HF Plasma Etching of Silicon-Containing Films With Low-Temperature Selectivity
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Solution Overview
Problem
Existing plasma etching methods face challenges in achieving selectivity when etching silicon-containing films compared to masks, particularly with silicon oxide films and masks containing amorphous carbon or organic polymers, as they often result in inadequate differentiation between the etching rates of the film and the mask.
Innovation Solution
A substrate processing method involving a plasma processing apparatus that controls the substrate temperature to 0 °C or lower and uses a first process gas with hydrogen fluoride gas having the highest flow rate, along with carbon-containing gases like fluorocarbon or hydrofluorocarbon gases, to enhance the selectivity of silicon-containing film etching over mask etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching methods are used with hydrocarbon and hydrofluorocarbon gases, then etching of silicon-containing films can be achieved, but selectivity between film etching and mask etching is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the process gas by introducing hydrogen fluoride gas (HF) as a key component. This parameter change transforms the etching chemistry to achieve high selectivity: HF reacts specifically with silicon oxide in the film while carbon-containing masks are resistant to HF-based etching, thereby resolving the selectivity contradiction without sacrificing etching rate
Solution Approach 2:
The patent uses a composite process gas system combining hydrogen fluoride gas with carbon-containing gases (fluorocarbon or hydrofluorocarbon). This composite approach creates a synergistic effect where HF provides selective silicon oxide etching capability while the carbon-containing component contributes to overall etching progress, achieving both high selectivity and maintained productivity
2Manufacturing precision
If substrate temperature is not controlled to low temperatures, then processing efficiency is maintained, but selectivity in etching silicon-containing films over masks deteriorates
Solution Approach 1:
The patent introduces temperature as a critical control parameter, specifying substrate temperature should be 0°C or lower. This parameter change exploits the temperature-dependent reactivity differences between silicon oxide and carbon-containing materials in HF-based plasma, enhancing selectivity. The temperature control requirement, while adding device complexity, is essential for achieving the desired etching selectivity
3Manufacturing precision
If hydrogen fluoride gas is used with highest flow rate among non-inert components, then selectivity is improved, but process gas complexity increases
Solution Approach 1:
The patent specifies that hydrogen fluoride gas should have the highest flow rate among all non-inert gas components in the process mixture. This parameter specification ensures sufficient HF concentration at the substrate surface to drive selective silicon oxide etching. The gas flow control system must be configured to maintain this priority flow rate relationship, adding control complexity but ensuring consistent selectivity performance
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 approach significantly improves the selectivity of silicon-containing film etching over mask etching, allowing for higher etching rates of the film while minimizing mask etching, which is crucial for manufacturing complex structures like NAND flash memory with three-dimensional structures, and reduces chamber cleaning time and deposition gas usage.
Implementation Method 1
etching the silicon-containing film with plasma generated from a first process gas containing a hydrogen fluoride gas and at least one carbon-containing gas
Implementation Method 2
etching the silicon-containing film with a chemical species contained in the plasma
Implementation Method 3
controlling a temperature of a substrate support on which the substrate is placed to 0 °C or lower
Data Source
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AI summary
A technique improves selectivity in etching of a silicon-containing film over etching of a mask in plasma etching. A substrate processing method includes providing a substrate in a chamber in a plasma processing apparatus. The substrate includes a silicon-containing film and a mask on the silicon-containing film. The substrate processing method further includes controlling a temperature of a substrate support on which the substrate is placed to 0 °C or lower. The substrate processing method further includes etching the silicon-containing film with plasma generated from a first process gas containing a hydrogen fluoride gas and at least one carbon-containing gas selected from the group consisting of a fluorocarbon gas and a hydrofluorocarbon gas. The etching includes etching the film with a chemical species contained in the plasma. The hydrogen fluoride gas has a highest flow rate among non-inert components of the first process gas.