A hybrid chemical modification strategy for monocrystalline silicon micro-grinding: Experimental investigation and synergistic mechanism

For high performance manufacturing of micro parts and features, a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition. The strategy, namely UV -light and IR-laser hybrid chemical modification (UVIR-CM) strategy, includes two steps, an ultra-violet light (UV-light) catalytic advanced oxidation and an infrared laser (IR-laser) assisted selective modification based on Fenton liquid-solid reaction for monocrystalline silicon. The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation, cross-section transmission electron microscopy (TEM) observation, Raman spectroscopy analysis and nanoindentation test. Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples' IR-laser scanned area. And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium. But for the UVIR-CM strategy, a uniform and amorphous silicate layer is detected in a certain boundary. The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step. Attributing to synergism of photochem-ical, photothermal and kinetic effects induced by IR-laser, the modified layer displays layered struc-ture with about 600 nm thickness, (2.7 & PLUSMN; 0.60) GPa nanohardness, and (93.7 & PLUSMN; 22.9) GPa indentation modulus. And the layered structure is amorphous layer, nanocrystal and micro-twins layer from the surface to the interior of sample. Consequently, it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area. Meanwhile, its original excellent mechanical properties also are maintained under a certain depth. The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.& COPY; 2022 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Automated summary

A hybrid chemical modification strategy that combines UV-light and IR-laser is proposed to decrease the energy barrier for the mechanical removal of hard and brittle crystal materials in high performance manufacturing of micro parts. The strategy includes UV-light catalytic oxidation and IR-laser assisted selective modification. The modified layer formed by the UVIR-CM strategy exhibits a layered structure with good mechanical properties and facilitates subsequent mechanical removal. Experimental results demonstrate the effectiveness of the strategy in achieving collaborative manufacturing of structure shape and surface integrity for micro parts and features.