LDMOS Field-Oxide Layout for Higher Breakdown Voltage
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Solution Overview
Problem
Lateral diffused MOS (LDMOS) transistors face limitations in breakdown voltage due to electric field peaks near the bird's beak of the field oxide, leading to device breakdown failures, as the deep n-well is not fully depleted, causing an imbalance in dopant concentrations that adversely affect the electric field.
Innovation Solution
A p-type doped region is introduced near the bird's beak of the field oxide, with a dopant concentration higher than the n-type dopant concentration in the deep n-well, to achieve charge balance and reduce the electric field peak, thereby enhancing the breakdown voltage by increasing the p-type dopant concentration near the source region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the deep n-well is not fully depleted to maintain dopant concentration balance, then the manufacturing process is simpler, but the electric field peak causes device breakdown failure
Solution Approach 1:
The patent applies local quality by creating a p-type doped region specifically at the bird's beak area where the electric field peak occurs. This localized doping modifies only the critical region rather than the entire device structure, reducing the electric field peak and preventing breakdown while maintaining overall device functionality and relatively simple manufacturing processes.
2Productivity
If the process node is shrunk to improve integration density, then the integration density increases, but new techniques are required to maintain transistor performance
Solution Approach 1:
The patent applies parameter changes by modifying the dopant concentration distribution through selective p-type doping at the bird's beak region. This parameter modification addresses the performance degradation that occurs during process node scaling, allowing transistors to maintain their breakdown voltage and other performance characteristics even as the device dimensions are reduced to achieve higher integration density.
3Reliability
If the p-type dopant concentration is increased near the source region, then the breakdown voltage is enhanced, but the device structure becomes more complex
Solution Approach 1:
The patent uses the p-type doped region as an intermediary element that mediates between the field oxide and the deep n-well. This intermediary doping layer manages the electric field distribution by creating a transition zone that reduces the electric field peak, thereby enhancing breakdown voltage while avoiding the need for fundamentally complex device structures.
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 approach effectively improves the breakdown voltage of LDMOS transistors by reducing the electric field peak and preventing device breakdown, allowing for increased operational reliability and performance.
Implementation Method 1
doping a second impurity of a second conductivity type into the first-type deep well to form a second-type doped region
Implementation Method 2
electric field peaks near the bird's beak of the field oxide
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a deep n-well, a field oxide, a gate structure, a p-type doped region, a source region, and a drain region. The deep n-well is in the semiconductor substrate. The field oxide is partially embedded in the deep n-well and having a tip corner in a position substantially level with a top surface of the semiconductor substrate. The gate structure is on the field oxide and laterally extends past the tip corner of the field oxide. The p-type doped region is in the deep n-well and is interfaced with the tip corner of the field oxide. The source region and a drain region are laterally separated at least in part by the p-type doped region and the field oxide.