Papers by Keyword: High Aspect Ratio

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.

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: Damage-free drying becomes increasingly difficult with the scaling of semiconductor devices. In this work, we studied a new sublimation drying technology for 3nm node and beyond. In order to investigate the collapse factor by conventional sublimation drying, we observed the pattern with cryo-SEM and revealed that the collapse occurred when the liquid film on the substrate solidified. Based on this result, we considered that it was important to deposit a solidified film uniformly from the substrate side to suppress collapse. Two key process parameters were evaluated to achieve the uniform formation of the solidified film. One is interfacial free energy and the other is film thickness of solution just before solidification. By optimizing two key parameters, it was successfully demonstrated to suppress pattern collapse of challenging devices. In this paper, we report on a new drying method: sublimation drying by LPD (Liquid-phase deposition).

Abstract: For many years traditional injection moulding has been the norm for obtaining polymer based products, and yet this cycle still shows potential for improvement. This paper will encompass the potential in the thermal part of the cycle, by introducing a novel approach to conventional tubular cooling designs, empowered by additive technologies this reiterates what’s being known as conformal cooling. Different geometries and techniques are compared to determine the optimal cross section layout of the fluid channels and inner surface of the moulding parts. If the cooling achieved is sufficiently fast the crystallographic growth of the material can be manipulated to obtain specific properties observable in the mesoscale. This however can be transversely applied in other heat exchanging structures in future studies.

Abstract: Aluminum alloy die casting products are used for automotive LED lamp installation parts. The high aspect ratio shape used for large-volume heat problems needs thin rib parts. In the present study, we obtained basic data for the development of long axis type end mill tools for electrical discharge machining carbon material processing. At the same time, to evaluate the prototype development work, a special tool that enables high aspect ratio thin rib geometry processing was used. Longitudinal direction traverse cutting was done with a small diameter ball end mill tool in the carbon material for electrical discharge machining mold. The transfer accuracy and pick feed shape in the finished surface, the cutting resistance force, and the cutting edge shapes were examined to clarify the relationship between the cutting conditions set. Prototype development of the small-diameter end mill tool with a high rigidity, long axis was done using FEM numerical analysis method. The results showed that the small-diameter ball end mill tool with a tapered length axis in the prototype development had transfer accuracy of the cutting edge shape, and it was possible to reduce the finished surface roughness. Factors such as differences in tool shape are considered to greatly affect the tool rigidity.

Abstract: Wetting efficiency of microstructures or nanostructures patterned on Si wafers is a real concern in integrated circuits manufacturing. We present here a high-frequency acoustic method which enables the local determination of the wetting state of a liquid on real DTI and TSV structures. Partial wetting states for non-hydrophobic surfaces or low surface tension liquids are detectable with this method. Filling time of TSV structures has also been measured.

Abstract: This letter presents the morphology of femtosecond Bessel beams induced high-aspect-ratio structural change regions in bulk silicon carbide. An axion is engaged in transforming Gaussians beams to Bessel beams, which are then focused on the surface or below the surface of the sample by combination of a plano-convex lens and a microscope objective. The sample is scanned by the focused femtosecond Bessel beams at the preset patterns. Through this method, the high-aspect-ratio uniform laser induced structure change regions have been produced and the highest respect ratio can reach 206 with the depth of 330 μm, the width of 1.6 μm in optimized conditions of appropriate focusing position and pulse energy. This result is attributed to uniform energy distribution in the long propagation distance of Bessel beams with nondiffracting. This technique will have great potential applications to make high-aspect-ratio microgrooves in wide-gap and transparent materials.

Abstract: This study aims to develop a polishing process improvement technology for deep micro-hole knockout hole wall with high aspect ratio, and discuss the optimal polishing parameter combination of abrasive jet machining method and micro-elastic abrasive particles for deep micro-hole knockout hole wall surface. A micro-elastic abrasive process technology was thus developed. The experimental results showed that the micro-elastic abrasive has better grinding effect on the surface roughness of knockout hole wall in length of 300 mm and in inside diameter of ψ2mm in the machining conditions of jet pressure 0.5MPa, volume mixing ratio 2:1 of abrasive particles to additive and vacuum attraction 70 cmHg. It was improved from 2.39 μm Ra (10.74 μm Rmax) to 0.08 μmRa (1.12 μm Rmax), proving the feasibility of micro-elastic abrasive. The surface was improved well, and the process time was shortened greatly.

Abstract: As semiconductor devices continue to scale down to smaller sizes, high aspect ratio (HAR) structures are required to achieve the desired device performance. As such, wet processing becomes a very challenging process step due to the capillary forces that are generated during drying. The strength of the capillary force is dependent on the surface tension and contact angle of the fluid that is being dried, as well as the feature spacing and AR. If the drying forces are too high (Figure 1), then the features may break or collapse onto each other resulting in poor device yield. Other factors affecting a structure’s susceptibility to collapse include pattern geometry and material composition [1].

Abstract: In cylindrical traverse grinding of a long workpiece with high aspect ratio, the shape accuracy of a workpiece worsens due to its low stiffness. In this study, the grinding force was measured during grinding process to calculate the elastic deformation of a workpiece caused by the normal grinding force. By comparing calculated elastic deformation with the measured shape error of ground workpiece, the cause for the shape error in case of grinding a long workpiece was investigated experimentally. From experimental results, it is confirmed that the main factor of the shape error of the long workpiece is its elastic deformation during grinding process.