Residual stresses and crystalline quality of heavily boron-doped diamond films analysed by micro-Raman spectroscopy and X-ray diffraction

Abstract

X-ray diffraction analysis and micro-Raman spectroscopy measurements have been used for stress studies on HFCVD diamond films with different levels of boron doping. The boron incorporation in the film varied in the range 10 18–10 21 boron/cm 3. The grain size, obtained from SEM images, showed grains with 2–4-μm average size, which decreases when the doping level increases. The thickness of the films obtained by SEM cross-section view decreased from 8 to 5 μm as the doping level increased from 0 (undoped film) to 10 21 boron/cm 3. The total residual stress was determined by measuring, for each sample, the (331) diamond Bragg diffraction peak for Ψ-values ranging from −60° to +60°, and applying the sin 2 ψ method. For the micro-Raman spectroscopy the spectral analysis performed on each sample allowed the determination of the residual stress, from the diamond Raman peak shifts, and also the diamond purity, which decreases from 99 to 75% as the doping level increases. The type and magnitude of the residual stress obtained from X-ray and micro-Raman measurements agreed well only for undoped film, disagreeing when the doping level increased. We attributed this discrepancy to the domain size characteristic of each technique.