Chemical mechanical polishing (CMP) has become the key planarization technology in ultralarge scale integration (ULSI) silicon device manufacturing to fabricate sub-quarter-micrometer metal and dielectric lines. [1][2][3][4] In the CMP process, planarization is achieved by polishing a wafer with uneven topography using a colloidal slurry consisting of sub-micrometer sized abrasive particles. The particles are dispersed in an aqueous solution containing various chemicals, which make up the slurry. These chemicals, depending on their identity, play different roles such as oxidizers [Fe(NO 3 ) 3 , (NH 4 )S 2 O 8 , H 2 O 2 ], passivating agents (benzotriazole, benzimidazole), slurry stabilizers [poly(ethylene glycol), arabic gum], etc. While several slurry chemistries are available for Cu CMP and significant progress has been made in utilizing them in manufacturing, very little fundamental information about them is available in the published literature.Copper CMP in a highly acidic pH regime leads to corrosion problems, while Cu CMP in alkaline conditions is faced with an unfavorable polish rate selectivity with respect to SiO 2 , leading to interlayer dielectric (ILD) erosion. Thus, an intermediate pH range 4-7 appears to be a better choice for Cu CMP. 5-7 One of the more attractive slurries in this intermediate pH range consists of hydrogen peroxide, glycine (an amino acid), and an abrasive. Hirabayashi et al. 8,9 demonstrated that slurries containing hydrogen peroxide, glycine, and silica particles (abrasive) can be used for Cu CMP. They successfully fabricated inlaid copper wiring using the damascene process with very little dishing (less than 60 nm in the linewidth range of 0.5-100 m) with the above slurry. The mechanism, as proposed by them, consists of the oxidation of Cu to copper oxide by H 2 O 2 in the recessed region, thereby preventing the dissolution of Cu from the recessed areas of the wafer. The oxide formed in the protruded regions, on the other hand, is removed by the abrasives exposing the underlying metallic Cu surface to the slurry. According to Hirabayashi et al. copper is then converted into Cu(H 2 O) 4 2ϩ by the hydrogen peroxide in the slurry which in turn reacts with glycine (also in the slurry) to form a Cu 2ϩ -glycine chelate that is soluble in water. Thus, while the formation of copper oxide prevents the direct etching of Cu in the low lying regions, Cu in the protruded regions is removed by both direct dissolution as well as by the removal of the oxide formed. However, they did not describe the interaction between the Cu 2ϩ -glycine complex and hydrogen peroxide and its effect on Cu removal or the role of hydroxyl radicals. It has been well established that the decomposition of hydrogen peroxide leads to the formation of hydroxyl radicals (*OH) which are a much stronger oxidizing agent than hydrogen peroxide itself. 10,11 There is also a rich collection of information concerning the catalytic generation of *OH from hydrogen peroxide, with various metal ions and metal ion complexes acting ...

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We examined the effect of the structure of corrosion inhibitors benzotriazole ͑BTA͒ and 1,2,4-triazole ͑TAZ͒ on the Cu removal rate during chemical mechanical planarization. Removal rates were higher for solutions containing TAZ than solutions containing BTA. Corrosion inhibitor films were characterized using atomic force microscopy, cyclic voltammetry, impedance spectroscopy, surface-enhanced Raman spectroscopy, and mass spectrometry. Inhibitor films formed from TAZ were thicker, more permeable, and rougher than films formed from BTA. The addition of glycine to the corrosion inhibitor containing solutions showed an increase in corrosion for the TAZ-covered Cu surface, little change for the BTA-covered surface, and an increase in removal rate for both systems. This study correlates removal rate with the physical properties of these two different corrosion inhibitors.

Chemical-mechanical planarization (CMP) slurries can be classified into two general categories according to their applications: metal CMP slurry and nonmetal CMP slurry. Two most important metals incorporated into IC chip manufacturing via CMP are W and Cu. Depending upon integration schemes, a metal CMP slurry may or may not carry out the function of removing the film(s) immediately below the overburden metal such as cap, adhesion, and barrier layers. For tungsten CMP, a single-step slurry is typically used to remove both excess tungsten and its barrier/adhesion layer. For copper CMP, after the removal of copper, a subsequent barrier removal step is often required. This chapter reviews the basic requirements for the key components found in common metal slurries.It is generally understood that a metal CMP slurry chemically modifies the surface to be polished and yields a softer and porous complex layer, which is then removed by mechanical force in the process. Although these metals may differ in their physical and chemical properties, the underlying principle for the design of slurries is the same. A production-worthy metal CMP slurry must address several issues, such as material removal rate (MRR), within-wafer nonuniformity (WIWNU), step height reduction efficiency, dishing/erosion, minimum ILD loss, corrosion, scratching, slurry residue, and other surface defects. Typical metal CMP slurry may contain an oxidant, a chelating agent, abrasive particles, a surfactant, and other additives. These components must work in concert to produce adequate material removal rate, high planarization efficiency, and Microelectronic Applications of Chemical Mechanical Planarization, Edited by Yuzhuo Li

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