JP2006208210A - Method and device of inspecting optical component of exposing optical system - Google Patents
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本発明は電子製品などの製造に用いられる、フォトマスクなどの露光光学系光学部品の表面の汚染物質である硫酸アンモニウム汚染を検出する検査方法及び検査装置に関する。 The present invention relates to an inspection method and an inspection apparatus for detecting ammonium sulfate contamination, which is a contaminant on the surface of an exposure optical system optical component such as a photomask, used in the manufacture of electronic products and the like.
多くの電子製品、例えば、半導体、フラットパネルディスプレイなどは微細パターンの加工手段としてリソグラフィ技術を用いている。リソグラフィ技術はフォトマスクまたはレチクルと呼ばれる原版をシリコンウエハなどの基板に光学的に投影転写する方法である。リソグラフィ技術による半導体などの製造工程では、その多くはクリーンルームで実施されている。近年、気体中の浮遊分子汚染物質または気相分子汚染物質(Air bone Molecular Contamination:AMC、以下AMCと表記)が材料表面に化学的相互作用によって付着し、表面分子汚染(Surface Molecular Contamination:SMC,以下SMCと表記)として性能劣化や不良の要因となる問題が発生している。このようなSMCは半導体プロセスでは、例えばレジストのT―トッピング、不完全なエピタキシャル成長、不均質な酸化物成長、腐蝕工程の不均一反応、配線材料の密着性不良などを引き起こし、電子製品として正常な電気的特性が得られなくなる原因となる。 Many electronic products, such as semiconductors and flat panel displays, use lithography techniques as means for processing fine patterns. The lithography technique is a method of optically projecting and transferring an original plate called a photomask or reticle onto a substrate such as a silicon wafer. Many of the manufacturing processes of semiconductors and the like by lithography technology are performed in a clean room. In recent years, floating molecular contaminants or gas phase molecular contaminants (AMC, hereinafter referred to as AMC) in gas have been attached to the material surface by chemical interaction, and surface molecular contamination (SMC, (Hereinafter referred to as SMC), a problem that causes performance degradation and failure has occurred. Such SMCs cause normal T-topping of resists, incomplete epitaxial growth, inhomogeneous oxide growth, non-uniform reaction in the corrosion process, poor adhesion of wiring materials, etc. It becomes a cause that electrical characteristics cannot be obtained.
有害なSMCを引き起こす種々のAMCはクリーンルームではその存在が当該分野では公知であり、例えば半導体分野では米国ではSEMI規格F21−95クラスA,B,C,Dにグループ分類されている。 The existence of various AMCs that cause harmful SMCs is known in the field in the clean room. For example, in the semiconductor field, the AMCs are grouped into SEMI standards F21-95 classes A, B, C, and D in the United States.
また、最近ではAMC,SMC物質単体ではなく、リソグラフィの露光工程で用いられるレーザーなどの光源による光エネルギー照射を受けたAMC,SMC物質が光化学反応(CVD)により新たな生成物を発生させる問題が生じている。 Also, recently, AMC and SMC substances are not single substances, but AMC and SMC substances irradiated with light energy from a light source such as a laser used in lithography exposure process generate new products by photochemical reaction (CVD). Has occurred.
