DE1260445B - Process for diffusing gaseous doping material into a semiconductor crystal - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

BOIj

German class: 12 g -17/34

Number:
File number:
Registration date:
Display day:

1260445
S95820IVc / 12g
March 8, 1965
February 8, 1968

In the manufacture of semiconductor components based on silicon, silicon carbide and other semiconductor materials, a doping process is often used in which gaseous doping material is made to diffuse into a semiconductor crystal. The semiconductor crystal to be doped can be used together with a mixture of an oxide, a chloride, bromide or iodide of the dopant and an inert carrier substance, e.g. B. SiO ₂ , heat in a closed vessel, so that doping gas develops from the mixture, which is brought into contact with the semiconductor crystal. This method is used in particular for doping with boron, in which a powdery mixture of B ₂ O ₃ and SiO _{2 is used} as the source for the doping gas.

This process is often used - especially when using silicon-containing semiconductor materials - Surface defects observed that lead to uneven diffusion fronts. These disturbances, which are partly based on the deposition of dust particles during the diffusion process (and which also occur with more careful preparation of the semiconductor surface), can with a Method for diffusing a gaseous doping material into a semiconductor crystal which heated together with a dopant-containing mixture in a vessel and with that of the Mixture released gaseous doping material is brought into contact, switched off, if, according to the invention, a fluorine-containing substance is admixed with the doping gas.

In a known method for producing a semiconducting electrode system with at least a rectifying electrode and an ohmic connection is the finished semiconductor component exposure to halogen prior to installation in a cover to be sealed in a vacuum-tight manner and / or exposed to a halogen-hydrogen compound. This allows the semiconductor surface to be stabilized for higher operating temperatures reach.

In contrast, the invention serves to equalize a diffusion front during diffusion a doping gas.

The equalization of the doping fronts obtained in this way is important for reproducibility of pn junctions and thus the electrical properties of the semiconductor arrangements obtained of considerable advantage.

As a particularly ge method for the present purpose for diffusing gaseous doping material into a semiconductor crystal

Applicant:

Siemens Aktiengesellschaft, Berlin and Munich, 8000 Munich 2, Wittelsbacherplatz 2

Named as inventor:

Franz-Xaver Wassermann, 8000 Munich

Suitable fluorine-containing substances are hydrogen fluoride and ammonium fluoride. These will expediently added to the mixture developing the doping gas in such a small amount that one

ao noticeable obstruction of the doping and an etching effect on the semiconductor or the other present Substances is not possible.

A powdery mixture of pure SiO ₂ with a

Oxide or a chloride, bromide or iodide of the doping substance can be used. It is sufficient if the mixture contains fluorine-containing substance such. B. NH ₄ F, added in small traces (z. B. less than 1% of the total weight). It is also possible to build the fluorine-containing substance into the wall of the doping vessel. There is therefore the possibility, especially when using a doping vessel made of quartz, to incorporate both the dopant (e.g. boron) and the fluorine-containing substance into the wall of the doping vessel by heating the doping vessel in contact with the said substances. During the actual doping process, the wall of the reaction vessel then serves in a manner known per se as a source for the dopant and at the same time, according to the invention, as a source for the fluorine-containing substance.

The drawing shows an apparatus suitable for carrying out the method according to the invention. The doping vessel 1 consists of a quartz ampoule, in which the semiconductor single crystals 3 made of silicon rest on a sieve-like base 2 made of quartz. Below the base 2, on the bottom of the doping vessel 1, there is a mixture 4 of SiO ₂ and B ₂ O _{3 which serves as a source for the doping gas}

809 507/603

or P ₂ O ₅ . The arrangement is placed in a furnace 5, through which both the semiconductor crystals 3 and the source 4 for the dopant are heated to the required temperature.

Claims (4)

5 claims: 1. A method for diffusing a gaseous doping material into a semiconductor crystal, which is heated together with a mixture containing dopants in a vessel and brought into contact with the gaseous doping material given off by the mixture is, characterized in that a mixture of the doping gas and a fluorine-containing substance is used. 2. The method according to claim 1, characterized in that the fluorine-containing substance Hydrogen fluoride or ammonium fluoride is used. 3. The method according to claim 1 or 2, characterized in that the fluorine-containing substance is added to the mixture serving as a source for the doping gas. 4. The method according to any one of claims 1 to 3, characterized in that at least the fluorine-containing substance before the diffusion process by loading into the wall of the doping vessel is installed. Considered publications:
German interpretative document No. 1052 573. 1 sheet of drawings 809 507/603 1.68 © Bundesdruckerei Berlin