Gold Film Etching Chemistry Without NMP for Fine Patterning
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Solution Overview
Problem
The existing etching solutions for gold and gold alloys, particularly iodine-based solutions, face challenges with the use of N-methyl-2-pyrrolidone (NMP), which are hazardous and subject to stricter regulations, necessitating the development of NMP-free alternatives that maintain excellent wettability, microfabrication properties, and solution longevity.
Innovation Solution
An etching solution comprising iodine, iodide, and specific organic solvents such as 3-methoxy-N,N-dimethylpropanamide, 1,4-butanediol, or diethylene glycol, which provide excellent wettability, microfabrication properties, and long solution life without NMP, while effectively etching gold and gold alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If NMP is used as an organic solvent in iodine-based etching solution, then wettability and microfabrication properties are improved, but health hazards and regulatory restrictions increase
Solution Approach 1:
The patent extracts and removes NMP from the etching solution formulation, replacing it with alternative organic solvents such as N,N-dimethylformamide, N-methyl-2-pyrrolidone, or their mixtures with water, thereby eliminating the health hazards associated with NMP while maintaining the desired microfabrication properties
Solution Approach 2:
The patent changes the chemical composition parameters of the organic solvent component in the etching solution, transitioning from NMP-based formulations to alternative solvent systems with adjusted concentrations and ratios to achieve comparable or improved performance without the harmful effects of NMP
2Reliability
If aqua regia-based solution is used for etching gold films, then etching capability is achieved, but etching speed is slow and handling difficulty increases due to strong acidity
Solution Approach 1:
The patent changes the chemical composition parameters by replacing the strongly acidic aqua regia system with an iodine-based system containing iodine, potassium iodide, and organic solvents, which provides comparable etching capability with significantly improved etching speed and easier handling due to neutral or mildly acidic pH
Solution Approach 2:
The patent substitutes the chemical mechanism of etching by replacing the nitric acid-hydrochloric acid redox system of aqua regia with an iodine-based complexation and dissolution system, achieving the same functional outcome through a different chemical pathway that offers superior performance
3Productivity
If cyanide-based solution is used for etching gold, then etching ease is improved, but handling difficulty and toxicity increase due to strong basicity and cyanide toxicity
Solution Approach 1:
The patent extracts and removes cyanide from the etching solution formulation, replacing it with iodine-based systems that provide comparable or superior etching ease without the extreme toxicity and handling difficulties associated with cyanide compounds
Solution Approach 2:
The patent converts the harmful cyanide-based chemistry into a beneficial iodine-based chemistry, where the iodine-iodide system provides effective gold etching through complexation and dissolution mechanisms that are inherently safer and more environmentally friendly while maintaining high productivity
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
The solution achieves controlled etching rates, improved wettability, surface smoothing, reduced side etching, and inhibited iodine volatilization, ensuring high precision and stability in etching processes.
Implementation Method 1
gold easily forms a complex with cyanide ions
Implementation Method 2
gold easily forms a complex with cyanide ions
Implementation Method 3
organic solvents are included in the iodine-based etching solution to improve wettability
Implementation Method 4
the wafer is vacuum sucked or mechanical chucked onto a support stage and sprayed with the etching solution while it is rotated
Data Source
AI summary
It is known that when etching gold films using etching solutions containing iodine and iodide, N-methyl-2-pyrrolidinone (NP) is added to improve the etching solution's wettability, microfabrication property, and solution life. However, in recent years, the use of NMP has been regulated due to its adverse effects on human health. The present invention provides an etching solution and etching method for gold film that improves wettability, microfabrication property, and solution life without containing NP. In order to address the problem of the prior art, the present invention provides etching solutions and etching methods for gold films that improve wettability, microfabrication property, and liquid life without NMP, characterized by the inclusion of a specific organic solvent in the etching solution containing iodine and iodide.