Middle-Of-Line Interconnect Etching for Rivet-Shaped Plug Adhesion
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Solution Overview
Problem
In semiconductor fabrication, the lack of a glue layer in middle-of-line interconnects leads to poor adhesion of the interconnect plug to the via walls, resulting in slurry leakage and material loss during planarization, which can cause the plug to break away from the device.
Innovation Solution
Introducing a dopant element like germanium into the cobalt interconnect layer to alter etch characteristics, enabling anisotropic etching that forms a rivet-shaped profile with a larger lateral extent, securing the plug without damaging underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a glue layer is forgone to achieve lower contact resistance, then contact resistance is reduced, but adhesion of the interconnect plug to the via walls deteriorates
Solution Approach 1:
The patent applies local quality by creating a dopant-enriched region specifically at the interface between the interconnect plug and via walls, rather than uniformly doping the entire plug. This localized doping provides enhanced adhesion precisely where needed (at the via walls) while maintaining low contact resistance at the contact interface, thus resolving the contradiction between adhesion strength and contact resistance.
Solution Approach 2:
The patent changes the chemical composition parameter by introducing a dopant element into the interconnect plug material. This compositional change modifies the etch characteristics and adhesion properties of the plug, enabling it to adhere strongly to via walls without requiring a separate glue layer, thereby maintaining low contact resistance while improving adhesion.
2Ease of manufacture
If isotropic etching is used to form the interconnect plug, then the plug can be formed, but slurry leakage and material loss occur during planarization
Solution Approach 1:
The patent changes the etch selectivity parameter by doping the interconnect plug with a specific element that creates differential etch rates. This results in an anisotropic etch profile where the plug etches slower laterally than vertically, forming a tapered shape that prevents slurry leakage during planarization while maintaining ease of manufacture through standard etching processes.
Solution Approach 2:
The patent introduces asymmetry in the plug geometry through controlled anisotropic etching, creating a tapered profile with different lateral and vertical dimensions. This asymmetric shape provides mechanical interlocking that prevents slurry leakage and material loss during planarization, while still allowing the plug to be formed using conventional manufacturing steps.
3Strength
If the lateral extent of the plug is increased to prevent pull-up, then adhesion is improved, but underlying layers may be damaged
Solution Approach 1:
The patent applies local quality by concentrating the dopant element specifically at the lateral interfaces of the plug where adhesion to via walls is needed, rather than uniformly increasing the plug size. This localized compositional modification enhances adhesion strength at critical interfaces without requiring an increased lateral extent that would damage underlying layers.
Solution Approach 2:
The patent creates a composite interconnect plug structure by combining the base plug material with a dopant element. This composite material provides enhanced adhesion properties at the via walls through the dopant-enriched region, achieving strong bonding without needing to increase the overall lateral dimensions of the plug, thus avoiding damage to underlying layers.
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 effectively prevents slurry leakage and plug pull-up while maintaining the integrity of the interconnect layer, reducing instances of material loss and ensuring the plug remains securely attached during planarization.
Implementation Method 1
Introducing a dopant element like germanium into the cobalt interconnect layer to alter etch characteristics, enabling anisotropic etching that forms a rivet-shaped profile
Implementation Method 2
introducing a dopant element like germanium into the cobalt interconnect layer
Data Source
AI summary
A method for making a middle-of-line interconnect structure in a semiconductor device includes forming, near a surface of a first interconnect structure comprised of a first metal, a region of varied composition including the first metal and a second element. The method further includes forming a recess within the region of varied composition. The recess laterally extends a first distance along the surface and vertically extends a second distance below the first surface. The method further includes filling the recess with a second metal to form a second interconnect structure that contacts the first interconnect structure.