Electrostatic Protection Circuit Trigger Voltage Control
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Solution Overview
Problem
Existing electrostatic discharge (ESD) protection circuits for semiconductor integrated circuit devices face challenges in setting trigger voltage freely without special process steps and suffer from significant leakage current during normal operation.
Innovation Solution
An electrostatic protection circuit is designed with a series connection of a transistor, a predetermined number of diodes, and an impedance element between two nodes, where the diodes are connected between the source and back gate of the transistor, allowing the trigger voltage to be set freely without requiring a special process step and minimizing leakage current by preventing current flow through the diodes until the transistor is turned on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a zener diode is used to set the trigger voltage of the SCR circuit, then the trigger voltage can be precisely adjusted, but a special process step (impurity doping) is required
Solution Approach 1:
The patent changes the parameter control method from special process steps (impurity doping) to standard process parameters. By using the number of diodes in series and their connection configuration, the trigger voltage can be adjusted through circuit topology rather than requiring special manufacturing processes, thus resolving the contradiction between precision and ease of manufacture
Solution Approach 2:
The patent replaces the expensive and complex zener diode (requiring special process steps) with ordinary diodes that can be formed using standard process steps. Multiple ordinary diodes connected in series provide the necessary voltage control without requiring special manufacturing, effectively using simpler, more readily available components
2Ease of manufacture
If MOS transistors are used instead of zener diodes to avoid special process steps, then ease of manufacture is improved, but fine adjustment of trigger voltage is not possible and leakage current increases
Solution Approach 1:
The patent segments the voltage control function into multiple discrete diode elements connected in series. Each diode contributes a fixed voltage drop, and by selecting different numbers and configurations of diodes, precise trigger voltage adjustment is achieved without requiring MOS transistors, thereby reducing leakage current while maintaining ease of manufacture
Solution Approach 2:
The patent changes the approach from using MOS transistor characteristics (breakdown voltage, snapback voltage) to controlling voltage through the number and arrangement of diodes. This parameter change allows fine adjustment of trigger voltage through circuit configuration rather than relying on transistor characteristics, reducing leakage current while maintaining manufacturing simplicity
3Ease of manufacture
If diodes are connected in series in the forward direction to adjust trigger voltage, then ease of manufacture and voltage adjustment are improved, but leakage current becomes large under normal operation
Solution Approach 1:
The patent inverts the conventional diode connection approach by using diodes in reverse bias configuration or specific series arrangements where they do not conduct during normal operation. This inversion allows the diodes to set the trigger voltage threshold without creating continuous conduction paths that would cause leakage current, resolving the contradiction between ease of manufacture and energy loss
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 provides an electrostatic protection circuit with minimal leakage current under normal conditions and allows for flexible setting of the trigger voltage, enhancing the protection of semiconductor integrated circuit devices from ESD without the need for additional processing steps.
Implementation Method 1
at least a predetermined number of diodes D1 and D2 are connected between a source S and a back gate B of the transistor QN1
Implementation Method 2
a potential difference occurs between the source and back gate of the transistor QN1 due to the diodes D1 and D2, and the effective threshold voltage of the transistor QN1 rises due to a back gate effect
Implementation Method 3
a series circuit including a transistor QN1, a predetermined number of diodes D1 and D2 and an impedance element R1 that are connected in series between a first node N1 and a second node N2
Implementation Method 4
A positive charge is discharged to the second terminal via the electrostatic protection circuit when a positive charge is applied to the first terminal by electrostatic discharge or like, thus enabling damage to the internal circuit to be prevented since an excessive voltage is not applied to the internal circuit
Data Source
AI summary
Provided is an electrostatic protection circuit that has little leakage current under normal operation and allows a trigger voltage to be set comparatively freely, without requiring a special process step. This electrostatic protection circuit is provided with a series circuit including a transistor, a predetermined number of diodes and an impedance element that are connected in series between the first node and the second node, and a discharge circuit configured to send current from the first node to the second node following an increase in a potential difference that occurs between both ends of the impedance element, when the first node reaches a higher potential than the second node and current flows through the series circuit. The predetermined number of diodes are connected between the source and the back gate of the transistor.