Convergent Fin and Nanosheet Transistor Layout for Tight Gate Spacing

The fabrication process is segmented into multiple patterning steps (e.g., self-aligned double-patterning, self-aligned triple-patterning) where each step creates a portion of the final pattern. This segmentation allows achieving finer spacing between gate structures and fins that cannot be obtained with single-patterning, directly resolving the contradiction between manufacturing precision and process complexity by breaking down the complex task into manageable sequential steps.

The patent introduces vertical dimensionality through multi-layered spacer formation and etch-stop layers at different depths. By utilizing the vertical stacking of spacer layers (first spacer, second spacer, third spacer at different positions) and etch-stop layers, the process achieves superior lateral patterning precision without proportionally increasing lateral process complexity, effectively resolving the spacing precision versus process complexity contradiction.

Etch-stop layers are formed preliminarily at specific depths before the final gate patterning step. These pre-positioned etch-stop layers (at different vertical levels) provide precise depth references that guide subsequent etching processes, ensuring that gate structures and fins are spaced correctly even as device density increases through scaling. This preliminary action enables maintaining manufacturing precision despite increased functional density requirements.

Multiple spacer layers act as intermediary structures that mediate between the lithographically defined patterns and the final gate structures. The spacers (first, second, third spacers at different positions) serve as intermediate patterning elements that translate coarse lithographic features into fine-spaced gate-fin structures, enabling increased functional density while maintaining precise spacing control through the intermediary spacer formation process.

The patent employs self-aligned patterning techniques where each patterning step automatically aligns itself to previously formed structures without requiring additional alignment operations. For example, spacers are formed conformally on existing structures and then etched back, with the etch automatically stopping at pre-formed etch-stop layers. This self-service approach enables multi-patterning to achieve superior spacing precision while minimizing the increase in fabrication complexity by eliminating manual alignment steps.

The fabrication process utilizes parameter changes in the form of selective etching based on depth and material composition. By varying etch selectivity parameters (etch rate, stopping depth, material specificity) across different process steps, the patent achieves precise spacing control through multi-patterning while managing fabrication complexity. The etch-stop layers enable parameter-based control where etching automatically adjusts its depth based on encountering different material layers, simplifying the overall manufacturing process despite multiple patterning steps.