Memory Controller State Shaping Encoder for MLC Reliability

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Solution Overview

Problem

Multi-level memory cells in nonvolatile memory devices face reliability degradation due to operational effects like F-poly coupling and back pattern dependency, which are influenced by data storage patterns, leading to reduced data integrity over time.

Innovation Solution

A memory controller with a state shaping encoder that alters incoming write data to reduce the occurrence probability of high-order program states, thereby mitigating degradation by encoding data to avoid adverse patterns that affect reliability, using state shape mapping information to select and reorder logical pages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multi-level memory cells are configured to store 2 or more data bits per MLC to increase storage density, then storage capacity is improved, but reliability of stored data deteriorates due to operational effects like F-poly coupling and back pattern dependency

Engineering Contradiction:

Improvestorage capacityVSAvoiddata reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The state shaping encoder performs preliminary encoding on write data before it is programmed into the MLC array. By proactively modifying the data pattern to reduce occurrences of high-order program states and adverse patterns, the system prevents reliability degradation before it occurs, rather than attempting to correct it after programming

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the parameter distribution of stored data by selectively modifying write data to alter the occurrence probability of different program states. Specifically, it reduces the frequency of high-order program states (e.g., P7, P15) and adjusts the statistical distribution of data patterns across the MLC array, thereby mitigating operational effects that cause reliability degradation

Inventive Principle:

Principle #35Parameter changes

2Productivity

If data is programmed with high occurrence of high-order program states to maximize storage utilization, then storage efficiency is improved, but adverse operational effects like F-poly coupling and back pattern dependency increase

Engineering Contradiction:

Improvestorage efficiencyVSAvoidoperational effects

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The state shaping encoder modifies the parameter distribution of program states by reducing the occurrence probability of high-order program states. This changes the statistical characteristics of data patterns in the MLC array, thereby mitigating adverse operational effects while maintaining acceptable storage efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention converts the potentially harmful concentrated programming of high-order states into a beneficial distributed pattern. By intentionally reducing high-order state occurrences and diversifying the data pattern distribution, the system transforms what would be a reliability problem into a solution that maintains storage efficiency while reducing operational effects

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9734898B2Memory controller having state shaping engine and method of operating same

Publication Date: 2017.08.15 SAMSUNG ELECTRONICS CO LTD

AI summary

A memory controller includes a state shaping encoder that receives k-bit write data, selects a logical page with reference to state shape mapping information, and changes data of the logical page to decrease an occurrence probability of a high-order program state among program states used to program the k-bit data in multi-level memory cells.