Intelligent process control of indium tin oxide sputter deposition using optical emission spectroscopy

The dc sputtering of indium tin oxide (ITO) is a high deposition rate proce ss yielding a low-resistivity, high-transmission thin film that is useful t o the display, photovoltaics, and optoelectronics industries. However, a nu mber of deposition variables that are not typically controlled during sputt ering, such as target age and history, and water partial pressure, can caus e ITO film properties to deviate from their optimum values. Control of such deviations is necessary to maintain high yield and low costs in manufactur ing. Optical emission spectroscopy (OES) can be used to monitor the deposit ion process and maintain optimum him properties. Basic relationships betwee n the OES signals during deposition and the ITO film properties were establ ished. Closed-loop control of the ITO deposition was implemented using OES. Improved yield-specifically, decreased resistivity, decreased variance in resistivity, and decreased variance in thickness - was demonstrated. (C) 19 99 American Vacuum Society. [S0734-2101(99)01401-3].