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Prosecution History Estoppel Applied Where Amendment in Response to Section 112 Rejection Was Not Tangential

February 11, 2008

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Last Month at the Federal Circuit - March 2008

Judges: Linn (author), Dyk, Prost

[Appealed from: C.D. Cal., Judge Real]

In International Rectifier Corp. v. IXYS Corp., Nos. 07-1063, -1141, -1165 (Fed. Cir. Feb. 11, 2008), the Federal Circuit reversed a jury’s verdict of infringement under the DOE and vacated the damages award and permanent injunction. The Court found that a claim amendment made to overcome a rejection under 35 U.S.C. § 112 could not have been characterized as only tangentially related to the alleged equivalent and, therefore, prosecution history estoppel barred infringement under the DOE.

International Rectifier Corporation (“IR”) sued IXYS Corporation (“IXYS”) for infringing U.S. Patent Nos. 4,959,699 (“the ’699 patent”), 5,008,725 (“the ’725 patent”), and 5,130,767 (“the ’767 patent”). All three patents disclose metal-oxide-semiconductor field effect transistors (MOSFETs). A jury found that the accused devices infringed the ’699 patent under the DOE, but did not infringe the ’725 and ’767 patents.

On appeal, the Federal Circuit first discussed whether IXYS filed a notice of appeal on time. The Court noted that IXYS failed to timely file a document styled as a notice of appeal, but IXYS did file with the district court a motion to stay the permanent injunction pending appeal within the thirty-day time period for filing a notice of appeal. Because both IR and the district court were therefore on notice of IXYS’s intent to appeal, the Federal Circuit held that IXYS’s motion to stay qualified as a notice of appeal.

Next, the Federal Circuit addressed IXYS’s argument that prosecution history estoppel barred application of the DOE because IR added the claim term “adjoining” during prosecution of the ’699 patent to overcome rejections under 35 U.S.C. § 112, ¶¶ 1-2, and prosecution history estoppel. IR responded that prosecution history estoppel did not apply because its addition of the term “adjoining” broadened the claim language and because its amendment was only tangentially related to the asserted equivalent. The Federal Circuit agreed with IXYS that prosecution history estoppel barred application of the DOE, because IR’s claim amendment narrowed the scope of the claim, at least with respect to the addition of the term “adjoining.”

In addition, the Federal Circuit disagreed with IR that the purpose of the amendment was tangential to the asserted equivalent. The Court explained that “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.” Slip op. at 9. Accordingly, the Federal Circuit held that prosecution history estoppel barred IR from asserting infringement of the “adjoining” limitation under the DOE, and reversed the district court’s entry of judgment on the “adjoining” claims.

The Federal Circuit next turned to the district court’s conclusion that IXYS had admitted that its accused devices satisfied an “annular” claim limitation with respect to the ’699 patent only, because IXYS did not list the “annular” claim limitation as a disputed claim term for the ’699 patent, which constituted an admission under the Central District of California Local Rules. The jury, however, found that claims in the ’725 and ’767 patents reciting the “annular” limitation were not satisfied by the accused devices. The Federal Circuit rejected the district court’s decision, noting that it had already implicitly rejected IR’s argument on this issue in its prior appeal. The Court concluded that its mandate in the prior appeal required the district court to treat the “annular” limitation the same in all three patents, and thus the jury’s verdict of noninfringement as to the “annular” limitation in the ’725 and ’767 patents carried over to the corresponding limitation in the asserted claims of the ’699 patent.