Ex Parte Chua et al

Board of Patent Appeals and Interferences

Apr 23, 2008

10430499 (B.P.A.I. Apr. 23, 2008)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________________

Ex parte LAY-LAY CHUA, YANG YANG, and CHUN-TING LIU
____________________

Appeal 2007-4445
Application 10/430,499
Technology Center 2800
____________________

Decided: April 23, 2008
____________________

Before CHUNG K. PAK, ROMULO H. DELMENDO, and
LINDA M. GAUDETTE, Administrative Patent Judges.

DELMENDO, Administrative Patent Judge.

DECISION ON APPEAL

STATEMENT OF THE CASE
Appellants appeal under 35 U.S.C. § 134(a) from a final rejection of
all pending claims (claims 1-11, 21-29). (Final Office Action entered
December 8, 2005). We have jurisdiction under 35 U.S.C. § 6(b).
We AFFIRM.
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Appellants’ invention relates to a method of manufacturing bipolar
transistors having compound semiconductors. (Spec. ¶ 0001). According to
Appellants, “[t]he method includes depositing a compound semiconductor
layer over a semiconductor substrate and forming a patterned metal layer on
the compound semiconductor layer.” (Spec. ¶ 0006). Using the metal layer
as an etch mask, the compound semiconductor layer is dry etched so the
etched perimeter of the compound semiconductor layer is “substantially
coextensive” with the perimeter of the metal layer. (Spec. ¶ 0014).
Representative claims 1, 2, 6, 7, 24, and 27 read as follows:
1. A method of manufacturing a bipolar transistor, comprising:
depositing a compound semiconductor layer over a
semiconductor substrate;
forming a patterned metal layer on said compound
semiconductor; and
performing a dry etch of said compound semiconductor layer in
a manner that uses said metal layer to align said dry etch, wherein said dry
etch causes a perimeter of said compound semiconductor layer to be
substantially coextensive with a perimeter of said metal layer.

2. The method as recited in Claim 1, wherein performing said dry
etch causes an undercut of said compound semiconductor layer to vary by
less than ±20 percent on all sides of said perimeter.

6. The method as recited in Claim 1, wherein said dry etching
includes an etchant gas comprising chlorine and boron.

7. The method as recited in Claim 6, wherein said etchant gas further
includes boron trichloride gas provided at between about 0.1 sccm and about
50 sccm.

24. The method as recited in Claim 1, wherein said dry etching
includes etching said compound semiconductor along a [001] lattice
direction at a first rate and etching said compound semiconductor along a
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[011] lattice directions [sic] at a second rate, a ratio of said first rate to said
second rate being in a range of about 0.8:1 to about 1.2:1.

27. The method as recited in Claim 2, wherein said undercut is
greater than about 0.01 microns and less than about 0.03 microns.

The prior art references relied upon by the Examiner to reject the
claims on appeal are:
Bayraktaroglu US 5,648,294 Jul. 15, 1997
Hamm US 6,165,859 Dec. 26, 2000
Hwang US 6,265,318 B1 Jul. 24, 2001
Pullela US 6,645,819 B2 Nov. 11, 2003
Akagi US 4,739,379 Apr. 19, 1988

The following rejections are before us for review:
Claims 1, 3, 6 and 8-11 are rejected under 35 U.S.C. § 102(b) as
anticipated by Bayraktaroglu.
Claims 2, 7, 24, and 27 are rejected under 35 U.S.C. § 103(a) as
unpatentable over Bayraktaroglu.
Claims 4 and 5 are rejected under 35 U.S.C. § 103(a) as unpatentable
over Bayraktaroglu in view of Hamm.
Claims 21-23 are rejected under 35 U.S.C. § 103(a) as unpatentable
over Bayraktaroglu in view of Hwang.
Claims 25 and 26 are rejected under 35 U.S.C. § 103(a) as
unpatentable over Bayraktaroglu in view of Pullela.
Claims 28 and 29 are rejected under 35 U.S.C. § 103(a) as
unpatentable over Bayraktaroglu in view of Akagi.

