Role of Surfactant Molecules in Post-CMP Cleaning

Abstract

In order to understand the effects of surfactant molecules on post-chemical mechanical planarization ͑CMP͒ cleaning, we used a tribology setup to simulate the cleaning process. An anionic surfactant ͑alcohol ether sulfates͒ was used during cleaning. Effects of surfactant concentration ͑below and above its critical micelles concentration͒ and temperature on cleaning were experimentally tested. Results showed that increase in surfactant concentration ͑over 0.75 wt %͒ can promote bilayer interaction of micelles on the hydrophilic particles. An interactive explanation of surface molecules with the wafer surface and the role of nanoparticles through friction is discussed. This understanding serves as a guideline to achieve effective particle removal for microelectronic industries.For more than two decades, chemical mechanical planarization ͑CMP͒ has been used to planarize integrated circuits. 1-3 A considerable amount of particles remains on the wafer surface after the initial post-CMP rinse. In order to increase wafer yields, an effective cleaning process has yet to be achieved.Surfactants are surface active agents that can modify the surface properties of liquids or solids and have been used in our daily life for cleaning purposes. Studies have shown that the use of surfactants can reduce the level of particulate contamination on wafer surfaces by several orders of magnitude. 4,5 The complexity of the cleaning process is partly due to the surfactant's unique molecular structure. When a long-chained organic head group comes into contact with a particle, it reduces the bond strength of the particle ͑Fig. 1͒. The effectiveness of the surfactant in reducing particulate contamination is due to steric forces that prevent the particles from adhering as tightly to the underlying substrate surface. 4 In order to suppress particles redepositing on the wafer surface, it is essential that the wafer surface and the particles have the same polarity of the zeta potential. A certain amount of the nondominant surface charge has to be present in order to remove particles effectively. In such a condition, an increased zeta potential or repulsive charge between particle and substrate is necessary. Due to the small size of the slurry particles, the attractive force between these particles and the wafer surface is large. Typically, electrostatic charge or van der Waals forces are involved in particle adhesion to the wafer surface. If the surface tension is reduced, the van der Waals force present in the system is likely to be weakened. In the present study, we focus on the adhesion between particles and the particle-wafer interface.Two cleaning methods have been proposed: one is a directcontact cleaning method which employs a double-sided brush, and the other is noncontact cleaning, which uses only chemical solution. The direct-contact cleaning method is proven to be effective in particles removal. 6-10 Related studies consist of proposing the adhesion model to investigate the particle removal mechanisms. 10-14 Further work has focused o...

Cleaning Solutions for Removal of ∼30 nm Ceria Particles from Proline and Citric Acid Containing Slurries Deposited on Silicon Dioxide and Silicon Nitride Surfaces

“…Furthermore, triton X-100 is well known for its superior surface cleaning action and has been widely used in post-CMP cleaning solutions. 5,29,30 While triton X-100 by itself is incapable of breaking any of the relevant bonds here, it can assist the other components in the solution to access sub-100 nm particles and facilitate their removal. 26,27 Triton X-100 can coat the particles and reduce adhesion between them and the film surface, making it easier for them to be lifted away.…”

“…The wafer surfaces, post-CMP, are typically cleaned using suitable cleaning solutions in conjunction with poly vinyl alcohol (PVA) brush scrubbing and/or megasonics. [3][4][5] For example, Tseng et al 6 polished patterned STI wafers with a commercial ceria slurry and cleaned them using DI water or 2-10 wt% H 2 O 2 in a megasonic tank and a basic cleaning solution having a pH value of 10.5 in brush stations 1 and 2 for 14 nm STI and poly-open CMP (POC) process. They found that the particle contamination levels were higher on nitride surface than on oxide surface.…”

Conductivity, Surface Tension, and Comparative Antibacterial Efficacy Study of Different Brands of Soaps of Nepal

“…e cleaning is not effective due to fewer micelle formation in the cleaning solution as it is superconcentrated. Fewer micelles and foaming in the cleaning solution are not beneficial in the cleaning application [28].…”

Decontamination of Surfaces Exposed to Carbon‐Based Nanotubes and Nanomaterials

“…However, critical micelle concentrations for these surfactants from the literature are far less than 10 mg/mL [76]. In the use of surfactants as the cleaning media combined use of surfactants and mechanical removal might be necessary to fully overcome the adherence of NMs to substrates [110,112].…”