Semiconductor Interconnect Airgap Structure for Lower RC Delay
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Solution Overview
Problem
Existing semiconductor technologies face challenges in reducing the effective dielectric constant of interconnect structures, leading to increased resistance-capacitance delays and reduced performance due to the difficulty in implementing low-κ dielectric materials and the susceptibility of these materials to damage during processing.
Innovation Solution
Incorporation of an airgap within a dielectric liner layer by forming a protuberance layer on the sidewalls of metal lines and connecting it with a liner layer, which allows for a larger airgap to be formed, reducing the need for additional processing steps and improving electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low-κ dielectric materials are used to reduce the dielectric constant, then signal propagation speed is improved, but the materials are susceptible to damage during processing
Solution Approach 1:
A liner layer is introduced as an intermediary between the metal lines and the airgap. This liner layer protects the underlying structures during the airgap formation process while still allowing the airgap to achieve its intended low-dielectric-constant function. The liner layer acts as a buffer that prevents direct exposure and potential damage to the structures during subsequent processing steps.
2Speed
If airgap is introduced to lower the effective dielectric constant, then signal propagation speed is improved, but additional processing steps are required
Solution Approach 1:
The formation of the airgap is merged with the existing liner layer deposition process. Instead of adding a separate airgap formation step, the liner layer is deposited conformally over the metal lines and then etched back, with the airgap naturally forming in the spaces between adjacent metal lines during this integrated process. This combines multiple functions into a single process flow.
Solution Approach 2:
The liner layer is deposited preliminarily over the metal lines before the airgap is fully formed. This preliminary deposition of the liner layer provides a protective framework that guides the subsequent airgap formation process and ensures proper positioning of the airgap relative to the metal lines, simplifying the overall fabrication sequence.
3Speed
If larger airgap is formed to reduce the effective dielectric constant, then signal propagation speed is improved, but manufacturing precision requirements increase
Solution Approach 1:
The dielectric constant parameter is changed by introducing air (εr≈1) instead of using traditional dielectric materials. By controlling the size and distribution of the airgap through the liner layer thickness and etch depth parameters, the effective dielectric constant is reduced while maintaining manufacturable tolerance ranges. The liner layer acts as a spacer that defines the airgap dimensions with controllable precision.
Data Source
AI summary
A semiconductor device includes a substrate, a plurality of metal lines on the substrate, a protuberance layer formed on upper portions of sidewalls of the metal lines, and a liner layer formed between the metal lines and between the protuberance layer. The liner layer connects the protuberance layer, and an airgap exists in the liner layer below a bottom surface of the protuberance layers.