Air Filtration Technology and Future Developments for AMC Control Chris Muller ASHRAE Distinguished Lecturer Member 2013 ITRS Yield Enhancement & Wafer Environment Contamination Control Technical Working Groups Technical Director Purafil, Inc. 2654 Weaver Way Doraville, GA USA
34
Embed
Air Filtration Technology and Future Developments … Muller...Air Filtration Technology and Future Developments for AMC Control Chris Muller ASHRAE Distinguished Lecturer Member 2013
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Air Filtration Technology and Future
Developments for AMC Control
Chris MullerASHRAE Distinguished Lecturer
Member 2013 ITRS Yield Enhancement & Wafer Environment
Contamination Control Technical Working Groups
Technical Director
Purafil, Inc.
2654 Weaver Way
Doraville, GA USA
Introduction
• Contamination control in the microelectronics industry still has a
primary focus on the removal of airborne particulate matter.
• However, all leading-edge manufacturers have incorporated preventive
airborne molecular contamination (AMC) measures into their operational,
facilities, and contamination control activities.
• As wafer size approach 450 mm and device geometries drop below 20 nm,
the effects of AMC become magnified.
• Manufacturers have fully recognized the fact that sensitive electronic and
electrical equipment and components will be damaged if they are exposed
to AMC.
12/12/2013 Page 2
The ITRS and AMC
• The development of the ITRS AMC control guidelines has come through
the Yield Enhancement (YE) Technical Working Group (TWG) and more
specifically, with the Wafer Environment Contamination Control (WECC)
sub-TWG.
• The WECC provides guidance on the types and
levels of AMC found in and around manufacturing
facilities, recommended control levels for AMC,
as well as options for effective assessment,
control and monitoring.
12/12/2013 Page 3
Wafer Environment Contamination Control
• Wafer environment control includes the ambient space
around the wafer at all times, whether the wafers are open
to the cleanroom air or stored in PODs/FOUPs.
• AMC needs to be controlled in the front-end and back-end
of line operations in semiconductor fabs.
• This control may be achieved fab-wide or at
certain critical processes, potentially also at
different levels for different processes.
12/12/2013 Page 4
WECC – Recent Activities
• Introduction of two new tables in the latest ITRS roadmap
version:
• “AMC monitoring methods”
• “Supporting table for on-line methods”
• Chapter review and text update for the WECC section and AMC
information.
• Clarification on refractory limits and footnote explanations have been
introduced.
12/12/2013 Page 5
WECC – Ongoing & Planned Activities
• Introduction of “AMC Definition” as a new table.
• Review requirements for 450 mm manufacturing.• Update of “Potential Solutions” for 450 mm process.
• Investigation of EUV related contamination.
• Introduction of moisture as new chemical contaminant for
critical processes and reticle environment.
• Investigate HNOx impact on different process steps and
clarification of analytical procedures.
12/12/2013 Page 6
AMC Control Drivers for 300 mm
• Definition of Airborne Molecular Contamination (AMC).
• Ultra-clean manufacturing.
• Unintended contamination of layers.
• Dimensional, structural and compositional information.
• Depth resolved quantification.
• Non-volatile organic surface contamination.
• Current AMC levels for 300 mm wafers / 45nm devices.
Correlation of contamination level to yield !!!
12/12/2013 Page 7
Work Plan for 450 mm Wafer Readiness
• Critical Contamination on fab level down to the wafer level.
Total other corrosive (oxidizing) species (as Cl2) 11,,000000
Reticle Exposure (Cleanroom/POD/Box ambient)
Total inorganic acids (as SO4) 550000 ((TTBBDD))
Total organic acids (as SO4) TTBBDD
Total bases (as NH3) 22,,550000 ((TTBBDD))
Total surface molecular condensable (SMC) organics on wafers, 00..2299 nngg//ccmm22//ddaayy
Requirements for AMC Control (2)
• One of the major challenges identified for future editions is that
of “AMC integration” with other working groups: especially
Factory Integration (FI) and Lithography (Litho).
12/12/2013 Page 12
12/12/2013
The Total AMC Concept
• One focus area requiring innovative solutions for Factory Integration (FI)
is the prevention and control of AMC.
