Kick-off Speech Among Highlights at CleanRooms `94 West
By Merideth E. Lawrie
Santa Clara, CA–CleanRooms `94 West, held October 17-20 at the Santa Clara Convention Center, attracted more than 100 exhibitors and 1,738 registered attendees (31 percent over last year), and was highlighted by an opening day kick-off speech given by Dr. Dariush Rafinejad, vice president of engineering at Lam Research (Fremont, CA).
According to Adam Japko, Group Publisher for the Micro Contamination Control Group of PennWell Publishing (Nashua, NH), pre-registration was up more than 100 percent over last year`s CleanRooms West show. CleanRooms magazine, sponsors of the show, and CleanRooms `94 West were acquired by Pennwell Publishing in May. Japko also adds that because of the company`s strong market position, they were able to attract leading speakers, such as Rafinejad.
In his lecture entitled “Contamination Control in Semiconductor Processing Equipment–The Continuing Challenge,” Rafinejad expressed his concern about evolving the wafer processing environment in response to contamination control needs for future devices. He specifically highlighted defect reduction and particle sources, generation, transport and control. He also gave his views of what the future focus should be in contamination control.
“The name of the game today is cost reduction, yield enhancement and productivity,” he says. “This means you have to have very low particle levels to maximize your yields.”
In what he outlined as a “Defect Reduction Roadmap,” Rafinejad illustrated, through three generations–1993, 1996 and 1999–that: critical dimensions are going from 0.5- to 0.25-microns; DRAM capacity is going from 16 to 256 Mbytes; particles on 8-in. wafers are going from 6 to 0.6. These numbers were derived in response to Lam Research`s customers` future requirements.
“This demonstrates that contamination control is more important today than ever, and will become even more important in the future,” he says.
Rafinejad sees the major particle sources coming from cleanrooms, process gas sources/delivery and process equipment, including the reaction chamber, which Rafinejad says is today`s major contributor of particle sources. He also believes that deposits of by-products on solid surfaces are the primary source of particle generation.
“When you get deposits on these surfaces, at some point they shake loose.” This, he attributes to mechanical movements from valves or doors, which are constantly opening and closing. From there, the particles can get trapped throughout later processes and are transported by gravity at low pressure, fluid drag at high pressure, ion drag, electrostatic and thermophoresis.
To aid in particle control, Rafinejad stresses the importance of utilizing both particle reduction and particle management strategies, saying that particle management is, for the most part, overlooked in the industry. “Everyone is after particle reduction, which is fine, but in the reality of IC manufacturing, customers are equally concerned about particle management.”
Some particle reduction strategies he suggests are: constant wall temperatures; “clean” chemistry; and operating a control strategy with the valve/gate sequence. Some particle management strategies Rafinejad suggests include: particle monitoring–realtime and in situ, and in-line inspection; using a wet clean methodology; and encompassing a recovery procedure.
Rafinejad envisions several future focuses, such as making designing for low particles the highest priority, using alternate chemistries, and having a broader understanding of surface deposition mechanisms. He says, however, that there`s an urgent need for partnering between all involved parties.
“You can go off on a tangent and do all sorts of fancy things, but to make contamination control cost-effective and provide yield enhancements, suppliers, manufacturers and users must communicate their needs.” n