DETAILED ACTION
This is the Office action based on the 17908177 application filed August 30, 2022, and in response to applicant’s argument/remark filed on August 28, 2025. Claims 1-6 are currently pending and have been considered below.
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on August 28, 2025 has been entered.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102 of this title, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries set forth in Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), that are applied for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-6 rejected under 35 U.S.C. 103 as obvious over Lin et al. (U.S. PGPub. No. 20220293594), hereinafter “Lin’594”, in view of Lebby et al. (U.S. Pat. No. 5034092), hereinafter “Lebby”.
--Claims 1, 5, 6: Lin’594 teaches a method of fabricating a Gate All Around stacked transistor ([0011]), comprising providing a substrate 302 comprising silicon germanium ([0018], Fig. 3B), then patterning the substrate 302 to form fins 402 and 404 ([0020], Fig. 4B);forming dummy fins 602 and 604 over the substrate 302, the dummy fins comprise hafnium oxide ([0033], Fig. 6B);forming a gate structure layer 702 over the fins and dummy fins ([0038-0043], Fig. 7B);forming a photoresist mask 902 that cover a dummy fin 602 ([0021, 0049-0051], Fig. 9A);performing a first etching the gate structure layer 702 to expose the dummy fin 604 ([0059]), then performing a second etching to completely remove the dummy fin while fins 402 and 404 remain intact ([0059], Fig. 12B), wherein second etching may comprise a plasma of a mixture of an etch gas and a passivation gas, wherein the etch gas may comprise chlorine, hydrogen bromide, carbon tetrafluoride, fluoroform, difluoromethane, fluoromethane, hexafluoro-1,3-butadiene, boron trichloride, sulfur hexafluoride, hydrogen, nitrogen trifluoride, and the passivation gas may comprise nitrogen (N2), oxygen (O2), carbon dioxide (CO2), sulfur dioxide (SO2), carbon monoxide (CO), methane (CH4), silicon tetrachloride (SiCl4)” ([0070]). It is noted that Fig. 11B and 12B shows that the dummy fin layer 604-1 is completely etched away while the layer 404 remains intact. Lin’594 further teaches to use boron trichloride as the etch gas when etching a dummy fin comprising hafnium oxide ([0071]), and that the etch gas and/or the passivation gas may be diluted with a gas such as Ar, He, Ne or other suitable dilutive gas ([0070]). Lin’594 fails to teach the claimed feature that the second etch uses a mixed gas of BCl3 and SiCl4, and wherein the flow rate of the SiCl4 is smaller than a flow rate of the BCl3 gas. Lebby, also directed to plasma etching a semiconductor substrate, teaches that the etching may be advantageously performed by using a plasma comprising silicon tetrachloride and boron trichloride to provide an etching that has less etch damage, a greater degree of anisotropy and a more controlled etch (abstract). Lebby further teaches that “(s)ilicon tetrachloride gas is injected into the plasma reactor so that a range between 20 percent and 90 percent by volume is maintained” and “(b)oron trichloride gas is also injected into the plasma reactor so that a range between 10 percent and 90 percent by volume is maintained” (Col. 3, Lines 24-33). It is noted that this is equivalent to a ratio SiCl4:BCl3 of 25% to 900%, and a ratio of SiCl4:total gas flow of 20 vol .% to 90 vol.% Therefore, it would have been obvious to one of ordinary skill in the art at the effective filing date of the invention to select SiCl4 from the list of the passivation gases to be used with the BCl3 gas in the invention of Lin’594 because Lebby teaches that this would provide an etching that has less etch damage, a greater degree of anisotropy and a more controlled etch. It would have been obvious to one of ordinary skill in the art at the effective filing date of the invention, in routine experimentations, to select a ratio SiCl4:BCl3 of 25% or a ratio of SiCl4:total gas flow of 20 vol .% because Lin’594 is silent about the gas flow amount and Lebby teaches that such gas flows would be effective. It is noted this reads on the gas ratio recited in claims 1 and 5--Claim 2: Since the dummy fin is etched completely from the substrate, it would have been obvious, in routine experimentations, that it is etched from all directions, one of which is perpendicular to the direction that the layer 404 is formed.--Claims 3, 4: Since Lin’594 teaches that the SiCl4 is a passivation gas and the etching is selective to the dummy fin layer 604-1, it would have been obvious to one of ordinary skill in the art at the effective filing date of the invention to flow the passivation gas and the etch gas such as the passivation layer formed by the passivation gas is thicker on the other layers and thinner on the dummy fin layer 604-1 since it has been held that where the general conditions of a claim are disclosed in the prior art, discovering the optimum or workable ranges involves only routine skill in the art. In re Aller, 105 USPQ 233.
