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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An ultrahigh power output from a triboelectric nanogenerator (TENG) with a serrated electrode in a low‐frequency contact‐separation mode which is able to directly drive high voltage‐operating devices without the need for an external power supply is demonstrated. When a serrated electrode‐based TENG (SE‐TENG) is driven, the microstructurally serrated electrode creates a spark discharge in the gap between the serrated electrode and a wire, resulting in tremendously boosted triboelectric power output. Based on the spark discharge phenomenon, a boost adaptor is designed to secondarily boost the triboelectric power output performance, and consequently an ultrahigh triboelectric output voltage of 5 kV and current density of 2 A m−2 are achieved. The boost adaptor concept can be applied to any typical TENG for achieving higher power‐generating performance. Finally, two high voltage applications, a Crookes tube and plasma generation, are demonstrated using the SE‐TENG and boost adaptor without any external power supply equipment. The ultrahigh power‐generating SE‐TENG based on the spark discharge phenomenon occurring in the unique electrode structure has considerable potential to operate high voltage applications directly in harsh environments where electricity cannot be supplied. [ABSTRACT FROM AUTHOR]

Single-sided lapping is crucial in sapphire wafering processes for improving flatness and achieving the target wafer thickness using loose abrasives. In single-sided lapping process, the Material removal rate (MRR) is a key factor for reducing process time and cost. However, the MRR is limited when using loose abrasives because abrasives mostly act by rolling and sliding. Many researchers have studied fixed abrasives to increase the MRR, but the MRR decreases with time. To solve this problem, the self-dressing effect was studied with various pressures, velocities, cutting fluids and wafers. The MRR decreased due to the wear of abrasives, and the pressure and velocity have little effect on the self-dressing. Lapping experiments were done using cutting fluid with a lapped wafer and sawed wafer. The MRR, plate roughness and thickness were measured to study the wear of the abrasive and the self-dressing effect. The cutting fluid delayed the wear of the abrasives and thus improved the decrease in MRR, but it had little effect on the self-dressing effect, like in the case when water was used. When using cutting fluid and a sawed wafer, the MRR was high and did not decrease. A concentrated load on the plate caused by shape error and saw marks on the sawed wafer could produce the self-dressing effect. We verified that a sawed wafer could produce the self-dressing effect on even a worn plate. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Wafer cleaning is one of the most critical processes in the semiconductor device manufacturing. Poly(vinyl alcohol) (PVA) brush scrubber cleaning is much attractive when compared with traditional wet-batch cleaning which causes the cross-contamination among the wafers in a bath and environmental issues with huge amount of chemical and deionized water (DIW) usages. The mechanical forces generated from PVA brush contact can remove the particles on a wafer surface under low concentration of chemical solution without cross-contamination. In this research, we monitored the change of the dynamic forces including normal and friction force generated by PVA brush contacts during cleaning process, and also investigated the effects of scrubbing conditions of PVA brush overlap and velocity, and the surface tension (low- or high-hydrophilic) of the wafer on the particle removal efficiency. The results show that the driving mechanism to remove the particle on a wafer surface can be changed by the PVA brush overlap and velocity condition such as the hydrodynamic drag force in the brush soft contact condition and friction force in the brush hard contact condition. The particle removal efficiency is higher under the low-hydrophilic surface having a low surface tension compared to high-hydrophilic surface. [ABSTRACT FROM AUTHOR]

Conditioning is the process of removing the glazing area from a polishing pad surface and restoring the quality of the surface to maintain a stable polishing performance. However, the conditioning process can induce a non-uniform profile variation of the pad, which can result in nonuniform material removal rates across the wafer. In this paper, a kinematical model based on Preston's equation is proposed to examine the pad profile variation (PPV) induced by swing arm conditioning with a diamond disk. The proposed model was simulated with various swing arm velocity profiles (SAVPs), and the results were compared with experimental results. The results showed the relationship between kinematical parameters and the PPV. The PPV was proportional to sliding distance based on the kinematical model, and then the sliding distance distribution across the pad was dependent on the SAVP. This study has proven the effectiveness of the kinematical model on the PPV during conditioning in chemical mechanical polishing (CMP). [ABSTRACT FROM AUTHOR]

