e sc 412 nanotechnology: materials, infrastructure, and
TRANSCRIPT
© 2013 The Pennsylvania State University
E SC 412
Nanotechnology: Materials, Infrastructure, and
Safety
Wook Jun Nam
© 2013 The Pennsylvania State University
Unit 2
Infrastructure
Lecture 2
Facilities
© 2013 The Pennsylvania State University
• Infrastructure
* What is it ?
* Why do we need it in nanotechnology ?
• Facilities
• Equipment Systems
* Vacuum Based Systems
* Non-vacuum Based Systems
Unit Outline
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• Introduction
• Facilities
− Why do we need special facilities ?
− Types
* Clean work stations
* Tunnel/Bay structures
* Cleanrooms
* Mini-environments
Lecture Outline
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Why do we need special
facilities ?
• Place for manufacturing
• Safety
• Contamination control
• Protection of workers and environment
• Process control
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What are some examples of
the facilities used ?
• Clean Work Stations
• Tunnel/ Bay Structures
• Cleanrooms
• Mini-environments
− SMIF boxes
http://techon.nikkeibp.co.jp/NEA/archive/200205/183172/
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Clean Work Stations
• One approach in nanofabrication and synthesis
is to create individual work stations, such as
chemical hoods with air filters and non-shedding
materials.
• A large room with the work stations (or hoods)
arranged in rows, so products under fabrication
can be moved to each station, without coming in
contact with “dirty” air.
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Clean Work Stations
• Filters in the clean hoods are known as High
Efficiency Particle Attenuation (HEPA) filters.
• HEPA filters consist of large, porous fibers
folded into a filter holder in an accordion design.
• HEPA filters allow a large volume of air to pass
at a low velocity (90-100 ft/min.) and have a
filtering efficiency of 99.99%.
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The HEPA Filter Design
Dirty Air
Clean Air
Public Domain: Image Generated by
CNEU Staff for free use
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Clean Work Stations
• A typical clean hood has a HEPA filter mounted in the top.
• “Dirty” air is pushed through the filter and exits in a laminar pattern.
• A shield directs the exiting air over the work area in the hood.
• These type of hoods are known as vertical laminar flow (VLF) hoods.
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VLF Hood Cross Section
Public Domain: Image Generated by
CNEU Staff for free use
PerfilterBlower
Air Flow
Work surface
HEPA Filter
Clean
Air
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Glove box
• Glove box is an enclosed workstation which provides inert atmosphere.
• The gas (argon, nitrogen or helium) continuously circulates between the
glove box and the gas purification system. The gas is purified to a value
of < 1 ppm in relation to moisture and Oxygen.
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Basic Components of Glove boxGlove Box
Vacuum-tight stainless steel
working space.
Glove Ports / Gloves
Butyl gloves for comfortable
working.
Antechamber : For material
transfer.
Vacuum Pump
- to evacuate the system
- To pump antechamber
- for final cleaning of the
purifiers at the end of the
regeneration cycle
http://home2.btconnect.com/MBRAUN-UK/technical-guide.htm
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Gas Purification System
Usually attains < 1 ppm
Oxygen
Usually attains < 1 ppm
moisture
Purifier can be regenerated
using hydrogen/nitrogen
mixed gas
Control Panel
For central controlling and
monitoring of the systemhttp://home2.btconnect.com/MBRAUN-UK/technical-guide.htm
Basic Components of Glove box
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Basic Operation of Glove boxG : Gas flow
Circulation between box and purifier
F : Exhaust filter
Inlet/outlet of the circulation tubes
are protected by aerosol filters. The
filters supply particle-free
atmosphere and separate the box
from the purifier(s) and tubes
V : Valves
Usually electropneumatic valves
C : Cooling (heat exchanger)
Electric heat as well as compression
heat increase the gas temperaturehttp://home2.btconnect.com/MBRAUN-UK/technical-guide.htm
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P : Purifier Unit (regenerable)
Oxygen: Removed by chemical
binding at polydispersed copper
Moisture (water vapor): Removed by
adsorption in microporous
molecular sieve
Other gases: Removes all gases that
react with Cu or CuO. Traps gases
that fit into the 1.3 nm holes of the
molecular sieve
B : Blower (circulation unit)
Causes the circulation of gas flow. It
is encapsulated in a vacuum-tight
containerhttp://home2.btconnect.com/MBRAUN-UK/technical-guide.htm
Basic Operation of Glove box
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Glove Box Applications
• Allows work with anaerobic organisms or anaerobes. (living organisms that do not require oxygen for survival and could possibly react negatively, and even die, if oxygen is present)
• Allows use of oxygen/moisture sensitive materials
• Allows inert welding
• Allows battery production; e.g., lithium batteries need a moisture free production environment
• Allows deposition of relatively contamination-free thin films; e.g., Al, Cu, P3HT/PCBM
• Can be used to allow work with hazardous materials such as high-biosafety level pathogens and radio active material
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Tunnel/Bay Concept
• For more stringent particulate control clean hoods are less popular because of the potential for personnel induced contamination
• This contamination issue can be solved by dividing the fabrication/synthesis area into clean regions called “bays” or “tunnels”
• Work stations are then located in these bays/tunnels
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Tunnel/Bay Concept
• In this design, clean air enters into a bay or tunnel from above by HEPA filters built into the ceiling
• Materials are less vulnerable to personnel-generated contamination because there are fewer workers in the immediate area
• On the downside, tunnel/bay designs are more expensive to construct than hoods and are less versatile than cleanrooms, when it comes to process changes
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Tunnel/Bay Design
HEPA Filters
Clean
Air
Public Domain: Image Generated by
CNEU Staff for free use
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The Cleanroom Approach
• Simply stated, a cleanroom is a volume (a
room) where contamination is reduced and
controlled
• A cleanroom is designed to minimize
contaminants
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© 2013 The Pennsylvania State University
Cleanroom Contamination
• Humans are the biggest source of cleanroom contamination.– A cleanroom operator, even after air showering, can
give off between 100,000 and 1,000,000 particles per minute-this number increases when a person is in motion
• At two miles per hour, a human gives off up to 5 million particles per minute!
