Planar Cell ONO Cut via In-Situ Polymer Deposition

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Solution Overview

Problem

In the fabrication of flash memory devices, particularly NAND flash memory, the charge storage ONO layer separation is challenging, leading to potential cell shorting and charge leakage issues if not properly separated, which affects the density and reliability of the memory cells.

Innovation Solution

A method involving the deposition of a polymer layer on top of the ONO layer, followed by planarization and controlled etching to expose and separate the higher regions over shallow trenches while protecting the regions over source/drain areas, ensuring precise separation of the ONO layer to define individual memory cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional etching methods are used to separate the ONO layer, then the separation process becomes complex and difficult to control, but the ONO layer may not be properly separated leading to cell shorting and charge leakage

Engineering Contradiction:

ImproveONO layer separation reliabilityVSAvoidseparation process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A polymer layer is deposited as an intermediary material on top of the ONO layer. This polymer layer serves as a protective mask during the etching process, allowing selective removal of ONO material in trench regions while preserving ONO over source/drain areas. The intermediary polymer layer simplifies the separation process by providing a clear distinction between regions to be etched and protected, thereby improving separation reliability without increasing process complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The polymer layer is deposited in advance before the etching process. This preliminary action creates a protective coating that defines which regions will be etched and which will be protected. By performing this preparatory step, the subsequent etching process becomes more controlled and reliable, avoiding the need for complex real-time control during etching while ensuring proper ONO layer separation

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the ONO layer is not properly separated, then cell shorting and charge leakage occur, but achieving proper separation requires additional fabrication steps

Engineering Contradiction:

Improvememory cell isolation reliabilityVSAvoidfabrication process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The polymer layer acts as an intermediary protective mask that simplifies the manufacturing process. By depositing this layer before etching, the process automatically protects source/drain regions while exposing trench regions for etching. This approach ensures reliable memory cell isolation without requiring complex multi-step fabrication sequences or precise real-time control during etching

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The polymer layer deposition process itself serves the dual function of both protecting regions that should retain ONO material and defining regions where ONO should be removed. The self-aligned nature of the polymer deposition ensures that the protection pattern is automatically generated without requiring additional masking steps, thereby maintaining fabrication simplicity while achieving reliable cell isolation

Inventive Principle:

Principle #25Self-service

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 effectively separates the charge storage ONO layer, preventing cell shorting and charge leakage, thereby enhancing the density and reliability of NAND flash memory devices while maintaining a cost-effective fabrication process.

Implementation Method 1

a polymer layer is deposited on top of an oxide-nitride-oxide (ONO) layer

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

a polymer layer is deposited on top of an oxide-nitride-oxide (ONO) layer

Methodology Applied

Scientific EffectChemical Vapour Deposition: Chemical Vapour Deposition

Implementation Method 3

the polymer layer is planarized

Methodology Applied

Scientific EffectPlanarization:

Implementation Method 4

Etching is performed on the polymer layer to expose the first region of the ONO layer

Methodology Applied

Scientific EffectPlasma Etching: Plasma

Implementation Method 5

leaving the second region of the ONO unexposed

Methodology Applied

Scientific EffectPhysical Barrier Protection: Physical Containment

Data Source

PatentUS8790530B2Planar cell ONO cut using in-situ polymer deposition and etch

Publication Date: 2014.07.29 SPANSION LLC

AI summary

A method and manufacture for charge storage layer separation is provided. A layer, such as a polymer layer, is deposited on top of an ONO layer so that the polymer layer is planarized, or approximately planarized. The ONO includes at least a first region and a second region, where the first region is higher than the second region. For example, the first region may be the portion of the ONO that is over the source/drain region, and the second region may be the portion of the ONO that is over the shallow trench. Etching is performed on the polymer layer to expose the first region of the ONO layer, leaving the second region of the ONO unexposed. The etching continues to occur to etch the exposed ONO at the first region so that the ONO layer is etched away in the first region and the second region remains unexposed.