[15a-2Q-1~12] 8.4 Plasma etching

△ [15a-2Q-5] Selective Cyclic Etching of SiN Using Infrared Irradiation

〇Nobuya Miyoshi¹, Hiroyuki Kobayashi¹, Kazunori Shinoda¹, Kenji Maeda¹, Yutaka Kudo², Tadamitsu Kanekiyo², Masaru Izawa² (1.Hitachi, 2.Hitachi High-Tech)

Keywords:etching,SiN

The removal of the (NH₄)₂SiF₆ layer using IR irradiation was investigated to achieve high-throughput cyclic etching. The reactive layer of (NH₄)₂SiF₆ was formed on a silicon nitride sample after exposure to radicals in fluorocarbon-based plasma. After formation of the reactive layer, IR light was irradiated to the sample for removal. The results show that IR irradiation is expected to result in fast removal of the reactive layer within 10 s. The etching depth after IR irradiation saturated at 1 nm as the radical exposure time was increased to over 300 s. Therefore, a self-limiting process for silicon nitride was obtained by forming and removing the (NH₄)₂SiF₆ layer. Finally, the number of cycles was changed between 1 and 10. The total etching depth increased linearly with the number of cycles. In contrast the etching depth of SiO₂ was 0 nm. These results demonstrate the selective cyclic etching of silicon nitride with high precision.