Nanocrystalline Diamond Hard Mask for Smooth High-Selectivity Etching
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Solution Overview
Problem
Current hard mask films used in 3D NAND technology, such as amorphous carbon, face issues with delamination, poor morphology, and increased opacity with thickness, leading to pillar striations and other manufacturing challenges due to high surface roughness and low etch selectivity.
Innovation Solution
The use of nanocrystalline diamond films with two distinct processing recipes to achieve high hardness and modulus while maintaining low surface roughness, either by cycling the recipes or exposing the first nanocrystalline diamond layer to inert gas plasma, resulting in films with high etch selectivity and reduced stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nanocrystalline diamond is used as hard mask film, then hardness and modulus are improved, but surface roughness increases
Solution Approach 1:
The patent divides the hard mask film into two distinct nanocrystalline diamond layers with different properties. The first layer (higher roughness) provides the required thickness and etch selectivity, while the second layer (lower roughness) provides the smooth surface needed for subsequent processing. This segmentation allows each layer to optimize for its specific function rather than requiring a single layer to satisfy all contradictory requirements.
Solution Approach 2:
The patent applies local quality by creating two layers with deliberately different surface characteristics. The bottom layer has higher roughness optimized for etch selectivity and thickness, while the top layer has lower roughness optimized for surface quality. Each layer's properties are locally optimized for its specific role in the overall hard mask function.
2Ease of manufacture
If amorphous carbon is used as hard mask film, then ease of manufacture is improved, but etch selectivity and hardness are reduced
Solution Approach 1:
The patent changes the material parameter from amorphous carbon to nanocrystalline diamond, which fundamentally alters the etch selectivity and hardness properties. The nanocrystalline diamond structure provides superior etch resistance and mechanical properties compared to amorphous carbon, while the two-layer configuration maintains manufacturability by using standard PECVD processes with optimized recipes.
3Manufacturing precision
If hard mask film thickness is increased to control slit etch profile, then etch profile control is improved, but photo alignment precision deteriorates due to increased opacity
Solution Approach 1:
The patent segments the thick hard mask requirement into two layers: the first layer provides the necessary thickness for etch profile control, while the second thinner layer maintains optical transparency for photo alignment. This segmentation allows the structure to satisfy both the mechanical requirement (thickness for etch control) and the optical requirement (transparency for alignment).
Solution Approach 2:
The patent applies local quality by concentrating the thickness requirement in the bottom layer where it serves the etch profile control function, while the top layer maintains lower thickness and higher transparency for photo alignment. Each layer's local properties are optimized for its specific function rather than uniformly distributing all properties throughout the entire film thickness.
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 nanocrystalline diamond films provide improved etch selectivity, reduced surface roughness, and enhanced mechanical properties, addressing the limitations of traditional hard mask films and enabling more precise and durable semiconductor manufacturing processes.
Implementation Method 1
exposing the first nanocrystalline diamond layer to an inert gas plasma to form a smooth nanocrystalline diamond layer
Implementation Method 2
depositing a first nanocrystalline diamond layer on a substrate
Implementation Method 3
Current hard mask films include pure or doped plasma enhanced chemical vapor deposition (PECVD) amorphous carbon (aC:H) based films
Data Source
AI summary
Methods to manufacture integrated circuits are described. Nanocrystalline diamond is used as a hard mask in place of amorphous carbon. Provided is a method of processing a substrate in which nanocrystalline diamond is used as a hard mask, wherein processing methods result in a smooth surface. The method involves two processing parts. Two separate nanocrystalline diamond recipes are combined—the first and second recipes are cycled to achieve a nanocrystalline diamond hard mask having high hardness, high modulus, and a smooth surface. In other embodiments, the first recipe is followed by an inert gas plasma smoothening process and then the first recipe is cycled to achieve a high hardness, a high modulus, and a smooth surface.