Dry Etching Method for 3D Memory via NF3 and CH3F Gas Mixture
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Solution Overview
Problem
Conventional dry etching methods for three-dimensional memory structures face issues with side etching and scalloping shapes when processing high aspect ratio via layers, leading to differences in memory characteristics between upper and lower layers due to insufficient mask residual amounts and excessive fluorine-based gas compositions.
Innovation Solution
A dry etching method using a mixed gas of NF3 and CH3F, with adjustments in gas ratios and the addition of Ar and N2 gases, along with a time-modulated radio frequency bias, to suppress side etching and scalloping, while maintaining high selectivity and anisotropy, is employed to etch silicon-containing films and silicon dioxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mixed gas containing NF3 and CH2F2 is used for dry etching high aspect ratio structures, then the etching capability is improved, but side etching and scalloping occur due to excessive fluorine-based gas composition
Solution Approach 1:
The patent changes the gas composition parameters by replacing CH2F2 with CH3F and adding Ar and N2 gases to the etching mixture. This parameter adjustment reduces the fluorine-based gas composition while maintaining etching capability, thereby suppressing side etching and scalloping effects during high aspect ratio structure fabrication
Solution Approach 2:
The patent uses a composite gas system consisting of NF3, CH3F, Ar, and N2. This composite approach combines the etching effectiveness of fluorine-based gases with the benefits of inert Ar and N2 gases, achieving balanced etching performance with reduced harmful side effects compared to using only fluorine-based gases
2Productivity
If the mask residual amount is insufficient during etching, then the etching process speed is improved, but side etching occurs to the inorganic film
Solution Approach 1:
The patent adjusts gas flow ratios and plasma processing conditions to optimize the balance between etching speed and mask protection. By modifying the gas composition parameters (adding Ar and N2, changing CH2F2 to CH3F), the process maintains sufficient mask residual amount while achieving high etching speed without side etching
3Manufacturing precision
If a high aspect ratio via is vertically etched using taper shape widening, then the via formation is improved, but CD shift occurs between upper and lower layer parts
Solution Approach 1:
The patent changes gas composition parameters to achieve more uniform etching throughout the high aspect ratio via. By reducing fluorine-based gas composition and adding Ar and N2, the etching profile becomes more uniform from upper to lower layer parts, minimizing CD shift while maintaining via formation quality
Solution Approach 2:
The patent employs time-modulated radio frequency bias to create periodic action during etching. This periodic modulation helps maintain uniform etching conditions throughout the via depth, reducing CD variation between upper and lower layers while achieving vertical via 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
The method effectively reduces side etching and scalloping, improves mask selectivity, and minimizes CD shift, achieving a more uniform etching profile and enhanced memory characteristics by optimizing gas flow ratios and plasma processing conditions.
Implementation Method 1
a dry etching method for plasma etching an inorganic film for forming a hard mask and a plurality of pair layers
Implementation Method 2
etching the inorganic film and the second laminated film by a mixed gas of an NF3 gas and a CH3F gas
Data Source
AI summary
In the present invention, a dry etching method for plasma etching a second laminated film in which a first laminated film in which a silicon-containing film and a silicon dioxide film are laminated is laminated in plurality and an inorganic film arranged over the second laminated film, includes etching the inorganic film and the second laminated film by a mixed gas of an NF3 gas and a CH3F gas.