DETAILED ACTION
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 .
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and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114.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 September 26, 2025 has been entered.
Claim Rejections - 35 USC § 103
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 (i.e., changing from AIA to pre-AIA ) 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.
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, 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 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, 8-10 are rejected under 35 U.S.C. 103 as being unpatentable over Brown (U.S. 2012/0247505) and Heo et al (U.S. 2003/0203632).
Regarding claim 1. Brown et al discloses an etching method (Abstract; claims 16-25) comprising: selectively etching a silicon nitride layer against a silicon oxide layer (Abstract), under pressurization conditions ([0040], i.e. Pressure for the steam water vapor mixture can be in the range from 0.2 to 2.0 MPa), using an etching composition including a phosphoric acid based on a total weight of the etching composition ([0040], i.e. composition of 85% phosphoric acid by weight),
wherein the etching composition does not include a compound containing a silicon atom ([0030], i.e. The chemical reactions for etching silicon nitride: Si3N4+4H3PO4+12H2O → 3Si(OH)4+4NH4H2PO4 ; [0040]; claims 16-25; examiner makes note that 4H3PO4+12H2O does not include a compound containing a silicon atom).
wherein the pressurization conditions are 2 to 20 atm ([0040], i.e. Other combinations of steam water vapor mixtures with aqueous phosphoric acid can be tested to determine the etch rate and etch selectivity of silicon nitride that meet the objectives of an application. Pressure for the steam water vapor mixture can be in the range from 0.2 to 2.0 MPa).
wherein the following (A) to (C) are satisfied:
(A) an etching rate of the silicon nitride layer is 50 A/min or more ([0036], i.e. Silicon nitride etch processes are slow (30-60 Angstrom/min, or A/min) in hot phosphoric acid at 16.degree. C. If the etch rate of silicon nitride can be increased to over 180 A/min),
(B) an etching rate of the silicon oxide layer is 0 to 10 A/min ([0036]; claims 16-18; examiner makes note ((etch rate silicon nitride)/(etch rate of silicon oxide)=(selectivity of silicon nitride to silicon oxide) that etch rate of silicon nitride is 30- over 180 Angstrom/min and with a selectivity of silicon nitride to silicon oxide of 10:1 to 1000:1 would give an silicon oxide rate of 0.18-3 A/min), and
(C) an etching selectivity of the silicon nitride layer to the silicon oxide layer is 2 to 400 (claims 16-18; i.e. etch selectivity ratio is in the range from 10:1 to 1000:1).
Brown et al fails to explicitly disclose wherein the etching composition includes 30 to 70 wt% of the phosphoric acid.
However, Heo et al teaches wherein the etching composition includes 30 to 70 wt% of the phosphoric acid ([Abstract]; water solution containing phosphoric acid (H3PO4) of a concentration of 50-70% by weight).
Since Brown et al and Heo et al discloses etching composition of 85% for silicon nitride, it would have been obvious to one having ordinary skill in the art of semiconductors before the effective filing date of the claimed invention to have combined the etching method as disclosed to modify Brown et al with the teachings of wherein the etching composition includes 30 to 70 wt% of the phosphoric acid as disclosed by Heo et al. The use of water solution containing phosphoric acid of a concentration of 50-70% by weight in Heo et al provides for the etch rate of the nitride film is increased, and the selectivity between the nitride film and an oxide film is kept very high (Heo et al, [Abstract]).
Regarding claim 6. Brown et al and Heo et al discloses all the limitation of the etching method of claim 1 above.
Brown et la further discloses wherein the etching composition has an etching selectivity of 10 to 400 (claims 16-18; i.e. etch selectivity ratio is in the range from 10:1 to 1000:1)
Regarding claim 8. Brown et al and Heo et al discloses all the limitations of the etching method of claim 1 above.
Brown et al further discloses wherein an object to be etched of the etching composition is a wafer (Claim 16) in which both silicon nitride layer (Claim 16) and silicon oxide layer (Claim 16) are exposed to a surface (Claim 16) or a wafer having a stack structure having the silicon nitride layer and the silicon oxide layer as a unit layer.
Regarding claim 9. Brown et al and Heo et al discloses all the limitations of the etching method of claim 1 above.
Brown et al further discloses wherein the etching method is performed at a high temperature of 100°C or higher ([0040], claim 19).
Regarding claim 10. Brown et al and Heo et al discloses all the limitations of the etching method of claim 1 above.
Brown et al further discloses A method of manufacturing a semiconductor device ([0027]) using the etching method of claim 1 (claims 14-16).
Claims 4 are rejected under 35 U.S.C. 103 as being unpatentable over Brown et al (U.S. 2012/0247505) and Heo et al (U.S. 2003/0203632) as applied to claim 1 above, and further in view of Kim et al (U.S. 2022/0089951).
Regarding claim 4. Brown et al and Heo et al discloses all the limitations of the etching method of claim 1 above.
