JP2008020374A - Defect inspection method and device therefor - Google Patents

Defect inspection method and device therefor Download PDF

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JP2008020374A
JP2008020374A JP2006193549A JP2006193549A JP2008020374A JP 2008020374 A JP2008020374 A JP 2008020374A JP 2006193549 A JP2006193549 A JP 2006193549A JP 2006193549 A JP2006193549 A JP 2006193549A JP 2008020374 A JP2008020374 A JP 2008020374A
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defect
polarization
light
sample
detected
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Yuta Urano
雄太 浦野
Rei Hamamatsu
玲 浜松
Shunji Maeda
俊二 前田
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Hitachi High Tech Corp
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Hitachi High Technologies Corp
Hitachi High Tech Corp
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Priority to JP2006193549A priority Critical patent/JP2008020374A/en
Priority to US11/776,572 priority patent/US7664608B2/en
Publication of JP2008020374A publication Critical patent/JP2008020374A/en
Priority to US12/647,246 priority patent/US8427634B2/en
Priority to US13/846,441 priority patent/US8755041B2/en
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Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem a defect signal is missed and sensitivity is degraded by light scattered by a pattern in the irregular circuit pattern portion. <P>SOLUTION: An inspection device comprises: a stage for mounting a substrate sample and freely moving in each direction of X-Y-Z-θ; a lighting system for irradiating the substrate sample form an oblique position; and an image forming optical system for forming an inspection region that is lighted on a photoreciever, and the device condenses reflection scattered light produced on the substrate sample by irradiating the light in the lighting system. Further, the device comprises a polarized-light detector for simultaneously detecting a plurality of polarized components that are different from each other. Further, a plurality of the polarized-component signals different from each other that are detected by the polarized-light detector are compared in a plurality of chips or in an image in a predetermined region, and then a statistical outlier is inspected as a defect in the sample. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、半導体製造工程、液晶表示素子製造工程プリント基板製造工程等、基板上にパターンを形成して対象物を製作していく製造工程で発生する異物等の欠陥を検出し、分析して対策を施す製造工程における異物等の欠陥の発生状況を検査する欠陥検査方法およびその装置に関する。   The present invention detects and analyzes defects such as foreign matter generated in a manufacturing process of forming an object by forming a pattern on a substrate, such as a semiconductor manufacturing process, a liquid crystal display element manufacturing process, a printed circuit board manufacturing process, etc. The present invention relates to a defect inspection method and apparatus for inspecting the occurrence state of defects such as foreign matters in a manufacturing process for which measures are taken.

従来の半導体製造工程では、半導体基板(被検査対象基板)上に異物が存在すると配線の絶縁不良や短絡などの不良原因になり、さらに半導体素子が、微細化して半導体基板中に微細な異物が存在した場合にこの異物が、キャパシタの絶縁不良やゲート酸化膜などの破壊の原因にもなる。これらの異物は、搬送装置の可動部から発生するものや、人体から発生するもの、プロセスガスによる処理装置内で反応生成されたもの、薬品や材料に混入していたものなど種々の原因により種々の状態で混入される。   In a conventional semiconductor manufacturing process, if foreign matter exists on a semiconductor substrate (substrate to be inspected), it may cause a failure such as a wiring insulation failure or a short circuit. Further, the semiconductor element is miniaturized and fine foreign matter is generated in the semiconductor substrate. If present, this foreign substance also causes a failure of insulation of the capacitor and a breakdown of the gate oxide film. These foreign substances are various due to various causes such as those generated from the moving part of the transfer device, those generated from the human body, those generated by reaction in the processing apparatus by the process gas, those mixed in chemicals and materials, etc. It is mixed in the state of.

同様の液晶表示素子製造工程でも、パターン上に異物が混入するなど、何らかの欠陥が生じると、表示素子として使えないものになってしまう。プリント基板の製造工程でも状況は同じであって、異物の混入はパターンの短絡、不良接続の原因になる。
従来のこの種の半導体基板上の異物を検出する技術の1つとして、特開昭62−89336号公報(従来技術1)に記載されているように、半導体基板上にレーザを照射して半導体基板上に異物が付着している場合に発生する異物からの散乱光を検出し、直前に検査した同一品種半導体基板の検査結果と比較することにより、パターンによる虚報を無くし、高感度かつ高信頼度な異物及び欠陥検査を可能にするものがある。また、特開昭63−135848号公報(従来技術2)に開示されているように、半導体基板上にレーザを照射して半導体基板上に異物が付着している場合に発生する異物からの散乱光を検出し、この検出した異物をレーザフォトルミネッセンスあるいは2次X線分析(XMR)などの分析技術で分析するものがある。
Even in the same liquid crystal display element manufacturing process, if any defect occurs such as foreign matter mixed in the pattern, it cannot be used as a display element. The situation is the same in the manufacturing process of the printed circuit board, and mixing of foreign matters causes short-circuiting of the pattern and defective connection.
As one of the conventional techniques for detecting foreign matters on a semiconductor substrate of this type, as described in Japanese Patent Application Laid-Open No. 62-89336 (conventional technique 1), a semiconductor is irradiated with a laser to produce a semiconductor. By detecting scattered light from foreign matter generated when foreign matter is attached to the substrate and comparing it with the inspection result of the same type semiconductor substrate inspected immediately before, there is no false information due to the pattern, and high sensitivity and high reliability There are those that allow frequent foreign object and defect inspection. Further, as disclosed in Japanese Patent Application Laid-Open No. 63-135848 (Prior Art 2), the scattering from the foreign matter generated when the semiconductor substrate is irradiated with a laser and the foreign matter adheres to the semiconductor substrate. There is one that detects light and analyzes the detected foreign matter by an analysis technique such as laser photoluminescence or secondary X-ray analysis (XMR).

また、上記異物を検査する技術として、被検査対象基板にコヒーレント光を照射して被検査対象基板上の繰り返しパターンから射出する光を空間フィルタで除去し繰り返し性を持たない異物や欠陥を強調して検出する方法が知られている。   In addition, as a technique for inspecting the above foreign matter, the substrate to be inspected is irradiated with coherent light, and the light emitted from the repetitive pattern on the substrate to be inspected is removed by a spatial filter to emphasize foreign matters and defects having no repeatability. There are known methods for detecting them.

また、被検査対象基板上に形成された回路パターンに対して該回路パターンの主要な直線群に対して45度傾けた方向から照射して主要な直線群からの0次回折光を対物レンズの開口内に入力させないようにした異物検査装置が、特開平1−117024号公報(従来技術3)において知られている。この従来技術3においては、主要な直線群ではない他の直線群を空間フィルタで遮光することについても記載されている。   Further, the circuit pattern formed on the substrate to be inspected is irradiated from a direction inclined by 45 degrees with respect to the main line group of the circuit pattern, and the 0th-order diffracted light from the main line group is opened in the objective lens. A foreign substance inspection apparatus which is not allowed to be input to the inside is known from Japanese Patent Laid-Open No. 1-117024 (prior art 3). This prior art 3 also describes shielding other straight line groups that are not the main straight line group with a spatial filter.

また、異物等の欠陥検査装置およびその方法に関する従来技術としては、特開平1−250847号公報(従来技術4)、特開平6−258239号公報(従来技術5)、特開平6−324003号公報(従来技術6)、特開平8−210989号公報(従来技術7)、および特開平8−271437号公報(従来技術8)が知られている。   Further, as prior art relating to a defect inspection apparatus and method for foreign matters, etc., Japanese Patent Laid-Open No. 1-250847 (prior art 4), Japanese Patent Laid-Open No. 6-258239 (prior art 5), and Japanese Patent Laid-Open No. 6-324003. (Prior Art 6), JP-A-8-210989 (Prior Art 7), and JP-A-8-271437 (Prior Art 8) are known.

また、複数の偏光成分を同時に検出し、検査対象基板上に形成された薄膜の膜厚および薄膜の物性を求める表面検査装置が、特開2006−145305号公報(従来技術9)において知られている。   Further, a surface inspection apparatus that simultaneously detects a plurality of polarization components and obtains the thickness of a thin film formed on a substrate to be inspected and the physical properties of the thin film is known in Japanese Patent Laid-Open No. 2006-145305 (prior art 9). Yes.

また、複数の偏光成分を同時に検出する技術として、チャネルスペクトルを用いた偏光計測法が非特許文献1において、複屈折ウェッジを用いた偏光計測法が非特許文献1、非特許文献2において、振幅分割プリズムを用いた偏光計測法および微小偏光素子アレイを用いた偏光計測法が非特許文献3において知られている。   Further, as a technique for simultaneously detecting a plurality of polarization components, a polarization measurement method using a channel spectrum is disclosed in Non-Patent Document 1, and a polarization measurement method using a birefringence wedge is disclosed in Non-Patent Document 1 and Non-Patent Document 2. Non-Patent Document 3 discloses a polarization measurement method using a split prism and a polarization measurement method using a micro polarization element array.

特開昭62−89336号公報JP-A-62-89336 特開昭63−135848号公報JP-A 63-135848 特開平1−117024号公報Japanese Patent Laid-Open No. 1-117024 特開平1−250847号公報JP-A-1-250847 特開平6−258239号公報JP-A-6-258239 特開平6−324003号公報JP-A-6-324003 特開平8−210989号公報JP-A-8-210989 特開平8−271437号公報JP-A-8-271437 特開2006−145305号公報JP 2006-145305 A 岡和彦, 「チャネルスペクトルを利用した分光偏光計測」, O plus E, , Vol. 25, No. 11, p1248 (2003)Kazuhiko Oka, “Spectropolarimetry using channel spectrum”, O plus E,, Vol. 25, No. 11, p1248 (2003) K. Oka, "Compact complete imaging polarimeter using birefringent wedge prisms", Optics Express, Vol. 11, No. 13, p1510 (2003)K. Oka, "Compact complete imaging polarimeter using birefringent wedge prisms", Optics Express, Vol. 11, No. 13, p1510 (2003) 菊田久雄他, 「偏光画像計測システム」, O plus E, Vol. 25, No. 11, p1241 (2003)Hisao Kikuta et al., "Polarization Image Measurement System", O plus E, Vol. 25, No. 11, p1241 (2003)

しかしながら、上記従来技術1〜8では、不規則な回路パターン部分では、パターンからの散乱光によって欠陥信号が見落とされ、感度が低下する課題があった。   However, in the prior arts 1 to 8, there is a problem that in the irregular circuit pattern portion, the defect signal is overlooked by the scattered light from the pattern, and the sensitivity is lowered.

また、上記従来技術9は薄膜の膜厚および薄膜の物性を求めるためのものであり、欠陥検出の感度向上に直接寄与することはない。   The prior art 9 is for obtaining the thickness of the thin film and the physical properties of the thin film, and does not directly contribute to improving the sensitivity of defect detection.

本発明の目的は、上記課題を解決すべく、欠陥と同等の強度の散乱光を発するパターンを有する被検査対象基板上の欠陥を、高速で、しかも高精度に検査できるようにした欠陥検査装置およびその方法を提供することにある。   SUMMARY OF THE INVENTION An object of the present invention is to provide a defect inspection apparatus capable of inspecting a defect on a substrate to be inspected having a pattern that emits scattered light having the same intensity as that of a defect at high speed and with high accuracy in order to solve the above-described problems. And providing a method thereof.

上記目的を達成するために、本発明は、光源から出射した光を検査対象基板上の所定の領域に所定の偏光状態をもって導く照明光学部と、 前記所定領域において生じ所定の方位角範囲および所定の仰角範囲に伝播する反射散乱光を受光器に導き電気信号に変換する検出光学部と、前記電気信号に基づいて欠陥を示す信号を抽出する欠陥判定部とを備えた欠陥検査装置において、前記検出光学部において互いに異なる複数の偏光成分を独立に検出し各々の偏光成分に対応した複数の信号を得る偏光検出手段を有し、前記欠陥判定部において前記各々の偏光成分あるいはそれら演算によって得られる物理量を軸として張られる空間における前記複数の信号に対応するベクトルの終点の分布に基づいて欠陥を示す信号を抽出することを特徴とする。   In order to achieve the above object, the present invention provides an illumination optical unit that guides light emitted from a light source to a predetermined region on a substrate to be inspected with a predetermined polarization state, a predetermined azimuth angle range and a predetermined In a defect inspection apparatus comprising: a detection optical unit that guides reflected and scattered light propagating to an elevation angle range of the light to a light receiver and converts the light into an electrical signal; and a defect determination unit that extracts a signal indicating a defect based on the electrical signal. The detection optical unit has polarization detection means for independently detecting a plurality of different polarization components and obtaining a plurality of signals corresponding to the respective polarization components, and the defect determination unit obtains each of the polarization components or their calculation. A signal indicating a defect is extracted based on a distribution of end points of vectors corresponding to the plurality of signals in a space spanned by a physical quantity.

以上説明したように、前記構成によれば、散乱光を発するパターンが存在する検査対象基板に対して、微小な欠陥を高速で、しかも高精度に検査することができる。   As described above, according to the above configuration, a minute defect can be inspected at high speed and with high accuracy on a substrate to be inspected having a pattern that emits scattered light.

本発明の第一の実施の形態を図1から図9を用いて説明する。以下では、半導体ウェハ上の欠陥検査を例にとって説明する。   A first embodiment of the present invention will be described with reference to FIGS. Hereinafter, a defect inspection on a semiconductor wafer will be described as an example.

図1は、第一の実施の形態に係る欠陥検査装置の構成を示す。光源1、照明光学系100、検査対象基板W、対物レンズ3a、空間フィルタ4a、結像レンズ5a、偏光検出部200a、信号処理部300、全体制御部6、表示部7、演算部8、記憶部9、X-Y-Z-θステージドライバ10、X-Y-Z-θステージ11、光源ドライバ12から構成されている。光源1、照明光学系100、対物レンズ3a、空間フィルタ4a、結像レンズ5a、偏光検出部200aを合せて光学系1000とする。   FIG. 1 shows the configuration of the defect inspection apparatus according to the first embodiment. Light source 1, illumination optical system 100, inspection target substrate W, objective lens 3a, spatial filter 4a, imaging lens 5a, polarization detection unit 200a, signal processing unit 300, overall control unit 6, display unit 7, calculation unit 8, storage The unit 9 includes an XYZ-θ stage driver 10, an XYZ-θ stage 11, and a light source driver 12. The light source 1, the illumination optical system 100, the objective lens 3a, the spatial filter 4a, the imaging lens 5a, and the polarization detection unit 200a are combined to form an optical system 1000.

