Platinum Thin-Film Etching with a Cap Layer for Residue-Free Patterning
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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 using a mixture of nitric acid and hydrochloric acid, which effectively removes the platinum-containing layer without residue.
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 capability is improved, but etching uniformity deteriorates and residue is generated
Solution Approach 1:
A cap layer is introduced as an intermediary material between the etchant and the platinum-containing layer. This cap layer is selectively removed to expose the platinum layer for etching, while preventing direct contact between strong acids and the underlying layers, thereby improving etching uniformity and reducing residue generation
Solution Approach 2:
The cap layer is formed in advance before the etching process. This preliminary action allows the platinum-containing layer to be protected during subsequent processing steps and enables controlled exposure only where needed, improving overall etching precision and reducing the need for overetching
2Manufacturing precision
If sputter etching is used to etch platinum-containing layer, then selectivity is improved, but redeposition and contamination occur
Solution Approach 1:
The mechanical sputter etching process is replaced with a chemical wet etching process using the cap layer approach. This substitution eliminates the physical bombardment that causes redeposition, while the cap layer ensures selective etching through chemical specificity rather than mechanical force
Solution Approach 2:
The cap layer serves as a mediator that enables selective removal of platinum-containing material without the need for direct sputter etching. By controlling where the cap layer is removed, selective etching is achieved without the harmful redeposition effects of sputter etching
3Productivity
If sputter etching is used to etch platinum-containing layer, then etching speed is improved, but chamber contamination increases
Solution Approach 1:
The sputter etching process is replaced with wet etching using a cap layer structure. While wet etching is generally slower, the cap layer enables more efficient processing by allowing selective area etching without the need for complex plasma process setup and teardown, reducing overall chamber contamination
Solution Approach 2:
The platinum-containing layer is selectively extracted from specific areas by removing the cap layer in those regions. This approach allows etching to be performed in isolated areas rather than requiring the entire chamber to be processed, minimizing contamination spread
4Manufacturing precision
If overetch is performed to achieve uniform patterned layer, then lateral dimension control is improved, but etching time increases
Solution Approach 1:
The cap layer is formed in advance with precise thickness and material composition control. This preliminary structuring allows the etching process to stop cleanly at the desired depth without requiring excessive overetching, thereby maintaining lateral dimension control while reducing total etching time
Solution Approach 2:
The etching parameters are optimized by changing from direct platinum etching to cap layer removal followed by controlled platinum etching. This parameter change enables more precise control of etching depth and lateral dimensions, reducing the need for time-consuming overetching cycles
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 residue-free etching process, reducing overetch time and ensuring consistent lateral dimensions of the patterned platinum layer, thereby enhancing the reliability and uniformity of microelectronic devices.
Implementation Method 1
The cap layer and the platinum-containing layer are subsequently removed by a wet etch process
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
A microelectronic device (200) is formed by forming a platinum-containing layer (220) on a substrate (202) of the microelectronic device (200). A cap layer (232) is formed on the platinum-containing layer (220) so that an interface between the cap layer (232) and the platinum-containing layer (220) is free of platinum oxide. The cap layer (232) is etchable in an etch solution which also etches the platinum-containing layer (220). The cap layer (232) may be formed on the platinum-containing layer (220) before platinum oxide forms on the platinum-containing layer (220). Alternatively, platinum oxide on the platinum-containing layer (220) may be removed before forming the cap layer (232). The platinum-containing layer (220) may be used to form platinum silicide (226). The platinum-containing layer (220) may be patterned by forming a hard mask or masking platinum oxide (264) on a portion of the top surface of the platinum-containing layer (220) to block the wet etchant.