GAA Gate Structure With Metal Cap Threshold Voltage Tuning
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Solution Overview
Problem
The semiconductor industry faces challenges in manufacturing low-cost, high-performance, and low-power integrated circuits due to increased complexity from scaling down semiconductor IC dimensions, particularly in achieving effective gate control and mitigating short-channel effects in multi-gate transistors.
Innovation Solution
The development of a semiconductor device with a gate-all-around (GAA) transistor structure, where a gate structure wraps around multiple channel structures, using a first metal component for threshold voltage determination and a second metal component for forming a metal cap between adjacent channel structures, allowing for different threshold voltages and work functions in transistors, facilitating the fabrication of transistors with varied performance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-gate transistor structures are introduced to improve gate control and reduce short-channel effects, then transistor performance is improved, but device complexity increases
Solution Approach 1:
The gate structure completely wraps around the channel structure in a nested configuration, with the gate enclosing the channel on all sides. This nested doll-like structure provides 360-degree gate control over the channel, significantly improving gate control and reducing short-channel effects while maintaining a compact footprint.
Solution Approach 2:
The gate structure transitions from planar 2D control to 3D all-around control by wrapping vertically and laterally around the channel. This dimensional change from surface-level gating to volumetric gating enables superior electrostatic control and mitigates short-channel effects that cannot be addressed by traditional planar gates.
2Productivity
If scaling down semiconductor IC dimensions is pursued to improve production efficiency and lower costs, then productivity increases, but manufacturing complexity increases
Solution Approach 1:
The transistor structure is segmented into distinct functional components: channel structures formed from alternating semiconductor layers, gate structures wrapping around channels, and metal caps positioned between adjacent channels. This segmentation allows each component to be optimized and fabricated independently using specialized processes, improving overall manufacturing efficiency despite the complex final structure.
Solution Approach 2:
The device employs composite material structures including alternating layers of first and second semiconductor materials with different properties, multiple metal layers with different work functions, and various dielectric materials. These composite structures enable simultaneous optimization of electrical performance, mechanical stability, and manufacturability across different process steps.
3Adaptability or versatility
If different metal components with different work functions are used to form transistors with varied threshold voltages, then device versatility increases, but manufacturing complexity increases
Solution Approach 1:
Different metal components with different work functions are selectively placed in specific locations: first metal caps between adjacent channels of first transistors, second metal caps between adjacent channels of second transistors. This local differentiation enables independent threshold voltage tuning for different transistor types (e.g., NFET vs PFET) without affecting other devices, achieving high versatility through localized material properties.
Solution Approach 2:
The threshold voltage of transistors is controlled by changing the work function parameter of the metal gate material. By selecting metals with different work functions (e.g., tungsten for one transistor type, titanium nitride for another), the invention enables precise adjustment of threshold voltages to meet different circuit requirements, achieving versatility through parameter optimization.
Data Source
AI summary
Aspects of the disclosure provide a semiconductor device and a method for forming the semiconductor device. The method for forming a semiconductor device includes forming a first stack of channel structures that extends between a source terminal and a drain terminal of a first transistor in a first region of the semiconductor device. The first stack of channel structures includes a first channel structure and a second channel structure. The method further includes forming a first gate structure that wraps around the first stack of channel structures with a first metal cap between the first channel structure and the second channel structure. The first metal cap has a different work function from another portion of the first gate structure.