Copper Interconnection Grain Boundary Stabilization
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Solution Overview
Problem
Copper interconnections in semiconductor devices face issues such as oxidation, diffusion of metal atoms into insulating films, and electromigration, particularly at narrower widths, leading to reliability concerns and increased resistance.
Innovation Solution
A barrier layer with Cu—N—R bonds, where R is an organic group, is formed at the grain boundaries of copper interconnections to prevent oxidation and diffusion, enhancing electromigration resistance by stabilizing copper ions and reducing void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper interconnections are made finer (narrower width) to increase integration density, then the number of connections and circuit complexity increase, but oxidation and electromigration become more severe leading to reduced reliability
Solution Approach 1:
A barrier layer comprising a metal nitride film (such as tantalum nitride, tungsten nitride, or molybdenum nitride) is introduced as an intermediary between the copper interconnection and the surrounding environment. This barrier layer prevents direct contact between copper and oxidizing agents, thereby eliminating oxidation issues while enabling the use of finer copper interconnections to achieve higher integration density.
Solution Approach 2:
The interconnection structure employs a composite material system consisting of copper interconnections combined with a metal nitride barrier layer. This composite structure leverages the high electrical conductivity of copper while utilizing the oxidation-resistant properties of the metal nitride barrier, thus achieving both high integration density and reliable oxidation protection.
2Productivity
If copper interconnection width is reduced to 2 μm or less to achieve finer designing, then integration density improves, but electromigration resistance deteriorates causing metal atoms to move and voids to form
Solution Approach 1:
The metal nitride barrier layer serves as a protective intermediary that constrains copper atoms within the interconnection structure. By preventing direct interaction between copper atoms and the surrounding insulating film or environment, the barrier layer reduces electromigration effects and prevents void formation, thereby maintaining reliability even at interconnection widths of 2 μm or less.
Solution Approach 2:
The invention changes the physical and chemical parameters of the barrier layer, specifically using metal nitrides with appropriate thickness (5 nm to 50 nm) and material properties (such as tantalum nitride, tungsten nitride, or molybdenum nitride). These parameter optimizations ensure the barrier layer is thin enough to maintain electrical performance while thick and chemically stable enough to prevent electromigration and oxidation.
3Use of energy by moving object
If copper interconnections are used to achieve low electrical resistance, then conductivity improves, but diffusion of Cu atoms into insulating film occurs causing leakage between interconnections
Solution Approach 1:
The metal nitride barrier layer acts as an intermediary diffusion barrier between the copper interconnection and the insulating film. This barrier layer has low copper diffusivity, effectively blocking Cu atoms from migrating into the insulating film, thereby preventing leakage current while allowing the copper interconnection to maintain its low electrical resistance properties.
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 Cu—N—R bonds effectively prevent oxidation and diffusion, improving the long-term reliability and reducing electromigration in copper interconnections, even at widths of 2 μm or smaller, by stabilizing copper ions and minimizing void formation.
Implementation Method 1
the interconnection structure having a Cu—N—R bond (provided that R is an organic group) in a portion of a grain boundary in a surface of the copper interconnection
Data Source
AI summary
After a copper interconnection is formed above a substrate, a surface of the copper interconnection is activated by performing acid cleaning. Thereafter, the substrate is immersed in a BTA (Benzo triazole) aqueous solution to form a protection film covering the surface of the copper interconnection. At this time, Cu—N—R bonds (R is an organic group) are formed in grain boundary portions in the surface of the copper interconnection. Thereafter, the protection film is removed by performing alkaline cleaning. The Cu—N—R bonds remain in the grain boundary portions in the surface of the copper interconnection even after the protection film is removed. Subsequently, the surface of the copper interconnection is subjected to an activation process, and a barrier layer is formed thereafter by electroless-plating the surface of the copper interconnection with NiP or CoWP.