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 .
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, 3, 5, 7, 11, 13, 15, and 18 are rejected under 35 U.S.C. 103 as being unpatentable over US 20220137499 A1 (hereby referred to as Hsu).
The Examiner notes that the instant application claims priority from JP2020-217573, which has a filing date of 25 December 2020. Hsu claims priority from U.S. Provisional Application 63/108,187, which has a filing date of 30 October 2020, and thus qualifies as prior art per 35 U.S.C. 102(d)(2). Refer to MPEP 2154.01(b).
Regarding Claims 1 and 7, Hsu discloses extreme ultraviolet (EUV) masks. Fig. 3A-3L of Hsu depict the mask at various stages of the manufacturing process (Hsu, paragraph 0006). A reflective multilayer stack (110) is formed over a substrate (102) (Hsu, paragraph 0019 and Fig. 3A), a capping layer (120) is formed over the reflective multilayer stack (Hsu, paragraph 0026 and Fig. 3B), and a buffer layer (130) is formed over the capping layer (Hsu, paragraph 0030 and Fig. 3C). An absorber layer (140) is then formed over the buffer layer (Hsu, paragraph 0032 and Fig. 3D). Additional layers are present above the absorber layer, such as a hard mask layer (160) and a photoresist layer (170) (Hsu, paragraph 0041 and Fig. 3E), to complete the EUV mask blank depicted in Fig. 3E of Hsu. Following several processing steps, the absorber layer is etched and a patterned absorber layer is obtained (Hsu, paragraph 0048-0049 and Fig. 3H). As the absorber layer, a Ta-based alloy comprised of Ta and at least one alloying element is used, wherein the Ta-based alloy is either Ta-rich (having a Ta content between 50 atomic% and 90 atomic%) or alloying element-rich (having an alloying element content between 50 atomic% and 90 atomic%) (Hsu, paragraph 0035). The alloying element may be iridium (Ir), and a tantalum iridium (TaIr) alloy is explicitly named as an exemplary alloy (Hsu, paragraph 0036). The Ir-rich version of the TaIR alloy would comprise iridium and tantalum, with an iridium content of 50 atomic% or more. Whilst Hsu does not explicitly disclose an absorber film according to instant claims 1 and 7, one having ordinary skill in the art would find an TaIr absorber film comprising more than 50 atomic% Ir obvious in view of the disclosure of Hsu. Refer to MPEP 2143 I. E.
Regarding Claims 3, 11, 13, and 18, when the Ir-rich TaIr alloy discussed above is used as the absorber layer material, the TaIr alloy comprises 50 atomic% to 90 atomic% Ir, and thus comprises the balance (10 atomic% to 50 atomic%) Ta. The Ir:Ta ratio is thus between 50:50 (equivalent to 1:1) and 90:10 (equivalent to 9:1). The ranges of the iridium and tantalum contents overlap with the ranges recited by instant claims 3, 11, 13, and 18, and thus per MPEP 2144.05 I., a prima facie case of obviousness exists.
Regarding Claims 5 and 15, Hsu discloses that the absorber layer is disposed directly over a buffer layer (Hsu, paragraph 0032-0033 and Fig. 3D). The buffer layer may be a chromium material, such as chromium oxide (CrO) or chromium nitride (CrN) (Hsu, paragraph 0031). The absorber layer, which was discussed above, comprises iridium and tantalum.
Claim(s) 4, 10, 12, 14, 17, and 19 are rejected under 35 U.S.C. 103 as being unpatentable over US 20220137499 A1 (hereby referred to as Hsu) as applied to claims 1 and 7 above, and further in view of US 20140011123 A1 (hereby referred to as Okamura).
Regarding Claims 4, 10, 12, 14, 17, and 19, Hsu renders obvious a reflective mask blank and a reflective mask accordingly to instant claims 1 and 7, respectively, as discussed above. Hsu discloses that the Ta-based alloy is doped with one or more interstitial elements such as boron (B), carbon (C), nitrogen (N), and oxygen (O) (Hsu, paragraph 0037). In some embodiments, the absorber layer includes TaIrON (Hsu, paragraph 0037), which is a material comprising iridium, tantalum, oxygen, and nitrogen.
However, Hsu is silent in regards to the oxygen content of such an absorber layer. Okamura teaches photomasks and methods of using the same. The photomask comprises a substrate with a multilayer reflection film, a capping layer, a buffer layer, and a light absorber layer formed thereon (Okamura, paragraph 0044 and Fig. 1). The absorber layer is formed of a tantalum-based alloy (Okamura, paragraph 0077), which is analogous to the Ta-based alloy used by Hsu for the absorber layer. Okamura prefers that oxygen is not present in the absorber layer (Okamura, paragraph 0078), but further states that the oxygen content in the absorber layer is preferably less than 25 atomic% (Okamura, paragraph 0079). Okamura recognizes that the oxygen content of the absorber layer has an effect on the etching rate (Okamura, paragraph 0080).
Hsu and Okamura are analogous art because both references pertain to reflective masks 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 have the oxygen content of the absorber film taught by Hsu be in the range of 0 to 25 atomic%, as taught by Okamura, because it has been recognized by the prior art that oxygen content of the absorber layer has an effect on the etching rate during patterning via a dry etching process (see Okamura, paragraph 0080). Thus, one having ordinary skill in the art would be motivated to routinely optimize the oxygen content of the absorber layer, based upon the teachings of Hsu and Okamura, in order to obtain a desired etching rate. One having ordinary skill in the art would wish to adjust the etching rate to ensure high accuracy etching whilst simultaneously preventing damage to other layers of the mask structure (see Okamura, paragraph 0079-0080). Refer to MPEP 2144.05 II.
