Gate-All-Around Transistor Channel Orientation for Leakage Reduction
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Solution Overview
Problem
The integrated circuit industry faces challenges in scaling down to smaller technology nodes while maintaining effective gate control and reducing short-channel effects, particularly in the fabrication of multi-gate devices like FinFETs and GAA transistors, where precise control over channel regions is necessary to minimize leakage and enhance performance.
Innovation Solution
A method for fabricating gate-all-around (GAA) transistors involves forming an alternating series of semiconductor layers on a substrate, recessing the workpiece to create fins, depositing dummy gate stacks, and replacing them with gate stacks that wrap around channel regions, using high-K dielectric materials and work function layers to enhance gate control and reduce leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-gate devices like FinFETs and GAA transistors are introduced to improve gate control, then gate-channel coupling and control over channel regions are improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The gate structure completely surrounds the channel region in a nested configuration, with the gate wrapping around the channel from multiple sides. This nested arrangement maximizes gate-channel coupling by enclosing the channel within the gate structure, providing superior control over carrier flow while managing the inherent complexity through a systematic nested design approach
Solution Approach 2:
The invention transitions from planar two-dimensional gate control to three-dimensional gate-all-around control by extending the gate structure vertically and horizontally to surround the channel region. This dimensional expansion allows the gate to control the channel from multiple spatial directions simultaneously, dramatically improving control efficiency despite increased structural complexity
2Productivity
If geometry size is decreased to increase functional density, then production efficiency increases and costs decrease, but gate control effectiveness and leakage reduction become more difficult to maintain
Solution Approach 1:
The nested gate-all-around structure provides intensified gate control at reduced dimensions by enclosing the channel region completely. This nested configuration maintains effective gate control even as geometry scales down, because the gate surrounds the channel from multiple sides, ensuring that control effectiveness does not degrade with reduced feature sizes
Solution Approach 2:
The invention employs composite material structures including high-k dielectric materials combined with metal gate materials, and alternating layers of different semiconductor materials (e.g., SiGe and Si) with different bandgaps. These composite material choices enable maintained or improved gate control and leakage characteristics at smaller technology nodes, allowing continued scaling while preserving reliability
3Reliability
If gate-all-around structures are formed to reduce short-channel effects, then leakage current is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The fabrication process employs preliminary patterning and preparation steps that establish the gate-all-around structure framework before final channel formation. Dummy gates are formed early in the process to define the gate region, and alternating semiconductor layers are prepared in advance with controlled thicknesses and compositions. These preliminary actions reduce the precision burden on subsequent steps by pre-establishing critical dimensions and alignments
Solution Approach 2:
The nested gate-all-around structure provides inherent manufacturing tolerance compensation because the gate surrounds the channel from multiple sides. If slight dimensional variations occur during fabrication, the enclosed nested configuration ensures that the gate maintains control over the channel from all directions, reducing the impact of single-point fabrication errors and relaxing overall precision requirements
Data Source
AI summary
A semiconductor device and a method of forming the same are provided. The semiconductor device includes a first gate-all-around (GAA) transistor over a first region of a substrate and a second GAA transistor over a second region of the substrate. The first GAA transistor includes a plurality of first channel members stacked along a first direction vertical to a top surface of the substrate and a first gate structure over the plurality of first channel members. The second GAA transistor includes a plurality of second channel members stacked along a second direction parallel to the top surface of the substrate and a second gate structure over the plurality of second channel members. The plurality of first channel members and the plurality of second channel members comprise a semiconductor material having a first crystal plane and a second crystal plane different from the first crystal plane. The first direction is normal to the first crystal plane and the second direction is normal to the second crystal plane.