INTERFEROMETRIC REAL-TIME MEASUREMENT OF UNIFORMITY FOR PLASMA-ETCHING

A new technique has been developed to measure etch rate uniformity in situ using a charge coupled device (CCD) camera which views the wafer during plasma processing. The technique records the temporal modulation of plasma emission or laser illumination reflected from the wafer; this modulation is caused by interferometry as thin films are etched or deposited. The measured etching rates compared very well with those determined by helium-neon laser interferometry. This technique is capable of measuring etch rates across 100 nun or larger wafers. It can resolve etch rate variations across a wafer or within a die. The CCD measurement technique is a valuable tool for process development and has potential use as a real-time diagnostic for process control.