Chemical Mechanical Planarization of Copper Damascene Structures

Abstract

We describe the chemical mechanical planarization (CMP) of copper damascene structures using an IC1400 pad and four different types of slurries. Two alumina-based slurries and two silica-based slurries were evaluated. After successful removal of the excess Cu, we examined the topography of the planarized structures using scanning electron microscopy. The effects of the CMP process on spacer erosion, Cu line recess, corrosion of submicrometer Cu lines, liner removal selectivity, and contamination of the patterned structures are presented. It was found that minimizing the etch rate (ϳ10 nm/min) of the slurry is required to achieve reproducible removal rates and unrecessed (etched) damascene structures. No dishing was observed with the utilized pad. We also show that corrosion is prone to occur in low Cu pattern density areas and that the removal of the liner material (tantalum) remains problematic because of its chemical inertness.

A wafer-scale material removal rate profile model for copper chemical mechanical planarization

“…Recently, copper has been used to replace aluminum as the interconnect material in integrated circuits (ICs) because of its low resistivity and high electromigration resistance [2]. However, reactive ion etching has become impractical as a means of patterning copper because volatile copper compounds are formed only at high temperatures [3]. The copper damascene process provides a solution to problems arising from the lack of directional copper etching capacity [4].…”

Effect of Ceria Abrasives on Planarization Efficiency in STI CMP Process

“…Therefore, the removal rate of active oxide will be higher than that of field oxide, and the planarization of oxide patterns can be achieved according to polishing time. [13][14][15][16]. Assuming that the removal rate is related to the α p value at constant velocity, the removal rate according to pressure can be classified into three features based on increase of α values, as shown in Figure 4(a).…”

“…The dependency of material removal rate on pressure P and relative velocity V is defined by Preston's equation in which the removal rate is linearly proportional to these two values [12]. However, many modifications of Preston's equation have been developed to compensate for inaccuracies in the original equation from the late 1920s [13][14][15][16]. Today, the generalized form of Preston's equation, which is widely accepted and used in the CMP process, can be written as follows:…”

Why CMP?

“…Compared to aluminum, copper is also more liable to diffuse into SiO 2 . To address the adhesion and diffusion issues, a barrier is placed between the copper and the dielectric [1,42]. There are several possible candidates for barrier materials, a combination of Ta and TaN has been the choice for many successful manufacturing processes.…”