Last Wednesday, the Federal Circuit issued its holding in Samsung Electronics Co., LTD. v. ELM 3DS Innovations, LLC, upholding the Board’s finding that a person of ordinary skill in the art would not have reasonably expected success in combining the prior art — i.e., the prior art does not invalidate the Challenged Patents.

Eleven patents were at issue on appeal. Claim 129 of U.S. Patent No. 8,653,672 (“the ‘672 Patent”) and Claim 30 of the 8,796,862 (“the ‘862 Patent”) are considered representative.

129. An integrated circuit structure comprising:

a first substrate comprising a first surface supporting interconnect contacts;

a substantially flexible semiconductor second substrate comprising a [i] first surface and [ii] a second surface at least one of which supports interconnect contacts, wherein the second surface is opposite the first surface and wherein the second surface of the second substrate is formed by removal of semiconductor material from the second substrate and is smoothed or polished after removal of the semiconductor material;

conductive paths between the interconnect contacts supported by the first surface of the first substrate and of the interconnect contacts supported by the second substrate;

wherein the first substrate and the second substrate overlap fully or partially in a stacked relationship; and

wherein the integrated circuit structure further comprises a low-stress silicon-based dielectric material having a stress of 5×108 dynes/cm2 tensile or less.

30. A stacked circuit structure comprising:

a plurality of stacked, thin, substantially flexible circuit layers at least one of which comprises a thinned, substantially flexible monocrystalline semiconductor substrate of one piece;

wherein at least one of the substantially flexible circuit layers comprises at least one memory array comprising memory cells and a low stress silicon‑based dielectric material; and

at least one vertical interconnection that passes through at least one of the plurality of stacked, thin, substantially flexible circuit layers.

Claim Construction

The parties dispute the meaning of “substantially flexible.”

Notably, because the Challenged Patents are each derived from the same parent application and use the phrase “substantially flexible” throughout, the phrase is construed the same way for each of the Challenged Patents. See SlightSound Tech., LLC v. Apple Inc., 809 F.3d 1307, 1316 (Fed. Cir. 2015) (“Where multiple patents derive from the same parent application and share many common terms, we must interpret the claims consistently across all asserted patents.” (internal citations omitted)).

Samsung argues that the intrinsic record supports a construction of “substantially flexible” substrate as a “substrate that has been thinned to a thickness of less than 50 µm and subsequently polished or smooth.”

More particularly, Samsung directs the Board’s attention to the specification of the ‘672 Patent, which states while detailing Step 2A of the fabrication sequence of the circuit structure:

Grind the backside or exposed surface of the second circuit substrate to a thickness of less than 50 µm and then polish or smooth the surface. The thinned substrate is now a substantially flexible substrate.

Elm criticizes Samsung’s proposed construction as departing form the ordinary meaning, since the flexibility of a material depends on more than the thinness and polish surface of the substrate. In support of its argument, Elm directs the Court’s attention to the testimony of its expert’s witness, who stated that flexibility of a semiconductor substrate depends on the substrate’s elastic modulus, crystal orientation, and dimensions.

The Federal Circuit disagrees with both proposed constructions.

The Claims: The Court holds that at least in some situations, thinning and polishing a substrate is one way of forming a substantially flexible substrate. For example, Claim 147 of the ‘862 Patent recites “the polished or smooth backside [of a thinned, monocrystalline semiconductor substrate] enables the . . . substrate to be substantially flexible, and the polished or smoothed backside reduces the vulnerability of the . . . substrate to fracture as a result of flexing.” However, the Court is careful to note that under at least the doctrine of claim differentiation such a process of polishing and thinning cannot be the only way to achieved substantially flexibility.

Prosecution History: The Court therefore turns its attention to the collective prosecution history. For example, during prosecution of the application leading to U.S. Patent No. 8,907,449 (“the ‘449 Patent”), the Examiner objected to the used of the term “substantially flexible” as rendering the claim’s scope unclear. In response, Elm directs the Examiner’s attention to the portion of the specification detailing Step 2A, as set-forth above. In doing such, the Court holds Elm “clearly and unambiguously disclaimed claim scope.” As such, the Court holds that “[f]or a semiconductor substrate to be ‘substantially flexible’ according to the claims, it must be thinned to 50 microns or less and polished or smoothed.”

Further, in a response involving another related application, Elm stated that “Two features [we]re required to achieve substantial flexibility. One is that the semiconductor material must be sufficiently thin, e.g., 50 microns or less . . . . The other is that the dielectric material used in processing the semiconductor material must be sufficiently low stress. Otherwise, substantial flexibility is defeated.” As such, the Court further held that “the prosecution history clearly and unambiguously demonstrates that a substantially flexible circuit layer, and similar terms, must contain a substantially flexible semiconductor substrate and a sufficiently low tensile stress dielectric material.”

Further still, the prosecution history makes clear that “substantially flexible” cannot be read to cover rigid substrates and circuit layers.

As such the Federal Circuit “interpret[ed] a substantially flexible semiconductor substrate as a semiconductor substrate that is thinned to 50 µm and subsequently polished or smoothed such that it is largely able to bend without breaking.” Likewise, the Court “interpret[ed] a substantially flexible circuit layer as a circuit layer that is largely able to bend without breaking and contains a substantially flexible semiconductor substrate and a sufficiently low tensile stress dielectric material.”

Takeaway

Always consider the subsequent effects of statements made during prosecution and, in instances of patent families, always makes sure language and/or disclaimers are consistent throughout the patent family.