Poly bipolar emitter for semiconductor process technology

[longstar]

The emitter of BJT is poly, how to make it in semiconductor process technology, and what is the advantage?
Rgds.
longstar

 

[DenisMark]

Look at the bipolar

Emitter junction is created by diffusion from poly source that have implanted impurity (resistance of poly about 50 Ohm/sq). It's allow to create shallow emitter junction and descrease p-well junction depth, ans associated capacitances too. 2 base let to decrease base resistance. All of this are usefull for high-frequencies and low-noise application.

 

[tandr123]

Re: Look at the bipolar

The transistor is high-speed device for little BE junction capicitor . So if u
don't use poly-emmiter bipolar process , you must choose other advanced
process . such as oxide isolation process .

 

[longstar]

Look at the bipolar

Thanks.
But we can look at the bipolar as a MOS.