Stress control of sputtered W film using W/WN multilayer

• Pasting layers for W sputtering are optimized for enhancement of productivity.
• Decreasing of the Ar flow results in increase of the residual stress of pasting layer.
• Increasing of N2 flow results in decrease of the residual stress of pasting layer.
• Reduction of particle generation of 21% and suppression of outliers could be obtained.
• Film stress control is effective for improving good semiconductor productivity.

For the purpose of enhancement of productivity by reducing opportunity of preventive maintenance, it is very important to form a tungsten and tungsten-nitride pasting layer onto the chamber wall inside a tungsten sputter deposition system. In this study, looking for the optimum usage condition of reactive sputter facility, we controlled the stress levels of both of W and WN films by utilization of change of gas composition and operating pressure. The stress of W film was changed from tensile to compressive with decreasing the working pressure during deposition. And the WN film showed compressive stress, which follows a linear behavior by increasing N2/Ar ratio. Sputter deposited tungsten film applied to the metal gate often showed high tensile stress of ~ 2000 MPa. Based on an experimental data, we found that stacked W/WN films with various stress levels could be steadfastly built-up and stability of adhesions of these films was quantitatively measured by scratch tester. From this adhesion test, it was observed that the optimized W/WN multilayer stack could be persistently maintained by compensating the tensile stress of W layer, which suppresses the delamination of films. Based on the above experimentally observed facts, we could suppress the particle generation resulting in chamber contamination, and thus improve productivity by elongating the period of non-stopping use of process chamber.