3D Memory Device Silicon Protection Layer Etching
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Solution Overview
Problem
NAND flash memory devices face challenges in the integration and performance due to damage from etching solutions during the removal of silicon nitride sacrificial layers, which affects the charge storage layer.
Innovation Solution
A method is developed to form a three-dimensional memory device by using silicon protection layers between the charge storage layer and sacrificial layers, which protects the charge storage layer from phosphoric acid-based etching solutions, employing selective chemical vapor deposition to form silicon protection layers with curved surfaces and specific thicknesses, and replacing sacrificial layers with electrode layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphoric acid-based etching solution is used to remove silicon nitride sacrificial layers, then the sacrificial layers are effectively removed, but the charge storage layer is damaged
Solution Approach 1:
A silicon protection layer is introduced as an intermediary between the phosphoric acid etching solution and the charge storage layer. This protection layer is selectively removed after serving its protective function, allowing the etching solution to access and remove the sacrificial layers without damaging the charge storage layer directly
Solution Approach 2:
The silicon protection layer is formed on the charge storage layer before the phosphoric acid etching process. This preliminary protective action ensures that the charge storage layer is shielded during the subsequent sacrificial layer removal, preventing damage before it can occur
2Reliability
If protection layers are added between charge storage layer and sacrificial layers, then the charge storage layer is protected from etching damage, but the device structure becomes more complex
Solution Approach 1:
The silicon protection layer is designed as a temporary structure that is discarded after serving its protective purpose. It is selectively removed in a subsequent etching step using ammonium hydroxide, leaving no permanent residue and restoring the original structure without the protection layer
Solution Approach 2:
The protection layer utilizes selective etching parameters - it is resistant to phosphoric acid (protecting the charge storage layer during that process) but susceptible to ammonium hydroxide (allowing easy removal later). This parameter-based differentiation enables the protection function without permanent structural complexity
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
The silicon protection layers effectively prevent damage to the charge storage layer during etching, enhancing the performance and reliability of the three-dimensional memory device by maintaining the integrity of the charge storage layer.
Implementation Method 1
the protection layers are formed on surfaces of the sacrificial layers exposed by a sidewall of the first opening... effectively prevent damage to the charge storage layer during etching
Implementation Method 2
the step of forming the protection layers includes performing a selective chemical vapour deposition process... a reaction gas includes silane
Data Source
AI summary
A method of forming a three-dimensional memory device is provided. Insulating layers and sacrificial layers are stacked alternatively on a substrate. At least one first opening is formed through the insulating layers and the sacrificial layers. Protection layers are formed on surfaces of the sacrificial layers exposed by the sidewall of the first opening. A charge storage layer is formed on the sidewall of the first opening and covers the protection layers. A channel layer is formed on the charge storage layer. The sacrificial layers and the protection layers are replaced with electrode layers. A three-dimensional memory device is further provided.