Integrated Breakdown Protection Diode for LDMOS Reliability
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Solution Overview
Problem
High-side power MOS transistors, such as LDMOS devices, face intrinsic breakdown events that can lead to device degradation or failure when operating at high voltages, and existing solutions like clamping with a second device increase fabrication costs.
Innovation Solution
Integration of a breakdown protection diode within the LDMOS device, configured to break down at a lower voltage than the transistor, relocating the breakdown site from the conduction path to the diode, which is internally integrated and scalable with device size without additional fabrication steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second device is used to clamp the drain voltage to prevent intrinsic breakdown, then device reliability is improved, but fabrication cost increases
Solution Approach 1:
The patent combines the breakdown protection function with the existing LDMOS device structure by integrating a protection diode formed from the drift region and body region. This merging eliminates the need for a separate second device, thereby maintaining breakdown protection while avoiding additional fabrication costs associated with discrete components.
Solution Approach 2:
The drift region of the LDMOS device serves dual purposes: it functions as the active drift region for power switching operations and simultaneously forms the cathode of the breakdown protection diode. This multi-functionality allows the same structure to provide both power switching and breakdown protection without requiring additional components.
2Reliability
If a second device is added in parallel to clamp drain voltage, then intrinsic breakdown is prevented, but device complexity increases
Solution Approach 1:
The protection diode is integrated within the existing LDMOS device structure, sharing the drift region and body region. This merging reduces device complexity by eliminating the need for a separate parallel second device and its associated connections, while still providing effective breakdown protection.
3Reliability
If the breakdown voltage of the protection structure is set below the intrinsic breakdown voltage, then breakdown is relocated to a safe location, but the protection structure may affect normal device operation
Solution Approach 1:
The protection diode is positioned in a specific location within the device structure (formed by the drift region and body region) where its breakdown does not interfere with the normal conduction path. The local breakdown occurs in a region that is electrically isolated from the main channel, allowing breakdown protection without affecting normal 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 integrated breakdown protection diode prevents destructive breakdown events, maintaining device performance and operational characteristics, and avoids increased fabrication costs by integrating the protection within the existing process without altering the device footprint.
Implementation Method 1
The integrated breakdown protection diode prevents destructive breakdown events, maintaining device performance and operational characteristics
Data Source
AI summary
A device includes a semiconductor substrate having a first conductivity type, a device isolating region in the semiconductor substrate, defining an active area, and having a second conductivity type, a body region in the active area and having the first conductivity type, and a drain region in the active area and spaced from the body region to define a conduction path of the device, the drain region having the second conductivity type. At least one of the body region and the device isolating region includes a plurality of peripheral, constituent regions disposed along a lateral periphery of the active area, each peripheral, constituent region defining a non-uniform spacing between the device isolating region and the body region. The non-uniform spacing at a respective peripheral region of the plurality of peripheral, constituent regions establishes a first breakdown voltage lower than a second breakdown voltage in the conduction path.