High‐rate sputtering of aluminum for metallization of integrated circuits

Films of pure aluminum and alloys were deposited using planar magnetron sources in a load‐locked system with linear substrate motion. The influence on aluminum film properties due to the effects of sputtering gas pressure, source‐to‐substrate distance, deposition angle, substrate temperature, background gas level, and substrate‐temperature rise during deposition was studied for silicon wafers and other substrates. Substrate‐temperature rise during deposition was found to be a limiting factor in obtaining smooth, highly reflecting films. Ways to circumvent this limit will be discussed. They are the use of side shields to eliminate low‐angle deposition, reducing the nitrogen partial pressure, increasing the sputtering pressure, and deposition of the film in two or more passes over a source. High‐rate sputtering deposition and its effects on film and device properties are discussed. Radiation damage, which was minimal, was removed by annealing in forming gas at 425°C for 5 min. Step coverage of films deposited at ambient and at 300°C substrate temperature is also discussed.