Working principle:

• The DRIE process provides thin films of a few microns protective coatings on the sidewalls during the etching process.
• It involves the use of a high – density plasma source.
• The process allows alternating process of plasma (ion) etching of the substrate material and the deposition of etching-protective material on the sidewalls.
• Special polymers are frequently used for side wall protective films.

What DRIE can do:

• The DRIE process has produced MEMS structures with A/P** = 30 with virtually vertical walls of θ = ±20 for several years.
• Recent developments have used better sidewall protecting materials. For example, silicon substrates with A/P over 100 was achieved with θ = ±20 at a depth of up to 300 µm. The etching rate, however was reduced to 2-3 µm/min.
• A/P = Aspect ratio = the dimension in vertical to horizontal directions.