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ISSUES
Have Appellants shown error in the Examiner’s determination that
Bayraktaroglu anticipates the subject matter of claims 1, 3, 6, and 8-11?
Have Appellants shown the Examiner erred in determining claims 2,
4, 5, 7, and 21-29 would have been obvious to one of ordinary skill in the art
over the applied prior art?

FINDINGS OF FACT
1. Appellants’ Specification establishes that “substantially coextensive”
means “a maximum uniform undercut on all sides of the compound
semiconductor 105, and the respective sides of the patterned metal layer 115,
following dry etching.” (Spec. ¶ 0015; Figures 1A-1E).
2. The Specification explains that the term “uniform,” with respect to an
undercut, means “varying by less than ±20 percent on all sides of the
perimeter” of the compound semiconductor. (Id. ¶ 0019).
3. The “substantially coextensive” limitation of the claims therefore
requires an undercut on all sides of the perimeter of the compound
semiconductor that varies by less than ±20 percent. (Id. ¶ 0015, 0019).
4. The Specification explains that “dry etching comprises exposing the
compound semiconductor 105 and the patterned metal layer 115 to an
etching plasma.” (Id. ¶ 0016; Figures 1A-1E).
5. The Specification states that “[t]he compound semiconductor 105
comprises Group IIA and IVA or Group IIIA and VA elements from the
Periodic Table of the Elements (Groups 2 and 4 or Groups 3 and 5 of the
IUPAC convention).” (Id. ¶ 0014).
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6. The Specification states “the compound semiconductor 105 is dry
etched in a manner in which the metal layer 115 functions as an etch mask.”
(Id. ¶ 0014; Figures 1A-1E).
7. The Specification discloses “[t]he metal layers 115, 135 can comprise
any metal commonly used in the semiconductor industry, such as gold,
titanium, platinum, palladium or composite layers thereof.” (Id. ¶ 0021;
Figures 1A-1E).
8. The Specification states that the etching is performed with an etchant
gas and that the etchant gas desirably includes “chemical components [that]
are dissociated into free radicals that interact with and etch the compound
semiconductor,” with boron trichloride being the more preferred chemical
component of the etchant gas. (Id. ¶ 0018).
9. While the Specification describes use of inert gases to provide a
physical component of etchant gases that have a “desirable feature” of
giving an etch rate “substantially independent of the orientation of the
crystal comprising the compound semiconductor,” Appellants do not
identify any portion of the Specification stating that this “desirable feature”
is an absolute requirement for achieving the substantially coextensive
characteristic of the final product; furthermore, Appellants do not identify
any portion of the Specification stating that the chemical component of the
etchant gases alone does not provide a physical component as well. (Id. ¶
0017-0018).
10. The Specification indicates to one skilled in the relevant art that
suitable etching conditions within the scope of the invention, with respect to
pressure, temperature, and power, are not particularly limited:
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In preferred embodiments, dry etching comprises exposing the
compound semiconductor 105 and the patterned metal layer
115 to an etching plasma. In one embodiment, the conditions
for dry etching via inductively coupled plasma reactive ion etch
(ICP RIE) includes a bias power of between about 1 Watt and
about 100 Watts and a source power of between about 20 Watts
and about 2000 Watts and pressure of about 0.1 to about 20
mTorr. More preferably, the ICP RIE conditions include a
power of between about 5 Watts and about 100 Watts and a
source power of between about 100 Watts and about 1000
Watts. Preferably, dry etching is performed in a temperature
range of between about 25°C and about 300°C, and more
preferably between about 150°C and about 300°C. One skilled
in the art would understand that the above-described conditions
for dry etching are machine-dependent, and therefore vary such
conditions according to the particular characteristics of the
instrument used for dry etching.

(Id. ¶ 0016).

