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 .
Information Disclosure Statement
The information disclosure statement (IDS) submitted on 12/16/2025 is being considered by the examiner.
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.
Claim 19 is rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Claim 17 recites that the capping layer of the EUV mask is free of the oxide layer that is disposed over the patterned absorber layer. Claim 19 then recites that the oxide layer contacts the capping layer at an intersection of the sidewalls of the absorber layer and the capping layer – if this is the case then the capping layer is not free of the side wall.
Applicant’s specification states at [0038] that in some embodiments the oxide layer may physically contact bottom corners – however this section also appears to recite a separate embodiment wherein the exposed portion is also “substantially” free of oxide layers. The word “substantially” is not used in the claim language.
For the purposes of examination the examiner elects, in light of the specification, to consider “free” in claim 17 to include situations where the capping layer is contacted by the sidewall oxide layer at the corners of the absorption layer.
Claim Rejections - 35 USC § 103
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.
As a matter of claim interpretation – the claims using “comprising” and “containing” language are considered to not exclude unrecited steps or elements. Any prior art having additional steps or elements/components is not excluded (See MPEP 2111.03.)
Claim(s) 1-16 is/are rejected under 35 U.S.C. 103 as being unpatentable over Liu et al (US 20210232040 A1) and Hsu et al (US 20210033960 A1).
Regarding Claims 1-10, Liu teaches an EUV mask blank, a method for manufacturing such, and production systems therefor (Abstract).
The mask blank of Liu is embodied in Figure 4, wherein the blank 302 comprises a substrate 304, multilayer stack structure 306 having reflective layers formed over the substrate, and a capping layer 308 formed over the multilayer stack 306. Formed atop the capping layer 308 is an absorber layer 310, and a hard mask layer 318 is formed atop the absorber layer 310 (See [0063]-[0066].
Materials and methods for forming these layers are laid out from [0067]-[0091]. Hardmasks may be formed from materials such as ruthenium and tantalum (such as a TaRu material – applicant’s specification recites at [0025 that the hard mask may comprise Ta and/or Ru).
The hard mask of Liu is etched with an oxygen free chemistry - a Cl2 etch chemistry is used in an exemplary embodiment to etch a hard mask layer at [0086], where the method comprises etching the hard mask and the absorber layer ([0101].
However, the method of Liu does not describe how far the etch of the absorber is carried out – whether the capping layer is reached, and does not recite a second etch using a combination of Cl2 and O2 etchants.
These limitations are met by Hsu.
Hsu discloses a method of patterning a semiconductor wafer using EUV lithography (EUVL) and a mask for EUV lithography, as well as a method of making a the EUV mask (Abstract). Specifically, Hsu is concerned with the use of oxide formation as a result of etching as a way to control critical dimensions in etched features ([0003], [0046])
The EUVL mask formation method is described in Figure 2A-2B and [0030]-[0050], and depicted in Figs 3A-3F.
The EUVL mask comprises a substrate 210, a reflective multilayer structure 220 over the substrate 210, a capping layer 230 deposited over the multilayer structure 220, and an absorber layer 250 disposed atop the capping layer. An optional protection layer may be disposed over the absorption layer but is not depicted in the cross-sectional embodiment of Figs 1B-1C, which are referenced back to by [0031]. A conductive layer 205 may be disposed beneath the substrate 210 for electrostatic chucking purposes. The materials of the substrate and layers are discussed from [0025-[0029].
These layers may be formed through methods such as PVD or CVD as described from [0027] – the reference contemplates the formation of a capping layer over a multilayer structure, forming an absorber layer over the capping layer.
The EUVL mask formation method as described in Figure 2A-2B and [0030]-[0060], and depicted in Figs 3A-3F comprises the receiving of the workpiece described above, after which the absorber layer is patterned to form a trench having first width W1 and a thickness T1 (Operation 204).
An optional step 306 comprising the patterning of the absorber layer, capping layer, and reflective multilayer to create a trench with width W4 and thickness T4.
After patterning the absorber layer in step 304 (or 306), the EUVL mask is moved to a CD-SEM to measure trench width (operation 308), then moved to a plasma etcher (operation 310).
The EUVL mask is treated with O2 plasma etching to enhance oxide layer growth on the first and second sidewalls of the trench, increasing the sidewall thickness to T2 and trench width to W2 (Operation 312). As per [0042], the O2 plasma reacts with the absorber layer to grow an oxide layer on the top surface portion 25a of the absorber layer and on the sidewalls 250b
A second etch with N2 plasma is performed to protect the capping layer while also etching the first and second sidewalls to a thickness T2 and width W3 (Operation 318).
