REAL-TIME PROCESS AND PRODUCT DIAGNOSTICS IN RAPID THERMAL CHEMICAL-VAPOR-DEPOSITION USING IN-SITU MASS-SPECTROMETRIC SAMPLING

Mass spectrometry has been exploited for rapid real-time sensing of bo th reactant and product species in single-wafer rapid thermal chemical vapor deposition (RTCVD) of polycrystalline Si from SiH4. Active mass spectrometric sampling at pressures to 5 Torr is achieved using two-s tage differential pumping of a sampling aperture in the exhaust stream , leading to response times as short as similar to 3 sec to concentrat ion and pressure changes in the reactor during a process carried out i n similar to 30 sec. In addition to reactant species, gaseous reaction byproducts have been identified and differentiated from cracking frag ments of the reactant through relative intensities of mass fragments a s a function of wafer temperature (i.e., reaction rate). For RTCVD of poly-Si from SiH4, carried out in the range 450-800 degrees C at 5 Ton in 10% SiH4/Ar, mass spectra reveal not only the time dependence of r eactant (monitored by SiH2+, 30 amu), but also-at higher temperatures- reactant depletion and product generation (from H-2(+), 2 amu). These results demonstrate a basis for using mass spectrometry in real-time p rocess diagnostics and control. (C) 1995 American Vacuum Society