AVS 50th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoA

Paper PS-MoA10
Post-etch Wafer Cleaning by a New Dry-cleaning Technique using Both Gas Flow and Plasma

Monday, November 3, 2003, 5:00 pm, Room 314

Session: Plasma Sources
Presenter: Y. Momonoi, Hitachi Ltd., Japan
Authors: Y. Momonoi, Hitachi Ltd., Japan
K. Yokogawa, Hitachi Ltd., Japan
M. Izawa, Hitachi Ltd., Japan
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Because wafer cleaning ultimately affects yield and reliability, it is one of the crucial issues in fabricating semiconductor devices. Regarding devices, scaling-down and adoption of new materials impose an imminent demand for new developments in particle cleaning. Dry-cleaning techniques have been proposed recently as other approaches for particle removal. Their removal efficiency, however, is less than that of wet cleaning, because it is difficult to balance chemical cleaning and physical cleaning. In light of the above circumstances, the authors have developed a new concept of dry particle cleaning, named dry scrubber.@footnote2@ The dry scrubber utilizes both the mechanical effects of gas flow and the chemical effects of a down-flow plasma. Regarding the gas flow, narrowing the flow space along the wafer increases the viscous friction, which causes particles to remove from the wafer surface, and they are transported away. Regarding the plasma, a gas mixture of CF@sub 4@ and O@sub 2@ is induced in it, which weakens the adhesion force of particles chemically. The basic cleaning capabilities of the dry scrubber were evaluated by using it to remove Al@sub 2@O@sub 3@ particles on 8-inch p-type <100> bare silicon wafers. The evaluation showed that the plasma enhanced the particle removal of the gas flow; namely, the combination of a down-flow plasma and a fast gas flow removed particles at an efficiency of 98% in 60 sec. It was also found that the dry scrubber produces an etching depth for poly-silicon of 0.17 nm. The cleaning capabilities of the sample with etched contact-hole patterns were also evaluated. This sample had residues of photo-resist on its surface and particles in the holes. These results confirm that the new cleaning technique can effectively removes the residues and the particles from a patterned surface. @FootnoteText@@footnote 1@Dr. K. Mosig et al., IITC2001@footnote 2@Y. Momonoi, K. Yokogawa, M. Izawa, Proc. Inter. Sym. Dry Process, (2002), p.113.