Claim differentiation presumptively bars a narrowing claim interpretation when its defining characteristics are recited in the dependent claims, even when the interpretation itself may not be literally recited there. Here, for example, the claimed “etching” step was found to be broader than the “net etching” operation described in the specification because the defining characteristics of “net etching” were recited elsewhere in the dependent claims, even though the term “net etching” itself was not.
Background / Facts: The application on appeal here from the PTO as part of an interference proceeding relates to depositing and etching barrier materials on wafer substrates. The specification of the junior application prompting the interference describes a metal diffusion barrier formed in part by “net etching” in the bottom of the vias and “net deposition” on the side walls, where the “net etching” has an “etch to deposition ratio” or “E/D” that is greater than 1. The copied independent claims, however, more generically recite “etching”—as opposed to “net etching”—with the deposition ratio being further recited in dependent claims.
Issue(s): Whether “etching” requires “net etching”—which occurs when there is more etching than deposition—in all the claims.
Holding(s): No. “[The junior applicant] improperly attempts to read limitations into the claims based on the embodiments described in his written description, limitations which are absent from the claim language.” Notably, the court pointed to one of the dependent claims, which further specifies “that the etch to deposition ratio is greater than 1 in the bottom of the plurality of vias.” “First, this claim language uses the term ‘etch’ as part of its description of ‘net etching’ for the bottom of the plurality of vias. Second, this very same claim requires an etch to deposition ratio less than 1 on the field. If the term ‘etching’ required ‘net etching,’ then an etch to deposition ratio less than 1 would not make any sense, or at least be redundant. Accordingly, this claim language supports the PTAB’s broader construction of the term ‘etching.’”