Multi-State NVM Programming via Hot Carrier Injection Binning

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Solution Overview

Problem

Multi-state non-volatile memories (NVMs) face challenges in programming efficiency due to the lengthy process of achieving separated threshold voltage distributions for multiple programmed states, which complicates both programming and reading operations.

Innovation Solution

The method employs hot carrier injection (HCI) programming, where NVM cells are initially programmed and categorized into bins based on threshold voltage ranges, allowing for targeted programming pulses to achieve desired programmed states with minimal pulses, optimizing the separation of threshold voltages for efficient reading and writing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multiple programmed states are implemented in multi-state NVM, then storage density and space efficiency are improved, but programming time and process complexity increase significantly

Engineering Contradiction:

Improvestorage densityVSAvoidprogramming time

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The patent segments the programming process into multiple distinct stages, where each stage programs cells to specific threshold voltage ranges. This segmentation allows systematic progression through multiple programmed states without attempting to program all states simultaneously, thereby reducing overall programming time while maintaining high storage density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs preliminary classification of memory cells into bins based on their initial threshold voltage distributions before programming. This preliminary action enables tailored programming pulses to be applied to each bin, ensuring efficient programming to target states without unnecessary programming steps, thus reducing programming time while preserving multi-state capacity.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If sufficient separation in threshold voltage is achieved for multiple programmed states, then reading reliability is improved, but programming process complexity increases

Engineering Contradiction:

Improvereading reliabilityVSAvoidprogramming process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by tailoring programming pulses to specific bins of memory cells based on their individual threshold voltage characteristics. Each bin receives customized programming parameters that ensure reliable separation of threshold voltage distributions for its target programmed state, maintaining reading reliability while managing programming complexity through localized rather than uniform programming approaches.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes parameter changes by adjusting programming pulse characteristics (such as voltage magnitude and duration) based on the specific bin and target programmed state. These parameter adjustments enable precise control over threshold voltage separation, ensuring reliable state differentiation without requiring overly complex programming processes.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If programming pulses are applied to achieve multiple programmed states, then storage capacity per cell is improved, but programming speed decreases

Engineering Contradiction:

Improvestorage capacity per cellVSAvoidprogramming speed

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

The patent employs periodic action through its multi-stage programming approach, where programming pulses are applied in sequential stages rather than continuously. Each stage completes a specific programming task before the next stage begins, enabling efficient progression through multiple programmed states and maintaining programming speed while achieving high storage capacity per cell.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly reduces the time required for programming multi-state NVMs by ensuring that cells can be reliably and quickly programmed to multiple states with precise voltage adjustments, enhancing the overall efficiency of memory cell programming.

Implementation Method 1

The NVM cells are programmed using hot carrier injection (HCI) programming pulses

Methodology Applied

Scientific EffectHot carrier injection:

Implementation Method 2

The NVM cells are erased using Fowler-Nordheim tunneling

Methodology Applied

Scientific EffectFowler-Nordheim tunneling:

Data Source

PatentUS8842469B2Method for programming a multi-state non-volatile memory (NVM)

Publication Date: 2014.09.23 NXP USA INC

AI summary

A method is provided for programming a multi-state flash memory having a plurality of memory cells. A first programming pulse is provided to the flash array; determining a threshold voltage distribution for the plurality of memory cells after providing the first programming pulse. The plurality of memory cells is categorized into at least two bins based on a threshold voltage of each memory cell of the plurality of memory cells. A first voltage is selected for a second programming pulse for programming a first bin of memory cells of the at least two bins, the first voltage based on both a threshold voltage of the first bin and a first target threshold voltage. A second voltage is selected for a third programming pulse for programming a second bin of memory cells of the at least two bins, the second voltage based on both the threshold voltage of the second bin and on a second target threshold voltage.