ROM Local Extreme Doping Region Mitigates 2nd-Bit Effect
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In 2 bits/cell ROMs, the 2nd-bit effect causes read errors and reliability issues due to interaction between stored bits, leading to increased threshold voltage and reduced sense margin during read operations.
Innovation Solution
Incorporating a local extreme doping region with a high doping concentration region between the source and drain regions, which has a doping concentration three times or more than the low doping concentration region, to mitigate the 2nd-bit effect by creating a channel with a large doping concentration difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reverse read operation is performed to read separated charges at two sides of one 2 bits/cell memory, then read operation is completed, but the existing bit poses a direct impact on the memory cell, thus increasing a barrier and a threshold voltage (Vt) for reading
Solution Approach 1:
The patent introduces a local extreme doping region with non-uniform doping concentration distribution between the source and drain regions. This local quality variation creates a doping concentration gradient that generates an internal electric field, which counteracts the 2nd-bit effect and reduces the threshold voltage shift during read operations, thereby improving both read accuracy and device reliability
Solution Approach 2:
The patent changes the doping concentration parameter by creating an extreme doping region with doping concentration at least three times higher than the surrounding regions. This parameter change modifies the electrical characteristics of the channel, reducing the barrier height and threshold voltage increase that normally occurs during read operations, thus mitigating the 2nd-bit effect
2Quantity of substance
If charges are stored by a localized charge trapping structure to form a 2 bits in one cell memory, then data storage capacity is increased, but the 2 bits in one cell may still interact, thus leading to relevant problems
Solution Approach 1:
The extreme doping region creates a localized electrical environment that isolates the two charge trapping regions. The high doping concentration area generates an electric field that prevents charge interaction between the two bits, allowing both bits to be stored and read independently without mutual interference
3Power
If the 2nd-bit effect occurs when the other side of the memory cell is being read, then a voltage in the portion where a high current is expected may drop, but this increases a barrier and a threshold voltage (Vt) for reading
Solution Approach 1:
By introducing the extreme doping region with significantly higher doping concentration, the patent changes the electrical parameters of the channel. This creates a lower resistance path and reduces the threshold voltage, allowing high current to flow during read operations without causing voltage drops that would hinder reading operations
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 reduces the 2nd-bit effect, improving read accuracy and device reliability by minimizing the impact of stored bits on read operations, thereby enhancing the operating margin and threshold voltage window.
Implementation Method 1
a local extreme doping region which includes a low doping concentration region and at least one high doping concentration region, wherein the high doping concentration region is disposed between the low doping concentration region and one of the source region and the drain region, and a doping concentration of the high doping concentration region is three times or more than three times a doping concentration of the low doping concentration region
Data Source
AI summary
A read only memory including a substrate, a source region and a drain region, a charge storage structure, a gate, and a local extreme doping region is provided. The source region and the drain region are disposed in the substrate, the charge storage structure is located on the substrate between the source region and the drain region, and the gate is configured on the charge storage structure. The local extreme doping region is located in the substrate between the source region and the drain region and includes a low doping concentration region and at least one high doping concentration region. The high doping concentration region is disposed between the low doping concentration region and one of the source region and the drain region, and a doping concentration of the high doping concentration region is three times or more than three times a doping concentration of the low doping concentration region.