LOW-PRESSURE CHEMICAL-MECHANICAL POLISHING METHOD FOR SURFACE OF COPPER WIRING IN ULTRA-LARGE SCALE INTEGRATED CIRCUIT

摘要

A low-pressure chemical-mechanical polishing (CMP) method for the surface of the copper wiring in ultra-large scale integrated circuit is disclosed. The operational steps are as follows: (1) preparing polishing solution by uniformly mixing the following components i.e. nano SiO2 abrasive (35-80 wt%), deionized water (12-60 wt%), oxidant (1-3 wt%), activating agent (1-4 wt%), and FA/OII type chelating agent (0.5-1.5 wt%); (2) setting the polishing process parameters as follows: polishing pressure of 2-5 KPa, polishing temperature of 20-50?, flowing rate of 120-250 ml/min, and rotational speed of 30-60 rpm/min. The oxidant in the polishing solution oxidizes the copper, the FA/OII type chelating agent with extremely powerful inherent chelating ability quickly reacts with the oxidized copper, and the resultant soluble chelate compound rapidly escapes from the copper surface, thus avoiding removal of the copper on the surface mainly dependent on the mechanical friction effect and realizing the copper polishing with low mechanical intensity. During the chelating process, the removal of material is achieved by breaking the molecular bonds, so there is less damage to the material surface. The chemical action of CMP is reinforced under low pressure to compensate for the effect of the mechanical action on the polishing rate.