Semiconductor Memory Hole Formation Using Sidewall Film Masks
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Solution Overview
Problem
In the miniaturization of semiconductor devices, there is a significant challenge in maintaining uniformity in the diameter and shape of memory holes, which affects the performance and reliability of semiconductor memory devices, particularly due to variations in the manufacturing process.
Innovation Solution
A method involving the formation of columnar masks, followed by the deposition of a sidewall film and subsequent etching processes, allows for the creation of memory holes with uniform diameters smaller than the resolution limit of photolithography, using a combination of hard masks and isotropic/anisotropic etching techniques to control hole dimensions and shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography is used to form holes, then manufacturing process is simple, but hole diameter uniformity deteriorates when miniaturizing
Solution Approach 1:
The manufacturing process is divided into multiple stages: first forming columnar masks with initial holes, then forming sidewall films on the masks, removing the masks, and finally forming holes using the sidewall films as new masks. This segmentation allows each stage to optimize for its specific function, achieving uniform hole diameters that would be impossible in a single photolithography step.
Solution Approach 2:
Sidewall films serve as intermediary structures between the columnar masks and the final holes. The sidewall films are formed on the masks, then the masks are removed, leaving the sidewall films as self-aligned masks that define the final hole positions and dimensions with high precision.
2Manufacturing precision
If hole diameter is reduced for miniaturization, then device density improves, but variation in hole diameter becomes remarkable
Solution Approach 1:
Columnar masks are formed first with precise dimensions before the actual holes are created. These masks serve as templates that pre-determine the position and spacing of holes. The sidewall films are then formed on these pre-positioned masks, ensuring that when the masks are removed, the holes will be formed with controlled dimensions and minimal variation.
Solution Approach 2:
The process transforms the problem from directly forming holes with photolithography to forming sidewall films with controlled thickness parameters. The sidewall film thickness, controlled by deposition conditions, directly determines the final hole diameter, providing a more controllable parameter for achieving uniform small-hole dimensions.
3Manufacturing precision
If advanced lithography like EUV is used, then hole diameter uniformity improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces the need for advanced photolithography systems (mechanical/optical systems like EUV) with a chemical vapor deposition process to form sidewall films. This substitution uses simpler, more cost-effective equipment while achieving comparable or superior hole uniformity through the self-aligned nature of the sidewall film formation.
Solution Approach 2:
Columnar masks are used as disposable temporary structures that are formed, used to define hole positions, and then removed. These masks don't need to be perfectly durable since they serve their purpose and are discarded, allowing the use of simpler mask materials and formation processes rather than requiring expensive, highly precise lithography equipment.
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 memory holes with consistent dimensions and shapes, reducing variations and improving the manufacturing process efficiency, allowing for the production of semiconductor memory devices with finer pitches without requiring advanced techniques like EUV lithography, while maintaining cost-effectiveness.
Implementation Method 1
a sidewall film is formed on a sidewall of the columnar masks
Implementation Method 2
Anisotropic etching is conducted to remove the deposition layer in the opening
Data Source
AI summary
In this embodiment, a mask material is formed above a film to be processed, and a plurality of sacrifice films are formed above the mask material, each of the sacrifice films having a columnar shape. Then, a sidewall film is formed on a sidewall of the sacrifice films, and then the sacrifice films are removed. Thereafter, the sidewall films are caused to flow. In addition, a plurality of holes are formed in the mask material using the sidewall film as a mask. Then, isotropic etching is performed for the mask material to etch back the sidewall of the mask material with respect to a sidewall of the sidewall film by a first distance. Thereafter, a deposition layer is deposited inside the plurality of holes to close an opening of the plurality of holes with the deposition layer. Anisotropic etching is conducted to remove the deposition layer in the opening.