Patent Publication Number: US-2015083045-A1

Title: Mask fixing device and deposition apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2013-0114024, filed on Sep. 25, 2013, the contents of which are hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field 
     The described technology generally relates to a mask fixing device and a deposition apparatus including the same. 
     2. Description of the Related Technology 
     Organic light-emitting diode (OLED) displays are increasing in popularity due to their favorable qualities such as low power consumption and superior display quality when compared to liquid crystal displays (LCDs). OLED displays have an OLED formed in each pixel area thereof. Each OLED includes a cathode, an anode, and an organic light-emitting layer interposed between them. 
     Generally, deposition or thermal transfer is used in forming the organic light-emitting layer on a substrate. When a deposition method is used to form the organic light-emitting layer, a mask is fixed to the substrate in order to pattern the organic light-emitting layer on the substrate. 
     SUMMARY OF CERTAIN INVENTIVE ASPECTS 
     One inventive aspect is a mask fixing device capable of stably fixing a mask to a substrate. 
     Another aspect is a mask fixing device including a plate and a magnetic assembly. The magnetic assembly is fixed to the plate. The magnetic assembly includes first magnetic members each having a first magnetic pole contacting the plate and extending in a first direction and second magnetic members each having a second magnetic pole contacting with the plate and extending in the first direction. The first and second magnetic poles have different polarities. The magnetic members are arranged such that a pair of first magnetic members and a pair of second magnetic members are alternately arranged in a second direction crossing the first direction. 
     Another aspect is a deposition apparatus including a chamber, a deposition source, and a mask fixing device. The deposition source is disposed in the chamber to provide a deposition material to a substrate and the mask fixing device is disposed in the chamber to fix a mask to the substrate. The mask fixing device includes a plate and a magnetic assembly. The magnetic assembly applies a magnetic force to fix the mask to the substrate. The substrate is interposed between the magnetic assembly and the mask. The magnetic assembly is fixed to the plate. The magnetic assembly includes first magnetic members each having a first magnetic pole contacting the plate and extending in a first direction and second magnetic members each having a second magnetic pole contacting the plate and extending in the first direction. The first and second magnetic poles have different polarities. The magnetic members are arranged such that at least two neighboringfirst magnetic members and at least two neighboring second magnetic members are alternately and repeatedly arranged in a second direction crossing the first direction. 
     Another aspect is a mask fixing device that fixes a mask to a substrate for a display device including a magnetic assembly. The magnetic assembly includes first magnetic members and second magnetic members. The first and second magnetic members each respectively having first and second magnetic poles and configured to contact the substrate, wherein the first and second magnetic members are configured to apply a magnetic force to the mask to fix the mask to the substrate, wherein the substrate is interposed between and contact the magnetic assembly and the mask, wherein the first and second magnetic poles have different polarities, and wherein first magnetic members and the second magnetic members are alternately arranged. 
     The mask fixing device further includes a plate holding at least a part of the magnetic assembly, wherein the plate does not contact the substrate. Recesses are defined in a surface of the plate facing the magnetic assembly and at least a part of the magnetic assembly is accommodated in the recesses. 
     According to at least one embodiment, the magnetic force applied to the mask is substantially uniform due to the configuration of a magnetic assembly included in the mask fixing device. Therefore, the mask may be fixed to the substrate using the magnetic assembly and the mask may be prevented from being detached from the substrate. In addition, when the mask fixing device is employed in the deposition apparatus, the quality of the deposition pattern formed on the substrate using the deposition material may be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view showing a mask fixing device according to an exemplary embodiment. 
         FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 . 
         FIG. 3A  is a cross-sectional view showing the fixing a mask to a substrate according to an embodiment. 
         FIG. 3B  is a graph showing the magnetic force intensity according to positions on a mask. 
         FIG. 4  is a plan view showing a mask fixing device according to another exemplary embodiment. 
