TW202129409A - Method for determining an optical phase difference of measurement light of a measurement light wavelength over a surface of a structured object - Google Patents

Method for determining an optical phase difference of measurement light of a measurement light wavelength over a surface of a structured object Download PDF

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TW202129409A
TW202129409A TW109135563A TW109135563A TW202129409A TW 202129409 A TW202129409 A TW 202129409A TW 109135563 A TW109135563 A TW 109135563A TW 109135563 A TW109135563 A TW 109135563A TW 202129409 A TW202129409 A TW 202129409A
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field distribution
phase
phase difference
image
measurement
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馬庫斯 寇奇
德克 海爾維格
克里斯托夫 胡澤曼
倫佐 坎培里
勞夫 格爾克
葛賽達 克絲汀
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德商卡爾蔡司Ｓｍｔ有限公司
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/82—Auxiliary processes, e.g. cleaning or inspecting
    • G03F1/84—Inspecting
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
    • G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
    • G03F7/705—Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/956—Inspecting patterns on the surface of objects

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Abstract

To determine an optical phase difference (|φabs – φML |) of measurement light (1i , 1j ) of a measurement light wavelength over a surface of a structured object (8), the following is carried out Initially, a series of 2D images of the object (8) is measured in each case in different focal planes for recording a 3D aerial image of the object (8). Next, an image-side field distribution including amplitude and phase of an electric field of the 3D aerial image is reconstructed from the 3D aerial image. Thereafter, the phase difference (|φabs – φML |) is determined from the reconstructed field distribution with the aid of a phase calibration. The phase difference (|φabs – φML |) in this case is the difference between an absorber structure phase φabs of the measurement light 1i , reflected by absorber structures (9) of the object (8), and a reflector structure phase φML of the measurement light (1j ), reflected by reflector structures (10) of the object (8). The phase difference (|φabs – φML |) is determined as a characteristic that is applicable overall over an object structure to be measured. A metrology system having an optical measurement system is used to perform this determination method. The result is a phase difference determination method that yields highly usable values during the optimization of an image contrast when using the structured object as a reflection lithography mask.

Description

確定結構物體表面上測量光波長的測量光的光學相位差的方法Method for determining the optical phase difference of the measuring light of the measuring light wavelength on the surface of the structure object

[交互參照][Cross Reference]

本專利申請案主張德國專利申請案DE 10 2019 215 800.5之優先權利，其內容通過引用併入本文中。This patent application claims the priority right of German patent application DE 10 2019 215 800.5, the content of which is incorporated herein by reference.

本發明係關於確定測量光波長超過結構化物體表面的測量光之光學相差之方法。The present invention relates to a method for determining the optical phase difference of the measuring light whose wavelength exceeds the surface of a structured object.

從H.Nozawa等人發表於Photomask and Next-Generation Lithography Mask Technology XVI，第7379, 737925冊SPIE會議錄中的論文「Phase-shift/Transmittance measurements in micro pattern using MPM193EX」中，以及從S. Perlitz等人發表於2007年3月，文章編號65184 R號SPIE會議錄中的論文「PhameTM : a novel phase metrology tool of Carl Zeiss for in-die phase measurements under scanner relevant optical settings」中，知道了相位測量系統及可執行的測量方法。From the paper "Phase-shift/Transmittance measurements in micro pattern using MPM193EX" published in Photomask and Next-Generation Lithography Mask Technology XVI, No. 7379, 737925 SPIE Proceedings by H. Nozawa et al., and from S. Perlitz et al. Published in March 2007, article number 65184 R in the paper "Phame TM : a novel phase metrology tool of Carl Zeiss for in-die phase measurements under scanner relevant optical settings" in the SPIE Proceedings, he learned about the phase measurement system And executable measurement methods.

關於EUV光罩相位的測量，可進一步參考Sherwin等人發表於第11147 111471F-1至1114721F-11冊SPIE會議錄中的論文「Measuring the Phase of EUV Photomasks」，在本申請案的優先日期之後發布。For the measurement of EUV mask phase, you can refer to the paper "Measuring the Phase of EUV Photomasks" published by Sherwin et al. published in the SPIE Proceedings of volumes 11147 111471F-1 to 1114721F-11, which will be released after the priority date of this application. .

從Erdmann等人J. Micro/Nanolith. MEMS MOEMS 18 (1), 011005 (2018)的論文「Attenuated phase shift mask for extreme ultraviolet: can they mitigate three-dimensional mask effects?」一文中，可知道特定吸收材料的理想相位和反射率的理論確定值。From the paper "Attenuated phase shift mask for extreme ultraviolet: can they mitigate three-dimensional mask effects?" by Erdmann et al. J. Micro/Nanolith. MEMS MOEMS 18 (1), 011005 (2018), the specific absorption material can be known The theoretically determined value of the ideal phase and reflectivity.

Constancias等人發表於SPIE會議錄6151, Emerging Lithographic Technologies X, 61511W (2006年3月23日)的論文中討論了用於EUV微影的相移光罩。Constancias et al. discussed phase shift masks for EUV lithography in a paper published in SPIE Proceedings 6151, Emerging Lithographic Technologies X, 61511W (March 23, 2006).

在Rosenbluth等人發表於SPIE會議錄4346，Optical Microlithography XIV，(2001年9月14日)中討論了用於印刷已知形狀的最佳光罩與光源圖案。In Rosenbluth et al., published in SPIE Proceedings 4346, Optical Microlithography XIV, (September 14, 2001), the best photomask and light source pattern for printing known shapes are discussed.

Liu等人發表於SPIE會議錄9048，Extreme Ultraviolet (EUV) Lithography V, 90480Q (2014年4月17日)中討論了用於7 nm節點及以後的EUV光源光罩優化。Liu et al. published in SPIE Conference Proceedings 9048, Extreme Ultraviolet (EUV) Lithography V, 90480Q (April 17, 2014) and discussed the optimization of EUV light source masks for 7 nm node and beyond.

本發明目的在於提供一種相差確定方法，當使用結構化物體作為反射微影光罩時，在影像對比的最佳化期間產生可用度相當高之值。The object of the present invention is to provide a method for determining phase difference, when a structured object is used as a reflection lithography mask, a very high usability value is generated during the optimization of image contrast.

根據本發明藉由具備申請專利範圍第1項內指定特徵的確定方法來達成此目的。According to the present invention, this objective is achieved by a method of determining the characteristics specified in item 1 of the scope of the patent application.

根據本發明已發現，與僅定期考慮相位值而不是相關振幅值的先前技術之相位確定方法相比，從其中包括電場之振幅和相位的重構場分佈中確定相差產生有意義的結果，因為特別是在小振幅情況下，相位值的加權較小。所產生的相差是可整體用於所測量結構化物體的影像對比合格度之參數。因此，可基於分別測得的相差來最佳化物體結構的設計，從而產生儘可能強的影像對比。根據本發明的確定方法不取決於該物體結構的可能任意確定表面積上之相位值傳遞，這也增加所確定光學相差的可靠性和可再現性。According to the present invention, it has been found that, compared with the prior art phase determination method that only periodically considers the phase value instead of the correlation amplitude value, the determination of the phase difference from the reconstructed field distribution including the amplitude and phase of the electric field produces meaningful results because of the particular In the case of small amplitude, the weight of the phase value is small. The resulting phase difference is a parameter that can be used as a whole for the image contrast qualification of the measured structured object. Therefore, the design of the object structure can be optimized based on the phase difference measured separately, so as to produce the strongest possible image contrast. The determination method according to the present invention does not depend on the transfer of the phase value on the possibly arbitrarily determined surface area of the object structure, which also increases the reliability and reproducibility of the determined optical phase difference.

相位校正可轉換為計算演算法，這意味著可自動進行相位校正。The phase correction can be converted into a calculation algorithm, which means that the phase correction can be performed automatically.

可確定相差的物體結構是線結構、接觸孔或接觸銷結構以及在二維上延伸的一般結構形式，特別是週期性結構形式。具有這種物體結構的物體可用來當成微影光罩。The object structure that can determine the phase difference is a line structure, a contact hole or a contact pin structure, and a general structure form extending in two dimensions, especially a periodic structure form. An object with this structure can be used as a lithography mask.

物體的頂部結構可具體實施為吸收體材料的吸收體結構，例如被塗覆在底部反射體結構上。此外，該物體的頂部結構可具體實施為頂部反射體結構。在這種情況下，一方面的頂部反射體結構和另一方面的底部反射體結構可通過蝕刻一相應反射體結構來製造，特別是多層反射體結構。The top structure of the object can be embodied as an absorber structure of absorber material, for example coated on a bottom reflector structure. In addition, the top structure of the object can be embodied as a top reflector structure. In this case, the top reflector structure on the one hand and the bottom reflector structure on the other hand can be manufactured by etching a corresponding reflector structure, especially a multilayer reflector structure.

