Magnetron etching of polysilicon: Electrical damage

We report comparison of etch damage between reactive ion and magnetron plasma etch environments and propose a qualitative model. Gate oxide damage is controlled by both plasma current and voltage and under some conditions can be worse for magnetron etching, especially in the case of very thin gate oxide. Moderate magnetron voltages (<50 V) may still be high enough (given the increased plasma density) to charge polysilicon gates causing degradation. Further reduction of voltage (and hence current) through modification of geometry and chemistry can reduce this damage to gate oxide and the gate edge diode for magnetron etching, producing results superior to reactive ion etching.