Solid State Phenomena Vol. 346

Abstract: The new laser ablation technique has been developed for analysis of metallic impurities in SiC and GaN wafers. Particles generated by a femto-second laser ablation were aspirated by an ejector and introduced to an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) via a Gas Exchange Device (GED) and analyzed. A Metal Standard Aerosol Generation (MSAG) was used for quantitation of metallic impurities in SiC and GaN wafers.

Abstract: With the advent of EUV lithography and other emerging processes such as area selective deposition, and SOIC hybrid bonding, the need to identify the chemical composition of defects is of paramount importance. The defects of concern range from 10nm to 500nm in lateral size and as thin as ~ 1 nm in thickness, which the current batch of molecular analytical tools cannot address adequately since the indications are that many of the defects and residues detected are organic in nature. In this paper, a relatively new nanoscale technique called infrared photo-induced force microscopy (IR PiFM), which combines non-contact atomic force microscopy (AFM) and infrared (IR) spectroscopy with ~ 5 nm spatial resolution, is introduced. The paper will show how the nanoscale hyperspectral IR PiFM data can provide unambiguous and speedy feedback to process engineers engaged in EUV lithography and other advanced semiconductor processes.

Abstract: This paper offers a preliminary study for the analysis of metallic contamination on front-end patterned wafers obtained by two different techniques based on the etching of the whole patterns, LPD-Bulk and VPD-Bulk coupled with an ICPMS. To elaborate the analysis of patterned wafers, methods were first verified and optimised on reference Si wafers. Both techniques are complementary methods for the etching of wafers. LPD-Bulk enables a fast etching of several micrometres of Si but with less precision than VPD-Bulk, which is more adapted for the etching of layers thinner than 1 micrometre. The intentional contamination in SC1 and H₂O bath of monitoring wafers showed that contamination in H₂O is better controlled due to the absence of chemical reactions, competition between oxidation and etching processes occurring during SC1. And diffusion of contaminants at the tested temperatures from 20°C to 80°C, does not occur. Heat treatment should be applied to allow the diffusion of metallic contaminants in the bulk of the wafers.

Abstract: Self-assembled monolayers (SAMs) can be used for surface functional control to assist with pattern collapse prevention and as a protective layer to enable Area Selective Deposition (ASD). To be successful, these applications require the formation of a high-density, defect-free, so-called well-packed SAM at the nm scale. In this paper, we describe a method to map the nm scale defects of octadecyltrichlorosilane (ODTS) SAMs using a post-etching AFM analysis of the surface of the substrate and used this technique to develop a process to form high-density, defect-free SAM layer at the nm scale. This was achieved by optimizing the water concentration in the solvent for the precursor solution and annealing after SAM formation.

Abstract: As more and more wafer dies are produced at the edge of the wafer, wafer edge cleaning and etching has become increasingly important in the manufacturing process of complex thin film laminated integrated circuits. If the edge cut accuracy is not well controlled, the effective removal of film and contaminants will not be achieved. In this paper, we propose a fine edge cut control process with a novel and high precision wafer centering method. A high precision wafer centering system for determining and correcting the position of a wafer on its chuck so as to ensure the uniformity of the width of the wafer edge etched. A fine edge cut profile is beneficial for subsequent film growth, and excellent cleaning capability can prevent buildup of flakes and defects on the bevel. All the above advantages contribute to the improvement of wafer edge yield in the future of chip manufacturing.

Abstract: This research focuses on the crucial task of identifying the viscous sublayer in improving wet cleaning processes. Computational fluid dynamics (CFD) is employed to manipulate fluid properties and process parameters for optimizing cleaning efficiency. The research findings encompass the evolution of thickness across the wafer radius, characterization of the wavy air-liquid interface, velocity profile within the liquid, and measurement of the viscous sublayer's thickness. Key findings highlight the significance of small-scale turbulent structures, the competition between Coriolis and viscous forces, and the successful utilization of CFD LES (Large Eddy Simulation) for quantifying and visualizing the viscous sublayer and eddy flow.

Abstract: Etch profile control of the wafer surface is a key application for single-wafer wet process equipment. Wet etch processes are grouped into two types, either uniform flat etch profiles or specific non-flat etch profiles that are required for downstream processes. For both groups of etch profile it can consume time and resources to obtain the processing conditions to achieve the desired etch profile due to the complex interactions in the process. Etch profile prediction models can provide process engineers a valuable tool to identify processing conditions to get the desired etch profile in less time. In this paper, we introduce an etch profile prediction model using a Convolutional Neural Network [1] and validation of the prediction model against actual experimental data. We also investigated methods on how to select the comprehensive learning conditions and understand the relationship with prediction accuracy and the number of learning conditions. We found the choice of parameter type to describe a process condition can affect prediction accuracy. The prediction model reproduced the trend of etch profiles even when learned on a small dataset.

Abstract: In the manufacture of semiconductor chips, the cleaning process is an important process. A two-fluid spray is used in single-wafer cleaning. However, two-fluid spray cleaning has the problem of electrostatic discharge (ESD) on devices on the wafer. In this study, we measured the current generated by two-fluid spraying of pure water using a prototype Faraday cage. We also measured the velocity and size of flying droplets using a shadow doppler particle analyzer (SDPA) to clarify the relationship between the generated current and flying droplet characteristics. As a result, it was confirmed that the current generated during two-fluid spraying shows positive polarity and that the amount of droplet charge increases as the flying droplet velocity increases. To reduce ESD generated during two-fluid spray cleaning, we have confirmed that the amount of electrification of pure water droplets can be controlled by installing an induction charging device immediately after the injection of pure water.

Abstract: The process of quickly removing abrasive particles of silica and ceria slurries is important in the use of CMP equipment. Megasonic cleaning of nozzle injection type is one of a variety of post-CMP cleaning methods and its performance including cleaning efficiency and erosion was explored experimentally with parametric studies. In the cleaning process, it is favorable to achieve both high efficiency and low damage. The cleaning efficiency was defined by particle removal efficiency (PRE) with a glass sample spin-coated with small silica particles; the damage was detected from mass loss of aluminum foils after the cleaning. The cleaning tests show that the performance of nozzle injection megasonic cleaning depends significantly on ultrasound frequency and water temperature. Toward more efficient and less erosive cleaning, the nozzle injection angle is also expected to play a key role.

Abstract: Cleaning tests with ultrasound-superposed water jets are performed to explore the optimal injection distance from the jet nozzle to a glass plate spin-coated with small silica particles (as a cleaning sample). The cleaning performance is evaluated based on particle removal efficiency (PRE) that is calculated using the haze method. Visualization of the water jet and liquid film flow over the cleaning target shows that the jet flow with short injection distance tends to be in a steady state, while the water jet shape instability grows for long injection distance, leading to atomization of the jet. The cleaning tests with varying the injection distance suggest that there exists an optimal injection distance at which the PRE becomes maximal.