JP2009038232A - Semiconductor manufacturing apparatus, and semiconductor device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor manufacturing apparatus and a semiconductor device manufacturing method, for preventing occurrence of scratches. <P>SOLUTION: CMP equipment 10 includes: a surface table 11 holding a polishing pad 12; a first motor 13 for rotating the table 11; a polishing solution supply mechanism 15 for supplying a polishing solution to the polishing pad 12; a polishing head 16 which has a membrane 23 provided with each of pressure adjustable air bags 24a-24d at each of a plurality of sectioned zones and holds a substrate W; a second motor 17 for rotating the polishing head 16; a pressing mechanism 18 for pressing the polishing head 16 to the polishing head 12; an air supply mechanism 19 for supplying air to the air bags 24a-24d; and a control part 20 for adjusting the pressure of the air bags 24a-24d through the air supply mechanism 19 so as to fix one or both of the load current values of the first motor 13 and the second motor 17 during the CMP treatment of the substrate W. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor manufacturing apparatus and a semiconductor device manufacturing method for performing a CMP process on a semiconductor substrate.

  As one of the manufacturing processes of a semiconductor device, after embedding a metal in a trench wiring formed in an insulating layer, a chemical process is performed in order to remove an unnecessary metal film deposited on the surface and uniformly planarize the surface. A mechanical polishing (CMP) process is performed. In general, the CMP process supplies a polishing liquid to the polishing pad while rotating the surface plate holding the polishing pad, and pushes the semiconductor substrate against the polishing pad while rotating the polishing head holding the semiconductor substrate. Done by hitting.

  In the CMP process, as the polishing process progresses and the planarization of the film to be polished (metal film) proceeds, and the base of the film to be polished is exposed, the frictional force between the polishing surface and the polishing pad increases. This causes scratches (scratches) in the film to be polished. Since this scratch causes deterioration of insulation characteristics, such as short-circuiting metal groove wiring, development of abrasives and polishing pads that can reduce the frictional force and suppress generation of scratches, material design And improvements have been made actively (see, for example, Patent Documents 1 and 2).

However, deterioration of the polishing pad due to wear over time is inevitable, and this change with time of the polishing pad has a great influence on the change in frictional force as the polishing process proceeds. Further, it is difficult to completely cope with the change in frictional force due to the temperature rise of the polishing pad with the progress of the polishing process only by the material design. Therefore, in order to reduce the occurrence of scratches, not only approaches from abrasives and polishing pad materials, but also approaches from the viewpoint of the configuration of the CMP apparatus and process control are required.
JP 2005-11932 A (paragraphs [0014] to [0016] etc.) JP 2004-281812 (paragraphs [0023], [0024], etc.)

  It is an object of the present invention to provide a semiconductor manufacturing apparatus and a semiconductor device manufacturing method that suppress the occurrence of scratches on the CMP processing surface.

The present invention provides, as a first invention, a semiconductor manufacturing apparatus for CMP processing of a semiconductor substrate, a surface plate holding a polishing pad, a first motor for rotating the surface plate,
A polishing head that has a polishing liquid supply mechanism for supplying a polishing liquid to the polishing pad and a membrane having a pressure-adjustable airbag for each of a plurality of zones, and holds a semiconductor substrate in contact with the membrane A second motor that rotates the polishing head, a pressing mechanism that presses the polishing head against the polishing pad, and a load current value of the first motor during the CMP process of the semiconductor substrate held by the polishing head And a control unit that adjusts the pressure of the airbag for each of the plurality of zones so that one or both of the load current value of the second motor is constant. I will provide a.

  As a second aspect of the present invention, the polishing liquid is supplied to the polishing pad while rotating the surface plate holding the polishing pad, and the semiconductor substrate is pushed against the polishing pad while rotating the polishing head holding the semiconductor substrate. When CMP is performed on the semiconductor substrate, air pressure is used as a force for pressing the semiconductor substrate against the polishing pad directly from the opposite side of the polishing surface of the semiconductor substrate in the polishing head. Further, the air pressure can be applied to each of the plurality of zones, and the air pressure is controlled for each of the plurality of zones so that one or both of the rotational load of the surface plate and the rotational load of the polishing head is constant. A method for manufacturing a semiconductor device is provided.

