Novel Shallow Trench Isolation Process from Viewpoint of Total Strain Process Design for 45 nm Node Devices and Beyond

In this paper, a novel shallow trench isolation (STI) process is proposed for 45 nm node technologies and beyond. The major features of this process are the use of a fluorine-doped (F-doped) SiO2 film for gap filling and high-temperature rapid thermal oxidation (HT-RTO) for gate oxidation. Voidless filling of a narrow trench can be realized by F-doped high-density plasma chemical vapor deposition (F-doped HDP-CVD). Moreover, electron mobility degradation caused by STI stress and junction leakage currents can be minimized using F-doped HDP-CVD with HT-RTO. It was also confirmed that compressive stress in the F-doped HDP-CVD sample is smaller in every measurement point around STI than that in the conventional HDP-CVD sample by convergent-beam electron diffraction (CBED). The Si-F bonds in the oxide film play a very important role in stress reduction. By utilizing HT-RTO, Si-F bonds remain and make the SiO2 film in the trench coarse. This technique is a very promising 45 nm node STI scheme with high performance and high reliability.