CVD MASK ALIGNMENT FOR OLED PROCESSING
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] Embodiments of the present invention generally relate to a chemical vapor deposition (CVD) apparatus having a mask alignment system for organic light emitting diode (OLED) display fabrication.
Description of the Related Art
[0002] OLEDs are used in the manufacture of television screens, computer monitors, mobile phones, other hand-held devices, etc. for displaying information. A typical OLED may include layers of organic material situated between two electrodes that are all deposited on a substrate in a manner to form a matrix display panel having individually energizable pixels. The OLED is generally placed between two glass panels, and the edges of the glass panels are sealed to encapsulate the OLED therein.
[0003] There are many challenges encountered in the manufacture of such display devices. In one example, there are numerous labor intensive steps necessary to encapsulate the OLED between the two glass panels to prevent possible contamination of the device. In another example, different sizes of display screens and thus glass panels may require substantial reconfiguration of the process and process hardware used to form the display devices.
[0004] Therefore, there is a continuous need for new and improved apparatus and methods for forming OLED display devices.
SUMMARY OF THE INVENTION
[0005] The present invention generally relates to a CVD apparatus for OLED processing. For OLED processing, a mask is oftentimes utilized during the CVD process. Properly aligning the mask over the substrate can be accomplished by utilizing two X-Y-Z motion alignment elements together with two Z motion alignment
elements and one or more alignment visualization systems. The mask is initially disposed on the alignment elements. The visualization systems confirm whether the mask is properly aligned. If realignment is necessary, then the two X-Y-Z alignment elements move the mask while the two Z alignment elements remain stationary. The visualization systems then confirm the mask is properly aligned so that the CVD process may then proceed.
[0006] In one embodiment, processing chamber comprises a substrate support disposed within a chamber body and a mask alignment system at least partially disposed within the chamber body. The mask alignment system has at least a portion thereof that extends through the substrate support.
[0007] In another embodiment, a processing chamber is disclosed. The chamber includes a substrate support disposed in a chamber body, a mask disposed in the chamber body and a mask alignment system at least partially disposed in the chamber body. The mask alignment system comprises a first actuator and a first alignment element coupled to the first actuator and capable of movement in three planes. The first alignment element is coupled with the mask and extends through the substrate support. The mask alignment system also comprises a second alignment element coupled to the second actuator and capable of movement in only one plane. The second alignment element is coupled with the mask and extends through the substrate support.
[0008] In another embodiment, a method for aligning a mask is disclosed. The method comprises disposing a substrate on a substrate support in a processing chamber, the substrate having an alignment mark thereon that is visible through an opening formed in the substrate support. The method also comprises illuminating a light through the opening in the substrate support such that the alignment mark, a boundary of an opening through a mask that is disposed over the substrate, and a shadow mask are visible. The method additionally comprises measuring a distance that the alignment mark is from the center of the boundary of the opening through the mask and moving the mask.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
[0010] Figure 1 is a schematic cross-sectional view of a CVD apparatus according to one embodiment.
[0011] Figure 2 is a bottom view of a shadow frame according to one embodiment.
[0012] Figure 3 is a schematic illustration showing an alignment element relative to a visualization system.
[0013] Figure 4 is a bottom view through a substrate illustrating proper alignment of the mask over the substrate.
[0014] Figure 5 is a schematic isometric view of a mask and alignment system according to one embodiment.
[0015] Figures 6A and 6B are schematic cross-sectional views of an alignment element engaging the mask.
[0016] Figures 7A and 7B are schematic isometric illustrations of crevices that may be formed in the mask.
[0017] Figures 8A-8C show a schematic illustration of aligning a mask over a substrate.
[0018] Figure 9A is an isometric illustration of the mask according to one embodiment.
[0019] Figure 9B illustrates an exaggerated view of the mask positioned on the substrate.
[0020] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
DETAILED DESCRIPTION
[0021 ] The present invention generally relates to a CVD apparatus for OLED processing. For OLED processing, a mask is oftentimes utilized during the CVD process. Properly aligning the mask over the substrate can be accomplished by utilizing two X-Y-Z motion alignment elements together with two Z motion alignment elements and one or more alignment visualization systems. The mask is initially disposed on the alignment elements. The visualization systems confirm whether the mask is properly aligned. If realignment is necessary, then the two X-Y-Z alignment elements move the mask while the two Z alignment elements remain stationary. The visualization systems then confirm the mask is properly aligned so that the CVD process may then proceed.