  According to the present invention, the generation of scratches on the polished surface of a semiconductor substrate can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a CMP apparatus for performing a CMP process on a semiconductor substrate (hereinafter referred to as “substrate”) W.

  The CMP apparatus 10 includes a surface plate 11, a polishing pad 12 attached to the surface of the surface plate 11, a first motor 13 that rotates the surface plate 11, and a polishing liquid nozzle that discharges the polishing liquid to the polishing pad 12. 14, a polishing liquid supply mechanism 15 that supplies the polishing liquid to the polishing liquid nozzle 14, a polishing head 16 that holds the substrate W, a second motor 17 that rotates the polishing head 16, and the entire polishing head 16 is moved up and down and polished. A pressing mechanism 18 for pressing the head 16 against the polishing pad 12 and a control unit 20 for controlling the process of the entire CMP apparatus 10 are provided.

  In the CMP apparatus 10, the polishing liquid is supplied from the polishing liquid supply mechanism 15 to the polishing pad 12 through the polishing liquid nozzle 14 while rotating the surface plate 11 holding the polishing pad 12, and the polishing head 16 is rotated while rotating the polishing head 16. The substrate W held by 16 is pressed against the polishing pad 12 to perform the CMP process on the substrate W.

  A vertical sectional view showing the schematic structure of the polishing head 16 is shown in FIG. 2A. The polishing head 16 includes a disc portion 21, a retainer ring 22 attached to the outer peripheral portion of the lower surface of the disc portion 21, and a membrane 23 provided inside the retainer ring 22. Although the substrate W is not shown in FIG. 2A, the substrate W contacts the lower surface of the membrane 23 and is pressed against the polishing pad 12 with the retainer ring 22 surrounding the outer periphery of the substrate W.

  FIG. 2B shows a plan view of the membrane 23. As shown in FIGS. 2A and 2B, the membrane 23 has a structure in which an airbag is provided for each of a plurality of divided zones. Here, the membrane 23 is divided into four zones arranged concentrically, and a central airbag 24a, a ripple airbag 24b, an outer airbag 24c, and a peripheral airbag are arranged in each zone from the center toward the outer periphery. 24d is provided.

  The CMP apparatus 10 further includes an air supply mechanism 19 that supplies air independently to the airbags 24a to 24d. The air supply mechanism 19 has an APC (Auto Power Control) function, and can control the pressure (internal pressure) of the airbags 24a to 24d in accordance with a command signal from the control unit 20. Details of the air supply path are not shown in FIGS.

  The controller 20 controls the rotation of the first motor 13 during the CMP process of the substrate W held by the polishing head 16. At that time, the control unit 20 feeds back the pressures of the airbags 24a to 24d using the APC function of the air supply mechanism 19 so that the load current value (drive current value) of the first motor 13 is constant. Adjustment is performed by control (hereinafter, such adjustment (control) is referred to as “APF control; Airbag Pressure Feedback Control”), thereby suppressing generation of scratches on the polishing surface of the substrate W.

  In more detail, in the APF control, the load current value of the first motor 13 is monitored, and the set pressures of the airbags 24a to 24d are changed so as to be constant, and the changed pressure is maintained. Such control is repeatedly performed at predetermined time intervals (for example, several milliseconds to several seconds).

  In order to explain a specific example of the CMP process using the APF control, FIG. 3 shows a control flow chart of the load current value of the first motor 13 and FIG. 4 shows the change of the load current value of the first motor 13 during the CMP process. An example of the form of is shown. In FIG. 4, a line M indicating a change in the load current value when the APF control is performed and a line N indicating a change in the load current value of the first motor 13 not performing the APF control are shown. Here, it is assumed that control parameters other than the pressures of the airbags 24a to 24d and affecting the load current value of the first motor 13 are fixed.