動作の概略を説明する。光源1より発した光は照明光学系100により被検査対象基板Wに照射される。検査対象基板Wから発した反射散乱光は対物レンズ3aで集光された後、空間フィルタ4a、結像レンズ5aを介して検出系光路14を通り、偏光検出部200aにて電気信号に変換される。得られた電気信号に基づき信号処理部300において検査対象基板上の欠陥が判定される。判定された結果は全体制御部6を介し、記憶部9に記憶され、表示部7に表示される。   An outline of the operation will be described. Light emitted from the light source 1 is applied to the inspection target substrate W by the illumination optical system 100. The reflected and scattered light emitted from the inspection target substrate W is collected by the objective lens 3a, passes through the detection system optical path 14 via the spatial filter 4a and the imaging lens 5a, and is converted into an electrical signal by the polarization detection unit 200a. The Based on the obtained electrical signal, the signal processing unit 300 determines a defect on the inspection target substrate. The determined result is stored in the storage unit 9 via the overall control unit 6 and displayed on the display unit 7.

空間フィルタ4aは、対物レンズ3aの出射側の瞳位置又はその共役な位置に配置されており、被検査対象基板W上に形成された微小なピッチの繰り返しパターンを照明することにより発生する回折光パターンを遮光するためのものであって、例えば特開2000−105203号公報に記載されているような、ピッチが可変な複数の直線状の遮光パターンを備えているものである。   The spatial filter 4a is arranged at the exit pupil position of the objective lens 3a or a conjugate position thereof, and diffracted light generated by illuminating a repetitive pattern with a minute pitch formed on the inspection target substrate W. The light-shielding pattern is provided with a plurality of linear light-shielding patterns with variable pitches as described in, for example, Japanese Patent Laid-Open No. 2000-105203.

検査対象基板Wを高照度で照明するためには、光源1は、レーザ光源が適している。微小な欠陥の散乱効率を上げるためには、深紫外光レーザ(DUV(Deep Ultraviolet)光)・真空紫外光レーザ・YAGレーザ第3あるいは第4高調波・水銀ランプ・キセノンランプなどの短波長の光源が適している。これらを満たす光源にはまた、光学系を構成する部品コストおよびメンテナンスコストを抑えるにはYAGレーザ第2高調波・ハロゲンランプ・水銀ランプ・キセノンランプなどの可視光波長の光源が適している。また、特定の偏光状態の照明光を高効率に生成するには、偏光度の高いレーザ光源が適している。   In order to illuminate the inspection target substrate W with high illuminance, the light source 1 is suitably a laser light source. In order to increase the scattering efficiency of minute defects, short-wavelength light such as deep ultraviolet laser (DUV (Deep Ultraviolet) light), vacuum ultraviolet light laser, YAG laser third or fourth harmonic, mercury lamp, xenon lamp, etc. A light source is suitable. As a light source satisfying these requirements, a light source having a visible light wavelength such as a second harmonic of a YAG laser, a halogen lamp, a mercury lamp, or a xenon lamp is suitable for suppressing the cost of components constituting the optical system and the maintenance cost. A laser light source with a high degree of polarization is suitable for generating illumination light in a specific polarization state with high efficiency.

図2(a)は照明光学系100の構成を示す。光源1から発射した光はアッテネータ101により、照明光の強度が制御される。偏光板102が必要に応じて設置され、光源より発する照明光の偏光が直線偏光に揃えられる。位相子103、104により、照明光の偏光状態が任意に設定される。位相子103、104は、光軸の周りに回転可能なλ/2板あるいはλ/4板あるいは位相量を制御可能な位相子で構成される。位相子103、104を透過した光はビームエキスパンダ105によって、照明光のビーム径が拡大される。ビームエキスパンダ105によって、ビーム径が拡大された照明光はミラー群M1〜M9およびシリンドリカルレンズ109、110、111によって検査対象基板W上に導かれる。図2(a)においては、ミラーM4とシリンドリカルレンズ109、ミラーM7とが重なり合う状態となるため、シリンドリカルレンズ109とミラーM7の表示を省略した。ミラーM5とシリンドリカルレンズ109、ミラーM8との関係、及びミラーM6とシリンドリカルレンズ110、ミラーM9との関係も同様になるので、シリンドリカルレンズ109、110及びミラーM8、M9の表示を省略した。   FIG. 2A shows the configuration of the illumination optical system 100. The intensity of the illumination light of the light emitted from the light source 1 is controlled by the attenuator 101. A polarizing plate 102 is installed as necessary, and the polarization of illumination light emitted from the light source is aligned with linearly polarized light. The polarization state of the illumination light is arbitrarily set by the phase shifters 103 and 104. The phase shifters 103 and 104 are composed of λ / 2 plates or λ / 4 plates that can rotate around the optical axis, or phase shifters that can control the phase amount. The light transmitted through the phase shifters 103 and 104 is expanded in beam diameter by the beam expander 105. The illumination light whose beam diameter has been expanded by the beam expander 105 is guided onto the inspection target substrate W by the mirror groups M1 to M9 and the cylindrical lenses 109, 110, and 111. In FIG. 2A, since the mirror M4, the cylindrical lens 109, and the mirror M7 are in an overlapping state, the display of the cylindrical lens 109 and the mirror M7 is omitted. Since the relationship between the mirror M5 and the cylindrical lens 109 and the mirror M8 and the relationship between the mirror M6 and the cylindrical lens 110 and the mirror M9 are the same, the display of the cylindrical lenses 109 and 110 and the mirrors M8 and M9 is omitted.

以下、光路106をとった場合を例にとって説明する。ミラーM1およびM2を光路より退避することで、照明光はミラーM3、ミラーM4により反射され、光路106をとる。図2(b)はミラーM4から検査対象基板Wまでの構成を示す側面図である。シリンドリカルレンズ109により検査対象基板W上で楕円状又は線状の領域F1に集光される。ミラーM7を矢印の方向へ平行移動及び回転させることにより、検査対象基板W表面と成す角(照明光の検査対象基板への入射角:仰角)を変更可能である。   Hereinafter, a case where the optical path 106 is taken will be described as an example. By retracting the mirrors M1 and M2 from the optical path, the illumination light is reflected by the mirrors M3 and M4 and takes the optical path 106. FIG. 2B is a side view showing the configuration from the mirror M4 to the inspection target substrate W. FIG. The light is condensed on an elliptical or linear region F1 on the inspection target substrate W by the cylindrical lens 109. By translating and rotating the mirror M7 in the direction of the arrow, the angle formed with the surface of the inspection target substrate W (incident angle of illumination light to the inspection target substrate: elevation angle) can be changed.

光路107に関しても同様に、ミラーM5から検査対象基板Wまでの間にミラーM8およびシリンドリカルレンズ110が、光路108に関しても同様に、ミラーM6から検査対象基板Wまでの間にミラーM9およびシリンドリカルレンズ111が設置される。シリンドリカルレンズ110、111は、各々を通過する照明光が検査対象基板W上で集光領域の中心位置および長手方向がシリンドリカルレンズ109により照射される領域F1と同じになるよう、あおりおよび光軸周りの回転が加えられている。上記構成により、互いに異なる複数の方位および仰角から選択的に照明光を照射し、かつ検査対象基板W上の同一位置を照射することが可能となる。また、ミラーM1および/またはM2をハーフミラーで構成することにより、検査対象基板W上の領域F1を複数の方位及び仰角方向から同時に照明することもできる。   Similarly, regarding the optical path 107, the mirror M8 and the cylindrical lens 110 are provided between the mirror M5 and the inspection target substrate W. Similarly, regarding the optical path 108, the mirror M9 and the cylindrical lens 111 are provided between the mirror M6 and the inspection target substrate W. Is installed. The cylindrical lenses 110 and 111 are arranged around the tilt and the optical axis so that the illumination light passing through each of the cylindrical lenses 110 and 111 has the same central position and longitudinal direction of the condensing region as the region F1 irradiated by the cylindrical lens 109 on the inspection target substrate W. The rotation is added. With the above configuration, it is possible to selectively irradiate illumination light from a plurality of different azimuths and elevation angles, and to irradiate the same position on the inspection target substrate W. In addition, by configuring the mirror M1 and / or M2 with a half mirror, the region F1 on the inspection target substrate W can be illuminated simultaneously from a plurality of directions and elevation directions.

照明光学系100の光路中に、照明光の光学条件を高速に変化させる手段を設け、後述する偏光検出部の受光器の蓄積時間より短い時間の間に照明光の光学条件を変化させ、受光器において変化した照明光学条件による信号を蓄積することで、検出可能な欠陥種の拡大や検査S/Nの向上を図ることが可能である。照明光の光学条件を高速に変化させる手段としては、特開2000−193443に記載のある瞳上で光束位置を走査する手段や、特開2003−177102に記載のある拡散板を回転させる手段などが挙げられる。   In the optical path of the illumination optical system 100, a means for changing the optical condition of the illumination light at high speed is provided, and the optical condition of the illumination light is changed during a time shorter than the accumulation time of the light receiver of the polarization detector described later. By accumulating signals according to illumination optical conditions that have changed in the instrument, it is possible to increase the number of defect types that can be detected and improve the inspection S / N. As means for changing the optical condition of the illumination light at high speed, means for scanning a light beam position on a pupil described in JP-A-2000-193443, means for rotating a diffusion plate described in JP-A-2003-177102, etc. Is mentioned.

対物レンズ3aおよび結像レンズ5aにより、検査対象基板W表面の照明領域F1の拡大像が形成される。検査対象基板W上に形成された周期的パターンによる回折光が対物レンズ3aの瞳共役位置に集光されるため、これを空間フィルタ4aにより遮光することにより、検査対象基板W上に形成された周期的パターンの像が除去される。   An enlarged image of the illumination area F1 on the surface of the inspection target substrate W is formed by the objective lens 3a and the imaging lens 5a. Since the diffracted light of the periodic pattern formed on the inspection target substrate W is condensed at the pupil conjugate position of the objective lens 3a, it is formed on the inspection target substrate W by shielding it with the spatial filter 4a. The periodic pattern image is removed.

偏光検出部200aについて、図3から図5を用いて説明する。   The polarization detection unit 200a will be described with reference to FIGS.

図3(a)は偏光検出部200aの振幅分割法により実現する構成として互いに異なる2種類の偏光成分を検出する偏光検出部200a'の構成を示す。偏光検出部200a'は、無偏光ビームスプリッタ(ハーフミラー)201、偏光板あるいは位相板の組み合わせで構成されて透過する光の偏光状態を調整可能な偏光選択手段210,211、および受光器220,221とによって構成される。各々の受光器220、221は対物レンズ3aおよび結像レンズ5aによって拡大結像された検査対象基板W表面の像を検出するよう設置される。対物レンズ3aおよび結像レンズ5aによる検査対象基板W表面の像に対する像面共役位置を像面230として一点鎖線で示した(受光器221の前面の一転鎖線も像面共役位置を表わす)。受光器220、221として、エリアセンサ、リニアセンサ、あるいはTDI(Time Delay Integration)センサを用いることで、各々の偏光成分に対応する画像が得られる。   FIG. 3A shows a configuration of a polarization detection unit 200a ′ that detects two different types of polarization components as a configuration realized by the amplitude division method of the polarization detection unit 200a. The polarization detection unit 200a ′ includes a non-polarization beam splitter (half mirror) 201, a polarizing plate or a phase plate, and polarization selection means 210 and 211 that can adjust the polarization state of transmitted light, and a light receiver 220, 221. Each of the light receivers 220 and 221 is installed so as to detect an image of the surface of the inspection target substrate W that is enlarged and formed by the objective lens 3a and the imaging lens 5a. The image plane conjugate position with respect to the image on the surface of the inspection target substrate W by the objective lens 3a and the imaging lens 5a is indicated by an alternate long and short dash line as the image plane 230 (the one-dot chain line on the front surface of the light receiver 221 also represents the image plane conjugate position). By using an area sensor, linear sensor, or TDI (Time Delay Integration) sensor as the light receivers 220 and 221, an image corresponding to each polarization component can be obtained.

エリアセンサ、リニアセンサ、あるいはTDIセンサの方式として、CCD方式あるいはCMOS方式など時間積分型の受光器を用い、照明光学系100において受光器220,221の積分時間より短い時間内に高速に光学条件を変化することで、複数の光学条件の照明光による散乱光を積分して一括に検出することが可能である。   As an area sensor, linear sensor, or TDI sensor system, a time integration type light receiver such as a CCD system or a CMOS system is used. In the illumination optical system 100, the optical conditions are set at high speed within a time shorter than the integration time of the light receivers 220 and 221. By changing, it is possible to integrate and detect scattered light by illumination light under a plurality of optical conditions.

また、受光器220、221として光電子増倍管を用いた場合には、高感度検出が実現される。
ここでは受光器220によって検査対象基板W上の主要な配線パターンに平行な方位の直線偏光成分を、受光器221によって検査対象基板W上の主要な配線パターンに垂直な方位の直線偏光成分を検出する場合を例にとって説明する。
In addition, when a photomultiplier tube is used as the light receivers 220 and 221, high sensitivity detection is realized.
Here, the linearly polarized light component in the direction parallel to the main wiring pattern on the inspection target substrate W is detected by the light receiver 220, and the linearly polarized light component in the direction perpendicular to the main wiring pattern on the inspection target substrate W is detected by the light receiver 221. This will be described as an example.

無偏光ビームスプリッタ201を透過した光成分のうち、検査対象基板W上の主要な配線パターンに平行な方位の直線偏光成分を透過する偏光板によって構成された偏光選択手段210を透過した光成分は、受光器220によって検出される。一方、無偏光ビームスプリッタ201によって反射した光成分のうち、検査対象基板W上の主要な配線パターンに垂直な方位の直線偏光成分を透過する偏光板によって構成された偏光選択手段211を透過した光成分は、受光器221によって検出される。   Of the light components that have passed through the non-polarizing beam splitter 201, the light component that has passed through the polarization selecting means 210 constituted by a polarizing plate that transmits a linearly polarized light component parallel to the main wiring pattern on the inspection target substrate W is: , Detected by the light receiver 220. On the other hand, among the light components reflected by the non-polarizing beam splitter 201, the light transmitted through the polarization selection unit 211 constituted by the polarizing plate that transmits the linearly polarized component in the direction perpendicular to the main wiring pattern on the inspection target substrate W. The component is detected by the light receiver 221.

