DETAILED ACTION
Table of Contents
I. Notice of Pre-AIA or AIA Status 3
II. Drawings 3
III. Claim Rejections - 35 USC § 112 4
A. Claims 1-20 are rejected under 35 U.S.C. 112(b) as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor regards as the invention. 4
1. Claim 1 4
2. Claim 9 5
3. Claim 15 6
IV. Claim Rejections - 35 USC § 103 6
A. Claims 1-14 and 17-20 are rejected under 35 U.S.C. 103 as being unpatentable over US 2024/0371935 (“Tang”) in view of US 2016/0126102 (“Chang”) and US 2023/0411496 (“Lin”), and as evidenced by US 2007/0111519 (“Lubomirsky”) for claim 3 only. 6
B. Claims 15-16 are rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chang and Lin, as applied to claim 1 above, and further in view of US 2020/0091011 (“Khaderbad”). 19
Conclusion 20
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I. 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 .
II. Drawings
The drawings are objected to under 37 CFR 1.83(a). The drawings must show every feature of the invention specified in the claims. Therefore, the process step of “selectively depositing the third metal layer on the second metal layer”, as required in claim 20, must be shown or the feature(s) canceled from the claim(s). No new matter should be entered.
Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application. Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as “amended.” If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency. Additional replacement sheets may be necessary to show the renumbering of the remaining figures. Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either “Replacement Sheet” or “New Sheet” pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
III. Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
A. Claims 1-20 are rejected under 35 U.S.C. 112(b) as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor regards as the invention.
1. Claim 1
Claim 1 recites the following limitations in lines 1-5:
1. A method of forming a contact structure on a semiconductor substrate, comprising:
removing material from surfaces of [1] a feature formed in a surface of a substrate,
wherein [2] the feature comprises a plurality of contact structures disposed within [3] the feature formed in the substrate,
First, the differing language directed to the “feature” results in limitations [2] and [3] having unclear antecedent basis in the claim.
Second, it is unclear whether “the feature” is formed in the surface of the substrate or within the substrate itself.
Third, the limitation, “the feature comprises a plurality of contact structures disposed within the feature formed in the substrate” is unclear because the contacts cannot simultaneously be part of “the feature” and also be within “the feature” as this would require the contacts, or the feature to be within itself/themselves.
Fourth, it is unclear whether the limitation, “a plurality of contact structures”, has antecedent basis to the “a contact” structure recited in the preamble making the antecedent basis unclear.
For the purposes of examination, the claims will be interpreted as broadly as allowed by the explicit claim language.
Claims 2-20 are rejected for including the same indefinite feature by depending from claim 1.
2. Claim 9
Claims 9 and 10 read,
9. The method of claim 8, wherein filling the feature with the conductor material comprises selectively forming the conductor material on the first metal layer, which comprises exposing the first metal layer to a fluorine-containing precursor.
10. The method of claim 9, wherein selectively forming the conductor material comprises exposing the second metal layer to a metal precursor that comprises molybdenum (Mo).
With regard to claim 9, the first metal layer cannot be exposed to the fluorine-containing precursor because claim 1, from which claim 9 indirectly depends, requires the first metal layer be covered by the selectively deposited second metal layer. Therefore, it is unclear how the first metal layer is exposed to the fluorine-containing precursor. In addition, claim 10, which depends from claim 9, requires the second metal layer to be exposed to a Mo precursor. It is unclear how “the conductor material” can simultaneously be formed by exposing the first metal layer to a fluorine-containing precursor and exposing the second metal layer that is on the first metal layer to a Mo precursor.
As such, it will be presumed that the exposure is indirect and does not require direct contact with the fluorine-containing precursor.
Claims 10 and 11 are rejected for including the same indefinite feature by depending from claim 9.
3. Claim 15
Claim 15 twice recites the limitation, “the contact surface”. There is insufficient antecedent basis in the claim for this limitation.
Claim 16 is rejected for including the same indefinite feature by depending from claim 15.
IV. 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 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 of this title, 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.
A. Claims 1-14 and 17-20 are rejected under 35 U.S.C. 103 as being unpatentable over US 2024/0371935 (“Tang”) in view of US 2016/0126102 (“Chang”) and US 2023/0411496 (“Lin”), and as evidenced by US 2007/0111519 (“Lubomirsky”) for claim 3 only.