First, an initial pressure value is set for each of the airbags 24a to 24d (ST1). The pressure of the central airbag 24a is indicated as “CAP”, the pressure of the ripple airbag 24b as “RAP”, the pressure of the outer airbag 24c as “OAP”, and the pressure of the peripheral airbag 24d as “EAP”. If “1” indicating the presence is indicated by a subscript such as “CAP ₁ ”, for example, [CAP ₁ <RAP ₁ <OAP ₁ <EAP ₁ ] can be set. Alternatively, [CAP ₁ = RAP ₁ = OAP ₁ = EAP ₁ ] may be set, or [CAP ₁ = RAP ₁ <OAP ₁ = EAP ₁ ] or [CAP ₁ = RAP ₁ <OAP ₁ < As in EAP ₁ ], two or more selected from CAP, RAP, OAP, and EAP may be set to the same value, and the rest may be set to different values. The optimum setting condition can be obtained by a preliminary test or the like.

After the pressure of each of the airbags 24a to 24d reaches the initial pressure value in ST1 by supplying air from the air supply mechanism 19, measurement of the load current value of the first motor 13 is started (ST2) and set in advance. The CMP process is started according to the sequence (ST3). As shown in FIG. 4, the CMP processing start time is “t ₀ ”.

Although an excessive current temporarily flows at the start of rotation of the first motor 13 (FIG. 4), since this is a starting characteristic of the first motor 13, the control unit 20 ignores the excessive current. Each of the pressure of the air bag 24a~24d is up to time _{t 1} (described later) is held at the initial pressure value determined by ST1, APF control is not performed between the time _t 0 ~t _1. The preset sequence is divided into processing times, and the pressing force of the polishing head 16 to the polishing pad 12 by the pressing mechanism 18 and the discharge amount of the polishing liquid in each section, the rotation of the first motor 13 and the second motor 17. Numbers etc. are assigned.

  When the CMP process is started, the film to be polished provided on the polishing surface of the substrate W is flattened, and frictional heat is generated, so that the frictional force between the polishing surface and the polishing pad 12 gradually increases. . Thus, the load current value of the first motor 13 increases (FIG. 4).

When the load current value of the first motor 13 exceeds a certain value, the occurrence of scratches becomes significant. FIG. 6 is a graph showing the relationship between the load current value of the first motor 13 and the amount of scratch generation. When the load current to exceed the current value A _L in FIG. 6 flows through the first motor 13, it is understood that the number of scratches becomes suddenly large.

As described above, the “upper limit current value” that serves as a reference for suppressing the occurrence of scratches to a certain level is experimentally obtained in advance. For example, the current value A _L shown in FIG. 6 is determined as the upper limit current value A _L. Can do. The upper limit current value _AL is set in the control unit 20 in advance.

When the load current value of the first motor 13 has reached the time t ₁ to the upper limit current value A _L (S1), APF control starts so that the load current value of the first motor 13 is held by the upper limit current value A _L (ST4). That is, the set pressures of the airbags 24a to 24d are changed according to the monitored load current value of the first motor 13. Then, the air supply mechanism 19 operates so that the pressure of the airbags 24a to 24d quickly becomes a new set pressure. Such control is repeatedly performed at predetermined time intervals until time t ₃ (details will be described later), so that the load current value of the first motor 13 becomes the upper limit current value _AL . Retained.

As shown in FIG. 4, when the APF control is not performed, the load current value of the first motor 13 tends to increase between the times t _{1 and} t ₂ (that is, between the polishing surface of the substrate W and the polishing pad 12). It can be seen that the frictional force between them tends to increase). Therefore, in the time t ₁ ~t ₂ sections, as a whole, so as to hold sequentially changed to a value smaller respective pressure than the initial pressure value of the air bag 24 a to 24 d, APF control. The air supply mechanism 19 sets and holds the airbags 24a to 24d at the newly set pressure by reducing the gas pressure sent to the airbags 24a to 24d.

As a specific method of sequentially changing the pressure of the airbags 24a to 24d to a value smaller than the initial pressure value, a changing method of uniformly reducing a constant value from the initial pressure values of the airbags 24a to 24d is preferably used. For example, when the initial pressure value is [CAP ₁ <RAP ₁ <OAP ₁ <EAP ₁ ], the new set pressure is [CAP ₁ −α <RAP ₁ −α <OAP ₁ −α <EAP ₁ −α ( α <CAP ₁ )], and a method of repeating such a change or a new set pressure is [CAP ₁ −α ₁ <RAP ₁ −α ₂ <OAP ₁ −α ₃ <EAP ₁ −α ₄ (α ₁ , and at least one value of α ₂ , α ₃ , and α ₄ is different from the other values, and one value may be 0)].

