DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 08/22/2025 has been entered.
Status of the Claims
This is a non-final office action in response to the applicant’s arguments and remarks filed on 08/22/2025. Claims 1-20 are pending in the current office action. Claims 1, 10, 14 and 15 have been amended by the applicant.
Status of the Rejection
All 35 U.S.C. § 103 rejections from the previous office action are withdrawn in view of the Applicant’s amendment.
New grounds of rejection under 35 U.S.C. § 103 are necessitated by the amendments.
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 1 and 4 are rejected under 35 U.S.C. 103 as being unpatentable over Ambati et al. (US-20220344165-A1) in view of Flachowsky et al. (US-20130029464-A1).
Regarding Claim 1, Ambati teaches a method for fabricating a semiconductor device (Paragraph [0002] methods related to the manufacture of semiconductor devices), the method comprising:
forming a pattern of trenches (Paragraph [0007], Figure 3A shows an embodiment of the device created by the method that includes a pattern of trenches) by etching a first layer formed over an underlying layer of a substrate (Paragraph [0020] teaches that the substrate can be a SOI (silicon-on-insulator) type substrate, such that the substrate (element 101) shown in Figure 3A comprises an insulator layer under the layer shown in the figure), each of the trenches having an aspect ratio (AR) in a range with a lower limit of a first AR and an upper limit of a second AR, the pattern including a first trench having the first AR and a second trench having the second AR, the AR of a trench being a ratio of its depth to its opening width (Paragraphs [0037-0038], Figure 3A, trenches have an aspect ratio that can be defined by H, the height of the fins on either side of the trench, and P-W, the pitch between fins minus a width of a fin. See Reference Image 1 below)
Reference Image 1:
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Ambati fails to teach that the etching comprises: executing a first recipe in a plasma chamber to anisotropically etch the first layer for a first duration by flowing etchants through the chamber, an etch rate of the first layer being higher on the first trench relative to that on the second trench; and after executing the first recipe, executing a second recipe in the plasma chamber to etch the first layer anisotropically and concurrently deposit oxygen-containing etch byproducts to passivate exposed portions of sides of the trenches, the etch rate of the first layer being lower on the first trench relative to that on the second trench, wherein executing the second recipe increases a relative oxygen content in the plasma chamber from a first value during the executing of the first recipe to a second value.
However, Ambati does teach a first etching process and a second etching process (Paragraph [0012] method includes multiple etching processes that includes a “first etching process” and a “second etching process”) that are to be conducted in a plasma chamber and these etching processes are anisotropic (Paragraph [0033], first and second etching processes are in part controlled by power source of the plasma etching chamber in which the etching is conducted. There is an “anisotropic behavior of the etching processes”). Ambati teaches that the first etching process includes O2 within the etching chemistry and that the sidewalls are passivated, in part, by oxygen (Paragraph [0030]). Ambati further teaches that that the high aspect ratio features etch faster than the low aspect ratio features (Paragraph [0030] the nested fins (the high aspect ratio features, 111N in Figure 3A) etch faster than the isolated fins (the low aspect ratio features, 111I in Figure 3A)). Ambati teaches a second etching process where the low aspect ratio features etch faster than the high aspect ratio features (Paragraph [0031] the isolated fins (the low aspect ratio features, 111I in Figure 3A) etch faster than the nested fins (the high aspect ratio features, 111I in Figure 3A)). Ambati teaches that during the first etching process the etch chemistry used comprises HBr, O2, and CF4 (Paragraph [0030]) and during the second etching process the etch chemistry used comprises Cl2, Ar, and CH4 (Paragraph [0031]). Since the second etching process does not include oxygen in the etch chemistry, the relative oxygen content in the chamber during the second etching process is lower than it is during the first etching process which does include oxygen in the etch chemistry.
Ambati further teaches that the multiple etching processes taught are used to produce uniform fin widths when nested and isolated fins are formed on the same structure (Paragraph [0010]). Ambati teaches that this goal is accomplished by one etching process that has a higher lateral passivation rate for isolated fins than nested fins (Paragraph [0012] “the first substrate etching process may have a lateral passivation rate that is greater for isolated fins than the lateral passivating rate for nested fins”) and the another etching process that has a greater lateral etch rate for isolated fins than nested fins (Paragraph [0012] “The second etching process may equalize the widths of the fins by utilizing an etching chemistry that has a lateral etch rate that is greater for isolated fins than the lateral etch rate for nested fins”), where the use of both etching processes on the same substrate can result in equal widths for both types of fins.
