JPS61196516A - Silicon molecular beam growth method - Google Patents

Abstract

PURPOSE:To reduce microscopic silicon grains adhering to a silicon substrate as well as to prevent the breakage of a silicon source by a method wherein fused silicon is prevented from coming into contact with the house of an electron gun at the rising part attached to the circumference of the silicon source. CONSTITUTION:A rising part is provided on the circumference of a silicon source 1 by shaving its upper surface by performing an electric discharge machining leaving an edge 2 at the end part. When the edge 2 is provided, the silicon fused from the beginning is gathered in the edge 2, it does not come in contact with a copper house 3, and as there is no mixture of impurities, the density of microscopic silicon grains is made lower. According to this method, the generation of the microscopic silicon grains adhering to the silicon substrate can be reduced when silicon molecular beam is grown using an electron gun heating silicon source, and also the exchange replacement of the silicon source can be performed easily without breaking the silicon source.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing semiconductor thin films, particularly to a silicon molecular beam growth method.

[Conventional technology]

In recent years, it has been developed for application to high-speed bipolar devices, microwave devices, superlattice structure devices, etc. Compared to conventional silicon thin film growth technology, growth is performed at a lower temperature, and therefore the impurity distribution is hardly disturbed. Silicon molecular beam growth technology in high vacuum is being actively researched and developed.

According to the silicon molecular beam growth method, the center of the silicon source is heated by an electron gun and only the center is melted to generate silicon molecular beams, so it has the characteristic that there is very little contamination of impurities.

[Problem that the invention seeks to solve]

However, there is a phenomenon in which silicon comes out of the silicon source not in molecular form but in liquid or solid form, and microscopic silicon particles with a diameter of 5 to 6 μm adhere to the substrate.

There are several to several hundred of these microscopic silicon grains per square centimeter.

When these minute silicon particles adhere, the growth of the semiconductor film is inhibited in that portion, which poses a major problem when using the silicon molecular beam growth method in the semiconductor device manufacturing process. Another problem is that when the center of the silicon source is melted, a portion of the melted area spreads and comes into contact with the copper house of the electron gun, causing the silicon source to crack.

The purpose of the present invention is to eliminate such conventional drawbacks, reduce the number of minute silicon particles adhering to a silicon substrate, and solve the problem of cracking of the silicon source in the silicon molecular beam growth method using an electron gun heated silicon source. [Means for solving the problem] The present invention is directed to a silicon molecular beam growth method in which a silicon source is heated by an electron gun to generate a silicon molecular beam.
This is a silicon molecular beam growth method characterized by preventing contact between molten silicon and the 71us of an electron gun at a rising portion attached to the periphery of a silicon source.

〔Example〕

This will be explained in detail below using the drawings. FIG. 1 shows a silicon source that provides a detailed explanation of the invention.

In the figure, l is a cylindrical high-purity silicon source for an electron gun that is generally used for silicon molecular beam growth. The upper surface of this silicon source 1 is ground by electrical discharge machining, leaving a 4-inch edge 2 at the end, thereby providing a raised portion at the periphery. 3 shows the copper house of the electron gun.

In the case of using a normal cylindrical silicon source without a rising part due to the edge 2, the thickness is 1 μm as shown in Fig. 2.
The density of micro silicon grains on the substrate after epitaxial growth becomes very large immediately after replacing the silicon north with a new one, and decreases with the thickness of the radial growth film.
It becomes approximately constant at about 20 μm growth mantissa α-2.

However, when edge 2 is provided, as shown in Figure 2, the density of micro silicon grains on the substrate after 1 μm epitaxial growth decreases immediately after replacing the silicon source with a new one, and after 2 to 3 μm growth. In all cases, it becomes constant at several CIIL-2-ci.

The reason for this is thought to be as follows: If there is no edge 2, after replacing the silicon source, the upper surface of the silicon source is flat in the early stage, so the molten silicon spreads, causing the electron gun's copper hole to spread.
Close to us. At this time, it is thought that impurities such as heavy metals were mixed into the molten silicon, and these impurities became nuclei and flew out as minute silicon particles. As the thickness of the line-grown film increases, a depression is created in the center of the silicon source, in which molten silicon collects and is no longer in contact with the copper nozzle. Furthermore, after the impurities mixed in at an early stage are released as nuclei of micro silicon particles, it is thought that the density of micro silicon particles adhering to the substrate decreases. When the edge 2 is provided, the molten silicon accumulates in the edge 2 from the beginning and does not come into contact with the copper nozzle 3, and there is no contamination of impurities, resulting in a decrease in the density of micro silicon grains.

In this example, the edge 2 is vertically raised from the upper surface of the silicon source, but the point is that the molten silicon does not come into contact with the house 3, so the shape of the edge 2 is set vertically. In addition, in this example, the thickness of the edge was 4 fl, but it is generally preferable to have a thickness of 2 n or more. If it is less than 2 fl, there is a risk that the silicon source will crack when it comes into contact with molten silicon. There is. Furthermore, if there is no rim 2, the molten silicon will fill the space between the source and the 71st, making it difficult to take out the source from the 71st when replacing the source, and the source will need to be broken open, but with the rim 2. This allows the sauce to be easily taken out of the house after use.

〔Effect of the invention〕

As explained in detail above, according to the present invention, it is possible to reduce the generation of minute silicon particles adhering to a silicon substrate during silicon molecular beam growth using an electron gun-heated silicon source, and there is no damage to the silicon source. It also has the advantage of being easy to replace.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional perspective view of a silicon source that explains the present invention in detail, and Fig. 2 shows the density of micro silicon grains on a substrate after epitaxial growth to a thickness of 1 μm and the line growth film thickness after replacement. FIG. l...Silicon source 2...Edge 3...Electron gun house

Claims (1)

[Claims] (1) In the silicon molecular beam growth method, in which a silicon source is heated with an electron gun to generate a silicon molecular beam, molten silicon contacts the house of the electron gun at the rising edge of the silicon source. Silicon molecular beam growth method characterized by blocking.