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Various methods such as transmission electron microscopy, scanning electron microscopy, dynamic light scattering (DLS), and scanning mobility particle sizer were utilized to measure size distributions for sub-100 nm colloidal silica. Compared to electron micrographs, hydrodynamic diameter of sample is dependent on its concentration from ~60 nm to ~90 nm and it is difficult to measure the poly dispersed nanoparticles and analyze its own properties due to limitation of DLS method, whereas, nano nebulizer (NN)-SMPS method distinguished two different size nanoparticles (51 nm and 82 nm) perfectly and is considerably stable to alternations of concentration and dispersity.

One of the main factors affecting the production yield of semiconductor circuits is contamination by fine particles. Therefore, the wafer cleaning process has become important to the semiconductor manufacturing process. The best method for a cleaning evaluation is to use the actual wafers in the manufacturing process, but where a general cleaning evaluation is required, contaminated wafers cannot be obtained from this source. This study proposes a separate cleaning evaluation wafer as a method for the semiconductor cleaning evaluation. We here describe 300-mm wafers that had nanoparticles of silica (SiO2) and polystyrene latex spheres (PSLs) deposited in multiple designated areas by changing the electric field from 2 kV to 11.2 kV to make spots with diameter from 20 to 50 mm. A numerical analysis was performed to predict the particle trajectory during deposition, and the ensuing experimental results were in good agreement with the simulation, with an average error of 4.2%. Next, some actual wafers were cleaned to demonstrate possible cross-contaminations on the 300-mm wafer, and good effectiveness was achieved. These results provide useful data for optimizing cleaning conditions to improve semiconductor cleaning processes.

This study details the improved ceria abrasive removal on SiO2 wafer during the post CMP water polishing (buff clean) process. Initially, the zeta potentials of the wafer and ceria abrasive were measured according to pH and compared with the zeta potential and pH change during water polishing. From these measurements, it was determined that the zeta potential difference between the ceria abrasive and the wafer decreased during water polishing. The electrical repulsion between them decreased as well. Additionally, ceria abrasive removal was measured using a surface defect inspection system. The abrasive removal increased when water polishing conditions such as pressure, rotation speed and processing time increased. Chemical enhancement and a pad cleaning process also increased the ceria abrasive removal. Consequently, the total defect counts were reduced by 91.8% with the optimized water polishing condition. These results provide useful data for determining optimal water polishing conditions for more effective post CMP cleaning.

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.

In this study, the effect of viscosity on ceria abrasive removal during the buff clean process was investigated. First, a numerical simulation was performed to observe the shear stress on the wafer. The shear stress increased as the viscosity increased. These results imply that the viscosity increases the drag force acting on the abrasives, which can improve abrasive removal. Based on the results of the numerical simulation, the ceria abrasive removal was measured using inductively coupled plasma mass spectroscopy (ICP-MS). The ICP-MS results showed that the increased viscosity improved the cleaning efficiency of the ceria abrasive removal by 70%. In addition, a lowering of the water temperature also resulted in an increase in abrasive removal as the viscosity increased. These results can be used to improve ceria abrasive removal during the buff clean process.

In the present study, hydrogen water was applied to ceria abrasive removal in post-CMP cleaning. The surface of the ceria abrasive was reduced by the hydrogen water from the Ce4+ to Ce3+ state. Reduction of the ceria abrasive can weaken the bonding between ceria and the SiO2 wafer surface. X-ray photoelectron spectroscopy (XPS) and UV–visible observations were utilized to reveal the reduction from Ce4+ to Ce3+ by hydrogen water. Thus, the remaining ceria particles and Ce-ion concentrations were reduced by 70% and 63%, respectively.

In this study, we analyzed the coefficient of friction (COF) of film surface and pad interface during the wafer polishing process to make a correlation with the existence of polyelectrolyte additive in the slurry, which is adsorbed onto the wafer surface. The poly-acrylic acid (PAA) polymer was added to the slurry in this study because of its proven effect on SiO2 (Oxide)/Si3N4 (Nitride) removal selectivity. Different contact conditions between the wafer surface and the slurry with PAA were established for various PAA concentrations and slurry pHs in polishing experiments. The COF was increased with the adsorption amount of PAA on the wafer surface whereas the dissolved PAA in the slurry served as lubricant that lowered the COF. The lateral force microscope (LFM) with a pad debris particle attached tip, which simulates single asperity contact, confirmed the COF result in a wafer scale experiment. Finally, the direct measurement of absorbed PAA by atomic force microscopy (AFM) in aqueous condition revealed that COF increased with changes of surface morphology and roughness.