Gallium-phosphorus simultaneous diffusion process

Claim 2

A process for forming a junction within a silicon wafer having opposed, substantially parallel major surfaces comprising: providing an oxide layer on one major surface, locating the wafer in a closed tube containing only an inert non-oxidizing atmosphere and a non-limiting source of gallium and phosphorus vapors, heating the wafer and vapor source within the closed tube to a temperature in excess of 1000° C for about 35 to 40 hours to generate a vaporous mixture of gallium and phosphorus without oxidizing the surface of the wafer not previously provided with said oxide layer, diffusing gallium through the oxide layer and into the one major surface to form a P conductivity type layer while substantially blocking phosphorus vapor penetration through the oxide layer, and simultaneously, diffusing both gallium and phosphorus into the remaining major surface of the wafer while maintaining the atmosphere in the closed tube saturated with phosphorus vapor to establish a phosphorus diffusion profile of the form shown in FIG. 3 with a magnitude and depth exceeding that of gallium entering the wafer through the remaining major surface to form an N conductivity type layer.

Claim 3

A process for simultaneously forming, in a silicon wafer having opposed substantially parallel major surfaces, a P + conductivity type layer adjacent one major surface and an N + conductivity type layer adjacent the opposite major surface comprising: providing an oxide layer on said one major surface, locating the wafer in a closed tube containing only an inert non-oxidizing atmosphere and a non-limiting source of gallium and phosphorus vapors, heating the wafer and vapor source within the closed tube to a temperature in excess of 1000° C for about 35 to 40 hours to generate a vaporous mixture of gallium and phosphorus without oxidizing the surface of the wafer not previously provided with said oxide layer, diffusing gallium through the oxide layer and into the one major surface to form the P + conductivity type layer while substantially blocking phosphorus vapor penetration through the oxide layer, and simultaneously, diffusing both gallium and phosphorus into the remaining major surface of the wafer while maintaining the atmosphere in the closed tube saturated with phosphorus vapor to establish a phosphorus diffusion profile of the form shown in FIG. 3 with a magnitude and depth exceeding that of gallium entering the wafer through the remaining major surface to form the N + conductivity type layer.

Claim 4

A process for simultaneously forming, in a silicon wafer having opposed substantially parallel major surfaces, a P + conductivity type layer adjacent one major surface and an N + conductivity type layer adjacent the opposite major surface comprising: providing an oxide layer on said one major surface, locating the wafer in a closed tube containing only an inert non-oxidizing atmosphere and a non-limiting source of gallium and phosphorus vapors, heating the wafer and vapor source within the closed tube to a temperature in excess of 1000° C for about 35 to 40 hours to generate a vaporous mixture of gallium and phosphorus without oxidizing the surface of the wafer not previously provided with said oxide layer, diffusing gallium through the oxide layer and into the one major surface to form the P + conductivity type layer while substantially blocking phosphorus vapor penetration through the oxide layer, and simultaneously, diffusing both gallium and phosphorus into the remaining major surface of the wafer while maintaining the atmosphere in the closed tube saturated with phosphorus vapor to establish a phosphorus diffusion profile of the form shown in FIG. 3 with a magnitude and depth exceeding that of gallium entering the wafer through the remaining major surface to form the N + conductivity type layer.

Claim 5

A process according to claim 2 in which said wafer and vapor source is maintained at approximately 1250° C.

Claim 6

A process according to claim 2 wherein said inert non-oxidizing atmosphere is 0.2 atmospheres of Argon.

Claim 7

A process for forming a junction within a silicon wafer having opposed, substantially parallel major surfaces comprising: oxidizing the entire exterior surface of the silicon wafer, selectively removing oxide from a portion of the surface, locating the wafer in a closed tube containing an inert atmosphere with a non-limiting source of gallium and phosphorus vapors, heating the wafer and vapor source within the closed tube to a temperature in excess of 1000° C for about 35 to 40 hours to generate a vaporous mixture of gallium and phosphorus, diffusing gallium through the oxidized portion of the exterior surface of the silicon wafer to form a P conductivity type layer while substantially blocking phosphorus vapor penetration through the oxidized surface portion, and simultaneously, diffusing both gallium and phosphorus into the wafer over the surface portion haivng oxide selectively removed therefrom to establish a phosphorus diffusion profile of the form shown in FIG. 3 with a magnitude and depth exceeding that of gallium entering the wafer through the same surface portion to form an N conductivity type layer.

Claim 8

A process for forming a junction within a silicon wafer having opposed, substantially parallel major surfaces comprising: oxidizing the entire exterior surface of the silicon wafer, selectively removing oxide from a portion of the surface, locating the wafer in a closed tube containing an inert atmosphere with a non-limiting source of gallium and phosphorus vapors, heating the wafer and vapor source within the closed tube to a temperature in excess of 1000° C for about 35 to 40 hours to generate a vaporous mixture of gallium and phosphorus, diffusing gallium through the oxidized portion of the exterior surface of the silicon wafer to form a P conductivity type layer while substantially blocking phosphorus vapor penetration through the oxidized surface portion, and simultaneously, diffusing both gallium and phosphorus into the wafer over the surface portion haivng oxide selectively removed therefrom to establish a phosphorus diffusion profile of the form shown in FIG. 3 with a magnitude and depth exceeding that of gallium entering the wafer through the same surface portion to form an N conductivity type layer.

Claim 9

A process according to claim 5 in which said wafer and vapor source is maintained at approximately 1250° C.

Claim 10

A process according to claim 5 wherein said inert non-oxidizing atmosphere is 0.2 atmospheres of Argon.

Claim 11

A process according to claim 5 in which a low level P conductivity type impurity is initially uniformly distributed through the silicon wafer.

Claim 12

A process according to claim 5 in which a low level N conductivity type impurity is initially uniformly distributed through the silicon wafer.

Claim 13

A process according to claim 5 wherein the gallium diffusing through the oxidized portion diffuses more deeply, than does the phosphorus diffusing through the surface portion having the oxide removed therefrom.