JP2008177256A - Electron beam drawing apparatus and mask manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam lithography apparatus that measures the height of a mask precisely. <P>SOLUTION: The electron beam lithography apparatus deflects an electron beam by a deflector to draw a pattern on the surface of a sample fixed on a stage. The electron beam lithography apparatus includes: a light source for setting the level position of the sample; an optical system that irradiates light emitted from the light source onto the surface of the sample; a detector that detects the level position of the sample, based on the reception position of light reflected from the surface of the sample, which is made of a light-receiving element; and a level calibrating element which is disposed on the stage and has a step for correcting the level of the sample surface by reflecting light from the light source. The level calibrating element is made of a metal material having a 30 to 60 (%) reflection factor against the wavelength of the light source. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electron beam drawing apparatus and a mask manufacturing method, and more particularly to an electron beam drawing apparatus capable of accurately aligning a mask, which is a drawing target in the electron beam drawing apparatus. The present invention relates to a method of manufacturing a mask on which a fine pattern is formed by an electron beam drawing apparatus.

  In order to form a semiconductor integrated circuit pattern on a mask or a resist applied on a semiconductor wafer, an electron beam drawing apparatus is used. In this electron beam drawing apparatus, scanning is performed by deflecting an electron beam by an electromagnetic means, and a predetermined region on a mask or a semiconductor wafer is irradiated.

  In this way, when a predetermined pattern is drawn on a resist-coated mask or the like by the electron beam drawing apparatus, the drawing is performed while being fixed on the XY stage on which the mask or the like is mounted and moved. In this case, since the electron beam is incident from an oblique direction in a narrowed state, if the position of the mask is displaced, the electron beam is not irradiated at a predetermined position, and the drawing pattern is displaced. , Problems such as blurring occur.

In order to solve such a problem, a method has been proposed in which the height of a mask or the like is measured and corrected. Specifically, in Patent Document 1, a method of correcting the height by measuring a capacitance between a detection electrode arranged inside the electron beam drawing apparatus and a Cr film formed on the surface of a glass substrate or the like. Discloses a method of detecting and correcting a positional deviation of the height of a mask or the like every time the stage is moved by an XY stage. Patent Documents 2 and 3 disclose a method in which measurement is performed by a laser displacement sensor provided in an electron beam drawing apparatus, and correction is performed based on the measurement by the displacement sensor.
JP 56-64434 A JP 9-22859 A JP 2005-252269 A

  The present invention provides an electron beam drawing apparatus with improved positional accuracy of a mask or the like when drawing with an electron beam, and by using this electron beam drawing apparatus, a highly accurate fine pattern can be formed. A method for manufacturing a mask or the like is provided.

  An electron beam drawing apparatus according to an aspect of the present invention is an electron beam drawing apparatus that draws a pattern on a sample surface fixed to a stage by deflecting an electron beam with a deflector, the height position of the sample being The height position of the sample is detected by the light source for setting the light, the optical system for irradiating the surface of the sample with the light emitted from the light source, and the light receiving position of the light reflected from the surface of the sample comprising the light receiving element. A detector and a height calibration element having a step for correcting the height of the sample surface by reflecting light from the light source, the height calibration element being a light source It is characterized by being made of a metal material having a reflectance of 30% to 60% with respect to the wavelength of.

  An electron beam drawing apparatus according to one embodiment of the present invention is an electron beam drawing apparatus that draws a pattern on a sample surface fixed to a stage by deflecting an electron beam with a deflector, The height position of the sample is determined by the light source for setting the position, the optical system for irradiating the surface of the sample with the light emitted from the light source, and the light receiving position of the light reflected from the surface of the sample comprising the light receiving element. A detector for detecting, and a height calibration element provided on a stage and having a step for correcting the height of the sample surface by reflecting light from the light source. The substrate is formed by depositing a metal material having a reflectance of 30% to 60% with respect to the wavelength of the light source on a substrate having a step.

  In the electron beam lithography apparatus according to one embodiment of the present invention, the metal material is chromium or chromium oxide.

  In the electron beam lithography apparatus according to one embodiment of the present invention, the metal material is the same material as the metal material formed on the surface of the sample.

