MOSFET Decoupling Circuit Biasing to Limit Gate Oxide Stress
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Solution Overview
Problem
Existing semiconductor devices face challenges in effectively decoupling from voltage variations due to the susceptibility of thin gate oxides and current leakage in MOSFETs, particularly in high-frequency applications, which can lead to breakdown and increased energy loss.
Innovation Solution
A decoupling capacitance system is implemented using thin-oxide MOSFETs in a decap circuit coupled in series with a bias circuit, such as a self-bias or boosted bias circuit, to reduce voltage drops and minimize gate oxide breakdown and current leakage, while maintaining efficient capacitive decoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MOSFETs are used in decoupling capacitance circuits to provide decoupling function, then decoupling capability is improved, but MOSFETs become susceptible to gate oxide breakdown and current leakage especially at high frequencies or high voltage drops
Solution Approach 1:
A bias circuit is introduced as an intermediary component between the power supply and the decoupling capacitance circuit. This bias circuit generates a bias voltage that is combined with the power supply voltage to create a reduced voltage drop across the decoupling capacitance circuit, thereby protecting the MOSFETs from breakdown and leakage while maintaining decoupling functionality.
Solution Approach 2:
The invention changes the voltage parameter across the decoupling capacitance circuit by introducing a bias voltage that offsets part of the power supply voltage. This parameter change reduces the effective voltage drop across the MOSFETs in the decoupling circuit, preventing gate oxide breakdown and current leakage while maintaining the decoupling capacitance value.
2Reliability
If voltage drop across decap circuit is reduced using bias circuit, then MOSFET breakdown and leakage are minimized, but device complexity increases
Solution Approach 1:
The bias circuit is designed to perform multiple functions: it generates the bias voltage, combines it with the power supply voltage, and simultaneously protects the decoupling capacitance circuit. This multi-functionality reduces the need for additional separate protection circuits, thereby limiting the increase in overall device complexity.
3Productivity
If thin oxide MOSFETs are used in decap circuit, then capacitive decoupling efficiency is improved, but susceptibility to breakdown and leakage increases
Solution Approach 1:
The bias circuit acts as a protective intermediary that reduces the voltage stress on thin oxide MOSFETs. By offsetting the power supply voltage and reducing the effective voltage drop across the decoupling capacitance circuit, the bias circuit enables thin oxide MOSFETs to operate reliably without breakdown or leakage while maintaining their high capacitive decoupling efficiency.
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
The solution provides enhanced protection for thin gate oxides and reduces current leakage, ensuring reliable operation even at high frequencies by minimizing voltage drops across the decap circuit, thus maintaining efficient capacitive decoupling and reducing energy loss.
Implementation Method 1
a decoupling capacitance (decap) system 208A is provided which includes a decap circuit 210
Implementation Method 2
A voltage drop across the decap circuit 210 is Vdcp... one or more thin oxide metal-oxide-semiconductor field-effect transistors (MOSFETs) in the decap circuit 210 have an advantage of being less susceptible to breakdown of the thin gate oxide
Data Source
AI summary
A method (of decoupling from voltage variations in a first voltage drop between first and second reference voltage rails) includes: electrically coupling one or more components to form a decoupling capacitance (decap) circuit; electrically coupling one or more components to form a filtered biasing circuit; and making an unswitched series electrical coupling of the decap circuit and the filtered biasing circuit between the first and second reference voltage rails.