Self-Aligned Conductive Lines via Sacrificial Mandrels
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Solution Overview
Problem
As semiconductor devices scale down, aligning and patterning conductive lines in desired locations becomes increasingly challenging due to limitations in previous patterning methods, which fail to achieve desired trench alignment as pitch scales down.
Innovation Solution
A method is developed for forming conductive lines by distinguishing mandrel lines and non-mandrel lines during formation, using sacrificial mandrels and spacers to create trenches that can be selectively filled with conductive material, allowing for self-alignment with a greater margin of error, even at smaller pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional patterning methods are used, then manufacturing process is simple, but alignment precision deteriorates as pitch scales down
Solution Approach 1:
The patterning process is divided into multiple stages: forming sacrificial mandrels, depositing spacers, selective removal of mandrels, and trench formation. This segmentation allows each step to be optimized independently, achieving high alignment precision through the self-aligned nature of spacer formation while managing overall process complexity through systematic breakdown of operations.
Solution Approach 2:
Sacrificial mandrels are formed in advance before the actual conductive line patterning. These mandrels serve as preliminary structures that define the eventual trench locations. By performing this preliminary action, the subsequent spacer deposition is self-aligned to the desired pattern, ensuring high alignment precision without requiring complex final patterning steps.
2Area of moving object
If pitch is reduced for scaling, then device density increases, but alignment precision deteriorates
Solution Approach 1:
The spacer structures serve themselves as alignment references for trench formation. The spacers are deposited conformally on the sacrificial mandrels, and their positions automatically define the trench locations through self-aligned etching. This self-service mechanism ensures that even at reduced pitches, the trench alignment precision is maintained because the alignment is determined by the spacer geometry rather than by complex lithographic alignment at the final pattern scale.
3Manufacturing precision
If multi-step patterning is implemented, then alignment precision improves, but manufacturing time increases
Solution Approach 1:
Multiple functions are merged into the spacer deposition step: the spacers simultaneously serve as alignment references, as etch masks for trench formation, and as definitions of the final conductive line positions. This merging reduces the number of separate patterning steps needed, thereby reducing manufacturing cycle time while maintaining the alignment precision benefits of the multi-step approach.
Solution Approach 2:
The spacer structures perform multiple functions throughout the process: they are formed by conformal deposition that provides self-alignment, they serve as the template for trench etching, and they define the final conductive line geometry. This multi-functionality eliminates the need for separate alignment and patterning steps, reducing overall manufacturing time while achieving high alignment precision.
Data Source
AI summary
A method for forming conductive lines on a wafer comprises forming a first sacrificial mandrel and a second sacrificial mandrel. Spacers are formed adjacent to the first and second sacrificial mandrels. A filler material is deposited on the second hardmask. A first mask is formed on a portion of the second sacrificial mandrel. A first cavity and a second cavity are formed that expose portions of the second hardmask, and exposed portions of the second mask and exposed portions of the filler material are removed to expose portions of the first hardmask. Exposed portions of the first hardmask, the planarizing layer and the first hardmask are removed to expose portions of the insulator layer. Exposed portions of the insulator layer are removed to form a trench in the insulator layer and the trench is filled with a conductive material.