Key Points

  • The Federal Circuit affirmed two Patent Trial and Appeal Board decisions holding that Micron and Intel failed to show claims 1 and 13-17 of BeSang's U.S. Patent 7,378,702 unpatentable.
  • The court upheld the board's finding that the Watanabe reference was not enabled because its 900-1000 degree Celsius bonding process would risk destroying underlying electronics, and held that this was an enablement finding rather than an implicit claim construction.
  • Because Micron relied solely on Watanabe for one ground and offered no other enabling evidence, that obviousness ground failed; substantial evidence also supported the board's finding of no motivation to combine Watanabe with the Lee patent.
  • Intel waived any challenge to the board's finding that the Lee application did not teach limitation 13[b], and the board did not abuse its discretion in reading Intel's petition.
  • The court held the board did not implicitly construe claim 1's dielectric-separation limitation, noting Intel's own arguments about electrical separation; the decision is nonprecedential.

A federal appeals court on Oct. 30 left intact six claims of a BeSang Inc. patent on stacked memory chips, rejecting appeals by Micron Technology Inc. and Intel Corp., which had sought to cancel the claims as obvious in light of earlier inventions.

A three-judge panel of the U.S. Court of Appeals for the Federal Circuit affirmed two decisions of the Patent Trial and Appeal Board. Together, the decisions found that the chipmakers had not shown claims 1 and 13-17 of BeSang's U.S. Patent 7,378,702 unpatentable. Circuit Judge Lourie wrote for the panel, which also included Circuit Judges Reyna and Hughes, in a decision designated nonprecedential.

Micron's appeal turned on enablement. The panel upheld the board's finding that an earlier patent calling for bonding chip layers at 900 to 1,000 degrees Celsius was not enabled, because the heat would risk destroying the electronics underneath. Intel's appeal failed largely because it did not challenge the board's finding that its main reference lacked a required element of claim 13.

The '702 patent covers "a plurality of vertically oriented semiconductor memory devices, or cells," that "may be added to a separately fabricated substrate that includes electrical devices and/or interconnect lines," according to the board's description quoted in the opinion. The invention's goal is to reduce the lateral area that transistors occupy on a chip. Claim 1 covers a structure using DRAM memory cells, and claim 13 covers one using nonvolatile memory cells, each built in a "stackable add-on layer" bonded onto the substrate.

Micron and Intel each filed petitions for inter partes review. Both attacked claims 13-17, and Intel also challenged claim 1. The board instituted both reviews and ruled for BeSang in decisions issued Nov. 13 and Dec. 11, 2024.

Micron's lead argument rested on a single earlier patent, which the opinion calls Watanabe. Judge Lourie quoted the court's 2021 decision in Raytheon Technologies Corp. v. General Electric Co., which held that "a standalone ยง 103 reference must enable the portions of its disclosure being relied upon" absent other supporting evidence.

The board concluded that Watanabe was not enabled because the temperature of its bonding process "would severely impact its structure and risk destroying the underlying electronic components in its substrate," Judge Lourie wrote. He said the finding rested on testimony from Micron's own expert and a declaration from BeSang's expert, both placing the danger point above 650 degrees.

Micron argued that the board had quietly read a 650-degree temperature cap from the patent's specification into claim 13, an implicit claim construction. "The Board made no such construction," Judge Lourie wrote. "That is a conclusion on enablement, not claim construction, and the factual findings underlying that conclusion were supported by substantial evidence," he wrote.

The panel also rejected Micron's reliance on a "thermal budget," a concept that weighs both time and temperature, under which Micron said engineers would understand that high-temperature bonding could occur briefly. The board considered and rejected that evidence in light of the expert testimony, Judge Lourie wrote. Because Micron relied solely on Watanabe for that ground, "Micron points us to no other evidence that would enable a skilled artisan to make the claimed invention, so that ground must fail."

Micron's second ground paired Watanabe with an earlier patent the opinion calls the Lee Patent. The board found no motivation to combine them, reasoning that any benefit would be outweighed by the damage Watanabe's bonding heat would cause to the Lee device. The panel held that the same expert testimony supported that conclusion. It also rejected Micron's contention that the board had demanded proof of a specific improvement, pointing to the board's own statement that "[i]n general, a petitioner need not demonstrate that a particular alternate method would improve a prior art device in order to show a motivation to combine."

Intel's challenge to claim 13 relied on a published patent application the opinion calls the Lee Application, alone and combined with two other references. The board found that Intel had not shown the Lee application taught limitation 13[b], the claim's requirement of "a stackable add-on layer having a plurality of vertically oriented semiconductor memory cells." Intel did not appeal that finding, "so any argument with respect to that factual finding is thus waived," Judge Lourie wrote.

Intel instead argued that it had addressed the same "stackable add-on layer" term in its arguments on a neighboring limitation, 13[c], and that the board abused its discretion by ignoring them. The panel disagreed, noting that Intel's petition cross-referenced only the Lee application for limitation 13[b] and set the two limitations under separate subheadings. Quoting its 2023 decision in Netflix, Inc. v. DivX, LLC, the court wrote: "The Board is entitled to discretion in how it interprets petitions."

On claim 1, the dispute centered on the requirement that memory cells be "separated from each other by dielectric material." Intel relied on a combination of two earlier references, Park and Kim. The board found that Park's adjoining cells shared electrodes, and it concluded that "the presence of some dielectric material between the memory cells, but not enough to electrically separate the cells from each other, [did] not meet the claim."

Intel argued that the board had implicitly construed claim 1 to require electrical separation. The panel called that argument unpersuasive, noting that Intel itself had told the board that a skilled artisan would recognize "the need to separate the memory cells with dielectric material for proper operation (e.g., avoiding shorts)." The board, Judge Lourie wrote, "disposed of Intel's argument by comparing Park's memory cells to the text of the claim."

Xin-Yi Zhou of O'Melveny & Myers LLP argued for Micron. Michelle Armond of Armond Wilson LLP argued for BeSang.

The panel said it had considered the companies' remaining arguments and found them unpersuasive. It affirmed both board decisions without a remand, leaving claims 1 and 13-17 standing against these two challenges. It did not reach Micron's argument on nonvolatile memory or the merits of Intel's claim 13 combinations.