Etching is a crucial part of wafer fabrication. This process helps remove materials from the float zone wafer. There are two major types of etching: dry and wet etching. In this article, we will discuss the process of wet etching and its importance.
Wet Etching is the process of utilizing liquid chemicals or etchants to get rid of materials from the float zone wafer. These materials refer to the patterns which are not covered by the photolithography mask from the lithography process. There are three basic steps in wet etching: diffusion of the liquid chemical on the surface for removal; reaction between the liquid chemical and the material being removed; and diffusion of the reaction outgrowth from the reacted surface.
Commonly, wet etching is isotropic, but in some cases it’s anisotropic. If an etching process proceeds only in one direction, then it’s completely anisotropic. In the production of semiconductors, a high degree of anisotropy is necessary because the outcome is more superior. It produces a more reliable copy of the mask pattern since the etchant only removes the material which is not directly under the mask. Isotropic liquid chemicals, on the other hand, can etch away some of the material that's directly under the photolithography mask. When a fraction of the material under the mask is etched away, it sacrifices the features of the wafer. To achieve the desired feature on the wafer, the etched away material must be compensated.
Despite some limitations of wet etching, it is widely used in wafer fabrication because of the following advantages: low cost, highly reliable, higher output, and exceptional selectivity. Using an automated wet etching system will add even more advantages, like convenience, higher reproducibility, and higher efficiency.
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