Interconnect Air Gaps Reduce RC Delay
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Solution Overview
Problem
The reduction in size of semiconductor devices and interconnect line widths leads to increased line resistance and parasitic capacitance, resulting in RC delay, which negatively impacts computing speed and performance, and existing methods for forming air gaps are unreliable and not suitable for mass production.
Innovation Solution
A method for manufacturing interconnect structures with air gaps involves forming recesses in an insulating layer, sealing them with additional insulating layers to create air gaps adjacent to conductive lines, and incorporating a via structure and landing marks to provide structural support and electrical connectivity, thereby improving mechanical strength and simplifying routing design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the line width of conductive lines is reduced to increase device density, then device density is improved, but line resistance and parasitic capacitance are increased leading to increased RC delay
Solution Approach 1:
The patent extracts the problematic dielectric material between adjacent conductive lines and replaces it with air gaps. By removing the solid dielectric material (which has high permittivity and contributes to parasitic capacitance) and replacing it with air (which has permittivity close to vacuum), the parasitic capacitance between adjacent lines is significantly reduced, thereby reducing RC delay while maintaining high device density
Solution Approach 2:
The patent introduces air gaps (porous structure) between conductive lines as an insulating medium. These air gaps serve as low-permittivity regions that reduce parasitic capacitance between adjacent lines. The porous air gap structure achieves lower effective permittivity compared to solid dielectric materials, thus reducing RC delay while maintaining compact interconnect spacing for high device density
2Reliability
If air gaps are formed between conductive lines to reduce parasitic capacitance, then parasitic capacitance and RC delay are reduced, but mechanical strength is insufficient and reliability issues arise
Solution Approach 1:
The patent applies different material properties to different regions: air gaps are placed locally between adjacent conductive lines where parasitic capacitance reduction is needed, while solid dielectric material is retained in other regions (such as beneath conductive lines and in non-critical areas) to provide mechanical support. This localized application of air gaps achieves capacitance reduction without compromising overall structural integrity
Solution Approach 2:
The patent creates a composite interconnect structure combining air gaps (for electrical performance) with solid dielectric materials and conductive lines (for mechanical support). The composite structure integrates the low-permittivity advantage of air with the mechanical strength of solid materials, achieving both reduced parasitic capacitance and adequate mechanical support
3Reliability
If conventional air gap formation processes are used to reduce RC delay, then parasitic capacitance is reduced, but the process is complicated and not suitable for mass production
Solution Approach 1:
The patent performs preliminary patterning of the air gap regions before final interconnect formation. By pre-defining where air gaps will be located through earlier processing steps (such as mandrel formation and selective removal), the subsequent air gap creation becomes a straightforward byproduct of the manufacturing flow rather than a complex separate process, enabling mass production compatibility
Solution Approach 2:
The patent designs the air gap formation process to be self-organizing or self-aligned with existing interconnect structures. The air gaps automatically form in the correct positions relative to conductive lines through self-aligned processes (such as spacer formation or selective etching), eliminating the need for additional complex alignment and patterning steps, thus simplifying manufacturing for mass production
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 reduces parasitic capacitance and RC delay while enhancing the mechanical strength of the interconnect structure, making it more reliable and suitable for mass production by introducing interconnect units with conductive lines, landing marks, and via structures that separate air gaps, thus improving performance and manufacturing efficiency.
Implementation Method 1
parasitic capacitance is related to dielectric constant (k) of the insulating material between the two conductive lines, it can be reduced when the insulating material (s) having lower dielectric constant is adopted. Additionally, insulating material (s) having dielectric constant lower than 2.5-3.5, also known as low-k insulating material (s) not only reduces parasitic capacitance and RC delay
Implementation Method 2
air gap not only reduces RC delay, but also has advantage of low heat conductivity
Data Source
AI summary
A method for manufacturing an interconnect structure with air gaps includes the following steps. A substrate including a first insulating layer formed thereon is provided. Plural conductive lines are formed in the first insulating layer. A patterned hard mask is formed on the first insulating layer and the conductive lines and exposes portions of the first insulating layer and portions of the conductive lines. The exposed portions of the first insulating layer are then removed to form a plurality of recesses in the first insulating layer. After that, a second insulating layer and a third insulating layer are formed in the recesses to seal the recesses and to form a plurality of air gaps in the recesses. At least two air gaps are respectively formed at two sides of one conductive line of the plurality of conductive lines. A via structure is then formed on the one conductive line.