The recently patented design of the RC™ crystal is insensitive to frequency shifts caused by source radiation or film stress. This is accomplished by adjusting the stress coefficients of the quartz plate using advanced fabrication methods.

For ultra-thin film thickness measurements, in the 10 to 100 Angstrom range, a combination of frequency shifts caused by heat, stress and film build-up can lead to thickness errors of 100% or more. As a result, the vacuum process becomes uncontrollable. A new quartz crystal has been developed that mitigates these factors. Called the RC™ crystal, this recently patented design is insensitive to frequency shifts caused by source radiation or film stress.

The RC™ crystal will not show a rate spike when the deposition source shutter is opened. This was demonstrated in a test set-up in the BeamTec lab comparing processes using both a standard AT-cut quartz and the new RC™ quartz.

Typically, opening the source shutter causes a frequency shift of up to 100 Hz, which translates for films such as aluminum, to rate changes of 50 Angstroms. Further, the noise associated with the intense energy of impinging atoms in sputtering is dramatically reduced, owing to the stress insensitivity of the crystal. These are very real advantages in the measurement of nanometer films used in the manufacture of OLED’s, precision optical interference films, or next generation electronic devices.

RC™ crystals can be used in place of standard AT-cut quartz in all commercially available film thickness monitors and controllers. Please see here for an overview of available versions.