該結構化物體可為一微影光罩，特別適合於EUV微影。尤其是，結構化物體可具體實施為一相位光罩，尤其是具體實施為相移光罩(PSM)，例如當成硬PSM。這種相位光罩在蝕刻底部結構與未蝕刻頂部結構之間可能需要180°的光學相差。The structured object can be a lithography mask, which is particularly suitable for EUV lithography. In particular, the structured object can be embodied as a phase mask, especially as a phase shift photomask (PSM), for example as a hard PSM. Such a phase mask may require an optical phase difference of 180° between the etched bottom structure and the unetched top structure.

這樣的相位光罩可包括在蝕刻底部結構和未蝕刻頂部結構之間的蝕刻停止層(ESL)。這種相位光罩的蝕刻區域和非蝕刻區域間之相差取決於蝕刻深度和ESL的厚度。由ESL引起的光學相移對ESL厚度的依賴性為非線性，因此需要仔細確定。Such a phase mask may include an etch stop layer (ESL) between the etched bottom structure and the unetched top structure. The phase difference between the etched area and the non-etched area of this phase mask depends on the etching depth and the thickness of the ESL. The dependence of the optical phase shift caused by the ESL on the thickness of the ESL is nonlinear, so it needs to be carefully determined.

光學相差確定方法可當成製造相位光罩期間的製備方法，在這種方法期間，生產具有校正結構的原始相位光罩。這些校正結構包括在ESL上方具有所需高度的頂部結構，即產生所需的光學相差，例如180°。進一步，這種原始相位光罩包括具有已知厚度的ESL。The optical phase difference determination method can be regarded as a preparation method during the manufacturing of the phase mask. During this method, the original phase mask with the correction structure is produced. These correction structures include a top structure with a required height above the ESL, that is, a required optical phase difference, such as 180°. Further, this original phase mask includes ESL having a known thickness.

在生產這種原始相位光罩之後，進行光學相差確定，以確定相位光罩的頂部結構和底部結構間之光學相差。之後，改變ESL的厚度及或頂部(校正)結構的蝕刻深度，以確保一方面在頂部結構相位與在另一方面底部反射體結構相位之間存在期望的光學相差。After the original phase mask is produced, the optical phase difference is determined to determine the optical phase difference between the top structure and the bottom structure of the phase mask. Afterwards, the thickness of the ESL and or the etching depth of the top (correction) structure is changed to ensure that there is a desired optical phase difference between the phase of the top structure on the one hand and the phase of the bottom reflector structure on the other hand.

在將要確定其相差的結構化物體當成微影光罩的情況下，對該結構化物體成像，以在微影製造過程中使用的投影曝光設備之像平面中或附近產生該光罩結構之3D影像。在這種投影曝光設備中的3D成像效果可能導致對比降低，即可能導致較低的影像品質。對這種較低影像品質的貢獻可能是焦平面的位移、影響成像遠心的效果以及影響結構在像平面上橫向位移的其他效果。這些貢獻全都可看成是3D效果，即至少部分由在微影生產過程中要成像的光罩上之結構所產生。這些3D效果應最小化，以獲得所需的成像品質。When the structured object whose phase difference is to be determined is regarded as a lithography mask, the structured object is imaged to generate a 3D of the mask structure in or near the image plane of the projection exposure equipment used in the lithography manufacturing process image. The 3D imaging effect in this kind of projection exposure equipment may cause a decrease in contrast, that is, may result in a lower image quality. Contributions to this lower image quality may be the displacement of the focal plane, the effect of telecentric imaging, and other effects that affect the lateral displacement of the structure on the image plane. These contributions can all be regarded as 3D effects, that is, at least partly produced by the structure on the mask to be imaged during the lithography production process. These 3D effects should be minimized to obtain the desired image quality.

根據上述Erdmann等人的參考文獻，已知確定一給定吸收體材料的理想吸收體相位和吸收體反射率，以使這種3D效果最小化。此後，使用根據本發明光學相差確定方法的相位度量用於確定特別是吸收體材料的複反射率。之後，改變結構化物體的吸收體結構厚度，以便調整吸收體材料的期望相位和反射率，以獲得最小化的3D效果。According to the aforementioned reference by Erdmann et al., it is known to determine the ideal absorber phase and absorber reflectivity for a given absorber material in order to minimize this 3D effect. Thereafter, the phase metric using the optical phase difference determination method according to the present invention is used to determine the complex reflectivity of the absorber material in particular. After that, the thickness of the absorber structure of the structured object is changed in order to adjust the desired phase and reflectivity of the absorber material to obtain a minimized 3D effect.

用於確定光學相差的方法可用作修復缺陷的方法一部分。在這種校正方法期間，根據本發明的光學相差確定方法，特別是包括相位計量學，用於根據該修復吸收劑材料的厚度和成分，來確定修復吸收劑材料的複反射率。使用這種光學相差確定方法，特別是包括相位計量學，還可確定要修復的光罩吸收體結構之吸收體材料的複反射率。在一方面確定該修復吸收體材料的複反射率並且另一方面確定要修復的光罩吸收體材料之複反射率之後，選擇相應的吸收體材料成分和吸收體材料厚度用於修復步驟，使得修復材料的複反射率與要修復的光罩吸收體材料之複反射率匹配。The method used to determine the optical phase difference can be used as part of the method of repairing defects. During this correction method, the optical phase difference determination method according to the present invention, in particular including phase metrology, is used to determine the complex reflectivity of the repair absorbent material based on the thickness and composition of the repair absorbent material. Using this optical phase difference determination method, especially including phase metrology, the complex reflectivity of the absorber material of the photomask absorber structure to be repaired can also be determined. After determining the complex reflectivity of the repaired absorber material on the one hand and the complex reflectivity of the photomask absorber material to be repaired on the other hand, select the corresponding absorber material composition and absorber material thickness for the repair step, so that The complex reflectivity of the repair material matches the complex reflectivity of the photomask absorber material to be repaired.

此外，根據本發明用於確定光學相差的方法可用作最佳化過程的一部分，以確保一方面以給定的光罩佈局在晶圓上產生期望的結構，另一方面使用給定的照明設定，特別是部分相干照明分佈，期望地確保盡可能大的處理窗口。關於這種光源光罩最佳化(SMO)，請參考以上引用的Rosenbluth等人和Liu等人之論文。In addition, the method for determining the optical phase difference according to the present invention can be used as part of the optimization process to ensure that on the one hand the desired structure is produced on the wafer with a given mask layout, and on the other hand, the given illumination is used. The settings, especially the partially coherent illumination distribution, desirably ensure the largest possible processing window. For this light source mask optimization (SMO), please refer to the papers cited above by Rosenbluth et al. and Liu et al.

光源光罩最佳化需要光罩上吸收體結構的吸收體材料之複反射率作為輸入參數，SMO的結果取決於這種複反射率。使用根據本發明用於確定光學相差的方法可為校正過程的一部分，以最佳化用於光源光罩最佳化的微影光罩參數。在這種校正過程中，用於確定光學相位差，特別是包括相位計量學的方法，用於確定給定吸收體材料的複反射率，該材料用於要進行校正的微影光罩之吸收體結構。然後，將通過這種確定方法確定的複反射率用作光源光罩最佳化的輸入參數，以確定光罩佈局並確定照明設定。The optimization of the light source mask requires the complex reflectivity of the absorber material of the absorber structure on the mask as an input parameter, and the result of SMO depends on this complex reflectivity. Using the method for determining optical phase difference according to the present invention can be part of the calibration process to optimize the lithography mask parameters for light source mask optimization. In this correction process, the method used to determine the optical phase difference, especially including phase metrology, is used to determine the complex reflectivity of a given absorber material, which is used for the absorption of the lithography mask to be corrected体结构。 Body structure. Then, the complex reflectance determined by this determination method is used as an input parameter for the optimization of the light source mask to determine the mask layout and determine the lighting settings.

在裝配方法中，最初非線性的輸出函數可線性化。In the assembly method, the initially non-linear output function can be linearized.

如申請專利範圍第3項之建模，允許對該影像側場分佈的實部以及虛部使用不同的建模參數。這可以增加計算方法的穩定性。For example, the third item of the scope of patent application allows different modeling parameters to be used for the real and imaginary parts of the side field distribution of the image. This can increase the stability of the calculation method.

借助於如申請專利範圍第4項之迭代裝配方法，可在每個迭代步驟中通過線性裝配來追蹤非線性函數依賴性。With the aid of an iterative assembly method such as the fourth item in the scope of the patent application, linear assembly can be used in each iteration step to track the nonlinear function dependency.

