Etching Method for 3D NAND Multilayered Films
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Solution Overview
Problem
In the manufacturing of NAND type flash memory devices with a three-dimensional structure, existing etching methods struggle to form spaces with desirable shapes in both regions with alternately stacked dielectric films and single-layered silicon oxide films while maintaining an optimal etching rate and preventing mask clogging.
Innovation Solution
An etching method involving two plasma processes is employed, where a first plasma process with a fluorocarbon and oxygen gas mixture at a higher temperature enhances etching of the silicon nitride films, and a second plasma process with hydrogen, nitrogen trifluoride, and carbon-containing gases at a lower temperature increases the etching rate of the silicon oxide films, maintaining mask openness and reducing depth differences between regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single plasma process is used to etch both the multilayered film region and the single-layered silicon oxide film region, then the process is simple, but it is impossible to form spaces with desirable shapes in both regions while maintaining optimal etching rates
Solution Approach 1:
The etching process is divided into two distinct plasma processes: a first plasma process for etching the silicon nitride films in the multilayered region, and a second plasma process for etching the silicon oxide films. This segmentation allows each process to be optimized for its specific target material, enabling precise control over the shape and depth of spaces formed in different regions while maintaining overall process efficiency
Solution Approach 2:
Different plasma conditions (gas composition, power, pressure, temperature) are applied to different regions of the processing target object. The first plasma process uses conditions optimized for silicon nitride etching in the multilayered film region, while the second plasma process uses conditions optimized for silicon oxide etching, achieving locally optimized etching quality in each region
2Productivity
If the etching process continues to increase etching rate, then productivity improves, but mask clogging occurs due to deposit adhesion
Solution Approach 1:
The etching process alternates between two plasma processes with different characteristics. The first plasma process etches silicon nitride at a certain rate, and the second plasma process etches silicon oxide while also serving to remove deposits from the mask openings. This periodic alternation maintains mask openness throughout the process, preventing clogging while achieving high overall etching rates
Solution Approach 2:
The second plasma process serves dual purposes: it continues the etching action on the silicon oxide films while simultaneously cleaning the mask openings by removing adhered deposits. This continuous dual-function action maintains productivity without interruption and prevents mask clogging that would otherwise require process interruption
3Reliability
If the temperature of the processing target object is increased to prevent mask clogging, then mask openness is maintained, but the etching rate of the first region decreases
Solution Approach 1:
The process uses different temperature parameters for different plasma processes. The first plasma process operates at a temperature optimized for silicon nitride etching rate, while the second plasma process operates at a temperature optimized for both silicon oxide etching and deposit removal from the mask. This parameter optimization for each specific process maintains high etching rates while preventing mask clogging
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 method effectively forms spaces with desirable shapes in both regions while suppressing etching rate decrease and mask clogging, improving throughput by allowing consecutive plasma processes without gas substitution.
Implementation Method 1
mounting the processing target object on an electrostatic chuck provided within a processing vessel of a plasma processing apparatus
Implementation Method 2
generating plasma of a first processing gas containing a fluorocarbon gas and an oxygen gas within the processing vessel
Implementation Method 3
The etching by the plasma of the first processing gas is characterized in that an etching rate of the second region is higher than an etching rate of the first region
Data Source
AI summary
A method of etching a first region including a multilayered film, in which first dielectric films and second dielectric films serving as silicon nitride films are alternately stacked, and a second region including a single-layered silicon oxide film is provided. The etching method includes a first plasma process of generating plasma of a first processing gas containing a fluorocarbon gas and an oxygen gas within a processing vessel of a plasma processing apparatus; and a second plasma process of generating plasma of a second processing gas containing a hydrogen gas, nitrogen trifluoride gas and a carbon-containing gas within the processing vessel. A temperature of an electrostatic chuck is set to a first temperature in the first plasma process, and the temperature of the electrostatic chuck is set to a second temperature lower than the first temperature in the second plasma process.