Solid State Phenomena Vol. 346

Abstract: Fluorinated chemistries can lead to severe corrosion damage towards silicon and germanium based materials when wafers have a significant amount of electrostatic charges. This corrosion is evidenced on both single wafer and batch tools. It can be prevented by the presence of enough light, and wafer charging can also be eradicated by photo emission with UV light.

Abstract: This paper focuses on the mechanism and methodology of the dissolution of Alternative Dipole Material (ADM) and its inhibition through the use of functional waters. The study investigates the etching behavior of ADM in different solutions, examines the surface state of ADM before and after cleaning, and evaluates the impact of the functional water process on its electrical properties.

Abstract: The selective etching of Si in multi-stacked Si and SiGe structures is a key process to fabricate the next-generation of FET, Gate-all-around FET. In this study, we investigated the mechanism of wet chemical etching process at the molecular level for two common ionic solutions, potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH). One of the important factors in the etching process is the reaction rate between the water and Si surface. Therefore, the water dynamics in i) bulk system and ii) Si wall confined system were mainly analyzed using molecular dynamics simulations. As a feature of bulk, TMAH showed the larger hydration structure around cation and the lower mobility of water in the hydration shell compared to KOH. In the Si wall confined system, the water and ion dynamics on the OH-terminated Si surface were distinctive. TMAH showed the lower mobility of water as in bulk system. Furthermore, the concentration and long stay of cation near the Si surface were observed in TMAH. This behavior of cation may directly prevent water from contacting surface. These characteristics of TMAH may slow down the Si etching process. However, if the blocking effect for etching depends on the surface composition, it will be useful for selective etching.

Abstract: With the increasing use of III-nitride semiconductors, more knowledge is needed about the manufacturing processes and reactions with different chemicals. Gallium nitride semiconductors show a different behavior in wet chemistry compared to the known silicon technologies [4,5]. The different behavior can be explained, among other things, by the polar axis in the c-direction [0001] [6]. Surface characterization is necessary to gain a better understanding of the native surface and after different processes. We have used Low Energy Ion Scattering (LEIS) with its very high sensitivity for surface characterization to characterize the surface of different gallium nitride semiconductors and to establish a depth profile by sputtering [1,8].

Abstract: In this study, we investigated the effect of the post-etch cleaning of GaAs surfaces. We found that a plasma damage layer was formed on GaAs surfaces by dry etching, and an As-rich layer remained after post-etch cleaning. The As rich layer needs to be removed because it is replaced by micron-sized particles when stored in an air. We also found that a pure GaAs surface can be obtained by performing additional cleaning consisting of oxide formation and removal.

Abstract: Pattern collapse in CMOS image sensors is discussed, where silicon pillars are separated by trenches of few microns deep. Both analytical and numerical models are given and match experimental results. The trench profile is also taken into account to predict such collapse.

Abstract: Capillary condensation, a ubiquitous phenomenon involving the heterogeneous nucleation of liquid droplets, has significant implications in various industrial, biological, and atmospheric processes. Strong capillary forces induced by highly curved menisci of condensates can have potentially significant impact on the structural integrity and functionality of nanodevices. While the influence of surface properties on the nucleation and growth of water droplets has been extensively studied at microscale, our understanding of water condensation at the nanoscale remains limited due to experimental challenges in imaging liquids at nanometer scales. In this study, we employ in situ liquid phase TEM imaging and for the first time present real-time observations of water condensation dynamics on arrays of vertical silicon (Si) nanopillars. Experimental and simulation results show that nucleation of water droplets occurs at the edges of the nanopillars and substrate, followed by the growth of an interfacial layer resembling a corona around the nanopillars. Subsequently, the formation of bridges between adjacent growing coronas leads to the development of symmetric and asymmetric bridged nanopillar geometries. Importantly, we find that the formation of bridges can induce bending and collapse of the nanopillars, depending on their aspect ratios. Overall, this study provides valuable insights into the nanoscale dynamics of capillary condensation and paves the way for advanced engineering applications and optimization of various technological processes.

Abstract: Pattern collapse, also as known as leaning, has become one of the most common and challengeable defects in semiconductor manufacturing process due to device shrinkage. In single wafer wet cleaning, Isopropyl Alcohol (IPA) rinse is widely used after Deionized Water (DIW) rinse. Fingering instabilities are observed at the mixing boundary of IPA and DIW, where dry spots are formed due to unbalanced capillary force amid patterns. Unlike previous DRAM devices, we have found that recent 1x-nm DRAM devices have become more vulnerable to pattern collapse induced by dry spots related to fingering instability. In this paper, we examine factors and phenomenon related to fingering-induced leaning through both experiments and simulation analysis. In addition, we also propose improved rinsing methods which could prevent fingering and related pattern collapse by adjusting nozzle configurations (i.e. speed, flow rate and etc.).

Abstract: Molecular dynamics simulations were used to model <100> silicon pillars with diameter and spacing of 2.2nm and in a square lattice. Isopropanol (IPA) was added as a wetting liquid, and evaporation of the IPA was simulated to induce capillary forces that can cause pattern collapse. The cylinders were stable up to an aspect ratio of 8, while pillars higher than that collapsed. Additionally we simulated the thermal vibration of silicon pillars with diameters and spacing of both 2.2nm and 4.3nm without the presence of liquid at 300K. The Young's modulus of these pillars was estimated using the mean square displacement of the vibrating pillar tips, and results showed that the modulus decreases significantly from the bulk value for these structures.

Abstract: As miniaturization progresses, pattern collapse during the drying step of wet cleaning processes has become a critical issue in the semiconductor industry. In this study, we used reactive molecular dynamics simulations to analyze pattern collapse, with a focus on bondings and reactions. To simulate pattern deformation during the drying process of wet cleaning, we created a FinFET model as a HAR structure. The surface of this model was terminated with hydrogen atoms. The widths between the patterns were changed in order to create a Laplace pressure difference when water molecules were placed on the surface. The model was simulated by placing water molecules up to half the height of the pattern. As a result, the pattern was deformed. Furthermore, by removing water molecules and changing the Laplace pressure balance, it was found that the pattern contacted each other at the tip. The pattern remained in contact when water molecules were removed from the model. In the contact area, the covalent bonds, such as Si-Si and Si-O-Si, were not formed, but instead, hydrogen-to-hydrogen van der Waals bonds were formed between patterns. We calculated the total van der Waals forces between hydrogen atoms at the contact surfaces using the Hamaker equation and calculated the elastic force of the patterns using the beam deflection formula. Our calculations showed that the total van der Waals forces between hydrogen atoms at the contact surfaces were larger than the elastic force of the patterns, indicating that van der Waals forces could be a factor in maintaining the contact of the patterns.