11. Bayraktaroglu describes a preferred embodiment using a compound
semiconductor made of Al0.3Ga0.7As and GaAs, (col. 4, ll. 3-4); where Al
(Aluminum), Ga (Gallium), and As (Arsenide) are elements from Groups
IIIA and VA of the Periodic Table of Elements.
12. Appellants’ disclosed materials used for the compound semiconductor
in the inventive method encompass the compound semiconductor materials
used in the prior art. (Spec. ¶ 0014; Bayraktaroglu, col. 4, ll. 3-4).
13. Bayraktaroglu discloses plasma etching with BCl3 (boron trichloride),
where the etching conditions are such that the etching is conducted
“generally anisotropically.” (Col. 4, ll. 56-61).
14. Bayraktaroglu teaches “the BCl3 etch could include diluents” (i.e.,
inert etching components). (Col. 8, l. 1).
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15. Bayraktaroglu teaches the metal emitter contact 142 masks portions of
the compound semiconductor when etching with BCl3 to form emitter 140
and emitter cap 141. (Col. 4, ll. 53-57; Figures 2a, 3a-3c).
16. Bayraktaroglu teaches “an overetch allows a controlled undercut of
emitter contact 142 so that emitter contact 142 has an overhang of about
0.05 to 0.1 µm.” (Col. 4, ll. 64-67; Figures 2a, 3a-3c).

PRINCIPLES OF LAW
“To anticipate a claim, a prior art reference must disclose every
limitation of the claimed invention, either explicitly or inherently.” In re
Schreiber, 128 F.3d 1473, 1477 (Fed. Cir. 1997).
“A reference includes an inherent characteristic if that characteristic is
the ‘natural result’ flowing from the reference's explicitly explicated
limitations.” Eli Lilly and Co. v. Barr Laboratories, Inc., 251 F.3d 955, 970
(Fed. Cir. 2001) (citing Continental Can Co. USA, Inc. v. Monsanto Co., 948
F.2d 1264, 1269 (Fed. Cir. 1991)).

ANALYSIS
Appellants have defined “substantially coextensive” in their
Specification as “a maximum uniform undercut on all sides of the compound
semiconductor 105, and the respective sides of the patterned metal layer 115,
following dry etching.” (FF 1). Furthermore, the Specification explains that
an undercut is “uniform” when the compound semiconductor has a perimeter
varying by less than ±20 percent on all sides. (FF 2). From these
definitions, it is clear that the “substantially coextensive” limitation of the
claims requires an undercut on all sides of the compound semiconductor that
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varies by less than ±20 percent. (FF 3). In re Morris, 127 F.3d 1048, 1054
(Fed. Cir. 1997) (“[I]t would be unreasonable for the PTO to ignore any
interpretive guidance afforded by the applicant’s written description . . . .”);
In re Zletz, 893 F.2d 319, 321 (Fed. Cir. 1989) (“When the applicant states
the meaning that the claim terms are intended to have, the claims are
examined with that meaning . . . .”).