これらの生成物は露光光学系で用いられているレンズなどの光学部品やフォトマスク表面上で発生し、析出型パーティクル欠陥として出現し、フォトマスクにおいては回路パターンの形状不良として判定される。このような生成物の一例として硫酸アンモニウム((NH4)2SO4)(結晶)が挙げられる。半導体製造工場のクリーンルーム空気内には微量ながら二酸化硫黄(SO2)やアンモニア(NH4)などの物質が存在する。これらの物質が露光エネルギーにより空気中の酸素(O2)および水蒸気(H2O)と結びつき、硫酸アンモニウムが生成されると考えられている。半導体露光装置内の露光光学系部品においてはレンズなどの透過率、反射ミラーにおいてはその反射率が低下して照明効率が低下する不都合があった。このため、半導体露光装置においては硫酸アンモニムの発生監視方法や(特許文献1)、シリコンウエハ上に形成された半導体回路パターンの検査光学系におけるくもりの発生を抑制する検査装置(特許文献2)が考案されている。 These products are generated on the surface of an optical component such as a lens used in the exposure optical system and the photomask, appear as precipitation-type particle defects, and are determined as a circuit pattern shape defect in the photomask. An example of such a product is ammonium sulfate ((NH 4 ) 2 SO 4 ) (crystal). A small amount of substances such as sulfur dioxide (SO 2 ) and ammonia (NH 4 ) exist in the clean room air of a semiconductor manufacturing factory. It is considered that these substances are combined with oxygen (O 2 ) and water vapor (H 2 O) in the air by exposure energy to produce ammonium sulfate. In the exposure optical system parts in the semiconductor exposure apparatus, the transmittance of a lens or the like is lowered, and in the reflection mirror, the reflectance is lowered, and the illumination efficiency is lowered. For this reason, in the semiconductor exposure apparatus, there is an ammonium sulfate generation monitoring method (Patent Document 1) and an inspection apparatus (Patent Document 2) that suppresses the occurrence of clouding in an inspection optical system of a semiconductor circuit pattern formed on a silicon wafer. It has been devised.
以下に公知の文献を示す。
硫酸アンモニム(結晶)は前記の通りフォトマスクにおいてはパーティクル欠陥となるため、被露光物へのパターン転写品質に影響を及ぼす。硫酸アンモニウム(結晶)は露光機での光源エネルギーとの反応による析出型のためフォトマスクの製造時点では事前検査が不可能である。 Since ammonium sulfate (crystal) becomes a particle defect in the photomask as described above, it affects the quality of pattern transfer onto the object to be exposed. Ammonium sulfate (crystal) is a precipitation type that reacts with light source energy in an exposure machine, and therefore cannot be pre-inspected at the time of manufacturing the photomask.
フォトマスクはその製造工程で用いられるレジストなどの有機物除去に硫酸を用いた化学洗浄が行われている。この洗浄で残った硫酸残渣とクリーンルーム気相環境中に存在するアンモニアが硫酸アンモニウムの材料源となる。硫酸の洗浄残渣については微細パターンの遮光層や位相シフト層であるCrやCrO,CrON,MoSi,MoSiON合金などの金属や金属酸化膜の膜質との関係が挙げられる。これらの膜は一般にスパッタリング工程により形成するが、堆積形成の原理上、膜中で原子レベルで最密にはならず空孔が発生する。この空孔中に浸透したイオン性硫酸がリンスで除去困難なのが残渣の原因と考えられている。 The photomask is subjected to chemical cleaning using sulfuric acid to remove organic substances such as a resist used in the manufacturing process. The sulfuric acid residue remaining in this washing and the ammonia present in the clean room gas-phase environment are sources of ammonium sulfate. Regarding the cleaning residue of sulfuric acid, there is a relationship with the film quality of the metal or metal oxide film such as Cr, CrO, CrON, MoSi, MoSiON alloy which is a light shielding layer of fine pattern or phase shift layer. These films are generally formed by a sputtering process, but due to the principle of deposition formation, vacancies are generated in the film without being close-packed at the atomic level. It is considered that the ionic sulfuric acid that has penetrated into the pores is difficult to remove by rinsing, causing the residue.
本発明は上記問題点に鑑みなされたもので、フォトマスクなど露光光学系光学部品上に析出した結晶の硫酸アンモニウムを検出する露光光学系光学部品の検査方法及び検査装置を提供することを課題とする。 The present invention has been made in view of the above problems, and an object thereof is to provide an exposure optical system optical component inspection method and inspection apparatus for detecting ammonium sulfate in crystals precipitated on an exposure optical system optical component such as a photomask. .
