Pursuant to 35 U.S.C. § 141 (1994), S. Sheffield Eaton, Jr. (“Eaton”) appeals from a decision of the United States Patent and Trademark Office Board of Patent Appeals and Interferences (the “PTO Board”) awarding priority of invention to Joseph T. Evans, Jr. (“Evans”) for a nonvolatile, ferroelectric memory cell. See Evans v. Eaton, Patent Interference No. 102,727 (Bd. Pat.App. & Int. Mar. 1, 1996) (Final Decision); Evans v. Eaton, Patent Interference No. 102,727 (Bd. Pat.App. & Int. Nov. 19, 1998) (Reconsideration Decision). Because we hold that the PTO Board erred as a matter of law in finding that Evans reduced the count to practice by December 1986, we vacate the PTO Board’s priority determination and remand for further findings regarding Evans’s date of reduction to practice and Eaton’s dates of conception and reduction to practice.
*1096 BACKGROUND
On November 15, 1991, the PTO declared an interferenсe between Eaton’s United States Patent No. 4,873,664 (“the ’664 patent”), which was filed on February 12, 1987, and Evans, William D. Miller, and Richard H. Womack’s patent application Serial No. 07/057,100. The technology involves a memory cell that can store data аfter its power is removed without requiring the data to be periodically refreshed. The single count at issue, as established by the PTO, describes the memory cell as follows:
A nonvolatile ferroelectric memory cell having a word line and first' and second complimentary bit lines coupled to a sense amplifier,
the memory cell comprising first and second ferroelectric capacitors, each said capacitors having first and second plate electrodes, the first plate electrode of said first capacitor coupled selectively to said first bit line and the first plate electrode of said second capacitor coupled selectively to said seсond bit line;
said memory cell including first and second access transistors each having a control electrode coupled to said word line, said first and second transistors being coupled respectively to first plate electrоdes of said first and second fer-roelectric capacitors, each said transistor being located within said memory cell, said transistor being selectively actuable to couple said first plate electrodes of said сapacitors to said first and second bit lines associated with said memory cell in response to a voltage on said word line;
said sense amplifier being responsive to a difference in voltage between said first and second bit linеs; and
said memory cell further including a plate line distinct from said bit line, said plate line coupled to said second plate electrode of both said capacitors.
In 1985, Evans co-founded Krysalis Corporation .(“Krysalis”) with the goal оf developing nonvolatile memory circuits using ferroelectric materials. By April 1986, Evans began designing single-cell memory circuits consisting of two transistors and two ferroelectric capacitors. Sometime between July and August of that year, Richard Womack, a Krysalis employee, developed a prototype of the single-cell memory circuit that could be fabricated by semiconductor foundries; Krysalis identified the prototype as the TD01. At the same time, Waynе Kinney (“Kinney”), also a Krysalis employee, generated characterization studies and began testing the TD01. Throughout the testing period, a sense amplifier was never part of, or used with, the TD01.
In determining priority, the PTO Board first found that Evans concеived the subject matter of the count in interference no later than October 3, 1986. That conclusion rested on Kinney’s deposition testimony and a schematic sketch of the TD01 in his laboratory notebook dated October 3, 1986. Although the sketch did not illustrate a sense amplifier, the PTO Board was persuaded by Kinney’s testimony that he and others at Krysalis intended to use a sense amplifier with each memory circuit.
Next, the PTO Board found that Evans reduced the count to practice by no later than December 1986. In reaching that conclusion, the PTO Board once again relied on Kinney’s testimony and laboratory notebook, which illustrated that the TD01 successfully stored data following a read-write-read operation. Cognizant that the TD01 was tested with an oscilloscope rather than a sense amplifier, the PTO Board, relying on
Scott v. Finney,
Finally, the PTO Board addressed Eaton’s case for priority by assuming that he was entitled to February 12, 1987 — the date he filed his application — as his date of constructive reduction tо practice. The *1097 PTO Board then reasoned that even if Eaton conceived the invention prior to Evans, Eaton could not prevail because his activities were directed to commercial improvements and therefore did not constitute reasonable diligence. The PTO Board also found that Eaton did not establish attorney diligence before Evans’s date of conception. Accordingly, the PTO Board awarded priority to Evans without determining Eaton’s date of conception or addressing Evans’s argument that the ’664 patent is invalid for lack of enablement, failure to disclose the best mode, and unenforceable due to inequitable conduct. This appeal followed.
DISCUSSION
Pursuant to Seсtion 135(a), when a party files a patent application with a claimed invention that would interfere with the claim of another pending application or with a claim of an unexpired patent, the PTO Commissioner has authority to dеclare an interference to determine which party.was the first to invent the claimed subject matter.
See
35 U.S.C. § 135(a) (1994). To determine priority, the PTO Board may evaluate “not only the respective dates of conception and reduction to practice of the invention, but also the reasonable diligence of one who was first to conceive and last to reduce to practice, from a time prior to conception by the other.” 35 U.S.C. § 102(g) (1994). Priority of invention, thеrefore, belongs to the first party to reduce the invention to practice unless the other party can establish that it was the first to conceive the invention and that it exercised reasonable diligence in later reducing the invention to practice.
See Price v. Symsek,
In an interference proceeding, a party seeking to establish an actual reduction to practice must satisfy a two-prong test: (1) the party constructеd an embodiment or performed a process that met every element of the interference count, and (2) the embodiment or process operated for its intended purpose.
See Cooper,
In the present case, the count, at issue explicitly calls for a “nonvolatile fer- *1098 roelectric memory cell having ... complimentary bit lines coupled to a sense amplifier” and the “sense amplifier being responsive to a difference in voltage between ... bit lines.” (emphasis added). The PTO Board found that in December 1986 a “sense amplifier was not utilized ,in the testing of the [TDOl] .wafer cells.” Nonetheless, relying оn Scott v. Finney, the PTO Board concluded that Evans reduced the count to practice because the TDOl test results established a reasonable expectation that the invention would work for its intended purpose. On appeal, Evans readily concedes that the TDOl did not use a sense amplifier. Notwithstanding that absence, Evans contends that he reduced the count to practice because the TDOl reliably stored nonvolatile data.
We hold that the PTO Board erred as a matter of law in awarding Evans an actual reduction to practice date of December 1986. As discussed above, an actual reduction to practice requires that a constructed embodiment include every elemеnt of the interference count.
See, e.g., Correge,
Moreover, by relying on
Scott v. Finney
to support its finding that Evans reduced the count to practice, the PTO Board in effect reasoned that satisfying the requirement that a constructed embodiment work for its intended purpose eliminates, or acts as a surrogate- for, the requirement that the embodiment contain every element of the count. That analysis, however, misapprehends this Court’s precedent and conflates the two requirements. In
Scott,
which was an appeal from an interference decision, the issue of whether the constructed embodiment contained every element of the count was not disputed.
CONCLUSION
We hold that the PTO Board erred as a matter of lаw in finding that Evans reduced the count to practice by December 1986. Accordingly, we vacate the PTO Board’s decision awarding priority of invention to Evans, and we remand for further findings as to Evans’s date of actual reduction to practice and Eaton’s dates of conception and reduction to practice, be it actual or constructive.
VACATED and REMANDED.
COSTS
Each party shall bear its own costs.