Sacrificial Layer Planarization for Hard Disk Drive Read Heads
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Solution Overview
Problem
In the fabrication of multi-sensor read devices for hard disk drives, existing planarization techniques such as chemical-mechanical polishing (CMP) can introduce surface topography and cause deleterious effects at material junctions, leading to performance degradation due to the formation of bumps and recesses at the interface between structured and backfilled layers, especially in the nanometer size range.
Innovation Solution
A method involving the deposition of a sacrificial layer over the structured and backfilled materials, followed by chemical-mechanical planarization and subsequent physical removal of the sacrificial layer, which helps in smoothing the surface topography while minimizing adverse effects on material interfaces, ensuring a smooth surface for further device layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical-mechanical polishing (CMP) is used to planarize the surface at the junction of structured layer and backfilled material, then surface topography is reduced, but the wet chemical in CMP slurry etches or corrodes the materials at the material interfaces
Solution Approach 1:
A sacrificial layer of material X is deposited over the backfilled material and structured layer. This sacrificial layer acts as an intermediary barrier that prevents the CMP slurry's wet chemical from contacting and etching the material interfaces. The sacrificial layer is removed after planarization, having protected the underlying structures during the chemical-mechanical process.
Solution Approach 2:
The sacrificial layer is deposited in advance before the CMP process to establish a protective barrier. This preliminary action ensures that when CMP is applied to planarize the surface, the harmful chemical effects are prevented from reaching the material interfaces, allowing surface planarization without interface degradation.
2Manufacturing precision
If ion milling process is used to remove film portions, then desired thin film structure is created, but surface topography such as bumps and recesses forms at the junction areas
Solution Approach 1:
The sacrificial layer serves as a mediator that fills and smooths surface topography features (bumps and recesses) created during ion milling and backfilling processes. By depositing this layer over the structured surfaces and then planarizing with CMP, the underlying topography is eliminated without affecting the precision of the thin film structure created by ion milling.
Solution Approach 2:
The fabrication process is segmented into distinct stages: ion milling to create the thin film structure, backfilling to fill recesses, deposition of sacrificial layer to cover topography, CMP planarization to smooth surfaces, and final removal of sacrificial layer. This segmentation allows each process to optimize for its specific function without compromising the other.
3Productivity
If multiple sensor read devices are stacked to increase data storage density, then higher areal density is achieved, but topography from lower structures degrades performance of upper readers
Solution Approach 1:
The sacrificial layer and CMP planarization process are applied as preliminary actions after fabricating each stacked reader structure. This ensures that before the next reader layer is deposited, the surface is perfectly planarized, preventing topography propagation that would degrade upper reader performance.
Solution Approach 2:
The sacrificial layer acts as an intermediary planarization layer between stacked reader structures. It absorbs and eliminates surface topography from lower readers, providing a flat interface for subsequent layers. This intermediary approach enables high-density stacking while maintaining the precision required for upper reader functionality.
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 planarizes the surface of microelectronic devices without creating new topographies, enhancing the performance of multi-sensor read devices by reducing inter-sensor spacing and maintaining material integrity, thus improving data storage density and transfer speeds.
Implementation Method 1
physically removing the remainder of the sacrificial layer and, while removing the sacrificial layer, at some point also physically removing at least a portion of at least one of the first and second materials
Implementation Method 2
performing a chemical-mechanical planarization process on a surface of the sacrificial layer surface and planarizing the surface of the sacrificial layer
Data Source
AI summary
Methods of planarizing materials, such as where surface topographies are created as part of a thin film device fabrication process are described. These methods find particular application in the creation of nano-sized devices, where surface topographical features can be effectively planarized without adversely creating other surface topographies and/or causing deleterious effects a material junctions. Methods include the step of depositing a sacrificial layer overlying at least a portion of a first material layer and at least a portion of a backfilled second material at a junction between the first and second materials. The sacrificial layer substantially retains the surface topography of the microelectronic device. Chemical-mechanical planarization is performed on a surface of the sacrificial layer but leaving a remainder portion of the thickness of the sacrificial layer. Then, physical or dry chemical process is conducted for removing the remainder of the sacrificial layer and at least a portion of at least one of the first and second materials.