FS-IGBT Field Stop Layer Impurity Density Control
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Solution Overview
Problem
Existing power devices, such as Insulated Gate Bipolar Transistors (IGBTs), face challenges in achieving optimal electrical characteristics and efficient field stop functionality due to limitations in adjusting the thickness and impurity density of the Field Stop (FS) layer, which affects the device's switching performance and breakdown voltage.
Innovation Solution
A power device structure is developed with a Field Stop layer based on a semiconductor substrate, where the FS layer is formed using a combination of ion implantation and epitaxial growth, allowing for adjustable impurity density profiles and reduced thickness, enabling improved control over the FS layer's function and electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the FS layer thickness is reduced to improve switching speed, then switching performance is improved, but field stop functionality deteriorates
Solution Approach 1:
The patent applies local quality by creating different impurity density regions within the FS layer. The first FS layer region has a first impurity density while the second FS layer region has a second impurity density that is higher than the first. This spatial variation in impurity density allows the thin FS layer to maintain effective field stop functionality in the high-density region while keeping the overall thickness reduced for improved switching speed.
Solution Approach 2:
The patent changes the impurity density parameter within the FS layer by forming regions with different impurity concentrations. The second FS layer region has a higher impurity density than the first FS layer region, which allows the FS layer to be thinner while maintaining adequate field stop capability. This parameter change enables simultaneous achievement of fast switching and reliable field stop function.
2Reliability
If the impurity density of the FS layer is increased to improve field stop function, then field stop functionality is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the FS layer into multiple regions with different impurity densities. The first FS layer region and second FS layer region are formed separately with different doping characteristics. This segmentation allows independent optimization of each region's impurity density to achieve the desired field stop function while using standard manufacturing processes for each segment.
Solution Approach 2:
The patent forms the first FS layer region with a lower impurity density before forming the second FS layer region with higher impurity density. This preliminary action allows the subsequent high-density region to be formed using standard ion implantation and annealing processes, avoiding the need for complex single-step high-density formation while achieving the required field stop functionality.
3Manufacturing precision
If the FS layer thickness is reduced to adjust impurity density, then impurity density control is improved, but breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating a second FS layer region with higher impurity density specifically positioned to maintain breakdown voltage. While the overall FS layer thickness is reduced for better impurity density control, the localized high-density region compensates for the thickness reduction by providing adequate electric field termination, thus maintaining the required breakdown voltage.
Solution Approach 2:
The patent creates a composite FS layer structure with two different FS layer regions having different impurity densities. This composite structure combines the benefits of thin thickness (for impurity density control) with localized high-density regions (for breakdown voltage maintenance), achieving both improved manufacturing precision and adequate electrical strength.
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 proposed solution enhances the power device's switching performance and reduces the thickness of the FS layer, resulting in improved electrical characteristics, such as high-speed switching and easier adjustment of impurity densities, while maintaining effective field stop functionality.
Implementation Method 1
a FS layer which is formed on the semiconductor substrate through a first-conductive-type ion implant
Implementation Method 2
a drift region which is formed on the FS layer by growing a first-conductive-type epitaxial layer
Data Source
AI summary
A power device, which has a Field Stop (FS) layer based on a semiconductor substrate between a collector region and a drift region in an FS-IGBT structure. The FS layer includes multiple implants for improved functionality of the power device.