Nonvolatile Memory Index Programming Reduce Verify Steps

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Solution Overview

Problem

Conventional programming techniques for non-volatile memory require numerous verify operations, especially for multi-state memory cells, leading to increased programming time and reduced performance due to the need for multiple sensing operations across various threshold voltage levels.

Innovation Solution

The implementation of index programming, where a program index is maintained for each memory cell to track the last programming voltage level, allowing for inhibited programming and reducing the need for verify steps between pulses, thereby enabling programming without intermediate verify operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional programming techniques are used with multiple verify operations for multi-state memory cells, then programming precision is improved, but programming time increases and productivity decreases

Engineering Contradiction:

Improveprogramming precisionVSAvoidprogramming speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies preliminary action by maintaining a program index that records the last programming voltage level for each cell before the actual programming operation. This pre-stored index information allows the system to determine the appropriate programming voltage without performing intermediate verify operations, thereby achieving both precision and speed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and eliminates the verify operation step from the conventional programming sequence. By using the program index to directly determine the programming voltage level, the patent removes the unnecessary intermediate verification process, transforming the programming operation into a single-step process that maintains precision while significantly improving productivity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If multiple verify operations are performed across various threshold voltage levels, then programming accuracy is improved, but the number of sensing operations increases and device complexity increases

Engineering Contradiction:

Improveprogramming accuracyVSAvoidnumber of sensing operations

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes the verify operation and sensing operations from the programming process. By using the program index to directly determine the programming voltage, the system eliminates the need for multiple sensing operations across different threshold voltage levels, thereby reducing device complexity while maintaining programming accuracy.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The program index serves itself by automatically providing the correct programming voltage information without requiring external verify operations or sensing operations. The index acts as a self-contained data structure that enables accurate programming through a single operation, eliminating the need for complex multi-step verification processes.

Inventive Principle:

Principle #25Self-service

3Reliability

If verify steps are performed between programming pulses, then programming reliability is improved, but programming time increases

Engineering Contradiction:

Improveprogramming reliabilityVSAvoidprogramming time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-storing the program index that contains the last programming voltage level information before the actual programming operation. This pre-computed index allows the system to directly determine the correct programming voltage without time-consuming intermediate verify steps, thereby maintaining reliability while significantly reducing programming time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent skips the intermediate verify steps by using the program index to directly determine the programming voltage level. Instead of performing multiple verify operations between programming pulses, the system rushes through to the essential programming operation by using the pre-stored index information, thereby maintaining reliability with minimal time loss.

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS7826271B2Nonvolatile memory with index programming and reduced verify

Publication Date: 2010.11.02 SAMSUNG ELECTRONICS CO LTD

AI summary

In a non-volatile memory a group of memory cells is programmed respectively to their target states in parallel using a multiple-pass index programming method which reduces the number of verify steps. For each cell a program index is maintained storing the last programming voltage applied to the cell. Each cell is indexed during a first programming pass with the application of a series of incrementing programming pulses. The first programming pass is followed by verification and one or more subsequent programming passes to trim any short-falls to the respective target states. If a cell fails to verify to its target state, its program index is incremented and allows the cell to be programmed by the next pulse from the last received pulse. The verify and programming pass are repeated until all the cells in the group are verified to their respective target states. No verify operations between pulses are necessary.