JP6780441B2 - Charged particle beam drawing device and charged particle beam drawing method - Google Patents

Description

The present invention relates to a charged particle beam drawing apparatus and a charged particle beam drawing method.

With the increasing integration of LSIs, the circuit line width of semiconductor devices has been miniaturized year by year. In order to form a desired circuit pattern on a semiconductor device, a high-precision original image pattern formed on quartz using a reduction projection type exposure device (a mask, or one used especially in a stepper or a scanner is also called a reticle). ) Is reduced and transferred onto the wafer. The high-precision original image pattern is drawn by an electron beam drawing apparatus, and so-called electron beam lithography technology is used.

In the conventional electron beam drawing device, while moving the stage on which the substrate to be drawn is placed, the electron beam is deflected based on the stage position, and the electron beam is irradiated to a desired position on the substrate to draw a pattern. ing.

A laser interferometer is used to measure the position of the stage. The laser interferometer has a plurality of optical components such as a polarizing beam splitter, a λ / 4 plate, and a reflector. When the laser light is incident on the polarizing beam splitter, it is divided into measurement light (measurement light) toward the stage and reference light toward the reflector. The measurement light reflected by the stage and the reference light reflected by the reflector are combined by the polarizing beam splitter to become interference light. The stage position is measured from the interference fringes generated by the optical path difference between the measurement light and the reference light.

When the wavelength of the laser beam fluctuates, a measurement error of the stage position occurs. Therefore, in the laser oscillator, control is performed to stabilize the output, but it is extremely difficult to completely eliminate the wavelength fluctuation. With the recent miniaturization of patterns, this error becomes non-negligible, and there is a risk that the drawing accuracy may be lowered.

JP-A-2009-218248 Japanese Unexamined Patent Publication No. 5-315221 Jitsufuku No. 7-16982 JP-A-2015-75461 Japanese Unexamined Patent Publication No. 7-167607 Japanese Unexamined Patent Publication No. 2010-56390

An object of the present invention is to provide a charged particle beam drawing apparatus and a charged particle beam drawing method capable of accurately measuring the stage position and preventing a decrease in drawing accuracy.

The charged particle beam drawing apparatus according to one aspect of the present invention includes a drawing chamber in which a movable stage on which a sample is placed is installed, a laser source that outputs laser light, and a branch portion that branches the laser light. , The laser interferometer that measures the position of the stage using the laser light branched by the branch portion, the wavelength fluctuation detection unit that detects the wavelength fluctuation of the laser light, and the sample are irradiated with a charged particle beam. A drawing unit for drawing a pattern and a drawing control unit for controlling the drawing unit are provided, and the wavelength fluctuation detection unit uses the laser light branched by the branching unit as a first laser light and a second laser light. The beam splitter, the reflector arranged in the drawing chamber, and the first laser light are separated into the first measurement light and the first reference light, and the second laser light is separated into the second measurement light and the second measurement light. A first measurement light that reciprocates m times (m is an integer of 1 or more) between the polarized beam splitter and the reflecting mirror, and the first reference light that are combined with the polarized beam splitter that separates the reference light. The second measurement light and the second reference light that detect one composite light, output a first beat signal, and reciprocate between the polarization beam splitter and the reflector n times (n is an integer larger than m). It has a detector that detects the second synthesized light obtained by combining the above and outputs the second beat signal, and the drawing control unit measures the length from the difference between the first beat signal and the second beat signal. The fluctuation is calculated, and the wavelength of the laser light is calculated based on the length measurement fluctuation, the optical path difference between the first measurement light and the first reference light, and the optical path difference between the second measurement light and the second reference light. It is characterized in that a fluctuation coefficient is calculated, the position information of the stage measured by the laser interferometer is corrected by using the wavelength fluctuation coefficient, and the drawing unit is controlled based on the corrected stage position information. It is a thing.

In the charged particle beam drawing apparatus according to one aspect of the present invention, the detector synthesizes the first measurement light and the first reference light that make one round trip between the polarization beam splitter and the reflector. The second composition in which the first beat signal is output by detecting the first composite light, and the second measurement light and the second reference light that make two reciprocations between the polarization beam splitter and the reflector are combined. It is characterized in that it detects light and outputs the second beat signal.

