| 摘要 |
PURPOSE: A method for fabricating a bipolar transistor is provided to fabricate a bipolar transistor having a high cutoff frequency and a high speed by preventing a silicon substrate from being damaged by an etch process. CONSTITUTION: A silicon substrate(1) having a P-well(2) is prepared. A collector N+ epi layer(3) is formed on the P-well. A field oxide layer(4) is formed to define an active region through an isolation process. A base polysilicon layer(5) doped with P+ type impurities and an oxide layer(6) are sequentially formed on the field oxide layer including the N+ epi layer. The oxide layer and the base polysilicon layer are patterned to overlap a part of the N+ epi layer and a part of the field oxide layer. A spacer is formed on the side of the patterned oxide layer and base polysilicon layer. After a pedestal ion implantation process using BF2 is performed on the exposed region of the N+ epi layer, a heat treatment process is carried out to form a P- diffusion region(8). An emitter polysilicon layer(9) doped with N+ type impurities is formed on the P- diffusion region and the edge of the oxide layer.
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