Effect of Viscosity on Ceria Abrasive Removal during the Buff Clean Process

Self Cite

We have established a new buff clean method using deionized water (DIW) with 2000 ppm surfactants to remove ceria particles from the surface of SiO2 after chemical mechanical polishing. Six kinds of surfactants have been compared. The scanning electron microscopy and atomic force microscopy results show that with CAO and LAPAO, the ceria particles can be fully removed in the buff clean process. The molecular activity and adsorption energy of surfactants are calculated based on the density functional theory to clarify the mechanism of the buff clean process. The surfactants adsorbing on the SiO2 surface can be fully removed after the buff clean process.

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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

Wang

Sun

et al. 2023

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“…17,18 Smaller ceria particles with a high concentration of Ce 3+ species on the surface 19 have a strong affinity towards the oxide surface and, hence, a higher oxide removal rate. At the same time, since these particles form strong Ce-O-Si bonds with the oxide surface, it is very difficult to remove them 20,21 as shown recently by several authors who evaluated the effectiveness of different cleaning chemistries 22,23 and techniques 24,25 to clean them. These studies make it clear that the post-CMP cleaning process should be capable not only of dislodging these particles from the substrate but also, as stated above, preventing their subsequent redeposition on the substrate.…”

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confidence: 99%

Real-Time Visualization of the Cleaning of Ceria Particles from Silicon Dioxide Films Using PVA Brush Scrubbing

Ranaweera

Khajornrungruang

Hamada

et al. 2021

Brush scrubbing is commonly employed for cleaning contaminated polished wafers, especially after chemical mechanical polishing. Here we report the results from real-time video imaging of the brush cleaning of ∼90 nm ceria particles from thin oxide films on transparent glass substrates using evanescent wave microscopy to identify the interactions among the particles, brush, film and cleaning liquid. Two cleaning liquids, DI water (pH ∼ 6) and 0.1 M NH4OH solution at pH ∼ 11, were used. It was found that purely hydrodynamic forces are unable to remove the ceria particles from the oxide film surface and direct contact between brush asperities and film is crucial for particle detachment to occur. However, such a direct contact also causes significant particle loading of the brush as well as redeposition of some of the already dislodged particles. Preventing such redeposition is crucial for efficient surface cleaning. The dislodged particles that are transferred into the fluid flow on the film continued to move without redepositing. Since the 0.1 M NH4OH solution at high alkaline pH created an environment for charge repulsion among the ceria particles, PVA brush and oxide film, particle removal from the film is more rapid and somewhat more efficient compared to DI water.

“…3 These contaminants can cause circuit defects on the wafer, 4 and various cleaning methods have been suggested to improve post-CMP cleaning. [5][6][7] Recently, it has been reported that small ceria particles remaining on the silicon dioxide wafer are difficult to remove after polishing. 8,9 In addition, problems with agglomeration of slurry particles by shear-induced which can affect to slurry stability have been reported in the CMP process.…”

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confidence: 99%

Communication—A Novel Method to Improve Cleaning Performance by Removing Small Particles in CMP Slurry

Lee

Hong

Seo

et al. 2021

Self Cite

In the present study, a separation system with a tangential flow filter (TFF) was applied to reduce the number of small ceria particles in chemical mechanical polishing slurry. The small ceria particles were reduced by 30.7% via the TFF system, and slurry properties of particle mean diameter, pH, zeta potential, and solids concentration were maintained. There was no significant difference in removal rate between original and TFF-treated slurry. In addition, the cleaning efficiency with the TFF system was improved by 34.7% compared to that without the TFF system.