Aluminum Oxide Crucibles for E-Beam Sources

Several factors can lead to crucible damage during e-beam evaporation. The two primary causes include improper ramp/soak settings and abrupt power shutdowns.

1. Incorrect Ramp/Soak Settings

A standard e-beam evaporation recipe involves two ramp/soak power levels that heat the material gradually until deposition begins. Errors in these settings can cause significant problems:

• Transition to PID Loop: When deposition starts, power control shifts to a PID loop that manages the e-gun power supply and quartz crystal controller. If the ramp2/soak2 power level is not near the level required to achieve the specified deposition rate (e.g., 1 Ångström/sec), the PID loop may overcompensate.
  • Power Fluctuations: The PID loop may cause power to oscillate between extremes (+90% to 0%), rapidly liquefying and condensing the material. These cycles stress the crucible, leading to cracks.
  • Solution: Align ramp2/soak2 levels closely with the power needed for the deposition rate. This reduces PID adjustments and prevents harmful rapid phase changes.

2. Abrupt Power Shutdowns

Another common issue arises from improper handling of power supply post-deposition.

• Sudden Cooling Stress: Turning off the power supply abruptly or using a very short ramp-down period causes the melt to solidify rapidly. This rapid solidification creates stress on the crucible liner, potentially leading to cracks or breakage.
  • Preventive Measure: Use a gradual ramp-down process to allow the melt to cool evenly and reduce stress on the liner.