Indium Target Crystal Aspect Ratio for Sputtering Stability
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Solution Overview
Problem
Traditional indium targets for CIGS system thin-film solar cells have issues with deposition rate and discharge voltage stability, with high initial discharge voltage and variability over sputtering time due to mixed granular and columnar crystal structures formed by traditional melting and casting methods.
Innovation Solution
The indium target is manufactured with a crystal particle aspect ratio of 2.0 or less by rolling an indium ingot into a tile and bonding it onto a backing plate, resulting in a high deposition rate and stable discharge voltage, with a deposition rate of 4000 Å/min or more and initial discharge voltage of 350V or less under specific sputtering conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional melting and casting method is used to produce indium target, then manufacturing process is simple, but deposition rate is low and discharge voltage is high and unstable
Solution Approach 1:
The invention changes the crystal structure parameters of indium by controlling the cooling rate during casting. Specifically, it uses a multi-stage cooling process with different cooling rates to achieve a crystal grain structure with aspect ratio of 2.0 or less, which directly improves deposition rate to 4000 Å/min or more and stabilizes discharge voltage
Solution Approach 2:
The invention creates local quality differences in the crystal structure by applying different cooling rates to different regions of the molten indium. The surface layer is cooled faster than the bulk, creating a specific gradient crystal structure that optimizes sputtering performance while maintaining manufacturing feasibility
2Power
If traditional melting and casting method is used to produce indium target, then manufacturing process is simple, but initial discharge voltage is high
Solution Approach 1:
The invention changes the crystal structure parameters by controlling cooling rate, achieving an aspect ratio of 2.0 or less. This structural parameter change directly reduces initial discharge voltage to 350V or less by improving electron transport and reducing scattering at grain boundaries
3Reliability
If traditional melting and casting method is used to produce indium target, then manufacturing process is simple, but deposition rate and discharge voltage are unstable over time
Solution Approach 1:
The invention stabilizes the crystal structure by controlling the aspect ratio to 2.0 or less through specific cooling rates. This structural parameter ensures uniform sputtering erosion and stable plasma discharge throughout the target's operational life, maintaining deposition rate within 0.5% variation and discharge voltage within 0.2% variation over time
Solution Approach 2:
The invention performs preliminary crystal structure optimization during the casting process by applying controlled cooling rates before the target is used. This preliminary action of structure control during manufacturing ensures long-term stability during operation without requiring additional processing steps
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 method provides a high and stable deposition rate, low initial discharge voltage, and minimal change in discharge voltage over time, improving the efficiency and consistency of sputtering performance compared to traditional methods.
Implementation Method 1
Indium is used as sputtering target for forming photoabsorption layer of Cu—In—Ga—Se system (CIGS system) thin-film solar cell
Data Source
AI summary
The present invention provides an indium target and manufacturing method thereof, where deposition rate is high, initial discharge voltage is low, and deposition rate and discharge voltage, from the start of sputtering to the end of sputtering, are stable. In the indium target, an aspect ratio (length of longer direction/length of shorter direction) of crystal particle, observed from cross-section direction of the target, is 2.0 or less.