Single crystal silicon: surface evolution regularity of chemical etching and effect of nano jet polishing on damage precursor

Single crystal silicon is a chemically active semiconductor material with good processing characteristics. With the development of technology, the role of single crystal silicon components in the field of ICF is becoming more and more important. Restricted by traditional processing method and MRF, damage precursors such as scratches and impurities still remain on the surface after processing. That may influence the performance of the elements. In this paper, we study the effect on the surface by two chemical etching methods and the influence on the damage precursors of nano jet polishing. We used HF solution/HNO₃ and KOH/ isopropanol to etch the surface of the element. When the etching depth comes to 0.2 μm, pits and scratches could be easily found on the surface. After the etching process, the element was processed by nano jet polishing and the roughness decreased from 1.264nm to 0.986nm.We used nano jet polishing method to process the element polished by MRF in order to research the evolution of comet-tail scratch. The In-situ tracking method was also applied in this study. After the polishing process, the W-D (width to depth ratio) increased from 30.51 to 45.84. The scratch was deactivated and the PTA (photothermal absorption) decreased from 1.5413nA to 1.3500nA. The Ce impurities were also removed. Its concentration decreased from 0.1162mg/L to 0.0005mg/L and the PTA of the element decreased from 0.3044nA to 0.0652nA. From the research, we can easily know that the subsurface damage exposed after the etching process. That may lay the foundation of the nondestructive processing of single crystal silicon. After nano jet polishing process, the quality of the element became better. The roughness and concentration of Ce impurities decreased. The damage precursors were deactivated and the PTA decreased. In a word, chemical etching could expose the surface damage of single crystal silicon and nano jet polishing can improve the laser damage resistance.