burried layer and epitaxial layer

[bicave]

I have a puzzle.
Why we need these layer and the role of them. What will it make performance of MOS better?

thanks

 

[engrak]

epitaxial means growing layer by layer , it quality is good in epi layer , epi layer is used for latch up protection .

 

[fly6987]

epi layer is most asked for optical applications to avoid cross talk phenomena.

 

[deepak242003]

these two layers are implemented to reduce latchup immunitty...

epi layer is normally used in CMOS process where as NBL is used in pure BJT of BiCMOS process.

 

[dick_freebird]

Epi does not really suppress latchup. The heavily doped
handle wafer does that; the epi layer is what allows you to
manufacture CMOS with a tolerably low threshold, on top
of such a heavily doped base.

Buried layers are used for subcollector structures that need
to be patterned.

 

[deepak242003]

Epi does not really suppress latchup. The heavily doped
handle wafer does that; the epi layer is what allows you to
manufacture CMOS with a tolerably low threshold, on top
of such a heavily doped base.

corect.. Heavilly doped substrate makes it possible to decrease your substrate resistance so that more current is required to turn on parasitic BJT.

Buried layers are used for subcollector structures that need
to be patterned.

Can you elaborate this point..??

Deepak

 

[powerwaywafer]

epitaxial means growing layer by layer , it quality is good in epi layer , epi layer is used for latch up protection .

it is! but not exactly, for example, Xiamen Powerway produce GaN epitaxy on Sapphire substrate, just to get GaN, because free standing gan is more expensive to get.

 

[dick_freebird]

corect.. Heavilly doped substrate makes it possible to decrease your substrate resistance so that more current is required to turn on parasitic BJT.



Can you elaborate this point..??

Deepak

The handle wafer doping under an epi layer is uniform and
unpatterned. A buried layer is a deep implant that is mask
defined (else, you'd just use the preferred starting material).
I have seen deep (40 - 150V) bonded wafer flows which
actually have epi deposited after a buried layer pair (N+BL,
P+BL) shot, because you can't get the implant range deep
enough to do what needs to be done. Talking 15-30um deep
tubs with the buried layer occupying the bottom 2-5um.

If devices that do, and devices that don't want a specific
buried layer underneath them coexist on the die, then it
(BL) has to be selective.

 

[marvel321]

burried layer and epitaxial layer another point is isolation the device, so the substrate voltage can use your needed

 

[Prashanthanilm]

what do you mean by latch up problem?