Nanofabrication facility - Equipment - Etching

Etching

Etching is used in nanofabrication to chemically remove layers from the surface of a sample during manufacturing. Etching is a critically important process module. For many etch steps, part of the sample is protected from the etchant by a "masking" material which resists etching. In some cases, the masking material is a photoresist which has been patterned using photolithography. Other situations require a more durable mask, such as silicon nitride or metal. If the etch is intended to make a cavity in a material, the depth of the cavity may be controlled approximately using the etching time and the known etch rate. More often, though, etching must entirely remove the top layer of a multilayer structure, without damaging the underlying or masking layers. The etching system's ability to do this depends on the ratio of etch rates in the two materials (selectivity).

ICP-RIE (Inductively Coupled Plasma - Reactive Ion Etching) is a dry etching method that combines both chemical and physical etching to allow isotropic and anisotropic material removal. The etching process is carried out in chemically reactive plasma containing positively and negatively charged ions generated from gases that are pumped into the reaction chamber. A mask on top of the substrate is used to protect designated areas from etching, exposing only the areas to be etched. Dry etching offers excellent process control for cleanliness, homogeneity, etch-rate, etch-profile, selectivity and run-to-run consistency, which is critical for high-fidelity pattern-transfer in micro- and nano-system technologies.

Wet Etching is an etching process that utilizes liquid chemicals or etchants to remove materials from the sample. Wet etching is generally isotropic, i.e., it proceeds in all directions at the same rate.  An etching process that is not isotropic is referred to as 'anisotropic.'  An etching process that proceeds in only one direction (e.g., vertical only) is said to be 'completely anisotropic'.

 

Process

Type

Chemistry used

Instrument

ICP-RIE

Dry etching

Fluorine gases

Oxford PlasmaPro 100 Cobra

Chemical etching

Wet etching

Acids (HCl, HF)

Fumehood