同等の機能を実現する別の構成例として、無偏光ビームスプリッタ201の代わりに、検査対象基板W上の主要な配線パターンに平行な方位の直線偏光成分を透過する偏光ビームスプリッタを配置し、偏光選択手段211として検査対象基板W上の主要な配線パターンに垂直な方位の直線偏光成分を透過する偏光板を設置することも可能である。前者は検出する偏光の方位を変更する場合に偏光選択手段210、211の変更だけで対応可能であるというメリットがある。後者は、無偏光ビームスプリッタ201に残留する偏光特性を考慮する必要がなく、前者より精度の高い偏光測定が可能であるというメリットがある。なお、上記のように互いに直交する直線偏光成分を検出することで、得られた測定値に基づく演算により、偏光成分によらない光の全強度、成分の検査対象基板W上の主要な配線パターンに平行な方位の直線偏光度、(楕円)偏光の長軸方位角などの、偏光に関する物理量を算出ことができる。   As another configuration example that realizes an equivalent function, a polarization beam splitter that transmits a linearly polarized component having an orientation parallel to the main wiring pattern on the inspection target substrate W is disposed instead of the non-polarization beam splitter 201, As the selection means 211, it is possible to install a polarizing plate that transmits a linearly polarized light component having an orientation perpendicular to the main wiring pattern on the inspection target substrate W. The former has an advantage that it is possible to cope with the change of the polarization direction to be detected only by changing the polarization selection means 210 and 211. The latter has the advantage that it is not necessary to consider the polarization characteristics remaining in the non-polarizing beam splitter 201, and the polarization measurement can be performed with higher accuracy than the former. In addition, by detecting linearly polarized light components orthogonal to each other as described above, the main wiring pattern on the inspection target substrate W of the total light intensity and components not depending on the polarized light components is calculated based on the obtained measurement values. The physical quantity relating to the polarization, such as the linear polarization degree in the direction parallel to the long axis and the major axis azimuth angle of the (elliptical) polarization, can be calculated.

図3(b)は偏光検出部200aの振幅分割法により実現する構成として互いに異なる4種類の偏光成分を検出する偏光検出部200a''の構成を示す。偏光検出部200a''は、無偏光ビームスプリッタ202〜204、偏光選択手段212〜215、および受光器222〜225によって構成される。検出系光路に沿い偏光検出部200a''に入射した光は、無偏光ビームスプリッタ202〜204により分岐され、各々が別々の受光器222〜225に入射する構成となっている。偏光選択手段212〜215は、各々が偏光板あるいは位相板の組み合わせで構成されており、透過する光の偏光状態を各々独立に調整できるよう設定される。   FIG. 3B shows a configuration of a polarization detection unit 200a ″ that detects four different types of polarization components as a configuration realized by the amplitude division method of the polarization detection unit 200a. The polarization detection unit 200a ″ is configured by non-polarization beam splitters 202 to 204, polarization selection means 212 to 215, and light receivers 222 to 225. The light that has entered the polarization detection unit 200a ″ along the detection system optical path is branched by the non-polarization beam splitters 202 to 204, and each enters the separate light receivers 222 to 225. Each of the polarization selection means 212 to 215 is configured by a combination of a polarizing plate or a phase plate, and is set so that the polarization state of transmitted light can be adjusted independently.

各々の受光器222〜225は対物レンズ3aおよび結像レンズ5aによって拡大結像された検査対象基板W表面の像を検出するよう設置される。図3(a)の場合と同様に、各受光器222〜225の前面の一転鎖線は、対物レンズ3aおよび結像レンズ5aによる検査対象基板W表面の像に対する像面共役位置を示す。受光器222〜225として、エリアセンサ、リニアセンサ、あるいはTDI(Time Delay Integration)センサを用いることで、各々の偏光成分に対応する画像が得られる。   Each of the light receivers 222 to 225 is installed so as to detect an image of the surface of the inspection target substrate W that is enlarged and formed by the objective lens 3a and the imaging lens 5a. Similarly to the case of FIG. 3A, a one-dot chain line in front of each of the light receivers 222 to 225 indicates an image plane conjugate position with respect to an image on the surface of the inspection target substrate W by the objective lens 3a and the imaging lens 5a. By using an area sensor, a linear sensor, or a TDI (Time Delay Integration) sensor as the light receivers 222 to 225, an image corresponding to each polarization component is obtained.

エリアセンサ、リニアセンサ、あるいはTDIセンサの方式として、CCD方式あるいはCMOS方式など時間積分型の受光器を用い、照明光学系100において受光器220,221の積分時間より短い時間内に高速に光学条件を変化することで、複数の光学条件の照明光による散乱光を積分して一括に検出することが可能である。   As an area sensor, linear sensor, or TDI sensor system, a time integration type light receiver such as a CCD system or a CMOS system is used. In the illumination optical system 100, the optical conditions are set at high speed within a time shorter than the integration time of the light receivers 220 and 221. By changing, it is possible to integrate and detect scattered light by illumination light under a plurality of optical conditions.

また、受光器220、221として光電子増倍管を用いた場合には、高感度検出が実現される。   In addition, when a photomultiplier tube is used as the light receivers 220 and 221, high sensitivity detection is realized.

ここでは受光器222によって検出系光路14の周りの所定方位(αとする)の直線偏光成分を、受光器223によって方位α+90度の直線偏光成分を、受光器224によって方位α+45度の方位の直線偏光成分を、受光器225によって左回り円偏光成分を検出する場合を例にとって説明する。   Here, a linearly polarized light component having a predetermined azimuth (α) around the detection system optical path 14 is received by the light receiver 222, a linearly polarized light component having an azimuth α + 90 degrees is received by the light receiver 223, and a straight line having an azimuth direction of α + 45 degrees is received by the light receiver 224 The polarization component will be described by taking as an example a case where the counterclockwise circular polarization component is detected by the light receiver 225.

無偏光ビームスプリッタ202を透過した光成分は、無偏光ビームスプリッタ203によってさらに分岐される。無偏光ビームスプリッタ203により反射された光成分は、所定方位αの直線偏光成分を透過する偏光板により構成された偏光選択手段212を透過し、受光器222により検出される。無偏光ビームスプリッタ203を透過した光成分は、方位α+90度の直線偏光成分を透過する偏光板により構成された偏光選択手段213を透過し、受光器223により検出される。無偏光ビームスプリッタ202により反射された光成分は、無偏光ビームスプリッタ204によってさらに分岐される。無偏光ビームスプリッタ204を透過した光成分は、方位α+45度の直線偏光成分を透過する偏光板により構成された偏光選択手段214を透過し、受光器224により検出される。無偏光ビームスプリッタ204により反射された光成分は、方位0度に設定したλ/4板と方位α+45度の直線偏光成分を透過する偏光板により構成された偏光選択手段215を透過し、受光器225により検出される。   The light component transmitted through the non-polarizing beam splitter 202 is further branched by the non-polarizing beam splitter 203. The light component reflected by the non-polarizing beam splitter 203 is transmitted through the polarization selection means 212 constituted by a polarizing plate that transmits the linearly polarized light component having the predetermined azimuth α, and is detected by the light receiver 222. The light component that has passed through the non-polarizing beam splitter 203 passes through the polarization selecting means 213 constituted by a polarizing plate that transmits the linearly polarized light component having the azimuth α + 90 degrees, and is detected by the light receiver 223. The light component reflected by the non-polarizing beam splitter 202 is further branched by the non-polarizing beam splitter 204. The light component that has passed through the non-polarizing beam splitter 204 passes through the polarization selection unit 214 configured by a polarizing plate that transmits the linearly polarized light component having the azimuth α + 45 degrees, and is detected by the light receiver 224. The light component reflected by the non-polarizing beam splitter 204 is transmitted through the polarization selecting means 215 constituted by a λ / 4 plate set at 0 ° azimuth and a polarizing plate that transmits the linearly polarized light component at azimuth α + 45 °. 225.

受光器222、223、224、225によって検出された光成分の強度を各々I1、I2、I3、I4とすると、以下の式によって、偏光検出部200aに入射した光成分の偏光状態を表すストークスパラメータS0〜S3を求めることができ、偏光状態を完全に決定することが可能である。また、ストークスパラメータS0〜S3に基づき、前記の偏光に関する物理量に加えてさらに、偏光度、楕円率などを算出することができる。
S0=I1+I2
S1=I1−I2
S2=2*I3−(I1+I2)
S3=2*I4−(I1+I2)
互いに異なる3種類の偏光成分を検出する構成は、図3(a)(b)より容易に類推可能である。互いに異なる3種類の偏光成分として、検出系光路14の周りの所定方位αの直線偏光成分、方位α+45度の方位の直線偏光成分、および左回り円偏光成分を検出し、さらに偏光検出部200aに入射した光成分が完全偏光であると仮定することで、偏光検出部200aに入射した光成分の偏光状態を決定することが可能である。
Assuming that the intensities of the light components detected by the light receivers 222, 223, 224, and 225 are I1, I2, I3, and I4, respectively, the Stokes parameter that represents the polarization state of the light component incident on the polarization detection unit 200a is represented by the following equation. S0 to S3 can be obtained, and the polarization state can be completely determined. Further, based on the Stokes parameters S0 to S3, the degree of polarization, ellipticity, and the like can be calculated in addition to the physical quantity related to the polarization.
S0 = I1 + I2
S1 = I1-I2
S2 = 2 * I3- (I1 + I2)
S3 = 2 * I4- (I1 + I2)
A configuration for detecting three different types of polarized light components can be easily inferred from FIGS. 3 (a) and 3 (b). As three different types of polarized light components, a linearly polarized light component with a predetermined azimuth α around the detection system optical path 14, a linearly polarized light component with an azimuth α + 45 degrees, and a counterclockwise circularly polarized light component are detected. By assuming that the incident light component is completely polarized, it is possible to determine the polarization state of the light component incident on the polarization detector 200a.

図4、図5は図3に示した構成と異なる偏光検出部200aの構成例を示す。   4 and 5 show a configuration example of the polarization detector 200a different from the configuration shown in FIG.

図4(a)は複屈折ウェッジを用いた偏光検出部200a'''の構成を示す。偏光検出部200a'''は、周波数変調画像取得部250とフーリエ解析部255により構成される。図4(b)は周波数変調画像取得部250の構成を示す。周波数変調画像取得部250は、検出光軸14周りの所定の方位(0度方位とする)を進相軸、90度方位を遅相軸とし、位相量が方位90度方向に線形に変化するプリズム素子251と、45度方位を進相軸、135度方位を遅相軸とし、位相量が方位0度方向に線形に変化するプリズム素子252と、0度方位の直線偏光成分を透過する偏光板253と、イメージセンサ254とで構成される。イメージセンサ254は、対物レンズ3aおよび結像レンズ5aによってプリズム素子251、252および偏光板253を透過し拡大結像された像を検出するよう設置される。上記構成により、偏光成分ごとに異なる周波数で空間的に変調された画像信号がイメージセンサ254より出力される。出力された画像信号は周波数解析部255においてFFT処理し周波数解析を行うことで、画像上の各位置ごとに偏光状態に対応する複数のパラメータが得られる。   FIG. 4A shows a configuration of a polarization detecting unit 200a ′ ″ using a birefringent wedge. The polarization detection unit 200a ′ ″ includes a frequency modulation image acquisition unit 250 and a Fourier analysis unit 255. FIG. 4B shows the configuration of the frequency modulation image acquisition unit 250. The frequency-modulated image acquisition unit 250 uses a predetermined azimuth (around 0 degree azimuth) around the detection optical axis 14 as a fast axis and 90 degrees azimuth as a slow axis, and the phase amount linearly changes in the azimuth 90 degrees direction. The prism element 251, the prism element 252 having a 45-degree azimuth as the fast axis and the 135-degree azimuth as the slow axis and the phase amount linearly changing in the 0-degree direction, and the polarized light transmitting the linearly polarized light component having the 0-degree azimuth It consists of a plate 253 and an image sensor 254. The image sensor 254 is installed so as to detect an image that is transmitted through the prism elements 251 and 252 and the polarizing plate 253 and enlarged and formed by the objective lens 3a and the imaging lens 5a. With the above configuration, the image sensor 254 outputs an image signal spatially modulated at a different frequency for each polarization component. The output image signal is subjected to FFT processing in the frequency analysis unit 255 and subjected to frequency analysis, whereby a plurality of parameters corresponding to the polarization state are obtained for each position on the image.

図5(a)は微小偏光素子アレイを用いた偏光検出部200a''''の構成を示す。偏光検出部200a''''はイメージセンサ261とその受光面に設置された微小偏光素子アレイ262とで構成される。微小偏光素子アレイ262の構造を図5(b)に示す。画素毎に異なる偏光成分を透過する構成になっている。図5(b)の例では、イメージセンサ261画素配列の横方向に平行な直線偏光(方位0度)を透過する画素263、縦方向に平行な直線偏光(方位0度)を透過する画素264、45度方位の直線偏光を透過する画素265、0度、0度方位に90度の位相遅れを与えた後45度方位の直線偏光を透過する画素266の4つの画素を1単位267として1つの偏光状態が得られる。   FIG. 5A shows a configuration of a polarization detection unit 200a ″ ″ using a micro polarization element array. The polarization detection unit 200a ″ ″ includes an image sensor 261 and a micro polarization element array 262 installed on the light receiving surface thereof. The structure of the micropolarizing element array 262 is shown in FIG. It is configured to transmit different polarization components for each pixel. In the example of FIG. 5B, the pixel 263 that transmits linearly polarized light (azimuth 0 degree) parallel to the horizontal direction of the image sensor 261 pixel array and the pixel 264 that transmits linearly polarized light parallel to the vertical direction (azimuth 0 degree). , A pixel 265 that transmits linearly polarized light with a 45 degree azimuth, a pixel 266 that transmits a linearly polarized light with a 45 degree azimuth after giving a phase delay of 90 degrees to the 0 degree and 0 degree azimuth, and 1 pixel as one unit 267 Two polarization states are obtained.

このような微小偏光素子アレイ262の作成方法として、撮像素子または基板の上にミクロンオーダからサブミクロンオーダ厚の薄膜状の偏光板を載せ、画素の大きさに合せて不要な部分をエッチングで除去し、さらに主軸方位の異なる薄膜偏光板あるいは波長板を載せて同様のパターニングを繰り返す方法がある。別の方法としては、使用する光の波長より短い周期を持つ微細格子をパターニングによって作成することで、画素毎に光学異方性を持たせる方法がある。また、対物レンズ3aおよび結像レンズ5aの結像性能で決まる光学解像度(錯乱円の径)を、偏光状態を決める1単位となる4画素を合せた幅と同等以上とすることで、同4画素の間での像面強度変化の影響を低減し高精度な偏光計測を行うことが可能である。   As a method for producing such a micropolarizing element array 262, a thin-film polarizing plate having a thickness of micron order to submicron order is placed on an image sensor or a substrate, and unnecessary portions are removed by etching according to the size of the pixel. In addition, there is a method of repeating similar patterning by placing thin film polarizing plates or wave plates having different principal axis orientations. As another method, there is a method of giving optical anisotropy to each pixel by forming a fine grating having a period shorter than the wavelength of light to be used by patterning. Further, the optical resolution (diameter of the circle of confusion) determined by the imaging performance of the objective lens 3a and the imaging lens 5a is set to be equal to or greater than the combined width of four pixels as one unit for determining the polarization state. It is possible to reduce the influence of the change in image plane intensity between pixels and perform highly accurate polarization measurement.

