双步激光辐射提升纳秒激光抛光单晶硅的表面

Surface of Nanosecond Laser Polished Single-Crystal Silicon Improved by Two-Step Laser Irradiation

单晶硅是一种重要的半导体材料。通常,铸锭切片后的单晶硅表面易产生较深的沟槽、凹坑和裂纹等缺陷。针对这一问题,提出了一种双步激光辐射的方法,其在修复表面缺陷的同时,可以降低表面粗糙度。首先,通过有限元法模拟对不同激光参数下可修复的缺陷深度进行预测。然后,在0.50 J/cm^(2)的较高能量密度下,利用较深的表面层熔化修复各种深度的表面缺陷。然而,由于高能量密度下引发的热毛细管流易造成高频特征残留在表面上,故会导致表面粗糙度增加。接着,使用一个0.20 J/cm^(2)的低能量密度再次辐射同一表面,可有效消除残留的高频特征。最终,原始表面粗糙度为1.057μm的表面经过双步激光辐射后可获得一个表面粗糙度为26 nm的无缺陷光滑表面。

Single-crystal silicon is an important semiconductor material.Generally,the surface of single-crystal silicon after ingot slicing is prone to deep surface defects,such as grooves,pits,and cracks,etc.To solve this problem,a two-step laser irradiation method is proposed,which can repair surface defects and decrease surface roughness at the same time.First,the repairable defect depth is forecasted by finite element method(FEM) simulation under different laser parameters.Then,surface defects with various depths can be repaired by using the deeper surface layer melting at a higher energy density of 0.50 J/cm~2.However,the thermal capillary flow caused by high energy density can easily lead to the residual high-frequency features on the surface,which will lead to the increase of surface roughness.Subsequently,the residual high frequency features can be effectively eliminated by re-radiating the same surface with a low energy density of 0.20 J/cm~2.Finally,the surface with the original surface roughness of 1.057 μm is irradiated by the two-step laser to obtain a defect-free smooth surface with a surface roughness of 26 nm.