Double Capa Implant EEPROM for Voltage Loss Reduction
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Solution Overview
Problem
Existing EEPROM memory cells face challenges in minimizing voltage loss during erase and program operations, which requires high voltages and can lead to instability and leakage, while also compromising the reliability of data retention and transistor performance.
Innovation Solution
The implementation of a double capa implant zone structure with varying dopant concentrations and oxide thicknesses, where a second capa implant zone with a higher dopant concentration is used adjacent to the first capa implant zone, allowing for reduced voltage loss and improved electric field strength across the tunnel oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high voltages are used for erase and program operations, then programming speed is improved, but voltage loss increases and reliability deteriorates
Solution Approach 1:
The patent applies local quality by creating a double capa implant zone structure where the first capa implant zone has a first dopant concentration and the second capa implant zone has a second dopant concentration. This non-uniform dopant distribution optimizes the electric field locally at the tunnel oxide interface, enabling effective programming at lower voltages while maintaining reliability.
Solution Approach 2:
The patent changes the parameter of dopant concentration by implementing two distinct capa implant zones with different dopant concentrations. The first zone has a lower dopant concentration while the second zone has a higher dopant concentration, creating an optimized gradient that improves voltage utilization and reduces voltage loss during programming operations.
2Productivity
If high voltages are applied during programming, then programming efficiency is improved, but MOS breakdown risk increases
Solution Approach 1:
The double capa implant zone structure creates localized regions with optimized dopant concentrations. The second capa implant zone with higher dopant concentration is positioned to specifically enhance the electric field at the tunnel oxide interface, allowing efficient charge injection at lower applied voltages and thereby reducing the risk of MOS breakdown.
Solution Approach 2:
The patent converts the potential harmful effect of high voltage stress into a beneficial outcome by using the higher dopant concentration in the second capa implant zone to create a more efficient charge injection mechanism. This allows the system to achieve effective programming at lower voltages, transforming the voltage stress issue into an advantage through optimized electric field distribution.
3Loss of time
If tunnel oxide thickness is reduced to improve programming speed, then programming time is reduced, but voltage control precision deteriorates
Solution Approach 1:
The patent applies local quality by creating a specific dopant concentration profile in the double capa implant zone structure. The higher dopant concentration in the second zone compensates for the reduced tunnel oxide thickness, maintaining precise voltage control and electric field distribution even with thinner oxide, thereby enabling fast programming without sacrificing voltage control precision.
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 enables lower program activation voltages, improved data retention, and increased reliability by maintaining acceptable voltage levels and reducing the risk of MOS breakdown, while allowing for more flexible trade-offs between tunnel oxide thickness, applied voltage, and programming time.
Implementation Method 1
improved electric field strength across the tunnel oxide layer
Implementation Method 2
double capa implant zone structure with varying dopant concentrations
Implementation Method 3
a gate oxide region insulating the floating gate electrode from the channel region, the first capa implant zone and the second capa implant zone
Data Source
AI summary
An EEPROM includes a floating gate transistor having a source region, a channel region and a drain region. A first capa implant zone on a drain-side of the floating gate transistor has a first dopant concentration level. A second capa implant zone in the first capa implant zone adjacent the drain region has a second dopant concentration level that is greater than the first dopant concentration level. A gate oxide region insulates the floating gate electrode from the channel region, first capa implant zone and second capa implant zone. A thickness of the gate oxide region is thinner at the second capa implant zone than at the channel region and first capa implant zone.