6H-SiC单晶的激光刻蚀及光谱分析

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355 nm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 Ablation of 6H-SiC Single Crystals and Spectral Characterization

Laser micromachining has proven to be a useful tool for precision processing of semiconductors .For Silicon Carbide (SiC) single crystals ,ablation with ultraviolet wavelength laser could lead to the maximum absorption efficiency of incident energy . In this paper , laser ablations were performed on 6H‐SiC single crystals through a 355 nm solid state laser .Different confining media were also employed to find the optimal processing condition .The surface of SiC after laser ablation was characterized by Raman spectroscopy .Amor‐phous silicon and nanocrystalline graphite were found to be the main compositions left .For SiC wafers ablation in air ,the amorphous silicon exhibited mainly around rather than inside the ablated crater .However ,the amorphous silicon showed opposite spatial distribution features for samples processing under liquid .Through analysis of the compositions left on the ablated surface ,the ablation mechanism was investigated from another point of view .For liquid confined laser processing ,previous studies mainly concentrate on the thickness and viscosity of the liquids ,little information has been done on the reducibility of liquids .To investigate the influ‐ence of liquid reducibility ,the surface morphology and oxygen content of ablation under different confining media were checked by confocal laser scanning microscopy and energy dispersive spectroscopy .Results showed that the reducibility of confining liquid also played a vital role in the ablation process under liquid .Utilizing liquids with deoxidizing ability as confining media will result in a remarkable reduction of surface oxygen con‐tent and a more regular morphology .