Polysilicon Diode Conductive Layer Leakage Current
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Solution Overview
Problem
The challenge lies in producing lateral diodes made of polysilicon with a high on-state current and low leakage current, as the doping level affects the leakage current under reverse bias, and reducing the intrinsic zone length is limited by dopant diffusion.
Innovation Solution
A diode structure comprising a polycrystalline silicon bar with doped regions and an intrinsic region, along with a conductive layer capable of being biased, separated by a dielectric layer, which modulates the reverse leakage current by applying bias voltage, and the use of fluorine atoms in the intrinsic region to further improve the on-state to leakage current ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the doping level is increased to improve on-state current, then the on-state current increases, but the leakage current under reverse bias increases
Solution Approach 1:
The invention segments the doped region into two distinct zones: a first doped region adjacent to the intrinsic zone with lower dopant density, and a second doped region further from the intrinsic zone with higher dopant density. This segmentation allows the first region to maintain low leakage current while the second region provides high on-state current, resolving the contradiction between these two opposing requirements.
2Reliability
If the length of the intrinsic zone is decreased to improve the on-state current to leakage current ratio, then the ratio improves, but the dopant diffusion from doped regions increases
Solution Approach 1:
The invention applies local quality by creating a spatially varying dopant density distribution within the doped region. The dopant density is locally adjusted to be lower near the intrinsic zone and higher farther from it, allowing the intrinsic zone length to be optimized for high current ratio while the graded dopant profile prevents excessive diffusion effects.
3Object-generated harmful factors
If a conventional PIN diode structure is used to achieve low leakage current, then the leakage current is reduced, but additional fabrication expenses are introduced
Solution Approach 1:
The invention achieves low leakage current by changing the dopant density parameter within the doped region, creating a graded profile instead of a uniform distribution. This parameter change is implemented through standard ion implantation processes with multiple doses, avoiding the need for additional complex fabrication steps while achieving the desired electrical characteristics.
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 approach effectively decreases leakage current and enhances the on-state to leakage current ratio, allowing for improved diode performance without additional fabrication complexities, and is compatible with existing semiconductor processes.
Implementation Method 1
the conductive layer allows the characteristics of the diode to be modulated according to the bias, in particular the reverse leakage current in the off state
Implementation Method 2
A positive or negative bias allows the reverse leakage current flowing through the polycrystalline silicon intrinsic region to be boosted or moderated, respectively
Implementation Method 3
the use of fluorine atoms in the intrinsic region to further improve the on-state to leakage current ratio
Data Source
AI summary
A diode is formed by a polycrystalline silicon bar which includes a first doped region with a first conductivity type, a second doped region with a second conductivity type and an intrinsic region between the first and second doped regions. A conductive layer extends parallel to the polycrystalline silicon bar and separated from the polycrystalline silicon bar by a dielectric layer. The conductive layer is configured to be biased by a bias voltage.