Semiconductor Device Field Plate for Reverse Voltage Withstanding
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Solution Overview
Problem
Conventional X-ray sensors face limitations in reverse voltage withstanding capability due to intense electric fields at the edge of high impurity concentration P-type diffusion layers, leading to breakdown and reduced detection sensitivity.
Innovation Solution
The semiconductor device incorporates a conductor surrounding the high impurity concentration P-type diffusion layer and P-well diffusion layer, acting as a field plate to suppress potential rise and enhance reverse voltage withstanding ability, with specific configurations and shapes of conductors and semiconductor regions to optimize electrical field relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high impurity concentration P-type diffusion layer is used as the anode of the diode, then the diode can be formed in the low impurity concentration N-type substrate, but an intense electric field occurs at the edge of the P-type diffusion layer causing breakdown and limiting reverse voltage withstanding ability
Solution Approach 1:
A P-well diffusion layer is introduced as an intermediary structure between the N-type substrate and the P-type diffusion layer. This P-well layer acts as a mediator that gradually transitions the impurity concentration, thereby relaxing the intense electric field at the edge of the P-type diffusion layer and preventing breakdown, which resolves the contradiction between forming a functional diode and withstanding reverse voltage.
Solution Approach 2:
The invention changes the impurity concentration parameter by creating a P-well diffusion layer with intermediate impurity concentration between the low impurity N-type substrate and the high impurity P-type diffusion layer. This parameter transition smooths the electric field distribution and enables the diode to withstand higher reverse voltages without breakdown.
2Reliability
If a P-well diffusion layer is formed to cover the P-type diffusion layer to relax the electrical field, then the reverse voltage withstanding ability is improved, but the large potential difference within the P-well diffusion layer causes problems from the perspective of withstand voltage
Solution Approach 1:
The P-well diffusion layer is segmented into multiple regions with different impurity concentrations: a first P-well region with lower impurity concentration and a second P-well region with higher impurity concentration. This segmentation divides the potential difference into smaller steps, reducing the large potential difference within the P-well layer while maintaining the electric field relaxing effect, thus resolving the contradiction between withstanding reverse voltage and managing internal potential differences.
Solution Approach 2:
Different regions of the P-well diffusion layer are assigned different impurity concentrations tailored to their specific functions: the first P-well region with lower impurity concentration is optimized for electric field relaxation, while the second P-well region with higher impurity concentration is optimized for withstanding potential differences. This local quality differentiation resolves the contradiction by optimizing each region for its specific requirement.
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 solution effectively raises the reverse voltage withstanding ability of the diode, reducing potential differences within the P-well diffusion layer and enhancing detection sensitivity during X-ray irradiation.
Implementation Method 1
a conductor surrounding the high impurity concentration P-type diffusion layer and P-well diffusion layer, acting as a field plate to suppress potential rise and enhance reverse voltage withstanding ability
Implementation Method 2
a photodiode and a amplification transistor for amplifying a signal from charge photoelectric converted
Data Source
AI summary
A semiconductor device includes: a first semiconductor layer of a first conductivity type; an insulation layer on the first semiconductor layer; a second semiconductor layer in the insulation layer; an active element in the second semiconductor layer; a first semiconductor region on the first semiconductor layer and of a second conductivity type; a second semiconductor region in the first semiconductor region and of the second conductivity type with a higher impurity concentration than the first semiconductor region; a first conductor in a through hole in the insulation layer and connected to the second semiconductor region; a second conductor above or within the insulation layer, the second conductor surrounding the first conductor such that an outside edge thereof is outside the second semiconductor region; a third conductor connecting the first and second conductors; and a fourth conductor connected to the first semiconductor layer.