Semiconductor Stack Through-Hole Formation via Staged Etching
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Solution Overview
Problem
The complexity of forming through structures in semiconductor devices increases with the height of the stack structure, making the process complicated and prone to defects due to the need for multiple etching steps and precise layer formation.
Innovation Solution
A method is introduced where a first and second stack structure are formed with alternating material layers, preliminary holes or slits are created, and specific material layers are used to define air-gaps, allowing through holes or slits to be formed by penetrating from the second stack structure to the first, with distinct etching processes for each stack to prevent excessive extension and ensure etch margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of stacked conductive patterns and insulating patterns is increased to improve integration degree, then the integration degree of memory string is improved, but the height of stack structure increases and the process of forming through structure becomes complicated
Solution Approach 1:
The through structure formation process is divided into multiple stages: first forming preliminary holes through the second stack structure, then forming through holes connected to the preliminary holes. This segmentation reduces the complexity of forming a single deep through hole by breaking it into manageable steps with different etching conditions.
Solution Approach 2:
Preliminary holes are formed through the second stack structure before forming the complete through holes. This preliminary action prepares the path for subsequent through hole formation, allowing better control over etching depth and preventing excessive penetration into the first stack structure.
2Ease of manufacture
If etching process is performed to form through holes penetrating deep stack structures, then through structures are formed, but excessive extension and defects occur due to difficulty in controlling etch depth
Solution Approach 1:
Preliminary holes are formed through the second stack structure with controlled depth before forming the complete through holes. This preliminary etching step establishes a defined path and depth reference, preventing excessive penetration into the first stack structure and reducing defects.
Solution Approach 2:
The etching process is divided into two separate steps: first etching preliminary holes through the second stack structure, then etching through holes connected to these preliminary holes. This segmentation allows independent optimization of each etching step's depth and conditions, improving overall precision.
3Productivity
If single etching process is used to form through holes, then process steps are reduced, but uniformity of memory cell operation characteristics cannot be maintained
Solution Approach 1:
The etching process is divided into two distinct steps with different objectives: first forming preliminary holes through the second stack structure, then forming through holes connected to these preliminary holes. This segmentation enables better control over etch depth and uniformity, ensuring consistent memory cell operation characteristics.
Solution Approach 2:
Preliminary holes are formed as a preparatory step before completing the through holes. This preliminary action establishes a controlled path that guides subsequent etching, ensuring uniform depth and preventing variations that would affect memory cell operation consistency.
Data Source
AI summary
A method of manufacturing a semiconductor device includes forming on a lower structure, a first stack structure in which first material layers and second material layers are alternately stacked, forming, on the first stack structure, a second stack structure in which third material layers and fourth material layers are alternately stacked, forming preliminary holes penetrating the second stack structure, forming a fifth material layer covering the preliminary holes on the second stack structure to define a first air-gap inside the preliminary holes, and forming through holes connected to the preliminary holes by penetrating from the fifth material layer overlapping the preliminary holes to the first stack structure.