ESD Protection Transistor with Offset Ballast Resistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ESD protection techniques for semiconductor integrated circuits face challenges in uniformly distributing breakdown current across MOSFETs, leading to localized heating and potential damage, and require additional processing steps that increase complexity and cost, while also affecting off-state leakage and switching speed.
Innovation Solution
A semiconductor device with a deeply implanted, lightly doped p-type region offset from the gate edge acts as a ballast resistor to reduce breakdown voltage in central regions, avoiding damage to sensitive transistor channels and maintaining electrical performance, and a modified transistor layout ensures uniform breakdown voltage across the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deeply implanted, lightly doped p-type region is added to reduce breakdown voltage in central regions, then ESD protection capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The deeply implanted, lightly doped p-type region is formed during the well formation step before transistor fabrication, preparing the structure in advance to guide ESD current away from sensitive channels during breakdown events
Solution Approach 2:
The lightly doped p-type region automatically performs dual functions: forming the well for transistor isolation and acting as a current diversion path during ESD events, eliminating the need for separate ESD protection structures
2Reliability
If breakdown voltage is reduced in central regions to protect against ESD, then ESD protection is improved, but localized heating occurs leading to potential damage
Solution Approach 1:
The breakdown voltage is made non-uniform across the device area by creating a lightly doped p-type region in central areas while maintaining higher doping at the periphery, causing ESD current to concentrate in robust central diode regions rather than sensitive transistor channels
Solution Approach 2:
The lightly doped p-type region acts as an intermediary structure that redirects ESD current through robust diode areas, preventing direct current flow through sensitive transistor channels and reducing localized heating in critical regions
3Reliability
If additional implanted layers are added to control breakdown voltage, then ESD protection is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The deeply implanted, lightly doped p-type region serves multiple functions simultaneously: well formation for transistor isolation, ESD current diversion path, and breakdown voltage control, eliminating the need for separate ESD protection implants
Solution Approach 2:
The ESD protection functionality is merged with the well formation process by using the same implant step to create both the transistor well and the ESD current diversion path, reducing the total number of manufacturing 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
The solution effectively disperses ESD surge currents into robust diode areas, reducing self-heating and maintaining low series resistance, thus enhancing ESD protection without adverse effects on off-state leakage or switching speed, and can be integrated into standard CMOS processes without additional complexity or cost.
Implementation Method 1
acts as a ballast resistor to reduce breakdown voltage in central regions
Implementation Method 2
leading to localized heating and potential damage
Implementation Method 3
ESD pulses tend to have a very short duration and can be discharged into an IC through its electrical terminals
Data Source
AI summary
A semiconductor device for electrostatic discharge (ESD) protection including a source, a gate, a drain having a drain diffusion, and a diffusion region extending from, or located under, the drain diffusion. The source, the gate, the drain and the diffusion region are located in or on a substrate. The diffusion region is laterally spaced from at least one of the gate or the outer edge of the drain diffusion.