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by conducting the taught “second etching process” as the first recipe, and then conducting the taught “first etching process” as the second recipe. With this modification, all of the limitations of claim 1 would be met.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The taught “first etching process”, conducted as the second etching step in the modified method, would have predictable result of conducting a partial etching of the features where the etching process has a higher passivation rate for the isolated fins compared to the nested fins. The taught “second etching process”, conducted as the first etching step in the modified method, would have predictable result of conducting a partial etching of the features where the etching process has a higher etching rate for the isolated fins compared to the nested fins. After both of these etching processes are conducted the modified method would have the predictable result of producing isolated and nested fins with equal widths. See MPEP 2143(I)(A).
Ambati fails to teach that the first layer comprises amorphous silicon.
Ambati teaches that substrate to be processed can be composed of any material suitable for semiconductor device fabrication (Paragraph [0020]) but fails to mention amorphous silicon as a possible material.
Flachowsky teaches methods related to fabricating integrated circuits on semiconductor substrates (Paragraph [0005]). Flachowsky teaches a substrate that comprises a gate insulator layer, that can be silicon oxide, that is overlying a silicon substrate (Paragraph [0015] Figure 1 gate insulator layer (element 114) is formed over silicon substrate (element 116). The gate insulator layer can be silicon oxide). Flachowsky teaches that the substrate can comprise a gate electrode material, that can be amorphous silicon, that is overlying the gate insulator layer (Paragraph [0015] gate electrode material (element 118) is overlying the gate insulator layer (element 114). The gate electrode material can be amorphous silicon).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by selecting as the unspecified substrate, a substrate that comprised an amorphous silicon layer overlying an underlying layer as taught by Flachowsky.
This modification would have been the simple substitution of one substrate suitable for forming semiconductor devices with another. The simple substitution of one known element for another is likely to be obvious when predictable results are achieved. See MPEP §2143(B). Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP § 2144.07.
Regarding Claim 4, Ambati teaches executing the first recipe comprises maintaining a ratio of a flow rate of etchants to a flow rate of oxygen to a first ratio, and wherein executing the second recipe comprises maintaining a ratio of a flow rate of etchants to a flow rate of oxygen to a second ratio, the second ratio being lower than the first ratio (Note: the relationship of the second ratio being lower than the first ratio is being interpretated here to mean that the value of the flow rate of etchants in the second recipe divided by the total flow rate of oxygen and etchants in the second recipe is smaller than the value of the flow rate of etchants in the first recipe divided by the total flow rate of oxygen and etchants in the first recipe. Paragraph [0030] the flow rates of the “first etching process”, equivalent to the second recipe as outlined above, include a HBr flow rate of 200 sccm and CF4 flow rate of 15 sccm, both of which may be considered etchants, and a O2 flowrate of 3.3 sccm. Paragraph [0031] the flow rates of the “second etching process”, equivalent to the first recipe as outlined above, includes a Cl2 flow rate of 100 sccm, which can be considered an etchant. The taught “second etching process” includes no oxygen flow rate. Therefore the second ratio can be considered ((200+15)/(200+15+3.3))= 0.98, and the first ratio can be considered (100/100)=1, and 0.98 is lower than 1).
Claims 2 and 3 are rejected under 35 U.S.C. 103 as being unpatentable over Ambati in view of Flachowsky as applied to claim 1 above, and further in view of Kong et al. (US-20150099345-A1).
Regarding Claim 2, modified Ambati teaches all the limitations of claim 1 as outlined above. Ambati further teaches that the first recipe comprises exposing the substrate to plasma (Paragraph [0035] “second etching process” utilizes a plasma). Ambati further teaches that the first recipe supplies an etching chemistry that comprises halogens, hydrogen, and an inert species (Paragraph [0031] etching chemistry comprises Cl2 (a halogen), Ar (an inert gas), and CH4 (containing hydrogen)). Ambati further teach the flow rates of the “first etching process”, equivalent to the second recipe as outlined above, include a HBr flow rate of 200 sccm and CF4 flow rate of 15 sccm, both of which may be considered etchants, and a O2 flowrate of 3.3 sccm (Paragraph [0030]).
Ambati fails to teach an embodiment of the plasma of the first recipe that comprises halogens, hydrogen, an inert species, and oxygen.
Kong teaches methods related to semiconductor fabrication (Paragraph [0002]). Kong teaches methods of forming features in a substrate that include plasma etching (Paragraph [0005] and [0027] where the process gas is formed into a plasma). Kong teaches a process gas for use in plasma etching that contains halogens, hydrogen, an inert species, and oxygen (Paragraph [0026] an example process gas includes hydrogen bromide (includes hydrogen and bromide, a halogen), chlorine (a halogen), oxygen, and helium or argon (an inert species). Kong teaches that during the first duration the flow rate of chlorine can be 50-1000 sccm and the flow rate of hyrdrogen bromide can be 10-500 sccm (Paragraph [0022], both chlorine and hydrogen bromide can be considered etchants). Kong teaches that during the first duration the flow rate of oxygen can be 100 or less (Paragraph [0024]).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by using the process gas taught by Kong as the process gas for forming the plasma.