如申請專利範圍第5項之影像側場分布的實部和虛部之獨立裝配可提高裝配方法的精度。For example, the independent assembly of the real and imaginary parts of the image side field distribution in item 5 of the scope of patent application can improve the accuracy of the assembly method.

如申請專利範圍第6項之傅立葉轉換，可簡化該裝配方法。For example, the Fourier transform of item 6 in the scope of patent application can simplify the assembly method.

如申請專利範圍第7項之測量，允許精準確定該相差。投影光學單元可從物體到影像側引導甚至大於兩個數量級的繞射，例如三個、四個或甚至更多個數量級的繞射。For example, the measurement in item 7 of the scope of patent application allows accurate determination of the phase difference. The projection optical unit can guide even more than two orders of diffraction from the object to the image side, such as three, four, or even more orders of diffraction.

如申請專利範圍第8或9項之計量系統的優點對應於上面已經參考根據本發明確定方法所解釋的優點。The advantages of the metering system as in item 8 or 9 of the scope of the patent application correspond to the advantages explained above with reference to the determination method according to the present invention.

如申請專利範圍第10項之計量系統，允許以非常高的解析度進行測量。EUV光源所提供的測量光波長可在介於5 nm與30 nm之間的波長範圍內。因此，測量光波長適合於投影曝光設備的典型照明波長，其中以微影光罩形式測量的結構化物體可用於半導體晶片生產中。For example, the measurement system of item 10 in the scope of patent application allows measurement with very high resolution. The wavelength of the measurement light provided by the EUV light source can be in the wavelength range between 5 nm and 30 nm. Therefore, the measurement light wavelength is suitable for the typical illumination wavelength of the projection exposure equipment, and the structured object measured in the form of a lithography mask can be used in the production of semiconductor wafers.

圖1以對應於子午截面的截面圖顯示計量系統2中的EUV照明光或EUV成像光1之光路。照明光1由EUV光源3產生。Fig. 1 shows the optical path of the EUV illuminating light or EUV imaging light 1 in the metering system 2 in a cross-sectional view corresponding to the meridian cross-section. The illumination light 1 is generated by the EUV light source 3.

為了幫助呈現位置關係，此後都使用笛卡爾xyz座標系統。圖1內的x軸垂直延伸出該圖式平面，圖1內的y軸向右延伸，圖1內的z軸向上延伸。In order to help present the positional relationship, the Cartesian xyz coordinate system is used since then. The x-axis in FIG. 1 extends vertically out of the drawing plane, the y-axis in FIG. 1 extends to the right, and the z-axis in FIG. 1 extends upward.

光源3可以是雷射電漿源(LPP；雷射產生的電漿)或放電源(DPP；放電產生的電漿)。原則上，也可使用同步加速器型光源，例如自由電子雷射(FEL)。照明光1的使用波長可在介於5 nm與30 nm之間的範圍內。原則上，在投影曝光設備2的變型情況下，也可將光源用於其他使用的光波長，例如用於193 nm的使用波長。The light source 3 may be a laser plasma source (LPP; plasma generated by laser) or a discharge source (DPP; plasma generated by discharge). In principle, synchrotron-type light sources such as free electron lasers (FEL) can also be used. The use wavelength of the illuminating light 1 may be in a range between 5 nm and 30 nm. In principle, in the case of a modification of the projection exposure apparatus 2, the light source can also be used for other used light wavelengths, for example, for the use wavelength of 193 nm.

照明光1在計量系統2中一照明系統的照明光學單元4中調節，如此提供該照明的特定照明設定，也就是特定照明角度分佈。照明光學單元4的照明光瞳內照明光1之特定強度分佈對應至該照明設定。為了指定該照明設定，照明光學單元4可具有圖中未例示的一設定停止。The illuminating light 1 is adjusted in the illuminating optical unit 4 of an illuminating system in the metering system 2, so as to provide a specific lighting setting of the lighting, that is, a specific lighting angle distribution. The specific intensity distribution of the illumination light 1 in the illumination pupil of the illumination optical unit 4 corresponds to the illumination setting. In order to specify the lighting setting, the lighting optical unit 4 may have a setting stop which is not illustrated in the figure.

照明光學單元4與成像光學單元或投影光學單元8一起構成計量系統2的光學測量系統。The illumination optical unit 4 and the imaging optical unit or the projection optical unit 8 constitute an optical measurement system of the metrology system 2.

利用分別設置的照明設定，照明光1照明計量系統2的物平面7中之物場6。在物平面7中佈置有一微影光罩8，也稱為倍縮光罩(reticle)，當成一反射物體。倍縮光罩8是一結構化物體的範例，其光學相差將通過將在下文中描述的方法來確定。物平面7與xy平面平行延伸。With the separately set illumination settings, the illumination light 1 illuminates the object field 6 in the object plane 7 of the metering system 2. A lithography mask 8 is arranged in the object plane 7, also called a reticle, as a reflective object. The zoom mask 8 is an example of a structured object, and its optical phase difference will be determined by the method described below. The object plane 7 extends parallel to the xy plane.

物體8具有線性結構，該結構具有彼此平行且平行於x方向延伸的線型吸收體頂部結構9。反射體底部結構10分別位於兩個相鄰的吸收體結構9之間。The object 8 has a linear structure with a linear absorber top structure 9 extending parallel to each other and parallel to the x direction. The reflector bottom structure 10 is located between two adjacent absorber structures 9 respectively.

為了說明的目的，圖1在物平面7上方顯示待測量的倍縮光罩8之平面圖，其相較於該測量位置中的倍縮光罩8繞y軸傾斜90°到所示的平面圖位置。吸收體結構9和分別位於吸收體結構之間的反射體結構10在該平面圖中可看成平行於z方向延伸之線性結構。For illustrative purposes, FIG. 1 shows a plan view of the zoom mask 8 to be measured above the object plane 7, which is tilted 90° around the y-axis to the position shown in the plan view compared to the zoom mask 8 in the measurement position. . The absorber structure 9 and the reflector structure 10 respectively located between the absorber structure can be seen as a linear structure extending parallel to the z direction in this plan view.

與反射體結構10相比，吸收體結構9具有在z方向上的高度範圍habs (參見圖2)。每個吸收體結構9都可具有多層結構，該多層結構具有相對少的個別層91 、92 。Compared with the reflector structure 10, the absorber structure 9 has a height range h abs in the z direction (see FIG. 2). Each absorber structure 9 may have a multilayer structure with relatively few individual layers 9 1 , 9 2 .

反射體結構10設計為具有多個別層10i的高反射性多層結構。吸收體結構9就其本身而言位於該多層結構上。The reflector structure 10 is designed as a highly reflective multilayer structure having a plurality of other layers 10i. The absorber structure 9 is on the multilayer structure as such.

圖1另外顯示根據用於照明光1在物場6中的電場之公式圖示：

Figure 02_image001
(1)Fig. 1 additionally shows a diagram according to the formula used for the electric field of the illuminating light 1 in the object field 6:
Figure 02_image001
(1)

這裡的Eret 表示照明光的電場強度，φret 表示照明光1的電場之相位。Here E ret represents the electric field intensity of the illuminating light, and φ ret represents the phase of the electric field of the illuminating light 1.

對於照明光1的兩光線1i 、1j ，圖2例示吸收體結構9和反射體結構10的相應層構造對光線1i 、1j 的相應反射比例之影響。在這種情況下，光線1i 入射在如圖2所示的吸收體結構9上，而光線1j 入射在反射體結構10上。根據該公式，圖2描繪用於吸收體結構9的反射率rabs 和用於反射體結構10的反射率rML 。以下為真：

Figure 02_image003
(2)
Figure 02_image005
(3) 在此φabs 和φML 表示已反射光線1i 、1j 的相位。底下也將相差
Figure 02_image007
表示為Δφ。For the two light rays 1 i and 1 j of the illuminating light 1, FIG. 2 illustrates the influence of the corresponding layer structure of the absorber structure 9 and the reflector structure 10 on the corresponding reflection ratios of the light rays 1 i and 1 j. In this case, the light 1 i is incident on the absorber structure 9 as shown in FIG. 2, and the light 1 j is incident on the reflector structure 10. According to this formula, FIG. 2 depicts the reflectivity r abs for the absorber structure 9 and the reflectivity r ML for the reflector structure 10. The following is true:
Figure 02_image003
(2)
Figure 02_image005
(3) Here φ abs and φ ML represent the phases of the reflected light 1 i and 1 j. Underneath will also be different
Figure 02_image007
Expressed as Δφ.

