Spatial phase-resolved optical emission spectroscopy for understanding plasma etching uniformity

Plasma chemistry of an oxygen-argon discharge in an electron cyclotron resonance (ECR) plasma etcher with a SiO₂ wafer is observed. The study involves: Phase-resolved optical emission spectroscopy (PROES) of neutral atomic argon (Ar I) and oxygen (O I) spectral lines, spectroscopic ellipsometry of the wafer and a magnetic-field measurement of the ECR etcher's electro-magnet. Spatial PROES results together with the ellipsometry and magnetic-field measurements are used to assess the plasma etching uniformity of the SiO₂ wafer. To evaluate the cross-dependences of the measured outputs for a wide range of process parameters, a design-of-experiment approach is taken. Spatial PROES of the oxygen atom shows a different spectral radiation pattern for the oxygen from the gas phase and those from the solid phase due to surface etching.