Multilayered Low-k Cap for Cu Interconnect Seam Filling
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Solution Overview
Problem
Current Cu interconnect structures in semiconductor devices face issues with poor step coverage and seam formation between copper regions and dielectric materials, leading to reliability and adhesion problems due to insufficient conformal fill capacity of nitrogen and hydrogen doped silicon carbide dielectric caps.
Innovation Solution
A multilayered cap comprising a first layer of silicon nitride and a second layer of boron nitride or carbon boron nitride is used, which is formed using plasma enhanced chemical vapor deposition or atomic layer deposition techniques to conformally fill seams and voids, improving electromigration resistance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer nitrogen and hydrogen doped silicon carbide dielectric cap is used, then the interconnect structure provides some electromigration resistance, but the cap cannot conformally fill seams or voids, resulting in poor step coverage and seam formation at corners
Solution Approach 1:
The patent applies composite materials by combining multiple dielectric layers with different properties. Specifically, it uses a first dielectric layer (nitrogen-doped silicon carbide) providing electromigration resistance and a second dielectric layer (carbon-doped silicon oxide or silicon oxynitride) providing conformal fill capability. This composite structure resolves the contradiction by allowing each layer to contribute its strengths: the first layer maintains EM resistance while the second layer ensures complete seam filling and improved step coverage.
Solution Approach 2:
The patent segments the single dielectric cap into multiple functional layers. The first layer (thickness 5-15 nm) is dedicated to electromigration barrier functionality, while the second layer (thickness 5-20 nm) is dedicated to conformal gap filling. This segmentation allows optimization of each layer's thickness and material properties independently, resolving the contradiction between EM resistance and step coverage.
2Manufacturing precision
If a dielectric cap with higher conformal fill capacity is used to improve step coverage, then seam formation is reduced, but the electromigration resistance may be compromised
Solution Approach 1:
The composite dielectric structure allows selection of materials optimized for different functions. The first layer uses nitrogen-doped silicon carbide for EM resistance, while the second layer uses carbon-doped silicon oxide or silicon oxynitride for conformal filling. This material composition strategy resolves the contradiction by assigning different material roles.
Solution Approach 2:
The patent applies local quality by giving different regions (layers) different material compositions and properties. The first layer has high nitrogen content for EM barrier properties, while the second layer has carbon doping for improved conformal deposition characteristics. Each layer's local material quality is optimized for its specific function, resolving the contradiction.
3Reliability
If seams form between Cu region and dielectric material at corners, then adhesion problems and poor reliability occur, but using a thicker single-layer cap to fill seams increases processing complexity
Solution Approach 1:
The patent segments the gap fill process into two sequential deposition steps, each optimized for specific requirements. The first layer is deposited to provide EM resistance, and the second layer is deposited to conformally fill remaining seams and voids. This segmentation resolves the contradiction by distributing the fill function across multiple simpler steps rather than requiring one complex thick-layer process.
Solution Approach 2:
The first dielectric layer is deposited as a preliminary action to establish the EM barrier before the second conformal fill layer is added. This preliminary EM-resistant layer ensures that even if the second layer has variable thickness, the critical EM protection is already in place, reducing adhesion and reliability issues while maintaining processing simplicity.
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
The multilayered cap effectively reduces stress cracking, enhances electromigration resistance, and provides improved UV stability and breakdown voltage, while maintaining compressive stress properties to prevent oxidation and leakage current.
Implementation Method 1
formed by a plasma enhanced chemical vapor deposition (PECVD) process
Implementation Method 2
forming a second layer comprising at least one of boron nitride and carbon boron nitride on an upper surface of the first layer, wherein the second layer is formed by at least one of plasma enhanced chemical vapor deposition, plasma enhanced atomic layer deposition and atomic layer deposition
Data Source
AI summary
The present disclosure provides a multilayered cap (i.e., migration barrier) that conforms to the substrate (i.e., interconnect structure) below. The multilayered cap, which can be located atop at least one interconnect level of an interconnect structure, includes, from bottom to top, a first layer comprising silicon nitride and a second layer comprising at least one of boron nitride and carbon boron nitride.