• Increased importance of AMC requires revisiting contamination control procedures with
new methods and materials, which could also affect facility components used during
construction.
• Facility operations will also require coordination with production equipment vendors to
ensure proper AMC control.
• FI needs to specify general cleanroom conditions with respect to
environmental AMC limits.
• Although FOUPs and pods have help to shrink the exposed wafer environment significantly,
they are now considered to be concentrators (multipliers) and distributors for contaminants.
• Discussions between FI and YE are ongoing to determine whose responsibility this will be.
Page 13
12/12/2013
The Total AMC Concept (2)
• AMC control guidelines for Lithography are based in large part on inputs
from the photolithography tool suppliers.
• Control of AMC is critical to maximizing yield by minimizing local
poisoning of the photoresist and mitigating the formation of progressive
defects on masks during exposure.
• All photolithography tools should have chemical filters on the makeup air
to the internals of the tools.
• These filters have a finite lifetime, which is dependent on the contaminant load.
• Providing a chemically cleaner cleanroom ambient environment will extend the life of these
filters.
Page 14
12/12/2013
The Total AMC Concept (3)
• The use of inert environments to transport and store wafers is expected to
increase with process sensitivities.
• Pre-gate and pre-contact clean and salicidation are processes that
currently require this capability.
• Other potential solutions for WECC relative to AMC include:
• On-line monitoring for AMC contaminants,
• Reduced cost of ownership for AMC control,
• Development of emergency response procedures and measures for fugitive emissions,
• Verification for AMC limits relative to metal corrosion.
Page 15
The Total AMC Concept (4)
• Discussions of an “AMC integrated option” between the WECC sub-TWG
and the FI and Litho working groups have identified that:
• FOUP characterization and monitoring is becoming more important due to the introduction
of new construction materials, e.g., flame retardants and the potential for cross
contamination.
• AMC is becoming much more of a concern in reticle handling.
• SEMI (Semiconductor Equipment and Materials International) Standards are not optimized
and because of this no testing has or is being done, due in large part to the high costs for
non-standardized tests. SEMI is interested in updating these standards but it will take time.
• The Total AMC Concept illustrates the responsibility interface between
YE, FI, and Litho.
12/12/2013 Page 16
AMC-Related Aspects & Interfaces to FI
FOUP FOUPFOUP
AMC
FilterTools / ME
NV
Stocker/Purgable LP
Data collection +
integration
AMC Integrated Option
12/12/2013 Page 18
The ITRS Today
• Previous editions of the ITRS took advantage of experts from around the
world to help identify the technical challenges related to AMC and
establish AMC control strategies and guidelines for advanced
semiconductor device manufacturing.
• Requirements have been added for the control of total acids in addition to total bases in the
cleanroom ambient for lithography.
• In the 2014 update (and beyond), YE will put in requirements addressing
specific acids – not just total.
• Additional changes for AMC control proposed include total acids being reduced to < 20
ppbv (5 ppbv long-term), total condensable organics being reduced to < 100 ppbv, and
dopants being reduced to < 10 pptv.
12/12/2013 Page 19
WECC Near-term Challenges
• Process stability vs. absolute contamination level• Methods and data are needed for correlating defects caused by wafer environment and
handling.
• Requires determination of control limits for gases, chemicals, air, precursors, ultrapure
water and substrate surface cleanliness.
• Challenges exist for accurate measurement of AMC• In low-volume compartments (Pods, carriers).
• Quickly under highly dynamic conditions.
• Precisely standardized from surface depositions.
• Detection of non-volatile organic contamination on surfaces.• The detection and speciation of nonvolatile organics on surfaces is currently not possible in
the fab.
• There is no laboratory scale instrumentation available.
12/12/2013 Page 20
AMC Control Technology
• As the semiconductor industry has progressed, so, too, has
AMC control technology. This progress comes in the form of:
• AMC filters that can address essentially any AMC issue.
• Filtration systems that can be integrated into existing air handling
equipment (MAU, RAU, FFU, tools).
• Monitoring instrumentation and devices that can provide real-time, accurate
environmental assessments.
• The technical competence to work with manufacturers to provide effective