Hitachi Chemical has developed silicon nitride (SiN) slurries that are etched and exhibited at the 12th International Nanotech 2013 (nano tech 2013). As long as the slurry is shaped using a screen printing process, only SiN under the slurry can be removed. Hitachi Chemical's goal is to use this paste for solar cells and MEMS manufacturing processes.
In a manufacturing process of a crystalline silicon solar cell, an antireflection film is generally formed of SiN on the light-receiving side of the silicon cell. After the Ag electrode is formed on the anti-reflection film, a "Fire Through" process is further performed, and the Ag electrode is contacted with the silicon cell by heating at several hundred degrees Celsius.
With this paste, Ag electrodes and silicon cells can be contacted without using the high-temperature process Fire Through.
In the etching process, first, a paste is printed on a portion to be etched using a screen printing process, and then heated at 170° C. for 5 minutes. At this time, an etchant is generated in the paste, and SiN under the paste is etched. After the etching, as long as it is washed with water, the slurry and its underlying SiN portion can be removed to obtain a silicon cell. Finally, an Ag electrode is formed on the portion where SiN is removed, so that the Ag electrode can be contacted with the silicon cell.
At present, the paste can be formed with a line width of about 100 μm and the etchable SiN depth is 100 nm. In the future, Hitachi Chemical will continue to promote development in accordance with the needs of solar cell manufacturers and other targets, such as further thinning.
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