  An electron beam drawing apparatus according to one embodiment of the present invention is an electron beam drawing apparatus that draws a pattern on a sample surface fixed to a stage by deflecting an electron beam with a deflector, A light source for setting the position, an optical system for irradiating the surface of the sample with light emitted from the light source, and a light receiving element, and the light receiving position of the light reflected from the surface of the sample And a height calibration element provided on the stage and having a step for correcting the height of the sample surface by reflecting the light from the light source. The calibration element is characterized in that a dielectric multilayer film having a reflectance of 30% to 60% with respect to the wavelength of the light source is formed on a stepped substrate.

  According to another aspect of the present invention, there is provided a mask manufacturing method for a sample in which a light blocking film is formed on a surface of a glass substrate, and a resist that is exposed to an electron beam on the light blocking film is applied. To 5. The step of exposing the resist by drawing the electron beam using the electron beam drawing apparatus according to any one of claims 5 to 5, the step of developing the resist after exposing it, and etching the light blocking film in the region where the resist has been removed after the development And a step of removing the resist after etching.

  According to the present invention, the positional accuracy of a mask or the like in an electron beam lithography apparatus can be increased, and a mask or the like on which a high-precision fine pattern is formed by manufacturing the mask or the like using the electron beam lithography apparatus. Can be obtained.

[Electron beam lithography system]
One embodiment of the present invention will be described below.

  FIG. 1 is a configuration diagram of an electron beam drawing apparatus according to the first embodiment of the present invention. A stage 3 on which a sample 2 such as a mask on which an electron beam is drawn is provided in a sample chamber 1 of the electron beam drawing apparatus. The stage 3 is driven by the stage drive circuit 4 in the X direction (left-right direction on the paper surface) and the Y direction (vertical direction on the paper surface). The moving position of the stage 3 is measured by a position circuit 5 using a laser length meter or the like.

  An electron beam optical system 10 is installed above the sample chamber 1. The optical system 10 includes an electron gun 6, various lenses 7, 8, 9, 11, 12, a blanking deflector 13, a beam dimension changing deflector 14, a beam scanning main deflector 15, and a beam scanning The auxiliary deflector 16 and the two beam shaping apertures 17 and 18 are formed.

  As shown in FIG. 2, in the normal electron beam drawing, the pattern 51 to be drawn on the sample 2 is divided into strip-shaped frame regions 52, and each frame region 52 is moved while the stage 3 is continuously moved in the X direction. draw. The frame area 52 is further divided into subfield areas 53, and only necessary portions in the subfield areas 53 are drawn by deflecting the electron beam 54, which is a variable shaped beam. For this reason, the main deflector 15 and the sub deflector 16 and the two-stage deflector are used, the subfield region 53 is positioned in the frame region 52 by the main deflector 15, and the drawing in the subfield region 53 is performed in the subfield region 53. This is performed by the deflector 16.

  When drawing is performed in the electron beam drawing apparatus, the main deflector 15 positions the predetermined subfield region 53, the subdeflector 16 positions the pattern drawing position in the subfield region 53, and the beam dimensions. The beam shape is controlled by the variable deflector 14 and the beam shaping apertures 17 and 18, and drawing is performed in the subfield region 53 while the stage 3 is continuously moved in one direction. In this way, when drawing in one subfield region 53 is completed, drawing in the next subfield region 53 is performed. Here, the frame area 52 is a strip-shaped drawing area determined by the deflection width of the main deflector 15, and the subfield area 53 is a unit drawing area determined by the deflection width of the sub-deflector 16.

  Further, after the drawing of the frame area 52, which is a set of a plurality of subfield areas 53, is completed, the stage 3 is moved stepwise in a direction orthogonal to the direction in which the stage 3 is continuously moved as necessary to draw the next frame area 52. I do.

  On the other hand, the control computer 20 is connected to a magnetic disk 21 as a storage medium, and stores mask drawing data. The drawing data read from the magnetic disk 21 is temporarily stored in the pattern memory 22 for each frame area 52. The pattern data for each frame area 52 stored in the pattern memory 22, that is, the frame information composed of the drawing position and the drawing data, etc. is sent via the data expansion unit 30 to the pattern data decoder 23 and the drawing data decoder which are data analysis units. 24.

  The data expansion unit 30 has a function of selecting and extracting data included in the frame area set by the control computer 20 from data stored in the pattern memory 22.

