In situ Fourier transform infrared spectroscopy of radio frequency glow discharges

The utility of in situ Fourier transform infrared spectroscopy (FTIR) as a diagnostic tool for radio-frequency (rf) glow discharges has been investigated. The development of reliable plasma diagnostic tools is needed to improve understanding of basic discharge chemistry and physics so that glow discharges can be better utilized as materials processing technique. FTIR is well-suited for the detection of a wide range of molecular species in plasmas and can probe species not easily investigated by existing diagnostic methods. Research has focused on low (8 cm{dollar}sp{lcub}-1{rcub}{dollar}) and moderate (0.65 cm{dollar}sp{lcub}-1{rcub}{dollar}) resolution studies of the plasma decomposition of N{dollar}sb2{dollar}O, a typical plasma processing feedstock, and on detection of the products of two etching systems of industrial importance: Al/Cl{dollar}sb2{dollar} and poly-Si/Cl{dollar}sb2{dollar}.; In the low resolution (8 cm{dollar}sp{lcub}-1{rcub}{dollar}) studies of 13.56 MHz N{dollar}sb2{dollar}O plasmas, areas of two N{dollar}sb2{dollar}O infrared absorption bands were used to estimate relative gas-phase dissociation as a function of rf power and flow rate at 500 mT. Band areas decreased with decreasing flow rate (increasing reactor residence time) over the range of powers investigated (10 to 90 W). At a given flow rate, band areas decreased with increasing rf power; the effect of power on band areas, however, diminished above 40 W due to poor plasma confinement.; The in situ FTIR technique has also been utilized to detect gas-phase product species resulting from the dry etching of aluminum and heavily-doped, n-type polycrystalline silicon (n+ poly-Si) in Cl{dollar}sb2{dollar}. The products of aluminum etching in Cl{dollar}sb2{dollar} were investigated in the presence and absence of a plasma. With the plasma off, Al{dollar}sb2{dollar}Cl{dollar}sb6{dollar} was the only infrared-active etch product detected at both low (50{dollar}spcirc{dollar}C) and high ({dollar}>{dollar}120{dollar}spcirc{dollar}C) sample temperatures. With the discharge on, the spectra were more complex, indicating partial fragmentation of the dimer etch product in the plasma forming AlCl{dollar}sb3{dollar} and, perhaps, AlCl. Silicon tetrachloride was the only infrared-absorbing product detected during the Cl{dollar}sb2{dollar} plasma etching of n+ poly-Si. Unsaturated silicon chlorides (SiCl{dollar}sb{lcub}rm x{rcub}{dollar}, x = 1-3) were not present at detectable levels. These results are compared with those of ultrahigh vacuum (UHV) beam studies. This comparison must take into account the limitations of both techniques. When these allowances are made, the results of this work seem consistent with those obtained in UHV experiments. (Abstract shortened with permission of author.)...