Self-aligned conductive lines via sacrificial mandrel spacers
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Solution Overview
Problem
As semiconductor devices scale down, aligning and patterning conductive lines in desired locations on the chip becomes increasingly challenging, with previous methods failing to achieve desired trench alignment as pitch scales down.
Innovation Solution
A method for forming conductive lines on a semiconductor wafer involves a series of hardmask and sacrificial mandrel layers, spacer material deposition, and selective etching processes to create trenches that can be filled with conductive material, allowing for self-aligned patterning and differentiation between mandrel and non-mandrel lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical lithography is used for patterning conductive lines, then manufacturing process is simple, but manufacturing precision deteriorates as pitch scales down
Solution Approach 1:
The patterning process is divided into multiple stages: first forming mandrel lines with initial hardmasks, then forming spacers adjacent to the mandrels, and finally using the spacers as new mandrels for trench formation. This segmentation allows each stage to be optimized independently, achieving high precision without requiring overly complex single-step lithography.
Solution Approach 2:
The method performs preliminary patterning actions by first forming the mandrel lines and then depositing spacer material around them before final trench etching. This preliminary action creates self-aligned structures that guide subsequent processing steps, ensuring precise trench alignment without requiring additional alignment operations.
2Productivity
If device scaling is performed to reduce costs and power consumption, then productivity improves, but manufacturing precision deteriorates
Solution Approach 1:
The structure is formed with nested layers: hardmasks are nested within the trench structure, spacers are nested adjacent to mandrel lines, and multiple processing steps are nested sequentially. This nesting approach allows continuous scaling of device dimensions while maintaining precise alignment through self-aligned fabrication steps.
Solution Approach 2:
The method transitions from two-dimensional planar patterning to three-dimensional structures by forming vertical trenches and depositing spacer material around mandrel lines. This dimensional transition enables continued scaling in the lateral direction while using vertical spacer thickness to define horizontal trench positions, decoupling scaling from alignment precision.
3Manufacturing precision
If self-aligned patterning is implemented, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The spacer structures serve multiple functions: they act as alignment references for trench formation, define trench width through their thickness, and provide self-aligned masks for selective etching. This multi-functionality reduces the need for separate alignment and dimensioning steps, offsetting the complexity of multi-layer hardmasks with process integration.
Solution Approach 2:
The structure uses itself for alignment: the spacers are formed directly from the mandrel lines and then serve as the alignment reference for trench formation. This self-service approach eliminates the need for external alignment marks or additional reference structures, reducing overall device complexity while maintaining high precision.
Data Source
AI summary
A method for forming conductive lines comprises forming a hardmask on an insulator layer, a planarizing layer on the hardmask, and a hardmask on the planarizing layer, removing exposed portions of a layer of sacrificial mandrel material to form first and second sacrificial mandrels on the hardmask, and depositing a layer of spacer material in the gap, and over exposed portions of the first and second sacrificial mandrels and the hardmask. Portions of the layer of spacer material are removed to expose the first and second sacrificial mandrels. A filler material is deposited between the first and second sacrificial mandrels. A portion of the filler material is removed to expose the first and second sacrificial mandrels. Portions of the layer of spacer material are removed to expose portions of the hardmask. A trench is formed in the insulator layer, and the trench is filled with a conductive material.