JP4897604B2 - Etching solution for photomask manufacturing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching solution for a photo mask, which is excellent in moistness wettability with respect to a material to be etched (a metallic thin film), especially, to an electron beam resist pattern, and also excellent in storage stability with a stable and highly and finely precise etching effect. <P>SOLUTION: The etching solution contains a compound expressed by a general expression (1), wherein Rf1 and Rf2 are a 1-4C straight-chain fluorocarbon group, where H in an alkyl group is entirely substituted with F or are a branched fluorocarbon group; X is kalium, lithium, or natrium ion. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an etching solution used for manufacturing a photomask, and more particularly, to a photolithographic photomask used for manufacturing a semiconductor integrated circuit with high fine accuracy and high yield corresponding to advancement and miniaturization of an integrated circuit. It is related with the etching liquid from which a mask is obtained.

  In general, an etching solution used for manufacturing a photomask is used in an etching process in the next photomask manufacturing process. That is, the photomask manufacturing process includes soda lime glass such as soda lime, white crown, borosilicate, low expansion glass such as alkali-free and aluminosilicate, quartz glass such as synthetic quartz, and metal thin film such as chromium. Is formed by a method such as vapor deposition or sputtering, and a method such as a spin coater method, a dipping method, a spray method, or a paddle method is applied to an electron beam resist such as a positive electron beam resist or a negative electron beam resist or a resist such as an ultraviolet resist. After the metal thin film is uniformly coated with, a desired pattern is exposed and drawn with an electron beam or the like, and then developed with a developer such as an organic solvent or an aqueous alkali solution. After development, the resist film is hardened by baking, etc., followed by a descum (slightly scraping the chromium and resist surface) process, and after etching a metal thin film such as chromium with an etching solution, the resist film is peeled off and photo Manufactures masks. The etching solution used in the photomask manufacturing process is used alone or with the addition of a surfactant for the purpose of improving wettability.

  In recent years, the degree of integration of photomasks as original plates for printing a semiconductor integrated circuit diagram on a silicon wafer has increased so as to require ultrafine accuracy of 0.13 micrometers or less. For this reason, the resist used for manufacturing the photomask is also being replaced by an electron beam resist that can obtain a photomask with ultrafine accuracy from an ultraviolet resist. However, since the electron beam resist described above has poor wettability with respect to an etching solution as compared with an ultraviolet resist, high-precision etching accuracy cannot be obtained in etching.

  However, in the photomask manufacturing process described above, the etching solution to which a hydrocarbon surfactant such as a conventional alkylaryl sulfonate or sulfosuccinate is added has chemical stability such as oxidation resistance and storage stability. In addition, sufficient performance in wettability cannot be exhibited. In particular, there is a tendency to change with time depending on the etching agent of a strong acid, and therefore there is a problem in obtaining a highly accurate etching effect, and it is desired to provide an etching solution using an alternative surfactant.

  Therefore, an etching solution (Patent Document 1) that uses a certain type of fluorine-based surfactant as a surfactant other than the above-mentioned additives has been proposed so far. Performance such as compatibility, resist pattern and wettability to the material to be etched (metal thin film such as chromium) and storage stability are not enough, and appearance quality such as shape defects after etching (chromium etching chromium residue) is a problem. Occurs. Therefore, at present, there is no etching solution corresponding to higher accuracy by increasing the degree of integration such as pattern dimension accuracy such as etching processing accuracy.

Japanese Patent No. 3809444

  The present invention provides a photomask etching solution with respect to a material to be etched (a metal thin film such as chromium) and particularly an electron beam resist pattern, compared to a conventional etching solution to which a hydrocarbon or fluorine-based surfactant is added. An object of the present invention is to provide an etching solution for a photomask which has excellent wet wettability, has a stable and highly precise etching effect, and has good storage stability.

（上記式中のＲｆ１およびＲｆ２は、いずれも、アルキル基のＨの全部をＦで置き換えた炭素数が４の直鎖のフッ化炭素基または分岐鎖を有するフッ化炭素基であり、Ｘは、カリウム、リチウム、またはナトリウムイオンである。）
また、本発明の好ましい実施形態では、前記Ｘがカリウムであり、エッチング液１００質量部に対してＥ成分を０．００１〜０．１質量部含有しており、エッチング剤の濃度が、１５〜２５質量％であり、表面張力が１９〜２５ｍＮ／ｍであるエッチング液を提供する。 As a result of intensive studies to solve the above problems, the present inventor has found that an etching solution containing a compound represented by the following general formula (1) (hereinafter referred to as “E component”) type surfactant is to be etched. Excellent wettability to materials (metal thin films such as chromium) and resist patterns, solubility / compatibility with aqueous etching solution, storage stability, etc., and high-precision etching for higher integration It was found that the etching solution has an effect. The present invention relates to an etching solution for use in the production of a photomask using a metal thin film made of chromium and / or chromium oxide , a compound represented by the following general formula (1), ceric ammonium nitrate and perchlorine. An etching solution for producing a photomask , comprising: an etching agent containing an acid .