The resultant EUVL mask at Figure 3F meets the limitations of the claim for where the method of forming the mask forms:
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A multilayer structure (reference 220)
A capping layer disposed over the multilayer structure (230)
A patterned absorber layer over the capping layer having an opening that exposes a portion of the capping layer (250b).
Hsu fails to teach a specific patterning layer placed over the absorption layer in a figure – however, a protective layer may be placed over the absorption layer as recited at [0023]. The operation of the method at (304) recites a patterning step to pattern the absorption layer, such patterning would use a protective layer as an etch mask, such protective layer being the hard mask of Liu.
Hsu recites that ruthenium based materials may react with the oxygen plasma to form oxides and thus weaken them – the ruthenium-bearing hard mask of Liu is etchable with chlorine gas plasma as per the disclosure of Liu, but is also etchable with the oxygen etch of Hsu. The etch with Hsu’s oxygen plasma allows for formation of the oxide layer for critical dimension attenuation using the patterned absorbing layer – performing an etch with chlorine gas to remove a portion of the hardmask layer and then finishing with a mixed chlorine and oxygen etch to remove the remainder of hardmask and begin forming an oxide layer would allow for greater control over critical dimension in the resultant etch than a chlorine etch alone.
In [0040] of Hsu, operation 312 is performed to treat the various exposed surfaces of the workpiece so as to control oxidation - this may be a local process or a global process, wherein a local process treats specific portions of the workpiece using a plasma beam or plasma spot. In [0045], Hsu states that oxidation of the capping lay may occur and may be deleterious to the functioning of the capping layer. Using a plasma beam or spot to avoid exposing the capping layer surface would avoid this deleterious effect. Further, when this local beam exposure is employed, the concentration of oxygen nearby the surface of the capping layer (an ‘oxygen region’) would be substantially reduced to near-zero as this operation occurs under a vacuum (claim 6). Switching from a Cl2 plasma as directed by Liu to a mixed Cl2 + O2 plasma by including the O2 plasma process of Hsu at a time when most of the hard mask layer (most of its thickness, where most would mean “more than half”) is gone would further reduce the likelihood of oxygen contamination of the capping layer as there would be less time for oxygen generated to contact the capping layer (claim 4). This timing would also limit the thickness of any portion of a tip on the sidewalls near the surface of the capping layer as the low oxygen formation at the capping layer would minimize contact and cause a tapering in line with the oxygen gradient, reducing it to near-zero at the capping layer, where the thickness of the oxide layer tip in such conditions would be substantially near-zero ( claim 9 and 10). Further, the addition of O2 to the Cl2 etch gas would increase the rate of etching as both gases may etch the material (claim 5).
A person having ordinary skill in the art would have found it obvious to arrive at the claimed invention by incorporating the oxygen etching step of Hsu as a mixed chlorine-oxygen etch into the method of Liu so as to arrive at a process better able to control the critical dimensions of the workpiece by attenuating the width and thickness of trench pattern(s) with oxide formation/removal steps.
Regarding Claim 11-16, Liu teaches an EUV mask blank, a method for manufacturing such, and production systems therefor (Abstract).
The mask blank of Liu is embodied in Figure 4, wherein the blank 302 comprises a substrate 304, multilayer stack structure 306 having reflective layers formed over the substrate, and a capping layer 308 formed over the multilayer stack 306. Formed atop the capping layer 308 is an absorber layer 310, and a hard mask layer 318 is formed atop the absorber layer 310 (See [0063]-[0066].
Materials and methods for forming these layers are laid out from [0067]-[0091]. Hardmasks may be formed from materials such as ruthenium and tantalum (such as a TaRu material – applicant’s specification recites at [0025 that the hard mask may comprise Ta and/or Ru).
The hard mask of Liu is etched with an oxygen free chemistry - a Cl2 etch chemistry is used in an exemplary embodiment to etch a hard mask layer at [0086], where the method comprises etching the hard mask and the absorber layer ([0101].
However, the method of Liu does not describe how far the etch of the absorber is carried out – whether the capping layer is reached, and does not recite a second etch using an oxygen based etchant.
These limitations are met by Hsu.
Hsu discloses a method of patterning a semiconductor wafer using EUV lithography (EUVL) and a mask for EUV lithography, as well as a method of making a the EUV mask (Abstract). Specifically, Hsu is concerned with the use of oxide formation as a result of etching as a way to control critical dimensions in etched features ([0003], [0046])
The EUVL mask formation method is described in Figure 2A-2B and [0030]-[0050], and depicted in Figs 3A-3F.
