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Reduction of Trenching Near Edges in Reactive Ion Etching

IP.com Disclosure Number: IPCOM000103146D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Chrisman, G: AUTHOR [+4]

Abstract

By minimizing number of energetic and reactive ions having trajectories other than normal to the substrate surface, high etch rate at the base of edges (trenching) is reduced. Thus, physical and electrical integrity of a thin layer under an etched feature is maintained.

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Reduction of Trenching Near Edges in Reactive Ion Etching

      By minimizing number of energetic and reactive ions having
trajectories other than normal to the substrate surface, high etch
rate at the base of edges (trenching) is reduced. Thus, physical and
electrical integrity of a thin layer under an etched feature is
maintained.

      Referring to the figure,  thin gate oxide 2 is deposited on
substrate 4.  Thick polysilicon 6, having an etch mask of nitride 8,
is shown at a time near the end of reactive ion etching (RIE) layer 6
to form a feature, e.g., a gate electrode.  The dotted surface
profile shows the trenching found when care is not taken to minimize
ion trajectories which are other than normal to the substrate
surface.  In this case, oxide 2 is ion bombarded near the base of the
etched edge while polysilicon 6 is being completely removed
elsewhere.  By reducing the number of ions having other than normal
trajectories and energy and reactivity of particles recoiling from
the etched edge, etching is completed more uniformly and trenching is
minimized as indicated by the solid line surface profile of etched
polysilicon 6.

      Means to reduce number of ions having off-normal trajectories
includes minimizing process pressure, thus minimizing collisions of
ions before striking the substrate. Magnetic field can be applied to
reduce plasma sheath thickness, thus collisions of ions within the
sheath.

      Reducing ion energy to the threshold...