WO2016107614A1 - 用于套刻误差检测的装置和方法 - Google Patents

用于套刻误差检测的装置和方法 Download PDF

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Publication number
WO2016107614A1
WO2016107614A1 PCT/CN2016/073630 CN2016073630W WO2016107614A1 WO 2016107614 A1 WO2016107614 A1 WO 2016107614A1 CN 2016073630 W CN2016073630 W CN 2016073630W WO 2016107614 A1 WO2016107614 A1 WO 2016107614A1
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Prior art keywords
detecting
objective lens
light
detector
error according
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PCT/CN2016/073630
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English (en)
French (fr)
Inventor
彭博方
陆海亮
王帆
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上海微电子装备有限公司
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Application filed by 上海微电子装备有限公司 filed Critical 上海微电子装备有限公司
Priority to JP2017534800A priority Critical patent/JP6473508B2/ja
Priority to SG11201705343XA priority patent/SG11201705343XA/en
Priority to KR1020177020780A priority patent/KR101966572B1/ko
Priority to US15/541,342 priority patent/US10268125B2/en
Publication of WO2016107614A1 publication Critical patent/WO2016107614A1/zh

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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
    • 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
    • G03F7/70605—Workpiece metrology
    • G03F7/70616—Monitoring the printed patterns
    • G03F7/70633—Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
    • 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
    • G03F7/70216—Mask projection systems
    • G03F7/70275—Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
    • 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
    • G03F7/70605—Workpiece metrology
    • G03F7/70616—Monitoring the printed patterns
    • G03F7/7065—Defects, e.g. optical inspection of patterned layer for defects

Definitions

  • the present invention relates to the field of lithography, and in particular, to an apparatus and method for detecting lap error.
  • the measurement accuracy requirement for lithography process parameter overlay has entered the sub-nano field. Due to the limitation of imaging resolution limit, the traditional imaging and image recognition based engraving measurement technology (English name: Imaging-Based overlay, referred to as: IBO) has gradually failed to meet the requirements of the new process node for the engraving measurement.
  • the Diffraction-Based overlay (DBO) based on the detection of diffracted light is gradually becoming the main means of engraving measurement.
  • the biggest problem faced by DBO technology is that the large mark size occupies too much effective exposure area, which causes the mark cost to be large; and in order to meet the requirement of the higher process node for the measurement accuracy of the scribe, it needs to be performed in the exposure field.
  • large markers will not be suitable for in-field measurements. Therefore, reducing the size of the engraved mark is an inevitable trend in the development of DBO technology.
  • a DBO technique is disclosed in the prior art which obtains a registration error by measuring the asymmetry between the same diffraction orders in the angular resolution spectrum of the engraved mark.
  • the diffraction angle of the diffracted light changes with the incident angle of the incident light.
  • the so-called diffracted optical angle resolution spectrum refers to the intensity distribution of the diffracted light formed at different angles after the incident light of different angles is diffracted by the mark.
  • Figure 1a shows the distribution of the angular resolution spectrum of each diffraction order (-2, -1, 0, 1, 2) on the CCD detector in the ring illumination mode
  • Figure 1b shows the structure of the device of the technical solution.
  • the emitted light is focused by the lens L2 and passed through the interference filtering device 30 to form a narrow-bandwidth incident light.
  • the objective lens L1 concentrates the incident light onto the silicon wafer 6 on a set of marks consisting of two linear gratings, F being the objective lens focal length. .
  • the reticle mark detector 32 is located at the back focal plane 40 of the objective lens L1, and the diffracted light of the scribed mark is collected by the objective lens L1 and then detected by the reflective surface 34. Receiver 32 receives.
  • the reticle mark detector 32 measures the angular resolution spectrum of the diffracted light at each angle. In order to obtain a wide range of angular resolution spectra, a large numerical aperture (NA) objective lens is used in this scheme.
  • NA numerical aperture
  • the size of the engraved mark is large, and it is not feasible to reduce the mark size by using a grating with a smaller period or reducing the number of mark periods, respectively, because the grating is
  • the high-order diffracted light may cause the evanescent wave to be unable to be collected, which will result in the inability to obtain the engraved signal.
  • the number of engraved marking periods is reduced to a certain number, the diffracted light at each level will no longer strictly follow the grating.
  • the diffraction equation, the resulting diffracted light signal will not be applied to the engraving calculation. Therefore, the scheme cannot perform small mark measurement engraving, and it is even impossible to achieve on-site measurement.
