EEPROM Cell Read Circuit Using Charge Pumping
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Solution Overview
Problem
Modern EEPROM devices face challenges with low on-cell current due to narrow active regions and increased threshold voltage, leading to reduced programming and erasing efficiency and operational failures during data reading.
Innovation Solution
A method and structure for an EEPROM cell that involves applying a higher voltage to the word line using a charge pumping circuit to boost the voltage, increasing the on-cell current, and comparing it with a reference current to accurately read data, while maintaining the threshold voltage of the memory transistor at a low level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the gate length of the memory cell transistor is narrowed to reduce device size, then the device size is reduced, but the capacitance of the memory cell is lowered, causing low programming and erasing efficiency and increased threshold voltage
Solution Approach 1:
The patent applies dynamic voltage boosting to the selection transistor gate during read operations. A charge pumping circuit dynamically generates a boosted voltage (VBST) that is applied to the word line of the selection transistor only when needed for reading, allowing the narrow-gated device to achieve sufficient on-cell current without increasing size or permanently altering the memory cell structure.
2Reliability
If the threshold voltage of the memory cell is increased to maintain data storage, then data retention is improved, but the on-cell current is decreased, causing sense amplifier discrimination failures
Solution Approach 1:
The patent introduces a charge pumping circuit as an intermediary component that generates a boosted voltage applied to the selection transistor's word line during read operations. This intermediary voltage boosting mechanism compensates for the low on-cell current caused by high threshold voltage, enabling the sense amplifier to successfully discriminate between programmed and erased states without altering the memory cell's threshold voltage characteristics.
3Area of moving object
If the selection transistor is designed with short gate length and gate width to reduce device size, then device integration is improved, but the current passing through the selection transistor is reduced, failing to sufficiently increase on-cell current
Solution Approach 1:
The patent changes the voltage parameter applied to the selection transistor gate from a standard voltage to a dynamically boosted voltage (VBST) generated by the charge pumping circuit. This parameter change in gate voltage compensates for the reduced current-carrying capacity of the small-sized selection transistor, enabling sufficient on-cell current flow during read operations while maintaining the compact transistor dimensions.
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 enhances the on-cell current, reducing reading failures and maintaining the threshold voltage, thereby improving the data reading accuracy and reliability of EEPROM cells.
Implementation Method 1
a charge pumping circuit to boost the voltage applied to the selection transistor, increasing the on-cell current by applying a higher voltage to the word line compared to the sense line
Implementation Method 2
using a resistance line to decompress the boosted voltage
Data Source
AI summary
In a method of reading data in an EEPROM cell, a bit line voltage for reading is applied to the EEPROM cell including a memory transistor and a selection transistor. A first voltage is applied to a sense line of the memory transistor. A second voltage greater than the first voltage is applied to a word line of the selection transistor. A current passing through the EEPROM cell is compared with a predetermined reference current to read the data stored in the EEPROM cell. An on-cell current of the EEPROM cell may be increased in an erased state and the data in the cell may be readily discriminated.