Selective Cobalt Capping on Copper to Prevent Dewetting and Diffusion
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Solution Overview
Problem
Current metallization processes for semiconductor devices face challenges in preventing copper dewetting and diffusion, leading to reliability issues and increased resistivity due to the instability of copper boundary regions with dielectric materials, particularly at higher aspect ratios and under varying process conditions.
Innovation Solution
A method involving the selective deposition of a cobalt capping layer on copper surfaces using a cobalt precursor and reducing agents, followed by a plasma treatment, to enhance adhesion and prevent copper diffusion, while maintaining the integrity of dielectric surfaces during vapor deposition processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If copper is used for interconnects to reduce cost and improve processing properties, then manufacturing cost decreases and processing ease improves, but copper diffusion and dewetting occur at boundary regions leading to reliability degradation
Solution Approach 1:
A cobalt-containing material is deposited as an intermediary layer between copper and dielectric materials. This intermediate layer acts as a mediator that prevents direct interaction between copper and dielectric, thereby eliminating copper diffusion and dewetting while maintaining the ease of copper processing.
Solution Approach 2:
The invention uses composite material structures where cobalt-containing material is combined with copper interconnects and dielectric layers. This composite approach creates a multi-layer system that leverages the advantages of each material: copper for conductivity and ease of processing, cobalt for boundary stability and diffusion prevention.
2Reliability
If barrier and capping layers are deposited to contain copper, then copper diffusion is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The cobalt-containing material performs multiple functions simultaneously: it acts as a barrier layer to prevent copper diffusion, a capping layer to stabilize copper boundaries, and an adhesion promoter to enhance interface strength. This multi-functionality reduces the need for separate layers, thereby simplifying device structure and processing.
Solution Approach 2:
The invention merges the functions of barrier layers and capping layers into a single cobalt-containing material layer. Instead of depositing separate barrier and capping layers, the cobalt material provides both protective functions, reducing processing steps and device complexity while maintaining effective copper containment.
3Productivity
If conventional vapor deposition processes are used to deposit cobalt, then deposition speed is maintained, but deposition thickness control precision and film conformality deteriorate
Solution Approach 1:
The invention changes the chemical parameters of the deposition process by using organometallic precursors with specific molecular structures and reactivity. By controlling precursor chemistry, temperature, and pressure parameters, the process achieves both high deposition rates and precise thickness control, overcoming the limitations of conventional physical vapor deposition.
Solution Approach 2:
The invention replaces mechanical physical vapor deposition processes with chemical vapor deposition mechanisms. Instead of relying on physical sputtering or evaporation, the process uses chemical reactions of organometallic precursors to deposit cobalt, enabling better thickness control and conformality while maintaining high deposition speeds through optimized reaction kinetics.
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 cobalt capping layer improves the stability and uniformity of copper layers, reducing electromigration and dewetting, thereby enhancing the reliability and performance of semiconductor interconnects by promoting better adhesion and uniformity at the copper-dielectric interfaces.
Implementation Method 1
exposing the contaminated copper surface to a reducing agent while forming a metallic copper surface
Implementation Method 2
exposing the substrate to a cobalt precursor gas to selectively form a cobalt capping layer over the metallic copper surface during a vapor deposition process
Implementation Method 3
exposing the cobalt capping layer to a plasma during a post-treatment process
Data Source
AI summary
Embodiments of the invention provide processes to selectively form a cobalt layer on a copper surface over exposed dielectric surfaces. In one embodiment, a method for capping a copper surface on a substrate is provided which includes positioning a substrate within a processing chamber, wherein the substrate contains a contaminated copper surface and a dielectric surface, exposing the contaminated copper surface to a reducing agent while forming a copper surface during a pre-treatment process, exposing the substrate to a cobalt precursor gas to selectively form a cobalt capping layer over the copper surface while leaving exposed the dielectric surface during a vapor deposition process, and depositing a dielectric barrier layer over the cobalt capping layer and the dielectric surface. In another embodiment, a deposition-treatment cycle includes performing the vapor deposition process and subsequently a post-treatment process, which deposition-treatment cycle may be repeated to form multiple cobalt capping layers.