Word Line Hook Up Protected Air Gap

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Solution Overview

Problem

In NAND flash memory technologies, connecting very small word lines to larger contact pads is challenging due to air gaps, which can lead to solvent penetration and damage during cleaning processes, resulting in electrical shorts and reduced production yield.

Innovation Solution

A dummy structure, such as a ring with an inner open area, is formed opposite an air gap between word lines, and the contact pad cut terminates within this inner open area, preventing solvent penetration and maintaining the air gap's isolation from the contact pad cut.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If air gaps are exposed in hook up areas during cleaning, then cleaning effectiveness is improved, but solvent penetration occurs causing electrical shorts and reduced yield

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidelectrical short prevention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A dummy structure is introduced as an intermediary element positioned between the air gap and the contact pad cut. This dummy structure acts as a barrier that prevents solvent from penetrating into the air gap during cleaning operations, while not interfering with the overall cleaning effectiveness of the process.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The dummy structure is formed in advance during the manufacturing process, before the cleaning step. This preliminary action ensures that the protective barrier is already in place to prevent solvent penetration during subsequent cleaning operations, addressing the reliability issue before it can manifest.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If contact pad cuts are made to separate neighboring contact pads, then contact pad isolation is improved, but air gaps become exposed to solvent penetration

Engineering Contradiction:

Improvecontact pad isolationVSAvoidsolvent penetration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The dummy structure serves as a protective intermediary that remains positioned between the contact pad cut and the air gap. Even when contact pad cuts are made to achieve proper isolation, the dummy structure blocks the pathway that would otherwise allow solvent to reach and penetrate the air gap.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If dummy structure is formed to protect air gap, then solvent penetration is prevented, but device complexity increases

Engineering Contradiction:

Improveair gap protectionVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The dummy structure is a simple, inexpensive geometric pattern that can be easily formed using standard photolithography and etching processes. While it adds a structural element, it uses conventional materials and processes, minimizing the increase in overall device complexity and manufacturing cost.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS9484314B2Word line hook up with protected air gap

Publication Date: 2016.11.01 SANDISK TECHNOLOGIES LLC

AI summary

A method of forming a semiconductor device includes forming a plurality of word lines separated by air gaps with contact pad structures connected to the word lines, and forming a dummy structure directly opposite an air gap between neighboring word lines. Subsequently, the contact pad structures are cut into individual contact pads by a contact pad cut that intersects the dummy structure.