Patent ID: 8767203
Filing Date: 2014-07-01
Classification: H05H

Abstract:
1. A process monitoring device comprising: plasma generating unit comprising; a hollow cylindrical first electrode having a length extending in a length direction; a second electrode having a length extending in the length direction and positioned within and displaced from the first electrode, wherein the first electrode has an inner diameter and the second electrode has an outer diameter selected to vary the distance between the electrodes in the length direction so that the plasma generating unit generates a plasma by ionizing a gas flowing between the electrodes at a different position in the length direction based on a pressure of the gas, wherein the inner diameter of the first electrode varies substantially uniformly in the length direction, and wherein the outer diameter of the second electrode varies substantially uniformly in the length direction and decreases as the inner diameter of the first electrode increases; an optical emission spectroscopy unit positioned proximate the plasma generating unit that is configured to analyze light emitted from the plasma generated by the plasma unit, and a power supply coupled to the first and second electrodes configured to power the electrodes to ionize the gas flowing therebetween.