Pt patterns of the 0.25 µ m design rule were etched at 20° C using a magnetically enhanced reactive ion etcher. The main problem of this device integration process is the redeposition of the etch products onto the pattern sidewall, making it difficult to reduce the pattern size. In both cases using a photoresist mask and an oxide mask, the redeposits of the etch products onto the sidewall were reduced by the addition of Cl2 to Ar, although the etch slope was lowered to 45°. Using the oxide mask, by adding O2 to the Cl-containing gas, the etch slope was increased up to 70°, and the redeposits were removed by an HCl cleaning process.

The instabilities caused by the reflected rf power in a pulsed-plasma operation employing modulated rf power was studied. By suppressing the side-band modes in the frequency domain, the pulsed plasma became more stable and produced less reflected power. The mode-suppressed pulsed plasma showed almost the same plasma characteristics as the conventional step-function-modulated pulsed plasma. The mode-suppressed plasma was applied to etch a polysilicon pattern. The etched polysilicon profile showed no charge-up defects, suggesting that the mode-suppressed plasma can be utilized for controlling the electron temperature in a more stable operation.

No abstract