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BJT in a CMOS tech, Can it be??!

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ahmad_abdulghany

ahmad_abdulghany

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Can I make a relatively low quality Bipolar Transistor in a CMOS techonlogy?
Such as a PNP transistor of β≈30-60, Can it really be? How to in the layout and circuit design point of view? (It may be parasitic one in that case)

Is there any real application or studies regarding that issue?

I know that one BJT transistor in the BiCMOS technology costs a lot of money, is that correct?

Thank you for clarification,
Regards,
Ahmad,
 

BJT in CMOS technology is a parasitic one provided by the process. Betas of 60. I do not think so. Don't you think that Beta depends on the minority carrier concentration in the base? It is very difficult to realize it in a CMOS process. It is a very high Beta to be realized in a CMOS process. In CMOS process, we realize vertical PNP for mimicking a diode.
 
Well, but i thought that there may be some techniquies to realize that doping profile! Or it's non-designer controlled issue? I think so :(

Ok, then, how large can Beta be practically?

And what does "mimicking a diode" mean?

Thank you,
Ahmad,
 

The Beta of a bipolar transistor should be depended on the minority carrier concentration in the base,in fact, It depended on the length of the base,but it must be hard to achieve some ideal length in the CMOS process~maybe ~
regards.
 
in CMOS process , u can use the Bipolar (bad one) to do a diode which can be used in places like Bandgap refrences
 
in standard CMOS tech, BJT's Base must short to GND or VDD, it can only use as diode,such as in bandgap.
 
typically, beta of vertical pnp transistor is about 10 to 30 in cmos process.
 
I have used the lateral PNP as a parasitic device in CMOS process, beta will be less than 10, I think it's impossible to get an 30's beta for parasitic PNP, when we decrease the base width that will show pounchthrough.
 
If your process have twin wells, then you can use both pnp and npn, although their performance is not good enough.
 

cmos process library has npn and pnp, but i never use them
 

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