圖3以兩個吸收體材料變體(表示為AM1和AM2)的範例，顯示吸收體結構9的高度habs 上相差Δφ的函數。隨著吸收體結構9的高度habs 增加，相差Δφ也增加。這種增長不是單調的，而是周期性的。此外，不同吸收體材料變體導致該相差Δφ隨吸收體結構9的高度habs 函數之該成長有不同斜率。Fig. 3 shows an example of two absorber material variants (denoted as AM1 and AM2) as a function of the difference Δφ in the height h abs of the absorber structure 9. As the height h abs of the absorber structure 9 increases, the phase difference Δφ also increases. This growth is not monotonous, but cyclical. In addition, different absorber material variants cause the phase difference Δφ to have different slopes with the growth of the height of the absorber structure 9 as a function of the height habs.

相差Δφ應在180°的範圍內，以便在使用投影光學單元5對物體8的結構進行成像期間獲得良好的影像對比。在圖3中，具有相差Δφ在180°的區域中之吸收體結構高度habs 都會標上星形記號。可以看出，吸收體結構9的這些結構高度habs 強烈取決於各個吸收體材料變體。為此，必須使用計量系統2精確確定相差Δφ，其中該相差值Δφ應與吸收體結構9在物平面7中的結構擴展無關，也就是說尤其是與間距無關，也就是說與吸收體結構9在物場6上的周期性無關。底下會更詳細說明此確定方法。The phase difference Δφ should be within the range of 180° in order to obtain good image contrast during the imaging of the structure of the object 8 using the projection optical unit 5. In Fig. 3, the height of the absorber structure h abs in the region with a phase difference of Δφ at 180° will be marked with a star mark. It can be seen that these structural heights h abs of the absorber structure 9 strongly depend on the individual absorber material variants. For this purpose, the measurement system 2 must be used to accurately determine the phase difference Δφ, where the phase difference Δφ should be independent of the structural expansion of the absorber structure 9 in the object plane 7, that is to say especially independent of the distance, that is to say the absorber structure The periodicity of 9 on the object field 6 is irrelevant. This determination method will be explained in more detail below.

如圖1中示意性所示，照明光1從微影光罩8反射，並在入射光瞳平面中進入成像光學單元5的入射光瞳。成像光學單元5的使用入射光瞳可具有圓形或橢圓形邊界。As schematically shown in FIG. 1, the illumination light 1 is reflected from the lithography mask 8 and enters the entrance pupil of the imaging optical unit 5 in the entrance pupil plane. The used entrance pupil of the imaging optical unit 5 may have a circular or elliptical boundary.

在成像光學單元5之內，該照明或成像光1在入射光瞳平面與出射光瞳平面之間傳播。成像光學單元5的圓形出射光瞳位於出射光瞳平面內。Within the imaging optical unit 5, the illumination or imaging light 1 travels between the entrance pupil plane and the exit pupil plane. The circular exit pupil of the imaging optical unit 5 is located in the exit pupil plane.

成像光學單元5將物場6成像到計量系統2的像平面12內之像場11中。像平面12也稱為測量平面。在使用投影光學單元5的成像期間，成像比例大於500。根據投影光學單元5的具體實施例，該放大成像比例可大於100、可大於200、可大於250、可大於300、可大於400並且也可顯著更大500。投影光學單元8的成像比例通常小於2000。The imaging optical unit 5 images the object field 6 into the image field 11 in the image plane 12 of the metrology system 2. The image plane 12 is also called the measurement plane. During imaging using the projection optical unit 5, the imaging ratio is greater than 500. According to specific embodiments of the projection optical unit 5, the magnification imaging ratio may be greater than 100, may be greater than 200, may be greater than 250, may be greater than 300, may be greater than 400, and may also be significantly greater than 500. The imaging ratio of the projection optical unit 8 is usually less than 2,000.

投影光學單元5用於將物體8的一部分成像到像平面12中。The projection optical unit 5 is used to image a part of the object 8 into the image plane 12.

類似於圖1中物體8的平面圖例示，在垂直於附圖平面的像平面12下方例示物體8的成像之空拍影像13的平面圖。此空拍影像13是整個3D空拍影像的部分資料集，其測量將說明如下。Similar to the plan view of the object 8 in FIG. 1, a plan view of the aerial image 13 of the object 8 is illustrated below the image plane 12 perpendicular to the plane of the drawing. This aerial image 13 is a partial data set of the entire 3D aerial image, and its measurement will be explained as follows.

像場11中照明光1的電場可描述為：

Figure 02_image009
(4)The electric field of the illumination light 1 in the image field 11 can be described as:
Figure 02_image009
(4)

在將照明光1的電場從物場6轉移到像場11的過程中，投影光學單元5的像差和散焦影響電場的形式。In the process of transferring the electric field of the illumination light 1 from the object field 6 to the image field 11, the aberration and defocus of the projection optical unit 5 affect the form of the electric field.

計量系統2的空間分辨偵測裝置14佈置在像平面12中，此偵測裝置可為CCD相機。偵測裝置14用於測量強度I，為此：

Figure 02_image011
(5)The spatial resolution detection device 14 of the metrology system 2 is arranged in the image plane 12, and this detection device may be a CCD camera. The detection device 14 is used to measure the intensity I, for this:
Figure 02_image011
(5)

偵測裝置14可在z方向上移動，並且在圖1中例示為在凹陷位置處，距像平面12一定距離。在測量操作期間，偵測裝置14佈置在像平面12中或附近。因此，偵測裝置14的偵測平面15可與像平面12重合或與像平面12具有界定的距離。The detection device 14 can move in the z-direction, and is illustrated in FIG. 1 as being at a recessed position at a certain distance from the image plane 12. During the measurement operation, the detection device 14 is arranged in or near the image plane 12. Therefore, the detection plane 15 of the detection device 14 may coincide with the image plane 12 or have a defined distance from the image plane 12.

計量系統2用於執行用來確定光學相差Δφ的方法，該光學位差是可整體應用於待測量物體結構的特徵。然後，在通過投影曝光設備對物體8進行成像期間，該特徵可用於相對於其對比特性來鑑定物體8。The metrology system 2 is used to perform a method for determining the optical phase difference Δφ, which is a feature that can be applied to the structure of the object to be measured as a whole. Then, during the imaging of the object 8 by the projection exposure equipment, this feature can be used to identify the object 8 with respect to its contrast characteristics.

該確定方法的主要步驟將另外參照圖4進行說明。The main steps of the determination method will be described with reference to FIG. 4 in addition.

在測量步驟16中，分別在不同的焦平面中測量物體8的一系列二維影像I (x,y)，以使用投影光學單元5記錄物體8的三維空拍影像。在每次2D影像測量之後，在其期間記錄2D影像強度值I (x,y)，借助於偵測位移裝置(未顯示)使偵測裝置14位移指定的增量Δz。例如，以不同的z值記錄五、七、九、十一或十三個這樣的2D影像I (x,y)，以完整測量3D空拍影像。在此測量期間，由物體8繞射的照明光或測量光1之至少兩個繞射級由投影光學單元5引導至像場11，也就是說，引導至計量系統2的像側。In the measurement step 16, a series of two-dimensional images I (x, y) of the object 8 are measured in different focal planes, so that the projection optical unit 5 is used to record the three-dimensional aerial image of the object 8. After each 2D image measurement, the 2D image intensity value I (x, y) is recorded during the period, and the detecting device 14 is moved by a specified increment Δz by means of a detecting displacement device (not shown). For example, record five, seven, nine, eleven, or thirteen 2D images I (x, y) with different z values to fully measure 3D aerial images. During this measurement, at least two diffraction levels of the illumination light or measurement light 1 diffracted by the object 8 are guided by the projection optical unit 5 to the image field 11, that is, to the image side of the metrology system 2.

在隨後的重建步驟17中，重建包括3D空拍影像的電場E之振幅和相位的像側電場分佈frec (x,y)。 In the subsequent reconstruction step 17, the image-side electric field distribution f rec (x, y) including the amplitude and phase of the electric field E of the 3D aerial image is reconstructed.

圖5藉由範例顯示作為具有線性結構的物體8之重建步驟17結果，在像場11上的相位分佈。吸收體結構9在30°的區域中具有與反射體結構10在210°的區域中絕對相位不同的絕對相位φ。FIG. 5 shows, by way of example, the phase distribution on the image field 11 as a result of the reconstruction step 17 of the object 8 having a linear structure. The absorber structure 9 has an absolute phase φ that is different from the absolute phase of the reflector structure 10 in the area of 210° in the area of 30°.

重建步驟17可借助於從WO 2017/207 297 A1已知的方法來進行。The reconstruction step 17 can be carried out by means of a method known from WO 2017/207 297 A1.

