| 摘要 |
RESOLUTION DOUBLING LITHOGRAPHY TECHNIQUE A lithography system is disclosed which is capable of doubling the spatial frequency resolution associated with conventional systems. A spatial filter (e.g., 20), positioned to intercept the Fraunhofer diffraction pattern of the mask (e.g., 18) being exposed, is configured to prevent certain orders of the diffraction pattern (in most cases the 0-order and +2nd, 3rd, ... orders) from reaching the wafer's surface. The remaining orders reaching the wafer surface in most cases the + first-order beams) will produce a cos-type interference pattern with a period half of that if the mask grating were imaged without spatial filtering. Therefore, for a system with a given magnification factor m, a mask grating with a period pwill be exposed on the wafer surface as a grating with a period of p'-pm/2. Advantageously, the spatial filtering technique of the present invention allows for a variety of different structures (conventional gratings, chirped and phase-shifted gratings, grids, Fresnel zone plates, etc.), as well as structures of different sizes and orientations, to be included on one mask and transferred to the wafer with asingle exposure cycle. |
