Air Gap Metal Interconnect Structure for RC Delay Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As device dimensions shrink, increased line resistance and parasitic capacitance lead to slower chip speeds and higher power consumption, and while air gaps can reduce RC signal delay, they compromise the mechanical strength of integrated circuits, necessitating a method to form air gaps within metal interconnect structures without weakening the device.
Innovation Solution
A method involving a substrate with an inter-metal dielectric layer, forming metal interconnections, creating spacers adjacent to these connections, and using them as masks to remove parts of the dielectric layer and form openings, which are then filled with a low-k dielectric material to create air gaps, thereby enhancing mechanical strength and reducing RC delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If air gaps are formed between interconnect lines to reduce dielectric constant, then RC signal delay is reduced and chip performance is improved, but mechanical strength is reduced and structural deformation occurs
Solution Approach 1:
The patent combines air gaps (dielectric constant ≈1) with a hybrid dielectric material comprising porous silicon oxide and organic compounds (dielectric constant 2.0-3.5) to create a composite dielectric structure. This composite approach allows the structure to achieve lower effective dielectric constant for reduced RC delay while the hybrid material provides enhanced mechanical strength compared to pure air gaps, thereby resolving the contradiction between signal performance and structural integrity
Solution Approach 2:
The patent applies different dielectric materials in different locations: air gaps are formed in specific regions where maximum capacitance reduction is needed, while the hybrid dielectric material is used in other regions to provide mechanical support. This localized application of different material properties allows simultaneous optimization of both electrical performance (low RC delay) and mechanical strength
2Productivity
If spacing between conducting lines is reduced to increase packing density, then more lines can be wired up, but parasitic capacitance increases
Solution Approach 1:
The patent changes the dielectric constant parameter of the material between conductive lines from conventional values (SiO2: 4.1-4.5) to lower values by introducing air gaps and hybrid dielectric materials with dielectric constants of 2.0-3.5. This parameter change reduces parasitic capacitance C, allowing reduced line spacing to be implemented without proportionally increasing capacitance, thereby enabling higher packing density while controlling parasitic effects
Solution Approach 2:
The patent introduces air gaps and hybrid dielectric materials as intermediary substances between adjacent conducting lines. These intermediary materials with low dielectric constants act as mediators that reduce the electric field coupling between lines, thereby reducing parasitic capacitance and enabling closer line spacing for increased packing density
3Stability of the object's composition
If conventional SiO2 is used as dielectric material, then thermal and chemical stability is maintained, but dielectric constant is too high to reduce RC delays effectively
Solution Approach 1:
The patent creates a composite dielectric structure combining air gaps (dielectric constant ≈1) with hybrid dielectric materials comprising porous silicon oxide and organic compounds (dielectric constant 2.0-3.5). This composite approach achieves an effective dielectric constant significantly lower than conventional SiO2 (4.1-4.5), reducing RC signal delay while the hybrid material composition provides thermal and chemical stability comparable to or better than conventional SiO2
Data Source
AI summary
A method for fabricating metal interconnect structure is disclosed. The method includes the steps of: providing a substrate having a first inter-metal dielectric (IMD) layer thereon; forming a metal interconnection in the first IMD layer; removing part of the first IMD layer; forming a spacer adjacent to the metal interconnection; and using the spacer as mask to remove part of the first IMD layer for forming an opening in the first IMD layer.