Etch method comparison
How wet and dry (plasma) etching differ, conceptually — mechanism, isotropy, selectivity, equipment, applications, and limitations.
| Dimension | Wet etching | Dry (plasma) etching |
|---|---|---|
| Mechanism | A chemical reaction in a liquid dissolves the material | A plasma of reactive species, often with directional ion bombardment |
| Isotropy | Usually isotropic — etches sideways as well as down | Can be highly anisotropic — nearly vertical sidewalls |
| Selectivity | Often very high and gentle for the right chemistry | Tunable; can drop when ion energy is high |
| Equipment | Wet benches, controlled chemical baths and rinses | Vacuum plasma chambers with RF power and gas delivery |
| Typical applications | Blanket strips, cleaning, and less-critical layers | Fine, dense, and high-aspect-ratio features |
| Limitations | Undercut limits fine features; chemical handling | More complex and costly; can add damage or charging effects |
No universal ranking
Dry etching is not automatically better. Wet etching remains the right choice when its speed, gentleness, cost, or very high selectivity suit the job; dry etching wins where fine, directional profiles are required.