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Conducting layers for charged particle beam projection lithography masks Disclosure Number: IPCOM000013253D
Original Publication Date: 2000-Nov-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 4 page(s) / 66K

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Conducting layers for charged particle beam projection lithography masks

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Conducting layers for charged particle beam projection lithography masks

Conducting layers for charged particle beam projection lithography masks

Stencil masks are advantageously fabricated using diamond as the membrane material as described in a previous disclosure now filed with the US Patent Office. However, during the fabrication of these masks, issues with the diamond film being an electrical insulator have been discovered during mask processing. This causes difficulties both during mask fabrication and during use as a charged particle beam mask. Typical stencil masks are made from silicon membranes that are electrically conducting, but diamond provides advantages for stiffness and thermal conductivity.

Charging phenomena have been observed during e-beam write and SEM inspection with a typical diamond stencil mask process. The stack in this case was diamond with a dielectric hardmask and photoresist (all insulating layers).

This idea describes the use of thin discharge layers on the diamond membranes. The layers would be added at the beginning of the mask. The discharge layers could be thin metal layers or, more preferably for diamond, thin graphite layers formed by changing the deposition conditions during the diamond deposition or by modifying surface of the diamond layer after deposition.

In an alternative arrangement, the thin graphite discharge layer could be used to provide electrical conductivity to SCALPEL-type membrane masks. It would be formed with the membrane deposition, again by modifying the deposition parameters or modifying the surface layer.

The thin discharge layers provide electrical conductivity along the mask both during fabrication (e-beam write and e-beam inspection) and use in a charged-particle beam stepper.

A representative process flow is shown below, but it should also be noted that variations exist in stencil mask processing. Both wafer flow (stencil etch before membrane etch) and membrane flow (membrane etch before stencil etch) are possible. In addition, it is within the scope of this invention that the discharge layers may be above or below the diamond layer.

A process for implementing the preferred embodiment would start with a substrate, usually a silicon wafer, but other materials are possible. The diamond layer would be deposited upon the substrate and then a thin discharge layer formed upon the diamond. The preferred material for the discharge layer would be a graphite-like layer formed by modifying the diamond deposition parameters to form graphite (sp2 bonded carbon) instead of diamond (sp3 bonded carbon).


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The process flow for stencil mask f...