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 16-35 are pending in the application and are currently being examined. Claims 1-15 have been canceled. New claims 21-35 have been added.
Election/Restrictions
As claims 1-15 have been cancelled in response to the Restriction/Election Requirement of 10/23/2025, the restriction/election requirement is now moot and is thus withdrawn.
Information Disclosure Statement
The information disclosure statement (IDS) submitted on 5/10/2023 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 Objections
Claim 29 objected to because of the following informalities: Line 8 says “forming a second isolation structure covering the first source/drain epitaxy”. This appears to be a typo meant to read “forming a second isolation structure covering the second source/drain epitaxy”. Appropriate correction is required.
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) 16-23 and 25-28 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 Chiu et al. (US 2020/0135858 A1, hereafter Chiu).
Regarding claim 16, Figs. 1-12 of Xie teaches a method, comprising:
forming a first stack (106a, column 7 line 23) of alternating first channel layers (110, column 5 line 4) and first sacrificial layers (108, column 5 line3) over a substrate (102, column 5 line 5) (Fig. 1);
forming a second stack (160b, column 7 line 24) of alternating second channel layers (110, column 5 line 9) and second sacrificial layers (108, column 5 line 9) over the first stack (106a) (Fig. 1);
forming first source/drain epitaxy structures (126, column 7 line 52) on opposite ends of each of the first channel layers (Fig. 6);
after the [first source/drain epitaxy structures (126) is] formed, forming second source/drain epitaxy structures (130, column 8 line 50) on opposite ends of each of the second channel layers (110) (Fig. 8);
removing the first sacrificial layers (108) and the second sacrificial layers (108) (Figs. 9-10);
forming a first gate structure (134, column 9 line 20) wrapping around each of the first channel layers (110) and a second gate structure (134) wrapping around each of the second channel layers (110) (Fig. 11);
Xie fails to teach forming first metal silicide layers over the first source/drain epitaxy structures, respectively; and after the first and second gate structures are formed, forming second metal silicide layers over the second source/drain epitaxy structures, respectively.
However, in Figs. 3G and 5G Chiu teaches two methods to deposit metal silicide layers (140, [0028]), one depositing a metal silicide over the entire source drain region (120, [0027]) (Fig. 3G), and one to selectively deposit the metal silicide (140) in an opening [0052] on a selected portion of the source/drain (120) (Fig. 5G).
As the first metal silicide is formed before any etching step, one of ordinary skill in the art can assume that this metal silicide layer is formed around the entirety of the source/drain region (126 of Xie), as shown in Fig. 3G of Chiu. However, as no further information is provided about the second metal silicide, one of ordinary skill in the art would be able to utilize either method depending on the device specifications. The metal silicide of Chiu is formed to provide adhesion between the epitaxial source/drain region and a metal contact without the need of a glue layer ([0022] of Chiu). 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 metal silicide deposition methods of Chiu.
Regarding claim 17, Xie in view of Chiu teach the method of claim 16. Xie further teaches forming a first isolation structure (128, column 8 line 39) over the first metal silicide layers (140 of Chiu, [0028]);
forming a second isolation structure (132, column 8 line 59) over and in contact with the second source/drain epitaxy structures (130, column 8 line 50); and
etching the first isolation structure (128) and the second isolation structure (132) to form contact openings (where contacts 138 and 140 reside, column 9 line 43, between Figs. 10 and 11),
Xie in view of Chiu teach wherein the second metal silicide layers (142, [0030]) are formed over the second source/drain epitaxy structures (130) through the contact openings (as noted above in claim 16, Chiu teaches a method of selectively depositing the metal silicide if Fig.5G ).
Regarding claim 18, Xie in view of Chiu teach the method of claim 17. The method of claim 17 fails to teach forming metal caps over and in contact with the first metal silicide layers, wherein the contact openings expose the metal caps. However, Figs. 3G and 5G of Chiu discloses forming a metal cap (seed layer 142, [0030]) above the metal silicide (140, [0028]). Chiu has this seed layer (142) deposited to remove the need for a glue layer between the metal contact and the source/drain much like the metal silicide [0022]. 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 Chiu to include a deposition of a metal cap over the metal silicide layer.
