JP4058149B2 - Mask alignment method for vacuum deposition system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, a vacuum deposition apparatus odor Te relates mask alignment method for aligning a mask for pattern formation with respect to the substrate.
[0002]
[Prior art]
In many cases, the thin film formed on the substrate in a vacuum finally has a predetermined linear or dot pattern. Dry etching is often used as a means for forming a thin film on a substrate into a fine pattern. This dry etching is accompanied by plasma discharge and high temperature heating in vacuum.
[0003]
By the way, as a promising technique for realizing a color display panel, a technique using an organic electroluminescence thin film (for example, aluminum quinolinol) is known. Since this organic electroluminescent thin film cannot withstand an environment such as plasma discharge or high temperature heating (150 ° C. is the limit), a pattern cannot be formed using dry etching as described above. Therefore, it is required to form a film in a predetermined pattern from the beginning at the stage of thin film formation.
[0004]
FIG. 9A is a front sectional view of the prior art in which a mask is attached to a substrate to form an organic electroluminescent thin film in a predetermined pattern. The mask 12 is attached in close contact with the surface of the substrate 10. A large number of minute openings 14 are formed in the mask 12. A vapor deposition material 16 (organic electroluminescent material) is deposited on the surface of the substrate 10 through the opening 14.
[0005]
When an organic electroluminescence thin film is used as a color display panel, the size of the pixel (light emitting particle) is about several μm. The pixels of the three colors red, green, and blue are regularly arranged at intervals of several tens of μm. The mask 12 has an opening at a position corresponding to such a pixel.
[0006]
By the way, since the size of the pixel (that is, the size of the opening 14) is very small as described above, if the thickness of the mask 12 is relatively thick (0.5 to 1.0 mm), FIG. As shown to (A), the phenomenon that the peripheral part 18 of the vapor deposition film 16 in the opening part 14 becomes the shadow of the mask 12, and a film thickness becomes thinner than a center part.
[0007]
In order to eliminate such film thickness non-uniformity, a thin mask 20 was used as shown in FIG. In this case, the shadow problem due to the mask 20 disappeared, and the thickness of the deposit 24 at the opening 22 became uniform. As the thickness of the mask 20 is thinner, the shadow problem caused by the mask 20 does not occur. Therefore, the mask 20 should be as thin as possible. .
[0008]
[Problems to be solved by the invention]
In FIG. 9B, when the mask 20 is made thinner, the problem of looseness of the mask 20 occurs. The size of the substrate 10 of the display panel is, for example, an A4 size or a 300 mm square size. It may be larger than that. The size of the mask 20 is almost the same as that of the substrate 10. When such a large-sized mask 20 is made of a very thin plate, when the mask 20 is attached to the surface of the substrate 10, the mask 20 is located near the center of the mask 20 as shown in FIG. A gap 26 is formed between the mask 20 and the surface of the substrate 10 by slacking downward. With a substrate size of about 300 mm square, there may be a gap of about 5 mm in the center of the substrate. Then, the vapor deposition film 24 enters the gap 26, and “bleeding” occurs in the peripheral portion of the vapor deposition pattern. Such “bleeding” reduces the resolution of the electroluminescent image.
[0009]
This invention has been made to solve the above problems, and its object is Ru near to provide a mask alignment method, such as loosening of the mask does not occur even when using a thin mask.
[0010]
[Means for Solving the Problems]
According to the mask alignment method of the present invention, a thin plate-like mask in which a large number of through holes are formed is aligned with respect to the substrate, and then the mask is attached to the substrate surface. A mask made of a magnetic material is temporarily magnetically attracted by a mask adsorber containing an electromagnet, and then the mask and the substrate are aligned, and then placed on the back side of the nonmagnetic material substrate. The mask is attracted and fixed to the substrate surface by the magnetic attraction force of the back magnet. In order to align the mask and the substrate, the mask alignment mark and the substrate alignment mark are observed with an imaging device (for example, a CCD camera) to detect the amount of misalignment between them so that the amount of misalignment becomes zero. The mask adsorber is moved relative to the substrate. The mask suction body can move in a plane parallel to the substrate surface (this performs alignment), and can move in a direction perpendicular to the substrate surface (this can change the distance between the mask suction body and the substrate). .
[0011]
Since the mask after alignment is closely fixed to the substrate surface by a magnetic attractive force, even a thin mask is closely adhered to the substrate surface, and no gap is generated between the mask and the substrate surface. Therefore, there is no “bleeding” of the deposited film. If this mask attaching / detaching apparatus is used for organic electroluminescence film formation, the resolution of the image is improved.
[0012]
Further, since the mask is tightly fixed to the substrate surface by a magnetic attractive force, the mask is not displaced when the mask set substrate is transferred from the mask attaching / detaching zone to the film forming zone.
