Independent Etching and Passivation Gas Control for Selective Silicon Oxide Etching
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Solution Overview
Problem
Conventional methods for selective etching of silicon oxide relative to silicon nitride in semiconductor manufacturing lack independent control of etching and passivation components, leading to inadequate flexibility and selectivity, especially when using fluorocarbon or hydrofluorocarbon gases.
Innovation Solution
A plasma processing method that separates the etching and passivation components by exposing a substrate with both silicon oxide and silicon nitride films to a plasma-excited passivation gas containing carbon or sulfur, without fluorine or hydrogen, and a plasma-excited etching gas containing fluorine, allowing for independent control and enhanced selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fluorocarbon or hydrofluorocarbon gases are used for selective silicon oxide etching, then etching capability is provided, but independent control of etching and passivation components is lost
Solution Approach 1:
The patent segments the plasma processing gas into separate functional components: a passivation gas (e.g., CO, COS, CS2, CCl4, C2Cl4, CCl2Br2, SCl2, or S2Cl2) that provides protective carbon or sulfur layers, and an etching gas (e.g., F2, XeF2, ClF3, HF, or NF3) that provides fluorine for silicon oxide removal. This segmentation allows independent control of passivation and etching rates, resolving the contradiction between adaptability and selectivity.
Solution Approach 2:
The patent extracts the passivation function from conventional fluorocarbon/hydrofluorocarbon gases by using dedicated passivation gases containing carbon or sulfur but no fluorine or hydrogen. This extraction eliminates the coupling between etching and passivation components, enabling independent optimization of both functions for enhanced etch selectivity.
2Manufacturing precision
If conventional etching gases containing C4F6/C4F8 are used, then passivation is provided, but etching component control is reduced
Solution Approach 1:
The patent segments passivation and etching functions into separate gas components: passivation gases (CO, COS, CS2, CCl4, C2Cl4, CCl2Br2, SCl2, or S2Cl2) that provide carbon or sulfur without fluorine or hydrogen, and etching gases (F2, XeF2, ClF3, HF, or NF3) that provide fluorine. This segmentation enables independent control of both passivation and etching components.
Solution Approach 2:
The patent extracts the passivation function from conventional etching gases by using dedicated passivation gases that contain carbon or sulfur but explicitly exclude fluorine and hydrogen. This extraction allows independent optimization of passivation control while maintaining full etching component control through separate etching gases.
3Ease of manufacture
If single FC or HFC gas is used for etching, then process simplicity is maintained, but flexibility for selective etching is inadequate
Solution Approach 1:
The patent segments the plasma processing system into separate passivation gas delivery and etching gas delivery channels, allowing independent control of each function. This segmentation provides flexibility for selective etching of silicon oxide relative to silicon nitride while maintaining process simplicity through standardized plasma processing equipment.
Solution Approach 2:
The patent employs a multi-functional plasma processing system that can deliver different passivation gases (CO, COS, CS2, CCl4, C2Cl4, CCl2Br2, SCl2, or S2Cl2) and different etching gases (F2, XeF2, ClF3, HF, or NF3) through the same reactor. This universality provides flexibility for selective etching while maintaining ease of manufacture by using existing plasma processing infrastructure.
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 provides improved etch selectivity and processing window by utilizing the volatility differences of carbon and sulfur by-products on silicon oxide and nitride surfaces, enabling precise control over the etching process.
Implementation Method 1
exposing the substrate to a plasma-excited passivation gas containing carbon, sulfur, or both carbon and sulfur
Implementation Method 2
The method utilizes independent control of etching and passivation gas components for highly selective silicon oxide/silicon nitride etching
Implementation Method 3
exposing the substrate to a plasma-excited etching gas containing fluorine
Implementation Method 4
utilizing the volatility differences of carbon and sulfur by-products on silicon oxide and nitride surfaces
Data Source
AI summary
A method for selective plasma etching of silicon oxide relative to silicon nitride is described. The method includes providing a substrate containing a silicon oxide film and a silicon nitride film, and selectively etching the silicon oxide film relative to the silicon nitride film by: a1) exposing the substrate to a plasma-excited passivation gas containing carbon, sulfur, or both carbon and sulfur, where the plasma-excited passivation gas does not contain fluorine or hydrogen, and b1) exposing the substrate to a plasma-excited etching gas containing a fluorine-containing gas. The method can further include, between a1) and b1), an additional step of a2) exposing the substrate to a plasma-excited additional passivation gas containing a fluorocarbon gas, hydrofluorocarbon gas, a hydrochlorocarbon gas, a hydrochlorofluorocarbon gas, or a hydrocarbon gas, or a combination thereof.