Integrated Low Leakage Diode Parasitic Substrate Current
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Solution Overview
Problem
High voltage diodes in power integrated circuits face challenges with parasitic substrate leakage current, which affects their performance and efficiency.
Innovation Solution
The integration of a diode with a parasitic vertical transistor is addressed by connecting a highly doped region forming the base of the transistor to an anode terminal, utilizing a stepped gate oxide and specific dopant concentrations to reduce parasitic substrate leakage current, and employing a hybrid MOS-bipolar mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a high voltage diode is formed in a power integrated circuit, then the diode can be integrated with other circuit components, but parasitic substrate leakage current increases
Solution Approach 1:
The patent extracts the parasitic PNP transistor from the harmful leakage path by connecting its base region to the anode terminal. This configuration removes the transistor's ability to amplify leakage current while maintaining the diode's rectification function, effectively eliminating the harmful parasitic effect
Solution Approach 2:
The patent converts the parasitic PNP transistor, which originally caused harmful leakage, into a beneficial structure by configuring it as a diode-connected transistor. The base-collector junction of the transistor forms an additional parallel diode path that actually helps conduct forward current with low voltage drop, transforming the harmful parasitic element into a useful current conduction path
2Ease of manufacture
If a parasitic vertical transistor is formed in the diode structure, then the diode can be formed integrally with the power integrated circuit, but the transistor amplifies substrate leakage current
Solution Approach 1:
The patent extracts the transistor's amplification function from the leakage path by connecting the base to the anode terminal. This configuration removes the transistor's ability to amplify leakage current while maintaining the diode's rectification function, effectively eliminating the harmful parasitic effect
Solution Approach 2:
The anode terminal serves as an intermediary connection that links the base region to the highly doped P-type region. This intermediary connection reconfigures the transistor's operation, preventing it from amplifying leakage current while allowing it to contribute to forward current conduction through its base-collector junction
3Manufacturing precision
If a stepped gate oxide is used, then the gate control is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating a stepped gate oxide structure with different thicknesses in different regions. The thinner oxide region provides stronger electric field and better gate control where needed, while the thicker region provides insulation and structural support, optimizing performance locally without requiring complete structural redesign
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 approach significantly reduces substrate leakage current, enhances current flow with low forward voltage, and improves breakdown voltage performance, as demonstrated by measured plots showing reduced substrate current and beta values of the parasitic PNP transistor.
Implementation Method 1
a highly doped region which is connected to an anode terminal of the diode
Data Source
AI summary
An integrated low leakage diode suitable for operation in a power integrated circuit has a structure similar to a lateral power MOSFET, but with the current flowing through the diode in the opposite direction to a conventional power MOSFET. The anode is connected to the gate and the comparable MOSFET source region which has highly doped regions of both conductivity types connected to the channel region to thereby create a lateral bipolar transistor having its base in the channel region. A second lateral bipolar transistor is formed in the cathode region. As a result, substantially all of the diode current flows at the upper surface of the diode thereby minimizing the substrate leakage current. A deep highly doped region in contact with the layers forming the emitter and the base of the vertical parasitic bipolar transistor inhibits the ability of the vertical parasitic transistor to fully turn on.