MBCFET Gate Structure Layout for Cleaner Source/Drain Interfaces
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Solution Overview
Problem
In the manufacturing of multi-bridge channel field effect transistors (MBCFETs), the removal of sacrificial layers can lead to residue on the source/drain layers, deteriorating their interface characteristics and affecting the device's performance.
Innovation Solution
A semiconductor device design where a gate structure is formed with protruding sidewalls that extend through a portion of the epitaxial layer but do not contact the higher impurity concentration layer, enhancing the interface characteristics of the source/drain layers and reducing leakage current by increasing the length of the gate structure in contact with the source/drain layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sacrificial layers are removed to form gaps for gate structure, then gate structure can be formed properly, but residue of sacrificial layers remains on source/drain layer surfaces deteriorating interface characteristics
Solution Approach 1:
A cleaning layer is formed on the source/drain layer surface before removing the sacrificial layer. This preliminary action ensures that when the sacrificial layer is removed, the cleaning layer prevents residue from contaminating the source/drain layer surface, thus maintaining interface characteristics while allowing proper gate structure formation.
Solution Approach 2:
The cleaning layer acts as an intermediary between the source/drain layer and the sacrificial layer. It provides a protective interface that prevents direct contact and potential contamination between these layers during the manufacturing process, ensuring clean interfaces after sacrificial layer removal.
2Strength
If gate structure sidewalls contact the second epitaxial layer, then structural support is provided, but leakage current increases
Solution Approach 1:
The gate structure is designed with different sidewall configurations at different locations. The first sidewalls extend through the first epitaxial layer to contact the second epitaxial layer for structural support, while the second sidewalls stop within the first epitaxial layer to avoid contact with the second epitaxial layer, preventing leakage current. This local differentiation resolves the contradiction between needing support and avoiding leakage.
3Object-generated harmful factors
If gate structure sidewalls do not contact the second epitaxial layer, then leakage current is reduced, but structural support is compromised
Solution Approach 1:
The gate structure employs asymmetric sidewall design where first sidewalls provide structural support by contacting the second epitaxial layer, while second sidewalls maintain electrical isolation by stopping within the first epitaxial layer. This localized functional differentiation allows the gate structure to simultaneously achieve both mechanical support and leakage current reduction.
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
The solution improves the interface characteristics of the source/drain layers and reduces leakage current, while maintaining the high impurity concentration support for channel current and stress, thereby enhancing the overall performance of the semiconductor device.
Implementation Method 1
a first epitaxial layer covering a lower surface of the second epitaxial layer and covering first and second sidewalls in the first direction of the second epitaxial layer
Data Source
AI summary
A semiconductor device includes channels, a gate structure, and a source/drain layer. The channels are stacked in a vertical direction. Each channel extends in a first direction. The gate structure extends in a second direction. The gate structure covers the channels. The source/drain layer is connected to each of opposite sidewalls in the first direction of the channels on the substrate, and includes a doped semiconductor material. The source/drain layer includes first and second epitaxial layers having first and second impurity concentrations, respectively. The first epitaxial layer covers a lower surface and opposite sidewalls in the first direction of the second epitaxial layer. A portion of each of opposite sidewalls in the first direction of the gate structure protrudes in the first direction from opposite sidewalls in the first direction of the channels to partially penetrate through the first epitaxial layer but not to contact the second epitaxial layer.