Copper Interconnect TFR Barrier Structure Against Diffusion
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Solution Overview
Problem
Integrating metal thin film resistors (TFRs) in the backend of line (BEOL) of an integrated circuit manufacturing flow adds cost and cycle time, and there is a need to protect TFRs from copper diffusion/migration in advanced interconnect technologies.
Innovation Solution
Incorporating a metallic barrier layer at the header ends of TFRs within copper interconnects to mitigate copper diffusion and migration, using materials like TaN for both the barrier layer and copper vias, and employing a process that allows for reduced TFR thickness and integration with copper interconnect schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal TFRs are integrated in the BEOL of an integrated circuit manufacturing flow, then the parasitic capacitance is reduced, but the cost and cycle time increase
Solution Approach 1:
The patent combines the TFR formation process with the copper interconnect BEOL process by using the same dielectric layers, barrier materials, and fabrication steps for both the resistor structure and the interconnect structure. The metallic barrier layer serves dual purposes as both the diffusion barrier for the TFR and the barrier for copper vias, merging previously separate process flows into a unified manufacturing sequence that reduces cycle time while maintaining the low parasitic capacitance advantage of BEOL resistors.
2Reliability
If metal TFRs are integrated in the BEOL of an integrated circuit manufacturing flow, then the parasitic capacitance is reduced, but the manufacturing cost increases
Solution Approach 1:
The patent employs universal materials and processes where the metallic barrier layer (e.g., TaN) serves multiple functions: as the diffusion barrier for the TFR, as the barrier layer for copper vias, and as the seed layer for copper deposition. The same dielectric materials and fabrication techniques are used for both TFR formation and copper interconnect formation, eliminating the need for separate specialized process equipment and materials, thereby reducing manufacturing cost while achieving low parasitic capacitance.
3Reliability
If a metallic barrier layer is added at the header ends of TFRs to prevent copper diffusion, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a metallic barrier layer as an intermediary material between the TFR and the copper interconnect structures. This barrier layer (e.g., TaN, TiN, or WN) acts as a mediator that prevents copper diffusion into the TFR while maintaining electrical continuity and mechanical integrity. The barrier layer is integrated into the existing copper interconnect process flow, using the same deposition and patterning steps, so while it adds a functional layer, it does not significantly increase process complexity.
4Area of stationary object
If the TFR thickness is reduced for better integration, then the area is reduced, but the resistivity characteristics may be affected
Solution Approach 1:
The patent optimizes the TFR thickness parameter within a specific range (e.g., 50-200 nm) to achieve the desired balance between area reduction and resistivity maintenance. By carefully controlling the thickness parameter and adjusting other parameters such as the resistive material composition and the barrier layer thickness, the patent maintains the resistivity characteristics even with reduced TFR thickness, enabling better integration with advanced copper interconnect technologies.
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
Enhances the reliability and integration of TFRs in copper interconnects by preventing copper diffusion, maintaining resistivity characteristics, and reducing thickness, thus improving process flow integration with minimal impact.
Implementation Method 1
a metallic barrier layer between the via and the resistive layer... to mitigate copper diffusion and migration
Data Source
AI summary
An integrated circuit (IC) including a TFR is disclosed. In one example, the IC comprises a dielectric layer over a semiconductor substrate, a resistive layer over the dielectric layer, a metal interconnect trace over a header end of the resistive layer, a via extending from the metallic interconnect trace toward the resistive layer, and a metallic barrier layer between the via and the resistive layer.