3D NAND Channel Layer Step Coverage via Dynamic Spray Etching
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Solution Overview
Problem
In three-dimensional NAND flash memory devices, controlling the etch rate during chemical etching of semiconductor wafers is challenging, particularly in achieving uniform step coverage in high-aspect ratio openings, which affects the formation of channel layers.
Innovation Solution
The method involves mixing an etchant solution, allowing it to reach a quiescent state, and then submerging substrates with material layers into the bath for a predetermined time, ensuring controlled etching that reduces the material layer thickness uniformly across the openings, thereby improving step coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemical etching is performed by placing wafers into a solution bath, then the etching process can be performed, but the etch rate becomes difficult to control and step coverage is poor
Solution Approach 1:
The patent applies dynamics by transitioning from a static bath etching process to a dynamic spray etching process. The etchant is delivered through nozzles that spray the solution onto the wafer surface, creating a dynamic flow pattern that improves etch rate control and step coverage. The spray mechanism allows the etchant to reach high-aspect ratio openings more effectively while maintaining uniform etching across the wafer surface.
Solution Approach 2:
The patent utilizes hydraulics by employing a spray-based liquid delivery system instead of a static bath. The etchant solution is pumped through a network of nozzles that spray the liquid onto the wafer surface, providing controlled hydraulic flow that enhances etchant penetration into high-aspect ratio structures while improving manufacturability and step coverage.
2Reliability
If multiple deposition steps are used to form the channel layer, then the material layer can be formed, but the process complexity increases
Solution Approach 1:
The patent merges multiple deposition steps into a single etching-based approach. Instead of performing separate deposition operations to build up the channel layer material, the process uses a unified etching step with controlled spray delivery to selectively remove material and define the channel layer structure, thereby reducing process complexity while maintaining reliability.
Solution Approach 2:
The patent applies parameter changes by modifying the etching process parameters (spray pressure, flow rate, nozzle positioning, etchant concentration) to achieve precise control over channel layer formation. By optimizing these parameters, the single etching step can replace multiple deposition steps, reducing device complexity while ensuring reliable channel layer formation.
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 allows for improved step coverage of the channel layer along the side walls of high-aspect ratio openings, reducing the number of deposition steps and enhancing the formation of three-dimensional memory device structures.
Implementation Method 1
Chemical etching of semiconductor wafers using wet etchants is commonly performed in the industry to remove various materials, or to etch the semiconductor wafer itself
Data Source
AI summary
Embodiments of an etching method for a material layer of a NAND memory device are disclosed. An example method of chemically etching a material layer on one or more substrates includes mixing an etchant solution within a bath and allowing the etchant solution to reach a quiescent state. After the etchant solution has reached the quiescent state, the method includes loading the one or more substrates into the bath. The one or more substrates includes a plurality of openings having the material layer disposed on an inside surface of the plurality of openings. The method also includes allowing the one or more substrates to remain in the bath for a predetermined time period, such that a thickness of the material layer is reduced by the etchant solution.