In the charged particle beam drawing apparatus according to one aspect of the present invention, the stage can move in the first direction and the second direction orthogonal to the first direction, and the stage position in the first direction is measured. The laser interferometer and the second laser interferometer for measuring the stage position in the second direction are provided, and the laser source, the branch portion, and the wavelength fluctuation detection unit are the first laser. It is characterized in that it is provided corresponding to each of the interferometer and the second laser interferometer.

In the charged particle beam drawing device according to one aspect of the present invention, the stage can move in the first direction and the second direction orthogonal to the first direction, and the stage position in the first direction is measured. The laser interferometer and the second laser interferometer for measuring the stage position in the second direction are provided, and the first laser interferometer and the second laser interferometer are the same laser source. It is characterized in that measurement is performed using the laser beam output from.

The charged particle beam drawing method according to one aspect of the present invention includes a step of branching the laser light output from the laser source and a position of a stage in which the laser interferometer is installed in the drawing room by using the branched laser light. The step of separating the branched laser light into the first laser light and the second laser light, and the step of separating the first laser light into the first measurement light and the first reference light by the polarizing beam splitter. Then, between the step of separating the second laser beam into the second measurement light and the second reference light and the polarizing beam splitter and the reflector arranged in the drawing chamber m times (m is an integer of 1 or more). ) N times between the step of detecting the first synthesized light obtained by combining the reciprocating first measurement light and the first reference light and outputting the first beat signal, and the polarization beam splitter and the reflecting mirror. (N is an integer larger than m) A step of detecting a second synthesized light obtained by combining the reciprocating second measurement light and the second reference light and outputting a second beat signal, and the first beat signal and the above. The length measurement variation is calculated from the difference from the second beat signal, and the length measurement variation, the optical path difference between the first measurement light and the first reference light, and the second measurement light and the second reference light A step of calculating the wavelength fluctuation coefficient of the laser beam based on the optical path difference , a step of correcting the position information of the stage measured by the laser interferometer using the wavelength fluctuation coefficient, and a stage position after correction. Based on the information, the sample placed on the stage is irradiated with a charged particle beam to draw a pattern.

According to the present invention, since the fluctuation amount of the laser wavelength is detected and the length measurement error is corrected, the stage position can be measured with high accuracy and the deterioration of drawing accuracy can be prevented.

It is the schematic of the electron beam drawing apparatus which concerns on embodiment of this invention. It is the schematic of the stage and the laser interferometer which concerns on this embodiment. It is the schematic of the laser interferometer which concerns on the same embodiment. It is a figure which shows the optical path of a laser beam. It is a figure which shows the optical path of a laser beam.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of an electron beam drawing apparatus according to an embodiment of the present invention. The drawing device 1 shown in FIG. 1 is a variable molding type including a drawing unit 2 that irradiates a substrate W to be drawn with an electron beam to draw a desired pattern, and a control unit 3 that controls the operation of the drawing unit 2. It is a drawing device of.

The drawing unit 2 has a drawing chamber 2a for accommodating the sample W to be drawn, and an optical lens barrel 2b connected to the drawing chamber 2a. The optical lens barrel 2b is provided on the upper surface of the drawing chamber 2a, and forms and deflects an electron beam to irradiate the sample W in the drawing chamber 2a. The inside of the drawing chamber 2a and the optical lens barrel 2b is decompressed and is in a vacuum state.

A stage 11 for supporting the sample W is provided in the drawing chamber 2a. The stage 11 can move in the X-axis direction and the Y-axis direction (hereinafter, simply referred to as the X direction and the Y direction) which are orthogonal to each other in the horizontal plane. A sample W such as a mask or a blank is placed on the stage 11. A measuring unit 4 for measuring the position of the stage 11 is provided on the outer periphery of the drawing chamber 2a. The configuration of the measuring unit 4 will be described later.

Inside the optical lens barrel 2b, there are an emission unit 21 such as an electron gun that emits an electron beam B, an illumination lens 22 that concentrates the electron beam B, a first molding aperture 23 for beam shaping, and a projection lens 24. , Molding deflector 25, second molding aperture 26 for beam forming, objective lens 27 for focusing the beam on sample W, sub-deflector 28 and main deflector for controlling the beam shot position with respect to sample W. 29 and are arranged.

