Dielectric Air Gaps for Semiconductor Interconnects
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Solution Overview
Problem
Conventional dielectric materials with air gaps in semiconductor devices lack mechanical strength, making them unsuitable for demanding applications like middle-of-line (MOL) dielectrics due to the weakening effect of air gaps on the dielectric layers.
Innovation Solution
The method involves forming a dielectric layer with cylindrical air gaps oriented normal to the surface, using a block copolymer masking layer to create a patterned masking layer that allows for selective etching, maintaining mechanical strength while reducing the dielectric constant, and utilizing a hexagonal honeycomb pattern to ensure robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If air gaps are introduced into dielectric layers to decrease dielectric constants and reduce interconnect capacitance, then the dielectric constant is reduced, but the mechanical strength of the dielectric layers is reduced
Solution Approach 1:
The patent applies local quality by creating specific localized air gap structures (cylindrical, spherical, or pyramidal voids) at predetermined locations within the dielectric layer, rather than uniformly distributing air gaps throughout. This localized approach allows the dielectric constant to be reduced in specific regions while maintaining mechanical strength in other areas, particularly preserving structural integrity around metal interconnects and contact regions.
Solution Approach 2:
The patent utilizes porous materials by introducing controlled air gaps (voids) into the dielectric layer to create a porous structure. These air gaps reduce the effective dielectric constant of the material while the patent specifically designs the pore distribution and morphology to maintain adequate mechanical strength, addressing the contradiction between dielectric performance and structural integrity.
2Loss of energy
If air gaps are introduced into dielectric layers to reduce interconnect capacitance, then interconnect capacitance is reduced, but the dielectric layer may buckle or collapse during processing
Solution Approach 1:
The patent applies preliminary action by forming the air gaps within the dielectric layer before subsequent metal deposition and interconnect formation steps. This ensures that the dielectric structure with its reduced capacitance is established in advance, while the overlying metal layers and additional dielectric layers provide mechanical support during processing, preventing buckling or collapse.
Solution Approach 2:
The patent creates a composite structure by combining the air-gap-containing dielectric layer with metal interconnects and additional dielectric layers. This composite architecture provides both the electrical benefit of reduced interconnect capacitance and the mechanical benefit of structural support from the metal and overlying layers, preventing buckling during processing steps.
3Quantity of substance
If conventional dielectric materials with air gaps are used for MOL dielectrics, then the dielectric constant is reduced, but the mechanical weaknesses make them unsuitable for demanding applications
Solution Approach 1:
The patent applies local quality by strategically positioning air gaps in specific regions of the MOL dielectric layer where they provide electrical benefits without compromising mechanical strength in critical areas. The air gaps are localized to regions away from high-stress zones, allowing the dielectric constant to be reduced while maintaining suitability for demanding MOL applications.
Solution Approach 2:
The patent utilizes controlled porous structures with specific morphology (cylindrical, spherical, or pyramidal voids) that reduce the dielectric constant while maintaining adequate mechanical strength for MOL applications. The controlled pore structure provides the electrical performance needed while the specific geometry and distribution ensure mechanical suitability for diffusion contacts and interconnect structures.
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 enables dielectric layers with air gaps to withstand processing steps like lithography and etching without buckling, making them suitable for demanding applications such as MOL dielectrics by balancing mechanical strength and reduced dielectric constant.
Implementation Method 1
This block copolymer is caused to separate into two phases
Data Source
AI summary
Aspects of the invention are directed to a method for forming a semiconductor device. A dielectric layer is formed on a semiconductor substrate. Subsequently, a metallic contact is formed in the dielectric layer such that it lands on the semiconductor substrate. A masking layer comprising a block copolymer is then formed on the dielectric layer. This block copolymer is caused to separate into two phases. One of the two phases is selectively removed to leave a patterned masking layer. The patterned masking layer is used to etch the dielectric layer. The patterned air gaps reduce the interconnect capacitance of the semiconductor device while leaving the dielectric layer with enough mechanical strength to serve as a middle-of-line dielectric.