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 .
Response to Arguments
Applicant's arguments, see pages 2-4, filed 13 January 2026, with respect to the rejection(s) of claim(s) 1-11 under 35 U.S.C. 102(a)(1), or, in the alternative, under 35 U.S.C. 103 have been fully considered and are persuasive. Therefore, the rejection has been withdrawn. However, upon further consideration, a new ground(s) of rejection is made in view of US 20030082460 A1 (hereby referred to as Stivers).
Applicant’s response to the previous office action does not include claim amendments, but rather argues against the previous rejection made in view of the prior art reference “Hsieh”. Particularly, Applicant argues that the previous rejection should be withdrawn because Hsieh fails to teach or suggest the claimed feature “an etching clear time of the light-absorbing film on fluorine-based dry etching under one condition is longer than an etching clear time of the first layer of the hard mask film on the fluorine-based dry etching under the same condition”. To support this argument, the Applicant states that the etching clear time is determined by not only the constituent components of the film(s), but also the contents and thicknesses of the layers. Applicant argues that Hsieh is silent about the contents and thickness of the absorber layer (120) and therefore the etching clear time of the absorber cannot be assumed and compared to the instant application’s invention. Upon review of Hsieh’s disclosure, the Applicant is correct in that the absorber layer thickness is not disclosed. Therefore, the Applicant’s arguments are found to be persuasive and the previous rejection is withdrawn. However, a new rejection is presented in view of US 20030082460 A1 (hereby referred to as Stivers), as explained below.
Further, in response to the Applicant’s arguments that the concentration/content of the layer has an effect on the clear time, the Examiner refers to Tables 1 and 2 of the instant application’s specification (pages 28 and 30 of the instant application’s specification). As a note, the light-absorbing film in each example is a TaN film of undisclosed tantalum and nitrogen contents having a thickness of 64 nm (see the second-to-last paragraph on page 26 of the instant application’s specification). Table 1 shows the composition of the first layer for each example. The thickness of the first layer in Examples 1-4 is 10 nm. Table 2 shows that the etching rate differs depending on the content of the silicon, oxygen, and nitrogen of the first layer. However, the fluorine-based dry etching rate of the first layer is greater than and/or comparable to the fluorine-based dry etching for the light-absorbing film in each embodiment (see Table 2). As the thickness of the first layer is significantly smaller than the thickness of the light-absorbing film (10 nm vs. 64 nm), the resulting clear time of the first layer ends up being significantly faster. Thus, whilst it is apparent that the content of the layer has an effect on the etching rate, it is apparent, based on the Applicant’s own examples, that the effect of the content of the first layer is less significant than the effect of the thickness of the first layer, when it comes to the clear time with respect to the light-absorbing film. In Hsieh’s disclosure, the middle layer (which corresponds to the first layer of the instant application’s invention) preferably has a thickness from about 2 nm to 30 nm (Hsieh, paragraph 0051). Similarly, the middle layer may comprise SiO, SiON, or SiN (Hsieh, paragraph 0051), which are the materials used in Examples 1-4 of the instant application. It would be expected by one having ordinary skill in the art that the etching rate of the middle layer of Hsieh is comparable to the etching rate of the first layer of Examples 1-4 of the instant application, as the materials of Hsieh and the instant application are similar or identical. Likewise, the absorber layer taught by Hsieh comprises tantalum-based materials, such as nitrides (Hsieh, paragraph 0057). Therefore, given an absorber layer having a significantly greater thickness than the middle layer, one having ordinary skill in the art would reasonably conclude that the clear time of the middle layer is lower than the clear time of the absorber layer, based upon the fact that Hsieh utilizes similar materials to the instant application for both layers. This rationale is relied upon for the new rejection, which is presented below.
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.
Claim(s) 1-10 are rejected under 35 U.S.C. 103 as being unpatentable over US 20210333717 A1 (hereby referred to as Hsieh) in view of US 20030082460 A1 (hereby referred to as Stivers).
