Chen Juan, Shi Junqin, Wang Yunpeng, Sun Jiapeng, Han Jing, Sun Kun, Fang Liang
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University Xi'an 710049 China
College of Mechanics and Materials, Hohai University Nanjing 210098 China.
RSC Adv. 2018 Apr 3;8(23):12597-12607. doi: 10.1039/c7ra13638b.
A fundamental understanding of the mechanical properties and deformation behaviors of surface modified silicon during chemical mechanical polishing (CMP) processes is difficult to obtain at the nanometer scale. In this research, MD simulations of monocrystalline silicon covered with an amorphous SiO film with different thickness are implemented by nanoindentation, and it is found that both the indentation modulus and hardness increase with the growing indentation depth owning to the strongly silicon substrate effect. At the same indentation depth, the indentation modulus decreases shapely with the increase of film thickness because of less substrate influence, while the hardness agrees well with the trend of modulus at shallow depth but mismatches at larger indentation depth. The observed SiO film deformation consists of densification and thinning along indentation direction and extension in the deformed area due to the rotation and deformation of massive SiO tetrahedra. The SiO film plays an important role in the onset and development of silicon phase transformation. The thinner the SiO film is, the earlier the silicon phase transformation takes place. So the numbers of phase transformation atoms increase with the decrease of SiO film thickness at the same indentation depth. It is suggested that the thicker film should be better during CMP process for higher material removal rate and less defects within silicon substrate.
在化学机械抛光（CMP）过程中，很难在纳米尺度上对表面改性硅的力学性能和变形行为有一个基本的了解。在本研究中，通过纳米压痕对覆盖有不同厚度非晶SiO薄膜的单晶硅进行了分子动力学（MD）模拟，发现由于强烈的硅衬底效应，压痕模量和硬度均随着压痕深度的增加而增大。在相同的压痕深度下，由于衬底影响较小，压痕模量随着薄膜厚度的增加而急剧下降，而硬度在浅深度时与模量趋势一致，但在较大压痕深度时不匹配。观察到的SiO薄膜变形包括沿压痕方向的致密化和变薄以及由于大量SiO四面体的旋转和变形而在变形区域的扩展。SiO薄膜在硅相变的起始和发展中起着重要作用。SiO薄膜越薄，硅相变发生得越早。因此，在相同压痕深度下，相变原子的数量随着SiO薄膜厚度的减小而增加。建议在CMP过程中使用较厚的薄膜，以获得更高的材料去除率并减少硅衬底内的缺陷。
