Etching is the process in which strong acid is used to remove the unprotected parts of a metal surface as after thin film deposition on the wafer surface, they are removed directly from the wafer surface and desired pattern of the of the film is left on the wafer surface.
Etching can be done either in wet or dry environment. In wet etching etchant solution, which is used is in liquid form and the wafer is usually immersed in the etchant solution and the exposed material is etched away by the chemical process. In dry etching etchant solution, is in gaseous form in plasma. Here etching takes place by chemical and physical process. Hence dry etching is also called Plasma Etching.
Effects of Etching:
Ferric Chloride is widely used etchant and is commonly used in chemical etching. FeCl3 produces a smooth side wall after etching and FeCl3 is commonly used to etch white metals such as iron and nickel based alloys as well as Zi, Al, Mg etc. Another advantage of using FeCl3 is that it can be regenerated within process. Although FeCl3 increases regenerating capability but on the other hand it increases volume of the etching solution.
Cupric Chloride is most commonly used etchant as it is capable of continuo us regeneration at a steady rate condition. It has etch rate half than FeCl3 but than also it is most commonly etchant. Because of etching surface imperfection occurs due to uneven chemical attack of etchant solution.
Author - Somya Bisaria
(Intern at Silicon Mentor)