Source Side Field Plate for MOSFET Vt Shift Reduction
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Solution Overview
Problem
Microelectronic devices, such as MOSFETs, experience threshold voltage shifts (Vt shifts) due to gate electrode stress over time, which affects their reliability, especially in applications with long use lifetimes in harsh conditions.
Innovation Solution
A source side field plate extending from the gate electrode more than a quarter of the distance over the source region is introduced, reducing the electric field near the gate electrode corner and minimizing electron trapping in the gate oxide, thereby reducing Vt shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional field plates are formed in MOS transistors, then device structure is provided, but threshold voltage shifts are not protected against
Solution Approach 1:
The field plate structure is configured with different extension distances on opposite sides of the gate electrode. The first field plate extends a first distance and the second field plate extends a second distance, creating asymmetric local electric field distribution that specifically addresses threshold voltage shifts while maintaining overall device functionality.
Solution Approach 2:
The field plate is divided into two separate field plates positioned on opposite sides of the gate electrode. This segmentation allows independent optimization of each field plate's extension distance, enabling precise control over electric field distribution to prevent threshold voltage shifts.
2Reliability
If gate electrode stress is applied over time, then device operation is maintained, but Vt shifts occur affecting reliability
Solution Approach 1:
The asymmetric field plate configuration is designed in advance to counteract the harmful effects of gate electrode stress that will occur during device operation. By pre-configuring the electric field distribution with different extension distances, the structure proactively prevents threshold voltage shifts before they can occur during long-term use.
Solution Approach 2:
The field plate extension distances are optimized as specific parameters to control electric field distribution. By adjusting the first and second distances of field plate extension, the electric field parameters are tuned to minimize stress-induced threshold voltage shifts while maintaining device operation.
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 source side field plate effectively reduces gate injection current and electron trapping, leading to improved long-term reliability of microelectronic devices by minimizing threshold voltage shifts.
Implementation Method 1
The source side field plate reduces the electric field of the transistor near the gate electrode corner on the source side of the transistor
Data Source
AI summary
The present disclosure introduces a microelectronic device including a source side field plate in a microelectronic device. The microelectronic device may be configured as a metal oxide semiconductor (MOS) transistor, a laterally diffused metal oxide semiconductor (LDMOS) transistor, a drain extended metal oxide semiconductor (DEMOS) transistor, a bipolar junction transistor, a junction field effect transistor, a CMOS transistor, or a gated bipolar device. The source side field plate extends over the source region by a distance which is more than a quarter of the width of the source region. Transistors may suffer from Vt shifts during gate and drain stress over time. The source side field plate reduces the electric field of the transistor near the gate electrode corner on the source side of the transistor. The gate injection current on the source side and electron trapping in the gate oxide thereby reduced which reduces Vt shifts over time.