Nonvolatile Memory Programming Voltage Control

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Solution Overview

Problem

Existing nonvolatile memory devices face challenges in efficiently programming memory cells between different logic states due to variations in threshold voltages, leading to program failures and reduced operation speed, particularly when dealing with multiple program states and coupling effects.

Innovation Solution

A method is introduced that varies the number of program voltages applied to a selected word line based on the threshold voltage differences between logic states, using multiple program voltages in one loop to manage coupling effects and optimize programming speed, with specific approaches for least significant bits, central significant bits, and most significant bits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fixed number of program voltages is applied to all memory cells regardless of threshold voltage differences, then the programming process is simple to control, but program failures occur due to variations in threshold voltages between different logic states

Engineering Contradiction:

Improveprogramming reliabilityVSAvoidprogramming control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies dynamic programming control by varying the number of program voltages applied to memory cells based on their current logic state and threshold voltage characteristics. Different logic states (e.g., S0, S1, S2, S3) receive different numbers of program voltages (1, 2, or 3), allowing the programming process to adapt to the specific needs of each cell state rather than using a fixed approach for all cells.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of program voltage quantity dynamically during the programming process. By adjusting the number of program voltages applied based on the threshold voltage difference between current and target logic states, the system optimizes programming effectiveness for each specific case, resolving the contradiction between reliability and simplicity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple program voltages are applied to all memory cells in every programming operation, then programming reliability for high threshold voltage differences is improved, but programming time increases and operation speed decreases

Engineering Contradiction:

Improveprogramming reliabilityVSAvoidprogramming speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies partial action by using multiple program voltages only when necessary (i.e., when the threshold voltage difference exceeds a certain threshold). For smaller threshold voltage differences, fewer program voltages are sufficient. This avoids the excessive application of multiple voltages in all cases, thereby maintaining high reliability when needed while improving overall programming speed.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system dynamically determines the number of program voltages to apply based on real-time assessment of threshold voltage differences. This dynamic approach ensures that multiple voltages are used selectively rather than universally, optimizing the balance between reliability and programming speed.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If the number of program voltages is increased to handle large threshold voltage differences, then programming coverage across all logic states is improved, but coupling effects between adjacent memory cells increase

Engineering Contradiction:

Improvelogic state coverageVSAvoidcoupling effects

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by tailoring the number of program voltages to the specific requirements of each logic state transition. Instead of applying the same number of voltages uniformly to all cells, the system adjusts the voltage quantity locally based on the threshold voltage difference characteristics of each specific programming operation, thereby achieving comprehensive logic state coverage while minimizing unnecessary coupling effects.

Inventive Principle:

Principle #3Local quality

4Measurement precision

If verify voltages are applied after each program voltage to check programming status, then programming accuracy is improved, but programming time and operation complexity increase

Engineering Contradiction:

Improveprogramming accuracyVSAvoidprogramming time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent implements feedback control by applying verify voltages after programming operations to check whether the threshold voltage has reached the target range. This feedback mechanism allows the system to confirm programming accuracy and adjust subsequent operations accordingly, ensuring high precision while managing time through efficient verification strategies.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8331155B2Method for programming nonvolatile memory device

Publication Date: 2012.12.11 SAMSUNG ELECTRONICS CO LTD

AI summary

A method programs a nonvolatile memory device to program memory cells from one or more first logic states to two or more second logic states. In the method, a number of program voltages are provided to a selected word line, and verify voltages corresponding to the second logic states are provided to the selected word line. The number of the program voltages provided to the selected word line varies according to the threshold voltage difference between each of the first logic states and each of the second logic states.