Claim 1 reads,
1. A method of forming a contact structure on a semiconductor substrate, comprising:
[1a] removing material from surfaces of a feature formed in a surface of a substrate, wherein
[1b] the feature comprises a plurality of contact structures disposed within the feature formed in the substrate,
[1c] the contact structures comprise a plurality of contacts that each comprise silicon (Si) or silicon germanium (SiGe),
[1d] each of the plurality of contacts are spaced apart in a first direction by a dielectric layer, and
[1e] the method of removing material comprises:
[1e-1]selectively forming a reaction product material over a surface of each of the plurality of contacts; and
[1e-2] heating the substrate to a first temperature to remove the reaction product material from the surface of each of the plurality of contacts;
[2] selectively forming a first metal layer on the surface of each of the plurality of contacts;
[3a] forming a second metal layer on the first metal layer, wherein forming the second metal layer on the first metal layer comprises
[3b] selectively depositing the second metal layer on the first metal layer, and
[3c] selectively forming the second metal layer comprises exposing the surface of the selectively formed first metal layer to a fluorine-free metal containing precursor to form the second metal layer;
[4] filling the feature with a conductor material, wherein the conductor material comprises tungsten (W) or molybdenum (Mo); and
[5] depositing a capping layer on the conductor material.
With regard to claim 1, Tang discloses, generally in Figs. 19-25, 27, and 29,
1. A method of forming a contact structure on a semiconductor substrate, comprising:
[1a] removing material [i.e. “native oxide” formed on the upper surface of the Si or SiGe “etch stop layer 145” (¶¶ 46-49, 62—especially ¶ 48; Fig. 12; see explanation below)] from surfaces of a feature 143 [i.e. “contact openings 143”; Fig. 19] formed in a surface of a substrate 101 [¶ 16], wherein
[1b] the feature 143 (¶ 40) comprises a plurality of contact structures 448(148) [in Figs. 27, 29, and 11 (¶¶ 76, 78, 40-45); see explanation below)] disposed within the feature 143 formed in the substrate 101,
[1c] the contact structures 448(148) comprise a plurality of contacts 448(148) that each comprise silicon (Si) or silicon germanium (SiGe) [¶ 44],
[1d] each of the plurality of contacts 448(148) are spaced apart in a first direction by a dielectric layer 144 [i.e. “dielectric spacers 144” (¶ 38)], and
[1e] the method of removing material [, i.e. the “native oxide” formed on the upper surface of the Si or SiGe etch stop layer 145 (¶ 62)] comprises:
[1e-1]-[1e-2] … [not taught] …
[2] selectively forming a first metal layer 184(177) on the surface of each of the plurality of contacts 448(148) [¶¶ 63-64; the selectivity shown in each of Figs. 20-21, 27, and 29];
[3a]-[3c] … [not taught] …
[4] filling the feature with a conductor material [i.e. 486(186) in Figs. 27 and 25 (¶¶ 66-67, 76) and 686(186) in Figs. 29 and 25 (¶¶ 66-67, 78)], wherein the conductor material comprises tungsten (W) or molybdenum (Mo) [¶ 67: “In some embodiments, the S/D contacts 186 are formed of Co, W, Ru, or Mo.”]; and
[5] depositing a capping layer [486(192) in Figs. 27 and 25 and 692(192) in Figs. 29 and 25 (¶¶ 73, 76, 78)] on the conductor material 486(186), 686(186).
With regard to features [1a]-[1d] of claim 1, the “epitaxial bottom layer blocks 448” shown in each of Figs. 27 and 29 (¶¶ 76, 78) are formed in the same manner as the “epitaxial bottom layer 148” in the embodiment shown in Figs. 9-25 (¶ 5) particularly at Figs. 9-11, as explained at paragraphs [0005] and [0075]-[0078], noting the following:
The epitaxial bottom layer 348 may include the same material as the epitaxial bottom layer 148, and may be deposited using a conformal deposition technique, or any suitable deposition process in a similar fashion as discussed above with respect to FIG. 11. After the formation of the epitaxial bottom layer 348, an etch stop layer (e.g., etch stop layer 145) and a sacrificial layer (e.g., sacrificial layer 150) may be sequentially formed over the epitaxial bottom layer 348.
