished, a silicon wafer 21 is set in a vacuum chamber. After the vacuum chamber has been evacuated to the vaccum state of 1X10<-5>Pa or below, it is heated up to the temperature range of 600 deg.C-900 deg.C, and silicon steam of gas partial pressure of 8X10<-5>-1X10<-7>Pa is introduced therein. The SiO2 film 22 formed by chemical washing is turned into volatile gas of SiO type by the reaction with silicon steam. The oxide film 22 on the surface of the silicon wafer 21 is evaporated, and it is finally removed. As a result, a clean surface is obtained on the silicon wafer 21. Besides, the time required for performance of the above-mentioned procedures is 2-30min or thereabout.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a method for manufacturing a semiconductor device, and more specifically, to a method for manufacturing a semiconductor device.

The present invention relates to a method for cleaning semiconductor surfaces, particularly silicon surfaces.

(Prior Art) Conventionally, CVD (chemical vapor deposition) has been used to epitaxially grow crystals on a single crystal substrate such as silicon, but to obtain an epitaxial layer with good crystallinity using this method, It is necessary to decompose gases such as silane at high temperatures of around 900 degrees Celsius or higher for epitaxial growth.

In contrast, recently, techniques for performing epitaxial growth at relatively low temperatures (about 600° C.), such as molecular beam epitaxial method and solid phase epitaxial method, have been attracting attention. In order to perform epitaxial growth using such a method, it is necessary that the surface of the crystal of the substrate be sufficiently clean.

Conventionally, sputter cleaning has been used as a method to obtain good cleanliness of the substrate surface. This method removes impurities deposited on the surface of the substrate by bombarding them with argon ions, etc. However, even after sputtering at around 500 degrees Celsius, damage to the crystals due to spatter remains. There's a problem. Alternatively, instead of the sputter cleaning method, the substrate is heated to a high temperature of 1000° C. or higher in a vacuum of about 10-” Pa,
There is also a method of evaporating surface impurities, but this is not the case.

From the point of view of low-temperature processing and bitaxial growth.

Since the substrate is heated to a high temperature once, this method destroys the characteristics of the single-molecule beam epitaxial method.

(Objective of the Invention) This invention was made in view of the above points, and its object is to provide a method for manufacturing a semiconductor device that can realize surface cleaning at a low temperature of 900° C. or lower and without damaging the substrate. It is about providing.

(Summary of the Invention) The main point of this invention is to heat a semiconductor substrate on which an oxide film has been formed on the surface by chemical cleaning in a vacuum at a gas partial pressure of silicon vapor or silicon compound gas of Bxlo-' to 1x10-'Pa. By evaporating the oxide film by
The goal is to obtain a clean surface.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show one embodiment of the present invention.
The figure is an explanatory diagram of the steps, and FIG. 2 is a sectional view of the silicon wafer A in some of the steps.

As shown in Step 1 of FIG. 1, in one embodiment of the present invention, sulfuric acid (H, SO4) and hydrogen peroxide (Hz O!
) is heated to about 100°C, and silicon urethane as a semiconductor substrate is infiltrated into it for about 5 minutes (
This process removes organic substances such as oil and fats and inorganic substances such as heavy metals from the surface of the silicon wafer. next,
After washing the silicone urethane with pure water for 5 minutes as shown in step 2 in Figure 1, it was washed with 5 liters of hydrofluoric acid (HF) as shown in step 3 in Figure 1. Soak in the liquid for 2 minutes (
De-rag) to remove the oxide film formed on the surface of the silicone by cleaning with sulfuric acid and hydrogen peroxide.

Thereafter, the silicon wafer is washed with pure water (rinsed with pure water) for 5 minutes as shown in step 4 of FIG.

Note that these steps are generally widely used cleaning methods.

After that, as shown in step 5 of FIG. 1, hydrochloric acid (HCJ
), water (H,0), and hydrogen peroxide (Hoot ), 31
Silicon wafers are infiltrated (de-raged) for about 5 minutes in a 3:1 mixture of chemicals heated to about 80°C, and then silicon wafers are soaked (de-lag) for about 5 minutes as shown in steps 6 and 7 in FIG.
Rinse with water (pure water) for 0 minutes.

dry. Here, the hydrochloric acid-water/hydrogen peroxide mixture is
In addition to removing inorganic contaminants such as heavy metals from the silicon wafer surface, the oxide film (S
in,) is formed to a thickness of about 2OA. A silicon wafer with this oxide film formed thereon is shown in FIG. 2(b), and a silicon wafer before the oxide film is formed is shown in FIG. 2(aJ).

In these figures, 21 is a silicon wafer and 22 is an oxide film. In the following description, the silicon wafer will be denoted by 21, and the oxide film will be denoted by 22.

After completing the series of chemical cleaning operations as described above, the silicon wafer 21 is then set in a vacuum chamber as shown in step 8 in FIG.

Then, as shown in step 9 in FIG.
After evacuating to a vacuum of about 'Pa, the silicon wafer 21 is heated at 600'0 to 900°C as shown in step 10 of FIG.
Heat to. Furthermore, as shown in step 11 of FIG.
Gas partial pressure is 8 X 10-"-I X 10-'Pa
.

