Emission spectroscopy using a microfabricated inductively coupled plasma-on-a-chip - Invited Lecture

In this work a novel, microfabricated inductively coupled plasma (mICP) generator for emission spectroscopy is described. The spatial distribution of light emitted from the mICP, the electron temperature and ion density of the plasma, and the detection of trace amounts of SO2 excited by the mICP are presented. The miniature ICP system consists of a planar, spiral-shaped inductor and an impedance matching network that are microfabricated on a glass wafer and subsequently bonded to a miniature aluminum vacuum chamber. The plasma operates from 0.1 to 10 Torr, and requires less than 4 W of power at a frequency of 490 MHz. The chamber was designed to maximize the excitation and emission from SO2 molecules. An SO2 fraction as low as 3 ppm is directly measured using the intensity of atomic sulfur emission at 469.5 nm. The detection limit, however, is found to improve with both increasing plasma power and argon pressure, and is as low as 190 ppb. It is also clear from the optical emission spectra that this mICP has the ability to excite the entire SO2 molecule, which suggests that it is also a promising molecular detection tool.