Fine Pattern Formation Using Etching Gas Protection Films
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Solution Overview
Problem
The existing fine pattern forming methods, such as the LLE process, face challenges in reducing the number of processes and achieving consistent critical dimension values between first and second patterns due to the deposition of a silicon oxide film, which can deform the first pattern and result in varying etching rates.
Innovation Solution
A method involving the formation of a protection film using reaction products of etching gases on the first photoresist patterns, followed by the creation of second photoresist patterns with a shifted pitch, and subsequent trimming and etching, reduces the number of processes and ensures consistent critical dimension values by using etching gases like fluorocarbon and halogen-containing gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon oxide film is deposited on the first pattern to protect it during second photoresist formation, then the first pattern is protected from dissolution, but the number of processes increases and the first pattern may be deformed
Solution Approach 1:
The patent extracts the protective function from a separate silicon oxide film deposition process and integrates it into the etching process itself. The protection film is formed in-situ during etching by controlling etching gas flow rates, eliminating the need for a separate deposition process while maintaining pattern protection.
Solution Approach 2:
The patent merges the protection film formation step with the etching process. By adjusting etching gas composition and flow rates, the protection film is deposited simultaneously with etching operations, combining two previously separate processes into one unified operation.
2Reliability
If a silicon oxide film is deposited on the first pattern, then the first pattern is protected, but the etching rate varies between first and second patterns resulting in inconsistent critical dimension values
Solution Approach 1:
The patent changes the parameters of the etching process, specifically the gas flow rates of CF4 and C2F6. By optimizing these parameters, the protection film has controlled etching characteristics that allow both first and second patterns to be etched at consistent rates, achieving uniform critical dimension values across all patterns.
3Productivity
If the number of processes is reduced in the LLE process, then production cost is reduced, but it becomes difficult to protect the first pattern and maintain pattern integrity
Solution Approach 1:
The etching gas system is given multiple functions: it performs both the etching of underlying layers and the formation of the protection film. By selecting appropriate gases (CF4 and C2F6) and controlling their flow rates, the same process equipment and gas delivery system accomplish both protective and etching functions without requiring additional dedicated equipment or processes.
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 minimizes process variations, maintains pattern integrity, and achieves consistent critical dimension values, enhancing the precision and efficiency of fine pattern formation below the photolithography resolution limit.
Implementation Method 1
a protection film is formed by depositing reaction products of an etching gas on the trimmed first patterns
Implementation Method 2
depositing reaction products of an etching gas on the trimmed first patterns
Implementation Method 3
etching the film using the first patterns and the second patterns
Implementation Method 4
etching gases like fluorocarbon and halogen-containing gases
Data Source
AI summary
A disclosed fine pattern forming method includes steps of: forming patterns made of a first photoresist film, arranged at a first pitch on a film; trimming the patterns made of the first photoresist film; depositing a protection film on the patterns made of the first photoresist film on the trimmed patterns made of the first photoresist film, the protection film being made of reaction products of an etching gas, thereby obtaining first patterns; forming other patterns made of a second photoresist film, arranged at a second pitch, on the protection film, the other patterns made of the second photoresist film being shifted by half of the first pitch from the corresponding patterns made of the first photoresist film; trimming the other patterns made of the second photoresist film into second patterns; and etching the film using the first patterns and the second patterns.