Method for fabricating a semiconductor device

Claim 1

A method for forming a shallow high-concentration impurity layer adjacent to a surface of a semiconductive bulk region in a device structure, characterized in that the method comprises the steps of: a. forming a source layer in contact with at least a preselected area of the surface, the source layer being doped to a high concentration with a suitable impurity; b. and heating the source layer at an appropriate temperature in the presence of an appropriate reactant to cause a reaction which completely consumes the source layer at a rate exceeding the rate at which the impurity diffuses in the bulk region, the reaction yielding a reaction product and the impurity having a source-layer-material/reaction-product segregation coefficient significantly greater than unity, so as to form an impurity concentration at the interface between the reaction product and the bulk region that is substantially larger than the initial impurity concentration in the source layer, which impurity concentration at the interface exceeds the solid solubility of the impurity in the bulk region.

Claim 2

A method for forming a shallow high-concentration impurity layer adjacent to a surface of a semiconductive bulk region in a device structure, characterized in that the method comprises the steps of: a. forming a source layer in contact with at least a preselected area of the surface, the source layer being doped to a high concentration with a suitable impurity; b. and heating the source layer at an appropriate temperature in the presence of an appropriate reactant to cause a reaction which completely consumes the source layer at a rate exceeding the rate at which the impurity diffuses in the bulk region, the reaction yielding a reaction product and the impurity having a source-layer-material/reaction-product segregation coefficient significantly greater than unity, so as to form an impurity concentration at the interface between the reaction product and the bulk region that is substantially larger than the initial impurity concentration in the source layer, which impurity concentration at the interface exceeds the solid solubility of the impurity in the bulk region.

Claim 9

A method as recited in claims 5, 6 or 7 further characterized in that the source layer is doped with arsenic, the source layer is heated in a steam ambient at a temperature in the range of 800 degrees C. to 950 degrees C. to cause complete oxidation thereof, and after oxidation of the source layer the bulk region is annealed at a temperature in the range of 850 to 1000 degrees C. for a time in the range of 10 minutes to 4 hours.

Claim 13

A method for forming in a silicon monocrystalline body a shallow surface layer having a high dopant concentration, said method comprising the steps of forming a polycrystalline silicon layer of thickness less than the thickness of the shallow layer desired and having a high dopant concentration, heating the body in an oxidizing atmosphere for a time and at a temperature to oxidize the polycrystalline layer completely and to transfer substantially all of the dopant in such polycrystalline layer into a surface layer of the body of first thickness approximately equal to the thickness of the polycrystalline layer whereby the concentration of the dopant at the interface between the oxidation product and the silicon body is substantially larger than the initial concentration in the layer, and heating the body for a time and at a temperature to activate the dopant transferred into the body and to increase the thickness of the dopant layer in the body to no more than approximately twice the first thickness.

Claim 14

A method for forming in a silicon monocrystalline body a shallow surface layer having a high dopant concentration, said method comprising the steps of forming a polycrystalline silicon layer of thickness less than the thickness of the shallow layer desired and having a high dopant concentration, heating the body in an oxidizing atmosphere for a time and at a temperature to oxidize the polycrystalline layer completely and to transfer substantially all of the dopant in such polycrystalline layer into a surface layer of the body of first thickness approximately equal to the thickness of the polycrystalline layer whereby the concentration of the dopant at the interface between the oxidation product and the silicon body is substantially larger than the initial concentration in the layer, and heating the body for a time and at a temperature to activate the dopant transferred into the body and to increase the thickness of the dopant layer in the body to no more than approximately twice the first thickness.