In-situ damascene trench RIE depth monitor using infrared interferometric spectrometry

In-situ damascene trench RIE depth monitor employing infrared interferometric spectrometry is investigated. Infrared light transmitted through the window of the RIE chamber was incident on the sample, and the trench etch depth of the line and space damascene pattern was calculated from the interferometric spectrum of the lights reflected at the interfaces located above the top wiring layer of the multi-level interconnects structure, because the infrared light does not transmit below it. This effect makes it possible to calculate the trench etch depth in-situ and without being affected by the structure of multilevel interconnects.