ArF Resist Film Hardening via CF4 COS Plasma Modification
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Solution Overview
Problem
In semiconductor manufacturing, the use of ArF resist films as masks during etching processes results in low plasma resistance, leading to high resist film reduction and line width roughness, with existing hardening methods using H2 gas causing silicon residue deposition, which adversely affects the etching process.
Innovation Solution
A plasma processing method using a modifying gas mixture of CF4, COS, and an inert gas, such as argon, is applied to the resist film before etching, with a negative direct current voltage applied to the upper electrode, to enhance etch resistance and reduce resist film reduction, thereby improving pattern precision and reducing line width roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If H2 gas is used during hardening step to increase etch resistance of resist film, then etch resistance is improved, but silicon residues are deposited in open areas inside processing container, adversely affecting etching process
Solution Approach 1:
The patent changes the chemical composition parameters of the modifying gas from H2-based to CF4/COS-based mixture, thereby altering the plasma chemistry to achieve etch resistance enhancement without silicon residue deposition. This parameter change resolves the contradiction by finding a different chemical pathway that achieves the same functional goal without the harmful byproduct.
Solution Approach 2:
The patent converts the potentially harmful CF4 gas (which can leave fluorocarbon residues) into a beneficial modifying gas when combined with COS gas. The specific CF4/COS ratio creates a plasma environment that enhances etch resistance through a different mechanism that does not produce silicon residues, effectively converting a potential harm into a benefit.
2Manufacturing precision
If ArF resist film is used as mask during etching, then pattern formation is achieved, but plasma resistance is low causing high resist film reduction and line width roughness
Solution Approach 1:
The patent applies a preliminary modifying treatment to the ArF resist film before the main etching process. This preliminary action enhances the plasma resistance of the resist film, preventing excessive erosion and maintaining pattern fidelity during subsequent etching. The modification is performed in advance to prepare the resist film for the demanding etching conditions.
Solution Approach 2:
The patent changes the physical and chemical parameters of the resist film through plasma modification using CF4/COS gas mixture. This parameter change increases the plasma resistance and etch selectivity of the resist film, allowing it to maintain its structural integrity and pattern definition during the etching process while preventing line width roughness.
3Reliability
If CF4 gas flow rate is increased in modifying gas to enhance etch resistance, then etch resistance improves, but fluorocarbon residues may be generated
Solution Approach 1:
The patent optimizes the CF4/COS gas flow rate ratio to achieve a balance where sufficient CF4 is present to enhance etch resistance through plasma modification, while the presence of COS gas prevents excessive fluorocarbon residue formation. This parameter optimization allows operating at higher CF4 flow rates without the harmful side effects.
Solution Approach 2:
The patent uses a composite gas mixture of CF4 and COS instead of pure CF4 gas. This composite approach combines the benefits of CF4 (etch resistance enhancement) with the benefits of COS (reduced fluorocarbon residues), achieving a synergistic effect that resolves the contradiction between etch resistance improvement and residue prevention.
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 lowers resist film reduction and maintains critical dimension values, reducing line width roughness and preventing silicon residue deposition, allowing for precise pattern formation on the layer to be etched.
Implementation Method 1
modifying the resist film with plasma generated from a modifying gas including a CF4 gas, a COS gas and an inert gas
Implementation Method 2
applying a negative direct current voltage to a second electrode provided inside the plasma processing apparatus while applying the high frequency power to the first electrode provided inside the plasma processing apparatus so as to generate the plasma from the modifying gas
Implementation Method 3
applying high frequency power to a first electrode provided inside the plasma processing apparatus so as to generate the plasma from the etching gas
Data Source
AI summary
A plasma processing method includes: etching an anti reflection coating film with plasma generated from an etching gas by using a resist film that is patterned as a mask, in a deposited film in which an Si-ARC film constituting the anti reflection coating film is formed on a layer to be etched and the ArF resist film is formed on the anti reflection coating film; and modifying the ArF resist film with plasma generated from a modifying gas including a CF4 gas, a COS gas and an Ar gas by introducing the modifying gas into a plasma processing apparatus, wherein the modifying is performed before the etching.