Deep Reactive-ion Etching - Applications

Applications

RIE "deepness" depends on application:

• in DRAM memory circuits, capacitor trenches may be 10–20 µm deep,
• in MEMS, DRIE is used for anything from a few micrometers to 0.5 mm.

What distinguishes DRIE from RIE is etch depth: Practical etch depths for RIE (as used in IC manufacturing) would be limited to around 10 µm at a rate up to 1 µm/min, while DRIE can etch features much greater, up to 600 µm or more with rates up to 20 µm/min or more in some applications.

DRIE of glass requires high plasma power, which makes it difficult to find suitable mask materials for truly deep etching. Polysilicon and nickel are used for 10–50 µm etched depths. In DRIE of polymers, Bosch process with alternating steps of SF₆ etching and C₄F₈ passivation take place. Metal masks can be used however are expensive to use in that several additional photo and deposition steps are always required. Metal masks are not necessary however on various substrates (Si, InP or glass ) if using chemically amplified negative resists.

Gallium ion implantion can be used as etch mask in cryo-DRIE. Combined nanofabrication process of focused ion beam and cryo-DRIE was first reported by N Chekurov et al in their article "The fabrication of silicon nanostructures by local gallium implantation and cryogenic deep reactive ion etching" (Nanotechnology, 2009).