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Supersonic Reactive Gas Jet Chemical Processing

IP.com Disclosure Number: IPCOM000109065D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 93K

Publishing Venue

IBM

Related People

Eldridge, BN: AUTHOR [+2]

Abstract

A technique is described whereby supersonic reactive gas jets are used in a reactor to produce chemical reactions in a shorter length of time and at reduced temperatures than are produced in conventional laminar flow chemical reactors. The process is particularly applicable in the etching of silicon wafers, as used in semiconductor integrated circuit fabrication; however, it is also applicable to general processing reactions that use gas phase reactants.

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Supersonic Reactive Gas Jet Chemical Processing

       A technique is described whereby supersonic reactive gas
jets are used in a reactor to produce chemical reactions in a shorter
length of time and at reduced temperatures than are produced in
conventional laminar flow chemical reactors.  The process is
particularly applicable in the etching of silicon wafers, as used in
semiconductor integrated circuit fabrication; however, it is also
applicable to general processing reactions that use gas phase
reactants.

      In prior art, many dry chemical processes, such as chemical
vapor deposition (CVD), introduce reactive gas into the reactor in a
slow laminar flow.  The reaction rate is usually controlled by the
temperature of the solid surfaces.  The concept described herein uses
supersonic jets of reactive gases to increase the rate of reaction
and decrease the process temperature, as compared to the laminar flow
process.

      Typically, when a gas at high pressure is allowed to expand
through a small nozzle into a low pressure region, the energy
associated with the random thermal motion of the molecules, together
with the mechanical energy in the expansion, are converted to the
kinetic energy of the molecules moving in the forward direction.
This produces a high-speed gas jet.  In addition, if the gas is mixed
with a gas of lower molecular weight, such as hydrogen or helium,
called "seeding", beams of molecules with kinetic energies in the
order of one electron volt can be generated.  This can be compared to
only 0.039 electron volts averaged kinetic energy, at room
temperature, of a gas molecule in thermal equilibrium.

      It has been previously shown (1,2) that the sticking
coefficient of molecules on solid surfaces can be enhanced by
increasing the kinetic energy of the molecules.  Also, the rate of
silicon etching using oxygen can be enhanced, particularly when the
oxygen beam impinges perpendicular to the surface.  Howeve...