晶体取向对固结磨料磨削单晶硅亚表面损伤的影响

School of Aerospace Engineering, Xiamen University, Xiamen 361005, China.

Fine Optical Engineering Research Center, Chengdu 610041, China.

Micromachines (Basel). 2021 Mar 28;12(4):365. doi: 10.3390/mi12040365.

Subsurface damage (SSD) produced in a grinding process will affect the performance and operational duration of single-crystal silicon. In order to reduce the subsurface damage depth generated during the grinding process by adjusting the process parameters (added), experiments were designed to investigate the influence of machining factors on SSD. This included crystal orientation, diamond grit size in the grinding wheel, peripheral speed of the grinding wheel, and feeding with the intention to optimize the parameters affecting SSD. Compared with isotropic materials such as glass, we considered the impact of grinding along different crystal directions <100> and <110> on subsurface damage depth (added). The Magnetorheological Finishing (MRF) spot technique was used to detect the depth of SSD. The results showed that the depth of SSD in silicon increased with the size of diamond grit. SSD can be reduced by either increasing the peripheral speed of the grinding wheel or decreasing the feeding rate of the grinding wheel in the <100> crystal orientation, if the same size of diamond grit was employed. In addition, we proposed a modified model around surface roughness and subsurface crack depth, which considered plastic and brittle deformation mechanisms and material properties of different crystal orientations. When the surface roughness (R) exceeded the brittle-plastic transition's critical value R (R > 1.5 μm, R > 0.8 μm), cracks appeared on the subsurface. The experimental results were consistent with the predicted model, which could be used to predict the subsurface cracks by measuring the surface roughness. However, the model only gives the approximate range of subsurface defects, such as dislocations. The morphology and precise depth of plastic deformation subsurface defects, such as dislocations generated in the fine grinding stage, needed to be inspected by transmission electron microscopy (TEM), which were further studied.

磨削过程中产生的亚表面损伤（SSD）会影响单晶硅的性能和使用寿命。为了通过调整工艺参数（补充）来减小磨削过程中产生的亚表面损伤深度，设计了实验来研究加工因素对亚表面损伤的影响。这包括晶体取向、砂轮中的金刚石粒度、砂轮的圆周速度以及进给量，目的是优化影响亚表面损伤的参数。与玻璃等各向同性材料相比，我们考虑了沿不同晶体方向<100>和<110>磨削对亚表面损伤深度（补充）的影响。采用磁流变抛光（MRF）点技术检测亚表面损伤的深度。结果表明，硅中亚表面损伤的深度随金刚石粒度的增大而增加。如果采用相同粒度的金刚石，在<100>晶体取向中，通过提高砂轮的圆周速度或降低砂轮的进给速度，可以减小亚表面损伤。此外，我们提出了一个围绕表面粗糙度和亚表面裂纹深度的修正模型，该模型考虑了不同晶体取向的塑性和脆性变形机制以及材料特性。当表面粗糙度（R）超过脆塑性转变的临界值R（R>1.5μm，R>0.8μm）时，亚表面会出现裂纹。实验结果与预测模型一致，该模型可通过测量表面粗糙度来预测亚表面裂纹。然而，该模型仅给出了亚表面缺陷（如位错）的大致范围。精细磨削阶段产生的塑性变形亚表面缺陷（如位错）的形态和精确深度需要通过透射电子显微镜（TEM）进行检测，并进一步研究。