| 摘要 |
<p>1,115,101. Semi-conductor devices. SIEMENS A.G. 12 Jan., 1966 [13 Jan., 1965], No. 1401/66. Heading H1K. After removing material from the surface of a semi-conductor by vaporization in a diffusion chamber, impurity is introduced by means of an inert or reducing reaction gas and diffused into the body without removing it from the chamber, thereby avoiding contamination of the prepared surface. Typically in making PNP transistors silicon wafers are disposed in a quartz tube containing a source of gallium trioxide and heated in vacuo for an hour at 1100‹ C. to remove the surface to a depth of 5 Á. Then while moist argon flows through the tube the wafers are heated at 1100‹ C. for an hour, and then at 1200‹ C. for 2 hours, to oxidize the surface. The argon flow is then replaced by a reverse flow of moist hydrogen which in passing over the gallium trioxide reduces it to volatile gallium oxide which is carried forward to the wafers. Continuation of the process for 10 hours with the silicon at 1200‹ C. provides a diffused P layer 18 Á thick. In an alternative method the wafers are first oxidized in a separate vessel, photolithographically processed to form apertures in the oxide coating, and then placed in a tube with a source of boron trioxide and the tube evacuated. After heating at 1100‹ C. to remove the wafer surface, a flow of argon or nitrogen is directed through the tube and a movable heater brought up to evaporate the boron trioxide into the flow. After continuing for 2 hours to provide P zones in the masked wafers the process is terminated by removing the heater and replacing the inert gas flow with oxygen.</p> |
