Fin-Based Adjustable Resistor for RF Noise Reduction
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Solution Overview
Problem
Existing resistors in CMOS processes, such as poly resistors and planar gate transistors, lack adjustable resistance, leading to issues like crosstalk and noise in RF analog circuits due to high conductivity and limited adjustability.
Innovation Solution
A fin-based adjustable resistor is developed, where the resistance is controlled by varying the voltage applied to the gate, allowing for linear adjustment and complete depletion of the fin channel to block conduction, fabricated using a CMOS process compatible with integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polysilicon resistor is used in CMOS process, then the resistor can be integrated with other circuit components, but the resistance cannot be adjusted and remains highly conductive causing crosstalk and noise
Solution Approach 1:
The patent applies the dynamics principle by transforming the static polysilicon resistor into a dynamic device where resistance can be continuously adjusted through voltage control. The finFET structure enables the channel conductivity to be dynamically modulated by applying different voltages to the gate, allowing the resistance to transition from highly conductive to fully depleted states, thereby eliminating crosstalk and noise while maintaining CMOS compatibility
Solution Approach 2:
The patent employs parameter changes by utilizing voltage as a control parameter to adjust the resistance value. By varying the gate voltage, the electrical parameters of the fin channel (carrier concentration, conductivity) are changed, enabling continuous resistance adjustment from low to high values, thus resolving the contradiction between integration and adjustability
2Ease of operation
If a planar gate transistor is used as a resistor, then the resistance can be adjusted by gate voltage, but the resistance changes in a highly non-linear manner making it difficult to control
Solution Approach 1:
The patent applies dimensionality change by transitioning from a planar gate structure to a three-dimensional wrapped gate structure that surrounds the fin channel on multiple sides. This geometric transformation provides more uniform electric field distribution across the channel, resulting in improved linearity between gate voltage and resistance, making the device easier to control with predictable characteristics
3Adaptability or versatility
If a planar gate transistor is used as a resistor, then resistance adjustment is possible, but the adjustment range is limited as the channel inverts before complete depletion
Solution Approach 1:
The wrapped gate structure enables complete depletion of the fin channel by applying sufficient gate voltage, achieving a dynamic range from highly conductive to fully depleted states. This extended dynamic range exceeds the capabilities of planar gate transistors, which invert before complete depletion, thereby ensuring reliable prevention of crosstalk and noise while maintaining broad resistance adjustment capability
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 fin-based resistor provides flexible and effective resistance adjustment, significantly reducing crosstalk and noise in RF analog circuits by allowing for substantial linear control of resistance and complete depletion of the fin channel.
Implementation Method 1
varying a width of the depletion region in the fin channel
Data Source
AI summary
According to one exemplary embodiment, a fin-based adjustable resistor includes a fin channel of a first conductivity type, and a gate surrounding the fin channel. The fin-based adjustable resistor also includes first and second terminals of the first conductivity type being contiguous with the fin channel, and being situated on opposite sides of the fin channel. The fin channel is lower doped relative to the first and second terminals. The resistance of the fin channel between the first and second terminals is adjusted by varying a voltage applied to the gate so as to achieve the fin-based adjustable resistor. The gate can be on at least two sides of the fin channel. Upon application of a depletion voltage, the fin channel can be depleted before an inversion is formed in the fin channel.