Plasma etching is an essential tool in today’s world, enabling many of the technologies we take for granted. For example, the smartphone would not be possible without it. Plasma etching is a way of creating features in virtually any material, the features can be on the nm scale or 100s of microns; the technique can be used to make them all.
Inductively Coupled Plasma Reactive-Ion Etching (ICP-RIE)
One of the leading technologies for plasma etching is ICP-RIE it offers many advantages in process performance:
- Controllable etch rates from extremely high to ultra-low
- Low damage
- High selectivity to mask and underlying materials
- Great profile control
To take profile control and illustrate its benefits: Moore’s Law has driven device critical dimensions (CD) down to well below µm level. If you have a feature that etches in the same direction vertically and horizontally such a closely packed array of devices will soon interfere with one another.
ICP-RIE plasma etching can produce perfectly vertical features so CD is maintained. It is widely used compared to wet etching precisely for this reason.
Reactive Ion Etching
Plasma etching by RIE has been widely used for decades, whilst it’s performance does not match that of ICP-RIE it is a simple technique that is very effective for many applications.
Plasma etching of dielectric masks for example usually does not require high rates and RIE provides sufficient verticality to create great masks.
Plasma Enhanced (PE) Etching
PE etching is the least directional of the plasma etching solutions it is therefore unsuitable for creating fine, vertical features. It is used for highly selective isotropic processes where undercut is acceptable it can be useful for clearing large areas of material selectively to an underlying layer.