Gallium-phosphorus simultaneous diffusion process
AssigneeGeneral Electric Company
InventorRaymond L. Marcotte
Life of this patent
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Abstract
By protecting one surface of a silicon element with an oxide layer while leaving another surface exposed it is possible to diffuse both gallium and phosphorus into the silicon element simultaneously in a selective manner. Gallium will penetrate the oxide layer while phosphorus will not, thereby forming a P conductivity type layer beneath the oxide layer. At the same time both gallium and phosphorus will diffuse into the remaining surfaces of the element. A higher concentration of phosphorus than gallium will diffuse to all depths, thereby forming an N conductivity type layer adjacent the exposed surface of the silicon element.
Claims10
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.degree. 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.
A process for simultaneously forming, in a silicon wafer having opposed substantially parallel major surfaces, a P.sup.+ conductivity type layer adjacent one major surface and an N.sup.+ 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.degree. 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.sup.+ 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.sup.+ conductivity type layer.
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.degree. 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.
Dependencies are inferred from the claim text.