3D Memory Contact Via Etch Control Using Sacrificial Metal Plates
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Solution Overview
Problem
The increasing number of electrically conductive layers in three-dimensional memory devices poses challenges in forming contact via structures, leading to increased depth variations in via cavities, higher probabilities of etch-through and electrical shorts, and incomplete via etches, which complicates the manufacturing process and increases costs.
Innovation Solution
The use of sacrificial metal plates in the staircase region during the formation of contact via structures helps reduce or prevent overetch or underetch, allowing for the formation of all contact via structures in a single via etch and fill process by acting as etch stop structures and ensuring complete contact with electrically conductive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of electrically conductive layers is increased to achieve higher storage density, then storage capacity is improved, but depth variations in via cavities increase and manufacturing complexity increases
Solution Approach 1:
Sacrificial metal plates are formed in advance at the staircase region before via etching. These pre-positioned plates serve as etch stop structures that define the etching depth, allowing consistent via formation across multiple conductive layers without increasing manufacturing complexity
Solution Approach 2:
Sacrificial metal plates act as intermediary structures between the etching process and the final contact via structures. They temporarily exist during manufacturing to control etch depth, then are removed after serving their purpose, enabling precise via formation without affecting the final device complexity
2Ease of manufacture
If conventional via etching is used without etch stop structures, then processing is simpler, but overetch or underetch occurs leading to electrical shorts or incomplete via formation
Solution Approach 1:
Sacrificial metal plates serve as intermediary etch stop structures that mediate between the etching process and the underlying layers. They provide precise depth control during etching, preventing both overetch (which causes shorts) and underetch (which causes incomplete vias), while maintaining processing simplicity through a single etch process
Solution Approach 2:
The sacrificial metal plates are temporary, disposable structures used only during the via formation process. They are removed after serving their etch stop function, having fulfilled their purpose without needing to persist in the final device, thus enabling precision without permanent complexity
3Reliability
If multiple via etch and fill processes are used to ensure complete contact, then via formation reliability is improved, but processing time and cost increase
Solution Approach 1:
Sacrificial metal plates are pre-formed at the staircase region before the via etching process. This preliminary action establishes the etch depth reference in advance, enabling a single etch process to achieve complete contact with all target conductive layers reliably, eliminating the need for multiple iterative etch and fill cycles
Solution Approach 2:
The invention merges multiple via formation operations into a single etch and fill process. By combining the depth-control function (previously requiring separate steps) with the via formation step through the use of sacrificial plates, the process achieves the same reliability as multiple processes but in one operation, reducing time and cost
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 enables the formation of reliable contact via structures with reduced processing complexity and cost, minimizing the risk of electrical shorts and ensuring complete via formation, thereby improving the manufacturing efficiency of three-dimensional memory devices.
Implementation Method 1
forming a first contact via cavities through the first retro-stepped dielectric material portion employing the sacrificial metal plates as etch stop structures
Data Source
AI summary
An alternating stack of insulating layers and sacrificial material layers is formed with stepped surfaces. Sacrificial metal plates are formed on the top surfaces of the sacrificial material layers, and a retro-stepped dielectric material portion is formed over the sacrificial metal plates. Contact via cavities are formed through the retro-stepped dielectric material portion employing the sacrificial metal plates as etch stop structures. The sacrificial metal plates are replaced with portions of insulating spacer layers. Sacrificial via fill structures within remaining volumes of the contact via cavities. The sacrificial material layers are replaced with electrically conductive layers. The sacrificial via fill structures are replaced with portions of staircase-region contact via structures that contact the electrically conductive layers.