FIGURE 7.16 H13 tooling created with LENS™ process. SOURCE: Courtesy of Sandia National Laboratories.
A common opportunity exists among these techniques to increase the precision of three-dimensional manufacturing. If shorter-wavelength lasers and imaging were available, it would be possible to reduce the scale of the smallest-possible three-dimensional voxel (a three-dimensional pixel).
In general, one important part of additive manufacturing is an increased emphasis on in situ metrology that uses coherent optics (interference) for feedback and control, especially when the dimensions of parts shrink. Pattern-placement metrology, used ordinarily for lithographic purposes, can rely on phase-coherent fiducial gratings patterned by interference lithography.70 Potential uses include measuring process-induced distortions in substrates, patterning distortions in pattern-mastering systems, and measuring field distortions and alignment errors in steppers and scanners. For example, spatial-phase-locked electron-beam lithography has been implemented to correct pattern-placement errors at the nanometer level.71
70 Schattenburg, M.L., C. Chen, P.N. Everett, J. Ferrera, P. Konkola, and H.I Smith. 1999. Sub-100 nm metrology using interferometrically produced fiducials. Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 17(6):2692-2697.
71 Hastings, J.T., F. Zhang, and H.I. Smith. 2003. Nanometer-level stitching in raster-scanning electron-beam lithography using spatial-phase locking. Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 21(6):2650-2656.