Air pressure pick-up tool

Claim 1

In combination: a head member having therein a central gas passage: a flat, annular minor surface portion in the head member surrounding the gas passage; a flat, annular major surface portion surrounding the minor surface portion and having an area larger than the area of the minor surface portion; the flat major and minor surface portions both being substantially perpendicular to the central gas passage; the minor surface portion being displaced inwardly in the head member from the major surface portion and being connected to the major surface portion by a step portion, whereby the minor surface portion and the step portion define a cavity surrounding the gas passage; a semiconductor wafer; the area of the minor surface portion being smaller than the area of one surface of the wafer; means for directing gas through the gas passage toward the wafer at a sufficient velocity to permit the wafer, with a flat surface thereof parallel to the major surface portion and generally centered on the gas passage, to be suspended in close proximity to the major surface portion in accordance with the Bernoulli principle; the major surface portion being substantially solid and continuous along its entire area, whereby the gas is ejected from the entire periphery of the major surface portion into free space surrounding the head member; the cavity has a general shape of a conical section; a plurality of elements extends from the periphery of the head member each adapted to bear against only the periphery of the wafer; the area of the flat major surface portion plus the area of the flat minor surface portion is more than one-half the surface area of one surface of the wafer; the cavity depth is greater than fifteen mils; and the step portion interconnecting the minor surface portion to the major surface portion extends at an angle with respect to the flat major surface portion of about 70 degrees.