Memory Array Intervening Tier for Charge-Blocking Oxide Integrity

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Solution Overview

Problem

The formation of charge-blocking material in memory arrays is hindered by the tendency for etching to remove sacrificial materials, leading to gaps and incomplete formation of the charge-blocking oxide, which affects the functionality of memory cells.

Innovation Solution

The introduction of an intervening tier with specific composition and thickness between the upper and lower stacks in the memory array structure, which facilitates the formation of channel-material strings and reduces the issues associated with etching and sacrificial material removal, allowing for complete formation of charge-blocking regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If etching is used to remove sacrificial material, then sacrificial material removal is achieved, but gaps and incomplete formation of charge-blocking oxide occur

Engineering Contradiction:

Improvesacrificial material removalVSAvoidcharge-blocking oxide formation completeness

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

An intervening tier composed of polysilicon and oxide is introduced between the upper and lower stacks. This intervening tier acts as a mediator that prevents direct contact between etching tools and the charge-blocking oxide in lower channel openings, thereby preventing etching-induced damage while still allowing sacrificial material removal to proceed

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution adds a vertical dimension to the structure by inserting an intervening tier between the upper and lower stacks. This additional layer provides a protective barrier that prevents the etching process from reaching and damaging the charge-blocking oxide in the lower channel openings, thus resolving the contradiction between easy manufacturing and manufacturing precision

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If no intervening tier is present, then structure simplicity is maintained, but charge-blocking material formation is hindered

Engineering Contradiction:

Improvecharge-blocking material formationVSAvoidmemory array structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The intervening tier serves as a protective intermediary layer that enables complete and uniform formation of charge-blocking oxide without compromising the overall structural integrity. The tier is composed of standard polysilicon and oxide materials that can be integrated into existing fabrication processes, thus achieving improved manufacturing precision with minimal increase in device complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If etching removes sacrificial material completely, then sacrificial material removal is achieved, but charge-blocking oxide is damaged

Engineering Contradiction:

Improvesacrificial material removal completenessVSAvoidcharge-blocking oxide integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The intervening tier acts as a protective shield during the etching process. It allows complete removal of sacrificial material from the upper stack while preventing the etching tools from accessing and damaging the charge-blocking oxide in the lower channel openings, thus simultaneously achieving complete sacrificial material removal and preserving charge-blocking oxide integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The intervening tier is positioned beforehand to cushion and protect the charge-blocking oxide from the harmful effects of the etching process. This pre-positioned protective layer ensures that the charge-blocking oxide remains intact throughout the sacrificial material removal process, maintaining its integrity for reliable memory cell operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS11476274B2Memory arrays comprising strings of memory cells and methods used in forming a memory array comprising strings of memory cells

Publication Date: 2022.10.18 MICRON TECHNOLOGY INC

AI summary

A memory array comprising strings of memory cells comprises an upper stack above a lower stack. The lower stack comprises vertically-alternating lower conductive tiers and lower insulative tiers. The upper stack comprises vertically-alternating upper conductive tiers and upper insulative tiers. An intervening tier is vertically between the upper and lower stacks. The intervening tier is at least predominantly polysilicon and of different composition from compositions of the upper conductive tier and the upper insulative tier immediately-above the intervening tier and of different composition from compositions of the lower conductive tier and the lower insulative tier immediately-below the intervening tier. Channel-material strings of memory cells extend through the upper stack, the intervening tier, and the lower stack. Other structures and methods are disclosed.