  • the scheme obtains the engraving information by measuring the diffracted light intensity signal, and the system illumination uniformity and transmittance uniformity will affect the engraving measurement accuracy.
  • the present invention provides an apparatus and method for detecting a registration error to measure the position error of the diffracted light.
  • the present invention provides an apparatus for detecting a registration error, comprising: a light source, an illumination system, an objective lens, and a detector, wherein the light source is used to generate measurement light.
  • the illumination system is configured to inject the measurement light into the objective lens;
  • the objective lens is configured to incident the measurement light onto a set of inscribed marks while collecting the main maximum diffracted lights diffracted from the engraved mark, And converge each main diffracted light onto a pupil plane of the objective lens;
  • the detector is located on the pupil plane of the objective lens for detecting the position of each main maximum diffracted light on the detector to obtain The engraving error of the engraved mark.
  • the illumination system comprises, in order of the measurement light propagation direction, a collimating beam mirror, a filter, a first lens, a field stop, a second lens, and a beam splitter.
  • said illumination system further comprises a polarizer positioned between said filter and said first lens.
  • the number of cycles of the overprint mark is less than 20 and the size is less than or equal to 10 ⁇ m*10 ⁇ m.
  • said illumination system comprises an aperture stop between said filter and said first lens, said aperture stop being a circular aperture or slit.
  • the circular holes or slits are provided with two sets, the two sets of circular holes or slits being symmetrical along the center of the aperture stop.
  • the circular holes or slits are provided in three or more groups.
  • each of the principally diffracted lights is positive and negative first order diffracted light.
  • the reticle mark is composed of upper and lower two-layer grating structures formed on a substrate.
  • the invention also provides a method for detecting the error of the engraving, the light source emits the measuring light, and the measuring light is incident into an objective lens through an illumination system, the objective lens injects the measuring light onto the engraved marking and collects from the engraving Marking the diffracted main maximal diffracted lights, and concentrating each of the main maximal diffracted lights onto the pupil plane of the objective lens, and a detector located on the pupil plane of the objective lens detects each of the main maximal diffracted lights on the detector The position to obtain the engraving error.
  • the number of cycles of the overprint mark is less than 20 and the size is less than or equal to 10 ⁇ m*10 ⁇ m.
  • said illumination system comprises an aperture stop, said aperture stop being a circular aperture or slit.
  • the circular holes or slits are provided with two sets, the two sets of circular holes or slits being symmetrical along the center of the aperture stop.
  • the circular holes or slits are provided in three or more groups.
  • each of the principally diffracted lights is positive and negative first order diffracted light.
  • the engraving error is obtained by linearly fitting the detected position of each of the principally maximal diffracted lights on the detector.
  • the present invention has the following advantages:
  • the present invention uses the position information of the diffracted light to measure the engraving error, and the measurement signal is not affected by illumination uniformity and transmittance uniformity;
  • the measurement mark size is smaller, the effective exposure area occupied is smaller, thereby reducing the cost of the engraving mark;
  • Figure 1a shows the distribution of the angular resolution spectrum of each diffraction order on the CCD detector during ring illumination
  • 1b is a structural diagram of a device of a DBO technical solution in the prior art
  • FIG. 2 is a schematic structural diagram of an apparatus for detecting a registration error according to Embodiment 1 of the present invention
  • FIG. 3 is a schematic structural view of a scribe mark in Embodiment 1 of the present invention.
  • FIG. 4 and FIG. 5 are schematic diagrams of diffraction according to Embodiment 1 of the present invention.
  • FIG. 6 is a schematic diagram showing the relationship between positive and negative main extreme difference signals and engraving in the first embodiment of the present invention
  • FIG. 7a and 7b are respectively schematic structural views of an aperture stop in Embodiment 1 of the present invention.
  • FIGS. 8a, 8b are schematic diagrams of diffracted light signals formed by the aperture stop shown in Figs. 7a, 7b, respectively;
  • FIGS. 9a and 9b are respectively schematic structural views of an aperture stop according to Embodiment 1 of the present invention.
  • 10a, 10b are schematic diagrams of diffracted light signals formed by the aperture stop shown in Figs. 9a, 9b, respectively;
  • FIG. 11 is a schematic structural diagram of an apparatus for detecting a registration error according to Embodiment 2 of the present invention.
