Barrier layer stack for bit line air gap formation

摘要

Air gaps are formed between conductive metal lines that have an inner barrier layer and an outer barrier layer. An etch step to remove sacrificial material is performed under a first set of process conditions producing a byproduct that suppresses further etching. A byproduct removal step performed under a second set of process conditions removes the byproduct.

主权项

1. A method of forming an air gap between adjacent conductive lines comprising:
forming a plurality of trenches in a dielectric layer that is formed of a dielectric material; subsequently forming a first barrier layer in the plurality of trenches; subsequently forming a second barrier layer over the first barrier layer; and subsequently filling the plurality of trenches with a conductive metal to form bit lines; subsequently removing dielectric material between bit lines by: (a) performing a Chemical Dry Etching (CDE) step
under a first set of process conditionsthereby substantially etching the dielectric material and the second barrier layer simultaneouslywithout substantially etching the first barrier layer such that the first barrier layer extends above the dielectric material and second barrier layer,the etching of the dielectric material under the first set of process conditions
producing a byproduct that suppresses the etching of the dielectric material; and (b) subsequently performing a removal step
to remove the byproduct of the etching of the dielectric material in the CDE stepunder a second set of process conditions.