Selective Etch Using XeF2 and CF3I Gas Mixture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for selectively etching materials in semiconductor manufacturing, such as electron beam etching, face challenges in achieving precise control over etch rates and material selectivity, particularly when dealing with similar materials like oxides and nitrides, leading to inadequate visualization of layer boundaries and potential damage to silicon features.
Innovation Solution
A method using a focused beam, such as an electron beam, ion beam, or laser beam, that employs competing reactions between etchant precursor gases and auxiliary gases to selectively etch one material over another, minimizing damage and allowing precise control over the etching process, particularly by using a combination of gases like XeF2 and CF3I to preferentially etch silicon dioxide while preserving silicon and nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If XeF2 is used for electron beam etching of SiO2, then etching capability is improved, but silicon etching damage increases due to higher spontaneous etch rate
Solution Approach 1:
The patent introduces CF3I as an intermediary gas that mediates between XeF2 and silicon. CF3I forms a protective carbon-containing film on silicon surfaces that suppresses spontaneous etching by XeF2, while allowing electron beam-induced etching of SiO2 to proceed. This intermediary layer acts as a selective barrier that protects silicon from harmful spontaneous etching while permitting controlled etching of the target oxide material.
Solution Approach 2:
The patent changes the chemical parameters of the etching environment by introducing CF3I gas alongside XeF2. This alters the surface chemistry of silicon, creating a protective carbonaceous layer that changes the etching kinetics. The parameter change transforms the spontaneous etching reaction into a controlled, beam-induced process with suppressed background etching rates.
2Measurement precision
If electron beam etching is used to make interfaces visible, then boundary visualization is improved, but selectivity between similar materials like oxides and nitrides deteriorates
Solution Approach 1:
CF3I serves as a selective intermediary that differentially interacts with oxide and nitride surfaces. The gas forms protective films at different rates on different materials, creating selective etching behavior. This allows the electron beam to differentiate between similar materials by exploiting the different kinetics of CF3I film formation and decomposition on oxide versus nitride surfaces.
Solution Approach 2:
The introduction of CF3I changes the chemical reactivity parameters of the etching system. Different materials exhibit different reactivity toward CF3I, creating variations in etch rates that enhance contrast between similar materials. This parameter change enables differentiation of materials that would otherwise etch at similar rates with XeF2 alone.
3Productivity
If high etch rates are used for decoration, then processing speed is improved, but control over etch depth deteriorates
Solution Approach 1:
The electron beam operates in a periodic scanning pattern, delivering energy in discrete pulses as it scans across the surface. This periodic energy delivery allows the etching process to proceed in controlled increments, with each beam pass removing a small, predictable amount of material. The periodic nature of beam exposure provides inherent control over etch depth while maintaining reasonable processing speed.
Solution Approach 2:
The patent changes the etching kinetics by introducing CF3I, which creates a more gradual and controllable etching process. The chemical interactions between CF3I, XeF2, and the substrate create a self-regulating etch rate that responds to beam parameters. This parameter change allows for precise depth control while maintaining adequate processing efficiency.
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 enables precise and controlled selective etching, reducing damage to the substrate and improving the visibility of layer boundaries, allowing for accurate delineation of integrated circuit layers with low etch rates and minimal material alteration.
Implementation Method 1
electron beam-induced etching of silicon dioxide (SiO2)
Implementation Method 2
physical sputter damage is eliminated
Implementation Method 3
laser beam
Implementation Method 4
competing reactions, both beam-induced reactions and spontaneous reactions
Implementation Method 5
combination of gases like XeF2 and CF3I
Implementation Method 6
scanning electron microscope forms an image by collecting secondary electrons that are emitted from a surface
Data Source
AI summary
A method and apparatus for selective etching a substrate using a focused beam. For example, multiple gases may be used that are involved in competing beam-induced and spontaneous reactions, with the result depending on the materials on the substrate. The gases may include, for example, an etchant gas and an auxiliary gas that inhibits etching.