X-Y-Z-θステージ10をX方向およびY方向に走査することで、対物レンズ3a、結像レンズ5a、および偏光検出部200a''''によって定まる検査対象基板W上の視野を検査対象基板Wに対し相対的に走査する。X方向走査およびY方向走査を順次繰返し、検査対象基板W全面あるいはその一部から偏光成分検出信号を得ることができる。   By scanning the XYZ-θ stage 10 in the X and Y directions, the visual field on the inspection target substrate W determined by the objective lens 3a, the imaging lens 5a, and the polarization detection unit 200a ″ ″ is inspected. Scanning is performed relative to the target substrate W. By sequentially repeating the X-direction scanning and the Y-direction scanning, a polarization component detection signal can be obtained from the entire inspection target substrate W or a part thereof.

信号処理部300の構成を図6に示す。図6(a)は、検査対象基板Wにて設計上同一パターンが形成された隣接チップ間における、偏光検出部200a'(図3(a))より出力された信号の差分を基に欠陥を判定する方式を実現する信号処理部300′の構成を示す。   The configuration of the signal processing unit 300 is shown in FIG. FIG. 6A shows a defect based on the difference in signal output from the polarization detection unit 200a ′ (FIG. 3A) between adjacent chips on the inspection target substrate W on which the same pattern is formed by design. The structure of signal processing part 300 'which implement | achieves the system to determine is shown.

図6(a)に示す信号処理部300′は、遅延メモリ301、302、差分演算部303、304、欠陥判定部305、および欠陥判定基準算出部306により構成され、偏光検出部200a'より出力された信号I(図6(a)では2つの偏光成分に対応する信号I、I)の入力に対し、欠陥情報307を出力する。次に動作を説明する。信号Iは差分演算部303と遅延メモリ301に入力される。遅延メモリ301は信号を蓄積し1チップの処理時間分を遅らせて出力する。差分演算部303には、信号Iと、遅延メモリ301より出力された隣接チップの対応位置の信号が入力され、それらの差分ΔIを出力する。得られた信号Iの隣接チップとの差分信号は欠陥判定部305および欠陥判定基準算出部306に入力される。信号Iに対応する偏光成分と異なる偏光成分に対応する信号Iについても同様に隣接チップとの差分がとられ(ΔI)、欠陥判定部305および欠陥判定基準算出部306に入力される。欠陥判定基準算出部306は隣接チップ間差分信号ΔI、ΔIに基づいて欠陥判定基準308を出力する。欠陥判定部305は隣接チップ間差分信号ΔI、ΔIの入力に対して欠陥判定基準308に基づいて欠陥判定を行い、欠陥情報307を出力する。 The signal processing unit 300 ′ illustrated in FIG. 6A includes delay memories 301 and 302, difference calculation units 303 and 304, a defect determination unit 305, and a defect determination reference calculation unit 306, and is output from the polarization detection unit 200a ′. The defect information 307 is output in response to the input of the signal I k (signals I 1 and I 2 corresponding to two polarization components in FIG. 6A). Next, the operation will be described. The signal I 1 is input to the difference calculation unit 303 and the delay memory 301. The delay memory 301 accumulates the signal and outputs it after delaying the processing time of one chip. The difference calculation unit 303 receives the signal I 1 and the signal at the corresponding position of the adjacent chip output from the delay memory 301 and outputs the difference ΔI 1 between them. The obtained difference signal of the signal I 1 from the adjacent chip is input to the defect determination unit 305 and the defect determination reference calculation unit 306. The difference between the same adjacent chips for the signals I 2 corresponding to the polarization components to the polarization component different corresponding to the signal I 1 is taken (ΔI 2), are input to the defect determination unit 305 and the defect judgment criterion calculating unit 306 . The defect determination reference calculation unit 306 outputs a defect determination reference 308 based on the adjacent chip difference signals ΔI 1 and ΔI 2 . The defect determination unit 305 performs defect determination based on the defect determination reference 308 with respect to the input of the inter-adjacent-chip difference signals ΔI 1 and ΔI 2 , and outputs defect information 307.

図6(b)は、検査対象基板W上の所定の領域内に対応し、偏光検出部200a'(図3(a))より出力される一連の信号(画像信号)を基に欠陥を判定する方式を実現する信号処理部300''の構成を示す。偏光検出部200a'より出力された画像信号Iは、所定の偏光成分を、検査対象基板W上の所定の領域内の位置ごとに検出した画像信号に相当する。同じく偏光検出部200a'より出力された画像信号Iは、画像信号Iと異なる偏光成分を、検査対象基板W上の所定の領域内の位置ごとに検出した画像信号に相当する。画像信号IおよびIは欠陥判定基準算出部311および欠陥判定部312に入力される。欠陥判定基準算出部311は画像信号IおよびIに基づいて欠陥判定基準314を出力する。欠陥判定部312は画像信号I、I、および欠陥判定基準314に基づいて欠陥判定を行い、欠陥情報313を出力する
欠陥判定基準算出部306又は311にメモリを備え、先に検出した複数のチップにおける対応位置の偏光成分検出信号に基づいて欠陥判定基準308又は314を算出することもできる。信号処理部300'または300''から出力される欠陥情報307又は313は、欠陥の位置、欠陥部差画像、偏光成分ごとの欠陥部差画像、欠陥部差画像から算出した欠陥特徴量、欠陥分類結果などを含む。なお、欠陥分類は、欠陥判定部305又は312において実施することも、欠陥情報307又は313に基づいて演算部8において実施することも可能である。
FIG. 6B corresponds to a predetermined area on the inspection target substrate W, and a defect is determined based on a series of signals (image signals) output from the polarization detector 200a ′ (FIG. 3A). The structure of signal processing part 300 '' which implement | achieves the system to perform is shown. Image signal I 1 output from the polarization detecting unit 200a 'has a predetermined polarization component, which corresponds to an image signal detected for each position of a predetermined region on the substrate to be inspected W. Image signal I 2 outputted from the polarizing detector 200a 'also includes the image signal I 1 and the different polarization components, corresponding to the image signal detected for each position of a predetermined region on the substrate to be inspected W. The image signals I 1 and I 2 are input to the defect determination reference calculation unit 311 and the defect determination unit 312. The defect determination criterion calculation unit 311 outputs a defect determination criterion 314 based on the image signals I 1 and I 2 . The defect determination unit 312 performs defect determination based on the image signals I 1 and I 2 and the defect determination standard 314, and outputs defect information 313. The defect determination standard calculation unit 306 or 311 includes a memory, and a plurality of previously detected plural The defect criterion 308 or 314 can also be calculated based on the polarization component detection signal at the corresponding position in the chip. The defect information 307 or 313 output from the signal processing unit 300 ′ or 300 ″ includes the defect position, the defect difference image, the defect difference image for each polarization component, the defect feature amount calculated from the defect difference image, and the defect. Includes classification results. The defect classification can be performed in the defect determination unit 305 or 312, or can be performed in the calculation unit 8 based on the defect information 307 or 313.

また、ここでは信号処理部300'または300''の構成として図3(a)で説明した偏光検出部200a'から出力される二つの偏光成分I、Iを処理する場合を例にとって説明したが、図3(b)で説明した偏光検出部200a''、図4で説明した偏光検出部200a'''及び図5で説明した偏光検出部200a''''のそれぞれから出力される4つの偏光成分を検出する場合も、図6(a)及び(b)で説明した構成を応用することができる。すなわち、4つの偏光成分からなる画像信号I〜Iを入力して処理する場合は、図6(a)及び(b)で説明した画像信号I及びIを処理する回路構成を4つの入力信号を処理する構成とすることにより容易に実現できる。 Further, here, a case where the two polarization components I 1 and I 2 output from the polarization detection unit 200a ′ described in FIG. 3A are processed as an example of the configuration of the signal processing unit 300 ′ or 300 ″ will be described. However, it is output from each of the polarization detection unit 200a ″ described in FIG. 3B, the polarization detection unit 200a ′ ″ described in FIG. 4, and the polarization detection unit 200a ″ ″ described in FIG. The configuration described with reference to FIGS. 6A and 6B can also be applied when detecting four polarization components. That is, when the image signals I 1 to I 4 composed of four polarization components are input and processed, the circuit configuration for processing the image signals I 1 and I 2 described with reference to FIGS. This can be easily realized by adopting a configuration for processing one input signal.

欠陥判定基準算出部306あるいは311(以下、欠陥判定基準算出部)における欠陥判定基準算出方法および欠陥判定部305あるいは312(以下、欠陥判定部)における欠陥判定方法について図7〜図9を用いて説明する。   A defect determination standard calculation method in the defect determination reference calculation unit 306 or 311 (hereinafter referred to as a defect determination reference calculation unit) and a defect determination method in the defect determination unit 305 or 312 (hereinafter referred to as a defect determination unit) will be described with reference to FIGS. explain.

図7を用いて、互いに異なる二つの偏光成分を検出した信号を利用して欠陥を判定する方法を説明する。   A method for determining a defect using a signal obtained by detecting two different polarization components will be described with reference to FIG.

図7(a−1)および(a−2)は、単一の偏光成分のみを利用して欠陥を判定する従来技術の例を示す。図7(a−1)は偏光成分信号Iの分布を示す。プロットされた各マークA〜Fは、欠陥判定基準算出部に蓄えられた複数チップの各々に対応する偏光成分信号Iを示す。プロットされた各マーク○△×に対応する記号A〜Fの分布より、多数がI値範囲401に含まれ、Aの信号のみが範囲401の外にある。範囲401は、プロットされた各マークの分布の平均値や標準偏差などの統計量から算出される欠陥判定基準に相当する。範囲401の内部を正常部、外部を欠陥部と判定することで、Aが欠陥部であり、C〜Fが正常部であると正しく判定されるが、Bが正常部であると誤判定されてしまう。 FIGS. 7A-1 and 7A-2 show examples of the prior art for determining defects using only a single polarization component. Figure 7 (a-1) shows the distribution of the polarization component signal I 1. Each mark A~F plotted shows the polarization component signals I 1 corresponding to each of the plurality of chips stored in the defect judgment criterion calculating unit. From the distribution of the symbols A to F corresponding to each of the marked marks ◯ Δ ×, many are included in the I 1 value range 401, and only the signal of A is outside the range 401. A range 401 corresponds to a defect determination criterion calculated from statistics such as an average value and standard deviation of the distribution of each plotted mark. By determining the inside of the range 401 as a normal part and the outside as a defective part, it is correctly determined that A is a defective part and C to F are normal parts, but B is erroneously determined as a normal part. End up.

一方、図7(a−2)は偏光成分信号I2の分布を示し、図7(a−1)と同様の方法で欠陥判定基準に相当する範囲402を算出して欠陥判定を行った場合、Bが欠陥部でありC〜Fは正常部であると正しく判定されるが、Aが正常部であると誤判定されてしまう。   On the other hand, FIG. 7A-2 shows the distribution of the polarization component signal I2, and when the defect determination is performed by calculating the range 402 corresponding to the defect determination reference by the same method as FIG. Although B is a defective part and C to F are correctly determined to be normal parts, A is erroneously determined to be a normal part.

図7(a−3)は、本発明による互いに異なる二つの偏光成分を利用して欠陥を判定する方法を説明する図であり、偏光成分信号Iを横軸に、偏光成分信号I2を縦軸にとり、欠陥判定基準算出部に蓄えられた複数チップの各々に対応する偏光成分信号(I,I)をプロットした図である。欠陥判定基準算出部306あるいは311において、各プロットされた点の分布の平均値や標準偏差などの統計量を用いて分布の多数が含まれるような矩形領域404を欠陥判定基準として算出し、欠陥判定部において矩形領域404の内部を正常部、外れ値である矩形領域404の外部を欠陥部と判定することで、A、Bがともに欠陥部であり、C〜Fが正常部であると、誤判定なく正しく欠陥判定を行うことができる。欠陥判定基準として各プロットされた点の分布の平均値や標準偏差などの統計量を用いて円形領域403を算出しても同様に正しい判定が可能である。 Figure 7 (a-3) is a diagram illustrating a method of determining a defect by utilizing the two polarization components different from each other according to the present invention, the horizontal axis polarization component signal I 1, the vertical polarization component signal I2 taken as the axis is a plot of polarization component signals (I 1, I 2) corresponding to each of the plurality of chips stored in the defect judgment criterion calculating unit. In the defect determination criterion calculation unit 306 or 311, a rectangular region 404 including a large number of distributions is calculated as a defect determination criterion using a statistical amount such as an average value or standard deviation of the distribution of each plotted point, The determination unit determines that the inside of the rectangular area 404 is a normal part and the outside of the rectangular area 404 that is an outlier is a defective part, so that A and B are both defective parts, and C to F are normal parts. Defect determination can be performed correctly without erroneous determination. Even if the circular region 403 is calculated using a statistical value such as an average value or standard deviation of the distribution of each plotted point as a defect determination criterion, the correct determination can be similarly performed.

なお、図7(b)に示したように、偏光成分信号Iに対し範囲401の外にプロットされる信号(I<Th1− OR I>Th1+ :ただし、TH1+は範囲401の上限値、TH1−は範囲401の下限値を示す)が欠陥であるという判定基準(J1)を適用し、偏光成分信号I2に対し範囲402の外にプロットされる信号(I<Th2− OR I>Th2+ :ただし、TH2+は範囲402の上限値、TH2−は範囲402の下限値を示す)が欠陥であるという判定基準(J2)を適用し、どちらかの判定基準を満たす条件(J1)OR(J2)を最終的な欠陥判定基準として適用した場合でも、上記と同様に正しい判定が可能である。これは、上記矩形領域404の外部にプロットされる信号が欠陥であるとする欠陥判定条件と等価である。 As shown in FIG. 7B, the signal plotted outside the range 401 with respect to the polarization component signal I 1 (I 1 <Th1-OR I 1 > Th1 +: where TH1 + is the upper limit value of the range 401 , TH1- indicates a lower limit value of the range 401), a criterion (J1) that is defective is applied, and the signal (I 2 <Th2-OR I 2) plotted outside the range 402 with respect to the polarization component signal I2 > Th2 +: where TH2 + represents the upper limit value of the range 402 and TH2- represents the lower limit value of the range 402), and applies the criterion (J2) that satisfies either criterion (J1) OR Even when (J2) is applied as the final defect determination criterion, the correct determination can be made as described above. This is equivalent to a defect determination condition that a signal plotted outside the rectangular area 404 is a defect.

