3D Memory Structure Metal Word Line Decoder Area Reduction

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Solution Overview

Problem

The shrinking size of memory devices makes the two X-decoders method harmful to array efficiency, and existing methods like metal word line processes are difficult to implement, especially for vertical gate structures due to process flow and yield control issues.

Innovation Solution

A 3D memory structure is designed with parallel strings and conductive lines where metal layers connect end regions of the conductive lines, reducing the need for one X-decoder and allowing high-conductivity paths for signal transfer, thereby shrinking the device size and improving RC delay.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If two X-decoders are used at opposite sides of memory array region, then RC delay of word line signal is improved, but device area increases and array efficiency decreases

Engineering Contradiction:

ImproveRC delay of word line signalVSAvoidarea of X-decoders

Core Design Contradiction:

Loss of timeVSArea of stationary object

Solution Approach 1:

The patent extracts and eliminates one of the two X-decoders from the system. By using metal word line process, the word line signal can be transferred directly to the array region without requiring both X-decoders, thus removing one decoder while maintaining signal transfer efficiency

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the material parameter of the word line from poly-silicon to metal. This parameter change enables higher conductivity and allows the word line to be connected directly to the array region, eliminating the need for one X-decoder and reducing the decoder area

Inventive Principle:

Principle #35Parameter changes

2Loss of time

If metal word line process is used to improve conductivity, then RC delay is improved, but process complexity increases and yield control becomes difficult

Engineering Contradiction:

ImproveRC delay of word line signalVSAvoidprocess flow and yield control

Core Design Contradiction:

Loss of timeVSEase of manufacture

Solution Approach 1:

The patent makes the metal word line process compatible with existing 3D memory manufacturing processes. The metal layer is formed using standard deposition techniques that can be integrated into the vertical gate structure fabrication process, allowing the process to serve multiple functions without requiring entirely new manufacturing steps

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9536573B23D memory structure and method for manufacturing the same

Publication Date: 2017.01.03 MACRONIX INTERNATIONAL CO LTD

AI summary

A 3D memory structure and a method for manufactured the same are provided. The 3D memory structure comprises a plurality of strings, a plurality of first conductive lines, a plurality of second conductive lines and a plurality of third conductive lines. The strings are disposed in parallel. The first conductive lines are disposed over the strings. Center regions of the first conductive lines are disposed perpendicular to the strings. The second conductive lines are disposed over the first conductive lines. The second conductive lines connect end regions of half of the first conductive lines. The third conductive lines are disposed over the second conductive lines. The third conductive lines connect end regions of the other half of the first conductive lines.