Ru Mask Dry Etching for Al2O3 Film Selectivity
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Solution Overview
Problem
Existing methods for dry etching alumina (Al2O3) films used in magnetic heads face challenges in achieving high selectivity and perpendicular processing due to the difficulty in processing nonvolatile mask materials like NiCr alloy films, especially as miniaturization increases, leading to inaccurate and slow milling processes.
Innovation Solution
Employing a ruthenium (Ru) film as the mask material, which can be dry-etched using a Cl2 and O2 gas mixture, and using a BCl3, Cl2, and Ar gas mixture for dry etching the Al2O3 film, allowing for high selectivity and perpendicular processing of the Al2O3 film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If NiCr alloy film is used as mask material, then selectivity is improved, but processing difficulty increases due to nonvolatile nature requiring milling
Solution Approach 1:
The patent replaces mechanical milling processing with chemical dry etching to process the NiCr alloy mask material. By using a fluorine-based gas mixture (SF6, CF4, C2F6) in a reactive ion etching process, the NiCr alloy can be selectively removed without mechanical contact, enabling both the mask material and Al2O3 film to be processed through dry etching rather than requiring milling for the mask layer.
2Productivity
If milling process is used for NiCr alloy film, then processing capability is maintained, but accuracy and processing rate deteriorate due to miniaturization
Solution Approach 1:
The patent substitutes mechanical milling with chemical dry etching for processing the NiCr alloy mask material. This chemical process enables better control at miniaturized dimensions through plasma-based selective etching, improving both accuracy and processing rate compared to mechanical methods.
Solution Approach 2:
The patent changes the processing method from mechanical to chemical by adjusting gas composition parameters (using fluorine-based gases like SF6, CF4, C2F6) and plasma conditions to achieve selective etching of the NiCr alloy mask material, enabling fine processing at miniaturized dimensions with improved accuracy and rate.
3Productivity
If conventional dry etching is used for Al2O3 film, then processing speed is maintained, but selectivity and perpendicularity deteriorate due to tapered surface from milling
Solution Approach 1:
The patent performs preliminary dry etching of the NiCr alloy mask material before processing the Al2O3 film. This preliminary action removes the tapered surface created during milling, establishing a perpendicular baseline that enables subsequent perpendicular etching of the Al2O3 film while maintaining high selectivity and processing speed.
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 fine and perpendicular processing of Al2O3 films with high selectivity, overcoming the limitations of traditional milling methods and achieving efficient dry etching of both the mask material and the Al2O3 film.
Implementation Method 1
The ruthenium film is dry-etched using a gas mixture containing Cl2 and O2
Implementation Method 2
the Al2O3 film could be dry-etched using a gas mixture mainly containing BCl3 and also containing Cl2 and Ar
Data Source
AI summary
The invention provides a dry etching method for processing a wafer having an Ru film formed on a thick Al2O3 film to be used for a magnetic head, capable of realizing high selectivity. In the etching of a wafer having disposed on an NiCr film 15 an Al2O3 film 14, an Ru film 13, an SiO2 film 12 and a resist mask 11, the Ru film 13 is etched via plasma using a processing gas containing Cl2 and O2 (FIG. 1(c)), and thereafter, the Ru film 13 is used as a mask to etch the Al2O3 film 14 via plasma using a gas mixture mainly containing BCl3 and also containing Cl2 and Ar (FIG. 1(d)).