Zr、Cr掺杂对铜互连薄膜结构及性能的影响

Effect of Zr and Cr doping on the structure and properties of copper interconnection thin films

摘要:

本文研究了Zr和Cr元素掺杂对Cu互连薄膜的结构及性能的影响。利用直流磁控溅射技术在SiO₂/Si衬底上沉积了Cu、Cu(Zr)、Cu(Cr)、Cu(ZrCr)四种薄膜,并在400℃-800℃的不同温度下对薄膜真空退火1h。通过扫描电子显微(SEM)、X射线衍射仪(XRD)和四探针法对不同薄膜的表面形貌、微观结构与电学性能进行测试分析。结果表明, Zr或Cr单元素掺杂均能在一定程度上提高Cu互连薄膜的热稳定性。Zr或Cr元素的析出阻止了Cu膜与Si基底的互扩散以及晶粒的长大和团聚,使薄膜层保持良好的性能,经700℃真空退火后,Cu(Zr)和Cu(Cr)薄膜的电阻率小于10μΩ?cm(纯Cu薄膜为74.70μΩ?cm)；Zr和Cr元素共掺杂进一步提升Cu互连薄膜的热稳定性,同时保持较低的电阻率和互连可靠性,尤其经800℃退火后,合金薄膜的电阻率低至3.23μΩ?cm(纯Cu薄膜为103.50μΩ?cm)。

Abstract:

In this study, the effects of zirconium (Zr) and chromium (Cr) elements doping on the structure and properties of Copper (Cu) interconnection thin films were investigated. Cu, Cu (Zr), Cu (Cr), and Cu (ZrCr) interconnection films were deposited on SiO₂/Si substrates by direct current (DC) magnetron sputtering technology, and the films were annealed under vacuum condition at different temperatures from 400 ℃ to 800 ℃ for 1 hour. The surface morphologies, microstructure, and electrical properties of the films were tested and analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and four probes method. The results showed that single element doping of Zr or Cr improved the thermal stability of Cu interconnect films. The precipitation of Zr or Cr elements prevented mutual diffusion between Cu film and Si substrate, and suppressed the growth and aggregation of the grain, which made the films maintain good properties. After vacuum annealing at 700 ℃, the resistivity of the Cu(Zr) or Cu(Cr) film was less than 10 μΩ ? cm (pure Cu film was 74.70 μΩ ? cm). The co-doping of Zr and Cr elements further improved the thermal stability of Cu interconnection films while maintaining low resistivity and interconnect reliability. Especially after vacuum annealing at 800 ℃, the resistivity of Cu(ZrCr) film as low as 3.23 μΩ ? cm (pure Cu film was 103.50 μ Ω ? cm).