[0013]
The back magnet may be an electromagnet or a permanent magnet, but is preferably a permanent magnet. This permanent magnet is held by a magnet holder. When the magnet holder is formed of a material having good heat conduction, the heat of the substrate can be released through the magnet holder during film formation, and the temperature rise of the substrate can be suppressed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view showing an example of a mask attaching / detaching apparatus for carrying out the mask alignment method of the present invention, and FIG. 2 is a front sectional view thereof. A magnet holder 32 is provided above the substrate 30 (on the back side), and four permanent magnets 34 in the shape of an elongated rectangular parallelepiped are fixed to the magnet holder 32. The four permanent magnets 34 are arranged so that adjacent permanent magnets have opposite polarities (see FIG. 2). The permanent magnet 34 corresponds to the back magnet in the present invention. A thin plate-like mask 36 is provided below the substrate 30 (on the front surface side), and a large number of minute openings 38 are formed in the mask 36, and the many openings 38 are regularly arranged. . The dimension of the opening 38 is several μm, and the interval between the adjacent openings 38 is several tens of μm. In FIG. 1 and FIG. 2, the opening 38 is illustrated in an enlarged manner for easy understanding of the drawings.
[0015]
The substrate 30 is made of a nonmagnetic material (for example, glass). The mask 36 is made of a magnetic material (for example, iron). In this embodiment, the thickness of the mask 36 is as thin as 0.05 mm. The magnet holder 32 is made of a metal material having good heat conduction, such as copper or aluminum.
[0016]
Below the mask 36 is a mask adsorber 40. The mask attracting body 40 contains four electromagnets 42. When two of these electromagnets are excited, an N pole is generated on the upper surface, and when the remaining two electromagnets are excited, an S pole is generated on the upper surface. The mask adsorbing body 40 is movable in the up-down direction, that is, the Z direction (direction perpendicular to the substrate surface) with respect to the substrate 30, and is two-dimensional in the horizontal plane, that is, the XY direction (a plane parallel to the substrate surface). In a two-dimensional direction). Furthermore, the mask adsorbing body 40 can rotate θ around the axis perpendicular to the substrate surface with respect to the substrate 30. That is, as shown in FIG. 2, the mask suction body 40 is mounted on the XY drive stage 84, the Z drive stage 86, and the θ rotation stage 88.
[0017]
Next, with reference to FIG. 3, the operation of the mask attaching / detaching apparatus when an organic electroluminescent thin film for color display is formed will be described. In FIG. 3A, a mask adsorbing body 40 is arranged in the mask attaching / detaching zone. First, the substrate 30 is carried into the mask attachment / detachment zone and stopped at a predetermined position. Then, the magnet holder 32 is attached in close contact with the back side of the substrate 30. Thus, the substrate 30 and the magnet holder 32 are integrated, and the substrate 30 and the magnet holder 32 can be handled as a unit until film formation is completed. Note that the substrate 30 and the magnet holder 32 may be fixed to each other in advance and then transferred to the mask attachment / detachment zone. The magnet holder 32 is mechanically attached to the substrate 30 using, for example, claw-like parts or screws.
[0018]
Next, a mask 36 (first mask) for depositing red luminescent particles is carried between the mask adsorbing body 40 and the substrate 30. Since the mask 36 is away from the substrate 30, the mask 36 is not attracted to the permanent magnet 34 on the back side of the substrate 30. At this time, the electromagnet 42 of the mask attracting body 40 is still in a non-excited state.
[0019]
Next, when the electromagnet 42 of the mask attracting body 40 is excited, the magnetic mask 36 is magnetically attracted to the surface of the mask attracting body 40 as shown in FIG.
[0020]
Next, as shown in FIG. 4A, the mask adsorbing body 40 is raised to bring the mask 36 closer to the substrate 30. An appropriate distance between the mask 36 and the substrate 30 when approaching is about 1 to 1.5 mm. At this time, the mask 36 receives a magnetic attraction force from the permanent magnet 34, but the mask 36 remains adsorbed on the mask attraction body 40 because the magnetic attraction force by the mask attraction body 40 is stronger. The magnitude of the magnetic attraction force of the mask attracting body 40 can be determined experimentally. To adjust the magnetic attraction force, the current flowing through the electromagnet 42 may be adjusted.
