JPS6362314A - Manufacture of semiconductor thin film - Google Patents

Abstract

PURPOSE:To perform a high density boron-doping operation in an excellent controllability using an ordinary Knudsen cell by a method wherein, when a semiconductor thin film is formed on a substrate using a molecular epitaxial method, the molecular beam obtained by heating HBO2 is made to irradiate on a substrate. CONSTITUTION:When a semiconductor thin film is formed on a substrate using a molecular beam epitaxial method, the molecular beam obtained by heating HBO2 is made to irradiate on the substrate. By using the HBO2 as the source of doping, a doping can be performed at a low temperature in the density higher than that of the case where B2O3 is used as the source of doping. As a result, in the silicon molecular beam, boron can be doped in an excellent controllability in a high degree of density using the ordinarily used Knudsen cell, not using a special cell.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for growing semiconductor thin films on single crystals.

[Conventional technology]

In recent years, growth has been performed at lower temperatures than conventional silicon thin film growth techniques, with the aim of applying it to high-speed bipolar devices, microwave devices, superlattice structure devices, etc.
Therefore, silicon molecular beam growth (SiMB) in a high vacuum has the characteristic of hardly disturbing the impurity distribution.
E) Technology is being actively researched and developed.

In such a silicon molecular beam growth technique, a method generally used for doping is to blow out medieval molecular or atomic impurities from a molecular beam cell at the same time as silicon. The impurity for doping is antimony (n), which can be easily removed from the molecular beam cell.
(type) and gallium (p-type).

[Problem that the invention seeks to solve]

However, in the current semiconductor device manufacturing process, n
Arsenic and phosphorus are used as type impurities, and boron is used as p-type impurities, and there is a lot of accumulated technology for these impurities.Furthermore, the solid solubility limit of antimony is 4X10"3-3, and arsenic is currently used in semiconductor processes. It is not possible to form a high-concentration impurity region for ohmic contact of 10"aIl-, which is currently being created. Also, gallium has a very large diffusion coefficient in the silicon oxide film, and the gallium doped layer in contact with the silicon oxide film cannot be formed. Because it diffuses into the oxide film, it is not used at all in the normal silicon semiconductor manufacturing process.Also, even if the device structure is such that the gallium-doped layer does not come into contact with the oxide film, the solidity of gallium Since the solubility limit is about 1011al''3, it is not possible to create a p-type high concentration region of 10''Ql''3 like boron.

So, R, Knee, Kubiak (R, A, A).

Kubiak) etc. are Applied, Physics, Letters (Appl, Phys, Lett,) 44 (
9) (1984) 878 by heating elemental boron to ~2000°C in a special doping cell;
It has been found that the amount of boron doped is between 700°C and 900°C and does not depend on the silicon substrate temperature. but,
Since the cell temperature is still low, the maximum concentration is 4X10”Q
It remains at 1″″3. Because the heat resistance of the crucible material is limited, it is difficult to raise the cell temperature any higher.Furthermore, with this method, the cell temperature is very high, so there is a high risk of contamination with substances other than boron, and It is also difficult to provide thermal insulation from the

Furthermore, Kashiwazaki, Tatsumi et al.
ndad Abstracts of the 17
th Confsrence on 5-olid 5
tateDevices and Materials
ls, Tokyo, 1985゜PP, 301-304)
As described in , doping with boron is carried out by heating a mixture of B20□ and BN as diffusion materials in a conventional cell to achieve a maximum concentration of 7X10.
High-concentration doping of "aIl-" has been achieved. However, since an oxide is used as a doping source, high-concentration doping causes problems such as oxygen incorporation into the epitaxial film and deterioration of crystallinity. Also,
7X10" am-1 cell heat resistance limit 1350
This was achieved at low temperature and at a low growth rate, and higher doping concentrations cannot be expected.

The purpose of the present invention is to eliminate such conventional drawbacks and to develop a semiconductor thin film that can be doped with boron at a high concentration with good control using a commonly used Knudsen cell rather than a special cell in silicon molecular beams. The purpose is to provide a manufacturing method.

