By Paul Drake

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.

Fabrication of MEMS can be done through several processes, including deposition, patterning, and etching. In this article, however, we are going to focus on the etching process and its different types.

There are several methods used in MEMS etching but they can be divided into two broad categories - the wet etching and the dry etching process.

Dry etching - in this process, the material is dissolved using reactive ions or a vapor phase enchant. One advantage of this method is capable of defining small feature size that is less 100 nm). But it has a number of limitations as well such as high cost, low throughput, poor selectivity, hard to implement, and the potential for radiation damage.

Sample of dry etching

Xenon fluoride etching - this dry vapor phase isotropic etch process was first utilized in 1995; it is mainly for the purpose of releasing metal and dielectric structures by undercutting silicon.

Plasma etching - this process includes the generation of reactive species, diffusion of these species, and then adsorption. (note: plasma source is also called etch species)

Wet etching - the material, in this process, is dissolved through immersion using chemical solution inside a wet bench. Several advantages this process has to offer - it is easy to implement has high etching rate, can be done at a lower cost, and good selectivity for most materials. However, it has some limitations as well such as the inadequacy for defining feature size that is less than 1 micrometer.

Sample of wet etching

Isotropic etching - it is known as the non-directional removal of material from a substrate though a chemical process using a substance or mixture called as etchant.

Hydrofluoric acid etching - a process that uses an aqueous etchant for silicon dioxide.

There are several processes involved in etching - each has advantages and limitations. One thing is certain, however - etching is essential for micro fabrication as this is needed for the production of devices that play a huge part for industry's continuous development.

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