Tapered Waveguide Structures in EAMR Heads
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Solution Overview
Problem
Conventional energy-assisted magnetic recording (EAMR) head fabrication methods face challenges in manufacturability and performance due to issues with planarization, where either the wider portions of the waveguide and test structures remain covered in cladding or the narrow portions are overpolished, affecting the exposure and integrity of the waveguide structures.
Innovation Solution
The method involves providing a mask structure with a planarization stop layer, a low-density planarization assist layer, and a hard mask layer, where the pattern is transferred to the waveguide layer, and optical materials are used for cladding, with a planarization process that efficiently removes the cladding and assist layer, ensuring proper exposure of all waveguide portions without overpolishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If planarization is carried out until the narrow portion of the waveguide is exposed, then the narrow portion is properly exposed, but the wider portions remain covered in cladding material
Solution Approach 1:
The mask structure is segmented into multiple functional layers: a hard mask layer for pattern definition, a planarization stop layer for controlling removal depth, and a planarization assist layer to facilitate selective removal. This segmentation allows the planarization process to be precisely controlled to expose only the narrow waveguide portions while leaving wider portions covered.
Solution Approach 2:
The planarization assist layer acts as an intermediary between the hard mask and the cladding material. It has intermediate removal characteristics that enable the CMP process to remove cladding from narrow portions while being stopped by the stop layer before reaching wider portions, thus mediating the selective exposure process.
2Manufacturing precision
If planarization is carried out until the wider portions of the waveguide are exposed, then the wider portions are properly exposed, but the narrow portion is overpolished and core material is removed
Solution Approach 1:
The planarization stop layer is deposited beforehand at the precise location where planarization should terminate. This preliminary action creates a physical barrier that prevents the CMP process from removing the narrow waveguide portions, thus protecting waveguide integrity while enabling exposure of wider portions.
Solution Approach 2:
The planarization stop layer serves as an intermediary barrier that controls the depth of material removal. It allows the CMP process to proceed through the cladding on wider portions while being stopped before reaching the narrow waveguide portions, thus mediating between exposure requirements and protection needs.
3Ease of manufacture
If a conventional hard mask structure is used without a planarization assist layer, then the mask structure is simple, but the planarization process cannot selectively expose different waveguide portions
Solution Approach 1:
The mask structure is divided into functionally distinct layers: the hard mask layer provides pattern definition, the planarization stop layer controls removal depth, and the planarization assist layer enables selective removal. This segmentation transforms a simple mask into a multi-functional structure that achieves selective exposure.
Solution Approach 2:
Different layers of the mask structure have different local properties: the hard mask layer has high etch resistance for pattern transfer, the planarization stop layer has controlled removal characteristics, and the planarization assist layer has low density for easy removal. These local quality differences enable selective exposure of different waveguide portions.
Data Source
AI summary
A method for providing waveguide structures for an energy assisted magnetic recording (EAMR) transducer is described. The waveguide structures have a plurality of widths. At least one waveguide layer is provided. Mask structure(s) corresponding to the waveguide structures and having a pattern are provided on the waveguide layer(s). The mask structure(s) include a planarization stop layer, a planarization assist layer on the planarization stop layer, and a hard mask layer on the planarization assist layer. The planarization assist layer has a low density. The pattern of the mask structure(s) is transferred to the waveguide layer(s). Optical material(s) that cover the waveguide layer(s) and a remaining portion of the mask structure(s) are provided. The optical material(s) have a density that is at least twice the low density of the planarization assist layer. The method also includes performing a planarization configured to remove at least a portion of the optical material(s).