Patent ID: 7569483

Claim:
A method of forming a nickel silicide layer, comprising: positioning a wafer between an upper hot plate and a lower hot plate in a heating apparatus containing a heat transferring gas therein, wherein a spacing between the upper hot plate and an upper surface of the wafer is equal to or greater than twice a thickness of the wafer and the lower hot plate and a bottom surface of the wafer are spaced apart a distance equal to or greater than twice the thickness of the wafer by a plurality of quartz supports disposed on the lower hot plate, the wafer including: a doped silicon layer on a substrate; a nickel layer on the doped silicon layer; and a titanium nitride layer on the nickel layer; performing a first convective heating step at a first temperature in a range from 200° C. to 400° C., to thereby heat the wafer and convert a first portion of the nickel layer into a nickel silicide layer while a second portion of the nickel layer remains; unloading the wafer from the heating apparatus; then removing the titanium nitride layer and the second portion of the nickel layer, outside the heating apparatus; then repositioning the wafer between the upper hot plate and the lower hot plate in the heating apparatus; and performing a second heating step at a second temperature in a range from 300° C. to 600° C., to thereby convert the first nickel silicide layer into a second nickel silicide layer having a different nickel-to-silicon ratio therein relative to the first nickel silicide layer, wherein the first temperature and the second temperature are the same as temperatures of the upper and lower hot plates, times to reach the first temperature and the second temperature from the upper and lower plates to the wafer are more than one minute, and fluctuations in the first and second temperatures are controlled to be less than 5° C. during the first convective heating step and the second heating step, respectively.