Brushing – scrubbing – and general cleaning – Machines – Brushing
Reexamination Certificate
2002-04-29
2004-10-19
Jones, Deborah (Department: 1775)
Brushing, scrubbing, and general cleaning
Machines
Brushing
C015S088300, C134S153000, C134S902000
Reexamination Certificate
active
06804851
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a holder for a flat wafer, in particular a semiconductor wafer in an apparatus for cleaning a semiconductor surface with the aid of brushes. The holder contains a carrier part, a plurality of carrying arms, which extend in a spider-like manner from the carrier part, a plurality of bearing devices, which are intended for positioning the wafer horizontally and are each assigned to a carrying arm, and a plurality of guide rollers, which are intended for positioning the wafers vertically and are each mounted rotatably on the carrying arm.
Such holders are known in general and are used, in particular, for determining the position of the semiconductor wafers for a cleaning and drying process following chemical-mechanical polishing. Chemical-mechanical polishing processes serve, within the context of the production of semiconductor components, for leveling out trench fillings, metal plugs, intermediate oxides or intermetallics. In the case of chemical-mechanical polishing, the semiconductor wafer which is to be processed is forced, by a wafer carrier, against a rotatably disposed polishing table, on which there is located an elastically perforated bearing device containing a polishing material. The semiconductor wafer and polishing table here rotate in opposite directions, as a result of which the protruding locations on the surface of the semiconductor wafer are polished away until a planar wafer surface is achieved.
Following the chemical-mechanical polishing operation, however, impurities remain behind on the surface of the semiconductor wafer, and these have to be removed before the semiconductor wafer is processed further. For this purpose, following the completion of the chemical-mechanical polishing process, the semiconductor wafer is transferred, with the aid of an automatic apparatus, from the polishing installation into a cleaning installation, in which the semiconductor wafer is processed by a brush apparatus, a so-called brush cleaner, in order to free the semiconductor surface of the impurities. During the brush cleaning, the semiconductor surface is flushed continuously with a wetting-agent-containing a cleaning liquid, for example ammonia or distilled water. Following the completion of the brush cleaning, the semiconductor wafer is then freed of the cleaning liquid by centrifugal drying.
The brush cleaning and the centrifugal drying preferably take place here in a combined installation, in order to avoid further transfer of the semiconductor wafer. For the combined brush-cleaning and drying process, the semiconductor wafer is inserted into a holder which, on the one hand, allows the semiconductor wafer to rotate, this being brought about by the rotation of the brushes on the semiconductor surface during the brush-cleaning process, and, on the other hand, makes it possible for the semiconductor wafer to be centrifuged at a high speed during the drying process.
The holder for the semiconductor wafer generally has a turntable from which there extends, in a spider-like manner, preferably four symmetrically disposed carrying arms, on which the semiconductor wafer is seated by way of its outer border. For positioning the semiconductor wafer horizontally on the carrying arms, use is made here of a plastic bearing device at the top ends of the carrying arms, the semiconductor wafer resting thereon. For positioning the semiconductor wafer vertically, guide rollers are provided on the carrying arms. The guide rollers enclose the semiconductor wafer laterally and secure it. The guide rollers are mounted rotatably on the carrying arms in order to make it possible for the semiconductor wafer to rotate during the brush cleaning. The turntable of the holder, furthermore, is driven by a motor in order for it to be possible for the entire holder to execute a rotary movement for the centrifugal drying of the semiconductor wafer following the brush cleaning.
The turntable and the carrying arms of the holder generally are formed of coated steel. However, the process-induced contact with the chemical cleaning agent used during the brush cleaning and also the polishing-material residues from the preceding chemical-mechanical polishing operation, as well as the pronounced mechanical loading as a result of the high speeds during centrifugal drying, give rise to the risk of the coating loosening from the holder elements and of the steel located there-beneath corroding.
In the case of the known holders, the guide rollers for positioning the semiconductor wafer vertically are disposed on accommodating pins, provided on the carrying arms, and are further fixed by plastic plates. The accommodating pins for the guide rollers, like the turntable and the carrying arms of the holder, are produced from coated steel. However, the rotation of the guide rollers during the brush-cleaning process may give rise to abrasion of the coating becoming established, the abrasion resulting in the guide rollers rotating non-uniformly and thus in increased wear. A further problem with the known holders may arise during exchange of the guide rollers since there is a risk, during removal, of the plastic plates damaging the coating of the accommodating pin. Furthermore, the plastics plates can generally only be used once.
The bearing surfaces provided on the carrying arms for positioning the semiconductor wafers horizontally are usually produced from plastic, preferably POM. In the case of the bearing devices, in turn, there is a risk of them breaking up as a result of the continual contact with the cleaning agent used in the brush-cleaning operation and/or the polishing material used in the chemical-mechanical polishing operation, which then results in additional impurities on the semiconductor surface. Since the bearing surfaces on the carrying arms are disposed a fair way in front of the guide rollers, the semiconductor wafer is also supported a fair way inward in the radial direction, with the result that little clearance remains for the brush installation on the holder, which may result in pronounced bending of, and thus damage to, the semiconductor wafer.
U.S. Pat. No. 5,498,199 discloses a holder which is intended for semiconductor wafers in a brush-cleaning installation and in the case of which the bearing device for positioning the semiconductor wafer horizontally and the rotatable guide roller for positioning the same vertically are configured in one piece, this combined positioning configuration being mounted rotatably on a carrying arm with the aid of a ball bearing. The single-piece configuration allows simplified production and reliable mounting of the semiconductor wafers. The disadvantage with this embodiment, however, is the complicated rotary mounting via a ball bearing, which results in high installation and maintenance outlay.
U.S. Pat. No. 5,052,886, furthermore, discloses a bolt mounting for a guide roller, which serves for transmitting a rotary movement from a motor to the guide roller.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a holder for semiconductor wafers in a brush-cleaning installation which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which is intended for semiconductor wafers in a brush-cleaning installation and is distinguished by ease of maintenance and straightforward installation and, furthermore, reliably avoids damage to, and impurities on, the semiconductor wafer.
With the foregoing and other objects in view there is provided, in accordance with the invention, a holder for a wafer. The holder contains a carrier part, a plurality of carrying arms extending in a spider-shaped manner from the carrier part and each having a bore formed therein, a plurality of bolts, and a plurality of guide rollers for positioning the wafer vertically and each mounted rotatably on one of the carrying arms. Each of the guide rollers has an annular collar for positioning the wafer horizontally. Each of the guide rollers with the annular collar f
Fehr Matthias
Hunger Rüdiger
Mieth Thomas
Bahta Abraham
Greenberg Laurence A.
Infineon - Technologies AG
Jones Deborah
Locher Ralph E.
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