Nitrided Conductor Surface Recess for Interconnect Diffusion Control
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Solution Overview
Problem
The direct contact between metal interconnects and insulating materials in integrated chips leads to diffusion issues, degrading the conductivity of interconnects, and conventional liners affect resistance differently, necessitating an improved method for forming conductive vias.
Innovation Solution
The process involves nitridizing exposed surfaces of a conductor and etching away the nitridized material to create a recessed area, followed by depositing a conductive via that forms a contact with the underlying conductor, using a liner metal to prevent diffusion and enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liner of tantalum nitride is deposited between the interconnect and the dielectric to prevent diffusion, then the interconnect material diffusion is prevented, but the resistance of the interconnect is affected differently by different liner materials
Solution Approach 1:
The patent introduces a liner layer made of tantalum, tungsten, or their nitrides as an intermediary between the copper interconnect and the dielectric material. This liner serves as a diffusion barrier while being carefully controlled in thickness (5-50 nm) to minimize its impact on interconnect resistance. The liner prevents copper diffusion into the dielectric while maintaining acceptable electrical properties through optimized thickness and material selection.
Solution Approach 2:
The patent changes the parameters of the liner layer, specifically controlling its thickness to be between 5-50 nm and selecting from multiple material options (tantalum, tungsten, tantalum nitride, tungsten nitride). By adjusting these parameters, the patent achieves a balance between providing sufficient diffusion protection and maintaining low interconnect resistance, allowing manufacturers to optimize based on specific process requirements.
2Ease of manufacture
If the interconnect metal is formed in direct contact with the insulating material, then the fabrication process is simplified, but the interconnect material diffuses into the dielectric material degrading the conductivity
Solution Approach 1:
The patent introduces a thin liner layer as an intermediary between the copper interconnect and dielectric material. This liner is deposited using standard PVD or CVD techniques, adding only one additional process step to the fabrication sequence. The liner thickness is controlled at 5-50 nm, which is thin enough to minimize electrical impact while sufficient to prevent copper diffusion into the dielectric, thus maintaining interconnect conductivity.
3Reliability
If different liner materials are used to prevent diffusion, then the diffusion protection is achieved, but the resistance of the interconnect varies
Solution Approach 1:
The patent provides multiple liner material options (tantalum, tungsten, tantalum nitride, tungsten nitride) with controlled thicknesses of 5-50 nm. Each material offers different combinations of diffusion barrier properties and electrical characteristics. By selecting from these standardized material and thickness options, manufacturers can choose the combination that best matches their specific process requirements, achieving both diffusion protection and acceptable resistance levels through parameter optimization rather than trial and error.
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 method improves the conductive qualities of vias by reducing resistance and preventing material diffusion, while maintaining effective contact between the interconnect and the via, thus enhancing the performance of metal interconnects in integrated chips.
Implementation Method 1
nitridizing exposed surfaces of a first layer and an exposed surface of a conductor underlying the first layer to form a layer of nitridation at the exposed surfaces
Data Source
AI summary
A conductive interface includes a first conductor having a recessed area in least one surface. A dielectric layer has a trench positioned over the first conductor. A nitridized layer is formed on a top surface of the first conductor around the recessed area, to a depth on the first conductor that is shallower than a depth of the recessed area. A second conductor is formed in the trench and the recessed area to form a conductive contact with the first conductor.