The EUVL mask comprises a substrate 210, a reflective multilayer structure 220 over the substrate 210, a capping layer 230 deposited over the multilayer structure 220, and an absorber layer 250 disposed atop the capping layer. An optional protection layer may be disposed over the absorption layer but is not depicted in the cross-sectional embodiment of Figs 1B-1C, which are referenced back to by [0031]. A conductive layer 205 may be disposed beneath the substrate 210 for electrostatic chucking purposes. The materials of the substrate and layers are discussed from [0025-[0029].
These layers may be formed through methods such as PVD or CVD as described from [0027] – the reference contemplates the formation of a capping layer over a multilayer structure, forming an absorber layer over the capping layer.
The EUVL mask formation method as described in Figure 2A-2B and [0030]-[0060], and depicted in Figs 3A-3F comprises the receiving of the workpiece described above, after which the absorber layer is patterned to form a trench having first width W1 and a thickness T1 (Operation 204).
An optional step 306 comprising the patterning of the absorber layer, capping layer, and reflective multilayer to create a trench with width W4 and thickness T4.
After patterning the absorber layer in step 304 (or 306), the EUVL mask is moved to a CD-SEM to measure trench width (operation 308), then moved to a plasma etcher (operation 310).
The EUVL mask is treated with O2 plasma etching to enhance oxide layer growth on the first and second sidewalls of the trench, increasing the sidewall thickness to T2 and trench width to W2 (Operation 312). As per [0042], the O2 plasma reacts with the absorber layer to grow an oxide layer on the top surface portion 25a of the absorber layer and on the sidewalls 250b
A second etch with N2 plasma is performed to protect the capping layer while also etching the first and second sidewalls to a thickness T2 and width W3 (Operation 318).
The resultant EUVL mask at Figure 3F meets the limitations of the claim for where the method of forming the mask forms:
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A multilayer structure (reference 220)
A capping layer disposed over the multilayer structure (230)
A patterned absorber layer over the capping layer having an opening that exposes a portion of the capping layer (250b).
Hsu fails to teach a specific patterning layer placed over the absorption layer in a figure – however, a protective layer may be placed over the absorption layer as recited at [0023]. The operation of the method at (304) recites a patterning step to pattern the absorption layer, such patterning would use a protective layer as an etch mask, such protective layer being the hard mask of Liu.
Hsu recites that ruthenium based materials may react with the oxygen plasma to form oxides and thus weaken them – the ruthenium-bearing hard mask of Liu is etchable with chlorine gas plasma as per the disclosure of Liu, but is also etchable with the oxygen etch of Hsu. The etch with Hsu’s oxygen plasma allows for formation of the oxide layer for critical dimension attenuation using the patterned absorbing layer – performing an etch with chlorine gas to remove a portion of the hardmask layer and then finishing with an oxygen etch to remove the remainder of hardmask and begin forming an oxide layer would allow for greater control over critical dimension in the resultant etch than a chlorine etch alone.
In [0040] of Hsu, operation 312 is performed to treat the various exposed surfaces of the workpiece so as to control oxidation - this may be a local process or a global process, wherein a local process treats specific portions of the workpiece using a plasma beam or plasma spot. In [0045], Hsu states that oxidation of the capping lay may occur and may be deleterious to the functioning of the capping layer. Using a plasma beam or spot to avoid exposing the capping layer surface would avoid this deleterious effect. Further, when this local beam exposure is employed, the concentration of oxygen nearby the surface of the capping layer (an ‘oxygen region’) would be substantially reduced to near-zero as this operation occurs under a vacuum (claim 15). Switching from a Cl2 plasma as directed by Liu to an O2 plasma as directed by Hsu at a time when most of the hard mask layer (most of its thickness) is gone would further reduce the likelihood of oxygen contamination of the capping layer as there would be less time for oxygen generated to contact the capping layer (claims 13 and 14). This timing would also limit the thickness of any portion of a tip on the sidewalls near the surface of the capping layer as the low oxygen formation at the capping layer would prevent contact and cause a tapering in line with the oxygen gradient, reducing it to near-zero at the capping layer, where the thickness of the oxide layer tip in such conditions would be substantially near-zero (claim 16).
A person having ordinary skill in the art would have found it obvious to incorporate the oxygen etching step (and, optionally, the nitrogen etching step) of Hsu into the method of Liu so as to arrive at a process better able to control the critical dimensions of the workpiece by attenuating the width and thickness of trench pattern(s) with oxide formation/removal steps.
Claim(s) 17- 20 is/are rejected under 35 U.S.C. 103 as being unpatentable over Hsu et al (US 20210033960 A1)
Regarding Claim 17-20, Hsu discloses a method of patterning a wafer using an extreme ultraviolet lithography mask (EUVL mask), as well as a method of producing the mask (Abstract.)
