Deposition of silicon oxychloride films on chamber walls during Cl2/O2 plasma etching of Si

The chemical nature and deposition rate of the silicon oxychloride films deposited on the chamber walls during Cl2/O2 plasma etching of Si were investigated using multiple total internal reflection-Fourier transform infrared spectroscopy. The differences in the infrared spectra of films deposited under different etching conditions were quantified through the Si-O and OSi-Cl absorption band intensities and positions to determine the growth rate and composition of these films. The changes in the film's deposition rate and composition with rf bias power and O2 flow rate gave insight into the deposition mechanism. Based on our experimental observations, we propose that the silicon oxychloride film is deposited through oxidation of SiClx molecules adsorbed on the reactor walls and suggest a kinetic expression for the film deposition rate. This kinetic expression may also be used judiciously for describing the silicon oxychloride deposition on the sidewalls of etched features in gate etching and shallow trench isolation