本発明は係る課題を解決するものであり、本発明の請求項1の発明は、光学的透過性を有する露光光学系光学部品の表面の硫酸アンモニウム(結晶)を、分光反射スペクトルを用いて検出することを特徴とする露光光学系光学部品の検査方法としてものである。 The present invention solves this problem, and the invention of claim 1 of the present invention detects the ammonium sulfate (crystal) on the surface of an optical component having optical transparency by using a spectral reflection spectrum. This is an inspection method for optical components of the exposure optical system.
本発明の請求項2の発明は、光学的透過性を有する露光光学系光学部品の表面の硫酸アンモニウム(結晶)を、分光反射スペクトルを用いて検出する検出手段を有することを特徴とする露光光学系光学部品の検査装置としたものである。 According to a second aspect of the present invention, there is provided an exposure optical system comprising a detecting means for detecting ammonium sulfate (crystal) on the surface of an optical component having optical transparency by using a spectral reflection spectrum. This is an optical component inspection apparatus.
本発明は該検査対象物の光学的反射スペクトルから硫酸アンモニウム(結晶)を検出する方法及び装置を提供する。 The present invention provides a method and apparatus for detecting ammonium sulfate (crystals) from the optical reflection spectrum of the test object.
本発明は以上のような構成であるから、フォトマスクなど露光光学系光学部品のパーティクル検査など、形態検査手段で検出された欠陥のうち、部品表面上堆積した結晶の硫酸アンモニウムの物質判定を可能とする露光光学系光学部品の検査方法及び検査装置とすることができる。 Since the present invention is configured as described above, among the defects detected by the form inspection means, such as particle inspection of exposure optical system optical components such as a photomask, it is possible to determine the substance of ammonium sulfate in crystals deposited on the surface of the component. It can be set as the inspection method and inspection apparatus of the exposure optical system optical component.
以下、本発明の検査方法の工程の一例を図1に示す。まず、フォトマスクなど露光光学系光学部品の反射スペクトルを分光光度計にて波長150から300nm、少なくとも露光光源として用いられているエキシマレーザーの波長である、波長248nm (KrFレーザー)、193nm(ArFレーザー)、157nm(F2レーザー)のいずれかを包含して測定する(S1)。スペクトル差異の有無を、事前に測定した硫酸アンモニウムの発生が無い基準反射スペクトルと比較判定する(S2)。差異の有無で硫酸アンモニウムの有無を判定する(S3、S4)。すなわち、本発明の方法では、測定した反射スペクトルと、基準となる反射スペクトルとを比較することで、硫酸アンモニウムの有無を検出する。尚、フォトマスクでの測定箇所は、ハーフトーン型位相シフトマスクでは、ハーフトーン部あるいはガラス基板のどちらかが表面に一様に露出している部分が好ましい。また、通常のバイナリーマスクやレベンソン型位相シフトマスクなどの場合は、ガラス基板
が一様に露出している箇所が好ましく、その大きさは、測定光のスポットサイズとなる。
An example of the process of the inspection method of the present invention is shown in FIG. First, the reflection spectrum of an exposure optical system optical component such as a photomask is measured with a spectrophotometer at a wavelength of 150 to 300 nm, at least the wavelengths of an excimer laser used as an exposure light source, wavelengths 248 nm (KrF laser), 193 nm (ArF laser) ) Measurement is performed including any of 157 nm (F2 laser) (S1). The presence / absence of the spectral difference is determined by comparison with a reference reflectance spectrum measured in advance and free of ammonium sulfate (S2). The presence or absence of ammonium sulfate is determined based on the presence or absence of a difference (S3, S4). That is, in the method of the present invention, the presence or absence of ammonium sulfate is detected by comparing the measured reflection spectrum with a reference reflection spectrum. In the halftone phase shift mask, the measurement location on the photomask is preferably a portion where either the halftone portion or the glass substrate is uniformly exposed on the surface. In the case of an ordinary binary mask, Levenson-type phase shift mask, or the like, a portion where the glass substrate is uniformly exposed is preferable, and the size is the spot size of the measurement light.
