JP3576685B2 - Exposure apparatus and device manufacturing method using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure apparatus and a method of manufacturing a device using the same. For example, a so-called stepper, which is an apparatus for manufacturing various devices such as an IC, an LSI, a CCD, a liquid crystal panel, and a magnetic head, is illuminated with exposure light from light source means. A circuit pattern on an original plate (hereinafter, referred to as a “reticle”) such as a photomask or a reticle is projected and transferred onto a wafer surface coated with a photosensitive agent, which is suitable for manufacturing a device.
[0002]
[Prior art]
In recent semiconductor device manufacturing techniques, various attempts have been made to change the exposure wavelength from g-line to i-line and improve the resolving power by an exposure method using an ultra-high pressure mercury lamp. Also, various methods have been proposed for improving the resolving power by using pulse light of a shorter wavelength represented by an excimer laser.
[0003]
Means for reducing the resolution line width as an exposure apparatus (method) include increasing the NA and shortening the wavelength. As the NA increases, the resolution line width decreases in inverse proportion to NA, but at the same time, the depth of focus further decreases in inverse proportion to the square of NA. Since it is desirable to have a large depth of focus, there is naturally a limit in increasing the NA.
[0004]
On the other hand, the present applicant changes the illumination method on the reticle surface in various ways, that is, by changing the light intensity distribution (effective light source distribution) of the zero-order light formed on the pupil plane of the projection optical system. For example, Japanese Patent Application Laid-Open Nos. 4-267515 and 5-47628 propose an exposure method with a higher resolution and a projection exposure apparatus using the same.
[0005]
The illumination methods proposed in these are called so-called oblique incidence illumination, and among them, annular illumination and quadrupole illumination are particularly well known. In the annular illumination method (annular), an effective light source shape having a donut shape 111 as shown in FIG. 11 is provided on a pupil plane of the projection optical system. This is a technique for improving the resolving power by cutting off light near the center of the effective light source that does not contribute to image formation with a narrow line width using a diaphragm or the like. As shown in FIG. 12, the quadrupole illumination includes four effective light sources 121 to 124 having predetermined intensities at circumferential positions having a predetermined radius around the optical axis Sa on the pupil plane of the projection optical system. Have. By cutting the light in the cross-shaped region 125 in addition to the light near the center of the effective light source, the resolution and depth of focus of the pattern in the vertical and horizontal directions are dramatically improved. Generally, circuit patterns of ICs and LSIs are mostly constituted by figures having sides in vertical and horizontal directions, and there are few patterns having sides in oblique directions. Therefore, such an illumination method is particularly effective.
[0006]
[Problems to be solved by the invention]
The modified illumination method (oblique incidence illumination method) has the feature that the resolution can be increased or the depth of focus can be made relatively long, but it has the following problems.
・ Easy patterns stick together.
・ Isolated patterns tend to be thin.
・ Illuminance is lower than normal illumination.
-There are restrictions on pattern density and directionality. In particular, quadrupole illumination has a low resolution of oblique patterns.
[0007]
In order to solve these problems, the applicant of the present invention disclosed in Japanese Patent Application Laid-Open No. 5-47639 a method of adding a certain amount of light near the center of the effective light source and in a cross-shaped area to the effective light source distribution of the quadrupole illumination, so An illumination method for forming an effective light source similar to a quadrupole is proposed.
[0008]
FIG. 13 is a schematic diagram of the shape of the effective light source at this time. This illumination method (hereinafter, referred to as “illumination method A”) hardly has the disadvantages of the modified illumination, and has a depth of focus that is higher than that of the normal illumination as shown in FIG. Has gained depth of focus. In this illumination method A, the illuminance near the center of the effective light source is about 10 to 40% of the peak light intensity, and the illuminance between the peaks (peak-to-peak illuminance) is 35 to 65% of the peak. The degree and the position of the peak (the distance from the center of the effective light source to the peak) are about 0.5 to 0.6, and good results are obtained.
