Hd Silicon Solutions LLC v. Microchip Technology Inc.

United States Court of Appeals
for the Federal Circuit
______________________
HD SILICON SOLUTIONS LLC,
Appellant
v.
MICROCHIP TECHNOLOGY INC.,
Appellee
______________________
2023-1397
______________________
Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2021-
00752.
______________________
Decided: February 6, 2025
______________________
SARAH S. BROOKS , Venable LLP, Los Angeles, CA, ar-
gued for appellant. Also represented by J USTIN J. O LIVER ,
Washington, DC.
BRETT M. SCHUMAN, Goodwin Procter LLP, San Fran-
cisco, CA, argued for appellee. Also represented by RACHEL
M. WALSH ; SANJEET D UTTA, Redwood City, CA;
ROHINIYURIE T ASHIMA, Washington, DC.
______________________
Before L OURIE, STOLL , and CUNNINGHAM , Circuit Judges.
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 2
L OURIE, Circuit Judge.
HD Silicon Solutions LLC (“HDSS”) appeals from a fi-
nal written decision of the United States Patent and Trade-
mark Office Patent Trial and Appeal Board (“the Board”)
holding claims 1–7 and 9–17 of U.S. Patent 6,774,033 (“the
’033 patent”) unpatentable as obvious. Microchip Tech.
Inc. v. HD Silicon Sols. LLC, No. IPR2021-00752, 2022 WL
16748547 (P.T.A.B. Nov. 7, 2022) (“Decision”). For the fol-
lowing reasons, we affirm.
BACKGROUND
The ’033 patent is directed to a local interconnect layer
in an integrated circuit. ’033 patent, col. 1 ll. 49–50. To
connect transistors within an integrated circuit, a local in-
terconnect layer “provide[s] relatively short electrical
paths between” the transistors. Id. col. 1 ll. 31–32. The
challenged claims include independent claims 1 and 15.
Claim 1 recites:
1. A method of forming a local interconnect layer
in an integrated circuit, the method comprising:
depositing a first film over an oxide layer,
the first film comprising titanium nitride;
and
depositing a second film over the first film,
the second film comprising tungsten, the
first film and the second film forming a
metal stack of the local interconnect layer.
Id. col. 5 l. 55–col. 6 l. 4 (emphasis added). The dependent
claims add limitations specifying the technique used to de-
posit the films, the thickness of one or both of the films, and
the type of etchant used to etch the films. See generally id.
col. 6 ll. 5–56.
Microchip Technology Inc. (“Microchip”) petitioned for
inter partes review (“IPR”), arguing that all claims of the
’033 patent would have been obvious over U.S. Patent
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 3
5,847,463 (“Trivedi”). Trivedi is directed to a method of
forming a local interconnect structure that has “tungsten
silicide and titanium nitride layers, or has a tungsten layer
covered on opposite sides thereof with titanium nitride.”
Trivedi, col. 1 ll. 10–12.
At the Board, the parties disputed the construction of
the term “comprising tungsten,” found in all challenged
claims. Based on the text of the claims, the specification,
and extrinsic evidence, the Board construed “comprising
tungsten” to mean any form of tungsten, including both el-
emental tungsten and tungsten compounds. Decision at
*3–6. The Board then held that Microchip had met its bur-
den to show that all claims of the ’033 patent, except claim
8, are unpatentable, based on either Trivedi alone or
Trivedi in combination with one or more secondary refer-
ences. Id. at *6–32.
HDSS timely appealed. We have jurisdiction under
28 U.S.C. § 1295(a)(4)(A).
D ISCUSSION
HDSS presents two main arguments on appeal. The
principal argument is that the Board improperly construed
the phrase “comprising tungsten.” In the alternative,
HDSS separately challenges the Board’s motivation to
combine findings as to certain dependent claims.
Although we conclude that the Board’s claim construc-
tion was erroneous, we determine that that error was
harmless. We further reject HDSS’s challenges to the
Board’s motivation to combine findings.
I
We interpret claim terms from the perspective of a per-
son of ordinary skill in the art at the time of the invention,
who is “deemed to read the claim term not only in the con-
text of the particular claim in which the disputed term ap-
pears, but in the context of the entire patent, including the
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 4
specification.” Phillips v. AWH Corp., 415 F.3d 1303, 1313
(Fed. Cir. 2005) (en banc). Evidence extrinsic to the patent
may also be useful in construing claim terms, but is gener-
ally viewed as “less reliable than the patent” itself. Id. at
1318.
“Claim construction is ultimately a question of law, de-
cided de novo on review . . . [b]ut we review any underlying
fact findings about extrinsic evidence . . . for substantial-
evidence support when the appeal comes from the Board.”
Intel Corp. v. Qualcomm Inc., 21 F.4th 801, 808
(Fed. Cir. 2021).
