At photo level CD-SEM metrology, the Std Deviation is always higher than the
Etch level due to e-beam charging on the insulating layer like photoresist. The
std deviation can be lowered by selecting an appropriate CD-SEM operational
parameters like beam current, accl voltage, scan length & time and of course by
selecting a proper algorithm. That is the reason the CD-SEM recipes for phot
level and the etch level are generally different. Before you determine the
dynamic precision of the CD-SEM metrology tool, it is always better to determine
the static precision of the tool first to have a feeling about the CD-SEM tool
behavior on different layers like photoresist, metal etc.

  Best of luck.


jedidi nader  wrote:
  Hello everybody,

I've done some measurements of Gate CD after Photo & after Etch to get an idea
about the intra-field variation of CD. this intra-field variation (Std
Deviation) was surprisingly more important after photo than after etch. So I
wonder if the CDSEM measurements are precise enough, knowing that the technology
I am working on is of 0.13 µm.

Do u have any idea about the repeatability (how accurate) of CD measurement
after photo ?

I thank you in advance. Nader