[0009]
The above-mentioned illumination method A by the present applicant uses an incoherent optical system in which an excimer laser is used as a light source, a light beam is once divided into a plurality of light beams, and then superimposed again.
[0010]
The present invention further improves the above-described illumination method A by the present applicant, and particularly simplifies the entire illumination optical system and effectively uses the illumination light flux when using a light source means that emits incoherent light such as an ultra-high pressure mercury lamp. An object of the present invention is to provide an exposure apparatus capable of appropriately illuminating a pattern on a reticle surface (on one original plate) while easily utilizing the same so as to easily obtain a high resolution, and a method of manufacturing a device using the same.
[0011]
[Means for Solving the Problems]
The exposure apparatus according to claim 1 is
Exposure for guiding a light beam from a light source means to an optical integrator via an optical system, illuminating a pattern on an original plate surface with a light beam from an emission surface of the optical integrator, and projecting the pattern onto a substrate by a projection optical system In the device,
In front of the entrance surface of the optical integrator, having a stop means movable in the optical axis direction having a specific aperture shape,
A light intensity distribution of a predetermined value is provided in a central area on the pupil plane of the projection optical system by the aperture means, and a light intensity distribution of a predetermined value is provided at a plurality of equally spaced positions in the circumferential direction around the central area. It is characterized in that an effective light source having a distribution is formed.
[0012]
The invention of claim 2 is the invention according to claim 1,
The aperture means is detachable from the optical path.
[0013]
The invention according to claim 3 is the invention according to claim 1,
The optical system has an optical unit whose focal length can be changed.
[0014]
The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The optical system is characterized in that the light emitting surface of the light source means and the incident surface of the optical integrator have a substantially conjugate relationship.
[0015]
The method for manufacturing a device according to the invention of claim 5 includes:
A device is manufactured by exposing a wafer using the exposure apparatus according to any one of claims 1 to 4 , and developing the exposed wafer.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic configuration diagram showing a first embodiment of an exposure apparatus of the present invention, and is an example in which the present invention is applied to a reduction-type projection exposure apparatus called a so-called stepper.
[0022]
In FIG. 1, reference numeral 1 denotes a light source (light source means) such as a high-intensity ultra-high pressure mercury lamp which emits ultraviolet light, far ultraviolet light, or the like, and its light emitting portion 1a is arranged near the first focal point of the elliptical mirror 2. The light emitted from the light source 1 is condensed by the elliptical mirror 2 and forms an image (light emitting unit image) 1b of the light emitting unit 1a near the second focal point 2a of the elliptical mirror 2.
[0023]
Reference numeral 3 denotes an optical system, which has two lens systems, a lens system (first condenser lens) 3a and a lens system (second condenser lens) 3C, and emits a light-emitting part image 1b formed near the second focal point 2a. An image is formed on an incident surface 4a of the optical integrator 4 via an optical element 3b described later. The optical element 3b is formed of a quadrangular pyramid prism that can be inserted and removed from the optical path, and deflects the incident light beam in a predetermined direction.
[0024]
The lens system 3c is composed of a zoom lens (optical means) that can be inserted into and removed from the optical path and is interchangeable with another lens system having a different focal length or a variable focal length. The optical system 3 is telecentric on the emission side. The optical element 3b is located near the pupil plane of the optical system 3.
[0025]
The optical integrator 4 is configured by two-dimensionally arranging a plurality of microlenses, and forms a secondary light source near the exit surface 4b. Reference numeral 5 denotes a mirror for bending the optical path.
[0026]
Reference numeral 6 denotes a lens system which collects a light beam from the exit surface 4b of the optical integrator 4 via a mirror 5 and illuminates a reticle (original plate) 7 which is a surface to be irradiated placed on a reticle stage.
[0027]
Reference numeral 8 denotes a projection optical system, which reduces and projects a pattern drawn on the reticle 7 onto a wafer (substrate) 9 surface mounted on a wafer chuck. In the present embodiment, the secondary light source near the exit surface 4b of the optical integrator 4 is formed by the lens system 6 near the pupil 8a of the projection optical system 8.
