Recessing Embedded Copper Interconnects via Nitrided Surface
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Solution Overview
Problem
Existing processes for recessing embedded copper interconnects within interlayer dielectric substrates result in uneven topography, leading to reliability concerns due to gaps formed between recessed surfaces and additional layers, exacerbating issues like time-dependent dielectric breakdown and device failure.
Innovation Solution
The process involves nitriding the exposed surface of embedded copper features to form a layer of copper nitride, which is then selectively etched to recess the copper features, achieving a uniform and even recessed surface with minimal surface roughness by utilizing etchants that preferentially etch copper nitride over copper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet etch techniques are used to recess embedded copper interconnects, then copper ions migration is reduced, but uneven topography is created on the recessed surface
Solution Approach 1:
A copper nitride layer is introduced as an intermediary substance between the copper interconnect and the etching process. This layer serves as a protective mediator that allows selective etching to occur uniformly, preventing direct etching of copper that would cause uneven surfaces while still enabling the recessing function
Solution Approach 2:
The chemical composition and surface properties of the copper interconnect are changed by forming a copper nitride layer. This parameter change enables selective etching behavior where the nitride layer etches at a different rate than pure copper, creating uniform recesses while maintaining surface integrity
2Productivity
If aspect ratio of copper interconnects is maximized to minimize spacing, then device density is improved, but time dependent dielectric breakdown is exacerbated
Solution Approach 1:
The copper interconnects are recessed below the dielectric surface before the dielectric is fully formed or cured. This preliminary action creates a barrier that prevents copper ions from migrating into the dielectric, thereby preemptively counteracting the TDDB effect that would otherwise be exacerbated by high device density
3Ease of manufacture
If PECVD is used to form additional layers over recessed copper, then layer formation is achieved, but gaps form between recessed surfaces and additional layers due to uneven topography
Solution Approach 1:
The copper nitride layer acts as an intermediary that provides a uniform, planar surface for subsequent PECVD layer deposition. This intermediary surface allows the PECVD process to form conformal layers without gaps, as the nitride layer fills in the irregularities that would otherwise prevent good layer-to-surface contact
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 ensures the formation of integrated circuits with embedded copper interconnects having a recessed surface with average surface roughness of less than 20 nm, reducing device reliability concerns and improving the conformity of additional layers deposited over the recessed surfaces.
Implementation Method 1
The exposed surface of the embedded copper feature is nitrided to form a layer of copper nitride in the embedded copper feature
Implementation Method 2
Copper nitride is selectively etched from the embedded copper feature to recess the embedded copper feature within the substrate
Data Source
AI summary
Integrated circuits, a process for recessing an embedded copper feature within a substrate, and a process for recessing an embedded copper interconnect within an interlayer dielectric substrate of an integrated circuit are provided. In an embodiment, a process for recessing an embedded copper feature, such as an embedded copper interconnect, within a substrate, such as an interlayer dielectric substrate, includes providing a substrate having an embedded copper feature disposed therein. The embedded copper feature has an exposed surface and the substrate has a substrate surface adjacent to the exposed surface of the embedded copper feature. The exposed surface of the embedded copper feature is nitrided to form a layer of copper nitride in the embedded copper feature. Copper nitride is selectively etched from the embedded copper feature to recess the embedded copper feature within the substrate.