Pulsed Remote Plasma Etching for Ion Damage Reduction

The patent applies periodic pulsed plasma generation instead of continuous wave plasma. The plasma is generated in discrete pulses with controlled duration and frequency, allowing the substrate to be exposed to reactive species without continuous ion bombardment. This temporal modulation resolves the contradiction by providing chemical reactivity during plasma ON periods while reducing ion damage through OFF periods between pulses.

The patent dynamically controls plasma parameters including power level, pulse duration, and duty cycle to optimize the balance between etching productivity and ion damage reduction. By making plasma generation dynamic rather than static, the system can adapt the intensity and duration of plasma exposure to achieve effective etching while minimizing harmful ion effects on the substrate.

Pulsed plasma generation creates periodic cycles of reactive species formation and depletion. During ON periods, radicals are generated for chemical reactions; during OFF periods, radical density decreases while ion damage is minimized. This periodic modulation improves etch rate uniformity across the substrate by preventing excessive radical accumulation that causes non-uniform etching in continuous wave systems.

The patent changes key plasma parameters including power level, pressure, gas flow rate, and pulse timing to optimize both chemical reaction activation and etch uniformity. By carefully controlling the duty cycle and pulse width, the system maintains sufficient radical density for effective etching while preventing the conditions that lead to non-uniform etch rates across the substrate surface.