Source and Drain are swapped in RCX netlist!! What let them

[Reotaro Hashemoto]

Hi,

I'm working on the phisical verification using Assura flow, there's
two files: RSF_pre and T35FL.pre ..
When running:

assura RSF_pre
and checking the output netlist, I noticed that all MOSFET transistors

have thier Source and drain swapped!!! What is the possible reason
that can cause such swapping???

Could any one help me please?
Thanks in advance,
Ahmad

 

[Guenther Sohler]

Its normal behavior for layout extraction that the tool sometimes swaps
drain and source of a transistor because they look similar.
However, there is no need to get this fixed, because its not a problem for
the simulation. Simulators usually handle this issue correctly



On Wed, 12 Sep 2007 07:50:24 -0700, Reotaro Hashemoto wrote:

Hi,

I'm working on the phisical verification using Assura flow, there's
two files: RSF_pre and T35FL.pre ..
When running:
assura RSF_pre
and checking the output netlist, I noticed that all MOSFET transistors
have thier Source and drain swapped!!! What is the possible reason
that can cause such swapping???

Could any one help me please?
Thanks in advance,
Ahmad

 

[Edward Kalenda]

On Wed, 12 Sep 2007 07:50:24 -0700, Reotaro Hashemoto
<ahmad.abdulghany@gmail.com> wrote:

Hi,

I'm working on the phisical verification using Assura flow, there's
two files: RSF_pre and T35FL.pre ..
When running:
assura RSF_pre
and checking the output netlist, I noticed that all MOSFET transistors
have thier Source and drain swapped!!! What is the possible reason
that can cause such swapping???

Could any one help me please?
Thanks in advance,
Ahmad

This happens because source and drain on a MOS device are only a
convention. There is no physical difference the device recognition
software can use to determine which diffusion region is source and which
is drain.

 

[DReynolds]

On Sep 20, 3:09 pm, Edward Kalenda <d...@cadence.com> wrote:

On Wed, 12 Sep 2007 07:50:24 -0700, Reotaro Hashemoto

ahmad.abdulgh...@gmail.com> wrote:
Hi,

I'm working on the phisical verification using Assura flow, there's
two files: RSF_pre and T35FL.pre ..
When running:
assura RSF_pre
and checking the output netlist, I noticed that all MOSFET transistors
have thier Source and drain swapped!!! What is the possible reason
that can cause such swapping???

Could any one help me please?
Thanks in advance,
Ahmad

This happens because source and drain on a MOS device are only a
convention. There is no physical difference the device recognition
software can use to determine which diffusion region is source and which
is drain.

I would agree with this only to a point... source and drain are
swappable if the device is symmetric... for example a single finger
device has a single source diffusion and a single drain diffusion. Now
how about a 2 finger device? The default layout for this structure
has a shared drain diffusion and two source diffusions. The source and
drain can no longer be swapped......

Have you looked at any specific devices in your netlist to see if the
capacitances are consitent with what you should see?

David

David Reynolds