# Effect of Duty Cycle on Amorphous Silicon Carbon Nitride Films Deposited by Microwave Sheath–Voltage Combination Plasma

## TL;DR

This study shows how changing the duty cycle in plasma deposition affects the properties of a-SiCN films, including hardness and bonding.

## Contribution

The study reveals how duty cycle controls effective temperature and ion flux, influencing film hardness and bonding in a-SiCN.

## Key findings

- Deposition rate peaks at 30% duty cycle (~208 μm/h) and decreases at higher duty.
- Hardness peaks at 50% duty cycle (980 °C) and decreases at 70% due to sp2-rich clustering.
- XPS analysis shows increased Si–N and C=N bonding at higher duty cycles.

## Abstract

What are the main findings?
Duty cycle tunes effective substrate temperature/ion flux from 180 to 1040 °C.Deposition rate peaks at 30% duty (~208 μm/h) and decreases at higher duty.Hardness peaks at 50% duty (980 °C) and drops at 70% due to sp2-rich clustering.XPS shows increased Si–N and C=N bonding at higher duty.

Duty cycle tunes effective substrate temperature/ion flux from 180 to 1040 °C.

Deposition rate peaks at 30% duty (~208 μm/h) and decreases at higher duty.

Hardness peaks at 50% duty (980 °C) and drops at 70% due to sp2-rich clustering.

XPS shows increased Si–N and C=N bonding at higher duty.

What are the implications of the main findings?
Effective substrate temperature is a practical indicator of coupled thermal and ion effects.Maximizing hardness requires promoting C=N bonding.High ion flux at low duty (denser plasma/bias control) may enable low-temperature hard a-SiCN.

Effective substrate temperature is a practical indicator of coupled thermal and ion effects.

Maximizing hardness requires promoting C=N bonding.

High ion flux at low duty (denser plasma/bias control) may enable low-temperature hard a-SiCN.

This study investigates the deposition of amorphous silicon carbon nitride (a-SiCN) films using a microwave sheath–voltage combination plasma (MVP) source under duty-cycle-controlled deposition conditions. Duty ratios of 10, 30, 50, and 70% resulted in substrate temperatures of 180, 600, 980, and 1040 °C, respectively. The deposition rate reached a maximum of approximately 208 μm/h at a duty ratio of 30%. The atomic ratios of C, N, and Si remained nearly constant for duty ratios from 30% to 70%. X-ray diffraction confirmed that all films were amorphous. Raman spectra revealed features characteristic of amorphous carbon (a-C) for duty ratios of 30% or higher, suggesting the incorporation of a-C-like structures into the a-SiCN matrix. The film hardness increased as the duty-cycle-controlled deposition conditions shifted from 10% to 50% (180 to 980 °C), reaching a maximum of 22.65 ± 6.78 GPa at a duty ratio of 50%, and then decreased at 70% (1040 °C). These variations in hardness are suggested to be associated with coupled changes in hydrogen incorporation, C–N bonding, and the evolution of sp2-rich carbon clustering (graphite-like short-range ordering) under elevated temperature and ion-bombardment conditions.