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and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114.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 5/26/2026 has been entered.
Claim Objections
Claim 2 is objected to because of the following informalities: the superscripts within the contact resistance range of claim 2 need to be returned to the presentation as originally filed. Appropriate correction is required.
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claim(s) 1, 3-9, 11-14, 21-27 is/are rejected under 35 U.S.C. 103 as being unpatentable over Smith et al. (US 2020/0075574 A1) in view of Amano et al. (US 2018/0247954 A1).
Regarding claim 1, Smith discloses a semiconductor device (Fig. 7), comprising a top field effect device (FET device corresponding to 720b) over a bottom field effect device (FET device corresponding to 715a);
a bottom contact (see annotated copy of Fig. 7, below) electrically connecting a bottom source/drain (715a) of the bottom field effect device to a first buried power rail (720);
a bottom contact cap (see annotated copy of Fig. 7, below) on the bottom contact, the bottom contact cap comprising a dielectric material; and
a sidewall spacer (see annotated copy of Fig. 7, below).
Smith does not disclose a trench liner as claimed.
However, it was well known in the art to line the trenches in which conductive contacts are made with a trench liner (combination of “backside blocking dielectric layer 44” and “metallic barrier layer 46A” in Fig. 9D, ¶ 0088 and 0091 of Amano).
There is a benefit to forming such liners in that it reduces the likelihood of deleterious diffusion (¶ 0091 of Amano).
It would have been obvious to one having ordinary skill in the art at the time the Application was filed to form liners along the entirety of the contacts of Smith for this benefit.
In the resulting structure (shown in the annotated copy of Fig. 7, below), the trench liner is on opposite sides of the bottom contact cap and the bottom contact, the trench liner comprising a dielectric material; the trench liner is directly between a side surface of the bottom contact (surface of the bottom side) and a side surface of the sidewall spacer (surface of the top side), see annotated copy of Fig. 7, below.
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Regarding claim 3, Smith further discloses a top source/drain contact (see annotated copy of Fig. 7, above) electrically connecting a top source/drain of the top field effect device to a second buried power rail (725).
Regarding claims 4 and 5, Smith does not explicitly state whether the top field effect device is a PFET (claim 4, NFET for claim 5) and the bottom field effective device is an NFET (claim 4, PFET for claim 5).
However, Smith discloses a recognized need for forming the semiconductor device by alternating PFET and NFET devices (¶ 0031). Further, there is a finite number of potential solutions to this recognized need (PFET then NFET, or NFET then PFET). Further, one having ordinary skill in the art could have pursued the known potential solution with a reasonable expectation of success as either combination would yield a functional device. As such, one having ordinary skill in the art at the time the application was filed would have found it obvious to try to make the top field effect device a PFET (claim 4, NFET for claim 5) and the bottom field effective device an NFET (claim 4, PFET for claim 5). (MPEP 2143(I)(E).
Regarding claim 6, Smith further discloses a portion of the sidewall spacer (see annotated copy of Fig. 7, above) separating the bottom contact from a substrate.
Regarding claim 7, the bottom contact cap separates the bottom source/drain from a top source/drain (see Fig. 7).
Regarding claim 8, the trench liner is on an interlayer dielectric layer (see annotated copy of Fig. 7, above) between the bottom source/drain and the top source/drain of the top field effect device (the interlayer dielectric layer is laterally between the two source/drains).
Regarding claim 9, Smith discloses a semiconductor device (Fig. 7), comprising a top field effect device (FET device corresponding to 720b) having a top source/drain (720b) over a bottom field effect device (FET device corresponding to 715a) having a bottom source/drain (715a);
a bottom contact (see annotated copy of Fig. 7, below) in electrical contact with the bottom source/drain of the bottom field effect device;
a bottom contact cap (see annotated copy of Fig. 7, below) on the bottom contact, the bottom contact cap comprising a dielectric material, wherein a portion of the bottom contact and a portion of the bottom contact cap separate the bottom contact cap separate the bottom source/drain from the top source/drain (see Fig. 7); and
a sidewall spacer (see annotated copy of Fig. 7, below).
Smith does not disclose a trench liner as claimed.
However, it was well known in the art to line the trenches in which conductive contacts are made with liners (combination of “backside blocking dielectric layer 44” and “metallic barrier layer 46A” in Fig. 9D, ¶ 0088 and 0091 of Amano)
There is a benefit to forming such liners in that it reduces the likelihood of deleterious diffusion (¶ 0091 of Amano).
It would have been obvious to one having ordinary skill in the art at the time the Application was filed to form liners along the entirety of the contacts of Smith for this benefit.
In the resulting structure (shown in the annotated copy of Fig. 7, below), the trench liner is on opposite sides of the bottom contact cap and the bottom contact, the trench liner comprising a dielectric material; the trench liner is directly between a side surface of the bottom contact (surface of the bottom side) and a side surface of the sidewall spacer (surface of the top side), see annotated copy of Fig. 7, below.
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Regarding claim 11, Smith further discloses a top source/drain contact (see annotated copy of Fig. 7, above) in electrical contact with the top source/drain of the top field effect device.
Regarding claim 12, the top source/drain contact electrically connects the top source/drain to a first buried power rail (725).
