Selective Silicon Deposition in 3D Memory via Surface Termination
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Solution Overview
Problem
Current methods for forming three-dimensional memory structures, such as vertical NAND strings, face challenges in selectively growing silicon-containing semiconductor materials while preventing deposition on certain dielectric surfaces, leading to inefficiencies in memory device fabrication.
Innovation Solution
A method involving the formation of -NH terminated and -OH terminated surfaces, followed by silylation to convert -OH terminated surfaces to -OSi(CH3)3 terminated surfaces, allowing selective growth of silicon-containing semiconductor materials on -NH terminated surfaces without deposition on -OSi(CH3)3 terminated surfaces, and converting outer portions of silicon-containing semiconductor portions into dielectric material portions for floating gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods are used to form silicon-containing semiconductor materials, then deposition occurs on all exposed surfaces including dielectric surfaces, but this leads to unwanted deposition on -OH terminated dielectric surfaces reducing manufacturing precision
Solution Approach 1:
The patent applies preliminary action by performing silylation treatment on -OH terminated dielectric surfaces before the silicon deposition step. This pre-treatment converts the dielectric surfaces to -OSi(CH3)3 terminated surfaces, which are rendered non-reactive to subsequent silicon-containing precursor gases, thereby preventing unwanted deposition and achieving selective growth only on -NH terminated memory film surfaces.
Solution Approach 2:
The patent changes the chemical state of the dielectric surface by converting -OH terminated surfaces to -OSi(CH3)3 terminated surfaces through silylation. This parameter change in surface chemistry creates a fundamental difference in reactivity between dielectric surfaces and memory film surfaces, enabling selective silicon deposition based on surface termination type rather than relying on complex deposition process control.
2Manufacturing precision
If selective growth control is achieved through surface termination differentiation, then deposition precision is improved, but additional processing steps are required increasing manufacturing complexity
Solution Approach 1:
The patent introduces silylation as an intermediary chemical process that mediates between the dielectric surface and the silicon deposition step. The silylation agent acts as a mediator that selectively modifies only the dielectric surfaces without affecting the memory film surfaces, creating a clear distinction that simplifies the subsequent deposition process by eliminating the need for complex selective deposition parameter optimization.
3Manufacturing precision
If outer portions of silicon-containing semiconductor portions are converted to dielectric material, then floating gate electrode structure is optimized, but additional processing steps increase fabrication complexity
Solution Approach 1:
The patent merges multiple functions into the silylation step: it not only prevents unwanted silicon deposition on dielectric surfaces during the deposition step, but also later enables selective conversion of outer silicon portions to dielectric material. This consolidation of functions reduces the total number of processing steps required to achieve both selective deposition and floating gate structure formation.
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 precise control over silicon growth, enhancing the fabrication efficiency of three-dimensional memory devices by preventing unwanted deposition and optimizing the structure of floating gate electrodes.
Implementation Method 1
The -NH terminated first dielectric surface and the -OH terminated second dielectric surface are exposed to a silylation agent containing an -Si(CH3) 3 group to convert the -OH terminated second dielectric surface to an -OSi(CH3) 3 terminated second dielectric surface
Implementation Method 2
A silicon-containing semiconductor material is selectively grown on the -NH terminated first dielectric surface while the silicon-containing semiconductor material is not deposited on the -OSi(CH3) 3 terminated second dielectric surface
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A method of forming a three-dimensional memory device includes forming a stack of alternating first (32) and second material layers over a substrate, forming a memory opening through the stack, forming a memory film (50') and a semiconductor channel (60) in the memory opening, and forming backside recesses by removing the second material layers selective to the first material layers and the memory film, where an outer sidewall of the memory film is physically exposed within each backside recess. The method optionally also includes forming at least one set of surfaces selected from silicon deposition inhibiting surfaces on the first material layers and silicon deposition promoting surfaces over the memory film in the back side recesses, selectively growing a silicon-containing semiconductor portion (52) laterally within each backside recess. Furthermore, the method comprises forming at least one blocking dielectric (53) within the backside recesses, and forming conductive material layers (46) by depositing a conductive material within the backside recesses.