Time-resolved ion energy distribution in pulsed inductively coupled argon plasma with/without DC bias

Abstract

Pulsed plasmas have emerged as promising candidates as a means for precise control of ion energy/angle dependent surface processes and surface chemistry during the plasma process, which are key to 3 nm and beyond device fabrication. The ion energy distribution functions (IEDFs) and ion fluxes over a pulsed period are important to understand as they directly influence the feature profile, damage, and selectivity. We have developed an advanced plasma diagnostics (APD) system with advanced pulsing capability, including source, bias, and synchronous pulsing. It is a compact inductively coupled plasma system with a RF source frequency of 13.56 MHz intended to diagnose the general behavior of biased high density plasmas. We report the effect of the pulse frequency (2–10 kHz), RF duty cycle (25%–75%), DC duty cycle (5%–50%), phase lag (50–60  μs), RF power (120–180 W), DC bias voltage (0–150 V), and discharge pressure (20–80 mTorr) on the IEDFs and ion flux over a pulse period on the APD system. The time-resolved IEDFs and ion flux were measured using a retarding field energy analyzer. The ion energy transitions in a pulsed period from a plasma ignition stage to a stable stage and from plasma in a glow period to an afterglow period are studied. The results indicate that the ion energy and ion flux are tailored by RF pulsing and RF-DC pulsing. The time-resolved IEDF demonstrates the merits of pulsing to precisely control ion energy and flux, and the ion energy spread was narrowed by the pulsed plasma.