接下來，借助於相位校正步驟18，從重建的場分佈frec 確定相差。在相位校正期間，通過導入基於物場分佈的模型來計算像側場分佈fim ，該物場分佈取決於物體8的物體週期或間距p、物體8的臨界尺寸CD、吸收體結構9的複反射率rabs 以及反射體結構10的複反射率rML 。像側場分佈fim 是物場分佈與投影光學單元5的相干點擴展函數PSF之捲積結果。該相干點擴展函數是相干光學傳遞函數的傅立葉變換。Next, by means of a phase correction step 18, the phase difference is determined from the reconstructed field distribution f rec. During the phase correction, the image-side field distribution f im is calculated by importing a model based on the object field distribution. The object field distribution depends on the object period or pitch p of the object 8, the critical dimension CD of the object 8, and the complex of the absorber structure 9. The reflectivity rabs and the complex reflectivity r ML of the reflector structure 10. The image-side field distribution f im is the convolution result of the object field distribution and the PSF of the coherent point spread function of the projection optical unit 5. The coherent point spread function is the Fourier transform of the coherent optical transfer function.

這說明於圖6內。圖6在左側顯示物場分佈fobj ，其取決於空間坐標x、反射體結構10的反射率rML 、吸收體結構9的反射率rabs 、佔空比d以及週期(間距) p，對於佔空比d：d = CD/p。This is illustrated in Figure 6. Fig. 6 shows the object field distribution f obj on the left, which depends on the spatial coordinate x, the reflectivity r ML of the reflector structure 10, the reflectivity r abs of the absorber structure 9, the duty cycle d and the period (pitch) p, for Duty cycle d: d = CD/p.

基於此物體結構fobj ，其分為實部(指標r)和虛部(指標i)，現在通過與投影光學單元5的點擴展函數PSFcoh 進行卷積計算，將投影光學單元5對物場分佈成像產生的影響納入考慮。這顯示在圖6的中心，其中分別針對不同的參數r、d，指定每一情況內的實部和虛部。物場分佈與點擴展函數PSF卷積的結果為像側場分佈fim 的實部fr im 和虛部fi im ，如圖6右側所示。該像側場分佈fim 又取決於空間坐標x、反射體結構10和吸收體結構9的反射率rML 、rabs 、佔空比的虛部di 和實部dr 、間距p。Based on this object structure f obj , it is divided into real part (index r) and imaginary part (index i). Now through the convolution calculation with the point spread function PSF coh of the projection optical unit 5, the projection optical unit 5 is compared to the object field The influence of distributed imaging is taken into consideration. This is shown in the center of Figure 6, where the real and imaginary parts in each case are specified for different parameters r and d, respectively. The result of the field distribution and the convolution of the point spread function PSF of the image-side field distribution f im the real part and the imaginary part f r im f i im, the right side as shown in FIG. The image-side field distribution f im turn depends on the spatial coordinates x, 10 and the absorbent body structure of the reflective structure of the reflectance r 9 ML, r abs, the duty ratio of the imaginary part and the real part d i d r, the pitch p.

隨後，將由此已經以模型方式計算出的像側場分佈fim 與重建的像側場分佈frec 進行比較。為此，借助於裝配方法，通過改變模型參數物體週期(間距p)、臨界尺寸CD和複反射率rML 、rabs 中至少一者，來使該場分佈之間的差異最小化。這藉助優值函數完成，該函數被認為在x-y場範圍內積分並最小化。此優值函數M可編寫如下：

Figure 02_image013
Figure 02_image015
(6)Subsequently, the image-side field distribution f im thus calculated in a model manner is compared with the reconstructed image-side field distribution f rec . To this end, with the aid of the assembly method, the difference between the field distributions is minimized by changing at least one of the model parameter object period (pitch p), critical dimension CD, and complex reflectivity r ML , rabs. This is done with the aid of a merit function, which is considered to be integrated and minimized in the xy field. This merit function M can be written as follows:
Figure 02_image013
Figure 02_image015
(6)

為了最小化根據上式(6)針對實部和虛部獨立實現的優值函數，對重建的像側場分佈frec 以及計算出的像側場分佈fim 進行傅立葉變換。然後，這些傅立葉變換Frec 、Fim 取決於空間頻率νx、νy。In order to minimize the merit function independently implemented for the real and imaginary parts according to the above equation (6), Fourier transform is performed on the reconstructed image side field distribution f rec and the calculated image side field distribution f im. Then, these Fourier transforms F rec and F im depend on the spatial frequencies νx and νy.

借助於該傅立葉變換Frec 、Fim ，其又被分解為實部和虛部，可以將優值函數M編寫如下：

Figure 02_image017
Figure 02_image019
Figure 02_image021
(7)With the help of the Fourier transforms F rec and F im , which are decomposed into real and imaginary parts, the merit function M can be written as follows:
Figure 02_image017
Figure 02_image019
Figure 02_image021
(7)

頻域中的積分可通過對各個自變量偏離0的頻率求和來代替週期性結構，其中物體8的考慮線性結構為頻率νx = j/p for j = -jmax … jmax 。The integral in the frequency domain can replace the periodic structure by summing the frequency of each independent variable deviating from 0. The linear structure of the object 8 is considered as the frequency ν x = j/p for j = -j max … j max .

在這種情況下，jmax 是由投影光學單元5透射的最大繞射級。In this case, j max is the maximum diffraction level transmitted by the projection optical unit 5.

為了使投影光學單元5滿足條件|jmax |≥ 2，必須滿足以下物體8的間距p之條件：p≥ 2λ/NA。In order for the projection optical unit 5 to satisfy the condition |j max | ≥ 2, the following condition of the distance p of the object 8 must be satisfied: p ≥ 2λ/NA.

在此，λ是照明光1的波長，NA是投影光學單元5的物體側數值孔徑。Here, λ is the wavelength of the illumination light 1, and NA is the object-side numerical aperture of the projection optical unit 5.

優值函數的實部和虛部之總和與反射率rML 、rabs 的實部和虛部之線性相關。

Figure 02_image023
(8)The sum of the real and imaginary parts of the merit function is linearly related to the real and imaginary parts of the reflectivity r ML and rabs.
Figure 02_image023
(8)

此線性符號的係數另外非線性地取決於佔空比d之實部和虛部dr、di。這些非線性佔空比輸出函數可如下所述進行線性化。The coefficient of this linear sign is also non-linearly dependent on the real and imaginary parts dr, di of the duty cycle d. These non-linear duty cycle output functions can be linearized as described below.

然後可通過迭代裝配方法來實現佔空比和反射率rML 和rabs 的實部和虛部dr 、di 最優化，以使優值函數最小化，其中取用佔空比d的實部和虛部之初始起始值d0 r,i ，然後計算反射率的相應起始值rr,i ML,0 和rr,i abs,0 。Then the assembly may be achieved by an iterative method and the duty ratio of the real and imaginary parts of d r ML and R & lt reflectivity of r abs, d I optimized so to minimize the merit function, wherein the duty cycle d of the real access The initial initial values of the part and the imaginary part d 0 r,i , and then the corresponding initial values of the reflectance r r,i ML,0 and r r,i abs,0 are calculated.

為此，可在初始迭代步驟中按如下所示編寫優值函數：

Figure 02_image025
(9)To this end, the merit function can be written as follows in the initial iteration step:
Figure 02_image025
(9)

在此，Ŝ表示反射率r的係數，其又取決於佔空比d的實部和虛部。在這種情況下，Ŝ是具有jmax 列的矩陣，並且由於該矩陣對兩個反射率rM1 、rabs ，兩欄的影響。反射率rr,i ML,0 和rr,i abs,0 的起始值基於佔空比d0 r,i 的起始值，通過線性最佳化來確定。Here, Ŝ represents the coefficient of reflectivity r, which in turn depends on the real and imaginary parts of the duty cycle d. In this case, Ŝ is a matrix with j max columns, and due to the influence of this matrix on the two reflectivities r M1 and rabs , the two columns. The initial values of the reflectance r r,i ML,0 and r r,i abs,0 are determined by linear optimization based on the initial value of the duty cycle d 0 r,i.

Ŝ的各個矩陣元素現在可圍繞泰勒級數的佔空比起始值來擴展。此泰勒級數的第二項在值Δd0 r,i 中是線性的，也就是說，對於佔空比d的初始值來說是實部和虛部的修正值。該修正值為對於該迭代方法下一步驟必須改變起始值之修正值。Each matrix element of Ŝ can now be expanded around the starting value of the duty cycle of the Taylor series. The second term of this Taylor series is linear in the value Δd 0 r,i , that is, for the initial value of the duty cycle d, it is a correction value of the real and imaginary parts. The correction value is the correction value that must change the initial value for the next step of the iterative method.

將泰勒展開直至Δd的階數***到等式(8)中，將導致線性關係取決於反射率和佔空比的修正值。

Figure 02_image027
(10)Inserting the Taylor expansion until the order of Δd into equation (8) will result in a linear relationship depending on the correction value of the reflectivity and the duty cycle.
Figure 02_image027
(10)

修改後的矩陣Ŝ2 僅取決於佔空比的已知起始值和反射率的已計算起始值。The modified matrix Ŝ 2 only depends on the known starting value of the duty cycle and the calculated starting value of the reflectivity.

