Effect of Gas Species on the Depth Reduction in Silicon Deep-Submicron Trench Reactive Ion Etching

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Abstract
In silicon deep-submicron trench reactive ion etching (RIE), a clearly larger micro-loading effect is found in fluorinated gas than in chlorinated gas. To elucidate the gas effect, a model experiment is carried out in Cl2 and SF6. Etched depth dependence on pattern width is also calculated considering both shadowing effect and surface migration of etching species. Based on the results, it is revealed that the micro-loading effect is caused by: (1) decreasing etching species concentration on the trench bottom with increasing trench depth and/or decreasing trench width, and (2) larger change in etch rate with the change in etching species concentration is in fluorinated gas than in chlorinated gas. It is also noted that adoption of a heavier halogen for the etching gas offers one way to eliminate the micro-loading effect because ion-assisted etching is dominant in heavier halogen etching.

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