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 .
Status of the Claims
Claims 1-15 and 25-25 are pending in the application and are currently being examined. No claims have been amended. Claims 16-20 have been cancelled. New claims 21-25 have been added.
Election/Restrictions
As claims 16-20 have been cancelled the election/restriction requirement of 10/24/2025 is moot and is thus withdrawn.
Information Disclosure Statement
The information disclosure statement (IDS) submitted on 6/21/2023 and 7/30/2025 is being considered by the examiner.
Specification
The title of the invention is not descriptive. A new title is required that is clearly indicative of the invention to which the claims are directed.
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.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claim(s) 1-13, 15, and 21-25 is/are rejected under 35 U.S.C. 103 as being unpatentable over Xie et al. (US 11,069,684 B1, hereafter Xie), in view of Smith et al. (US 2022/0122892 A1, hereafter Smith), and further in view of Chiu et al. (US 2020/0135858 A1, hereafter Chiu).
Regarding claim 1, in Fig. 14 Xie teaches a method, comprising:
forming a bottom-tier transistor (106a column 7 line 23) and a top-tier transistor (106b column 7 line 24) over the bottom-tier transistor (106a), the top-tier transistor (106b) comprising a first channel layer (see annotated Fig. 14), a first gate structure (see annotated Fig. 14) around the first channel layer, and a plurality of first source/drain regions (130, column 8 line 50) on opposite sides of the first channel layer;
forming a first dielectric layer (132 as in Fig. 10, column 8 line 59) over the first source/drain regions (130) of the top-tier transistor (106b).
Xie fails to teach etching the first dielectric layer to form a first opening exposing one of the first source/drain regions of the top-tier transistor;
selectively forming a first silicide on the one of the first source/drain regions;
forming a front-side contact.
However, Smith teaches in Figs 23-27 a similar transistor device as Xie, in which the first dielectric layer is etched to form a first opening exposing one of the first source/drain regions of the top-tier transistor [0085];
selectively forming a first silicide (2405, [0085]) on the one of the first source/drain regions (1205 of Smith, [0070]);
forming a front-side contact (2410, [0085]).
Smith teaches the silicide lowers contact resistance [0045] and the contact is useful to provide a common signal track between the devices [0085]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie to include the step of etching the dielectric, forming a silicide, and creating a front-side contact.
Xie in view of Smith fail to teach the silicide is specifically a metal silicide. Smith in particular is silent on the exact material of the silicide. However, one of ordinary skill in the art would know to use a suitable silicide and Chiu teaches a similar method, and the silicide layer (140, [0028]) can contain titanium silicide (TiSi) [0028], which is a metal silicide.
Xie in view of Smith fail to teach selectively forming a first metal cap on the first metal silicide and not on the first dielectric layer; and the front-side contact on the first metal cap.
However, Chiu shows in Fig. 5G a metal cap (seed layer 142, [0030]) being formed on a metal silicide (140, [0028]) and not on the dielectric layer (154, [0035]), and the front side contact (160, [0029]) on the first metal cap (142). The seed layer (142) acts as a glue layer and has a lower contact resistance with the silicide layer (140) and a relatively low resistivity [0033]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith to include the deposition of a metal cap as taught by Chiu.
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Regarding claim 2, Xie in view of Smith in view of Chiu teach the method of claim 1. Smith is silent on the exact material of the metal silicide. However, one of ordinary skill in the art would know to use a suitable metal silicide and Chiu teaches a similar method, and the metal silicide layer (140, [0028]) can contain titanium silicide (TiSi) [0028].
Regarding claim 3, Xie in view of Smith in view of Chiu teach the method of claim 1. Chiu further discloses the first metal cap (seed layer 142, [0030]) comprises a fluorine-free tungsten ([0030] fluorine is not on the list of elements).
Regarding claim 4, Xie in view of Smith in view of Chiu teach the method of claim 1. Smith discloses the front-side contact (2410, [0085]) can comprise ruthenium or cobalt. Chiu discloses ruthenium or cobalt as suitable materials for the metal cap (seed layer 142, [0030]). This combination means the first metal cap comprises a same metal element as the front-side contact.
Regarding claim 5, Xie in view of Smith in view of Chiu teach the method of claim 1. Smith fails to teach the front-side contact comprises tungsten. However, Chiu teaches the metal cap (seed layer 142, [0030]) can comprise tungsten [0030]. Chiu further discloses that the front side contact and the metal cap can be formed of the same material [0040]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the front side contact of Smith to be made of tungsten like the metal cap in order to speed up the formation of the contact metal layer as Chiu teaches in [0040].
