Tungsten Composite Mask for High-Aspect-Ratio Memory Hole Etching
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Solution Overview
Problem
In three-dimensional memory manufacturing, high-aspect-ratio memory holes are challenging to form due to deformation and blocking of oxide masks during etching, which affects the precision and integrity of the memory cell patterns.
Innovation Solution
A method involving the use of a tungsten or tungsten compound film as a mask to prevent deformation by selectively forming it on the resist film and using a reducing gas to process the organic film, thereby maintaining the mask's integrity and preventing pattern blockage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an oxide mask is used for etching high-aspect-ratio memory holes, then the mask material is highly resistant to etching and can be made very thick, but the oxide mask gradually deforms due to ion collision during prolonged etching and blocks the memory hole pattern
Solution Approach 1:
The patent uses a composite mask structure consisting of a tungsten-containing film (such as tungsten nitride or tungsten carbide) combined with an organic mask material. The tungsten-containing layer provides high etching resistance while the organic material offers structural stability and resistance to ion-induced deformation, creating a mask that maintains both strength and compositional stability during prolonged etching processes
Solution Approach 2:
The patent changes the material composition parameter of the mask from pure oxide to a composite containing tungsten compounds. This parameter change increases the mask's resistance to ion collision damage while maintaining etching resistance, preventing the gradual deformation that occurs with traditional oxide masks during high-aspect-ratio hole formation
2Stability of the object's composition
If the film thickness of the mask is increased to maintain pattern integrity during etching, then the mask becomes more resistant to deformation, but the etching process becomes more complex and requires additional processing steps
Solution Approach 1:
The patent divides the mask into multiple functional layers: a tungsten-containing film layer providing etching resistance and a thinner organic mask layer providing pattern definition. This segmentation allows each layer to perform its specific function efficiently, maintaining pattern integrity without requiring excessive total thickness or complex multi-step processing
Solution Approach 2:
The tungsten-containing film acts as an intermediary layer between the etching environment and the organic mask material. It provides the necessary etching resistance to protect the underlying structure while allowing the organic layer to maintain the pattern definition, simplifying the overall process compared to using thick oxide masks
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 the precise formation of high-aspect-ratio memory holes without blockage, ensuring the intended pattern is maintained and enhancing the manufacturing process's reliability and efficiency.
Implementation Method 1
ions in the etching gas may collide with the oxide mask for a long period of time. This may gradually deform the oxide mask
Implementation Method 2
a lower portion of the film to be processed may be processed with a reducing gas using the tungsten or the tungsten compound as a second mask
Data Source
AI summary
A method for manufacturing a semiconductor device includes forming a resist film on a film to be processed. An upper portion of the film to be processed is processed using the resist film as a first mask. Tungsten or a tungsten compound is selectively formed on the resist film. A lower portion of the film to be processed is processed with a reducing gas using the tungsten or the tungsten compound as a second mask.