つぎに、図1の工程で実測した測定結果の一例を説明する。本実施例では、くもりが未発生の基準フォトマスク(a),と発生したフォトマスク(b)2種類を用いる。また、フォトマスク(a),(b)はArF(波長193nm)用途の6インチサイズの位相シフトマスクであり、片側面にモリブデンとシリコンの合金膜(MoSi)を製膜した石英硝子基板(Qz)を用いた。ブランクにパターンを形成した後、くもりの発生したフォトマスクは、露光機に設定し上記レーザー光を照射して作成した。 Next, an example of the measurement result actually measured in the process of FIG. 1 will be described. In this embodiment, a reference photomask (a) in which no clouding has occurred and two types of photomasks (b) in which fogging has occurred are used. The photomasks (a) and (b) are 6-inch size phase shift masks for ArF (wavelength 193 nm), and a quartz glass substrate (Qz) having an alloy film of molybdenum and silicon (MoSi) formed on one side. ) Was used. After the pattern was formed on the blank, a cloudy photomask was prepared by setting the exposure machine and irradiating the laser beam.
図2にくもり未発生の基準フォトマスク(a)とくもりが発生したフォトマスク(b)の反射スペクトルを示す。横軸は露光光の波長(単位nm)、縦軸は反射率(単位%)を表す。基板への入射角度は15度とし、波長領域は150から300nmとした。未発生の反射スペクトルAは上記の基準反射スペクトルである。これに対し、発生した反射スペクトルBは図示した波長領域150から300nm全域に亘って概ね3%減少しており、表1に示した通り、ArFレーザー波長の193.2nmでは3%の低下が認められた。 FIG. 2 shows reflection spectra of a reference photomask (a) where no clouding occurs and a photomask (b) where clouding occurs. The horizontal axis represents the wavelength (unit: nm) of exposure light, and the vertical axis represents the reflectance (unit:%). The incident angle on the substrate was 15 degrees, and the wavelength region was 150 to 300 nm. An ungenerated reflection spectrum A is the above-described reference reflection spectrum. On the other hand, the generated reflection spectrum B is reduced by approximately 3% over the entire wavelength range from the illustrated wavelength region 150 to 300 nm. As shown in Table 1, a decrease of 3% is observed at the ArF laser wavelength of 193.2 nm. It was.
また硫酸アンモニウム有無の検証は、イオンクロマトグラムで分析して実施した。分析方法は基板上に純水を滴下・捕集し、液中に溶解した成分を調べる方法とした。分析はフォトマスクの位相シフト膜側であるモリブデンシリコン合金膜面(MoSi)と反対面のガラス(Qz)面を片側づつ実施し、表2に結果を示す。硫酸アンモニウムの成分である硫酸イオン(SO4−)とアンモニアイオン(NH3+)が、くもりが発生したフォトマスク(b)では多量検出されることが確認された。 In addition, verification of the presence or absence of ammonium sulfate was performed by analysis with an ion chromatogram. The analysis method was a method in which pure water was dropped and collected on the substrate and the components dissolved in the liquid were examined. The analysis was performed for each side of the glass (Qz) surface opposite to the molybdenum silicon alloy film surface (MoSi) on the phase shift film side of the photomask, and the results are shown in Table 2. It was confirmed that sulfate ions (SO 4 −) and ammonia ions (NH 3 +), which are components of ammonium sulfate, are detected in large amounts in the cloudy photomask (b).
なお、スペクトルの測定データからその差分を算出し、所定の値以上であれば低下したと判断することもでき、これを検出手段とすることも出来る。 Note that the difference is calculated from the measurement data of the spectrum, and if it is equal to or greater than a predetermined value, it can be determined that the value has decreased, and this can be used as a detection means.
図2及び、表1、表2の結果から、硫酸アンモニウムの検査が反射スペクトルで可能なことが示された。 The results of FIG. 2 and Tables 1 and 2 showed that inspection of ammonium sulfate was possible in the reflection spectrum.
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JP2008165104A (en) * | 2007-01-04 | 2008-07-17 | Fujitsu Ltd | Inspection method of reticle and method for controlling reticle |
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