  • the apparatus for detecting the flaw error of the embodiment includes the following components:
  • the light source 41 is for generating measurement light.
  • the light source 41 may be a white light source, a broadband source, or a composite source composed of a plurality of discrete lines.
  • the white light source may adopt a Xe light source or the like;
  • the wide band refers to generating light including a combination of ultraviolet, visible, and infrared bands or the above-mentioned band;
  • the composite light source may be obtained by mixing a plurality of lasers of different wavelengths.
  • An illumination system for injecting measurement light into the objective lens 410.
  • the illumination system along The light propagation direction includes, in order, a collimating beam mirror 42 for collimating the measuring light, a filter 43 for generating monochromatic light, a polarizing plate 44 for generating polarized light, and a first for collecting light.
  • the second lenses 46, 48 are for separating the measuring light into the beam splitter 49 in the objective lens 410.
  • the illumination system can also include a lens group 412 between the objective lens 410 and the detector 413.
  • the aperture is used to modulate the measurement light into incident light that is symmetric about the optical axis of the objective lens 410.
  • the aperture includes an aperture stop 45 and a field stop 47 for generating a spot that satisfies the requirements of the objective lens 410 for the size of the incident light, the aperture stop 45 being disposed in front of the first lens 46, The field stop 47 is disposed between the first lens 46 and the second lens 48.
  • the aperture stop 45 is used to generate a spot that satisfies the shape of the objective lens 410 for incident light, which may be a circular aperture 451 as shown in Figure 7a or a slit 452 as shown in Figure 7b.
  • the circular hole 451 or the slit 452 may be two groups as shown in FIGS. 9a and 9b, and the two sets of circular holes 451 or the two sets of slits 452 are respectively symmetric along the center of the aperture stop 45.
  • the objective lens 410 is configured to inject the measurement light onto the engraved mark 411, the measurement light is diffracted on the engraved mark 411, and the objective lens 410 collects the diffracted light from the engraved mark 411, especially the main maximum diffracted light, and The diffracted light is concentrated on the pupil plane of the objective lens 410.
  • the detector 413 is located on the pupil plane of the objective lens 410 and is also the back focal plane of the objective lens 410 for detecting the diffracted light signal of the engraved mark 411. Further, the detector 413 employs a CCD detector.
  • the measurement light emitted from the light source 41 is collimated by the collimator beam mirror 42, and is incident on the narrow-band filter 43 to obtain a single-wavelength light, and then passes through the polarizing plate 44 to obtain linearly polarized light, which is incident on the aperture stop. 45, and then condensed by the first lens 46, constraining the spot size incident on the engraved mark 411 via the field stop 47, passing through the second lens 48 and then incident on the beam splitter 49, which is incident on the objective lens 410, The incident light is diffracted on the engraved mark 411, and the diffracted light is collected by the objective lens 410, and then incident on the detector 413 via the lens group 412.
  • FIGS. 8a and 8b and FIGS. 10a and 10b The +/-1 order diffracted optical signals obtained by the detector 413 are respectively shown in FIGS. 8a and 8b and FIGS. 10a and 10b, wherein the diffracted optical signal in FIG. 8a corresponds to the aperture stop 45 shown in FIG. 7a.
  • Figure 8b corresponds to the aperture stop 45 shown in Figure 7b
  • Figure 10a corresponds to the aperture stop 45 shown in Figure 9a.
  • Figure 10b corresponds to the aperture stop 45 shown in Figure 9b.
  • L1 and L2 are not equal, and the engraving error of the engraved mark 411 can be calculated based on the relationship between the two. The specific calculation method will be described in detail below.
  • the higher order diffracted light can also be calculated by detecting its main maximum position.
  • the engraved mark 411 is composed of upper and lower two-layer grating structures formed on a silicon substrate.
  • the previous grating structure (lower grating) is made by a semiconductor process such as development, etching, deposition, etc. of the previous exposure pattern, and the latter grating structure (upper grating) is usually the exposed and developed photoresist pattern.
  • the splicing error refers to the position error between exposures. When the number of grating periods is large, the diffracted light generally strictly follows the grating diffraction equation.
  • d represents a grating period
  • ⁇ represents a wavelength of incident light
  • ⁇ represents a diffraction angle
  • diffracted light is incident on the objective lens 410 along a corresponding diffraction angle ⁇ .
