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Research on Characteristics of IPA Evaporation Process Inside Vertical Pores Under Micro/nano Scales

Author: YangKangJun
Tutor: DingGuoLiang
School: Shanghai Jiaotong University
Course: Refrigeration and Cryogenic Engineering
Keywords: Isopropanol Vertical microporous Evaporation rate Curved liquid Diffusion coefficient Molecular dynamics simulations
CLC: TN405
Type: Master's thesis
Year: 2010
Downloads: 50
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Abstract

In the production of the integrated circuit manufacturing process, the wafer cleaning and drying process is used most frequently, the highest number of processes is repeated. After cleaning is finished, the grooved structure of the wafer surface nanometer scale residual liquid of isopropyl alcohol (IPA). Under a nitrogen atmosphere and placed in the drying process, the wafer chuck through the high-speed rotation, to accelerate the evaporation of its surface of IPA. Wafer vertical microporous different size, different position from the axis of rotation, the micropores the IPA liquid evaporation rate is not the same. IPA different evaporation rates of respective micropores will lead to the liquid surface of the same time under the different micropores have different heights, in the role of the liquid surface tension, will result in the structure between the adjacent holes Unevenness, eventually leading to the wafer surface configuration the collapse of the type such that the wafer scrap. Therefore predictable and grasp the grooved structure on the nanometer scale of the wafer surface in the evaporation rate of IPA liquid has important significance for controlling the entire wafer processing time and quality. The purpose of this paper is to study the evaporation characteristics of nanometer-scale hole type structure IPA to predict the evaporation rate of IPA in the wafer surface configuration. In this paper, a combination of experimental and theoretical, the first to study the evaporation characteristics of micron scale hole type structure IPA, and then according to the findings of the micrometer scale, further consider the size effect, the establishment of the IPA in the nano-scale hole type structure evaporation model. The main work and conclusions of this study are as follows: (1) According to the IPA liquid evaporation process in the micropores of the wafer surface, to design and build a nitrogen atmosphere mm / micron scales IPA evaporation experiment station. The experimental Taichung, available for the study of microporous minimum inner diameter of up to 50 μm. (2) vertical hole type structure on the micrometer scale, the IPA liquid evaporation characteristics of the experimental study. The results show that in the test conditions, the IPA evaporation rate decreases with decreasing the orifice airflow velocity, but the gas stream velocity on the rate of evaporation of the increase in height with IPA vapor weakened orifice more airflow velocity. large, the evaporation rate with the IPA evaporated height decreased more intense. IPA evaporation rate and the diffusion coefficient with the ambient temperature rises accelerated. IPA evaporation rate decreases with decreasing the vertical hole diameter, but the pore size in the 0.05 mm to 0.2 mm range, the evaporation rate with the aperture changes are no longer evident. IPA local mass transfer coefficient according to the IPA evaporation rate hole in hole (aperture gt; different variation of 3 mm) and micropores (pore size lt; 0.5 mm), were used to develop the local mass transfer coefficient correlations accuracy : 3 mm to 5 mm diameter hole, and its predicted value and 88% of the experimental data, the error less than ± 20%, with an average error of 12.6%; 0.05 mm to 0.2 mm diameter of the micropores, the predicted value 86% of the experimental data error is less than ± 30%, with an average error of 17.6%. (3) Based on the results of the experimental study for the micron scale vertical micropores IPA liquid evaporation process model and the accuracy of the model was verified with experimental results. Microporous in IPA vertical evaporation mass transfer process is divided into two different types, depending on the orifice nitrogen flow speed, in this article were established the two evaporation model: a) when the the smaller orifice nitrogen flow speed (v lt; 1 m / s), the hole IPA evaporation mainly to molecular diffusion, convective mass transfer in the orifice at the IPA vapor and nitrogen. In this paper, we consider the bent the liquid face the spread of influence derivation IPA evaporation model under low-speed conditions. The predicted value of the low-speed model with the experimental data, the average error is about 10.5%; model and relatively flat meniscus, higher accuracy in the small aperture area. b) When the orifice nitrogen flow velocity (v gt; 10 m / s), vertical hole IPA evaporation process has the presence of strong convection (direct blow away), hole mass transfer and hole molecular diffusion. stages. Experienced strong convection stage the the near orifice at the IPA liquid flow directly carry away the IPA to enter two stages (called stable evaporation stage), the hole in the IPA the local mass transfer coefficient presented from fast to slow. Compared with the low-speed situations, there is always the airstream. Molecular diffusion stage, close to the orifice at the hole area A prediction value of the high-speed model with the experimental data comparing the average error is about 5%. (4) IPA evaporation model based on the micron scale, the introduction of a monocrystalline silicon walls of the vertical hole facing the hole IPA molecules adsorption effects of the application of continuity assumption, the establishment of the IPA evaporation model belonging to the transition zone of the grooved structure of the nano-scale. Molecular dynamics simulation, and analysis of nano-scale pores, IPA and nitrogen interdiffusion coefficient by the pore size of the impact. The results show that the diffusion coefficient increases with the decrease of the aperture increases, but within the scope of the article is for the transition state (aperture GT; 50 nm), and its variation is small, so the parameter values ??of the physical properties of the nano-scale model of IPA still The micron scale experimental value.

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