High-Rate Sputtering of CdTe Thin Films on Large Substrates
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Solution Overview
Problem
The challenge in large-scale production of cadmium telluride (CdTe) photovoltaic modules lies in the difficulty of sputtering thin films with high uniformity and efficiency, particularly when using semiconducting targets with large surface areas, which is crucial for cost-effective and sustainable solar energy production.
Innovation Solution
A method involving sputtering thin films on substrates within a vacuum chamber using a planar magnetron with ionized gas and high-frequency power, maintaining a sputtering pressure below 50 mTorr and a temperature of 50° C to 200° C, allowing for continuous conveyance at a constant rate to achieve uniform film thickness with minimal non-uniformity, suitable for substrates of 1000 cm² to 2500 cm².
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sputtering is used on large area substrates, then production cost is reduced, but film uniformity deteriorates
Solution Approach 1:
The patent divides the large substrate (1000-2500 cm²) into multiple smaller processing zones by using a linearly movable sputtering system that processes different regions sequentially. This segmentation allows each zone to receive optimized sputtering parameters, achieving uniform film deposition across the entire large substrate while maintaining high production efficiency through continuous linear motion.
Solution Approach 2:
The invention employs a dynamic sputtering system where the sputtering source moves linearly across the substrate at a controlled speed. This dynamic approach replaces static conventional sputtering, enabling uniform film deposition on large substrates while the continuous motion maintains high productivity. The system dynamically adjusts parameters such as gas flow rate and power during the sputtering process to optimize film uniformity.
2Productivity
If high rate sputtering is used, then productivity is improved, but film uniformity deteriorates
Solution Approach 1:
The patent implements continuous sputtering deposition while the source moves linearly across the substrate. The process maintains continuous useful action by ensuring that sputtering occurs continuously throughout the traversal, with optimized gas flow and power parameters. This continuous process achieves high deposition rates while maintaining film uniformity through the sustained, controlled sputtering action across the entire substrate area.
Solution Approach 2:
The invention dynamically changes sputtering parameters during the deposition process, including gas flow rate, power levels, and substrate temperature, to optimize both deposition rate and film uniformity. By adjusting these parameters in real-time during the linear traversal, the system achieves high-rate sputtering while maintaining consistent film quality across the large substrate area.
3Area of stationary object
If large area targets are used, then substrate area coverage is improved, but sputtering difficulty increases
Solution Approach 1:
Instead of using a single large area target that is difficult to process, the invention segments the coverage task into multiple smaller target zones processed sequentially during linear traversal. This approach covers large substrates (1000-2500 cm²) effectively while maintaining ease of manufacture by using smaller, more manageable target areas that are simpler to fabricate and operate.
Solution Approach 2:
The patent replaces the static large target approach with a dynamic linear traversal system. The sputtering source moves continuously across the substrate, allowing smaller target areas to cover larger substrates over time. This dynamic approach improves ease of manufacture by using smaller, easier-to-handle targets while still achieving complete substrate coverage through the continuous motion process.
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
This approach enables the deposition of thin films with an average thickness of 50 nm to 250 nm and non-uniformity of 7% to 15%, facilitating efficient and uniform large-scale production of CdTe PV modules, enhancing the scalability and cost-effectiveness of solar energy systems.
Implementation Method 1
the individual substrates can be conveyed into a sputtering chamber and past a planar magnetron continuously sputtering a target by an ionized gas at the sputtering pressure such that a thin film is formed on a surface of the individual substrate
Implementation Method 2
The target can be subjected to a high frequency power having a frequency from about 400 kHz to about 4 MHz at power levels of greater than about 1 kW
Data Source
AI summary
Methods are generally provided for sputtering thin films on individual substrates. Individual substrates can be conveyed into a vacuum chamber to draw a sputtering pressure that is less than about 50 mTorr. Then, the individual substrates can be conveyed into a sputtering chamber and past a planar magnetron continuously sputtering a target by an ionized gas at the sputtering pressure such that a thin film is formed on a surface of the individual substrate. The target is subjected to a high frequency power having a frequency from about 400 kHz to about 4 MHz at power levels of greater than about 1 kW. In one particular embodiment, the method can be generally directed to sputtering thin films on individual substrates defining a surface having a surface area of about 1000 cm2 to about 2500 cm2.