また、図7(c)に示したように、偏光成分信号Iと偏光成分信号I2に対し所定の演算処理した値をプロットし、これにたいして正常部あるいは欠陥部と判定する値の範囲を定めて欠陥を判定することもできる。図7(c)は、偏光成分信号Iと偏光成分信号Iに対する演算として、
f(I, I) = (I-a)+(I-b)
を算出してAからFをプロットし、これに対して範囲405の外部にプロットされる信号(f(I,I)>Th)を欠陥と判定する例である。この方法でも、前記と同様に正しい判定が可能である。なお、これは、上記円形領域403の外部にプロットされる信号が欠陥であるとする欠陥判定条件と等価である。一般に、欠陥判定条件がIとIのN次式で表される場合、IとIを軸として張られる平面に信号をプロットし、N次曲線に含まれる範囲を正常部あるいは欠陥部と判定する問題に帰着できる。
Further, as shown in FIG. 7 (c), the value obtained by a predetermined arithmetic processing to the polarization component signal I 1 and the polarization component signal I2 is plotted, delimits a determining value and the normal portion or the defective portion relative to this It is also possible to determine defects. FIG. 7C shows the calculation for the polarization component signal I 1 and the polarization component signal I 2 .
f (I 1 , I 2 ) = (I 1 -a) 2 + (I 2 -b) 2
This is an example of plotting A to F and determining a signal (f (I 1 , I 2 )> Th) plotted outside the range 405 as a defect. Even with this method, a correct determination can be made as described above. This is equivalent to a defect determination condition that a signal plotted outside the circular area 403 is a defect. In general, when a defect determination condition is expressed by N the following formula I 1 and I 2, I 1 and the I 2 plots the signals on the plane mapped as an axis, the normal portion or defect range included in N order curve The problem can be determined as part.

複数の偏光成分信号に基づいて得られる物理量を軸にとり、偏光成分信号をプロットし、欠陥判定を行うこともできる。図8(a)に示すように、複数の偏光成分信号に対する任意の演算により得られる物理量を各々の軸にとる。   It is also possible to determine the defect by plotting the polarization component signal with the physical quantity obtained based on the plurality of polarization component signals as an axis. As shown in FIG. 8 (a), a physical quantity obtained by an arbitrary calculation on a plurality of polarization component signals is taken on each axis.

図8(b)は、物理量として横軸に光の全強度、縦軸に偏光の楕円率をとった例である。なお、異物等粒子状の欠陥による散乱を考えた場合、光の波長に対して粒径が小さいレイリー散乱領域では、直線偏光照明に対し散乱光も直線偏光となるのに対し、光の波長に対して粒径が同等あるいはそれ以上のミー散乱領域では、直線偏光照明に対し散乱光が楕円偏光となることが知られている。従って、欠陥寸法が大きいほど検出する散乱光の偏光成分の楕円率が高くなる傾向がある。これより、検出された欠陥部の偏光成分の楕円率に基づいて欠陥の寸法を推定することが可能である。   FIG. 8B shows an example in which the horizontal axis represents the total intensity of light and the vertical axis represents the ellipticity of polarization as a physical quantity. When scattering due to particulate defects such as foreign matter is considered, in the Rayleigh scattering region where the particle size is small with respect to the wavelength of light, the scattered light is also linearly polarized with respect to linearly polarized illumination, whereas the wavelength of light is On the other hand, it is known that the scattered light becomes elliptically polarized light with respect to the linearly polarized illumination in the Mie scattering region where the particle diameter is equal or larger. Therefore, the ellipticity of the polarization component of the scattered light to be detected tends to increase as the defect size increases. Accordingly, it is possible to estimate the size of the defect based on the detected ellipticity of the polarization component of the defect portion.

図8(c)は、物理量として横軸に光の全強度、縦軸に偏光の長軸方位角をとった例である。なお、欠陥あるいはパターンの種類によって、照明光の偏光方向に対する反射散乱光の偏光方向が異なる場合があることが知られている。図8(c)では検出した欠陥の偏光成分の長軸方位角に基づいて異物とスクラッチを分類する例を示した。   FIG. 8C shows an example in which the horizontal axis represents the total intensity of light and the vertical axis represents the major axis azimuth of the polarization as physical quantities. It is known that the polarization direction of the reflected scattered light with respect to the polarization direction of the illumination light may differ depending on the type of defect or pattern. FIG. 8C shows an example in which foreign substances and scratches are classified based on the major axis azimuth angle of the detected polarization component of the defect.

図8(d)は、物理量として既知である照明光の偏光状態と、検出した複数の偏光成分信号より、エリプソメトリで用いられる振幅反射率比Ψと位相差Δを算出し、縦軸、横軸にとった例である。これらの物理量より、各々の位置における薄膜の膜厚や屈折率に関する情報が得られるため、それに基づいた処理を行うことが可能である。   FIG. 8 (d) calculates the amplitude reflectance ratio Ψ and phase difference Δ used in ellipsometry from the polarization state of illumination light, which is known as a physical quantity, and a plurality of detected polarization component signals. This is an example taken on the axis. Information on the film thickness and refractive index of the thin film at each position can be obtained from these physical quantities, and therefore processing based on the information can be performed.

図9は複数の偏光成分信号に基づいて得られる三つの物理量に基づく値を軸にとり、偏光成分信号あるいはそれらの演算により得られる値をプロットした例である。図9(a)は偏光検出部200aにおいて四つの互いに異なる偏光成分信号を取得しストークスパラメータS0〜S3を求め、ストークスパラメータS1〜S3をストークスパラメータS0で規格化した値を軸にとった例である。これは、偏光状態を半径1のポアンカレ球で表示したもの対応し、偏光状態に対応する点が、完全偏光であればポアンカレ球面上、部分偏光であればポアンカレ球の内部にプロットされる。   FIG. 9 is an example in which values based on three physical quantities obtained based on a plurality of polarization component signals are plotted, and polarization component signals or values obtained by their calculation are plotted. FIG. 9A shows an example in which the polarization detector 200a acquires four different polarization component signals to obtain the Stokes parameters S0 to S3, and the values obtained by normalizing the Stokes parameters S1 to S3 with the Stokes parameter S0 are used as axes. is there. This corresponds to the polarization state represented by a Poincare sphere with a radius of 1, and the point corresponding to the polarization state is plotted on the Poincare sphere if it is completely polarized, or inside the Poincare sphere if it is partially polarized.

欠陥判定基準として、欠陥部であるあるいは正常部であると判定する3次元空間内の領域を算出し、欠陥判定を行う。光の強度S0で規格化するため、元の散乱光の明るさ変動が大きい場合などでも、その影響を受けることなく、偏光状態の違いを反映した分布に基づいた欠陥検出が可能である。また、図9(b)に示すように、ポアンカレ球表示においてS1−S2平面を赤道面としたときの緯度が偏光の楕円率角(楕円率の逆正接)、経度が偏光の長軸方位角の2倍に対応することから、図8(b)(c)に示した方法と同様に、欠陥寸法の推定および欠陥種の分類が可能である。また、図9(c)に示すように、S0で規格化することなくS1〜S3をそのままプロットすることで、偏光状態に加えて光の強度を加味した分布に基づいた欠陥検出を行うことが可能である。   As a defect determination criterion, an area in the three-dimensional space that is determined to be a defective part or a normal part is calculated, and defect determination is performed. Since normalization is performed with the light intensity S0, defect detection based on a distribution reflecting the difference in polarization state is possible without being affected by variations in the brightness of the original scattered light. 9B, in the Poincare sphere display, when the S1-S2 plane is the equator plane, the latitude is the ellipticity angle of polarization (the arctangent of the ellipticity), and the longitude is the major axis azimuth of the polarization. Therefore, the defect size can be estimated and the defect type can be classified in the same manner as the method shown in FIGS. 8B and 8C. Further, as shown in FIG. 9C, defect detection based on a distribution in which light intensity is taken into account in addition to the polarization state can be performed by plotting S1 to S3 without being normalized by S0. Is possible.

図10から図13を用いて、上記第一の実施例の第一の変形例を説明する。   A first modification of the first embodiment will be described with reference to FIGS.

図10は第一の変形例の構成を示す。前記第一の実施例に対し、対物レンズ3b、空間フィルタ4b、結像レンズ5b、偏光検出部200bが追加された構成となっている。対物レンズ3b、空間フィルタ4b、および結像レンズ5bにより斜方検出系500bが構成され、対物レンズ3aと異なる仰角および方位角に反射散乱する光成分が偏光検出部200bに導かれる。偏光検出部200bの構成は前記第一の実施例における偏光検出部200aの構成として説明した200a'〜200a''''の何れかの構成を採用することができる。偏光検出部200bの構成は偏光検出部200aの構成と同じであることが望ましいが、必ずしも同じ構成でなくてもよい。偏光検出部200bにて検出された複数の偏光成分信号は、偏光検出部200aにて検出されたものと同様に信号処理部300に入力される。信号処理部300にて、偏光検出部200aにて検出された複数の偏光成分信号および偏光検出部200bにて検出された複数の偏光成分信号に基づいて欠陥判定がなされる。また、信号処理部300とは別に信号処理部300b(図示せず)を設け、検出部200bにて検出された複数の偏光成分信号に基づく欠陥判定を信号処理部300とは独立に行うことも可能である。   FIG. 10 shows the configuration of the first modification. The objective lens 3b, the spatial filter 4b, the imaging lens 5b, and the polarization detector 200b are added to the first embodiment. The oblique detection system 500b is configured by the objective lens 3b, the spatial filter 4b, and the imaging lens 5b, and a light component reflected and scattered at an elevation angle and an azimuth angle different from those of the objective lens 3a is guided to the polarization detection unit 200b. The configuration of the polarization detector 200b can employ any of the configurations 200a ′ to 200a ″ ″ described as the configuration of the polarization detector 200a in the first embodiment. The configuration of the polarization detection unit 200b is preferably the same as the configuration of the polarization detection unit 200a, but the configuration is not necessarily the same. A plurality of polarization component signals detected by the polarization detection unit 200b are input to the signal processing unit 300 in the same manner as those detected by the polarization detection unit 200a. The signal processing unit 300 makes a defect determination based on the plurality of polarization component signals detected by the polarization detection unit 200a and the plurality of polarization component signals detected by the polarization detection unit 200b. In addition, a signal processing unit 300b (not shown) may be provided separately from the signal processing unit 300, and defect determination based on a plurality of polarization component signals detected by the detection unit 200b may be performed independently of the signal processing unit 300. Is possible.

図11は斜方検出系500bの検出方向と照明方向との関係を示す。検出方位がステージX方向と同じになるよう斜方検出系500bを設置する。照明方位角は図2で説明したように選択可能である。ここでは、ステージX方向を基準とした照明進行方位角をθ(θが0度のときは検出方向と同じ方位角になる)とし、θを0度から−90度の間とした例と−90度から−180度の間とした例を図示した。θを0度から−90度の間とした配置は、斜方検出系500bに欠陥による前方散乱光が入射するため、波長に対して比較的大きい欠陥を検出するのに適する。一方、θを−90度から−180度の間とした配置は、斜方検出系500bに欠陥による後方散乱光が入射するため、波長に対して比較的小さい欠陥を検出するのに適する。   FIG. 11 shows the relationship between the detection direction of the oblique detection system 500b and the illumination direction. The oblique detection system 500b is installed so that the detection direction is the same as the stage X direction. The illumination azimuth can be selected as described in FIG. Here, the illumination traveling azimuth angle relative to the stage X direction is θ (when θ is 0 °, the same azimuth angle as the detection direction), and θ is between 0 ° and −90 °, and − An example of between 90 degrees and -180 degrees is shown. The arrangement in which θ is between 0 ° and −90 ° is suitable for detecting a relatively large defect with respect to the wavelength because forward scattered light due to the defect is incident on the oblique detection system 500b. On the other hand, an arrangement in which θ is between −90 degrees and −180 degrees is suitable for detecting defects that are relatively small with respect to the wavelength because backscattered light due to defects enters the oblique detection system 500b.

図12は斜方検出系500bの検出方向と、X-Y-Z-θステージ10の主走査方向St1と副走査方向St2と、照明領域F1の長手方向との関係を示す。照明領域F1の長手方向を主走査方向と垂直とすることで、検査対象基板Wの全面を効率良く走査することができる。検出方向を主走査方向S1に対し平行かつ照明領域F1に対し垂直とすることで、斜方検出系500bの受光器にリニアセンサを用いた場合に検査対象基板Wを高スループットで検査することができる。   FIG. 12 shows the relationship between the detection direction of the oblique detection system 500b, the main scanning direction St1 and sub-scanning direction St2 of the XYZ-θ stage 10, and the longitudinal direction of the illumination area F1. By making the longitudinal direction of the illumination area F1 perpendicular to the main scanning direction, the entire surface of the inspection target substrate W can be efficiently scanned. By making the detection direction parallel to the main scanning direction S1 and perpendicular to the illumination area F1, the inspection target substrate W can be inspected at a high throughput when a linear sensor is used as the light receiver of the oblique detection system 500b. it can.

図13は照明方向と検出方向に関して図11と異なる構成例を示す。ステージ主走査方向St1と垂直な方位に照明光を入射し、シリンドリカルレンズSLの円筒面回転軸をステージ主走査方向St1と平行とし、照明領域F1の長手方向がステージ主走査方向St1と垂直になるようシリンドリカルレンズSLを配置する。これにより、照明光の絞り方向に照明仰角を傾斜させた場合と比べて照明領域F1の短手方向を細く絞ることができ高い照明効率が得られるとともに、X-Y-Z-θステージ10走査中のZ方向の微小変動に伴う照明領域F1の短手方向の位置変動を抑えることができるため検出感度が安定する。   FIG. 13 shows a configuration example different from FIG. 11 with respect to the illumination direction and detection direction. Illumination light is incident in a direction perpendicular to the stage main scanning direction St1, the cylindrical surface rotation axis of the cylindrical lens SL is parallel to the stage main scanning direction St1, and the longitudinal direction of the illumination area F1 is perpendicular to the stage main scanning direction St1. A cylindrical lens SL is arranged. As a result, the short direction of the illumination area F1 can be narrowed narrowly compared with the case where the illumination elevation angle is inclined in the aperture direction of the illumination light, and high illumination efficiency can be obtained, and XYZ-θ stage 10 scanning is performed. Since the positional variation in the short direction of the illumination area F1 due to the minute variation in the Z direction can be suppressed, the detection sensitivity is stabilized.

図14は、前記第一の実施例の第二の変形例における光学系1000の構成を示す。光源1から発した照明光は照明光学系100’を介しハーフミラー150および対物レンズ3aにより検査対象基板W上の照明領域F1に導かれる。本構成によれば偏光検出部200において明視野画像が検出される。偏光検出部200から出力された検出信号は、信号処理部300において処理され、欠陥が検出される。   FIG. 14 shows a configuration of an optical system 1000 in a second modification of the first embodiment. The illumination light emitted from the light source 1 is guided to the illumination area F1 on the inspection target substrate W by the half mirror 150 and the objective lens 3a through the illumination optical system 100 '. According to this configuration, the bright field image is detected by the polarization detection unit 200. The detection signal output from the polarization detection unit 200 is processed in the signal processing unit 300, and a defect is detected.

