Deep Barrier Layer IGBT Manufacturing via Segmented Trench Etching
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Solution Overview
Problem
Conventional IGBTs with high emitter side charge carrier density face challenges such as short channel effects and increased off-state leakage current due to shallow potential barrier layers, which limit the depth of the barrier layer and impact the body region height.
Innovation Solution
The method involves etching trenches to a first depth, doping the substrate to form a deep doped region, and then extending the trenches deeper, allowing for a body region above the doped region without impacting the body region height, thereby forming a deep potential barrier that reduces short channel effects and enhances the barrier's doping concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the potential barrier layer is formed shallow in the drift zone using conventional implantation, then the barrier depth is limited by implantation energy, but the body region height is reduced causing short channel effects
Solution Approach 1:
The patent performs the doping action at an intermediate stage during trench formation, before the trench is completed to its final depth. The doping is performed when the trench is at a first depth, then the trench is extended deeper afterward. This preliminary doping action allows the barrier to be formed at the correct depth without being constrained by final trench depth requirements.
Solution Approach 2:
The trench formation process is segmented into multiple stages: first etching to an intermediate depth, then doping the surrounding region, then continuing to etch deeper to the final depth. This segmentation allows independent optimization of barrier depth and trench depth, resolving the contradiction between achieving sufficient barrier depth and maintaining adequate body region height.
2Length of stationary object
If the implantation dose is increased to form a deeper barrier, then the barrier depth increases, but the body region height is reduced leading to punch through and leakage current
Solution Approach 1:
The doping is performed as a preliminary action during the intermediate stage of trench formation, before the trench reaches its final depth. This timing allows the barrier to be formed at the optimal depth in the drift zone without compromising the body region height, thereby preventing punch through and reducing off-state leakage current.
Solution Approach 2:
The patent changes the temporal parameter of when doping occurs during the trench formation process. Instead of doping after trench completion, the doping is performed at an intermediate depth during the etching process itself. This parameter change in process sequencing allows independent control of barrier depth and body region height.
3Ease of manufacture
If conventional implantation and annealing is used to form the barrier layer, then the process is simple, but the barrier depth is limited by implantation energy and diffusion processes
Solution Approach 1:
The doping action is performed as a preliminary step during trench formation at an intermediate depth. This timing allows the use of conventional implantation and annealing processes while achieving the desired barrier depth, as the doping occurs before the trench is completed and before significant diffusion can occur that would shallow the barrier.
Solution Approach 2:
The manufacturing process is segmented to perform doping at a specific intermediate stage rather than as a single post-trench operation. This segmentation allows conventional implantation processes to achieve deeper barriers by utilizing the intermediate depth state during trench formation, combining process simplicity with increased barrier depth.
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 approach avoids short channel effects and reduces the on-state voltage drop (VCEON) while minimizing implantation damage and allowing for higher potential barrier doping, improving the overall performance of the IGBT.
Implementation Method 1
doping a region of the semiconductor substrate surrounding a bottom of the trenches at the first depth to form a doped region in the semiconductor substrate
Implementation Method 2
etching a plurality of trenches to a first depth in a semiconductor substrate; after the doped region is formed, etching the plurality of trenches deeper into the semiconductor substrate to a second depth greater than the first depth
Data Source
AI summary
A method of manufacturing a semiconductor device includes: etching a plurality of trenches to a first depth in a semiconductor substrate; doping a region of the semiconductor substrate surrounding a bottom of the trenches at the first depth to form a doped region in the semiconductor substrate; after the doped region is formed, etching the plurality of trenches deeper into the semiconductor substrate to a second depth greater than the first depth, adjacent ones of the trenches being separated from one another by a semiconductor mesa; and forming a body region above the doped region in the semiconductor mesas.