Dae-hyuk Kang

Effect of SPM-based cleaning POR on EUV mask performance

EUV masks include many different layers of various materials rarely used in optical masks, and each layer of material has a particular role in enhancing the performance of EUV lithography. Therefore, it is crucial to understand how the mask quality and patterning performance can change during mask fabrication, EUV exposure, maintenance cleaning, shipping, or storage. The fact that a pellicle is not used to protect the mask surface in EUV lithography suggests that EUV masks may have to undergo more cleaning cycles during their lifetime. More frequent cleaning, combined with the adoption of new materials for EUV masks, necessitates that mask manufacturers closely examine the performance change of EUV masks during cleaning process. We have investigated EUV mask quality and patterning performance during 30 cycles of Samsungs EUV mask SPM-based cleaning and 20 cycles of SEMATECH ADT exposure. We have observed that the quality and patterning performance of EUV masks does not significantly change during these processes except mask pattern CD change. To resolve this issue, we have developed an acid-free cleaning POR and substantially improved EUV mask film loss compared to the SPM-based cleaning POR.

Effect of Ashing, Strip and Annealing Process on the Dopant Concentration of Silicon

Introduction Silicon has been used successfully for semiconductor material because it can have a high degree of purity at a low cost, and shows the good mechanical, chemical and electrical properties. In the respect of electrical properties, the pure silicon is an insulator, thus the ion implantation process is necessary to make insulating silicon into semiconductor. Generally, the electrical properties of silicon based semiconductors are determined by the characteristics of dopant. Hence the study for the change of dopants concentration in following process such as ashing, strip, and annealing, is very important. (Shown in Figure 1.) In this study, we will discuss about the loss of dopant by strip process using fluorine-based stripper and annealing.