This modification would have been the simple substitution of one plasma process gas for another. The simple substitution of one known element for another is likely to be obvious when predictable results are achieved. See MPEP §2143(B). Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP § 2144.07. It would be obvious to one of ordinary skill in the art to substitute the process gas taught by Ambati with process gas taught by Kong since this process gas is known to be capable of forming an etching plasma and the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP 2144.07.
It would have been obvious to one of ordinary skill in the art to have selected and incorporated a flow rate for chlorine at a level within the disclosed range of 50-1000 sccm, a flow rate for hydrogen bromide at a level within the disclosed range of 10-500 sccm and a flow rate for oxygen with in the disclosed range of 100 sccm or less, including selections for the three flow rates at amounts such that the relative oxygen content in the plasma chamber during the claimed first recipe was less than the oxygen content provided in the claimed second recipe, as required by claim 1. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Regarding Claim 3, modified Ambati teaches executing the first recipe comprises maintaining a chamber pressure of the plasma chamber at a first chamber pressure (Paragraph [0031] pressure is 1-2 mTorr), and wherein executing the second recipe comprises maintaining a chamber pressure of the plasma chamber at a second chamber pressure (Paragraph [0030] pressure is 3.1 mTorr).
Ambati fails to teach that the second chamber pressure being lower than the first chamber pressure.
Kong teaches methods related to semiconductor fabrication (Paragraph [0002]). Kong teaches methods of forming features in a substrate that include plasma etching (Paragraph [0005]). Kong teaches that during plasma etching the pressure is between about 3 to 50 mTorr (Paragraph [0028]).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by using the pressure taught by Kong during the first recipe.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The use of the pressure taught by Kong during the first recipe would have had the predictable result of allowing the etching process to be conducted. See MPEP 2143(I)(A).
It would have been obvious to one of ordinary skill in the art to have selected and incorporated a pressure during the first recipe at a level within the disclosed range of 3-50mTorr, including at amounts greater than 3.1mTorr, such that the second chamber pressure is lower than the first chamber pressure as claimed. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Claim 5 is rejected under 35 U.S.C. 103 as being unpatentable over Ambati in view of Flachowsky as applied to claim 1 above, and further in view of Kim et al. (US-20150064919-A1) and Hawke et al. (US-20150021745-A1).
Regarding claim 5 modified Ambati teaches all the limitations of claim 1 as outlined above.
Ambati fails to teach terminating the execution of the second recipe after a predetermined second duration, wherein the second duration is configured to produce, at the end of the second duration, an exposed portion of a surface of the underlying layer in the second trench, and wherein the first duration is configured to produce, at the end of the first duration, an exposed portion of a surface of the underlying layer in the first trench.
Kim teaches methods of etching high aspect ratio and low aspect ratio features on a substrate (Paragraph [0002]). Kim teaches a method that includes two distinct plasma etching steps that etch the features (Paragraph [0005] step (c) and step (d) both etch the features). Kim teaches one etching step includes etching a high aspect ratio feature to expose the bottom of the high aspect ratio feature (Paragraph [0022] Figure 1, element 106 is the step of etching. Figure 2D and 2E, Figure 2D showing the etching step in process and Figure 2E showing the high aspect ratio feature (element 202) after the etching having an exposed bottom (element 208)). Kim teaches another etching step includes etching a low aspect ratio feature to expose the bottom of the low aspect ratio feature (Paragraph [0023] Figure 1, element 108 is this etching step. Figure 2E and 2F, Figure 2E showing the etching in process and Figure 2F showing the low aspect ratio feature (element 204) after the etching having an exposed bottom (element 210)). Kim teaches that the etching processes are conducted as needed to reach the desired depth (Paragraph [0025], steps 106 and 109 can be repeated until the low aspect ratio feature and high aspect ratio feature have the desired depth).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati such that the second recipe is conducted expose a desired bottom of the high aspect ratio feature (the claimed second trench) and the first recipe is conducted to expose the expose a desired bottom of the low aspect ratio feature (the claimed first trench).
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result of causing the two etching recipes to etch the two features to the desired depth. See MPEP 2143(I)(A).
The method of modified Ambati as outlined above, fails to explicitly teach that a desired bottom of the features is such that they expose an underlying layer. However, Ambati teaches that the substrate to be etched contains an underlying layer (Paragraph [0020] substrate may be a silicon-on-insulator, such that the silicon layer being etched has an insulator layer under it).