         FIG. 5  is a cross-sectional view showing a deposition apparatus according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS 
     One method of fixing a mask to a substrate includes mechanically fixing both side portions of the mask to the substrate using a tool, e.g., pin, clip, etc. Another method includes magnetically fixing the mask to the substrate using magnetic force. 
     It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the described technology. 
     Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,  “ upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein are to be interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the described technology. As used herein, the singular forms, “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the described technology belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, the described technology will be explained in detail with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view showing a mask fixing device according to an exemplary embodiment and  FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a mask fixing device  100  includes a plate  10  and a magnetic assembly MA. 
     The plate  10  is coupled to the magnetic assembly MA to fix the magnetic assembly MA to the plate  10 . In the present exemplary embodiment, the plate  10  includes recesses  11  formed on a surface thereof, which face the magnetic assembly MA. The magnetic assembly MA is accommodated in the recesses  11 , and thus, the magnetic assembly MA is fixed to the plate  10 . 
     The magnetic assembly MA includes first magnetic members M 1  and second magnetic members M 2 . A first magnetic pole of each of the first magnetic members M 1  and a second magnetic pole of each of the second magnetic members M 2  contact the plate  10 . The first and second magnetic poles have different polarities. According to some embodiments, the first magnetic pole is a south (S) pole and the second magnetic pole is a north (N) pole, however, the described technology is not limited thereto or thereby. That is, according to other embodiments, the first and second magnetic poles are N and S poles, respectively. 
     The first and second magnetic members M 1  and M 2  are arranged on the plate  10 . In detail, two first magnetic members M 1  are alternately arranged with two second magnetic members M 2  on the plate  10 . That is, two first magnetic members are sequentially placed on the plate  10 , two second magnetic members are sequentially placed after the two first magnetic members, a second set of two first magnetic members are sequentially placed after the two second magnetic members, and then a second set of two second magnetic members are sequentially placed after the “second set of two first magnetic members”. 
     In the present exemplary embodiment, each of the first and second magnetic members M 1  and M 2  has a bar shape extending in a first direction D 1 . In addition, the first and second magnetic members M 1  and M 2  are arranged on the plate  10  in a second direction D 2  substantially perpendicular to the first direction D 1 . 
     The mask fixing device  100  is disposed to face a mask  30  with a substrate  20  interposed between the mask fixing device  100  and the mask  30 . The mask  30  is provided with openings  31  formed therethrough to form a pattern on the substrate  20 . The mask fixing device  100  generates a magnetic force which is applied to the mask  30 , and thus, the mask  30  is fixed to the substrate  20  by the magnetic force. 
     In the present exemplary embodiment, the first and second magnetic members M 1  and M 2  are permanent magnets, however, the described technology is not limited thereto or thereby. That is, the first and second magnetic members M 1  and M 2  may be electromagnets. 
       FIGS. 3A and 3B  are views illustrating the fixing the mask  30  to the substrate  20  according to an embodiment. In detail,  FIG. 3A  shows a cross-sectional view taken along line I-I′ of  FIG. 1  and  FIG. 3B  is a graph showing the relative intensities of the magnetic force according to positions on the mask  30 . 
     Referring to  FIG. 3A , the two first magnetic members M 1  are alternately and repeatedly arranged with the two second magnetic members M 2  on the plate  10 . One of the first magnetic members M 1  is adjacent to a pair of second magnetic members M 2 . Hereinafter, the distance between a center of the first magnetic member and a center of the first of the pair of second magnetic members which is adjacent to the first magnetic member is referred to as a first distance or first pitch a 1 . The distance between the center of the first magnetic member and a center of the second of the pair of second magnetic members is referred to as a second distance or second pitch a 2 . The first magnetic member and the second of the pair of second magnetic members are arranged with the first of the pair of second magnetic members interposed therebetween. 
     The first pitch a 1  has a value in the range of about 40% to about 60% of the second pitch a 2 . For instance, when the second pitch a 2  is about 22 mm, the first pitch a 1  is between about 9 mm to about 13 mm. 
