“The CAFC said the patent’s consistent use of precise language to reference a compound form…plus the specification’s reference to tungsten as a singular component and the prosecution history all suggest that the claim term’s reference to ‘tungsten’ on its own indicates elemental tungsten.”
The U.S. Court of Appeals for the Federal Circuit (CAFC) today issued a decision marked precedential that found the Patent Trial and Appeal Board (PTAB) construed HD Silicon Solutions’ patent claims erroneously, but that the error was harmless, thus upholding the PTAB’s invalidation of the claims as obvious.
HD Silicon owns U.S. Patent 6,774,033, titled “Metal Stack for Local Interconnect Layer,” generally covers integrated circuit technology. Microchip Technology, Inc. filed for inter partes review (IPR) of the ‘033 patent, arguing all claims would have been obvious over U.S. Patent 5,847,463 (“Trivedi”). All of the challenged claims of the ‘033 patent included the term “comprising tungsten,” which was disputed by the parties at the Board. Ultimately, the PTAB construed the claim term to mean “any form of tungsten, including both elemental tungsten and tungsten compounds,” according to the CAFC opinion, and held all of the claims obvious.
On appeal, HD Silicon argued first that the Board construction of “comprising tungsten” was improper and, alternatively, challenged its motivation to combine findings regarding certain dependent claims. The PTAB’s reasoning for construing the “comprising tungsten” claim term to include both elemental tungsten and tungsten compounds relied on a sentence in the patent that read: “The first film may comprise titanium nitride, while the second film may comprise tungsten, for example.” But the CAFC said the patent’s consistent use of precise language to reference a compound form—i.e., “the recitation of another element”—plus the specification’s reference to tungsten as a singular component and the prosecution history all suggest that the claim term’s reference to “tungsten” on its own indicates elemental tungsten.
The court acknowledged that the sentence the Board relied upon for its construction “refers to tungsten as an exemplary embodiment of a ‘second film comprising tungsten,’” but said the Board’s conclusion that this means the claim cannot be narrowed to elemental tungsten “is flawed because it assumes that there are only two forms of tungsten—purely elemental tungsten and tungsten compounds. But that is not the case.” It’s possible that “additional minute materials” may be incorporated during the deposition process but still not be a compound, said the opinion, and this explains how “the description of elemental tungsten as an ‘example’ is not inconsistent with the ’033 patent’s disclosures indicating that the patent requires elemental tungsten.”
While HD Silicon said a finding of an erroneous claim construction required reversal of vacatur of the PTAB’s decision, the CAFC disagreed. “The Board found that Trivedi discloses both a tungsten-silicide and an elemental tungsten layer, and either disclosure would render the ‘second film comprising tungsten’ limitation of claim 1 obvious,” wrote the court. Thus the obviousness findings are “equally supported regardless whether Trivedi’s elemental tungsten or tungsten-silicide layers are used to render claim 1 obvious,” so the error was harmless.
HD Silicon also argued that some of the Board’s obviousness findings were not supported by substantial evidence with respect to certain dependent claims because the decision 1) “misinterpreted [the prior art reference] Trivedi’s disfavor of certain deposition and etching techniques disclosed by the other references, and (2) did not explain why a person of ordinary skill in the art would combine Trivedi and the other references to meet certain dependent claims’ specific thicknesses.” But the CAFC said the PTAB provided “thorough and well-reasoned explanations” for the latter and thoroughly considered all of the arguments. “At bottom, [HD Silicon] asks us to reweigh the evidence, which we decline to do,” wrote the court.
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