HD Silicon Sols. LLC v. Microchip Tech. Inc

Authored by: Jeremy J. Gustrowsky

In a recent decision, the Federal Circuit addressed a key issue in the patent dispute between HD Silicon Solutions LLC and Microchip Technology Inc. over U.S. Patent No. 6,774,033. The patent in question covers a method for forming a local interconnect layer in integrated circuits, specifically involving layers of titanium nitride and a second film “comprising tungsten.” The heart of the dispute was what exactly “comprising tungsten” means—does it include tungsten compounds, or only elemental tungsten?

The Patent Trial and Appeal Board (PTAB) had previously decided that “comprising tungsten” could mean either elemental tungsten or tungsten compounds. However, the Federal Circuit disagreed, finding that the patent’s language, specification, and prosecution history all pointed to “comprising tungsten” meaning only elemental tungsten. The court noted that when the patent meant to refer to a compound, it did so explicitly (like “titanium nitride”), and that all references to tungsten in the patent were to the elemental form.

Despite this win for HD Silicon Solutions on claim construction, it did not change the outcome. The court found that the prior art (specifically, the Trivedi patent) disclosed both elemental tungsten and tungsten compounds, and either would have made the claimed invention obvious. Therefore, the PTAB’s finding that the patent claims were unpatentable as obvious was affirmed, even under the narrower interpretation of “comprising tungsten.”

This case is a reminder that while precise claim language and proper claim construction are critical in patent law, they do not guarantee patentability if the invention is still rendered obvious by prior art. The decision also highlights the importance of how materials are described in patent claims and specifications, as these details can significantly impact the outcome of a patent dispute.