FUNDAMENTAL CHARACTERIZATION OF TRIBOLOGICAL, THERMAL, FLUID DYNAMIC AND WEAR ATTRIBUTES OF CONSUMABLES IN CHEMICAL MECHANICAL PLANARIZATION

Abstract

This dissertation presents several studies relating to fundamental characterization of CMP consumables in planarization processes. These are also evaluated with the purposes of minimizing environmental impact and reducing cost of ownership (COO).The first study is conducted to obtain the retaining ring wear rate in a typical ILD CMP process and is specifically intended to investigate the effect of retaining ring materials and slot designs during the CMP process. The results show that retaining ring materials have effect on the COF, pad temperature and retaining ring wear rate, while retaining ring slot designs affect the pad surface abruptness. The second study is performed to compare the effect of different retaining ring slot designs on the slurry film thickness within the pad-wafer interface. A novel non-intrusive optical technique, dual emission UV-enhanced fluorescence (DEUVEF), was applied to accurately measure the film thickness of the slurry underneath the wafer during polishing. It is indicated that the optimized retaining ring slot design can significantly reduce the COO of CMP processes by increasing slurry utilization.A COF method is applied to measure the slurry mean residence time (MRT) during CMP. This technique uses transient COF data induced by a shift in slurry concentration to determine MRT. Variations in consumables as well as sliding velocity, pressure and slurry flow rate can affect the slurry MRT. One study in this dissertation focus on the effect of retaining ring slot designs on the slurry MRT. Another study compares the slurry MRT under same polishing conditions using pads with different groove width. Both studies are conducted on multiple sliding velocity, pressure and slurry flow rate variations to understand the characteristics of consumable designs. The method of measuring MRT during polishing presented in this dissertation can be easily applied in general CMP processes.The subsequent studies focus in the diamond conditioner discs characterization techniques. A newly developed method for determining active diamonds and aggressive diamonds on a diamond conditioner disc under a certain vertical load is elaborated in this dissertation. Later, this technique together with scanning electron microscopy (SEM) imaging is implemented to analyze diamond pullout and fracture in CMP. Five different types of diamond conditioner discs are subjected to a novel accelerated wear test respectively to compare the extent of diamond pullout and fracture under the same conditioning condition