SEMI standard dissipates fab ESD contamination
Tammy Wright
MOUNTAIN VIEW, CA — SEMIconductor Equipment and Materials International (SEMI) has released a standard that aims to clean up static-related contamination in fabs.
SEMI International standard — SEMI E78-0998-Electrostatic Compatibility – Guide to Assess and Control Electrostatic Discharge (ESD) and Electrostatic Attraction (ESA) for Equipment — provides a matrix of recommended maximum levels of static charge on products, reticles, carriers, and the input and exit ports of production equipment or minienvironments, where the majority of static related problems reportedly occur. The document also defines types and test methods for assessing ESD damage to semiconductor devices and investigating electrostatic particle attraction.
“SEMI developed [the standard] to help equipment makers partner with chip manufacturers in achieving higher productivity through reducing the damage to wafers caused by static charge,” says Tom Reed, vice president of SEMI. “Good static control programs provide significant benefits by reducing the cost of preventable damage.”
According to industry, key components in SEMI E78-0998 are the descriptions of commonly used static control methods, including grounding techniques, static dissipative materials and air ionization.
Jim Curtis, business unit manager for the static control and cleanroom products group at Simco, an ionization equipment manufacturer in Hatfield, PA, says the standard is important because it discusses direct discharge damage, electrostatic attraction, and electromagnetic interference that can be caused by ESD and result in soft errors, which he says are like hiccups and allow machinery to fix itself, or result in hard errors, where equipment is unable to reset itself.
“This standard is the first to comprehensively address the impact of ESD in front-end processes,” Curtis adds, noting that lately many of Simco`s customers claim to be installing ionization equipment to help reduce these process errors.
Arnold Steinman, SEMI ESD Task Force leader and chief technology officer at Ion Systems (Berkeley, CA) says, “The document provides a common language so that users and suppliers of semiconductor equipment can work together to overcome static problems before equipment is delivered to the semiconductor factory. This is the most cost-effective approach to the static problem.”
Curtis also believes SEMI E78-0998 serves as a credible source for clearing up confusion about the effects of ESD on the semiconductor manufacturing process.
“It makes a powerful blanket statement. It says that electrostatic charge is the primary contributor to particle contamination in cleanrooms and that it is a benefit to control static in the manufacturing process,” he contends.
While SEMI E78-0998 is targeted at the semiconductor industry, Curtis believes it can be helpful to the flat-panel display industry and other fields concerned about contamination.
For example, he says one of Simco`s pharmaceutical customers recently installed an ionization system in its gowning area.
“The company was having a rash of problems with microbial contamination in its cleanroom. Skin flecks were attaching to workers` gowns, so by dissipating the static charge on the gowns, they tend to not attract and hold microbes, which then can`t colonate and cause contamination,” Curtis explains, noting that recent testing has shown a reduction in the company`s contamination levels.
To school equipment manufacturers and end users on guidelines, SEMI is holding a standards technical education program on July 12 during the Semicon West conference and exhibition. For details, call (650) 940-6904 or visit SEMI`s web site at www.semi.org.