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 .
This Office action is in response to Amendments filed 11/5/2025.
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, and 21-23 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; 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 (liner 46A in Fig. 9D 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 and the sidewall spacer is directly between a side surface of the bottom contact and a side surface (rightmost side surface) of the trench liner.
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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 (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, 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 (liner 46A in Fig. 9D 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 and the sidewall spacer is directly between a side surface of the bottom contact and a side surface (rightmost side surface) of the trench liner.
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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 source/drain 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 sidewall of the bottom contact cap (see annotated copy of Fig. 7, above) and the bottom portion being in direct contact with a sidewall 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 sidewall of the bottom contact cap (see annotated copy of Fig. 7, above) and the bottom portion being in direct contact with a sidewall of the bottom contact (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 11/5/2025 have been fully considered but they are not persuasive.
Applicant argues that Smith in view of Amano does not disclose the newly added limitation that the sidewall spacer is directly between a side surface of the bottom contact and a side surface of the trench liner. This argument is not persuasive as Applicant has not yet claimed that the entirety of the sidewall spacer is directly between a side surface of the bottom contact and a side surface of the trench liner. As a portion of the sidewall spacer is directly between a side surface of the bottom contact and a side surface of the trench liner, the claim limitation is satisfied.
Applicant further argues that Smith does not disclose the specific method of deposition steps of required to form the device and that if a particular method step assumed by the Applicant is used then it would not result in the claimed structure when combined with the teachings of Amano. This argument is not persuasive as Applicant has not claimed the specific method steps for forming the device. Further, as one having ordinary skill in the art could form the layers sequentially, one having ordinary skill in the art could form the device of the combination.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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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/C.A.C/ Examiner, Art Unit 2815
/JOSHUA BENITEZ ROSARIO/Supervisory Patent Examiner, Art Unit 2815