Middle-Of-Line Interconnect Etching for Rivet-Shaped Plug Adhesion
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Solution Overview
Problem
In semiconductor fabrication, interconnect plugs without a glue layer experience poor adhesion to via sidewalls, leading to slurry leakage and material loss during planarization, which can result in the plug pulling up and breaking away from the device.
Innovation Solution
Incorporating 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 to secure the interconnect without damaging underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If planarization is performed directly after plug deposition without a glue layer, then the contact resistance Rc of the plug is reduced, but the plug adhesion to via sidewalls deteriorates causing slurry leakage and material loss
Solution Approach 1:
The patent modifies the etch characteristics of the cobalt interconnect layer by introducing a dopant element (germanium), which changes the physical-chemical parameters of the material. This enables selective anisotropic etching that forms a rivet-shaped profile with enhanced lateral adhesion while maintaining low contact resistance, resolving the contradiction between plug adhesion and contact resistance
Solution Approach 2:
The dopant element is introduced specifically at the via sidewall region of the cobalt interconnect layer, creating a local modification rather than uniform change throughout the entire layer. This localized quality enhancement provides targeted adhesion improvement at the critical interface without affecting other properties of the interconnect structure
2Strength
If isotropic etching is used to form rivet profile, then plug adhesion is improved, but underlying layers are damaged due to punch-through
Solution Approach 1:
By doping the cobalt interconnect layer with germanium, the etch selectivity parameters are fundamentally changed. The doped region exhibits enhanced etch rate and anisotropic behavior, allowing the formation of a rivet profile that adheres strongly to via sidewalls while stopping precisely at the intended depth without punching through underlying layers
Solution Approach 2:
The patent replaces the conventional isotropic chemical etching mechanism with a controlled anisotropic etching process enabled by dopant introduction. This substitution allows directional material removal that creates the desired rivet shape with precise depth control, avoiding the uncontrolled lateral etching that causes punch-through in traditional approaches
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 pull-up of the interconnect plug while maintaining the integrity of the interconnect layer by increasing the lateral etch rate without affecting the vertical etch rate, thus ensuring secure adhesion and preventing unintentional punch-through.
Implementation Method 1
Incorporating a dopant element like germanium into the cobalt interconnect layer to alter etch characteristics
Implementation Method 2
enabling anisotropic etching that forms a rivet-shaped profile with a larger lateral extent
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.