(Rf1 and Rf2 in the formula are all carbon atoms of the total replaced by F of H alkyl group is 4 linear fluorocarbon Motoma other is fluorocarbon group having a branched chain, X is a potassium, lithium, or sodium ion.)
Further, in a preferred embodiment of the present invention, before Symbol X is potassium, and contain 0.001 to 0.1 parts by weight of component E to the etching solution 100 parts by weight, the concentration of ET etching agent, a 15 to 25% by weight, surface tension is to provide an etching solution which is 19~25mN / m.

According to the present invention, excellent etchant sophistication and etch rate high fine accuracy and yield good photomask corresponding to miniaturization is obtained the Integrated Circuit is provided.

（上記式中のＲｆ１およびＲｆ２は、いずれも、アルキル基のＨの全部をＦで置き換えた炭素数が４の直鎖のフッ化炭素基または分岐鎖を有するフッ化炭素基であり、Ｘは、カリウム、リチウム、またはナトリウムイオンである。）
上記のＥ成分であるビスペルフルオロアルキルスルフォンイミド塩は、単独でも、あるいは２種以上の混合物としても使用することができる。 Next, the present invention will be described in more detail with reference to preferred embodiments. The E component that mainly characterizes the present invention is a compound surfactant represented by the following general formula (1).

(Rf1 and Rf2 in the formula are all carbon atoms of the total replaced by F of H alkyl group is 4 linear fluorocarbon Motoma other is fluorocarbon group having a branched chain, X is a potassium, lithium, or sodium ion.)
The bisperfluoroalkylsulfonimide salt as the E component can be used alone or as a mixture of two or more.

The number of carbon atoms of the fluorocarbon group constituting the component E, have shifted also 4. When the number of carbon atoms exceeds 4, there is a problem that the solubility in the etching solution is deteriorated. When the number of carbon atoms is less than 4, the E component is easily dissolved in the etching solution, but the performance as a surfactant is poor. There is a problem.

  The metal salt of the E component is a potassium, lithium, or sodium salt. Other salts such as ammonium salts tend to become cloudy when added to the etchant, and other metal salts are not preferred because they are not very soluble in the etchant. Of the above metal salts, potassium salts are particularly effective.

  Examples of the E component in which the fluorocarbon group has 4 carbon atoms and the metal salt thereof is potassium include bisperfluorobutanesulfonimide potassium salt. In particular, when the above compound is used as a photomask etching solution, an etching solution exhibiting excellent effects on etching property, solubility, surface tension, and storage stability can be obtained.

等の陰イオン界面活性剤、

等の陽イオン界面活性剤、ＲｆＯＨ、ＲｆＢＮ（Ｃ₂Ｈ₄Ｏ）_nＨ等の非イオン界面活性剤、両性イオン界面活性剤等の上記の化学式のフッ素系界面活性剤がある。なお、上記式においてＲｆはフッ化炭素基であり、ＢはＣＯまたはＳＯ₂であり、Ｒ’及びＲ”はＨまたは低級アルキル基であり、Ｍはアルカリ金属またはアルカリ土類金属であり、Ｙはハロゲン酸根であり、ＨＹは酸を示す。しかしながら、これらの従来のフッ素系界面活性剤は、ある一定の表面張力の低下、熱安定性および耐酸化性等の性能では、従来の界面活性剤より特徴があるが、フォトマスクのエッチング液との溶解性や相溶性が悪く、クロム等の金属薄膜上に形成された超微細のレジストパターンの間隙に対する湿潤濡れ性が悪く、間隙部の底のコーナー部に泡溜りが発現し、エッチングむらが発生しやすい。特に、エッチング液中のこれらフッ素系界面活性剤は、溶解性が悪く界面活性剤の結晶が析出したり、沈殿したり、あるいは混合した時点では、溶解しているが、数日放置以降には沈殿物が発現するため、エッチング液を濾過して使用しなければならない。また、濾過後も経時変化によって再結晶や沈殿の発現の問題があり、フォトマスクのエッチング工程において、これらの析出物は微量でもエッチングむらの原因にもなる。また、エッチング効果に影響を及ぼす濡れ性の表面張力にバラツキが発現し、安定した歩留のよい高精度のフォトマスクが得られない。このために、エッチング効果に影響を及ぼす濡れ性、エッチング性、エッチング液の経時変化の保存安定性等のフォトマスク用エッチング液としての性能がとりづらいために好ましくない。 In general, in addition to the above-mentioned E component, RfCOOM, RfSO ₂ N (R ′) CH ₂ COOM, RfBNR′C ₂ H ₄ OSO ₃ M, RfCH ₂ OC _m H _2m SO ₃ M,

