Patent ID: 8491252
Filing Date: 2013-07-23
Classification: H01L

Abstract:
1. A method for transporting disk-shaped semiconductor workpieces in a vacuum process facility, the workpieces each having a thickness and a total maximum up and down deflection that is due to any internal stress of the workpiece and to the workpiece being supported by opposite peripheral regions of the workpiece, the method comprising: providing at least one transport robot with a horizontally movable transport arm having one end with only two spaced-apart, elongated and horizontally extending carrying rods for substantially horizontally receiving a workpiece thereon to be transported, each of the only two carrying rods having a diameter; providing a cassette having opposite sides each with a comb structure with a plurality of vertically spaced combs each in a comb plane that is separated from an adjacent comb by a comb distance corresponding to a maximum vertical system tolerance for substantially horizontally receiving a plurality of vertically spaced workpieces between the combs on each side of the cassette, each workpiece having opposite peripheral regions that are each supported on a comb of the cassette and the cassette being loaded with a plurality of said workpieces; selected the diameter of the carrying rods and the comb distance between the combs so that the carrying rods can be introduced between two adjacent, spaced-apart combs of the comb structure and be free of contact with the workpieces deposited on the combs and in the cassette; spacing and positioning the only two carrying rods at the one end of the transport arm so that each rod is located at a respective one of a pair of strip-shaped handling zones in respective peripheral regions of said workpieces, the carrying rods being spaced so that they engage a workpiece only at the respective handling zones, the width of each handling zone and therefore the spacing and positioning of each carrying rod, being determined to prevent further deformation of the workpiece when the carrying rods engage the workpiece, said handling zones being arranged close to and along the comb structures substantially parallel to the comb structures when the workpiece is inserted into the cassette, the width of the handling zones being determined by the sum of the maximum up and down deflections of the workpiece when lying on a horizontal plane; horizontally moving the transport arm with respect to the cassette for to insert the carrying rods into the space between combs on which a workpiece to be moved is supported and under respective handling zones of the peripheral region of the workpiece to be moved; thereafter lifting the transport arm with respect to the cassette to bring the carrying rods into engagement with the handling zones of the workpiece to be moved and for lifting the workpiece to be moved from the combs; thereafter horizontally moving the transport arm with respect to the cassette to remove the workpiece to be moved and that is now engages on the carrying rods, from the cassette; using a scanning beam having an optical path and being in a region along and between two adjacent comb planes on one side of the cassette for detecting a workpiece in a workpiece plane in the cassette and for detecting the presence of a workpiece in the cassette, said scanning beam emanating beside a comb on one side of the cassette and close to one of the peripheral regions of said workpiece; and positioning a height of the scanning beam relative to the cassette and tilting the scanning beam at a small angle with respect to the horizontal plane so that the scanning beam generates a projection of the workpiece which is of significantly greater thickness than an actual thickness of the workpiece, wherein the angle of tilt of the scanning beam is defined such that when the beam is guided along two adjacent parallel combs, the comb distance is not exceeded.