[0022] Figure 1 is a schematic cross-sectional view of a CVD apparatus 100 according to one embodiment. The apparatus 100 includes a chamber body 102 having an opening 104 through one or more walls to permit one or more substrates 106 and the mask 108 to be inserted therein. The substrate 106, during processing, is disposed on a substrate support 1 10 opposite a diffuser 1 12 having one or more openings 1 14 therethrough to permit processing gas to enter the processing space 1 16 between the diffuser 1 12 and the substrate 106.
[0023] For processing, the mask 108 is initially inserted into the apparatus 100 through the opening 104 and disposed upon multiple motion alignment elements 1 18. The substrate 106 is then inserted though the opening 104 and disposed upon multiple lift pins 120 that extend through the substrate support 1 10. The substrate
support 1 10 then raises to meet the substrate 106 so that the substrate 106 is disposed on the substrate support 1 10. The substrate 106 is aligned while on the substrate support 1 10.
[0024] Once the substrate 106 is aligned on the substrate support 1 10, one or more visualization systems 122 determine whether the mask 108 is properly aligned over the substrate 106. If the mask 108 is not properly aligned, then one or more actuators 124 move one or more motion alignment elements 1 18 to adjust the location of the mask 108. The one or more visualization systems 122 then recheck the alignment of the mask 108.
[0025] Once the mask 108 is properly aligned over the substrate 106, the mask 108 is lowered onto the substrate 106, and then the substrate support 1 10 raises on the stem 126 until the shadow frame 128 contacts the mask 108. The shadow frame 128, prior to resting on the mask 108, is disposed in the chamber body 102 on a ledge 130 that extends from one or more interior walls of the chamber body 102. The substrate support 1 10 continues to rise until the substrate 106, mask 108 and shadow frame 128 are disposed in the processing position opposite the diffuser 1 12. Processing gas is then delivered from one or more gas sources 132 through an opening formed in the backing plate 134 while a bias is provided to the diffuser.
[0026] In order to properly align the mask 108 over the substrate 106, the visualization system operates by illuminating a light through an opening 302 formed through the substrate support 1 10. The light shines through the substrate 106 to see the location of the mask 108. As will be discussed below, the substrate 106 will have one or more alignment marks 402 thereon that are centered in one or more openings 304 formed in the mask 108 when properly aligned. Thus, when viewing the alignment mark 402 through the substrate support 1 10, the one or more visualization systems 122 will view the shadow frame 128 as well as the boundary of the opening 304 of the mask 108. The shadow frame 128 may be fabricated of anodized aluminum. However, because anodized aluminum has a grey color, the one or more visualization systems 122 may have a difficult time viewing the alignment mark 402
on a grey the shadow frame 128. Therefore, the shadow frame 128 may be modified to accommodate the visualization systems 122.
[0027] Figure 2 is a bottom view of the shadow frame 128 according to one embodiment. To accommodate the visualization systems 122, the shadow frame 128 has a location 202 corresponding to where the light from each visualization system 122 will illuminate light. The locations 202 are a portion of the shadow frame 128 that is not anodized aluminum. The remainder of the shadow frame 128 is anodized aluminum. It is to be understood that while four locations 202 have been shown, more or less locations 202 may be present. There is sufficient contrast between the mark on the substrate 106 and the location 202 on the shadow frame 128 to ensure the visualization system 122 can effectively visualize the mark on the substrate 106. Additionally, there is sufficient contrast between the anodized portion of the shadow frame 128 and the locations 202 such that the visualization systems 122 can distinguish between the portions of the shadow frame 128. The locations 202 may have bare, non-anodized aluminum, which would have a shiny-silver appearance rather than the grey of anodized aluminum. Alternatively, the locations 202 may comprise a ceramic material inserted into the shadow frame 128 such that the location 202 has a white appearance for alignment purposes. The locations 202 improve the contrast relative to the anodized shadow frame 128 when the visualization system 122 operates.