Anionic surfactants such as

Cation surfactants such as RfOH, nonionic surfactants such as RfBN (C ₂ H ₄ O) _n H, and zwitterionic surfactants such as fluorinated surfactants of the above chemical formula. In the above formula, Rf is a fluorocarbon group, B is CO or SO ₂ , R ′ and R ″ are H or a lower alkyl group, M is an alkali metal or alkaline earth metal, Y Is a halogen acid radical, and HY represents an acid, however, these conventional fluorosurfactants have a certain surface tension reduction, thermal stability and oxidation resistance, and the like. Although it has more features, it has poor solubility and compatibility with the photomask etching solution, poor wet wettability with respect to the gaps of ultrafine resist patterns formed on metal films such as chromium, and the bottom of the gaps. Bubbles appear in the corners, and etching unevenness is likely to occur.In particular, these fluorosurfactants in the etching solution are poorly soluble and may cause precipitation or precipitation of surfactant crystals. Is dissolved at the time of mixing, but precipitates appear after standing for a few days, so the etching solution must be filtered and used. In the photomask etching process, these precipitates may cause etching unevenness even in a small amount, and the wettability surface tension, which affects the etching effect, may vary, resulting in a stable process. For this reason, the performance as a photomask etching solution such as wettability that affects the etching effect, etching property, and storage stability of the etching solution over time is taken into consideration. It is not preferable because it is difficult.

  As an etching agent which comprises the etching liquid of this invention, Preferably what contains ceric ammonium nitrate and perchloric acid or an acetic acid is mentioned. Among the above-mentioned etching agents, a mixture of ceric ammonium nitrate and perchloric acid is particularly preferably used. In order to exhibit an excellent effect as a photomask etching solution, 3 to 35 parts by mass of ceric ammonium nitrate is mixed with 5 to 10 parts by mass of perchloric acid, and these are dissolved in ion-exchanged water. An aqueous solution having a concentration of ˜40 mass%, preferably 15 to 25 mass% is suitably used. When the upper limit concentration of the above-mentioned etching agent is exceeded, the solubility of the etching agent is deteriorated, and when it is less than the lower limit of the above-mentioned etching agent, there is a problem that the etching rate is slowed down. It should be noted that additives other than the E component may remain as residues on the photomask after etching, and it is preferable not to add them as much as possible because of the influence on the resolution of the photomask.

  The E component is used in a proportion of 0.001 to 0.1 parts by mass, preferably 0.002 to 0.06 parts by mass with respect to 100 parts by mass of the etching solution. If the use amount of the E component exceeds the above upper limit part by mass, the solubility of the E component will deteriorate, and if it is less than the above lower limit part by mass, the surface tension of the etching solution will not decrease and good wettability There is a problem that the effect of can not be obtained.

  The etching liquid of the present invention preferably has a surface tension of 19 to 25 mN / m, more preferably a surface tension of 19 to 23 mN / m. When the surface tension exceeds 25 mN / m, the wet wettability is deteriorated, the wettability of the resist pattern formed on the metal thin film such as chromium is deteriorated, and the etching effect is lowered. On the other hand, when the surface tension is less than 19 mN / m, there is no effective effect on etching.

  The etching solution of the present invention can be used for the production of a photomask using a metal thin film of chromium, chromium oxide, molybdenum, tantalum or the like and a composite metal thin film thereof. As an example of use in the manufacture of a chrome photomask, after washing quartz glass, a thin film having a thickness of 800 to 1200 nm is formed on the quartz glass by sputtering or vacuum deposition, and polybutylsulfone and polyglycidyl are formed thereon. Negative electron beam resists such as methacrylate-polyethyl acrylate copolymers, positive electron beam resists, positive ultraviolet decomposition resists such as phenol formaldehyde resins containing diazonaphthoquinone sensitizers, X-ray curable resists, etc. The resist is coated to a film thickness of 400 to 600 nm, the integrated circuit pattern is exposed and drawn with an electron beam or the like, developed with a developer, subjected to baking curing of the resist film, and a descum process. 2 by spraying or dipping using etching solution High quality photomask is obtained by performing the second to 80 seconds etching.

