Semiconductor Super Junction Structure for Low ON Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power MOSFETs face a tradeoff between breakdown voltage and ON resistance, with existing devices limited by material constraints, necessitating a solution to achieve low ON resistance while maintaining high breakdown voltage.
Innovation Solution
The semiconductor device employs a super junction structure with a periodic array of n-type and p-type pillar layers, where the impurity concentration in the outermost peripheral portion is reduced to half of that in the inner portions, and a high resistance layer with lower impurity concentration is used in the termination region to enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the impurity concentration in the drift layer is increased to reduce ON resistance, then the ON resistance decreases, but the breakdown voltage decreases
Solution Approach 1:
The drift layer is segmented into multiple regions with different impurity concentrations: a first drift layer region with higher impurity concentration to reduce ON resistance, and a second drift layer region with lower impurity concentration to maintain breakdown voltage. This segmentation allows each region to optimize for its specific function.
Solution Approach 2:
Different regions of the drift layer are assigned different impurity concentrations based on their functional requirements. The first drift layer region under the active area has higher impurity concentration for low resistance, while the second drift layer region in the termination area has lower impurity concentration for high breakdown voltage.
2Reliability
If a low-concentration drift layer is provided in the termination region, then the breakdown voltage is maintained, but the ON resistance increases
Solution Approach 1:
The device structure is segmented into an active region with super junction structure for low ON resistance and a termination region with low-concentration drift layer for high breakdown voltage. This spatial segmentation resolves the contradiction by allowing each region to optimize for its primary function.
Solution Approach 2:
The termination region is given different local quality (lower impurity concentration) compared to the active region, allowing it to maintain high breakdown voltage while the active region maintains low ON resistance through its super junction structure.
3Reliability
If the impurity concentration in the outermost peripheral portion is reduced, then the breakdown voltage is enhanced, but the ON resistance increases
Solution Approach 1:
The outermost peripheral portion of the super junction structure is given different local quality with reduced impurity concentration (approximately half) compared to inner portions. This localized modification enhances breakdown voltage at the periphery where electric field concentration occurs, while the inner portions maintain low ON resistance.
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 configuration allows for a significant reduction in ON resistance while maintaining high breakdown voltage, effectively overcoming material limitations and improving device performance.
Implementation Method 1
Since the SJ structure includes almost the same amount of p type impurities in the p-type pillar layer with an n-type impurity in the n-type pillar layer, the drift layer becomes a pseudo non-doped layer with a balance of the negative charges in the p-type pillar and the positive charges in the n-type pillar
Implementation Method 2
it is possible to form a highly doped n-type pillar layer with low resistance, through which the current flows
Data Source
AI summary
According to one embodiment, a semiconductor device includes a first semiconductor layer of a first conductive type, and a periodic array structure having a second semiconductor layer of a first conductive type and a third semiconductor layer of a second conductive type periodically arrayed on the first semiconductor layer in a direction parallel with a major surface of the first semiconductor layer. The second semiconductor layer and the third semiconductor layer are disposed in dots on the first semiconductor layer. A periodic structure in the outermost peripheral portion of the periodic array structure is different from a periodic structure of the periodic array structure in a portion other than the outermost peripheral portion.