Planar FET Cell with MOS-Gated Diode for Reverse Power Loss Reduction
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Solution Overview
Problem
Semiconductor devices with field effect transistors face significant power losses during reverse operation due to the forward operation of the body diode, which affects the efficiency of circuit applications like DC-DC converters.
Innovation Solution
A semiconductor device comprising a first planar field effect transistor cell acting as a MOS gated diode (MGD) connected in parallel with a second field effect transistor cell, where the first cell has a drain extension region for voltage blocking and a thinner gate dielectric to reduce threshold voltage, allowing current flow before the body-drain diode's forward voltage is reached, thereby minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If field effect transistor cells are used in circuit applications such as DC-DC converters, then the desired current-carrying capacity is achieved, but power losses increase during reverse operation due to body diode forward operation
Solution Approach 1:
The transistor cell is segmented into two distinct cells: a first field effect transistor cell configured as a MOS-gated diode (MGD) and a second field effect transistor cell configured as a load transistor. This segmentation allows each cell to be optimized for its specific function, with the MGD handling reverse operation current to reduce power losses while the load transistor handles forward operation current.
Solution Approach 2:
The MGD cell is given local quality differences through a thinner gate dielectric layer compared to the load transistor, creating a lower threshold voltage specifically in the MGD cell. This local modification enables the MGD to activate earlier during reverse operation, reducing power losses without affecting the load transistor's performance.
2Loss of energy
If a thinner gate dielectric is used in the first field effect transistor cell to reduce threshold voltage, then power loss during reverse operation is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The gate dielectric layer is made locally different between the two transistor cells, with the MGD cell having a thinner gate dielectric than the load transistor. This local quality differentiation is achieved through selective processing steps that modify the gate dielectric thickness or properties only in the MGD region, thereby reducing the overall manufacturing precision burden while still achieving the desired threshold voltage reduction.
Solution Approach 2:
The threshold voltage of the MGD is adjusted by changing the gate dielectric thickness parameter. By making the gate dielectric thinner in the MGD cell compared to the load transistor, the threshold voltage is reduced, allowing the MGD to conduct current at lower voltages during reverse operation, thus reducing power losses.
3Power
If multiple field effect transistor cells are connected in parallel to increase current-carrying capacity, then the desired power handling is achieved, but device complexity increases
Solution Approach 1:
The parallel connection of transistor cells is segmented into functionally distinct roles: one MGD cell for reverse operation and one load transistor for forward operation. This functional segmentation simplifies the control architecture compared to using identical cells, as the MGD's body diode provides inherent reverse conduction path without requiring external control signals.
Solution Approach 2:
The MGD cell serves multiple functions: it acts as a diode for reverse operation current conduction, provides a low-loss path during reverse bias, and still functions as a transistor when needed. This multi-functionality reduces the need for separate dedicated components, thereby managing device complexity while maintaining high current-carrying capacity.
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 solution effectively reduces power losses during reverse operation by enabling current flow through the MGD before the body-drain diode's forward voltage is reached, enhancing the efficiency of circuit arrangements, particularly in DC-DC converters.
Implementation Method 1
a first thickness of a first gate dielectric arranged on the channel region of the first planar field effect transistor cell is less than a second thickness of a second gate dielectric arranged on the channel region of the second planar field effect transistor cell
Data Source
AI summary
The disclosure relates to a semiconductor device including a first planar field effect transistor cell and a second planar field effect transistor cell. The first planar field effect transistor cell and the second planar field effect transistor cell are electrically connected in parallel and each include a drain extension region between a channel region and a drain terminal at a first surface of a semiconductor body. A gate electrode of the first field effect transistor cell is electrically connected to a source terminal, and a gate electrode of the second field effect transistor cell is connected to a gate terminal that is electrically isolated from the source terminal.