Controlling the relative rates of adlayer formation and removal during etching in inductively coupled plasmas

Laser desorption (LD) of the adlayer coupled with laser induced fluorescence (LIF) and plasma induced emission (PIE) of desorbed adsorbates is used to investigate the relative rates of chlorination and sputtering during the etching of Si in inductively coupled Cl₂-Ar plasmas. Such an analysis is a two-fold process: surface analysis and plasma characterization.; Surface analysis of Si etching using LD-LIF and LD-PIE techniques combined with etch rate measurements have revealed that the coverage of SiCl₂ and etch rate increases and coverage of Si decreases abruptly for a chlorine fraction of 75% and ion energy of 80 eV. The precise Cl₂ fraction for which these abrupt changes occur increases with an increase in ion energy. These changes may be caused by local chemisorption-induced reconstruction of Si <100>. Furthermore, the chlorination and sputtering rates are increased by ∼ an order of magnitude as the plasma is changed from Ar-dominant to Cl-dominant.; Characterization of the plasma included determination of the dominant ion in Cl₂ plasmas using LIF and a Langmuir probe and measurement of the absolute densities of Cl₂, Cl, Cl+, and At + in Cl₂-Ar discharges using optical emission actinometry. These studies reveal that Cl+ is the dominant positive ion in the H-mode and the dissociation of Cl₂ to Cl increases with an increase in Ar fraction due to an increase in electron temperature. Furthermore, for powers exceeding 600 W, the neutral to ion flux ratio is strongly dependent on Cl₂ fraction and is attributed mostly to the decrease in Cl density. Such dependence of the flux ratio on Cl₂ fraction is significant in controlling chlorination and sputtering rates not only for Si etching, but for etching other key technological materials.; ICP O₂ discharges were also studied for low-κ polymeric etch applications. These studies reveal that the electron temperature is weakly dependent on rf power and O₂ dissociation is low (∼2%) at the maximum rf power density of 5.7 Wcm−2, and is attributed to the high rate of O-atom recombination on the mostly stainless steel walls.