Stacked Multi-Gate Source/Drain Isolation for Leakage Control
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Solution Overview
Problem
The semiconductor industry faces challenges in fabricating stacked device structures, such as complementary field effect transistors (C-FET), due to issues like current leakage and dopant diffusion between source/drain epitaxial structures, which affect device performance and complexity in manufacturing.
Innovation Solution
The introduction of a diffusion stopping layer between source/drain epitaxial structures in C-FET devices, along with doped isolation structures and semiconductive isolation layers, to prevent dopant diffusion and enhance electrical isolation, is implemented using specific epitaxial growth processes and ion implantation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stacked device structures are implemented to increase functional density, then device density is improved, but current leakage and dopant diffusion occur between source/drain epitaxial structures
Solution Approach 1:
A diffusion stopping layer is introduced as an intermediary structure between the first and second source/drain epitaxial structures. This layer acts as a mediator that prevents dopant diffusion from the first source/drain structure into the second source/drain structure, thereby eliminating current leakage while maintaining the high device density provided by the stacked configuration.
2Productivity
If stacked device structures are implemented to increase functional density, then device density is improved, but dopant diffusion occurs between source/drain epitaxial structures
Solution Approach 1:
The diffusion stopping layer serves as a barrier structure that prevents the mixing of dopants between the first and second source/drain epitaxial structures. By placing this intermediary layer at the interface, the dopant distribution in each structure remains stable and distinct, preventing contamination while maintaining the benefits of the stacked device architecture.
3Reliability
If diffusion stopping layer is added to prevent current leakage and dopant diffusion, then electrical isolation is improved, but device complexity increases
Solution Approach 1:
Rather than implementing complex isolation structures throughout the entire device, the diffusion stopping layer is applied locally only at the critical interface between the first and second source/drain epitaxial structures. This localized approach provides the necessary electrical isolation and dopant barrier precisely where needed, while minimizing the overall structural complexity of the device.
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 configuration effectively reduces current leakage and dopant intermixing, improving device performance and manufacturing efficiency by enhancing the electrical isolation between source/drain epitaxial structures in stacked multi-gate devices.
Implementation Method 1
The diffusion stopping layer is formed by implanting ions into the semiconductor substrate at a first energy level to form a first ion implanted region, and by implanting ions into the semiconductor substrate at a second energy level to form a second ion implanted region
Implementation Method 2
a first epitaxial layer over the first ion implanted region and in contact with the first source/drain region, and a second epitaxial layer over the second ion implanted region and in contact with the second source/drain region
Data Source
AI summary
A method includes forming a fin structure including a first channel layer, a sacrificial layer, and a second channel layer over a substrate; forming a dummy gate structure across the fin structure; recessing the fin structure; epitaxially growing first source/drain epitaxial structures on opposite sides of the first channel layer; forming first dielectric layers to cover the first source/drain epitaxial structures, respectively; epitaxially growing second source/drain epitaxial structures on opposite sides of the second channel layer; removing the dummy gate structure and the sacrificial layer to form a gate trench between the first source/drain epitaxial structures and between the second source/drain epitaxial structures; and forming a metal gate structure in the gate trench. The second source/drain epitaxial structures are over the first dielectric layers, respectively.