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激光微加工是半导体精密加工的一个有效方法。对于碳化硅(SiC)单晶,使用紫外波段激光可以获得对入射能量最大的吸收效率。使用355nm全固态激光器对6H-SiC单晶进行刻蚀。同时将样品置于不同的介质下以探究最优加工条件。使用拉曼光谱表征激光刻蚀后的SiC表面。刻蚀后表面主要由无定形硅及纳米晶石墨组成,对于空气下刻蚀的SiC晶片,无定形硅主要分布于刻蚀坑的周围,刻蚀坑内较少。而在液体下刻蚀的样品,无定形硅的空间分布相反。通过分析残留在表面的物质,在另一角度研究了激光刻蚀的反应机理。对于液体辅助的激光加工,以往的研究主要关注液层的厚度及粘度,对液体还原性的研究很少。为确定液体还原性的影响,使用共聚焦激光扫描显微镜及能量色散谱检测了不同液体辅助加工样品的表面形貌及氧含量。结果表明,液体还原性在激光刻蚀过程中有着较大的影响,使用有着还原性的液体作为介质可以有效减少表面氧化并获得更规则的表面形貌。
Laser micromachining is an efficient method of semiconductor precision machining. For silicon carbide (SiC) single crystals, the absorption efficiency of the incident energy is maximized using the ultraviolet laser band. The 6H-SiC single crystal is etched using a 355 nm all-solid-state laser. At the same time the sample is placed under different media to explore the optimal processing conditions. Raman spectroscopy was used to characterize the laser etched SiC surface. The etched surface is mainly composed of amorphous silicon and nanocrystalline graphite. For SiC wafers etched under air, amorphous silicon is mainly distributed around the etching pit and less in the etching pit. In the samples etched under liquid, amorphous silicon had the opposite spatial distribution. By analyzing the material remaining on the surface, the mechanism of laser etching reaction is studied from another perspective. For liquid-assisted laser processing, previous studies mainly focused on the thickness and viscosity of the liquid layer, and little research on the liquid reducibility. To determine the effect of liquid reducibility, confocal laser scanning microscopy and energy dispersive spectroscopy were used to examine the surface morphology and oxygen content of different liquid-assisted machining samples. The results show that the liquid reducibility has a great influence on the laser etching process. Using a reductive liquid as a medium can effectively reduce surface oxidation and obtain more regular surface topography.