Hawke teaches a method of etching a substrate to form a higher aspect ratio feature and a lower aspect ratio feature (Paragraph [0006]). Hawke teaches that a desired end point for an etching of both a higher aspect ratio feature and a lower aspect ratio feature is when those features are etched through one layer to expose an underlying layer (Paragraph [0049] during a second etching stage both “wider features” (equivalent to lower aspect ratio features) and “narrow features” (equivalent to higher aspect ratio features) are etched until they both break through to an underlying layer).
It would have been obvious to one of ordinary skill in the art to have modified the method outlined above such that the desired depth of the features being etched exposed the underlying insulator layer.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result of both the high aspect ratio feature and the low aspect ratio feature having an exposed underlying insulator layer at their bottom after the etching recipes. See MPEP 2143(I)(A).
Claims 6-9 are rejected under 35 U.S.C. 103 as being unpatentable over Ambati in view of Flachowsky as applied to claim 1 above, and further in view of Ko et al. (US-20180076083-A1).
Regarding Claim 6, modified Ambati teaches all the limitations of claim 1 as outlined above.
Ambati fails to teach wherein the etching further comprises: after executing the second recipe, executing an overetch recipe in the plasma chamber to remove material from the first layer for an overetch duration.
Ko teaches methods of processing a substrate (Paragraph [0005]). Ko teaches a method to remove a footing (Paragraph [0041] Figure 3, method (element 300) can be used to remove a footing). Ko teaches a method that includes an overetch step performed after other processing steps (Paragraph [0053] an overetch step is performed after removal operations). Ko teaches that this overetch is used to fully remove parts of the layer that had been etched in the previous steps (Paragraph [0053] Figures 4A-4D overetch is performed to fully remove nitride layer (element 410), while nitride layer (element 410) had been previously subject to removal operations to form the features).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati as outlined above by including the overetch step taught by Ko to remove material from the layer that had been etched by the process outlined above.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result of removing any unwanted remaining material, such as a footing, from the layer previously etched. See MPEP 2143(I)(A).
Regarding Claim 7, modified Ambati, as outlined above in regards to claim 6, teaches wherein executing the first recipe comprises powering a plasma in the plasma chamber with a first radio frequency (RF) bias signal that is pulsed RF signal (Ambati Paragraph [0033], the RF power source can be pulsed during etching processes), and wherein executing the overetch recipe comprises powering the plasma in the plasma chamber with an overetch radio frequency (RF) bias signal that is a continuous wave RF signal (Ko Paragraph [0043] power is provided at a set wattage to form the plasma. Ko Paragraph [0034] RF coupled electrodes can energize the plasma and use set frequencies, such as 13.56MHZ or 60MHz).
Regarding Claim 8, modified Ambati, as outlined above in regards to claim 6, teaches wherein executing the first recipe comprises maintaining a chamber pressure of the plasma chamber at a first chamber pressure (Ambati Paragraph [0031] pressure is to be 1-2 mTorr); and wherein executing the overetch recipe comprises maintaining a chamber pressure of the plasma chamber at a overetch chamber pressure (Ko Paragraph [0056] pressure should be about 20 mTorr) , wherein the overetch chamber pressure is higher than first chamber pressure (overetch pressure of 20 mTorr is higher than first chamber pressure of 1-2 mTorr).
Modified Ambati fails to teach an embodiment wherein executing the first recipe comprises flowing etchants at a first flow rate; and wherein executing the overetch recipe comprises flowing etchants at an overetch flow rate, wherein the overetch flow rate is higher than the first flow rate.
While Ko teaches that the overetch recipe comprises a flow rate of etchants where fluorine-containing precursors, such as fluorine-substituted hydrocarbons, are used (Paragraph [0046] plasma is formed from fluorine-containing precursor, which can be a fluorine-substituted hydrocarbon, that is flowed to the plasma region to generate plasma), Ko fails to teach a flowrate for the etchants.
However, Ambati further teaches that the first recipe comprises a flow rate of etchants (Paragraph [0031] a flow rate of Cl2 is 100 sccm, a flow rate for a combination of Ar and CH4 is 28 sccm. Where Cl2 is considered an etchant here). Ambati additionally teaches a method of etching that comprises utilizing a gas mixture of O2, Ar, and CH3F. Where CH3F has a flow rate 150-200 sccm (Paragraph [0025] a method of etching can use CH3F as an fluourine source for etching. Paragraph [0026] a flow rate for CH3F can be 150-200 sccm).
It would have been obvious to one of ordinary skill in the art to have selected as a fluorine-substituted hydrocarbon flow rate, as required by the teachings of Ko, a CH3F flow rate of 150-200 sccm as taught by Ambati. With this modification, the overetch recipe would contain a flow rate of etchants of 150-200 sccm, which is greater than the flow rate of 100 sccm for etchants in the first recipe, thereby meeting the claimed limitation.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result providing the overetch process a suitable flowrate of etchants. See MPEP 2143(I)(A).
