Direct-current-magnetron deposition of molybdenum and tungsten with rf-substrate bias

It has recently been shown that the stress of many refractory thin films deposited by dc-magnetron sputtering can be influenced by the sputtering pressure. Usually the transition from compressive to tensile stress is too sharp for pressure to be a reliable variable for stress control. This is particularly true in applications such as x-ray optics and lithography where extremely low stress is required owing to minimal substrate rigidity. In this paper, we show that there exists a broad region of the parameter space of current, pressure, and rf-substrate bias where tungsten and molybdenum may be deposited with low stress. A detailed study of the effects of these parameters upon stress, plasma etch rate, and resistivity is reported