JP7367446B2 - Coating method and coating device - Google Patents

Description

The present invention relates to a coating method and a coating device.

For example, in a semiconductor manufacturing process, a liquid functional material is applied to a semiconductor wafer. Conventionally, spin coating is used as a coating method. As a substrate to which a liquid such as a functional material is applied, there is a substrate 90 having a plurality of grooves 92 formed on its surface 91, as shown in FIG. According to spin coating, the liquid 99 applied to the center of the substrate 90 immediately spreads in the radial direction from the center. For this reason, as shown in FIG. 9, a portion is created in the groove 92 where there is no place for gas to escape, and air bubbles 93 tend to remain between the substrate 90 and the applied liquid 99. When forming a film of functional material on the substrate 90, the remaining bubbles 93 become defects.

Therefore, Patent Document 1 discloses a technique in which a liquid is applied by spin coating to a substrate having grooves formed on its surface, and then the atmosphere of the substrate is brought to a pressure exceeding atmospheric pressure.

Japanese Patent Application Publication No. 2014-143341

According to the method disclosed in Patent Document 1, it is possible to eliminate air bubbles remaining in the grooves after applying the liquid. However, in this case, after the liquid is applied to the substrate, equipment is required to create a high-pressure atmosphere around the substrate, and treatment is also required to eliminate air bubbles in the grooves after application, which increases costs. Cause. In addition to substrates such as wafers, there are also sheet-like members that are long in one direction as members (substrates) on which grooves are formed on the surface to which the liquid is applied.

Therefore, an object of the present disclosure is to provide a new technical means that makes it possible to apply a liquid to a base material having grooves formed on its surface while suppressing the remaining air bubbles.

In the coating method of the present disclosure, a liquid is applied to the surface of a base material provided with linear grooves on the surface using an applicator having a long slit in one direction and capable of discharging the liquid from the opening of the slit. The method includes a coating step of discharging a liquid from the opening onto the surface while relatively moving the base material and the applicator while the opening and the surface are close to each other, In the coating step, the base material and the applicator are relatively moved in such a state that when the opening is projected onto the surface, the longitudinal direction of the projected opening and the longitudinal direction of the groove are inclined. At the same time, the liquid is discharged from the applicator onto the base material.

According to the coating method of the present disclosure, when the opening of the slit is projected onto the surface of the base material, the longitudinal direction of the projected opening and the longitudinal direction of the groove are inclined, so that the coating is not discharged from the applicator. The liquid is applied to the surface of the substrate along the grooves, expelling air bubbles. Therefore, it becomes possible to apply the liquid to the surface of the base material while suppressing the remaining air bubbles.

Preferably, the longitudinal direction of the projected opening and the relative moving direction between the base material and the applicator are orthogonal to each other, and the longitudinal direction of the projected opening and the moving direction are respectively perpendicular to each other. , inclined with respect to the longitudinal direction of the groove.
In this case, the liquid discharged from the applicator can easily expel air bubbles along the grooves.

Preferably, the method for applying a liquid to the surface of the base material includes forming a liquid pool between the applicator and the surface during relative movement between the applicator and the base material. However, this is capillary coating in which the liquid in the applicator is kept at a negative pressure relative to atmospheric pressure.
In the case of capillary coating, the liquid spreads along the groove surface of the base material and is applied. Therefore, the liquid has a high effect of pushing out air bubbles along the grooves. Therefore, it becomes possible to apply the liquid while further suppressing the remaining air bubbles.

The coating device of the present disclosure is a device that applies a liquid to the surface of a base material provided with linear grooves on the surface, and includes a long slit in one direction and is capable of discharging the liquid from the opening of the slit. an applicator, a moving mechanism for relatively moving the base material and the applicator, and a longitudinal direction of the groove relative to a longitudinal direction of the projected opening when the opening of the slit is projected onto the surface; and a stage that holds the base material so that the base material is tilted.
The coating device enables the coating method. Therefore, it becomes possible to apply the liquid while suppressing the remaining air bubbles.

Preferably, the coating device further includes an adjustment mechanism that adjusts the orientation of the base material held on the stage.
The adjustment mechanism may be installed outside the stage or inside the stage. When the adjustment mechanism is installed outside the stage, the coating device further includes a conveyance device that conveys the substrate whose orientation has been adjusted by the adjustment mechanism to the stage. According to the adjustment mechanism, when applying the coating liquid to the substrate, the substrate is held on the stage so that the longitudinal direction of the groove is inclined with respect to the longitudinal direction of the opening projected on the surface of the substrate. state.

