Method of making and laterally filling key hole structure for ultra fine pitch conductor lines

Claim 1

A method of laterally depositing metal into a trench positioned under an overhang, said trench being formed on a substrate of a semiconductor integrated circuit chip, the method comprising the steps of: depositing on said substrate a first insulating layer followed by a second insulating layer, said first and second insulating layers being of a different chemistry; defining an interconnect line pattern having a predetermined width; reactive ion-etching said second insulating layer; reactive ion-etching said first insulating layer at a pressure of at least 35 μm, followed by a wet chemical etch; forming an undercut equivalent to about one-third of said predetermined width at each edge of said trench; depositing on said substrate a conductive material layer with a thickness exceeding the depth of said trench, while maintaining said substrate at a temperature below 80° C., filling said trench with said conductive material leaving voids under said overhang; depositing a non-conductive layer on said conductive material layer while maintaining said substrate at approximately 400° C., said non-conductive layer placing said conductive material layer under compressive stress; heating for at least one hour said substrate in an inert atmosphere, at a temperature above 450° C.; and removing an excess of said conductive material outside of said trench, the combination of said heating and said compressive stress inducing said conductive material in said trench to micro-creep into said voids.

Claim 2

A method of laterally depositing metal into a trench positioned under an overhang, said trench being formed on a substrate of a semiconductor integrated circuit chip, the method comprising the steps of: depositing on said substrate a first insulating layer followed by a second insulating layer, said first and second insulating layers being of a different chemistry; defining an interconnect line pattern having a predetermined width; reactive ion-etching said second insulating layer; reactive ion-etching said first insulating layer at a pressure of at least 35 μm, followed by a wet chemical etch; forming an undercut equivalent to about one-third of said predetermined width at each edge of said trench; depositing on said substrate a conductive material layer with a thickness exceeding the depth of said trench, while maintaining said substrate at a temperature below 80° C., filling said trench with said conductive material leaving voids under said overhang; depositing a non-conductive layer on said conductive material layer while maintaining said substrate at approximately 400° C., said non-conductive layer placing said conductive material layer under compressive stress; heating for at least one hour said substrate in an inert atmosphere, at a temperature above 450° C.; and removing an excess of said conductive material outside of said trench, the combination of said heating and said compressive stress inducing said conductive material in said trench to micro-creep into said voids.