Silicon Etching via Hydrogen Halide and Fluorine Gas Cycling
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Solution Overview
Problem
Conventional etching methods for silicon substrates, particularly for forming high aspect ratio trenches or via holes, result in irregular sidewalls and damage to protective films due to isotropic etching and fluorine radical movement, making it difficult to achieve desired shapes and aspect ratios.
Innovation Solution
A method involving alternating steps of hydrogen halide-containing gas etching, fluorine-containing gas etching, protective film formation, and protective film removal, using a plasma etching apparatus to control the etching process, allowing for anisotropic etching and protection of sidewalls, thereby enabling the formation of trenches or via holes with desired shapes and aspect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorine-containing gas-based etching is performed to etch silicon substrate, then etching speed is improved, but sidewall irregularities occur and protective film damage happens
Solution Approach 1:
The patent changes the chemical parameters of the etching process by switching between fluorine-containing gas (high etching speed) and hydrogen halide-containing gas (smooth sidewalls). This parameter switching allows the system to achieve both high productivity and high precision at different stages of the etching process
Solution Approach 2:
The patent employs periodic alternation between fluorine-containing gas etching and hydrogen halide-containing gas etching. This periodic action allows the process to periodically remove material at high speed while periodically smoothing the sidewalls, thereby achieving both high etching speed and smooth sidewall profiles
2Manufacturing precision
If protective film is formed on sidewalls to prevent etching, then sidewall protection is improved, but etching process complexity increases
Solution Approach 1:
The patent extracts the protective function from a separate protective film formation step and integrates it into the etching process itself by using hydrogen halide-containing gas to smoothly etch the sidewalls. This eliminates the need for separate protective film deposition and removal steps, thereby reducing process complexity while maintaining sidewall protection
Solution Approach 2:
The etching process itself provides the protective function by using hydrogen halide-containing gas to smoothly etch the sidewalls during the fluorine-containing gas etching process. The process serves its own protection need without requiring external protective films, thereby simplifying the overall process
3Productivity
If fluorine radicals are used for etching, then etching efficiency is improved, but protective film damage occurs due to radical movement
Solution Approach 1:
The patent changes the chemical environment by introducing hydrogen halide-containing gas that reacts with mobile fluorine radicals to form less mobile hydrogen fluoride molecules. This parameter change maintains etching efficiency while protecting the protective film from damage by reducing radical mobility
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 trenches or via holes with desired shapes and aspect ratios by reducing sidewall irregularities and protecting the protective film, allowing for precise and efficient etching of silicon substrates with reduced step complexity.
Implementation Method 1
a plasma is generated in a processing chamber to etch a to-be-processed object made of silicon
Implementation Method 2
the silicon substrate is etched using fluorine radicals produced by forming a plasma of a fluorine-containing gas
Implementation Method 3
forming a protective film on the to-be-processed object by sputtering a solid material disposed to face the to-be-processed object
Implementation Method 4
removing part of the protective film by applying radio frequency bias power to the substrate electrode
Data Source
AI summary
There is provided an etching method which can form trenches or via holes having desired aspect ratios and shapes in a to-be-processed object made of silicon. The etching method includes: a hydrogen halide-containing gas-based etching step of etching a silicon substrate by introducing a hydrogen halide-containing gas into a vacuum chamber; a fluorine-containing gas-based etching step of etching the silicon substrate by introducing a fluorine-containing gas into the vacuum chamber; a protective film formation step forming a protective film on the silicon substrate by sputtering a solid material; and a protective film removal step of removing part of the protective film by applying radio frequency bias power to a substrate electrode. The fluorine-containing gas-based etching step, the protective film formation step, and the protective film removal step are repeatedly performed in this order.