図15は、前記第一の実施例の第三の変形例における光学系1000の構成を示す。光源1から発した照明光は照明光学系100’を介し暗視野対物レンズ3a’により検査対象基板W上の照明領域F1に導かれる。本構成によれば偏光検出部200において輪帯照明暗視野画像が検出される。   FIG. 15 shows a configuration of an optical system 1000 in a third modification of the first embodiment. The illumination light emitted from the light source 1 is guided to the illumination area F1 on the inspection target substrate W by the dark field objective lens 3a 'via the illumination optical system 100'. According to this configuration, the annular illumination dark field image is detected by the polarization detection unit 200.

照明光学系100’の構成を図16に示す。アッテネータ101’により、照明光の強度が制御される。偏光板102’を必要に応じて設け、光源より発する照明光の偏光が直線偏光に揃えられる。光軸の周りに回転可能なλ/2板103’、およびλ/4板104’により、照明光の偏光状態が任意に設定される。なお、光源1としてレーザ光源を用いる場合は、スペックル低減手段111’を設置することでスペックルノイズの発生を抑えることができる。スペックル低減手段としては、互いに光路長の異なる複数の光ファイバあるいは石英板あるいはガラス板等を用いて、互いに異なる光路長を持つ複数の光束を生成しこれを重ね合わせる方法、あるいは回転拡散板を通過させる方法などがある
前記第一の実施例の第三の変形例における光学系1000およびX-Y-Z-θステージ10の構成を図17に示す。光源1’として断続的に発光するストロボ光源を用いる。具体的には、パルスレーザ、LD励起Qスイッチパルスレーザ、ランプ励起Qスイッチパルスレーザ、フラッシュランプなどが適している。また、偏光検出部200の受光器としてエリアセンサを用いる。この構成で光源1’の発光、X-Y-Z-θステージ10の走査、および受光器の信号蓄積を同期してストロボ撮像を行うことで、歪みのない2次元画像を取得することができ、高精度なチップ比較が可能となる。また、X-Y-Z-θステージ10の代わりにr−θ回転ステージ10’を用いることで、XY走査と比較してより高速に検査対象基板W全面を走査することが可能となる。
The configuration of the illumination optical system 100 ′ is shown in FIG. The intensity of the illumination light is controlled by the attenuator 101 ′. A polarizing plate 102 ′ is provided as necessary, and the polarization of the illumination light emitted from the light source is aligned with linearly polarized light. The polarization state of the illumination light is arbitrarily set by the λ / 2 plate 103 ′ and the λ / 4 plate 104 ′ that can rotate around the optical axis. In addition, when using a laser light source as the light source 1, speckle noise generation | occurrence | production can be suppressed by installing speckle reduction means 111 '. As speckle reduction means, a method of generating and superimposing a plurality of light beams having different optical path lengths using a plurality of optical fibers or quartz plates or glass plates having different optical path lengths, or a rotating diffusion plate is used. FIG. 17 shows the configuration of the optical system 1000 and the XYZ-θ stage 10 in the third modification of the first embodiment. A strobe light source that emits light intermittently is used as the light source 1 ′. Specifically, a pulse laser, an LD excitation Q-switch pulse laser, a lamp excitation Q-switch pulse laser, a flash lamp, and the like are suitable. In addition, an area sensor is used as a light receiver of the polarization detection unit 200. With this configuration, a stroboscopic image can be obtained by synchronizing the light emission of the light source 1 ′, the scanning of the XYZ-θ stage 10, and the signal accumulation of the light receiver, thereby obtaining a distortion-free two-dimensional image. High precision chip comparison becomes possible. Further, by using the r-θ rotation stage 10 ′ instead of the XYZ-θ stage 10, it is possible to scan the entire surface of the inspection target substrate W at a higher speed than XY scanning.

前記第一の実施例の第四の変形例の構成を図18に示す。検査対象基板W1とW2は設計上同じパターンが形成されている。光源1’より発した光は分岐され、r−θ回転ステージ10’上に載置された検査対象基板W1とW2各々に照射される。検査対象基板W1からの反射散乱光は対物レンズ3a、結像レンズ5aを介し、偏光検出部200に入射する。検査対象基板W2からの反射散乱光は対物レンズ3a−2、結像レンズ5a−2を介し、偏光検出部200−2に入射する。光源1’の発光、X-Y-Z-θステージ10の走査、偏光検出部200内の受光器の信号蓄積および偏光検出部200−2内の受光器の信号蓄積を同期してストロボ撮像を行う。   FIG. 18 shows the configuration of a fourth modification of the first embodiment. Inspected substrates W1 and W2 are designed to have the same pattern. The light emitted from the light source 1 ′ is branched and applied to each of the inspection target substrates W <b> 1 and W <b> 2 placed on the r-θ rotation stage 10 ′. The reflected and scattered light from the inspection target substrate W1 enters the polarization detection unit 200 via the objective lens 3a and the imaging lens 5a. The reflected and scattered light from the inspection target substrate W2 enters the polarization detection unit 200-2 via the objective lens 3a-2 and the imaging lens 5a-2. Strobe imaging is performed in synchronization with light emission of the light source 1 ′, scanning of the XYZ-θ stage 10, signal accumulation of the light receiver in the polarization detector 200, and signal accumulation of the light receiver in the polarization detector 200-2. Do.

r−θ回転ステージ10’を用いて回転走査を行う場合、図19(a)に示すように、検査対象基板W、W1、W2上における視野位置によって、検査対象基板上に形成されたパターンに対する照明の偏光状態、および偏光検出部200あるいは200−2の方位が異なる。照明光の偏光状態を光軸周りに対称な円偏光あるいは無偏光とするか、視野位置に対応するステージ回転角に応じて、照明光の偏光状態の長軸方位角を回転することで、検査対象基板上に形成されたパターンに対する照明の偏光状態を一定に保つことが可能である。さらに、図19(b)に示すように、視野位置に対応するステージ回転角に応じて、検出した偏光成分の方位角を回転するよう補正を加えることで、検査対象基板上に形成されたパターンに対する偏光検出部方位の回転の影響を除去し、検査対象基板上に形成されたパターンに対する偏光検出部方位の回転によらず検査対象基板全面を一定の感度で検査することが可能である。     When rotational scanning is performed using the r-θ rotation stage 10 ′, as shown in FIG. 19A, the pattern formed on the inspection target substrate depends on the visual field position on the inspection target substrates W, W1, and W2. The polarization state of illumination and the orientation of the polarization detector 200 or 200-2 are different. Inspection by changing the polarization state of the illumination light to circularly polarized light or non-polarization symmetric around the optical axis, or rotating the major axis azimuth angle of the polarization state of the illumination light according to the stage rotation angle corresponding to the visual field position It is possible to keep the polarization state of illumination with respect to the pattern formed on the target substrate constant. Further, as shown in FIG. 19B, the pattern formed on the inspection target substrate is corrected by rotating the azimuth angle of the detected polarization component according to the stage rotation angle corresponding to the visual field position. It is possible to remove the influence of the rotation of the polarization detection unit orientation on the entire surface of the inspection target substrate with a constant sensitivity regardless of the rotation of the polarization detection unit orientation with respect to the pattern formed on the inspection target substrate.

次に、第2の実施例として、図1及び2で説明した構成において、光源1の代わりにパルス発振のUVレーザ光源2001を用いた場合に照明光学系100に変わる光学系の実施例を図20乃至23を用いて説明する。 Next, as a second embodiment, an embodiment of an optical system that changes to the illumination optical system 100 when a pulsed UV laser light source 2001 is used instead of the light source 1 in the configuration described in FIGS. 20 to 23 will be used for explanation.

光源2001にパルス発振のUVレーザを用いる場合,例えば大きさが10nm前後の極微小な異物欠陥から検出するのに十分な強度の散乱光を得るためには照射するパルスレーザの光量を大きくする必要が有るが、その結果として、パルス発振レーザの必要な平均出力に対して,尖頭値(最大出力)が非常に大きくなる。例えば,平均出力2[W],発光周波数100MHzでパルス間隔10[ns],パルス幅10[ps]のレーザの場合,尖頭値(最大出力)は2[kW]にもなり,試料にダメージを与える恐れがある。このために,平均出力を維持したままで尖頭値(最大出力)を低減させることが望ましい。   When a pulsed UV laser is used as the light source 2001, for example, in order to obtain scattered light having a sufficient intensity to detect from a very small particle defect having a size of about 10 nm, it is necessary to increase the amount of the pulse laser to be irradiated. As a result, the peak value (maximum output) becomes very large with respect to the required average output of the pulsed laser. For example, in the case of a laser with an average output of 2 [W], a light emission frequency of 100 MHz, a pulse interval of 10 [ns], and a pulse width of 10 [ps], the peak value (maximum output) is 2 [kW], causing damage to the sample. There is a risk of giving. For this reason, it is desirable to reduce the peak value (maximum output) while maintaining the average output.

この平均出力を維持した状態で尖頭値を低減させる方法として、本実施例では、図20に示すように、光源2001から発射されたレーザビームL0をビーム拡大光学系2016で拡大し、パルス分岐光学系2017に入射させて光路長が異なる複数の光路に分岐した後光路を合体させることで、光源から発射された1パルス分のレーザビームを尖頭値を小さくした複数のパルスに分割し、この分割した複数のパルスレーザを分岐光学要素2018(図2のミラーM1からM9及びシリンドリカルレンズ109,110および111で構成される光学系に相当)に入射させて光路L1,2,3の何れか(図2の光路106,107,108に相当)の方向に導いてスリット状ビームに形成してウェハWのスリット状の領域2100に照射するように構成した。   As a method of reducing the peak value while maintaining this average output, in this embodiment, as shown in FIG. 20, the laser beam L0 emitted from the light source 2001 is expanded by a beam expanding optical system 2016, and pulse branching is performed. Splitting the laser beam for one pulse emitted from the light source into a plurality of pulses with reduced peak values by combining the optical paths after entering the optical system 2017 and branching into a plurality of optical paths having different optical path lengths, The plurality of divided pulse lasers are incident on the branching optical element 2018 (corresponding to the optical system composed of the mirrors M1 to M9 and the cylindrical lenses 109, 110, and 111 in FIG. 2) and any one of the optical paths L1, 2, 3 It is guided in the direction (corresponding to the optical paths 106, 107, and 108 in FIG. 2) to form a slit beam and irradiate the slit region 2100 of the wafer W. Configured.

また、パルスレーザビームを複数に分割して照射することにより、例えば、被検査対象基板Wを載置するX−Y−Z−θステージ11のX方向(図11参照)への移動速度を毎秒20cm、図3(a)に示した偏光検出部200a'の検出器220または221をCCD方式あるいはCMOS方式など時間蓄積型のリニアイメージセンサで構成したときの1画素あたりの検出視野を1μmとし、発光周波数100MHzのUVパルスレーザビームを上記した条件で複数に分割して照射すると、検出器220または221の1画素で検出する領域に数百パルスを超えるレーザビームが重ねて照射されるので、レーザビームにより発生するスペックルノイズを時間的に平均化して撮像することができ、ノイズが低減された画像を得ることができる。   In addition, by irradiating the pulse laser beam in a plurality of portions, for example, the movement speed in the X direction (see FIG. 11) of the XYZ-θ stage 11 on which the substrate W to be inspected is placed is changed per second. When the detector 220 or 221 of the polarization detection unit 200a ′ shown in FIG. 3A is composed of a time accumulation type linear image sensor such as a CCD method or a CMOS method, the detection visual field per pixel is 1 μm. When a UV pulse laser beam with an emission frequency of 100 MHz is divided into a plurality of parts under the above-described conditions and irradiated, a laser beam exceeding several hundred pulses is irradiated on the region detected by one pixel of the detector 220 or 221. Speckle noise generated by the beam can be averaged over time and imaged, and an image with reduced noise can be obtained.

パルス光分割光学系2017の一例を図21(a)に示す。この例においては,パルス光分割光学系2017を、1/4波長板1711,PBS(偏光ビームスプリッタ)1712a,1712bとミラー1713a,1713bの組合せで構成する。ビーム拡大光学系2016で拡大されて直線偏光(この例ではP偏光)で入射したレーザビームを1/4波長板1711aで楕円偏光にし,偏光ビームスプリッタ1712aでP偏光とS偏光に分離する。分離された一方のP偏光成分は偏光ビームスプリッタ1712aと偏光ビームスプリッタ1712bとを通過する。分離された他方のS偏光成分は偏光ビームスプリッタ1712a,ミラー1713a,ミラー1713b,偏光ビームスプリッタ1712bでそれぞれ反射して偏光ビームスプリッタ1712aと1712bとを通過してきたP偏光成分と同一光軸に戻る。このとき,偏光ビームスプリッタ1712aとミラー1713a,偏光ビームスプリッタ1712bとミラー1713bの間隔をL/2[m]とすると,S偏光成分とP偏光成分との間にはL[m]の光路差ができる。光速をc[m/s]とすると,S偏光成分とP偏光成分との間には
t[s]=L[m]/c[m/s] (数1)
の時間差が生じ,図21(b)に示すようなレーザ光源2001から発射された時間間隔Tで発振された2パルスのビームを時分割することにより、図21(c)に示すように各1パルスのレーザを時間間隔tでP偏光とS偏光各1パルスずつの計2パルスに分割して,尖頭値を1/2に低減させることができる。
An example of the pulsed light splitting optical system 2017 is shown in FIG. In this example, the pulsed light splitting optical system 2017 is configured by a combination of a quarter wavelength plate 1711, PBS (polarization beam splitter) 1712a, 1712b, and mirrors 1713a, 1713b. The laser beam expanded by the beam expanding optical system 2016 and incident as linearly polarized light (P-polarized light in this example) is converted into elliptically polarized light by the quarter-wave plate 1711a, and is separated into P-polarized light and S-polarized light by the polarizing beam splitter 1712a. One separated P-polarized component passes through the polarization beam splitter 1712a and the polarization beam splitter 1712b. The other separated S-polarized component is reflected by the polarized beam splitter 1712a, mirror 1713a, mirror 1713b, and polarized beam splitter 1712b, respectively, and returns to the same optical axis as the P-polarized component that has passed through the polarized beam splitters 1712a and 1712b. At this time, if the distance between the polarizing beam splitter 1712a and the mirror 1713a and the distance between the polarizing beam splitter 1712b and the mirror 1713b is L / 2 [m], there is an optical path difference of L [m] between the S-polarized component and the P-polarized component. it can. If the speed of light is c [m / s], t [s] = L [m] / c [m / s] (Equation 1) between the S polarization component and the P polarization component
Time difference is generated, and two beams of pulses emitted from the laser light source 2001 as shown in FIG. 21 (b) and oscillated at the time interval T are time-divided. The pulse laser can be divided into two pulses, one each for P-polarized light and S-polarized light at time intervals t, and the peak value can be reduced to ½.

