Thyristor Drift Region Doping for Lower On-State Voltage
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Solution Overview
Problem
Semiconductor devices, such as thyristors, face challenges in reducing peak on-state voltage while maintaining voltage blocking capability during reverse bias, as existing fabrication techniques do not effectively minimize the thickness of the drift region without compromising electrical performance.
Innovation Solution
The formation of a tub structure within the substrate layer reduces the thickness of the drift region by doping the substrate, which in turn decreases the peak on-state voltage without impairing the voltage blocking capability, achieved through a method involving multiple doping stages and layer formation in the semiconductor device fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thickness of the drift region is reduced to decrease peak on-state voltage, then the peak on-state voltage is reduced, but the voltage blocking capability during reverse bias is compromised
Solution Approach 1:
The patent applies local quality by creating a tub structure with different doping concentrations in specific regions of the drift region. The drift region has a non-uniform doping profile with higher doping concentration near the cathode junction and lower concentration toward the anode, allowing localized optimization of electrical properties to reduce on-state voltage while maintaining reverse bias blocking capability
Solution Approach 2:
The patent changes the doping concentration parameter throughout the drift region by forming a tub structure with graded doping. The doping concentration varies spatially, with the tub structure providing localized high doping regions that modify the electric field distribution, enabling reduced peak on-state voltage while preserving voltage blocking through parameter optimization
2Manufacturing precision
If conventional fabrication techniques are used, then the manufacturing process is simple, but the drift region thickness cannot be effectively minimized without compromising electrical performance
Solution Approach 1:
The patent segments the drift region by forming a tub structure that divides the region into different zones with distinct doping characteristics. The tub structure creates separate regions with different electrical properties, allowing independent optimization of on-state voltage and reverse bias blocking without requiring complete redesign of the entire device structure
Solution Approach 2:
The patent applies preliminary action by forming the tub structure with appropriate doping concentrations before final device assembly and operation. The doping profile is established in advance during fabrication, pre-configuring the drift region to achieve optimal electrical performance in both on-state and reverse bias conditions
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 allows for the fabrication of semiconductor devices with reduced peak on-state voltage without compromising voltage blocking capabilities, ensuring efficient power switching performance.
Implementation Method 1
The formation of a tub structure within the substrate layer reduces the thickness of the drift region by doping the substrate
Data Source
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AI summary
Techniques for reducing peak on-state voltage of a thyristor semiconductor device fabricated in a wafer. A substrate layer (112) is provided. An isolation structure (122) is provided to laterally isolate the semiconductor device from other semiconductor devices in the wafer. A p-type tub structure (132) is formed in the substrate layer. A p-type base layer (142) is provided such that the base layer is disposed under the substrate layer. The base layer includes an anode (214) having an associated active region that includes an n-type drift region (225) in the substrate layer. The tub structure is disposed inside the active region such that presence of the tub structure reduces a thickness (226) of the drift region (225). The device further comprises insulation trenches / moats (214).