KR20190034726A - Nozzle unit and apparatus for treating substrate - Google Patents

Abstract

The present invention relates to a substrate processing apparatus, including: a cup having a processing space having an opened upper portion; a support unit supporting a substrate in the processing space; a nozzle unit having a nozzle supplying processing liquid into the substrate supported on the support unit; a home port provided on the outside of the cup and having a waiting space in which the nozzle waits; and a nozzle actuator moving the nozzle between the cup and the home port, wherein the nozzle unit has: a support supporting the nozzle; and a cleaning member discharging cleaning liquid cleaning an outer surface of the nozzle, thereby providing an advantage of clearly cleaning each of the nozzles by the cleaning member provided on one sides of each of the nozzles.

Description

[0001] The present invention relates to a nozzle unit and a substrate processing apparatus,

The present invention relates to a nozzle unit and a substrate processing apparatus, and more particularly, to a nozzle unit and a substrate processing apparatus having a nozzle cleaning member.

Various processes such as deposition, photolithography, etching, cleaning and the like are performed to manufacture a semiconductor device. In each step, the process liquid is supplied to the substrate through the nozzles.

When the treatment liquid is applied to the outer surface of the nozzle when the treatment liquid is supplied to the substrate, these treatment liquids act as particles to contaminate the substrate to be subsequently treated.

Korean Patent Laid-Open No. 10-2007-0036865 (hereinafter referred to as Prior Art 1) discloses an example of cleaning a nozzle. According to the prior art document 1, a cleaning liquid supply member capable of jetting a cleaning liquid such as thinner or the like and a drying gas supply member capable of jetting dry gas are provided inside a housing on a box with an opened upper surface. When the nozzle is inserted into the housing, the nozzle is cleaned and dried by the cleaning liquid supply member and the dry gas supply member. Also, as disclosed in Korean Patent Laid-Open Publication No. 10-2011-0126572 (hereinafter referred to as Prior Art 2), a nozzle unit in which a plurality of nozzles are integrated is used.

However, when the nozzle unit of the prior art document 2 is cleaned in the same manner as the prior art document 1, as shown in FIG. 1, the area X where the adjacent nozzles face is not cleaned well.

Korean Patent Publication No. 10-2007-0036865 (April 04, 2007) Korean Patent Laid-Open Publication No. 10-2011-0126572 (November 23, 2011)

The present invention provides a nozzle unit and a substrate processing apparatus capable of improving the cleaning efficiency of a nozzle unit in which a plurality of nozzles are arranged in a row.

The problems to be solved by the present invention are not limited thereto, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

An embodiment of the present invention provides a nozzle unit and a substrate processing apparatus. The substrate processing apparatus is characterized in that the substrate processing apparatus is an apparatus for processing a substrate, the apparatus comprising: a cup having an upper open processing space; a support unit for supporting the substrate in the processing space; A nozzle port provided on the outside of the cup and having an atmospheric space in which the nozzle waits; and a nozzle driver for moving the nozzle between the cup and the groove port, wherein the nozzle unit includes a nozzle And a cleaning member for discharging a cleaning liquid for cleaning the outer surface of the nozzle.

The nozzle unit may be provided with a plurality of nozzles, and the plurality of nozzles may be supported by the support.

The plurality of nozzles may be arranged in a line on a support.

The nozzle includes a body fixed to a support and a nozzle tip attached to a bottom surface of the body, and the nozzle tip can be coupled to only a part of the bottom surface of the body.

The cleaning member may be provided as a plurality of outlets on the outside of a part of the bottom surface of the body where the nozzle tips are coupled.

The plurality of discharge ports provided in the cleaning member may be provided to cover one surface of the nozzle tip in contact with the body in combination with each other.

The substrate processing apparatus of one embodiment of the present invention further includes a controller for controlling the cleaning member, and the controller can control the cleaning member such that when the nozzle is located in the atmospheric space, the nozzle is cleaned.

The treatment liquid may be a photoresist, and the cleaning liquid may be thinner.

The substrate processing apparatus of one embodiment of the present invention further includes a drying member for drying the nozzle tip, wherein the drying member can be provided on the body with a plurality of nozzles outside a part of the bottom surface of the body to which the nozzle tip is coupled have.

The plurality of ejection openings may be provided between the ejection openings, respectively.