[0028]
The exit surface 4b and the reticle surface 7 of the optical integrator 4 have a relationship between an image and a pupil. The light intensity distribution on the optical integrator 4 on the reticle 7 surface corresponds to the intensity distribution characteristics depending on the angle of the light beam.
[0029]
Therefore, in the present embodiment, the prism of the optical element 3b is selectively switched into the optical path according to the directionality of the pattern of the reticle 7, the resolution line width, and the like, and the focal length of the lens system 3c is changed as necessary. I have. As a result, various oblique incidence illuminations are created by changing the light intensity distribution of the secondary light source image formed on the pupil plane 8a of the projection optical system 8, and projection exposure capable of high resolution is performed.
[0030]
Next, in the present embodiment, the light intensity distribution on the entrance surface 4a of the optical integrator 4 is changed by using the optical element 3b and the lens system 3c, and the secondary light source image formed on the pupil plane 8a of the projection optical system 8 A method for changing the light intensity distribution of the first embodiment will be described.
[0031]
In the present embodiment, on the pupil plane 8a of the projection optical system 8, an effective light source having a predetermined intensity is provided in the vicinity of the center of the optical axis, and a plurality of positions at equal intervals in the circumferential direction having a predetermined radius around the optical axis. The reticle 7 is illuminated on the reticle 7 with a plurality of (four) effective light sources (quadrupole illumination) having a predetermined intensity, thereby achieving the illumination method A.
[0032]
In order to obtain the illumination method A in the present embodiment, an optical element 3b composed of a quadrangular pyramid prism is inserted between the light source 1 and the optical integrator 4 at a position where the optical integrator 4 has a pupil relationship, and thereby the light beam And the focal length of the lens system 3c is changed to adjust the illuminance distribution on the entrance surface 4a (exit surface 3b) of the optical integrator 4.
[0033]
FIG. 2 shows an optical element 3b provided between the lens system 3a and the optical integrator 4 and a lens system 3c in this embodiment, which are constituted by a zoom lens or an interchangeable lens system, and whose focal lengths are variously changed. FIG. 4 is an explanatory diagram of a light path at that time and a light intensity distribution (illuminance distribution) formed on an incident surface 4a (exit surface 4b) of the optical integrator 4.
[0034]
In the present embodiment, the light intensity distribution on the exit surface 4b of the optical integrator 4 is changed, and the light intensity distribution on the pupil plane 8a of the projection optical system 8 having a conjugate relationship therewith is changed. The lens system 3c enlarges and reduces the secondary light source image formed on the exit surface 4b of the optical integrator 4 by zooming.
[0035]
FIG. 2A shows a state of normal illumination in which the optical element (prism) 3b is not inserted. Since the light source 1 and the incident surface 4a of the optical integrator 4 have a substantially conjugate relationship, the luminance distribution of the light source 1 is imaged on the optical integrator 4 as an image, which is the illuminance distribution as it is. Since the luminance distribution of the light source 1 is usually represented by a Gaussian distribution, a light intensity distribution having a Gaussian distribution shape having a peak at the center is obtained on the optical integrator 4.
[0036]
FIG. 2B shows that the image of the light source formed on the optical integrator 4 can be enlarged or reduced by adjusting the focal length of the lens system 3c.
[0037]
FIG. 2C shows a state in which the prism 3b1 having a pyramid shape is inserted at a position that becomes a pupil with respect to the optical integrator 4 in the state of FIG. In this state, the light beam is bent at each surface of the quadrangular pyramid, and four light intensity peaks appear on the optical integrator 4. Also in this case, similarly to FIG. 2A, each peak has a Gaussian distribution shape.
[0038]
That is, since the tails of the respective Gaussian distributions are overlapped, the light intensity is not zero even near the center of the effective light source and in the region between the peaks. In such an effective light source shape, the illumination system A is configured by adjusting the position of the peak (the distance from the center of the peak), the illuminance at the center, and the illuminance between the peaks to appropriate values.
