ON-LINE FIBRE OPTIC BASED INSPECTION USING CHROMATIC MODULATION FOR SEMICONDUCTOR MATERIALS PROCESSING

Abstract

This contribution describes the use of chromatic sensing for monitoring and controlling the state of industrial processing plasmas and for providing an indirect but approximate indication of the quality of the end product of the process on-line.

Control systems for a Silicon Nitride plasma deposition and a Reactive Ion Etching system have been developed utilising the chromaticity of the optical emissions from the plasma as a control feedback. It is shown that there is a correlation between the plasma chromaticity and the refractive index of the thin film of semiconductor being deposited so that the chromaticity parameters can be used as indicators of the film quality. This indicates that a chromaticity monitoring system may be used as the basis of an on-line intelligenl control system. It has been demonstrated that there exists potential advantages in combining such chromatic sensing with neural network methodologies to achieve significant improvements in reliability and efficiency of such approaches.

Keywords:

• Chromatic sensing
• semiconductor processing
• fibre optics,
• silicon nitride
• plasma deposition
• reactive ion etching