Removal of Carbon Contamination on Si Wafers with an Excimer Lamp
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INTRODUCTION
AN Ar excimer lamp has been developed recently as a light source in the vacuum ultraviolet region.[1,2,3] The lamp is based on the excitation of Ar by dielectric barrier discharge. Although the lamp cannot provide intense light at high fluence as an Ar excimer laser, the advantage is the compactness and low cost. The lamp provides a continuous light contrary to an excimer laser. The lamp is small enough to be installed in a small chamber for semiconductor processing. Despite the low photon density, the high photon energy is as attractive for applications as an excimer laser. High photon energy is surely one of the key points for the application of light to industrial photophysical and photochemical processes. Takigawa et al. demonstrated experimentally that an Ar excimer laser is capable of the dissociation of SiO2 only by the irradiation.[4] This is because the photon energy (9.8 eV) is larger than the binding energy of Si-O bonds. Hence, a light source of high photon energy has the possibility to realize a new process technology.[5] The surface cleaning of silicon wafers is undoubtedly an important issue for semiconductor manufacturing. The Radio Corporation of America (RCA) method is one standard method for the cleaning of Si wafers in semiconductor manufacturing, eliminating contamination as well as natural oxide on the surface.[6] Ultraviolet light irradiation with ozone treatment is also anticipated for surface cleaning. Because the RCA method is basically the wet chemical method, we can hardly apply MAYUMI TODE, Student, YASUO TAKIGAWA, Associate Professor, and TAIZO IGUCHI and HIDEHARU MATSUURA, Professor, are with the Department of Electronic Engineering and Computer Science, Osaka Electro-Communication University, Neyagawa, Osaka 572-8530, Japan. MASATO OHMUKAI, Associate Professor, is with the Department of Electrical and Computer Engineering, Akashi College of Technology, Akashi, Hyogo 6748501, Japan. Contact e-mail: [email protected] WATARU SASAKI, Researcher, is with the NTP Inc., c/o CRC, University of Miyazaki, Gakuenkibanadai, Miyazaki 889-2192, Japan. Manuscript submitted October 14, 2006. Article published online April 5, 2007. 596—VOLUME 38A, MARCH 2007
this method in a process chamber. On the other hand, ozone is harmful at higher concentration. We expect that the Ar excimer lamp can be applied for the cleaning of silicon surfaces. In this article, we report the evidence of the capability of surface cleaning of silicon wafers with only an Ar excimer lamp.
II.
EXPERIMENTAL
Figure 1 shows the experimental setup of two chambers connected through a gate: one for the irradiation of an Ar excimer lamp and the other for the Auger electron spectroscopic analyzer (PerkinElmer Inc., USA). The irradiation chamber was evacuated in advance to 3Æ10)9 Torr with a turbo molecular pump, and then high-purity argon gas flowed at the rate of 10 L/min into the argon excimer lamp, where 10 kV was applied for the discharge and then driven toward the sample. During the discharge, the pressure was ke
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