Interferometric Taper Waveguide Fabrication for HAMR
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Solution Overview
Problem
Current methods for manufacturing interferometric taper waveguides (I-TWGs) for heat-assisted magnetic recording (HAMR) face challenges in achieving dimensional accuracy and uniformity on a single substrate, leading to inefficiencies, high power consumption, and reduced head life due to structural variances.
Innovation Solution
A method involving the deposition of a film stack with specific hard mask and cladding layers, using deep ultraviolet lithography and reactive ion etching processes to define and transfer patterns, followed by chemical mechanical planarization, to create an I-TWG with precise critical dimensions and improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multi-substrate construction is used for I-TWG, then manufacturing complexity is reduced, but dimensional accuracy and uniformity deteriorate
Solution Approach 1:
The patent merges multiple waveguide components (taper, splitter, directional coupler) that were previously fabricated on separate substrates into a single integrated waveguide structure on one substrate. This integration enables precise control of critical dimensions (taper angle, length, CDU, LER, splitter asymmetry, MC-to-taper overlay) through unified fabrication processes, directly resolving the contradiction between manufacturing ease and dimensional accuracy.
2Manufacturing precision
If I-TWG components are built on a single substrate, then dimensional accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The patent segments the manufacturing process into distinct lithography and etching stages, each targeting specific waveguide components. By using separate photoresist patterns and etch processes for different sections (taper, splitter, directional coupler), the complex single-substrate fabrication is broken down into manageable steps, reducing overall process complexity while maintaining dimensional accuracy.
Solution Approach 2:
The patent applies preliminary patterning actions by first defining the overall waveguide footprint and then progressively refining specific components through sequential lithography steps. Critical dimensions are pre-established through initial patterning, and subsequent steps build upon this foundation, making the complex fabrication process more controllable and systematic.
3Ease of manufacture
If dimensional accuracy of I-TWG is insufficient, then manufacturing is easier, but HAMR performance deteriorates
Solution Approach 1:
The patent replaces conventional less-precise fabrication methods with deep ultraviolet (DUV) lithography and reactive ion etching (RIE) processes. These advanced techniques provide the dimensional accuracy (CDU < 5nm, LER < 2nm) required for optimal HAMR performance while maintaining manufacturing feasibility through established semiconductor fabrication infrastructure.
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 method enables the efficient delivery of laser light with extended head life and reduced power consumption by achieving superior critical dimension uniformity and line edge roughness, allowing for a less than 50 nm spot size on the recording media surface.
Implementation Method 1
defining a first pattern in a photoresist layer on the film stack
Implementation Method 2
transferring the pattern to a first hard mask layer
Implementation Method 3
planarizing a top surface of the waveguide
Implementation Method 4
delivered through I-TWG 200 to near field transducer (NFT) 250 at air bearing surface (ABS) 270
Implementation Method 5
focuses the laser generated light energy into a less than 50 nm spot on the PMR media surface
Data Source
AI summary
A method for making an interferometric taper waveguide (I-TWG) with high critical dimension uniformity and small line edge roughness for a heat assisted magnetic recording (HAMR) head, wherein the method includes creating an I-TWG film stack with two hard mask layers on top of an I-TWG core layer sandwiched between two cladding layers, defining a photoresist pattern over the I-TWG film stack using deep ultraviolet lithography, transferring the pattern to the first hard mask layer using reactive ion etching (RIE), forming a temporary I-TWG pattern on the second hard mask layer using RIE, transferring the temporary pattern to the I-TWG core using RIE, refilling the cladding layer, and planarizing using chemical mechanical planarization (CMP).