ESD Protection Device Vertical Discharge Path
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Solution Overview
Problem
Conventional ESD protection circuits in deep-submicron CMOS technologies face challenges in enduring high electrostatic discharge stresses due to the low breakdown voltage of gate oxide, leading to burnout of NMOS transistors and reduced ESD endurance.
Innovation Solution
The ESD protection device incorporates a semiconductor substrate with a buried layer and a second well of opposing conductivity type to create a vertical discharge path for electrostatic current, alongside the traditional horizontal path, thereby increasing the discharge path and reducing heat-induced damage, without requiring additional masks for manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional NMOS transistor structure is used in ESD protection circuits, then the device can provide electrostatic discharge protection, but the shallow channel region burns out when large electrostatic current flows through it, reducing ESD endurance
Solution Approach 1:
The patent introduces a vertical discharge path by adding a second well extending from the surface to the buried layer, perpendicular to the traditional horizontal channel. This dimensional change allows electrostatic current to flow vertically through the second well and buried layer, bypassing the shallow channel region and avoiding burnout, thereby improving ESD endurance while maintaining current carrying capacity
Solution Approach 2:
The patent segments the discharge path into multiple independent regions: the traditional horizontal channel path and the new vertical path through the second well and buried layer. This segmentation allows the current to be distributed across different paths, preventing concentration of heat in the vulnerable shallow channel region while maintaining overall protection functionality
2Ease of manufacture
If the well having the second conductive type is used to divide the first well into first well and second well, then the manufacturing cost is reduced by not requiring additional masks, but the device structure becomes more complex
Solution Approach 1:
The patent merges the formation of the second well with the existing first well structure by using the same ion implantation process and mask pattern. The second well is formed as an extension of the first well region, allowing both wells to be created simultaneously without requiring additional photomask layers, thus reducing manufacturing cost while adding functional complexity
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 configuration enhances the ESD endurance of the protection device by providing multiple discharge paths, preventing burnout and increasing the device's ability to handle high electrostatic currents while reducing manufacturing costs.
Implementation Method 1
an electrostatic discharge (ESD) protection device, and more particularly, to an ESD protection device having a path for discharging electrostatic current along a vertical direction
Implementation Method 2
the well having the second conductive type contacts the buried layer, and the well having the second conductive type and the buried layer are jointly used to isolate the first well from the second well
Data Source
AI summary
An electrostatic discharge (ESD) includes a semiconductor substrate having the first conductive type, a well having the first conductive type, a buried layer having the second conductive type and a well having the second conductive type. The buried layer having a second conductive type is disposed in the semiconductor substrate under the well having the first conductive type. The well having the second conductive type disposed to divide the well having the first conductive type into a first well and a second well. The well having the second conductive type contacts the buried layer, and the well having the second conductive type and the buried layer are jointly used to isolate the first well from the second well.