  The output of the pattern data decoder 23 is connected to a blanking circuit 25 and a beam shaper driver 26. Specifically, the pattern data decoder 23 creates blanking data based on the data and sends the data to the blanking circuit 25. Furthermore, desired beam size data is also created, and this beam size data is sent to the beam shaping driver 26. Then, a predetermined deflection signal is applied from the beam shaping driver 26 to the beam dimension varying deflector 14 of the electron optical system 10, thereby controlling the dimension of the electron beam.

  The output of the drawing data decoder 24 is sent to the main deflector driver 27 and the sub deflector driver 28. A predetermined deflection signal is applied from the main deflector driver 27 to the main deflection unit 15 of the electron optical system 10, whereby the electron beam is deflected and scanned to a predetermined main deflection position. In addition, a predetermined sub deflection signal is applied from the sub deflector driver 28 to the sub deflector 16, thereby drawing inside the sub field region 53.

[Mask height detection]
Next, a mask height detector in the electron beam lithography apparatus according to the present embodiment will be described with reference to FIG. FIG. 3 shows an optical path diagram of the optical system of the mask height detector.

  The laser beam of 633 [nm] emitted from the light source 61 is linearly polarized and reflected by the first mirror 63 via the first lens 62. Thereafter, the light is reflected by the second mirror 64 and the third mirror 65, passes through the λ / 2 plate 66, and then condensed by the second lens 67. The condensed laser light is reflected by the fourth mirror 68 and irradiated onto the surface of the sample 2 that is a mask. On the surface of the sample 2, the incident laser light is reflected, reflected by the fifth mirror 69, then reflected by the sixth mirror 71, the seventh mirror 72, and the eighth mirror 73 via the third lens 70, and The light is condensed by the four lenses 74 and enters the detector 75. Since the incident position of the laser beam incident on the detector 75 varies depending on the height of the sample 2 (position in the Z-axis direction), the position of the sample 2 in the Z-axis direction is detected based on the amount of variation in the incident position of the light. Is. Specifically, as shown in FIG. 4, a method of detecting the height position by changing the optical path of the reflected light depending on the height position and causing a change in the incident position of the reflected light in the detector 75. Used.

  In the mask height detection apparatus having the optical system having such a configuration, the reflectance of the laser beam differs due to the influence of interference due to the film thickness of the resist applied to the surface of the sample 2. As a result, in the case of the sample 2 having a low reflectance, the amount of laser light incident on the detector 75 decreases, the intensity change of the position detection signal is weak, and the measurement accuracy is low. The resist used in the present embodiment is made of a polymer, and has a refractive index of 1.56 after baking after coating and a transmittance of 98% at a film thickness of 300 nm. Value.

  Moreover, although the sample 2 is normally supported by the support body, the sample 2 may bend due to this. Such a deflection or the like can be accurately detected in the height detection device when the light amount of the laser light incident on the detector 75 is low because the light amount fluctuation with respect to the height of the sample 2 surface is small. It becomes difficult.

  Specifically, as shown in FIG. 5, when the surface (mask surface) of the sample 2 has a deflection or the like, the electron beam for drawing is incident from an oblique direction. When the deviation occurs, the height position (Z-axis direction) irradiated with the electron beam is shifted by ΔZ from the reference plane, and the irradiated position in the X-axis direction is also shifted by ΔX. As a result, the electron beam that is supposed to be irradiated at an accurate position on the reference plane is actually irradiated to the position shifted by ΔX due to the positional deviation in the height direction, and the drawing accuracy of the electron beam is deteriorated.

  In addition, as shown in FIG. 6, when the height is displaced, if the reference plane is used, drawing is performed at the focused position of the electron beam. Drawing is performed at the focus position. At the defocus position, since the electron beam spreads with respect to the focus position, the line width of the drawing pattern becomes a wide pattern, making it difficult to perform fine drawing.

  As described above, when the height position of the sample 2 is optically detected, the laser light emitted from the light source 61 is irradiated to the height calibration element 77 by the metal step provided on the XY stage 3. The height detector is calibrated by making the reflected light incident on the detector 75.