(Tang: ¶ 75; emphasis added)
[0076] FIG. 27 illustrates a cross-sectional side view of a semiconductor device structure 400, in accordance with some alternative embodiments. This embodiment is similar to the embodiment shown in FIG. 26 except that an epitaxial bottom layer is formed primarily on the first semiconductor layers 106, resulting in a plurality of epitaxial bottom layer blocks 448.
(Tang: ¶ 76; emphasis added)
FIG. 29 illustrates a cross-sectional side view of a semiconductor device structure 600, in accordance with some alternative embodiments. This embodiment is similar to the embodiment shown in FIG. 27 …
(Tang: ¶ 78; emphasis added)
Because the “epitaxial bottom layer blocks 448” are formed in the same manner as “epitaxial bottom layer 148” but for the being formed in blocks separated by the dielectric spacers 144, the rest of the overall contact structures shown in Figs. 27 and 29, including the silicide layer 184, and the contact structures 486 (in Fig. 27) and 686, 692 (in Fig. 29) are also formed by the processes explained in conjunction with the embodiment in Figs. 9-25, particular in Figs. 19-25.
With regard to features [1e]-[1e-2] of claim 1 and claims 2 and 3,
[1e] the method of removing material comprises:
[1e-1] selectively forming a reaction product material over a surface of each of the plurality of contacts; and
[1e-2] heating the substrate to a first temperature to remove the reaction product material from the surface of each of the plurality of contacts;
2. The method of claim 1, wherein the reaction product material will include a silica salt containing material.
3. The method of claim 2, wherein silica salt containing material comprises an ammonium hexafluorosilicate.
As explained above, the contacts 448 in Figs. 27 and 29 as the shared contact 148 in Figs. 9-25; therefore, the Si or SiGe etch stop layer 145 (¶¶ 46-49) would also have been applied to each of the “epitaxial bottom layer blocks 448” in each of Figs. 27 and 29, which would then also have been oxidized to form a “native oxide” (¶ 48) prior to forming the sacrificial layer 150, in order to gain a good etch profile when removing the sacrificial layer 150 to expose the etch stop layer 145 (¶ 48):
[0048] In some embodiments, the etch stop layer 145 is further subjected to an oxidation process to oxidize an outer portion of the etch stop layer 145. The oxidation process converts the outer portion of the etch stop layer 145 to a native oxide layer, which can enhance etching reaction at the surface of the etch stop layer 145. The native oxide layer helps the etch stop layer 145 with better etching profile control at a later stage when removing the subsequent sacrificial layer 150 for the S/D contact formation. In cases where the etch stop layer 145 is formed of silicon, germanium, or silicon germanium, the etch stop layer 145 may have the outer portion in the form of either (Si, Ge)O2 or germanium oxide (e.g., GeO2), and an inner portion containing silicon, germanium, or silicon germanium. The oxidation process may be thermal oxidation process, a rapid thermal oxidation (RTO) process, an in-situ stream generation (ISSG) process, or an enhanced in-situ stream generation (EISSG) process. …
(Tang: ¶ 48; emphasis added)
Although not discussed in Tang, in order to form the silicide layer 184 in the upper surface of the Si or SiGe etch stop layer 145 (Figs. 18-20; ¶¶ ), the “native oxide” (¶ 48) would necessarily have to be removed after removing the Si or SiGe sacrificial layer 150 (¶ 49) by “one or more etching processes, such as an anisotropic etching process. The one or more etching processes may be a plasma etching process employing etchants such as chlorine-containing gas, a bromine-containing gas, and/or a fluorine-containing gas” (¶ 62; Figs. 18-19).
Tang does not, however, explain how the native oxide is removed and therefore does not teach the claimed removal process in features [1e]-[1e-2] of claim 1 and claims 2 and 3.
Chang, like Tang, teaches a method of forming a S/D contact structure 74/80 to S/D regions 38 in a contact opening 60 (Chang: ¶ 27, 36, 39; Fig. 16) including forming a silicide layer 74 on the epitaxial S/D regions 38 (Chang: Fig. 12: ¶ 36). Also like Tang, Chang teaches that, after etching the contact opening 60, the epitaxial S/D regions have “native oxide” regions 64 formed on them (Chang: ¶ 28-29). Chang further teaches that a “pre-clean process” is performed to remove the native oxide (id.) in order to reduce contact resistance (Chang: ¶ 30).
