Cleanroom facility for nanotechnology research

Cleanrooms are defined as the rooms which are constructed in such a way that it covers enclosed spaces which are environmentally controlled with respect to the different parameters including temperature, humidity, air pressure, airborne particulates, air motion, airflow patterns, vibration, noise, living organisms and lighting. Particulate control includes particulate and microbial contamination and particulate concentration and dispersion.

Nanotechnology has been defined as research and technology development dealing with particles and systems with particle dimensions of approximately 1 to 200 nanometres. In fact, nanotechnology has been present on scientists’ radar for over two decades. Over the past decade, nanotechnology has become the interesting topic for the researchers to carry out the researches owing to its potential advantages over the conventional techniques.

Nanotechnological researches include theoretical studies, modelling, surface characterization, development of equipment for nano-scale manipulation, atomic manipulation itself, and nano-scale manufacturing. These branches require widely differing physical environments. Many of these accomplishments are due in large part to the clean room facilities built to meet the stringent requirements presented by many nanometre scale research programs. Existing design and construction guidelines do not fully address the requirements of this new facility type.

Owing to different environments required for nanotechnology, a number of nanotech facilities have been constructed and are now fully operational. During this time, the Institute of Environmental Sciences and Technology (IEST) has derived important practical information from these nanotech facilities. In fact, many types of nanoscale research require specialized laboratories designed to meet an array of special criteria. For example, some researches require strict control over airborne particulates; others need temperature and humidity controlled to a specific value; while some require limited vibration and noise. It may be possible that the control over the temperature and humidity in one area will affect the vibration and noise limits in other areas. However, nanoscale research processes such as nano fabrication, atomic level measurements and characterization require critical environments that can control the specified environmental characteristics within the laboratory.

These technical considerations might involve controlling temperature and humidity levels, isolating vibration and acoustic noise, reducing the quantity and size of airborne particulates, and shielding from electrical, electromagnetic, and radio frequency interferences. Electron microscopes are most sensitive to many of the above “noise” sources. Additionally, temperature fluctuation along the length of a laser beam could cause distortion and therefore lose focus and accuracy in measurements. The beam could also be misaligned by vibrations while electromagnetic interference causes the wavelength to change introducing errors in measurements.

It is more difficult to achieve the required temperature and maintaining it constant than it seems. This condition can be achieved by designing the systems that can circulate the volume of air inside the room with a high number of air changes per hour. In typical laboratories, temperature fluctuations are controlled to ± 1 degree Celsius. Closer temperature control is sometimes needed and the tolerance can range from 0.5 degree Celsius down to a range of ± 0.01 degree Celsius in highly critical spaces. Similarly, humidity control, depending on the research requirements, may vary between ± 5% down to 1% of relative humidity (RH). The National Institute of Standards and Technology (NIST) Advanced Measurement Laboratory project (AML) provides the best example of how to deal with tightly controlled environments in a nano scale research facility.

Vibration is an important and complex issue. Invalidation of the results can be obtained with the slight vibration while capturing an image at the atomic scale. Electron microscope is more sensitive to the extremely small motions which might produce distort images. As a solution for the vibration control, first the vibration level tolerated must be determined. From this the building design should be selected. A solution could be as simple as setting the building backs an adequate distance from the street to minimize the vibration caused by traffic. However, not all building sites can provide for such setbacks. Second, the vibration is also reduced by building two of the facility’s five wings underground, minimizing the effects of predominant surface vibrations. With the sensitive area about 40 feet below the surface, the floor vibrations can be reduced by more than fifty percent. For specialized laboratories where limiting vibration is essential, it makes sense to build underground.

The most critical parameter for the nano scale research is some spaces require the control of airborne particles and others may require control of molecular contamination (biological matter). These two controls require different engineering and architectural solutions. It might be achieved by segregation of spaces, in addition to air management systems that will provide positive or negative pressurization in the space where research or fabrication is conducted.

The Birck Nanotechnology Center (BNC) at Purdue University was the first to build up the nano fabrication facility in the traditional room and generating the pharmaceutical grade cleanroom for molecular-based bioscience research. While both spaces are within the same building envelope, the engineering solutions and protocols used are customized for each of the unique environments.

Before the NIST AML was built, NIST was trying to carry out cutting-edge research in laboratories built in the 1960s. The age and set-up of the buildings caused a number of problems. For instance, small pieces of the fan belts on the air handling unit motor would flake off, travel down the ductwork, and get blown into the space, landing at some random location. Those little specks didn’t seem big, but when they landed on materials being fabricated at the nano scale, they easily ruined experiments and samples. Dust particles also had a negative impact on their devices. The completed 8,000 square feet nano fabrication facility at the NIST Center for Nano scale Science and Technology (CNST) is outfitted with Class 100 bay and chase cleanroom laboratories to operate as a shared-access user facility.

Many of the instruments used by nano scale researchers are highly sensitive to electrical and electromagnetic interference. Everything from a small fluctuation in the electrical power supply to electromagnetic interference (EMI) or radio frequency interference (RFI) can degrade research. At the outset of design, it is important to understand the specific requirements of the anticipated research in order to determine if EMI or RFI could be problematic.

Strict control is required if the source of interference comes from outside the building. An outside interference issue arose during early planning phases at the Center for Functional Nano materials (CFN) at Brookhaven National Laboratory. Concerns arose regarding the radio frequency (RF) emissions produced by a National Oceanic Atmospheric Administration (NOAA) Doppler radar located about a mile away. The site was tested specifically for that issue. Fortunately, the RF interference was low enough that it could be handled with local attenuation.

From an interior perspective, designers working to limit interference must be cognizant of how different types of labs are arranged. For example, labs that are particularly sensitive to electromagnetic interference should not be located near elevators or lab equipment that will produce strong electromagnetic fields. Certain systems necessary for maintaining the building must be taken into account. Transformers, rotating equipment, and pumps are examples of equipment required to keep basic building systems operational, but can also wreak havoc with laboratories. These essential building systems should be located where they are as benign as possible; and if necessary, local shielding can help create an environment appropriate for nano scale research.

Generally, when designing the interior of a nano scale research facility, components known to cause interference should be segregated from research areas as much as possible. In addition to the technical requirements for the nano technological researches discussed above , the human criteria should also be considered. Designing spaces for nanotechnology research is not only about how atoms, materials and machines interact but also about how people interact.