例えば、パルス間隔10ns(10−8秒),パルス幅10ps(10−11秒)のレーザを用いて、偏光ビームスプリッタ1712aとミラー1713a及び偏光ビームスプリッタ1712bとミラー1713bの間隔をそれぞれ15cm(0.15m)に設定した場合、S偏光成分とP偏光成分との間の時間差は1ns(10−9秒)となる。すなわち、ウェハ表面は、10nsの間に1ns間隔でP偏光とS偏光各1パルスずつの計2回、尖頭値が半減されたレーザビームがパルス状に照射されることになる。 For example, the pulse interval 10 ns (10-8 sec), using a laser pulse width 10 ps (10 -11 seconds), the polarization beam splitter 1712a and the mirror 1713a, and the polarization beam splitter 1712b respectively 15cm spacing mirror 1713b (0. 15m), the time difference between the S-polarized component and the P-polarized component is 1 ns (10-9 seconds). That is, the wafer surface is irradiated with a laser beam whose peak value is halved twice in a pulsed manner at intervals of 1 ns for 10 ns each time, each pulse of P-polarized light and S-polarized light.

1/4波長板1711aの回転角を調整して,偏光ビームスプリッタ1712aの入射ビームのS偏光成分とP偏光成分の比率を1:1(円偏光)にすると,使用する光学部品(偏光ビームスプリッタ1712a,1712bとミラー1713a,1713b)の損失(反射率,透過率)により,偏光ビームスプリッタ1712bの出射ビームでのS偏光成分とP偏光成分のパルス光の尖頭値が異なってしまう。各パルス光の尖頭値の最大値を低くするには、各パルス光の尖頭値をほぼ同じ大きさにする必要がある。   When the rotation angle of the quarter wave plate 1711a is adjusted so that the ratio of the S-polarization component and the P-polarization component of the incident beam of the polarization beam splitter 1712a is 1: 1 (circular polarization), the optical component to be used (polarization beam splitter) 1712a, 1712b and the loss (reflectance, transmittance) of the mirrors 1713a, 1713b), the peak values of the pulsed light of the S-polarized component and the P-polarized component in the outgoing beam of the polarizing beam splitter 1712b are different. In order to reduce the maximum value of the peak value of each pulsed light, the peak value of each pulsed light needs to be set to substantially the same size.

図21(a)に示したパルス分割光学系2017の構成において,P偏光成分は偏光ビームスプリッタ1712a,1712bのP偏光透過率(Tp)が影響するだけであるが,S偏光成分は偏光ビームスプリッタ1712a,1712bのS偏光反射率(Rs)とミラー1713a,1713bのS偏光反射率(Rm)が影響する。損失比率(Pl)はS偏光成分損失をLs,P偏光成分損失をLpとすると
P1=Ls/Lp=Rm×Rs/Tp (数2)
となる。
In the configuration of the pulse splitting optical system 2017 shown in FIG. 21 (a), the P-polarized component is only affected by the P-polarized light transmittance (Tp) of the polarizing beam splitters 1712a and 1712b. The S-polarized reflectance (Rs) of 1712a and 1712b and the S-polarized reflectance (Rm) of the mirrors 1713a and 1713b are affected. The loss ratio (Pl) is P1 = Ls / Lp = Rm 2 × Rs 2 / Tp 2 (Equation 2 ), where Ss polarization component loss is Ls and P polarization component loss is Lp.
It becomes.

したがって,偏光ビームスプリッタ1712aの入射ビーム偏光の楕円率を上記損失比率と等しくなるように,1/4波長板1711aの回転角を調整することにより,偏光ビームスプリッタ1712bの出射ビームでのS偏光成分とP偏光成分のパルス光の尖頭値をほぼ等しくすることができる。この尖頭値がほぼ等しくなるように分割されたP偏光成分とS偏光成分のパルス光はそれぞれの光路長差に応じた時間間隔を持って図2(a)に示した光路106,107,108の何れかを通ってウェハWに照射される。   Therefore, by adjusting the rotation angle of the quarter-wave plate 1711a so that the ellipticity of the incident beam polarization of the polarization beam splitter 1712a is equal to the loss ratio, the S polarization component in the output beam of the polarization beam splitter 1712b is adjusted. And the peak value of the pulsed light of the P-polarized component can be made substantially equal. The P-polarized component and S-polarized component pulse lights divided so that the peak values are substantially equal have optical paths 106, 107,... Shown in FIG. The wafer W is irradiated through any of 108.

上記説明ではパルス分割光学系2017を用いてパルス光を2分割する方法について説明したが,分割数を更に増やすためのパルス分割光学系2017の変形例として、4分割する方法について図22(a)および(b)を用いて説明する。図22(a)に示したパルス分割光学系2217の構成は,図21(a)に示したパルス分割光学系2017の構成を2段にしたものである。2段目の偏光ビームスプリッタ1732cとミラー1733cとの間隔,及び偏光ビームスプリッタ1732dとミラー1733dとの間隔を、それぞれ1段目の偏光ビームスプリッタ1732aとミラー1733a,及び偏光ビームスプリッタ1732bとミラー1733bとの間隔の2倍に設定する。   In the above description, the method of dividing the pulsed light into two using the pulse division optical system 2017 has been described. However, as a modification of the pulse division optical system 2017 for further increasing the number of divisions, a method of dividing into four is illustrated in FIG. And it demonstrates using (b). The configuration of the pulse division optical system 2217 shown in FIG. 22A is a two-stage configuration of the pulse division optical system 2017 shown in FIG. The distance between the second-stage polarization beam splitter 1732c and the mirror 1733c and the distance between the polarization beam splitter 1732d and the mirror 1733d are respectively set to the first-stage polarization beam splitter 1732a and the mirror 1733a, and the polarization beam splitter 1732b and the mirror 1733b. Set to twice the interval.

1段目の偏光ビームスプリッタ1732bからの射出ビームは,P偏向パルス光と時間遅れをもつS偏向パルス光である。このパルス光列を1/4波長板1731bにより円偏光にすることにより,1/4波長板1731bを透過したパルス光列の1/2の強度がP偏光となって偏光ビームスプリッタ1732c, 1732dを透過し,1/2の強度がS偏光となって偏光ビームスプリッタ1732cおよびミラー1733c, 1733dで反射し, 偏光ビームスプリッタ1732dで反射してP偏光と同一光軸に戻る。これにより,パルス光が4つに分割されて,それぞれの尖頭値が光源2001から出射したパルスレーザビームの1/4に低減する。厳密には上述のように光学部品の損失があるため,1/4より低減する。   The outgoing beam from the first-stage polarization beam splitter 1732b is S-polarized pulse light having a time delay with respect to the P-polarized pulse light. By making this pulse light train circularly polarized by the ¼ wavelength plate 1731b, the half intensity of the pulse light train transmitted through the ¼ wavelength plate 1731b becomes P-polarized light, and the polarization beam splitters 1732c and 1732d are turned on. The light is transmitted, becomes half-polarized light, is reflected by the polarizing beam splitter 1732c and the mirrors 1733c and 1733d, is reflected by the polarizing beam splitter 1732d, and returns to the same optical axis as the P-polarized light. As a result, the pulsed light is divided into four, and each peak value is reduced to ¼ of the pulsed laser beam emitted from the light source 2001. Strictly speaking, since there is a loss of optical parts as described above, it is reduced from 1/4.

図22(a)の構成において、偏光ビームスプリッタ1732cを通過して偏光ビームスプリッタ1732dを通過したP偏光パルスレーザと、ミラー1733dで反射し偏光ビームスプリッタ1732dで反射したS偏光パルスレーザとは同一の光軸を通って1/4波長板1731cで円偏光にされ、偏光ビームスプリッタ1734に入射してP偏光とS偏光とに光路が分離される。光路が分離された一方のP偏光成分のレーザビームは、光路L1に入って円筒レンズ1735(図2(b)のシリンドリカルレンズ109又は110または111に相当)で成形されてウェハ1上の線状の領域2110を照明する。   In the configuration of FIG. 22A, the P-polarized pulse laser that passes through the polarizing beam splitter 1732c and passes through the polarizing beam splitter 1732d is the same as the S-polarized pulse laser that is reflected by the mirror 1733d and reflected by the polarizing beam splitter 1732d. The light passes through the optical axis and is circularly polarized by the quarter-wave plate 1731c, enters the polarization beam splitter 1734, and the optical path is separated into P-polarized light and S-polarized light. The laser beam of one P-polarized component from which the optical path is separated enters the optical path L1 and is shaped by the cylindrical lens 1735 (corresponding to the cylindrical lens 109, 110, or 111 in FIG. 2B) to be linear on the wafer 1. Illuminate the area 2110.

一方、偏光ビームスプリッタ1734で反射されて光路を90°曲げられたS偏光ビームは、光路L2に入ってミラー1736及び1737で反射して光路を変更して円筒レンズ1738で成形されてウェハW上の線状の領域2110を、光路L2方向から照明するP変更成分のレーザビームに対してウェハW面上で直角方向から照明する。   On the other hand, the S-polarized beam which is reflected by the polarization beam splitter 1734 and whose optical path is bent by 90 ° enters the optical path L2, is reflected by the mirrors 1736 and 1737, is changed by the optical path, and is molded by the cylindrical lens 1738 and is formed on the wafer W. The linear region 2110 is illuminated from the direction perpendicular to the surface of the wafer W with respect to the laser beam of the P-changing component that is illuminated from the direction of the optical path L2.

このとき光路L1と光路L2とは光路長が異なるように設計されており、ウェハW上の線状の領域2110に照射されるP偏光レーザビームとS偏光レーザビームとは、図22(b)に示すように光路長差分だけ時間差tが発生し、タイミングがずれて照射される。これにより、線状の領域2110に照射されるP偏光レーザビームとS偏光レーザビームとの間の干渉の発生を防止することができる。 At this time, the optical path L1 and the optical path L2 are designed to have different optical path lengths. The P-polarized laser beam and the S-polarized laser beam applied to the linear region 2110 on the wafer W are shown in FIG. As shown in FIG. 5, a time difference t 0 is generated by an optical path length difference, and irradiation is performed with a timing shift. Thereby, the occurrence of interference between the P-polarized laser beam and the S-polarized laser beam irradiated on the linear region 2110 can be prevented.

また、レーザ光源2001からの照明による反射散乱光を検出する光検出器220と221とは、それぞれ1画素分を検出する時間内に90°ずれた方向からの照明による反射散乱光を検出することになり、照明方向の違いによる検出感度のばらつきを低減することが可能になり、より微小な異物欠陥を安定に検出することができるようになる。なお、このとき図10に示したような斜方検出系500bも用いた場合には、斜方検出系500bの検出の方向は、矢印1740の方向への反射散乱光を検出をする。   The photodetectors 220 and 221 that detect reflected and scattered light from illumination from the laser light source 2001 detect reflected and scattered light from illumination from a direction shifted by 90 ° within the time for detecting one pixel. Therefore, it becomes possible to reduce the variation in detection sensitivity due to the difference in illumination direction, and it becomes possible to detect more minute foreign matter defects stably. At this time, when the oblique detection system 500b as shown in FIG. 10 is also used, the detection direction of the oblique detection system 500b detects the reflected scattered light in the direction of the arrow 1740.

また、図23には、図22(a)に示した構成における光路L2を光路L3に変更した構成を示す。この構成においては、偏光ビームスプリッタ1734で反射されて光路を90°曲げられたS偏光ビームを、光路L3でミラー1736、1747及び1748で反射して光路を変更して円筒レンズ1749で成形されてウェハW上の線状の領域2110を、光路L1と対向する方向から照明する。   FIG. 23 shows a configuration in which the optical path L2 in the configuration shown in FIG. 22A is changed to the optical path L3. In this configuration, the S-polarized beam reflected by the polarizing beam splitter 1734 and bent by 90 ° in the optical path is reflected by the mirrors 1736, 1747 and 1748 in the optical path L3, and the optical path is changed to be molded by the cylindrical lens 1749. The linear region 2110 on the wafer W is illuminated from the direction facing the optical path L1.

図22(a)及び図23に示した構成においては、1/4波長板1731cと偏光ビームスプリッタ1734を用いる構成を示したが、1/4波長板1731cを削除して偏光ビームスプリッタ1734の代わりに無偏光ビームスプリッタ(図示せず)を用いることにより、光路L1,L2,L3それぞれの方向からP偏光とS偏光がそれぞれ異なるタイミングでウェハWを照明する。このとき、光検出器220と221とは、それぞれ1画素分を検出する時間内に90°または180°ずれた方向からP偏光とS偏光とで順次照明されることによる反射散乱光を検出することになる。これにより、1画素分を検出する時間内に複数の照明条件で照明されたウェハWからの反射散乱光を検出することになり、単一の照明条件で照明された場合に比べて検出感度を向上させることが可能になり、より微小な異物欠陥を安定に検出することができるようになる。   In the configuration shown in FIG. 22A and FIG. 23, the configuration using the ¼ wavelength plate 1731c and the polarization beam splitter 1734 is shown, but the ¼ wavelength plate 1731c is deleted and replaced with the polarization beam splitter 1734. By using a non-polarizing beam splitter (not shown), the wafer W is illuminated at different timings for the P-polarized light and the S-polarized light from the directions of the optical paths L1, L2, and L3. At this time, each of the photodetectors 220 and 221 detects reflected / scattered light by sequentially illuminating with P-polarized light and S-polarized light from a direction shifted by 90 ° or 180 ° within the time for detecting one pixel. It will be. As a result, reflected / scattered light from the wafer W illuminated under a plurality of illumination conditions is detected within a time period for detecting one pixel, and the detection sensitivity is higher than that when illuminated under a single illumination condition. It becomes possible to improve, and it becomes possible to detect more minute foreign matter defects stably.

光検出器220と221とで検出した信号は、第1の実施例で説明したのと同様に信号処理部300で処理されて欠陥が検出される。   Signals detected by the photodetectors 220 and 221 are processed by the signal processing unit 300 in the same manner as described in the first embodiment, and defects are detected.

なお、第2の実施例において、偏光検出部200aとして図3(a)の構成を用いて説明したが、図3(b)、図4または図5で説明した偏光検出部を用いてもよい。   In the second embodiment, the polarization detection unit 200a has been described using the configuration in FIG. 3A. However, the polarization detection unit described in FIG. 3B, FIG. 4 or FIG. 5 may be used. .