[0028] Figure 3 is a schematic illustration showing an alignment element 1 18 relative to an alignment visualization system measurement location. As shown in Figure 3, the substrate support 1 10 has openings therethrough not only for the lift pins 120 (See Figure 1 ), but also for the alignment elements 1 18 to extend therethrough. Openings 302 are also present at locations corresponding to where the alignment visualization systems 122 will operate. It is to be understood that the alignment visualization systems 122 may be disposed outside of the apparatus 100 and utilize a visualization element, such as a camera, and an illumination element, such as a light source, to view into the apparatus 100. The alignment visualization systems 122 operate by illuminating a light in the direction shown by arrow "A"
through the opening 302 formed in the substrate support 1 10, through the substrate 106, through the opening 304 formed in the mask 108 and at the location 202 on the shadow frame 128. The alignment visualization systems 122 then measure the distance that the alignment mark 402 is from the boundary of the opening 304 formed through the mask 108.
[0029] Figure 4 is a bottom view through a substrate 106 illustrating proper alignment of the mask 108 over the substrate 106. The substrate 106 has an alignment mark 402 thereon. Upon insertion within the chamber, the substrate 106 is aligned on the substrate support 1 10. Then, the mask 108 is aligned. For proper alignment, an alignment mark 402 is centered not only in the opening 302 formed in the substrate support 1 10 (which occurs prior to mask 108 alignment), but also within the opening 304 formed in the mask 108. Once the mask 108 is properly aligned over the substrate 106, the alignment elements 1 18 may lower the mask 108 onto the substrate 106.
[0030] Figure 5 is a schematic isometric view of a mask 108 and alignment system according to one embodiment. As discussed above, the mask 108 is initially inserted into the apparatus 100 using an end effector that disposes the mask 108 onto one or more alignment elements 1 18. In the embodiment shown in Figure 5, four alignment elements 1 18A-1 18D are present. It is to be understood that the invention is not limited to four alignment elements 1 18A-1 18D. Each alignment element 1 18A-1 18D is coupled to one or more actuators 124 that control the movement of the alignment elements 1 18A-1 18D.
[0031 ] The alignment elements 1 18A-1 18D are not identical. Two alignment elements 1 18A, 1 18D are X-Y-Z alignment elements (i.e., movable via the actuator in three distinct planes) while the other two alignment elements 1 18C, 1 18D are Z motion alignment elements (i.e., movement via the actuator in only one plane). Thus, all four alignment elements 1 18A-1 18D are capable of movement in the plane perpendicular to the substrate 106 deposition surface while only two alignment elements 1 18A, 1 18D are capable of movement within the plane parallel to the substrate 106 deposition surface. In the embodiment shown in Figure 5, the X-Y-Z
alignment elements 1 18A, 1 18D are not adjacent each other, but rather, are opposite one another. Similarly, the Z alignment elements 1 18B, 1 18C are not adjacent each other, but rather, are opposite one another.
[0032] Figures 6A and 6B are schematic cross-sectional views of alignment elements 1 18A-1 18D engaging the mask 108. As shown in Figures 6A and 6B, each of the alignment elements 1 18A-1 18D engage the mask 108 in a different manner. Alignment elements 1 18B, 1 18C, which are Z alignment elements, can only move in the Z direction. Thus, the Z alignment elements 1 18B, 1 18C engage the flat, bottom surface 604 of the mask 108. The Z alignment elements 1 18B, 1 18C have a ball bearing 602A that is movable so that the mask 108 can be moved without scratching the mask 108 and generating particles. The mask 108 is moved by the X-Y-Z alignment elements 1 18A, 1 18D.
[0033] As shown in Figure 6B, the X-Y-Z alignment elements 1 18A, 1 18D also have a ball bearing 602B, but the ball bearing 602B is generally stationary or fixed relative to the mask 108. Thus, the ball bearing 602B engages a crevice 606 formed in the bottom surface of the mask 108. Because the ball bearing 602B has engaged the crevice 606 of the mask 108, the X-Y-Z alignment elements 1 18A, 1 18D can move in the X-Y plane and move the mask 108 therewith to align the mask 108 over the substrate 106. When the alignment elements 1 18A, 1 18D move in the X-Y plane, the mask 108 moves in the X-Y plane, the ball bearing 602A rotates along the bottom surface of the mask 108, ball bearings 602B do not rotate, and the Z- alignment elements 1 18B, 1 18C remain stationary.