Regarding claim 19, Xie in view of Chiu teach the method of claim 17. In Fig. Xie further teaches etching the first isolation structure (128, column 8 line 39) and the second isolation structure (132, column 8 line 59) to form the contact openings (where contacts 138 and 140 reside, column 9 line 43, between Figs. 10 and 11), is performed such that portions of the second source/drain epitaxy structures (130, column 8 line 50) are removed. This is inherent, as when normal etching processes occur, etching down to a layer includes etching away a portion of that layer, even on a microscopic level. Thus, etching the hole to the second source/drain epitaxy structures as taught by Xie would include etching some of the second source/drain epitaxy structure.
Xie in view of Chiu teach the first source/drain epitaxy structures (126, column 7 line 52) are protected by the first metal silicide layers (140 of Xie, [0028]) during etching the first isolation structure (128) and the second isolation structure (132). As the hole is not formed into the first source/drain epitaxy structures (126), the first metal silicide (140) is a protective layer, preventing any of the first source/drain epitaxy structures (126) from being etched away.
Regarding claim 20, Xie in view of Chiu teach the method of claim 16. Chiu further teaches wherein a material of the first metal silicide layers has a higher melting point than a material of the second metal silicide layers. In particular, Chiu teaches that metal silicides (140, [0028]) can comprise different metals depending on if they are an n-type device or p-type device [0028]. Titanium as a component of titanium silicide in an n-type transistor has melting point of ~1668C, while cobalt of cobalt silicide in a p-type transistor has a melting point of ~1495C. 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 Chiu in order to have one metal silicide to contain titanium and the other metal silicide to contain cobalt in order to have devices of different polarities.
Regarding claim 21, Figs. 1-12 of Xie teaches a method, comprising:
forming a first channel layer (see annotated Fig. 14) and a second channel layer (see annotated Fig. 14);
forming a first source/drain epitaxy structure (126, column 7 line 52) alongside the first channel layer;
after the [first source/drain epitaxy structures (126)] are formed, forming a second source/drain epitaxy structure (130, column 8 line 50) alongside the second channel layer (110) and vertically above the first source/drain epitaxy structure (126) (Fig. 8).
Xie fails to teach forming a first metal silicide layer over the first source/drain epitaxy structure, wherein the first metal silicide layer comprises a first metal element, forming a second metal silicide layer over the second source/drain epitaxy structure, wherein the second metal silicide layer comprises a second metal element that is different from the first metal element.
However, in Figs. 3G and 5G Chiu teaches two methods to deposit metal silicide layers (140, [0028]), one depositing a metal silicide over the entire source drain region (120, [0027]) (Fig. 3G), and one to selectively deposit the metal silicide (140) in an opening [0052] on a selected portion of the source/drain (120) (Fig. 5G). Chiu also teaches that metal silicides (140, [0028]) can comprise different metals depending on if they are an n-type (titanium) device or p-type device (cobalt) [0028], and one of ordinary skill in the art would include two different metals if they wanted devices of different polarity.
As the first metal silicide is formed before any etching step, one of ordinary skill in the art can assume that this metal silicide layer is formed around the entirety of the source/drain region (126 of Xie), as shown in Fig. 3G of Chiu. However, as no further information is provided about the second metal silicide, one of ordinary skill in the art would be able to utilize either method depending on the device specifications. The metal silicide of Chiu is formed to provide adhesion between the epitaxial source/drain region and a metal contact without the need of a glue layer ([0022] of Chiu). 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 metal silicide deposition methods of Chiu.
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Regarding claim 22, Xie in view of Chiu teach the method of claim 21. Xie in view of Chiu further teach a material of the first metal silicide layer has a higher melting point than a material of the second metal silicide layer as titanium has a melting point of ~1668C and cobalt has a melting point of ~1495C.
Regarding claim 23, Xie in view of Chiu teach the method of claim 21. The method of claim 21 fails to teach forming a metal cap over the first metal silicide layer prior to forming the second source/drain epitaxy structure. However, Figs. 3G and 5G of Chiu discloses forming a metal cap (seed layer 142, [0030]) above the metal silicide (140, [0028]). Chiu has this seed layer (142) deposited to remove the need for a glue layer between the metal contact and the source/drain much like the metal silicide [0022]. 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 Chiu to include a deposition of a metal cap over the metal silicide layer.
