Magnetron-Enhanced Reactive-Ion-Etching of Al-1%Si-2%Cu Alloy

Abstract

ABSTRACTPlasma etching of Al-1%Si-2%Cu presents serious challenges in corrosion, residue, and critical dimension (CD) control in single wafer etchers. One approach is to pattern the metal with oxide mask so chlorine can no longer be trapped in resist and sidewall polymers to cause corrosion. The magnetron-enhanced reactive-ion-etching (MERIE) offers a high degree of ionization at very low pressure, so anisotropic etching with reasonably high etch rate can be achieved even without sidewall protection. This paper summarizes our MERIE process characterization in terms of the effects of SiCl4 flow rate and plasma power on selectivity and CD control using an oxide mask. Typical etching was performed at 1000 watts and 40 sccm SiCl4 with the unthrottled pressure at 4.0 mTorr and a self-induced dc bias of 75 V. A 2-minute NF3 plasma at 250 watts and 100 sccm of NF3 flow served as the passivation step. This metal etch process has been successfully implemented in a doublelayer-metal interconnect technology.