According to the invention of the present disclosure, it is possible to apply a liquid to a base material having grooves formed on its surface while suppressing the remaining air bubbles.

FIG. 2 is a schematic configuration diagram of the coating device viewed from the side. It is a perspective view showing a part of a coating device. It is a top view which shows the base material on a stage, and an applicator. FIG. 2 is a plan view showing the overall schematic configuration of the coating device. It is a figure for explaining the modification of a coating method, and is a top view showing a base material on a stage, and an applicator. It is a figure for demonstrating the case where a base material is a rectangle, and is a top view which shows the base material on a stage, and an applicator. It is a figure explaining other examples of the groove provided in a base material. FIG. 2 is a plan view illustrating a coating method using spin coating. FIG. 2 is a cross-sectional view of a substrate viewed from the side in the case of a coating method using spin coating.

[Configuration of coating device]
FIG. 1 is a schematic configuration diagram of the coating device viewed from the side. FIG. 2 is a perspective view showing a part of the coating device. The coating device 10 shown in FIGS. 1 and 2 is a device for coating a liquid (hereinafter referred to as “coating liquid”) on a substrate 7. For this purpose, the coating device 10 includes an applicator 12, a stage 14 that holds the base material 7, a moving mechanism 16 that relatively moves the applicator 12 and the stage 14, and is connected to the applicator 12 and applies the coating liquid. A supply mechanism 18 for supplying to the container 12 is provided. The applicator 12 is also called a slit die.

The base material 7 of the present disclosure is a circular substrate such as a semiconductor wafer. FIG. 3 is a plan view showing the base material 7 on the stage 14 and the applicator 12. A plurality of grooves 9 are formed on the surface 8 of the base material 7. As the grooves 9, a first linear groove 9a that is long in one direction and a second linear groove 9b that is long in the other direction are formed on the surface 8. A coating liquid is applied to this surface 8 by a coating device 10 . The first groove 9a and the second groove 9b intersect, forming a grid-like groove 9. Although the angle at which the first groove 9a and the second groove 9b intersect shown in FIG. 3 is 90 degrees, the angle may be any other angle. The longitudinal direction of the first groove 9a is called the "L direction", and the longitudinal direction of the second groove 9b is called the "M direction". The L direction and the M direction are perpendicular to each other on the surface 8. In each figure, the "L direction" is indicated by an arrow (L), and the "M direction" is indicated by an arrow (M).

In addition to being a circular substrate, the base material 7 may be a square or rectangular substrate, or may be a continuous sheet-like member. As shown in FIG. 6, the base material 7 may be a rectangular (or square) substrate, in which case the first groove 9a is formed parallel to one side, and the first groove 9a is formed parallel to the other sides. Thus, a second groove 9b is formed.

In FIGS. 1 and 2, the applicator 12 is a member that is elongated in one direction, and has a liquid reservoir space 40 in which a coating liquid is collected and a slit 42 formed therein. One side of the slit 42 is connected to the liquid reservoir space 40, and the other side is open to the outside. The liquid reservoir space 40 and the slit 42 are also formed in a long straight line along the longitudinal direction of the applicator 12. The slit 42 is open at the tip surface (lower end surface) 13 of the applicator 12. The opening of the slit 42 in the distal end surface 13 is designated by "42a". The coating liquid in the liquid reservoir space 40 is discharged to the outside through the slit 42.

The longitudinal dimension of the slit 42 is larger than the diameter (width dimension) of the base material 7. The direction perpendicular to the longitudinal direction of the applicator 12 is the direction of relative movement between the applicator 12 and the stage 14, and this direction is the application direction. The longitudinal direction of the applicator 12 is referred to as the "X direction", and the application direction is referred to as the "Y direction". In each figure, the "X direction" is indicated by an arrow (X), and the "Y direction" is indicated by an arrow (Y). As described above, the applicator 12 of the present disclosure includes a linear slit 42 that is long in one direction (X direction), and can discharge the coating liquid from the opening 42a of the slit 42.

