Ji Chul Yang

Study of Polishing Characteristics of Monodisperse Ceria Abrasive in Chemical Mechanical Planarization

In this study, the monodisperse abrasive deposition (MDAD) system was developed to investigate the polishing mechanism of ceria abrasives for the chemical mechanical planarization of a wafer. Using the MDAD system, groups of ceria particles with a specific size were collected from slurry with various particle size distributions, and each group was deposited on a blanket silicon wafer to study the size effect of the ceria particle on polishing results. The effects of the ceria particle size on surface roughness, contact area ratio, and subsurface damages on the surface and subsurface crystallographic structure were investigated using atomic force microscopy, transmission electron microscopy, and a surface inspection system. A similar set of experiments was performed with types of ceria abrasive particles with the same diameter but different morphologies to investigate the effect of the ceria abrasive geometry on polishing results. In addition, the effect of the ceria particle size on the pattern loading was investigated by polishing the shallow trench isolation and high aspect ratio patterned wafers.

Measurement of CMP Slurry Abrasive Size Distribution by Scanning Mobility Particle Sizer

This article introduces an abrasive particle size measurement by a scanning mobility particle sizer (SMPS) to measure precise size distribution in the nanoregime. Static light scattering (SLS), which is a conventional method, is compared with the SMPS-based technique. Both measurement techniques differ in the measurement of SiO 2 and CeO 2 abrasive particle sizes. Results showed that SMPS is more sensitive than the SLS equipment due to a single-particle count, which is suitable for representing nanoparticle abrasives. To the best of our knowledge, there has been no article yet about the use of an SMPS for the measurement of abrasive size in chemical mechanical planarization (CMP) technology.

Effects of Ceria Abrasive Particle Size Distribution below Wafer Surface on In-Wafer Uniformity during Chemical Mechanical Polishing Processing

In this study, the abrasive size distribution of ceria-based slurry below wafer and its effect on in-wafer uniformity were examined. Based on our observation, the abrasive size varies depending on the location on the wafer. Hence process parameters such as pad surface morphology and slurry viscosity were thoroughly investigated to observe their effect on the distribution on the wafer surface. It was found that the small size particles were considerably reduced near the center location of the wafer surface during the pad lifetime with reduced slurry viscosity and high polishing pressure. Hence, the contact conditions and the characteristic of fluid should be simultaneously considered in order to obtain the stable in-wafer uniformity.

Optimization of CMP Pad Surface by Laser Induced Micro Hole

In this paper, the optimization of the chemical mechanical planarization (CMP) pad design is investigated to reduce defect generation during the CMP process. Recently, obtaining the optimum performance from the viewpoint of scratch generation has become the most challenging area in the CMP process. To achieve uniform performance of the process at the defect level, the surface texture and/or groove of the CMP pads should be designed effectively, and their original surface should be maintained throughout their lifetime. Because the transport of slurry and wear debris, which is the source of CMP scratches, is highly dependent on the surface geometry of the CMP pad, maintaining suitable process conditions is considered the most important design factor. In this work, the surface geometries of two CMP pads with different body structures are modified by a laser-induced micro hole; one is a porous-type pad and the other is a nonporous type. Based on the experimental and numerical simulation results, the micro-hole induced pads had a lower defect level than the conventional porous pads without holes because the micro holes acted as a defect source or coarse particle reservoir to prevent micro scratch during the process. In addition, the micro holes of the porous pad showed a lower defect generation than the holes of the nonporous pad as the process time increased.