[0039]
In the present embodiment, the angle of the prism is changed to adjust the illuminance between the center and the peak. FIG. 2D shows a state in which the prism 3b2 having a smaller angle (a lower height from the bottom surface to the vertex) is installed. When prisms having different angles are provided, the angle at which the light beam is bent changes, and the distance between the light intensity peaks changes (however, the shape of each peak is substantially constant). Then, the degree of overlap of the base of each peak changes, that is, the illuminance between the effective light source center and the peak also changes. For example, comparing FIG. 2 (C) and FIG. 2 (D), the center illuminance and the inter-peak illuminance are higher in FIG. 2 (D) since the distance between the peaks of the intensity distribution is shorter.
[0040]
In the present embodiment, an illuminance value between the center and the peak is appropriately obtained by disposing a prism having an appropriate angle as an optical element by utilizing such a property.
[0041]
Next, the zoom mechanism of the lens system 3c is used to adjust the position of the peak. By adjusting the lens system 3c, the distance from the center of the Gaussian distribution peak is changed with almost no change in the illuminance at the center and the illuminance between the peaks as shown in FIG.
[0042]
FIG. 2F shows a state in which a prism 3b3 having an octagonal pyramid shape, a shape obtained by cutting off the ridges and apex angles, or a shape similar thereto is used as the optical element.
[0043]
As the shape of the prism, for example, the shape shown in FIG. The illumination system A can also be configured using a prism having such a shape.
[0044]
In this case, the center illuminance and the peak-to-peak illuminance are not adjusted according to the degree of overlap of the skirts of the light intensity peaks as in the case of the above-described quadrangular pyramid-shaped prism. Independent peaks are created separately from the two peaks, and each intensity is adjusted according to its intensity. Each peak is formed by a light beam that is bent on each surface of the substantially octagonal pyramid. That is, each surface of the substantially octagonal pyramid corresponds to each light intensity peak on the optical integrator 4. The intensity of each peak is determined by the amount of light passing through that surface. In this case, the effective light source shape is determined by the area ratio of each surface of the prism and the illuminance distribution in the direction perpendicular to the optical axis at the place where the prism is inserted.
[0045]
In the present embodiment, the central illuminance and the peak-to-peak illuminance are set within appropriate values by selecting a prism having an appropriate shape and setting the amount of light passing through the surface to an appropriate value.
[0046]
As described above, in this embodiment, a polygonal pyramid prism such as a quadrangular pyramid-shaped prism or an octagonal pyramid-shaped prism is used as an optical element, and the focal length of the lens system 3c is changed so that a desired shape can be obtained on the pupil plane of the projection optical system. Illumination system A having the following illuminance distribution. In addition, since the prism as the optical element in the present embodiment can be inserted into and removed from the optical path, it can be easily switched to another illumination method, for example, normal illumination or annular illumination.
[0047]
As a method of fine adjustment when a desired center illuminance and peak-to-peak illuminance cannot be obtained even when a prism is used, a means for moving the light source position in the optical axis direction may be provided. By moving the light source in the direction of the optical axis, the luminance distribution can be changed, and the shape of the Gaussian distribution (for example, half-value width) can be changed, so that the center illuminance and the peak-to-peak illuminance may be adjusted accordingly.
[0048]
Next, a second embodiment of the present invention will be described. The present embodiment is different from the first embodiment in that the illumination system A is configured using a transmittance control unit having a partially different transmittance instead of a prism as an optical element. Is the same.
[0049]
In the present embodiment, an ND filter having a transmittance distribution partially different from the optical path and having a transmittance different from that of the optical integrator 4 shown in FIG. Make up. Normally, the illuminance distribution on the optical integrator 4 has a Gaussian distribution shape or a uniform shape. The illuminance distribution of the illumination system A is created by controlling the transmittance of the Gaussian distribution shape. At this time, the transmittance distribution shape of the ND filter 41 is, for example, as shown in FIG.