  Specifically, as shown in FIG. 7, a height calibration element 77 based on a metal step is installed on the XY stage 3 and the sample 2 is fixed. The height calibration element 77 based on the metal level difference is formed with a level difference, and has a region where the laser beam from the light source 61 is reflected at each level difference. Since the height of the step and the height of the stage 3 correspond to each other, the height detection device is calibrated by the reflected light from the height calibration element 77 due to the metal step, and the height from the stage 3 on the surface of the sample 2 It is possible to detect the height.

  Here, the height calibration element 77 based on the metal step used in this way is usually made of aluminum (Al) having a high reflectance, and is different from the reflectance of the sample 2. Therefore, when the reflected light from the sample 2 is measured by the detector 75, the reflected light from the height calibration element 77 due to the metal step made of aluminum is set to be detected. In the case of measuring the height of the sample 2, the amount of reflected light from the sample 2 is small, so the error increases and it is difficult to accurately detect the position.

  Therefore, in the embodiment of the present invention, when detecting the reflected light from the actual sample 2, in order to be able to take a sufficient dynamic range, chromium or the like, which is a material having a lower reflectance than aluminum, A height calibration element 77 is formed by a metal step. Note that a material having a low reflectance may be formed on the surface of a substrate provided with a step for height calibration.

  Specifically, as shown in FIG. 8, the height calibration element 77 by the metal step in the present embodiment is formed of chromium having a step of 10 [μm]. Accordingly, the height calibration element 77 based on the metal step is formed of the same material as the chromium film, which is a metal film formed on the sample 2, so that the reflectance can be set to approximately the same value as that of the sample 2. Thereby, the dynamic range of the detector 75 in the height detection can be sufficiently taken.

Further, as shown in FIG. 9, a low reflection film made of a material having a lower reflectance than aluminum in the wavelength region of the laser light from the light source 61 on the height calibration substrate 78 having a step of 10 [μm]. By forming 79, the height calibration element 77 by a metal step may be configured. The material constituting the low-reflection film 79 is preferably close to the reflectance of the sample 2, and is 30% or more and 60% or less in the wavelength region of the laser beam used for the height measuring device. It is desirable that Specifically, a material such as chromium is used as the metal material. The low reflection film 79 may be composed of a dielectric multilayer film in which a dielectric film is laminated in addition to a metal material that reflects laser light at the interface. Since the dielectric multilayer film can obtain a desired reflectance by adjusting the film thickness and the refractive index of the material used for light in a predetermined wavelength region due to light interference, the same effect can be obtained. Because it can. Specifically, a laminated film of titanium oxide (TiO ₂ ) and silicon oxide (SiO ₂ ), a laminated film of aluminum oxide (Al ₂ O ₃ ) and silicon oxide (SiO ₂ ), and aluminum oxide (Ta ₂ O ₅ ) A laminated film of silicon oxide (SiO ₂ ) or the like can be given.

  FIG. 10 shows the reflectance of various masks to be the sample 2, the reflectance of a conventional height calibration element made of aluminum, and the reflectance of a height calibration element made of chromium according to the present embodiment.

  As shown in FIG. 10, the reflectivity of various masks to be the sample 2 is 30 [%] to 60 [%], whereas the reflectivity of a conventional height calibration element (conventional step) made of aluminum is used. The rate is 80 [%] or more, which is higher than that of the mask. On the other hand, the reflectance of the height calibration element (Cr level difference) made of chromium according to the present embodiment is about 48 [%], and is included in the range of the reflectance of the mask. For this reason, the detector 75 can take a sufficient dynamic range and can accurately detect the height.

  As shown in FIG. 10, since the reflectance of the mask, which is the sample 2, is in the range of 30 [%] to 60 [%], the reflectance of the material constituting the height calibration element, and the surface composition. The reflectance of the low reflection film 79 to be formed is preferably in the range of 30 [%] to 60 [%], because the dynamic range of the detector 75 can be widened most in this range.

  Next, a drawing procedure of the electron beam drawing apparatus in the present embodiment will be described.

  First, the sample 2 is set on the stage 3 in the sample chamber 1. Thereafter, the position of the stage 3 is detected by the position circuit 5, and the stage 3 is moved to a position where drawing can be performed by the stage driving circuit 4 based on a signal from the control computer 20.