Regarding Claim 9, modified Ambati, as outlined above in regards to claim 6, teaches wherein the overetch duration is configured to produce a vertical side profile with no footing proximate a base of the second trench (Ko Paragraphs [0055] and [0057] Figure 4C displays the substrate during the overetch process. Figure 4D displays the substrate after the overetch process, where no footing is present and the features have vertical side profiles).
Modified Ambati as outlined above fails to teach wherein the overetch duration is configured to expose a surface of the underlying layer.
However, Ko teaches that the overetch operation removes a footing as well as a portion of an underlying layer (Paragraphs [0053] and [0057], Figures 4A-4D etching is conducted to remove modified regions of footing (element 407) and the pad oxide layer (element 405), which is an underlying layer to nitride layer (element 410) as seen in Figure 4A. This exposes a portion of the pad oxide layer). Additionally, Ambati teaches that the substrate to be etched contains an underlying layer (Paragraph [0020] substrate may be a silicon-on-insulator, such that the silicon layer being etched has an insulator layer under it).
It would have been obvious to modified the method outlined above in regards to claim 6 such that the features were configured such that the underlaying insulator layer of the substrate is exposed when the features are etched in the overetch process, as taught by Ko.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result the overetch process exposing a portion of an underlying layer. See MPEP 2143(I)(A).
Claims 10-11 are rejected under 35 U.S.C. 103 as being unpatentable over Ambati in view of Flachowsky and Kong.
Regarding Claim 10, Ambati teaches a method for fabricating a semiconductor device (Paragraph [0002] methods related to the manufacture of semiconductor devices), the method comprising:
in a plasma chamber (Paragraph [0033] first and second etching processes are conducted with a plasma etching chamber), anisotropically etching a silicon layer formed over an underlying layer of a substrate (Paragraph [0030] Figure 3A features are formed in a substrate. Paragraph [0020] substrate can be a SOI (silicon on insulator) substrate, such that the layer etched is silicon and the claimed underlying layer is the insulator layer) through an etch mask (Paragraph [0015] Figure 1, a masking stack is formed over the substrate. Paragraph [0029-0030] portions of the masking stack are removed to allowing a “first substrate etching process” to proceed through the openings in the masking stack) to form features comprising a plurality of sides with vertical side profiles (Paragraph [0016] features are formed in the substrate. Paragraph [0036] Figure 3A, features have vertical side profiles), the plurality of sides including a first side with a first aspect ratio (AR) and a second side with a second AR higher than the first AR (See Reference Image 2 below) the etching comprising:
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forming a portion of the features by exposing the substrate, for a first duration, to plasma (Paragraph [0031] a “second etching process” etches the features);
and performing, for a second duration, an aspect ratio dependent passivation (ARDP) while etching the silicon layer (Paragraph [0030] Figure 3A, the passivation rate is greater for the isolated fins (element 111I), equivalent to the first side, than it is for the nested fins (element 111N), equivalent to the second side), the etching of the silicon layer during the second duration being slower on the first side than on the second side (Paragraph [0030] sidewalls of the nested fins etch faster than sidewalls of isolated fins) and wherein, during the performing, oxygen-containing etch byproducts are deposited to passivate exposed portions of the sides, the deposition being faster on the first side than on the second side (Paragraph [0030] Figure 3A, the passivation rate is greater for the isolated fins (element 111I), equivalent to the first side, than it is for the nested fins (element 111N), equivalent to the second side).
Ambati further teaches that the multiple etching processes taught are used to produce uniform fin widths when nested and isolated fins are formed on the same structure (Paragraph [0010]). Ambati teaches that this goal is accomplished by one etching process that has a higher lateral passivation rate for isolated fins than nested fins (Paragraph [0012] “the first substrate etching process may have a lateral passivation rate that is greater for isolated fins than the lateral passivating rate for nested fins”) and the another etching process that has a greater lateral etch rate for isolated fins than nested fins (Paragraph [0012] “The second etching process may equalize the widths of the fins by utilizing an etching chemistry that has a lateral etch rate that is greater for isolated fins than the lateral etch rate for nested fins”), where the use of both etching processes on the same substrate can result in equal widths for both types of fins.
Ambati fails to teach that the claimed second duration is performed after the end of the first duration.
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by conducting the taught “second etching process” as the first duration, and then conducting the taught “first etching process” as the second duration.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The taught “first etching process”, conducted as the second duration in the modified method, would have predictable result of conducting a partial etching of the features where the etching process has a higher passivation rate for the isolated fins compared to the nested fins. The taught “second etching process”, conducted as the first duration in the modified method, would have predictable result of conducting a partial etching of the features where the etching process has a higher etching rate for the isolated fins compared to the nested fins. After both of these etching processes are conducted the modified method would have the predictable result of producing isolated and nested fins with equal widths. See MPEP 2143(I)(A).
