Plasma End Point Detection
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
The end-point of the reactive ion etch process for silicon nitride, polycrystalline silicon, metal silicides, etc., may be determined by monitoring the change in magnitude of the co-emission at 519.8 nm. The detector shown in the figure is an amplifier-photocell arrangement with the photocell having a bandwidth (BW) of 550 A (55.0 nm) at peak sensitivity of 515.0 nm. This wide bandwidth enables the detector 5 to respond to other emissions, thus increasing the background level or noise upon which the end-point signal rides. If a narrow band-pass optical filter 6 (typical BW of less than 6 nm) is inserted between the quartz chamber window 7 and the photocell 5, the background noise is greatly reduced, which results in the improvement of the signal-to-noise ratio.