Argon ion etching in a reactive gas

It is shown that the sputtering yield of various materials submitted to argon ion (1 ke V) bombardment decreases strongly with increase of oxygen pressure in the atmosphere of the sputtering chamber. The sputtering yields are plotted against the “poisoning ratio” (the poisoning ratio is defined as the ratio of the rate of arrival of oxygen molecules at the target surface to that of the rate of removal of sputtered atoms). On the curves representing the sputtering yield versus the poisoning ratio, two particular values are pointed out for each material. Between these two values the sputtering yield decreases as the poisoning ratio increases, out of these values the sputtering yield is quite independent of the poisoning ratio. In the region of high poisoning ratio value, the spread of the sputtering yield for investigated materials is wider than in the region of low poisoning ratio value. Thus, we observed, in terms of etching rate, a ratio of 7 between silica and chromium and a ratio of 10 between silica and vanadium when the oxygen pressure introduced in the target chamber is 10⁻⁴ Torr. These results are used in order to obtain deep grooves in silica, when such metals are used as masking materials. New data on the sputtering yield of various materials is provided.