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Modeling >> Semiconductor Devices >> About the channel legth modulation
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Message started by Richardyi on Jan 14^th, 2008, 11:55pm

Title: About the channel legth modulation
Post by Richardyi on Jan 14^th, 2008, 11:55pm

Why the factor of channel legth modulation is different for nmos and pmos? Even for the channel length.
Can anyone help me?
Thanks.

Title: Re: About the channel legth modulation
Post by sheldon on Feb 8^th, 2008, 2:59am

Richard,

In older processes, the bulk substrate concentration is different for
the n-channel and p-channel transistors. Usually one device is built
into well, while the other exists in the substrate. The well doping
needs to "counter-dope" the substrate doping and is typically ~10x
higher in concentration. As a result, the depletion regions change at
different rates with applied bias for n-channel and p-channel transistors.
The difference in the rate of change of the Drain-Bulk depletion region
is a significant contributor to the difference in the channel length modulation.

Best Regards,

Sheldon

Title: Re: About the channel legth modulation
Post by Berti on Feb 8^th, 2008, 3:34am

Hi Sheldon,

Quote:

In older processes,...

Is it diffierent for advanced processes?

Title: Re: About the channel legth modulation
Post by sheldon on Feb 10^th, 2008, 8:55am

Berti,

It should be a reasonable first-order approximation.

Best Regards,

Sheldon