within a component reduces the
total wetted surface area, which, in
turn, improves purging and moisture
removal. While these characteristics
are important to maintain cleanliness in both semiconductor and PV
processes, PV production systems are
generally more tolerant of particles in
the fluid stream that may result from
less polished surfaces. However, some
process gases, such as silane and
nitrogen tri-fluoride, require high-purity systems to avoid excessive
particle generation from moisture
or corrosion. Solar cell manufacturers must therefore utilize the right
components to match the processing
environment.
The disparity between system
needs, based on the properties of
the process gas being used, provides
an opportunity to differentiate gas
system components by design, material selection, and surface treatments.
UHP valve and fitting designs, such as
springless diaphragm valves and metal
face seal fittings, typically are offered in
highly refined 316 stainless steel with
fine surface finish. Electropolished
flow passages are suitable for more
demanding gas systems. Standard
finish, non-electropolished versions
of these products are suitable for less
demanding gases where containment
remains a priority, such as toxic and
pyrophoric gases. Other gases may
be safely contained by high-purity
or even general-industry component
designs with an appropriate level of
cleaning.
It is important to examine product performance criteria, including
moisture characteristics, particle generation, and ionic cleanliness, to make
sure these products will not adversely
affect process yields. In this way, the
appropriate level of technology can be
applied for the best cost of ownership.
SC-06 helps to define the appropriate
component manufacturing protocols
to meet this goal.
Moving Forward
The areas in which UHP semiconductor and PV component manu-
Figure 1. As part of the manufacturing cleanliness chain, an ultrasonic
bath (top) is used to rinse stainless steel components (bottom), removing
any impurities prior to final assembly and/or packaging. The SC-06 process
specification calls for the appropriate level of cleaning to match needs for PV
processing applications.
