Radical Generation Mechanism and Radical Effect on Aluminum Anisotropic Etching in SiCl4 Reactive Ion Etching

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Abstract
The radical generation mechanisms and the effect of radical composition in a SiCl4 discharge on the directionality of aluminum etching are discussed using the results of optical emission spectra and plasma density measurements. It was found that the chlorine radical concentration is almost proportional to gas pressure and plasma density, while the silicon radical density is almost proportional to the square of the plasma density, but is weakly dependent on the gas pressure. At lower pressure or a higher power density, where the ratio of silicon radical concentration to chlorine radical concentration increases, lateral side etching is inhibited by the silicon deposition, and anisotropic etching can be achieved. From these experiments, it is concluded that a control of gas dissociation is needed for a more precise control of the anisotropic etching.

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