As another specific method for sequentially changing the pressure of the airbags 24a to 24d to a value smaller than the initial pressure value, the new set pressure is [CAP ₁ × β <RAP ₁ × β <OAP ₁ × β. A method of repeatedly changing the initial pressure value of the airbags 24a to 24d at a constant rate so that <EAP ₁ × β (0 <β <1)] or a new set pressure is [CAP ₁ × β ₁ < RAP ₁ × β ₂ <OAP ₁ × β ₃ <EAP ₁ × β ₄ (0 <β ₁ , β ₂ , β ₃ , β ₄ ≦ 1, and at least one of β ₁ , β ₂ , β ₃ , β ₄ It is also preferable to use a change method that repeats the change to be reduced at different rates so that one value is different from the other values. Furthermore, these changing methods may be combined.

When the APF control is not performed as shown in FIG. 4, the load current value of the first motor 13 tends to be small during the time t _{2 to} t ₃ (that is, the polishing surface of the substrate W and the polishing pad 12 The tendency that the frictional force between the two becomes smaller) appears. This trend continues after time t _3, but it depends on the abrasive and is not a general trend. For example, there is a case where a copper wiring is formed on the surface of the oxide film via a barrier metal, and this is subjected to CMP treatment using an abrasive whose polishing rate is (barrier metal, copper)> oxide film. In this case, the polishing surface is formed of barrier metal and copper at the initial stage of polishing, and the barrier metal is removed as the polishing proceeds. At that time, polishing of the oxide film starts. However, if the polishing agent has the above-described selection ratio, the polishing force of the oxide film is slow and the frictional force decreases, thereby reducing the load current value of the first motor 13. Become.

Therefore, in the section of time t _{2 to} t ₃ , the respective pressures of the airbags 24 a to 24 d as a whole are sequentially changed to values larger than the respective set values at time t ₂ (hereinafter referred to as “t ₂ set values”). APF control to be held is performed.

As the specific method, by multiplying one or more predetermined values uniformly to t ₂ set value or adding the constant value, or to t ₂ set value, a method of changing the set pressure of the air bag 24a~24d Can be mentioned. The air supply mechanism 19 increases the gas pressure sent to the airbags 24a to 24d to hold the airbags 24a to 24d at the newly set pressure.

Such APF control is performed between the time _t 1 ~t _3. From the viewpoint of scratches suppressed, the load current value of the first motor 13 need only become less than the upper limit current value A _L. However, if the load current value of the first motor 13 is kept small, the polishing rate becomes small and the processing time becomes long. Therefore, from the viewpoint of maintaining a constant polishing rate, it is preferable to maintain the load current value of the first motor 13 at the upper limit current value A _L.

Incidentally, at time _t 1 ~t ₂ interval, by had too small a set pressure of the air bag 24 a to 24 d, got a load current value of the first motor 13 becomes smaller than the upper limit current value _{A L} In such a case, control is performed to increase the set pressure at a constant value or at a constant rate from the set pressure at that time. On the other hand, at time _t 2 ~t ₃ sections, by excessively increasing the set pressure of the air bag 24 a to 24 d, when the load current value of the first motor 13 has exceeded the upper limit current value _{A L} Is controlled to reduce the set pressure at a constant value or at a constant rate from the set pressure at that time. The mode is the same as general PID control.

As shown in FIG. 4, the time t ₃ or later in a state where the load current value of the first motor 13 is below the upper limit current value A _L. For example, previously determined in advance upper limit pressure value to each of the set pressure air bag 24 a to 24 d, starting point of the state be maintained the upper limit load current value of the first motor 13 falls below the upper limit current value A _L is the point of time _{t 3.} Thus, APF control at time _{t 3} is finished (S2).

The time _{t 3} or later, and holds the set pressure of the airbag 24a~24d in this upper limit pressure value, performs a CMP process until the sequence end time _{t 4} (ST5), thus CMP process ends. In FIG. 3, ST5 is described as “final processing”. An initial pressure value can be used as the upper limit pressure value, but is not limited thereto.

