Selective Capping Layer Deposition for Copper Interconnects
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Solution Overview
Problem
Conventional methods of depositing cobalt capping layers in semiconductor devices lead to diffusion issues, contaminating metal liners and gap fills, thereby increasing resistivity and deteriorating interconnect performance.
Innovation Solution
A method involving selective deposition of a capping layer using a metal precursor and reactant, promoting higher growth rates on copper and metal liners compared to dielectric materials, utilizing chemistries that form a self-assembled monolayer to direct metal deposition, such as molybdenum, ruthenium, or tungsten, to avoid contamination and enhance conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cobalt capping layer is deposited on copper gap fill, then the capping layer provides protective coverage, but cobalt diffuses into the metal liner and gap fill, increasing resistivity and deteriorating interconnect performance
Solution Approach 1:
The patent introduces a self-assembled monolayer (SAM) as an intermediary between the cobalt capping layer and the copper/metal liner surfaces. This SAM acts as a diffusion barrier that prevents cobalt from contaminating the underlying metal layers while still allowing the capping layer to form and provide protective coverage. The SAM is formed by exposing the substrate to a molecular precursor that self-organizes into a monolayer on the metal surface before capping layer deposition.
Solution Approach 2:
The patent applies preliminary action by forming the self-assembled monolayer on the metal surfaces before depositing the cobalt capping layer. This pre-treatment step modifies the surface chemistry to create a barrier that will prevent subsequent cobalt diffusion, addressing the contamination problem before it occurs during the capping layer formation process.
2Manufacturing precision
If conventional deposition methods are used to deposit capping layer, then deposition process is simple, but selectivity of deposition on copper surfaces versus dielectric materials is poor
Solution Approach 1:
The patent changes the chemical parameters of the deposition process by introducing a self-assembled monolayer that modifies the surface energy and reactivity of copper surfaces. This parameter change creates high selectivity for copper surfaces over dielectric materials, as the SAM forms preferentially on metal surfaces and directs subsequent deposition only on those surfaces, achieving high manufacturing precision.
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 method achieves high-selectivity deposition of the capping layer on copper surfaces, reducing contamination and improving the overall performance of semiconductor devices by maintaining conductivity and preventing diffusion into dielectric materials.
Implementation Method 1
exposing a top surface of a substrate to a reactant and a metal precursor to selectively deposit a capping layer on the top surface of the substrate
Implementation Method 2
utilizing chemistries that form a self-assembled monolayer to direct metal deposition
Implementation Method 3
the reactant promotes the growth rate of the capping layer on the filled gap versus the dielectric layer
Implementation Method 4
preventing the copper from diffusing into the dielectric layer
Data Source
AI summary
Provided are methods of forming a semiconductor device. The method includes exposing a top surface of a substrate to a reactant and a metal precursor to selectively deposit a capping layer on the top surface of the substrate, the substrate comprising at least one feature formed in a dielectric layer, the dielectric layer defining a filled gap including sidewalls and a bottom, a barrier layer on the sidewalls of the filled gap, and a metal liner on the barrier layer, the capping layer depositing on one or more of the filled gap, the barrier layer, and the metal liner.