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Tungsten W-O Coating of Silicon Membranes

IP.com Disclosure Number: IPCOM000109580D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Bassous, E: AUTHOR [+3]

Abstract

Boron-doped silicon membrane structures with small orifices are used as focusing electrodes (i.e., microlenses) in STM-based field emission electron beam systems. The electrical and thermal conductivities of silicon are barely adequate for this application. Considerable improvement in functional performance could be achieved by coating the exposed silicon surfaces with an adherent, conformal, low-stress, low resistivity metallic film that is thermally and mechanically stable. Conventional metal deposition techniques lack one or more of the latter characteristics.

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Tungsten W-O Coating of Silicon Membranes

       Boron-doped silicon membrane structures with small
orifices are used as focusing electrodes (i.e., microlenses) in
STM-based field emission electron beam systems.  The electrical and
thermal conductivities of silicon are barely adequate for this
application.  Considerable improvement in functional performance
could be achieved by coating the exposed silicon surfaces with an
adherent, conformal, low-stress, low resistivity metallic film that
is thermally and mechanically stable.  Conventional metal deposition
techniques lack one or more of the latter characteristics.

      Disclosed is a method to improve the performance
characteristics of silicon membrane structures that are used as
focusing electrodes (microlenses) in miniaturized field emission
electron-beam systems.  The performance of boron-doped silicon
membrane microlenses, typically 1 mm thick with one or more orifices
or through-holes 1 mm diameter, can be enhanced considerably by
coating the membrane surface with a W-O layer embedded in W matrix
obtained by the following reactions:
2 WF6 + 3 Si T 2 W + 3 SiF4
WF6 + H2O + Si T W-O + SiF4 + 2HF

      The second reaction forms W-O in the presence of H2O and gives
thermal stability to the W layer and reduces the stress levels.

      The reaction is performed at 300-400~C in the pressure range
0.2 to 1 Torr in a Low Pressure Chemical Vapor Deposition (LPVCVD)
cold wall reactor.  A desired W film can be deposited accurately and
controllably on a silicon surface to produce a conf...