Depending on the abrasive used, there is a case where a state of the case of not using the APF control load current value of the first motor 13 is continuously between the time t ₁ ~t ₄ exceeds the upper limit current value A _L. For such a configuration, APF control is applied between times t _{1 and} t ₄ .

  When performing APF control as described above, the control accuracy of the load current value of the first motor 13 can be increased by controlling other processing parameters that vary the load current value of the first motor 13.

  Other processing parameters for changing the load current value of the first motor 13 include a pressing force that presses the entire polishing head 16 against the polishing pad 12 (hereinafter referred to as “polishing head pressure”), and the rotation speed of the surface plate 11 (= The rotational speed of the polishing pad 12 = the rotational speed of the first motor 13), the rotational speed of the polishing head 16 (= the rotational speed of the substrate W = the rotational speed of the second motor 17), and the polishing liquid supply flow rate by the polishing liquid supply mechanism 15. It is preferable to control one or more amounts selected from these.

  5A shows the relationship between the polishing head pressure and the load current value of the first motor 13, FIG. 5B shows the relationship between the rotation speed of the surface plate 11 and the load current value of the first motor 13, and FIG. FIG. 5D shows the relationship between the rotation speed and the load current value of the first motor 13, and FIG. Here, the APF control is not performed during the CMP process.

  As shown in FIGS. 5A to 5D, by decreasing the polishing head pressure, by decreasing the rotational speed of the surface plate 11, by decreasing the rotational speed of the polishing head 16, and by increasing the polishing liquid flow rate, The load current value of the first motor 13 tends to decrease.

Using this trend, as a specific method of retaining the load current value of the first motor 13 at the upper limit current value A _L, after starting the CMP process, the load current value of the first motor 13 has an upper limit Upon reaching the current value a _L (time t ₁ in FIG. _4), the set pressure of the air bag 24a~24d changed to the second set value set in advance from the initial pressure value and holds. As the second set value, a value obtained by subtracting a constant value from the initial pressure values of the airbags 24a to 24d, a value obtained by reducing the initial pressure value at a constant rate, or the like is preferably used.

In APF control of the air bag 24 a to 24 d, if the change of the next set pressure of the air bag 24 a to 24 d from the time _{t 1} after Delta] t has elapsed is performed, the load of the first motor 13 during the time _t 1 ~t ₁ + Delta] t When the current value shows a tendency to increase, the control unit 20 controls the operation of the pressing mechanism 18 to move the polishing head 16 away from the polishing pad 12 in order to reduce the polishing head pressure, or the polishing head 16. The second motor 17 is rotated to reduce the number of rotations (the number of rotations of the substrate W), or the number of rotations of the first motor 13 is decreased to decrease the number of rotations of the surface plate 11. holding the load current value of the first motor 13 to the upper limit current value a _L.

Conversely, when tended load current value of the first motor 13 is reduced during the time t ₁ ~t 1 ₊ Delta] t, the control unit h20 is polishing the polishing head 16 in order to increase the polishing head pressure The operation of the pressing mechanism 18 is controlled so as to press against the pad 12, or the second motor 17 is increased to increase the rotation speed of the polishing head 16, or the first rotation speed of the surface plate 11 is increased. and the like increasing the rotational speed of the motor 13, to hold the load current value of the first motor 13 to the upper limit current value a _L. After time t ₁ + Δt, the same control is repeated until time t ₃ is reached.

By performing the control in consideration of the relationship shown in this FIG. 5A-5D, it is possible to hold at higher accuracy upper limit current value A _L of the load current value of the first motor 13.

  The controller 20 also controls the rotation of the second motor 17 during the CMP process for the substrate W held by the polishing head 16. Therefore, the APF control is performed so that the load current value of the second motor 13 is constant, similar to the case where the APF control is performed so that the load current value of the first motor 13 is constant as described above. Can do.

  Further, the change in the frictional force between the polishing surface of the substrate W and the polishing pad 12 tends to increase or decrease both the load current value of the first motor 13 and the load current value of the second motor 17. Therefore, the APF control can be performed so that both the load current value of the first motor 13 and the load current value of the second motor 17 are maintained constant.

