Top Via Structure With Spacer-Modulated CD Control
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Solution Overview
Problem
The challenge in semiconductor manufacturing is controlling the via critical dimension (CD) in damascene via schemes due to lack of good etch selectivity, leading to difficulties in achieving self-aligned vias and maintaining acceptable via CD control, which affects device reliability and increases parasitic capacitance.
Innovation Solution
A method involving the formation of a unique via profile by modulating spacer thickness to achieve self-aligned vias with controlled via CD, eliminating the need for barrier metal at the via bottom and preventing line wiggling or via distortion, while maximizing contact area between the via and line without over etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If aggressive scaling down of IC dimensions is implemented, then device integration density is improved, but via-to-line breakdown occurs and device reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure with controlled dimensions and shape before depositing the via liner and fill material. The mandrel is designed with specific aspect ratio and top surface configuration that pre-determines the final via dimensions, ensuring proper via-to-line spacing is established before subsequent processing steps occur. This preliminary structuring prevents via-to-line breakdown while maintaining high integration density.
Solution Approach 2:
The patent introduces a mandrel as an intermediary structure that mediates between the patterning process and the final via formation. The mandrel serves as a temporary structure that defines via locations and dimensions, allowing precise control of via critical dimensions without directly exposing the via fill material to the patterning process. This intermediary approach enables reliable via formation at scaled dimensions.
2Manufacturing precision
If via critical dimension control is attempted through conventional etching, then via CD precision is improved, but etch selectivity requirements increase process complexity
Solution Approach 1:
The patent applies self-service by designing a mandrel structure that automatically defines via critical dimensions through its geometric properties rather than requiring precise etching of the via opening itself. The mandrel's top surface area and shape self-determine the via footprint, eliminating the need for complex etch selectivity control. The process serves itself by using deposition and planarization rather than etching to control via dimensions.
Solution Approach 2:
The patent replaces the mechanical/chemical etching process with a deposition-based approach. Instead of using etch chemistry to define via openings, the patent uses physical vapor deposition or chemical vapor deposition to form conformal liner layers around a mandrel, followed by planarization. This substitution of deposition for etching eliminates selectivity issues and provides better CD control.
3Ease of manufacture
If self-aligned vias are formed without barrier metal, then manufacturing steps are reduced, but via bottom protection may be compromised
Solution Approach 1:
The patent extracts the barrier metal function from the traditional via structure by using the mandrel itself as the defining structure. The mandrel material and configuration provide the necessary protection and definition without requiring a separate barrier metal layer. The via liner is deposited directly on the mandrel surface, and the mandrel's geometric properties ensure proper adhesion and protection without additional barrier layers.
Data Source
AI summary
A method of via formation including forming a sacrificial mask over a conductive layer, forming a plurality of pillars in the sacrificial mask and the conductive layer, wherein each pillar of the plurality of pillars includes a sacrificial cap and a first conductive via, depositing a spacer between the plurality of pillars, masking at least one of the sacrificial caps, removing at least one of the sacrificial caps to create openings, forming second conductive vias in the openings, and depositing a dielectric coplanar to a top surface of the second conductive vias.