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Ion Beam Projection Lithography (IPL) for Minimizing Pattern Distortion and Mask Replacement/Repair

IB-1383

Maskless Approach to IPL

APPLICATIONS OF TECHNOLOGY:

  • Lithography
  • Ion implantation/doping
  • Magnetic storage

ADVANTAGES:

  • Uses a thick fixed mask instead of a thin stencil mask (thickness of 30 µm vs. 3 µm for a typical stencil mask)
    • Easier mask fabrication
    • Longer mask lifetime
    • Minimizes pattern distortion

ABSTRACT:

In conventional IPL systems, high-energy ions (~10KeV) impinge on a very thin stencil mask, causing heating, scattering, and sputtering that distort the pattern and eventually ruin the mask. Berkeley Lab researchers have invented an ion projection lithography (IPL) system in which low energy ions (< 30eV) impinge on an electrode that also serves as a mask.

Ka-Ngo Leung and colleagues eliminate the acceleration stage between the ion source and stencil mask by positioning a thick, fixed pattern mask that is also used as a beam forming or extraction electrode directly next to the plasma source. The plasma contacts the entire electrode or mask and is extracted through its holes or apertures. The extracted beam then passes through an accelerator and reduction column to produce a demagnified pattern on a resist-coated wafer or other targets.

An additional advantage of the Berkeley Lab IPL system design is that the accelerator and reduction column can be designed either with beam crossover or without. Beam crossover can increase the longitudinal energy spread of the beam and produce image blur. This effect puts an upper limit on the maximum beam current and therefore on throughput.

This technology also features a mask design for creating a circular ring pattern, which is typically difficult to achieve with lithography.

STATUS: U.S. Patent #6,486,480. Available for licensing or collaborative research

REFERENCE NUMBER: IB-1383

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Last updated: 08/12/2013