  • the relationship between the pupil plane radius ⁇ and the diffraction angle ⁇ satisfies:
  • f is the focal length of the objective lens
  • ⁇ is the diffraction angle, which is also equal to the angle at which the diffracted light is incident on the pupil plane. Therefore, the radius of the pupil plane is proportional to the sine of the maximum incident angle (ie, the numerical aperture of the objective lens).
  • the objective lens 410 When the objective lens 410 is used to collect +/- 1st order diffracted light, as shown in FIG. 4 and FIG. 5, it can be obtained that the position of the +/- 1st order diffracted light on the pupil plane is equal to the distance from the center of the pupil plane, and Can be expressed as:
  • the diffraction angles of different sub-lights can be faithfully reacted on the pupil plane, and finally can be collected using a CCD detector.
  • the main principal diffraction angles (different main diffraction angles corresponding to different principal maxima on the pupil plane) will change with the change of the engraving error, as shown in Fig. 8a.
  • the variation error is used to measure the overlay error.
  • the engraving error can be performed by using the linear relationship between each main diffraction angle (that is, each main maximum position) and the engraving or other fitting relationship (such as curve fitting, trigonometric fitting, etc.) Measurement. Due to the reduced number of grating periods, the engraved measurement mark size can be made smaller, for example, the entire engraved measurement mark size can be within 10 ⁇ m * 10 ⁇ m.
  • the engraving error when the engraving error is near +/-0.05Pitch (Pitch stands for grating pitch), the main diffraction angle is linear with the engraving error, and the relationship can be obtained by linear fitting.
  • the engraving error Specifically, the measurement of the registration error can be completed by using three sets of engraved marks reserved with a certain deviation, and the three sets of engraved mark positional relationships are set in the second and third sets of the first set of engraved marks. Engraved in the middle.