  Thereafter, an electron beam is emitted from the electron gun 6. The electron beam is condensed by the illumination lens 7 and the blanking deflector 13 performs an operation as to whether or not the sample 2 is irradiated with the electron beam.

  Thereafter, the electron beam incident on the aperture 17 passes through the opening in the aperture 17, is deflected by the beam size varying deflector 14 controlled by the beam shaper driver 26, and is provided in the beam shaping aperture 18. By passing through the opening, a spot pattern having a desired beam shape is finally obtained. The spot pattern is a drawing unit of an electron beam irradiated on the sample 2, and one drawing pattern is formed by a plurality of spot patterns.

  The beam shape of the electron beam, which is a spot pattern after the beam shape is formed, is reduced by the reduction lens 11. The irradiation position of the electron beam drawn on the sample 2 on the sample 2 is controlled by the main deflector 15 controlled by the main deflector driver 27 and the sub deflector 16 controlled by the sub deflector driver 28. The main deflector driver 15 positions the electron beam in a predetermined sub-deflection area in the sample 2, that is, positions the frame area 52. Further, the sub deflector driver 16 positions the pattern drawing position in the subfield region 53.

  Drawing with the electron beam on the sample 2 moves the stage 3 in one direction, scans and irradiates the electron beam on the sample 2, and thereby draws the pattern in the subfield region 53.

  Next, drawing control by the control computer 20 will be described. The control computer 20 reads the mask drawing data recorded on the magnetic disk 21 in the storage medium, and the read drawing data is temporarily stored in the pattern memory 22 for each frame region 52.

  Drawing data for each frame region 52 stored in the pattern memory 22 is formed, and a blanking circuit 25, a beam shaper driver 26, and a main deflector are passed through a pattern data decoder 23 and a drawing data decoder 24 which are data analysis units. It is sent to the driver 27 and the sub deflector driver 28.

  The pattern data decoder 23 creates blanking data based on the drawing data sent from the data development unit 30 and sends this blanking data to the blanking circuit 25. Further, desired beam shape data is created based on the drawing data, and this beam shape data is sent to the beam shaper driver 26.

  In the beam shaper driver 26, a predetermined deflection signal is applied to the beam size varying deflector 14 of the optical system 10, and thereby the size of the electron beam is controlled.

  The drawing data decoder 24 creates subfield positioning data based on the drawing data, and sends this subfield positioning data to the main deflector driver 27. Thereafter, a predetermined deflection signal is applied from the main deflector driver 27 to the main deflector 15, whereby the electron beam is deflected and scanned to a predetermined subfield position.

  The drawing data decoder 24 generates a scanning control signal for the sub deflector 16 based on the drawing data, and sends the control signal to the sub deflector driver 28. Then, a predetermined sub-deflection signal is applied from the sub-deflector driver 28 to the sub-deflector 16, thereby drawing in the sub-field region 53.

  Thus, in the present embodiment, the reflectance from the sample 2 can be increased without depending on the film thickness of the photoresist, so that the height position of the sample 2 can be accurately grasped. . Thereby, the irradiation position of the electron beam can be accurately grasped, and drawing with a fine electron beam can be performed accurately. Therefore, a fine pattern can be formed in the mask manufactured thereby.

[Manufacturing method of mask]
Next, a method for manufacturing an exposure mask will be described with reference to FIG. In the exposure mask, a light blocking film that blocks exposure light is formed on a substrate that transmits exposure light, such as glass.

  Specifically, as shown in FIG. 11A, a light blocking layer 82 made of chromium (Cr) or chromium oxide is formed on a glass substrate 81, but a resist 83 is applied on the light blocking layer 82. With respect to the sample that has been formed, only a predetermined region is drawn with an electron beam to be exposed. The specific method is as described above.

  Thereafter, as shown in FIG. 11B, by developing the sample, the resist in the region that transmits light is removed and the resist in the region that blocks light remains when the sample is completed as a mask. A resist pattern 83 a is formed on the light blocking layer 82.

  Thereafter, as shown in FIG. 11C, the light blocking film 82 made of Cr (chromium), chromium oxide or the like in the region where the resist is removed is removed by RIE (Reactive Ion Etching). A pattern 82a is formed.

