Effect of Hydrogen Plasma Parameters on Amorphous Carbon Thin Film Growth in CBr₄ PEALD Process

The formation of an amorphous carbon based sidewall protection layer was investigated using PEALD with atomic-scale precision. The process enables conformal and tightly bonded passivation with highly controllable thickness, aiming to improve sidewall smoothness and yield in high aspect ratio etching. A PEALD process utilizing CBr₄ precursor was developed, where self-limiting growth was achieved through cyclic exposure to H₂ plasma, facilitating bromine removal after precursor adsorption. Depositions were performed on SiO₂ substrates in a 13.56MHz CCP reactor. Plasma power (150–350 W), exposure time per cycle (10–20 s), and substrate temperature (250–350 °C) were varied to optimize film growth. Film morphology was characterized by FE-SEM, while bonding configurations were analyzed via Raman spectroscopy and FTIR. Additionally, hydrogen plasma during deposition were modeled using 2-D plasma fluid simulation to correlate plasma parameters with film properties. As a result, increasing the power and exposure time of hydrogen plasma decreases the axial growth rate per cycle while promoting lateral growth, leading to layer-by-layer film formation through increased cluster density. These changes are attributed to variations in the behavior of radical and ion species within the hydrogen plasma, providing insight into mechanisms that influence film growth.