Formation of Ammonium Salts and Their Effects on Controlling Pattern Geometry in the Reactive Ion Etching Process for Fabricating Aluminum Wiring and Polysilicon Gate

2002/04/15 by Shuichi Saito, Kazuyuki Sugita, Junichi Tonotani +1
Engineering · Materials Science · #Semiconductor materials and devices #Plasma Diagnostics and Applications #Copper Interconnects and Reliability

paper · doi:10.1143/jjap.41.2220

Abstract

The role of N2 gas addition in the reactive ion etching (RIE) processes for aluminum wiring and polysilicon gate fabrication was investigated. With an increase in the amount of N2 gas added to the etching gas, the pattern profile changed from a reverse to an ordinary taper and the pattern width increased. By AES analysis, nitrogen was detected in the pattern sidewall passivation layer when N2 gas was added. Optical emission spectroscopy of the plasma revealed that hydrogen was supplied from the decomposition product of the photoresist in RIE of aluminum with BCl3/Cl2. XPS, FT-IR and TDS analyses were carried out to study the structure of the passivation layer. Consequently, it was confirmed that nitrogen combined with hydrogen to form N–H bonds in NH4+, and that NH4+ coupled with Cl-, AlCl4- and SiF62- during aluminum and polysilicon RIE, respectively. It was also found that ammonium salts were deposited on the pattern sidewall, and played a major role in controlling the etching profile and pattern width.

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