THE IMPORTANCE OF STRATEGICALLY RECITING CHEMICAL ELEMENTS IN SEMICONDUCTOR PATENTS
February 24, 2025 — “Comprising tungsten”—the touchstone of the Federal Circuit’s opinion issued in HD Silicon Solutions LLC v. Microchip Technology Inc., No. 23-1397 (Fed. Cir. 2025). The decision emphasizes the need for patent practitioners in the semiconductor arts to strategically define and claim the chemical elements of a semiconductor device to avoid unintended claim construction and claim interpretation during enforcement and prosecution, respectively.
Summary of HD Silicon Solutions (HDSS)
The patent at dispute, U.S. Patent 6,774,033 (the ‘033 patent) assigned to HDSS, recites methods of forming a local interconnect layer of an integrated circuit. Representative Claim 1 recites:
1. A method of forming a local interconnect layer in an integrated circuit, the method comprising:
depositing a first film over an oxide layer, the first film comprising titanium nitride; and
depositing a second film over the first film, the second film comprising tungsten, the first film and the second film forming a metal stack of the local interconnect layer.
The PTAB (in the corresponding IPR) construed “comprising tungsten” to mean any form of tungsten, including both the elemental form of tungsten and tungsten compounds. Based on this construction, the PTAB found Claim 1 to be unpatentable in view of U.S. Patent 5,847,463 (“Trivedi”).
On appeal, HDSS argued that this term should be construed to mean only elemental tungsten (and not chemical compounds including tungsten). The Federal Circuit agreed with HDSS, noting that the specification and the claims explicitly delineate chemical compounds and chemical elements. For example, claim 1 explicitly and separately recites a chemical compound (the first film comprising titanium nitride), and tungsten is recited in isolation. The detailed description describes tungsten (and the benefits thereof) in isolation, and open-ended modifiers are provided to collectively refer to both compound and elemental forms of an element (e.g., chlorine-based etchant, such as boron trichloride or chlorine).
Stated differently, the Federal Circuit relied on the precise and clear intrinsic evidence of the ‘033 patent to identify the patentee’s intent to limit tungsten to its elemental form. Ultimately, the Federal Circuit found that the error was harmless, holding that because Trivedi disclosed the use of both tungsten and tungsten-silicide layers, Claim 1 was nevertheless unpatentable.
The Key Takeaways of HDSS
Practitioners should consider providing explicit statements in the detailed description that unambiguously define the desired scope of recited chemical elements (e.g., elemental forms of a given element and/or chemical compounds including the given element). Explicit statements indicating whether elemental forms include or do not include impurities that may be introduced during a deposition process should also be considered. Importantly, the claim language should explicitly delineate recitations of elemental forms, chemical compounds, or combinations thereof as needed.
If you have any questions related to patent preparation and prosecution strategies in the semiconductor arts, please contact George Patsarikas at gpatsarikas@myersbigel.com or Rohan Saba at rsaba@myersbigel.com.