In the drawing unit 2, the electron beam B is emitted from the emitting unit 21 and is irradiated to the first molded aperture 23 by the illumination lens 22. The first molded aperture 23 has, for example, a rectangular opening. When the electron beam B passes through the first molded aperture 23, the cross-sectional shape of the electron beam is formed into a rectangular shape and projected onto the second molded aperture 26 by the projection lens 24. The projection position can be deflected by the molding deflector 25, and the shape and dimensions of the electron beam B can be controlled by the deflection of the projection position. The electron beam B that has passed through the second molded aperture 26 is focused on the sample W on the stage 11 by the objective lens 27 and irradiated. At this time, the shot position of the electron beam B with respect to the sample W on the stage 11 is deflected by the sub-deflector 28 and the main deflector 29.

The control unit 3 includes a storage unit 3a for storing drawing data, a shot data generation unit 3b for processing drawing data to generate shot data, and a drawing control unit 3c for controlling the drawing unit 2. The shot data generation unit 3b and the drawing control unit 3c may be configured by hardware such as an electric circuit, may be configured by software such as a program that executes each function, or both of them. It may be composed of the combination of.

The drawing data is data converted into a format for the drawing device 1 so that the design data (layout data) created by the designer of the semiconductor integrated circuit can be input to the drawing device 1, and is converted from an external device. It is input to and stored in the storage unit 3a. As the storage unit 3a, for example, a magnetic disk device, a semiconductor disk device (flash memory), or the like can be used.

The above-mentioned design data usually includes a large number of minute patterns (figures, etc.), and the data size is large. If this design data is directly converted to another format, the amount of data after conversion will be further increased. For this reason, in drawing data, the amount of data is compressed by a method such as layering the data or displaying an array of patterns. Such drawing data is data that defines a drawing pattern of a chip area, or a drawing pattern of a virtual chip area that is regarded as one chip by virtually merging a plurality of chip areas under the same drawing conditions. ..

The shot data generation unit 3b divides the drawing pattern defined by the drawing data into a plurality of stripe-shaped (strip-shaped) striped regions (the longitudinal direction is the X direction and the lateral direction is the Y direction), and further. , Divide each stripe area into a large number of matrix-like sub-areas. The shot data generation unit 3b determines the shape, size, position, etc. of the figure in each sub-region, further divides the figure into a plurality of subregions that can be drawn in one shot, and generates shot data. .. The length of the stripe region in the lateral direction (Y direction) is set to a length that allows the electron beam B to be deflected by the main deflection.

When drawing the drawing pattern, the drawing control unit 3c positions the electron beam B in each sub-region by the main deflector 29 while moving the stage 11 in the longitudinal direction (X direction) of the stripe region, and the sub-deflector 28. To draw a figure by shooting at a predetermined position in the sub area. After that, when the drawing of one stripe area is completed, the stage 11 is stepped in the Y direction, the next stripe area is drawn, and this is repeated to draw the entire drawing area of the sample W with the electron beam B. Do. Since the stage 11 is continuously moving in one direction during drawing, the drawing origin of the sub region is tracked by the main deflector 29 so that the drawing origin follows the movement of the stage 11. ..

In this way, the electron beam B is deflected by the sub-deflector 28 and the main deflector 29, and its irradiation position is determined while following the continuously moving stage 11. The drawing time can be shortened by continuously moving the stage 11 in the X direction and making the shot position of the electron beam B follow the movement of the stage 11.

The drawing control unit 3c controls the sub-deflector 28, the main deflector 29, and the like, that is, the beam irradiation position, by using the position information of the stage 11 measured by the meter side unit 4.

Next, the configuration of the total side portion 4 will be described. As shown in FIG. 2, the meter side portions 4 are provided at two locations, and the first meter side portion 4 located on the lower side in FIG. 2 measures the position of the stage 11 in the Y direction. Further, the second total side portion 4 located on the left side in FIG. 2 measures the position of the stage 11 in the X direction. Since these first and second total side portions 4 have the same structure, their common structure will be described below.