本実施例によれば、UVパルスレーザビームを尖頭値を低減してウェハに照射することができるために、0.1μm前後、またはそれよりも小さい極微小な欠陥をウェハにダメージを与えずに高感度に検出することが可能になった。   According to the present embodiment, the peak of the UV pulse laser beam can be reduced and the wafer can be irradiated, so that an extremely small defect of about 0.1 μm or smaller is not damaged to the wafer. It became possible to detect with high sensitivity.

本発明に係る欠陥検査装置の第一の実施の形態を示す概略構成図である。It is a schematic block diagram which shows 1st embodiment of the defect inspection apparatus which concerns on this invention. 本発明に係る照明光学系の構成を示す概略構成図である。It is a schematic block diagram which shows the structure of the illumination optical system which concerns on this invention. 本発明に係る偏光検出部の振幅分割法を用いた構成例を示す概略構成図である。It is a schematic block diagram which shows the structural example using the amplitude division method of the polarization | polarized-light detection part which concerns on this invention. 本発明に係る偏光検出部の複屈折ウェッジを用いた構成例を示す概略構成図である。It is a schematic block diagram which shows the structural example using the birefringent wedge of the polarization | polarized-light detection part which concerns on this invention. 本発明に係る偏光検出部の偏光光学素子アレイを用いた構成例を示す概略構成図である。It is a schematic block diagram which shows the structural example using the polarizing optical element array of the polarization detection part which concerns on this invention. 本発明に係る信号処理部を示す概略構成図である。It is a schematic block diagram which shows the signal processing part which concerns on this invention. 本発明に係る信号処理部における互いに異なる二つの偏光成分信号に基づく欠陥判定方法を示す概念図である。It is a conceptual diagram which shows the defect determination method based on two mutually different polarization component signals in the signal processing part which concerns on this invention. 本発明に係る信号処理部における互いに異なる複数の偏光成分信号より算出される二つの物理量に基づく欠陥判定方法を示す概念図である。It is a conceptual diagram which shows the defect determination method based on two physical quantities computed from the mutually different several polarization component signal in the signal processing part which concerns on this invention. 本発明に係る信号処理部における互いに異なる複数の偏光成分信号より算出される三つの物理量に基づく欠陥判定方法を示す概念図である。It is a conceptual diagram which shows the defect determination method based on the three physical quantities calculated from the mutually different several polarization component signal in the signal processing part which concerns on this invention. 本発明に係る欠陥検査装置の第一の変形例における光学系を示す概略構成図である。It is a schematic block diagram which shows the optical system in the 1st modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第一の変形例における斜方検出系の検出方向を示す概略図である。It is the schematic which shows the detection direction of the oblique detection system in the 1st modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第一の変形例における斜方検出系の検出方向とステージ走査方向および照明領域長手方向の関係を示す概略図である。It is the schematic which shows the relationship between the detection direction of an oblique detection system, a stage scanning direction, and an illumination area longitudinal direction in the 1st modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第一の変形例における照明領域の形成方法が第一の実施例と異なる構成例の概略構成図である。It is a schematic block diagram of the structural example from which the formation method of the illumination area in the 1st modification of the defect inspection apparatus which concerns on this invention differs from a 1st Example. 本発明に係る欠陥検査装置の第二の変形例における光学系を示す概略構成図である。It is a schematic block diagram which shows the optical system in the 2nd modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第三の変形例における光学系を示す概略構成図である。It is a schematic block diagram which shows the optical system in the 3rd modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第二、第三、第四、第五の変形例における照明光学系を示す概略構成図である。It is a schematic block diagram which shows the illumination optical system in the 2nd, 3rd, 4th, 5th modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第四の変形例における光学系およびステージを示す概略構成図である。It is a schematic block diagram which shows the optical system and stage in the 4th modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第五の変形例における光学系およびステージを示す概略構成図である。It is a schematic block diagram which shows the optical system and stage in the 5th modification of the defect inspection apparatus which concerns on this invention. 本発明に係る欠陥検査装置の第四、第五の変形例における、検査対象基板に対する視野の回転と検出偏光成分の回転との関係を示す概念図である。.It is a conceptual diagram which shows the relationship between the rotation of the visual field with respect to a test object board | substrate and rotation of a detection polarization component in the 4th, 5th modification of the defect inspection apparatus which concerns on this invention. . 第2の実施例におけるビーム拡大光学系の側面図である。It is a side view of the beam expansion optical system in the 2nd example. (a)第2の実施例における光路分岐光学系の概略構成を示すブロック図,(b)レーザ光源から発射されたペルスレーザの波形信号図、(c)レーザ光源から発射された1パルスのレーザを2パルスに分割した状態を示すパルス波形信号図である。(A) A block diagram showing a schematic configuration of the optical path branching optical system in the second embodiment, (b) a waveform signal diagram of a pels laser emitted from a laser light source, and (c) a one-pulse laser emitted from the laser light source. It is a pulse waveform signal diagram which shows the state divided | segmented into 2 pulses. (a)第2の実施例におけるパルス分割光学系の変形例における概略構成を示すブロック図,(b)パルス分割の状態を示すパルス波形信号図である。(A) It is a block diagram which shows schematic structure in the modification of the pulse division | segmentation optical system in 2nd Example, (b) It is a pulse waveform signal figure which shows the state of a pulse division | segmentation. 第2の実施例におけるパルス分割光学系の別の変形例における概略構成を示すブロック図である。It is a block diagram which shows schematic structure in another modification of the pulse division | segmentation optical system in a 2nd Example.

符号の説明Explanation of symbols

1…光源、3a…対物レンズ、4a…空間フィルタ、5a…結像レンズ、200a…偏光検出部、300…信号処理部、6…全体制御部、7…表示部、8…演算部、9…記憶部、10…X−Y−Z−θステージ、100…照明光学系、1000…光学系、W…検査対象基板
DESCRIPTION OF SYMBOLS 1 ... Light source, 3a ... Objective lens, 4a ... Spatial filter, 5a ... Imaging lens, 200a ... Polarization detection part, 300 ... Signal processing part, 6 ... Overall control part, 7 ... Display part, 8 ... Calculation part, 9 ... Storage unit, 10 ... XYZ-θ stage, 100 ... Illumination optical system, 1000 ... Optical system, W ... Substrate to be inspected

Claims (14)

レーザを発射する光源手段と、
該光源手段から発射されたレーザの偏光の状態を制御して表面にパターンが形成された試料の該表面に対して傾斜した方向から照射する照明光学系手段と、
該照明光学系手段によりレーザが照射された前記試料からの反射散乱光を空間フィルタを介して該反射散乱光の偏光成分ごとに分離して検出する検出手段と、
該検出手段で偏光成分ごとに分離して検出した前記偏光成分ごとの検出信号を処理して前記試料上の欠陥を検出する信号処理手段と、
該信号処理手段で処理して得た欠陥の情報を出力する出力手段と
を備えたことを特徴とする欠陥検査装置。
Light source means for emitting a laser;
Illumination optical system means for controlling the polarization state of the laser emitted from the light source means and irradiating the sample having a pattern formed on the surface from a direction inclined with respect to the surface;
Detecting means for separating and detecting reflected and scattered light from the sample irradiated with laser by the illumination optical system means for each polarization component of the reflected and scattered light through a spatial filter;
A signal processing means for detecting a defect on the sample by processing a detection signal for each polarization component separated and detected by the detection means for each polarization component;
A defect inspection apparatus comprising: output means for outputting information on defects obtained by processing by the signal processing means.
前記信号処理手段は、偏光成分ごとに分離して検出された検出信号のうちP偏光成分の検出信号を処理して得た情報とS偏光成分の検出信号を処理して得た情報とを用いて前記試料上の欠陥を検出し、該検出した欠陥を分類することを特徴とする請求項1記載の欠陥検査装置。   The signal processing means uses information obtained by processing the detection signal of the P polarization component among the detection signals detected separately for each polarization component and information obtained by processing the detection signal of the S polarization component. The defect inspection apparatus according to claim 1, wherein defects on the sample are detected and the detected defects are classified. 前記信号処理手段は、前記分離して検出した偏光成分ごとの検出信号を処理して複数の欠陥候補を抽出し、該抽出した複数の欠陥候補の特徴量を比較し、統計的に外れた特徴量を有する欠陥候補を欠陥として検出することを特徴とする請求項1記載の欠陥検査装置。   The signal processing means processes a detection signal for each of the polarization components detected separately and extracts a plurality of defect candidates, compares the feature quantities of the extracted defect candidates, and statistically deviates features. The defect inspection apparatus according to claim 1, wherein a defect candidate having a quantity is detected as a defect. 前記照明光学系手段はシリンドリカルレンズを有し、該シリンドリカルレンズを介して前記試料の表面に対して傾斜した方向から該試料表面の楕円状又は直線状の領域に前記レーザを照射することを特徴とする請求項1乃至3の何れかに記載の欠陥検査装置。   The illumination optical system means has a cylindrical lens, and irradiates the elliptical or linear region of the sample surface from a direction inclined with respect to the sample surface via the cylindrical lens. The defect inspection apparatus according to any one of claims 1 to 3. 前記照明光学系手段は光路切換え部を有し、前記偏光の状態を制御したレーザを前記試料の表面に照射する方位角及び/または仰角を前記切換え部で切換えが可能であることを特徴とする請求項1乃至3の何れかに記載の欠陥検査装置。   The illumination optical system means has an optical path switching unit, and the switching unit can switch the azimuth angle and / or elevation angle for irradiating the surface of the sample with the laser whose polarization state is controlled. The defect inspection apparatus according to claim 1. 前記検出手段は前記レーザが照射された前記試料からの反射散乱光のうち前記試料の表面に対して第1の仰角方向に反射散乱した光を検出する第1の検出光学系部と前記試料の表面に対して第2の仰角方向に反射散乱した光を検出する第2の検出光学系部とを有することを特徴とする請求項1乃至3の何れかに記載の欠陥検査装置。   The detection means includes: a first detection optical system unit that detects light reflected and scattered in a first elevation angle direction with respect to the surface of the sample out of the reflected and scattered light from the sample irradiated with the laser; 4. The defect inspection apparatus according to claim 1, further comprising: a second detection optical system unit that detects light reflected and scattered in a second elevation angle direction with respect to the surface. 前記光源手段はパルス発振レーザを発射し、前記照明光学系手段は光路長の異なる複数の光路を有して前記光源手段から発射されたパルス発振レーザの1パルスを前記複数の光路に導入して複数のパルスに分割して前記試料の表面に照射することを特徴とする請求項1乃至3の何れかに記載の欠陥検査装置。   The light source means emits a pulsed laser, and the illumination optical system means has a plurality of optical paths having different optical path lengths and introduces one pulse of the pulsed laser emitted from the light source means into the plurality of optical paths. 4. The defect inspection apparatus according to claim 1, wherein the surface of the sample is irradiated by being divided into a plurality of pulses. 光源から発射されて偏光の状態が制御されたレーザを表面にパターンが形成された試料に対して傾斜した方向から照射し、
該レーザが照射された前記試料からの反射散乱光を空間フィルタを介して該反射散乱光の偏光成分ごとに分離して検出し、
該偏光成分ごとに分離して検出した前記偏光成分ごとの検出信号を処理して前記試料上の欠陥を検出し、
該検出した欠陥の情報を出力する
ことを特徴とする欠陥検査方法。
Irradiate the sample whose pattern is formed on the surface with a laser emitted from a light source and whose polarization state is controlled.
The reflected and scattered light from the sample irradiated with the laser is separated and detected for each polarization component of the reflected and scattered light through a spatial filter,
Processing the detection signal for each polarization component detected separately for each polarization component to detect defects on the sample;
A defect inspection method characterized by outputting information on the detected defect.
前記偏光成分ごとに分離して検出された検出信号のうちP偏光成分の検出信号を処理して得た情報とS偏光成分の検出信号を処理して得た情報とを用いて前記試料上の欠陥を検出し、該検出した欠陥を分類することを特徴とする請求項7記載の欠陥検査方法。   Among the detection signals detected separately for each polarization component, information obtained by processing the detection signal of the P polarization component and information obtained by processing the detection signal of the S polarization component are used on the sample. 8. The defect inspection method according to claim 7, wherein a defect is detected and the detected defect is classified. 前記分離して検出した偏光成分ごとの検出信号を処理して複数の欠陥候補を抽出し、該抽出した複数の欠陥候補の特徴量を比較し、統計的に外れた特徴量を有する欠陥候補を欠陥として検出することを特徴とする請求項7記載の欠陥検査方法。   A plurality of defect candidates are extracted by processing a detection signal for each polarization component detected by separation, and feature quantities of the extracted defect candidates are compared, and defect candidates having statistically deviated feature quantities are detected. 8. The defect inspection method according to claim 7, wherein the defect is detected as a defect. 前記光源から発射されて偏光の状態が制御されたレーザを、シリンドリカルレンズを介して前記試料の表面に対して傾斜した方向から該試料表面の楕円状又は直線状の領域に照射することを特徴とする請求項8乃至10の何れかに記載の欠陥検査方法。   A laser whose polarization state is controlled by being emitted from the light source is irradiated onto an elliptical or linear region of the sample surface from a direction inclined with respect to the sample surface via a cylindrical lens. The defect inspection method according to any one of claims 8 to 10. 前記偏光の状態を制御したレーザを前記試料の表面に対する方位角及び/または仰角を切換えて照射することを特徴とする請求項8乃至10の何れかに記載の欠陥検査方法。   11. The defect inspection method according to claim 8, wherein the laser whose polarization state is controlled is irradiated while switching the azimuth angle and / or elevation angle with respect to the surface of the sample. 前記レーザが照射された前記試料からの反射散乱光のうち前記試料の表面に対して第1の仰角方向に反射散乱した光を検出して得た信号と前記試料の表面に対して第2の仰角方向に反射散乱した光を検出して得た信号とを用いて欠陥を検出することを特徴とする請求項8乃至10の何れかに記載の欠陥検査方法。   Of the reflected and scattered light from the sample irradiated with the laser, a signal obtained by detecting light reflected and scattered in the first elevation direction with respect to the surface of the sample and a second with respect to the surface of the sample 11. The defect inspection method according to claim 8, wherein a defect is detected using a signal obtained by detecting light reflected and scattered in an elevation angle direction. 前記レーザはパルス発振レーザであって、該パルス発振レーザの1パルスを光路長の異なる複数の光路に導入して複数のパルスに分割し、該複数のパルスに分割したレーザを前記試料の表面に照射することを特徴とする請求項8乃至10の何れかに記載の欠陥検査方法。
The laser is a pulsed laser, and one pulse of the pulsed laser is introduced into a plurality of optical paths having different optical path lengths and divided into a plurality of pulses, and the laser divided into the plurality of pulses is applied to the surface of the sample. 11. The defect inspection method according to claim 8, wherein irradiation is performed.
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