The native-oxide-removing process is “process gas comprising NF3 and NH3, which process gas is also referred to as SiCoNi (a registered trade mark of Applied Materials, Inc.)” (Chang: ¶ 31)—which is the same pre-clean process as that disclosed in the Instant Application and claimed in features [1e]-[1e-2] of claim 1 and claims 2 and 3. In this regard, Chang explained that the SiCoNi process includes the following:
[1e] the method of removing material [i.e. native oxide 64 relative to epitaxial Si or SiGe S/D region 38 (Chang: ¶ 29)] comprises:
[1e-1] selectively forming a reaction product material 70 [i.e. NH4SiF6] over a surface of each of the plurality of contacts 38 [¶¶ 31-32]; and
[1e-2] heating the substrate to a first temperature [100 ℃ to 300 ℃] to remove the reaction product material 70 from the surface of each of the plurality of contacts 38 [¶¶ 33-34; Fig. 10];
2. The method of claim 1, wherein the reaction product material will include a silica salt containing material [i.e. NH4SiF6 (¶ 32: Eq. 1)].
3. The method of claim 2, wherein silica salt containing material comprises an ammonium hexafluorosilicate [i.e. NH4SiF6 (¶ 32: Eq. 1)].
That this is the SiCoNi process and that NH4SiF6 is ammonium hexafluorosilicate is evidenced by Lubomirsky—which is commonly assigned to the same assignee as is the Instant Application (at ¶¶ 203-216—especially ¶¶ 204 and 213-216).
Inasmuch as Tang merely fails to provide the details as to how the “native oxide” is removed from each of the Si or SiGe etch stop layers 145 on each of the epitaxially-grown Si or SiGe S/D contact blocks 448 after the Si or SiGe sacrificial layer 150, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to use the SiCoNi process taught in Chang to remove said native oxide from said etch stop layers 145, because Chang teaches that the SiCoNi process removes native oxide from S/D region regions and thereby results in lower contact resistance (Chang: ¶ 30). (See MPEP 2143(I)(A), (C), and (E).)
With regard to features [3a]-[3c] of claim 1 and claims 5-11 and 20,
[3a] forming a second metal layer on the first metal layer, wherein forming the second metal layer on the first metal layer comprises
[3b] selectively depositing the second metal layer on the first metal layer, and
[3c] selectively forming the second metal layer comprises exposing the surface of the selectively formed first metal layer to a fluorine-free metal containing precursor to form the second metal layer;
5. The method of claim 1, wherein the fluorine-free metal containing precursor comprises tungsten and a halogen containing gas.
6. The method of claim 5, wherein the fluorine-free metal containing precursor is selected from a group consisting of tungsten pentachloride (WCl5), tungsten hexachloride (WCl6), tungsten pentabromide (WBr5), and tungsten hexabromide (WBr6).
7. The method of claim 1, wherein the fluorine-free metal containing precursor comprises molybdenum and a halogen containing gas.
8. The method of claim 7, wherein the fluorine-free metal containing precursor is selected from a group consisting of molybdenum pentachloride (MoCl5), molybdenum hexachloride (MoCl6), and molybdenum oxytetrachloride (MoOCl4).
9. The method of claim 8, wherein filling the feature with the conductor material comprises selectively forming the conductor material on the first metal layer, which comprises exposing the first metal layer to a fluorine-containing precursor.
10. The method of claim 9, wherein selectively forming the conductor material comprises exposing the second metal layer to a metal precursor that comprises molybdenum (Mo).
11. The method of claim 9, wherein selectively forming the conductor material comprises exposing the second metal layer to a metal precursor that comprises tungsten hexafluoride (WF6).
20. The method of claim 1, further comprising
[1] forming a third metal layer on the second metal layer,
[2] wherein forming the third metal layer on the second metal layer comprises selectively depositing the third metal layer on the second metal layer.
