AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Experimental Investigation of Haze and Particle Formation by Airborne Molecular Contamination under Irradiation
CHANG HYUK KIM, Zhili Zuo, David Pui, University of Minnesota
Abstract Number: 332 Working Group: Control Technology
Abstract During the last couple of decades, most problems related to airborne particles in semiconductor industry have been solved by using HEPA and ULPA filtration systems. However, as lasers with shorter wavelength and photo masks with smaller feature size are used during the manufacturing process, the control of non-filterable airborne molecular contamination (AMC) has become a new problem. Though at very low concentration levels (several ppb to ppt), AMC can be converted to nanoparticles once irradiated by high energy beams, causing haze formation on photo masks and consequently significant yield reduction and increased fabrication cost. Therefore, it is important to understand the mechanisms for AMC- and radiation-induced particle formation.
The objective of this study was to determine the critical conditions for particle nucleation and haze formation. Ammonia and sulfuric dioxide, two major components of AMC, were diluted with nitrogen or air down to ppb level, mixed with each other, and delivered to the irradiation chamber. The chamber was made of stainless steel and prebaked at 200 degrees Celsius to minimize interference from impurities such as chamber outgassing. The nucleation of the gas mixture in the chamber was assisted by the irradiation of soft X-ray, which simulates an extreme condition of the radiation-induced nucleation. A photo mask was also placed in the irradiation chamber for monitoring haze formation. An ultrafine condensation particle counter was used to measure the number concentration of generated particles and the degree of haze formation on the surface of the photo mask was quantified by a wafer surface scanner. Correlations between the AMC concentrations and the level of haze/particle formation are presented. The effect of humidity, temperature and residence time will be also investigated.