Kinematic Prediction and Experimental Demonstration of Conditioning Process for Controlling the Profile Shape of a Chemical Mechanical Polishing Pad

The uniformity of the wafer in a chemical mechanical polishing (CMP) process is vital to the ultra-fine and high integration of semiconductor structures. In particular, the uniformity of the polishing pad corresponding to the tool directly affects the polishing uniformity and wafer shape. In this study, the profile shape of a CMP pad was predicted through a kinematic simulation based on the trajectory density of the diamond abrasives of the diamond conditioner disc. The kinematic prediction was found to be in good agreement with the experimentally measured pad profile shape. Based on this, the shape error of the pad could be maintained within 10 μm even after performing the pad conditioning process for more than 2 h, through the overhang of the conditioner

Effect of the Lapping Platen Groove Density on the Characteristics of Microabrasive-Based Lapping

Microabrasive-based lapping is widely used in the manufacturing of single-crystal substrates such as sapphire, SiC, and GaN. Although many studies have been conducted to improve the lapping process characteristics, most of them focused on process conditions or consumables. In this study, the effect of the lapping platen groove density on the lapping characteristics was studied using a sapphire substrate. Groove density was defined as the ratio of groove width to groove pitch, and the displacement of the lapping head was measured to calculate the oil film thickness. It was confirmed that, for groove densities below 0.30, hydroplaning occurs when the oil film thickness increases. When the oil film thickness is larger than the abrasive particle size, the material removal rate is low because the abrasive does not participate in the lapping process. When the oil film was developed, the experimental results showed a high surface roughness and poor flatness of the substrate, as only large abrasive particles participated in the lapping process. Therefore, to improve the lapping characteristics, it is important to reduce the groove density by reducing the groove pitch, which prevents the development of the oil film

Effect of Ceria Abrasives on Planarization Efficiency in STI CMP Process

The strong Ce-O-Si bonding between CeO2 abrasives and SiO2 film surface; i.e., the chemical tooth effect, improved planarization efficiency in CMP using ceria-based slurry as a result of nonlinear behavior of the removal rate. Removal rate is a power function of pressure and relative velocity (i.e., RR = kPαV β ). In particular, the high dependency of removal rate on pressure when α >1 results in a much higher material removal rate in the upper pattern than in the lower pattern. Therefore, the planarization efficiency of ceriabased slurry is better, from initial polishing time to the completion of the polishing step, than that of conventional silica-based slurry with an exponent value of α ≈1

Technological Approaches in Nanopolishing for Microstructures

Polishing technology has been broadly used in manufacturing of components to enhance the surface quality at final processing stage. On the threshold for the 21th century, all of technologies are changing more rapidly than the past. One of them is the miniaturization of the smart systems that require new technological approaches in manufacturing processes. Scientists and engineers have some responsibilities to revise the terminology and expand the area of each technology from the conventional one to nanoengineering. This paper focuses on the introduction of new technological approaches in nanopolishing for microstructures that imply new additional concepts on the conventional polishing. New concepts include damage-free, planarization, nanotopography and conformalization. Damage-free means to get not only atomic level surface roughness, but also subsurface without any physical defects. As one of the emerging methods, chemical mechanical polishing (CMP) is introduced with chemical reaction on the conventional mechanical polishing. Planarization is one of the fabrication processes for semiconductor devices, to make flat from the bumpy or rugged pattern surfaces for rearrangement of ULSI below quarter microns. Representative applications are reported with IMD, STI, copper and low-k CMP. Nanotopography means nanofeatures having 0.2~20mm wave length covered between nanoroughness (10-100nm) and flatness. It influences on the deterioration of threshold voltage, dielectric breakdown and failure of CMP of thin blanket film. Final issue is pointed to the conformalization which means isotropic removal of microstructures to improve the roughness while maintaining the micro three dimensional forms. Electrorheological and magnetorheologi- cal fluid (ERF or MRF) assisted polishing techniques are summarized with their material removal mechanisms and some results

Material Removal Model for Lapping Process Based on Spiral Groove Density

The increasing demand for single-crystal wafers combined with the increase in diameter of semiconductor wafers has warranted further improvements in thickness variation and material removal rate during lapping to ensure price competitiveness of wafers; consequently, the lapping process has gained the attention of researchers. However, there is insufficient research on the effect of platen grooves on the lapping process. In this study, the parameters to describe grooves were defined in order to understand their influence on the lapping process, and a material removal model was suggested based on indentation theory and subsequently experimentally validated. The results indicate that changes in groove density affect the lubrication condition at the contact interface as well as the probability of abrasive participation by varying the oil film thickness. When fabricating the groove for a lapping platen, a groove density at the critical groove density (CGD) or higher should be selected. The higher the groove density, the easier it is to avoid the CGD, and the higher is the material removal rate. The results of this study will enable engineers to design lapping platen grooves that are suitable for the production of modern semiconductor wafers

Development of the CO2 Emission Evaluation Tool for the Life Cycle Assessment of Concrete

With the goal of reducing greenhouse gas (GHG) emissions by 26.9% below business-as-usual by 2020, the construction industry is recognized as an environmentally harmful industry because of the large quantity of consumption and waste with which it is associated, and the industry has therefore been requested to become more environmentally friendly. Concrete, a common construction material, is known to emit large amounts of environmentally hazardous waste during the processes related to its production, construction, maintenance, and demolition. To aid the concrete industry’s efforts to reduce its GHG emissions, this study developed a software program that can assess GHG emissions incurred over the life cycle of a concrete product, and a case study was conducted to determine the impact of the proposed concrete assessment program on a construction project