Platinum Patterning via Aluminum Alloying and Selective Etching
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Solution Overview
Problem
Current methods for patterning platinum in microelectronic devices face challenges due to its inertness, leading to contamination risks and difficulties in mass production, especially for thick films, which are essential for harsh environment sensors and bio-MEMS devices.
Innovation Solution
A method involving the deposition of a platinum layer on a substrate, followed by forming a patterned photoresist layer and alloying with a sacrificial aluminum layer, which is then etched away to create a patterned platinum layer, using a combination of wet etching processes and annealing in a nitrogen atmosphere to form a platinum-aluminum alloy, allowing for selective removal and pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum is used for its inertness and chemical stability, then reliability is improved, but manufacturing precision deteriorates due to difficulty in patterning
Solution Approach 1:
A sacrificial aluminum layer is deposited on the platinum layer before patterning. This preliminary action enables selective etching of the aluminum layer to define patterns in the underlying platinum layer, solving the patterning difficulty caused by platinum's inertness
Solution Approach 2:
The sacrificial aluminum layer acts as an intermediary material that facilitates pattern transfer to the platinum layer. The aluminum layer is selectively etched away, leaving the desired pattern in the platinum while the platinum itself remains unaffected by the etching process
2Ease of manufacture
If conventional platinum patterning methods are used, then manufacturing simplicity is maintained, but harmful factors increase due to contamination risks
Solution Approach 1:
The sacrificial aluminum layer serves as a mediator that protects the platinum from direct exposure to etching chemicals and processing steps. This intermediary approach eliminates contamination risks while maintaining process simplicity
Solution Approach 2:
The sacrificial aluminum layer is a temporary, disposable material that is intentionally deposited and then completely removed after serving its patterning function. This disposable approach prevents contamination of the platinum layer while enabling precise pattern formation
3Reliability
If thick platinum films are used for harsh environment sensors, then reliability is improved, but device complexity increases due to patterning difficulties
Solution Approach 1:
The sacrificial aluminum layer is deposited and patterned before the final platinum structure is completed. This preliminary patterning action simplifies the overall process for creating thick platinum films by avoiding direct manipulation of the inert platinum material
Solution Approach 2:
The aluminum layer mediates the patterning process for thick platinum films, enabling complex patterns to be formed without directly processing the platinum. This intermediary approach reduces device complexity while maintaining the reliability benefits of thick platinum films
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 enables reliable and controlled patterning of platinum, overcoming contamination issues and achieving high process control, allowing for the production of patterned platinum layers suitable for microelectronic devices and sensors with improved feature sizes and aspect ratios.
Implementation Method 1
A first platinum layer and a second aluminum layer are alloyed together
Implementation Method 2
The patterned photoresist layer is removed, exposing the underlying platinum and aluminum layers
Implementation Method 3
The sacrificial aluminum layer and platinum-aluminum alloy are selectively removed, leaving the patterned platinum layer
Implementation Method 4
A first platinum layer is deposited on a substrate
Implementation Method 5
A second aluminum layer is deposited over the platinum layer
Data Source
AI summary
There is provided a method of patterning platinum on a substrate. A platinum layer is deposited on the substrate, and a patterned photoresist layer is formed over the platinum layer leaving partly exposed regions of the platinum layer. An aluminum layer is deposited over the partly exposed regions of the platinum layer. An alloy is formed of aluminum with platinum from the partly exposed regions. The platinum aluminum alloy is etched away leaving a remaining portion of the platinum layer to form a patterned platinum layer on the substrate. In an embodiment, a thin hard mask layer is deposited on the platinum layer on the semiconductor substrate before the patterned photoresist layer is formed.