     In addition, the position of the mask  30  facing the center of each of the first magnetic members M 1  or the center of each of the second magnetic members M 2  is referred to as a first point (or a first portion) P 1 . The position of the mask  30  facing the edge of each of the first magnetic members M 1  or the edge of each of the second magnetic members M 2  is referred to as a second point (or a second portion) P 2 . According to at least one embodiment, the intensities of the magnetic force generated by the magnetic assembly MA and applied to each of the first and second points P 1  and P 2  may be substantially uniform. This will be described in detail with reference to  FIG. 3B . 
     In  FIGS. 3A and 3B , first, second, third, and fourth graphs G 1 , G 2 , G 3 , and G 4  illustrate a comparative example and embodied examples of the described technology. Each of the first to fourth graphs G 1  to G 4  represents the relative intensities of the magnetic force according to the positions on the surface of the mask  30 . In addition, each of the first to fourth graphs G 1  to G 4  represents normalized values obtained by dividing the value of the intensity of the magnetic force measured at each position on the surface of the mask  30  by the maximum value of the measured magnetic force. The surface of the mask  30  referred to in the graphs is the surface of the mask  30  facing the substrate  20  and disposed closer to the substrate  20 . 
     The first graph G 1  represents the relative intensities of the magnetic force according to the positions on the surface of the mask  30  in the comparative example. In the magnetic assembly according to the comparative example, a first magnetic member and a second magnetic member are alternately and repeatedly arranged. 
     Each of the second to fourth graphs G 2  to G 4  represents the relative intensities of the magnetic force according to embodied examples. In detail, the second graph G 2  represents the relative intensities of the magnetic force for an embodiment where the first pitch a 1  is about 13 mm and the second pitch a 2  is about 22 mm. The third graph G 3  represents the relative intensities of the magnetic force for an embodiment where the first pitch a 1  is about 11 mm and the second pitch a 2  is about 22 mm, and the fourth graph G 4  represents the relative intensities of the magnetic force for an embodiment where the first pitch a 1  is about 9 mm and the second pitch a 2  is about 22 mm. 
     In the first graph G 1 , the difference between the intensities of the magnetic forces applied to the first and second points P 1  and P 2  is referred to as a first value b 1 . Similarly, the difference between the intensities of the magnetic forces applied to the first and second points P 2  in the second graph G 2  is referred to as a second value b 2 . As illustrated in  FIG. 3B , the second value b 2  is less than the first value b 1 . 
     Similarly, when the difference between the intensities of the magnetic forces applied to the first and second points P 1  and P 2  in the third graph G 3  is referred to as a third value b 3 . Here, the third value b 3  is less than the first value b 1 . In addition, the difference between the intensities of the magnetic forces applied to the first and second points P 1  and P 2  in the fourth graph G 4  is referred to as a fourth value b 4 . The fourth value b 4  is also less than the first value b 1 . 
     As described above, the difference between the intensities of the magnetic forces applied to the first and second points P 1  and P 2  is reduced in the embodied examples when compared with the comparative example. Therefore, when the magnetic assembly MA has the above-mentioned structure according to the present exemplary embodiment, the intensity of the magnetic force applied to the mask  30  may be more uniform than that of the comparative example. In addition, since the intensity of the magnetic force applied to the second point P 2  is comparatively high, the distribution of magnetic field applied to the mask  30  is comparatively broad. 
     In other words, the magnetic force applied to each of the first and second points P 1  and P 2  is determined based on the first and second pitchs a 1  and a 2 . Consequently, the uniformity of the magnetic force applied across the width of each magnetic member M 1  or M 2  can be selected by varying the first and second pitchs a 1  and a 2 . 
