Split-Gate ESD Diode for High-Speed I/O Voltage Tolerance
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Solution Overview
Problem
Gated diodes used for ESD protection face limitations in long-term reliability due to hot carrier degradation, resulting in reduced voltage tolerance, which restricts their application in high-speed and small-footprint I/O pin designs.
Innovation Solution
A split gate diode structure is introduced, where the gate is divided into two sections, each connected to the anode and cathode, and isolated by nitride spacers, allowing for polysilicon gate structures that are half the length of traditional gates, enhancing reverse voltage breakdown without compromising forward current-voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional gated diode structure is used, then forward current is improved (40% increase over composite diodes), but voltage tolerance deteriorates due to hot carrier degradation of the gate oxide
Solution Approach 1:
The gate is divided into two separate gate structures (first gate and second gate) that are isolated from each other by nitride spacers. This segmentation allows each gate to be independently optimized and prevents hot carrier degradation in one gate from affecting the other, thereby maintaining voltage tolerance while preserving forward current benefits
Solution Approach 2:
Nitride spacers are introduced as intermediary structures between the first and second gates. These spacers provide electrical isolation and physical separation, preventing the propagation of hot carrier effects between gates while maintaining the overall compact structure needed for high-speed applications
2Speed
If the gate length is reduced to increase speed, then operating frequency is improved (enabling 10 GHz applications), but voltage breakdown decreases
Solution Approach 1:
The gate is segmented into two shorter gate structures instead of one long gate. Each gate can be optimized for high-speed operation with reduced length, while the combined structure maintains adequate breakdown voltage through the isolation provided by nitride spacers
Solution Approach 2:
The isolation between gates is achieved not by increasing horizontal distance but by introducing a vertical dimension with nitride spacer layers. This allows compact horizontal layout for high speed while providing sufficient electrical isolation for voltage tolerance
Data Source
AI summary
In a gated diode ESD protection structure, the gate is split into two parts to divide the total reverse voltage between two gate regions.