AVS 47th International Symposium
    Manufacturing Science and Technology Friday Sessions
       Session MS-FrM

Paper MS-FrM8
The Effect of Molecular Weight of Organic Contaminants on their Adsorption on Si-wafers

Friday, October 6, 2000, 10:40 am, Room 304

Session: Langmuir Award/Ultra Clean Society and Contamination Free Manufacturing
Presenter: Y. Wakayama, Tohoku University, Japan
Authors: Y. Wakayama, Tohoku University, Japan
S. Kobayashi, Taisei Corporation, Japan
T. Ishii, Taisei Corporation, Japan
S. Sugawa, Tohoku University, Japan
T. Ohmi, Tohoku University, Japan
Correspondent: Click to Email
It is well known that organic contaminants adsorbed on silicon wafer surface degrade the performance of ULSI devices. However, there have been no reports on relation of adsorption behavior of organic contaminants to the silicon or silicon oxide surfaces and their molecular weight. In this study, we have found that the amount of adsorbates on a silicon oxide suface depends on the molecular weight of organic substances. In order to investigate the adsorption behavior of organic contaminants on silicon oxide surfaces, we used solid waxes with aliphatic hydrocarbons, polyvinyl chloride sheets with phthalic esters and silicone sealing materials containing cyclosiloxanes with different molecular weights(Mw) as a contamination source. Each of these materials was separately stored in a closed vessel with a wafer with oxide film for 24 hours. The above organic adsorbates on the oxide surface were analyzed by thermally desorbed and gas chromatography-mass spectroscopy. It was found from our data that as the molecular weight of the organic compounds on the oxide suface increases the amount of adsorbates from oxide surface increases as well and reaches a maximum. Thereafter the amount gradually decreases down to the detection limit of the instruments. It is thought that the phenomenon is related in some way to the balance between the heat of adsorption of organic substances and the vapor pressure. Because, The heat of adsorption that determines the adsorption ability of organic compounds on Si-wafer increases with increase of Mw. On the other hand, the vapor pressure of organic compounds that also determine their rates of adsorption on Si-wafer decreases with increase of Mw.