[0021]
In this state, the mask 36 and the substrate 30 are aligned. That is, the two alignment marks 48 and 50 on the surface of the substrate 30 and the two alignment marks 52 and 54 on the mask 36 are observed with the two CCD cameras 44 and 46 so that they coincide with each other. Next, the mask suction body 40 is moved in the XY directions and rotated by θ. This will be described in detail. The alignment marks 48, 50 on the substrate 30 and the alignment marks 52, 54 on the mask 36 are captured as images by the CCD cameras 44, 46, and the amount of positional deviation between them is detected. Then, the mask adsorbing body 40 is finely adjusted in the XYθ direction. These alignment operations are automatically performed by a computer.
[0022]
Since the substrate 30 is transparent, it is possible to see through the alignment marks 48 and 50 on the front surface side of the substrate and the alignment marks 52 and 54 on the mask 36 using the CCD cameras 44 and 46 disposed on the back side of the substrate 30. Although the shape of these alignment marks is not particularly limited, for example, a cross-shaped mark can be used.
[0023]
By this alignment operation, the mask 36 and the substrate 30 are positioned with an accuracy of several μm.
[0024]
When the alignment of the mask 36 is completed, the electromagnet 42 of the mask attracting body 40 is de-energized. Then, as shown in FIG. 4B, the mask 36 is magnetically attracted to the permanent magnet 34 on the back side of the substrate 30 and is attracted onto the surface of the substrate 30. As a result, the substrate 30, the mask 36 and the magnet holder 32 are integrated (this integrated substrate is referred to as a mask set substrate 56). Since the thin mask 36 made of a magnetic material is attracted to the surface of the substrate 30 by the magnetic attraction force, the mask 36 does not sag and no gap is formed between the mask 36 and the substrate surface.
[0025]
Next, after the mask adsorbing body 40 is lowered, the mask set substrate 56 is transferred from the mask attaching / detaching zone to the film forming zone. Since the mask is firmly magnetically attracted to the substrate surface, the mask 36 is not displaced when the mask set substrate 56 is transferred. In the film forming zone, organic electroluminescent red light emitting particles are formed into a pattern on the substrate. The thickness of the deposited film is 100 to 1000 μm. In the present invention, since the mask 36 is magnetically attracted, there is no gap between the mask 36 and the substrate surface, and “bleeding” of the deposited film does not occur.
[0026]
When film formation of red luminescent particles is completed, the mask set substrate 56 is returned to the mask attachment / detachment zone, and then the red mask 36 is removed from the substrate 30 as follows. In FIG. 5A, the mask adsorbing body 40 is raised with respect to the mask set substrate 56 returned to the mask attaching / detaching zone, and the upper surface of the mask adsorbing body 40 is brought close to the surface (lower surface) of the mask 36. Then, the electromagnet 42 of the mask attracting body 40 is excited. Thereby, the mask 36 is magnetically attracted to the mask attracting body 40.
[0027]
Next, as shown in FIG. 5B, after the mask attracting body 40 is sufficiently lowered, the electromagnet 42 is de-energized and the mask 36 is removed from the mask attracting body 40.
[0028]
Next, as shown in FIG. 6A, a green mask 58 (second mask) is placed on the mask attracting body 40 and magnetically attracted by the electromagnet 42. Thereafter, in the same manner as the first mask, the second mask 58 is aligned as shown in FIG. 4 to produce a mask set substrate including the second mask 58. In this case, a thin film pattern for red is already formed on the substrate, and the opening (for green) of the mask 58 is located at a position different from the red color. When the formation of the green light emitting particles is completed, the blue light emitting particles are formed in the same manner using the third mask. In this manner, a color display panel using an organic electroluminescence thin film is completed by sequentially forming red, green, and blue light emitting grains using the three types of masks on the same substrate.
[0029]
Next, another example of a mask alignment method, that is, a mask alignment method using a deposited film trace will be described. In the three masks, a pair of alignment openings is formed at exactly the same position. An alignment mark may not be formed on the substrate. First, the first mask is set on the substrate. At this time, the alignment between the first mask and the substrate does not need to be so strict. Using the first mask, red light emitting grains are formed. At this time, as shown in FIG. 7A, a pair of deposited film traces 84 is formed on the substrate 30 through a pair of openings for alignment of the first mask. Next, when aligning the second mask 86 with respect to the substrate 30, the pair of CCD cameras 44 is used to align the pair of openings 88 for alignment of the second mask 86 and the above-described pair of vapor depositions. A film trace 84 is observed. FIG. 7 (B) shows a state where the deposited film trace 84 and the opening 88 are seen with a CCD camera. The mask adsorber carrying the second mask is moved so as to eliminate this shift. As a result, the positions of the first mask and the second mask are the same with respect to the substrate. When the green light emitting particles are formed using the second mask, the vapor deposition film trace by the second mask is formed at the same position so as to overlap the vapor deposition film trace 84 of FIG. Next, when the third mask is aligned, the deposited film trace is used in the same manner.
