Superjunction Semiconductor Peripheral Region Structure
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Solution Overview
Problem
Conventional semiconductor devices face a trade-off between high breakdown voltage and low on-resistance, with peripheral regions requiring additional processing steps and being prone to misalignment, leading to increased manufacturing costs and reduced robustness against surface charges, and difficulties in controlling impurity concentrations in n-type surface regions.
Innovation Solution
A superjunction semiconductor device with a peripheral region structure featuring p-type partition regions with decreasing impurity concentration, n-type surface regions with controlled impurity concentrations, and conductive field plates connected to p-type guard rings, which reduces the risk of autodoping and enhances electric field relaxation, thereby maintaining high breakdown voltage and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick n-drift layer is used to achieve high breakdown voltage, then the breakdown voltage is improved, but the on-resistance increases and conduction loss increases
Solution Approach 1:
The n-drift layer is segmented into alternating n-type columns and p-type columns, forming a superjunction structure. This segmentation allows the n-type regions to carry current while the p-type regions provide field control, enabling high breakdown voltage with lower on-resistance compared to a conventional thick n-drift layer.
Solution Approach 2:
Different regions of the drift layer have different properties: n-type columns have high carrier concentration for current conduction, while p-type columns have controlled impurity concentrations (decreasing from surface to substrate) for electric field control. This local differentiation optimizes both breakdown voltage and on-resistance.
2Reliability
If a peripheral region is added to maintain high breakdown voltage, then the breakdown voltage is improved, but the device complexity and manufacturing cost increase due to additional processing steps
Solution Approach 1:
The peripheral region is merged with the active region by extending the alternating n-type and p-type column structure from the active area into the peripheral area. This integration eliminates the need for separate peripheral region processing steps while maintaining breakdown voltage control.
Solution Approach 2:
The superjunction structure serves multiple functions: it provides current conduction paths, controls electric fields, and maintains breakdown voltage characteristics all within the same alternating column structure, eliminating the need for separate dedicated peripheral regions.
3Reliability
If a peripheral region with guard rings and field plates is added to improve robustness against surface charge, then the robustness is improved, but the manufacturing precision requirements increase due to misalignment risks
Solution Approach 1:
The guard ring and field plate functions are merged into the alternating n-type and p-type column structure that extends into the peripheral region. This integration eliminates the need for separate guard ring and field plate alignment steps, reducing manufacturing precision requirements while maintaining robustness against surface charge.
Solution Approach 2:
The alternating n-type and p-type column structure in the peripheral region provides multiple functions simultaneously: it acts as a guard ring to control surface charges, provides field plates for electric field control, and maintains breakdown voltage, all without requiring separate aligned structures.
4Stability of the object's composition
If the n-type surface region impurity concentration is reduced to control autodoping, then the autodoping effect is reduced, but the manufacturing precision requirements increase to maintain impurity concentration control
Solution Approach 1:
The p-type columns have impurity concentrations that decrease from the surface toward the substrate, creating a gradient structure. This local quality variation controls autodoping effects while the alternating structure provides self-alignment that reduces manufacturing precision requirements.
Solution Approach 2:
The p-type columns are formed with predetermined impurity concentration gradients before the n-type surface region is formed. This preliminary action establishes a structure that inherently controls autodoping during subsequent processing steps, reducing the need for precise impurity concentration control in later steps.
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 enables the production of semiconductor devices with high breakdown voltage and robustness against surface charges using a high-productivity process, minimizing the impact of autodoping and maintaining reliability by optimizing impurity concentration and field relaxation.
Implementation Method 1
p-type partition regions 2 of the parallel pn layers Z has an impurity concentration distribution such that the impurity concentration decreases from the surface of the pn layers Z toward the semiconductor substrate 11
Implementation Method 2
conductive field plate 33 positioned on the inner and outer circumferential sides of p-type guard rings 32, and electrically connected to the surface of p-type guard rings 32
Data Source
AI summary
A semiconductor device is disclosed wherein a peripheral region with a high breakdown voltage and high robustness against induced surface charge is manufactured using a process with high mass productivity. The device has n-type drift region and p-type partition region of layer-shape deposited in a vertical direction to one main surface of n-type semiconductor substrate with high impurity concentration form as drift layer, alternately adjacent parallel pn layers in a direction along one main surface. Active region through which current flows and peripheral region enclosing the active region include parallel pn layers. P-type partition region has impurity concentration distribution where concentration decreases from surface toward substrate side, n-type surface region disposed on parallel pn layers in peripheral region, p-type guard rings disposed separately from each other on n-type surface region, and field plate disposed on inner and outer circumferential sides of p-type guard rings, and electrically connected.