April 07, 2003
Handling Haz Mat
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Manufacturing semiconductor products can be a messy business. Among the numerous, potentially dangerous substances used in the process are the acids needed for etching features onto the silicon wafer. Those acids may include hydrofluoric acid, sulfuric acid, some nitric acid, and a bit of hydrochloric acid here and there. This caustic brew swirls about in the etching baths of semiconductor fabs, just itching to escape and make life miserable for anyone who might be living or working nearby.
Semiconductor fabs can be found in lots of places around the world - even within the municipalities of Silicon Valley, municipalities like the City of Santa Clara. Dr. David Parker, Hazardous Materials (Haz Mat) Administrator for the City of Santa Clara Fire Department, says there are standard industry practices which have been developed over the years to insure that dangerous substances like wafer etching chemicals don't, in fact, escape - and that the ground water and sewage systems serving fabrication facilities are functioning under strict specifications and environmentally conscientious oversight. With a Ph.D. in chemistry and 20 years' experience with the Fire Department, Parker is
well qualified to discuss the regulations under which semiconductor fabs operate in the City of Santa Clara.
during and after the materials are used.”
Parker says that once a business operating in the city discards hazardous waste, it's then the business of the City of Santa Clara, the Fire Department, and the publicly-owned sewage treatment plant to be sure that the disposal is carried out safely and within prescribed guidelines. To understand how these agencies attend to public safety, Parker briefly describes the manufacturing process. He starts by saying he's not a “semiconductor guy,” that his point of view is one of an informed industry observer, not an expert participant.
With that disclaimer in place, Parker says, “After designated features are etched onto the wafer, copious amounts of water are used to wash away the etching acids along with the bits of unwanted, doped silicon. The amounts of silicon and doping agents (boron, arsenic, etc.) which are discarded with the effluence are small and may be of concern, but it's the etching acids which are of the greatest concern. The biggest problem with letting untreated acids out into the main sewage flow is that they are corrosive, an acute environmental problem more than a long-term insidious toxic issue. The acids must be neutralized to minimize their effect downstream from the fab.”
unlivable environment for the aquatic life forms that required some minimal level of saline.
According to Parker, there are a number of agencies with oversight responsibilities in various jurisdictions across the United States. There are city government departments - Fire Departments, Planning Commissions, Building Departments, and publicly owned Sewage Treatment Works. There are county governmental agencies - Health Departments and Joint Powers Authorities. There are state governments with Health and Environmental Protections Agencies. And there is the Federal Government with OSHA, EPA, etc.
Parker says if you want to build a semiconductor manufacturing facility, some or all of these agencies may have a say in how you're building your fab, where you're building your fab, how you handle the dangerous materials at your manufacturing site to ensure the safety of the employees and the neighborhood, and how you dispose of the materials once you've finished using them.
He adds, “Our overarching concern here in the City of Santa Clara Fire Department, for instance, is to have companies within the city limits store and use their chemicals in an appropriate manner. They must file a report with us each year - whether it's Fred's Autobody Shop or Bob's Dry Cleaners or a semiconductor fab - listing the chemicals they use at their site and providing an updated map of the facility. We use that information to help us and to help them respond to any emergencies or to any accidental release of chemicals.”
Parker says the Fire Department approaches its haz mat responsibilities from the perspective of preventing problems. “We go out every year to the businesses and inspect the facilities. We walk through and see if the chemicals are being stored properly. In the process, we inspect everyone from 'mom and pop' operations to companies as large as Intel [headquartered in Santa Clara]. With the smaller businesses, we tend to just start at one end and walk through to the other end. That way we can see any improvements that may have been made since the previous year's inspection, or see how problems have been dealt with that were revealed in previous visits.”
“When we inspect smaller companies, we're probably talking to the owner, who is often the only employee. At Intel, on the other hand, there are professional environmental safety and health personnel on board. We make appointments to visit those facilities when we can be assured that the appropriate staff members will be there, ready to answer our questions during the inspection.”
“During a visit, we read the labels on all hazardous material containers - tanks, pipes, etc. The companies are required to have appropriate labels on all containers - all etching baths, all equipment, all pipelines are required to be marked, for instance. Generally within a fab, the required chemicals are stored outside of the building or in specially designed closets or rooms. Only a small amount of the chemicals are allowed into the processing area at a time. They are piped into those areas in specially designed, acid-proof pipes that must be labeled every 20 feet to indicate their contents.”
The chemicals used for wafer etching may be reused over and over again, Parker says. He adds that the number of times a chemical is reused is driven by economic factors, not by environmental concerns. “The etching chemicals loose some potency after each use and can only be reused so many times. When the chemicals are ready to be discarded, the discharge goes through specially designed pipes into big collection tanks at the site. The acids are then neutralized and sent on through a sanitary sewage system to the sewage treatment plant, where they mix with public sewage - everything from dishwater to the output of flushed toilets.”
“At the sewage treatment plant - currently in Silicon Valley, there are sewage treatment plants in San Jose, Sunnyvale, and Palo Alto - you'll find Industrial Waste Inspectors, folks who regularly go out to chip manufacturers, printed circuit board manufactures, platers, etc., and check the discharge. They're checking to see that the pH of the discharge is appropriate and that the heavy metal content is within prescribed limits.”
city of Santa Clara.”
of the law, we definitely have a vigorous enforcement policy. There are a variety of reasons why
a company closes a facility. Often it is because the facility is in an aging building and it would be more expensive to upgrade the building and the equipment, than it would be to build a new facility elsewhere.”
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-- Peggy Aycinena, EDACafe.com Contributing Editor.
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