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Product Briefing Outline: Stangl Semiconductor Equipment AG is introducing a new wet chemical etching tool, the Materia Pce, for removing surface contaminants from chunks of polysilicon or upgraded metallurgical silicon (UMG) as a result of the crushing process.

Problem: Higher conversion efficiencies for solar cells are a key element of reducing the cost per watt. Polysilicon and UMG material with reduced impurities enables higher cell efficiencies. Removing contaminants before cell processing begins is required.

Solution: The Materia operates in a batch mode by loading the chunks into baskets, which are moved by linear robots through various chemical and cleaning process stations. Each basket can accommodate 25kg of silicon chunks, varying in diameter from 10 to 180mm. After the treatment, the chunks are rinsed and dried to remove any traces of chemicals. This CE-compliant wet bench is designed to etch 5 to 20 µm on the peripherals of the chunks to get rid of the organic residues and metallic contaminated layers. According to Stangl, the Materia can be configured to support polysilicon production volumes from 500 to 2,500 tons per year. The setup offers flexibility in terms of the main chemical agents used for etching. The etching device is designed to handle alkaline as well as acidic etchants, and even a process sequence combining both. It uses HF and HNO3 as acidic media and NaOH and KOH as alkaline agents.

Applications: Cleaning of polysilicon or upgraded metallurgical silicon (UMG)

Platform: The device, which occupies 7.2 × 2.3m of factory floor space, can process two to 10 baskets per hour with an uptime of more than 95%. Stangl is offering additional accessories at an extra charge, such as chemical supply systems, process engineering, custom-built baskets and loading/unloading containers, and RFID chips for tagging products.

Availability: March 2009 onwards.