Wet Cleaning Efficiency and Wetting Characteristics of Semiconductor High Aspect Ratio Structures

Abstract

Due to the complexity and high aspect ratio characteristics, the wet cleaning process is facing challenges such as the wetting efficiency of cleaning chemicals and the pattern damage after a drying process. Among all the problems, analysis of wetting characteristics is a major concern. This is because the analysis is more difficult as the structure becomes more complex. Also, if both the aspect ratio and the distance between the upper and lower layers of the structure increases, the penetration of the cleaning solution in the High Aspect Ratio (HAR) structure is difficult. Therefore, in this study, an analysis method of wetting characteristics in a HAR structure was proposed and cleaning efficiency was evaluated. There are two types of wetting characteristic analysis: static and dynamic analysis. For static analysis, Nano-sized colloidal silica particles as an indicator were added to the solution to verify the wetting characteristic and penetration efficiency of the solution. The wetting characteristics of a solution could be evaluated depending on the position of the colloidal silica particles inside the pattern by inclined-AFM. This method has the advantage of visualizing the wetting behavior of the solution. Colloidal silica particles of various sizes were used to suggest optimal analysis conditions, and the use of 20 nm particles was the most suitable for analysis. The optimal particle size may vary depending on the properties of the particles used in the analysis, aspect ratio and the surface conditions. And the FTIR was employed for the dynamic analysis. The wetting characteristic was analyzed using the substitution behavior of two solutions by FTIR. In the first, DIW was spread on the wafer, then the same amount of IPA was added on the DIW, and the Peak change due to the behavior of the two solutions was measured continuously. And the differences according to the presence or absence of patterns were compared to verify the wetting behavior in the HAR structure. Furthermore, the oxide and organic, which are contaminants remaining inside the high aspect ratio structure, were cleaned with various solutions to evaluate the wet cleaning efficiency. In addition, the pattern damage caused by the cleaning solution was evaluated using AFM, and a method of preventing pattern damage was suggested through the addition of Surfactants.