Aluminum oxide was adopted into solar cell processing with PERC, but the dielectric has an even more crucial role to play in TOPCon, as it becomes the emitter passivation layer. Whether it be PERC or TOPCon, ALD and PECVD are the 2 mainstream methods for aluminum oxide deposition. ALD systems, however, were the first to facilitate the deposition of aluminum oxide for PV.
The fundamentals of ALD can be found in our earlier PERC reports, e.g., PERC Solar Cell Technology 2017 Edition. ALD reactors function on the principle that alternate dosing of the precursor, which is trimethyl aluminum (TMA) and water vapor serving as oxidant, is accomplished in the same reactor chamber. While a few companies did tweak this fundamental principle by making it spatial and truly inline, they are currently commercially inactive, at least for this application.
TaiyangNews’ latest Market Survey on Solar Cell Production Equipment 2025 features ALD-based tools from 3 companies. Chinese solar cell production equipment manufacturer Shenzhen S.C is also offering an ALD solution for aluminum oxide deposition. Called ALD-800, the tool is a vertical batch system equipped with 4 process chambers. While the company has not explicitly mentioned throughputs in hourly metric, the per-batch throughput is given as 15,915 M10 wafers or 11,368 G12 wafers. While the tool supports adjusting the film thickness between 1 and 10 nm, the above throughput refers to 4 nm film thickness. ALD-800 operates at 150 to 300°C and 1 to 100 mbar, and uses TMA and H₂O/O as precursors. Scheduled maintenance includes a 1-year cleaning interval and a 12-hour chamber cleaning using sandblasting and pure water. The tool requires up to 260 kW of power. Given a cycle time of 2,280 seconds, the rated batch throughput mentioned above is most likely the hourly capacity. The tool is rated for an uptime of 98%.