Tang does not provide the details of the CVD, PVD, or ALD process used to form the (metal S/D contact 686)/(contact metal layer 692) in Fig. 29 or metal contact 486 in Fig. 27, which is equivalent to, e.g., the (metal S/D contact 186)/(contact metal layer 192) in Fig. 25 [¶ 73]).
Lin, like Tang, teaches a method of forming a S/D contact structure 910/920/930 to S/D regions 356 in a contact opening 820 (Lin: ¶¶ 43-80; Figs. 9A-9E) that may be applicable to gate-all-around (GAA) transistors (Lin: ¶ 13) as in Tang, including selectively forming a silicide layer 910 on the epitaxial S/D regions 356 (Lin: Fig. 9B: ¶ 44) and a contact metal fill 930 that may be W or Mo (Lin: ¶ 75; Fig. 9D).
Lin further teaches that, before the metal fill 930 is formed a “metal capping layer 920” is selectively deposited on the metal silicide 910 that is made of either W or Mo, using fluorine-free precursors, e.g. MoClx or WClx (Lin: ¶ 46)—as required by claims 5-8—in order to provide a nitride-free or nitrogen-free surface on the silicide which reduces contact resistance relative to a metal nitride and aids in the bottom-up filling of the contact opening with the W or Mo contact fill 930 (Lin: ¶ 45) that is selectively deposited on the metal capping layer 920 using fluorine-containing precursors (Lin: ¶¶ 75, 78, 80)—as further required by claims 9-11. By “selectively deposited” with regard to the W or Mo contact fill 930 is meant the following:
[0076] In some embodiments, parameters of the deposition process 950 for the conductive material 930 are tuned, such that the conductive material 930 is deposited in the openings 810, 820 and 830 in a non-conformal bottom-up manner from the metal capping layer 920. In some embodiments, the parameters of the deposition process 950 are tuned, such that a deposition rate of the conductive material 930 on materials of the first ILD 362 and the second ILD 780 is reduced or suppressed compared to a deposition rate of the conductive material 930 on a material of the metal capping layer 920. In this manner, the conductive material 930 is selectively formed on the metal capping layer 920 and fills the openings 810, 820 and 830 in a bottom-up manner, which allows for reducing or avoiding the formation of voids in the conductive material 930.
(Lin: ¶ 76; emphasis added)
Inasmuch as Lin is merely silent to the process by which the contact fill 486(186), 686 in the embodiments shown in Figs. 27 and 29, respectively, it formed, it would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to use the process taught in Lin, including (1) selectively forming a nitrogen-free Mo or W capping layer, i.e. the claimed “second metal layer” on each of the silicide layers 184 on each of the contact blocks 448, using fluorine-free precursors, e.g. MoClx or WClx (Lin: ¶ 46) in order to reduce contact resistance and aid the bottom-up filling of the Mo or W contact fill 486, 686, as taught in Lin (Lin: ¶ 45), and (2) selectively forming the Mo or W contact fill 486, 686 on the metal capping layer using the fluorine-containing precursors (Lin: ¶¶ 78, 80) in order to use a bottom-up fill process that reduces void formation and thereby reduces resistance of the contact plugs, as taught in Lin (Lin: ¶ 76). As such, Lin may be seen as either filling the missing descriptive information on the contact fill not discussed in Tang or may be seen as an improvement to Tang in this aspect. (See MPEP 2143.)
With regard to claim 20, as explained in paragraph [0076] of Lin, Lin further teaches,
20. The method of claim 1, further comprising
[1] forming a third metal layer [i.e. portion of 930 that is initially selectively formed on the metal capping layer 920] on the second metal layer 920,
[2] wherein forming the third metal layer 930 on the second metal layer 920 comprises selectively depositing the third metal layer 930 on the second metal layer 920.
Thus forming the Mo or W fill process of Lin using the fluorine-containing Mo or W precursors to form the contact fill 486(186), 686 in Tang initially selectively forms the Mo or W fill on the metal capping layer 920 of Lin used on the silicide 184 of Tang, as explained above (Lin: ¶ 76, supra) until the portions selectively growing from the contacts 448 coalesce to form the Mo or W metal contact fill 486, 686.
