Single-mask dual damascene processes by using phase-shifting mask

Abstract

A simplified method is disclosed for forming dual damascene patterns using a phase-shifting mask in conjunction with a single photoresist process. First, a method is descried for fabricating a phase-shifting metal mask formed on a quartz substrate having opaque, transparent and semi-light-transmitting regions. The transparent regions comprise hole pattern while the semi-transmitting regions comprise line pattern for a dual damascene pattern. Then it is shown how the phase-shifting mask is used to form a dual damascene structure by forming a single photoresist on a silicon substrate having a tri-layer insulating layer, forming the hole and line patterns on the photoresist simultaneously by exposing it through the phase-shifting mask, and then transferring the patterns successively into the top and bottom layers of the insulating layer by etching. Having thus formed the vertical hole interconnect and line trench into the insulating layer, metal is deposited into the dual damascene structure. Any excess metal on the surface of the insulating layer is then removed by any number of ways including chemical-mechanical polishing, thereby planarizing the surface and readying it for the next semiconductor process.