Thyristor LDD Halo Implant Low Trigger Voltage ESD Protection
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Solution Overview
Problem
Conventional electrostatic discharge protection circuits in integrated circuits require high trigger voltages, leading to damage from lower voltage ESD events, as only high voltage ESDs can activate the discharge cells, leaving vulnerable components unprotected.
Innovation Solution
The method involves forming lightly doped source-drain regions and halo injections in bipolar transistors and thyristors, reducing the reverse conduction voltage of PN junctions and altering the PN junction position, thereby lowering the trigger voltage and enhancing the discharge capability of the devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bipolar transistor and thyristor structures are used in electrostatic protection circuits, then the device structure is simple and easy to manufacture, but the trigger voltage is too high, which fails to protect vulnerable components from lower voltage ESD events
Solution Approach 1:
The patent introduces a lightly doped drain (LDD) region and halo implant in specific local areas of the bipolar transistor structure. The LDD region is formed between the collector and base with a doping concentration lower than the base region, creating a localized low-doping area that reduces the reverse conduction voltage of the collector-base junction. This local modification allows the trigger voltage to be reduced without affecting the overall device structure or manufacturing process complexity.
Solution Approach 2:
The patent changes the doping concentration parameter by introducing a lightly doped drain region with doping concentration lower than the base region but higher than the collector region. This parameter change in the LDD region directly affects the reverse conduction characteristics of the collector-base junction, reducing the trigger voltage from conventional high levels to a lower level that can activate the protection circuit for vulnerable components. The halo implant further modifies the doping profile to optimize the voltage characteristics.
2Ease of manufacture
If high trigger voltage is used in discharge cells, then the device structure remains conventional and simple, but lower voltage ESD events cannot activate the protection circuit, causing damage to internal circuits
Solution Approach 1:
The patent applies local quality modification by introducing the LDD region and halo implant only in specific areas of the bipolar transistor where the collector-base junction is located. This localized doping modification reduces the reverse conduction voltage in that specific region, enabling the protection circuit to activate at lower voltages. The rest of the device structure remains conventional and unchanged, maintaining ease of manufacture while improving protection coverage for vulnerable components.
Solution Approach 2:
The halo implant is performed as a preliminary action before the final device operation. The halo implant introduces dopant atoms into the region beneath the LDD and source/drain regions, pre-modifying the doping profile to reduce the reverse conduction voltage. This preliminary doping action ensures that the bipolar transistor will have the desired low trigger voltage characteristics when the protection circuit is activated, without requiring complex post-processing steps.
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
This approach effectively reduces the trigger voltage, ensuring that all components in the integrated circuit can be protected from electrostatic discharge, improving the protective capacity by enabling discharge at lower voltages and preventing damage from high trigger voltage conventional devices.
Implementation Method 1
a lightly doped source-drain region portion is formed between the first N+ doped region and the shallow trench isolation connected thereto by using lightly doped source-drain technology, and a halo injection with inverse type of the lightly doped source-drain region is formed beforehand under the lightly doped source-drain region
Data Source
AI summary
The present invention provides a device for electrostatic discharge and the method of manufacturing thereof. P-well is formed on the substrate, and a first N+ doped region, a second N+ doped region and a P+ doped region are formed in the P-well; both ends of each doped region adopt shallow trench isolation for isolation. A lightly doped source-drain region portion is formed between the first N+ doped region and the shallow trench isolation connected thereto. Under the source-drain region, a halo injection with an inverse type is formed. The reverse conduction voltage of the collector of the bipolar transistor is lowered through the introduction of special doped region and the adoption of lightly doped source-drain technology for manufacturing the source-drain region as well as the manufacturing of halo injection with inverse type under the source-drain region, thus reducing the trigger voltage of the device.