METHOD OF FORMING POLYCRYSTALLINE SILICON EMITTER AND POLYCRYSTALLINE SILICON GATE BY USING SAME ETCHING OF POLYCRYSTALLINE SILICON ON THIN GATE OXIDE FILM

摘要

PURPOSE: To simultaneously form an emitter and a gate by forming a gate oxide layer and a polysilicon layer, removing them from an emitter region, adhering the polysilicon layer and masking and etching the emitter/gate regions. CONSTITUTION: A thin layer 70 of silicon dioxide is formed on the exposed surface of the silicon substrate 4, a thin polycrystalline silicon layer 72 is deposited and the remaining part of a photoresist layer 76 is set to be a mask. The exposed part of the polycrystalline silicon layer 72 is removed by etching and the exposed part of the oxide layer 70 is removed by etching with the photoresist layer 76 as the mask. Then, the polysilicon layer 74 is deposited on the remaining part of the polycrystalline silicon layer 72 and the exposed area of the silicon substrate 4. A photoresist layer 96 is deposited on the polysilicon layer 74 and all the areas of the polysilicon layer 74 are exposed excluding a region 100 forming the emitter of the bipolar device, a region 104 forming the gate of the NMOS device and a region 106 forming the gate on a PMOS device. Then, etching is executed until the exposed part is removed.