Strained FinFET Buffer Layer Alternating Layers

The fin channel is segmented into multiple alternating layers of different materials (e.g., SiGe and Si) with different lattice constants. This segmentation creates discrete strain zones throughout the channel length, preventing stress relaxation that would occur in a uniform strained layer. Each layer segment maintains localized strain, and the cumulative effect across all segments provides sustained mobility enhancement along the entire fin length.

Different regions of the fin channel are given different material compositions and strain characteristics. The alternating layers have locally optimized properties - some layers provide tensile strain while others provide compressive strain or serve as buffer layers. This local quality variation ensures that strain is maintained at critical locations (including fin edges) rather than being uniformly distributed, addressing the stress relaxation problem at specific positions.

By dividing the long fin channel into multiple short alternating layers, the segmentation principle allows each layer to maintain its strain independently. The strain in one layer does not relax into adjacent layers with opposite or different strain characteristics, effectively resetting the stress state at each interface. This enables the fin to achieve both increased length (for higher productivity) and maintained stress (through the segmented structure).

The fin channel is constructed as a composite structure with alternating layers of different semiconductor materials (e.g., SiGe/Si superlattice). This composite material approach allows the channel to combine the beneficial effects of different materials - some providing strain for mobility enhancement while others provide lattice matching to prevent relaxation. The composite structure maintains stress over longer fin lengths than a single-material fin could achieve.