Regarding claim 25, Xie in view of Chiu teach the method of claim 23. Xie further teaches in Fig. 11 forming a metal plug (140, column 9 line 43) interfacing with the metal cap (142 of Chiu, [0030]) and the second metal silicide layer (140 of Chiu, [0028]). Chiu further shows a metal plug (160, [0029]) interfacing elements 142 and 140 in both Figs. 3G and 5G.
Regarding claim 26, Xie in view of Chiu teach the method of claim 21. Xie further teaches forming an isolation structure (128, column 8 line 39) covering the first source/drain epitaxy structure (126, column 7 line 52), wherein the first source/drain epitaxy structure (126) is separated from the isolation structure (128) through the first metal silicide layer (140 of Chiu, [0028]). As stated in claim 21, the first metal silicide is deposited around the entirety of the first source/drain epitaxy structure, so the first metal silicide is between the first source/drain epitaxy and the isolation structure.
Regarding claim 27, Xie in view of Chiu teach the method of claim 26. Xie shows in Fig. 8 the second source/drain epitaxy structure (130, column 8 line 50) interfaces with a top surface of the isolation structure (128, column 8 line 39).
Regarding claim 28, Xie in view of Chiu teach the method of claim 21. Xie shows in Fig. 12 in a cross-sectional view, a widest width of the first source/drain epitaxy structure (126, column 7 line 52) is greater than a widest width of the second source/drain epitaxy structure (130, column 8 line 50).
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Claim(s) 24 is/are rejected under 35 U.S.C. 103 as being unpatentable over Xie in view of Chiu as applied to claim 23 above, and in further view of Chiu et al. (US 2021/0391438 A1, hereafter Chiu2).
Regarding claim 24, Xie in view of Chiu teach the method of claim 23. The method of claim 23 fails to teach wherein the metal cap is made of the first metal element (Ti). However, one of ordinary skill in the art would know that the seed layer can by any suitable material for an n-type device (as titanium is used in n-type devices according to Chiu [0028]). Chiu2 teaches that see layers in n-type devices can be made of titanium [0019]. 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 Chiu to form the metal cap of titanium as Chiu2 teaches.
Claim(s) 29 is/are rejected under 35 U.S.C. 103 as being unpatentable over Xie in view of Chiu, and in further view of Smith et al. (US 2022/0122892 A1, hereafter Smith).
Regarding claim 29, Figs. 1-12 of Xie teaches a method, comprising:
forming a first channel layer (see annotated Fig. 14) and a second channel layer (see annotated Fig. 14);
forming a first source/drain epitaxy structure (126, column 7 line 52) alongside the first channel layer;
forming a first isolation structure (128, column 8 line 39) covering the first source/drain epitaxy structure (126);
after the first isolation structure (128) is formed, forming a second source/drain epitaxy structure (130, column 8 line 50) alongside the second channel layer; and
forming a second isolation structure (132, column 8 line 59) covering the second source/drain epitaxy structure (130).
Xie fails to teach forming a first metal silicide layer over the first source/drain epitaxy structure, and forming a protective layer over the first metal silicide layer;
However, in Figs. 3G and 5G Chiu teaches two methods to deposit metal silicide layers (140, [0028]), one depositing a metal silicide over the entire source drain region (120, [0027]) (Fig. 3G), and one to selectively deposit the metal silicide (140) in an opening [0052] on a selected portion of the source/drain (120) (Fig. 5G). Chiu further discloses forming a protective layer (seed layer 142, [0030]) above the metal silicide (140, [0028])
As the first metal silicide and protective layer are formed before any etching step, one of ordinary skill in the art can assume that this metal silicide layer is formed around the entirety of the first source/drain epitaxy structure (126 of Xie), as shown in Fig. 3G of Chiu. As the second metal silicide is formed after an etching step, one of ordinary skill can assume it is selectively deposited as in Fig. 5G of Chiu. The metal silicide and seed layer of Chiu are formed to provide adhesion between the epitaxial source/drain region and a metal contact without the need of a glue layer ([0022] of Chiu). 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 metal silicide and metal cap deposition methods of Chiu.
