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Photolithography on three dimensional substrates.

Ivey, P.A. and McWilliam, R. and Maiden, A. and Williams, G.L. and Purvis, A. and Seed, N.L. (2006) 'Photolithography on three dimensional substrates.', in 56th Electronic Components and Technology Conference, 30 May-2 June 2006, San Diego, California ; proceedings. New York: IEEE, pp. 283-288.


Photolithography is the primary technique for patterning planar substrates. However, some higher-density packaging solutions require fine features to be patterned onto grossly non-planar substrates, for example, in mechanical, optical and fluidic microsystems and in novel packaging schemes. Standard photolithography cannot be used in these cases because the inevitable gap between the (planar) mask and (non-planar) substrate causes diffractive line broadening and loss of resolution. We address this issue by realising the mask as a Computer Generated Hologram (CGH), which can then be illuminated to generate an image in space corresponding to the required non-planar profile. The CGHs are derived from analytical expressions and encode both amplitude and phase information. We illustrate the performance with a 100μm line exposed onto a substrate in the form of a plane/slope/plane, in which the change in depth is 40mm. Enhancements to the line shape are discussed that make the technique more robust to manufacturing process variations. The fact that features in the range 10-100μm can be imaged at large distance whilst coping with significant changes of depth indicates that the technique shows great potential in the microelectronics packaging industry.

Item Type:Book chapter
Additional Information:IEEE catalog number 06CH377766C.
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Publisher statement:© 2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Record Created:29 Nov 2006
Last Modified:01 Nov 2010 15:36

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