Dual DNW Isolation Structure for RF Noise Reduction
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Solution Overview
Problem
RF semiconductor devices generate electronic noise that couples into other components, affecting their operation, particularly in high voltage applications like HVMOS devices, due to continuous scaling and increased proximity of analog and digital circuits in system-on-chip systems, leading to substrate noise coupling.
Innovation Solution
The implementation of dual deep N-well isolation structures surrounded by P+ guard rings, which absorb leakage current and prevent electronic noise from propagating, effectively isolating noise sources in RF semiconductor devices and reducing interference with other components on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If RF semiconductor devices operate at high frequencies and high voltages, then device performance and functionality are improved, but electronic noise is generated that couples into other components and degrades their operation
Solution Approach 1:
The isolation structure is segmented into multiple functional regions: a first deep N-well region surrounding the noisy RF device, a second deep N-well region surrounding sensitive devices, and intermediate P-type guard rings. This segmentation creates distinct zones that systematically block noise propagation paths while allowing the RF device to operate at high power levels.
Solution Approach 2:
P-type guard rings are introduced as intermediary elements between the noisy RF device and sensitive circuits. These guard rings act as mediators that intercept and redirect leakage current, preventing direct noise coupling while maintaining the high-frequency operation of the RF device.
2Productivity
If analog and digital circuits are placed in close proximity in system-on-chip systems, then chip integration and productivity are improved, but substrate noise coupling increases and adversely affects device operation
Solution Approach 1:
The isolation approach transitions from two-dimensional planar guard rings to three-dimensional deep N-well structures that extend vertically through the substrate. This dimensional change creates volumetric isolation barriers that effectively block noise coupling paths while maintaining compact horizontal spacing for high-density integration.
Solution Approach 2:
The isolation structure employs nested deep N-well regions where the first deep N-well surrounds the RF device and the second deep N-well surrounds sensitive devices, with P-type guard rings nested between them. This nested configuration creates multiple concentric barriers that systematically prevent noise propagation while maintaining compact layout.
3Reliability
If deep N-well isolation structures are implemented, then electronic noise isolation is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The isolation effectiveness is achieved by controlling dopant concentration parameters and geometric dimensions of the deep N-well regions and P-type guard rings. By optimizing these parameters, the structure achieves superior noise isolation while maintaining compatibility with standard CMOS manufacturing processes, avoiding excessive complexity.
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 dual deep N-well isolation structures significantly diminish leakage current, enhancing the operational stability of high-frequency and high-voltage semiconductor devices by effectively isolating electronic noise and preventing its coupling into other signals, thereby improving the performance of mixed-signal and radio-frequency functions.
Implementation Method 1
The first deep N-well (DNW) impurity region is formed in the substrate and surrounds the RF device. A second DNW impurity region is formed in the substrate and surrounds the first DNW impurity region. The DNW isolation structures absorb leakage current and prevent electronic noise from propagating.
Implementation Method 2
The implementation of dual deep N-well isolation structures surrounded by P+ guard rings, which absorb leakage current and prevent electronic noise from propagating, effectively isolating noise sources in RF semiconductor devices and reducing interference with other components on the substrate.
Data Source
AI summary
An isolation structure in a semiconductor device absorbs electronic noise and prevents substrate leakage currents from reaching other devices and signals. The isolation structure provides a duality of deep N-well (“DNW”) isolation structures surrounding an RF device or other source of electronic noise. The DNW isolation structures extend into the substrate at a depth of at least about 2.5 μm and may be coupled to VDD. P+ guard rings are also provided in some embodiments and are provided inside, outside or between the dual DNW isolation structures.