Such etch-resistant materials may include metals such as lead or platinum and semiconductors such as silicon, deposited by, for example, PECVD. Other materials which may be suitable are polymers such as polyethylene, polypropylene, polymethylpentene (PMP), and photo-patternable polymers such as SU8 developed by IBM Corporation of Armonk, N.Y. The thickness of the layer 3065 may be about 0.25 ??m o