An embodiment of the present invention provides a nozzle unit and a substrate processing apparatus. The nozzle unit includes a nozzle for spraying a treatment liquid toward the substrate, a support for supporting the nozzle, and a cleaning member for discharging a cleaning liquid for cleaning the outer surface of the nozzle.

The nozzle includes a body to which a treatment liquid is supplied from the outside and a nozzle tip attached to the body. The nozzle tip is coupled to only a part of the bottom surface of the body. And a plurality of discharge ports provided in the cleaning member are provided to surround one surface of the nozzle tip in contact with the body in combination with each other.

The nozzle unit of one embodiment of the present invention further includes a drying member for drying the nozzle tip, wherein the drying member is provided on the body as a plurality of ejection openings on the outside of a part of the bottom surface of the body where the nozzle tip is engaged, The number of ejection openings can be provided between the ejection openings, respectively.

According to the nozzle unit and the substrate processing apparatus in one embodiment of the present invention, each nozzle is cleaned by the cleaning member provided at one side of each nozzle.

Further, since the nozzle unit is cleaned by the cleaning member, the nozzle unit can be easily applied to any conventional substrate processing apparatus.

In addition, since the nozzle unit washed by the provided drying unit is dried, secondary contamination such as moss, mold and bacterium formation that may occur due to moisture in the nozzle is prevented.

FIG. 1 is a view showing a problem in cleaning a nozzle unit in which a plurality of nozzles are integrally provided through a conventional home port.
2 is a top view of a substrate processing apparatus according to an embodiment of the present invention.
Fig. 3 is a view of the equipment of Fig. 2 viewed from the direction AA.
Fig. 4 is a view of the equipment of Fig. 2 viewed from the BB direction. Fig.
Fig. 5 is a view of the equipment of Fig. 2 viewed from the CC direction.
FIG. 6 is a cross-sectional view showing a substrate processing apparatus provided in the application chamber of FIG. 2;
7 is a plan view showing the substrate processing apparatus of FIG.
FIG. 8 is a perspective view showing the home port of FIG. 6. FIG.
FIG. 9 is a perspective view showing a state in which the nozzle unit is inserted into the groove port of FIG. 6. FIG.
FIGS. 10 and 11 are views sequentially showing the state of washing and drying the nozzle of FIG.
12 is an exemplary view showing a state in which the nozzle of Fig. 9 is cleaned.

The facilities of this embodiment can be used to perform a photolithography process on a substrate such as a semiconductor wafer or a flat panel display panel. In particular, the apparatus of this embodiment can be used to perform a coating process and a developing process on a substrate, which is connected to an exposure apparatus. Hereinafter, a case where a wafer is used as a substrate will be described as an example.

FIGS. 2 to 5 are schematic views of a substrate processing apparatus according to an embodiment of the present invention. FIG. 2 is a view of the substrate processing apparatus viewed from above, FIG. 3 is a view of the apparatus of FIG. 2 viewed from the AA direction, FIG. 4 is a view of the apparatus of FIG. 2 viewed from the BB direction, In the CC direction.

2 to 5, the substrate processing apparatus 1 includes a load port 100, an index module 200, a first buffer module 300, a coating and developing module 400, a second buffer module 500 An exposure pre- and post-processing module 600, and an interface module 700.

Hereinafter, the load port 100, the index module 200, the first buffer module 300, the coating and developing module 400, the second buffer module 500, the pre-exposure processing module 600, 700 are referred to as a first direction 12 and a direction perpendicular to the first direction 12 as viewed from above is referred to as a second direction 14 and a direction in which the first direction 12 and the second And a direction perpendicular to the direction 14 is referred to as a third direction 16.

The substrate W is moved in a state accommodated in the cassette 20. At this time, the cassette 20 has a structure that can be sealed from the outside. For example, as the cassette 20, a front open unified pod (FOUP) having a door at the front can be used.

Hereinafter, the load port 100, the index module 200, the first buffer module 300, the application and development module 400, the second buffer module 500, the pre-exposure processing module 600, 700 will be described in detail.

The load port 100 has a mounting table 120 on which the cassette 20 accommodating the substrates W is placed. A plurality of mounts 120 are provided, and the mounts 120 are arranged in a line along the second direction 14. In Fig. 1, four placement tables 120 are provided.

