Selective CVD Noble Metal Cap on Copper Interconnects
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Solution Overview
Problem
Existing methods for depositing metal capping layers on Cu wires in VLSI circuits face challenges in selectively avoiding electrical shorts by depositing metal onto the dielectric matrix, leading to electromigration issues and void formation.
Innovation Solution
A Chemical Vapor Deposition (CVD) process using ruthenium carbonyl compounds like Ru3(CO)12 and Ru(CO)5 is employed, with a carrier gas free of carbon monoxide to selectively deposit a noble metal cap directly on Cu wires without extending onto the dielectric material, enhancing the deposition rate and preventing residue formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal cap is deposited on Cu wires to suppress electromigration, then electromigration resistance is improved, but metal may extend onto the dielectric material causing electrical shorts
Solution Approach 1:
The patent applies selective deposition to create different outcomes in different locations: metal cap is deposited on Cu wire surfaces to suppress electromigration, while the dielectric material surfaces are protected from metal deposition to prevent electrical shorts. This spatial differentiation of deposition behavior resolves the contradiction between improving electromigration resistance and preventing electrical shorts.
2Object-affected harmful factors
If a dielectric cap is used instead of metal cap to avoid electrical shorts, then electrical short risk is reduced, but electromigration suppression capability is weakened
Solution Approach 1:
Rather than using a uniform dielectric cap that would fail to suppress electromigration, the patent uses selective deposition to apply metal cap locally only where needed (on Cu wires) while leaving dielectric material uncovered. This localized application of metal cap provides both electromigration suppression and electrical short prevention simultaneously.
3Productivity
If conventional CVD process is used to deposit metal cap, then deposition rate is achieved, but selectivity between Cu wire and dielectric material is insufficient
Solution Approach 1:
The patent modifies process parameters including using specific precursor chemicals, controlling deposition temperature, and adjusting process pressure to achieve both high deposition rate and high selectivity. By optimizing these parameters, the process deposits metal cap rapidly on Cu wires while maintaining selectivity to prevent deposition on dielectric material.
Solution Approach 2:
The patent introduces a selective catalyst or surface treatment as an intermediary that enhances the difference in reactivity between Cu wire and dielectric material surfaces. This intermediary enables the CVD process to distinguish between the two surfaces, achieving high selectivity while maintaining productive deposition rates.
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 significantly improves electromigration reliability and extends the life of interconnect structures by forming a thicker, reliable noble metal cap on Cu wires without causing electrical shorts, thereby enhancing the integrity of the circuit.
Implementation Method 1
A Chemical Vapor Deposition (CVD) process using a ruthenium carbonyl compound, such as, Ru3(CO)12 and/or Ru(CO)5
Data Source
AI summary
A method of forming a noble metal cap on a conductive material embedded in a dielectric material in an interconnect structure. The method includes the step of contacting (i) a conductive material having a bare upper surface partially embedded in a dielectric material and (ii) vapor of a noble metal containing compound, in the presence of carbon monoxide and a carrier gas. The contacting step is carried out at a temperature, pressure and for a length of time sufficient to produce a noble metal cap disposed directly on the upper surface of the conductive material without substantially extending into upper surface of the dielectric material or leaving a noble metal residue onto the dielectric material.