The material removal characteristics of a silicon wafer were experimentally investigated with respect to the chemical dissolution and mechanical abrasion of the wafer during silicon chemical mechanical polishing (CMP) using an alkali-based slurry. The silicon surface without native oxide is rapidly dissolved by the slurry containing an amine agent, which effectively leads to the reduced hardness of the loaded silicon wafer due to Si–Si bond breaking during polishing. The abrasive particles in the slurry easily remove the reacted silicon surface, and the removal rate and wafer non-uniformity for abrasive concentrations of 1.5–3 wt % are better than those for other concentrations because of the low and steady coefficient of friction (COF) owing to the evenness of abrasive particles between the wafer and pad. Also, it was found that a high slurry flow rate of 700–1000 cm3/min improves wafer non-uniformity owing to the reduced temporal variation of temperature, because the slurry acts as a good cooling source during polishing. However, the removal rate remains almost constant upon varying the slurry flow rate because of the effective dissolution characteristic of the slurry with abundant amine as an accelerator, regardless of the reduction of average temperature with increasing slurry flow rate. In the break-in process used to stabilize the material removal, the viscoelastic behaviors of the pad and the ground wafer surface with native oxide and wheel marks cause a temporal change of the friction force during polishing, which is related to the removal rate and wafer non-uniformity. As a result, the stabilization of removal rate and wafer non-uniformity is achieved through a steady-state process with elevated temperature and reduced COF after a total polishing time of 60 min, based on the removal process of the wafer surface and the permanent deformation in the viscoelastic behavior of the pad. [ABSTRACT FROM AUTHOR]

Chemical–mechanical planarization (CMP) is a technique used for planarizing an overburden film in the fabrication of semiconductor devices by chemical treatment and mechanical abrasion. However, a variety of defects such as dishing of metal interconnects, erosion, delamination, and metal layer peeling are generated by a high down force in CMP. A high down force is required to generate a high material removal rate (MRR), which results in greater defects. To minimize these defects, a new planarization process is used, known as electrochemical mechanical planarization (ECMP), which requires electrochemical and mechanical energies. ECMP first involves using an electrochemical reaction to change the surface on the target material into a passivation film. Then, the passivation film is worn down using a polishing pad or abrasives on the contacted areas of the metal film with the polishing pad under a low down force. The electrochemical energy dissolves the copper solid into copper ions in an aqueous electrolyte on the contacted areas of the metal film and the polishing pad. Therefore, the low-down-force ECMP reduces the defects such as dishing, erosion, delamination and metal layer peeling to a greater degree than a conventional high-down-force CMP. Also, the MRR of the ECMP process is higher than that of the low-down-force CMP process because the MRR of the ECMP process is proportional to current density. However, some residual metal between the dielectric material was generated through the use of a nonconductive polishing pad in the ECMP process. Therefore, the CMP process is required for the final process to remove residual metals. In this research, we investigated a two-step polishing method that consists of ECMP with a nonconductive polishing pad and a conventional CMP process to planarize a micro-patterned wafer for microelectromechanical systems (MEMS). First, the ECMP process using a nonconductive polishing pad removed several tens of micrometers (µm) of bulk copper on the patterned wafer over a shorter process time than the copper CMP process only. Then, the residual copper was completely removed through the low-down-force copper CMP process. The total process time and the amount of dishing defects were reduced by applying the two-step polishing method. [ABSTRACT FROM AUTHOR]

The relationship between sliding friction and material removal was investigated using a sensor to measure dynamic friction force according to process parameters such as pressure, velocity, conditioning, abrasive concentration, and slurry pH during oxide chemical mechanical polishing (CMP). Friction force and material removal linearly depend on applied load and relative velocity. A high relative velocity also has an effect on the boundary condition between the wafer and the pad, and friction force reduces with increase in relative velocity. Friction force reduces with polishing time during oxide CMP with ex situ conditioning because of the changes in pad roughness parameters such as Ra, Rp, Rpk, and Rsk. Thus, the in situ conditioning method increases removal rate and improves nonuniformity. Friction force can be uniformly distributed on the oxide wafer as abrasive concentration increases owing to the reduction in friction force loaded on one abrasive particle, improving the nonuniformity of removal rate. In oxide CMP using alkali-based slurry, the effective formation and mechanical removal of the Si–OH bond layer on the SiO2 surface also affect the temporal decrease in friction force and result in a higher removal rate, in comparison with the results of a high friction force and a low removal rate in oxide CMP using neutral-based slurry. [ABSTRACT FROM AUTHOR]

Modern industries require more accurate and high power-efficient micro-electro-mechanical systems (MEMS) and integrated circuits (ICs). Because the structure of MEMS and ICs becomes complicated, chemical mechanical planarization (CMP) has been introduced to fabricate highly integrated electro-mechanical structures. This study aims to reduce dishing and erosion using a negative photoresist (PR) as a protective layer in CMP for thick copper. After bulk copper CMP, soft-landing was carried out using an acidic copper CMP slurry. Method I was the CMP of a thick copper pattern without a negative PR, and method II was a new concept for the CMP method which removed the copper and negative PR to reduce the amount of copper dishing and erosion. In comparison with method I, method II reduced the dishing and erosion by about 46 and 60%, respectively. [ABSTRACT FROM AUTHOR]