The index module 200 transfers the substrate W between the cassette 20 placed on the table 120 of the load port 100 and the first buffer module 300. The index module 200 has a frame 210, an index robot 220, and a guide rail 230. The frame 210 is provided generally in the shape of an inner rectangular parallelepiped and is disposed between the load port 100 and the first buffer module 300.

The first buffer module 300 has a frame 310, a first buffer 320, a second buffer 330, a cooling chamber 350, and a first buffer robot 360. The frame 310 is provided in the shape of an inner rectangular parallelepiped and is disposed between the index module 200 and the application and development module 400. The first buffer 320, the second buffer 330, the cooling chamber 350, and the first buffer robot 360 are located within the frame 310. The first buffer 320 and the second buffer 330 temporarily store a plurality of substrates W, respectively. The first buffer robot 360 transfers the substrate W between the first buffer 320 and the second buffer 330. The cooling chamber 350 cools the substrate W, respectively.

The application and development module 400 performs a process of applying a photoresist on the substrate W before the exposure process and a process of developing the substrate W after the exposure process. The application and development module 400 has a generally rectangular parallelepiped shape. The coating and developing module 400 has a coating module 401 and a developing module 402.

The application module 401 and the development module 402 are arranged so as to be partitioned into layers with respect to each other. According to one example, the application module 401 is located on top of the development module 402.

The application module 401 includes a process of applying a photosensitive liquid such as a photoresist to the substrate W and a heat treatment process such as heating and cooling for the substrate W before and after the resist application process.

The application module 401 has a resist application chamber 410, a bake chamber 420, and a transfer chamber 430. The resist application chamber 410, the bake chamber 420, and the transfer chamber 430 are sequentially disposed along the second direction 14. [ The resist application chamber 410 and the bake chamber 420 are positioned apart from each other in the second direction 14 with the transfer chamber 430 interposed therebetween.

A plurality of resist coating chambers 410 are provided, and a plurality of resist coating chambers 410 are provided in the first direction 12 and the third direction 16, respectively. In the figure, six resist coating chambers 410 are provided.

The bake chamber 420 heat-treats the substrate W. For example, the bake chambers 420 may be formed by a prebake process for heating the substrate W to a predetermined temperature to remove organic substances and moisture on the surface of the substrate W, A soft bake process is performed after coating the substrate W on the substrate W, and a cooling process for cooling the substrate W after each heating process is performed.

The transfer chamber 430 is positioned in parallel with the first buffer 320 of the first buffer module 300 in the first direction 12.

The developing module 402 includes a developing process for supplying a developing solution to obtain a pattern on the substrate W to remove a part of the photoresist and a heat treatment process such as heating and cooling performed on the substrate W before and after the developing process . The development module 402 has a development chamber 460, a bake chamber 470, and a transfer chamber 480. The development chamber 460, the bake chamber 470, and the transfer chamber 480 are sequentially disposed along the second direction 14.

The development chambers 460 all have the same structure. However, the types of developers used in the respective developing chambers 460 may be different from each other. The development chamber 460 removes a region of the photoresist on the substrate W where light is irradiated. At this time, the area of the protective film irradiated with the light is also removed. Depending on the type of selectively used photoresist, only the areas of the photoresist and protective film that are not irradiated with light can be removed.

The bake chamber 470 of the developing module 402 heat-treats the substrate W. [ For example, the bake chambers 470 may include a post-bake process for heating the substrate W before the development process is performed, a hard bake process for heating the substrate W after the development process is performed, And a cooling step for cooling the substrate W is performed.

The second buffer module 500 is provided as a path through which the substrate W is transferred between the coating and developing module 400 and the pre- and post-exposure processing module 600. The second buffer module 500 performs a predetermined process on the substrate W such as a cooling process or an edge exposure process. The second buffer module 500 includes a frame 510, a buffer 520, a first cooling chamber 530, a second cooling chamber 540, an edge exposure chamber 550, and a second buffer robot 560 I have.

The pre- and post-exposure processing module 600 can process a process of applying a protective film for protecting the photoresist film applied to the substrate W during liquid immersion exposure when the exposure apparatus performs the liquid immersion exposure process. In addition, the pre- and post-exposure processing module 600 may perform a process of cleaning the substrate W after exposure. In addition, when the coating process is performed using the chemically amplified resist, the pre- and post-exposure processing module 600 can process the post-exposure bake process.

