Improvement mechanism of brittle-plastic transition and residual stress in scratching 4H–SiC implanted by hydrogen ions

Abstract

This paper aims to improve the machining efficiency of silicon carbide (SiC), reduce residual surface stress, inhibit surface cracks, and reduce surface damage. Single-point diamond scratch experiments were performed on SiC samples after hydrogen ions implantation to study the macro-scale machining performance. The improvement mechanism by which ion implantation reduces surface cracks and machining defects in 4H–SiC samples under different loading forces was comparatively studied. Scale-like cracks and brittle fracture fragments in the scratched area of the ion-implanted samples were reduced significantly. Acoustic emission sensors were used to detect the acoustic signal of brittle fracture. The lower intensity of the acoustic emission signal in the ion-implanted sample indicates that less brittle fracture was generated during scratching. Variation of the contour line in the scratch area with loading force was measured using laser scanning confocal microscopy. The depths of the smooth contours in the scratched area of the samples without and with ion implantation were 96 nm and 360 nm, respectively. The scratch area was scanned by a Raman spectrometer to quantitatively study the effect of ion implantation on micro-level defects. Formulas illustrating the relationship between residual stresses and Raman shift displacement were derived by integrating Raman shift and a secular equation. The results show a reduction in defects at microscale, an enhancement of machinability, and a reduction in residual stresses on the surface of the ion-implanted sample. Ion implantation assisted machining technology can effectively improve the machining quality and efficiency of SiC wafers.