Magnetoresistive Element Fabrication Using Single Layer Mask
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Solution Overview
Problem
Conventional methods for fabricating magnetoresistive (MR) devices at higher memory densities and smaller critical dimensions face issues such as bilayer mask collapse, difficulty in controlling track width, reduced yield, delamination, shadowing, and non-uniform planarization, which hinder the production of MR devices with dimensions on the order of 0.06-0.08 μm or less.
Innovation Solution
A method and system utilizing a single layer photoresist mask to cover and expose MR element layers, followed by definition using an ion mill, deposition of a hard bias layer, and chemical mechanical polish (CMP) planarization, which avoids delamination and shadowing, and improves surface uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bilayer mask is used to fabricate MR elements at small critical dimensions, then the mask can provide structural support, but the mask tends to collapse and track width becomes difficult to control
Solution Approach 1:
The patent removes the lower layer of the bilayer mask structure, transitioning from a two-layer mask to a single-layer mask. This extraction eliminates the collapse issue inherent in bilayer masks while maintaining sufficient structural support through optimized single-layer design and processing parameters
Solution Approach 2:
The patent modifies critical parameters including mask thickness (optimized to specific ranges), etch selectivity ratios, and processing conditions to enable single-layer masks to achieve both the mechanical stability and precision required for sub-100nm track width control
2Quantity of substance
If memory density increases to achieve higher storage capacity, then the bit size decreases, but the critical dimensions of readers and writers become too small to fabricate reliably
Solution Approach 1:
The patent systematically optimizes multiple parameters including mask thickness, etch selectivity, and processing conditions to enable reliable fabrication at critical dimensions of 0.06-0.08 μm and below, thereby supporting higher memory densities
Solution Approach 2:
The patent replaces conventional mechanical bilayer mask structures with an optimized single-layer mask approach combined with controlled etching processes, achieving better dimensional control at smaller scales
3Ease of manufacture
If a single layer photoresist mask is used to avoid bilayer mask collapse, then fabrication simplicity improves, but delamination and shadowing issues occur
Solution Approach 1:
The patent optimizes mask thickness to specific ranges and controls etch selectivity parameters to prevent delamination while maintaining single-layer simplicity, eliminating the need for complex bilayer structures
Solution Approach 2:
The patent uses the single-layer mask to create precise negative impressions of the desired track patterns through controlled etching, achieving accurate pattern transfer without the complications of bilayer approaches
4Productivity
If conventional fabrication methods are used at small critical dimensions, then existing processes can be maintained, but yield is reduced due to mask collapse and track width control difficulties
Solution Approach 1:
The patent implements optimized parameter sets including mask thickness, etch selectivity ratios, and processing conditions that simultaneously improve track width control and fabrication yield at small critical dimensions
Solution Approach 2:
By removing the lower mask layer and simplifying the mask structure, the patent eliminates the primary source of yield loss from mask collapse while maintaining sufficient precision for high-density fabrication
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 fabrication of MR devices with critical dimensions as small as 0.6-0.8 μm, reduces asymmetry and resource consumption, and enhances yield by avoiding bilayer mask issues and improving planarization uniformity.
Implementation Method 1
A single layer photoresist mask is developed from the single layer of photoresist 60, via step 20
Implementation Method 2
The portions of the layers 56 and 58 exposed by the apertures 61 and 62 are removed, via step 22. Step 22 is typically performed using a reactive ion etch (RIE)
Implementation Method 3
The MR element is then defined, via step 24. Step 24 typically includes performing a critical junction ion mill
Implementation Method 4
chemical mechanical polish (CMP) planarization
Data Source
AI summary
The method and system for providing a magnetoresistive device are described. The method and system include depositing a plurality of magnetoresistive element layers which cover at least one device area and at least one field area. The method and system also include providing a single layer mask. The single layer mask covers a first portion of the magnetoresistive element layers in the device area(s) and exposes the magnetoresistive element layers in the field area(s). The method and system include defining the magnetoresistive element(s) using the single layer mask and depositing a hard bias layer on the device area(s) and the field area(s) after the magnetic element(s) are defined. The method and system further include performing a planarization after the hard bias layer is deposited.