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[moved] Processing of Native MOSFET Transitor

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quyleanh

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I have question about processing of Native MOS Transistor. Thank you for answering me.

As I know, Native MOS is N type MOS which is formed directly to substrate. In my working technology, there is layer call Native which cover all the area of Nselect layer (and of couse, Nisland as well).

My question is, if we see in 3D silicon structure, which will the Native be, and how will it form?
I try to draw the structure as picture below.

1.PNG

My understanding is there will be a light N type implant under Gate region which is doped to substrate to make the Threshold voltage small, or even negative (because the 2 N+ implant channel are already connected together with this above light N type implant).

Correct me if I am wrong. Thank you very much.
 

Re: Processing of Native MOSFET Transitor

The gate poly doping is part of the net threshold voltage.
It may be (or not) that Psub starting doping and N+ poly
give you roughly VT=0.

On the other hand a RF process that values "native" VT
devices highly, may use an explicit implant for more
control. High resistivity substrates might be under-doped
for VT=0 and a P+ gate (depletion mode) or might be
just right.

All of this is very flow-specific.
 

Re: Processing of Native MOSFET Transitor

dick_freebird said:
The gate poly doping is part of the net threshold voltage.
It may be (or not) that Psub starting doping and N+ poly
give you roughly VT=0.

On the other hand a RF process that values "native" VT
devices highly, may use an explicit implant for more
control. High resistivity substrates might be under-doped
for VT=0 and a P+ gate (depletion mode) or might be
just right.

All of this is very flow-specific.
Click to expand...

Thank you for replying.
I still hardly get your point. Could you explain it more clearly?

In my opinion, if the gate poly is doped with N+ as you said, so the higher Vg voltage required to get depletion region. Then more higher voltage to get reversion region. It means Vth will be higher?
 

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