SCORR one for the environment.

The fabrication of integrated circuits relies on a process known as photolithography, in which a photoreactive polymer, or pho-toresist, is applied to the surface of a silicon wafer. Integrated circuit manufacturers rely on photolithography to create the desired features in each layer of chip circuitry. The process requires the selective removal of hardened coatings (resists) from a wafer, leaving the intricate circuitry intact. The photoresist is hardened by exposure to light and then goes through several fabrication steps that uncover well-defined regions of the wafer surface and harden that surface to withstand subsequent fabrication steps. The photoresist is intended to develop the pattern of the particular circuitry being built as the wafer is etched around it and the mask is then removed. The process could be roughly compared to putting a patterned doily on top of a cake, then dusting it with powdered sugar. When you remove the doily, the pattern is left. It's very much the same in wafer fabrication, but the " doily " is much harder to remove. The exact makeup of the photoresist is proprietary information and varies from company to company. Generally, though, photoresists are made up of such ingredients as propylene glycol methyl ether acetate (a solvent), novolac (a phe-nol–formaldehyde resin), and diazonaph-thoquinone (a sensitizer). The problem for the industry lies in the removal of the photoresist. According to Craig Taylor, the principal investigator on a new photoresist removal technology at Los Alamos National Laboratory, the industry currently uses one of three general categories of photoresist removal technologies: aqueous-based acidic or alkaline solutions , nonaqueous organic solvents (usually containing some fraction of halogenated or polycyclic aromatic hydrocarbons), or radio-frequency plasmas of reactive species such as oxygen or fluorine. After one of these treatments, the chips are washed with highly purified water and then additionally processed with isopropyl alcohol to dry the chip's surface. On an average day of operation at a standard chip-making plant, millions of gallons of contaminated waste-water are produced. In addition, as semiconductor chips get smaller and smaller, yet are expected to hold more information and work faster, it becomes even more vital to be able to remove the tiniest particles from the wafer surface. Taylor says that with the sizes of features—or portions of the integrated circuit being constructed— measuring less than 0.13 µm, it will be imperative to remove all particles .10 µm and greater in size. Innovations L …