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1Q
Atomic Layer Etching (or ALE) is an advanced etch technique that allows for excellent depth control on shallow features. As device feature size reduces further and further ALE is required to achieve the accuracy required for peak performance. This tool is configured for etching materials used in quantum devices such as Niobium and Tantalum.
Atomic Layer Etching typically involves a cycle of 4 steps that is repeated as many times as necessary to achieve the required etch depth. This example shows ALE of Nb etching with CF4/Ar.
Step 1) Dosing of the substrate with an etching gas, which adsorbs on and reacts with the etch material. The etch gas is often plasma dissociated to enhance the rate of adsorption. With the correct choice of dosing gas and parameters, this can be self-limiting, if the chemical dose stops after adsorbing one monolayer.
Step 2) Purging of all residual dose gas.
Step 3) Bombardment of the surface with low energy inert ions which removes the reacted surface layer. This can be self-limiting if the energy of the ions is sufficient to remove the chemically modified layer, but insufficient to (sputter) etch the underlying bulk material.
Step 4) Etching products are purged from the chamber.