The meter side portion 4 includes a laser source 5, a branch portion 6 for branching the laser light emitted from the laser source 5, a length measuring unit 7 for measuring the distance to the stage 11 using the laser light, and a laser beam. It includes a wavelength fluctuation detection unit 8 for detecting wavelength fluctuations. For the laser light, for example, a helium neon laser can be used. For example, a half mirror can be used for the branch portion 6.

The length measuring unit 7 includes a laser interferometer 70 and a light receiving unit 71 that receives the interference light from the laser interferometer 70. For the light receiving unit 71, for example, a photodiode can be used.

One of the laser beams emitted from the laser source 5 and branched at the branch portion 6 is divided by the laser interferometer 70. One of the laser beams divided by the laser interferometer 70 advances to the stage 11. On the other hand, the other of the divided laser beams travels to a mirror (not shown) in the laser interferometer 70. These advanced laser beams are reflected by the stage 11 or the mirror, respectively, return to the laser interferometer 70, and interfere with the laser interferometer 70.

The interfering laser beam is received by the light receiving unit 71, and interference fringes generated due to the optical path difference are observed. The observation result is notified to the drawing control unit 3c. Such measurements are made in both the X and Y directions, the relative distance between the laser interferometer 70 on the first meter side 4 and the stage 11 in the Y direction, and the laser on the second meter side 4. The relative distance between the interferometer 70 and the stage 11 in the X direction is measured, and the position of the stage 11 is grasped from the relative distance information.

The laser interferometer 70 is housed in a storage room R1 formed on the side surface of the drawing room 2a. The laser source 5, the branch portion 6, the light receiving portion 71, and the like are provided outside the housing of the drawing portion 2.

As shown in FIGS. 2 and 3, the wavelength fluctuation detection unit 8 includes a laser interferometer 80, a reflector 88, and a light receiving unit 89 that receives interference light from the laser interferometer 80. The laser interferometer 80 is housed in a storage chamber R2 formed on the side surface of the drawing chamber 2a. The reflector 88 is arranged near the stage 11 in the drawing chamber 2a. The light receiving unit 89 is provided outside the housing of the drawing unit 2, and for example, a photodiode is used.

The laser interferometer 80 includes a beam splitter 81 that splits the other side of the laser beam branched at the branch portion 6, a polarizing beam splitter (PBS) 82, reflectors 83 to 85, and λ / 4 plates 86 and 87.

The laser interferometer 80 observes one-pass type laser interference that makes one round trip with the reflector 88 and two-pass type laser interference that makes two round trips. One laser beam L1 divided by the beam splitter 81 becomes a laser beam for one pass, and the other laser beam L2 becomes a laser beam for two passes. FIG. 3 shows up to the point where the divided laser beams L1 and L2 are incident on the polarizing beam splitter 82 for convenience of explanation.

As shown in FIG. 4, the laser beam L1 is separated into measurement light (length measurement light) and reference light by the polarization separation surface 82a of the polarization beam splitter 82. The reference light is reflected by the polarization separation surface 82a. The measurement light traveling straight on the polarization separation surface 82a is reflected by the reflector 85, reflected by the polarization separation surface 82a, passes through the λ / 4 plate 87, and travels straight toward the reflector 88. The measurement light reflected by the reflector 88 passes through the λ / 4 plate 87 and travels straight on the polarization separation surface 82a. The measurement light and the reference light are combined on the coaxial optical axis. The light receiving unit 89 detects the combined light and outputs a beat signal (first beat signal).

As shown in FIG. 5, the laser beam L2 is separated into the measurement light and the reference light by the polarization separation surface 82a of the polarization beam splitter 82. The reference light reflected by the polarization separation surface 82a is sequentially reflected by the reflectors 83 and 84 and the polarization separation surface 82a.

The measurement light traveling straight on the polarization separation surface 82a is reflected by the reflector 85, reflected by the polarization separation surface 82a, passes through the λ / 4 plate 87, and travels straight toward the reflector 88. The measurement light reflected by the reflector 88 passes through the λ / 4 plate 87 and travels straight on the polarization separation surface 82a. Then, it is reflected by the reflecting mirrors 83 and 84, goes straight on the polarization separation surface 82a, passes through the λ / 4 plate 87, and goes straight toward the reflecting mirror 88. The measurement light reflected again by the reflector 88 passes through the λ / 4 plate 87, is reflected by the polarization separation surface 82a, is reflected by the reflector 85, passes through the deflection separation surface 82a, and the measurement light and the reference light are coaxial. Synthesize on the optical axis. The light receiving unit 89 detects the combined light and outputs a beat signal (second beat signal).