Xie in view of Chiu fail to teach forming an opening extending through the first and second isolation structures to expose the second source/drain epitaxy structure and a top surface of the protective layer; forming a second metal silicide layer over the second source/drain epitaxy structure; and forming a contact plug in the opening
However, Smith teaches a similar device in Figs 24-26 in which an opening extending through the first and second isolation structures (both denoted as 905 [0063]) to expose the second source/drain epitaxy structure (1205, [0070]) and a top surface of the protective layer (silicide 2405 [0085] of Smith on source/drain 810 [0063] in Fig. 25, see annotated Fig. 12 of Xie); forming a second metal silicide layer (2405 over source/drain 1205 of Smith) over the second source/drain epitaxy structure (1205 of Smith); and forming a contact plug (2410, [0085]) in the opening. Smith creates one continuous contact to provide a common signal track between the devices [0085], see annotated Fig 12 of Xie for contact plug. 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 Chiu to include the etching and depositing step taught be Smith.
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Regarding claim 30, Xie in view of Chiu and in further view of Smith teach the method of claim 29. Chiu further teaches the protective layer (seed layer, 142, [0030]) is made of a conductive material (the seed layer is taught to comprise various metals or alloys, [0030]).
Regarding claim 31, Xie in view of Chiu and in further view of Smith teach the method of claim 29. Chiu further teaches the protective layer (seed layer, 142, [0030]) and the first metal silicide layer (140, [0028]) comprise a same metal element. The metal silicide layer may comprise cobalt [0028]. The seed layer may also include cobalt [0030].
Regarding claim 32, Xie in view of Chiu and in further view of Smith teach the method of claim 29. Chiu teaches a material of the first metal silicide layer is different from a material of the second metal silicide layer. In particular, the metal silicides (140, [0028]) can comprise different metals depending on if they are an n-type device or p-type device [0028]. Titanium silicide is used in an n-type transistor, while cobalt silicide in a p-type transistor. 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 Chiu in order to have one metal silicide to contain titanium and the other metal silicide to contain cobalt in order to have devices of different polarities.
Regarding claim 33, Xie in view of Chiu and in further view of Smith teach the method of claim 29. Chiu further teaches wherein a material of the first metal silicide layer has a higher melting point than a material of the second metal silicide layer. In particular, Chiu teaches that metal silicides (140, [0028]) can comprise different metals depending on if they are an n-type device or p-type device [0028]. Titanium as a component of titanium silicide in an n-type transistor has melting point of ~1668C, while cobalt of cobalt silicide in a p-type transistor has a melting point of ~1495C. 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 Chiu in order to have one metal silicide to contain titanium and the other metal silicide to contain cobalt in order to have devices of different polarities.
Regarding claim 34, Xie in view of Chiu and in further view of Smith teach the method of claim 29. Xie teaches forming the opening comprises performing an etching process, and the etching process removes a portion of the second source/drain epitaxy structure (130, column 8 line 50). This is inherent, as when normal etching processes occur, etching down to a layer includes etching away a portion of that layer, even on a microscopic level. Thus, etching the hole to the second source/drain epitaxy structures as taught by Xie would include etching some of the second source/drain epitaxy structure.
Regarding claim 35, Xie in view of Chiu and in further view of Smith teach the method of claim 29. Xie in view of Chiu and in further view of Smith teach once the opening is formed, the first metal silicide layer has a more symmetric cross-sectional profile than the second metal silicide layer in a cross-sectional view. See annotated Fig 12 in which the line of symmetry is drawn such that the metal silicide surrounding element 126 is symmetrical, but the lengths of the metal silicide on element 130 is not symmetrical.
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Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to SAMMANTHA K SALAZ whose telephone number is (571)272-2484. The examiner can normally be reached Monday - Friday 8:00am-5:00pm.
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/SAMMANTHA K SALAZ/Examiner, Art Unit 2892
/LEX H MALSAWMA/Primary Examiner, Art Unit 2892