Ellipsometric study of silicon surface damage in electron cyclotron resonance plasma etching using CF₄ and SF₆

In situ ellipsometry has been used to measure in real time the surface damage introduced during electron cyclotron resonance (ECR) plasma etching of silicon as a function of rf bias to the substrate. CF4 and SF 6 plasmas were employed. For all ECR plasma operating conditions, the amount of Si surface damage increases with the rf bias voltage, without an apparent damage threshold. It is shown that the surface damage depends on the ion current to the substrate and the gas, with SF6 plasmas resulting in the least surface damage.