Enlarged Backside Contact Structure for Lower Resistance in GAA FETs
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Solution Overview
Problem
As semiconductor devices continue to shrink, the challenge of maintaining device performance and reducing fabrication costs becomes increasingly difficult, particularly due to device performance degradation associated with defects and the need for more complex processing techniques.
Innovation Solution
The method involves forming an enlarged backside contact with a wider portion and a narrower portion for field-effect transistors (FETs), such as GAA FETs, by extending a recess deeper into the substrate, forming a dummy contact material, and then replacing it with a conductive material after removing the dummy contact structure and forming a spacer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the contact size is reduced to match smaller device geometries, then device scaling is achieved, but contact resistance increases and device performance degrades
Solution Approach 1:
The patent creates an enlarged contact opening by depositing a spacer layer around the dummy contact structure, effectively transitioning from a two-dimensional contact footprint to a three-dimensional enlarged contact region. This allows the contact opening to be larger than the original dummy contact structure, reducing contact resistance while maintaining compatibility with scaled device geometries
Solution Approach 2:
The patent introduces a dummy contact structure as an intermediary element that is eventually replaced by the final conductive contact. The dummy contact serves as a placeholder that enables the formation of an enlarged contact opening through spacer deposition, ultimately improving contact resistance while maintaining device scaling
2Ease of manufacture
If conventional contact formation methods are used, then fabrication process is simpler, but contact resistance is higher and device performance is degraded
Solution Approach 1:
The patent performs preliminary actions by forming a dummy contact structure and depositing a spacer layer around it before removing the dummy contact. This preliminary spacer deposition creates the enlarged contact opening that will accommodate the final conductive contact, enabling improved contact resistance without significantly complicating the overall fabrication process
Solution Approach 2:
The dummy contact structure serves as an intermediary that facilitates the formation of an enlarged contact opening. By using this temporary structure, the patent can achieve better contact resistance while keeping the fabrication process relatively simple, as the dummy contact is eventually replaced by the final conductive contact
3Productivity
If device pitch is reduced for higher density, then chip area utilization improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses spacer layer deposition around the dummy contact structure to create an enlarged contact opening in the vertical dimension. This approach allows for tighter horizontal pitch between devices while maintaining adequate contact opening sizes, thereby improving chip area utilization without excessively increasing manufacturing precision requirements
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 reduces resistance within the backside contact, thereby improving device performance and maintaining effective gate control, while also allowing for tighter pitch devices and reduced fabrication costs.
Implementation Method 1
performing a first etching process on a backside of a substrate to expose a dummy contact structure
Implementation Method 2
performing a first deposition process to deposit a first portion of an oxide layer around the dummy contact structure
Implementation Method 3
forming a spacer layer around the dummy contact structure
Implementation Method 4
filling the opening with a conductive material to form a conductive plug
Data Source
AI summary
A method includes performing a first etching process on a backside of a substrate to expose a dummy contact structure, performing a first deposition process to deposit a first portion of an oxide layer around the dummy contact structure, performing a second etching process to at least partially remove the first portion of oxide layer, forming a spacer layer around the dummy contact structure, performing a second deposition process to form a second portion of the oxide layer around the spacer layer, removing the spacer layer and the dummy contract structure to leave an opening, and filling the opening with a conductive material to form a conductive plug.