Impurity doping method with adsorbed diffusion source

Claim 1

A method for doping a region below a surface of a semiconductor substrate with an impurity comprising: covering a portion of the substrate surface with an oxide insulating film having a thickness of at least 100 Å so that a part of the substrate surface is not covered by the insulating film and constitutes a diffusion area; and removing any inert film from the semiconductor surface diffusion area, by a procedure which includes at least one of a reduction reaction and a heat treatment, to expose a chemically active surface of the semiconductor; applying to the chemically active semiconductor surface a boron hydrogen gas compound containing boron impurity atoms and heating the substrate to a temperature between 600° C. and 950° C. to form chemically an adsorption layer in the form of a composite layer composed of an impurity layer containing the boron impurity atoms and a semiconductor layer; and effecting solid phase diffusion into the region using the adsorption layer as an impurity diffusion source and effecting activation of the impurity, wherein the substrate is maintained continuously in a vacuum after said step of removing and during said step of applying.

Claim 2

A method for doping a region below a surface of a semiconductor substrate with an impurity comprising: covering a portion of the substrate surface with an oxide insulating film having a thickness of at least 100 Å so that a part of the substrate surface is not covered by the insulating film and constitutes a diffusion area; and removing any inert film from the semiconductor surface diffusion area, by a procedure which includes at least one of a reduction reaction and a heat treatment, to expose a chemically active surface of the semiconductor; applying to the chemically active semiconductor surface a boron hydrogen gas compound containing boron impurity atoms and heating the substrate to a temperature between 600° C. and 950° C. to form chemically an adsorption layer in the form of a composite layer composed of an impurity layer containing the boron impurity atoms and a semiconductor layer; and effecting solid phase diffusion into the region using the adsorption layer as an impurity diffusion source and effecting activation of the impurity, wherein the substrate is maintained continuously in a vacuum after said step of removing and during said step of applying.

Claim 9

A method for doping a region below a surface of a semiconductor substrate with an impurity comprising: covering a portion of the substrate surface except for the region with an oxide insulating film having a thickness of at least 100 Å to prevent an impurity adsorption layer from forming on the portion; placing the semiconductor substrate in a vacuum chamber; removing any inert film from the semiconductor surface diffusion area, by a procedure which includes at least one of a reduction reaction and a heat treatment in the vacuum chamber at a background pressure of less than 10 -4 Pa to expose and keep a chemically active surface of the semiconductor; applying to the chemically active semiconductor surface a boron hydrogen gas compound boron containing impurity atoms and heating the substrate in the vacuum chamber to form chemically the adsorption layer containing the boron impurity atoms; and effecting solid phase diffusion into the region using the adsorption layer as an impurity diffusion source and effecting activation of the impurity, wherein a silicon thin film is formed on the adsorption layer and solid phase diffusion is effected into the silicon thin film using the adsorption layer as an impurity diffusion source.

Claim 10

A method for doping a region below a surface of a semiconductor substrate with an impurity comprising: covering a portion of the substrate surface except for the region with an oxide insulating film having a thickness of at least 100 Å to prevent an impurity adsorption layer from forming on the portion; placing the semiconductor substrate in a vacuum chamber; removing any inert film from the semiconductor surface diffusion area, by a procedure which includes at least one of a reduction reaction and a heat treatment in the vacuum chamber at a background pressure of less than 10 -4 Pa to expose and keep a chemically active surface of the semiconductor; applying to the chemically active semiconductor surface a boron hydrogen gas compound boron containing impurity atoms and heating the substrate in the vacuum chamber to form chemically the adsorption layer containing the boron impurity atoms; and effecting solid phase diffusion into the region using the adsorption layer as an impurity diffusion source and effecting activation of the impurity, wherein a silicon thin film is formed on the adsorption layer and solid phase diffusion is effected into the silicon thin film using the adsorption layer as an impurity diffusion source.