High Aspect Ratio Hole Formation in 3D Memory via Pillar Expansion
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Solution Overview
Problem
The challenge in semiconductor technology is forming high aspect ratio features with improved uniformity, particularly for 3D memory structures, as existing etching processes often result in non-uniformly shaped structures as the aspect ratio increases.
Innovation Solution
A method involving the deposition of a metal film in substrate features, followed by volumetric expansion to form pillars, and subsequent deposition and removal of a blanket film to control pillar height, allowing for progressive growth and reformation of features to achieve high aspect ratio structures with uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional etching processes are used to form high aspect ratio structures, then the aspect ratio can be increased, but the uniformity of the structure shape deteriorates
Solution Approach 1:
The formation of high aspect ratio structures is divided into multiple sequential steps: depositing metal film in features, volumetric expansion to form pillars, depositing blanket film, removing blanket film, and reducing pillar height. This segmentation allows each step to be optimized independently, maintaining uniformity while achieving high aspect ratios that would be impossible with a single etching process.
Solution Approach 2:
Metal film is deposited in the features and volumetrically expanded to form pillars before the final structure formation. This preliminary action creates a scaffold that guides subsequent processing steps, ensuring uniform structure formation from the bottom up rather than relying on top-down etching that loses control at high aspect ratios.
2Productivity
If the aspect ratio of structures is increased, then the density and capacity of 3D memory structures improve, but the tendency to form non-uniformly shaped structures increases
Solution Approach 1:
The metal film undergoes volumetric expansion to form pillars that self-align and maintain uniform shapes throughout the high aspect ratio features. This self-organizing process eliminates the need for complex external control mechanisms during formation, allowing uniform structures to emerge naturally even at very high aspect ratios that enable increased memory density.
Solution Approach 2:
The process transforms the physical state and dimensions of materials through controlled parameter changes: metal film deposition, volumetric expansion ratios, blanket film thickness variations, and selective etching parameters. These parameter changes enable precise control over structure formation at each stage, maintaining uniformity while achieving the high aspect ratios needed for increased memory density.
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 method enables the reliable formation of high aspect ratio holes and trenches in 3D memory structures with improved uniformity, enhancing the quality and density of semiconductor devices by maintaining shape fidelity and allowing for precise control of feature height.
Implementation Method 1
The metal film is volumetrically expanded to form a pillar that extends straight out of the feature
Implementation Method 2
A blanket film comprising alternating oxide layers and nitride layers is deposited
Data Source
AI summary
Methods of forming memory structures are described. A metal film is deposited in the features of a structured substrate and volumetrically expanded to form pillars. A blanket film is deposited to a height less than the height of the pillars and the blanket film is removed from the top of the pillars. The height of the pillars is reduced so that the top of the pillars are below the surface of the blanket film and the process is optionally repeated to form a structure of predetermined height. The pillars can be removed from the features after formation of the predetermined height structure to form high aspect ratio features.