[0050]
The numerical value in FIG. 4B represents the transmittance (%). FIG. 4 (A) shows a Gaussian distribution illuminance distribution on the optical integrator 4. By using an ND filter 41 having a transmittance distribution as shown in FIG. 4B together with such an illuminance distribution, the illuminance distribution as shown in FIG. Forming a light source.
[0051]
The transmission region of the ND filter 41 in the present embodiment is mainly divided into nine regions, each having a shape having a unique transmittance. However, the transmittance changes continuously. No problem. In addition, even when the original shape of the effective light source is not Gaussian distribution, it can be dealt with by changing the transmittance distribution of the ND filter 41 to another shape. Since this filter can also be inserted and removed from the optical path, it is possible to easily switch between other illumination methods, for example, normal illumination and annular illumination. The filter may be inserted immediately before the entrance surface of the optical integrator 4.
[0052]
Next, a third embodiment of the present invention will be described. In the present embodiment, as compared with the first embodiment of FIG. 1, instead of a prism as an optical element, an adjusting means for adjusting an aperture diameter and a transmission intensity for at least one of each microlens constituting an optical integrator is provided. The difference is that the illumination system A is configured using the same, and the other configurations are the same.
[0053]
The optical integrator 4 generally has a configuration in which a plurality of microlenses 51 are two-dimensionally arranged and combined as shown in FIG. In the present embodiment, the amount of light emitted from each of the microlenses 51 constituting the optical integrator 4 is individually adjusted by adjusting means, and as a result, the illuminance distribution of the entire optical integrator 4 has the shape of the illumination system A.
[0054]
In the present embodiment, for example, a filter 61 that can be inserted into and removed from the optical path as shown in FIG. 6 is disposed immediately after the exit surface 4b of the optical integrator 4 in FIG. The filter 61 in FIG. 6 has a large aperture area at the position where the four peaks should be located in the illumination system A, and has a small aperture area near the center of the effective light source and between the peaks. Naturally, the light amount from a large opening area is large, and the light amount from a small opening area is small. By installing this filter 61 on the optical integrator 61, the illuminance distribution of the illumination system A is obtained.
[0055]
Also in this case, regardless of the original shape of the effective light source, the effective light source of the illumination system A can be obtained by adjusting the size of each opening area. The shape of the opening is not limited to a rectangle, but may be any shape. Also in this case, since this filter can be inserted and removed from the optical path, it is possible to easily switch between other illumination methods, for example, normal illumination and annular illumination. The filter may be inserted immediately before the entrance surface of the optical integrator.
[0056]
FIG. 7 is a schematic view of a main part of a part of an optical system according to Embodiment 4 of the present invention. In this embodiment, as compared with the first embodiment of FIG. 1, instead of a prism as an optical element, an aperture stop 71 having openings at four corners as shown in FIG. The difference is that the system A is configured, and the other configurations are the same.
[0057]
In the present embodiment, an aperture stop 71 having a specific aperture shape is disposed at a certain distance in front of the optical integrator 4. As the shape of the aperture stop 71, one having a cross-shaped light shielding region as shown in FIG. 8 is used.
[0058]
In the present embodiment, the aperture stop 71 is disposed not immediately before the entrance surface 4a of the optical integrator 4 but at a small distance. If it is placed immediately before, the cross-shaped portion 72 is completely shielded from light, but if it is installed at a distance, the illuminance of the central portion will not be zero due to the light that wraps around. A means for moving the aperture stop 71 in the optical axis direction is provided so that the aperture stop is moved in the optical axis direction to adjust the center illuminance and the peak-to-peak illuminance.
[0059]
Other suitable places for disposing the aperture stop 71 include the vicinity of the second focal plane 2 a of the elliptical mirror 2. Since the second focal plane 2a of the elliptical mirror and the entrance plane 4a of the optical integrator 4 have a substantially conjugate relationship, the image of the aperture stop 71 placed on the second focal plane 2a of the elliptical mirror 2 is formed on the optical integrator 4. Is done. At this time, similarly, by moving the aperture stop 71 in the optical axis direction, the image on the optical integrator 4 is blurred, so that the center illuminance and the peak-to-peak illuminance are adjusted.
