Platinum Thin-Film Etching Using a Protective Cap Layer
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Solution Overview
Problem
Etching platinum-containing metal layers in microelectronic devices is challenging due to the use of strong acids in wet etching, which results in non-uniformity and residue, while dry etching methods like sputter etching lead to redeposition and contamination.
Innovation Solution
A method involving the formation of a cap layer on the platinum-containing layer to prevent platinum oxide formation, allowing for a uniform wet etch process that removes the cap and platinum layers without residue, using a mixture of nitric acid and hydrochloric acid as the etchant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching with strong acids is used to etch platinum-containing layer, then etching can be achieved, but non-uniform etching and residue formation occur
Solution Approach 1:
A cap layer is introduced as an intermediary between the etchant and the platinum-containing layer. The cap layer is selectively removed to expose the platinum layer for etching, while protecting areas where platinum should remain. This mediator enables controlled wet etching without direct exposure of the entire platinum layer to the etchant, thereby achieving both etching capability and precision.
Solution Approach 2:
The platinum-containing layer is segmented into patterned regions through selective cap layer removal. The cap layer is removed only in specific areas where platinum etching is desired, creating discrete etching zones. This segmentation allows uniform etching within each zone while preserving platinum in protected areas, resolving the contradiction between etching capability and manufacturing precision.
2Ease of manufacture
If sputter etching is used to etch platinum-containing layer, then dry etching can be achieved, but redeposition and contamination occur
Solution Approach 1:
The cap layer serves as an intermediary that enables selective platinum removal without requiring sputter etching of the entire layer. By protecting non-patterned areas with the cap layer, the invention prevents redeposition of platinum material in those regions and eliminates contamination of the chamber from etching large areas. The cap layer mediates between the need for dry etching capability and the harmful effects of redeposition.
3Manufacturing precision
If overetch is performed to achieve uniform pattern dimensions, then lateral dimension control improves, but unwanted variation is introduced
Solution Approach 1:
The cap layer is preliminarily formed and patterned before the platinum etching step. This preliminary action defines the exact boundaries of where platinum should be removed, eliminating the need for overetching. The cap layer acts as a pre-established mask that protects platinum in areas where it should remain, allowing precise lateral dimension control without introducing variation through excessive etching.
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 a more controlled and efficient etching process with reduced overetching and contamination, resulting in a patterned platinum layer with consistent dimensions and improved reliability of microelectronic devices.
Implementation Method 1
wet etching requires very strong acids such as aqua regia, and results in platinum-containing residue in the etched areas
Implementation Method 2
The cap layer and the platinum-containing layer are subsequently removed by a wet etch process
Implementation Method 3
Dry etching may be accomplished by sputter etching, also referred to as ion milling
Implementation Method 4
The cap layer is etchable in an etch solution which is used to etch the platinum-containing layer
Data Source
AI summary
A microelectronic device includes a substrate a platinum-containing layer over the substrate. The platinum-containing layer includes a first segment and a second segment adjacent to the first segment, and has a first surface and a second surface opposite the first surface closer to the substrate than the first surface. A first spacing between the first segment and the second segment at the first surface is greater than a second spacing between the first segment and the second segment at the second surface. A width of the first segment along the first surface is less than twice a thickness of the first segment, and the second spacing is less than twice the thickness of the first segment.