3D Memory Conductive Spacers for Lower Interface Traps
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Solution Overview
Problem
Current semiconductor memory technologies face challenges in increasing the lifespan and endurance of memory arrays due to high interface trap densities between gate dielectrics and gate electrodes, which affect the number of read/write cycles they can sustain.
Innovation Solution
A three-dimensional memory array design is implemented with vertically stacked memory cells, using a work function material as conductive spacers to reduce interface traps and improve adhesion between word lines and insulating memory films, thereby enhancing the lifespan of the memory array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional gate electrode structures are used, then manufacturing is simpler, but interface trap density is high reducing memory lifespan
Solution Approach 1:
The gate electrode structure is segmented into multiple distinct layers: a first conductive layer (word line material) and a second conductive layer (work function material) deposited on its sidewalls. This segmentation allows each layer to perform its specialized function - the first layer provides low-resistivity electrical conduction while the second layer provides appropriate work function for the transistor channel, thereby reducing interface traps and extending memory lifespan without excessive complexity
Solution Approach 2:
The work function material is positioned in a third dimension - on the sidewalls of the word line structure rather than as a planar layer. This vertical/sidewall positioning creates a multi-dimensional gate electrode architecture where the work function material contacts the channel from the side, reducing interface trap density at critical interfaces while maintaining electrical functionality
2Reliability
If work function material is added as conductive spacer, then adhesion between word line and memory film improves, but manufacturing complexity increases
Solution Approach 1:
The work function material is deposited on the sidewalls of the word line structure before the insulating memory film is formed. This preliminary action ensures that the work function material is already in place to provide proper adhesion and reduce interface traps when the memory film is subsequently deposited, improving reliability while following a logical manufacturing sequence
Solution Approach 2:
The work function material acts as an intermediary layer between the word line conductive material and the insulating memory film. This intermediate layer provides appropriate surface properties for adhesion and reduces interface trap density, improving the interface quality between the two materials that would otherwise be in direct contact
Data Source
AI summary
In an embodiment, a device includes: a first word line over a substrate, the first word line including a first conductive material; a first bit line intersecting the first word line; a first memory film between the first bit line and the first word line; and a first conductive spacer between the first memory film and the first word line, the first conductive spacer including a second conductive material, the second conductive material having a different work function than the first conductive material, the first conductive material having a lower resistivity than the second conductive material.