SUBSTRATE TRANSFER APPARATUS FEATURING LOWER AND UPPER PNEUMATIC SUCKER ARMS, AND SUBSTRATE TRANSFER METHOD CARRIED OU IN SUCH SUBSTRATE TRANSFER APPARATUS
In a substrate transfer apparatus that pneumatically holds and transfers a substrate having first and second surfaces, a first pneumatic sucker arm has at least two first suction ports for pneumatically sucking the first surface of the substrate, and a second pneumatic sucker arm has at least two second suction ports for pneumatically sucking the second surface of the substrate. First and second drive mechanisms vertically move the first and second pneumatic sucker arms toward the respective first and second surfaces of the substrate, with the at least two first suction ports and the at least two second suction ports being directed to the respective first and surfaces of the substrate. The vertical movement of the first pneumatic sucker arm is stopped when any one of sucking pressures generated in the first suction ports is lowered to a predetermined low pressure, and the vertical movement of the second pneumatic sucker arm is stopped when any one of sucking pressures generated in the second suction ports is lowered to the predetermined low pressure.
1 . A substrate transfer apparatus that pneumatically holds and transfers a substrate having first and second surfaces, which apparatus comprises:
a first pneumatic sucker arm having at least two first suction ports for pneumatically sucking the first surface of said substrate;
a first drive mechanism that vertically moves said first pneumatic sucker arm toward the first surface of said substrate, with said at least two first suction ports being directed to the first surface of said substrate;
a plurality of first pressure sensors that detect respective sucking pressures generated in said at least two first suction ports;
a second pneumatic sucker arm having at least two second suction ports for pneumatically sucking the second surface of said substrate;
a second drive mechanism that vertically moves said second pneumatic sucker arm toward the second surface of said substrate, with said at least two second suction ports being directed to the second surface of said substrate;
a plurality of second pressure sensors that detect respective sucking pressures generated in said at least two second suction ports; and
a control circuit controls the vertical movement of said first pneumatic sucker arm in accordance with the respective sucking pressures detected by said first pressure sensors and the vertical movement of said second pneumatic sucker arm in accordance with the respective sucking pressures detected by said second pressure sensors.
2 . The substrate transfer apparatus as set forth in claim 1 , wherein said control circuit stops the vertical movement of said first pneumatic sucker arm when a sucking pressure in any one of said at least two first suction ports is detected as a predetermined low pressure by a corresponding one of said first pressure sensors, and wherein said control circuit stops the vertical movement of said second pneumatic sucker arm when a sucking pressure in any one of said at least two second suction ports is detected as a predetermined low pressure by a corresponding one of said second pressure sensors.
3 . The substrate transfer apparatus as set forth in claim 1 , wherein said control circuit stops a movement of said second pneumatic sucker arm when the sucking pressures in said at least two first suction ports are lowered to a predetermined low pressure.
4 . The substrate transfer apparatus as set forth in claim 1 , wherein said substrate is defined as a semiconductor wafer, said at least two first suction ports being spaced apart from each other so as to be in contact with respective diametrical side edge areas on the first surface of said semiconductor wafer, said at least two second suction ports being spaced apart from each other so as to be in contact with respective diametrical side edge areas on the second surface of said semiconductor wafer.
5 . The substrate transfer apparatus as set forth in claim 4 , wherein said at least two first suction ports are defined as endmost suction ports, said first pneumatic sucker arm further having an additional first suction port arranged between said endmost first suction ports.
6 . The substrate transfer apparatus as set forth in claim 4 , wherein said at least two second suction ports are defined as endmost suction ports, said second pneumatic sucker arm further having an additional first suction port arranged between said endmost first suction ports.
7 . The substrate transfer apparatus as set forth in claim 1 , wherein said substrate is defined as a semiconductor wafer, said second pneumatic sucker arm has two projections, said at least two suction ports being formed in said projections, and being spaced apart from each other so as to be in contact with respective diametrical side edge areas on the second surface of said semiconductor wafer.
8 . The substrate transfer apparatus as set forth in claim 7 , wherein said projections have a height which defines a sufficient space between said first and second pneumatic sucker arms to receive a maximum warped semiconductor wafer, without the second surface of said maximum warped semiconductor wafer brought into contact with the second pneumatic sucker arm.
9 . A method for transferring a substrate having first and second surfaces, which method comprises:
positioning a first pneumatic sucker arm having at least two first suction ports and a second pneumatic sucker arm having at least two second suction ports in place with respect to said substrate, so that said at least two first suction ports and said at least two second suction ports are directed to the respective first and second surfaces of said substrate;
moving said first pneumatic sucker arm toward the first surface of said substrate;
detecting respective first sucking pressures generated in said at least two first suction ports;
stopping the movement of said first pneumatic sucker arm when it is detected that any one of said first sucking pressures is lowered to a predetermined low pressure;
moving said second pneumatic sucker arm toward the second surface of said substrate;
detecting respective second sucking pressures generated in said at least two second suction ports; and
stopping the movement of said second pneumatic sucker arm when it is detected that any one of said second sucking pressures is lowered to said predetermined low pressure.
10 . A method for transferring a substrate having first and second surfaces, which method comprises:
positioning a first pneumatic sucker arm having at least two first suction ports and a second pneumatic sucker arm having at least two second suction ports in place with respect to said substrate, so that said at least two first suction ports and said at least two second suction ports are directed to the respective first and second surfaces of said substrate;
moving said first pneumatic sucker arm and said second pneumatic sucker arm toward the first and second surfaces of said substrate, respectively;
detecting respective first sucking pressures generated in said at least two first suction ports and respective second sucking pressures generated in said at least two second suction ports;
stopping the movement of said first pneumatic sucker arm when it is detected that any one of said first sucking pressures is lowered to a predetermined low pressure; and
stopping the movement of said second pneumatic sucker arm when it is detected that any one of said second sucking pressures is lowered to said predetermined low pressure.