The pre-exposure post-processing module 600 has a pre-processing module 601 and a post-processing module 602. The pre-processing module 601 performs a process of processing the substrate W before the exposure process, and the post-process module 602 performs a process of processing the substrate W after the exposure process.

In the pre-exposure processing module 600, the pre-processing module 601 and the post-processing module 602 are provided to be completely separated from each other.

The pretreatment module 601 has a protective film application chamber 610, a bake chamber 620, and a transfer chamber 630. The protective film application chamber 610, the transfer chamber 630, and the bake chamber 620 are sequentially disposed along the second direction 14.

The protective film application chamber 610 and the bake chamber 620 are positioned apart from each other in the second direction 14 with the transfer chamber 630 therebetween. A plurality of protective film application chambers 610 are provided and are arranged along the third direction 16 to form layers.

Alternatively, a plurality of protective film application chambers 610 may be provided in the first direction 12 and the third direction 16, respectively. A plurality of bake chambers 620 are provided and are disposed along the third direction 16 to form layers. Alternatively, a plurality of bake chambers 620 may be provided in the first direction 12 and the third direction 16, respectively.

The post-processing module 602 has a cleaning chamber 660, a post-exposure bake chamber 670, and a delivery chamber 680. The cleaning chamber 660, the transfer chamber 680, and the post-exposure bake chamber 670 are sequentially disposed along the second direction 14.

Accordingly, the cleaning chamber 660 and the post-exposure baking chamber 670 are positioned apart from each other in the second direction 14 with the transfer chamber 680 therebetween. A plurality of cleaning chambers 660 are provided and may be disposed along the third direction 16 to form layers.

Alternatively, a plurality of cleaning chambers 660 may be provided in the first direction 12 and the third direction 16, respectively. A plurality of post-exposure bake chambers 670 are provided and may be disposed along the third direction 16 to form layers. Alternatively, a plurality of post-exposure bake chambers 670 may be provided in the first direction 12 and the third direction 16, respectively.

The interface module 700 transfers the substrate W between the exposure pre- and post-processing modules 600. The interface module 700 has a frame 710, a first buffer 720, a second buffer 730, and an interface robot 740. The first buffer 720, the second buffer 730, and the interface robot 740 are located within the frame 710.

The first buffer 720 and the second buffer 730 are spaced apart from each other by a predetermined distance and are stacked on each other. The first buffer 720 is disposed higher than the second buffer 730. The first buffer 720 is positioned at a height corresponding to the preprocessing module 601 and the second buffer 730 is positioned at a height corresponding to the postprocessing module 602. The first buffer 720 is arranged in a line along the first direction 12 with the transfer chamber 630 of the preprocessing module 601 while the second buffer 730 is arranged in the postprocessing module 602, Are arranged in a line along the first direction 12 with the transfer chamber 630 of the transfer chamber 630. [

6 and 7 are respectively a cross-sectional view and a plan view showing an example of the resist coating chamber of FIG. The resist application chamber 800 includes a cup 810, a support unit 820, a nozzle unit 830, a groove port 840, a nozzle driver 850, and a controller (not shown).

The cup 810 has a processing space 811 in which the substrate W is processed. The processing space 811 is provided so that its upper portion is open. According to one example, a lift unit 870 is provided at one side of the cup 810. The elevating unit 870 drives the cup 810 in the vertical direction. The elevating unit 870 includes a bracket 871, a moving shaft 872, and a driver 873. The bracket 871 is fixed to the cup 810. A moving shaft 872, which is vertically moved by a driver 873, is fixedly coupled to the bracket 871.

The support unit 820 is provided in the center of the cup 810. The support unit 820 supports and rotates the substrate W. The support unit 820 includes a support plate 821 and a drive member 822. And the substrate W is seated on the upper surface of the support plate 821. The support plate 821 is vacuum-chucked so that the substrate W is not released. The area of the support plate 821 is smaller than the area of the substrate W. [

 The supporting plate 821 is rotated by the driving member 822. The driving member 822 is coupled to the bottom surface of the support plate 821. The driving member 822 includes a driving shaft (not shown) and a driver (not shown). The drive shaft is coupled to the bottom surface of the support plate 821.