The ’033 patent claims use precise language, i.e., the
recitation of another element, when referencing materials
in their compound form. Specifically, claim 1 recites that
the first film of the local interconnect “compris[es] titanium
nitride.” ’033 patent, col. 5 l. 58 (emphasis added). Com-
pare that to how claim 1 recites the composition of the sec-
ond film, that it “compris[es] tungsten,” without the
presence of another element. Id. col. 6 l. 2. This suggests
that the ’033 patent uses explicit language to refer to a com-
pound when a compound is intended, and when no such
language is included, only the elemental form is intended.
A claim to “tungsten,” on its own, therefore refers to ele-
mental tungsten.
Furthermore, the specification exclusively refers to
tungsten as a singular component, i.e., as an element. E.g.,
id. col. 3 ll. 8–10 (“Additionally, titanium nitride may serve
as a barrier and adhesion layer for a subsequently depos-
ited tungsten film.”). And when referencing the properties
of tungsten that make it a desirable material for use in a
local interconnect, the specification refers to properties
unique to tungsten itself—not compounds of tungsten—
such as low resistivity and chemical stability. Id. col. 3
ll. 41–42 (“Tungsten also has a relatively low resistivity
compared to titanium nitride.”); id. col. 3 ll. 47–48 (“Rela-
tively speaking, tungsten is also a chemically stable
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 5
material.”). Indeed, at oral argument, Microchip’s counsel
conceded that when “the specification refers to a layer of
tungsten . . . that is referencing elemental tungsten.” See
Oral Arg. at 15:50–16:03, available at https://oralargu-
ments.cafc.uscourts.gov/default.aspx?fl=23-1397_1106202
4.mp3. Not once is a tungsten compound mentioned in the
specification, let alone in the prosecution history.
Consistent with this understanding, the ’033 patent
uses an open-ended modifier when referring to materials
that include both compounds and elements. Dependent
claim 12 refers to a “chlorine-based etchant,” ’033 patent
col. 6 ll. 36 (emphasis added), which the specification de-
fines as including both chlorine compounds and elemental
chlorine, id. col. 4 ll. 13–16. (“In one embodiment, a chlo-
rine-based etchant, such as boron trichloride (BCl 3) or chlo-
rine (Cl 2), is employed to etch a film 103 of titanium nitride
stopping on oxide layer 102.”). See also id. col. 6 ll. 33 (“flu-
orine-based etchants”). That further demonstrates that
when the ’033 patent references “tungsten” on its own, it is
referring to tungsten in its elemental form.
The Board’s core reasoning in coming to its construc-
tion was based on one sentence in the ’033 patent: “The first
film may comprise titanium nitride, while the second film
may comprise tungsten, for example.” Id. col. 1 ll. 53–54;
see Decision at *5. According to the Board, the phrase, “for
example,” means that elemental tungsten is just “one ex-
emplary embodiment” of a “second film comprising tung-
sten,” and therefore the limitation cannot be so narrowed.
Decision at *5.
We agree with the Board that this sentence refers to
tungsten as an exemplary embodiment of a “second film
comprising tungsten.” Nevertheless, the Board’s reasoning
is flawed because it assumes that there are only two forms
of tungsten—purely elemental tungsten and tungsten com-
pounds. But that is not the case. As explained by HDSS’s
expert, “[b]y using the terminology of comprising tungsten,
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 6
[the claim] allows for the possibility of unintentional impu-
rities that might be incorporated during the deposition pro-
cess.” J.A. 3069 ¶ 48; see also Oral Arg. at 2:04–2:06, 4:08–
4:13 (counsel for HDSS explaining that the phrase “com-
prising tungsten” includes elemental tungsten attached to
other “minute particles” or “minute elements.”). The incor-
poration of minute materials with elemental tungsten does
not constitute a tungsten compound. Thus, when read in
accord with the understanding that elemental tungsten
may include additional minute materials, yet still not be a
compound, the description of elemental tungsten as an “ex-
ample” is not inconsistent with the ’033 patent’s disclo-
sures indicating that the patent requires elemental
tungsten.
The Board also relied on European Patent Application
Publication 0463373 (“Gunturi”) in coming to its construc-
tion. Decision at *6. Gunturi recites “forming [a] local in-
terconnect structure using a material comprising
tungsten,” Gunturi col. 4 ll. 28–29, and discloses that such
material may be “a thin layer of tungsten silicide,” a tung-
sten compound. Id. col. 3 l. 39. Accordingly, the Board rea-
soned that Gunturi “teaches that the phrase ‘comprising
tungsten’ includes” tungsten compounds. Decision at *6.
While the Board’s interpretation of Gunturi is certainly
reasonable, Gunturi is insufficient to support the Board’s
construction because it conflicts with the specification,
claims, and prosecution history of the ’033 patent, which
indicate that “comprising tungsten” requires elemental
tungsten. See Bell Atl. Network Servs., Inc. v. Covad
Commc’ns Grp., Inc., 262 F.3d 1258, 1269 (Fed. Cir. 2001)
(“[E]xtrinsic evidence may be used only to assist in the
proper understanding of the disputed limitation; it may not
be used to vary, contradict, expand, or limit the claim lan-
guage from how it is defined, even by implication, in the
specification or file history.”).