  Note that the CMP apparatus 10 is configured to be able to independently set, change, and hold the pressures of the airbags 24a to 24d, so that in-plane variations are unlikely to occur in the polishing rate and the polishing amount.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to such a form. For example, although various methods based on addition / subtraction / division / division have been illustrated for the method for changing the set pressure of the airbags 24a to 24d, it goes without saying that a new pressure can be set by combining the change methods exemplified in this way. .

Also, in the time period of time shown in FIG. 4 _t 0 ~t ₁ and _t 3 ~t _4, may be making changes to increase the set pressure of the air bag 24a~24d continuously or stepwise polishing rate Is increased to shorten the time period from t ₀ to t ₁ , the processing time of the entire CMP process can be shortened. It is possible to do a time t ₃ after a similar settings and this.

1 is a schematic configuration diagram of a CMP apparatus according to an embodiment of the present invention. FIG. 3 is a vertical sectional view showing a schematic structure of a polishing head. The back view which shows schematic structure of a grinding | polishing head. The control flowchart of the load current value of a 1st motor. The graph which shows the time-dependent change of the load current value of the 1st motor at the time of CMP process. The graph which shows the relationship between polishing head pressure and a 1st motor load electric current value. The graph which shows the relationship between a surface plate rotation speed and a 1st motor load current value. The graph which shows the relationship between polishing head rotation speed and a 1st motor load electric current value. The graph which shows the relationship between polishing fluid supply flow volume and a 1st motor load electric current value. The graph which shows the relationship between the load electric current value of a 1st motor, and the generation amount of a scratch.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... CMP apparatus, 11 ... Surface plate, 12 ... Polishing pad, 13 ... 1st motor, 14 ... Polishing liquid nozzle, 15 ... Polishing liquid supply mechanism, 16 ... Polishing head, 17 ... 2nd motor, 18 ... Pressing mechanism, DESCRIPTION OF SYMBOLS 19 ... Air supply mechanism, 20 ... Control part, 21 ... Disk part, 22 ... Retainer ring, 23 ... Membrane, 24a-24d ... Air bag.

Claims (5)

A semiconductor manufacturing apparatus for CMP processing of a semiconductor substrate,
A surface plate holding a polishing pad;
A first motor for rotating the surface plate;
A polishing liquid supply mechanism for supplying a polishing liquid to the polishing pad;
A polishing head having a membrane provided for each of a plurality of zones partitioned with a pressure-adjustable airbag, and holding a semiconductor substrate in contact with the membrane;
A second motor for rotating the polishing head;
A pressing mechanism for pressing the polishing head against the polishing pad;
During the CMP process of the semiconductor substrate held by the polishing head, for each of the plurality of zones, either one or both of the load current value of the first motor and the load current value of the second motor are constant. And a control unit for adjusting the pressure of the airbag.   The control unit further includes a pressing force for pressing the entire polishing head against the polishing pad, a rotation speed of the surface plate, a rotation speed of the polishing head, and a polishing liquid supply flow rate by the polishing liquid supply mechanism. 2. The semiconductor manufacturing apparatus according to claim 1, wherein one or a plurality of selected quantities are controlled.   The semiconductor manufacturing apparatus according to claim 1, wherein the plurality of zones are concentrically divided. The controller is
As the CMP process of the semiconductor substrate progresses, one or both of the load current value of the first motor and the load current value of the second motor is the load current value of the first motor and the load current value of the second motor. Air pressure adjustment control is started for each of the plurality of zones, and then the CMP process of the semiconductor substrate further proceeds as the first motor reaches a set upper limit current value. 4. The pressure adjustment control is terminated when one or both of a load current value and a load current value of the second motor become less than the upper limit current value. 5. The semiconductor manufacturing apparatus described in 1. A polishing liquid is supplied to the polishing pad while rotating the surface plate holding the polishing pad, and the semiconductor substrate is pressed against the polishing pad while rotating the polishing head holding the semiconductor substrate. When doing
In the polishing head, air pressure is used as a force for directly pressing the semiconductor substrate against the polishing pad from the opposite side of the polishing surface of the semiconductor substrate, and the air pressure can be applied to each of a plurality of partitioned zones. A method of manufacturing a semiconductor device, comprising: controlling the air pressure for each of the plurality of zones so that one or both of a rotational load of the disc and a rotational load of the polishing head is constant.

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