Cobalt Selectivity in Copper Interconnects via Methyl Preservation
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Solution Overview
Problem
Current methods for cobalt deposition in semiconductor manufacturing face challenges in achieving selectivity over copper surfaces while minimizing deposition on dielectric regions, which affects the barrier properties and reliability of interconnects, especially as device dimensions shrink and current density increases.
Innovation Solution
A method involving a substrate treatment process that includes exposing a copper surface to a preclean gas to remove contamination and preserve methyl groups, followed by cobalt precursor gas deposition at specific temperatures, and subsequent activation and regeneration of methyl groups using ammonia and carbon-containing gases to selectively form a cobalt-containing layer on copper surfaces, while avoiding deposition on dielectric surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device dimensions are reduced to increase circuit density, then manufacturing capability is improved, but selectivity of cobalt deposition becomes more difficult to achieve
Solution Approach 1:
As device dimensions shrink and circuit density increases, the patent maintains deposition selectivity by enhancing local quality differences through more sophisticated surface conditioning. The methyl group preservation on dielectric surfaces and activation on copper surfaces become even more critical at smaller scales, creating stronger local chemical environment differences that guide selective cobalt deposition despite reduced feature sizes.
Solution Approach 2:
The patent addresses the selectivity challenge in scaled devices by changing process parameters: adjusting deposition temperature, precursor flow rates, and surface treatment conditions to optimize selective deposition. These parameter changes compensate for the reduced dimensionality and maintain adequate selectivity margins even as feature sizes decrease to achieve higher circuit density.
2Productivity
If current density increases due to smaller interconnect dimensions, then device performance is improved, but electromigration becomes more severe
Solution Approach 1:
The patent introduces cobalt as an intermediary material between copper interconnects and dielectric barriers. This cobalt layer serves as a protective mediator that prevents direct interaction between copper and dielectric, blocking electromigration pathways while allowing the high current density needed for device performance. The selective deposition ensures cobalt is present only where needed to mediate the copper-dielectric interface.
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 enhances the selectivity of cobalt deposition on copper surfaces, improving adhesion, reducing diffusion and agglomeration, and maintaining uniformity, thereby addressing electromigration issues and maintaining the barrier properties of dielectric layers.
Implementation Method 1
exposing the substrate to a preclean gas during an anneal process at a first temperature, wherein the plurality of exposed methyl groups are preserved and wherein the contamination layer is removed
Implementation Method 2
exposing the substrate to a cobalt deposition gas comprising a cobalt precursor gas at a second temperature to form a cobalt-containing layer selectively over the copper surface
Implementation Method 3
forming a plasma in the presence of a treatment gas to create an activated treatment gas, the treatment gas comprising ammonia
Data Source
AI summary
Embodiments of the invention provide processes to selectively form a cobalt layer on a copper surface over exposed dielectric surfaces. Embodiments described herein control selectivity of deposition by preventing damage to the dielectric surface, repairing damage to the dielectric surface, such as damage which can occur during the cobalt deposition process, and controlling deposition parameters for the cobalt layer.