Abstract: Powder mass flow rates are measured by constraining the powder to flow within an apparatus which injects a charge into the powder at a first position and measures at a plurality of positions downstream from the first position the charge remaining in the powder and means for calculating from the injected and remaining charge the powder mass flow.

Abstract: A high precision, high throughput submicrometer workpiece positioning system, particularly useful as a workpiece positioning means in electron beam lithography tools. The positioning system increases mechanical stability by essentially eliminating mechanical hysteresis, which allows state of the art electron beam lithography systems to provide the repeatable, accurate and dense circuit patterns that modern semiconductor trends demand.The positioning system in preferred form comprises a movable positioning table, a workpiece supporting superstructure which is elastically joined to the movable positioning table by three geometrically distinct kinematic support means and a two-stage coupling means which mounts a workpiece (i.e., semiconductor mask or wafer) to the workpiece supporting superstructure. A laser interferometer locating-positioning system is utilized to position the workpiece. The interferometer mirrors are integral with the workpiece supporting superstructure.

Abstract: An elevator drive shaft is air pressure counter-balanced and dampened under varying load and system pressure conditions by applying required air pressure to an appropriate side of a piston moving with the drive shaft in an electron beam semiconductor wafer writing apparatus vacuum chamber. Air pressure counterbalancing load forces minimize the actuating forces required to drive the elevator, substantially minimizing vibratory shock and distortion to the electron beam writing system and increasing speed of wafer movement. This permits electron beam writing on one wafer simultaneously with a load/unload operation of a second semiconductor wafer. The counter-balancing load forces also minimize the probability of accidental damage to the system or semiconductor wafers due to uncontrolled high forces or upon mechanical impact between moving and fixed parts, during apparatus malfunction.

Abstract: An electron beam vacuum chamber is provided with an elevator mechanism within the chamber including a platform closing off an opening within a horizontal vacuum chamber wall and separating the vacuum chamber from an overlying antechamber partially defined by a vertically displaceable lid overlying the opening and moving towards and away from the opening. Resilient peripheral seals are fixed to the lid facing the chamber wall and the elevator platform. A coil spring partially compressible upon contact with the first peripheral seal carried by the lid with the face of the vacuum chamber wall forms a first mechanical override and an annular spring metal diaphragm fixedly mounted about its outer peripheral edge to the vacuum chamber adjacent the opening has its inner peripheral edge freely flexible and is contacted by the resilient peripheral seal of the platform to form a second mechanical override.

Abstract: A batch chip placement system for batch positioning semiconductor chips, or the like, upon a substrate containing an array of chip sites or footprints whose actual position on the substrate deviates from the theoretical or nominal position over successive substrates. The positioning is achieved by first sensing the X and Y offsets of a pair of alignment marks on the substrate from their theoretical or nominal position to determine the .DELTA.X and .DELTA.Y correction factors required to obtain the actual X,Y position of the alignment marks. The actual X,Y position of the alignment marks is used to determine actual X,Y chip position values, .theta. rotation and shrinkage factor corrections required to obtain proper orientation and positioning for batch chip placement.