FinFET HV Region Structure for Precise Fin Etching Control

The patent applies preliminary action by forming a mandrel structure before the fin structure, which serves as a template to guide subsequent self-aligned etching processes. This pre-formed mandrel enables precise fin definition without requiring direct lithographic patterning at the final fin dimensions, thereby achieving miniaturization while maintaining fabrication precision through self-aligned processes that eliminate alignment errors

The patent introduces a mandrel as an intermediary structure that mediates between the lithography step and the final fin structure. This intermediate mandrel allows the use of less precise lithography for defining the mandrel position, while the subsequent self-aligned etching processes transfer this pattern to the fin structure with high precision, effectively decoupling the lithography precision requirement from the final fin dimension control

The patent implements feedback control through selective etching processes that use the mandrel structure and sacrificial layers as etch stop references. The etching process is designed to stop automatically when it reaches predefined interfaces (such as the mandrel-substrate interface or sacrificial layer boundaries), providing real-time process control that prevents over-etching while ensuring complete fin formation. This self-limiting etch approach eliminates the need for extended etching times

The patent prepares sacrificial layers and mandrel structures in advance that serve as built-in etch stop references. These pre-formed structures create physical boundaries that automatically limit the etching depth, ensuring that the etching process stops exactly when the fin structure is complete without penetrating into the substrate. This preliminary preparation of etch boundaries prevents over-etching damage while guaranteeing complete fin formation