The effect of Ta to Si ratio on magnetron sputtered Ta-Si-N thin films

The role of composition on the resistivity and thermal stability of reactively sputtered Ta-Si-N films have been studied using x-ray diffraction, Rutherford backscattering spectrometry, and sheet resistance measurement. Films with higher silicon to tantalum ratio were found to be more thermally stable and have higher sheet resistance than films with lower Si to Ta ratio. While Ta sub(0.28)Si sub(0.07)N sub(0.65) starts to crystallize at about 900 degree C, for example, Ta sub(0.24)Si sub(0.10)N sub(0.66), and Ta sub(0.24)Si sub(0.12)N sub(0.64) remained amorphous and thermally stable for heat treatment up to 1100 degree C. In-situ sheet resistance measurement showed that the resistivity of the alloys varies with composition and decreases with temperature; films with higher Ta/Si ratio have lower resistivity. The resistivity of the films, at 30 degree C, was about 675 Omega -cm, 285 Omega -cm, and 135 Omega -cm and decreased to 61.5 Omega -cm, 22.5 Omega -cm, and 19.5 Omega -cm at 480 degree C for Ta sub(0.24)Si sub(0.12)N sub(0.64), Ta sub(0.24)Si sub(0.10)N sub(0.66), and Ta sub(0.28)Si sub(0.07)N sub(0.651) in that order. Our results indicate that the composition of Ta-Si-N films could be manipulated to obtain low resistivity films that could be used in device applications.