Measuring plastic yield stress of magnetron sputtered aluminum thin film by nanoindentation

• We promoted the utilization of theoretical model about the spherical indentation behavior at onset of the film's yielding.
• We extracted the plastic yield stress of aluminum thin film from nanoindention data utilizing least squares fitting method.
• FEM simulation verified the curve fitting process.
• We explored the limitations of this method and the potential difficulties in the application of this method.

Experimental determination of plastic properties of thin films with considerable residual stress is always a challenging task. A simple experimental technique is presented for measuring yield stress of aluminum (Al) thin film with residual stress by combining the curvature test with sphere-tip nanoindentation test. Both curvature and nanoindentation tests are carried out on an Al film/Si substrate system. A least square regression fitted equation is proposed and related to residual stress. The residual stress is measured to be 115 MPa (tensile) using curvature test, and the yield stress of Al films sputtered on the Si substrates is calculated to be 371 MPa using the new fitted equation. This method can also be used to study the plastic properties of other thin films or small volume materials.