Copper Interconnect Capping Layer for Electromigration Resistance
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Solution Overview
Problem
The increasing current density in copper interconnects of semiconductor devices enhances electromigration, leading to reliability issues due to surface diffusion of copper atoms, and existing methods to improve adhesion between copper and the etch-stop layer either compromise electrical characteristics or are difficult to integrate, especially as device integration density increases.
Innovation Solution
A non-conductive capping layer is formed using specific compounds like diazonium salts and amine compounds through dative or covalent grafting on copper surfaces, enhancing the adhesion with the etch-stop layer and diffusion barrier without affecting electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma treatments in reducing atmosphere are employed to reduce copper oxides and improve ESL adhesion, then adhesion strength between copper and ESL is improved, but copper sputtering occurs causing higher line-to-line leakage and increased line resistance
Solution Approach 1:
A silane-based intermediate layer is deposited between the copper surface and the ESL. This intermediate layer acts as a mediator that bonds to the copper surface without causing sputtering, while providing strong adhesion for the subsequent ESL deposition, thus resolving the contradiction between adhesion strength and copper loss
Solution Approach 2:
The mechanical/physical plasma treatment process is replaced with a chemical deposition process using silane-based compounds. This substitution eliminates the sputtering effect inherent in plasma treatments while achieving the desired adhesion improvement through chemical bonding mechanisms
2Strength
If silicidation of copper surface is proposed to enhance adhesion with Si-based ESL, then adhesion is improved, but copper consumption occurs resulting in increased line resistance
Solution Approach 1:
The silane-based intermediate layer serves as an intermediary that provides the necessary chemical interface for Si-based ESL adhesion without requiring copper consumption. The silane layer bonds to copper through its organometallic chemistry while presenting a silicon-containing surface for ESL adhesion, eliminating the need for copper silicide formation
3Productivity
If device integration density increases leading to decreased line width and via cross-section, then real estate efficiency is improved, but current density increases enhancing electromigration phenomenon
Solution Approach 1:
The silane-based intermediate layer is applied locally at the copper-ESL interface where electromigration occurs most severely. This localized treatment provides enhanced adhesion strength precisely where needed to prevent surface diffusion, allowing the overall line dimensions to be reduced for higher density while maintaining electromigration resistance
Solution Approach 2:
The interconnect structure becomes a composite system with distinct layers: copper interconnect, silane-based intermediate layer, and ESL. This composite structure combines the low resistivity of copper with the adhesion-enhancing properties of the silane layer, enabling both high density and reliability
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 significantly improves the adhesion between copper and the etch-stop layer, reducing surface diffusion and electromigration, while maintaining the electrical performance of the interconnects, as demonstrated by improved adhesion and electromigration resistance in examples.
Implementation Method 1
A non-conductive capping layer is formed using specific compounds like diazonium salts and amine compounds through dative or covalent grafting on copper surfaces
Data Source
AI summary
The present invention concerns a methods and compositions for preparing a multi layer composite device, such as a semiconductor device.Said method comprises(A) forming a dielectric layer on the surface of a composite material by bringing said surface into contact: a) either with a solution, comprising the diazonium salt of aniline, a diazonium salt bearing at least one functional group or an amine compound of formula H2N-A-X—Z as defined in claim 1: b) or witha first solution containing an aryl diazonium salt and successivelya second solution containing a compound bearing at least one functional group and bearing at least one functional group capable of reacting with the aryl radical grafted on the surface of the composite material thanks to the aryl diazonium salt;(B) forming an overlayer on said surface of said composite material obtained in step (A), said overlayer consisting of a Si-containing dielectric Cu-Etch Stop Layer and/or copper diffusion barrier.