SPUTTERING TECHNIQUE FOR COATING INSIDE WALLS OF THROUGH-HOLES IN SUBSTRATES

By sputter-etching a substrate with through-holes while the substrate rests on a sputtering target, material from the target coats the inside walls of the through-holes without appreciably coating the plane surfaces. The deposition rate is greatest when the sputtering voltage is low ( less than 1 kV), and the pressure- and target-sputtering yield are high. The rate is nearly independent of the hole aspect ratio (ratio of diameter to depth) for ratios greater than 0. 3, but decreases rapidly for smaller ratios. The uniformity of the films thus deposited depends mainly on the smoothness of the through-hole walls.