ECMP 적용을 위한 KNO3 전해액의 I-V 특성 연구

Abstract

The chemical mechanical polishing (CMP) process has been widely used to obtain global planarization of inter-metal dielectric (IMD) layers, inter-layer dielectric layers (ILD), and pre-metal dielectric (PMD) layers [1, 2]. Also, the CMP is the most commonly used planarization technique in the semiconductor process for ultra-large-scale integrated circuit (ULSI) applications [3, 4]. As its name indicates, the CMP process depends on the chemical interaction of the slurry with the wafer to be polished and on the mechanical down force applied to the wafer. Recently, the application of CMP has been especially popular in the fabrication of copper (Cu) damascene structures and for the in the multilevel interconnection process [5-7]. However, device structures of low-k materials at 65 nm and below, because of fragility, require low down-force mechanical polishing to maintain the structural integrity of the underlayer during fabrication [8]. Also, other problems faced by the Cu-CMP process are the lower removal rate due to the low mechanical down force required by the low k dielectric, dishing, and erosion. To overcome these problems, electrochemical mechanical polishing (ECMP), a new planarization technology that uses electrolyte chemistry instead of an abrasive slurry, was developed [8-11]. Current-voltage (I-V) curves were employed, in this paper, to evaluate the effect of the electrolyte concentration on the electrochemical surface reaction of the Cu electrode. From the I-V curves, active, passive, and trans-passive electrochemical states could be characterized [12, 13]. Then, we investigated how this chemical electrolyte affected the process of voltage-induced material removal in Cu-ECMP. To selectively probe the electrochemical effect of ECMP, all these measurements were performed in the absence of mechanical polishing.