Etching Composition Additive for Nitride Film Selectivity
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Solution Overview
Problem
Current etching compositions for removing nitride films in semiconductor manufacturing face challenges such as low selection ratio, particle formation, and difficulty in adjusting effective field oxide height, leading to defects and device characteristic issues.
Innovation Solution
An etching composition incorporating phosphoric acid and a reaction product of a silane compound with phosphoric anhydride, which forms silyl phosphate, is used to selectively remove nitride films while minimizing oxide film etching rate and preventing gelation, thereby enhancing etching selectivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phosphoric acid is used to remove nitride film, then etching rate is improved, but selection ratio deteriorates causing oxide film etching
Solution Approach 1:
A surfactant is introduced as an intermediary substance in the etching composition. The surfactant selectively adsorbs onto the oxide film surface, forming a protective layer that prevents phosphoric acid from etching the oxide film, while allowing the nitride film to be etched at a high rate. This mediator resolves the contradiction by enabling high etching speed without sacrificing selectivity.
Solution Approach 2:
The etching composition is formulated as a composite system containing phosphoric acid, water, and surfactant working together. The phosphoric acid provides the etching capability for the nitride film, while the surfactant component provides selective protection for the oxide film. This composite approach allows simultaneous achievement of high etching rate and high selection ratio.
2Speed
If deionized water is added to prevent etching rate decrease, then etching rate is maintained, but defects arise in nitride film removal
Solution Approach 1:
The composition parameters are optimized by controlling the water content within specific ranges (1-30 wt% or 1-20 wt%). This parameter control ensures sufficient water is present to maintain etching rate while preventing excessive water that would cause defects in nitride film removal. The surfactant addition also modifies the effective concentration parameters at the film surface.
3Speed
If phosphoric acid concentration is increased to improve etching rate, then etching rate is improved, but handling difficulty increases due to corrosiveness
Solution Approach 1:
The surfactant acts as a mediator that reduces the effective corrosiveness of phosphoric acid by forming a protective interface layer. This allows the use of phosphoric acid at concentrations that provide high etching rates while the surfactant mitigates the harsh handling characteristics, making the composition easier and safer to handle.
4Reliability
If etching time is extended to ensure complete nitride film removal, then removal completeness is improved, but oxide film etching increases due to reduced selection ratio
Solution Approach 1:
The surfactant provides continuous protective coverage on the oxide film throughout the extended etching process, maintaining high selection ratio even over longer exposure times. This allows complete nitride film removal to be achieved without compromising oxide film integrity, as the surfactant mediator prevents oxide etching regardless of etching duration.
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 etching composition achieves a high selection ratio for nitride film removal, reduces oxide film etching rate, and prevents particle formation, improving device characteristics and etching process efficiency.
Implementation Method 1
a reaction product of a silane compound with phosphoric anhydride, specifically silyl phosphate
Implementation Method 2
In a wet etching process for removing the nitride film, a mixture of phosphoric acid and deionized water is generally used
Data Source
AI summary
An etching composition providing a high selection ratio enabling selective removal of a nitride film and minimization of an etching rate, a preparation method thereof, an etching composition additive prepared through a reaction of phosphoric anhydride and a silane compound represented by Formula 1 below, a method for preparing the same and an etching composition including the same are provided: