Variable Program Start Voltage for Nonvolatile Memory
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Solution Overview
Problem
The existing incremental step pulse programming (ISPP) method for nonvolatile memory devices fixes the program start voltage, leading to widened threshold voltage distributions as the number of program and erase operations increases, resulting in decreased program speed and inefficiency.
Innovation Solution
A method that allows for the variable setting of the program start voltage based on the programmed state, updating the voltage when a memory cell is programmed higher than a verify voltage, thereby adapting to changes in program/erase numbers and maintaining consistent threshold voltage distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the program start voltage is fixed to a specific value, then the program operation is simple to control, but the threshold voltage distributions are widened as the number of program and erase operations increases
Solution Approach 1:
The patent applies the dynamics principle by making the program start voltage variable rather than fixed. The program start voltage is dynamically adjusted based on the number of program and erase operations performed on the memory device. Specifically, the controller stores the operation count and selects different program start voltages from a voltage table according to the accumulated operations, allowing the voltage to adapt to device degradation over time while maintaining controlled program operations
Solution Approach 2:
The patent implements parameter changes by modifying the program start voltage parameter based on the number of program and erase operations. The voltage parameter is changed from a fixed value to a variable value that depends on the operation history. The controller maintains a voltage table with multiple program start voltage values and selects appropriate values based on the accumulated operation count, thereby adjusting the voltage parameter to compensate for device aging effects
2Stability of the object's composition
If the program start voltage is fixed, then the program operation is consistent initially, but the program speed decreases and threshold voltage distributions widen as operations increase
Solution Approach 1:
The patent changes the program start voltage parameter based on the number of program and erase operations to maintain both consistency and productivity. By storing operation counts and selecting appropriate voltages from a voltage table, the system adapts the voltage parameter to compensate for device degradation, ensuring consistent program operations while maintaining acceptable program speeds throughout the device lifetime
Solution Approach 2:
The patent implements feedback by using the number of program and erase operations as a feedback signal to adjust the program start voltage. The controller continuously monitors the operation count and uses this information to select the appropriate program start voltage from the voltage table, creating a closed-loop control system that maintains optimal program performance despite device aging
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 ensures that the program start voltage is adjusted according to the number of program and erase operations, maintaining optimal program speed and preventing the widening of threshold voltage distributions, even as the number of operations increases.
Implementation Method 1
the nonvolatile memory cell is an element enabling electrical program/erase operations, and is configured to perform the program and erase operations by changing its threshold voltage as electrons migrate in response to a strong electric field applied to a thin oxide layer
Implementation Method 2
electrons migrate in response to a strong electric field applied to a thin oxide layer of 100 angstrom or less
Data Source
AI summary
According to an aspect of a method of programming a nonvolatile memory device, a first program operation command is input, and a program operation is executed according to a program start voltage stored in a program start voltage storage unit. Here, a program voltage, which is applied at a time point at which a memory cell programmed higher than a verify voltage while the program operation is performed occurs for the first time, is updated to a program start voltage.