Molybdenum Word Lines and Metal Oxide Spacers for 3D NAND
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently integrating molybdenum word lines and self-aligned tubular dielectric metal oxide spacers, which affect the scalability and manufacturing complexity of monolithic NAND string memory arrays.
Innovation Solution
A three-dimensional memory device is developed with an alternating stack of insulating layers and molybdenum word lines, featuring memory stack structures that include vertical tubular dielectric metal oxide spacers, a continuous silicon oxide blocking dielectric layer, charge storage material portions, and a tunneling dielectric layer, formed through a method involving selective etching and oxidation processes to create self-aligned spacer structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional manufacturing processes are used for integrating word lines and spacers, then manufacturing complexity increases and scalability is reduced, but if self-aligned spacer structures are implemented, then manufacturing is simplified and vertical scaling is enhanced
Solution Approach 1:
The molybdenum word line layers are formed with protruding portions that extend beyond the insulating layers before the spacers are formed. This preliminary configuration of the word lines creates pre-defined attachment sites for the spacers, eliminating the need for complex alignment processes and replacement steps during subsequent manufacturing stages
Solution Approach 2:
The tubular dielectric metal oxide spacers are formed to be self-aligned with the molybdenum word line protrusions through selective etching and oxidation processes. The spacers automatically position themselves on the word line protrusions without requiring additional alignment operations, and the word line protrusions serve as their own alignment references, making the structure self-defining and simplifying manufacturing
2Reliability
If standard dielectric materials are used, then electrical conductivity is insufficient and RC delay increases, but if molybdenum word lines are used, then electrical conductivity improves and RC delay is reduced
Solution Approach 1:
The word lines are constructed from molybdenum, a metal with superior electrical conductivity compared to conventional dielectric materials. This material parameter change directly reduces RC delay and improves signal transmission reliability. The molybdenum layers are deposited with controlled thickness and conductivity parameters to optimize electrical performance while maintaining compatibility with the surrounding dielectric structures
Solution Approach 2:
The device employs a composite structure where molybdenum metal layers are integrated with dielectric insulating layers and tubular dielectric spacers. This composite material approach combines the high electrical conductivity of molybdenum with the insulating properties of the dielectric materials, achieving both electrical performance and structural functionality in a single integrated architecture
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 configuration enhances vertical scaling, simplifies manufacturing by eliminating the need for replacement processes, and improves electrical conductivity, reducing RC delay in word lines, while maintaining effective charge storage and retention.
Implementation Method 1
forming annular recesses at each level of the molybdenum layers around the memory opening by laterally recessing the molybdenum layers selective to the insulating layers
Implementation Method 2
converting the vertical stack of tubular metal portions into a vertical stack of tubular dielectric metal oxide spacers
Data Source
AI summary
A three-dimensional memory device includes an alternating stack of insulating layers and word lines that are made of molybdenum layers located over a substrate, and memory stack structures extending through each layer in the alternating stack. Each of the memory stack structures includes a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film. Each memory film includes a vertical stack of discrete tubular dielectric metal oxide spacers in contact with a respective one of the molybdenum layers, a continuous silicon oxide blocking dielectric layer contacting an inner sidewall of each of the tubular dielectric metal oxide spacers, a vertical stack of charge storage material portions, and a tunneling dielectric layer contacting each of the charge storage material portions and the vertical semiconductor channel.