by Dennis Crouch
The Federal Circuit’s new claim construction decision in Monterey Research, v. STMicroelectronics highlights the ongoing difficulty of patentees to obtain narrow claim construction at the PTAB during IPR. Typically, patentees are seeking narrow claim construction in order to better differentiate the patent claims from the asserted prior art. And, although a patentee could expressly amend the claims, such an action could create problems in litigation such as eliminating back damages and potentially creating an estoppel problem. Broad claim interpretation at the PTAB was rampant in the early days as the administrative court applied the PTO standard “broadest reasonable interpretation.” More recently, the PTAB has moved to the narrower ordinary meaning standard, but the change has not been enough for many patentees to survive the IPR process.
Monterey’s U.S. Patent No. 6,534,805 covers an improved SRAM cell design for computer memory. The claim requires “a single local interconnect layer comprising local interconnects corresponding to bitlines and a global wordline.” Although not expressly included in the claim, the patentee argued that the interconnect layer should be construed to require lateral routing of signals along the interconnect layer. Monterey pointed to several elements from the prosecution history that support its contention.
- Figure 3 of the patent (above) shows the type of lateral routing of signals being discussed. During prosecution, Monterey distinguished its claim from the prior art by referencing Figure 3 and stting that “all the runs [i.e. interconnects] for the bitlines, Vcc, Vss and the wordline are provided in the single layer of Fig. 3” in contrast to Osada’s multi-layer arrangement.
- In fact, the “single local interconnect layer” limitation was specifically added to the claims in order to distinguish the invention from Osada.
The majority opinion authored by Judge Chen and joined by Judge Taranto rejected the patentee’s arguments — providing two key conclusions:
- The prosecution history statements did not clearly limit the claim scope but rather were too ambiguous and vague to constitute a disavowal of claim scope.
- Figure 3 does not clearly require lateral routing. Rather, Figure 3 only showed a single contact point on each relevant interconnect, rather than contacts on both ends that would necessitate lateral routing along the length.
Judge Dyk’s dissent, on the other hand, pointed to the prosecution history statements referencing Figure 3 as limiting the claim scope to lateral routing to overcome the prior art. Unlike the majority, Judge Dyk looked more to the purpose and context of the prosecution history rather than just the plain language.
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The standard conventional wisdom for patent prosecution is that a more limited record is better than one full of prosecution history statements and declarations. That approach has the benefit and tendency to lead to broader claim construction. But, this case represents another example of how that broad approach can come back to bite the patentee — especially in today’s world of AIA trials.
The conventional patent prosecution wisdom has long been that fewer prosecution history statements are generally better — because they allow for broader claim construction down the road. This approach stems from the desire to avoid unintentional disavowals or limitations on claim scope. However, as this case illustrates, that strategy can come back to haunt patentees in AIA trials.
In the current post-AIA environment, patent claims are frequently challenged in inter partes reviews (IPRs) before PTAB judges who are ready and willing to delve into the prior art to in a detailed obviousness analysis. Thus, patentees today find themselves arguing for narrower interpretations to avoid prior art — but are lacking clear prosecution history support. Vague or ambiguous statements meant to preserve claim scope have been be inadequate for this task as are intentionally broad and ambiguous claim limitations. This approach left Monterey’s claims vulnerable to invalidity in light of the broader interpretation.