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Porous Source for the Vapor Deposition of Thin Films in Vacuum

IP.com Disclosure Number: IPCOM000114034D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Mate, CM: AUTHOR [+3]

Abstract

This invention is a method for depositing thin liquid films on a substrate by evaporation of the liquid in vacuum followed by condensation on the substrate surface. The invention relies on the use of a porous material impregnated with the liquid material. This comprises the "source", which can be manufactured to suitable dimensions and can be held at any angle without draining of the liquid due to gravity. The source is heated to a temperature appropriate to cause evaporation from the source followed by condensation onto the nearby substrate. Faster evaporation and deposition rates can be induced by increasing the liquid vapor pressure by heating.

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Porous Source for the Vapor Deposition of Thin Films in Vacuum

      This invention is a method for depositing thin liquid films on
a substrate by evaporation of the liquid in vacuum followed by
condensation on the substrate surface.  The invention relies on the
use of a porous material impregnated with the liquid material.  This
comprises the "source", which can be manufactured to suitable
dimensions and can be held at any angle without draining of the
liquid due to gravity.  The source is heated to a temperature
appropriate to cause evaporation from the source followed by
condensation onto the nearby substrate.  Faster evaporation and
deposition rates can be induced by increasing the liquid vapor
pressure by heating.  Since liquid entrained in the fine porosity
experiences a reduction in vapor pressure and restricted flow through
the porous material, more control of the evaporation rate can be
achieved compared to a bulk liquid source.  The fastest deposition
rates are achieved by operating the source in vacuum where the mean
free path of the vapor molecules exceeds the source-substrate
separation distance.

      The Figure shows the deposition rate as a function of source
temperature achieved for the perfluoropolyether liquid lubricant
entrained in microporous glass with different pore sizes.  The Figure
shows how, as the pore size decreases, both the deposition rate and
slope in deposition rate versus temperature decreases at a given
temperature.  The decrease in slope with smaller pore size makes the
deposition rate less sensitive to fluctuations in the source
temperature a...