Papers by Keyword: Capillary Forces

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: Test structure development is critical for single wafer pattern collapse evaluations. A good test vehicle not only allows optimization and benchmarking of different processes, but also facilitates understanding of the underlying mechanism. For high aspect ratio silicon nanopillar arrays, by increasing the gap distance in one direction while keeping the other direction constant, an unexpected higher collapse rate is found. This preliminary finding is contradictory to the prevalent models that are based on equilibrium force balance between capillary and mechanical interactions. It is postulated that the asymmetric arrangement of pillars facilitates the formation of liquid bridge and thus more pattern collapse. Such test structures can bring useful insights to understand the dynamic mechanism of pattern 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: Analytical prediction of capillary pattern collapse is done by balancing the capillary forcesdue to the curved liquid interface with the elastic forces due to the bending of the structure. This paperintroduces a more realistic model where there is an array of repeating lines and spaces, and compares itto the traditional model of two single lines with liquid-filled space in between. This paper also includesthe influence of a non-vertical sidewall angle, and its effect on the overall elastic force. Results showthat the repeating structures and non-vertical sidewall angles both predict a higher critical height beforecollapse occurs compared to the traditional model.

Abstract: The consideration is given to a specific component of the creep of concrete which becomes apparent within one day from the moment of load application, the so called “short-term creep”. Since the entire creep of concrete is conditioned by its water content, the short-time creep must be assigned to the most mobile water – capillary water. As far as the capillary water behavior is determined by the capillary forces acting in it, the short-term creep of concrete is considered and described in the present work as expression of capillary forces. Such description is based on a modified capillary theory of concrete shrinkage: creep is interpreted as forced shrinkage arising due to the fact that application of load leads to disturbance of hygrometric equilibrium of concrete and environment. In view of the mentioned creep interpretation as the forced shrinkage the isotropic loading of the body is considered. The purpose of this work is to determine the degree in which the capillary forces are source of the short-term creep of concrete.

Abstract: The investigation of the present work brings out the effect of Raichur Fly Ash (RFA) and Nyveli Fly Ash (NFA) on California Bearing Ratio (CBR) of two extreme soils, Black Cotton soil and Red earth. CBR of soil fly ash mixtures assume great importance in their use for road construction. CBR are modified depending on the soaking condition. Thus the CBR of soil fly ash mixtures are determined as compacted and also in soaked condition. CBR of fly ashes under un-soaked conditions exhibit higher values because of additional resistance from capillary forces, for instance when 20% of RFA is added to black cotton soil under Unsoaked condition, blend has shown CBR of 10.38% as found in results. In presence of water fly ashes loose capillary forces and gives lesser CBR, where blend has shown CBR of 4.56% for addition of same quantity of RFA. Same additions when it is made to Red earth, the corresponding results are 11.74% for Unsoaked and 4.74% for soaked conditions. In cases of fly ash with calcium, they generate cementitious gel and impart strength to mix, which increases the CBR even in soaked condition [1]. Addition of cement to RFA and lime to NFA, the resistance of blends increases. CBR of soils with RFA exhibits pronounced peaks at fly ash contents of 20% and 80%. This is due to predominance of skeleton of soil and fly ash respectively. The CBR of soil with NFA addition further increases with soaking. CBR of soil with NFA addition increases continuously with fly ash content. The results reveal that when same 20% NFA is added to soil, the CBR of soil in unsoaked condition is 11.46%, whereas for soaked condition it is 23.62%.