現在可再次通過線性最佳化確定Δd0 r,i ，其結果是，基於起始值，然後可根據以下公式確定迭代的下一個值d1 r,i ：

Figure 02_image029
(11) Now Δd 0 r,i can be determined by linear optimization again. As a result, based on the initial value, the next value d 1 r,i of the iteration can be determined according to the following formula:
Figure 02_image029
(11)

現在，使用佔空比的新值更新上式(9)中的矩陣Ŝ，並執行反射率的新線性最佳化。Now, update the matrix Ŝ in the above equation (9) with the new value of the duty cycle, and perform a new linear optimization of reflectance.

重複此迭代方法，直到在迭代步驟m中，重複的修正Δdm r,i 低於指定的臨界值。This iterative method is repeated until the repeated correction Δd m r,i is lower than the specified critical value in the iterative step m.

在該迭代裝配方法收斂之後，將知道優值函數M最小的rML 、rabs 之反射率值。After the iterative assembly method converges, the reflectivity values of r ML and rabs at which the merit function M is the smallest will be known.

然後，從根據以下公式獲得的反射率值rML 、rabs ，得出相差Δφ的期望值：

Figure 02_image031
(12)Then, from the reflectance values r ML and rabs obtained according to the following formula, the expected value of the phase difference Δφ is obtained:
Figure 02_image031
(12)

因此，可基於對物體結構建模，來計算特定光罩結構的相差值，從而可檢查特定結構設計是否給予相對於影像對比最佳之相差。Therefore, the phase difference value of the specific mask structure can be calculated based on the object structure modeling, so that it can be checked whether the specific structure design gives the best phase difference relative to the image contrast.

圖7顯示物體20的另一範例，該物體的光學相差將使用上述方法具體實施例來確定。可使用這樣的物體20來代替上面特別關於圖2討論的物體8。FIG. 7 shows another example of the object 20, the optical phase difference of the object will be determined using the specific embodiment of the method described above. Such an object 20 may be used in place of the object 8 discussed above in particular with respect to FIG. 2.

物體20是硬相移光罩(PSM)，其具有由共用基座層23承載的頂部結構21和蝕刻的底部結構22。頂部結構21具體實施為具有反射率R1的反射體表面頂部結構部分。底部結構22具體實施為反射體表面底部結構，其從設置頂部和底部結構的多層中蝕刻而來。底部結構22具有反射率R2。對於反射率R1、R2，可能存在以下替代關係：R1 ＞ R2, R1 = R2。The object 20 is a hard phase shift mask (PSM), which has a top structure 21 carried by a common base layer 23 and an etched bottom structure 22. The top structure 21 is embodied as a top structure part of the reflector surface with reflectivity R1. The bottom structure 22 is embodied as a bottom structure of the reflector surface, which is etched from multiple layers where the top and bottom structures are arranged. The bottom structure 22 has a reflectivity R2. For reflectivity R1 and R2, the following alternative relationship may exist: R1> R2, R1 = R2.

頂部/底部結構21、22在測量光1上產生光學相差Δφ，其一方面由頂部結構21反射，另一方面由底部結構22反射。在圖7中h處顯示底部結構22相對於頂部結構21的蝕刻深度。The top/bottom structures 21, 22 produce an optical phase difference Δφ on the measuring light 1, which is reflected by the top structure 21 on the one hand and by the bottom structure 22 on the other hand. The etching depth of the bottom structure 22 relative to the top structure 21 is shown at h in FIG. 7.

根據上面討論的方法具體實施例，可確定由頂部結構21反射的測量光1之頂部結構相位與由底部結構22反射的測量光1之底部反射體結構相位之間，物體20的表面之上測量光1的相差Δφ。According to the specific embodiment of the method discussed above, it can be determined between the phase of the top structure of the measurement light 1 reflected by the top structure 21 and the phase of the bottom reflector structure of the measurement light 1 reflected by the bottom structure 22, measured on the surface of the object 20 The phase difference of light 1 is Δφ.

與物體8不同，在物體20中，頂部結構21也由多層材料製成。特別地，通過蝕刻多層基板來製造物體20。Unlike the object 8, in the object 20, the top structure 21 is also made of multiple layers of materials. In particular, the object 20 is manufactured by etching a multilayer substrate.

圖8顯示可代替上述物體8或20使用的物體25之另一具體實施例。上面特別針對圖2和圖7討論的組件和功能被賦予相同之術語和參考編號，並且不再詳細描述。FIG. 8 shows another specific embodiment of an object 25 that can be used in place of the aforementioned object 8 or 20. The components and functions discussed above in particular with respect to FIG. 2 and FIG. 7 are given the same terms and reference numbers, and will not be described in detail.

物體25在頂部結構21和底部結構22之間具有蝕刻停止層26，其材料不同於頂部和底部結構21、22的多層成分之層材料。這種蝕刻停止層用於在進行蝕刻直到到達蝕刻停止層26之前，在物體25的蝕刻生產過程中區分頂部結構部分和底部結構部分。The object 25 has an etch stop layer 26 between the top structure 21 and the bottom structure 22, the material of which is different from the layer material of the multilayer composition of the top and bottom structures 21, 22. This kind of etch stop layer is used to distinguish the top structure part and the bottom structure part in the etching production process of the object 25 before the etching is performed until the etch stop layer 26 is reached.

當然，物體25的蝕刻停止層26之反射率、材料和厚度影響一方面頂部結構相位與另一方面底部反射體結構相位之間測量光1的光學相差。這可在最佳化過程中用來產生硬相移光罩。在這樣的校正過程中，產生根據物體25的校正原始相移光罩。然後，確定這種原始校正光罩的頂部結構相位和底部反射體結構相位間之光學相差Δφ。之後，改變蝕刻停止層26的厚度及/或蝕刻深度h，以實現期望的相差Δφ，例如相差為180° (=π)。Of course, the reflectivity, material and thickness of the etching stop layer 26 of the object 25 affect the optical phase difference of the measuring light 1 between the phase of the top structure on the one hand and the phase of the bottom reflector structure on the other hand. This can be used to produce a hard phase shift mask during the optimization process. In such a correction process, a corrected original phase shift mask according to the object 25 is generated. Then, determine the optical phase difference Δφ between the phase of the top structure of the original correction mask and the phase of the bottom reflector structure. After that, the thickness and/or the etching depth h of the etching stop layer 26 are changed to achieve the desired phase difference Δφ, for example, the phase difference is 180° (=π).

圖9顯示物體27的另一具體實施例，該物體也可用作相移光罩並且可代替上述物體8、20和25。上面特別針對圖2和圖8討論的組件和功能被賦予相同之術語和參考編號，並且不再詳細描述。Fig. 9 shows another specific embodiment of the object 27, which can also be used as a phase shift mask and can replace the aforementioned objects 8, 20, and 25. The components and functions discussed above specifically with respect to FIG. 2 and FIG. 8 are given the same terms and reference numbers, and will not be described in detail.

物體27也包括蝕刻停止層26。與物體25的佈局不同，在底部結構22的底部結構部分處去除了物體27之蝕刻停止層26。The object 27 also includes an etch stop layer 26. Different from the layout of the object 25, the etch stop layer 26 of the object 27 is removed at the bottom structure portion of the bottom structure 22.

圖10顯示可用來代替上述物體8、20、25和27的物體30之另一具體實施例。上面特別針對圖2和圖9討論的組件和功能被賦予相同之術語和參考編號，並且不再詳細描述。FIG. 10 shows another specific embodiment of an object 30 that can be used in place of the aforementioned objects 8, 20, 25, and 27. The components and functions discussed above specifically with respect to FIG. 2 and FIG. 9 are given the same terms and reference numbers, and will not be described in detail.

物體30包括根據上面，特別參照圖2描述的那些頂部吸收體結構9和底部反射體結構10。The object 30 includes a top absorber structure 9 and a bottom reflector structure 10 according to those described above, in particular with reference to FIG. 2.

例如，在圖10中用9D 表示的這種吸收體結構9之一者包括一缺陷。這種缺陷通過減少吸收體結構9D 在x方向上的延伸而存在。For example, FIG. 10 in which D represents a 9 by 9 by one of the absorbent structure comprises a defect. This defect exists by reducing the extension of the absorbent structure 9D in the x direction.

