MOS Transistor Shield Layer for Lateral Breakdown Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MOS transistors used in broadcast applications do not meet the required ruggedness and bandwidth specifications, particularly in terms of lateral breakdown voltage, due to their design which is inadequate for high power and mismatch conditions.
Innovation Solution
The MOS transistor design includes a shield layer made of electrically conductive material that extends over the drain extension region with increasing distance from the gate electrode to the drain contact region, influencing the lateral electric field and enhancing the lateral breakdown voltage, which is achieved through multiple portions or stacked sub-layers with varying distances from the drain extension region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDMOS transistor design is used, then the device can operate at standard supply voltages (32V), but the lateral breakdown voltage is insufficient (70V-75V) to meet the ruggedness requirements for broadcast applications
Solution Approach 1:
The shield layer is divided into multiple portions extending over the drain extension region, with each portion positioned at different distances from the drain extension region. This segmented structure creates a gradient in electric field distribution, effectively increasing the lateral breakdown voltage while maintaining reliability for broadcast applications
Solution Approach 2:
The shield layer is positioned in the vertical dimension above the drain extension region, creating a three-dimensional electric field control structure. By varying the vertical distance of different shield layer portions from the drain extension region, the patent achieves enhanced lateral breakdown voltage without increasing lateral dimensions
2Power
If the supply voltage is increased to 40V for broadcast applications, then the power capability and load resistance are improved, but the existing transistor design cannot withstand the required voltage stress due to insufficient lateral breakdown voltage
Solution Approach 1:
The shield layer acts as an intermediary structure between the gate electrode and the drain region. By positioning conductive shield layers at specific heights above the drain extension region, the patent mediates the electric field distribution, allowing the transistor to withstand higher supply voltages (40V) required for broadcast applications while maintaining proper device operation
3Strength
If a stepped shield layer structure is implemented to increase lateral breakdown voltage, then the ruggedness for broadcast applications is achieved, but the device complexity and fabrication process are increased
Solution Approach 1:
Different portions of the shield layer are positioned at different local heights above the drain extension region, creating local variations in electric field control. This local quality approach allows targeted enhancement of lateral breakdown voltage in critical regions while maintaining simpler structures in other areas, balancing performance improvement with fabrication complexity
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 design increases the lateral breakdown voltage to meet the ruggedness requirements for broadcast applications, allowing operation at higher supply voltages and ensuring reliable performance across the required bandwidth, while also simplifying fabrication and reducing voltage application needs.
Implementation Method 1
the shield layer influencing the distribution of the lateral electric field in the drain extension region in such a way that the lateral breakdown voltage of the MOS transistor is increased
Data Source
AI summary
The MOS transistor (1) of the invention comprises a gate electrode (10), a channel region (4), a drain contact region (6) and a drain extension region (7) mutually connecting the channel region (4) and the drain contact region (6). The MOS transistor (1) further comprises a shield layer (11) which extends over the drain extension region (7) wherein the distance between the shield layer (11) and the drain extension region (7) increases in a direction from the gate electrode (10) towards the drain contact region (6). In this way the lateral breakdown voltage of the MOS transistor (1) is increased to a level at which the MOS transistor (1) may fulfill the ruggedness requirement for broadcast applications for a supply voltage higher than that used in base station applications.