ESD SCR with Lateral Gated Section for Low Capacitance
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Solution Overview
Problem
Integrated circuits face challenges in ESD protection due to the susceptibility of smaller transistors to damage from electrostatic discharge events, where existing ESD protection circuits either impose a large capacitive load or have slow response times, particularly in load-sensitive high-speed analog circuits.
Innovation Solution
The implementation of a shallow trench isolation (STI)-bound silicon-controlled rectifier (SCR) in parallel with a gated SCR, which is perpendicular to the STI-bound SCR, forming a low capacitive load and rapid response ESD protection circuit, with shared anodes to enhance triggering speed and reduce voltage overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If diodes are used for ESD protection, then the response speed is fast, but the capacitive load is large which reduces performance of high speed circuits
Solution Approach 1:
The ESD protection function is segmented into two distinct components: a diode for fast response and an SCR for low capacitive load. Each component handles different aspects of ESD protection, with the diode providing immediate response and the SCR providing sustained protection with minimal capacitive impact on high-speed circuits.
Solution Approach 2:
The patent merges the advantages of two different ESD protection mechanisms (diode and SCR) into a single hybrid circuit. The diode and SCR are connected in parallel, combining the fast response characteristic of the diode with the low capacitive load characteristic of the SCR, thereby resolving the technical contradiction between response speed and capacitive load.
2Use of energy by moving object
If SCRs are used for ESD protection, then the capacitive load is low, but the trigger and turn-on time is slow
Solution Approach 1:
The diode is positioned to act first in the ESD protection sequence. When an ESD event occurs, the diode immediately clamps the voltage and begins discharging the ESD current, providing preliminary protection while the SCR is still in its high-impedance state. This preliminary action by the diode compensates for the slow trigger time of the SCR.
Solution Approach 2:
The hybrid circuit merges the fast response of the diode with the low capacitive load of the SCR. The diode provides immediate response to ESD events, while the SCR provides sustained protection with minimal capacitive impact, together resolving the contradiction between trigger time and capacitive load.
3Reliability
If large ESD devices are integrated, then the ESD protection capability is enhanced, but the area consumption increases and performance of high speed circuits is reduced
Solution Approach 1:
The patent applies local quality by using different ESD protection mechanisms for different functional requirements within the same circuit. The diode is optimized for fast response in high-speed signal paths, while the SCR is optimized for low capacitive load in area-constrained regions. This localized optimization allows enhanced ESD protection capability without proportionally increasing area consumption.
Solution Approach 2:
The hybrid ESD protection circuit merges a diode and an SCR in parallel configuration, allowing the circuit to achieve enhanced ESD protection capability through the combined action of both devices while maintaining compact area utilization. The shared anode structure further reduces the overall area required compared to separate protection circuits.
Data Source
AI summary
In an embodiment, an ESD protection circuit may include an STI-bound SCR and a gated SCR that may be electrically in parallel with the STI-bound SCR. The gated SCR may be perpendicular to the STI-bound SCR in a plane of the semiconductor substrate. In an embodiment, the gated SCR may trigger more quickly and turn on more quickly than the STI-bound SCR. The STI-bound SCR may form the main current path for an ESD event. A low capacitive load with rapid response to ESD events may thus be formed. In an embodiment, the anode of the two SCRs may be shared.