Deep reactive ion etching
Deep reactive ion etching (DRIE) is a type of reactive ion etching aimed at creating very deep, high aspect ratio structures. While a standard RIE process can be used, they are often inadequate so a couple of variations have been developed for specific applications. The most common variant is the Bosch process, used mainly for etching silicon substrates. It is also possible to use cryogenic etching to create a high aspect ratio etch in silicon, compound semiconductors, and some polymers. Most dielectrics and metals are significantly more difficult to etch than these materials, so deep etches are uncommon. The LNF has one process for deep etching in glass and fused silica, known colloquially as DGRIE. An alternative for metals is using electroplating with a high aspect ratio photoresist, such as SU-8.
|Deep reactive ion etching|
STS Pegasus 4|
STS Pegasus 6
STS Glass Etcher
Oxford ICP RIE
The STS Pegasus is a tool that utilizes the Bosch process for high aspect ratio etching of silicon. It uses SF6 for the etch step and C4F8 for passivation. It can achieve etch rates of up to 20 μm/min and aspect ratios up to 50:1.
STS Glass Etcher
The STS Glass Etcher is a DGRIE tool for high aspect ratio etching of silicon dioxide, glass, and fused silica.
The Oxford Plasmalab is an ICP RIE system capable of cryogenic etching. While not configured to etch silicon, it can etch compound semiconductors and perform a cryogenic etch of polymers.
Method of operation
DRIE processes operate in a similar fashion to RIE processes, but the process is tuned to be highly vertical and capable of long, deep etches. In particular, high selectivity is necessary, since mask thicknesses are typically limited to less than 10 μm.