One-Molecular-Layer Protective Film Etching for High Aspect Ratio Patterns
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Solution Overview
Problem
Existing etching methods face challenges in forming patterns with high aspect ratios, as they often result in shape abnormalities like bowing and opening blockages due to the inability to accurately control the etching process, particularly in suppressing etching in the horizontal direction.
Innovation Solution
An etching method involving the formation of a protective film with a thickness corresponding to one molecular layer on the side walls of recesses using a first gas, followed by etching the target film with plasma from a second gas while maintaining the protective film on the side walls, and repeating this process to control the etching depth and prevent shape abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a protective film is formed on the opening side wall of the pattern to suppress etching in the horizontal direction, then shape abnormalities like bowing are suppressed, but opening blockages occur due to excessive protective film thickness
Solution Approach 1:
The patent changes the thickness parameter of the protective film from conventional multi-molecular layers to exactly one molecular layer (1 nm). This parameter change allows the film to provide sufficient protection against horizontal etching and bowing while being thin enough to prevent opening blockages, thus resolving the contradiction between shape accuracy and preventing harmful effects.
Solution Approach 2:
The patent employs periodic alternation between protective film formation and etching steps, repeating this cycle multiple times to achieve the desired etching depth. This periodic action allows precise control over both the protective film thickness and etching progression, preventing opening blockages while maintaining pattern shape accuracy throughout the multi-step process.
2Shape
If the protective film thickness is increased to suppress etching in the horizontal direction, then bowing is prevented, but the etching process becomes less precise due to reduced control over etching depth
Solution Approach 1:
The patent segments the etching process into multiple discrete cycles, each consisting of protective film formation followed by etching. By dividing the total etching depth into multiple small steps with one-molecular-layer protective films, the process achieves both side wall protection and precise depth control, as each segment contributes a controlled amount to the final etching depth.
Solution Approach 2:
The periodic repetition of thin protective film formation and etching steps enables precise cumulative control over etching depth. Each cycle adds a known, small amount of etching depth while maintaining side wall protection, allowing the total depth to be precisely controlled by the number of cycles performed.
3Productivity
If conventional etching methods are used without repeated protective film formation, then the etching process is simpler and faster, but shape abnormalities like bowing occur due to uncontrolled horizontal etching
Solution Approach 1:
The patent uses periodic formation of one-molecular-layer protective films during the etching process to continuously suppress horizontal etching and prevent bowing. The thin film thickness and periodic application maintain etching efficiency while ensuring shape accuracy throughout the etching process.
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 suppresses shape abnormalities and opening blockages by finely controlling the protective film thickness and etching rates, ensuring precise pattern formation without damaging the pattern side walls.
Implementation Method 1
a protective film having a thickness corresponding to one molecular layer is formed on a surface of the recess using a first gas
Implementation Method 2
the etching target film is etched with plasma generated from a second gas
Data Source
AI summary
An etching method includes: (a) etching a substrate including an etching target film and a mask formed on the etching target film to form a recess that reaches the etching target film; (b) forming a protective film having a thickness corresponding to one molecular layer on a surface of the recess using a first gas; (c) etching the etching target film with plasma generated from a second gas while leaving the protective film on a side wall of the recess; and (d) repeating (b) and (c).