Microstructure HF Vapor Etching With Residue Removal
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Solution Overview
Problem
Existing methods of etching silicon dioxide using hydrogen fluoride (HF) vapour in microstructure manufacturing leave behind undesirable residual layers, particularly impurities like silicon, carbon, and ammonium salt, which are not effectively addressed in current techniques.
Innovation Solution
A method involving the use of HF vapour etching followed by sequential or concurrent removal of residual layers using gases like hydrogen, oxygen, fluorine, or heating, along with vacuum pumping to eliminate impurities such as silicon, carbon, and ammonium salt, ensuring minimal residue formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HF vapour etching is used to remove silicon dioxide sacrificial layer, then the sacrificial layer is effectively removed, but residual layers containing impurities (silicon, carbon, ammonium salt) remain on the microstructure surfaces
Solution Approach 1:
The patent divides the etching process into multiple sequential stages: first HF vapour etching to remove the silicon dioxide sacrificial layer, then subsequent cleaning stages using oxygen plasma and/or hydrogen fluoride vapour to remove residual layers. This segmentation allows each stage to target specific contaminants without affecting the previously removed sacrificial layer.
Solution Approach 2:
The patent introduces intermediary cleaning agents (oxygen plasma and hydrogen fluoride vapour) that act as mediators between the HF etching process and the final clean microstructure. These intermediaries selectively react with residual impurities (carbon, silicon, ammonium salt) without significantly affecting the released microstructure, thereby eliminating harmful residues.
2Object-generated harmful factors
If additional cleaning steps are added to remove residual layers, then residual layer formation is reduced, but process complexity increases
Solution Approach 1:
The patent combines multiple cleaning functions into a unified process sequence that can be implemented in a single vacuum chamber. The HF vapour etching and subsequent cleaning steps (oxygen plasma, hydrogen fluoride vapour) are merged into one continuous process flow, eliminating the need for separate chambers or complex transfer mechanisms while effectively removing all types of residues.
Solution Approach 2:
The patent utilizes parameter changes (temperature, pressure, gas flow rates) to optimize each cleaning stage. By carefully controlling these parameters, the process achieves effective residual layer removal without requiring additional equipment or complex process steps, thereby managing complexity while maintaining high cleaning efficiency.
3Object-generated harmful factors
If multiple gases (hydrogen, oxygen, fluorine) are used for residual layer removal, then residual layer formation is reduced, but process time increases
Solution Approach 1:
The patent employs periodic action by applying different gases in sequential pulses rather than continuous exposure. Each gas (oxygen, hydrogen fluoride) is applied for a specific duration optimized for its particular cleaning function, then switched to the next gas. This periodic application removes residues efficiently while minimizing total process time compared to prolonged exposure to a single gas.
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 residual layers, particularly silicon-based residues, by employing controlled gas reactions and vacuum pumping, resulting in higher-quality microstructures with reduced impurities.
Implementation Method 1
An HF vapour etch is a plasma-less chemical etch and is described by the reaction equations: SiO2 + 4HF → SiF4 + 2H2O
Implementation Method 2
for HF vapour etching to proceed, with a usable etch rate, say greater than 30 nm/min, a condensed fluid layer 5 is required to be present on the surface to be etched
Implementation Method 3
removing a residual layer comprising silicon formed when HF vapour etching the layer of silicon dioxide
Implementation Method 4
removing a residual layer comprising carbon formed when HF vapour etching the layer of silicon dioxide
Implementation Method 5
employing a hydrogen fluoride (HF) vapour to etch a sacrificial layer of silicon dioxide (SiO2) and removing a residual layer
Data Source
AI summary
There is provided a method of producing a microstructure that comprises employing a hydrogen fluoride (HF) vapour to etch a sacrificial layer of silicon dioxide (SiO2) and thereafter removing a residual layer formed when HF vapour etching the layer of silicon dioxide. The residual layer may comprise silicon, ammonium salt or carbon and various techniques are disclosed for removing such layers. These techniques may be applied concurrently, or sequentially, to the microstructure. The described methodologies therefore produce microstructures that exhibits reduced levels of residue when as compared to those techniques known in the art.