The nozzle unit 830 supplies the photosensitive liquid onto the substrate W placed on the supporting unit 820. [ The nozzle unit 830 includes a nozzle 831, a support base 832, a cleaning member 833, and a drying member 834.

The nozzle 831 discharges the photosensitive liquid onto the substrate W. A plurality of nozzles 831 are provided. The types of the sensitizing solution discharged from the respective nozzles 831 are different from each other. A plurality of nozzles for directing the photosensitive liquid onto the substrate W are arranged in a line. The plurality of nozzles 831 are fixed to the support base 832. The nozzle 831 includes a body 831a and a nozzle tip 831b. The body 831a is fixed to the support 832. The nozzle tip 831b has a conical shape in which the nozzle tip 831b is formed in a cowl shape or the cross section becomes smaller as it goes downward. The nozzle tip 831b is provided so as to have an area smaller than the bottom surface of the body 831a. The nozzle tip 831b is engaged only in a part of the bottom surface of the body 831a. Thus, the bottom surface of the body 831a is formed with a ring-shaped unbonded portion A that is not covered with the nozzle tip 831b.

The cleaning member 833 ejects the cleaning liquid for cleaning the nozzle 831. [ A thinner may be used as the washing solution. The cleaning member 833 is provided in each of the nozzles 831 as a plurality of discharge ports. According to one example, the discharge port is formed in the non-engaging portion A in the bottom surface of the body. The plurality of ejection openings are arranged to form a ring in combination with each other, and are provided to surround the nozzle tip 831b.

The drying member 834 is provided in the form of a plurality of ejection openings in the above-described unmated portion A. A plurality of ejection openings formed by the drying member 834 in the unmated portion A are formed one each between adjacent two ejection openings. The drying member 834 in the form of an injection port is connected to the drying line for supplying nitrogen gas from the outside, the body 831a and the support 833. The support 833 is provided with a valve (not shown) for adjusting the injection amount of the nitrogen gas supplied through the drying line (not shown) and the injection pressure.

The home port 840 is provided in a waiting space in which the nozzle unit 830, which does not perform the coating process, is kept in an atmosphere and stored. The home port 840 discharges the thinner continuously or intermittently to each of the waiting nozzles 831 in the standby state. Each of the nozzles 831 discharges the sensitizing solution to prevent the sensitizing solution supplied to the substrate W from sticking. According to one example, a plurality of cleaning tools (not shown) for discharging the photosensitive liquid are formed on the inner wall surface of the groove port 840. The plurality of cleaning mouths are arranged at equal heights at regular intervals.

The nozzle driver 850 includes a guide rail 851, an arm 852, and a driver (not shown). The guide rail 851 is positioned on one side of the cup 810. The guide rails 851 are provided so that their longitudinal directions are directed in the first direction 12. An arm 852 is provided on the guide rail 851. The arm 852 is provided so as to have a bar shape.

The driver can provide a driving force to the guide rail 851 to reciprocate the arm 852 and the nozzle unit 830 in the first direction 12 or in the opposite direction. The arm 852 and the nozzle unit 830 mounted thereto are movable to the process position and the standby position by the guide rail 851 and the actuator. For example, the actuator may be a motor.

A controller (not shown) controls the cleaning member. The controller operates the cleaning member to clean the nozzle 831 when the nozzle 831 is waiting at the home port 840. [

In the embodiment of the present invention described above, a plurality of nozzles 831 are arranged in a row on the supporter 832. However, the shape of the nozzles 831 may be changed according to need, such as a circle, an X-axis,

In particular, the cleaning member 833 may be arranged such that a plurality of imaginary circles having different diameters are formed on the non-coupling portion A. [ According to another example, a plurality of discharge ports are formed at the same distance with respect to the center of the body 831a, so that the cleaning liquid supplied through the plurality of discharge ports may be in the shape of a pipe or a cone.

The cleaning liquid may be simultaneously supplied to all outer surfaces of the nozzle tip 831b by adjusting the arrangement of the plurality of discharge ports and the discharge angle of the cleaning liquid through the discharge port. Alternatively, the cleaning liquid may flow from the boundary point between the nozzle tip 831b and the body 831a along the outer surface of the nozzle tip 831b.