Claim(s) 6 and 16 are rejected under 35 U.S.C. 103 as being unpatentable over US 20220137499 A1 (hereby referred to as Hsu) as applied to claims 5 and 15 above, and further in view of US 20200057365 A1 (hereby referred to as Liao).
Regarding Claims 6 and 16, Hsu renders obvious a reflective mask blank and a reflective mask accordingly to instant claims 5 and 15, respectively, as discussed above. Hsu discloses that the thickness of the absorber layer is controlled to provide between 95% and 99.5% absorption of EUV light at 13.5 nm, and thus has a thickness between 5 nm and 50 nm (Hsu, paragraph 0039).
However, Hsu is silent in regards to the thickness of the buffer layer. Liao teaches a mask and a method of forming the same. The mask comprises a substrate, a reflective multilayer, a capping layer, a buffer layer, and an absorber layer (Liao, paragraph 0019-0022 and Fig. 3). The absorption layer includes tantalum-based compounds and alloys (Liao, paragraph 0022), which is analogous to the absorber layer of Hsu. The buffer layer comprises a chromium-based material (Liao, paragraph 0021), which is analogous to the buffer layer of Hsu. Liao teaches that the buffer layer preferably has a thickness between 2 and 5 nm (Liao, paragraph 0021), which is within the range recited by instant claims 6 and 16.
Hsu and Liao are analogous art because both references pertain to reflection masks 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 use a buffer layer having a thickness of 10 nm or less, as suggested by Liao, in the mask blank and reflective mask taught by Hsu because such a thin buffer layer sufficiently protects the reflective multilayer film during the etching of the absorption layer, allowing the mask to remain of relatively low overall thickness (Liao, paragraph 0021).
Claim(s) 20-23 are rejected under 35 U.S.C. 103 as being unpatentable over US 20220137499 A1 (hereby referred to as Hsu) as applied to claims 1 and 7 above, and further in view of US 20190265585 A1 (hereby referred to as Ikebe).
Regarding Claims 20-23, Hsu renders obvious a reflective mask blank and a reflective mask accordingly to instant claims 1 and 7, respectively, as discussed above. Hsu discloses that a hard mask film is disposed over the absorber layer (Hsu, paragraph 0041-0042 and Fig. 3E). The hard mask layer is considered equivalent to an etching mask film, as recited by instant claims 20-23.
However, Hsu is silent in regards to the hard mask layer comprising chromium and one or more of the light elements recited by instant claims 20-22, as well as a chromium content of the hard mask layer with respect to the chromium content of the buffer layer. Ikebe teaches a reflective mask blank and a method of manufacturing a reflective mask. The mask blank comprises a substrate, a reflective multilayer film, a protective film, an absorber film, and an etching mask film (an etching hard mask) (Ikebe, paragraph 0048 and Fig. 1). The mask blank structure of Ikebe is analogous to the mask blank structure taught by Hsu. Ikebe teaches that the etching mask film is formed on the absorber layer (Ikebe, paragraph 0078), and materials for the etching mask film include materials containing chromium (Ikebe, paragraph 0079). The chromium-containing compounds contain chromium and one or more elements selected from nitrogen, oxygen, carbon, and boron (Ikebe, paragraph 0080). Specific examples of materials include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, CrBOCN, and the like (Ikebe, paragraph 0080). The chromium content ratio in the etching mask film is between 50 and 100 atomic%, and is more preferably between 80 and 100 atomic% (Ikebe, paragraph 0080). Based upon the disclosures of Hsu and Ikebe, the chromium content of the buffer layer and the chromium content of the etching mask film may be different.
Hsu and Ikebe are analogous art because both references pertain to reflection masks. It would have been obvious to one having ordinary skill in the art before the filing date of the instant application to use a chromium-containing compound as the etching mask layer, as taught by Ikebe, in the mask blank and reflective mask taught by Hsu because the chromium-based etching mask layer taught by Ikebe offers high selectivity for etching when patterning the absorber layer (Ikebe, paragraph 0078-0080). Furthermore, the etching mask layer material taught by Ikebe allows for a relatively thin layer thickness for the etching mask layer that can precisely form a transfer pattern on the absorber film (Ikebe, paragraph 0083).
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. US 20210373430 A1 (hereby referred to as Tsai) teaches an EUV photo mask and a manufacturing method of the same. The EUV photo mask blank is of similar structure as the instant application’s mask blank. The absorber layer may be an iridium-based material, such as elemental iridium, or an iridium alloy, such as IrPt, IrAl, IrRu, IrB, IrN, IrSi, and/or IrTi (Tsai, paragraph 0025). The absorber layer may further include one or more additional metalloid elements, such as Si, B, Ge, Al, As, Sb, Te, Se, and/or Bi (Tsai, paragraph 0041). When the additional element is present in the absorber layer, the content of the additional element is in a range from 0.5 atomic% to 30 atomic%, more preferably in a range of 1 atomic% to 10 atomic% (Tsai, paragraph 0042). The absorber layer taught by Tsai teaches several of the other additive elements recited by instant claims 1 and 7.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to JAYSON D COSGROVE whose telephone number is (571)272-2153. The examiner can normally be reached Monday-Friday 10:00-18:00.
Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice.
If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Mark Huff can be reached at (571)272-1385. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/JAYSON D COSGROVE/Examiner, Art Unit 1737
/JONATHAN JOHNSON/Supervisory Patent Examiner, Art Unit 1734