Testing of thickness homogeneity of Si crystal membranes using GaAs Timepix detector

Abstract

Silicon (Si) membranes were prepared using high precision advance nanomachining technology utilizing single point diamond turning (SPDT). We showed that SPDT allowed to produce membranes with a surface undulation down to 500 nm over diameter of 7800 μm which corresponds to a high accuracy of the surface profile. We used X-ray digital radiography based on absorption contrast for a non-destructive measurement of the thickness distribution within a thin Si crystal membrane. The semi-insulating Gallium Arsenide (SI GaAs) pixel detector bump-bonded to the Timepix readout chip was used as a highly efficient single photon counting X-ray imaging detector. Comparison of thickness values obtained by the SI GaAs Timepix detector with values obtained with a surface stand-type micrometer gauge showed comparable results and the thickness variation within the membrane was clearly detected with a standard deviation down to 8.4 μm. The thickness resolution down to 5 μm over distances of 4–8 mm was achieved in selected areas of the sample.