Method for manufacturing bipolar transistors

A method for manufacturing an NPN bipolar transistor, the method comprising the steps of:

• forming an N type collector;
• forming an NPN epitaxial base over the N type collector;
• forming an NPN extrinsic base in the NPN epitaxial base;
• and
• forming an NPN emitter in electrical contact with the NPN extrinsic base;
• wherein forming the NPN extrinsic base comprises forming a first oxide layer over the NPN epitaxial base;
• and
• wherein forming the NPN emitter comprises:
• forming a second oxide layer over the first oxide layer;
• forming the NPN emitter over the second oxide layer;
• forming a mask over the NPN emitter;
• and
• removing portions of the first and second oxide layers not covered by the mask down to the NPN extrinsic base.

A method for manufacturing a PNP bipolar transistor and an NPN bipolar transistor, the method comprising the steps of:

• forming a P type collector;
• forming an N type collector;
• forming a PNP epitaxial base over the P type collector;
• forming an NPN epitaxial base over the N type collector;
• forming a PNP extrinsic base in the PNP epitaxial base;
• forming an NPN extrinsic base in the NPN epitaxial base;
• forming a PNP emitter in electrical contact with the PNP extrinsic base;
• and
• forming an NPN emitter in electrical contact with the NPN extrinsic base;
• wherein forming the PNP extrinsic base and forming the NPN extrinsic base comprise forming a first oxide layer over the PNP and NPN epitaxial bases;
• and
• wherein forming the PNP emitter and forming the NPN emitter comprise:
• forming a oxide layer over the first oxide layer;
• forming the PNP emitter and the NPN emitter over the second oxide layer;
• forming a mask over the PNP emitter and over the NPN emitter;
• and
• removing portions of the first and second oxide layers not covered by the mask down to the PNP extrinsic base and down to the NPN extrinsic base.