Specific Process Knowledge/Etch/OES: Difference between revisions

Inside the process chamber, the RF field will ionize the gas molecules to form ions, radicals and electrons. Much lighter and hence more mobile, the fast moving electrons collide with the gas constituents pushing the latter into excited states from which they may decay under emission of photons. This is what makes the plasma glow as these photons typically have an energy in the visible range. As each component in the plasma has a unique set of allowed excited states one can extract the information about composition of the plasma by analyzing the light coming out of it.

On a viewport preferably directly facing the plasma above the wafer is chosen. Here, a lens is mounted to focus the emitted light onto an optical fiber feeding it to a spectrometer. The Verity spectrograph has a 200 nm to 800 nm range with a 0.5 nm step.