[0060]
In the present invention, the methods of the above embodiments may be used in combination with each other, or may be used in combination with each other. Further, in the first to fourth embodiments, in addition to the exposure apparatus using i-line, the present invention can be similarly applied to an exposure apparatus using g-line or KrF line.
[0061]
Next, an embodiment of a method of manufacturing a semiconductor device using the above-described projection exposure apparatus will be described.
[0062]
FIG. 9 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).
[0063]
In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.
[0064]
On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is referred to as a preprocess, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer.
[0065]
The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including.
[0066]
In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).
[0067]
FIG. 10 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface.
[0068]
Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed on the wafer by exposure using the above-described exposure apparatus.
[0069]
Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist removal), the resist which has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.
[0070]
By using the manufacturing method according to the present embodiment, it is possible to easily manufacture a highly integrated semiconductor device which has been conventionally difficult to manufacture.
[0071]
【The invention's effect】
According to the present invention, by setting each element as described above, the simplification of the entire illumination optical system and the effective use of the illumination light flux when using a light source means that emits incoherent light, such as an ultra-high pressure mercury lamp, are used. Exposure apparatus that appropriately illuminates the pattern on the reticle surface (on one original plate) while easily achieving high resolution can be achieved, and a device manufacturing method using the same can be achieved.
[0072]
In particular, it is possible to improve the high resolution and the depth of focus with almost no problems caused by the oblique incidence illumination.
[Brief description of the drawings]
FIG. 1 is a schematic view of a main part of a first embodiment of the present invention. FIG. 2 is an explanatory diagram of a part of an optical path in FIG. 1 and a light intensity distribution on an optical integrator. FIG. 3 is an explanatory diagram of an optical element according to the present invention. FIG. 4 is an explanatory view of a transmittance control means according to the present invention. FIG. 5 is an explanatory view of an optical integrator. FIG. 6 is an explanatory view of an adjusting means according to the present invention. FIG. 8 is an explanatory view of a narrowing means according to Embodiment 4 of the present invention. FIG. 9 is a flowchart of a device manufacturing method of the present invention. FIG. 10 is a flowchart of a device manufacturing method of the present invention. FIG. 12 is an explanatory diagram of an effective light source image in illumination. FIG. 12 is an explanatory diagram of an effective light source image in quadrupole illumination. FIG. 13 is an explanatory diagram of an effective light source image in oblique incident illumination. Explanatory diagram with depth of focus
Reference Signs List 1 light source means 2 elliptical mirror 3 optical system 3a lens system 3b, 3b1, 3b2, 3b3 optical element 3c optical means 4 optical integrator 5 mirror 6 lens system 7 reticle (original plate)
8 Projection optical system 9 Substrate (wafer)
41 transmittance control means 61 adjusting means 71 aperture means

Claims (5)

Exposure for guiding a light beam from a light source means to an optical integrator via an optical system, illuminating a pattern on an original plate surface with a light beam from an emission surface of the optical integrator, and projecting the pattern onto a substrate by a projection optical system In the device,
In front of the entrance surface of the optical integrator, having a stop means movable in the optical axis direction having a specific aperture shape,
A light intensity distribution of a predetermined value is provided in a central area on the pupil plane of the projection optical system by the aperture means, and a light intensity distribution of a predetermined value is provided at a plurality of equally spaced positions in the circumferential direction around the central area. An exposure apparatus for forming an effective light source having a distribution. 2. An exposure apparatus according to claim 1 , wherein said stop means is detachable from an optical path. 2. An exposure apparatus according to claim 1 , wherein said optical system has an optical unit whose focal length can be converted. Wherein the optical system exposure apparatus according to any one of claims 1 to 3, and the light emitting surface and the incident surface of the optical integrator is characterized in that as a substantially conjugate relationship of the light source means. A device manufacturing method characterized by claim exposing the wafer from claim 1 by using the exposure apparatus according to any one of 4, and manufacturing a device by developing the wafer the exposed light.

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