Metal Liner Deposition for Low-Resistance Interconnect Vias
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Solution Overview
Problem
As transistors and interconnects scale to the 3 nm node and beyond, increasing via resistance in interconnects leads to reduced performance and increased power consumption, with conventional copper interconnect structures facing challenges in reducing barrier layer thickness and resistivity.
Innovation Solution
The method involves forming a dielectric layer with a gap, selectively depositing a self-assembled monolayer (SAM) on the gap bottom, forming a barrier layer on the SAM, and selectively depositing a metal liner on the barrier layer, with the metal liner thickness on sidewalls being greater than on the bottom, followed by removing the SAM and performing a gap fill process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barrier layer thickness is reduced to decrease via resistance, then via resistance decreases, but adhesion and diffusion prevention capabilities deteriorate
Solution Approach 1:
The barrier/adhesion function is segmented into two separate layers: a thin barrier layer for diffusion prevention and a thicker metal liner layer for adhesion. This allows the barrier layer to be made very thin (reducing via resistance) while the metal liner provides the necessary adhesion strength that would otherwise require a thicker barrier layer.
Solution Approach 2:
Different regions of the via structure are assigned different material properties: the barrier layer provides diffusion barrier properties, while the metal liner layer provides adhesion properties. This local differentiation of material functions allows optimization of each layer's thickness for its specific purpose, resolving the contradiction between thin barrier layers and sufficient adhesion.
2Reliability
If barrier layer thickness is reduced to decrease via resistance, then via resistance decreases, but diffusion prevention capability deteriorates
Solution Approach 1:
The diffusion barrier function is segmented from the adhesion function into a separate barrier layer. This thin barrier layer is sufficient for diffusion prevention, while the metal liner layer handles adhesion, allowing the barrier layer to be made very thin without compromising diffusion prevention.
Solution Approach 2:
The via structure uses a composite material system consisting of a barrier layer and a metal liner layer. This composite structure combines the diffusion barrier properties of the barrier layer with the adhesion properties of the metal liner, achieving both diffusion prevention and strong adhesion with reduced overall via resistance.
3Strength
If metal liner thickness on bottom is increased to improve adhesion, then adhesion improves, but via resistance increases
Solution Approach 1:
The metal liner thickness is differentiated by location: thicker on the sidewalls where adhesion is most critical for copper fill, and thinner on the bottom where adhesion requirements are lower. This local optimization reduces the overall metal liner volume and via resistance while maintaining sufficient adhesion where needed.
Solution Approach 2:
Instead of uniformly increasing metal liner thickness in all directions (which would increase via resistance), the solution distributes metal liner thickness differently across spatial dimensions: concentrating thickness on sidewalls rather than uniformly on the bottom, thereby optimizing adhesion without proportionally increasing via resistance.
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 reduces via resistance by at least 20% compared to structures without selectively deposited metal liners, improving interconnect performance and reducing power consumption.
Implementation Method 1
selectively depositing a self-assembled monolayer (SAM) on the bottom of the gap
Implementation Method 2
selectively depositing a metal liner on the barrier layer on the sidewall, the metal liner being deposited at a thickness on the sidewalls that is greater than a thickness of the metal liner deposited on the bottom
Data Source
AI summary
Methods of forming devices comprise forming a dielectric layer on a substrate, the dielectric layer comprising at least one feature defining a gap including sidewalls and a bottom. A self-assembled monolayer (SAM) is formed on the bottom of the gap, and a barrier layer is formed on the SAM before selectively depositing a metal liner on the barrier layer. The SAM is removed after selectively depositing the metal liner on the barrier layer.