Inverse Spacer Lithography for Sub-Lithographic Feature Patterning

The patterning process is divided into multiple discrete steps: forming mandrels, depositing first spacers, removing mandrels, depositing second spacers, and selective removal. Each step creates progressively smaller features, segmenting the complex task of achieving sub-lithographic dimensions into manageable sequential operations that maintain precision while controlling overall process complexity

Mandrel structures are formed in advance as sacrificial elements that define the positions of subsequent spacer features. The first spacers are deposited and patterned before the second spacers, creating a hierarchical preliminary structure that guides the final feature formation and ensures precise critical dimensions are achieved before final pattern transfer

Multiple patterning operations are merged into a single integrated process flow where mandrels, first spacers, and second spacers are formed and patterned in one continuous sequence without intermediate lithography steps. This combines what would traditionally require multiple separate patterning cycles into one unified process, maintaining high critical dimension uniformity while preserving throughput by eliminating repeated lithography tool interventions

Spacer materials serve as intermediary structures that transfer the pattern from lithographically-defined mandrels to the final target features. The spacers act as self-aligned masks and pattern definition elements, mediating between the lithography step and the final etched features, thereby achieving high precision without requiring additional lithography passes that would reduce throughput

The process allows dynamic adjustment of feature dimensions and configurations by varying spacer deposition thicknesses, mandrel geometries, and selective removal patterns. Special features such as fins, trenches, and contact holes can be dynamically created by modifying which spacers are retained or removed, providing high process flexibility while maintaining manufacturing simplicity through a unified spacer-based approach

Critical dimensions and feature geometries are controlled by changing physical parameters such as spacer material deposition thickness, etch selectivity ratios, and removal conditions. By adjusting these parameters, the same basic process flow can produce diverse feature types and dimensions, achieving versatility without complicating the manufacturing process