Wet Etching

Selective Etching

Wet etching etches in all directions (isotropic)

The rate of reaction is dictated by the Arrhenius Rule:

$$Rate=A\ast e^{-\frac{E_a}{RT}}$$

$E_a$ is the activation energy, $R$ the gas constant, $T$ the temperature

Another consideration that can affect the rate of etching is bubble forming. Especially with wet etching solutions that form gases.

Bubbles can form areas that aren’t etched correctly.

Things that you can do are:

• Add a surfactant This has the effect of reducing surface tension and having bubbles float off earlier
• Stir This has the effect of physically pushing off bubbles off the surface