Chemically Ordered Alloy Barrier for Copper Metallization
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Solution Overview
Problem
Advanced integrated circuits face challenges with electromigration in copper metal lines, which can lead to premature failure due to reduced cross-sectional areas and increased current densities, and existing deposition techniques lack flexibility in forming alloys that balance conductivity and resistance against electromigration.
Innovation Solution
An electrochemical deposition technique is developed that uses two consumable electrodes to deposit metals in situ, creating a chemically ordered alloy with enhanced resistance against electromigration while maintaining acceptable conductivity, by controlling current flows and voltage in a single electrolyte solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used to replace aluminum in metallization layers, then resistivity is reduced and resistance to electromigration is improved, but copper diffuses into silicon dioxide and low-k dielectric materials causing adhesion and diffusion problems
Solution Approach 1:
A barrier layer comprising a chemically ordered alloy of copper and another metal is introduced as an intermediary between the copper metallization and the dielectric material. This barrier layer prevents copper diffusion into the dielectric while maintaining electrical conductivity and adhesion properties, thus resolving the contradiction between utilizing copper's low resistivity and preventing its harmful diffusion.
Solution Approach 2:
The barrier layer is formed as a composite material with a chemically ordered alloy structure, where copper atoms are arranged in an ordered pattern with another metal. This composite structure provides both the electrical conductivity needed for metallization and the diffusion barrier properties required to prevent copper from migrating into the dielectric material.
2Productivity
If feature sizes are reduced to increase circuit element density, then functionality and performance are enhanced, but cross-sectional area of interconnect lines is reduced leading to increased current densities
Solution Approach 1:
The chemical order parameter of the metal alloy is changed to improve electrical conductivity. By creating a chemically ordered alloy structure in the barrier layer, the electrical conductivity is enhanced, allowing the interconnect lines to handle higher current densities without failure, thus enabling further scaling while maintaining reliability.
3Object-generated harmful factors
If a thick barrier layer is used to prevent copper diffusion, then diffusion suppression is improved, but adhesion properties and electrical conductivity are degraded
Solution Approach 1:
The barrier layer exhibits different local properties within its structure. The chemically ordered alloy structure provides diffusion barrier properties in regions where copper migration is prevented, while maintaining electrical conductivity and adhesion in regions that interface with the metallization and dielectric. This spatial variation in functional properties resolves the contradiction between diffusion prevention and maintaining electrical performance.
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 technique provides a high throughput process for forming copper-based alloys with improved resistance against electromigration and conductivity, reducing the risk of line degradation and device failure in highly scaled microstructures.
Implementation Method 1
contacting a surface to be plated with an electrolyte, wherein the electrolyte is in contact with a first consumable electrode comprised of a first metal and with a second consumable electrode comprised of a second metal
Implementation Method 2
a first current flow is established between the first consumable electrode and the surface via the electrolyte. Additionally, a second current flow is established between the second consumable electrode and the surface via the electrolyte
Data Source
AI summary
By providing two or more consumable electrodes within a single reactor vessel, an alloy having a high degree of chemical ordering may be deposited in situ in that the current flows of the individual consumable electrodes are controlled to obtain a substantially layered deposition of the two or more metals. Hence, especially in copper-based metallization layers, the advantage of enhanced resistance against electromigration offered by alloys may be achieved without unduly reducing the overall conductivity.