This is consistent with the Instant Application, which forms each of the second metal layer 404, the third metal layer 409, and the “conductor material” filling the feature from the same metal:
[0053] In FIG. 4C, the second metal layer 404 shown is formed by a second metal deposition process on top of the metal silicide layer 402. In one or more embodiments, the metal utilized for the second metal deposition process may comprise a fluorine-free tungsten (FFW) containing precursor. In one or more embodiments, the FFW containing precursor may comprise tungsten pentachloride (WCl5), tungsten hexachloride (WCl6), … In yet other embodiments, the metal utilized for the second metal deposition process may comprise molybdenum (Mo) that is formed by use of molybdenum containing precursor such as molybdenum pentachloride (MoCl5), molybdenum hexachloride (MoCl6), or molybdenum oxytetrachloride (MoOCl4)
(Instant Specification: ¶ 53; emphasis added)
the third metal layer 409 comprises W or Mo
(Instant Specification: ¶ 72; emphasis added)
[0074] In FIG. 4H, the opening 401 is shown filled with a conductor material 406 formed by a fourth metal deposition process on top of the third metal layer 409. In one or more embodiments, the conductor material 406 utilized for the fourth metal deposition process may comprise a precursor that comprises tungsten hexafluoride (WF6). In yet other embodiments, the conductor material utilized for the fourth metal deposition process may comprise molybdenum (Mo), which can, for example, be deposited by use of a molybdenum pentachloride (MoCl5) or molybdenum hexafluoride (MoF6) precursor.
(Instant Specification: ¶ 74; emphasis added)
With regard to feature [5] of claim 1, Tang shows the “contact metal layer 692”, i.e. the claimed “capping metal” in the embodiment in Fig. 29, it is not shown in the embodiment in Fig. 27. However, Tang explains that the contact metal layer 192, 692 reduces the overall contact resistance of the S/D contact (¶ 73).
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to include the contact metal layer 192 in the embodiment shown in Fig. 27 in order to reduce the contact resistance, as suggested in Tang (¶ 73).
This is all of the limitations of claims 1-3, 5-11, and 20.
With regard to claim 4, Tang and Lin each further disclose,
4. The method of claim 3, wherein the first metal layer 184(177) comprises a metal silicide layer that comprises titanium [Tang: ¶¶ 63-64; Lin: (see discussion under claim 1)].
Claims 12, 13, and 17 read,
12. The method of claim 1, wherein the first metal layer formed on the exposed surfaces comprises has a thickness of greater than or equal to about three nanometers.
13. The method of claim 12, wherein the first metal layer on the exposed surfaces comprises a first metal layer target thickness determined by a corresponding Schottky Barrier Height (SBH).
17. The method of claim 12, wherein the first metal layer on the exposed surfaces comprises a first metal layer target thickness determined by a corresponding gate contact structure resistance (Rc).
Tang does not teach the thickness of the metal silicide 184, i.e. the claimed “first metal layer”.
Lin further teaches that the metal silicide 910 is formed to be from about 1 nm to about 10 nm (Lin: ¶ 43).
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to make the thickness of the silicide 184 in Tang to be from 1 nm to 10 nm, e.g. any of 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, because Lin teaches that these thicknesses are suitable for reducing the contact resistance.
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. See In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); MPEP 2144.05(I)). In such a situation, Applicant must show that the particular ranges are critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range. See In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990). (See MPEP 2144.05(III)(A); emphasis added.)
Because the thickness can be greater than 3 nm, it is held, absent evidence to the contrary, that the thickness of the silicide 184 is inherently “determined by a corresponding Schottky Barrier Height (SBH)” and/or “a corresponding gate contact structure resistance (Rc)”, as the purpose of the silicide is to reduce the contact resistance, as is exceedingly well known in the art. As such, the burden of proof is shifted to Applicant to prove the contrary. (See MPEP 2112(I)-(V).)
Claim 14 reads,
14. The method of claim 1, wherein selectively depositing the second metal layer on an outer surface of the first metal layer on the exposed surfaces comprises a second metal layer thickness greater than or equal to about three nanometers.
As explained above under claim 1, the second metal layer, i.e. the metal capping layer 920 of Lin 920 is used on the silicide layer 184 of Tang. Lin further teaches that the thickness of the metal capping layer 920 is from 1 nm to 20 nm.
