Self-Aligned Via Formation Using Block Copolymer Self-Assembly
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Solution Overview
Problem
Conventional dual damascene integration schemes require multiple lithographic steps and critical masks to achieve alignment between via and line cavities, leading to increased manufacturing costs and overlay variations that affect the yield, performance, and reliability of metal interconnect structures in semiconductor manufacturing.
Innovation Solution
A self-aligned metal via is formed within a metal line using self-assembling block copolymers, where a recessed region with a line portion and a bulge portion is created in a hard mask layer, and the block copolymers are annealed to form a cylindrical polymeric block that self-aligns to the center of the bulge portion, allowing for the formation of a via cavity and line cavity with reduced overlay variations and a single lithographic step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dual damascene integration scheme with separate lithographic masks is used to pattern via cavities and line cavities, then alignment between via and line cavities can be achieved, but manufacturing cost increases significantly and overlay variations affect yield and reliability
Solution Approach 1:
The patent combines the patterning of via cavities and line cavities into a single lithographic step by forming a combined mask structure that defines both cavity types simultaneously. This eliminates the need for separate lithographic masks and processes, reducing manufacturing cost while maintaining alignment precision through self-aligned formation of both cavity patterns in one exposure step.
Solution Approach 2:
The patent employs self-aligned via formation where the via cavity pattern is automatically positioned relative to the line cavity pattern through the single lithographic mask structure. The mask design inherently provides the alignment relationship between via and line cavities without requiring additional overlay control processes, making the system self-aligning and eliminating costly critical mask requirements.
2Manufacturing precision
If critical masks with smallest overlay tolerance are used for patterning via and line cavities, then sufficient overlap between metal vias and metal lines is ensured, but manufacturing cost increases significantly
Solution Approach 1:
The patent merges the patterning functions of multiple critical masks into a single lithographic mask that simultaneously defines both via cavities and line cavities. This combined mask approach eliminates the need for expensive state-of-the-art lithographic equipment required for tight overlay tolerance, as the alignment is built into the single mask pattern rather than requiring precise overlay between separate masks.
Solution Approach 2:
The single lithographic mask structure provides self-aligned patterning where the relative positions of via and line cavities are determined by the mask geometry itself rather than by overlay control between separate exposure steps. This self-aligned approach eliminates the need for expensive critical mask lithography while ensuring sufficient overlap between resulting metal vias and lines.
3Ease of manufacture
If overlay variations between two lithographic images occur, then manufacturing cost can be reduced, but contact area between metal vias and metal lines decreases and yield performance and reliability are adversely affected
Solution Approach 1:
The patent combines the patterning of via and line cavities into a single lithographic step, eliminating overlay variations between separate lithographic images. The single mask structure ensures that the relative positions of via and line cavities are fixed by the mask geometry, guaranteeing sufficient contact area between resulting metal vias and lines while avoiding the reliability issues caused by overlay variations.
Solution Approach 2:
The self-aligned via formation through single lithographic patterning eliminates dependence on overlay control between multiple images. The via cavity positions are automatically determined relative to line cavities by the single mask pattern, ensuring consistent contact area and reliable electrical connections without the variability introduced by multi-step lithographic overlay.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach eliminates overlay variations between metal vias and lines, enhancing the yield, performance, and reliability of the interconnect structure while reducing manufacturing costs by integrating the via and line formation into a single lithographic step.
Implementation Method 1
Self-assembling block copolymers containing two or more different polymeric block components that are immiscible with one another are applied within the recessed region and annealed. A cylindrical polymeric block in the form of an elliptical cylinder and containing a first polymeric block component and a polymeric block matrix containing a second polymeric block component are formed within the recessed region. The cylindrical polymeric block is self-aligned to the center of the bulge portion.
Data Source
AI summary
A recessed region containing a line portion and a bulge portion is formed in a hard mask layer. Self-assembling block copolymers containing two or more different polymeric block components that are immiscible with one another are applied within the recessed region and annealed. A cylindrical polymeric block centered at the bulge portion is removed selective to a polymeric block matrix surrounding the cylindrical polymeric block. A via cavity is formed by transferring the cavity formed by removal of the cylindrical polymeric block into a dielectric layer. The pattern in the hard mask layer is subsequently transferred into the dielectric layer to form a line cavity. A metal via and a metal line are formed by deposition and planarization of metal. The metal via is self-aligned to the metal line.