What Does Etching Mean?
Etching, in the context of microfabrication, is the removal of wafer surface layers during the process of manufacturing. It is a crucial process, as each wafer should go through several etching steps prior to its completion.
In this process, the wafer is guarded by a type of material that is resistant to etching, known as a mask. In some cases, more durable masking material should be used, like silicon nitride.
Corrosionpedia Explains Etching
The etching process is usually done to monitor twin planes, grain boundaries, phase articles as well as microstructural constituents. It also exposes the propensity of a material toward particular corrosion mechanisms. For instance, there are materials that etch easily compared to others. In the case of aluminum, delineation of grain boundaries is a big challenge for a metallographer. Thus, it is required to conduct tests as to what type of etchants to use in order to achieve the appropriate resolution for ground boundaries.
The process of etching is essential in or micro electro mechanical systems (MEMS), in which miniaturized elements are manufactured through microfabrication techniques. With this process, forming a highly operational MEMS structure on a substrate is possible, and etching the thin films on the substrate is essential.
There are two forms of etching:
- Wet etching - In this process, the material is dissolved when submerged in chemical solutions.
- Dry Etching - The material is dissolved or sputtered through the aid of vapor etchant and reactive ions.
Wet etching is very simple and can yield good results, especially if the mask material and etchant matches its application. This works very well on thin films or the substrate itself. The only disadvantage with this process is that it can result in the mask layer undercutting by a distance similar to the depth of etching.
Dry etching is suitable for deep etching processes. However, this technology is quite expensive compared to wet etching, so this may not be the process of choice when feature resolution is not the main concern.