Appeal No. 1998-1850
Application No. 08/596,613
We also observe, in view of the arguments and counter-arguments with respect to
the rejections of claims 15 through 18, that appellants may have misapprehended the
basis of the examiner’s rejection of these claims. Appellants argue that limitations of claim
15 distinguish over the applied art. (See Brief, pages 10-15.) The examiner’s position
appears to be that the references of Doan, Davis, and Yu suggest ways of improving a
tungsten plug in a contact hole, and each of the methods of improving the plug would
ultimately result in the removal of at least a portion of the metal ions implanted into the
surface of the insulating layer around the contact opening, the ions being in place in
accordance with the teachings of Tsunohara. (Consistent with the examiner’s finding,
appellants admit at page 3 of the Reply Brief that ions would become embedded in an
insulating layer, when following the teachings of Tsunohara.)
Since we consider the scope of claims 15 through 18 to be indefinite, we reach no
conclusion as to whether or not the examiner has met his initial burden in establishing a
prima facie case of obviousness with respect to those claims. However, we agree with the
general proposition that the prior art need not explicitly teach removal of implanted metal
ions to show obviousness. If the prior art taught methods which resulted in the implantation
of metal ions in an insulating layer, and elsewhere the prior art taught removal of a portion
of the insulating layer, subsequent to placement of a tungsten plug in the contact opening,
for the purpose of improving properties of the device, then we agree that the combined
teachings would result in suggesting the action of removing implanted metal ions in the
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