Selective Conductive Caps for Low-Resistance Interconnect Contacts
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Solution Overview
Problem
The challenge in fabricating integrated circuits with smaller features is the increased resistance and capacitance due to reduced metal interconnect areas and contact resistance, exacerbated by existing capping materials that occupy excessive space and negatively impact device performance.
Innovation Solution
The use of selective deposition techniques for novel liner and cap materials, such as ruthenium-based liners and caps made of ruthenium, molybdenum, tungsten, rhodium, iridium, rhenium, and niobium, to encapsulate metal interconnects and transistor contacts, reducing resistance and improving reliability without occupying excessive space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing capping materials are used to encapsulate metal interconnects, then protection is provided, but excessive space is occupied and device performance deteriorates
Solution Approach 1:
The patent changes the material parameters by transitioning from conventional cap materials (such as tungsten or cobalt) to novel materials including ruthenium, rhodium, iridium, and their alloys. These material parameter changes enable achieving the same protective function with reduced thickness, thereby occupying less space while maintaining reliability
Solution Approach 2:
The patent employs composite material structures by combining different cap materials in multi-layer configurations (e.g., ruthenium-cobalt alloys, rhodium-iridium combinations). These composite structures provide enhanced protection efficiency, achieving superior protection with reduced overall cap thickness compared to single-material approaches
2Productivity
If metal interconnect areas are reduced to enable scaling, then device density increases, but resistance increases and performance deteriorates
Solution Approach 1:
The patent utilizes parameter changes in cap material properties, specifically selecting materials with lower resistivity (such as ruthenium and its alloys) to compensate for the reduced interconnect area. This material parameter optimization maintains electrical performance despite geometric scaling
Solution Approach 2:
The patent applies partial action by optimizing the cap thickness to be just sufficient for protection without excessive material deposition. This controlled, partial coverage approach maintains electrical conductivity while providing adequate protection, avoiding the performance degradation that would result from overly thick caps
3Reliability
If contact resistance is reduced to improve performance, then device performance enhances, but fabrication complexity increases
Solution Approach 1:
The patent employs composite cap structures with multiple material layers (e.g., combining ruthenium with cobalt, or rhodium with iridium) that provide both low contact resistance and protection against fabrication process damage. This composite approach achieves superior electrical contact properties while maintaining fabrication process compatibility
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 results in reduced resistance and improved reliability of metal interconnects and contacts, enabling further scaling and performance enhancement in integrated circuits.
Implementation Method 1
a conductive cap material is selectively deposited over the interface material and the conductive fill material
Data Source
AI summary
Selective metal capping and/or liner materials and processes described herein may enable hermetically encapsulating metal interconnects and metal-silicon interfaces in transistor contacts. In one example, an IC structure includes an interconnect layer with a conductive interconnect that is lined with a ruthenium-based liner, and capped with a selectively deposited cap that includes one or more of ruthenium, molybdenum, tungsten, rhodium, iridium, rhenium, and niobium individually or in an alloy. In another example, an IC structure includes a transistor contact structure with a selectively deposited conductive cap over an interface material, where the conductive cap material is absent or substantially thinner on sidewalls of the contact opening. In one example, the conductive cap material over the Si-metal interface includes one or more of ruthenium, molybdenum, tungsten, rhodium, iridium, platinum, rhenium, cobalt, and niobium individually or in combination.