PPROM and Flash Memory 3D Stacking for Density

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Solution Overview

Problem

Conventional memory structures, such as PPROM and SONOS flash memory, face challenges in meeting increasing memory density demands for new applications, necessitating the development of new techniques for memory structure design and fabrication.

Innovation Solution

Combining embedded flash memory with Physical Programmable Read-Only Memory (PPROM) structures, where PPROM cells are stacked on top of flash memory cells, and implementing three-dimensional PPROM structures to enhance density, with specific configurations and fabrication methods described, including the use of poly-diode structures and SONOS flash memory cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional PPROM or SONOS flash memory structures are used, then manufacturing cost and simplicity are maintained, but memory density cannot meet increasing demands

Engineering Contradiction:

Improvememory densityVSAvoidmemory structure complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent combines two different memory technologies (PPROM and SONOS flash memory) into a single integrated structure. The PPROM cells and SONOS flash memory cells are formed in the same semiconductor substrate using a unified fabrication process, merging the advantages of both memory types to achieve higher density while maintaining manufacturing simplicity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent transitions from two-dimensional planar memory structures to three-dimensional vertically-stacked memory cells. Multiple layers of memory cells are stacked above each other in the vertical dimension, significantly increasing the memory density per unit area without proportionally increasing device complexity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If three-dimensional PPROM structures are implemented to increase density, then memory density improves, but fabrication complexity increases

Engineering Contradiction:

ImprovePPROM densityVSAvoidfabrication ease

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent performs preliminary actions by forming all memory structures (both PPROM and SONOS cells) simultaneously during the fabrication process rather than sequentially. The well regions, oxide layers, and poly-silicon layers are created in a coordinated manner that enables three-dimensional stacking without requiring additional complex fabrication steps

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The fabrication process is designed to be universal, creating both PPROM cells and SONOS flash memory cells using the same sequence of steps and materials. This multi-functional approach allows the same fabrication equipment and processes to produce the entire memory structure, reducing manufacturing complexity despite the three-dimensional architecture

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS7755129B2Systems and methods for memory structure comprising a PPROM and an embedded flash memory

Publication Date: 2010.07.13 MACRONIX INTERNATIONAL CO LTD

AI summary

A memory structure that combines embedded flash memory and PPROM. The PPROM can be used as a memory structure. The flash memory can be used, e.g., as air replacement cells or back up memory, or additional memory cells. The PPROM cells are stacked on top of the flash memory cells and the PPROM density can be increased by implementing three-dimensional PPROM structure.