Brown et al fails to explicitly disclose wherein the following (D) is satisfied: (D) in a vertical stack structure having the silicon oxide layer and the silicon nitride layer as a unit layer, an outer thickness (To) to an inner thickness (Ti) of the silicon oxide layer satisfies the following Equation 1: [Equation 1]
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However, Kim et al teachers wherein the following (D) is satisfied: (D) in a vertical stack structure having the silicon oxide layer and the silicon nitride layer as a unit layer ([0046]), an outer thickness (To) to an inner thickness (Ti) of the silicon oxide layer satisfies the following Equation 1:
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([Abstract], i.e. not only no precipitate occurs but also anomalous growth in which the thickness of the silicon oxide film is rather increased does not occur)
Since Brown et al, Heo et al and Kim et al teach etching silicon nitride, it would have been obvious to one having ordinary skill in the art of semiconductors before the effective filing date of the claimed invention to have combined the etching method as disclosed to modify Brown et al and Heo et al with the teachings of an outer thickness (To) to an inner thickness (Ti) of the silicon oxide layer satisfies the following Equation 1: [Equation 1]
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16
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as disclosed by Kim et al. The use of not only no precipitate occurs but also anomalous growth in which the thickness of the silicon oxide film is rather increased does not occur in Kim et al provides for minimizing defects and reliability reduction (Kim et al, [Abstract]).
“[W]here the general conditions of a claim are disclosed in the prior art, it is not inventive to discover the optimum or workable ranges by routine experimentation.” See MPEP 2144.05 II. In re Aller, 220 F.2d 454, 456, 105 USPQ 233, 235 (CCPA 1955); see also Peterson, 315 F.3d at 1330, 65 USPQ2d at 1382; In re Hoeschele, 406 F.2d 1403, 160 USPQ 809 (CCPA 1969). For more recent cases applying this principle, see Merck & Co. Inc. v. Biocraft Lab. Inc., 874 F.2d 804, 10 USPQ2d 1843 (Fed. Cir.), cert. denied, 493 U.S. 975 (1989); In re Kulling, 897 F.2d 1147, 14 USPQ2d 1056 (Fed. Cir. 1990); and In re Geisler, 116 F.3d 1465, 43 USPQ2d 1362 (Fed. Cir. 1997); Smith v. Nichols, 88 U.S. 112, 118-19 (1874); In re Williams, 36 F.2d 436, 438 (CCPA 1929). See also KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 416 (2007). See MPEP 2144.05 II.
Response to Arguments
Applicant's arguments filed September 26, 2025 have been fully considered but they are not persuasive.
On page 11 of applicant’s remarks, applicant appears to argue in Brown that the internal pressure of the reactor is not maintained at a pressurized environment of 0.2-2.0 MPa.
In response to applicant's argument that the references fail to show certain features of the invention, it is noted that the features upon which applicant relies (i.e., internal pressure of the reactor is maintained at a pressurized environment of 0.2-2.0 MPa) are not recited in the rejected claim(s). Although the claims are interpreted in light of the specification, limitations from the specification are not read into the claims. See In re Van Geuns, 988 F.2d 1181, 26 USPQ2d 1057 (Fed. Cir. 1993).
On page 12 of applicant’s remarks, applicant appears to be arguing that Brown et al discloses in claim 20 a phosphoric acid equation solution that contains 10 ppm to 30 ppm of dissolved silica.
In response to applicant's argument that adding silica to the etching compound to sustain a target etching rate of silicon nitride, the fact that the inventor has recognized another advantage which would flow naturally from following the suggestion of the prior art cannot be the basis for patentability when the differences would otherwise be obvious. See Ex parte Obiaya, 227 USPQ 58, 60 (Bd. Pat. App. & Inter. 1985).
Furthermore, Examiner respectfully points out that claim 20 states The method of claim 16, wherein the steam water vapor mixture at elevated pressure and the treatment liquid are combined at high pressure prior to entering the etch processing chamber.
Furthermore, Examiner respectfully points out that Brown discloses wherein the etching composition does not include a compound containing a silicon atom ([0030], i.e. The chemical reactions for etching silicon nitride: Si3N4+4H3PO4+12H2O → 3Si(OH)4+4NH4H2PO4 ; [0040]; claims 16-25; examiner makes note that 4H3PO4+12H2O does not include a compound containing a silicon atom).
On page 12 of applicant’s remarks, applicant agrees that Heo discloses an etching composition 50-70 wt%, but appears to argue that Heo does not disclose the performing the etching process under a pressurized atmosphere nor at a temperature.
Examiner respectfully points out that Brown et al, as cited in the rejection above, discloses the performing the etching process under a pressurized atmosphere and a temperature.
Conclusion
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/S.E.B./ Examiner, Art Unit 2815
/JOSHUA BENITEZ ROSARIO/Supervisory Patent Examiner, Art Unit 2815