Dry etching techniques (RIE, ion beam and plasma etching) are intensively used at microfab for patterning of dielectrics, polysilicon and metal layers. Further important applications are the photoresist stripping and the anisotropic deep silicon trench etching (Deep Reactive Ion Etching - DRIE).
State-of-the-art monochromatic end point detection is applied with most RIE processes, ensuring a minimum of substrate loss due to overetching. Various etch masks (photoresist, SiO2, Ti, Cr, plasmanitride) can be combined, depending on the materials to be etched.
All processes were optimized regarding troughput, etch rate selectivity toward mask and substrate, CD loss (undercut), and etch profile (taper).
At the present time, microfab operates ten dry etching systems of which there are five RIE systems (STS multiplex, Alcatel 601E and AMS200) for dielectrics and metal etch and for deep silicon trench etching, one physical ion beam etcher (STS 340 PC) for noble metal etch, and four plasma etchers for resist strip processes (two Tepla barrel type etchers).
There are several standard processes available:
- RIE/ICP deep silicon trench etching (ASE process, up to 300 µm, aspect ratio 50:1)
- anisotropic RIE of dielectric layers (SiO2, Si3N4, Si:ON), up to 2000 nm
- anisotropic RIE of polysilicon (up to 2000 nm)
- isotropic RIE of polysilicon (up to 2000 nm)
- anisotropic RIE of Al and AlSiTi metal layers (up to 3000 nm)
- anisotropic RIE of bulk mono silicon (up to 5000 nm)
- isotropic RIE of Cr, Ti and WTi10 metal layers (up to 500 nm)
- anisotropic ion beam etching of Au and Pt layers (up to 500 nm)
- anisotropic RIE of polyimide and photoresist (up to 10 µm)
- isotropic strip of photoresist (up to 100 µm)