A novel pad conditioning disk design of tungsten chemical mechanical polishing process for deep sub-micron device yield improvement

Abstract

Chemical Mechanical Polishing (CMP) is widely used for global planarization in IC device structure. A pad conditioner is often used to remove polishing debris, and hence preventing the pad surface from glazing. The proper conditioning can assure the pad surface like new so it can hold slurry evenly for effective polishing. Diamond disks are commonly used for conditioning the CMP pads. The designs of diamond disks are critical as it determines the efficiency of the grooving action. All conventional diamond disks contain grits that are distributed randomly. A novel disk provided a regular diamond grits. They are set with a fixed diamond distance and diamond protrusion. These characteristics provide a smoothly slurry distribution and conditioning efficiency. Tungsten chemical mechanical polishing (WCMP) is used for W burden removal, but also is a challenging process due to metal-binder's corrosion on diamond disk during pad conditioning. Diamond segregation and diamond pullouts arising from metal dissolution of diamond disk not only make the conditioning inefficient, but also damage and contaminate the polished wafer surface. It is a major yield killer for deep sub-micro device. In this study, the new disk made by the novel diamond grid technology with a fixed diamond size and pitch appears feasible for in-situ WCMP application. It shows a relationship of polish performance between diamond size & diamond pitch. The higher polish performance got as diamond size decreasing and increasing working efficiency.