Equipment—Etching

Deep Reactive Ion Etcher (RIE 180)
Deep Reactive Ion Etcher (RIE 180)
Name: Oxford Plasma Lab ICP 180 RIE (Ar, O2, CHF3, SF6, C4F8)
Mfr.: Oxford Instruments
Model: Plasma Lab ICP 180
Type: Deep Reactive Ion Etcher
The Plasma Lab ICP 180 is also a reactive ion etcher but it has the capability to do Bosch etching and cryo etching. Ideally any etching method would etch straight down to create a trench with steep sidewalls; in reality the sides of the trench are also etched. Reactive ion etching can make trenches with steep side walls but Bosch and cryo etching can do much better. The Bosch process works by alternating between a reactive ion etch step and a step where octofluorocyclobutane (C4F8) reacts on the surface to create a protective polymer layer. During the etch step most of the ions target the bottom of the trench so the protective layer is destroyed and etching continues but the protective layer on the sidewall holds and prevents etching from occurring. In the cryo process, the sample is chilled to cryogenic temperatures which slows down the chemical reaction between the ions and the surface; etching is done primarily by sputtering which favors the bottom of the trench over the sidewalls. With these two techniques trenches can be made 20 times as deep as they are wide.