Influence of surface material on the boron chloride density in inductively coupled discharges

The relative density of BCl radicals has been measured in a modified Applied Materials decoupled plasma source commercial metal etch chamber using laser-induced fluorescence. In plasmas containing mixtures of BCl3 with Cl2, Ar, and/or N2, the relative BCl density was measured as a function of source and bias power, pressure, flow rate, BCl3/Cl2 ratio, and argon addition. To determine the influence of surface materials on the bulk plasma properties, the relative BCl density was measured using four different substrate types; aluminum, alumina, photoresist, and photoresist-patterned aluminum. In most cases, the relative BCl density was highest above photoresist-coated wafers and lowest above blanket aluminum wafers. The BCl density increased with increasing source power and the ratio of BCl3 to Cl2, while the addition of N2 to a BCl3/Cl2 plasma resulted in a decrease in BCl density. The BCl density was relatively insensitive to changes in the other plasma parameters.