Vertical Semiconductor Device RESURF Diffusion Layer Charge Adhesion
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Solution Overview
Problem
Vertical semiconductor devices with RESURF structures face a drop in withstand voltage due to the adhesion of external electric charges, which disrupts carrier distribution and affects the formation of the depletion layer.
Innovation Solution
A vertical semiconductor device with a diffusion layer in the non-cell region, featuring an impurity surface density gradient that is higher near the cell region and lower further away, with a polysilicon layer optionally laminated to trap carriers and improve breakdown strength, ensuring the depletion layer spreads to share voltage and prevent electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diffusion layer with uniform impurity concentration is used to form a RESURF structure, then the device achieves high withstand voltage, but external electric charges adhere to the surface and disturb carrier distribution, causing a drop in withstand voltage
Solution Approach 1:
The patent applies local quality by creating a diffusion layer with non-uniform impurity concentration distribution. Specifically, the impurity concentration is designed to be higher near the cell region and lower toward the periphery, so that different regions of the diffusion layer serve different functions: the high-concentration region compensates for carrier losses due to external charge adhesion, while the low-concentration region maintains the RESURF effect for voltage withstanding.
Solution Approach 2:
The patent changes the impurity concentration parameter of the diffusion layer from uniform to gradient distribution. By controlling the impurity concentration to decrease from the cell region toward the periphery, the patent creates a carrier reservoir that can compensate for carriers lost to external charge adhesion, thereby maintaining stable withstand voltage performance.
2Reliability
If the impurity concentration in the diffusion layer is increased to compensate for carrier losses, then the withstand voltage is maintained, but the electric field concentration problem in the non-cell region worsens
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatially varying impurity concentration. The diffusion layer has high impurity concentration near the cell region (to compensate for carrier losses) and low impurity concentration at the periphery (to avoid electric field concentration). This localized differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The patent employs asymmetry by designing an asymmetric impurity concentration distribution in the diffusion layer. Rather than uniform concentration, the concentration asymmetrically decreases from the cell region toward the periphery, creating a gradient that naturally balances carrier compensation needs against electric field distribution requirements.
3Ease of manufacture
If a uniform diffusion layer is used, then the manufacturing process is simple, but the carrier distribution is disrupted by external charges, requiring complex compensation mechanisms
Solution Approach 1:
The patent changes the impurity concentration parameter from uniform to gradient distribution, which can be achieved through controlled diffusion processes. This parameter change allows the diffusion layer to inherently compensate for carrier losses due to external charge adhesion, maintaining stable carrier distribution without requiring complex additional compensation mechanisms.
Solution Approach 2:
The patent applies self-service by designing the diffusion layer to automatically compensate for carrier losses. The gradient impurity concentration distribution creates a carrier reservoir that naturally supplies carriers to regions affected by external charge adhesion, enabling the device to self-correct without external intervention or complex control systems.
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 device maintains consistent withstand voltage despite external charge adhesion, as the steep and mild gradient regions in the diffusion layer compensate for carrier losses, and the polysilicon layer enhances breakdown strength and carrier distribution.
Implementation Method 1
When a voltage is applied to the non-cell region of this vertical semiconductor device, the voltage is shared by a depletion layer spreading from the interface of the diffusion layer, so that the electric field does not concentrate therein
Implementation Method 2
a polysilicon layer optionally laminated to trap carriers and improve breakdown strength
Data Source
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AI summary
A technology for a vertical semiconductor device having a RESURF structure, which is capable of preventing the drop of the withstand voltage when the adhesion of external electric charges occurs is provided. The vertical semiconductor device disclosed in the present specification has a cell region and a non-cell region disposed outside the cell region. This vertical semiconductor device has a diffusion layer disposed in at least part of the non-cell region. When the vertical semiconductor device is viewed in a plane, the diffusion layer has an impurity surface density higher than that satisfying a RESURF condition at an end part close to the cell region, and an impurity surface density lower than that satisfying the RESURF condition at an end part far from the cell region. When the vertical semiconductor device is viewed in a plane, a region in the diffusion layer that has the impurity surface density higher than that satisfying the RESURF condition has a greater mean gradient of the impurity surface density than a region in the diffusion layer that has the impurity surface density lower than that satisfying the RESURF condition.