Extended-Drain MOS Gate Structure for Threshold Voltage Tuning
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Solution Overview
Problem
High-voltage integrated circuits, such as those used in microwave and radiofrequency power amplifiers, require specialized circuit technology to handle higher voltages, and p-type extended-drain metal-oxide-semiconductor devices often exhibit undesirably high threshold voltage, necessitating adjustments during fabrication that can degrade linear drain current performance.
Innovation Solution
A structure and method for forming an extended-drain metal-oxide-semiconductor device with a semiconductor substrate, source and drain regions, and a gate electrode, where a semiconductor layer of differing composition is used, allowing for threshold voltage tuning without additional implants, thereby simplifying the fabrication process and maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an additional implant is performed into the well beneath the gate to adjust threshold voltage, then the threshold voltage is reduced, but the fabrication process complexity increases due to additional masks
Solution Approach 1:
The patent changes the material composition parameter of the semiconductor layer by incorporating germanium at different concentrations (e.g., 0% to 50% germanium) to adjust the threshold voltage. This eliminates the need for additional implantation masks while achieving the desired threshold voltage adjustment through material composition variation alone.
Solution Approach 2:
The patent employs a composite semiconductor layer structure with different materials (silicon and silicon-germanium) having different germanium concentrations. This composite structure allows threshold voltage adjustment without additional fabrication steps, as the material composition itself provides the necessary electrical characteristics.
2Manufacturing precision
If corrective measures are taken to adjust threshold voltage, then the threshold voltage is reduced, but the linear drain current performance degrades
Solution Approach 1:
The patent applies local quality by creating a semiconductor layer with spatially varying germanium concentration. The region beneath the gate has higher germanium content (50%) for threshold voltage adjustment, while other regions maintain lower germanium content (0-20%) to preserve linear drain current performance. This localized material differentiation resolves the contradiction between threshold voltage adjustment and current performance.
3Strength
If a metal gate is used in p-type extended-drain devices, then the device can handle higher voltages, but the threshold voltage becomes higher than desired
Solution Approach 1:
The patent changes the material composition parameter of the semiconductor layer beneath the metal gate by incorporating silicon-germanium with varying germanium concentrations. This material parameter change allows the device to maintain high voltage handling capability with the metal gate while adjusting the threshold voltage to desired levels without modifying the gate structure itself.
Data Source
AI summary
Structures for an extended-drain metal-oxide-semiconductor device and methods of forming a structure for an extended-drain metal-oxide-semiconductor device. The structure includes a semiconductor substrate containing a first semiconductor material, a source region and a drain region in the semiconductor substrate, a gate electrode positioned in a lateral direction between the source region and the drain region, and a semiconductor layer positioned on the semiconductor substrate. The semiconductor layer contains a second semiconductor material that differs in composition from the first semiconductor material. The gate electrode includes a first section positioned in a vertical direction over the semiconductor layer and a second section positioned in the vertical direction over the semiconductor substrate.