The thickness measurement of silicided films is a metrology challenge, due to the complexity of the metal and silicon reactions. It can lead either to non-homogeneous layers with incomplete phase transformation, or to complete silicidation that gives rise to significant surface roughness. Nickel Silicide (NiSi) is emerging as the choice material for contacting the transistors for the 65nm technology node and beyond. Jordan Valley's fast XRR technology gives thickness, density and roughness information of silicided films to control this critical front end of line process.
Variation of the density of the top Ni2Si layer after spike annealing at temperatures between 310°C and 450°C (top right). Schematic drawing of the cross-section of the nickel silicide film showing the occurrence of the Ni2Si and NiSi phases at different annealing temperatures (bottom right).
By measuring the silicide's density using the JVX series of systems, the anneal process can be optimized to achieve the desired silicide formation.
NiSi thicknesses can be quite different in n and p channels at the same anneal temperatures.
At low and high end of anneal temperatures, they react similarly. However, at intermediate temperatures, the thicknesses of NiSi in different channels can be quite different.
With the JVX XRR channel, the thickness and density of the Ni and NiSi layers can be measured to control the silicidation process.