LDMOS Body Region Layout for Gate Oxide Breakdown Protection
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Solution Overview
Problem
Existing semiconductor devices with LDMOS transistors suffer from breakdowns at the boundary between the body region and the semiconductor layer when high voltages are applied, leading to damage to the gate insulating film and variations in device properties such as static electricity tolerance and threshold voltage.
Innovation Solution
A semiconductor device configuration with a first conductivity type semiconductor substrate, a second conductivity type semiconductor layer, a body region with distinct portions in contact with both the gate insulating film and a thick insulating film, where the thick film portion is designed to absorb the high electric field and break down preferentially, reducing the load on the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the body region boundary is in contact with the gate insulating film, then the device structure is simple and manufacturing is easier, but breakdown occurs at the boundary when high voltage is applied, damaging the gate insulating film and causing property variations
Solution Approach 1:
A thick insulating film is introduced as an intermediary layer between the body region boundary and the gate insulating film. This thick insulating film serves as a mediator that directs the electric field and load concentration away from the gate insulating film, preventing breakdown while maintaining structural integrity. The thick insulating film absorbs the high voltage stress that would otherwise damage the gate insulating film.
2Device complexity
If the body region boundary is in contact with the gate insulating film, then the device structure is simpler, but high electric fields concentrate at the boundary causing breakdown and property variations
Solution Approach 1:
The thick insulating film acts as an intermediary that redistributes the electric field concentration. By positioning the thick insulating film between the body region boundary and the gate insulating film, the high electric fields are directed into the thick insulating film rather than concentrating at the gate insulating film interface, thereby preventing breakdown while adding minimal structural complexity.
3Reliability
If a thick insulating film is added to cover the body region boundary, then breakdown is prevented and reliability is improved, but the device structure becomes more complex
Solution Approach 1:
The thick insulating film is applied locally only at the critical body region boundary area where breakdown occurs, rather than uniformly across the entire device. This localized application provides the necessary reliability improvement at the specific problem location while minimizing the increase in overall device complexity and maintaining simplicity in other regions.
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 configuration enhances the reliability of the semiconductor device by suppressing damage to the gate insulating film and maintaining consistent properties by directing the high electric field to a specific portion that can break down without affecting the primary operational region.
Implementation Method 1
directing the electric field and load concentration to the second portion, thereby preventing breakdown in the first portion
Data Source
AI summary
A semiconductor device includes a first conductivity type semiconductor substrate, a second conductivity type semiconductor layer which is formed on the semiconductor substrate so as to be in contact with the semiconductor substrate, a first conductivity type body region which is formed in a front surface portion of the semiconductor layer, a second conductivity type source region which is formed in a front surface portion of the body region, a second conductivity type drain region which is formed apart from the body region, a gate insulating film which is formed in a front surface of the semiconductor layer so as to be in contact with the body region, a thick insulating film which is formed integrally with the gate insulating film so as to cover the semiconductor layer between the gate insulating film and the drain region and a gate electrode which is opposite to the body region via the gate insulating film. The body region includes a first portion in which a boundary with the semiconductor layer is in contact with the gate insulating film and a second portion in which a boundary with the semiconductor layer is in contact with the thick insulating film.