Flash Memory Programming Using Modulated Pulses
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Solution Overview
Problem
Non-volatile semiconductor memory devices face challenges in programming due to variations in cell characteristics, leading to uneven charge accumulation and deviations in threshold voltages, resulting in longer programming times and wider threshold voltage distributions.
Innovation Solution
The use of modulated pulses with adjustable voltage magnitudes and durations, generated by a pulse generator and applied through a pulse coupler, allows for precise setting and verification of threshold voltages in memory cells, accommodating variations in cell types such as fast and slow bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed voltage step programming pulses are used, then programming speed can be increased, but threshold voltage distribution becomes wider due to fast and slow cell variations
Solution Approach 1:
The patent applies dynamics by making the programming pulse parameters dynamic rather than fixed. The pulse width and voltage magnitude are adjusted based on the cell's response during programming. Fast cells receive shorter pulses or lower voltages to prevent over-programming, while slow cells receive longer pulses or higher voltages to ensure adequate programming, thereby maintaining narrow threshold voltage distribution while achieving fast programming speeds.
Solution Approach 2:
The patent changes physical parameters of the programming pulses (voltage magnitude and pulse width) adaptively during the programming process. By monitoring cell status and adjusting pulse parameters in real-time, the system optimizes programming speed for each cell type while maintaining precise threshold voltage control, resolving the contradiction between speed and precision.
2Loss of time
If programming voltage is increased to speed up programming, then programming time is reduced, but charge over-accumulation occurs in fast cells
Solution Approach 1:
The system dynamically adjusts pulse width and voltage magnitude based on cell characteristics. Fast cells are programmed with shorter pulses or lower voltages to prevent charge over-accumulation, while slow cells receive adequate programming energy. This dynamic adaptation reduces programming time without compromising charge control reliability.
Solution Approach 2:
The patent implements feedback mechanisms where the programming process monitors cell response and adjusts subsequent pulse parameters accordingly. This feedback loop prevents charge over-accumulation in fast cells by detecting when they reach target threshold voltage and reducing or stopping further programming pulses for those cells, thereby maintaining reliability while reducing overall programming time.
Data Source
AI summary
Methods and apparatuses for programming non-volatile semiconductor memory devices by using modulated pulses are disclosed. An apparatus may have a pulse generator, to create a sequence of pulses and set a threshold voltage of a non-volatile memory cell, and a pulse coupler. The apparatus may have a threshold verifier capable of verifying that the threshold voltage is set within an acceptable voltage range of a target threshold voltage. A pulse width modulator in some apparatuses may modulate the pulse durations early in the sequence when programming fast bits and late in the sequence when programming slow bits. An apparatus may generate a sequence of pulses, apply the sequence of pulses to a memory cell to set a threshold voltage of the memory cell, and modulate one or more of pulses in the sequence the parameters of pulse duration, pulse separation time, and step voltage magnitude.