Microelectromechanical Systems or more commonly known as MEMS is a technology designed for very small devices. It is made up of components between 1 to 100 micrometers in size; it is being used in numerous applications such as in electronics, biotechnology, communication, and medicine.
MEMS production/fabrication is carried out by a number of processes, which include deposition, parttering, and etching. However, in this content, we are to focus on the etching processes for MEMS.
There are numerous processes involved in MEMS etching but they can be categorized in two broad categories - dry and wet etching.
Dry etching - the material is dissolved using reactive ions or a vapor phase etchant; one advantage of this process is that it is capable of defining small feature size (<100 nm). It has several disadvantages as well, including: high cost, low throughput, poor selectivity, hard to implement, and the potential for radiation damage.
Sample of dry etching
- Xenon fluoride etching - primarily utilized for releasing metal and dielectric structures by undercutting silicon; this dry vapor phase isotropic etch process was first used in 1995.
- Plasma etching - a dry etching process, which process involves generation of reactive species, diffusion of these species, and then adsorption.
Wet etching - the material is dissolved through immersion in a chemical solution inside a wet bench. It has a number of advantages, including: low cost, easy to implement, high etching rate, and good selectivity for most materials. However, it has several disadvantages as well such as the inadequacy for defining feature size < 1 micrometer.
Sample of wet etching
Sample of wet etching
- Isotropic etching - known as the non-directional removal of material from a substrate in a chemical process with the help of a substance/mixture called an etchant.
- Hydrofluoric acid etching - a process that uses an aqueous etchant for silicon dioxide
There are quite a number of processes involved in etching - each has advantages and disadvantages. One thing is certain, however - etching is an important part of micro fabrication that essential to the production of devices needed in the industry and society.
