Mass spectrometric measurements on inductively coupled fluorocarbon plasmas: Positive ions, radicals and endpoint detection

Positive ions and radicals in C2F6 and CHF3 high density discharges were me asured using a direct-line-of-sight mass spectrometer. The ion energy distr ibutions of the dominant ions were measured as a function of process condit ions. Appearance potential mass spectrometry was performed to measure trend s of the radical densities. For C2F6 plasmas CF3 and CF3+ are the most abun dant neutral and ionic species, respectively. CF3 is the most abundant neut ral species for a CHF3 plasma, whereas CHF2+ and CF+ are the most abundant ionic species at 600-1000 and 1400 W, respectively. Erosion of the quartz c oupling window is an important contaminant source for our inductively coupl ed plasma system. For comparison, downstream mass spectrometry was also app lied using a closed ion source system since this approach is of interest fo r real-time monitoring and control. Endpoint detection for Si and SiO2 film etching in a CHF3 plasma was investigated using the downstream mass spectr ometer system and compared with data obtained simultaneously using the dire ct-line-of-sight mass spectrometer and optical emission spectroscopy, It wa s found that the downstream mass spectrometer system can be used for endpoi nt detection during SiO2 over Si selective etching. The signal changes of d ifferent species measured by these techniques for different SiO2 and Si etc hing processes as a function of time are reported and compared. (C) 1999 Am erican Vacuum Society. [S0734-2101 (99)09305-7].