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 7
For the foregoing reasons, the Board’s claim construc-
tion was erroneous. The term “comprising tungsten,” as
recited in the challenged claims, requires elemental tung-
sten.
II
A
We next consider how the Board’s obviousness deter-
minations are impacted by our rejection of the Board’s
claim construction. Obviousness is a question of law based
on underlying findings of fact. KSR Int’l Co. v. Teleflex Inc.,
550 U.S. 398, 427 (2007). We review the Board’s legal con-
clusion on obviousness de novo and its findings of fact for
substantial evidence. HTC Corp. v. Cellular Commc’ns
Equip., LLC, 877 F.3d 1361, 1369 (Fed. Cir. 2017). What a
reference teaches and the presence or absence of a motiva-
tion to combine references are questions of fact. PAR
Pharm., Inc. v. TWI Pharms., Inc., 773 F.3d 1186, 1196–97
(Fed. Cir. 2014).
HDSS asserts that reversal or vacatur of the Board’s
obviousness findings is required because the findings were
dependent on the Board’s incorrect construction of “com-
prising tungsten,” which is recited in each of the challenged
claims. HDSS Br. 28. Microchip argues the contrary, that
even under an elemental tungsten-requiring construction,
the Board’s findings should be affirmed because the main
prior art reference, Trivedi, discloses both elemental tung-
sten and tungsten-silicide layers, and the Board found that
both layers would have rendered the “second film compris-
ing tungsten” limitation obvious. Oral Arg. at 22:10–22:52
(Microchip counsel asserting that HDSS’s claim construc-
tion argument does not “matter” because Trivedi also
“teaches [elemental] tungsten as the second film and the
[Board] relied on that” disclosure).
We agree with Microchip. The Board found that
Trivedi discloses both a tungsten-silicide and an elemental
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 8
tungsten layer, and either disclosure would render the
“second film comprising tungsten” limitation of claim 1 ob-
vious: “Trivedi itself teaches that either tungsten silicide
or elemental tungsten may be used to form the [second] lo-
cal interconnect layer” of claim 1. Decision at *9. That
finding is consistent with what Trivedi discloses and is
therefore supported by substantial evidence. Trivedi col. 1
ll. 10–12. (“[T]he local interconnect has tungsten silicide
and titanium nitride layers, or has a tungsten layer covered
on opposite sides thereof with titanium nitride.” (emphasis
added)). Further recall that the dependent claims only add
limitations with respect to the technique used to deposit
the films, the thickness of one or both of the films, and the
type of etchant used to etch the films. See generally ’033
patent, col. 6 ll. 5–56. The Board’s obviousness findings are
equally supported regardless whether Trivedi’s elemental
tungsten or tungsten-silicide layers are used to render
claim 1 obvious. HDSS presents no argument in response.
Therefore, although the Board erred in construing
“comprising tungsten,” that error was harmless.
B
Finally, we address HDSS’s arguments challenging the
Board’s findings of obviousness with respect to certain de-
pendent claims.
HDSS contends that some of the Board’s obviousness
findings were not supported by substantial evidence be-
cause the Board: (1) misinterpreted Trivedi’s disfavor of
certain deposition and etching techniques disclosed by the
other references, and (2) did not explain why a person of
ordinary skill in the art would combine Trivedi and the
other references to meet certain dependent claims’ specific
thicknesses. We disagree on both counts.
The Board thoroughly considered HDSS’s arguments
as to Trivedi’s purported disfavor of certain deposition and
etching techniques and reasonably rejected them. See, e.g.,
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HD SILICON SOLUTIONS LLC v. MICROCHIP TECHNOLOGY INC. 9
Decision at *17 (“While Trivedi may have expressed a pref-
erence for [a non-sputtering process for the tungsten layer]
. . . Trivedi also teaches [a] [sputtering] process to form lay-
ers in the local interconnect.”). Moreover, the Board pro-
vided thorough and well-reasoned explanations, relying on
the testimony of Microchip’s expert, for why a person of or-
dinary skill in the art would be motivated to combine
Trivedi with one or more of the other references to arrive
at the specific thicknesses of the challenged dependent
claims. See, e.g., Decision at *21 (a person of ordinary skill
in the art would be motivated to “apply [another refer-
ence’s] thicknesses to Trivedi’s local interconnect” because
such a combination was a “predictabl[e]” combination of
known features). At bottom, HDSS asks us to reweigh the
evidence, which we decline to do. Roku, Inc. v. Universal
Elecs., Inc., 63 F.4th 1319, 1326 (Fed. Cir. 2023) (“An ap-
pellate court does not and should not reweigh evidence or
make factual findings.” (cleaned up)).
CONCLUSION
We have considered HDSS’s remaining arguments and
find them unpersuasive. For the reasons provided, we af-
firm.
AFFIRMED
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