A Study On The CMP Of Coper For Mulilevel Metallization In ULSI

In design of ULSI, with wire becoming thinner, the resistance rate goes up and the caloric released increased. Then, Al used for VLSI will transplant acute and this will effect the capability of chip. Because the resistivity of Cu is lower and the electromigration resistance is higher than Al, it can reduce wire thickness, multiplayer number, capacitance of multiplayer which will arose signal delay, power consumption and cross talk. The chip used Cu as multilevel metal can meet high frequency, high integration, big power, big capacitance and long life. So Cu is an attractive interconnect material for future sub micron multilevel technology.The four-steps mechanism model of copper CMP, which is compliant to alkali polishing, is firstly put forward in this paper. The four-steps are introduced as follows: First, surface layer was formed. Copper surface on wafer was oxidized in the environment of alkali slurry, and the surface layer comprise copper's oxidant, such as CuO and Cu2O; Secondly, selectivity CMP. Heave areas in copper surface were polished under the mechanical action, simultaneously, oxide surface layer keep the recessed areas from beening eroded further more; Thirdly, dissolution. Cu"1" and Cu2+ were combined to stable dissoluble compound. This step accelerates the balance of oxide action turnning to right, and copper ions contamination was effectively controlled too; Finally, compounds were taken out by turbulent slurry. This process goes round and round, and copper CMP was finished.Copper CMP includes two steps, so we studied for both to get slurries adapt to them. In the first step, high complex, low oxidation, small abrasive and high concentration model yield low scathe, high CMP rate, high selectivity, high planarization and high clean; In the second step, higher mechanical role and lower chemical role yield the final global planarization. In this way, copper CMP can achieves high rate, right selectivity, low scathe and high global planarization.Two kind of copper CMP slurry used in ULSI were put forward in this paper, non-contamination silicon colloid (15-20nm) was used as abrasive, non-metal ions organic alkali was used as pH stable reagent, promote oxide reagent and effective complex reagent for copper ions. High combination to copper ions avoids abrasive contamination and yields high CMP rate; Used non-metal ions oxidant simultaneously can avoids slurry turnning to gel, can making over polishing clean ease.To meet the requisition of copper CMP in ULSI, the experiment specialty, which are weak oxidant, strong complex and non-metal ions, achieved high CMP rate, appropriate non-contamination. By controlling the chemical action, technical parameters were under the control. It is so important to technical reliability and reproducibility.