IN-SITU MONITORING OF THE PRODUCTS FROM THE SIH4-VAPOR-DEPOSITION PROCESS BY MICROVOLUME MOSS SPECTROMETRY(WF6 TUNGSTEN CHEMICAL)

We have used a novel application of in situ high pressure mass spectro metry to monitor the SiH4 + WF6 tungsten chemical vapor deposition pro cess. We observed the production of both SiF4, and SiHF3, in ratios th at vary with the SIH4/WF6 inlet flow ratio. The SiF4 and SiHF3 partial pressures were monitored over a tungsten coated wafer at 320 degrees C as the SiH4/WF6 inlet flow ratio was varied from a selective (0.25) to a nonselective (3.0) regime. We observed the SiHF3/SiF4 product rat io to decrease dramatically at reactant ratios associated with the ons et of loss of selectivity (1-1.5). The reaction products were sampled by means of a fused silica capillary that was introduced between the r eacting tungsten coated wafer and a differentially pumped mass spectro meter. Gas phase reaction and thermodiffusion effects were also observ ed. These data provide insight concerning loss of selectivity mechanis ms, and illustrate the potential of this mass spectrometric technique for real-time in situ process control.