Air-Gap Formation in Semiconductor Interconnects
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Solution Overview
Problem
Conventional methods for forming air-gaps between interconnects in semiconductor devices face challenges such as difficulty in precise formation, limited adjustability of air-gap shape, non-selective formation, and the need for additional materials, which can degrade mechanical strength and introduce defects.
Innovation Solution
A method involving the formation of interconnect structures with sequential mask layers having micropores, where the pores coalesce to create microholes for etching, allowing for selective removal of insulating material and precise air-gap formation between interconnects using conventional materials as masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods (non-conformal deposition, thermal decomposable polymer, or di-block copolymer) are used to form air-gaps, then air-gap structure can be formed, but the air-gap cannot be easily formed at desired region at desired level and shape adjustment is difficult, causing defects
Solution Approach 1:
The mask layer is divided into multiple segments with different etch selectivities (first mask layer with first etch selectivity, second mask layer with second etch selectivity). This segmentation allows independent control of air-gap formation at different regions and levels, enabling precise placement while maintaining ease of manufacture through sequential processing steps.
Solution Approach 2:
Different portions of the mask structure are assigned different etch selectivities to achieve local quality control. The first mask layer portion has higher etch selectivity for forming air-gaps at first interconnect level, while the second mask layer portion has lower etch selectivity for forming air-gaps at second interconnect level, allowing shape and location adjustment without compromising formation ease.
2Reliability
If air-gap is formed between interconnects, then dielectric constant is reduced, but mechanical strength of semiconductor device is degraded
Solution Approach 1:
The mask structure uses composite material design with multiple layers having different etch selectivities. This composite structure provides both the electrical performance benefit of air-gaps (reduced dielectric constant) and mechanical strength support, as the multi-layer mask system distributes structural support across multiple components rather than relying on a single air-gap forming layer.
Solution Approach 2:
The mask layers serve as intermediary structures that enable air-gap formation indirectly. Instead of directly forming air-gaps which would compromise mechanical strength, the patent uses mask layers with controlled etch selectivities as mediators to define air-gap regions, allowing the air-gaps to form in a controlled manner that preserves overall device mechanical integrity.
3Ease of manufacture
If new material is used to form air-gap, then air-gap formation is enabled, but device complexity increases due to additional materials
Solution Approach 1:
The mask layers are designed with multi-functionality, serving both as patterning structures and as air-gap formation templates. By making the mask layers selectively removable through controlled etching, they perform multiple functions (patterning, air-gap definition, and potential sacrificial role) without requiring separate dedicated materials, thus enabling air-gap formation while minimizing device complexity.
Solution Approach 2:
The mask layers are designed to be selectively discarded (removed) after serving their purpose of defining air-gap regions. The first mask layer portion is removed to form air-gaps at the first interconnect level, and the second mask layer portion is removed to form air-gaps at the second interconnect level. This discarding approach enables air-gap formation capability without permanently adding complex material structures to the final device.
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
Enables precise and selective formation of air-gaps, improving mechanical strength and reducing defects by allowing control over air-gap shape and location, while utilizing existing materials, thus enhancing semiconductor device performance.
Implementation Method 1
coalescing the plurality of micropores in the second mask layer with each other and forming a plurality of first microholes in the second mask layer
Data Source
AI summary
Provided is a method for fabricating a semiconductor device, including forming an interconnect structure including first and second interconnects and an insulating material between the first and second interconnects, forming a first mask layer and a second mask layer having a plurality of micropores sequentially on the interconnect structure, coalescing the plurality of micropores in the second mask layer with each other and forming a plurality of first microholes in the second mask layer, forming a plurality of second microholes in the first mask layer using the plurality of first microholes, and removing the insulating material using the first mask layer with the plurality of second microholes as an etch mask so as to form an air-gap between the first and second interconnects.