High pressure carbon dioxide provides a very effective alternative for cleaning integrated circuits and masks. This
great cleaning ability is due to CO2 having the physical characteristics of both a liquid and a gas: like a gas, it
diffuses rapidly, has near zero surface tension, very low viscosity and thus penetrates easily into mask features or
deep wafer trenches and vias. As a liquid it can be utilized to clean particles and to solvate other chemicals such as
alcohols and fluorinated hydrocarbons.
This paper covers the analytical tests and characterizations carried out to assess impurity removal from 3.0 N CO2
(beverage grade) for its final utilization in mask cleaning applications.
The technological challenges that have been overcome to make extreme ultraviolet lithography (EUV) a reality have been
enormous1. This vacuum driven technology poses significant purity challenges for the gases employed for purging and
cleaning the scanner EUV chamber and source. Hydrogen, nitrogen, argon and ultra-high purity compressed dry air
(UHPCDA) are the most common gases utilized at the scanner and source level. Purity requirements are tighter than for
previous technology node tools. In addition, specifically for hydrogen, EUV tool users are facing not only gas purity
challenges but also the need for safe disposal of the hydrogen at the tool outlet. Recovery, reuse or recycling strategies
could mitigate the disposal process and reduce the overall tool cost of operation.
This paper will review the types of purification technologies that are currently available to generate high purity hydrogen
suitable for EUV applications. Advantages and disadvantages of each purification technology will be presented.
Guidelines on how to select the most appropriate technology for each application and experimental conditions will be
presented. A discussion of the most common approaches utilized at the facility level to operate EUV tools along with
possible hydrogen recovery strategies will also be reported.
The use of purified carbon dioxide (CO2) has become a reality for leading edge 193 nm immersion lithography scanners.
Traditionally, both dry and immersion 193 nm lithographic processes have constantly purged the optics stack with ultrahigh
purity compressed dry air (UHPCDA). CO2 has been utilized for a similar purpose as UHPCDA. Airborne molecular
contamniation (AMC) purification technologies and analytical measurement methods have been extensively developed to
support the Lithography Tool Manufacturers purity requirements. This paper covers the analytical tests and
characterizations carried out to assess impurity removal from 3.0 N CO2 (beverage grade) for its final utilization in 193
nm and EUV scanners.
KEYWORDS: Contamination, Statistical analysis, Chromatography, Solid state electronics, Solid state physics, Medium wave, Environmental monitoring, Ions, Mass spectrometry, Iron
Airborne molecular contamination (AMC) assessment approaches can vary greatly between different fabs and even
between different divisions within a given company. Some companies have very rigorous testing schedules (such as
those needed to maintain tool warranties) while others feel AMC testing is only necessary when they are having a
problem. While choosing to only test for AMC when a trouble arises may be cost effective in the short term it can have
significant impacts on tools, in particular tool optics, and product losses due to defects which can cost significantly more
in the long term than the AMC testing would have. Another critical issue in assessing AMC is what species you should
be testing for. Some volatile species may not cause an issue in your process while part-per-trillion volume (pptv)
amounts of others can do serious damage to your tools and/or products. Knowledge of which volatile compounds can
cause problems in your applications and at what levels is crucial in deciding what type of AMC assessment to perform
and at what frequency. Typically four classes of AMC are routinely monitored in clean rooms and tool environments:
acids, bases, hydrocarbons, and refractory compounds. Real world examples will be presented using the solely solid-state
trap collection methods utilized by SAES Pure Gas.
Assessing molecular contamination (MC) at part-per-billion (ppbV) or part-per-trillion volume (pptV) levels in
cleanroom air and purge gas lines is essential to protect lithography and metrology tools optics and components. Current
lithography and metrology tool manufacturer's specifications require testing of some contaminants down to single digit
pptV levels. Ideally this analysis would be performed with an on-line analyzer (capable of providing almost instant
results): the best analyzers currently available are only capable of providing 100 pptV detection. Liquid impinger
sampling has been the dominant sample collection method for sub ppbV acidic and basic MC analysis. Impinger
sampling suffers from some inherent problems that can dramatically reduce the collection efficiency such as analyte
solubility and evaporative losses. An innovative solid-state trapping technology has been recently developed by SAES
Pure Gas along with the CollectTorr sampling system. NIST traceable gas phase standards have been used to compare
the collection efficiency of the traditional impinger technology to that of the solid state trapping method. Results varied
greatly for the different acid gases with sulfur dioxide showing comparable collection efficiencies while hydrofluoric
acid and hydrochloric acid showed much lower recoveries in the impingers than the solid-state traps. Ammonia
collection efficiencies were slightly higher for the solid state traps and were improved in the impingers when an acidified
solution was used as the collection media. The use of solid-state traps, besides being much simpler from both the handling and logistical stand point, eliminates the analyte solubility and evaporation problems frequently seen with the impinger sampling.
This paper describes some of the results collected during the study of improved purification materials, qualification of regenerability performances and newly developed ways to detect Acids, Bases and Siloxanes at the sub-ppt levels. Removal validation down to single ppt levels has been demonstrated for several impurities such as: NH3, SO2 and Hexamethyldisiloxane (HMDSO).
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.