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DEEP nWELL for negative voltages

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YESH_23

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deep nwell

can any one help me in learning deep n well.

why is it used.?

how is it fabricatrd.?

the way it is connected in the layout......

THANX in advance
 

deep n-well

Drawn in layout is still the same..but the diffusionmust be strong to penetrate deep to the p substarte

Added after 39 seconds:

n well in layout is reresent by the the less dopant of n type
 
deep n well process

Deep nwell are basically used for isolation.Deep N-well or buried N-well is a nwell layer implanted deeper down in the substrate than the normal N-well. It is mainly to control the substrate leakage of N-mos and to provide the better isolation.These processes mainly used for high frequency (RF) circuits.
 
deep nwell process

YESH_23 said:
weather we can put psub2 on deep n well
Click to expand...


No, psub2 is used only for distinguishing differential gnd connectted to sub.
Deep nwell is formed by long time annealing and drivering fellowed implantion and a buried N+ layer is formed. With fellowing Nwell step, a p-type island will be surrounded by N+ area lateral and lognitudinal, So noise can be isolated. Deep Nwell is often used in RFIC,especially in PA.
 
deep n well structure

Deep N well is used to isolate to substrate noise.
The area will be about 1.5 times larger according to your layout.
 
deep n-well purpose

so if we want to connect a different potential than vdd and gnd we can connect it by putting a deep nwell and then taking the source and drain connections
 
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deep-nwell

In mixed signal ckts there is only an imaginary line to seperate the Digital and Analog parts.The SUB is common for both ,digital ckts usually operate at higher frequencies so thet switch on and off at very faster rate.They dump minority charge carriers in the SUB which can affect the analog nmos's behaviour.so there is a need to protect analog nMos transistors form this sub noise so there is a concept of Deep N Wells.Plz check the attachment to get the exact picture of Deep N Well..this is not the case with pMOS because we draw p MOS transistors in n Well
 
deepnwell

Deep N-WELL is a special purpose layer in CMOS process which serves the purpose same as the NLB(N- buried layer in Bipolar process). The purpose is to stop the vertical current coupling generated by the POWER devices to active devices.
 
deep n-well in mixed signal layout

Is ok for 2 NMOS to share N-Well instead of connecting two N-Wells together by metal? It seems ok to me though ideally connecting them by metal would be closer to the model provided by foundry. Anyone?

Thanks
 
psub2 cmos

I'm not sure about other process, but deep N-well device used in flash memory is not for isolation, it is for passing negtive voltage,
you all know that P device can probably be used to pass negtive voltage, but due to its negtive Vt, it is not so effective for this job.
however N device is good at passing small voltage, but the N+ diffusion prevent it from passing negtive voltage, that is how deep -N well device come out, there is another P-well embedded on top of the deep n well and an N device is build in the p-well, so that you can see by applying the P well also negtive voltage, this N device inside it can pass negtive voltage freely and effectively.
we use this kind of device a lot as negtive voltage switch.
 
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what is deep n well

Deep N-well and Deep Trench Isolation (an IBM name) does not really help that much. Deep trench is about 8-10 microns deep, regular n-well about a micron, and the deep n-well structures vary in depth between thos two extremes.

The deep trench isolation in the IBM 5HP Sige process was studied for it's isolation properties pretty thoroughly. (Real silicon, not simulations) and it helped a few db in noise reduction, but that was about it.

That is the reason we launched the 5-HPE process, it was about 6 weeks less time in the foundry, and it brought the wafer cost down a lot as well.

Jerry

www.effectiveelectrons.com

"chips that work"
 

nwell process

Now I am designing a transeiver for mobilevideo, which works at 1.4G. I have tsmc 0.18 models at hand, some are transistors with DNW, but others don't. I don't know which one i should use. anyone knows
 

what is nwell layer

BJT process moe use deep Nwel device

in gerneal , deep n-well can reduce "substrate coulpe noise " you should check tsmc 0.18um model

by the way , tsmc have nature nmos close 0 Vth
I never use . but why need zero Vth device ?
for RF design or other circuit ?
 

deep-n-well

vivek rajput said:
In mixed signal ckts there is only an imaginary line to seperate the Digital and Analog parts.The SUB is common for both ,digital ckts usually operate at higher frequencies so thet switch on and off at very faster rate.They dump minority charge carriers in the SUB which can affect the analog nmos's behaviour.so there is a need to protect analog nMos transistors form this sub noise so there is a concept of Deep N Wells.Plz check the attachment to get the exact picture of Deep N Well..this is not the case with pMOS because we draw p MOS transistors in n Well
Click to expand...

Hi, vivek rajput,
In your post the N-well below P-SUB should be DNW as well. Ion implantation energy is greater for DNW than for NW. Generally DNW is 3um below the surface while NW is 1.5um in UMC process.
 

what is deep n well

U can use the DNW to place some of the sensitive nmos devices (ofcourse there will be a pwell in the DNW as well)... Here we have an additional degree of freedom to even connect the body of the nmos to the source, hence eliminating the body effect...
 

n-well purpose

DNW is used to isolate primairly NMOS from PMOS in vareity of circuits, ranging from digital to analog to RF. It depends.

Usually, you put a DNW and then form a Doughnut shape of NWELL over it and in the "hemisphere" or TUB created by DNW-NWELL is used to create NMOS. Remeber, this helps certain times but sometimes the cap effect is not good. Also now you see parasitic BJT apart from parasitic Diode structures.

In Vivek Rajput's doc, the vertical is NWELL and horizontal is DNW.

Now PSUB2 has been recreated (in many cases) to help LVS pass through rather than for any fab purpose. Other readers put in your though if there are more purposes.

Srivats
 
deep n well wiki

Besides the isolation provided for reducing the substrate coupling. Also, deep N-well provides a possiblity to tie NMOS body to source with will get rid of body effect.
 
how to place un nw capa to the deep nwell

Hi friends,

Is anyone have knowledge about the Deep NWELL GR and Deep NWELL Pocket< and how the both techinique will differ interms of LOW and High frequency applicxation.

thanks in advance

Vinoth
 

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