ABSTRACT
The semiconductor industry is an important component of the electronics industry, whose global market yield has already exceeded that of the automobile industry. Anisotropic chemical wet etching is widely used in the semiconductor industry to fabricate microstructures on single crystal silicon wafers [1]. Of all the anisotropic etchants, the inorganic KOH (potassium hydroxide) and organic TMAH (tetramethyl ammonium hydroxide) solutions are the most commonly used [1, 2]. Moreover, TMAH solution has also attracted attention because it is clean room compatible, nontoxic, and easy to handle. It also exhibits excellent selectivity to silicon oxide and silicon nitride masks [3, 4]. It has been estimated that, for an 8 in
wafer manufacturing facility with a monthly production of 20,000 wafer units, TMAH is by far the most concentrated chemical in wastewater [5]. Biological processes are the most widely accepted treatment for organic wastewater of both domestic and industrial origins; however, available information on the biodegradability of TMAH is scarce. Chemical oxidation involving various forms of advanced oxidation processes (AOPs) can be employed as preliminary treatment to convert the potentially biorefractory compounds into intermediate products that are more amenable to biodegradation [6].
