Dissociative electron attachment dynamics in pulsed Cl2 plasma process: characteristic pulse-OFF time on chamber diameter

Abstract Pulsed-plasmas are widely used in semiconductor dry etching because of lower plasma-induced damage compared with continuous-wave (CW) operation. Notably, in electronegative gases such as Cl, significant amounts of negative ions form in the afterglow, producing an ion-ion plasma that enables the transport of low energy ions to the surface and thereby reducing defects of etch patterns. This work studies the impact of the chamber size on plasma loss characteristics and the resulting timescale for ion-ion plasma formation using time-resolved Langmuir probe measurements applied to plasma systems with two different diameters. Relative to the large diameter chamber, the small diameter chamber exhibited more than twice the radial electron diffusion loss and ion loss to the wall during the discharge. In the pulse-OFF phase, the plasma diffusion rates were ∼1.4 × 10 4 s − 1 and ∼2.9 × 10 3 s − 1 , demonstrating that chamber geometry strongly governs diffusion-driven losses and transient plasma behavior during upscaling. GaN etching revealed a chamber-size-dependent optimal OFF time: the etch rate peaked at 1.8 nm/min at 200 μs using the large diameter and 5.5 nm/min at 100 μs using the small diameter. These results provide practical guidance for pulse-OFF time optimization and establish a foundation for large diameter pulsed-plasma modeling toward mass manufacturing.