  Thereafter, as shown in FIG. 11D, the resist pattern 83a is removed with an organic solvent or the like, thereby completing an exposure mask in which a pattern 82a made of a light blocking layer is formed on the glass substrate 81. .

  In this way, a fine pattern exposure mask can be formed.

  As described above, the electron beam drawing apparatus and the electron beam drawing method according to the present invention have been described in detail in the embodiments. However, the present invention is not limited to the above-described embodiments, and can take other forms. is there.

Configuration diagram of electron beam lithography apparatus in the present embodiment Schematic diagram of electron beam writing method in the present embodiment Optical path diagram of optical height detector in the present embodiment Conceptual diagram of height detection in the optical height detector in the present embodiment Relationship between mask surface and electron beam (1) Relationship between mask surface and electron beam (2) Top view of stage of electron beam lithography system Sectional drawing of the element for height calibration in this Embodiment Sectional drawing of the element for another height calibration in this Embodiment Relationship between reflectance of mask and calibration element (calibration step) Process drawing of the manufacturing method of the mask in this Embodiment

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Sample chamber, 2 ... Sample (mask), 3 ... Stage, 4 ... Stage drive circuit, 5 ... Position circuit, 6 ... Electron gun, 7, 8, 9, DESCRIPTION OF SYMBOLS 11, 12 ... Various lenses, 10 ... Optical system, 13 ... Blanking deflector, 14 ... Beam size variable deflector, 15 ... Main deflector, 16 ... Sub Deflectors 17, 18 ... Aperture for beam shaping, 20 ... Control computer, 21 ... Magnetic disk, 22 ... Pattern memory, 23 ... Pattern data decoder, 24 ... Drawing data decoder 25 ... Blanking circuit, 26 ... Beam shaping driver, 27 ... Main deflection driver, 28 ... Sub deflection driver, 30 ... Data development unit

Claims (6)

An electron beam drawing apparatus for drawing a pattern on a sample surface fixed to a stage by deflecting an electron beam with a deflector,
A light source for setting the height position of the sample;
An optical system for irradiating the surface of the sample with light emitted from the light source;
A detector for detecting a height position of the sample by a light receiving position of light reflected from the surface of the sample comprising a light receiving element;
A height calibration element provided on the stage and having a step for performing height correction of the sample surface by reflecting light from the light source;
With
The electron beam drawing apparatus, wherein the height calibration element is made of a metal material having a reflectance of 30% to 60% with respect to the wavelength of the light source. An electron beam drawing apparatus for drawing a pattern on a sample surface fixed to a stage by deflecting an electron beam with a deflector,
A light source for setting the height position of the sample;
An optical system for irradiating the surface of the sample with light emitted from the light source;
A detector for detecting a height position of the sample from a light receiving position of light reflected from the surface of the sample comprising a light receiving element;
A height calibration element provided on the stage and having a step for performing height correction of the sample surface by reflecting light from the light source;
With
The height calibration element is formed by depositing a metal material having a reflectivity of 30% to 60% with respect to the wavelength of the light source on a stepped substrate. Electron beam drawing device.   The electron beam drawing apparatus according to claim 1, wherein the metal material is chromium or chromium oxide.   3. The electron beam drawing apparatus according to claim 1, wherein the metal material is the same material as the metal material formed on the surface of the sample. An electron beam drawing apparatus for drawing a pattern on a sample surface fixed to a stage by deflecting an electron beam with a deflector,
A light source for setting the height position of the sample;
An optical system for irradiating the surface of the sample with light emitted from the light source;
A detector comprising a light receiving element, and detecting a height position of the sample by a light receiving position of light reflected from the surface of the sample;
A height calibration element provided on the stage and having a step for performing height correction of the sample surface by reflecting light from the light source;
With
The height calibrating element is obtained by forming a dielectric multilayer film having a reflectance of 30% to 60% with respect to the wavelength of the light source on a stepped substrate. Beam drawing device. 6. An electron beam drawing apparatus according to claim 1, wherein a light-blocking film is formed on a surface of a glass substrate, and a sample coated with a resist that is exposed to an electron beam is applied to the light-blocking film. Exposing the resist by drawing an electron beam with
Developing after exposing the resist;
After the development, a step of removing the light blocking film in the region where the resist has been removed by etching;
Removing the resist after the etching;
A method for producing a mask for exposure, comprising:

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