MNS Lighthouse vFinal DR 27/6/08 10:27 Page 11
MICRONANOSYSTEMS 11
A point of use liquid particle
counter for high purity water
applications
Bill Shade, Lighthouse Worldwide Solutions, looks at the use
of high purity water in semiconductor manufacturing.
H
igh purity water is extremely critical in the management systems are being offered for local treatment of
manufacturing of semiconductors. Up to 1000 high purity water just prior to the point of use (POU) in such
gallons of water is required to process a single critical process steps.
wafer. As the semiconductor industry moves to smaller CMP and ECP processes are resulting in an increase in water
nanometer line widths and larger wafer sizes, the use of high consumption due to the number of metal layers. Single wafer
purity water will likely increase in accordance with the ITRS etch tools are using less water but have more cross
roadmap. High purity water usage will increase for the following contamination that does not allow for recycling of this water [2].
reasons [1]. The use of high purity water is expanding to other advanced
ring6Larger wafer sizes will drive larger volumes of water need applications including gasified DI for wafer cleaning, and
for each wafer humidification of clean air in lithography machines [3].
ring6Different types of chemicals will drive the need for Currently the main supply to the wafer fab is being monitored
additional rinsing with high purity water for particles due to the critical importance of high purity water.
ring6An increase in the number of process steps with drive the In the near future, the process drivers described above and the
need for additional rinsing with high purity water desire to improve the utilization efficiency of high purity water
ring6 Increase in production will see high purity water demand are likely to drive the need for monitoring particles in more point
of use locations throughout the wafer fab. This trend will in turn
It is important to note that the increase in demand for water is place additional demands on the liquid particle counters used to
driving a need to increase the efficiency of use of the raw feed monitor these particles including reduced size and cost of
water used in manufacturing. ownership for companies.
In addition there are a number of process trends that are Particle concentrations in semiconductor high purity water
impacting the use of high purity water in semiconductor systems are extremely low. The ITRS goals specify less than 0.3
manufacturing. Immersion Lithography is driving new quality
requirements on high purity water. In fact, high purity water
July 2008
www.micronanosystems.info
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