Stress Corrosion Cracking of Cu Interconnects during CMP with a Cu/Porous Low-k Structure

Abstract

Porous low-k materials are required in the construction of 45 nm node large-scale integrated devices. However, the extremely low Young's modulus values of these materials results in a high number of previously unreported defects. A porous low-k film stacked with a dense low-k film showed pronounced cracking in its Cu wiring, which was concentrated in isolated lines 0.18 m in width and was accelerated with longer chemical-mechanical polishing ͑CMP͒ times. Denser lines showed less cracking and the single structure of a dense low-k film showed no cracking. We hypothesized that this cracking might be categorized as stress corrosion cracking ͑SCC͒. Accordingly, we investigated the relation between stress and corrosion in certain kinds of slurry. We have also researched the effects on corrosion of temperature and various metals. In all of the slurry that we tested, tensile stress increased corrosion current in Cu samples. Furthermore, both finite element method analysis of stress during CMP and measurements of friction on the Cu/low-k surface by scanning probe microscopy indicated concentration of stress on low-k materials, especially at the edges of isolated wiring. Thus, we concluded that stress enhances corrosion during CMP and that there was a high possibility of SCC.

Effect of bis-(3-sodiumsulfopropyl disulfide) byproducts on copper defects after chemical mechanical polishing

“…Figure 2 shows that the PDS concentration increases from 0 to ϳ30 ppm as the bath idle-time increases from 0 to 20 days. 16 The result is consistent with the data of Fig. Long narrow strip defects such as scraping on the Cu surface are defined as scratch defects, and hollow hole defects such as removing a lump of Cu are defined as void defects.…”

“…Moffat et al proposed the kinetics of Cu electroplating in a cupric-sulfate electrolyte containing SPS-polyethylene glycol ͑PEG͒-Cl. [10][11][12][13][14][15][16][17][18] Conventional CMP slurries usually contain strong oxidizers and hard abrasives, easily leading to the formation of various defects on Cu metals. 8,9 Chemical mechanical polishing ͑CMP͒ is the most promising way to remove overburdened metals to realize planarization in the damascene metallization process.…”

In-Situ Measurements of Free-Standing, Ultra-Thin Film Cracking in Bending

“…These undergo multiple failure mechanisms such as delamination [4], channel cracking [5,6] and surface cracking which can be coupled with time-dependent damage from load cycling [7] and environmental degradation [8]. While multiple techniques and analyses exist for studying delamination or channel cracking of deposited thin films, direct measurements of fracture toughness values are relatively rare.…”

Integration of Low‐ k Dielectric Films in Damascene Processes

“…Introducing pores in a dielectric poses several challenges for successful integration into microelectronic circuits [17,18]. The mechanical strength of the dielectric is reduced by porosity, potentially leading to failure during chemical mechanical planarization (CMP) [19,20,21,22] or during wire bonding to the fi nished chip [23]. In addition, moisture, wet chemicals and gaseous species (such as precursors used during CVD) can penetrate into porous low-k materials, giving rise to an increase in both the dielectric constant and the leakage current [24].…”