[Means for solving problems]

The present invention is a method for producing a semiconductor thin film, which is characterized in that when a semiconductor thin film is formed on a substrate by a single molecular beam epitaxial method, the substrate is irradiated with a molecular beam obtained by heating HBO.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

)IBO, can be obtained as a boron diffusion source with extremely high purity. The commercially available powder was used as the raw material. The sample silicon substrate was mixed with 28% ammonia water and 3
Mix 0% hydrogen peroxide and water in a ratio of 1:4:20, wash in a boiling solution for 10 minutes to form a thin silicon oxide film on the silicon substrate surface, and then wash in a high vacuum. By heating to 600°C to 800°C for a short time, and then using electron beam evaporation in a high vacuum at 730°C or lower, a layer of 40% to 80% of the thickness of the thin silicon oxide film is deposited on the thin silicon oxide film on the substrate surface. Form a thick silicon film,
Thereafter, the surface was cleaned by heating at 730° C. or higher for a short time in a high vacuum. The doping concentration was determined by resistance value measurement using a four-probe probe and Hall measurement. The crystal defect density was determined by performing commonly used light etching and counting etch pits using an optical microscope.

Figure 1 is an Arrhenius plot of the relationship between the cell temperature of 1 (BO2) and the carrier concentration determined from resistance measurements.
It is an n-type silicon substrate with a resistance of Ω1. The growth temperature is 70
0°C, growth rate IOA/s, grown film thickness 1.5μ
Met. As can be seen from Figure 1, the plot was on a straight line, and the highest concentration of 6X10"GW""' could be achieved. Such high concentration doping was proposed by Kashiwazaki, Tatsumi et al. Page 301 of conference abstracts (Ext-ended Ab
structs of the 17th Confe
ranes on 5-olid 5tate Dev
ices and materials, Tokyo,
For comparison, 820.820. is shown in Figure 2 for comparison, but cannot be realized using B20, which is a diffusion raw material described in 1985゜PP, 301-304). The activation energy, which shows the relationship between cell temperature and carrier concentration in the case of doping from B20°, is 5.4aV when doping from B20°, and
The activation energy is very close to that of O1, but in the case of doping from HBO, it is 1.5 eV, which is close to HBO.

B and O in Figure 3.

This figure shows a comparison of the vapor pressures of I(BO,
The temperature required to obtain the same vapor pressure of 10-'at+a, which is twice as high, is 870°C for HBO3, while 1300°C for B20. From the results of more than 1 corresponding to the difference in cell temperature of the two B sources, the number of molecules evaporated when doping from 820. is 8□01, but HBO,
It can be considered that the doping from HBO is HBO. Therefore, in the case of doping from HBO□,
The vapor pressure increases and B20. It is thought that a higher concentration of doping can be achieved at a lower cell temperature than in the case of .

As a result of SIMS measurements, it was found that oxygen, which is thought to come flying together with boron during growth, is not incorporated into the epitaxial film when the growth temperature is 700° C. or higher.

As described above, it is clear that using HBO as a doping source has the effect of enabling higher concentration doping at a lower cell temperature than when using 8203 as a doping source. .

Note that although silicon wafers were targeted in this example,
The method of the present invention uses 5O5 (
Silicon on 5apphire) substrates and more generally 5OI (Silicon on In5ulat) substrates.
or) Of course, it can also be applied to substrates, etc.

Furthermore, in this embodiment, the case of epitaxial growth has been described, but it can of course also be applied to the case of doping polycrystals.

In addition, in the above explanation, the present invention is applied to a doping method in silicon molecular beam growth technology, but the present invention is not limited to this, and can be generally applied to a wide range of wafer processing processes such as integrated circuit manufacturing. It is something.

〔Effect of the invention〕

As described in detail above, according to the present invention, boron can be doped at a high concentration with good controllability in a silicon molecular beam using a commonly used Knudsen cell instead of a special cell. .

[Brief explanation of drawings]

Figure 1 is an Arrhenius plot of the relationship between the cell temperature of HBO and the carrier concentration determined from resistance measurement, and Figure 2 is a diagram showing the relationship between cell temperature and carrier concentration when doping from B,03. Figure 3 shows B30, and HBO,
It is a figure showing the comparison of the vapor pressure of.

Claims (1)

[Claims] (1) A method for producing a semiconductor thin film, which comprises irradiating the substrate with molecular beams obtained by heating HBO_2 when forming the semiconductor thin film on the substrate by molecular beam epitaxial method.