| 摘要 |
1,145,488. Semi-conductor devices. TEXAS INSTRUMENTS Inc. 7 April, 1966 [30 April, 1965], No. 15662/66. Heading H1K. An intermediate product from which mutually isolated semi-conductor components can be made consists of a mono-crystalline semiconductor wafer with at least one mesa on one face, and a support body, which is separated from the wafer at least in the region surrounding each mesa by a layer or layers of a material harder than the wafer material. In the preferred embodiment mesas 2 mils high are formed on an N+ silicon wafer by photoresist and etching steps and silicon carbide deposited on the resulting surface from a gaseous mixture of toluene and silicon tetrachloride in the carrier gas hydrogen. Amorphous or monocrystalline silicon of N, P or intrinsic type is then deposited to a depth of 7-8 mils. If desired a layer of molybdenum or tungsten is deposited before the carbide to provide a low resistance current path. In an alternative method silicon dioxide is thermally grown over the prepared surface of the wafer, and the silicon carbide deposited on top of it. A variant of this is to etch the dioxide from the inter-mesa areas and then deposit the carbide on the cleared areas through a silicon mask. In all cases the support body is next lapped down to the silicon carbide around the mesas which acts as a stop preventing the further lapping of the mesas which might otherwise occur in securing a flat surface on a warped body. The lapped surface is covered with oxide masking, which is removed over the centres of the mesas by photo-resist and etching steps. A pit is formed in each mesa by gas etching through the mask and is filled with higher resistivity N-type silicon by epitaxial deposition. Finally the base regions of transistors and resistive tracks and transistor emitter regions are formed in neighbouring mesas by successive masked diffusion processes and the resistors and transistors connected to form a logic circuit by depositing metal over an apertured masking layer and then etching it selectively to form the interconnections. Other hard materials such as alumina and boron may be used instead of silicon carbide. |
