Trench Interconnect with Deep Air Gaps for Reduced Fringe Capacitance
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Solution Overview
Problem
Current dual damascene interconnect structures using ultra-low-k (ULK) dielectric materials face issues with mechanical instability, poor adhesion, dielectric flopover, cracking, and voids due to reduced dielectric constant, which compromises structural stability and electrical performance.
Innovation Solution
Incorporating deep air gaps into a high modulus insulator to reduce capacitance between adjacent nanowires while maintaining structural stability, using a bi-layer dielectric structure with ULK dielectrics for vias and high modulus insulators for metal-filled trenches, and patterning dielectric U-shaped structures with selected width-to-spacing ratios to create these air gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultra-low-k (ULK) dielectric materials are used to reduce dielectric constant below 2.4, then capacitance between adjacent nanowires is reduced, but mechanical properties such as Young's modulus, cohesive strength, and adhesion are degraded
Solution Approach 1:
The patent uses a composite dielectric structure consisting of a first dielectric material (higher-k material with better mechanical properties) and a second dielectric material (lower-k material with better electrical performance). This composite approach allows the structure to simultaneously achieve the electrical performance benefits of low-k materials and the mechanical strength benefits of higher-k materials, resolving the contradiction between reduced capacitance and maintained mechanical properties
Solution Approach 2:
The patent applies different dielectric materials to different regions: the first dielectric material is used in regions where mechanical strength is critical (such as supporting high aspect ratio structures), while the second dielectric material is used in regions where capacitance reduction is most beneficial. This spatial differentiation of material properties allows each material to perform its optimal function without compromising the other
2Reliability
If porous ULK dielectric films are used to achieve low dielectric constant, then capacitance is reduced, but the films become mechanically unstable and prone to cracking
Solution Approach 1:
The patent combines a porous low-k dielectric material with a non-porous or less porous higher-k dielectric material to create a composite structure. The higher-k material provides mechanical stability and resistance to cracking, while the porous low-k material provides the desired electrical insulation and low capacitance. This composite approach resolves the contradiction between electrical performance and structural stability
3Productivity
If high aspect ratio via structures are formed to achieve vertical connections, then interconnect density is improved, but dielectric flopover occurs and metal voids form
Solution Approach 1:
The patent segments the dielectric layer into regions with different mechanical properties, placing higher-strength dielectric material in areas that provide structural support for high aspect ratio via structures. This segmentation allows the via structures to maintain their high aspect ratio for improved density while the reinforced dielectric regions prevent flopover and ensure uniform metal filling
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 approach effectively reduces capacitance between nanowires, enhances structural stability, prevents dielectric flopover, and ensures uniform metal fill, addressing the limitations of ULK dielectrics while maintaining mechanical strength and reducing fringe capacitance.
Implementation Method 1
reduce capacitance between adjacent nanowires
Data Source
AI summary
Ultra-low-k dielectric materials used as inter-layer dielectrics in high-performance integrated circuits are prone to be structurally unstable. The Young's modulus of such materials is decreased, resulting in porosity, poor film strength, cracking, and voids. An alternative dual damascene interconnect structure incorporates deep air gaps into a high modulus dielectric material to maintain structural stability while reducing capacitance between adjacent nanowires. Incorporation of a deep air gap having k=1.0 compensates for the use of a higher modulus film having a dielectric constant greater than the typical ultra-low-k (ULK) dielectric value of about 2.2. The higher modulus film containing the deep air gap is used as an insulator and a means of reducing fringe capacitance between adjacent metal lines. The dielectric layer between two adjacent metal lines thus forms a ULK/high-modulus dielectric bi-layer.