High-purity fluorine gas (F2) is the highest performing cleaning gas available. Onsite generation of the gas has been developed by Linde, delivering high-purity F2 on demand and at low pressure, eliminating the need for large-volume/high-pressure storage and ensuring safe and reliable supply to CVD process tools.
The fluorinated gases typically used for PECVD chamber cleaning (SF6 or NF3) have high global warming potential and contribute a significant amount of carbon footprint to the finished product–a critical factor for PV products which are perceived to be intrinsically green. In addition, for large panel sizes and high throughput processes, the large amount of energy required to create the fluorine radicals (which do the cleaning) from these gases presents many challenges for the deposition equipment manufacturer.
Fluorine has zero global warming potential and the low F-F bond energy means fluorine radicals are easily and efficiently produced leading to shorter cleaning times, higher tool throughput, and a reduction in the amount of material and power used. For the latest, largest panel sizes, the use of F2 enables existing processes to be scaled without the significant hardware modifications required with NF3 or SF6. By generating the gas onsite, on demand, and at low pressure, safety concerns regarding transport, storage, and safe delivery to the process tool can be more easily addressed.
Within large scale TFT-LCD and thin-film PV production, F2 is used to clean PECVD process chambers, displacing NF3 or SF6. Similar cleaning applications exist within semiconductor manufacturing, where it can also displace high-pressure cylinder F2 or ClF3. A number of process applications are under development.
The Generation-F platform has been delivering high-purity F2 for more than 10 years, and more than 30 modules are installed and running high-volume production worldwide; for PV applications more than 20MW of clean power has been delivered. The flexible modular design allows for a wide range of flows and quantities to be delivered from pilot line development through to high volume production.