Crystallinity-Dependent Aluminum Oxide Etching for Memory Dielectrics
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Solution Overview
Problem
Current methods for forming three-dimensional memory devices, such as vertical NAND strings, face challenges in selectively etching aluminum oxide layers to maintain crystalline portions while removing amorphous portions, which affects the integrity and performance of the memory stack structure.
Innovation Solution
A method involving the deposition of a thin amorphous aluminum oxide layer on both sacrificial and insulating surfaces, followed by a selective crystallization anneal process, allows for the crystallization of aluminum oxide portions on sacrificial surfaces while keeping amorphous layers on insulating surfaces, enabling selective wet etching to retain crystalline portions and remove amorphous ones, thereby forming a stable memory stack structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a selective etch process is used to remove amorphous aluminum oxide portions while retaining crystalline portions, then etching efficiency is improved and continuous charge paths are eliminated, but the process complexity increases due to the need for selective crystallization annealing
Solution Approach 1:
The patent utilizes phase transition between amorphous and crystalline states of aluminum oxide. A selective crystallization anneal process transforms aluminum oxide on sacrificial material surfaces from amorphous to crystalline phase, while aluminum oxide on insulating layer surfaces remains amorphous. This phase difference enables selective wet etching where crystalline portions are retained and amorphous portions are removed, eliminating continuous charge paths and improving etching efficiency without requiring complex dry etching processes.
Solution Approach 2:
The patent changes the physical-chemical parameters of aluminum oxide by controlling the crystallization annealing process. By adjusting temperature and time parameters of the anneal, the aluminum oxide on different surfaces undergoes different transformations - crystalline formation on sacrificial material surfaces versus remaining amorphous on insulating layer surfaces. This parameter control enables the selective etching process to differentiate between the two types of aluminum oxide portions.
2Reliability
If crystalline aluminum oxide portions are retained around memory stack structures, then data retention and memory device performance are enhanced, but the manufacturing process requires additional selective crystallization steps
Solution Approach 1:
The patent employs selective crystallization annealing to transform aluminum oxide on sacrificial material surfaces into crystalline phase, which provides superior data retention and memory device performance. The crystalline structure forms specifically on surfaces where sacrificial material is present, while aluminum oxide on insulating layer surfaces remains amorphous. This selective phase transition enhances reliability by eliminating continuous charge paths without requiring complex additional manufacturing steps.
Solution Approach 2:
The selective crystallization process automatically differentiates between aluminum oxide on sacrificial material surfaces and aluminum oxide on insulating layer surfaces based on the underlying material properties. The process self-organizes to create the desired crystalline structure in the correct locations without requiring additional masking or patterning steps, thereby enhancing reliability while maintaining manufacturing simplicity.
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 ensures the retention of crystalline aluminum oxide portions around memory stack structures, enhancing data retention and memory device performance by eliminating continuous charge paths and improving etching efficiency without requiring complex dry etching processes.
Implementation Method 1
performing a selective crystallization anneal process on the amorphous aluminum oxide layer, wherein the first portion of the amorphous aluminum oxide layer is crystallized into a crystalline aluminum oxide portion while the second portion of the amorphous aluminum oxide layer remains as an amorphous aluminum oxide portion
Implementation Method 2
selectively wet etching the amorphous aluminum oxide portion such that all or a predominant portion the crystalline aluminum oxide portion remains after the step of selectively wet etching
Data Source
AI summary
A method of forming a device includes forming an alternating stack of insulating layers and sacrificial material layers over a substrate, forming a memory opening extending through the alternating stack, and forming an aluminum oxide layer on sidewall surfaces of the sacrificial material layers and on sidewall surfaces of the insulating layers around the memory opening. First aluminum oxide portions of the aluminum oxide layer are located on sidewall surfaces of the sacrificial material layers, and second aluminum oxide portions of the aluminum oxide layer are located on sidewalls of the insulating layers. The method also includes removing the second aluminum oxide portions at a greater etch rate than the first aluminum oxide portions employing a selective etch process, such that all or a predominant portion of each first aluminum oxide portion remains after removal of the second aluminum oxide portions.