Nonvolatile Memory Programming via Three-Step Policy and Address Scrambling

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Solution Overview

Problem

As the number of bits per memory cell increases in nonvolatile memory devices, the reliability of stored data decreases due to coupling between adjacent memory cells, which affects the accuracy of program operations.

Innovation Solution

The implementation of a three-step programming process involving a first-step program operation, a coarse program operation, and a fine program operation, along with an address scrambling method to determine the programming order, reduces the effects of coupling and improves data reliability by ensuring precise threshold voltage distributions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the number of bits per memory cell increases, then storage capacity increases, but data reliability deteriorates due to coupling between adjacent memory cells

Engineering Contradiction:

Improvestorage capacityVSAvoiddata reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The programming process is divided into multiple steps (first-step program operation, coarse program operation, and fine program operation) to progressively program memory cells. This segmentation allows precise control of threshold voltage distributions while minimizing coupling effects between adjacent cells, thereby maintaining data reliability even as storage capacity increases through multi-bit per cell operation.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a three-step programming process is implemented, then data reliability improves, but programming time increases

Engineering Contradiction:

Improvedata reliabilityVSAvoidprogramming time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The first-step program operation performs preliminary programming of memory cells before the coarse and fine program operations. By establishing initial threshold voltage distributions in advance, the subsequent operations can focus on refinement, ensuring data reliability while optimizing the overall programming time through efficient staged processing.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If address scrambling is used to determine programming order, then coupling effects are reduced, but process complexity increases

Engineering Contradiction:

Improvedata reliabilityVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The address scrambling method dynamically determines the programming order of memory cells based on their addresses, creating a non-sequential programming pattern. This dynamic approach effectively reduces coupling effects between adjacent memory cells by avoiding systematic programming patterns, while the scrambling algorithm itself remains computationally simple to implement.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8995189B2Method and apparatus for managing open blocks in nonvolatile memory device

Publication Date: 2015.03.31 SAMSUNG ELECTRONICS CO LTD

AI summary

A memory system comprises a multi-bit memory device and a memory controller that controls the multi-bit memory device. The memory system determines whether a requested program operation is a random program operation or a sequential program operation. Where the requested program operation is a random program operation, the memory controller controls the multi-bit memory device to perform operations according to a fine program close policy or a fine program open policy.