Method for fabricating a bipolar transistor having self-aligned emitter and base
AssigneeNEC Compound Semiconductor Devices, Ltd.
InventorTomohiro Igarashi
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Abstract
A method for forming a self-aligned bipolar transistor includes the steps of combination etching a silicon substrate in an opening to form a concave surface on the silicon substrate, and forming an intrinsic base and an associated emitter on the concave surface. The combination etching includes an isotropic etching and subsequent wet etching. The concave surface increases the distance between the external base for the intrinsic base and the emitter to thereby increase the emitter-base breakdown voltage.
Claims5
A method for fabricating a bipolar transistor in a semiconductor device, said method comprising the steps of:
- forming a silicon layer on a semiconductor substrate;
- selectively etching said silicon layer to form an opening for exposing a first portion of said semiconductor substrate;
- conducting a combination etching to said first portion to form a concave surface thereon, said combination etching including consecutive isotropic dry etching and wet etching;
- implanting first-conductivity type impurities through said concave surface to said first portion to form an intrinsic base;
- and
- implanting second-conductivity type impurities into a surface portion of said intrinsic base to form an emitter on said intrinsic base.
Dependencies are inferred from the claim text.