Regarding Claim 1, Hsieh discloses an extreme ultraviolet (EUV) mask and method of manufacturing the same. Hsieh discloses an EUV photomask blank (101) that includes a middle layer (30) disposed over (in order) a hard mask layer (110), an absorber layer (120), a capping layer (130), a reflective multilayer (140), and a low thermal expansion material layer (150) (Hsieh, paragraph 0015 and Fig. 1A). The middle layer (30) has etching selectivity to the photoresist layer (20) (which is disposed over the middle layer, see Fig. 1A) and the hard mask layer (110) (Hsieh, paragraph 0020). For instance, when a silicon-based middle layer is etched with a fluorine-based etching gas, the etching rate observed is orders of magnitude greater than the etching rate of a chromium-based hard mask layer (Hsieh, paragraph 0020). The absorber layer functions to absorb EUV light from the EUV exposure source (Hsieh, paragraph 0023). The capping layer functions to protect the underlying multilayer from being etched (Hsieh, paragraph 0025). As can be seen in the patterning steps that result in the mask blank being processed into a photomask, the resist is patterned and the pattern is transferred to the middle layer, which is then further transferred to the hard mask layer and absorber layer (Hsieh, paragraph 0037-0049 and Fig. 4A-4F). Thus, it is apparent that the middle layer (30) is analogous to the first layer of the multilayer hard mask recited by instant claim 1 and the hard mask layer (110) is analogous to the second layer of the multilayer hard mask recited by instant claim 1. Similarly, the capping layer (130) is analogous to the protection film recited by instant claim 1 and the low thermal expansion material layer (150) is analogous to the substrate recited by instant claim 1. Hsieh discloses that the middle layer and the hard mask layer are etching using chlorine-based or fluorine-based etching gases, depending on the materials chosen for each (Hsieh, paragraph 0041). Hsieh does not explicitly state that the middle layer is resistant to chlorine-based dry etching and the hard mask layer is resistant to fluorine-based dry etching. However, Hsieh suggests this feature in that the etching selectivity of the middle layer to the hard mask layer is about 80:1 (Hsieh, paragraph 0040). Furthermore, Hsieh discloses that the middle layer may be formed of various materials, including silicon-based materials such as silicon oxide (SiO), silicon oxynitride (SiON), silicon nitride (SiN), silicon boronitride (SiBN), silicon borocarbide (SiBC), silicon boro carbonitride (SiBCN), or polysiloxanes (Hsieh, paragraph 0018). The hard mask layer may be formed of metallic species, such as chromium-based or tantalum-based materials including chromium oxynitride (CrON), tantalum oxide (TaO), and tantalum boroxide (TaBO) (Hsieh, paragraph 0021). As the middle layer has an etch selectivity with respect to the hard mask layer of up to 80:1 (Hsieh, paragraph 0020), it is apparent that Hsieh intends for a combination of a middle layer comprising a silicon-based material and a hard mask layer comprising a chromium-based material (Hsieh, paragraph 0020, 0051, and 0057). The instant application utilizes a similar configuration (see Example 1 on pages 26-27 of the instant application’s specification, which utilizes CrN for the lower layer and SiN for the upper layer). Thus, whilst not explicitly stated by Hsieh, it would be expected that the mask blank disclosed by Hsieh possesses an upper layer (the middle layer (30)) that is removable by fluorine-based dry etching and is resistant to chlorine-based dry etching, and a lower layer (the hard mask layer (110)) that is removable by chlorine-based dry etching and is resistant to fluorine-based dry etching. This would be expected due to the mask blank of Hsieh utilizing similar or identical materials for the corresponding layers as the instant application. Similarly, Example 1 of the instant application (see pages 26-27 of the instant application’s specification) utilizes tantalum nitride having a thickness of 64 nm as the absorber film, and the thickness of the first layer is 10 nm (see Table 1 of the instant application’s specification). Hsieh discloses that the absorber comprises tantalum or a tantalum-containing material including a nitride, carbide, oxide, or boron derivative (Hsieh, paragraph 0057), and the thickness of the middle layer is preferably between 2 nm and 30 nm (Hsieh, paragraph 0051). As the middle layer of Hsieh utilizes similar or identical materials as the first layer of the instant application, it would be expected by one having ordinary skill in the art that the etching rate of the middle layer of Hsieh is comparable to the etching rate of the first layer of the instant application. Similarly, as the absorber layer of Hsieh utilizes similar or identical materials as the light-absorbing film of the instant application, it would be expected by one having ordinary skill in the art that the etching rate of the absorber layer of Hsieh is comparable to the etching rate of the light-absorbing film of the instant application.
However, Hsieh is silent in regards to the absorber layer thickness. As evidenced by Table 2 of the instant application’s specification (see page 30 of the instant application’s specification), the clear time of a layer is directly proportional to the thickness of the layer. Stivers teaches photolithographic mask fabrication. The mask taught by Stivers comprises a substrate, a reflective multilayer, a buffer layer, and an absorber layer (Stivers, paragraph 0020). The absorber layer may be a material such as tantalum nitride (TaN) (Stivers, paragraph 0023). When TaN is used for the absorber layer, the thickness of the absorber layer may be in the range of 50 to 100 nm (Stivers, paragraph 0023).
