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As semiconductor device ground rules become more stringent, lithographers are driven to reduce the magnitude of system error budget components to near atomic scale levels. Near term requirements (1995) for semiconductor photomask image placement have already been defined at 25 nm and are presumed to become tighter. Error contributions from both the stage metrology platform and material handling subsystems must be improved to 10 nm, thus allowing the balance of the error budget to be apportioned to the electron-optics and the electronic subsystems. As a result, a new, automated state-of-the-art Material Handling System (MHS) was designed for the Lepton EBES4 E-Beam Reticle Generator. This MHS is capable of handling multiple products such as reticles up to 9 in. (229 mm), x-ray masks, and wafers. Accuracy, required to support future E-beam pattern-writing applications for the production of 256 Mb and 1 Gb DRAM substrates, was the principle objective in its design. Therefore key attributes of the MHS are: (1) Precise substrate positioning with a resolution of (lambda) /120 achieved by means of two high-stability dual linear/angular interferometers combined in a single, compact optical assembly. (2) Stringent thermal management within the vacuum environment via a unique low-pressure (50 torr) gas conduction isotherm mode of action, which represents a new approach for rapid substrate temperature equilibrium to less than +/- 0.02 degree(s)C control. This paper focuses on how the MHS design addresses the minimization of mechanical error contributions to lithographic accuracy. Tests results of numerous critical parameters are presented (aligner/robot-corrected substrate positioning accuracy, temperature equilibration and stability, stage smoothness of motion, and electromagnetic interference). In addition, 3D finite element models are included to demonstrate induced static and random distortions, and dynamic modes of the metrology platform.
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