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Resistor Voltage Coeff - salicided and un-salicided poly

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elbadry

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Resistor Voltage Coeff

Dear All,

What's the difference between salicided poly and un-salicided poly in terms of their voltage-coefficients?

Should we expect to have zero Voltage Coefficient for salicided poly resistors?
 

Re: Resistor Voltage Coeff

elbadry said:
Dear All,

What's the difference between salicided poly and un-salicided poly in terms of their voltage-coefficients?

Should we expect to have zero Voltage Coefficient for salicided poly resistors?
Click to expand...

all resistors have voltage coeff..... it depends on the foundry process that u use.... for my case the salicided has higher vco.... u can do a quick check by checking the value for vco1 and vco2 in the model and compare the value...... higher value will have higher voltage coeff.....

if I not mistaken, the voltage charac depends on doping concentration......
 

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    elbadry

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Re: Resistor Voltage Coeff

I checked the coeff for the resistor I am using and it was zero ( no voltage dependence )

I am not sure if this is the real case or it's just not modeled
 

Re: Resistor Voltage Coeff

elbadry said:
I checked the coeff for the resistor I am using and it was zero ( no voltage dependence )

I am not sure if this is the real case or it's just not modeled
Click to expand...

it is not modelled..... anyway, voltage coeff shud be small for poly res.... if u using island res, then the v coeff quite significant (relative)
 

Resistor Voltage Coeff

I think voltage coefficient for both poly resistors should be neglectable for most of cases, specially comparing with any diffusion resistor or well resistor. So most foundry never model it.
 

Re: Resistor Voltage Coeff

I noticed that:

1. High sheet resistance poly (1KOhm/sq) has a voltage coeff of about 0.8ppm/V
2. Normal poly resistors has no documented Voltage Coeff (would this mean that it is much smaller than High sheet resistance poly?)

Besides, the high-sheet resistance poly has a 2nd order temperature dependence while the normal has not ( I am not sure again if this is modeling issue )

Any idea on how high-sheet resistance is made? Is it just a salicide block mask?
 

Re: Resistor Voltage Coeff

elbadry said:
I noticed that:
1. High sheet resistance poly (1KOhm/sq) has a voltage coeff of about 0.8ppm/V
Click to expand...
Depends on tech. For my process (.18µ) VC1=0.36ppm/V
elbadry said:
2. Normal poly resistors has no documented Voltage Coeff (would this mean that it is much smaller than High sheet resistance poly?)
Click to expand...
The other way round: normal n-poly has more than 100-fold this VC, p-poly more than 300-fold, and both negative.
elbadry said:
Besides, the high-sheet resistance poly has a 2nd order temperature dependence while the normal has not ( I am not sure again if this is modeling issue )
Click to expand...
Correct. For a mature tech. process, always both VCs (and TCs) are modeled.
elbadry said:
Any idea on how high-sheet resistance is made? Is it just a salicide block mask?
Click to expand...
Salicide and (all) implants blocked.

Cheers, erikl
 

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    elbadry

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Re: Resistor Voltage Coeff

Thanks erikl

a last question: in my process, the high-sheet resistance poly has TC1, TC2 and VC modeled and documented, the other poly resistor has only TC1 with no TC2 or VC. Can I safely conclude that the model is correct ( for the other poly resistor?)
 

Resistor Voltage Coeff

I guess it will be correct to the first approximation. Normally, this should be enough. But in any case it is always better to use circuits which rely on resistor ratios than on their values.
 

Re: Resistor Voltage Coeff

erikl said:
I guess it will be correct to the first approximation. Normally, this should be enough. But in any case it is always better to use circuits which rely on resistor ratios than on their values.
Click to expand...

agreed.....
 

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