| 摘要 |
943,758. Semi-conductor devices. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. June 4, 1962 [July 3, 1961], No. 23948/61. Drawings to Specification. Heading H1K. The ohmic base contact of a mesa transistor is formed by protecting with resist material both an emitter contact which has previously been formed on a surface of a wafer of semiconductor material and an area of the surface surrounding the emitter contact, forming an ohmic contact with all the unprotected portion of the surface, enlarging the protected portion of the surface of the wafer to include part of the ohmic contact surrounding the previouslyprotected area, and then removing the unprotected portion of the ohmic contact and finally the resist material. As described, a first resist material (magnesium oxide or n-butyl methacrylate) is applied to the emitter contact and a surrounding area, a material which forms ohmic contact with the semiconductor wafer is deposited on the surface of the wafer and the resist material, the wafer is heated to form an ohmic contact over all the unprotected portion of the surface, the resist material (together with the overlying portion of the ohmic contact material) is removed (by means of heat, ultrasonic vibration, or acetic acid), a second resist material (paraffinwax) is applied to the previously protected part of the surface and to part of the ohmic contact surrounding it, an etching process removes the unprotected portion of the ohmic contact together with some of the underlying semi-conductor wafer, and finally the second resist material is removed. Specification 924,858 is referred to. |
