Method of implanting during manufacture of ROM device

Claim 1

An improved method of manufacturing a Read Only Memory device with an array of cells comprising: a) forming a plurality of spaced line regions with a first P or N impurity type in and adjacent to the surface of a semiconductor substrate having a background impurity type, b) forming an insulating layer on the surface of said substrate, c) forming a plurality of spaced, parallel, electrically conductive word lines on said insulating layer arranged orthogonally relative to said line regions, d) forming a glass insulating layer comprising an undopad glass sublayer having a thickness of about 1,000 Å over said conductive lines, followed by forming a of doped glass overlayer over said undopad glass sublayer, said overlayer having a thickness between about 1,000 Å and about 2,000 Å, e) reflowing said glass insulating layer at a temperature of about 900° C. to planarize said glass sublayer and said glass overlayer reducing the thickness of said overlayer with said overlayer and said sublayer having a combined thickness of about 2500 Å over said word lines, f) forming contacts, g) forming a metal layer and a titanium nitride layer on said glass insulating layer, h) depositing a resist layer on said metal layer, i) exposing said resist layer with a metal pattern, etching said metal layer and said glass overlayer through said resist layer to form patterned metal leaving behind said glass underlayer with a range of thickness of said glass underlayer with a thickness between about 500 Å and about 1,500 Å and then removing said resist layer, j) depositing a second resist layer onto said device, and exposing said second resist layer with an ion implantation pattern, k) developing said second resist layer into a mask, l) implanting impurity ions into said substrate adjacent to said conductive lines through said openings in said second mask, m) removing said second resist layer, n) passivating said device, and o) activating said implanted impurity ions by annealing said device at a temperature between about 400° C. and about 520° C. in a gas atmosphere, whereby the metallurgy and the electrical contacts to the substrate, line regions and conductor lines are protected from adverse effect during annealing.