Abstract
Based on 2-D device simulations and mixed-mode transient simulations, DC and transient discharge characteristics of a usual diode string utilizing a standard CMOS process, and a diode string utilizing a triple-well CMOS process, which can serve as an essential VDD-VSS clamp device for CMOS input ESD protection were compared. Transient discharge characteristics including peak voltages developed across gates oxides of transistors in input buffers, lattice heating inside ESD protection devices, and ratios of discharge current components at its peak inside the diode-string clamp were compared. DC standby current levels added per each input pad structure, which are the critical parameters determining usefulness of the devices, were also compared. We showed that the diode-string devices in comparison can serve successfully as a VDD-VSS clamp device for ESD protection by virtue of the dominant pnpn thyristor-related conduction mechanisms. Optimization of design parameters including anode-cathode contact spacing in each diode in the string, device width of the diode string, and number of diodes in the diode string was performed to present transient discharge and DC characteristics of some recommendable design examples, which can serve as a guideline in designing diode-string clamp devices.
Highlights
Based on 2-D device simulations and mixed-mode transient simulations, DC and transient discharge characteristics of a usual diode string utilizing a standard CMOS process, and a diode string utilizing a triple-well CMOS process, which can serve as an essential VDD-VSS clamp device for CMOS input electrostatic discharge (ESD) protection were compared
Optimization of design parameters including anode-cathode contact spacing in each diode in the string, device width of the diode string, and number of diodes in the diode string was performed to present transient discharge and DC characteristics of some recommendable design examples, which can serve as a guideline in designing diode-string clamp devices
CMOS chips are vulnerable to electrostatic discharge (ESD) due to thin gate oxides used, and protection devices are required at input pads
Summary
How to cite this paper: Choi, J.Y. (2019) A Comparison Study of Diode-String ESD Clamps for CMOS Input Protection. Received: January 12, 2019 Accepted: February 25, 2019 Published: February 28, 2019
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