SiGe Channel Side Regions for Threshold Voltage Modulation
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Solution Overview
Problem
In integrated circuit devices, varying germanium concentration profiles within the device channel can increase fabrication costs and lead to defects such as erosion or agglomeration, resulting in lower yields and unacceptable performance metrics.
Innovation Solution
The integration of vertically-graded silicon germanium (SiGe) regions adjacent to the channel in integrated circuit devices, which allows for modulation of the threshold voltage while minimizing additional processing steps and protecting the channel from defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If germanium concentration is varied within the device channel to modulate threshold voltage, then Vth modulation is achieved, but fabrication cost and complexity increase
Solution Approach 1:
The patent applies local quality by creating regions with different germanium concentrations specifically at the sides of the channel rather than varying it throughout the entire channel. The channel itself maintains uniform germanium concentration, while germanium-rich regions are localized to the sides under the gate, providing Vth modulation with simpler fabrication.
Solution Approach 2:
The patent segments the germanium distribution into distinct regions: a uniform germanium concentration in the channel and separate germanium-rich regions at the sides. This segmentation allows independent control of channel properties and threshold voltage modulation, simplifying the fabrication process compared to varying germanium throughout the channel.
2Adaptability or versatility
If germanium concentration profiles are varied within the device channel, then Vth modulation is achieved, but defects such as erosion or agglomeration occur
Solution Approach 1:
The patent localizes germanium-rich regions to the sides of the channel rather than creating gradients within the channel itself. This localized approach provides the necessary Vth modulation while avoiding the defects (erosion and agglomeration) that arise from varying germanium concentration profiles within the channel structure.
Solution Approach 2:
By segmenting the germanium distribution into uniform channel regions and separate side regions, the patent eliminates the harmful gradients that cause defects. The channel maintains uniform composition for reliable operation, while side regions provide the necessary electrical modulation.
3Ease of manufacture
If vertically-graded SiGe regions are added adjacent to the channel, then Vth modulation is achieved without additional processing, but device structure becomes more complex
Solution Approach 1:
The patent merges the Vth modulation function with the existing germanium doping process by forming germanium-rich regions at the sides of the channel during the same fabrication sequence. This integration achieves threshold voltage modulation without requiring additional processing steps, though it does increase structural complexity.
Data Source
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AI summary
An integrated circuit (IC) device is disclosed which includes a first transistor over a substrate. The first transistor includes a gate over the substrate and between a source region and a drain region. The transistor further includes a first region of vertically-graded silicon germanium ("SiGe") adjacent a first side of a channel under the gate, and a second region of vertically-graded SiGe adjacent a second side of the channel. The channel includes substantially uniformly-graded SiGe.