Regarding claim 6, Xie in view of Smith in view of Chiu teach the method of claim 1. Smith is silent on the method of forming the front-side contact (conductive metal, 2410 [0085]. However, Chiu teaches selectively forming the first metal cap (seed layer 140, [0028]) is performed by a different deposition process than forming the front-side contact (160, [0029]). Chiu teaches the metal cap (140) is taught to be formed by using process gases [0030], while the front-side contact (160) is formed using a CVD process [0040].
Regarding claim 7, Xie in view of Smith in view of Chiu teach the method of claim 1. Xie teaches wherein the bottom-tier transistor (106a, column 7 line 23) comprises a second channel layer (see annotated Fig. 14), a second gate structure (see annotated Fig. 14) around the second channel layer, and a plurality of second source/drain regions (126, column 7 line 52) on opposite sides of the second channel layer.
Xie fails to teach the method further comprising:
forming a second dielectric layer over the second source/drain regions of the bottom-tier transistor, wherein the first source/drain regions of the top-tier transistor are formed over the second dielectric layer;
etching the second dielectric layer to form a second opening in the second dielectric layer, the second opening exposing one of the second source/drain regions of the bottom-tier transistor; and
after etching the second dielectric layer, selectively forming a second metal silicide on the one of the second source/drain regions, wherein the second metal silicide is made of a different material than the first metal silicide.
However, Smith teaches forming a second dielectric layer (599 noted in Fig. 26, [0058]) over the second source/drain regions (810, [0063]) of the bottom-tier transistor (see annotated Fig. 26), wherein the first source/drain regions (1205, [0070]) of the top-tier transistor (see annotated Fig. 26) are formed over the second dielectric layer (599). Smith includes the second dielectric in order to act as a bonding layer between the two transistors [0058]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie to include the step of adding a second dielectric between the top and bottom transistors to get better adhesion between the devices.
Smith also teaches through Figs. 24-27 etching the second dielectric layer (599) to form a second opening in the second dielectric layer (599), the second opening exposing one of the second source/drain regions (810) of the bottom-tier transistor (note in Fig. 25 the etched-out region near 1205 exposes both 1205 and goes through 599); and
after etching the second dielectric layer (599), selectively forming a second metal silicide (2405 on 1205, [0088]) on the one of the second source/drain regions (810).
Smith fails to teach the second metal silicide is made of a different material than the first metal silicide. However, while Smith is silent on the exact material of the second metal silicide, one of ordinary skill in the art would know to use a suitable metal silicide and Chiu teaches a similar method, and the metal silicide layer (140, [0028]) can contain cobalt silicide (CoSi) [0028], which is materially different from titanium silicide, and is done if the devices are of different polarities [0028].
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Regarding claim 8, Xie in view of Smith in view of Chiu teach the method of claim 7. Smith further teaches that etching the second dielectric layer (599, [0058]) is performed until the front-side contact (2410, [0085]) is exposed. This is inherent as the metal 2410 in Fig 26 is continuous, so the etching must have gone through to the first contact shown in 25.
Regarding claim 9, Xie in view of Smith in view of Chiu teach the method of claim 7. Chiu shows in Fig. 5G a metal cap (seed layer 142, [0030]) being formed on a metal silicide (140, [0028]) and not on the dielectric layer (154, [0035]). The seed layer (142) acts as a glue layer and has a lower contact resistance with the silicide layer (140) and a relatively low resistivity [0033]. While not shown a second time, one of ordinary skill in the art would be able to perform this step a second time after flipping the device, as Smith teaches in [0083]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith and in further view of Chiu to include a second deposition of a metal cap with the steps as taught by Chiu.
Regarding claim 10, Xie in view of Smith in view of Chiu teach the method of claim 1. Chiu teaches forming the metal cap. Smith teaches prefilling a trench with the fill material (Smith teaches cobalt, though the modified device would use tungsten) in order to create a high quality liner [0100]. In tandem with Smith’s teaching of the metallization 2410 including a liner [0089], Xie in view of Smith and in further view of Chiu teach forming a liner lining the first opening, the liner having a same metal element as the front-side contact (2410, [0085]).
Regarding claim 11, in Fig. 14 Xie teaches a method, comprising:
forming a first semiconductive nanostructure (see annotated Figs. 14), and a second semiconductive nanostructure (see annotated Figs. 14) arranged in a vertical direction with the first semiconductive nanostructure;
forming a plurality of first epitaxial structures (130, column 8 line 50) on opposite sides of the first semiconductive nanostructure, and a plurality of second epitaxial structures (126, column 7 line 52) on opposite sides of the second semiconductive nanostructure; and
forming a first gate (see annotated Figs. 14) wrapping around the first semiconductive nanostructure, and a second gate (see annotated Figs. 14) wrapping around the second semiconductive nanostructure.
