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New Product: Toshiba & partners use electrolyzed sulfuric acid for resist stripping
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Product Briefing Outline: Toshiba Corporation,
Shibaura Mechatronics Corporation and Chlorine Engineers Corp. have
co-developed an innovative semiconductor resist stripping technology
that employs electrolyzed sulfuric acid. It is the first time that
electrolyzed sulfuric acid has been applied to resist stripping,
according to the companies. The partners have already developed a
single-wafer resist-stripping system that will be integrated into the
resist-stripping process at Toshiba's Yokkaichi Operations in April
2007.
Problem: Once circuits are etched, the resist must be
removed, which is typically done with peroxymonosulfuric acid, produced
by mixing sulfuric acid with hydrogen peroxide. However, once the
process is completed, it is difficult to recycle the sulfuric acid
because of dilution by the water released as a by-product of the
breakdown of the hydrogen peroxide in the mixture. The new technology
allows sulfuric acid to be recycled, as electrolyzing sulfuric acid
generates peroxymonosulfuric acid without producing water.
Solution:
The new technology was developed as a substitute for the current
sulfuric acid hydrogen peroxide Mixture (SPM) technology applied to the
"wet process" of resist stripping. The new technology reduces the
volume of sulfuric acid used in resist stripping by 70 percent and
totally eliminates use of hydrogen peroxide. As a result, it reduces
the overall environmental burden of the semiconductor wet process and
adds to the efficiency of wastewater treatment. The new process is also
more efficient, and contributes to improved productivity by shortening
resist stripping time by 20%.
Applications: Photoresist stripping
Platform:
Impact on resist-stripping process (pattern rework process): sulfuric
acid use reduced by approximately 70%; hydrogen peroxide use reduced to
zero
Availability: February 2007 onwards.
The
new technology achieves the same reaction and result as SPM, but uses
electrolyzed sulfuric acid. This is achieved by exciting the acid, as
shown below.
The new method allows reuse of sulfuric acid, as the water is also electrolyzed and does not dilute the sulfuric acid.
