LDMOS Field Plate Structure for High-Voltage Stability
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Solution Overview
Problem
High-voltage integrated circuits, such as those used in microwave/RF power amplifiers, require specialized circuit technology to handle higher voltages effectively, and existing laterally-diffused metal-oxide-semiconductor (LDMOS) devices need improved structures for enhanced voltage handling and reliability.
Innovation Solution
A structure for a laterally-diffused metal-oxide-semiconductor device is formed with a semiconductor substrate having a first well, a second well, a source region, and a drain region of opposite conductivity types, along with a field plate and contact made of the same metal, positioned to overlap with the drain region and adjacent portions, to enhance voltage handling and reduce parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDMOS structure is used, then the device can handle high voltages, but parasitic capacitance increases and safe operating area decreases
Solution Approach 1:
The device structure is segmented into distinct regions including a drift well, source well, source region, and drain region with different doping concentrations and types. This segmentation allows optimization of each region's electrical characteristics to reduce parasitic capacitance while maintaining voltage handling capability.
Solution Approach 2:
Different regions of the semiconductor device are assigned different local properties: the drift well has lightly-doped n-type regions for voltage handling, while the source and drain regions have heavily-doped regions for low resistance contacts. This local quality differentiation reduces parasitic capacitance in critical areas while maintaining overall high-voltage capability.
2Reliability
If a conventional LDMOS structure is used, then the device can handle high voltages, but current crowding increases and stability decreases
Solution Approach 1:
The device is divided into multiple functional segments including drift well, source well, and extended drain region. This segmentation distributes current flow paths more evenly, reducing current crowding effects and improving operational stability during high-current operations.
Solution Approach 2:
The invention introduces a vertical dimension to current flow management through the drift well structure, which extends the drain region vertically. This dimensional change provides additional current flow paths that reduce current crowding and improve device stability.
Data Source
AI summary
Structures for a laterally-diffused metal-oxide-semiconductor device and methods of forming a structure for a laterally-diffused metal-oxide-semiconductor device. The structure comprises a semiconductor substrate including a first well, a second well positioned within the first well, a source region positioned in the first well, and a drain region positioned in the second well. The first well has a first conductivity type, and the second well, the source region, and the drain region have a second conductivity type opposite to the first conductivity type. The structure further comprises a field plate over the semiconductor substrate and a contact connecting the field plate to the drain region. The field plate is positioned to overlap with the drain region and with a portion of the second well adjacent to the drain region. The contact and the field plate comprise the same metal.