Hsieh and Stivers are analogous art because both references pertain to photolithographic mask manufacturing. It would have been obvious to one having ordinary skill in the art before the filing date of the instant application to have the tantalum nitride absorber layer of Hsieh have a thickness between 50 nm and 100 nm, as taught by Stivers, because the thickness of the absorber layer of a photolithographic mask is mostly determined by the material used as the absorber (Stivers, paragraph 0023), and the range taught by Stivers provides suitable absorption of radiation for TaN layers (Stivers, paragraph 0023). The Examiner notes that when the teachings of Hsieh and Stivers are combined, a reflective photomask blank having the structure according to instant claim 1 is obtained. Specifically, the photomask blank comprises a middle layer (analogous to the claimed first layer) containing SiO, SiON, or SiN and having a thickness of 2 nm to 30 nm (Hsieh, paragraph 0051) and an absorber layer containing TaN and having a thickness between 50 nm and 100 nm (Stivers, paragraph 0023). The materials of the obtained mask blank are similar or identical to those utilized by the instant application’s invention (see Examples 1-4 on pages 26-28 and Tables 1 and 2 of the instant application’s specification), suggesting that the middle layer and the absorber layer would have comparable etching rates as the first layer and light-absorbing film, respectively, of the instant application. Additionally, the thickness of the absorber layer is significantly greater than the thickness of the middle layer. Therefore, one having ordinary skill in the art would expect that the etching clear time of the absorber layer on fluorine-based dry etching under one condition would be longer than the etching clear time of the middle layer (analogous to the first layer of the hard mask film) on the fluorine-based dry etching under the same condition.
Regarding Claim 2, Hsieh does not explicitly disclose the etching rate of the absorber layer with respect to the middle layer. However, Hsieh discloses that the absorber layer comprises tantalum or a tantalum derivative (such as a nitride) and the middle layer comprises a tantalum-based or silicon-based compound (such as SiN) (Hsieh, paragraph 0062). The instant application utilizes a tantalum nitride absorber layer (see page 26, lines 27-31 of the instant application’s specification) and a silicon nitride first layer (see page 27, line 4-12 of the instant application’s specification). Per Table 2 of the instant application’s specification (see page 30 of the instant application’s specification), the etching rate of the SiN layer was 0.50 nm/sec and the etching rate of the TaN layer was 0.40 nm/sec, yielding an etching rate ratio of 0.8 (
0.4
n
m
s
e
c
0.5
n
m
s
e
c
=
0.8
)
. As Hsieh utilizes similar or identical materials as Example 1 of the instant application, one having ordinary skill in the art would expect that the observed ratio of the etching rate of the absorber layer with respect to the etching rate of the middle layer in Hsieh’s invention would also be within the range of 0.4 to 2.
Regarding Claim 3, Hsieh discloses that the middle layer (which corresponds to the claimed first layer) may be formed of a silicon-based material, such as SiO, SiON, SiN, SiBN, SiBC, SiBCN, or polysiloxanes (Hsieh, paragraph 0051). These materials comprise silicon and are free of chromium.
Regarding Claim 4, Hsieh discloses that the hard mask layer (which corresponds to the claimed second layer) may be formed of a metallic material, such as chromium or tantalum or their alloys, such as CrON, TaB, TaO, TaBO, or TaBN (Hsieh, paragraph 0050). In the case that CrON is utilized, a material comprising chromium and free of silicon is used as the second layer.
Regarding Claim 5, Hsieh discloses that the middle layer (which corresponds to the claimed first layer) has a thickness between 2 nm and 30 nm (Hsieh, paragraph 0051). Hsieh does not disclose specific examples of the invention. However, per MPEP 2144.05 I., overlapping ranges establish a prima facie case of obviousness.
Regarding Claim 6, the combination of Hsieh and Stivers renders obvious the photomask blank of instant claim 1, as discussed above. Hsieh discloses that the middle layer (which corresponds to the first layer of the instant application) has a thickness between 2 nm to 30 nm (Hsieh, paragraph 0051). However, Hsieh is silent in regards to the thickness of the absorber layer.
Stivers teaches photolithographic mask fabrication. The mask taught by Stivers comprises a substrate, a reflective multilayer, a buffer layer, and an absorber layer (Stivers, paragraph 0020). The absorber layer may be a material such as tantalum nitride (TaN) (Stivers, paragraph 0023). When TaN is used for the absorber layer, the thickness of the absorber layer may be in the range of 50 to 100 nm (Stivers, paragraph 0023). Stivers further teaches that the thickness of the absorber is mostly determined by the radiation absorption of the material used as the absorber (Stivers, paragraph 0023).
Hsieh and Stivers are analogous art because both references pertain to photolithographic mask manufacturing. It would have been obvious to one having ordinary skill in the art before the filing date of the instant application to provide an absorber layer having a thickness of 50 nm to 100 nm, as taught by Stivers, for the mask blank disclosed by Hsieh because Hsieh and Stivers both utilize tantalum-based absorbers (Hsieh, paragraph 0068; Stivers, paragraph 0023) and it is known in the art that the thickness of the absorber layer is determined by the radiation absorption of the material used as the absorber (Stivers, paragraph 0023). Thus, one having ordinary skill in the art would be motivated to routinely optimize the thickness of the absorber layer disclosed by Hsieh within the range taught by Stivers in order to obtain desirable light-absorption behavior (Stivers, paragraph 0023). Refer to MPEP 2144.05 II. The Examiner notes that when the middle layer of Hsieh (which has a thickness of 2 to 30 nm, as mentioned above) is combined with the absorber of Stivers (which has a thickness of 100 nm in some embodiments (see Stivers, paragraph 0023)), the difference between the thickness of the middle layer and the absorber layer is not less than 30 nm, per instant claim 6.
