Diode String Well Biasing for ESD Leakage Prevention
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Solution Overview
Problem
Diode strings used for ESD protection in integrated circuits face issues with parasitic bipolar transistors becoming conducting due to overvoltage or turned-off supply voltages, leading to undesired leakage currents.
Innovation Solution
A diode string configuration where diodes are arranged in a semiconductor well of one polarity within a substrate of different polarity, with well biasing circuitry applying an intermediate voltage between the diode terminals to prevent parasitic bipolar transistors from conducting, using ohmic connections and well biasing to manage voltages and prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diodes are formed using well structures for ESD protection, then ESD protection capability is improved, but parasitic bipolar transistors become conducting under overvoltage or turned-off supply conditions causing leakage currents
Solution Approach 1:
An intermediate voltage is introduced to the well structure to prevent parasitic bipolar transistors from becoming conducting. This intermediate voltage acts as a mediator between the supply voltage and ground, ensuring that the well remains at a potential that prevents parasitic conduction while maintaining ESD protection functionality.
Solution Approach 2:
The voltage parameter of the well is dynamically adjusted to an intermediate level. By changing the well voltage from either supply voltage or ground to an intermediate voltage during normal operation, the patent prevents parasitic bipolar transistor conduction while preserving ESD protection capability under voltage stress conditions.
2Object-generated harmful factors
If well biasing circuitry is added to prevent parasitic conduction, then leakage prevention is improved, but device complexity increases
Solution Approach 1:
The well biasing circuitry is designed to automatically maintain the intermediate voltage without requiring external control signals or complex regulation circuits. The circuit self-regulates to provide the appropriate bias voltage, reducing overall system complexity while effectively preventing parasitic conduction.
Data Source
AI summary
Devices and methods are provided, wherein a diode string is provided in a well and the well is biased with an intermediate voltage between voltages applied to terminals of the diode string.