[0034] Figures 7A and 7B are schematic isometric illustrations of the crevices 606 that may be formed in the mask 108. The crevices 606 are different for each X-Y-Z alignment element 1 18A, 1 18D. As shown in Figure 7A, one of the crevices 602 may be a dent 702 that approximates a cone formed into the bottom surface of the mask 108. The ball bearing 602B engages the dent 702 and remains generally stationary therein. However, once engaged to the mask 108 within the dent 702 or slot 704, the ball bearing 602B may be permitted to rotate slightly as the engagement occurs, but will be fixed once fully engaged with the mask 108 (i.e., the
weight of the mask 108 is sufficient to prevent the ball bearing 602B from moving). As shown in Figure 7B, the other crevice 602 may be a slot 704. The slot 704, rather than a cone shape, permits thermal expansion of the mask 108. If a dent 702 were utilized at both locations where the X-Y-Z alignment elements 1 18A, 1 18D engage the mask 108, the mask may thermally expand and generate particles or even not properly engage the alignment element 1 18A, 1 18D. Due to the slot 704 shape, the mask 108 may thermally expand yet still properly engage the ball bearing 602B while minimizing particle generation. Slot 704 has two parallel portions 706A, 706B, and two rounded end portions 708A, 708B that connect the two parallel portions 706A, 706B. The slot 704 is arranged in the mask 108 such that the parallel portions 706A, 706B are perpendicular to a hypothetical line extending between the slot 704 and the dent 702.
[0035] The alignment elements 1 18A-1 18D described herein permit the mask 108 to be accurately aligned to within ± 5μιη. The X-Y-Z alignment elements 1 18A, 1 18D that engage the mask 108 at the dent 702 and slot 704 respectively hold the mask 108 rigidly while the other ball bearings 602A rotate on the bottom surface of the mask 108 smoothly to align the mask target openings 304 with the alignment marks 402 on the substrate. The two ball bearings 602B can drive the mask 108 alignment in a very precise manner. The alignment elements 1 18A-1 18D address the issue of when a robot transfers the mask 108 into the chamber so that the total alignment distance can be reduced and alignment accuracy can become more accurate.
[0036] Figures 8A-8C show a schematic illustration of aligning a mask 108 over a substrate 106. Once the substrate 106 has been inserted into the apparatus 100 and disposed on the substrate support 1 10, the alignment process may begin. As shown in Figure 8A, visualization systems 122 determine the location of mask 108 over the substrate 106 at four locations 801 -804. The marks 402 are not aligned with the center 805 of the openings 304 of the mask 108. The amount that each center 805 of the openings 304 of the mask 108 are off from the marks 402 in both the X and Y plane is calculated so that at each measurement location, a ΔΧ and ΔΥ are determined relative to the mark 402 for the measurement location. Then, the
average ΔΧ and ΔΥ for the centers 805 is calculated and the mask 108 is then shifted by moving the X-Y-Z alignment elements 1 18A, 1 18D in the X-Y plane such that the mask 108 slides along the ball bearings 602A of the Z alignment elements 1 18B, C. The amount of shift is the average ΔΧ and ΔΥ. Because the mask 108 has been shifted, the mask 108 should have its center aligned with the center of the substrate 106. Then, the mask 108 is rotated by moving the X-Y-Z alignment elements 1 18A, 1 18D such that the mask 108 rotates about its center. During the rotation, the mask 108 again moves along the ball bearings 602A of the Z alignment elements 1 18B, 1 18C. Following the rotation, the mask 108 should be properly aligned with the substrate 106 to within ± 5μιη. If the mask 108 is not aligned to within ± 5μιη, the alignment process is repeated. Once the alignment process has completed, the mask 108 is lowered onto the substrate 106. It is to be understood that while the description has been made with reference to the shifting occurring before the rotation, the rotation may occur prior to the shifting if desired.
[0037] Figure 9A is an isometric illustration of the mask according to one embodiment. Figure 9B illustrates an exaggerated view of the mask 108 positioned on the substrate 106. The substrate support 1 10 may include a convex surface 902 on which the substrate 106 and the mask 108 are supported. When the substrate 106 and the mask 108 are lifted by the susceptor 1 10, the weight of the shadow frame 128 at the edges of the mask 108 place the mask 108 in tension across the convex surface 902. The mask 108 is placed in tension on top of the substrate 106 to prevent movement or misalignment between the mask 108 and the substrate 106 during handling or processing. The mask 108 may include a mask support frame 904 in one embodiment. The mask support frame 904 may be a separate element from the mask 108 or may comprise a part of the mask 108 itself.
[0038] By properly aligning the mask over the substrate utilizing two X-Y-Z motion alignment elements together with two Z motion alignment elements and one or more alignment visualization systems, a mask in a processing chamber can be aligned to within ± 5μιη.
[0039] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.