Magnetic Head MR Sensor Patterning for Ultra-Fine CD Uniformity
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Solution Overview
Problem
Conventional patterning techniques for ultra-fine critical dimensions in magnetoresistive sensors face challenges in achieving within-wafer and wafer-to-wafer uniformity control, leading to issues in scaling down the critical dimension of MR sensors for higher areal density data recording in hard disk drives.
Innovation Solution
A method involving a film stack with a substrate, MR sensor layer, and hard mask layer, using multiple masks to pattern the hard mask layer, form a mandrel pattern, and create a sidewall spacer pattern through atomic layer deposition (ALD) to achieve precise critical dimension control, decoupling CD formation from other critical shape patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional patterning techniques are used to create ultra-fine CD, then the critical dimension can be reduced, but within-wafer and wafer-to-wafer uniformity control deteriorates
Solution Approach 1:
The patent segments the patterning process into two independent stages: first patterning the hard mask layer for non-CD critical shapes, then forming the mandrel pattern for CD control. This segmentation allows each stage to optimize for its specific function, preventing the compromise of CD uniformity by other pattern requirements.
Solution Approach 2:
The patent introduces a mandrel pattern as an intermediary structure that serves solely for CD definition. The mandrel is formed with high precision using a second mask, then used as a template for sidewall spacer formation. This intermediary decouples CD formation from other critical shape patterns, ensuring uniformity is not compromised by simultaneous patterning of multiple features.
2Manufacturing precision
If excessive trimming processes are used to achieve desired CD sizes, then the critical dimension can be controlled, but resist pattern edge roughness increases
Solution Approach 1:
The patent performs preliminary patterning of the hard mask layer before forming the mandrel pattern. This preliminary action defines the non-CD critical shapes early, allowing subsequent mandrel formation to focus exclusively on CD precision without requiring additional trimming that would roughen edges.
Solution Approach 2:
The sidewall spacers self-align to the mandrel pattern through conformal deposition, automatically defining the final CD without requiring additional trimming processes. This self-service mechanism eliminates the need for RIE or IBE techniques that cause edge roughness, while still achieving precise CD control.
3Device complexity
If conventional patterning methods are used, then the process is simple, but scaling capability for higher areal density deteriorates
Solution Approach 1:
The patent segments the patterning workflow into distinct modules: hard mask patterning for shape definition, mandrel formation for CD control, and sidewall spacer deposition for final pattern transfer. This modular segmentation maintains process simplicity through clear separation of functions while enabling scaling to smaller dimensions by adjusting mandrel and spacer dimensions independently.
Solution Approach 2:
The patent transitions from planar patterning to three-dimensional sidewall spacer formation through conformal deposition. This dimensional change enables precise CD control by defining dimensions in the vertical deposition direction rather than relying solely on lateral lithographic resolution, providing superior scaling capability for higher areal density.
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
Enables the scaling down of critical dimensions to 20 nm or less with tight uniformity control, addressing the limitations of conventional methods in achieving consistent patterning for magnetic head devices.
Implementation Method 1
depositing a conformal layer of spacer material by atomic layer deposition (ALD) on the mandrel pattern
Data Source
AI summary
Methods of critical dimension (CD) uniformity control for magnetic head devices are disclosed. In some embodiments, a method can include providing a film stack, the film stack including a substrate, a magnetoresistive (MR) sensor layer, and a hard mask layer, patterning the hard mask layer using a first mask that defines critical shape patterns other than the CD, forming a mandrel pattern using a second mask that defines the CD, and forming a sidewall spacer pattern on sidewalls of the mandrel pattern, and removing the mandrel pattern.