The stage 14 holds the base material 7 by, for example, suctioning air. The base material 7 is held on the stage 14 facing in a fixed direction. To explain specifically (see FIG. 2), as will be explained later, when the opening 42a of the slit 42 is projected onto the surface 8 of the base material 7, a groove is formed in the longitudinal direction of the projected opening (42a). The base material 7 is held on the stage 14 so that the longitudinal direction of (9a, 9b) is inclined.

FIG. 4 is a plan view showing the overall schematic configuration of the coating device 10. As shown in FIG. The coating device 10 of the present disclosure further includes an adjustment mechanism 20 that adjusts the orientation of the base material 7. A plurality of base materials 7 are stored in a storage location in piles. The adjustment mechanism 20 adjusts the orientation of the base material 7 taken out from the storage location. The base material 7 is provided with an alignment mark Q. In the present disclosure, the base material 7 is provided with a notch as an alignment mark Q. The alignment mark Q may be of any other type, and may be a straight line portion called an orientation flat.

The adjustment mechanism 20 includes a detection unit 22, such as a camera, that recognizes the alignment mark Q, and a rotation mechanism 24 that rotates the base material 7. The direction of the base material 7 is adjusted by the detection result of the detection unit 22 and the rotation of the base material 7 by the rotation mechanism 24. In this way, the adjustment mechanism 20 adjusts the orientation of the base material 7 based on the alignment mark Q. The base material 7 is held on the stage 14 in the adjusted orientation.

In the form shown in FIG. 4, the adjustment mechanism 20 is installed outside the stage 14, that is, in a separate area from the stage 14, but it may be installed inside the stage 14. In the present disclosure, since the adjustment mechanism 20 is installed in a different area from the stage 14, the coating device 10 includes a conveyance device 26 that conveys the substrate 7 whose orientation has been adjusted by the adjustment mechanism 20 to the stage 14. Prepare more. Note that in this embodiment, a case will be described in which the adjustment mechanism 20 is installed in a separate area from the stage 14, but the adjustment mechanism 20 may also be installed inside the stage 14, and in this case, the adjustment mechanism 20 may be installed in a region different from the stage 14. After the material 7 is placed within the stage 14, the orientation of the substrate 7 is adjusted by the adjustment mechanism 20. As shown in FIG. 4, all (four in the example) substrates 7 are held on the stage 14 by the adjustment mechanism 20 (and the conveyance device 26) with the alignment mark Q in a fixed direction. becomes. In other words, the first groove 9a of one base material 7 and the first groove 9a of another base material 7 are parallel, and the second groove 9b of one base material 7 and the second groove 9a of another base material 7 are parallel to each other. is parallel to the groove 9b. In the illustrated example, there are four base materials 7, but this is just an example, and the number of base materials 7 may be one or multiple.

In FIG. 1, a moving mechanism 16 of the present disclosure is configured to move an applicator 12 with respect to a stage 14 that is in a fixed state. Specifically, the moving mechanism 16 includes a moving body 46 on which the applicator 12 is mounted, and an actuator 47 that moves the moving body 46. The actuator 47 is, for example, a linear actuator.

The moving mechanism 16 moves the applicator 12 mounted on the moving body 46 along a direction parallel to the surface 8 of the base material 7 (that is, the direction indicated by the arrow (Y)). Further, the moving mechanism 16 moves the applicator 12 in a direction perpendicular to the surface 8 in order to adjust the distance (gap G) between the tip surface 13 of the applicator 12 and the surface 8 of the base material 7 on the stage 14. It can be moved. Note that, contrary to the case of the present disclosure, the applicator 12 may be in a fixed state and the stage 14 may be moved. That is, the moving mechanism 16 may be configured to move the base material 7 and the applicator 12 relatively. As described above, the applicator 12 can perform capillary coating by discharging the coating liquid from the slit 42 while moving relative to the surface 8 of the base material 7, as will be described later.

The supply mechanism 18 can supply the coating liquid to the applicator 12. The supply mechanism 18 includes a tank 32 that stores a coating liquid, and a pipe 34 that connects the tank 32 and the applicator 12. When the coating liquid is discharged from the applicator 12, that is, when the coating liquid is consumed, the coating liquid is supplied to the applicator 12 from the tank 32 (replenished). The coating of the coating liquid onto the substrate 7 performed by the coating device 10 of the present disclosure is capillary coating, which will be described later. For this purpose, the supply mechanism 18 includes an adjustment section 36 that adjusts the pressure of the coating liquid stored in the tank 32.

