Hybrid Gate Dielectric Transistor Layout for RF Breakdown and Ft
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Solution Overview
Problem
Transistor structures for RF applications face limitations in performance and reliability due to low cut-off frequency (Ft) and maximum oscillation frequency (Fmax) and low breakdown voltage.
Innovation Solution
A transistor structure with an asymmetric source/drain region and a hybrid gate dielectric structure, including a first and second gate oxide region and a high-K dielectric layer, which omits trench isolation in the drain region, providing a smaller areal footprint and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional gate dielectric structure with trench isolation is used, then device reliability is maintained, but areal footprint is large and breakdown voltage is low
Solution Approach 1:
The patent removes the trench isolation structure from the conventional gate dielectric configuration. By extracting this isolation element, the device achieves a smaller areal footprint while the gate dielectric directly contacts the drain region, maintaining reliability through the engineered dielectric structure rather than physical isolation
Solution Approach 2:
The patent employs a composite gate dielectric structure combining multiple dielectric materials with different properties. This composite approach enables the dielectric to simultaneously provide electrical isolation, mechanical support, and high breakdown voltage capability without requiring trench isolation, thus reducing footprint while maintaining reliability
2Productivity
If symmetric source/drain regions are used, then manufacturing is simpler, but cut-off frequency and maximum oscillation frequency are limited
Solution Approach 1:
The patent implements asymmetric source/drain regions where the drain region has different dimensions or doping characteristics than the source region. This asymmetry optimizes carrier transport and electric field distribution, enabling higher cut-off frequency and maximum oscillation frequency while the manufacturing complexity increase is managed through process integration
Solution Approach 2:
The patent applies different properties to different regions: the source region has one set of characteristics optimized for carrier injection, while the drain region has different characteristics optimized for carrier collection and high voltage handling. This local optimization of region-specific properties achieves high frequency performance without uniform complexity throughout the device
3Strength
If high-K dielectric layer is added to gate dielectric structure, then breakdown voltage is improved, but device complexity increases
Solution Approach 1:
The patent uses a composite gate dielectric structure where a high-K dielectric layer is integrated with other dielectric materials. The high-K layer provides enhanced breakdown voltage and capacitance, while the composite structure manages stress and interfaces to control the increase in manufacturing complexity
Solution Approach 2:
The patent changes the dielectric constant parameter of the gate dielectric by introducing high-K materials. This parameter change increases breakdown voltage and improves device performance, while the complexity increase is mitigated by optimizing layer thicknesses and integration methods in the manufacturing process
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
This configuration achieves a 10% increase in Ft and Fmax, doubles the breakdown voltage, and supports high voltage and high-performance RF power amplifiers capable of frequencies above 6 GHz with improved current gain and reduced capacitances.
Implementation Method 1
a high dielectric constant (high-K) dielectric layer contacting the semiconductor substrate and separating the first gate oxide region from the second gate oxide region
Data Source
AI summary
A transistor structure includes a semiconductor substrate with a source region and a drain region therein that are asymmetric. A gate dielectric structure includes a first gate oxide region over a portion of the source region, a second gate oxide region over a portion of the drain region, and a high dielectric constant (high-K) dielectric layer contacting the semiconductor substrate and separating the first gate oxide region from the second gate oxide region. A gate body is over the gate dielectric structure.