Particle contamination is the biggest concern for
maintaining a controlled cleanroom environment.
Cleanroom suits must be worn at all times to avoid cleanroom users’ skin and hair generating particulate contamination. Every item that users bring into the cleanroom
must be cleanroom compatible (especially with regard to
particle contamination) and fully decontaminated before
entering to maintain the required cleanroom conditions.
Non-cleanroom designed paper, notebooks, and cardboard containers are not allowed inside, and any chemical
bottles, plastic boxes, or other instruments need to be
wiped completely prior to taking inside the cleanroom.
Before a new piece of equipment can be installed in the
facility, it must be decontaminated multiple times in a
dedicated cleaning area. Any particle producing process
must be conducted in a well-ventilated area. The cleanroom staff checks particle levels on a regular basis to
monitor any changes in airborne contamination.
In the Pettit cleanroom, process equipment is located in
bays separated by chases which contain supporting items
such as pumps, chilled water, gas cabinets, exhaust scrubbers,
power supplies, and other support equipment. These supporting systems do not need to be in the highly controlled environment, so isolating them in the chases reduces the amount
of expensive cleanroom space one has to construct. In addition, allowable particle levels are controlled separately from
bay to bay. For example, the photolithography bay has a Class
10 environment while the metallization bay is Class 1,000. In
contrast, the Marcus inorganic cleanroom is a flow-through,
ballroom design where all equipment is located within the
same 10,000 sq. ft. open area. The challenge of maintaining
low particle counts throughout the facility is addressed by
maintaining a higher flow rate on the clean air return to those
cleanroom sections that require it. With this approach, we
have been successful in keeping these low particle count sections of the cleanroom at Class 100 level.
Many of the fabrication processes are sensitive not only
to particle levels, but also to other environmental parameters such as temperature, humidity, and vibration. The IEN
cleanroom has a network of sensors monitoring the variation in these parameters, and the data can be directly read
in real time via a web interface, along with historical data
covering longer periods of times to identify trends. Many of
the warnings and alarms from the sensor network are sent
immediately to cleanroom staff on their mobile devices so
they can rapidly identify problems and fix them.
Ultimately, maintaining the appropriate controlled
environment relies upon collaboration between staff and
users. Users report to staff any problems or concerns
about the cleanroom environment, and they also help
staff to identify potential problems, warn other users of
improper behavior, and do some routine housekeeping
work. Everyone who uses and benefits from the cleanroom has the responsibility of keeping the facility safe.
The product of a well-controlled environment is high
quality research. Supported by the IEN cleanroom,
Georgia Tech faculty, students, and research staff, as well
as our research affiliates from other universities and companies, have published journal articles, presented at conferences, and filed patents based on discoveries realized
within the IEN facilities. In addition, this research has led
to a number of successful startup companies founded by
GT faculty and students.
Dr. Paul J. Joseph is Principal Research Scientist and
Dr. Hang Chen is Research Scientist II at the Georgia Tech
Institute for Electronics and Nanotechnology. Drs. Joseph and
Chen wish to thank their support team at Georgia Tech for
their assistance with this article. www.ien.gatech.edu
Figure 5: Cleanroom staff
checks air supply and
filters for efficiency.
Figure 4: Cleanroom staff
measures particle counts
inside the cleanroom.