Cu-Ga Alloy Sputtering Target with Complex Fluoride Dispersion
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Solution Overview
Problem
The hygroscopic properties of alkali metal compounds like selenides and sulfides used in Cu-Ga alloy sputtering targets lead to moisture absorption, oxidation, and discoloration, causing defects during sputtering and hindering solar cell production, while potassium fluoride has a lower hygroscopicity but still poses storage challenges due to moisture absorption and potential oxidation.
Innovation Solution
A Cu-Ga alloy sputtering target with a composition of Ga 20-45 at%, Na and K 0.1-2 at% combined, and Cu balance, where sodium fluoride and potassium fluoride are mixed, forming complex fluorides dispersed in a Cu-Ga matrix, reducing hygroscopicity and preventing oxidation, with a maximum particle diameter of 30 µm and specific atomic ratios to ensure stable sputtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkali metal compounds (selenides or sulfides) are added to the sputtering target, then solar cell conversion efficiency is improved, but the target absorbs moisture from the air, causing oxidation and discoloration
Solution Approach 1:
The patent changes the chemical form of alkali metals from highly hygroscopic selenides/sulfides to fluorides with lower hygroscopicity. Specifically, it uses NaF and KF compounds and controls their particle size (D50: 1-10 μm) and content (Na: 0.01-1 wt%, KF: 0.01-1 wt%), transforming the material parameters to reduce moisture absorption while maintaining the efficiency-enhancing effect on solar cells
Solution Approach 2:
The patent creates a composite sputtering target by combining Cu-Ga alloy with alkali metal fluoride compounds (NaF and/or KF). The composite structure integrates the base Cu-Ga material with dispersed fluoride particles (maximum diameter 30 μm), achieving both the efficiency improvement from alkali metals and the stability from the low-hygroscopicity fluoride form
2Object-affected harmful factors
If potassium fluoride (KF) is added to reduce hygroscopicity, then moisture absorption is reduced compared to selenides, but the target still absorbs moisture and oxidizes when stored in atmosphere
Solution Approach 1:
The patent merges multiple alkali metal fluoride compounds (NaF and KF) into a single target system. By combining fluorides of different alkali metals with controlled ratios (Na/K atomic ratio: 0.1-9.9), it achieves synergistic effects that further reduce hygroscopicity and improve storage stability compared to using KF alone, while both compounds contribute to preventing oxidation and discoloration
Solution Approach 2:
The patent controls critical parameters of the fluoride compounds including particle size (D50: 1-10 μm, maximum diameter 30 μm) and concentration (NaF: 0.01-1 wt%, KF: 0.01-1 wt%). These parameter optimizations ensure the fluorides provide sufficient moisture protection without causing abnormal discharge during sputtering, resolving the storage stability issue
3Reliability
If alkali metal content is increased to improve solar cell efficiency, then conversion efficiency increases, but the target becomes more sensitive to moisture and oxidation
Solution Approach 1:
The patent optimizes the concentration parameters of alkali metal fluorides to achieve the efficiency benefit without excessive oxidation sensitivity. By limiting NaF to 0.01-1 wt% and KF to 0.01-1 wt%, and controlling particle size to D50: 1-10 μm, it maintains sufficient alkali metal content for efficiency improvement while the fluoride form and size control prevent excessive moisture absorption and oxidation
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 prevents discoloration and abnormal discharge during sputtering, maintaining the sputtering target's stability and efficiency, ensuring high conversion efficiency of solar cells by controlling the hygroscopicity and oxidation of the target.
Implementation Method 1
when heating and mixing sodium fluoride (NaF) and potassium fluoride (KF), the hygroscopic property is sufficiently improved
Implementation Method 2
a deposition method using a vapor deposition method is known
Implementation Method 3
moisture in the air is absorbed, and a surface of the sputtering target is oxidized and discolored
Data Source
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AI summary
A Cu-Ga alloy sputtering target having a composition including, as a metal component, Ga in a range of 20 at% or more and 45 at% or less, K and Na in a range of 0.1 at% or more and 2 at% or less in total, and a Cu balance including inevitable impurities, in which, complex fluorides containing Na, K, and F are dispersed in a matrix of a Cu-Ga alloy, a maximum diameter of an inscribed circle of the complex fluorides is 30 µm or less, and [Na]/([Na]+[K]) is set to be in a range of 0.3 or more and 0.9 or less, [Na] and [K] being atomic ratios of Na and K in the complex fluorides, respectively.