Hsu discloses a method of patterning a semiconductor wafer using EUV lithography (EUVL) and a mask for EUV lithography, as well as a method of making a the EUV mask (Abstract).
The EUVL mask formation method is described in Figure 2A-2B and [0030]-[00 and depicted in Figs 3A-3F.
The EUVL mask comprises a substrate 210, a reflective multilayer structure 220 over the substrate 210, a capping layer 230 deposited over the multilayer structure 220, and an absorber layer 250 disposed atop the capping layer. An optional protection layer may be disposed over the absorption layer but is not depicted in the cross-sectional embodiment of Figs 1B-1C, which are referenced back to by [0031]. A conductive layer 205 may be disposed beneath the substrate 210 for electrostatic chucking purposes. The materials of the substrate and layers are discussed from [0025-[0029].
The reflective multilayer structure may be a Mo/Si or Mo/Be structure, or any two materials with a large difference in refractive indices and small extinction coefficients ([0025]).
The capping layer acts as an etch stop layer to protect the multilayer structure, and may be made from ruthenium or ruthenium compounds such as RuB, RuSi, or RuO2 ([0026]).
The absorber layer may include a single layer or multiple layers of materials selected from tantalum boron nitride, aluminum oxide, chromium, chromium oxide or nitride, titanium, tantalum, hafnium, palladium, or another embodiment described in [0026]. In some embodiments, the absorber includes a 2nm-2nm thick layer of TaBO (tantalum boron oxide) over a layer of tantalum boron nitride or TaBN.
The EUVL mask formation method as described in Figure 2A-2B and [0030]-[00 and depicted in Figs 3A-3F comprises the receiving of the workpiece described above, after which the absorber layer is patterned to form a trench having first width W1 and a thickness T1 (Operation 204).
An optional step 306 comprising the patterning of the absorber layer, capping layer, and reflective multilayer to create a trench with width W4 and thickness T1.
After patterning the absorber layer in step 304 (or 306), the EUVL mask is moved to a CD-SEM to measure trench width (operation 308), then moved to a plasma etcher (operation 310).
The EUVL mask is treated with O2 plasma to enhance oxide layer growth on the first and second sidewalls of the trench, increasing the sidewall thickness to T2 and trench width to W2 (Operation 312). As per [0042], the O2 plasma reacts with the absorber layer to grow an oxide layer on the top surface portion 25a of the absorber layer and on the sidewalls 250b
A second etch with N2 plasma is performed to protect the capping layer while also etching the first and second sidewalls to a thickness T2 and width W3 (Operation 318).
The resultant EUVL mask at Figure 3F meets the limitations of the claim for where the mask has:
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A multilayer structure (reference 220)
A capping layer disposed over the multilayer structure (230)
A patterned absorber layer over the capping layer having an opening that exposes a portion of the capping layer (250b).
A metal oxide layer (250a) is disposed over the patterned absorber layer, wherein the oxide is further disposed along sidewalls that form the opening in the patterned absorber layer
The resultant EUVL mask does not meet the limitations of the claim for where an oxide layer is not present on the capping layer or the capping layer is free of the oxide.
These limitations are met by the general disclosure of the reference.
In [0040], operation 312 is performed to treat the various exposed surfaces of the workpiece so as to control oxidation - this may be a local process or a global process, wherein a local process treats specific portions of the workpiece using a plasma beam or plasma spot. In [0045], Hsu states that oxidation of the capping lay may occur and may be deleterious to the functioning of the capping layer. Using a plasma beam or spot to avoid exposing the capping layer surface would avoid this deleterious effect. Further, when this local beam exposure is employed, the concentration of oxygen nearby the surface of the capping layer (an ‘oxygen region’) would be substantially reduced to near-zero as this operation occurs under a vacuum (claim 18). This reduction in concentration would also limit the thickness of any portion of a tip on the sidewalls near the surface of the capping layer as the low oxygen formation at the capping layer would prevent contact and cause a tapering in line with the oxygen gradient, reducing it to near-zero at the capping layer, where the thickness of the oxide layer tip in such conditions would be substantially near-zero (claim 19).
A person having ordinary skill in the art would have found it obvious to arrive at the claimed invention by selectively treating the workpiece’s using a local treatment with a plasma beam to minimize the exposure of the capping layer to oxygen plasma during treatment, generating a capping-layer surface that is substantially free of metal oxides.
Conclusion
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/A.P.T./Examiner, Art Unit 1737
/John S. Chu/Primary Examiner, Art Unit 1737
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