Xie fails to teach selectively forming a first silicide layer on one of the first epitaxial structures, and a second silicide layer on one of the second epitaxial structures.
However, Smith teaches in Figs 23-27 a similar transistor device as Xie, in which selectively forming a first silicide (2405, [0085]) on the one of the first epitaxial structures (1205 of Smith, [0070]), and a second silicide (2405 on 1205, [0088]) on the one of the second epitaxial structures (810, [0063])
Smith teaches the silicide layer lowers contact resistance [0045]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie to include the step of forming a first and second metal silicide, as taught by Smith.
Xie in view of Smith fail to teach the silicide is specifically a metal silicide. Smith in particular is silent on the exact material of the silicide. However, one of ordinary skill in the art would know to use a suitable silicide and Chiu teaches a similar method, and the silicide layer (140, [0028]) can contain titanium silicide (TiSi) [0028], which is a metal silicide.
Xie in view of Smith fail to teach selectively forming a first fluorine-free metal layer on the first metal silicide layer, and a second fluorine-free metal layer on the second metal silicide layer.
However, Chiu shows in Fig. 5G a fluorine-free metal layer (seed layer 142, [0030], fluorine is not on the list of elements of composition) being formed on the metal silicide layer (140, [0028]). The seed layer (142) acts as a glue layer and has a lower contact resistance with the silicide layer (140) and a relatively low resistivity [0033]. While not shown a second time in Chiu, one of ordinary skill in the art would be able to perform this step a second time after flipping the device, as Smith teaches in [0083]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith to include the deposition of a metal cap as taught by Chiu.
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Regarding claim 12, Xie in view of Smith in view of Chiu teach the method of claim 11. Xie is silent on the exact composition of the epitaxial structures, so one of ordinary skill in the art would use materials known to by used in epitaxial regions. Smith’s structure teaches the first epitaxial structures comprise SiGe (810, [0063]), and the second epitaxial structures comprise SiP (1205, [0070]).
Regarding claim 13, Xie in view of Smith in view of Chiu teach the method of claim 11. Chiu fails to explicitly teach the second metal silicide layer has a different metal element than the first metal silicide layer, as Chiu only shows one metal silicide. However, Chiu teaches that the metal silicide layer (140, [0028]) can have different compositions depending on it the relevant device is a p-type or an n-type [0028]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith and in further view of Chiu to include separate metal silicide compositions.
Regarding claim 15, Xie in view of Smith in view of Chiu teach the method of claim 11. Chiu fails to explicitly teach the second fluorine-free metal layer is made of a same material as the first fluorine-free metal layer, as Chiu teaches a singular fluorine-free metal layer (142, [0030]). However, Chiu teaches that if the seed layer is the same material as the metal layer above it (160 in Chiu, 2410 of Smith), the formation of the contact metal layer can be sped up [0040]. Smith teaches the metal layer above is all the same material (2410 is shown to be continuous in Fig. 26). Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith and in further view of Chiu to make both the first and second fluorine-free metal layers comprise the same material.
Regarding claim 21, in Fig. 14 Xie teaches method, comprising:
forming a first transistor (106a column 7 line 23) over a substrate(102, column 5 line 5) the first transistor (106a) comprising:
a plurality of first semiconductor sheets (see annotated Fig. 14);
a first gate structure (see annotated Fig. 14) surrounding each of the first semiconductor sheets; and
a plurality of first source/drain structures (130, column 8 line 50) on either side of each of the first semiconductor sheets;
a second transistor (106b column 7 line 24) over the first transistor (106a), the second transistor (106b) comprising:
a plurality of second semiconductor sheets (see annotated Fig. 14);
a second gate structure (see annotated Fig. 14) surrounding each of the second semiconductor sheets; and
a plurality of second source/drain structures (126, column 7 line 52) on either side of each of the second semiconductor sheets.
Xie fails to teach forming a first silicide layer on one of the first source/drain structures.
However, Smith teaches in Figs 23-27 a similar transistor device as Xie, which includes selectively forming a first silicide layer (2405, [0085]) on the one of the first source/drain structures (1205 of Smith, [0070]).
Smith teaches the silicide layer lowers contact resistance [0045]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie to include the step of forming a first and second metal silicide, as taught by Smith.
Xie in view of Smith fail to teach the silicide is specifically a metal silicide. Smith in particular is silent on the exact material of the silicide. However, one of ordinary skill in the art would know to use a suitable silicide and Chiu teaches a similar method, and the silicide layer (140, [0028]) can contain titanium silicide (TiSi) [0028], which is a metal silicide.
