Reduction of
Chlorinated Solvents in GaAs Manufacturing
V.
Williams, H. Isom, T. Nagle, C. Sellers, S. Hillyard, S. Roadman, S. Varma
TriQuint
Semiconductor
Phone: (972)
994-5686; FAX: (972) 994-4537; E-mail: vwilliams@tqtx.com
Keywords: chlorinated solvents, wet chemical processing,
environmental, replacement chemistries, contact angle, surface roughness,
pHEMT, GaAs.
ABSTRACT
Chlorinated solvents have been
used historically in the semiconductor industry for applications such as
photoresist removal and surface treatments.
However, in recent years, this class of solvents has undergone increased
scrutiny, especially from customers in the European Union, leading to a need to
find environmentally safer alternatives.
Gallium arsenide, in particular, can be subject to surface changes or
surface degradation after wet chemical processing, making the selection of
replacement chemistries critical. This
paper discusses an approach taken successfully to replace chlorinated solvents
in some wet clean processes in a GaAs manufacturing facility, specifically
focusing on those processes that have been used for pHEMT fabrication. The primary requirement for the success of
this project was that the change in wet chemistry would not introduce any
parametric changes for existing device technologies. The chosen methodology included surveying a
range of chemistries by testing parameters that are predictors of future
performance, such as surface contact angles, surface roughness, and material
etch rates, followed by selection of solvents and subsequent processing and
testing of qualification wafers. Results
from all stages of this assessment are presented, including parametric data
from fabricated devices and the outcomes of associated DOEs. Potential pitfalls and sources of problems
are also discussed.