  • the engraved marks are in the opposite direction and the same size, expressed as -d. Let the actual measurement of the engraving error be ⁇ , then the actual lower layer offsets of each set of marks are d+ ⁇ -d 0 , d+ ⁇ , -d+ ⁇ respectively; using these three points to carry out the engraving error measurement calculation, Let this linear equation be:
  • the polarizing plate 44 is removed on the basis of Embodiment 1, and the remaining portions are the same, that is, the polarizing plate is not necessarily required, and the two different aperture apertures can be obtained without the polarizing plate. 45 different sets of engraved signals, and then calculate the engraving error.
  • the present invention has the following advantages:
  • the present invention uses the position information of the diffracted light to measure the engraving error, and the measurement signal is not affected by illumination uniformity and transmittance uniformity;
  • the measurement mark size is smaller, and the effective exposure area occupied is smaller, thereby reducing the cost of the engraving mark and the influence on the chip manufacturing;
  • the present invention can be distinguished from the prior art, and the in-field measurement of the exposure field can be realized to meet the requirement of higher node measurement accuracy of the overlay error.

Abstract

一种用于套刻误差检测的装置和方法，该装置包括：一光源（41）、一照明系统（42、43、44、46、48、49、412）、一物镜（410）以及一探测器（413），其中，所述光源（41）用于产生测量光；所述照明系统（42、43、44、46、48、49、412）用于将所述测量光入射到所述物镜（410）中；所述物镜（410）用于将测量光入射到一套刻标记（411）上，同时收集从套刻标记（411）衍射的各主极大衍射光，并将各主极大衍射光汇聚到所述物镜（410）的一光瞳面上；所述探测器（413）位于所述物镜（410）的光瞳面，用于探测各主极大衍射光在探测器（413）上的位置以获取所述套刻标记（411）的套刻误差。该方法采用衍射光的位置信息进行套刻误差的测量，测量信号不受照明均匀性、透过率均匀性等影响；套刻标记（411）尺寸更小，周期数小于20，所占用有效曝光区域更小，从而减少了套刻标记（411）的成本；可以实现场内测量，满足更高节点对套刻误差的测量精度的需求。

Description

用于套刻误差检测的装置和方法 技术领域
本发明涉及光刻技术领域，特别涉及一种用于套刻误差检测的装置和方法。
背景技术
随着光刻图形CD尺寸进入22nm及以下工艺节点，特别是双重曝光(Double Patterning)技术的广泛应用，对光刻工艺参数套刻(overlay)的测量精度要求已经进入亚纳米领域。由于成像分辨率极限的限制，传统的基于成像和图像识别的套刻测量技术(英文全称：Imaging-Based overlay，简称：IBO)已逐渐不能满足新的工艺节点对套刻测量的要求。基于衍射光探测的套刻测量技术(英文全称：Diffraction-Based overlay，简称：DBO)正逐步成为套刻测量的主要手段。目前，DBO技术所面临的最大问题是标记尺寸较大占用了过多的有效曝光区域，造成标记成本很大；且为了适应更高工艺节点对套刻测量精度的需求，需要在曝光场内进行套刻测量，大标记将不适合用做场内测量。因此，减小套刻标记尺寸是DBO技术发展的必然趋势。
