Study Of Pattern Generator For Nanometer E-beam Lithography System

The high speed pattern generator is a key unit for nanometer electron-beamlithography system based on commercial SEM. The pattern generatorcommunicates with the controlling computer through Universal Series Bus (USB)2.0. The Digital Signal Processor (DSP) is employed in the pattern generator, socoordinates of exposure points inside the complex shapes can be calculated asfast as 0.135μs per point (7.2MHz). The beam scanning is controlled by two set of16-bit Digital-to-Analog Converters (DAC), namely X and Y DAC. Either set ofDAC includes one main DAC and three multiplicative DACs. Therefore, users canadjust the scaling, rotation and shift of writing field respectively. The unit can alsogenerate blanking signals.The pattern generator can control laser stage for field stitching and obtain fieldstitching accuracy better than 0. 2μm. Using this technique, patterns may bewritten over a large area. Through identifying the marks on the wafer, the patterngenerator can make lay to lay exposure.Exposure data can be imported in common electron-beam data formats such asGDSII and CIF. Users can also edit new exposure data by its computer-aidedsoftware. The pattern generator can deal with such basic shapes as rectangles,trapezoids, lines, circles and circular arcs. Arbitrary shapes edited by user can besplit into one or more basic shapes. Not only imported data but also user prepareddata need converting into Exposure Data Files (EDF) which is recognizable bypattern generator.The pattern generator can be connected with SEM, FIB and SPM for patternwriting. Various patterns were wrote using this generator with JSM-6360 (LaB6cathode) SEM, S3000N SEM, JEM-2000EX TEM and so on. The minimum linewidth of 28 .6nm has been obtained.