Air-Gap Interconnect Structure for Low-Capacitance IC Wiring
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Solution Overview
Problem
Integrated circuit devices face challenges in reducing parasitic capacitance and current leakage in multi-layer wiring structures, which affect their electrical characteristics and reliability as they are scaled down.
Innovation Solution
The introduction of an air gap around wiring structures, covered by a capping layer and an insulating barrier layer, reduces parasitic capacitance and prevents time-dependent dielectric breakdown by creating a low dielectric constant environment and ensuring proper separation between wiring layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the line widths and pitches of multi-layer wiring structures are decreased to enable down scaling, then the integration density is improved, but the parasitic capacitance and current leakage increase
Solution Approach 1:
An air gap is introduced as an intermediary structure between adjacent wiring structures. This air gap, having a dielectric constant close to 1, acts as a mediator that reduces the electric field coupling between neighboring wires, thereby decreasing parasitic capacitance and suppressing current leakage while allowing continued downscaling of wiring dimensions
Solution Approach 2:
The dielectric constant parameter of the medium between wiring structures is changed from that of conventional dielectric materials (typically 3-10) to that of air (approximately 1). This parameter change fundamentally alters the electrical characteristics between adjacent wires, reducing parasitic capacitance by a factor of 3-10 times compared to traditional dielectric-filled structures
2Reliability
If air gaps are formed between wiring structures to reduce parasitic capacitance, then the electrical characteristics are improved, but the manufacturing complexity increases
Solution Approach 1:
A sacrificial layer is formed in advance at the desired air gap locations before wiring deposition. This preliminary action defines the air gap geometry and ensures proper positioning. The sacrificial layer is later removed to create the air gaps, avoiding the need for complex post-fabrication air gap formation processes
Solution Approach 2:
The sacrificial layer is selectively removed (taken out) from the structure after wiring deposition. This extraction process creates the air gaps without requiring direct manipulation of the air space itself, simplifying the manufacturing process by working with solid materials throughout most of the fabrication sequence
3Reliability
If capping layers and insulating barrier layers are added to cover air gaps, then current leakage is prevented, but the device structure becomes more complex
Solution Approach 1:
The capping layer and insulating barrier layer serve multiple functions simultaneously: they seal the air gaps to prevent contaminant ingress, provide mechanical support to the air gap structure, act as etch stop layers during subsequent processing, and contribute to the overall insulation scheme. This multi-functionality reduces the need for additional dedicated 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 enhances the electrical characteristics and reliability of integrated circuit devices by minimizing parasitic capacitance and current leakage, thereby improving their performance and reducing the risk of dielectric breakdown.
Implementation Method 1
reduces parasitic capacitance by forming an air gap around a wiring on which a via is located
Implementation Method 2
a capping layer covering an upper surface of the air gap
Implementation Method 3
an etch stop layer conformally covering upper surfaces of the lower wiring structures and the capping layer and having a protrusion and recess structure
Data Source
AI summary
An integrated circuit device according to the inventive concepts includes lower wiring structures formed on a substrate, an air gap arranged between the lower wiring structures, a capping layer covering an upper surface of the air gap, an etch stop layer conformally covering an upper surfaces of the lower wiring structures and the capping layer and having a protrusion and recess structure, an insulating layer covering the etch stop layer, and an upper wiring structure penetrating the insulating layer and connected to the upper surface of the lower wiring structure not covered with the etch stop layer, wherein the upper wiring structure covers a portion of an upper surface of the capping layer, and a level of the upper surface of the capping layer is higher than a level of the upper surface of the lower wiring structures.