现有技术中公开了一种DBO技术，该技术通过测量套刻标记衍射光角分辨谱中相同衍射级次间的非对称性得到套刻误差。衍射光的衍射角随入射光入射角度变化而改变，所谓衍射光角分辨谱是指不同角度的入射光在被标记衍射后衍射光在不同角度形成的光强分布。图1a为环形照明模式下，各个衍射级次(-2，-1,0,1,2)的角分辨谱在CCD探测器上的分布情况，图1b是该技术方案的装置结构图，光源2发出的光由透镜L2聚焦并经干涉滤波装置30后形成窄带宽的入射光，物镜L1将入射光汇聚到硅片6上一般由两层线性光栅组成的套刻标记上，F为物镜焦距。套刻标记探测器32位于物镜L1的后焦面40处，套刻标记的衍射光被物镜L1收集后经反射面34被套刻标记探测 器32接收。套刻标记探测器32测得套刻标记各个角度衍射光的角分辨谱。为了获得大范围的角分辨谱，该方案中使用大数值孔径(NA)的物镜。从上述描述可知，首先，根据其测量原理，其套刻标记尺寸较大，并且通过采用周期更小的光栅或者减小标记周期数以减小标记尺寸是不可行的，其原因分别为当光栅周期减小时，其高级次衍射光将可能产生倏逝波无法收集，将会导致无法得到套刻信号；当套刻标记周期数减少至一定数量时，各级次衍射光将不再严格遵循光栅衍射方程，所得到的衍射光信号将不能应用于套刻计算。因此该方案无法进行小标记测量套刻，更无法实现场内测量。其次，该方案通过测量衍射光强信号获得套刻信息，系统照明均匀性、透过率均匀性等会影响套刻测量精度。
发明内容
本发明提供一种用于套刻误差检测的装置和方法，从而对衍射光的位置信息进行套刻误差的测量。
为解决上述技术问题，本发明提供一种用于套刻误差检测的装置，其特征在于，包括：一光源、一照明系统、一物镜以及一探测器，其中，所述光源用于产生测量光；所述照明系统用于将所述测量光入射到所述物镜中；所述物镜用于将测量光入射到一套刻标记上，同时收集从套刻标记衍射的各主极大衍射光，并将各主极大衍射光汇聚到所述物镜的一光瞳面上；所述探测器位于所述物镜的光瞳面，用于探测各主极大衍射光在探测器上的位置以获取所述套刻标记的套刻误差。
作为优选，所述照明系统沿测量光传播方向依次包括：准直束镜、滤波片、第一透镜、视场光阑、第二透镜以及分束器。
作为优选，所述照明系统还包括偏振片，位于所述滤波片与所述第一透镜之间。
作为优选，所述套刻标记的周期数小于20且尺寸小于等于10μm*10μm。
作为优选，所述照明系统包括孔径光阑，位于所述滤波片与所述第一透镜之间，所述孔径光阑为圆孔或狭缝。
作为优选，所述圆孔或狭缝设置有两组，所述两组圆孔或狭缝沿孔径光阑的中心对称。
作为优选，所述圆孔或狭缝设置有三组以上。
作为优选，所述各主极大衍射光为正负1级衍射光。
作为优选，所述套刻标记由在衬底上制成的上下两层光栅结构组成。
本发明还提供一种用于套刻误差检测的方法，光源发出测量光，通过一照明系统将测量光入射到一物镜中，所述物镜将测量光入射到套刻标记上并收集从套刻标记衍射的各主极大衍射光，并将各主极大衍射光汇聚到所述物镜的光瞳面，位于物镜光瞳面的一探测器探测各主极大衍射光在所述探测器上的位置以获取所述套刻误差。
作为优选，所述套刻标记的周期数小于20且尺寸小于等于10μm*10μm。
作为优选，所述照明系统包括孔径光阑，所述孔径光阑为圆孔或狭缝。
作为优选，所述圆孔或狭缝设置有两组，所述两组圆孔或狭缝沿孔径光阑的中心对称。
作为优选，所述圆孔或狭缝设置有三组以上。
作为优选，所述各主极大衍射光为正负1级衍射光。
作为优选，通过对探测到的各主极大衍射光在探测器上的位置进行线性拟合以获取所述套刻误差。
与现有技术相比，本发明具有以下优点：
1、本发明采用衍射光的位置信息进行套刻误差的测量，测量信号不受照明均匀性、透过率均匀性等影响；
2、测量标记尺寸更小，所占用有效曝光区域更小，从而减少了套刻标记的成本；
3、可以实现场内测量，满足更高节点对套刻误差的测量精度的需求。
附图说明
图1a为环形照明时，各衍射级次的角分辨谱在CCD探测器上的分布；
图1b为现有技术中DBO技术方案的装置结构图；
图2为本发明实施例1中用于套刻误差检测的装置的结构示意图；
图3为本发明实施例1中套刻标记的结构示意图；
图4和图5为本发明实施例1的衍射示意图；
图6为本发明实施例1中正负主极大差分信号与套刻关系示意图；
图7a、7b分别为本发明实施例1中孔径光阑的结构示意图；
图8a、8b分别为图7a、7b中所示孔径光阑形成的衍射光信号示意图；
图9a、9b分别为本发明实施例1中孔径光阑的结构示意图；
图10a、10b分别为图9a、9b中所示孔径光阑形成的衍射光信号示意图；
图11为本发明实施例2中用于套刻误差检测的装置的结构示意图。
具体实施方式
为使本发明的上述目的、特征和优点能够更加明显易懂，下面结合附图对本发明的具体实施方式做详细的说明。需说明的是，本发明附图均采用简化的形式且均使用非精准的比例，仅用以方便、明晰地辅助说明本发明实施例的目的。
