Method for forming a contact opening with multilevel etching

摘要

A multilevel contact etching method to form a contact opening is provided. The method contains using an inductively coupled plasma (ICP) etcher to produce a high plasma density condition. The plasma gas etchant is composed of C4F8/CH2F2/CO/Ar with a ratio of 3:4:12:80 so that silicon nitride can be selectively etched while the silicon and silicide are not etched. Each content ratio of the plasma gas etchant allows a variance of about 20%. Wall temperature of the ICP etcher is about 100 DEG C.-300 DEG C. A cooling system for a wafer pad is about -20 DEG C.-20 DEG C. Chamber pressure is about 5-100 mtorr. Bias power on the wafer pad is about 1000 W-3000 W. Source power of an inductance coil is about 500 W-3000 W.