Regarding Claim 7, Hsieh discloses that the middle layer (which corresponds to the claimed first layer) has a thickness between 2 nm and 30 nm (Hsieh, paragraph 0051). The hard mask layer (which corresponds to the claimed second layer) has a thickness between 6 nm and 10 nm (Hsieh, paragraph 0050). Hsieh further discloses that the thickness ratio of the middle layer to the hard mask layer ranges from about 1:1 to about 25:1, wherein the ratio is chosen so that the dry etching chemistries are adjusted to have high etching selectivity without losing pattern fidelity (Hsieh, paragraph 0022). Hsieh does not disclose specific examples of the invention. However, per MPEP 2144.05 I., overlapping ranges establish a prima facie case of obviousness.
Regarding Claim 8, Hsieh discloses that the absorber layer may comprise tantalum or tantalum-based compounds, such as nitrides, carbides, oxides, and/or boron derivatives (Hsieh, paragraph 0023).
Regarding Claim 9, Hsieh discloses a method of manufacturing a reflective photomask comprising a pattern of the absorber film from the reflective mask blank (Hsieh, paragraph 0037 and Fig. 4A-4F). The method includes forming a resist layer (20) on top of the middle layer (30) (Hsieh, paragraph 0038, see Fig. 4A), patterning the resist film to form a resist pattern (Hsieh, paragraph 0038, see Fig. 4B), patterning the middle layer by dry-etching using a fluorine-based gas while utilizing the resist pattern as an etching mask (Hsieh, paragraph 0039, see Fig. 4C), stripping the resist layer (Hsieh, paragraph 0042), patterning the hard mask layer by dry-etching using a chlorine-based gas while utilizing the middle layer pattern as an etching mask (Hsieh, paragraph 0043, see Fig. 4D), patterning the absorber layer to form a pattern of the absorber layer by dry-etching using a fluorine-based gas whilst removing the middle layer by over-etching (Hsieh, paragraph 0044 and 0047, see Fig. 4E), and removing the hard mask layer by over-etching using a chlorine-based gas (Hsieh, paragraph 0047).
Regarding Claim 10, Hsieh discloses that the resist layer has a thickness of 2 nm to 150 nm (Hsieh, paragraph 0036). Hsieh does not disclose specific examples of the invention. However, per MPEP 2144.05 I., overlapping ranges establish a prima facie case of obviousness.
Claim(s) 11 is rejected under 35 U.S.C. 103 as being unpatentable over US 20210333717 A1 (hereby referred to as Hsieh) in view of US 20030082460 A1 (hereby referred to as Stivers), as applied to claim 9 above, and further in view of US 20030064296 A1 (hereby referred to as Yan).
Regarding Claim 11, the combination of Hsieh and Stivers renders obvious a method of manufacturing a reflective photomask according to instant claim 9, as discussed above. The method yields a patterned absorber layer (see Hsieh, paragraph 0044 and 0047 and Fig. 4E). However, Hsieh and Stivers are silent in regards to the patterned absorber layer’s line width.
Yan teaches a photolithographic mask fabrication method. The method includes preparing a mask blank (Yan, Fig. 4A) and patterning the mask (Yan, Fig. 4B-4F) (see Yan, paragraph 0041-0048). The mask comprises an absorber layer (430 as shown in Fig. 4A) that is etched to produce a patterned absorber layer (447 as shown in Fig. 4C) (Yan, paragraph 0042-0043). The absorber may be a material comprising tantalum, such as TaN (Yan, paragraph 0031). Yan teaches that the line width of the absorber on a mask is 12 nm when TaN is used (Yan, paragraph 0063).
Hsieh, Stivers, and Yan are analogous art because each reference pertains to photomasks and their manufacture. It would have been obvious to one having ordinary skill in the art before the filing date of the instant application to produce an absorber pattern having a line width of 25 nm or less, as taught by Yan, in the method of manufacturing a photomask obtained by combining the teachings of Hsieh and Stivers because a small line width, such as below 25 nm, allows for improved resolution and the ability to print smaller features on a semiconductor wafer (Yan, paragraph 0020).
Conclusion
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/JAYSON D COSGROVE/Examiner, Art Unit 1737
/JONATHAN JOHNSON/Supervisory Patent Examiner, Art Unit 1734