实施例1
如图2所示，本实施例的用于套刻误差检测的装置，包括以下部件：
光源41，用于产生测量光。具体地，光源41可以是白光光源、宽波段光源或是由若干个分立谱线组成的复合光源。其中，白光光源可以采用Xe光源等；宽波段指产生包括紫外、可见和红外波段或上述波段组合的光；复合光源可以由若干个不同波长的激光器通过混频得到。
照明系统，用于将测量光入射到物镜410中。具体地，所述照明系统沿 光传播方向依次包括：用于对测量光进行准直的准直束镜42，用于生成单色光的滤波片43，用于生成偏振光的偏振片44，用于聚光的第一、第二透镜46、48，用于将测量光入射到物镜410中的分束器49。此外，所述照明系统还可包括位于物镜410和探测器413之间的透镜组412。
光阑，用于将测量光调制为关于物镜410光轴中心对称的入射光。具体地，所述光阑包括孔径光阑45和用于生成满足物镜410对入射光尺寸需求的光斑的视场光阑47，所述孔径光阑45设置在所述第一透镜46前方，所述视场光阑47设置在所述第一透镜46与第二透镜48之间。如图7a和7b所示，所述孔径光阑45用以生成满足物镜410对入射光形状需求的光斑，其可以为如图7a所示的圆孔451或者如图7b所示的狭缝452。进一步的，圆孔451或者狭缝452可以如图9a和图9b所示的两组，两组圆孔451或两组狭缝452分别沿孔径光阑45的中心对称。
物镜410，用于将测量光入射到套刻标记411上，测量光在套刻标记411上进行衍射，同时物镜410收集来自套刻标记411的衍射光，尤其是各主极大衍射光，并将衍射光汇聚到物镜410的光瞳面上。
探测器413，位于物镜410光瞳面，也是物镜410的后焦面上，用于探测套刻标记411的衍射光信号。进一步的，探测器413采用CCD探测器。
光源41发出的测量光在经过准直束镜42准直后，入射至窄带滤波片43，获得单一波长的光，而后经过偏振片44，获得线偏振光，此线偏振光入射至孔径光阑45，而后经过第一透镜46会聚，经由视场光阑47约束入射至套刻标记411上的光斑尺寸，经过第二透镜48后入射至分束器49，该入射光正入射至物镜410中，入射光在套刻标记411上发生衍射，衍射光经过物镜410收集后，又经由透镜组412，最终入射至探测器413上。
其中，探测器413所得到的+/-1级衍射光信号分别如图8a、8b和图10a、10b所示，其中，图8a中的衍射光信号与图7a所示的孔径光阑45对应，图8b与图7b所示的孔径光阑45对应，图10a与图9a所示的孔径光阑45对应， 图10b与图9b所示的孔径光阑45对应。图中，L1与L2不相等，可以基于两者间的关系计算套刻标记411的套刻误差，具体计算方法将于下文详述。除了+/-1级衍射光外，高级次衍射光同样可以通过探测其主极大位置来计算所述套刻误差。
如图3所示，套刻标记411由在硅基底上制成的上下两层光栅结构组成。前一层光栅结构(下层光栅)由前一次曝光图形经显影、刻蚀、沉积等半导体工艺制成，后一层光栅结构(上层光栅)通常为本次曝光、显影后的光刻胶图形。套刻误差指两次曝光间的位置误差。当光栅周期数较多时，衍射光一般会严格遵循光栅衍射方程。
对于现有散射测量使用到的对于+/-1级衍射光，则有：
sin(θ)＝±λ/d   (1)
式(1)中，d表示光栅周期，λ表示入射光波长，θ表示衍射角，衍射光将沿着相应的衍射角θ入射至物镜410。
因此，对于满足阿贝成像的物镜410而言，光瞳面半径ρ与衍射角θ的关系满足：
ρ＝f*sin(θ)   (2)
式(2)中，f为物镜焦距，θ为衍射角，也等于衍射光入射至光瞳面的角度。因此，光瞳面半径与最大入射角度正弦值(即物镜数值孔径)成正比。
当使用物镜410收集+/-1级衍射光时，如图4和图5所示，即可以得到+/-1级衍射光在光瞳面上的位置相对光瞳面中心的距离相等，且可表示为：
L＝f*sin(θ)   (3)
因此，各级次光不同的衍射角度可以如实的反应在光瞳面上，最终可以使用CCD探测器采集。
当光栅周期数较少，入射光的衍射会出现各级主极大，其衍射角度将不再严格遵循光栅衍射方程，此时对于套刻标记411，作为优选，当光栅的周期 数小于或等于20时，其各主极大衍射角(不同的主极大衍射角度对应光瞳面上不同的主极大位置)将会随着套刻误差的变化而发生变化，如图8a、8b、10a、10b所示，图中L1与L2不相等，即由于套刻的存在，光瞳面(探测器)上+/-1级衍射光的主极大位置与光瞳中心的距离不等。本实施例采用该变化关系进行测量套刻误差。具体的，在特定的膜系结构下，套刻误差在特定范围内变化时，其正负主极大衍射角度(主极大峰值)亦随之发生变化。利用各主极大衍射角度(也即各主极大位置)与套刻之间存在的线性关系或者其它可拟合的关系(例如曲线拟合、三角函数拟合等)即可进行套刻误差的测量。由于光栅周期数减少，采用的套刻测量标记尺寸可以更小，例如整个套刻测量标记尺寸可在10μm*10μm以内。
为消除其他因素影响，可以使用正负主极大差分信号与套刻误差的关系进行求解。下面将对用于套刻误差检测的线性拟合方法举例说明；
