42    ELECTROCHEMICAL FLUORIDE REMOVAL IN
SEMICONDUCTOR WASTEWATER
Susan L. Cook, Environmental Engineer
Standard Microsystems Corporation
Hauppauge, New York 11788
Kevin D. Uhrich, Chief Process Engineer
Andco Environmental Processes, Inc.
Amherst, New York 14150
INTRODUCTION
Standard Microsystems Corporation (SMC) is a microelectronics manufacturing company involved
in the design, development, manufacture and sales of various integrated circuits and board level
products. The company's products are used in small business and personal computers, as well as in
data communications, computer terminals, and other peripheral equipment and telecommunications
equipment. In addition, the company manufacturers a wide variety of digital logic devices for industrial and commercial applications.
The fabrication of microelectronic devices is a highly sophisticated industry which employs
repeated photolithographic masking, etching and oxidation processes, high temperature diffusion
methods, ion implantation techniques and metal deposition under high vacuum. Up to one million
electrical components are constructed in this fashion per square centimeter.
The manufacturing environment is strictly controlled for temperature, humidity, and particulate
contamination. Wafer surfaces must be kept clean from ionic deposits, as well as particulate matter.
Ultrapure chemicals are used in the process and ultrapure water is required to rinse impurities from
the wafer surface. A sophisticated water purification system is employed to provide this supply of
ultrapure DI water. Some of the DI water specifications are: resistivity > 17.8 Megohm-cm, total
organic carbon of < 20 /»g/L, and total bacterial count of < 10 colony forming units per 100 mL.
Process solutions of ultrapure inorganic acids, semiconductor or electronic grade only, (with impurity levels in the microgram per liter range) are used for cleaning and etching the wafer surfaces. The
rinse waters from these processes are a major source of wastewater in the manufacturing process.
Other wastewater sources include the regeneration water from ion exchange operations and spent DI
water (resistivity < 0.5 Megohm-cm). These sources will be discussed in further detail in a later
section.
REGULATORY BACKGROUND
Standard Microsystems Corporation is located in Suffolk County, New York, an area of Long
Island served by a public water supply which relies on a sole source groundwater aquifer. New York
State has also maintained groundwater quality standards which typically dictate discharge standards
for industrial and municipal effluents requiring groundwater disposal. SMC's SPDES permit reflects
the groundwater standards for the state and are much more stringent than the pretreatment standards
required by semiconductor industries served by municipal sewers. Table I compares SMC's SPDES
permit limits with the pretreatment standards for the electrical and electronic industry category.
SMC was issued a SPDES permit in 1981 with effluent limits listed in Table I. By 1984, the NYS
Department of Environmental Conservation (DEC) issued an order of consent to SMC for compliance with its SPDES permit. At that time SMC had installed alumina columns and lime precipitation
for fluoride removal and pH control. It was clear, however, that this technology was not successful in
attaining the permit limits. By 1986, after SMC had unsuccessfully redesigned the alumina columns,
DEC informed SMC that either a permit variance or a consent order continuance had to be
requested.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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