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what is difference between N - active and N + implantation?

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Full Member level 4
Jan 31, 2005
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In CMOS process, I know N-ch mos consist of N+ diffususion and poly

but Some process layout technology, it is used N ACTIVE layer with N+ implantation layer to construct N MOSFET.

I don't know why N+ implantation layer used in CMOS process, for forming N MOSFET.

to form N MOSFET, is it enough to use N ACTIVE layer?

why does it need N+ implatation to form N MOSFET?

what is the role of N+ implatation layer?


yes, N+ diff form the NMOS.
and most the process neede active layer will have a Boolean calculation to form the N+ mask finally.

Re: what is difference between N - active and N + implantati

Active or sometimes called diff is area which specifies the opening in the oxide layer where the device will be.

Then you do the N+implant (or P+) . You can see that N+ is alwasy bigger then Active - this is to make sure the whole active area gets it implant in case of misalignment.

Usually before the N+ you deposit the poly layer (for creating the channel)

I recommend to read any book about CMOS design - there are 100 pages at the beginning describing the technology (in general terms but it is covering your questions)


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We need ACTIVE and N+ Implant/P+ Implant masks. The ACTIVE area enclosed by N+ implant will be n-ACTIVE. But some one prefers to use N-ACTIVE and P-ACTIVE even though N+ Implant and P+ Implant are drawn. N-ACTIVE and P-ACTIVE will be merged to form a single mask --- ACTIVE.

Re: what is difference between N - active and N + implantati

ok. I agree that I cannot explain which point I have wondered.

I wonder why we have to use N+ implantation layer.

in MAGIC, or simple layout tool, we do not have to use n+ implantation layer

but in practical CMOS process, we have to use it.


We always need N+ implant mask. However, sometimes we don't draw N+ implant layer, it can be generated by tools.

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