By Reza Mollaaghababa
In an inter partes review (IPR) proceeding, the meaning of terms used in challenged claims of an unexpired patent are given their broadest reasonable interpretation in light of the claim language and the specification. The Court of Appeals for the Federal Circuit (CAFC) recently reversed the Board’s interpretation of a claim term in an IPR proceeding (IPR2015-00460) in which Samsung had challenged the validity of certain claims of U.S. Patent No. 6,146,997 of Home Semiconductor Corp. (“Home”) because it found that Board had adopted a claim construction “without regard to the context” in which the term was used in the claims and the specification. In a decision written by Judge Lourie last month, the Federal Circuit panel found that the PTAB had adopted an erroneous interpretation and reversed the decision stating that the PTAB’s finding of invalidity based by anticipation of claim 2 was “not supported by substantial evidence.” (See, Home Electronics v. Samsung Electronics, CAFC Decision No. 2016-2215, July 25, 2017).
The ’997 Patent concerned “a simplified method for forming a self-aligned contact hole,” in which a conductive plug can be formed to electrically connect the semiconductor device to other circuit elements. Independent claim 1 of the ‘997 Patent recites a method of forming a self-aligned contact hole in a semiconductor substrate having a gate electrode and a diffusion region by
forming a conformal layer of etch barrier material overlying the substrate surface including the diffusion region and the upper surface and the sidewalls of the gate electrode,
forming an insulating layer overlying the barrier layer, etching an opening through the insulating layer self-aligned and borderless to the diffusion region by using the barrier layer as an etch stop, and
anisotropically etching the barrier layer underneath the opening, thereby exposing the diffusion region and simultaneously forming a spacer of the etch barrier material on the sidewall of the gate electrode.
Claim 2 of the ‘997 Patent, which depends on claim 1, further recites “forming an oxide layer over the diffusion region and on the sidewalls of the gate electrode by thermal oxidation prior to forming the barrier layer.”
The construction of the phrase “forming an oxide layer over the diffusion region” was at issue in this proceeding. The Patent Owner, Home, argued that this phrase should mean “forming an oxide layer covering the diffusion region,” while the Petitioner, Samsung, argued that the broadest reasonable construction of this phrase is “forming an oxide layer above the diffusion region.” Samsung argued that construing “over” as “covering” was too narrow a reading for a person of ordinary skill in the art. The Board adopted Samsung’s proposed construction for this term and hence held that claims 2 and 9-14 of the ‘997 Patent were anticipated by U.S. Patent No. 6,277,720 (“Doshi”).
The CAFC held that the Board’s construction of “over” as meaning “above” is unreasonable in light of the claim language and the specification. The CAFC noted that “[i]n adopting the ‘full breadth’ of the term as advocated by Samsung, the Board focused on the word ‘above,’ rather than the claim term ‘over.’ That was error.” The CAFC further emphasized that “[e]ven when giving the claim term the broadest reasonable interpretation, the Board cannot construe the claims ‘so broadly that its constructions are unreasonable under general claim construction principles.’”
The CAFC reasoned that the language at issue “is not simply ‘over,’ but is ‘forming an oxide layer over the diffusion region,” and the use of the term ‘over’ in ‘forming an oxide layer over the diffusion region’ connotes more than an insignificant or incidental vertical overlap between the oxide layer and the diffusion region. Although ‘over’ and ‘above’ can be interchangeable in certain contexts, they are not coextensive here, and the full scope of ‘above,’ which is not a claim term, cannot be adopted to give meaning to the actual claim term ‘over’ if that adoption would result in an unreasonable interpretation of the claim term in the context.”
In particular, the CAFC noted that the Board, in its claim construction, “brought into the claim the concept of the oxide layer being merely higher in position relative to the diffusion region regardless of the minor extent of the vertical overlap between the oxide layer and the diffusion region, which is contrary to the claim language itself and the specification.” The CAFC further stated that the Board’s construction of “forming an oxide layer over the diffusion region” is also inconsistent with the remaining language of claims 2 and 9. These claims indicate that the oxide is formed both ”over the diffusion region,” and “on the sidewall of the gate electrode.” The CAFC indicated that “[i]f ‘forming an oxide layer over the diffusion region’ is so broadly interpreted that forming an oxide on the side walls of the gate electrode that is merely higher than the diffusion region can correspond to ‘forming an oxide layer over the diffusion region,” then the remainder of the claim limitation, namely, ‘and on the sidewalls of the gate electrode,’ would be rendered superfluous.”
The CAFC, however, declined to adopt Home’s proposed construction of “over” as meaning an unqualified “covering.” Rather, CAFC concluded that “regardless of the arguments of the parties and the reasoning of the Board, ‘forming an oxide layer over the diffusion region’ should be understood in the context of ‘forming an oxide layer over the diffusion region and on the sidewalls of the gate electrode by thermal oxidation,’ which means forming an oxide layer over the diffusion region in addition to on the sidewalls of the gate electrode.”
Accordingly, CAFC held that Doshi did not anticipate the claims at issue.