Jeffrey Shields

Quantifying Via Charging Currents

Via charging currents during via over-etch have been measured for the first time using CHARM@-2 wafers and a special-purpose CHARM@-2-compatible photoresist mask with varying via density. The measurements confirm previous findings which showed increased charging potentials and current densities in the presence of patterned resist [l]. The measurements also show the presence of an additional effect - an increase in via charging currents with decreasing via density. This effect may have considerable implications for product damage, and for the evaluation and analysis of resist aspect-ratio dependent charging damage.

Electron shading effects during oxide etching in uniform and non-uniform plasmas

Potentials and current densities imposed on device structures during oxide etching due to electron shading effects are presented. Comparison of results obtained in etchers exhibiting good plasma uniformity with results from etchers exhibiting plasma non-uniformity emphasizes the importance of uniform plasma to minimize charging damage during IC manufacturing.

Study Of Pattern Dependent Charging In A High-density, Inductively Coupled Metal Etcher

It is becoming increasingly evident that pattern dependent charging or electron shading is a significant charging mechanism for high density plasma etch systems. This mechanism, described by Hashimoto , can occur in uniform plasmas and is caused by the difference in isotropy of electrons and ions crossing the plasma sheath to the wafer surface. As electrons and ions interact differently with closely spaced structures on the surface of the wafer this leads to a differential charging of the structure with the top charging more negatively than the bottom. In this paper the voltages and currents developed by electron shading at the wafer surface are measured directly using a modified CHARM wafer.