Ion-Implanted Cladding Mask for High-Aspect-Ratio NAND Openings
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Solution Overview
Problem
Existing methods struggle to efficiently create high aspect ratio openings in semiconductor devices, particularly in three-dimensional vertical NAND strings, due to limitations in patterning and etching processes.
Innovation Solution
A method involving an ion implanted, regrown cladding mask is used, where an alternating stack of material layers is formed over a substrate, followed by an etch mask layer, anisotropic deposition of a cladding material, and iterative etching processes to vertically extend openings, utilizing an integrated processing apparatus with multiple etch and deposition chambers to maintain vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to create high aspect ratio openings, then the openings can be formed, but the etch rate varies significantly leading to poor manufacturing precision
Solution Approach 1:
A cladding material layer is introduced as an intermediary between the etch mask and the alternating stack. This cladding layer has tailored etch selectivity that enables controlled anisotropic etching, allowing the etch process to proceed vertically through the alternating stack while maintaining consistent etch rates and preventing lateral erosion, thus improving manufacturing precision without excessive process complexity
Solution Approach 2:
The etch selectivity parameters are optimized by selecting specific cladding materials (such as silicon nitride or silicon oxide) with known etch rate ratios relative to the alternating stack materials. By controlling the thickness and composition of the cladding layer, the etch process parameters are tuned to achieve the desired high aspect ratio openings with precise dimensional control
2Manufacturing precision
If the etch mask material layer is used directly without additional cladding, then the process is simpler, but the structural integrity and precision of high aspect ratio openings deteriorates
Solution Approach 1:
The cladding material layer serves as a protective intermediary that conforms to the etch mask layer and provides mechanical support during the etching of high aspect ratio openings. This additional layer prevents mask erosion and maintains opening geometry, improving manufacturing precision while adding only one more deposition step to the process
Solution Approach 2:
The cladding material layer is deposited in advance before the anisotropic etching process. This preliminary action prepares a protective structure that will maintain its integrity during the etching process, ensuring that the openings are formed with the desired high aspect ratio and precise dimensions before any etching begins
3Length of moving object
If multiple etching steps are performed to create deep openings, then the openings reach the required depth, but the process time increases significantly
Solution Approach 1:
The cladding material layer acts as a guide and protective structure that enables a single continuous anisotropic etching step to reach the required depth. By preventing lateral erosion and maintaining vertical etch front stability, the cladding layer allows the etch process to proceed efficiently through the entire depth of the alternating stack in one operation, reducing total process time compared to multiple incremental etching steps
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 the formation of high aspect ratio openings with precise control, enhancing the manufacturing process for semiconductor devices like three-dimensional memory arrays by reducing etch rate variations and improving structural integrity.
Implementation Method 1
anisotropically depositing a cladding material on the etch mask material layer to form a cladding material layer
Implementation Method 2
ion implanting dopant atoms into the cladding material layer, and vertically extending the openings downward in the alternating stack by performing a second anisotropic etch process. The dopant atoms decrease an etch rate of the cladding material layer during the second anisotropic etch process
Implementation Method 3
performing a first anisotropic etch process that transfers a pattern in the etch mask material layer through a first subset of layers within the alternating stack
Data Source
AI summary
A method of patterning a structure includes forming an alternating stack of first material layers and second material layers over a substrate, forming an etch mask material layer over the alternating stack, forming openings in an upper portion of the alternating stack by performing a first anisotropic etch process that transfers a pattern in the etch mask material layer through a first subset of layers within the alternating stack, anisotropically depositing a cladding material on the etch mask material layer to form a cladding material layer, ion implanting dopant atoms into the cladding material layer, and vertically extending the openings downward in the alternating stack by performing a second anisotropic etch process. The dopant atoms decrease an etch rate of the cladding material layer during the second anisotropic etch process.