Hi Brian,

thanks for suggestion about spectroscopic reflectometer.

About stylus profilometer, i have a Veeco optical profilometer. In
principle i may use this tool to measure wafer thickness. But how can i be
sure that there will be not a small dust particle between the wafer and
the chuck where the wafer lean on ? This would alter the real wafer
thickness value.

Thanks,
Andrea

> Hi Andrea,
>
> If you have access to a spectroscopic reflectometer, you should be able to
> use it to measure the thickness of your membranes.  You should check with
> the manufacturer of the tool to see if your membranes fall within the
> thickness range accessible to the tool and how to configure the software
> film stack model.  I haven't tried this myself, but I know of at least one
> manufacturer that advertises this as a capability of their product.
>
> Another option is to use a stylus profilometer to measure the etch depth,
> and subtract this from the thickness of the wafer.  The accuracy of this
> measurement should be more dependent on the thickness tolerance of your
> wafer than the accuracy of the profilometer itself (which is usually
> around
> +/- 10nm).
>
> Good luck,
>
> Brian Stahl