Vertical Charge-Compensated Trenches for High-Voltage Power Switching
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Solution Overview
Problem
High voltage power-switching devices face a trade-off between breakdown voltage (BVdss) and on-state resistance (Rdson), with existing superjunction devices struggling to achieve robust performance and efficient manufacturing methods.
Innovation Solution
A semiconductor device structure incorporating charge-compensated trench regions and a trench gate control structure with sub-surface doped layers, which provides a sub-surface primary conduction path to isolate current flow from surface defects and simplify ohmic contact formation, enhancing both BVdss and Rdson performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional superjunction devices use heavily doped diffused n-type and p-type regions, then on-state resistance is reduced, but breakdown voltage performance deteriorates
Solution Approach 1:
The patent transitions from planar surface junctions to vertical trench structures extending into the bulk substrate. Charge compensation is achieved through vertically stacked n-type and p-type doped regions within trenches, creating a three-dimensional charge compensation mechanism that simultaneously reduces on-state resistance and maintains breakdown voltage through depth rather than surface area.
Solution Approach 2:
The device employs composite doped regions within trenches, combining n-type and p-type semiconductor materials in alternating layers. This composite structure enables charge compensation between opposite polarity regions, reducing effective resistance while the alternating polarity layers maintain electric field distribution for high breakdown voltage performance.
2Ease of manufacture
If surface conduction paths are used, then manufacturing is simplified, but device performance is reduced due to surface defects
Solution Approach 1:
The conductive path is moved from the surface plane to the vertical dimension by extending doped regions deep into the substrate through trenches. This vertical conduction path isolates the current flow from surface defects while maintaining manufacturing feasibility through standard ion implantation and diffusion processes applied to trench structures.
Solution Approach 2:
The patent extracts the conduction path from the surface environment by creating deep trench structures that extend into the bulk substrate. This separates the active conduction regions from surface contaminants and defects, while the trench walls provide physical isolation and the deep extent ensures connection to bulk material free from surface issues.
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 device structure improves breakdown voltage and reduces on-state resistance, providing more robust and efficient high voltage power-switching performance while simplifying the manufacturing process.
Implementation Method 1
the heavily doped n-type and p-type regions deplete into or compensate each other to provide a high BVdss
Implementation Method 2
In the on state, current flows through the heavily doped n-type regions, which lowers Rdson
Data Source
AI summary
In one embodiment, a semiconductor device is formed having vertical localized charge-compensated trenches, trench control regions, and sub-surface doped layers. The vertical localized charge-compensated trenches include at least a pair of opposite conductivity type semiconductor layers. The trench control regions are configured to provide a generally vertical channel region electrically coupling source regions to the sub-surface doped layers. The sub-surface doped layers are further configured to electrically connect the drain-end of the channel to the vertical localized charge compensation trenches. Body regions are configured to isolate the sub-surface doped layers from the surface of the device.