process variation in advanced technologies

[nassim_el85]

Is the absolute and relative variation of process increased in advanced technologies or not?

Does the answer is different if the technology assign for minimum energy sub-Vt circuits?

In analog design, it says that the matching of elements improve in advanced technologies. Does it mean that the relative variation of elements is decreased?

Does the sentence and the answer is different in digital design?

 

[koggestone]

In analog design, it says that the matching of elements improve in advanced technologies.

Matching of elements get worse with advanced technologies.

google for these terms
- lot-to-lot variations
- wafer-to-wafer variations (2 wafers are not same in a lot)
- die-to-die variations ( 2 dies are not same in a wafer)
- on-chip-variations ( 2 transistors are not same in a chip)

 

[nassim_el85]

Can you please give me a reference???

 

[koggestone]

refer to the Classic 1989 paper by Pelgrom titled
"Matching Properties of MOS Transistors"

the above paper is updated for latest process in 2003 by drennan
"Understanding MOSFET mismatch for analog design" JSSC march 2003

https://www.solidodesign.com/uploads/5_drennan_cicc02.pdf

In simple words ,
mismatch is proportional to 1 / sqrt( W . L)

i.e smaller the transistor width (W) and length (L) , bigger the mismatch
between 2 identical transistors. As we scale to advance processes , L and
W are shrinking, and hence one of the reason (not the only reason) why mismatch increases.

 

[nassim_el85]

But what about the coefficient of 1/sqrt(W.L)???? if we assume two same dimension transistors?

Actually I want to know what happens to dVt and dB (beta) parameters. Are these increase or decrease by improving technology??