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified. In addition, this invention is not limited to the following Example.
Examples 1 to 4 (Etching liquids K1 to K4)
Each component was mix | blended like Table 1, and it mixed well and stirred, and prepared etching liquid K1-K4 of this invention. In addition, the etching agent and E component in Table 1 are as follows.
[Etching agent]
A: ceric ammonium nitrate b: perchloric acid (40% aqueous solution)
[E component]
(C ₄ F ₉ SO ₂ ) ₂ NK (Bisperfluorobutanesulfonimide potassium salt)

上記表中の数値は部数を表わす。

The numerical values in the above table represent the number of copies.

(Comparative Examples 1 to 3) (Etching liquids L1 to L3)
Each component was mix | blended like Table 2, and it mixed well and stirred and prepared etching liquid L1-L3. In addition, the etching agent and surfactant in Table 2 are as follows.
[Etching agent]
A: ceric ammonium nitrate b: perchloric acid (40% aqueous solution)
[Surfactant]
C: C ₈ F ₁₇ SO ₃ K simple substance having a linear fluorocarbon group d: C ₈ F ₁₇ SO ₃ K simple substance having a branched fluorocarbon group e: Linear fluorocarbon group a mixture of C ₈ F ₁₇ SO ₃ K15 parts having a C ₈ F ₁₇ SO ₃ K85 parts and branched chain fluorocarbon groups having

上記表中の数値は部数を表わす。

The numerical values in the above table represent the number of copies.

The etching properties, storage stability, solubility and surface tension of each of the etching solutions obtained above were evaluated by the following measuring methods.
(Etching property)
A composite thin film layer composed of chromium 800 nm and then chromium oxide 300 nm is formed on the quartz glass substrate that has been cleaned using the respective etching solutions by sputtering, and an electron beam resist is formed on the thin film layer. [Toray Industries, Inc., EBR-9 HS 31] was applied to a film thickness of 400 nm, and after application, electron beam exposure and development were performed. After development, the developed resist pattern was sprayed by a spray etching machine (NE-Takizawa Sangyo) 7000), the etching residue on the chrome photomask was determined with a 1000 × microscope. The evaluation results are shown in Table 3.
Evaluation point A: No etching residue is observed.
X: Etching residue is recognized.

(Storability)
Each of the etching solutions was allowed to stand at 25 ° C. for 4 months or more, and the expression of precipitates and crystals and the change in surface tension were measured. The evaluation results are shown in Table 3.
Evaluation point (double-circle): An etching liquid WHEREIN: The expression of a precipitate and a crystallite, and the change of surface tension are not recognized.
X: The etching solution has the appearance of precipitates and crystals, resulting in high surface tension.

(Solubility)
The solubility of the E component or surfactant in each of the etching solutions in the etching solution was determined with the naked eye according to the following criteria. The evaluation results are shown in Table 3.
Evaluation point (double-circle): The crystal | crystallization of the said component does not precipitate or precipitate on the surface of a liquid, but solubility is favorable.
X: The above components are deposited or precipitated on the surface of the etching solution, and the solubility is poor.

(surface tension)
Each of the etching solutions was determined by an electron equilibrium method (platinum plate suspension method). The evaluation results (25 ° C., mN / m) are shown in Table 3.

  From the above evaluation results, the etching solution of the present invention is superior in wet wettability to the electron beam resist and the material to be etched, compared with the etching solution containing a conventional fluorosurfactant. It has been demonstrated that it has stable solubility and storage without the appearance of precipitates such as precipitates, and has excellent etching properties with which a highly fine etching effect can be obtained.

  The etching solution of the present invention can be effectively used as an etching solution for manufacturing a photomask used for manufacturing a semiconductor integrated circuit with high fine accuracy and high yield corresponding to advancement and miniaturization of an integrated circuit. it can.

Claims (5)

An etching solution used for manufacturing a photomask using a metal thin film made of chromium and / or chromium oxide,
A compound represented by the following general formula (1) (hereinafter referred to as “E component”) ;
An etching solution for producing a photomask , comprising: an etching agent containing ceric ammonium nitrate and perchloric acid .

(Rf1 and Rf2 in the formula are all carbon atoms of the total replaced by F of H alkyl group is 4 linear fluorocarbon Motoma other is fluorocarbon group having a branched chain, X is a potassium, lithium, or sodium ion.) The etching solution according to claim 1, wherein X is potassium. The etching liquid of Claim 1 or 2 which contains 0.001-0.1 mass part of said E components with respect to 100 mass parts of etching liquids. The etching solution according to any one of claims 1 to 3, wherein a concentration of the etching agent is 15 to 25% by mass. The surface tension is 19 to 25 mN / m, the etching solution according to any one of claims 1 to 4 .