Removal of Nanoceria Abrasive Particles by Using Diluted SC1 and Non-Ionic Surfactant

Abstract

Nanoceria abrasives have received intensive attention in the process of shallow trench isolation (STI) polishing since it can result in less scratch. However, the nanoceria particles are very difficult to remove after chemical mechanical polishing. In this study, it is found that by adding AEO-20, a nonionic surfactant with appropriate concentration in the SC1 (H2O2: NH4OH: H2O = 1: 1: 5 v/v/v) and SC1 solution with diluted ratio up to 10, the nanoceria abrasive particles on the contaminated SiO2 wafers can be completely removed. Multiple measurement results show that the SC1 can react with Ce3+ and form Ce4+ in the ceria slurry, and the Ce3+ will slightly react with AEO-20 while Ce4+ will not. It is concluded that AEO-20 will adsorb on the nanoceria particles and will not change the repulsive force between ceria and SiO2. The adsorbed surfactant will lift the particles off the SiO2 surface while the slight reaction between AEO-20 and Ce3+ will accelerate the lift-off process.

The Effect of Surfactants on the Removal of Ceria Particles in the Buff Clean Process

“…According to transmission electron microscopy (TEM) measurement results, the ceria particles were around 12 nm − 40 nm in size. 16 The cleaning solutions were prepared by using DIW with the addition of JFCE (RO-(CH 2 CH 2 O) n -H R = Isooctyl, 99% purity), 21 Triton X-100 (Short for TX100, C 8 H 17 C 6 H 4 (OCH 2 CH 2 ) n OH (n≈10), Biological stain), 22,23 CMP and buff clean experiments.-The initial ceria slurry was diluted with the same volume of DI water. The wafers were polished by use of Bruker-CP4 with a down force of 3 psi.…”

“…[13][14][15] Wu et al added non-ionic surfactant AEO-20 to SC1 to improve cleaning efficiency (CE), which could effectively remove particles with the SC1 10 times diluted. 16 To increase the CE of ceria particles on the surface of SiO 2 and Si 3 N 4 , Gowda et al used an alkaline cleaning solution with the addition of surfactant Triton X-100. 17 Song et al used a solution consisting of tetramethylammonium hydroxide (TMAH), ethylenediaminetetraacetic acid (EDTA), and Disponil for Post-CMP cleaning to remove nanoceria particles from the polished SiO 2 and Si 3 N 4 films.…”

Chemical–Mechanical Polishing of 4H Silicon Carbide Wafers

“…However, CeO 2 and Si atoms will combine to form SiOCe chemical teeth with strong binding energy, which presents challenges to the post-cleaning technology of residual CeO 2 particles at the surface of 4H-SiC wafer after the CMP. [89,90] In the meantime, the preparation of the rareearth material of CeO 2 requires complex purification processes, giving rise to the high price of commercial CeO 2 -based polishing slurries.…”

Coupling Supramolecular Assemblies and Reactive Oxygen Species (ROS) with Megasonic Action for Applications in Shallow Trench Isolation (STI) Post-Chemical Mechanical Planarization (p-CMP) Cleaning

“… 10 , 11 It has been widely accepted that the particle left on the TEOS wafer post-polish is predominantly Ce 3+ as the presence of surface oxygen vacancies is critical during the polishing step. 4 , 12 − 16 This strong noncovalent interaction between the CeO 2 nanoparticle and wafer surface means that the cleaning chemistries used in the p-CMP process require a redox-active cleaning environment so that the particle can be removed via the charge flipping mechanism (i.e., converting Ce 3+ to Ce 4+ ). While this has shown to be an effective mode of particle removal, there is an increase in the process shear force (mechanical component), which results in secondary defect formation (i.e., increased scratching/surface roughness).…”

“…With device feature size and complexity continuing to approach the 3 nm node, limiting induced defectivity during not only the polishing process but also the post-chemical mechanical planarization (p-CMP) process is of utmost importance. − To effectively achieve this, an understanding of the interactions between the slurry residue and cleaning formulations at the molecular level is crucial. Traditional p-CMP processes for STI involve a contact method of cleaning through PVA brush scrubbing. − This contact method has been coupled with different cleaning chemistry types, such as redox additives and surfactants, to effectively remove residual CeO 2 nanoparticles on the surface. , It has been widely accepted that the particle left on the TEOS wafer post-polish is predominantly Ce 3+ as the presence of surface oxygen vacancies is critical during the polishing step. ,− This strong noncovalent interaction between the CeO 2 nanoparticle and wafer surface means that the cleaning chemistries used in the p-CMP process require a redox-active cleaning environment so that the particle can be removed via the charge flipping mechanism (i.e., converting Ce 3+ to Ce 4+ ). While this has shown to be an effective mode of particle removal, there is an increase in the process shear force (mechanical component), which results in secondary defect formation (i.e., increased scratching/surface roughness). , More recently attention has shifted to developing p-CMP cleaning formulations that employ encapsulation of the CeO 2 nanoparticle using supramolecular chemistries (i.e., surfactants, polyelectrolytes, liposomes, etc.).…”