REAL-TIME CHEMICAL SENSING IN THIN FILM MULTICOMPONENT CVD

A quadrupole mass spectrometer (QMS) and an acoustic sensor have been used for real-time process monitoring and thickness metrology in W-CVD (3 H2 + WF6 → W + 6 HF) using an Ulvac cluster tool. The QMS recorded the time evolution of the partial pressures for the reactants (H2 /WF6) and the HF product, while the acoustic sensor monitored variations in the average molecular weight of the gas mixture in the reactor through the process cycle. Integrated signals from both sensors gave in-situ thickness estimates accurate to within ~7% cf. actual post-process thickness measurements, despite the poor reactant conversion rate (just a few percent) in the tool. For mainstream processes involving blanket CVD, where much higher conversion rates (~50%) are typical, we expect thickness metrology capability in the range of 1-2%, making these techniques attractive for thickness metrology and associated process control, in addition to fault detection and process chemistry determination.