The adjustment unit 36 includes a pump (vacuum pump) that sucks air and a regulator. The adjustment unit 36 sets the coating liquid in the tank 32 to a negative pressure with respect to atmospheric pressure. As a result, the coating liquid in the applicator 12 also has a negative pressure with respect to atmospheric pressure. The regulator of the adjustment unit 36 adjusts the pressure of the coating liquid stored in the tank 32 so that the pressure of the coating liquid in the applicator 12 is maintained at a predetermined value (negative pressure). This configuration enables capillary coating using the applicator 12.

[About capillary coating]
The applicator 12 discharges a coating liquid from the slit 42 onto the surface 8 of the base material 7 on the stage 14 while moving. Capillary coating is performed by this applicator 12. The coating method of the present disclosure is a downward capillary coating method.

Capillary coating will be further explained. Before the start of coating, the adjustment unit 36 adjusts the pressure of the coating liquid in the tank 32 to be lower than atmospheric pressure. Therefore, the pressure of the coating liquid in the applicator 12 is also negative, and the coating liquid is not discharged from the slit 42. The distal end surface 13 of the applicator 12 and the surface 8 of the base material 7 on the stage 14 are brought close to each other. The adjustment unit 36 adjusts the pressure of the coating liquid in the tank 32 to be slightly higher than atmospheric pressure. Then, the coating liquid is supplied from the tank 32 to the applicator 12 and is discharged from the opening 42a of the slit 42. When the coating liquid discharged from the applicator 12 comes into contact with the surface 8 of the base material 7, a liquid pool B ("bead") of the coating liquid is formed in the gap G between the tip end surface 13 and the surface 8, as shown in the enlarged view of FIG. B) is formed. This process is called a liquid application process. In the liquid application step, the applicator 12 is located directly above a part of the base material 7 (the application start position), and the applicator 12 is in a stopped state.

As soon as the liquid pool B is formed in the gap G, the adjusting section 36 adjusts the pressure of the coating liquid in the tank 32 to be lower than atmospheric pressure. As a result, the discharge of the coating liquid from the slit 42 is temporarily stopped. Thereafter, the adjustment unit 36 adjusts the pressure of the coating liquid in the applicator 12 to a predetermined pressure lower than atmospheric pressure. Then, the moving mechanism 16 moves the applicator 12 with respect to the base material 7. Along with this movement, in order to continuously form the liquid pool B (bead B), the coating liquid is drawn out from the applicator 12 so as to fill the gap G, and is continuously applied to the surface 8 of the base material 7. The coating liquid is applied to the surface. During application, the applicator 12 is replenished from the supply mechanism 18 with the amount of application liquid that is consumed.

In this way, in capillary coating, after the coating liquid from the applicator 12 adheres to the surface 8 of the base material 7, the coating liquid is affected by capillary action (surface tension) between the tip surface 13 and the surface 8, and during coating. is pulled out from the applicator 12 by the shear force acting on the liquid pool B. As a result, the coating liquid is applied to the surface 8 of the base material 7. In the case of FIG. 1, the moving direction of the applicator 12 during the coating operation is from right to left, and the direction shown by the arrow (Y) from right to left is the "coating direction."

[About the orientation of the base material 7 on the stage 14]
Here, the two-dot chain line shown in FIG. This is an imaginary line K along the longitudinal direction of the opening 42a.

As described above, the adjustment mechanism 20 holds the base material 7 on the stage 14 with the alignment mark Q in a fixed direction. The direction is as explained below. That is, as shown in FIG. 3, the base material 7 is placed on the stage 14 so that the longitudinal direction of the groove 9 is inclined with respect to the virtual line K that is the longitudinal direction of the opening 42a projected onto the surface 8 of the base material 7. Retained.
In the case of the present disclosure, the groove 9 includes a first groove 9a and a second groove 9b that intersect. The base material 7 is held on the stage 14 so that each of the first groove 9a and the second groove 9b is inclined with respect to the imaginary line K. The longitudinal direction of the first groove 9a is inclined at 45 degrees with respect to the imaginary line K, and the longitudinal direction of the second groove 9b is inclined at 45 degrees with respect to the imaginary line K.

