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Nanofabrication Facility
Capabilities & Equipment > Etching
PlasmaTherm 790 Fluorine RIE System
Photo of the PlasmaTherm 790
A photonic crystal waveguide etched in silicon-on-insulator (SOI) using this system.
Based primarily upon tetrafluoromethane (CF4) and hydrogen (H2) gas mixtures, the RIE system creates a plasma of reactive ions by flowing gases through a strong RF field, which breaks them into radicals which can then attack exposed regions of the sample under etch. By adding a bias voltage to the RF AC field, ions can be accelerated toward the sample, adding a mechanical component to the etching process and increasing the directionality of the etch. Further, ions of the noble gas Argon can be used for a purely mechanical etch. Other available gases include oxygen for removing organics such as photoresist residue. Finally, by controlling the flow rates of the CF4 and H2, the system can actually deposit flouropolymer coatings; deposition steps can be alternated with directional etching steps to yield highly anisotropic etches with vertical sidewalls, yielding results similar to those of Bosch processes.
Features:
- Recipes developed for etching of silicon, using metal hard masks and soft photoresist masks
- Bosch-like anisotropic etching via cycling between isotropic chemical etch, sidewall passivation by fluoropolymer deposition, and directional mechanical etch.
- Gases available for processes in the RIE include:
- tetrafluoromethane (CF4)
- sulfur hexafluoride (SF6)
- hydrogen (H2)
- oxygen (O2)
- argon (Ar)
