Quantitative Characterization of Surface and Subsurface Topography of An Optical Nano-Film/Substrate Using Scanning Probe Acoustic Microscopy

Using Scanning Probe Acoustic Microscopy (SPAM), we characterize the surface and subsurface topography of a nano HfO2 film on SiO2 substrate quantitatively. Surface topography shows that the roughness of the film’s surface is less than 3 nm, while the acoustic image of Sample Vibration Mode (SVM) shows that there are dozens of random lines at the film’s subsurface, which might be scratches from the polishing procedure. We also find that the detection depth of SPAM is sensitive to the frequency. After laser irradiation, the depth of laser-damaged hole in the film seems close to its thickness. Residual stress within film due to heat absorption is observed using a higher frequency. The phase images of Probe-Vibration Mode (PVM) show that the hydrophilicity of the damaged area seems higher than the undamaged area. This leads to stronger water vapor absorption in the air.