Sa Y K, Bang Junghwan, Son Junhyuk, Yu Dong-Yurl, Kim Yun-Chan
Advanced Deposition Materials Business Unit, Entegris, Suwon 16229, Korea.
Micro-Joining Center, Korea Institute of Industrial Technology, 156 Gaetbeol-ro, Yeonsu-gu, Incheon 406840, Korea.
Materials (Basel). 2021 Apr 28;14(9):2284. doi: 10.3390/ma14092284.
This paper reported the enhancement in thermo-mechanical properties and chemical stability of porous SiCOH dielectric thin films fabricated with molecularly scaled pores of uniform size and distribution. The resulting porous dielectric thin films were found to exhibit far stronger resistance to thermo-mechanical instability mechanisms common to conventional SiCOH dielectric thin films without forgoing an ultralow dielectric constant (i.e., ultralow-k). Specifically, the elastic modulus measured by nano-indentation was 13 GPa, which was substantially higher than the value of 6 GPa for a porous low-k film deposited by a conventional method, while dielectric constant exhibited an identical value of 2.1. They also showed excellent resistance against viscoplastic deformation, as measured by the ball indentation method, which represented the degree of chemical degradation of the internal bonds. Indentation depth was measured at 5 nm after a 4-h indentation test at 400 °C, which indicated an ~89% decrease compared with conventional SiCOH film. Evolution of film shrinkage and dielectric constant after annealing and plasma exposure were reduced in the low-k film with a self-organized molecular film. Analysis of the film structure via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated an increase in symmetric linear Si-O-Si molecular chains with terminal -CH bonds that were believed to be responsible for both the decrease in dipole moment/dielectric constant and the formation of molecular scaled pores. The observed enhanced mechanical and chemical properties were also attributed to this unique nano-porous structure.
本文报道了具有尺寸和分布均匀的分子尺度孔隙的多孔SiCOH介电薄膜的热机械性能和化学稳定性的增强。结果发现，所得的多孔介电薄膜对传统SiCOH介电薄膜常见的热机械不稳定性机制具有更强的抗性，同时又不放弃超低介电常数（即超低k）。具体而言，通过纳米压痕测量的弹性模量为13 GPa，大大高于通过传统方法沉积的多孔低k薄膜的6 GPa的值，而介电常数显示出相同的2.1的值。通过球压痕法测量，它们还表现出优异的抗粘塑性变形能力，该方法代表内部键的化学降解程度。在400°C下进行4小时压痕试验后，压痕深度测量为5 nm，这表明与传统SiCOH薄膜相比减少了约89%。具有自组装分子膜的低k薄膜在退火和等离子体暴露后薄膜收缩和介电常数的变化有所减少。通过傅里叶变换红外（FTIR）光谱和X射线光电子能谱（XPS）对薄膜结构进行分析表明，具有末端-CH键的对称线性Si-O-Si分子链增加，据信这是偶极矩/介电常数降低和分子尺度孔隙形成的原因。观察到的机械和化学性能增强也归因于这种独特的纳米多孔结构。
