Argon in concentrations up to has been found in after backsputter cleaning with 150V Ar+ ions in a low voltage triode sputtering apparatus. The argon has been detected directly by Rutherford backscattering analysis with 2 MeV He+ ions. The highest argon content was found in a sample subjected to 2 min of backsputtering at a rate of about 50 å/min. Immediately after this backsputtering, 2000å of tungsten was sputter deposited. During a subsequent vacuum anneal at 850° C for 20 min, bubbles about 10 μm in diameter appeared under the tungsten metallization. The bubbles apparently were caused by internal pressure resulting from the outdiffusion of the entrapped argon. Surface contamination of the backsputtered by W, Cu, and Fe was also detected. This was evidently caused by redeposition of sputtered material from adjacent parts of the sputtering apparatus since these elements increased steadily in concentration with backsputtering time. The maximum contamination of 8(10)14 copper atoms per cm−2 after 10 min is nearly a monolayer. Annealing experiments established that 20 min at 600°C was sufficient to reduce the argon level to near or below detection limits in both backsputtered Si and .