Trench-Gate Transistor Structure for Low Resistance High Voltage
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Solution Overview
Problem
There is a need to improve the tradeoff between on-state resistance, dimensions, and blocked off-state voltage in transistors, particularly in high-voltage applications where smaller transistors with higher blocked voltages result in increased on-state resistance.
Innovation Solution
The design includes a semiconductor region delimited by a trench with an electrically-conductive element, a channel area in contact with the semiconductor region, and a doped area, where the conductive element is located opposite the semiconductor region, and the gate is positioned within the trench, allowing for increased voltage blocking without increasing on-state resistance by optimizing the doping levels and trench structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the transistor size is reduced to decrease occupied surface area, then the on-state resistance increases
Solution Approach 1:
The patent introduces a vertical conductive element extending through the trench depth, transforming the horizontal conduction path into a three-dimensional structure. This allows current to flow through multiple dimensions (horizontal channel + vertical conductive element), effectively reducing on-state resistance without increasing the footprint area on the substrate surface.
Solution Approach 2:
The conductive element is nested within the trench structure, which itself is formed within the substrate. This nested configuration allows the conductive element to be positioned strategically at different depths within the trench, optimizing the conduction path while maintaining a compact overall structure that minimizes surface area occupation.
2Area of stationary object
If the transistor size is reduced to decrease occupied surface area, then the blocked voltage decreases
Solution Approach 1:
By extending the conductive element vertically through the trench, the patent creates a distributed voltage blocking structure along the depth dimension. The gate electrode can control the depletion region across this vertical extent, effectively increasing the voltage blocking capability without proportionally increasing the horizontal footprint area.
Solution Approach 2:
The patent applies different doping levels and material properties at different locations within the trench structure. The semiconductor region has varying doping concentrations from the surface to the trench bottom, creating localized regions optimized for different functions: voltage blocking near the surface and enhanced conduction near the channel, thereby achieving high voltage blocking in a compact area.
3Reliability
If the on-state resistance is reduced to improve current flow, then the occupied surface area increases
Solution Approach 1:
The vertical conductive element provides an additional conduction dimension, allowing the current to flow through a three-dimensional path rather than being constrained to a two-dimensional plane. This effectively increases the conduction cross-section without increasing the surface footprint, thereby reducing on-state resistance while maintaining compact area.
4Strength
If the blocked voltage is increased to improve voltage blocking capability, then the on-state resistance increases
Solution Approach 1:
The patent implements a graded doping profile in the semiconductor region, with higher doping concentrations near the surface for voltage blocking and lower doping concentrations near the channel region for reduced on-state resistance. This spatial variation in material properties allows simultaneous optimization of both voltage blocking capability and conduction efficiency.
Solution Approach 2:
The conductive element nested within the trench provides a low-resistance path that is strategically positioned to bridge the high-voltage blocking region and the channel region. This nested configuration allows the structure to handle high voltages in the off-state while providing a dedicated low-resistance conduction path in the on-state, effectively decoupling the two performance parameters.
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 enables transistors to maintain low on-state resistance while blocking higher voltages, achieving a better tradeoff between performance and size, with the ability to handle voltages up to 44 V and on-state resistance as low as 17 mΩ/mm² for a given surface area.
Implementation Method 1
field-effect transistors, for example, of MOS type, are used in a non-conductive state to block high voltages
Implementation Method 2
a doped area covering a portion of the channel area, said doped area being preferably electrically coupled to the conductive element
Data Source
AI summary
A transistor is disclosed. In an embodiment a transistor includes a first semiconductor region of a substrate, a first trench delimiting the first semiconductor region on a first side, a first electrically-conductive element located in the first trench, a channel area in contact with the first semiconductor region and a first area of contact with the first semiconductor region, wherein the channel area and the first area of contact are on the same surface side of the substrate.