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New Product: LiquidLens UPW purification system from Entegris designed for immersion lithography |
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Aug 17, 2006 at 04:13 PM |
 Product Briefing Outline: Entegris has introduced its
‘LiquidLens' ultrapure water (UPW) purification system that is designed
specifically for 193nm ArF immersion lithography systems. The
sub-system combines advanced technology and process expertise from both
Entegris and the former Mykrolis as a result of their merger in August
2005 to tackle high-purity issues associated with the needs of
immersion lithography.
Problem: Immersion is the newest lithography technique
for printing 45nm or smaller features on semiconductor wafers, using
ultra pure water between the optical lens and the wafer. The UPW lens
is utilized to significantly improve image resolution. The water must
be extremely pure as the smallest impurity can damage image resolution,
react with the photoresist. Ensuring ultrapure, consistent water
quality also preserves optic's life by controlling contaminants at the
point of use such as dissolved gases, micro bubbles and particles.
Solution:
Important factors in designing an ultrapure water system for immersion
lithography is the selection of high purity, inert construction
materials and the integration of purification techniques in an optimal
sequence. It is important to deliver a stable DI flow
precisely/repeatedly to the illuminated area to prevent any bubble
attachment on the wafer or the lens during the filling process. The
current flow rate control required is in the range from 0.4 to 3 LPM at
steady state with slower flow rate at initial fill, to ensure complete
filling under the lens, followed by a faster rate during scanning to
ensure byproduct removal and meniscus integrity during stage movement.
The contaminants to be removed from the UPW system include dissolved
gases and bubbles, particles, total oxidizable carbon (TOC) and
non-volatile residue (NVR), and ionic and organic extractables that are
added from the process materials and piping components. Temperature
control is also very important to ensure constant optical properties
(refractive index) and to ensure constant physical properties (e.g.
density, surface tension and gas solubility). A ‘pHasor' II membrane
contactor ensures the process water is free of bubbles by delivering
high dissolved gas concentrations with a low pressure drop over the
fluid path. Two UV lamps break down TOC levels in the water while an
ion exchange purifier removes the organics, ensuring a high purity
fluid stream. These elements are linked to an advanced process control
unit that monitors critical parameters, providing 48-hour rolling trend
data with configurable warning and error alarms.
Applications: 193nm ArF immersion lithography systems.
Platform:
Incorporates a ‘Durapore' 0.02 µm filter in a ‘Chemlock housing'. The
high zeta potential PVDF membrane filter is ideally suited for water
applications and the Chemlock housing preserves space while reducing
cost of ownership, according to the company. LiquidLens UPW
purification systems are built to customer specifications and
individually quoted.
Availability: July 2006 onwards.
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Product Briefings 
