R & D Department – long-term experience
At the beginning of the project “Sun Silicon” 2006 in Bitterfeld several in-house developments were started to optimize key equipments and establish basic processes for running the plant to fulfill requirements for solar-grade silicon. These development projects can be summarized as follows:
- A complete new design and a process for a high efficiency hydrogenation reactor (converter) with high conversion efficiency of SiCl4 to SiHCl3.
- Silver-plated bell jar of the Siemens reactors to reflect process heat and reduce power consumption.
- Implementation of boron-doped slim rods allowing a simple procedure for starting the silicon deposition process.
- Computer simulation methods for basic processes of the deposition process to find the best conditions for silicon deposition.
- Designing a new harvesting and crushing system to handle silicon rods weighting more than 200 kg each.
- Engineering of a new slim rod production process and equipment to reduce production cost for slim rods (filaments) including slim rod welding.
- Adapted slim rod graphite contacts.
- Trace analysis of impurities by micro-crystal pulling and micro-epitaxie and application of physical methods for interpretation.
Research and development on the Siemens process for the production of low-cost solar-grade silicon especially with the focus on cost reduction and quality improvement of silicon by using the following key equipment:
- Basic thermo- and fluid dynamic simulations of the deposition process have been performed to develop and optimize deposition processes.
- Deposition process with highest energy-efficiency.
- To reduce the break-off rate of the reactor caused by slim rod breakage, test and simulations to improve the start procedure are performed and an improved slim rod contacting was developed.
- Establishing a highly automated process control for silicon deposition to reduce man power and reaching a reproducible process.
- Process to harvest, crush and pack the produced silicon is established.
- Continuous runtimes of about 9 months have been achieved before graphite heaters need to be replaced.
- Tests, process simulations as well as construction and material revisions are performed to further improve the runtime, the yield and the capacity of the converters.
The developed processes, methods and workflows are already transferred to the production department and monitored during the production process in Bitterfeld.
Further R&D projects in cooperation with universities and institutes have been initiated and planned to diversify the range of products and ensure the further success of the company.