Once Again: Claim Amendment Sinks DOE

International Rectifier Corporation v. IXYS Corp. (2007-1063), September 11, 2007

Earlier, this case was tried before the CAFC, where the court vacated-in-part and reversed-in-part a summary judgment of direct infringement on patents relating to MOSFET technology. Subsequently at the district court, a jury found IXYS infringed patents under the doctrine of equivalents. IXYS appealed (again).

One set of claims required that the semiconductor wafer include a “lightly doped” region that is “adjoining” a “region of opposite conductivity type.” On appeal, IXYS argued that an amendment during prosecution adding the word "adjoining" should have precluded IR from claiming infringement under the doctrine of equivalents. IR responded that: (1) the amendment was broadening, not narrowing, since the claims are directed to structure rather than function, and the “adjoining” limitation simply clarified what structure was claimed; and (2) the amendment in question was "only tangentially related" to the asserted equivalent.

The CAFC did not find IR's arguments convincing:

IR is correct that the amendment broadened the claim in certain respects . . . At the same time, however, IR chose to introduce the term “adjoining.” This term excludes structures that might have been covered by the original claim language, because the “support body” of the old claim . . . was only required to “support[] said lightly doped major body portion,” not necessarily to touch it. The amendment therefore narrowed the scope of the claim, at least with respect to the addition of the term “adjoining.” Under such circumstances, IR cannot argue that the amendment was broadening merely because it eliminated some claim limitations.

As to IR’s second argument, we disagree with IR that the purpose of the amendment was tangential to the asserted equivalent . . . IR is correct that the claim is not necessarily limited to a particular mode of operation, but rather covers a particular structure that, in practice, may or may not function in unexpected ways. However, IR’s decision to claim that structure using the limiting term “adjoining,” whether or not required to overcome the rejection, cannot be described as only tangentially related to the equivalency of a structure with non-adjoining regions. With the amended language, IR recited precisely the structure it disclosed, and thereby overcame the examiner’s § 112 rejection.

[T]he damages award and permanent injunction are vacated. IXYS is entitled to entry of final judgment in its favor as to all claims. There shall be no further proceedings in this case regarding any questions of infringement, either literally or under the doctrine of equivalents.

REVERSED