Claims 1, 3, 6, and 8-11.
Appellants argue claims 1, 3, 6, and 8-11 together. Accordingly, we
select claim 1 as representative and confine our discussion to this claim. 37
C.F.R. § 41.37(c)(vii) (2005).
Appellants do not contest the Examiner’s finding that Bayraktaroglu
discloses the steps recited in claim 1 for manufacturing a bipolar transistor
by: 1) depositing a compound semiconductor layer over a semiconductor
substrate; 2) forming a patterned metal layer on said compound
semiconductor; and 3) performing a dry etch of said compound
semiconductor layer in a manner that uses said metal layer to align said dry
etch. (App. Br. 8-13; Reply Br. 2-4). Rather, Appellants argue that
Bayraktaroglu cannot anticipate claim 1 because the reference does not
describe “a dry etch that causes a perimeter of a compound semiconductor
layer to be substantially coextensive with a perimeter of a metal layer, as
recited in Claim 1.” (App. Br. 9). Though recognizing that Bayraktaroglu
discloses an undercut of 0.05-0.1 microns, Appellants argue that there is no
suggestion in the reference that the undercut is “uniform” because the
Examiner has not provided a basis for assuming Bayraktaroglu’s dry etch
method results in a “uniform” undercut. (App. Br. 10, ll. 11-17).
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We cannot agree with Appellants. Bayraktaroglu teaches plasma
etching a compound semiconductor made of elements from Group IIIA and
VA of the Periodic Table of the Elements, (FF 11), using BCl3 (boron
trichloride) in an etching gas, (FF 13), that may include diluents (i.e., inert
components), (FF 14), under conditions that are generally anisotropic. (FF
13). Bayraktaroglu further teaches a metal emitter contact 142 masks
portions of the compound semiconductor, (FF 15), to obtain a controlled
undercut of the metal mask, forming an overhang of 0.05 - 0.1 microns. (FF
16). In a strikingly similar fashion, Appellants’ Specification describes the
same etching method (dry etching) (FF 4), using the same boron trichloride
in an etchant gas, (FF 8), and employing a metal layer to serve as an etching
mask. (FF 6, 7).
The Specification encompasses more than just the disclosed
embodiments to achieve the claimed invention. The Specification does
describe an example to achieve uniform etching by “exposing a compound
semiconductor made of InP to BC13 and N2 gases supplied at about 5 and 15
sccm . . . [where t]he gases are supplied at a pressure of about 2 mTorr and
temperature of about 200°C, using bias and source powers of about 10 Watts
and about 500 Watts, respectively.” (Spec. ¶ 0019). However, other parts of
the disclosure indicate that a suitable range of materials include elements
selected from Groups IIIA and VA of the Periodic Table of Elements (FF 5).
These suitable materials encompass the semiconductor materials used in the
prior art. (FF 12). Also, while the Specification discloses that etchant gases
provide physical and chemical components for etching (FF 8-9), we have not
been directed to any evidence that the physical component is required to
achieve the “substantially coextensive” characteristic of the final product, or
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that the characteristic results only when inert gases are used. (FF 9). In any
event, Bayraktaroglu teaches the use of inert diluents, as in Appellants’
disclosure of the preferred embodiments. (FF 14). Furthermore, while
stating that the preferred etching conditions may vary depending on the
particular etching machine used, Appellants have not established that the
etching conditions that achieve the “substantially coextensive” characteristic
of the etched product are limited in any way. (FF 10).
To the contrary, Appellants’ Specification impresses one skilled in the
relevant art that dry etching compound semiconductor materials chosen from
Groups IIIA and VA using a preferred etchant such as boron trichloride,
under etching conditions similar to Appellants’ preferred disclosed
conditions, would inherently or necessarily provide etching that is
“substantially coextensive” as recited in appealed claim 1. Under these
circumstances, the burden was properly shifted to Appellants to prove that
the prior art method would not result in a “substantially coextensive”
structure. In re Best, 562 F.2d 1252, 1255 (CCPA 1977) (“Where, as here,
the claimed and prior art products are identical or substantially identical, or
are produced by identical or substantially identical processes, the PTO can
require an applicant to prove that the prior art products do not necessarily or
inherently possess the characteristics of his claimed product.”). In re Preda,
401 F.2d 825, 826 (CCPA 1968) (“[I]n considering the disclosure of a
reference, it is proper to take into account not only specific teachings of the
reference but also the inferences which one skilled in the art would
reasonably be expected to draw therefrom.”). Appellants failed to meet their
burden.
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Moreover, Appellants broadly define “substantially coextensive” to
include up to ±20 percent perimeter variations on all sides of the
semiconductor, (FF 3), and have not relied on any evidence that the prior
art’s similar dry etching method would result in a perimeter with over 20
percent variation. Instead, Appellants have relied on arguments that the
prior art does not disclose the “substantially coextensive” characteristic.
(App. Br. 9 - 10). These arguments do not satisfy Appellants’ burden to
show the Examiner erred in finding a prima facie case of anticipation. In re
Pearson, 494 F.2d 1399, 1405 (CCPA 1974) (“Attorney’s argument in a
brief cannot take the place of evidence.”).
For these reasons, we uphold the Examiner’s rejection on this ground.

