| 摘要 |
PURPOSE:To prevent the short-circuit between a collector and an emitter by a method wherein a base layer is provided by using a buried oxide film, a bird beak is removed by etching thereafter, selective oxidation is made again to prepare the second buried oxide film, and then an emitter layer is provided. CONSTITUTION:An Si3N4 mask 13 is given to a thermally-oxidized film 12 on an N type Si 11, wet oxidation is applied thereto at 1,000 deg.C, and thereby a buried oxide film 14 is formed. Then, a resist mask 18 being given, P type ions are implanted in the film to prepare a base layer 15. Next, the film 14 is etched about 0.7mum deep by a buffer HF solution to expose a part of a substrate, and, by using the Si3N4 again, wet oxidation is applied thereto for about one hour at 900 deg.C and under the atmospheric pressure of 6atm. Thereby the depth of junction is increased by about 0.2mum in the part wherein the oxide film is formed, by the distortion caused by oxidation, while the depth of base junction is almost unvaried. Then, an element is formed by a conventional method. The depth of base junction is made larger than that of other parts by an additional process of selective oxidation, an emitter pattern is transferred into a similar base pattern, and the width of a base is made larger than others. Accordingly, the short- circuit between a collector and an emitter is prevented and thus an yield rate is improved. |