Xie in view of Smith fail to teach selectively forming a first fluorine-free tungsten layer on the first metal silicide layer, and forming a first tungsten contact on the first fluorine-free tungsten layer.
However, Chiu shows in Fig. 5G a fluorine-free tungsten layer (seed layer 142, [0030], fluorine is not on the list of elements of composition while tungsten is) being formed on a first metal silicide layer (140, [0028]). The seed layer (142) acts as a glue layer and has a lower contact resistance with the silicide layer (140) and a relatively low resistivity [0033]. Chiu further discloses that the seed layer (124) and the metal layer (160, [0029]) can both comprise tungsten ([0033] and [0038]), and if they are the same material, the formation of the contact metal layer is sped up [0040]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith to include the first fluorine-free tungsten layer on the first metal silicide layer, and forming a first tungsten contact on the first fluorine-free tungsten layer.
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Regarding claim 22, Xie in view of Smith in view of Chiu teach the method of claim 21. Chiu teaches forming the first fluorine-free tungsten layer. Smith teaches prefilling a trench with the fill material (Smith teaches cobalt, though the modified device would use tungsten) in order to create a high-quality liner [0100]. In tandem with Smith’s teaching of the metallization 2410 including a liner [0089], Xie in view of Smith and in further view of Chiu teach forming a tungsten liner over the first fluorine-free tungsten layer prior to forming the first tungsten contact.
Regarding claim 23, Xie in view of Smith in view of Chiu teach the method of claim 21. Xie in view of Smith in view of Chiu also teach no metal nitride between the first tungsten contact and the one of the first source/drain structures, as Xie in view of Smith and in further of Chiu do not teach any metal nitride layer anywhere near the tungsten contact (seed layer of Chiu, 142, [0030]).
Regarding claim 24, Xie in view of Smith in view of Chiu teach the method of claim 21.
While Chiu does not show forming a second metal silicide layer on one of the second source/drain structures; forming a second fluorine-free tungsten layer on the second metal silicide layer; and forming a second tungsten contact on the second fluorine-free tungsten layer, one of ordinary skill in the art would be able to perform the steps of claim 21 a second time after flipping the device, as Smith teaches in [0083]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith and in further view of Chiu to include forming a second metal silicide layer on one of the second source/drain structures; forming a second fluorine-free tungsten layer on the second metal silicide layer; and forming a second tungsten contact on the second fluorine-free tungsten layer with the steps as taught by Chiu.
Regarding claim 25, Xie in view of Smith in view of Chiu teach the method of claim 24. Smith shows in Fig. 26 that the modified device of Xie in view of Smith and in further view of Chiu teaches the first tungsten contact (see annotated Fig. 26) has a first cross-sectional profile (see annotated Fig. 26) and a second cross-sectional profile (see annotated Fig. 26) between the first cross-sectional profile and the first fluorine-free tungsten layer (not shown in Fig. 26, seed layer 142, [0030] of Chiu), the second tungsten contact (see annotated Fig. 26) has a third cross-sectional profile (see annotated Fig. 26) and a fourth cross-sectional profile (see annotated Fig. 26) between the third cross-sectional profile and the second fluorine-free tungsten layer (not shown in Fig. 26, repeated seed layer of Chiu), the first cross-sectional profile has a wider width than the second cross-sectional profile (see annotated Fig. 26), and the third cross-sectional profile has a wider width than the fourth cross-sectional profile (see annotated Fig. 26).
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Claim(s) 14 is/are rejected under 35 U.S.C. 103 as being unpatentable over Xie in view of Smith and in further view of Chiu as applied to claim 11 above, and further in view of Li et al. (US 2020/0283896 A1, hereafter Li).
Regarding claim 14, Xie in view of Smith in view of Chiu teach the method of claim 11. While Chiu teaches the second metal silicide to comprise TiSi (140 of Chiu, [0028]), Chiu fails to teach the first metal silicide layer comprises MoSiGe. However, Chiu teaches that the metal silicide layer (140) can have different compositions depending on it the relevant device is a p-type or an n-type and that TiSi is used in n-type devices [0028].
One of ordinary skill in the art would know that Chiu does not provide an exhaustive list for metal silicide compositions used in p-type devices, and can use any metal silicide suitable for p-type devices. Li teaches molybdenum germanium silicide (MoSiGe) is suitable for use in PMOS transistors as the silicide film or layer [0011]. Thus, it would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Xie in view of Smith and in further view of Chiu to use MoSiGe as the metal silicide composition for the first metal silicide layer.
Conclusion
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/SAMMANTHA K SALAZ/Examiner, Art Unit 2892
/ERIC W JONES/Primary Examiner, Art Unit 2892