Claims 2, 4, 5, 7, and 21-29.
In discussing the Examiner’s rejections of claims 2, 4, 5, 7, and 21-29,
Appellants rely on similar arguments presented with respect to claim 1,
above, and submit separate arguments for claims 2 and 24. We address
these arguments accordingly.
Appellants do not argue the Examiner’s combination of Bayraktaroglu
with the other references, but rather they contend that Bayraktaroglu does
not establish a prima facie case of obviousness of dependent claims 2, 7, 24,
and 27 because these claims, like claim 1, require “a dry etch that causes a
perimeter of a compound semiconductor layer to be substantially
coextensive with a perimeter of a metal layer.” (App. Br. 11, ll. 8-13). With
this argument, Appellants rely on the same reasoning as set forth above
regarding claim 1.
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As discussed above, we find Appellants’ argument with respect to the
“substantially coextensive” limitation unpersuasive. Appellants failed to
direct us to sufficient evidence showing “substantially coextensive”
perimeters do not necessarily result when following the method taught by
Bayraktaroglu. Indeed, Appellants have produced no evidence to indicate
that an etched product that is made by uncontrolled and non-uniform (i.e.,
more than ±20% perimeter variation on all sides) etching would even have
been considered in the art to be useful.
Also, with respect to claim 2, Appellants argue that Bayraktaroglu
does not suggest an undercut that “varies by less than ±20 percent on all
sides of the perimeter [of] the compound semiconductor layer.” (App. Br.
11, ll. 14-16). Again, this argument is not persuasive. This limitation is
subsumed in the “substantially coextensive” limitation of claim 1 because
“substantially coextensive” requires an undercut of the compound
semiconductor’s perimeter that varies by less than ±20% on all sides. (FF
3). For the same reasons as discussed above, Appellants have not met their
burden to show the Examiner erred in determining claim 2 to be obvious to
one of ordinary skill in the art.
With respect to claim 24, Appellants additionally argue that
Bayraktaroglu does not teach the required ratio of a first etching rate to a
second etching rate because the reference is concerned with relative vertical
etching rates, which are irrelevant to the required features of substantially
coextensive perimeters and relative etch rates in lateral directions. (App. Br.
11 bridging to 12).
Again, Appellants have not satisfied their burden to show that the
Examiner erred in the obviousness determination. To begin with,
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Bayraktaroglu would necessarily be concerned with etching in a transverse
direction because the reference teaches a controlled undercut. (FF 16).
Furthermore, the Examiner found the ratio of a first etching rate along a first
direction and a second etching rate along a second direction to be a result
effective variable that one of ordinary skill in the art would modify by
routine optimization. (Ans. 9 bridging to 10). Appellants’ bare arguments
that Bayraktaroglu does not teach the limitations found in the claim are not
sufficient to overcome the Examiner’s finding. Here, Appellants have not
even asserted that the Examiner’s finding that the ratio is a result effective
variable is in error. (App. Br. 11-13; Reply Br. 3-4).
With respect to the grounds of rejection for claims 4, 5, 21-23, 25, 26,
28, and 29, Appellants rely on the same arguments as discussed above with
respect to claims 2, 7, 24, and 27. These arguments are unpersuasive to
show that the Examiner made reversible error in finding claims 4, 5, 21-23,
25, 26, 28, and 29 obvious to one of ordinary skill in the art, for the reasons
discussed above.
CONCLUSION
Appellants have failed to show that the Examiner reversibly erred in
determining that Bayraktaroglu anticipates claims 1, 3, 6, and 8-11. Also,
Appellants have not shown that the Examiner erred in determining that one
of ordinary skill in the art would have found the subject matter of claims 2,
4, 5, 7, and 21-29 obvious over the prior art. Therefore, we affirm the
decision of the Examiner to reject appealed claims 1-11 and 21-29.
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No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv).

AFFIRMED

tf/ls

HITT GAINES, PC
ALCATEL-LUCENT
P.O. BOX 832570
RICHARDSON, TX 75083
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