Sputtering Target Cleaning via Electrochemical Bath
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Solution Overview
Problem
Existing methods fail to effectively remove contaminants such as chromium, nickel, and vanadium from sputtering targets, particularly spent ruthenium targets, which are essential for re-use in display and photonic technologies, due to cross-contamination during the deposition process.
Innovation Solution
A multi-step process involving mechanical abrasion, solvent cleaning with C1-6 alcohols or ketones, immersion in an acidic caustic bath with a surfactant under an electric field, followed by a second abrasion step and verification through spectroscopy, effectively removes contaminants like chromium from sputtering targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing cleaning methods are used on sputtering targets, then the process is simple, but contaminant removal is ineffective
Solution Approach 1:
The cleaning process is divided into multiple sequential steps: mechanical abrasion to remove bulk contaminants, solvent cleaning to dissolve organic residues, and electrochemical cleaning in acidic caustic bath to remove metallic contaminants. Each step targets specific types of contaminants, achieving comprehensive cleaning that single methods cannot accomplish.
Solution Approach 2:
An electrolyte solution containing sulfuric acid, hydrochloric acid, and surfactant serves as an intermediary medium that facilitates the electrochemical removal of contaminants. The electric field applied through this electrolyte enables efficient contaminant dissolution and removal without direct mechanical contact that could damage the target substrate.
2Reliability
If multiple cleaning steps are implemented, then contaminant removal is thorough, but processing time increases
Solution Approach 1:
The cleaning process maintains continuous action through sequential steps without idle transitions. Mechanical abrasion immediately precedes solvent cleaning, which flows directly into the electrochemical bath, ensuring the substrate is continuously processed. The electrolyte solution is maintained at optimal temperature and composition throughout to maximize cleaning efficiency at each stage.
Solution Approach 2:
The electrolyte solution parameters (temperature, acid concentration, surfactant content) are optimized to accelerate the cleaning reaction rates. Applying an electric field further enhances the cleaning speed by driving electrochemical reactions that rapidly dissolve metallic contaminants, reducing the time required for effective contaminant removal.
3Reliability
If mechanical abrasion is used, then surface contaminants are removed, but surface damage may occur
Solution Approach 1:
Mechanical abrasion is performed as a preliminary step using controlled parameters to remove only surface contaminants without penetrating into the substrate. The abrasion process is followed by gentler cleaning methods that finish the job without additional mechanical stress, ensuring complete contaminant removal while preserving substrate integrity.
Solution Approach 2:
After the initial mechanical abrasion removes bulk contaminants, the process transitions to chemical and electrochemical cleaning methods that replace further mechanical action. The solvent cleaning and electrochemical bath use chemical reactions rather than mechanical force to remove remaining contaminants, eliminating the risk of surface damage associated with continued mechanical abrasion.
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 process ensures thorough removal of contaminants, as demonstrated by XRF imaging, allowing for the re-use of sputtering targets by achieving a chromium-free state, surpassing the limitations of previous methods that did not result in satisfactory contaminant removal.
Implementation Method 1
immersion in a caustic bath, which is acidic having a pH of from 1 to 4 and further including a surfactant
Implementation Method 2
the bath having a pH of from 1 to 4 and preferably 2.5 to 3.5, and further including a surfactant
Implementation Method 3
the substrate is directly or indirectly subjected to an electric field by means of application of the field across the substrate or to a container in which the substrate is contained
Implementation Method 4
the contaminated substrate or sputtering target is cleaned mechanically, such as by abrasion
Implementation Method 5
cleaning with a solvent that includes an C1-6 alcohol or ketone, and preferably a C1-3 alcohol or ketone
Data Source
AI summary
The present invention provides a process for the removal of contaminants on a spent sputtering target used in Plasma Vapor Deposition by the steps of grit abrasion, organic solvent cleaning, and being subjected to an electric field in an acidic bath including a surfactant, and followed by subsequent water and air rinse and further grit abrasion. Removal of the contaminants is verified by spectroscopy.