Improving stress stability in low-pressure chemical vapor deposited silicon dioxide films by ion implantation

Publication date: 1 January 2016
Source:Thin Solid Films, Volume 598
Author(s): Haiping Shang, Jianyu Fu, Changqing Xie, Zhigang Li, Dapeng Chen
The stress state of low-pressure chemical vapor deposition (LPCVD) silicon dioxide (SiO2) films fluctuates upon aging due to the ambient moisture. The related variation of the SiO2 films is a key factor of device reliability. In this study, ion implantation is introduced to improve film stress stability. The stress state modified by ion implantation is discussed in detail and an analytical model is presented. The evolution of the stress in as-deposited and P⁺-, As⁺-, and B⁺-implanted LPCVD SiO2 films upon aging is investigated, and the bonding nature of the films is also studied to provide insight into the physical mechanisms involved. It is demonstrated that low implantation energy slightly modifies the stress in films. In addition, P⁺ ion is the most appropriate impurity ion to improve film stress stability, and the stress in P⁺-implanted LPCVD SiO2 film can be stabilized with a low tensile stress of 67MPa when the film is implanted at 15keV with a dose of 1×10¹⁵ cm⁻².