為了修復這種缺陷，物體30攜帶由修復吸收體材料製成的結構補充物31。通常，這種修復吸收體材料不同於物體30的原始吸收體結構9之吸收體材料。與標稱吸收體結構9的高度h相比，修復結構補充物31具有通常與h不同的高度hD 。In order to repair this defect, the object 30 carries a structural supplement 31 made of repair absorbent material. Generally, this repaired absorbent body material is different from the absorbent body material of the original absorbent body structure 9 of the object 30. Compared to the height h of the nominal absorber structure 9, the repair structure supplement 31 has a height h D that is generally different from h.

在修復過程中，以上討論確定方法的相位計量之至少一個具體實施例，用於根據已確定用於結構補充的修復吸收體材料，來決定該複反射率。另外，如上所述，確定要修復物體30的吸收體材料之複反射率。在已確定一方面修復吸收體材料的複反射率並且另一方面待修復物體的吸收體材料之後，選擇該修復吸收體材料及其高度hD ，使得修復吸收體材料的複反射率與待修復光罩的吸收體材料之複反射率匹配。In the repair process, at least one specific embodiment of the phase measurement of the determination method discussed above is used to determine the complex reflectivity according to the repair absorber material that has been determined to be used for structural replenishment. In addition, as described above, the complex reflectivity of the absorber material of the object 30 to be repaired is determined. After the complex reflectivity of the repaired absorber material on the one hand and the absorber material of the object to be repaired on the one hand have been determined, the repaired absorber material and its height h D are selected so that the complex reflectivity of the repaired absorber material and the absorber material to be repaired The complex reflectivity of the absorber material of the photomask is matched.

該光學相差確定方法，尤其是相位計量學，可進一步用於最佳化相差Δφ，以最小化生產投影曝光設備中的物體3D對成像的影響。此外，這種確定方法，特別是相位計量學，可用於校正物體參數，尤其是用於光源光罩最佳化的微影光罩參數，例如，一方面用於光罩佈局並且另一方面用於生產投影曝光設備的照明設定之同時最佳化。The optical phase difference determination method, especially phase metrology, can be further used to optimize the phase difference Δφ, so as to minimize the influence of the 3D object in the production projection exposure equipment on the imaging. In addition, this determination method, especially phase metrology, can be used to correct object parameters, especially lithography mask parameters for light source mask optimization, for example, on the one hand for mask layout and on the other hand. Optimize the lighting settings of the projection exposure equipment at the same time.

特別是已理解到，各個物體的頂部結構佈置對相差Δφ有影響，因此可能影響生產投影曝光設備中的成像結果。In particular, it has been understood that the top structure arrangement of each object has an effect on the phase difference Δφ, and therefore may affect the imaging result in the production projection exposure equipment.

這種頂部結構效果可使用上述用於確定光學相差Δφ的方法具體實施例來測量，並且可針對不同的頂部結構佈置將這種頂部結構效果儲存在相差庫中，以供日後有關微影光罩的最佳化使用。This top structure effect can be measured using the specific embodiment of the method for determining the optical phase difference Δφ, and the top structure effect can be stored in the phase difference library for different top structure arrangements for future related lithography masks. Optimized use.

關於光學相差Δφ，多層結構中每一層的厚度和複反射率，即特別是反射率的吸收影響，都是影響參數。Regarding the optical phase difference Δφ, the thickness and complex reflectivity of each layer in the multilayer structure, that is, the absorption influence of the reflectivity in particular, are all influencing parameters.

1:照明光 1i、1j:光線 2:投影曝光設備 3:EUV光源 4:照明光學單元 5:投影光學單元 6:物場 7:物平面 8、20、25、27、30:物體 9:吸收體頂部結構 91、92、10i:層 9D:吸收體結構 10:反射體底部結構 11:像場 12:像平面 13:空拍影像 14:空間分辨偵測裝置 15:偵測平面 16:測量步驟 17:重建步驟 18:相位校正步驟 21:頂部結構 22:底部結構 23:共用基座層 26:蝕刻停止層 31:結構補充物1: Illumination light 1 i , 1 j : Light 2: Projection exposure equipment 3: EUV light source 4: Illumination optical unit 5: Projection optical unit 6: Object field 7: Object plane 8, 20, 25, 27, 30: Object 9 : Absorber top structure 9 1 , 9 2 , 10 i : layer 9 D : absorber structure 10: reflector bottom structure 11: image field 12: image plane 13: aerial image 14: spatial resolution detection device 15: detection Plane 16: Measurement Step 17: Reconstruction Step 18: Phase Correction Step 21: Top Structure 22: Bottom Structure 23: Common Base Layer 26: Etching Stop Layer 31: Structural Supplement

下面將參考圖式來更詳細解釋本發明的示範具體實施例，在圖式中：The exemplary embodiments of the present invention will be explained in more detail below with reference to the drawings, in which:

圖1為示意性例示用於確定要以微影光罩形式來測量的物體之空拍影像之計量系統，該系統具有一照明系統、一成像光學單元和一空間分辨偵測裝置，此外，其中例示出要測量的物體之平面圖，也例示藉由範例而產生並作為3D空拍影像的部分資料集之該物體的2D影像平面圖；Figure 1 is a schematic illustration of a measurement system for determining an aerial image of an object to be measured in the form of a lithography mask. The system has an illumination system, an imaging optical unit, and a spatial resolution detection device. In addition, Illustrates the plan view of the object to be measured, and also illustrates the 2D image plan view of the object generated by the example and used as a part of the 3D aerial image;

圖2與圖1相比大幅放大，顯示待測物體的一部分之截面，包括該物體的吸收體表面頂部結構部分和反射體表面底部結構部分，其中通過範例例示兩個照明或測量光線，其一由該吸收體表面部分之層反射，而另一則由反射體表面部分之層反射；Figure 2 is greatly enlarged compared with Figure 1, showing a cross section of a part of the object to be measured, including the top structure part of the absorber surface and the bottom structure part of the reflector surface of the object. Two illumination or measurement rays are illustrated by examples, one of which is It is reflected by the layer of the surface part of the absorber, and the other is reflected by the layer of the surface part of the reflector;

圖3顯示該吸收體表面部分的一吸收體結構之厚度或高度範圍habs 上，由該物體的吸收體表面部分反射的該照明或測量光之吸收體結構相位與由該物體的反射體反射表面部分反射的該測量光之反射體結構相位間之相差Δφ的依賴圖，其中對於兩種不同吸收體材料成分AM1和AM2例示出這種依賴性； 圖4顯示用於確定光學相差Δφ以及用於最佳化待測量結構化物體的物體結構，從而當在投影微影中使用該結構化物體時最佳化影像對比之流程圖；Figure 3 shows the thickness or height range h abs of an absorber structure on the surface of the absorber, the phase of the absorber structure of the illumination or measurement light reflected by the absorber surface part of the object and the phase of the absorber structure reflected by the reflector of the object The dependency graph of the phase difference Δφ between the phases of the reflector structure of the measuring light reflected by the surface part, where this dependence is illustrated for two different absorber material components AM1 and AM2; Figure 4 shows the optical phase difference Δφ and the To optimize the object structure of the structured object to be measured, so as to optimize the flow chart of image comparison when the structured object is used in projection lithography;

圖5顯示通過使用依照圖1中一物體具有線性結構的範例，依照圖4中該方法的一部分，來重新建構一影像側場分佈的結果中該吸收體表面相位和該反射體表面相位之相位值；Fig. 5 shows the phase of the absorber surface phase and the reflector surface phase in the result of reconstructing an image-side field distribution by using an example of an object having a linear structure in accordance with Fig. 1 and a part of the method in Fig. 4 value;

圖6顯示借助於模型的一影像側場分佈計算的例示，該模型基於所確定的物體分佈，該物體分佈取決於物體週期、物體的臨界尺寸、吸收體表面部分的複反射率和反射體表面部分的複反射率；Figure 6 shows an example of the calculation of the side field distribution of an image with the aid of a model based on the determined object distribution, which depends on the object period, the critical size of the object, the complex reflectivity of the surface part of the absorber, and the surface of the reflector Partial complex reflectivity;

圖7在類似於圖2的截面中，有待測量物體的進一步具體實施例，該物體具體實施為EUV相移光罩，其包括反射體表面頂部結構部分和反射體表面底部結構部分；Fig. 7 has a further specific embodiment of the object to be measured in a cross-section similar to Fig. 2. The object is embodied as an EUV phase shift mask, which includes a top structure part of the reflector surface and a bottom structure part of the reflector surface;

圖8在根據圖7的描繪中，結構化物體的另一具體實施例具體實施為一相移光罩，其具有位於反射體表面頂部結構部分與反射體表面底部結構部分之間的一蝕刻停止層，其中該蝕刻停止層覆蓋反射體表面底部結構；FIG. 8 In the depiction according to FIG. 7, another embodiment of the structured object is embodied as a phase shift mask with an etch stop located between the top structure portion of the reflector surface and the bottom structure portion of the reflector surface Layer, wherein the etching stop layer covers the bottom structure of the reflector surface;

圖9在與圖8相似的描述中，該結構化物體的具體實施例再次具體實施為一相移光罩，其中該蝕刻停止層從反射體表面底部結構部分去除；以及Fig. 9 is a description similar to Fig. 8, the specific embodiment of the structured object is again embodied as a phase shift mask, wherein the etch stop layer is partially removed from the bottom structure of the reflector surface; and

圖10在與圖2和圖7至圖9相似的描述中，待測量物體的進一步具體實施例包括吸收體表面頂部結構部分和反射體表面底部結構部分，其中該吸收體表面頂部結構部分之一者由一缺陷修復結構補充。Fig. 10 is a description similar to Fig. 2 and Figs. 7 to 9, a further specific embodiment of the object to be measured includes an absorber surface top structure part and a reflector surface bottom structure part, wherein one of the absorber surface top structure parts It is supplemented by a defect repair structure.

