Considerations on high resolution patterns engraved by ion etching

The theoretical model of a surface contour evolution under ion bombardment is applied to the study of the behavior of a mask during ion etching. Two new parameters are defined. The first gives an upper limit of the etching time when distortion-free patterns are needed. The second gives the lateral shift of the pattern if the previous limit is exceeded. Values of mask parameters were measured for various thin metal films under the following conditions: 1) Argon ion energy = 1 keV, 2) ion current density = 0.6 mA/cm², and 3) oxygen pressure in the sputtering chamber = 10^-4torr. It is shown that the introduction of oxygen improves the mask parameters.