Semiconductor Memory Sense Amplifier for Adaptive Threshold Verification
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Solution Overview
Problem
Existing NAND flash memory devices require multiple sensing operations to verify threshold voltage levels during data programming, which can increase processing time and complexity.
Innovation Solution
The semiconductor memory device implements a sense amplifier that performs a first sensing operation followed by either a second sensing operation at a higher or a third sensing operation at a lower voltage level, based on the result of the first sensing operation, to reduce the number of executions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensing operations are executed to verify threshold voltage levels during data programming, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The sense amplifier performs a preliminary first sensing operation at an initial voltage level before the actual verification. Based on the result of this preliminary sensing, the system determines whether to perform a second sensing operation at a higher voltage level or terminate the verification. This preliminary action allows the system to avoid unnecessary second sensing operations when the first sensing already provides sufficient confidence, thereby reducing overall programming time while maintaining verification accuracy.
2Reliability
If multiple sensing operations are executed to verify threshold voltage levels, then reliability is improved, but device complexity increases
Solution Approach 1:
The sensing operation structure is made dynamic rather than fixed. The sense amplifier adaptively determines the number of sensing operations to perform based on the results of previous sensing. Specifically, after the first sensing operation, the system dynamically decides whether to proceed to a second sensing operation at a higher voltage level or to terminate the verification process. This dynamic approach maintains high reliability by performing additional sensing only when necessary, while reducing the average complexity compared to always performing multiple fixed sensing operations.
3Measurement precision
If a second sensing operation at a higher voltage level is performed based on first sensing results, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The sensing operation uses different voltage levels as a parameter optimization strategy. The first sensing operation is performed at an initial voltage level, and only if additional verification is needed does the system perform a second sensing operation at a higher voltage level. This parameter change approach allows the system to achieve high measurement precision when necessary while minimizing energy consumption by avoiding unnecessary high-voltage sensing operations, thereby resolving the contradiction between measurement precision and energy usage.
Data Source
AI summary
A semiconductor memory device capable of reducing the number of executions of sensing is provided. The semiconductor memory device includes memory cells, word lines that are connected to the memory cells, bit lines that are connectable to the memory cells, and sense amplifiers connectable to the bit lines. A writing operation on the memory cell includes a program operation and a verifying operation. In the verifying operation, the sense amplifier executes a first sensing operation against a first voltage level and executes, based on a result of the first sensing operation, either a second sensing operation against a second voltage level that is higher than the first voltage level or a third sensing operation against a third voltage level that is lower than the first voltage level.