A Rotating Ring Disk Study of Accelerators with Cl^－ and Br^－ for Copper Damascene Electrodeposition

Abstract

The acceleration effects of bis（sodiumsulfopropyl） disulfide（SPS） and its derivatives in the presence of Cl^－ and Br^－ were studied using a rotating ring disk electrode（RRDE） in a CuSO₄/H₂SO₄ solution. The positive ring current increased with the addition of accelerators providing that the Cu（I） thiolate complex was formed during the dissolution step of electrodeposition. SPS and mercaptopropylsulfonic acid（MPS） show better acceleration effect with Cl^－ while propane-1,3-disulfonic acid（PDSH） has higher acceleration effect with Br^－. The highest acceleration effect is achieved with 4 ppm of PDSH and 50 ppm of Br^－. Copper electrodeposition, which was conducted using periodic pulse reverse current waveform with Ion ＝－20 mA/cm², achieved perfect filling with 2 ppm of PDSH and 50 ppm of Cl^－ in which the ring currents measured at dissolution step are significant. Results show that the cuprous complexes which formed during the dissolution step hastened via-filling.