Low-Temperature Sputtered Metal Silicide Layer for Copper Interconnects
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Solution Overview
Problem
Current copper interconnects in semiconductor devices face challenges with electromigration lifetime due to fast diffusion at the Cu/dielectric interface, which existing methods have not adequately addressed, particularly in high-speed integrated circuits with submicron design features.
Innovation Solution
A method involving the formation of a sputtered metal silicide layer over copper interconnects using a low-temperature sputtering process, where a metal silicide layer is deposited at temperatures between 20 and 180 degrees C, enhancing the electromigration lifetime by reducing diffusion and improving structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin dielectric layer is used to cap the Cu interconnect top surface, then the Cu interconnect structure is formed, but fast diffusion occurs at the Cu/dielectric interface reducing electromigration lifetime
Solution Approach 1:
A metal silicide layer is introduced as an intermediary between the copper interconnect and the dielectric capping layer. This silicide layer acts as a diffusion barrier that prevents fast diffusion paths at the Cu/dielectric interface, thereby enhancing electromigration lifetime while maintaining the protective capping structure.
Solution Approach 2:
The invention uses a composite structure consisting of copper interconnect, metal silicide layer, and dielectric capping layer. The metal silicide layer provides both mechanical protection and diffusion barrier properties, combining the advantages of different materials to solve the interface diffusion problem.
2Reliability
If high temperature processing is used to form the metal silicide layer, then the silicide layer is formed, but temperature-related defects such as voids and pull-out issues occur
Solution Approach 1:
The invention changes the processing temperature parameter from high temperature to low temperature (below 200°C) for forming the metal silicide layer. This parameter change prevents temperature-related defects such as void formation and pull-out issues while still achieving complete silicide layer formation through extended low-temperature processing.
3Productivity
If conventional high temperature silicide formation is used, then the silicide layer is formed quickly, but the process complexity and temperature control requirements increase
Solution Approach 1:
The invention uses low temperature processing with extended time to achieve silicide formation, trading speed for simplicity. This approach reduces process complexity and temperature control requirements while still forming a complete and functional silicide layer, making the process more manufacturable.
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
The low-temperature sputtered metal silicide layer effectively reduces diffusion and enhances the electromigration lifetime of copper interconnects, improving the reliability and conductivity of high-speed integrated circuits by forming a stable cap that mitigates temperature-related defects such as voids and pull-out issues.
Implementation Method 1
forming metal silicide layer over said copper interconnect using a sputter process
Data Source
AI summary
A method of fabrication of a sputtered metal silicide layer over a copper interconnect. We form a dielectric layer over a conductive layer. We form an interconnect opening in the dielectric layer. We form a copper layer at least filling the interconnect opening. We planarize the copper layer to form a copper interconnect in the interconnect opening. The copper interconnect is over polished to form a depression. We form metal silicide layer over the copper interconnect using a low temperature sputtering process. We can form a cap layer over the metal silicide layer.