Products and Technology - MEMS-CET Performance

The principles associated with gas phase etching offer many benefits over conventional Wet Bench/Supercritical Drying technology. The most significant benefit is the increased device yield due to the elimination of "stiction", caused during the liquid drying process (in conventional etching systems).

The HF/Methanol etching process is typically carried out at pressures of 50 - 300 torr: thus with its vacuum capability, the MEMS-CET system is able to stop the etching process by simply pumping the chamber down to low pressure, providing superior process controllability.

The MEMS-CET process provides a wide range of etch selectivity for differing oxides; thermal oxide has the lowest etch rate followed by CVD TEOS, Plasma TEOS and then BPSG. Selectivity is optimized by varying the temperature, pressure and HF/Methanol ratio. With the versatile system control software, a variety of process recipes can be established giving programmable variable etch conditions. Optimized etch rates are both oxide type and structure dependent.

Since the gas phase etching process is isotropic in nature, with equal vertical and lateral etch rates, the Primaxx MEMS-CET system offers the additional benefit of being able to remove extremely thin sacrificial oxide layers underneath small structures (this is frequently not possible with processes involving liquids).

MEMS-CET System capabilities include:

  • Variable reactor temperature and pressure provide a wide range of controllable etch rates
  • Etch uniformities are < 10 % within wafer, wafer to wafer, run to run
  • Vertical and lateral undercut etch rate variable between 0.1 and 10 microns per minute
  • Etch rates are oxide type dependent
  • Systems can process sacrificial SiO2 layers as thin as 0.05 microns
  • Compatible (high etch selectivities) with aluminum, gold and other metals; high etch selectivity to silicon nitride (~ 100:1)
  • Process capabilities are highly device structure dependent