Non-Volatile Memory Sector Erase Using Learned Pulse Parameters
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Solution Overview
Problem
Conventional sector erase operations in non-volatile FLASH memory, such as 'voltage stepping' and 'time stepping,' are time-consuming and inefficient due to the need for multiple pulses to ensure all cells in a sector are properly erased, often resulting in over-erased cells that require additional processing.
Innovation Solution
A method that records erase condition information from a initial sector's erase process and uses this information to determine an optimized initial erase pulse for subsequent sectors, reducing the number of pulses required for successful erasure by adapting the pulse magnitude or width based on previous sector data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage stepping or time stepping erase operations are used to ensure all cells in a sector are properly erased, then erase reliability is improved, but erase time and operational complexity increase significantly
Solution Approach 1:
The patent performs preliminary characterization of sector erase requirements by testing a sample sector and storing the resulting erase pulse sequence information. This preliminary action allows the system to retrieve and reuse optimized erase parameters for subsequent sectors, eliminating the need to perform complete voltage stepping or time stepping sequences for each sector individually, thereby significantly reducing erase time while maintaining reliability
Solution Approach 2:
The patent implements feedback by storing erase condition information from sample sector testing and using this information to determine initial erase pulse parameters for production sectors. The system retrieves stored erase pulse sequences based on sector identification and applies them to subsequent erase operations, creating a feedback loop where results from sample testing inform future erase operations, thereby reducing the time required for complete sector erasure
2Reliability
If multiple erase pulses are applied to ensure complete erasure of all cells in a sector, then erase completeness is improved, but the number of operational steps and processing complexity increase
Solution Approach 1:
The system performs preliminary testing on a sample sector to determine the optimal erase pulse sequence required for complete erasure. This preliminary characterization is stored and then reused for production sectors, eliminating the need to perform multiple iterative erase pulses for each sector individually. The patent thus reduces operational complexity by retrieving pre-determined pulse sequences rather than executing complex multi-step procedures for each sector
Solution Approach 2:
The patent copies the erase pulse sequence determined from sample sector testing and applies it to production sectors. By storing the erase condition information from the sample sector and retrieving it for use in erasing other sectors, the system creates a reusable template that simplifies the operational procedure. This copying approach maintains erase completeness while significantly reducing the number of operational steps required
3Ease of operation
If a fixed erase pulse sequence is used for all sectors, then operational simplicity is maintained, but adaptability to different sector characteristics is reduced
Solution Approach 1:
The patent introduces dynamics by allowing the erase pulse sequence to be selected based on sector identification rather than applying a fixed sequence to all sectors. The system retrieves stored erase pulse information corresponding to the specific sector being erased, enabling adaptive behavior that matches the actual characteristics of each sector. This dynamic approach maintains operational simplicity from the user perspective while providing adaptability to different sector characteristics
Solution Approach 2:
The patent changes the parameter of erase pulse sequence selection from a fixed universal approach to a variable approach that adapts to specific sector characteristics. By storing different erase pulse sequences for different sectors and selecting the appropriate sequence based on sector identification, the system allows parameter changes in the erase operation to match the actual requirements of each sector, thereby improving adaptability while maintaining ease of operation
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 significantly reduces the time and number of steps needed to erase sectors in non-volatile memory by leveraging learned erase conditions from previous sectors, ensuring efficient and accurate data erasure.
Implementation Method 1
The data stored in a cell is altered by applying a strong electric field between the control gate and the source of the field-effect transistor to remove or accumulate the electrons in the floating gate
Data Source
AI summary
A sector erase method for use in a non-volatile memory, such as a FLASH memory, including a plurality of memory cells in rows and columns, the memory cells being divided into a plurality of sectors. The sector erase method includes erasing the memory cells of a first sector by applying successive erase pulses that increase in voltage magnitude or pulse width, until erasure of the first sector is verified. Erase condition information corresponding to the first sector, is recorded, this information including a number of times successive erase pulses are needed to be applied in order to erase the memory cells of the first sector. Memory cells of a next sector are erased by applying a first erase pulse having a voltage magnitude or pulse width determined from the recorded erase condition information. The first erase pulse may be incremented if the first erase pulse fails to erase that next sector.