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C4F6 hexafluoro-1,3-butadiene for high aspect ratio chips

2018-07-30 14:08

Hexafluoro-1,3-butadiene (C4F6) is an environmentally-friendly etching gas with low greenhouse effect which mainly used in semiconductor dry etching process. With the application of technologies such as the Internet, Cloud Computing and Artificial Intelligence, the amount of global data will increase rapidly in the future and the requirements for storage capacity will become higher and higher. The 2D plane structure has reached the technical limit, and the 3D structure is inevitable for future development trend. With the development of 3D NAND technology, the consumption of C4F6 will increase greatly. In the process of NAND FLASH from 2D to 3D, the consumption of C4F6 for single-chip wafers is more than 6 times as before.

C4F6, also known as hexafluoro-1,3-butadiene, HFBD, has the following excellent properties for etching. Compared with C4F8 and C5F8, C4F6 can be used to obtain higher etching selection ratio and C4F6 has a higher selectivity to photoresist and silicon nitride than C4F8. These two etching advantages can improve the stability of the etching and the production efficiency, thereby they can improve the yield and reliability because as the device size advances to 0.13 um, the CD (critical dimension) of the hole is 30 % smaller than 0.18, the selection of the bonding layer needs to be higher so as to enlarge the etching window. In addition, C4F6 has a low global warming potential. Compared with C4F8, C4F6 can reduce PFC emissions by 65%-82% .

Comparison of etching performance

C4F6 can replace CF4 in dry etching process for KrF semiconductor capacitor patterns. C4F6 has anisotropy and could produce a ideal aspect ratio in silicon and silicon oxide etching. It could protect the sidewalls by forming a polymer film (photoresist) in etching process.