1H-Benzotriazole Incorporated Pad for Chemical Mechanical Planarization of Copper

Abstract

Chemical mechanical polishing ͑CMP͒ pads are generally designed to play a passive role in terms of chemical reactions that occur on the surface to be polished. For copper CMP, a pad that is capable of initiating and controlling various chemical reactions on the copper surface can bring another dimension of flexibility to the CMP process. This work investigates such a model pad for its potential applications in copper CMP. More specifically, the physical and chemical properties of a polyurethane pad containing 1H-benzotriazole ͑BTA͒ are examined. When applied to Cu blanket wafers, the BTA-containing pad yielded a higher removal rate compared to the conventional CMP process with the reference pad. For patterned wafer polishing, the results indicate that the BTA-containing pad is effective in improving the step height reduction efficiency and in minimizing dishing and erosion. The potential applications of a pad with such a design for gaining a fundamental understanding of the copper CMP process are discussed based on these experimental results.Chemical mechanical polishing ͑CMP͒ has become a main stream method in submicrometer integrated circuit manufacturing for its global and local planarization abilities, thereby more efficiently enabling the fabrication of multilevel interconnects. 1,2 The key consumables in a CMP process include pad, slurry, conditioner, and carrier. 3 During polishing, the pad carries the slurry and delivers it to the wafer surface. It also transmits the normal and shear forces from the polisher to the wafer. Therefore, the polishing pad plays a critical role in the CMP process and influences the outcomes such as removal rate ͑RR͒, step height reduction efficiency ͑SHRE͒, withinwafer nonuniformity ͑WIWNU͒, wafer-to-wafer nonuniformity, and defect counts. 4 The conventional Cu CMP slurry is comprised of an oxidizer, abrasive particles, passivating agent, and chelating agent. 5,6 Optional additives can be anions, surfactants, and rheological modifiers. The oxidizer commonly used is hydrogen peroxide ͑H 2 O 2 ͒ to generate copper ions from the surface. Among metal oxides, colloidal silica ͑SiO 2 ͒ has become the choice of abrasive particles in copper CMP due to its availability in various sizes, purity, and functionality. The passivating agent is often chosen from one of the azole derivatives such as benzotriazole ͑BTA͒, imidazole, or any organic compounds that can form an insoluble film on the Cu surface. The chelating agent can be any organic acids that can form water-soluble complexes. Examples of possible chelating agents include carboxylic acids and amino acids.The CMP process is well recognized for its power in providing global and local planarizations for wafer processing. 7 However, CMP processes also have disadvantages in terms of introducing defects such as dishing, erosion, scratches, and contamination. 8,9 Dishing and erosion affect the electrical resistance of interconnects because they change the dimension and properties of the cross section of the interconnects. 10 With the conven...

The effect of polymer hardness, pore size, and porosity on the performance of thermoplastic polyurethane-based chemical mechanical polishing pads

“…The polishing properties of CMP pads are both intrinsic and extrinsic functions of the polymer type used and the resulting foam morphology [5,[12][13][14][15][16][17]. Oliver et al [12] have shown that several factors contribute to the modification of pad properties.…”

“…Contact area has been shown to depend on surface morphology, which in turn depends on pore size, pore size distribution and material properties [30,31]. Therefore, it is desirable to manufacture pads with controlled porosity and pore size to increase pad-wafer contact area as well as to maintain pad-to-pad polishing consistency [15].…”

“…Moreover, very limited published studies exist that highlight the polishing performance of a polyurethane based CMP pads [16,17,[47][48][49][50][51]. Although, many studies exist that examine the influence of pad physical properties such as pad compressibility, modulus, and surface roughness [5,[52][53][54][55][56][57][58], only a few have reported the influence of pad pore size, porosity, polymer hardness and stiffness on CMP performance [15,50,59].…”

Synergistic Effect of Pad “Macroporous-Reactors” on Passivation Mechanisms to Modulate Cu Chemical Mechanical Planarization (CMP) Performance

“…Variations in defects and surface topography may be a result of galvanic corrosion/pitting, micro-scratching, particle contamination, line dishing, or edge-over-erosion, among others. [5][6][7][8][9][10] Modulating the chemical and physical stress at the Cu/slurry/pad interface will be key to limiting post-CMP defects and is controlled by selectively altering slurry chemistry. A typical Cu CMP slurry is a colloidal dispersion of nanoparticles coupled with chemical components including: complexing agents, corrosion inhibitors (passivating agents), oxidizers, rheological modifiers (i.e.…”

Chemical Mechanical Polishing (CMP) of SiC Wafer Using Photo-Catalyst Incorporated Pad

“…The key components in CMP process involve wafer, slurry and pad. 15,16 In order to obtain higher removal rate of SiC wafer and ultrasmooth surface, a novel photo-catalyst incorporated pad is developed z E-mail: zhouyanbebe@126.com; pangs@tsinghua.edu.cn for polishing of on-axis Si-face SiC wafer in the paper. TiO 2 could be release holes and electrons under UV light.…”