> Hi, I am wondering if there is any standard for the
> determination of Photoresist thickness when coated on Si
> wafer? If no, what is the common practise? Thanks for your help.
>

There are many common ways to measure photoresist thickness. For large
companies, the choice of measurement technique probably depends on who you
bought the equipment from. Resist thickness can be broken down into three
categories: optical, SEM, and profilometry.

Optical techniques are convenient because they can be quick and wafer
handling can be minimized. Some companies like Filmetrics
(www.filmetrics.com) make devices that rely on spectral reflectance.
Ellipsometry can also be used.

Many of the large scanning electron microscope (SEM) manufacturers make
inspection scopes. These are fairly expensive and (I think) are mostly used
for in-plane measurements, such as the width of a metal trace. Thickness
measurements are slightly more complicated, since the viewing angle must be
accounted for.

A stylus profilometer is an inexpensive and popular choice among researchers
and small volume foundries. Dektak (www.veeco.com) and Alpha Step
(www.tencor.com) have been popular choices, but there are probably others to
choose from. Because stylus profilometry is a contact method, there is a
risk of scratching the wafer. If the down force is controlled scratching can
easily be minimized.

Bill Eaton, Ph.D.
Materials & Analysis Manager
NP Photonics
www.parvenutech.com