Nonvolatile Memory Erase State Threshold Voltage Inversion

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Solution Overview

Problem

In nonvolatile memory devices, the reliability of multi-level cell data storage is compromised due to interference and program disturb phenomena, leading to widened threshold voltage distributions and potential read failures, as adjacent cells' programming affects the threshold voltage of memory cells.

Innovation Solution

The nonvolatile memory device is programmed such that the threshold voltage of the erasure state is set higher than that of the program state, using a modified program control logic to ensure the erasure state's threshold voltage is distinct from program states, thereby minimizing interference and maintaining data integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multi-level cell programming is performed to increase storage capacity, then storage density is improved, but threshold voltage distribution widens due to interference from adjacent cells

Engineering Contradiction:

Improvestorage capacityVSAvoidthreshold voltage distribution

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional threshold voltage relationship by making the erased state have a higher threshold voltage than programmed states. This inversion allows erased cells to be distinguished from programmed cells even when adjacent cells are programmed, thereby maintaining narrow threshold voltage distributions while achieving multi-level cell storage capacity.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies preliminary anti-action by pre-setting the erased state threshold voltage higher than programmed states before any programming operations occur. This preventive measure counteracts the interference from adjacent cell programming, preventing threshold voltage distribution widening before it can occur.

Inventive Principle:

Principle #9Preliminary anti-action

2Productivity

If conventional programming is performed with lower erased state threshold voltage, then programming speed is maintained, but read failures occur due to threshold voltage overlap

Engineering Contradiction:

Improveprogramming speedVSAvoidread accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

By inverting the threshold voltage relationship so that erased cells have higher voltages than programmed cells, the patent creates clear separation between erased and programmed states. This eliminates threshold voltage overlap that causes read failures, while maintaining programming speed through efficient single-pass programming operations.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS9224485B2Nonvolatile memory device and method of programming the same minimizing disturbance from adjacent cells

Publication Date: 2015.12.29 SAMSUNG ELECTRONICS CO LTD

AI summary

A nonvolatile memory device and a method of programming the same. The nonvolatile memory device includes a memory cell array including a plurality of memory cells and a program control logic circuit controlling the memory cell array. The program control logic circuit programs a first memory cell so that the threshold voltage of the first memory cell corresponding to data of erasure state is higher than the threshold voltage of a second memory cell corresponding to data of program state, in the memory cell array. The nonvolatile memory device controlled in this manner can provide higher reliability.