Claims 1-6 rejected under 35 U.S.C. 103 as obvious over Peng et al. (U.S. PGPub. No. 20220302257), hereinafter “Peng”, in view of Liu et al. (U.S. PGPub. No. 20090004870), hereinafter “Liu” and Lebby:
--Claims 1, 5, 6: Peng teaches a method of fabricating a FinFET transistor in an Gate All Around structure ([0014]), comprising forming a stack of SiGe layers 102a alternate with Si layers 102b (Fig. 1, [0018]);forming a dummy gate dielectric layer 618 on the stack, the dummy gate dielectric layer 618 may be made of HfO2 (Fig. 6, [0033-0034]);removing a top Si layer 102b to expose a SiGe layer 102a on the stack (Fig. 15-16, [0050]);selectively etching the dummy gate dielectric layer 618 along the sidewall of the stack (Fig. 17-18, [0051-0052]). Peng is silent about a method for the selectively etching. Liu, also directed to a method of etching a hafnium oxide layer 304 ([0031, 0040]) in the presence of a silicon-containing layer 306 ([0057]) by using BCl3 ([0052-0053], Fig. 4B-C)) during fabricating a semiconductor device, teaches that a silicon and halogen containing gas, such as SiCl4, may be used to passivate and protect the sidewall of the silicon-containing layer ([0050]) Therefore, it would have been obvious to one of ordinary skill in the art at the effective filing date of the invention, in routine experimentations, to select SiCl4 from the list of the passivation gas in the invention of Lin’594 because Liu teaches that this would advantageously passivate and protect the sidewall of the other silicon-containing layers that are exposed to the etching. Peng and Liu fail to teach the claimed feature a flow rate of SiCl4 is smaller than a flow rate of the BCl3 gas. Lebby, also directed to plasma etching a semiconductor substrate, teaches that the etching may be advantageously performed by using a plasma comprising silicon tetrachloride and boron trichloride to provide an etching that has less etch damage, a greater degree of anisotropy and a more controlled etch (abstract). Lebby further teaches that “(s)ilicon tetrachloride gas is injected into the plasma reactor so that a range between 20 percent and 90 percent by volume is maintained” and “(b)oron trichloride gas is also injected into the plasma reactor so that a range between 10 percent and 90 percent by volume is maintained” (Col. 3, Lines 24-33). It is noted that this is equivalent to a ratio SiCl4:BCl3 of 25% to 900%, and a ratio of SiCl4:total gas flow of 20 vol .% to 90 vol.% Therefore, it would have been obvious to one of ordinary skill in the art at the effective filing date of the invention to select SiCl4 from the list of the passivation gases to be used with the BCl3 gas in the invention of Lin’594 because Lebby teaches that this would provide an etching that has less etch damage, a greater degree of anisotropy and a more controlled etch. It would have been obvious to one of ordinary skill in the art at the effective filing date of the invention, in routine experimentations, to select a ratio SiCl4:BCl3 of 25% or a ratio of SiCl4:total gas flow of 20 vol .% because Lin’594 is silent about the gas flow amount and Lebby teaches that such gas flows would be effective. It is noted this reads on the gas ratio recited in claims 1 and 5--Claim 2: it is noted that the dummy gate dielectric layer 618 is etched from the lateral direction, which is perpendicular to the vertical direction that the layer 102a is formed.--Claims 3, 4: Since Liu teaches that the SiCl4 is a passivation gas and the etching is selective to the dummy gate dielectric layer 618, it would have been obvious to one of ordinary skill in the art at the effective filing date of the invention to flow the passivation gas and the etch gas such as the passivation layer formed by the passivation gas is thicker on the other layers and thinner on the dummy gate dielectric layer 618 since it has been held that where the general conditions of a claim are disclosed in the prior art, discovering the optimum or workable ranges involves only routine skill in the art. In re Aller, 105 USPQ 233.
Response to Arguments
Applicant's arguments filed August 28, 2025 have been fully considered as follows:--Regarding Applicant’s argument that the previously cited prior arts do not teach the amended feature because the specification shows that HfO2 is not etched at the gas ratio taught by Kobayashi, this argument is persuasive. New grounds of rejection based on newly found prior arts are shown above.
Conclusion
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/THOMAS T PHAM/Primary Examiner, Art Unit 1713