MONOS Storage Reference Cell Charge Stabilization
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Solution Overview
Problem
In semiconductor storage devices with a MONOS structure, variations in charge accumulation in the nitride film during readout operations can lead to improper data determination due to electric field stress or write operations, causing fluctuations in readout currents between reference and main storage regions.
Innovation Solution
A method involving a semiconductor storage device with a main and sub storage region, where data is written in two steps with different voltage applications to the first and second impurity regions, ensuring charge accumulation in both charge accumulation portions of the sub storage region, thereby stabilizing the readout current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If charge is accumulated only in one charge accumulation portion during write operation, then write speed is improved, but readout current varies due to electric field stress causing improper data determination
Solution Approach 1:
The charge accumulation portion is divided into two separate portions (first charge accumulation portion and second charge accumulation portion) located at opposite ends of the nitride film. By accumulating charge in both portions through two-step write operations, the patent prevents charge migration caused by electric field stress during readout, thereby maintaining stable reference current levels and improving data determination accuracy
Solution Approach 2:
The patent performs preliminary charge accumulation in both charge accumulation portions before readout operations. By pre-establishing balanced charge distribution through two-step write operations, the system prepares the reference cell to resist subsequent electric field stress during readout, preventing charge migration and maintaining stable reference current
2Measurement precision
If charge accumulates in the nitride film during readout operation, then readout current changes, but this causes improper determination between reference and main storage regions
Solution Approach 1:
The patent changes the charge distribution parameter by accumulating charge in both the first and second charge accumulation portions located at opposite ends of the nitride film. This dual-portion charge accumulation creates a balanced electric field that prevents charge migration during readout operations, maintaining stable reference current levels and enabling accurate data determination
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 reduces variations in readout current from the sub storage region, preventing improper data determination by maintaining consistent charge levels in both charge accumulation portions, thus enhancing data accuracy.
Implementation Method 1
a gate electrode 25 on a semiconductor substrate 21 which has a first impurity region 26 and a second impurity region 27 with a channel region 28 interposed therebetween; a first charge accumulation portion 23a between the first impurity region and the gate electrode; and a second charge accumulation portion 23b between the second impurity region and the gate electrode
Implementation Method 2
a positive voltage is applied to the source terminal and the gate terminal with the drain terminal at the ground voltage. This allows electrons travelling from the drain region to the source region through the channel to gain high kinetic energy in the vicinity of the source region and be turned to hot electrons, so that the positive voltage applied to the gate causes the hot electrons to be raised to immediately below the gate terminal, and the raised electrons are sustained in the nitride film
Data Source
AI summary
A method for writing data in a semiconductor storage device and a semiconductor storage device are provided, that can reduce variations in readout current from a sub storage region which serves as a reference cell for the memory cells of the semiconductor storage device, thereby preventing an improper determination from being made when determining the readout current from a memory cell. In the method, data is written on a memory cell in two data write steps by applying voltages to the first and second impurity regions of the memory cell, the voltages being different in magnitude from each other.