Foggy-Fine Programming Sequence Mitigates Wordline Interference

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

BiCS4 X4 quad-level cell memory experiences high failed bit counts due to reduced threshold voltage margin between foggy-fine programming, particularly at the edge wordline, caused by neighbor wordline interference (NWI) in high temperature conditions.

Innovation Solution

Implementing a foggy-fine programming sequence where either dummy data is programmed on neighboring wordlines or they are skipped entirely, allowing subsequent wordlines to be programmed with foggy-fine programming, thereby reducing neighbor wordline interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional programming sequence is used, then programming speed is maintained, but neighbor wordline interference causes high failed bit counts at edge wordline

Engineering Contradiction:

Improvefailed bit countVSAvoidprogramming speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by programming the neighboring wordline (WLn+1) with dummy data or skipping it entirely before programming the target wordline (WLn). This preliminary intervention prevents neighbor wordline interference from affecting the edge wordline programming, thereby reducing failed bit counts while maintaining overall programming efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts the problematic neighboring wordline (WLn+1) from the normal programming sequence by either programming it with dummy data or skipping it entirely. This separation removes the source of neighbor wordline interference, allowing the edge wordline (WLn) to be programmed without interference, thus improving reliability without significant productivity loss

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If foggy-fine programming is applied to all wordlines, then programming precision is improved, but neighbor wordline interference increases at edge wordline

Engineering Contradiction:

Improvethreshold voltage precisionVSAvoidneighbor wordline interference

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by differentiating the programming treatment between neighboring wordlines and target wordlines. The neighboring wordline (WLn+1) receives special treatment (dummy programming or skipping) while the target wordline (WLn) receives standard foggy-fine programming. This localized differentiation maintains precision where needed while eliminating interference in vulnerable areas

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces an intermediary approach by using dummy data programming or skipping the neighboring wordline as a buffer between programming operations. This intermediary action prevents direct interference between adjacent wordlines during foggy-fine programming, allowing precision programming to proceed without the harmful neighbor wordline interference effect

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11282580B2Data storage device with foggy-fine program sequence for reducing neighbor wordline interference

Publication Date: 2022.03.22 SANDISK TECHNOLOGIES LLC

AI summary

A memory controller includes, in one embodiment, a memory interface and a controller circuit. The memory interface is configured to interface with a memory having a plurality of wordlines. The controller circuit is configured to program, with foggy-fine programming, a first portion of the plurality of wordlines to store first program data, program, with the foggy-fine programming, one or more wordlines of the plurality of wordlines in a non-fine state, the one or more wordlines neighboring the first portion, and program, with the foggy-fine programming, a second portion of the plurality of wordlines to store second program data, the second portion neighboring the one or more wordlines.