Regarding claim 13, the bottom contact electrically connects the bottom source/drain to a second buried power rail (720).
Regarding claim 14, a portion of the sidewall spacer separates the bottom contact from a substrate (see annotated copy of Fig. 7, above).
Regarding claim 21, the sidewall spacer further separates the trench liner from the bottom source/drain (as seen in the annotated copy of Fig. 7, below, a portion of the sidewall spacer separates the right side portion of the trench liner from the bottom source/drain 715a. Although some of the left side portion of the trench liner directly contacts the bottom source/drain, this is consistent with Applicant’s invention which also has a portion of the trench liner directly contacting the bottom source/drain (as seen in Fig. 19 of Applicant’s drawings, the left side of the top surface of the bottom source/drain 215 is directly contacted by trench liner 270).
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Regarding claim 22, the sidewall spacer directly contacts a lower portion of a sidewall of the bottom source/drain (see annotated copy of Fig. 7 in the rejection of claim 21, above) and the bottom contact directly contacts an upper portion of the sidewall of the bottom source/drain (see annotated copy of Fig. 7 in the rejection of claim 21, above).
Regarding claim 23, the trench liner includes a top portion (portion directly on the top surface of the bottom contact) that is continuous with a bottom portion (portion on left sidewall of the bottom contact that is also on the right sidewall of the bottom portion of the bottom contact cap), the top portion being in direct contact with a side surface of the bottom contact cap (see annotated copy of Fig. 7, above) and the bottom portion being in direct contact with the side surface of the bottom contact (see annotated copy of Fig. 7, above).
Regarding claim 24, the trench liner includes a top portion (portion directly on the top surface of the bottom contact) that is continuous with a bottom portion (portion on left sidewall of the bottom contact that is also on the right sidewall of the bottom portion of the bottom contact cap), the top portion being in direct contact with a side surface of the bottom contact cap (see annotated copy of Fig. 7, above) and the bottom portion being in direct contact with the side surface of the bottom contact (see annotated copy of Fig. 7, above).
Regarding claim 25, at least a portion of a top source/drain of the top field effect device is on the bottom contact cap (see annotated copy of Fig. 7, above).
Regarding claim 26, the bottom contact cap electrically insulates a top source/drain of the top field effect device from the bottom contact and the bottom source/drain (see annotated copy of Fig. 7, above).
Regarding claim 27, at least a portion of the top source/drain is on the bottom contact cap (see annotated copy of Fig. 7, above).
Claim(s) 2 is/are rejected under 35 U.S.C. 103 as being unpatentable over Smith et al. (US 2020/0075574 A1) in view of Amano et al. (US 2018/0247954 A1) as applied to claim 1 above, and further in view of Chan et al. (US 2018/0096885 A1).
Regarding claim 2, Smith does not specify the contact resistance of the interface between the bottom source/drain and the bottom contact to determine if it falls within the claimed range.
However, it was well known in the art to form source/drains and the corresponding contacts from materials which result in a contact resistance of 5x10-9 Ohm/cm2 (¶ 0003 of Chan) which is in the claimed range.
There was a benefit to using such a low contact resistance in that it reduces the amount of energy loss to heat during the operation of the device.
It would have been obvious to one having ordinary skill in the art at the time the Application was filed to form the interface between the bottom source/drain and the bottom contact of Smith to have a contact resistance of 5x10-9 Ohm/cm2 for this benefit.
Response to Arguments
Applicant's arguments filed 5/26/2026 have been fully considered but they are not persuasive.
Applicant argues that the bottom contact cap of Smith is not a dielectric material. This argument is not persuasive as the bottom contact cap is the set of insulating layers (i.e., a dielectric) between the electrically conductive metal rails (“an alternating stack of insulating layers and electrically conductive layers located over the substrate”, ¶ 0005 of Smith).
With regards to the trench liner comprising a dielectric, although the trench liner as mapped in the prior Office action did not contain a dielectric material, the newly mapped trench liner includes a dielectric material, as discussed in the rejections above.
Applicant further argues that “the Office [a]ction identifies the sidewall spacer, not the trench liner, as the intervening structure”. This argument is not persuasive as the prior Office action identified the sidewall spacer as that was what the previously presented claim required. The present rejections have changed the identification to the trench liner to account for Applicant’s change in the Amendments.
Applicant further argues that Smith does not disclose a trench liner. This argument is not persuasive as Smith is not relied upon for disclosing a trench liner. In response to applicant's arguments against the references individually, one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986).
Applicant further argues that Amano does not disclose a bottom contact cap on the bottom contact and a sidewall spacer. This argument is not persuasive as Amano is not relied upon for disclosing these features. In response to applicant's arguments against the references individually, one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986).
Applicant’s remaining arguments that the combination of Smith and Amano does not disclose the limitations of claims 1 and 9 are not persuasive as the combination of Smith and Amano does disclose the limitations of claims 1 and 9, as discussed in the rejections above.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to CHRISTOPHER A CULBERT whose telephone number is (571)272-4893. The examiner can normally be reached M-F 9-5.
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/CHRISTOPHER A CULBERT/ Examiner, Art Unit 2815
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