Hydrogen-Passivated 3D Memory Channels via Segmented Silicon Nitride
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Solution Overview
Problem
Charge carrier mobility in vertical semiconductor channels of three-dimensional memory devices is hindered by dangling bonds at grain boundaries, and existing hydrogen passivation methods can introduce deleterious effects in underlying driver circuit CMOS devices.
Innovation Solution
A method involving the use of two silicon nitride layers with different hydrogen concentrations is employed, where the lower layer acts as a hydrogen source for passivating dangling bonds and the upper layer as a hydrogen barrier to prevent diffusion into the ambient, thereby enhancing charge carrier mobility while minimizing hydrogen introduction into CMOS devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen passivation is performed using conventional methods, then charge carrier mobility in semiconductor channels is improved, but hydrogen diffuses into underlying CMOS devices causing deleterious effects
Solution Approach 1:
The silicon nitride layer is segmented into two distinct layers with different hydrogen concentrations. The first silicon nitride layer (lower layer) has a higher hydrogen-to-nitrogen ratio and serves as the hydrogen source for passivation, while the second silicon nitride layer (upper layer) has a lower hydrogen-to-nitrogen ratio and acts as a hydrogen barrier to prevent diffusion into CMOS devices. This segmentation allows simultaneous achievement of effective passivation and hydrogen containment.
Solution Approach 2:
Different regions of the silicon nitride structure are assigned different hydrogen concentrations to fulfill different functions. The lower layer is engineered with high hydrogen content specifically for passivation purposes, while the upper layer is engineered with low hydrogen content specifically for barrier purposes. This local differentiation of material properties resolves the contradiction between providing hydrogen and preventing hydrogen diffusion.
2Device complexity
If a single silicon nitride layer is used for hydrogen passivation, then the structure is simple, but hydrogen diffuses into the ambient environment affecting CMOS devices
Solution Approach 1:
Rather than using a single uniform silicon nitride layer, the structure is divided into two layers with distinct hydrogen concentrations. This segmentation increases structural complexity but enables the system to simultaneously achieve passivation functionality and hydrogen barrier functionality, ultimately preventing harmful effects on CMOS devices.
Solution Approach 2:
The passivation structure employs a composite of two silicon nitride layers with different compositional characteristics (different hydrogen-to-nitrogen ratios). This composite structure combines the benefits of hydrogen-rich material for passivation with hydrogen-poor material for barrier protection, resolving the contradiction between simplicity and effectiveness.
3Reliability
If hydrogen concentration in silicon nitride is increased for better passivation, then dangling bonds are effectively passivated, but hydrogen diffusion into CMOS devices increases
Solution Approach 1:
The hydrogen source function and hydrogen barrier function are separated into different layers. The first silicon nitride layer is optimized with high hydrogen concentration specifically for passivating dangling bonds in the semiconductor channel, while the second silicon nitride layer is optimized with low hydrogen concentration specifically for preventing hydrogen diffusion into CMOS devices. This functional segmentation resolves the contradiction between passivation effectiveness and hydrogen containment.
Solution Approach 2:
The second silicon nitride layer acts as an intermediary barrier between the hydrogen-rich first layer and the CMOS devices. It mediates the hydrogen distribution by allowing sufficient hydrogen to reach the semiconductor channel for passivation while blocking excess hydrogen from reaching the CMOS devices, thus resolving the contradiction between effective passivation and preventing harmful diffusion.
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 approach effectively increases charge carrier mobility in semiconductor channels while maintaining the integrity of underlying CMOS devices, enhancing the performance of three-dimensional memory devices without introducing hydrogen-related issues.
Implementation Method 1
performing an anneal process at an elevated temperature to diffuse hydrogen from the first silicon nitride layer into the memory stack structures
Implementation Method 2
performing an anneal process at an elevated temperature to diffuse hydrogen from the first silicon nitride layer into the memory stack structures
Data Source
AI summary
A method of forming a three-dimensional memory device includes forming memory stack structures vertically extending through an alternating stack of insulating layers and electrically conductive layers over a substrate, such that each of the memory stack structures includes a memory film and a vertical semiconductor channel laterally surrounded by the memory film. The method also includes forming a stack of a first silicon nitride layer and a second silicon nitride layer over the memory stack structures, such that the first silicon nitride layer has a higher hydrogen-to-nitrogen ratio than the second silicon nitride layer, performing an anneal process at an elevated temperature to diffuse hydrogen from the first silicon nitride layer into the memory stack structures, and removing the first and second silicon nitride layers.