The Radial Distribution of Ions and Electrons in RF Inductively Coupled H₂/T₂B Plasmas

Abstract

A glow discharge polymer (GDP) was fabricated using trans-2-butene (T₂B) and hydrogen (H₂) via a plasma-enhanced chemical vapor deposition (PECVD) system. The uniformity of the GDP films was significantly affected by the radial distribution of the H₂/T₂B plasma parameters. The plasma properties while discharging by a multi-carbon gas source of mixed H₂/T₂B were investigated during the GDP deposition process. The main positive ions and ion energy distributions in inductively coupled H₂/T₂B plasmas were analyzed by energy-resolved mass spectrometer (MS), and the electron density and the effective electron temperature were mainly analyzed using a Langmuir probe. The MS results show that the main positive ions in the plasmas are ${\text{C}}_{ 2} {\text{H}}_{ 4}^{ + }$, ${\text{C}}_{ 2} {\text{H}}_{ 6}^{ + }$, ${\text{C}}_{ 3} {\text{H}}_{ 3}^{ + }$, ${\text{C}}_{ 3} {\text{H}}_{ 6}^{ + }$, ${\text{C}}_{ 3} {\text{H}}_{ 8}^{ + }$, ${\text{C}}_{ 4} {\text{H}}_{ 5}^{ + }$, ${\text{C}}_{ 4} {\text{H}}_{ 1 0}^{ + }$, ${\text{C}}_{ 5} {\text{H}}_{ 5}^{ + }$, and ${\text{C}}_{ 5} {\text{H}}_{ 7}^{ + }$ with mass-to-charge ratios (m/e) of 28, 30, 39, 42, 44, 53, 58, 65, and 67, respectively. For a normalized ion intensity, the relative intensities of saturated CH ions increase with increasing radial distance, while the unsaturated CH ions decrease with increasing radial distance. The ion energy distribution of ${\text{C}}_{ 2} {\text{H}}_{ 6}^{ + }$ (m/e = 30) presents a bimodal structure. Additionally, both the electron density and the effective electron temperature decrease with increasing radial distance.