The drawing control unit 3c acquires the first beat signal and the second beat signal output from the light receiving unit 89, and calculates the length measurement variation Δx from the difference between the two beat signals. This length measurement variation Δx indicates the degree of variation in the wavelength of the laser light emitted from the laser source 5. The wavelength of the oscillating laser light set in the laser source 5 is λ, the optical path difference between the measurement light and the reference light in the 1-pass method is X _a , and the optical path difference between the measurement light and the reference light in the 2-pass method is X. and is _b, using the wavelength variation coefficient k indicating the variation degree of the wavelength of the laser beam, measuring length variation Δx can be expressed by the following equation.

From the above equation, the wavelength coefficient of variation k is k = Δx / (X _b− X _a ). X _a and X _b are known values, and the drawing control unit 3c calculates the wavelength coefficient of variation k (always) in real time based on Δx obtained from the observation result in the light receiving unit 89. The drawing control unit 3c detects and measures the wavelength variation of the laser light emitted from each laser source 5 based on the wavelength coefficient of variation k in each of the first meter side unit 4 and the second meter side unit 4. The position in the X direction and the position information in the Y direction of the stage 11 measured by the long portion 7 are corrected. The drawing control unit 3c controls the drawing unit 2 using the corrected stage position information and performs drawing processing.

As described above, according to the present embodiment, the position of the stage 11 can be accurately obtained by the correction based on the wavelength coefficient of variation k, and the beam can be irradiated to the desired position, so that the drawing accuracy can be prevented from being lowered. ..

Consider the case where the position of the reflector 88 fluctuates and the distance between the polarizing beam splitter 82 and the reflector 88 fluctuates. When the position of the reflector 88 fluctuates by α, Δx = k ((X _b + 4α) − (X _a + 2α)) = k (X _b −X _a + 2α). The wavelength fluctuation coefficient k is k = Δx / (X _b −X _a + 2α).

Assuming that α = 1 mm, the coefficient of variation k is 0.001995 ppm. Even if the position of the reflector 88 fluctuates by 1 mm, the fluctuation amount of the wavelength coefficient of variation k is 5 × 10 ^-12, which is sufficiently small with respect to the laser wavelength stability. Therefore, the wavelength coefficient of variation k is hardly affected by the position variation of the reflecting mirror 88, and the wavelength variation of the laser beam can be detected with high accuracy.

In the above embodiment, the laser interferometer 80 observes one-pass type laser interference that makes one round trip with the reflector 88 and two-pass type laser interference that makes two round trips, but is limited to this. Instead, laser interference may be observed with the reflector 88 after three or more round trips.

In the above embodiment, calculates the length measurement variation Δx from a difference between the first beat signal and a second beat signal output from the light receiving unit 89 of the wavelength variation detection unit 8, it had been correct the position information of the stage 11 Further, the deformation of the drawing chamber 2a may be measured from the first beat signal or the second beat signal, and the position information of the stage 11 may be corrected in consideration of the deformation amount of the drawing chamber 2a.

In the above embodiment, the configuration in which the laser source 5 and the wavelength fluctuation detection unit 8 are provided in each of the first total side unit 4 and the second total side unit 4 has been described, but the laser source 5 is emitted from one laser source 5. The laser beam may be branched and used in the first meter side portion 4 and the second meter side portion 4. In this case, the wavelength fluctuation detection unit 8 may be provided on only one of them.

In the above embodiment, the drawing device that irradiates the electron beam has been described, but it may irradiate another charged particle beam such as an ion beam. Further, the drawing device may be a multi-beam drawing device.

