Report from saa seess Thin films: faster by computer Arthur G. Gross and Harry M. Kalish of Bell Telephone Laboratories have developed a computer program whose end product is a set of correctly sized photographic ‘‘masks’' for making prototype thin-film networks. The masks control the deposition and shapes of various widths and thicknesses of conductive, resistive, and dielectric materials that make up such circuits. (These frequently begin as tantalum, deposited onto a glass or ceramic substrate and chemically treated to produce desired electrical properties.) Controlled by the new program, a computer feeds a precision microfilm plotter which prints the masks on 35mm film (photo above). With this system, a prototype can be ready in a day, as against the weeks that may be involved in making high- precision masks for volume circuit production. Usually, for example, a drattsman must make rough sketches and prepare a list of numbers (coordinate points) accurately describing the geometry of the final circuit. Then the actual shapes—greatly enlarged—are cut into plastic sheets on a ‘‘coordinatograph.” Later, the plastic patterns are photographically reduced to circuitsized masks, perhaps % by 1 inch. In addition to reducing time and handling, Bell Laboratories’ new program relieves the engineer of — another tedious job: designing the meandering lines that constitute resistors in these An experimental thin-film filter network —in actual size—made from 35mm film masks. In the top photo,A. G. Gross (left) and H. M. Kalish hold three of the masks used. Each mask controls the formation of a layer of conductive, resistive, or dielectric material. The circuit is built up of a number of such layers. [_ -— circuits. And the computer fesetéa resistors are ‘‘optimized” ... fitted into the smallest possible area. To give the engineer freedom to use irregular plane shapes, the program inciudes a subroutine which closely approximates geometric figures used in making thin-film circuits. a) Bell Telephonetabiatoties ° Research and Develofmhent tinit of the Bell System we?