Equivalent width of a transistor (Cadence extraction)

[Xiaofeng Wang]

Hi, all:

I have a question on the effective width of a transistor layout.
the layout is at http://wangxf.nease.net/temp/transistor.bmp

(The drawing is not to scale, the shape is actually a square.)

I drawed the layout in cadence and did the extraction. Cadence gave an
effective transistor. The effective width is around 47um, while the effective
length is around 0.5um.

I know the effective width is due to the corner effect.
But I have some confusion about the effective length. Why it is half of the
physical length. I tried different length, and it seemed the effective length
is always half of the physical length. Can anyone tell me why? Is Cadence
extraction accurate?

Thanks.



Best Regards,

Xiaofeng

 

[Andrew Beckett]

Xiaofeng,

The answer is entirely dependent on the technology and the rules being used
to do the extraction - any computation of effective widths and lengths would be
done there, presumably. It's not something that the extraction tool (whichever
you're using) would do on a general basis.

Regards,

Andrew.

On 10 Oct 2003 15:27:54 -0700, cnboyemail@163.net (Xiaofeng Wang) wrote:

Hi, all:

I have a question on the effective width of a transistor layout.
the layout is at http://wangxf.nease.net/temp/transistor.bmp

(The drawing is not to scale, the shape is actually a square.)

I drawed the layout in cadence and did the extraction. Cadence gave an
effective transistor. The effective width is around 47um, while the effective
length is around 0.5um.

I know the effective width is due to the corner effect.
But I have some confusion about the effective length. Why it is half of the
physical length. I tried different length, and it seemed the effective length
is always half of the physical length. Can anyone tell me why? Is Cadence
extraction accurate?

Thanks.



Best Regards,

Xiaofeng

--
Andrew Beckett
Senior Technical Leader
Custom IC Solutions
Cadence Design Systems Ltd