The Study of Silicon Nitride Films Deposited In Batch ALD System

Silicon nitride (Si 3 N 4 ) is commonly applied as insulators and barriers in IC manufacture. It can be deposited by atomic layer deposition to achieve an excellent step coverage especially in high aspect ratio structure. ^[1] ALD process usually has a longer process time as lower throughput. To compensate this, batch ALD system such as vertical furnace has been designed for ALD process with a batch up to more than 100 wafers. However, the complex dynamic and chemisorption mechanism of the reactant gases alternatively blowing on the wafer surface makes it challenging to achieve better Si 3 N 4 film uniformity and higher quality. A Couple of flow mode comparison experiments on the Si source gas flush flow and soaking was conducted. The results show that flush flow improves the wafer to wafer thickness uniformity within a batch significantly. However, the contrast experiments indicate a better within wafer thickness uniformity with APC open. Based on these results, comparison experiments with different exposure time of Si source and NH3 as precursors were performed. The results demonstrate that as the exposure time of Si source on the wafer increases, the wet etch rate (WER) of Si 3 N 4 decreases which represents improved film densities, along with a steady increase in film uniformity. This provides a significant guidance for semiconductor device fabrication.