PERFORMANCE OF THE EL-3+ MASKMAKER

IBM's new e-beam maskmaker, designated EL-3 +, is installed and operating in the IBM Advanced Mask Facility in Burlington, Vermont. This tool represents a significant extension in the state of the art in the manufacture of masks, particularly in the areas of minimum feature size and overlay. The tool routinely operates with 0.35-mu-m ground rules at 70 nm (3-sigma) registration to grid. The tool has demonstrated the ability to work at 0.25-mu-m ground rules as well. The primary mission of the tool is the production of 1X x-ray masks. Some of the tool parameters include a 50 keV electron beam operating at a current density of 20 A/cm2. The system uses a shaped spot with a maximum size of 2 x 2-mu-m2. Exposures are made over areas with dimensions of up to 80 by 80 mm with a 2.1 mm field size. Deflection within a field is done through a combination of magnetic and electric deflection in a variable axis immersion lens (VAIL) configuration. During exposure the pattern data is stored on-line in a 1 G-byte buffer. The pattern buffers are loaded directly from a host IBM 4381. The system automatically corrects for any field distortions to a level of 6.25 nm using a calibrated reference grid.