| 摘要 |
PURPOSE:To obtain a bipolar transistor which has high speed and high integration by opening windows at triple films of SiO2, P<+> type polysilicon and Si3N4 on an Si substrate, sidewisely etching the SiO2 film, covering it with a polysilicon, and thermally oxidizing it to isolate the base from the emitter. CONSTITUTION:Triple films of SiO2 12, P<+> type polysilicon 13 and Si3N4 are formed on an N<-> type Si substrate 11, windows are opened by anisotropic plasma etching at the films 14, 13, the film 13 is etched at side surface 16 by isotropic plasma, the film 12 is then wet etched, and overhangs 17 are formed. A polysilicon 18 is accumulated by a pressure reducing CVD method in the amount more than 1/2 or larger than the thickness of the film 12 to bury the overhangs 17, and converted by high temperature wet oxidizing into an SiO2 film 19. At this time the film 13 is diffused through polysilicon 20 to the substrate 11, thereby forming a thin P type base 22. Then, the film 19 is removed by anisotropic etching to open a window 21, and the film 19 is allowed to remain on the side surface. Thereafter, an N<+> type emitter 25 is formed through a P<-> type base 24 and an N<+> type polysilicon electrode 23. According to this structure, a capacity CBC and a base parasitic resistance can be remarkably reduced, thereby enhancing the integration and performance. |
