3D NAND Gate Stack Reinforcement Against Etch-Induced Deformation
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Solution Overview
Problem
Conventional semiconductor processing technologies face challenges in forming high-quality, reinforced semiconductor structures, particularly in 3D NAND fabrication, where dielectric layers are prone to deformation and thinning during wet etching due to surface tension effects, leading to pattern collapse and reduced structural integrity.
Innovation Solution
The method involves forming a composite film with a silicon nitride layer and amorphous silicon layers between silicon oxide layers, which enhances the Young's modulus and resistance to deformation, using a combination of wet and dry etching processes to maintain structural integrity and prevent thinning, and incorporating nitrogen doping and silicon-rich stoichiometry to improve the mechanical properties of the dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional wet etching is used to remove silicon nitride layers, then the etching process is simple and cost-effective, but the dielectric layers deform and thin due to surface tension effects
Solution Approach 1:
The patent divides the etching process into two separate stages: a first wet etching step that selectively removes silicon nitride while leaving dielectric layers intact, followed by a second etching step that completes the removal. This segmentation allows each step to be optimized independently, preventing deformation during the critical first removal phase while maintaining process simplicity.
Solution Approach 2:
The patent performs preliminary reinforcement of dielectric layers by forming additional dielectric material layers and performing pre-treatment processes before the main wet etching operation. This preliminary action strengthens the dielectric structure in advance, making it resistant to surface tension-induced deformation during subsequent etching.
2Productivity
If dielectric layers are made thinner to achieve higher device density, then device capacity increases, but structural integrity and resistance to deformation decrease
Solution Approach 1:
The patent creates composite dielectric structures by forming stacks of alternating dielectric layers and silicon layers. The silicon layers act as spacers and structural reinforcement elements, providing mechanical strength to the overall structure. This composite approach enables the use of thinner individual dielectric layers for higher density while the silicon framework maintains overall structural integrity.
Solution Approach 2:
The patent modifies the physical and chemical parameters of dielectric layers through nitrogen doping and controlling silicon-rich stoichiometry. These parameter changes enhance the mechanical properties of the dielectric material, increasing its resistance to deformation and improving structural integrity even at reduced thicknesses required for high-density devices.
3Strength
If multiple alternating layers of dielectric and silicon materials are formed to reinforce structure, then resistance to deformation improves, but process complexity increases
Solution Approach 1:
The patent designs the silicon layers to serve multiple functions simultaneously: they act as spacers defining aperture positions, as structural reinforcement preventing dielectric deformation, and as etch stop layers controlling the etching process. This multi-functionality reduces the need for separate dedicated structures, thereby limiting the increase in overall process complexity despite the added reinforcement layers.
4Manufacturing precision
If silicon nitride layer is removed by wet etch to improve selectivity, then etching precision improves, but dielectric layers are prone to thinning and collapse
Solution Approach 1:
The patent provides beforehand cushioning by forming additional dielectric material layers adjacent to and supporting the original dielectric layers before the wet etching process begins. These cushioning layers absorb the harmful surface tension effects during etching, preventing the original dielectric layers from thinning or collapsing while allowing the wet etch to proceed with high selectivity.
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 produces semiconductor structures with improved resistance to deformation and thinning, maintaining structural integrity during etching and enhancing the mechanical properties of dielectric layers, resulting in better film hardness and breakdown voltage.
Implementation Method 1
The silicon nitride layer may be removed by a wet etch process
Implementation Method 2
The first silicon layer and the second silicon layer may be removed by a dry etch process
Implementation Method 3
The second silicon layer and the second silicon oxide layer may form a composite film characterized by a Young's modulus of greater than or about 90 GPa
Implementation Method 4
incorporating nitrogen doping and silicon-rich stoichiometry to improve the mechanical properties of the dielectric layers
Data Source
AI summary
Exemplary methods of forming a semiconductor structure may include forming a first silicon oxide layer overlying a semiconductor substrate. The methods may include forming a first silicon layer overlying the first silicon oxide layer. The methods may include forming a silicon nitride layer overlying the first silicon layer. The methods may include forming a second silicon layer overlying the silicon nitride layer. The methods may include forming a second silicon oxide layer overlying the second silicon layer. The methods may include removing the silicon nitride layer. The methods may include removing the first silicon layer and the second silicon layer. The methods may include forming a metal layer between and contacting each of the first silicon oxide layer and the second silicon oxide layer.