Double-Diffused Semiconductor Structure for Fast Flyback Rectification
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Solution Overview
Problem
In flyback converter circuits, general fast recovery diodes fail to suppress voltage spikes and circuit oscillations due to slow turn-on speed and large reverse recovery charge, while bipolar junction transistors (BJTs) have complex and costly manufacturing processes.
Innovation Solution
A semiconductor structure with a substrate having diffusion regions of specific conductivity types, fabricated using a double diffusion technique and glass passivation, which mimics the NPN or PNP structure of a BJT, allowing for higher turn-on speed and reduced reverse recovery time, thus suppressing voltage spikes and oscillations without the need for epitaxial growth or multiple mask layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a general fast recovery diode (FRD) is used, then the device structure is simple, but the turn-on speed is slow and reverse recovery charge is large, resulting in voltage spikes and circuit oscillations
Solution Approach 1:
The patent copies the functional structure of a BJT (bipolar junction transistor) to create a diode with superior performance. By designing the semiconductor device with a substrate, first diffusion layer, second diffusion layer, and multiple diffusion regions, it replicates the BJT's internal structure that enables fast turn-on speed and low reverse recovery charge, while maintaining diode functionality.
2Speed
If a bipolar junction transistor (BJT) is used with base and emitter short-circuited, then the turn-on speed is improved and reverse recovery charge is reduced, but the manufacturing process becomes complex and cost increases
Solution Approach 1:
The patent extracts the essential functional structure of a BJT (the layered diffusion structure with substrate, first diffusion layer, second diffusion layer, and diffusion regions) and removes unnecessary components. By eliminating the need for epitaxial growth and multiple mask layers while retaining the core BJT-like structure, it achieves fast turn-on speed with simplified manufacturing.
3Reliability
If a BJT structure is adopted, then the turn-on speed and reverse recovery characteristics are improved, but the manufacturing cost increases due to complex processes
Solution Approach 1:
The patent changes the manufacturing parameters and process steps to achieve BJT-like performance at lower cost. By modifying the diffusion process to create the layered structure without requiring epitaxial growth, and by optimizing the number of mask layers, it maintains excellent reverse recovery characteristics while reducing manufacturing complexity and cost.
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 semiconductor structure effectively suppresses voltage spikes and circuit oscillations with a simplified and cost-effective manufacturing process, improving circuit efficiency by utilizing a structure similar to BJT but with fewer mask layers and no epitaxial growth, enhancing turn-on speed and reducing reverse recovery time.
Implementation Method 1
diffusing into the substrate from the first surface of the substrate to form a first diffusion layer having the first conductivity type, and diffusing from the second surface of the substrate into the substrate to form a second diffusion layer having a second conductivity type
Data Source
AI summary
A semiconductor structure includes a substrate having a first surface and a second surface opposite to the first surface. The semiconductor structure also includes a first diffusion layer disposed in the substrate and adjacent to the first surface, and a first electrode layer disposed on the first diffusion layer. The semiconductor structure further includes a second diffusion layer disposed in the substrate and adjacent to the second surface, and a plurality of diffusion regions disposed in the second diffusion layer. The semiconductor structure further includes a second electrode layer disposed on the second diffusion layer and in contact with the plurality of diffusion regions. The second diffusion layer is coupled to the plurality of diffusion regions through the second electrode layer. The substrate is sandwiched between the first electrode layer and the second electrode layer.