Abstract: Improved systems, apparatus, and methods for detecting positions of moving stages and a reference position of a beam column are provided. For some embodiments, independent discrete interferometers may be utilized for distance measurements in each axis, rather than a cumbersome monolithic multi-axis interferometer utilized in conventional systems.

Abstract: We have developed a method and apparatus for cooling electromagnetic lens coils of the kind used in charged particle beams. The method and apparatus provide not only a symmetrical cooling effect around the optical axis of the charged particle beam, but also provide improved uniformity of heat transfer. This improved uniformity enables control over the optical axis of the charged particle beam within about 1 nm for high current charged particle beam columns, wherein the current ranges from about 100 nanoamps to about 1000 nanoamps. The use of a squat and wide electromagnetic lens coil in combination with an essentially flat modular cooling panel, which provides uniform cooling to the electromagnetic lens coil, not only enables control over the optical axis of the charged particle beam, but also provides mechanical stability for the charged particle beam column.

Abstract: Improved systems, apparatus, and methods for detecting positions of moving stages and a reference position of a beam column are provided. For some embodiments, independent discrete interferometers may be utilized for distance measurements in each axis, rather than a cumbersome monolithic multi-axis interferometer utilized in conventional systems.

Abstract: A laser beam or other parallel light beam divides at a beamsplitter into sample and reference beams. The sample beam reflects from a reflective surface back to the beamsplitter, and the reference beam reflects from a retroreflector back to the beamsplitter. The beams are then directed into a telescope. The angle between sample and reference beams at the telescope is proportional to the angle between the laser beam and the normal to the reflective surface. The telescope collects both sample beam and reference beam and transforms each beam into a sharply defined point image. The lateral separation between the two point images is proportional to the magnification of the telescope and to the angle formed at the telescope between the sample beam and the reference beam. If the reflective surface is accurately aligned relative to the laser beam, then the two point images are substantially superposed on one another.

Abstract: A laminar flow diffuser has a plurality of round, thin, stacked plates. A central bore penetrates all the plates with the exception of the bottom plate. The diffuser is secured to the vacuum chamber port. When gas enters the port, it enters the central bore and then flows radially outward through the interplate spaces to the outer circumference of the plates and subsequently into the periphery of the chamber. The diffuser thereby provides a controlled laminar flow which prevents turbulence in the chamber and hence, reduces the possibility of contamination to the workpiece in the chamber. The laminar flow diffuser is easily cleaned, both during its initial assembly and later after use, because it chiefly has flat surfaces which do not harbor dirt or gas.

Abstract: A specimen distance measuring system uses a plate (36) to obstruct the flux of backscattered electrons produced by an electron beam (18), and to cast a shadow across a measurement detector (32) which is sensitive to the position of the shadow. The shadow plate (36) and measurement detector (32) are aligned at an angle of approximately 45 degrees with a substrate (14) in order to allow calibration of the distance measuring system by scanning the electron beam (18). The measuring system is particularly useful as a height sensor (10) in an electron beam lithography apparatus (12) for sensing the height of a substrate (14). The distance measuring system may also include a reference detector (34) which is positioned in order to receive backscattered electron flux without obstruction from the shadow plate (36).

Abstract: An electrostatic cassette assembly comprising, a cassette body having a central opening for receiving a wafer to be processed in a particle beam lithographic system, a charge plate with a top surface having a coating of dielectric (nonconductive) material or a plurality of nonconductive means, or both, on which the wafer is supported, means for forcing said charge plate and wafer into contact with stop means to hold the wafer rigidly in said cassette assembly, and means for applying a potential difference between the wafer and the charge plate to flatten said wafer by Coulombic force so that the wafer is held both mechanically and electrostatically in said cassette assembly. Means are also provided for insuring a good electrical contact with the wafer and for aligning the wafer in the cassette assembly.