Ambati teaches that the plasma of the first duration is generated with Cl2, Ar, and CH4 ((Paragraph [0031] etching chemistry comprises Cl2 (a halogen), Ar (an inert gas), and CH4 (containing hydrogen)). However, this chemistry mixture does not contain oxygen and therefore, Ambati fails to teach that the plasma of the first duration is generated with chlorine, hydrogen bromide, oxygen, and an inert gas.
Kong teaches methods related to semiconductor fabrication (Paragraph [0002]). Kong teaches methods of forming features in a substrate that include plasma etching (Paragraph [0005] and [0027] where the process gas is formed into a plasma). Kong teaches a process gas for use in plasma etching that contains halogens, hydrogen, an inert species, and oxygen (Paragraph [0026] an example process gas includes hydrogen bromide (includes hydrogen and bromide, a halogen), chlorine (a halogen), oxygen, and helium or argon (an inert species).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by using the process gas taught by Kong as the process gas for forming the plasma of the claimed first duration.
This modification would have been the simple substitution of one plasma process gas for another. The simple substitution of one known element for another is likely to be obvious when predictable results are achieved. See MPEP §2143(B). Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP § 2144.07. It would be obvious to one of ordinary skill in the art to substitute the process gas taught by Ambati with process gas taught by Kong since this process gas is known to be capable of forming an etching plasma and the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP 2144.07.
With the modification of the process gas during the first duration as outlined above, the limitation of “reducing a ratio of a flow rate of etchants to a flow rate of oxygen, the etchants being chlorine and hydrogen bromide” is also met. Kong teaches that during the first duration the flow rate of chlorine can be 50-1000 sccm and the flow rate of hyrdrogen bromide can be 10-500 sccm (Paragraph [0022]). Kong teaches that during the first duration the flow rate of oxygen can be 100 or less (Paragraph [0024]). Ambati teaches that during the second duration the flow rate ratio of chlorine and hydrogen bromide to oxygen is 200 : 3.3 (Paragraph [0030] the flow rate of hydrogen bromide is 200 sccm and the flow rate of oxygen is 3.3 sccm). The relationship of the ratio of the second duration being a reduction relative to the ratio of the first duration is being interpretated here to mean that the value of the flow rate of etchants during the second duration divided by the total flow rate of oxygen and etchants during the second duration is smaller than the value of the flow rate of etchants during the first duration divided by the total flow rate of oxygen and etchants during the first duration. This value for the second duration is 0.98 (200/(200+3.3)=0.98).
It would have been obvious to one of ordinary skill in the art to have selected and incorporated a flow rate for chlorine at a level within the disclosed range of 50-1000 sccm, a flow rate for hydrogen bromide at a level within the disclosed range of 10-500 sccm, and a flow rate for oxygen with in the disclosed range of 100 sccm or less, including selections for the three flow rates at amounts such that the formula ((flow rate of chlorine) + (flow rate of hydrogen bromide))/ ((flow rate of chlorine) + (flow rate of hydrogen bromide) + (flow rate of oxygen)) is less than 0.98, so that the flow rate ratio decreases during the second duration as claimed. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Ambati teaches that during the claimed first duration the pressure is 1-2 mTorr (Paragraph [0031]) and during the claimed second duration the pressure is 3.1 mTorr (Paragraph [0030]). Therefore, modified Ambati as outlined above, fails to teach that the performing during the second duration comprises reducing the chamber pressure.
Kong teaches methods related to semiconductor fabrication (Paragraph [0002]). Kong teaches methods of forming features in a substrate that include plasma etching (Paragraph [0005]). Kong further teaches that during plasma etching the pressure is between about 3 to 50 mTorr (Paragraph [0028]).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by using the pressure taught by Kong during the first duration. With this modification, a pressure during the first duration would be 3 to 50 mTorr, while a pressure during the second duration would be 3.1 mTorr. When the second duration is considered as occurring immediately after the end of the first duration, the modified method as outlined above would require, along with the changing flow rates for gases required for the etching process of the second duration, a reduction in the pressure within the chamber for any embodiment where the value for the pressure during the first duration was greater than 3.1 mTorr.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The use of the pressure taught by Kong during the first duration would have had the predictable result of setting a suitable pressure for the etching process to be conducted during that duration. See MPEP 2143(I)(A).
It would have been obvious to one of ordinary skill in the art to have selected and incorporated a pressure during the first duration at a level within the disclosed range of 3-50mTorr, including at amounts greater than 3.1mTorr, such that the chamber pressure is decreases during the second duration as claimed. It has been held that obviousness exists where the claimed ranges overlap or lie inside ranges disclosed by the prior art. See MPEP 2144.05 (I).
