FinFET Work Function Layer Etching With an Adhesion Barrier

An adhesion layer is introduced as an intermediary between the hardmask layer and the patternable layer. This adhesion layer serves as a mediator that prevents etchant penetration through the layer interface, thereby protecting the work function layers from unintended removal while maintaining the etching precision provided by the hardmask and patternable layers. The adhesion layer acts as a barrier that mediates the interaction between etchants and the underlying work function layers.

The patent employs a composite multi-layer structure consisting of the hardmask layer, adhesion layer, and patternable layer. This composite material approach creates a more robust interface that resists etchant penetration. The combination of different materials with complementary properties (etch resistance, adhesion, and barrier characteristics) solves the problem of etchant penetration while maintaining manufacturing precision.

The adhesion layer serves as a protective intermediary between the patternable layer and the work function layers. During etching processes, this adhesion layer acts as a selective barrier that allows controlled etching of work function layers for threshold voltage adjustment while preventing unintended penetration through the patternable layer that would cause undesired loss of work function layers.

The adhesion layer is deposited beforehand to create a protective cushion or barrier over the work function layers. This pre-established protective layer prevents etchants from penetrating through the patternable layer and causing undesired loss of work function layers, while still allowing controlled etching where needed for threshold voltage control.