Patent ID: 6938340

Claim:
A method of forming a printhead comprising: providing a silicon-on-insulator (SOI) substrate comprising a first silicon layer, a thinner second silicon layer, and an oxide layer between said first silicon layer and said second silicon layer; forming a plurality of thin film layers on a first surface of said substrate, at least one of said layers forming a plurality of ink ejection elements; forming ink feed holes through said thin film layers; and forming at least one opening in said substrate by (a) etching said first silicon layer of said SOI substrate using a wet etch to etch a trench in said first silicon layer extending to said oxide layer; (b) etching at least one opening in said oxide layer; and (c) etching at least one opening in said second silicon layer to form an ink path between a backside of said SOI substrate and a topside of said SOI substrate to provide an ink path from a second surface of said substrate, through said substrate, and to said ink feed holes formed in said thin film layers, wherein said plurality of ink ejection elements reside over said first silicon layer.