Modified Ambati as outlined above fails to teach that the silicon layer is an amorphous silicon layer.
Flachowsky teaches methods related to fabricating integrated circuits on semiconductor substrates (Paragraph [0005]). Flachowsky teaches a substrate that comprises a gate insulator layer, that can be silicon oxide, that is overlying a silicon substrate (Paragraph [0015] Figure 1 gate insulator layer (element 114) is formed over silicon substrate (element 116). The gate insulator layer can be silicon oxide). Flachowsky teaches that the substrate can comprise a gate electrode material, that can be amorphous silicon, that is overlying the gate insulator layer (Paragraph [0015] gate electrode material (element 118) is overlying the gate insulator layer (element 114). The gate electrode material can be amorphous silicon).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati by selecting as the unspecified substrate, a substrate that comprised an amorphous silicon layer overlying an underlying layer as taught by Flachowsky.
This modification would have been the simple substitution of one substrate suitable for forming semiconductor devices with another. The simple substitution of one known element for another is likely to be obvious when predictable results are achieved. See MPEP §2143(B). Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP § 2144.07.
Regarding Claim 11, modified Ambati teaches all the limitations of claim 10 as outlined above. Ambati further teaches that the oxygen-containing etch byproducts deposited while performing the ARDP are materials comprising silicon oxide (SiO2), SiOHCl, SiOHBr, silicon oxychloride (SiOCl), or silicon oxybromide (SiOBr) (Paragraph [0030] the sidewalls, which comprise silicon, are passivated by oxygen, therefore silicon oxide would be a byproduct deposited).
Claims 12 and 13 are rejected under 35 U.S.C. 103 as being unpatentable over Ambati, Flachowsky, and Kong as applied to claim 10 above, and further in view of Ko.
Regarding Claim 12, modified Ambati teaches all the limitations of claim 10 as outlined above.
Modified Ambati fails to teach wherein the etching further comprises: at the end of the second duration, performing an overetch step for an overetch duration, wherein performing the overetch step comprises increasing the chamber pressure, increasing the ratio of the flow rate of etchants to the flow rate of oxygen, the second duration being configured to form a vertical side profile for the first side, and the overetch duration being configured to form a vertical side profile for the second side.
However, modified Ambati as outlined above teaches that the pressure during the second duration should be 3.1 mTorr. Ambati teaches that the etching of the second duration is configured to form a vertical side profile (Paragraph [0030] Figure 2C shows profile of features after the “first etching process”, equivalent to the claimed second duration, which have a vertical profile).
Ko teaches methods of processing a substrate (Paragraph [0005]). Ko teaches a method to remove a footing (Paragraph [0041] Figure 3, method (element 300) can be used to remove a footing). Ko teaches a method that includes an overetch step performed after other processing steps (Paragraph [0053] an overetch step is performed after removal operations). Ko teaches that the pressure during the overetch should be about 20 mTorr (Ko Paragraph [0056] pressure should be about 20 mTorr). Ko teaches that the overetch is configured to form a vertical side profile on the features where it is used (Paragraph [0053] Figures 4A-4D overetch is used to remove material that was not uniformly removed in previous etches, Figure 4D shows the features after the overetch process where the features have a vertical side profile).
It would have been obvious to one of ordinary skill in the art to have modified the method of Ambati as outlined above by including the overetch step taught by Ko to remove material from the layer that had been etched by the process outlined above. With this modification the method would meet the claimed limitations of wherein the etching further comprises: at the end of the second duration, performing an overetch step for an overetch duration, wherein performing the overetch step comprises increasing the chamber pressure, the second duration being configured to form a vertical side profile for the first side, and the overetch duration being configured to form a vertical side profile for the second side.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result of removing any unwanted remaining material, such as a footing, from the layer previously etched. See MPEP 2143(I)(A).
The method of modified Ambati as outlined above fails to teach that wherein performing the overetch step comprises increasing the ratio of the flow rate of etchants to the flow rate of oxygen.
Ko teaches that the overetch uses a process gas that contains fluorine-containing precursors to etch the material (Paragraph [0046]) but fails to teach the use of chlorine or hydrogen bromide as etchants.
Ambati teaches a method of etching that utilizes Cl2 as an etchant (Paragraph [0031] Cl2 is include in the etching gas and has the ability to etch features).
