Thierry Plasma Etcher

The advantages of wet etching processes are the simple equipment, high etching rate, and high selectivity. However, there are many disadvantages. Wet etching is generally isotropic, which results in the etchant chemicals removing substrate material under the masking material. Wet etching also requires large amounts of etchant chemicals because the substrate material has to be covered with the etchant chemical.

Furthermore, the etchant chemicals have to be consistently replaced in order to keep the same initial etching rate.

As a result, the chemical and disposal costs associated with wet etching are extremely high.

Some advantages of dry etching are its capability of automation and reduced material consumption. Dry etching (e.g., plasma etching) costs less to dispose of the products compared to wet etching. An example of purely chemical dry etching is plasma etching.

A disadvantage of purely chemical etching techniques, specifically plasma etching processes, is that they do not have high anisotropy because reacting species can react in any direction and can enter from beneath the masking material.

Anisotropy is when the etching exclusively occurs in one direction.

This property is useful when it is necessary to remove material only in the vertical direction since the material covered by the masking material would not be removed. In cases where high anisotropy is vital, dry etching techniques that use only physical removal or a combination of both physical removal and chemical reactions are used.

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