Self-Aligned Via Patterning With Hardmask and Antispacer Trenches
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Solution Overview
Problem
The formation of microscale and nanoscale structures within workpieces, such as microelectronic devices, faces challenges in achieving accurate via alignment, particularly for small feature sizes and high aspect ratios, which can lead to misalignment and reduced device performance.
Innovation Solution
The method involves forming a hardmask with hardmask line features and antispacer trenches that intersect to create fully self-aligned vias (FSAVs). These vias are self-aligned on two sides by the sidewalls of the hardmask trenches and on the remaining sides by the sidewalls of the antispacer trenches, eliminating the need for additional photomasks or selective area deposition processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography with photomasks is used to form patterned layers for via formation, then alignment precision can be improved, but device complexity and fabrication cost increase due to multiple mask steps
Solution Approach 1:
The hardmask lines serve as self-aligned etch masks that automatically define the via positions through their own geometry and intersections, eliminating the need for separate photomask alignment steps. The method uses the hardmask structure itself to guide via formation, achieving self-service patterning without additional masking complexity
Solution Approach 2:
The via formation process is segmented into distinct functional components: hardmask lines defining primary positions, antispacer trenches providing lateral confinement, and etch holes forming the final vias. Each segment performs a specific function that collectively achieves precise via formation without requiring complex photomask sequences
2Ease of manufacture
If conventional via formation methods are used, then fabrication process is simpler, but via alignment precision deteriorates leading to misalignment with lower layer structures
Solution Approach 1:
The hardmask lines are formed in advance with precise geometric definitions that pre-determine the via positions. The antispacer trenches are also formed preliminarily to establish lateral boundaries. These preliminary structures serve as self-aligned guides that ensure precise via placement without requiring subsequent alignment adjustments
Solution Approach 2:
The invention transitions from two-dimensional photomask patterning to three-dimensional self-aligned structure formation. The hardmask lines and antispacer trenches create a 3D configuration that automatically defines via positions through their spatial relationships, adding a dimensional aspect that eliminates alignment errors inherent in 2D photolithography
3Reliability
If small feature sizes and high aspect ratios are targeted, then device performance is improved, but via alignment becomes more challenging and overlay errors increase
Solution Approach 1:
The method changes the critical parameters from photomask dimensions to hardmask line geometry and antispacer trench dimensions. By controlling the width, spacing, and intersection geometry of these structures, precise via dimensions and positions are achieved independently of feature size scaling, maintaining alignment precision even for small features and high aspect ratios
Data Source
AI summary
A method of patterning a substrate includes forming a hardmask over an underlying layer supported by a substrate, forming antispacer trenches over the hardmask, and forming fully self-aligned vias (FSAVs) extending from the hardmask into the underlying layer. The hardmask includes hardmask line features defining hardmask trenches extending in a first direction. The antispacer trenches extend in a second direction nonparallel to the first direction. The FSAVs extend into the underlying layer at intersections of the hardmask trenches and the antispacer trenches. The FSAVs are self-aligned on two sides by sidewalls of the hardmask trenches and self-aligned on the remaining sides by sidewalls of the antispacer trenches.