Control of SiO2/Si interface defects generation during thin dielectric film etching using CHxFy/Ar/O2 plasma

Abstract

We investigated the quantitative control of SiO2/Si interface defects caused by CHxFy/Ar/O2 plasma etching. Both the number and the cause of interface defects generation strongly depended on the residual thicknesses of SiO2. When the residual thickness becomes small, in addition to the VUV/UV irradiation, ion injection caused a remarkable increase in the number of interface defects associated with Si dislocation. Complete recovery from damage was difficult by low-temperature thermal annealing, especially ion-induced damage. Ion-induced damage was suppressed by controlling the residual thickness of SiO2 to be larger than the ion penetration depth. VUV/UV-induces damage could be effectively suppressed by using a light shield layer such as SiN. Moreover, VUV/UV-induces damage under a fine space pattern is expected to be suppressed in comparison with a wide-open pattern. Thus, the process design of a film stack, pattern, etching condition, and thermal annealing condition are important for controlling SiO2/Si interface defect generation during plasma processing.