Temperature Sensing Diode Substructure for Stable MOSFET Output
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Solution Overview
Problem
Existing semiconductor devices require additional processes to stabilize the output of temperature sensing diodes due to the absence of a P well region in the manufacturing process of insulated gate type power transistors, leading to potential instability under drain voltage or substrate voltage fluctuations.
Innovation Solution
Incorporating a source field plate and P type diffusion layer into the substructure of the temperature sensing diode, connected to a source potential, which is formed simultaneously with the trenches of the MOSFET, stabilizing the forward output voltage without adding significant manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a P well region is formed below the polysilicon diode to stabilize the output, then the output stability is improved, but the manufacturing process complexity increases due to additional processes
Solution Approach 1:
The patent merges the temperature sensing diode structure with the MOSFET trench structure. The source field plate and P type diffusion layer are formed within the same trenches that define the MOSFET cells, combining two functions into a single structural element. This eliminates the need for separate P well formation processes while achieving output stability.
Solution Approach 2:
The trenches serve multiple functions: they define the MOSFET cell boundaries, contain the source field plate for voltage stabilization, and form the P type diffusion layer for the temperature sensing diode. This multi-functional design allows the same structural elements to serve both power transistor and temperature sensing purposes simultaneously.
2Reliability
If a P well region is added to stabilize the temperature sensing diode output, then the reliability is improved, but the manufacturing cost increases due to additional process steps
Solution Approach 1:
The patent combines the temperature sensing diode stabilization structure with the existing MOSFET manufacturing process. The source field plate and P type diffusion layer are formed using the same trench formation and doping processes already required for MOSFET fabrication, eliminating the need for additional costly process steps.
3Device complexity
If the temperature sensing diode is formed without a P well region, then the manufacturing process is simpler, but the output becomes unstable under drain voltage or substrate voltage fluctuation
Solution Approach 1:
The patent applies local quality by creating P type diffusion regions specifically at the bottom of the trenches where the temperature sensing diode is formed, while maintaining the overall MOSFET structure. The source field plate is positioned locally to counteract voltage fluctuations, providing stabilization only where needed without altering the global device architecture.
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 solution suppresses output instability of the temperature sensing diode by fixing it to a source potential, even under substrate potential fluctuations, while maintaining the breakdown voltage and reducing recovery surge effects, thus stabilizing the forward output voltage without increasing process costs.
Implementation Method 1
The source field plate and the diffusion layer are connected to a source potential, thereby making it possible to suppress an influence of a substrate potential fluctuation on a forward output voltage of the temperature sensing diode
Data Source
AI summary
On a lower layer side of a temperature sensing diode, trenches are periodically formed in a semiconductor substrate. A source field plate is arranged in the trenches via an insulating film. A P type diffusion layer is formed between adjacent trenches. The source field plate and the P type diffusion layer are connected to a source potential.