In this manner, according to the adjustment mechanism 20, when the opening 42a of the slit 42 is projected onto the surface 8 of the base material 7 when applying the coating liquid to the base material 7, the projected opening 42a is adjusted in the longitudinal direction of the projected opening. The orientation of the base material 7 is adjusted in advance so that the longitudinal direction of the grooves (9a, 9b) is inclined. Then, the base material 7 whose orientation has been adjusted is held on the stage 14 in a fixed orientation.

[About the application method]
A coating method performed by the coating device 10 having the above configuration will be described. The coating method includes a preparation step in which the substrate 7 is held on the stage 14, and a coating step in which the coating liquid is applied to the substrate 7. In the preparation step, the adjustment mechanism 20 functions. In the coating step, as shown in FIGS. 1 and 2, the applicator 12 is moved relative to the base material 7 in a state where the opening 42a of the slit 42 of the applicator 12 and the surface 8 of the base material 7 are close to each other. This is a step in which the coating liquid is discharged onto the surface 8 from the opening 42a.

Furthermore, in the coating process, the base material 7 is coated in such a manner that the longitudinal direction of the projected opening 42a, which is the direction along the virtual line K (see FIG. 3), and the longitudinal direction of each of the grooves (9a, 9b) are inclined. On the other hand, the coating liquid is discharged from the applicator 12 onto the base material 7 while moving the applicator 12 in the direction shown by the arrow (Y).

In this coating method, as described above, when the opening 42a of the slit 42 is projected onto the surface 8 of the base material 7, the longitudinal direction of the projected opening 42a and the longitudinal direction of each of the grooves 9a and 9b are inclined. It is in. Therefore, the coating liquid discharged from the applicator 12 is applied to the surface 8 of the base material 7 along each of the grooves 9a and 9b so as to expel air bubbles. Therefore, it becomes possible to apply the coating liquid to the surface 8 of the base material 7 while suppressing the remaining air bubbles. The direction in which bubbles are expelled along each of the grooves 9a and 9b is indicated by an arrow G in FIG.

In particular, in the method shown in FIG. 3, the longitudinal direction of the opening 42a projected onto the surface 8 of the base material 7 and the moving direction of the applicator 12 on the surface 8 of the base material 7 are orthogonal to each other. That is, the direction along the virtual line K (see FIG. 3) and the direction indicated by the arrow (Y), which is the coating direction, are orthogonal in plan view. The grooves (9a, 9b ) is inclined with respect to the longitudinal direction. Therefore, the coating liquid discharged from the applicator 12 can easily expel air bubbles along the grooves (9a, 9b).

Note that, as shown in FIG. 5, the longitudinal direction of the opening 42a does not have to be orthogonal to the coating direction shown by the arrow (Y), that is, the moving direction of the applicator 12. However, even in this case, the longitudinal direction (imaginary line K) of the opening 42a projected onto the surface 8 of the base material 7 is in an inclined relationship with the longitudinal direction of each of the grooves (9a, 9b). The applicator 12 moves while maintaining .
Also in this case, when the opening 42a of the slit 42 is projected onto the surface 8 of the base material 7, the longitudinal direction of the projected opening 42a and the longitudinal direction of the grooves (9a, 9b) are in an inclined relationship. Then, the coating liquid discharged from the applicator 12 is applied to the surface 8 of the base material 7 along the grooves (9a, 9b) so as to expel air bubbles. Therefore, it becomes possible to apply the coating liquid to the surface 8 of the base material 7 while suppressing the remaining air bubbles.

Further, in the present disclosure, the method of applying the coating liquid to the surface 8 of the base material 7 is capillary coating. In capillary coating, when the applicator 12 and the base material 7 move relative to each other, a liquid pool B (see the enlarged view of FIG. 1) is formed between the applicator 12 and the surface 8 of the base material 7. This is a method in which the coating liquid in the applicator 12 is kept at a negative pressure with respect to atmospheric pressure. According to such capillary coating, the coating liquid spreads on the surface 8 of the substrate 7 as it spreads along the surfaces of the grooves 9a and 9b of the substrate 7, and is applied. Therefore, the coating liquid has a high effect of pushing out air bubbles along the grooves 9a and 9b. Therefore, it becomes possible to apply the coating liquid while further suppressing the remaining air bubbles.

