Appeal No. 96-1848
Application 08/161,604
oxide layer so as to impede the lateral diffusion of
tungsten into the interface between said substrate and said
oxide layer." The sealing layer is disclosed to be silicon
nitride of a certain thickness and, hence, the silicon
nitride layer 28b in Haskell, which is of greater thickness,
is considered to perform the function of modifying stresses
to impede the lateral diffusion of tungsten into the
interface. Appellants have not shown otherwise. The
recited function of the sealing layer does not require,
expressly or implicitly, that the sealing layer extend
around the tungsten plug member and impede lateral diffusion
in all directions: the function of modifying stresses to
impede the lateral diffusion of tungsten into the interface
is broadly satisfied if the sealing layer is on one side of
the plug and lateral diffusion of tungsten is impeded in
that direction.
However, claim 26, similar to claim 10, recites
"a tungsten plug . . . extending up through a contact hole
etched through said bottom dielectric oxide layer, said
sealing dielectric layer, and said interlevel dielectric
layer." We interpret this limitation to require that the
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