     According to the comparative example, the intensity of the magnetic force applied to the mask  30  is non-uniform, and thus, the mask  30  may be deformed. According to the embodied examples, however, since the intensity of the magnetic force applied to the mask  30  is substantially uniform, the mask  30  may be prevented from being deformed. In addition, when the intensity of the magnetic force applied to the mask  30  is substantially uniform, the force acting between the mask  30  and the substrate  20 , which is required to adhere the mask  30  to the substrate, is substantially uniform for a wide range of positions on the surface of the mask  30 . Thus, the mask  30  may be prevented from being detached from the substrate  20 . 
       FIG. 4  is a plan view showing a mask fixing device according to another exemplary embodiment. In  FIG. 4 , the same reference numerals denote the same elements in  FIGS. 1 to 3 , and thus, detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 4 , the mask fixing device  101  includes a plate and a magnetic assembly MA- 1 . 
     The magnetic assembly MA- 1  includes first magnetic members M 1 - 1  and second magnetic members M 2 - 1 . The first magnetic pole of each of the first magnetic members M 1 - 1  and the second magnetic pole of each of the second magnetic members M 2 - 1  contact the plate  10 . The first and second magnetic poles have different polarities. 
     In the present exemplary embodiment, each of the first magnetic members M 1 - 1  includes first, second, third, fourth, and fifth magnets M 11 , M 12 , M 13 , M 14 , and M 15 , which are arranged in a first direction D 1  and contact each other. In addition, each of the second magnetic members M 1 - 2  includes sixth, seventh, eighth, ninth, and tenth magnets M 21 , M 22 , M 23 , M 24 , and M 25 , which are arranged in the first direction D 1  and contact each other. In the present embodiment, each of the first and second magnetic members M 1 - 1  and M 2 - 1  include five magnets, however, the described technology is not limited to five magnets in each magnetic member. 
     As described above, when each of the first and second magnetic members M 1 - 1  and M 2 - 1  include a plurality of magnets arranged in the first direction D 1 , the strength of the magnetic assembly MA- 1  is improved against external stress. 
       FIG. 5  is a cross-sectional view showing a deposition apparatus according to an exemplary embodiment. In  FIG. 5 , the same reference numerals denote the same elements in  FIGS. 1 to 3 , and thus, detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 5 , a deposition apparatus  200  includes a chamber CP, a deposition source SP, and a mask fixing device  100 . 
     The chamber CP accommodates the deposition source SP, the mask fixing device  100 , a mask  30 , and a substrate  20 . When a deposition process is performed on the substrate  20 , the inside of the chamber CP is brought to a vacuum. To maintain the vacuum in the chamber CP, a vacuum pump (not shown) may be connected to the chamber CP. 
     The deposition apparatus  200  may further include a holder SM disposed in the chamber CP to hold the substrate  20 . The holder SM may be rotated during the deposition process to substantially uniformly form a deposition pattern on the substrate  20 . 
     The substrate  20  may be a flat panel member configured to serve as a part of display panel. In the present exemplary embodiment, the substrate  20  may be a glass substrate. Hereinafter, the substrate  20  will be described as a display substrate for an OLED display. 
     The deposition source SP evaporates a deposition material DM and the evaporated deposition material DM is provided to the substrate  20 . The deposition source SP includes a container (not shown) accommodating the deposition material DM and a heater (not shown) that heats the deposition material DM. 
     The deposition material DM is deposited on the substrate through openings in the mask  30 , and thus, a deposition pattern formed of the deposition material DM may be formed on the substrate  20 . In the present exemplary embodiment, the deposition pattern may be an organic light-emitting layer. 
     As described with reference to  FIGS. 3A and 3B , the mask fixing device  100  allows a magnetic force to be applied to the mask  30  with a substantially uniform intensity. In this case, the mask  30  may be adhered to a lower surface of the substrate  20  without being deformed, and thus, the mask  30  can accurately define areas in which the deposition material DM is deposited. As a result, the yield of the process of patterning the organic light-emitting layer formed of the deposition material DM may be improved. 
     Although certain embodiments have been described, it is understood that the present invention should not be limited to these embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as hereinafter claimed.