Superjunction MOS Transistor with Asymmetric Pillar Doping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current superjunction semiconductor devices face limitations in current handling capacity while maintaining reverse breakdown voltage, with existing manufacturing methods being costly and difficult to produce.
Innovation Solution
A new superjunction structure with unevenly doped P-type and N-type pillars, where the P-type pillars are doped both vertically and laterally, and the N-type pillars are unevenly doped vertically, to enhance current surge capability without affecting reverse breakdown voltage, achieved through a manufacturing method involving trench formation and multiple filling steps with varying doping concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentrations of P-type impurities in the P-type pillars are unevenly distributed in the vertical direction to improve current handling capacity, then the current handling capacity is improved, but the manufacturing complexity and process difficulty increase significantly
Solution Approach 1:
The patent applies local quality by creating different doping concentration regions within the P-type pillars - specifically, a first doping concentration in the upper portion and a second doping concentration in the lower portion. This localized variation in doping quality enables improved current handling capacity during turn-off transients while maintaining a manageable manufacturing process through selective region modification rather than complete structure redesign
Solution Approach 2:
The P-type pillars are segmented into distinct doping regions (upper and lower portions with different doping concentrations). This segmentation allows independent optimization of electrical properties in different vertical zones, enabling improved current surge capability without requiring complete redesign of the entire superjunction structure, thus balancing performance improvement with manufacturing feasibility
2Strength
If optimized electric charge balance design is adopted to obtain maximum reverse breakdown voltage, then the reverse breakdown voltage is maximized, but the current handling capacity becomes insufficient
Solution Approach 1:
The patent maintains optimized electric charge balance for maximum reverse breakdown voltage while introducing local quality variations through uneven P-type doping distribution in the vertical direction. The different doping concentrations in upper and lower portions of P-type pillars create localized electrical field modifications that enhance current handling capacity without disrupting the overall charge balance required for high breakdown voltage
Solution Approach 2:
The patent introduces asymmetry in the doping concentration distribution within P-type pillars - the upper portion has a different doping concentration than the lower portion. This asymmetric doping profile enables improved current surge capability during turn-off transients while the overall symmetric alternating N-type and P-type pillar structure maintains the optimized electric charge balance for maximum reverse breakdown voltage
3Manufacturing precision
If existing manufacturing methods are used to create unevenly doped P-type pillars, then the desired doping profile can be achieved, but the process cost increases and manufacturing time extends
Solution Approach 1:
The patent employs preliminary action by forming the uneven doping concentration profile in P-type pillars during the epitaxial growth process itself, rather than requiring subsequent separate ion implantation steps. The doping concentrations are predetermined and incorporated during the initial structure formation, which simplifies the overall manufacturing process and reduces both cost and time while achieving the required doping precision
Solution Approach 2:
The patent merges the doping process with the epitaxial growth process - the uneven doping concentration distribution in P-type pillars is achieved through controlled in-situ doping during epitaxial formation. This combination of processes eliminates the need for separate, time-consuming ion implantation and thermal diffusion steps, thereby improving manufacturing efficiency while maintaining the precision of the doping profile
Data Source
AI summary
A superjunction structure with unevenly doped P-type pillars (4) and N-type pillars (2a) is disclosed. The N-type pillars (2a) have uneven impurity concentrations in the vertical direction and the P-type pillars (4) have two or more impurity concentrations distributed both in the vertical and lateral directions to ensure that the total quantity of P-type impurities in the P-type pillars (4) close to the substrate (8) is less than that of N-type impurities in the N-type pillars close to the substrate; the total quantity of P-type impurities in the P-type pillars close to the top of the device is greater than that of N-type impurities in the N-type pillars close to the top. A superjunction MOS transistor and manufacturing method of the same are also disclosed. The superjunction structure can improve the capability of sustaining current-surge of a device without affecting or may even reduce the on-resistance of the device.