[0030]
FIG. 8 is a schematic front sectional view of a vacuum film forming apparatus for an organic electroluminescent thin film having a mask attaching / detaching zone and a film forming zone. The mask attaching / detaching zone 60 is inside the mask attaching / detaching chamber 62, and the mask adsorbing body 40 is disposed here. The film formation zone 64 is inside a film formation chamber 66, where a vapor deposition source 69 and a substrate holder 70 are arranged above it. The mask attaching / detaching chamber 62 and the film forming chamber 66 are exhausted by separate exhaust systems 76 and 78, respectively. The substrate 30 and the mask 36 are taken out of the separate storage shelves 80 and 82 and transferred to the mask attaching / detaching zone. The mask set substrate 56 on which the mask 36 has been aligned and set in the mask attaching / detaching zone 60 passes through the gate valve 72 and is then transferred to the film forming zone 64. The mask set substrate 56 is attached in close contact with the lower surface of the substrate holder 70 in the film formation zone 60. That is, the upper surface of the magnet holder 32 is attached in close contact with the lower surface of the substrate holder 70. Since the cooling water 74 circulates inside the substrate holder 70 and is cooled, the substrate 30 is cooled by the substrate holder 70 via the magnet holder 32 during film formation. Thereby, the temperature rise of the substrate 30 during film formation can be prevented. Since the magnet holder 32 is made of copper or aluminum having good heat conduction, the heat of the substrate 30 efficiently escapes to the substrate holder 70 via the magnet holder 32. The mask set substrate 56 can be attached to the lower surface of the substrate holder 70 by scooping up a claw-like component, for example, by moving it up and down.
[0031]
【The invention's effect】
According to the mask alignment method of the present invention, the aligned mask is closely fixed to the substrate surface by magnetic attraction, so even a thin mask is closely adhered to the substrate surface, and there is a gap between the mask and the substrate surface. Does not occur. Therefore, there is no “bleeding” of the deposited film. If this mask alignment method is used for organic electroluminescence film formation, the resolution of the image is improved. Further, since the mask is tightly fixed to the substrate surface by a magnetic attractive force, the mask is not displaced when the mask set substrate is transferred from the mask attaching / detaching zone to the film forming zone.
[Brief description of the drawings]
FIG. 1 is a perspective view of an example of a mask attaching / detaching apparatus that implements a mask alignment method of the present invention.
FIG. 2 is a front sectional view of the mask attaching / detaching apparatus of FIG. 1;
FIG. 3 is a front sectional view showing the operation of the mask attaching / detaching apparatus.
FIG. 4 is a front cross-sectional view showing another operation of the mask attaching / detaching apparatus.
FIG. 5 is a front cross-sectional view showing still another operation of the mask attaching / detaching apparatus.
FIG. 6 is a front sectional view showing still another operation of the mask attaching / detaching apparatus.
FIG. 7 is an explanatory diagram showing another example of a mask alignment method.
FIG. 8 is a schematic front sectional view of a vacuum film forming apparatus.
FIG. 9 is a front sectional view of a conventional pattern film forming method using a mask.
[Explanation of symbols]
30 substrate 32 magnet holder 34 permanent magnet 36 mask 38 opening 40 mask attracting body 42 electromagnet 44, 46 CCD camera 48, 50 alignment mark 52, 54 mask alignment mark 56 mask set substrate 60 mask attachment / detachment zone 64 film formation zone

Claims (2)

In a mask alignment method of a vacuum film formation apparatus, a thin plate-like mask in which a large number of through holes are formed is aligned with a substrate to be deposited, and then the mask is attached to the surface of the substrate. A mask alignment method comprising the steps of (a) to (e).
(A) A step of exciting the electromagnet built in the mask adsorption body to temporarily magnetically adsorb the mask formed of a magnetic material on the surface of the mask adsorption body.
(A) A step of bringing a mask adsorber magnetically adsorbing the mask closer to the surface of the substrate formed of a nonmagnetic material.
(C) A step of observing the alignment mark on the mask and the alignment mark on the substrate with an imaging device.
(D) A step of moving the mask adsorbent relative to the substrate within a plane parallel to the substrate surface so that the position of the alignment mark on the mask matches the position of the alignment mark on the substrate.
(E) A step in which the electromagnet is de-excited and the mask on the mask attracting body is attracted and held on the substrate surface by the magnetic attraction force of the back magnet disposed on the back side of the non-magnetic material substrate. 2. The mask alignment method according to claim 1 , wherein when a plurality of types of film formation are sequentially performed using a plurality of masks on the same substrate, the alignment mark on the substrate is formed in the previous stage. A mask alignment method characterized by being a deposited film trace formed through an opening for alignment of the mask used in the above.

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