Method for opening contacts of different depths in a semiconductor wafer

Abstract

A method for opening contacts of different depths in a semiconductor wafer after salicide processing. A sacrificial layer is formed over the wafer wherein the wafer further includes a first silicide layer and a second silicide layer formed thereon. The sacrificial layer is selectively removed such that only a portion of the sacrificial layer remains on the first silicide layer. An interlayer dielectric layer is formed over the wafer. The interlayer dielectric layer is planed. Contact windows are patterned. Contacts are opened to reveal the first silicide layer and the second silicide layer as contacts wherein the position where the first silicide layer is formed is higher than that where the second silicide layer is formed. Further, the thickness Y of the sacrificial layer is determined according to the following relation: Y=.DELTA.X.times.R.sub.SAC /(R.sub.ILD -R.sub.SAC), wherein .DELTA.X is the height difference between the first silicide layer and the second silicide layer, and R.sub.SAC and R.sub.ILD are the etching rates of the sacrificial layer and the interlayer dielectric layer while being etched by the same etching matter respectively. Using the sacrificial layer prevents the contacts of shallower depths from being over etched and consequently the resistance of contacts in the shallower windows will not be increased abnormally due to being over etched.

Dependencies are inferred from the claim text.