Source/Drain Void Structure for Backside Contact Without Gate Shorts
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Solution Overview
Problem
Current semiconductor device fabrication methods face challenges in forming backside contacts over source/drain regions due to inaccurate backside overlay control, leading to potential gate shorts and adverse effects from residual placeholder materials, which degrade device performance.
Innovation Solution
The method involves creating a sacrificial placeholder under the source/drain region with an airgap, allowing for uniform placeholder formation and increased contact area, thereby enabling backside contacts without adverse effects on device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If backside contacts are formed over source/drain regions using conventional methods, then contact area is increased, but inaccurate backside overlay control causes gate shorts and residual placeholder materials degrade device performance
Solution Approach 1:
A sacrificial placeholder material is introduced as an intermediary element during fabrication. This placeholder is deposited conformally over the source/drain region, providing a temporary structure that enables precise contact formation. After backside contacts are established, the sacrificial placeholder is selectively removed, eliminating residual materials that would otherwise degrade device performance while maintaining the benefits of increased contact area
Solution Approach 2:
The sacrificial placeholder is deposited in advance before backside contact formation. This preliminary action creates a defined structure that guides subsequent processing steps, ensuring accurate contact placement while preventing overlay errors. The placeholder serves as a template that is removed only after it has fulfilled its guiding function
2Ease of manufacture
If conventional fabrication methods are used without sacrificial placeholders, then manufacturing process is simpler, but overlay control inaccuracies lead to gate shorts
Solution Approach 1:
The sacrificial placeholder acts as a mediating structure that bridges the gap between simple fabrication processes and precise overlay control. By depositing this temporary placeholder material, the process gains a reference structure for accurate contact formation without requiring complex overlay control systems
Solution Approach 2:
The sacrificial placeholder is a temporary, disposable structure used only during fabrication. It is deposited to enable precise manufacturing, then selectively removed after serving its purpose. This approach trades the cost of an additional deposition and removal step for significant improvements in manufacturing precision
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 computational power and power efficiency by increasing the BEOL region for signal wiring and providing a larger contact area for backside contacts, while minimizing stress-induced performance degradation.
Implementation Method 1
depositing a sacrificial placeholder liner conformally
Implementation Method 2
performing a sacrificial material overfill
Implementation Method 3
performing an etch back of the sacrificial material overfill
Implementation Method 4
performing S/D epitaxial (epi) growth over a remaining placeholder sacrificial liner to generate an S/D epi for the S/D
Data Source
AI summary
Embodiments are disclosed for a method for fabricating a semiconductor device. The method includes forming a recess under a region for a source/drain (S/D). The method further includes depositing a sacrificial placeholder liner conformally. Additionally, the method includes performing a sacrificial material overfill. Further, the method includes performing an etch back of the sacrificial material overfill. Also, the method includes performing S/D epitaxial (epi) growth over a remaining placeholder sacrificial liner to generate an S/D epi for the S/D.