Sputtering Target Fabrication via Sol-Gel Precursor Mixing
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Solution Overview
Problem
The existing methods for forming sputtering targets, particularly for doped compositions like Barium-Strontium Titanate, face challenges such as uneven distribution of minor constituents leading to blistering, low density, and reduced deposition rates due to contamination and non-uniform grain size distribution, which affect the quality and productivity of dielectric thin films.
Innovation Solution
A method involving a single mixing step of major and minor constituents, followed by thermal decomposition and calcination, to produce a precursor powder that is then hot-pressed into a sputtering target, ensuring uniform grain size and high density, thereby reducing contamination and enhancing deposition rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional two-step mixing and hot-pressing is used, then standard fabrication process is achieved, but uneven dopant distribution causes blistering and low target density
Solution Approach 1:
The patent applies preliminary action by incorporating dopants into the precursor powder mixture before the main hot-pressing process. The dopants are pre-distributed throughout the precursor mixture using a sol-gel or co-precipitation method, ensuring uniform distribution before sintering occurs. This preliminary incorporation prevents the blistering issue that arises from uneven dopant distribution in conventional two-step mixing processes.
Solution Approach 2:
The patent changes the chemical state and distribution parameters of dopants by converting them from separate additive powders into molecularly dispersed species within the precursor solution. Through controlled hydrolysis and condensation reactions, the dopants become uniformly integrated into the forming oxide network at the nanoscale, transforming their distribution from heterogeneous to homogeneous before the hot-pressing densification step.
2Manufacturing precision
If longer mechanical mixing is used to improve dopant distribution, then distribution improves, but micro-contamination from worn contacting parts increases
Solution Approach 1:
The patent replaces the mechanical mixing system with a chemical mixing approach. Instead of using ball mills or attritors that mechanically fracture and contaminate particles, the invention uses sol-gel chemistry where dopants are molecularly dispersed in a solution and uniformly precipitated as the oxide network forms. This chemical field substitution eliminates the mechanical wear and micro-contamination inherent in prolonged mechanical mixing while achieving superior dopant distribution.
Solution Approach 2:
The patent introduces a chemical intermediary (the precursor solution containing metal alkoxides or salts) that mediates the mixing process. This liquid intermediary allows dopants to be uniformly distributed at the molecular level throughout the precursor mixture, eliminating the need for prolonged mechanical contact between particles that causes contamination from mill media or worn contacting parts.
3Reliability
If hot-pressing is optimized to reduce blistering, then target density decreases and grain size distribution increases
Solution Approach 1:
The patent changes the microstructural parameters of the target material by controlling the sintering and hot-pressing conditions to achieve fine, uniform grain growth. By optimizing the heating rate, holding temperature, and pressure application timing, the process produces a dense microstructure with narrow grain size distribution. The uniform dopant distribution from the precursor stage ensures consistent local composition throughout, preventing the formation of large grains or blisters during densification.
Solution Approach 2:
The patent creates a composite microstructure where uniformly distributed dopant phases are integrated within the main oxide matrix at the nanoscale. This composite structure, formed through the precursor-derived homogeneous mixture, provides nucleation sites that promote fine, uniform grain growth during hot-pressing while maintaining high overall density. The intimate mixing at the molecular level in the precursor stage ensures that the composite microstructure forms uniformly throughout the target.
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 approach results in a sputtering target with a higher density (>99% of theoretical density) and increased deposition rate (up to 18 nm/min), improving the quality and productivity of dielectric thin films, and reducing manufacturing costs.
Implementation Method 1
The sputtering process is utilizing cathode plasma discharge in vacuum resulting in the material transfer from the target to a substrate
Implementation Method 2
The sputtering process is utilizing cathode plasma discharge in vacuum
Implementation Method 3
A method involving a single mixing step of major and minor constituents, followed by thermal decomposition and calcination
Implementation Method 4
followed by thermal decomposition and calcination, to produce a precursor powder that is then hot-pressed into a sputtering target
Implementation Method 5
the synthesized powder is thereafter hot pressed into a sintered compact
Data Source
Figure 1A~2B
Figure 2C
Figure 3
AI summary
The present invention discloses a method in which a selection is made for a first major constituent, a second major constituent and a minor constituent for forming a desired ceramic material. The method can include mixing the first major constituent, the second major constituent and the minor constituent in a single mixing step to provide a mixture of constituents. The method can include drying the mixture of constituents to provide a dried mixture of constituents and calcining the dried mixture of constituents. The method can include processing the calcinated mixture of constituents to provide a powder of constituents. Other embodiments are disclosed.