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to make the thickness of the metal capping layer 920 of Lin used in Tang to be from 1 nm to 20 nm, e.g. 3 nm through 20 nm, because Lin teaches that these thicknesses are suitable for it its intended purpose (supra).
In the case where the claimed ranges “overlap or lie inside ranges disclosed by the prior art” a prima facie case of obviousness exists. See In re Wertheim, 541 F.2d 257, 191 USPQ 90 (CCPA 1976); MPEP 2144.05(I)). In such a situation, Applicant must show that the particular ranges are critical, generally by showing that the claimed range achieves unexpected results relative to the prior art range. See In re Woodruff, 919 F.2d 1575, 16 USPQ2d 1934 (Fed. Cir. 1990). (See MPEP 2144.05(III)(A); emphasis added.)
Claim 18 reads,
18. The method of claim 1, wherein the second metal layer [i.e. the metal capping layer 920 of Mo or W of Lin used in Tang] provides an Oxygen (O) barrier, or a Fluorine (F) barrier, or both an O and F barrier.
Inasmuch as Lin uses the same metals, i.e. W or Mo, as used in the Instant Application for the second metal layer formed using F-free precursors, and then formed the fill using a F-containing Mo or F precursor, it is held, absent evidence to the contrary, that the second metal layer of Tang/Lin is a barrier to each of F and O, as evidenced by the admissions in the Instant Application. As such, the burden of proof is shifted to Applicant to prove the contrary. (See MPEP 2112(I)-(V).)
With regard to claim 19, Tang modified accord to Lin as explained above, further teaches,
19. The method of claim 1, wherein the second metal layer [i.e. the metal capping layer 920 of Mo or W of Lin used in Tang] acts as a seed layer for the conductor material 486, 686 [i.e. the W or Mo fill of Tang formed by the process of Lin because Lin explains that the W or Mo fill 930 selectively deposits on the metal capping layer 920 (Lin: ¶ 76, supra)].
B. Claims 15-16 are rejected under 35 U.S.C. 103 as being unpatentable over Tang in view of Chang and Lin, as applied to claim 1 above, and further in view of US 2020/0091011 (“Khaderbad”).
Claims 15 and 16 read,
15. The method of claim 1, wherein selectively forming a first metal layer on the plurality of contacts comprises introducing a hydrogen-containing reducer and a first metal containing precursor to the contact surface such that a first metal layer forms on top of the contact surface that comprises silicon or silicon germanium.
16. The method of claim 15, wherein the hydrogen-containing reducer includes molecular hydrogen (H2).
The prior art of Tang in view of Chang and Lin, as explained above, teaches each of the features of claim 1.
Tang further discloses that the first metal layer 177 from which the silicide layer 184 is formed may be selectively formed by, e.g. CVD or ALD (Tang: ¶ 63; Figs. 20-21), which necessarily requires a metal-containing precursor but does not provide the process conditions and does not consequently disclose claimed “hydrogen-containing reducer” of H2 as required by of claims 15 and 16.
Lin also teaches that the silicide 910 can be selectively formed on the exposed S/D regions 356 using CVD or ALD (Lin: ¶ 44) but does not indicate the metal precursor or the deposition conditions and does not consequently disclose claimed “hydrogen-containing reducer” of H2 as required by of claims 15 and 16.
Khaderbad, like each of Tang and Lin, selectively deposits a silicide layer 360, e.g. titanium silicide (TiSix), on exposed epitaxial layer 330A of a source/drain regions 220 (Khaderbad: ¶ 39; Fig. 4). Khaderbad further teaches that the selective deposition used a precursor, e.g. TiCl4, and hydrogen (H2) (id.).
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to use, e.g., TiCl4, and hydrogen (H2) to deposit the silicide layer 184 in Tang using the process in Khaderbad because Tang desires selective deposition of the metal silicide layer 184, as shown in Figs. 20-21, 27 and 29 but fails to provide the deposition details such that one having ordinary skill in the art would use known processes suitable for selectively depositing metal silicide on epitaxial regions of the S/D contact regions, such as the selective deposition process taught in Khaderbad.
This is all of the limitations of claims 15 and 16.
Conclusion
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Signed,
/ERIK KIELIN/
Primary Examiner, Art Unit 2814