Synergistic Mechanism And Experimental Investigations On A Hybrid Ultraviolet Light Catalyzed And Infrared Laser Assisted Chemical Modification For Monocrystalline Silicon

To solve the edge damage and surface/sub-surface damage problems in the micro-machining for monocrystalline silicon,a synergistic chemical mechanical micro-grinding method is proposed by ultraviolet light(UV-light)catalyzed and infrared laser(IR-laser)assisted.The modification strategy is called UVIR-CM strategy.Micro-grinding of monocrystalline silicon micro-structure is used as the research object to investigate the synergistic mechanism of the UVIR-CM strategy.The micro-morphology observation,modification products,mechanical properties and micro-grinding quality were evaluated.The influence of modification pattern on the laser energy inputs and the relationship between the pattern and processing precision was investigated.The purpose is to improve the machinability of monocrystalline silicon by the synergistic chemical mechanical micro-grinding method.The research findings help to build a novel multi-energy fields assisted hybrid micro-machining technique and give a theoretical and experimental foundation for the controllable machining in the precision and performance for monocrystalline silicon micro-structures.The specific work is as follows:(1)Due to the hardness and brittleness of monocrystalline silicon,the UVIR-CM method was designed using the chemical mechanical hybrid processing for monocrystalline silicon.In order to reveal the synergistic effects of UV-light and IR-laser multi-energy fields on the improvement of liquid-solid chemical reaction efficiency between monocrystalline silicon and modification solution,a series of modification strategies with different modification procedures and different IR-laser scanning media was designed.The surface morphology,modification products,and mechanical properties of the changed layer were chosen as indicators to develop the assessment system of modification effects for monocrystalline silicon.(2)The effects of modification procedures and methods on the IR-laser scanning medium were compared.Scanning electron microscopy(SEM),transmission electron microscopy(TEM),confocal Raman microscopy and nano-indenter were utilized to examine the surface morphology,modification products and mechanical properties of the modified area,which affect the machinability of monocrystalline silicon.The evolution of surface morphology,mechanical properties and subsurface micro-structures of the modified area were summarized.The interaction between IR-laser and scanning media was discussed.The synergistic mechanism of the multi-energy fields assisted chemical strategy of photocatalysis was revealed in the chemical modification process.The experimental results show that the UVIR-CM strategy can induce a low-hardness,uniformly distributed silicate layer with a thickness of 600 nm in the modified area through the synergistic effects of photochemical,photothermal and kinetic effects,then reduce the difficulty of mechanical removal.The subsurface of modified area is composed of amorphous,nanocrystal and micro-twins.The micro-twin can inhibit the liquid-solid interaction in the depth direction while preserving the original mechanical characteristics of the substrate.(3)To assess the impacts of the UVIR-CM strategy on monocystalline silicon machinability,micro-grinding tests were designed,and the average edge damage width,micro-morphology and surface profile were used as indicators to compare the micro-grinding process quality of the modified area,the unmodified area and the interface between the two areas.The impacts of the UVIR-CM strategy on monocrystalline silicon machinability were investigated.The results show that,compared with other samples,the UVIR-CM sample greatly reduce the edge damage of the micro-groove,the bottom of the micro-groove has high processing quality and small edge damage,and the machinability of monocrystalline silicon micro-grinding is improved.(4)IR-laser scanning patterns with the same scanning area coverage and different scanning intervals were designed to regulating the duration of IR-laser scanning.The modified area of different patterns was studied by micro-groove micro-grinding.The mapping relationship between the pattern route that influenced the energy input time of the IR-laser and the quality of future micro-grinding in the modified zone was explored.The results reveal that,on the premise of ensuring the machining quality,minimizing the IR-laser scanning area is beneficial to improve processing efficiency and reducing energy consumption.The sparse pattern can improve the machining quality of the bottom of the micro-groove and the dense pattern can improve the edge and bottom contour of the micro-groove.