Further, capillary coating is advantageous in the case of a substrate 7 where the coating width of the coating liquid varies. That is, as shown in FIG. 3, when the base material 7 is circular and the coating width to be coated varies, capillary coating is preferable. As shown in FIG. 6, the base material 7 is rectangular, one side of the base material 7 is parallel to the longitudinal direction of the first groove 9a, and the other side of the base material 7 is parallel to the longitudinal direction of the first groove 9b. When the two are parallel, capillary coating is preferred.

In the case of the base material 7 shown in FIG. 6, by tilting the direction of the base material 7 (long side) with respect to the coating direction shown by the arrow (Y) and holding the base material 7 on the stage 14, The longitudinal direction of the opening 42a projected onto the surface 8 of the base material 7 and the longitudinal direction of the grooves 9a and 9b are inclined. With this relationship, the coating liquid can be discharged from the applicator 12 onto the base material 7 while moving the base material 7 and the applicator 12 relatively.

Moreover, in each of the above embodiments, by capillary coating, it is possible to make the thickness of the coating film uniform. Furthermore, since capillary coating is used, there is no need to waste the coating liquid as in the case of spin coating.

In the embodiment described above, a case has been described in which the base material 7 is provided with lattice-shaped grooves 9. The grooves 9 may have other shapes. For example, as shown in FIG. 7(A), a plurality of grooves 9 extending in one direction may be arranged side by side (without intersecting each other). In FIG. 7A, the hatched area is the convex portion 6, and the area other than that area is the groove 9. Alternatively, although not shown, only one groove 9 may be formed in the base material 7 instead of a plurality of grooves 9 extending in one direction.
Further, as shown in FIG. 7(B), the hatched area may be a linear convex portion (convex strip 5), and the area other than that area may be a groove 9. That is, a plurality of protrusions 5 extending in one direction are formed side by side on the base material 7, and the grooves 9 are formed between the protrusions 5.
Further, as shown in FIG. 7C, the hatched area may be the convex portion 4, and the area other than the convex portion 4 may be the groove 9. The groove 9 shown in FIG. 7(C) is not an intentionally formed groove, but rather a plurality of convex portions 4 provided in a lattice-like arrangement on the base material 7, and the grooves between these convex portions 4 are formed. It is 9.

The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is not limited to the above-described embodiments, and includes all modifications within the scope of equivalents to the configurations described in the scope of the claims.

7: Base material 8: Surface 9: Groove 9a: First groove 9b: Second groove 10: Coating device 12: Applicator 14: Stage 16: Movement mechanism 20: Adjustment mechanism 42: Slit 42a: Opening B: Liquid Accumulation

Claims (5)

A method of applying a liquid to the surface of a base material provided with linear grooves on the surface using an applicator having a long slit in one direction and capable of discharging the liquid from the opening of the slit, the method comprising:
a coating step of discharging a liquid from the opening onto the surface while relatively moving the base material and the applicator in a state where the opening and the surface are close to each other;
In the coating step, the base material and the applicator are relatively moved in such a state that when the opening is projected onto the surface, the longitudinal direction of the projected opening and the longitudinal direction of the groove are inclined. A coating method in which a liquid is discharged from the applicator onto the substrate. The longitudinal direction of the projected opening and the relative movement direction of the base material and the applicator are orthogonal to each other,
Each of the longitudinal direction of the projected opening and the moving direction are inclined with respect to the longitudinal direction of the groove.
The coating method according to claim 1. The method of applying a liquid to the surface of the base material includes forming a liquid pool between the applicator and the surface when the applicator and the base material move relative to each other, and applying the liquid to the surface of the base material. It is a capillary application in which the liquid inside is under negative pressure relative to atmospheric pressure.
The coating method according to claim 1 or 2. A device for applying a liquid to the surface of a base material having linear grooves on the surface,
an applicator having a long slit in one direction and capable of discharging a liquid from the opening of the slit;
a movement mechanism that relatively moves the base material and the applicator;
A coating device comprising: a stage that holds the base material so that when the opening of the slit is projected onto the surface, the longitudinal direction of the groove is inclined with respect to the longitudinal direction of the projected opening. The coating device according to claim 4, further comprising an adjustment mechanism that adjusts the orientation of the base material held on the stage.

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