For example, a silicon vapor resistance of about I x 10-'Pa is introduced into the vacuum chamber.

When silicon vapor is introduced into the vacuum chamber, an oxide film (S) formed on the surface of the silicon wafer 21 by chemical cleaning is removed.
iOx ) 22 reacts with the silicon vapor to form Si
It becomes a volatile gas in the form of O. Therefore, the oxide film 22 on the surface of the silicon wafer 21 evaporates as shown in FIG. 2 (cJ), and is finally removed as shown in FIG. 2 (d). A clean surface can be obtained.The time required for this is about 2 to 30 minutes.In addition, the silicon vapor introduced into the vacuum chamber is obtained by heating and evaporating silicon.
゜ru.

After that, if necessary, after evacuating the silicon vapor in the vacuum chamber, as shown in step 12 of FIG. Molecular beam epitaxial growth is performed on 21. At this time, if the degree of vacuum in the chamber is set to I x 10-'Pa or less and the temperature of the silicon wafer 21 is maintained at 500 to 800°C, the oxide film 22 can be cleaned in the previous oxide film 22 removal process (cleaning process). Since there are no impurity atoms that interfere with epitaxial growth on the surface of the silicon wafer 21, a good epitaxial layer can be obtained. The silicon wafer 21 after forming this epitaxial layer is shown in FIG. 2 (eJ).

In the figure, 23 is an epitaxial layer.

In the above embodiment, steps 5 to 7 in FIG.
In order for the oxide film 22 formed to inactivate the surface of the silicon wafer 21, after drying the silicon wafer 21,
It is possible to prevent hydrocarbon compounds and the like from being adsorbed onto the surface of the silicon wafer 21 before it is placed in a vacuum chamber. Further, in order to evaporate this oxide film 22 by mere heat treatment, a temperature of 900° C. or higher is required, but in the above embodiment, volatile SiO is formed by exposing it to silicon vapor during μ heat treatment. Therefore, it becomes possible to remove the oxide film 22 at a low temperature of 600 to 900°C. Therefore, according to this method, 9
The surface of the silicon wafer 21 can be cleaned at a low temperature of 00° C. or lower and without damaging the silicon wafer 21.

'In the above embodiment, silicon vapor was introduced into the vacuum chamber during the heat treatment in order to remove the oxide film (Sin) 22 on the surface of the silicon wafer 21 at a low temperature of 600 to 900°C. The silicon compound gas may also be introduced into the vacuum chamber. That is, when a silicon compound gas such as dichlorosilane, trichlorosilane, or silane with a gas partial pressure of about I x 10-'Pa is introduced into a vacuum chamber, the silicon compound gas decomposes and forms an oxide film (Sin) on the surface of the silicon wafer. Silicon is deposited on top of the silicon.Then, the silicon and oxide film (S
i 02)” reacts, and the oxide film (Sin, ) changes to Si.
It becomes a volatile gas in the form of O. So in this case too %
The oxide film on the silicon wafer surface is evaporated at a low temperature of 600 to 900°C and is finally removed, thereby making it possible to obtain a clean silicon wafer surface.

(Effects of the Invention) As detailed above, according to the method of the present invention, a semiconductor substrate on which an oxide film has been formed on the surface by chemical cleaning is treated with a gas partial pressure of silicon vapor or silicon compound gas of 8 x 10-
Since the oxide film was evaporated by heat treatment in a vacuum of ~lXl0-'Pa to obtain a clean surface, the surface could be cleaned at a low temperature of 900°C or less without damaging the substrate. can be realized. The method of the present invention can be used for epitaxial growth of various crystalline materials and techniques for utilizing clean surfaces.

[Brief explanation of drawings]

1 and 2 show an embodiment of the method for manufacturing a semiconductor device of the present invention, FIG. 1 is an explanatory diagram of the steps, and FIG. 2 is a cross-sectional view of a silicon wafer in a part of each step jC. . 21.--Silicon cube, 22.--Oxide film. Figure 1 Figure 2 Procedural amendment July 16, 1980 Manabu Shiga, Commissioner of the Patent Office 1. Indication of the case Patent Application No. 1877 of 1987 2. Name of the invention.
3. Relationship with the case of the person making the amendment Patent Applicant (029) Oki Electric Industry Co., Ltd. 5 Date of amendment order Showa Month, Day (Spontaneous) 6.
Column 7 of the detailed description of the invention in the specification subject to amendment, Contents of amendment 7, Contents of amendment 1) Page 2 of the specification, line 14 “After sputtering at about 500°C”
is corrected to "approximately 500°C after sputtering".

Claims (1)

[Claims] After soaking the semiconductor substrate in an oxidizing chemical, cleaning with pure water and drying the semiconductor substrate;
Vacuum degree I
X 10-' ~ I X 10-' PaOPa medium terrorism o
A method for manufacturing a semiconductor device, comprising a step of heating at a temperature of 0° C. to 900° C. for 2 minutes to 30 minutes.