Superjunction Transistor Sidewall Implantation for Low Pitch Drift Regions
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Solution Overview
Problem
There is a need for a method to produce a drift region of a superjunction transistor device with a low pitch to reduce specific on-resistance while maintaining voltage blocking capability and high avalanche robustness.
Innovation Solution
The method involves forming alternating regions of first and second doping types in semiconductor layers, creating trenches, implanting dopant atoms into the sidewalls, and forming a control structure with transistor cells, including body, source, and gate electrodes, to achieve a low pitch and efficient device operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of transistor cells is increased to reduce specific on-resistance, then the specific on-resistance decreases, but the pitch is reduced making manufacturing more difficult
Solution Approach 1:
The drift region is segmented into multiple alternating doped regions (first doping type and second doping type) arranged in a superjunction structure. This segmentation allows increasing the number of transistor cells per unit area by creating fine-pitched alternating doped regions, thereby reducing specific on-resistance while maintaining manufacturability through the systematic segmented approach
Solution Approach 2:
The invention transitions from planar two-dimensional device scaling to three-dimensional vertical superjunction structure. By forming alternating doped regions extending vertically through the drift region and using sidewall implantation techniques, the patent achieves low pitch in the horizontal direction while utilizing the vertical dimension for dopant delivery, enabling reduced specific on-resistance without proportionally reducing manufacturable pitch
2Reliability
If the pitch is reduced to increase transistor cell density, then specific on-resistance decreases, but device complexity increases
Solution Approach 1:
The drift region is divided into multiple alternating doped regions (first doping type and second doping type) arranged in a periodic superjunction pattern. This segmentation creates the low pitch structure needed for reduced specific on-resistance while using regular repeating units that simplify fabrication compared to arbitrary complex patterns
Solution Approach 2:
Trenches are formed in the semiconductor layer before dopant implantation, and sidewall coatings are applied to the trenches prior to filling. These preliminary actions enable precise formation of alternating doped regions with low pitch by confining dopant delivery to specific locations, reducing device complexity through pre-planned structuring rather than requiring complex post-formation adjustments
3Manufacturing precision
If dopant atoms are implanted into sidewalls to form alternating regions, then manufacturing precision improves, but the number of process steps increases
Solution Approach 1:
The formation of trenches, sidewall coating, and dopant implantation are merged into an integrated sidewall implantation process. By combining these steps into a unified approach where trenches serve as both structural features and implantation templates, the patent achieves high manufacturing precision for alternating doped regions while reducing the total number of separate process steps
Solution Approach 2:
The trenches serve multiple functions: they define the pattern for alternating doped regions, provide sidewalls for dopant confinement during implantation, and act as templates for subsequent filling operations. This multi-functionality reduces process complexity by eliminating the need for separate patterning steps for each function
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 allows for a decrease in specific on-resistance while maintaining high avalanche robustness and cost-effectiveness by reducing the pitch of the superjunction transistor device.
Implementation Method 1
implanting at least one of first type dopant atoms and second type dopant atoms into sidewalls of the plurality of trenches
Implementation Method 2
at least one temperature process
Data Source
AI summary
A method includes forming first regions of a first doping type and second regions of a second doping type in first and second semiconductor layers such that the first and second regions are arranged alternately in at least one horizontal direction of the first and second semiconductor layers, and forming a control structure with transistor cells each including at least one body region, at least one source region and at least one gate electrode in the second semiconductor layer. Forming the first and second regions includes: forming trenches in the first semiconductor layer and implanting at least one of first and second type dopant atoms into sidewalls of the trenches; forming the second semiconductor layer on the first semiconductor layer such that the second layer fills the trenches; implanting at least one of first and second type dopant atoms into the second semiconductor layer; and at least one temperature process.