Magnetic Write Head Masking for Defect Reduction
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Solution Overview
Problem
The dry pole milling process for manufacturing write poles in perpendicular magnetic recording systems is prone to defects due to imperfections in the masking layers, which negatively impact the formation of high-quality magnetic write poles.
Innovation Solution
The method involves reactive ion etching a dielectric mask with a fluorine-based chemistry followed by reactive ion etching a polymeric underlayer with an oxygen-based chemistry, and then ion beam milling of magnetic and non-magnetic stack layers, maintaining specific gas flow ratios and power ratios to form a high-quality dielectric mask and uniformly etch the polymeric underlayer, thereby improving the ion milling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high quality mask is prepared to serve as mask during the ion mill process, then the manufacturing precision of magnetic write pole is improved, but the device complexity and process difficulty increase
Solution Approach 1:
The masking system is divided into multiple functional layers: a polymeric underlayer mask and a dielectric hard mask layer. The dielectric hard mask layer is further segmented into multiple etching stages (first RIE process and second RIE process) with different gas chemistries. This segmentation allows each layer to perform its specific function optimally, reducing the complexity of preparing a single perfect mask while improving overall manufacturing precision.
Solution Approach 2:
The polymeric underlayer mask is formed and patterned before the dielectric hard mask layer is applied. This preliminary action creates a foundation structure that guides subsequent etching processes. The underlayer mask is pre-configured with the desired pole geometry, and the dielectric hard mask is then deposited and patterned on top, ensuring that the final ion mill process produces high-precision magnetic write poles.
2Manufacturing precision
If the first reactive ion etching process parameters are optimized with specific gas flow ratios and power ratios, then the dielectric mask quality is improved, but the process complexity increases
Solution Approach 1:
The etching process uses specific parameter ranges: CF4 to CHF3 gas flow ratio between 1.3 to 2, CF4 to He gas flow ratio between 2.2 to 3, and RF source power to RF bias power ratio between 10 to 16. These parameter changes optimize the dielectric mask quality by controlling etch rate, anisotropy, and sidewall profile. The first RIE process uses fluorine-based chemistry with these specific ratios to achieve the desired mask quality without excessive process complexity.
3Productivity
If defects on the masking layers are eliminated, then the yield of magnetic write pole production is improved, but the manufacturing cost and process time increase
Solution Approach 1:
The dielectric hard mask layer acts as an intermediary between the polymeric underlayer mask and the ion mill process. It protects the polymeric underlayer from direct exposure to the ion mill, preventing defect formation. The dielectric mask absorbs the mechanical stress and ion bombardment, serving as a sacrificial intermediary that ensures defect-free production of magnetic write poles while maintaining reasonable process time.
Solution Approach 2:
The polymeric underlayer mask is formed beforehand to provide a cushioning layer that protects the underlying magnetic and non-magnetic stack layers during the ion mill process. This prior cushioning prevents defects by absorbing impact and distributing stress, ensuring high yield production without requiring excessive process time for additional protective measures.
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 effectively reduces defects in the polymeric underlayer, enhancing the production of high-quality magnetic write poles with improved magnetic performance and reducing the likelihood of top-defects, thus increasing the yield and accuracy of write heads.
Implementation Method 1
performing a first reactive ion etch process to remove the exposed second portion of the dielectric hard mask layer
Implementation Method 2
the first reactive ion etch process comprises exposing the second portion of the dielectric hard mask layer to an etching gas comprising CF4 and CHF3 and He
Implementation Method 3
performing a second reactive ion etch process to remove the exposed polymeric underlayer
Implementation Method 4
reactive ion etching a polymeric underlayer in a second reactive ion etching process with an oxygen based chemistry
Implementation Method 5
performing a ion milling process to form the magnetic write pole structure
Implementation Method 6
ion beam milling a magnetic and non-magnetic stack layers with Ar ion beam
Data Source
AI summary
Write heads may be formed by reactive ion etching (RIE) a dielectric mask and then reactive ion etching a polymeric underlayer. The first RIE affects the second RIE. The first portion of the first RIE process is performed with a ratio of CF4 to CHF3 between about 1.3 to 2, a gas flow ratio of CF4 to He between 2.2 and about 3, and a ratio of RF source power to RF bias power between about 10 and about 16. The second portion of the first RIE process is performed with a ratio of CF4 to CHF3 between about 0.3 to 0.8, a gas flow ratio of CF4 to He between about 1.2 and about 1.8, and a ratio of RF source power to RF bias between about 22 to 28. With the above parameters, the dielectric mask can be formed with minimized damage on the underlayer.