Laser Etch Monitoring
A number of our dry etching systems have Intellemetrics LEP500 Laser Etch monitors installed, for "endpoint detection". These systems allow you to end your etch at a known etch depth, or within a certain layer (with some caveats). This nearly eliminates the need to calibrate etch rates or to use timed etching only, which is especially important in our lab where etch rates can vary depending on the previous etches performed in the chamber.
Laser Etch monitoring works similarly to optical thin-film measurement via reflectivity spectra (eg. like our Filmetrics systems). However, instead of varying the optical wavelength and measuring a fixed thin-film, we measure a constant wavelength and a thin-film that is varying as it is etched. Thus, similar to the thin-film measurements, you can only measure a useful signal when the optical properties (reflection or interference) change during your etch.
For example, Etching from high-reflectivity Aluminum to Lower reflectivity Silicon will usually give you a clear drop showing that your Aluminum has been fully etched-through.
Etching films that are transparent at the laser monitor wavelength (670nm) produces a sinusoidal signal due to optical wave interference which gives you numerous possible stopping points to end the etch upon.
- Intellemetrics Laser Etch Monitor Procedure for Panasonic ICP Etchers
- Intellemetrics Laser Etch Monitor Procedure for Plasma-Therm Etchers
- Horiba Laser Etch Monitor Procedure for Unaxis VLR
- Custom Laser Etch Monitor Procedure for RIE#2
See the following pages for more information about laser endpoint detection.