Cleanroom concept allows for expansions and modifications down the road
by John J. Cerilli
In 1997, under the constraints of a very limited budget, SpeedFAM-IPEC Inc. (Chandler, AZ), a chemical mechanical planarization (CMP) systems manufacturer, was tasked with an in-house project of designing and building a 108,000-square-foot research and development facility for $20 million.
That task led to an invention that was patented last year; a cleanroom design by Joe Rapisarda, director of facilities, that later spun off as Northstar Cleanroom Concepts, a separate but equal division of the parent company, SpeedFAM-IPEC.
“We needed a flexible, versatile cleanroom design for tools that change every 18 months,” says Rapisarda. “At this time, we're going to architectural, project management and consulting firms as well as general contractors and showing them the design and offering them an agreement to use it.”
Firms currently using the design include Pryme (London), Greenwood Construction (Salt Lake City, UT), consulting firm AGI Inc. (Tempe, AZ) and Alpha-Tech Inc. (San Jose, CA).
At the time of this report, North Star was busy designing two fabs in China as well as a cleanroom for a university in the United States.
A working model
SpeedFAM-IPEC's facility includes 43,000 square feet of office space and 45,000 square feet of mechanical space for electrical, chemical and DI wastewater distribution.
It’s no surprise that cleanroom personnel are required to don full bunnysuits before entering SpeedFAM-IPEC’s ISO Class 3 cleanroom.
Most importantly, the facility includes the working model for Northstar Cleanroom Concepts, a 25,000-square-foot area of ISO Class 3 through ISO Class 7 cleanroom space. This design had to allow for upgrade flexibility and the capability to modify and add CMP and metrology tools to meet present and future customer needs.
Rapisarda completed the cleanroom suites with enhanced vibration, particle control and air-flow dynamics for improved cleanroom performance for significant cost savings over a traditional controlled environment with raised cleanroom floors, which Rapisarda says would have cost about $60 million to complete.
Using Rapisarda's design, SpeedFAM-IPEC's R&D facility has been operating for more than four years.
Central to the NorthStar Cleanroom Concepts is a honey comb floor design that solves several ordinary problems. The floor is solid, eliminating the need for raised cleanroom flooring or isolation pedestals and removing the affects of machinery vibration. It is also easy to expand and upgrade from ISO Class 7 to ISO Class 3.
By only using two levels in the overall design-cleanroom and sub-cleanroom-the b-floor acts not only as an air-return plenum with nine feet of ceiling space, but the entire electrical, chemical and utility distribution is located there. With the air handlers, Kathabar air-return and humidity-control units affixed to the roof, there is a significant overall construction cost savings using this approach.
Concerning particle counts, SpeedFAM has a 1999 “Certificate of Traceable Calibration,” from U.S. Test and Balance, using a Particle Measuring System, Lasair Model 110 Particle Counter, serial number 38154-0798-723. “The bottom line is that our four classes of cleanrooms, ISO Class 3 through ISO Class 8, far exceeded the standard particle-count requirements for their respective areas,” says Rapisarda (See Table on pg. 11).
“By optimizing the design, we have also been able to cut our operating costs by reducing the downtime for installation, realignment and relocation of tools. We have eliminated dedicated areas for utility, mechanical and chemical distribution as well as air and plenum returns,” Rapisarda adds.
With reduced floor space, maintenance becomes easier. “There is no disruption of normal production operations for cleaning and/or rearranging of equipment. ULPA filters last significantly longer because of high throughput airflow and the high throughput open-air return plenum design in the sub-fab. Further savings are realized through monitored energy management control systems (EMCS).
These photos show the inter-working of the honeycomb flooring beneath the cleanroom. One view shows the flooring directly under the cleanroom (right), while the other shows a return air plenum (Left).
Traditional cleanrooms often require multiple levels for adequate air distribution, with raised floors and pedestals to support heavy wafer fabrication equipment and even more costly isolation/vibration-free rooms for sensitive metrology equipment. When this design needs to be upgraded or changed, the costs soar even higher.
Adding it up
Another factor is the tool install cost. At a typical wafer fabrication facility, the tool install cost can range from 10 to over 20 percent of the tool cost. With this design, and with a tool cost of $1.5 million, SpeedFAM-IPEC spent $15,000, or 1 percent to install a tool in the facility.
Traditional cleanrooms require expensive retrofits when technology changes or room “Class” needs to be upgraded. The Northstar design has addressed those issues several ways:
- The cleanroom floor is a solid structure with equally placed openings that form a honeycomb effect. The floor is able to support cleanroom machinery without the use of expensive, raised pedestals and distributes the air in a unidirectional flow.
- The honeycomb effect in the solid floor suppresses vibration from machinery within 2 feet, allowing machinery to be placed at any location in the cleanroom.
- The sub-cleanroom will allow for the placement of mechanical and chemical infrastructure. This sub-cleanroom significantly improves the airflow and movement throughout the cleanroom.
- The solid floor is constructed to withstand the requirements for the most sensitive vibration yet allows for a flexible cleanroom that can accommodate future requirements easy to upgrade for using 300 mm technology.
- Equipment can be easily rearranged with minimal costs and no disruption to normal daily production. Tools are staged, and brought in and out of the cleanroom via a set of airlocks.
- The honeycomb structure is less expensive to construct than raised floors.
John Cirilli is vice president and general manager of the Surface Technology Group of SpeedFAM-IPEC, Inc. (Chandler, AZ).