Cu Planarization for ULSI Processing by Electrochemical Methods: A Review

Characterization of phosphate electrolytes for use in Cu electrochemical mechanical planarization

“…There is also a strong demand to meet increasing industrial standards, which include achieving higher planarization efficacy, causing less defects, and attaining higher throughputs at lower downforces [2,3]. This is challenging due to the reduction of feature sizes with increasing packing densities and the growing number of interconnect layers present in ICs [2].…”

“…ECMP utilizes an external circuit to oxide copper (Cu) and therefore can operate at low downforces [3,4,9] and may not require the use of strong oxidizers, complexing agents, and/or slurry particles which are known to make CMP waste slurry treatment costly. During CMP, slurry particles have a tendency to form aggregates that can be embedded in the wafer surface and also cause surface scratching.…”

An investigation of phosphate based ECMP electrolyte performance on feature scale planarization

“…However, conventional CMP processes are limited when addressing new challenges due to the use of abrasive slurry particles and strong downforce required to achieve planarization [6][7][8]. In addition to anticipated CMP limitations, there exists a strong demand to meet industrial standards to achieve higher planarization efficacy, while causing less defects (i.e., dishing, erosion, delamination), and attaining higher throughputs at lower downforce [3,6,8,9].…”

“…Electrochemical polishing (ECP) and electrochemical mechanical planarization (ECMP) have emerged to offer alternative means of planarization, due to their potential improvements in both the reduction of consumables use and the increase in planarization performance compared to current technologies [9][10][11]. However, recent studies have shown that the use of ECP alone will not suffice for future nodes, especially for planarization of low-aspect ratio features [5].…”

“…The use of an applied voltage causes Cu oxidation to occur without the use of oxidizing agents present in the electrolyte. Therefore, ECMP may not require strong oxidizers and/or abrasive slurry particles, which are known to contribute significantly to surface defectivity during the planarization process [9,10,12]. To quantify planarization capability of an ECMP electrolyte using a rotating disk electrode (RDE) on a simplified feature (Fig.…”