• Processing equipment is the second biggest source of cleanroom contamination.– Often processing support equipment is placed in the
chase area of a cleanroom
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Cleanroom Personnel
• Humans must be isolated as much as possible from the delicate materials and equipment found in a cleanroom
• Personnel must be covered in special cleanroom garments (“bunny suit”) consisting of a hood, facemask, coveralls, boots, and gloves
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Gowning
• Many cleanroom gowning procedures do
not protect a user from hazards of the
cleanroom. They only protect the
cleanroom from particles generated from
the users
• Additional protective equipment is required
for certain processes
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Gowning Protocol
• With the exception of shoe covers, gowning for the cleanroom occurs in a top down fashion:– This is done to reduce particulate shedding
• Gowning for the cleanroom occurs in the following order:– Shoe covers
– Facemask and hair net
– Hood
– Bunny suit
– Boots
– Gloves
– Goggles
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Air Shower
http://www.clearsphere.ie/products-equipment-accessories.htm#3 http://encyclopedia2.thefreedictionary.com/clean+room
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Total Cleanroom Strategy
• This strategy employs an open fabrication/synthesis area
• Air filtering is accomplished by HEPA filters in the ceiling with returns in the floor, to give a continuous flow of clean air
• The continuous flow of clean air allows for a faster recovery, which is the amount of time it takes for the filters to return the area to an acceptable condition after a disturbance
• A class 1 facility turns over air every 6 seconds!
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A Cleanroom
Van Aznt, Peter. Microchip Fabrication 4th Edition. McGraw Hill. New York. 2007
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The Modern Cleanroom
• The traditional cleanroom layout is the ballroomdesign, where individual process tunnels open into a central hallway
• Every cleanroom is a trade-off between cleanliness and cost, but all are built from a primary design– A sealed room that is supplied with clean air
– Building materials that are non-contaminating
– Systems to prevent accidental contamination
– Vibration control, for sensitive equipment
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Cleanroom Elements
Cleanrooms utilize a series of techniques to keep
contamination from adversely affecting the
fabrication/synthesis process:
– Adhesive floor mats
– Static control
– Gowning Area
– Double-door
pass-throughs
– Air pressure
– Shoe cleaners
– Air showers
– Glove cleaners
– Service bays
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The Mini-environment Approach
• Rising cleanroom costs with diminishing returns on effectiveness have resulted in another concept of isolating materials in as small an environment as possible
• The problem of how to string together a number of mini-environments, such that a product is never exposed to room air is solved by transporting the samples in a clean environment
• One example of the industrial application of this approach is Hewlett-Packard’s Standard Mechanical Interface (SMIF)
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The SMIF System
• SMIF systems have three main parts:
– The pod, or box ,for transportation of
materials
– The isolated mini-environment at the next
process station
– A mechanism for extracting and unloading
materials at each successive processing
station
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The SMIF System Isolated pod w/
vacuum or inert
atmosphere
Wafers in a cassette
Standard Mechanical
Interface (SMIF)Process
Chambers
Load lock
Robotic
loading arm
Internal seal to
main chamber
Public Domain: Image Generated by
CNEU Staff for free use
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The SMIF System
• SMIFs have the advantage of:
– Better temperature and humidity control
– Reduced yield losses due to contamination
• However, pods can be too heavy and expensive
• Robots can be used to handle SMIF boxes, which drives up cost and complexity
© 2013 The Pennsylvania State University
Unit 2
Infrastructure
Lecture 2
Facilities
© 2013 The Pennsylvania State University
Facilities
• Introduction
• Facilities
− Why do we need special facilities ?
− Types
* Clean work stations
* Tunnel/Bay structures
* Cleanrooms
* Mini-environments
SUMMARY