SCR Holding Voltage via Segmented Doping Regions
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Solution Overview
Problem
Silicon controlled rectifiers (SCRs) used for electrostatic discharge protection in semiconductor devices often latch up at power supply voltages higher than 1.2V, leading to burnout due to excessive current conduction during normal operation, and existing solutions like adding diodes or stacking SCRs are impractical due to increased area requirements and leakage issues.
Innovation Solution
A high holding voltage electrostatic discharge protection circuit is created using a silicon controlled rectifier (SCR) with compensation regions between the anode and cathode, introducing negative feedback mechanisms to increase the holding voltage and prevent latch-up, allowing operation at higher power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the holding voltage of the SCR is increased by adding diodes in series or stacking multiple SCRs, then the latch-up problem is solved and the SCR can operate at higher power supply voltages, but the area required increases significantly and leakage due to the Darlington effect becomes too high
Solution Approach 1:
The invention divides the SCR structure into multiple regions with different doping concentrations, specifically creating a first region with lower doping concentration and a second region with higher doping concentration. This segmentation allows the holding voltage to be increased through the doping profile rather than adding external diodes or stacking SCRs, thus avoiding the area penalty while preventing latch-up.
Solution Approach 2:
The patent applies local quality by creating regions with spatially varying doping concentrations within the SCR structure. The first region has a lower doping concentration while the second region has a higher doping concentration, allowing different parts of the device to contribute differently to the holding voltage characteristic. This localized property variation increases holding voltage without requiring additional external components that would increase device area.
2Reliability
If diodes are added in series with the SCR to increase holding voltage, then latch-up is prevented, but too many additional elements are necessary which makes the solution impractical and increases area
Solution Approach 1:
The invention merges the function of increasing holding voltage directly into the SCR structure itself by creating regions with different doping concentrations. Instead of adding separate diodes as external elements, the doping profile modification integrates the voltage-increasing function within the SCR, reducing the total number of elements and simplifying the device structure.
Solution Approach 2:
The patent changes the doping concentration parameter within the SCR structure to increase the holding voltage. By creating regions with different doping concentrations (lower in the first region, higher in the second region), the electrical characteristics of the SCR are modified to achieve higher holding voltage without adding external diodes, thus reducing device complexity.
3Reliability
If multiple SCRs are stacked in series to increase holding voltage, then latch-up is prevented, but it is not practical due to the large area required and high leakage from the Darlington effect
Solution Approach 1:
The invention segments the SCR into regions with different doping concentrations, creating a first region with lower doping and a second region with higher doping. This internal segmentation replaces the need to stack multiple SCRs in series, achieving the same latch-up prevention effect while maintaining a single SCR structure that avoids the Darlington effect and associated leakage currents.
Solution Approach 2:
The patent modifies the doping concentration parameter within the SCR structure to achieve higher holding voltage. By varying the doping concentration spatially (lower in the first region, higher in the second region), the device achieves improved reliability without stacking multiple SCRs, thereby reducing leakage current and avoiding the Darlington effect.
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
The solution effectively increases the holding voltage of the SCR, preventing latch-up and enabling safe operation at higher power supply voltages while maintaining high current capability, thus enhancing the reliability of electrostatic discharge protection in semiconductor devices.
Implementation Method 1
The compensation regions may introduce negative feedback mechanisms into the SCR device which may influence the loop gain of the SCR and cause it to reach regenerative feedback at a higher holding voltage.
Data Source
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AI summary
A high holding voltage (HVO electrostatic discharge (ESD) protection circuit comprises a silicon controlled rectifier (SCE) device and compensation regions located within the length between the anode and cathode (LAC) of the SCR device which increase the holding voltage of the SCR device. The compensation regions may introduce negative feedback mechanisms into the SCR device which may influence the loop gain of the SCR and cause it to reach regenerative feedback at a higher holding voltage.