E SC 412 Nanotechnology: Materials, Infrastructure, and

© 2013 The Pennsylvania State University

E SC 412

Nanotechnology: Materials, Infrastructure, and

Safety

Wook Jun Nam


Unit 2

Infrastructure

Lecture 2

Facilities


• Infrastructure

* What is it ?

* Why do we need it in nanotechnology ?

• Facilities

• Equipment Systems

* Vacuum Based Systems

* Non-vacuum Based Systems

Unit Outline


• Introduction

• Facilities

− Why do we need special facilities ?

− Types

* Clean work stations

* Tunnel/Bay structures

* Cleanrooms

* Mini-environments

Lecture Outline


Why do we need special

facilities ?

• Place for manufacturing

• Safety

• Contamination control

• Protection of workers and environment

• Process control


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/


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.


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%.


The HEPA Filter Design

Dirty Air

Clean Air

Public Domain: Image Generated by

CNEU Staff for free use


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.


VLF Hood Cross Section



PerfilterBlower

Air Flow

Work surface

HEPA Filter

Clean

Air


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.


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


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


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


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


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


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


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


Tunnel/Bay Design

HEPA Filters

Clean

Air




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



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


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


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


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


Air Shower

http://www.clearsphere.ie/products-equipment-accessories.htm#3 http://encyclopedia2.thefreedictionary.com/clean+room


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!


A Cleanroom

Van Aznt, Peter. Microchip Fabrication 4th Edition. McGraw Hill. New York. 2007


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


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


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)


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


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




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


Unit 2

Infrastructure

Lecture 2

Facilities


Facilities

• Introduction

• Facilities

− Why do we need special facilities ?

− Types

* Clean work stations

* Tunnel/Bay structures

* Cleanrooms

* Mini-environments

SUMMARY

Documents

E SC 412 Nanotechnology: Materials, Infrastructure, and