1i、1j:光線 1i, 1j: light

7:物平面 7: Object plane

8:物體 8: Object

9:吸收體頂部結構 9: Top structure of absorber

91、92、10i:層 9 1 , 9 2 , 10 i : layer

10:反射體底部結構 10: Bottom structure of reflector

Claims (10)

一種用於確定一測量光波長(λ)超過一結構化物體(8、20、25、27、30)表面的一測量光(1)之光學相差(Δφ)之方法，其中該相差(Δφ)介於以下之間： -    該測量光(1)的一頂部結構相位(φabs )，其由該物體(8、20、25、27、30)的頂部結構(9、21)反射，以及 -    該測量光(1)的一底部結構相位(φML )，其由該物體(8、20、25、27、30)的底部反射體結構(10、22)反射， 被確定為總體上適用於待測量物體結構的特徵， 包括以下步驟： -    在不同的焦平面中分別測量(16)物體(8、20、25、27、30)的一系列2D影像，以使用一投影光學單元(5)記錄該物體(8)的一3D空拍影像， -    從該3D空照影像重建(17)一影像側場分佈(frec )，包括該3D空照影像的電場振幅和相位， -    借助於一相位校正(18)，從重建的場分佈(frec )確定該相差(Δφ)， 其中在該相位校正(18)中執行以下步驟： -    通過導入一物體場分佈(fobj )之模型，來計算一影像側場分佈(fim)，該物體場分佈(fobj )： --   依照該物體(8、20、25、27、30)的一物體週期(p)以及/或 --   依照該物體(8、20、25、27、30)的一臨界尺寸(CD)以及/或 --   依照該頂部結構(9、21)的一複反射率(rr,i abs )以及/或 --   依照該反射體結構(10、22)的一複反射率(rr,i ML )， --   其中該像側場分佈(fim )是該物場分佈與該投影光學單元(5)的一相干點擴展函數(PSF)之一捲積結果， -    比較該計算出的像側場分佈(fim )和該重建的像側場分佈(frec )， -    通過變化該模型參數物體週期(p)以及/或臨界尺寸(CD)以及/或複反射率(rr,i abs,ML )的一裝配方法，將該已計算的影像側場分佈(fim)與該重建的影像側場分佈(frec)間之差異最小化， -    從該等模型參數計算該相差(Δφ)，從而使複反射率 (rr,i abs 和rr,i ML )最小。A method for determining the optical phase difference (Δφ) of a measuring light (1) whose wavelength (λ) exceeds a structured object (8, 20, 25, 27, 30) surface, wherein the phase difference (Δφ) Between:-a top structure phase (φ abs ) of the measurement light (1), which is reflected by the top structure (9, 21) of the object (8, 20, 25, 27, 30), and- A bottom structure phase (φ ML ) of the measuring light (1), which is reflected by the bottom reflector structure (10, 22) of the object (8, 20, 25, 27, 30), is determined to be suitable for The characteristics of the structure of the object to be measured include the following steps:-Measure (16) a series of 2D images of the object (8, 20, 25, 27, 30) in different focal planes to use a projection optical unit (5) Record a 3D aerial image of the object (8),-reconstruct (17) an image side field distribution (f rec ) from the 3D aerial image, including the electric field amplitude and phase of the 3D aerial image,-by means of a Phase correction (18), determining the phase difference (Δφ) from the reconstructed field distribution (f rec ), where the following steps are performed in the phase correction (18):-By importing a model of the object field distribution (f obj ), Calculate an image side field distribution (fim), the object field distribution (f obj ): - according to an object period (p) of the object (8, 20, 25, 27, 30) and/or - according to the object (8, 20, 25, 27, 30) a critical dimension (CD) and/or - according to a complex reflectance (r r, i abs ) of the top structure (9, 21) and/or - according to A complex reflectivity (r r, i ML ) of the reflector structure (10, 22), - where the image-side field distribution (f im ) is a coherence between the object field distribution and the projection optical unit (5) One of the convolution results of the point spread function (PSF),-compare the calculated image side field distribution (f im ) and the reconstructed image side field distribution (f rec ),-change the model parameter object period (p) And/or an assembly method of critical dimension (CD) and/or complex reflectivity (r r, i abs, ML ), the calculated image side field distribution (fim) and the reconstructed image side field distribution (frec The difference between) is minimized,-the phase difference (Δφ) is calculated from the model parameters, so that the complex reflectance (r r, i abs and r r, i ML ) is minimized. 如請求項1所述之方法，特徵在於，在該裝配方法中，通過該方法讓該已計算的影像側場分佈(fim )與該重建的影像側場分佈(frec )間之差異最小，實現最初非線性輸出函數的線性化。The method according to claim 1, characterized in that, in the assembly method, the difference between the calculated image side field distribution (f im ) and the reconstructed image side field distribution (f rec ) is minimized by the method , To achieve the linearization of the initial non-linear output function. 如請求項2所述之方法，特徵在於，在該影像側場分佈(fim )的計算中，使用彼此獨立的參數對一實部(fr im )和一虛部(fi im )進行建模。The method according to claim 2, characterized in that, in the calculation of the image side field distribution (f im ), a real part (f r im ) and an imaginary part (f i im ) are calculated using mutually independent parameters Modeling. 如請求項2或3所述之方法，特徵為一迭代裝配方法。The method described in claim 2 or 3 is characterized by an iterative assembly method. 如請求項2至4之一者所述之方法，特徵在於，該影像側場分佈(fim )的一實部(fr im )和一虛部(fi im )彼此獨立裝配。As one method to request entry of the person 24, characterized in that the image-side field distribution (f im) of a real part (f r im) and an imaginary part (f i im) independently of one another assembly. 如請求項2至5之一者所述之方法，特徵為至少一個傅立葉轉換當成該裝配方法的一構成部分。The method described in one of claims 2 to 5 is characterized in that at least one Fourier transform is used as a component of the assembly method. 如請求項1至6之一者所述之方法，特徵在於，在該測量(16)期間，由物體(8、20、25、27、30)繞射的測量光(1)之至少兩繞射級(j)由投影光學單元(5)引導到一影像側。The method according to one of claims 1 to 6, characterized in that, during the measurement (16), at least two of the measurement light (1) diffracted by the object (8, 20, 25, 27, 30) The radiation level (j) is guided to an image side by the projection optical unit (5). 一種具有一光學測量系統來執行如申請專利範圍第1至7項之一者的方法之計量系統(2)， -    具有一照明光學單元(4)，用於以指定的照明設定照明待檢驗的物體(8、20、25、27、30)， -    具有一成像光學單元(5)，其用於將該物體(8、20、25、27、30)的一部分成像到一測量平面(12)中，以及 -    具有一空間分辨偵測裝置(14)，其佈置在該測量平面(12)上。A measurement system (2) with an optical measurement system to perform the method such as one of items 1 to 7 in the scope of the patent application, -It has an illuminating optical unit (4), which is used to illuminate the object to be inspected (8, 20, 25, 27, 30) with a specified lighting setting, -It has an imaging optical unit (5), which is used to image a part of the object (8, 20, 25, 27, 30) into a measurement plane (12), and -It has a spatial resolution detection device (14), which is arranged on the measurement plane (12). 如請求項8所述之計量系統，特徵為該成像光學單元(5)的設計，使得在該測量(16)期間，由該成像光學單元(5)引導被該物體(8)繞射的測量光(1)之至少兩個繞射級(j)到該成像光學單元(5)的一影像側。The measurement system according to claim 8, characterized by the design of the imaging optical unit (5), so that during the measurement (16), the imaging optical unit (5) guides the measurement diffracted by the object (8) At least two diffraction levels (j) of the light (1) reach an image side of the imaging optical unit (5). 如請求項8或9所述之計量系統，特徵為一EUV光源(3)。The metering system according to claim 8 or 9, characterized by an EUV light source (3).
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