如图6所示，当套刻误差在+/-0.05Pitch(Pitch代表光栅栅距)附近时，其主极大衍射角度与套刻误差成线性关系，对此关系进行线性拟合可以求得套刻误差。具体地，可使用预留有一定偏差的三块套刻标记来完成对套刻误差的测量，所述三块套刻标记位置关系为第一块套刻标记设置在第二和第三块套刻标记中间。其中第一块套刻标记预设偏差为d＝0.05Pitch；第二块套刻标记相对第一块套刻标记偏移d0＝0.01Pitch；第三块套刻标记预设偏差与第一块套刻标记的方向相反，大小相同，表示为-d。设实际要测量套刻误差为ε，则各套刻标记实际上下层偏移量分别为d+ε-d0，d+ε，-d+ε；利用此三点进行套刻误差测量计算，设此线性方程为：
y＝k*x±b   (4)
将三块套刻标记的信息带入式(4)，则可得出：
Figure PCTCN2016073630-appb-000001
求解上述方程(5)，因此很容易得到套刻误差ε：
Figure PCTCN2016073630-appb-000002
实施例2
如图11所示，本实施例在实施例1基础上将偏振片44去除，其余部分相同，即偏振片不一定是必须的，无偏振片的情况下一样能够得到上述两种不同孔径光阑45的不同套刻信号，进而计算套刻误差。
与现有技术相比，本发明具有以下优点：
1、本发明采用衍射光的位置信息进行套刻误差的测量，测量信号不受照明均匀性、透过率均匀性等影响；
2、测量标记尺寸更小，所占用有效曝光区域更小，从而减少了套刻标记的成本和对芯片制造的影响；
3、由于采用了小尺寸测量标记，可以使本发明区别于现有技术，实现曝光场的场内测量，满足更高节点对套刻误差的测量精度的需求。
显然，本领域的技术人员可以对发明进行各种改动和变型而不脱离本发明的精神和范围。这样，倘若本发明的这些修改和变型属于本发明权利要求及其等同技术的范围之内，则本发明也意图包括这些改动和变型在内。

Claims (16)

  1. 一种用于套刻误差检测的装置，其特征在于，包括：一光源、一照明系统、一物镜以及一探测器，其中，所述光源用于产生测量光；所述照明系统用于将所述测量光入射到所述物镜中；所述物镜用于将测量光入射到一套刻标记上，同时收集从套刻标记衍射的各主极大衍射光，并将各主极大衍射光汇聚到所述物镜的一光瞳面上；所述探测器位于所述物镜的光瞳面，用于探测各主极大衍射光在探测器上的位置以获取所述套刻标记的套刻误差。
  2. 如权利要求1所述的用于套刻误差检测的装置，其特征在于，所述照明系统沿测量光传播方向依次包括：准直束镜、滤波片、第一透镜、视场光阑、第二透镜以及分束器。
  3. 如权利要求2所述的用于套刻误差检测的装置，其特征在于，所述照明系统还包括偏振片，位于所述滤波片与所述第一透镜之间。
  4. 如权利要求1所述的用于套刻误差检测的装置，其特征在于，所述套刻标记的周期数小于20且尺寸小于等于10μm*10μm。
  5. 如权利要求2所述的用于套刻误差检测的装置，其特征在于，所述照明系统包括孔径光阑，位于所述滤波片与所述第一透镜之间，所述孔径光阑为圆孔或狭缝。
  6. 如权利要求5所述的用于套刻误差检测的装置，其特征在于，所述圆孔或狭缝设置有两组，所述两组圆孔或两组狭缝沿孔径光阑的中心对称。
  7. 如权利要求5所述的用于套刻误差检测的装置，其特征在于，所述圆孔或狭缝设置有三组以上。
  8. 如权利要求1所述的用于套刻误差检测的装置，其特征在于，所述各主极大衍射光为正负1级衍射光。
  9. 如权利要求1所述的用于套刻误差检测的装置，其特征在于，所述套刻标记由在衬底上制成的上下两层光栅结构组成。
  10. 一种采用权利要求1至9任一项所述的用于套刻误差检测的装置进行套刻误差检测的方法，其特征在于，光源发出测量光，通过一照明系统将测量光入射到一物镜中，所述物镜将测量光入射到套刻标记上并收集从套刻标记衍射的各主极大衍射光，并将各主极大衍射光汇聚到所述物镜的光瞳面，位于物镜光瞳面的一探测器探测各主极大衍射光在所述探测器上的位置以获取所述套刻误差。
  11. 如权利要求10所述的套刻误差检测的方法，其特征在于，所述套刻标记的周期数小于20且尺寸小于等于10μm*10μm。
  12. 如权利要求10所述的套刻误差检测的方法，其特征在于，所述照明系统包括孔径光阑，所述孔径光阑为圆孔或狭缝。
  13. 如权利要求12所述的套刻误差检测的方法，其特征在于，所述圆孔或狭缝设置有两组，所述两组圆孔或两组狭缝沿孔径光阑的中心对称。
  14. 如权利要求12所述的套刻误差检测的方法，其特征在于，所述圆孔或狭缝设置有三组以上。
  15. 如权利要求10所述的套刻误差检测的方法，其特征在于，所述各主极大衍射光为正负1级衍射光。
  16. 如权利要求10所述的套刻误差检测的方法，其特征在于，通过对探测到的各主极大衍射光在探测器上的位置进行线性拟合以获取所述套刻误差。
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