Model for oxide damage from gate charging during magnetron etching

Charge damage is a consequence of plasma nonuniformity which leads to a local imbalance of ion and electron currents to the wafer surface. Damage during etching is found to occur near endpoint and to scale with gate electrode edge length. A model is proposed in which surface currents prevent charging during most of the time the gate is etching. Near endpoint, these currents are terminated while a temporary conductive halo still remains around the gate. During a brief period before it disappears, the halo can collect enough current to charge the thin oxide to the point of conduction and subsequent damage. This model is supported by plasma measurements, etching damage results, and simulations via the Simulation Program with Integrated Circuits Emphasis.