Copper Interconnect Air Gaps Reduce RC Delay
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Solution Overview
Problem
The increasing parasitic capacitance in copper interconnects due to shrinking dimensions and high wiring density in semiconductor chips leads to interconnect delay, which surpasses device delay and impacts circuit operating frequency, while low-k dielectric materials pose integration and reliability issues.
Innovation Solution
A method involving the formation of a copper interconnect structure with a first interconnect dielectric layer containing cavities and a second interconnect dielectric layer that seals these cavities, reducing the dielectric constant and improving chip performance by creating air gaps, thereby reducing RC delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the line width of the interconnect is reduced and wiring density is increased, then the integration degree and chip speed are improved, but the parasitic capacitance increases sharply leading to interconnect delay
Solution Approach 1:
The patent introduces air gaps (porous structures) into the interconnect dielectric layer to reduce the effective dielectric constant. By creating void spaces within the dielectric material, the overall capacitance between adjacent interconnect lines is reduced, thereby decreasing interconnect delay and RC time constant while maintaining high wiring density and fast chip speed.
2Object-generated harmful factors
If low-k dielectric materials are used to reduce parasitic capacitance, then the interconnect delay is reduced, but integration and reliability issues arise
Solution Approach 1:
The patent creates a composite dielectric structure combining solid dielectric material with air gaps (voids). This composite structure achieves an effective dielectric constant lower than conventional low-k materials while using proven reliable dielectric materials. The air gaps provide electrical isolation and reduce capacitance without introducing the mechanical and chemical stability issues associated with exotic low-k materials.
Solution Approach 2:
The patent extracts or removes portions of the dielectric material to create air gaps within the interconnect dielectric layer. By taking out material and replacing it with air (lower dielectric constant), the effective capacitance is reduced while maintaining the reliability of the remaining solid dielectric material that seals and supports the structure.
3Ease of manufacture
If conventional interconnect dielectric layers are used, then the manufacturing process is simple, but the dielectric constant cannot be reduced further to lower RC delay
Solution Approach 1:
The patent segments the continuous dielectric layer into regions with and without air gaps. The dielectric layer is divided into multiple sections where air gaps are strategically placed between adjacent interconnect lines. This segmentation approach reduces the effective dielectric constant in high-capacitance regions while maintaining structural integrity and compatibility with conventional manufacturing processes.
Solution Approach 2:
The patent introduces a vertical dimension to the dielectric structure by creating air gaps that extend through the dielectric layer thickness. Rather than merely adjusting horizontal dimensions, the solution adds vertical void spaces that reduce capacitance without affecting the planar layout and wiring density, thereby lowering RC delay while maintaining manufacturing 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
This approach effectively reduces the dielectric constant of the interconnect dielectric layers, lowering RC delay and enhancing chip performance while maintaining manufacturing efficiency by using a single mask for patterning air gaps and copper interconnect trenches or vias.
Implementation Method 1
The first interconnect dielectric layer, between neighboring conduits trenches, contains a plurality of cavities such that dielectric constant of the first interconnect dielectric layer is reduced
Data Source
AI summary
A method is disclosed for manufacturing a semiconductor device with a copper interconnect structure. The method includes providing a substrate, forming a first interconnect dielectric layer on the substrate, and forming a second interconnect dielectric layer on a surface of the first interconnect dielectric layer. The method also includes forming a plurality of conduits extending through the first interconnect dielectric layer and the second interconnect dielectric layer, and depositing copper in the plurality of conduits to form a copper interconnect layer of the copper interconnect structure. Further, the first interconnect dielectric layer, between neighboring conduits, contains cavities such that dielectric constant of the first interconnect dielectric layer is reduced. The second interconnect dielectric layer seals the top of the cavities, the substrate is the bottom of the cavities, and a width of the top of the cavities is less than a width of the bottom of the cavities.