Encoding of read only memory by laser vaporization

Claim 1

A method for producing a read-only memory by beam-lead technology comprising the steps of: forming a plurality of memory cells in a silicon substrate; forming metal conductors extending to each memory cell comprising the steps of first, forming an insulative layer of silicon dioxide of a major part of the substrate, second, forming a thin layer of titanium on the insulative layer, third, forming a thin layer of platinum on the titanium layer, and fourth, forming over the platinum layer a layer of gold that is relatively thick with respeCt to the platinum and titanium layers, thereby to provide structural support in accordance with the principles of beam-lead technology; forming a window in the gold portion of each conductor, thereby to expose a platinum-titanium bridge conductor in each conductor; and coding the read-only memory comprising the step of vaporizing selected platinum-titanium bridge conductors by directing a focused laser beam upon said selected conductors, the intensity of said focused beam being sufficiently high to vaporize the platinum-titanium bridge conductor, but being insufficiently high to vaporize the gold portion or to damage the silicon substrate.