Multi-Step Programming Pulses for NAND Flash Memory Cells
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Solution Overview
Problem
Traditional programming methods for NAND flash memory devices require numerous incremental step pulses, leading to high power consumption due to the need for precharging and discharging of word lines after each pulse, which inefficiencies in energy usage and processing time.
Innovation Solution
Implementing a multi-step programming pulse approach where memory cells are programmed in subsets with distinct voltage levels, allowing for selective enabling and disabling of programming based on their proximity to the intended data state, thereby reducing the number of pulses required and optimizing energy usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional incremental step pulse programming is used, then memory cells can be programmed to desired threshold voltage levels, but power consumption increases due to repeated precharging and discharging of word lines
Solution Approach 1:
The patent segments the programming process into two distinct phases: a first programming phase that programs a first subset of memory cells to a first threshold voltage level, and a second programming phase that programs a second subset of memory cells to a second threshold voltage level. This segmentation allows different word lines to be programmed with different voltage levels in different phases, enabling the controller to avoid unnecessary precharging and discharging operations for word lines that do not require full programming voltage, thereby reducing overall power consumption while maintaining programming precision for all memory cells
Solution Approach 2:
The patent applies local quality by allowing different subsets of memory cells to receive different programming treatments based on their specific requirements. The controller identifies which memory cells need programming to higher threshold voltage levels versus lower threshold voltage levels, and applies appropriate voltage levels to corresponding word lines. This localized approach ensures that each memory cell receives the precise programming voltage it needs without subjecting other word lines to unnecessary high voltage cycles, thus reducing power consumption while maintaining programming precision
2Manufacturing precision
If traditional incremental step pulse programming is used, then memory cells can be programmed sequentially, but processing time increases due to the large number of pulses required
Solution Approach 1:
The patent segments the memory cell population into multiple subsets based on their target threshold voltage levels and programs each subset using optimized pulse sequences. By dividing the programming task into targeted subsets rather than uniformly programming all cells with the same incremental step sequence, the system reduces the total number of pulses required while maintaining programming accuracy for each subset
Solution Approach 2:
The patent implements dynamic programming by allowing the controller to adaptively adjust programming parameters based on the specific characteristics of different memory cell subsets. The programming process dynamically switches between different voltage levels and pulse sequences depending on which subset of memory cells is being programmed, enabling faster programming times while maintaining the precision required for accurate threshold voltage programming
3Device complexity
If uniform programming pulses are applied to all memory cells, then the programming process is simple to control, but energy efficiency decreases because all word lines are precharged and discharged regardless of need
Solution Approach 1:
The patent segments the control process into distinct control signals for different subsets of memory cells. The controller generates first control signals for a first subset of word lines and second control signals for a second subset of word lines, allowing selective activation of precharging and discharging operations only for the word lines that actually require programming. This segmented control approach maintains reasonable control complexity while dramatically improving energy efficiency by eliminating unnecessary operations on non-programmed word lines
Solution Approach 2:
The patent applies local quality by tailoring the control signals to the specific programming needs of different word line subsets. Instead of applying uniform control signals to all word lines, the controller provides localized control that activates precharging and discharging only for word lines that require programming voltage changes. This localized control approach maintains sufficient control simplicity while significantly reducing energy waste from unnecessary 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
This method reduces power consumption and enhances programming efficiency by tailoring the programming process to the specific needs of each memory cell, improving the overall performance and reducing the time required to achieve the desired data states.
Implementation Method 1
a particular multi-step programming pulse has a first step having a first voltage level and a second step having a second voltage level different than the first voltage level
Data Source
AI summary
Memories having a controller configured to apply a particular multi-step programming pulse to a selected access line of a programming operation, enable for programming memory cells that have a particular desired data state for the programming operation and are deemed to have a threshold voltage lower than a first threshold voltage level while applying a first step of a multi-step programming pulse to the selected access line, and enable for programming memory cells that have the particular desired data state for the programming operation and are deemed to have a threshold voltage lower than a second threshold voltage level and higher than the first threshold voltage level while applying a second step of the multi-step programming pulse, lower than the first step of the multi-step programming pulse, to the selected access line.