Hydrophobic Modification of Diamond Conditioner for Prevention of Particle Adhesion During Oxide CMP

Abstract

Conditioning with a diamond conditioner is a routine practice in the chemical mechanical planarization process to maintain removal rate and uniformity. Electroplated Ni conditioner surfaces can be easily contaminated by polishing residues from the slurry, pad, and by-products during conditioning. In this study, a hydrophobic film was coated onto a Ni conditioner by vapor phase self assembled monolayer (V-SAM) deposition to prevent contamination. The film was deposited in a vacuum chamber at 0.5 Torr and 100 C using a fluorocarbon (FC) precursor. The modification of the Ni surfaces increased the contact angle from 50 to 105 . The adhesion force between the Ni surface and silica particles was approximately 100 nN in a solution of pH 11.2. The precursor coated Ni resulted in a five times lower adhesion force than the uncoated Ni conditioner. The coated conditioner did not attract any slurry residues on its surface, even after conditioning for 20 h with a fumed silica oxide slurry.Chemical mechanical planarization (CMP) consumables such as slurries, pads, conditioners and retainer rings have been adapted to achieve the required planarization of surfaces in semiconductor manufacturing. The surface asperity and porosity of CMP pads can greatly affect the material removal rate (MRR) and planarity during the polishing process. 1,2 However, the surfaces of the pads can undergo plastic deformation, so that the surface becomes smoother and the pores are filled with polishing residue, referred to as the 'glazing' effect. 3,4 Therefore, pad conditioning is necessary to maintain uniform MRR during CMP. 5 Ni conditioners with diamond particles are often heavily contaminated with slurry residues after conditioning. Once trapped in the conditioner surface, the residues remain and become harden, which reduces the conditioner life-time and causes the generation of unwanted particles from conditioner surfaces during polishing. These changes may generate scratches on oxide surfaces.The modification of surfaces with hydrophobic fluorocarbon films reduces the friction and stiction of two moving parts due to low surface energy and low friction coefficient characteristics. 5-9 A few methods are available for the preparation of hydrophobic films: self assembled monolayers (SAMs) and plasma polymerization. SAMs can be formed spontaneously on substrates from either liquid or vapor media. 10 Even though liquid SAMs are very simple to apply, it is difficult to control the process, which may therefore result in poor film quality and produce a large volume of waste. 11,12 Furthermore, liquid SAMs have limitations when coating nano or high-aspect-ratio structures due to high surface tension. 13 Vapor SAMs can be used in a vacuum by supplying a precursor in gas phase to a high temperature chamber. This method is easy to control and can be used to deposit multiple samples simultaneously. 13,14 Additionally, with the reaction of plasma and a precursor, the polymer can be polymerized and coated on the substrate at a desired deposition rate, which is...