Some of the outlets are provided to discharge the cleaning liquid toward the lower one of the outer surfaces of the nozzle tips 831b while the other portion is provided to discharge the cleaning liquid toward the upper one of the outer surfaces of the nozzle tips 831b .

The resist coating chamber 800 according to the embodiment of the present invention having the above structure is configured so that even when a plurality of nozzles 831 are arranged in a row to form the nozzle unit 830, All can be cleaned.

Since the nozzle unit 300 configured to clean the respective nozzles 310 by the cleaning member 330 provided at one side of each nozzle 310 is provided, .

In addition, since the nozzle 310 washed by the drying member 700 provided at one side of the nozzle 310 is dried, secondary contamination due to the cleaning solution can be prevented.

Although the nozzle unit 830 having a plurality of nozzles 831 is described as being provided in the resist application chamber in the above example, the nozzle unit 830 described above may be provided in another chamber such as a protective film application chamber, a development chamber, have.

In the above-described example, the apparatus for performing the coating and developing process on the substrate W is described as an example. However, the nozzle unit 830 described above may be provided in other types of apparatuses performing the etching or cleaning process, have.

The above description has been made in detail of a substrate processing apparatus according to an embodiment of the present invention. However, the present invention is not limited to the above-described example, and is applicable to all apparatuses for processing substrates.

800: Resist application chamber 810: Cup
820: support unit 830: nozzle unit
840: Home port 850: Nozzle driver
860:

Claims (13)

An apparatus for processing a substrate,
A cup having an upper open processing space;
A support unit for supporting the substrate in the processing space;
A nozzle unit having a nozzle for supplying a treatment liquid to the substrate supported by the support unit;
A groove port provided outside the cup and having an atmospheric space in which the nozzle waits;
And a nozzle driver for moving the nozzle between the cup and the groove port,
Wherein the nozzle unit comprises:
A support for supporting the nozzle;
And a cleaning member for discharging a cleaning liquid for cleaning the outer surface of the nozzle.
The method according to claim 1,
Wherein the nozzle unit is provided with a plurality of nozzles,
And the plurality of nozzles are supported by the support.
3. The method of claim 2,
Wherein the plurality of nozzles comprises:
And arranged in a line on the support.
4. The method according to any one of claims 1 to 3,
The nozzle
A body fixed to the support;
A nozzle tip attached to a bottom surface of the body,
Wherein the nozzle tip is engaged only in a part of the bottom surface of the body.
5. The method of claim 4,
Wherein the cleaning member comprises:
Wherein a plurality of discharge ports are provided on the outside of the part of the bottom surface of the body to which the nozzle tip is coupled.
6. The method of claim 5,
Wherein the plurality of ejection openings
Wherein the nozzle tip is provided to surround the nozzle tip in contact with the body in combination with each other.
The method according to claim 6,
Further comprising a controller for controlling said cleaning member,
The controller comprising:
And controls the cleaning member such that the nozzle is cleaned when the nozzle is located in the waiting space.
The method according to claim 6,
Wherein the treatment liquid is a photoresist, and the cleaning liquid is a thinner.
6. The method of claim 5,
Further comprising a drying member for drying the nozzle tip,
Wherein the drying member comprises:
Wherein the body is provided with a plurality of ejection openings on the outside of a part of the bottom surface of the body where the nozzle tips are coupled.
10. The method of claim 9,
The jetting port
Respectively, between the discharge ports.
A nozzle for spraying the treatment liquid toward the substrate;
A support for supporting the nozzle;
And a cleaning member for discharging a cleaning liquid for cleaning the outer surface of the nozzle.
12. The method of claim 11,
The nozzle
A body to which a treatment liquid is supplied from the outside;
A nozzle tip attached to the body,
Wherein the nozzle tip is engaged only in a part of the bottom surface of the body,
Wherein the cleaning member comprises:
Wherein a plurality of discharge ports are provided on the outside of the part of the bottom surface of the body to which the nozzle tip is coupled,
Wherein the plurality of ejection openings
Wherein the nozzle unit is provided to surround the nozzle tip in contact with the body in combination with each other.
13. The method of claim 12,
Further comprising a drying member for drying the nozzle tip,
Wherein the drying member comprises:
Wherein the body is provided with a plurality of ejection openings on the outside of a part of the bottom surface of the body where the nozzle tips are coupled,
The jetting port
And each of the nozzle units is provided between the ejection openings.

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