When renovating a cleanroom, or creating one from non-cleanroom space, understanding the details – of the site, building, planned research, and equipment – is essential. A cleanroom can be used for many things: semiconductor fabrication, microelectronics assembly, aeronautical assembly and testing, pharmaceutical research or manufacturing, or geochemistry. One size definitely does not fit all.
Start your planning with a candid discussion. Though users may request a Class 10 cleanroom, for example, investigate the actual requirements. It costs a lot more to build and operate Class 10 space than Class 1,000. It’s just as important to avoid over-designing as it is to provide an adequate facility.
Consider the ambient site conditions, including vibration, noise, and electromagnetic and radiofrequency interference, as well as the load limitations of the existing structure. These parameters may or may not pose a problem; a clear initial statement of the cleanroom’s use and desired processes will guide decisions.
In addition, identify the needed equipment or tools – not only for their specific environmental requirements, but also to make sure that a move-in is even possible. In older buildings, low and narrow elevators and corridors may derail your plans.
Code and infrastructure issues
Semiconductor and nanotechnology processes often require hazardous materials – especially toxic, pyrophoric, and flammable gases. Building and fire codes will limit the amount of these materials allowed in a “B Occupancy”: the most typical classification for university and lab buildings. If you can’t work within these limits, an H (Hazardous) Occupancy will be required, triggering construction upgrades (fire separations of one hour or more; isolated air make-up and exhaust systems; emergency power for HVAC systems; flammable and toxic gas detection; and limitations on how materials can move through the building). Some existing buildings may simply not support an H Occupancy.
Infrastructure capacity is also key – not just for equipment power and utilities, but also intensive mechanical systems. A typical office requires one or two air changes per hour (ACH, the number of times per hour all the air in a space is replaced). A typical lab might require six to 12 ACH; a Class 100 cleanroom usually needs 200. The higher rate in the cleanroom is required to “wash” the air through filters. This means additional filtration, heating, cooling, and humidity control so that air can be recirculated, using only enough fresh air to replace anything exhausted through tools and hoods, while maintaining positive room pressurization.
Mechanical systems are best located above or adjacent to the cleanroom. Is there enough floor-to-floor height? A good starting point is 10 ft of clearance above the cleanroom ceiling. Further complicating the issue is the typical need to avoid cross-contamination with other facilities by extending exhaust to the roof.
Contamination and construction issues
Most cleanrooms are used to fabricate and assemble devices or systems that must be protected. If users are concerned about airborne particulates, they are probably also concerned about contaminants from gases and water. Determine whether sufficient access to gases and water is possible, and whether quality will suit the processes involved.
Renovations and retrofits can pose significant challenges, especially if operations must continue during construction. Productivity wanes if construction workers have to gown up and down, clean tools before entering, and deal with limitations on their activity. If cutting or coring concrete or gypsum board within the space is necessary, activity must be tented and conducted with a HEPA vacuum, inflating construction costs. Some shutdowns are inevitable; pre-planning helps keep construction and cleanroom operations on track.
As with new construction, meticulous planning is the most essential tool for a successful critical environment renovation or retrofit.
DO
• Clearly identify requirements for maintaining operations during construction.
• Clearly establish the purpose and functions of the space. Use a recognized standard such as ISO 14644 to set the class of cleanliness as well as criteria such as temperature and humidity setpoints.
• Establish requirements for vibration performance based on specific tools and processes.
• Check vertical clearance for sufficient height to allow adequate space for mechanical systems.
• Investigate hazardous materials use, and confirm that the building can accommodate a Hazardous occupancy if required.
• Check clearances for equipment to be moved. Elevators can be tricky!
• Confirm that there is sufficient vertical shaft space for exhaust ducts from the cleanroom to the roof, and that shafts are accessible.
• Confirm the list of utilities, capacities, and quality required based on tools and processes used.
• Confirm that there will be sufficient power, with allowance for growth and change.
• Budget the project with a contingency for unforeseen conditions in the existing building (10% is a good starting point).
• Budget for atypical line items (cleanroom construction protocols and supervision; cleanroom certification; temporary gown room; temporary clean-pipe fabrication shop).
DON’T
• Locate the cleanroom on an exterior wall if it can be avoided.
• Locate the cleanroom below wet laboratories if it can be avoided. Ideally, the cleanroom should be located with a dedicated mechanical room directly above.
• Assume that users have fully considered their requirements. Test and confirm all assumptions.
• Assume your design team has experience in cleanroom design. Verify!
• Assume that the work can be completed by a contractor who doesn’t have experience building cleanrooms.
• Assume that the contractor will understand the requirements of “building clean” (starting the project out correctly, getting the space clean, and keeping it that way). Spell it out and get it in writing.
• Locate air intakes above a loading dock or service yard.
• Locate exhausts at grade level or in building side walls.
• Underestimate the size and space required for support equipment.
Real-Life Renovation: Fluke Hall
Fluke Hall, at the University of Washington, Seattle, was built in 1988. The three-story building consists of a cast-in-place concrete frame with storefront and corrugated metal panel systems. A recent facility assessment indicated that the mechanical, electrical, and piping systems needed renewal. Renovation will allow UW to repurpose Fluke Hall as a long-term core research resource in two capacities: as the Microfabrication Facility (MFF) for the College of Engineering, and as The Center for Commercialization New Venture Facility.
The Fluke Hall renovation will encompass ISO Class 5, 6, and 7 space. Plan: HDR
The project will improve environmental air classifications and reconfigure the cleanroom for greater capacity, quality, and throughput. The east side of Level 1 will be gutted and remodeled, creating 16,550 ft2 of new cleanroom space. Key features include:
• Maintaining operations by phasing construction to allow a functional area to be completed and relocated before beginning each phase.
• Maintaining operations of the E-beam lithography (EBL) facility without disruption (requiring special techniques and protocols).
• Upgrading and expanding lithography facilities to ISO Class 5 (Class 100).
• Upgrading and expanding thin film, etch, and hot process facilities to ISO Class 6 (Class 1000).
• Adding new ISO Class 7 (Class 10,000) labs for teaching and soft lithography, chemical synthesis, and back-end processes and device assembly.
• Replacing specialty gas systems and providing new safety systems.
• Replacing all mechanical systems infrastructure.
• Replacing electrical systems to improve flexibility. (A new “pipe and wire” system will feature branch panels dedicated to the tools.)
HDR is developing the facility, with completion projected in 2014. Phasing is critical to allow continuous functionality. Developing the cleanroom within the existing envelope is also challenging; the space is limited by a 16-ft floor-to-floor height, and wet laboratories are located directly above.
Responses to these challenges included incorporating a construction manager (CM) as early as possible; developing a modified air management scheme; and working with vendors to develop a cost-effective, unique concept.
Jack Paul, RA, LEED AP, is VP/senior professional associate at HDR Architecture. With more than 28 years of experience planning facilities for teaching, research, and manufacturing, he is a nationally recognized expert in planning and programming for the physical sciences, engineering research, and cleanroom users.
This article appeared in the February 2013 issue of Controlled Environments.
