Spectroscopic measurements of plasma parameter in a low-pressure magnetized capacitively coupled nitrogen plasma

Over the past few decades, the control of charged particle flux-energy through the dc self-bias has attracted substantial attention from researchers and industries, for high-aspect-ratio etching or ion implantation. However, the conventional geometric asymmetry method is hard to control the ion flux-energy. To address this limitation, a magnetized capacitively coupled plasma (MCCP) has been investigated.

The asymmetry effect can be effectively controlled in low pressure by adjusting the magnetic field strength. The magnetic field confines electrons near the electrode and generates the dc self-bias to balance the ion-electron flux. M. Oberberg et al. have reported the magnetized asymmetry effect (MAE) such as changes in the heating mechanism, and ionization rate, in an argon MCCP [1,2]. In order to adopt the MCCP in the semiconductor industry, however, it is imperative to investigate the MAE of various gas plasmas.

In this study, we investigate the magnetic asymmetry effect on the properties of magnetized nitrogen plasma using optical emission spectroscopy. The neodymium magnets are arranged on the grounded electrode and show 60 G of magnetic field strength on the surface of the electrode. The relative ionization rate and dissociation rate are analyzed by comparing the intensity of N₂ second positive system, N₂⁺ first negative system, and N I. In addition, plasma temperatures are determined by simulating the molecular spectra and fitting them to the observed emission bands of the molecule.