Every Word Counts: Specification Naming Conventions Can Limit Claim Scope

Written by: Douglas B. Wentzel

HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC.

Before: Lourie, Stoll, and Cunningham. Appeal from the Patent Trial and Appeal Board.

Summary: A patent’s specification established a naming convention that applied to terms in the patent’s claims.

Microchip Technology filed an IPR, arguing all claims of HD Silicon Solutions’ patent were invalid.  The challenged patent was directed to a method of forming local-circuit interconnects by “depositing a second film … comprising tungsten.”  The Board construed “comprising tungsten” to mean any form of tungsten, including elemental tungsten and tungsten compounds.  Based on that construction, the Board held all but one claim invalid as obvious.

The Federal Circuit disagreed with the Board’s construction of “comprising tungsten” but affirmed the Board’s holding under the proper construction of that term.  The court emphasized that the patent’s claims and specification consistently used the term “tungsten” alone, and the specification described the material properties of elemental tungsten.  The court contrasted this with the specification’s convention of using open-ended modifiers (e.g., “chlorine-based etchants”) when referencing materials that include compounds of an element in addition to the element itself.  Based on this naming convention, the court concluded the claimed “tungsten,” without any modifier, referred to elemental tungsten only.  Despite adopting a narrower construction than the Board’s, the Federal Circuit affirmed the Board’s finding of obviousness because Microchip’s asserted prior art reference disclosed elemental tungsten.

Editor: Sean Murray