Plasma Etching Sidewall Verticality in Multilayer Films
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Solution Overview
Problem
Conventional plasma etching techniques in low-temperature environments often result in bending of holes or grooves in multilayered films composed of alternately stacked silicon oxide and silicon nitride films, leading to degradation of verticality.
Innovation Solution
A plasma etching method involving a two-step process: the first etching process uses a mixed gas containing H2, CH2F2, NF3, and HBr to etch the multilayered film, followed by a second etching process with a gas mixture including a hydrogen-containing gas, a fluorine-containing gas, and a rare gas, such as Ar, to reduce the inclination of the inner sidewall of the hole or groove, thereby suppressing bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching is performed in a low-temperature environment (0°C or less) to etch silicon oxide films, then etching capability is improved, but the inner sidewall of holes or grooves in multilayered films becomes inclined causing bending
Solution Approach 1:
The etching process is divided into multiple sequential etching steps, each with optimized processing conditions. The first etching step uses conditions optimized for silicon oxide etching, while subsequent steps use conditions optimized for maintaining vertical sidewalls in silicon nitride films, thereby resolving the contradiction between etching capability and shape precision
Solution Approach 2:
The processing conditions (gas composition, pressure, power, temperature) are changed between different etching steps. By adjusting these parameters, the etching process can achieve both high etching capability in the first step and vertical sidewall formation in subsequent steps, eliminating the bending problem
2Ease of manufacture
If a single etching process is used to etch multilayered films, then process simplicity is maintained, but bending of holes or grooves occurs due to incompatible etching conditions for different materials
Solution Approach 1:
The etching process is segmented into multiple steps with different processing conditions optimized for different material layers. This segmentation allows each step to be tailored for specific material characteristics, preventing bending while maintaining overall process control and simplicity
3Productivity
If etching conditions are optimized for silicon oxide films, then etching rate is improved, but silicon nitride film sidewalls become inclined
Solution Approach 1:
The etching process is divided into steps where the first step optimizes etching rate for silicon oxide films, and subsequent steps optimize sidewall verticality for silicon nitride films. This segmentation allows high productivity in the first step without compromising the shape quality in subsequent 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
The method effectively reduces the inclination of the inner sidewall of the hole or groove, thereby suppressing bending and maintaining the verticality of the etched features in the multilayered film.
Implementation Method 1
a first etching process of etching, by plasma, a multilayered film including silicon oxide films and silicon nitride films alternately stacked on top of each other
Data Source
AI summary
Bending of a hole or a groove formed in a multilayered film including silicon oxide films and silicon nitride films alternately stacked on top of each other is suppressed. A plasma etching method includes a first etching process of etching, by plasma, the multilayered film including the silicon oxide films and the silicon nitride films alternately stacked on top of each other; and a second etching process of etching, by plasma, the multilayered film under a processing condition that an inclination of a portion of an inner sidewall of the hole or the groove, which is formed by the etching of the multilayered film, corresponding to the silicon nitride film with respect to a depth direction of the hole or the groove is reduced.