It would have been obvious to one of ordinary skill in the art to have modified the overetch method of Ko, such that the fluorine-containing precursor was replaced with Cl2. With this modification the overetch would have a flow rate of an etchant (Cl2) and no flow rate of oxygen. Therefore, performing the overetch step would comprise increasing the ratio of the flow rate of etchants to the flow rate of oxygen (The relationship of the ratio of the flow rate of etchants to a flow rate of oxygen increasing from the second duration to the overetch is being interpretated here to mean that the value of the flow rate of etchants during the second duration divided by the total flow rate of oxygen and etchants during the second duration is smaller than the value of the flow rate of etchants during the overetch divided by the total flow rate of oxygen and etchants during the overetch. With this interpretation the value for the second duration would be 0.98 as explained above in regards to claim 10, while the value for the overetch would be 1 ((flow rate of Cl2)/(flow rate of Cl2)=1), which is larger than 0.98).
This modification would have been the simple substitution of plasma etching precursor for another. The simple substitution of one known element for another is likely to be obvious when predictable results are achieved. See MPEP §2143(B). Furthermore, the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP § 2144.07. Additionally, it would be obvious to one of ordinary skill in the art to substitute the fluorine-containing precursor taught by Ko with Cl2 taught by Ambati since Cl2 is a known plasma etching precursor and the selection of a known material, which is based upon its suitability for the intended use, is within the ambit of one of ordinary skill in the art. See MPEP 2144.07.
Regarding Claim 13, modified Ambati, as outlined above in regards to claim 12, teaches after performing the overetch step, the first side and the second side are devoid of foot and notch defects (Ko Paragraphs [0055] and [0057] Figure 4C displays the substrate during the overetch process. Figure 4D displays the substrate after the overetch process, where no foot or notch defects are present).
Modified Ambati, as outlined above, fails to teach wherein the overetch duration is configured to expose a surface of the underlying layer.
However, Ko teaches that the overetch operation removes a footing as well as a portion of an underlying layer (Paragraphs [0053] and [0057], Figures 4A-4D etching is conducted to remove modified regions of footing (element 407) and the pad oxide layer (element 405), which is an underlying layer to nitride layer (element 410) as seen in Figure 4A. This exposes a portion of the pad oxide layer). Additionally, Ambati teaches that the substrate to be etched contains an underlying layer (Paragraph [0020] substrate may be a silicon-on-insulator, such that the silicon layer being etched has an insulator layer under it).
It would have been obvious to modified the method outlined above in regards to claim 6 such that the features were configured so that the underlaying insulator layer of the substrate is exposed when the features are etched in the overetch process, as taught by Ko.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result the overetch process exposing a portion of an underlying layer. See MPEP 2143(I)(A).
Claim 14 is rejected under 35 U.S.C. 103 as being unpatentable over Ambati, Flachowsky, and Kong as applied to claim 10 above, and further in view of Guler et al. (US-20220093589-A1) and Chen et al. (US-20220285513-A1).
Modifed Ambati teaches all the limitations of claim 10 as outlined above. Ambati further teaches that wherein the etch mask comprises a stack of layers (Paragraph [0015] Figure 2A masking stack (element 110) comprises layers etch stop (element 102), hard mask (element 103), and dummy hard mask (element 104)), the stack comprising a first hardmask layer comprising silicon oxide formed over the silicon layer (Paragraph [0019] Figure 2A etch stop layer (element 102) can be silicon oxide and is formed over the substrate to be etched), a second hardmask layer comprising silicon nitride formed over the first hardmask layer (Paragraph [0018] Figure 2A hard mask layer (element 103) can be silicon nitride and is formed over the etch stop layer), a third hardmask layer comprising silicon oxide formed over the second hardmask layer (Paragraph [0018] Figure 2A dummy hard mask layer (element 104) can be silicon dioxide and is formed over the hard mask layer).
Ambati fails to teach a fourth hardmask layer comprising silicon formed over the third hardmask layer.
Guler teaches methods of processing circuit structures (Paragraph [0001]). Guler teaches a method that utilizes a hardmask stack that includes a fourth hardmask layer (Paragraph [0030] Figure 1A a fourth hardmask layer (element 116) is on top of a third hardmask layer (element 114). Guler teaches that the fourth hardmask layer can contain silicon (Paragraph [0109] hardmask layers can contain silicon nitride or silicon oxide).
It would have been obvious to one of ordinary skill in the art to have modified the method outlined above so that the masking stack taught by Ambati further includes a fourth hardmask layer comprising silicon as taught by Guler.
This modification would have been obvious as it would have been the combination of prior art elements according to known methods to yield predictable results. The modification would have had the predictable result of having a fourth hardmask layer within the masking stack. See MPEP 2143(I)(A).
The modified method of Ambati outlined above fails to teach that the fourth hardmask layer being removed during etching the amorphous silicon layer. However, Ambati does teach that the mask layers are to be removed, but is silent on how or when they are removed (Paragraph [0007] Figure 3A displays a semiconductor device formed by the taught method, that has no mask layers within the structure)
Chen teaches a method for fabricating a semic