Traditionally, the primary customer base for photomasks has been the semiconductor industry. Today, the photomask industry has grown to include large area masks up to 2 meters in size. For the semiconductor industry, each design required a set of patterns to be imaged and transferred onto silicon wafers. These wafers would eventually become chips used in a variety of end-products, from automotive to telecommunications to computers. Chrome-on-glass (COG) photomasks have been the principal medium for pattern transfer. Other mask types include MOSI, and some include a pellicle layer. Utilizing a complementary set of electron beam and laser beam writing equipment, lithography engineers innovated processing technology capable of delivering everything from simple rectilinear patterns to intricate, sub-resolution optical proximity correction (OPC) features. Next, circuit designers began incorporating phase shift mask (PSM) techniques into their device lithographic strategies. The industry responded by developing and integrating the process by which the COG Manufacturing Lines in its select 'high end' facilities could build PSMs.
Many other industries depended on photomasks for their device patterns as well: thin film heads, large area masks, micro-electromechanical systems (MEMS), waveguides, metrology & characterization standards, and more. However, these markets, even combined, were not as large as the semiconductor industry.
After photomasks are used repeatedly for transferring images to wafer substrates they can become damaged. Typically the damage is a broken or missing part of a circuit, or an area where the COG has migrated to the point of causing a potential problem. Both of these problems cause a photomask to become un-usable and in need of repair. This is where Controlled Semiconductor, Inc. takes over with the MRT Series of photomask repair tools.