The present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

1 Drawing device 2 Drawing unit 2a Drawing room 2b Optical lens barrel 3 Control unit 3a Storage unit 3b Shot data generation unit 3c Drawing control unit 4 Meter side 5 Laser source 6 Branch unit 7 Length measuring unit 8 Wavelength fluctuation detection unit 11 Stage 21 Exit 22 Illumination lens 23 1st molded aperture 24 Projection lens 25 Molded deflector 26 2nd molded aperture 27 Objective lens 28 Sub-deflector 29 Main deflector

Claims (5)

A drawing room with a movable stage on which the sample is placed, and a drawing room
A laser source that outputs laser light and
A branch portion that branches the laser beam and
A laser interferometer that measures the position of the stage using the laser beam branched by the branch portion, and
A wavelength fluctuation detection unit that detects the wavelength fluctuation of the laser beam, and
A drawing unit that irradiates the sample with a charged particle beam to draw a pattern,
A drawing control unit that controls the drawing unit,
With
The wavelength fluctuation detection unit is
A beam splitter that separates the laser beam branched by the branching portion into a first laser beam and a second laser beam,
The reflector placed in the drawing room and
A polarization beam splitter that separates the first laser beam into the first measurement light and the first reference light, and separates the second laser beam into the second measurement light and the second reference light.
The first beat is detected by detecting the first composite light that combines the first measurement light and the first reference light that reciprocates m times (m is an integer of 1 or more) between the polarization beam splitter and the reflector. A signal is output, and the second composite light obtained by combining the second measurement light and the second reference light that reciprocates n times (n is an integer larger than m) between the polarization beam splitter and the reflector is detected. And a detector that outputs the second beat signal,
Have,
The drawing control unit calculates the length measurement variation from the difference between the first beat signal and the second beat signal, the length measurement variation, the optical path difference between the first measurement light and the first reference light, and The wavelength fluctuation coefficient of the laser light is calculated based on the optical path difference between the second measurement light and the second reference light, and the position information of the stage measured by the laser interferometer is obtained using the wavelength fluctuation coefficient. A charged particle beam drawing device characterized in that the drawing unit is controlled based on the corrected stage position information. The detector detects the first synthetic light obtained by combining the first measurement light and the first reference light that make one round trip between the polarization beam splitter and the reflector, and outputs the first beat signal. The second beat signal is output by detecting the second synthetic light obtained by combining the second measurement light and the second reference light, which are output and reciprocated twice between the polarization beam splitter and the reflector. The charged particle beam drawing apparatus according to claim 1. The stage is movable in a first direction and a second direction orthogonal to the first direction.
A first laser interferometer that measures the stage position in the first direction and a second laser interferometer that measures the stage position in the second direction are provided.
Claim 1 is characterized in that the laser source, the branch portion, and the wavelength fluctuation detection unit are provided corresponding to the first laser interferometer and the second laser interferometer, respectively. Or the charged particle beam drawing apparatus according to 2. The stage is movable in a first direction and a second direction orthogonal to the first direction.
A first laser interferometer that measures the stage position in the first direction and a second laser interferometer that measures the stage position in the second direction are provided.
The charged particle beam drawing according to claim 1 or 2, wherein the first laser interferometer and the second laser interferometer perform measurement using laser light output from the same laser source. apparatus. The process of branching the laser beam output from the laser source and
The process in which the laser interferometer measures the position of the stage installed in the drawing room using the branched laser light, and
The process of separating the branched laser light into the first laser light and the second laser light, and
A step of splitting the first laser beam into a first measurement light and a first reference light by a polarizing beam splitter, and separating the second laser beam into a second measurement light and a second reference light.
The first composite light obtained by combining the first measurement light and the first reference light that reciprocates m times (m is an integer of 1 or more) between the polarization beam splitter and the reflector arranged in the drawing chamber. The process of detecting and outputting the first beat signal,
The second beat is detected by detecting the second composite light obtained by combining the second measurement light and the second reference light that reciprocate n times (n is an integer larger than m) between the polarization beam splitter and the reflector. The process of outputting a signal and
The length measurement variation is calculated from the difference between the first beat signal and the second beat signal, and the length measurement variation, the optical path difference between the first measurement light and the first reference light, and the second measurement light A step of calculating the wavelength coefficient of variation of the laser beam based on the optical path difference from the second reference light, and
A step of correcting the position information of the stage measured by the laser interferometer using the wavelength coefficient of variation, and
Based on the corrected stage position information, the process of irradiating the sample placed on the stage with a charged particle beam to draw a pattern, and
A charged particle beam drawing method comprising.

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