JP3203147U - Vision alignment - Google Patents

Abstract

A visualization system is provided that is adapted to capture an image through a lens. A visualization system used for alignment includes dual light sources. The dual light source includes a first light source for viewing alignment mark 138 on substrate 106 and a second light source for viewing mask opening 140 or other alignment mark 138 on mask 108. By switching between the first light source and the second light source, alignment of the mask 108 with respect to the substrate 106 is facilitated. The visualization system is movable in the z-axis direction to focus the visualization system while imaging the mask 108, thereby resulting from modification of the mask 108 or other factors that affect the size of the mask 108. Facilitates determination of the displacement of the mask 108 from its original or standard position. [Selection] Figure 1B

Description

background

(Field)
Embodiments of the present disclosure generally relate to a mask and alignment apparatus and operation for a substrate, such as a semiconductor substrate.
(Description of related technology)

  During a deposition process on a substrate such as an OLED flat panel, a mask can be placed between the evaporation source and the substrate to prevent material deposition in selected areas on the substrate. As device features continue to shrink, accurate positioning and alignment of the mask becomes increasingly important to facilitate accurate deposition on the substrate surface. However, current mask alignment techniques may not have the accuracy necessary to enable next-generation devices.

  Accordingly, there is a need for an improved mask alignment apparatus and method.

Overview

  The present disclosure relates generally to an apparatus and method for aligning a mask with respect to a substrate. In one embodiment, the visualization system used for alignment includes a dual light source. The dual light source includes a first light source for viewing an alignment mark on the substrate and a second light source for viewing a mask opening or other alignment mark on the mask. In order to facilitate alignment of the mask with respect to the substrate, the first and second light sources can be switched. The visualization system can also be actuated in the z-axis direction for visualization system focus while imaging the mask, thereby allowing for mask refurbishment or mask dimensions. Facilitates the determination of mask displacement from the original or default position due to other influencing factors.

  In one embodiment, the visualization system is disposed between a first light source having a ring shape, a second light source adapted to direct light through the center of the first light source, and the first light source and the camera. The camera is directed through the center of the first light source and is adapted to capture an image through the lens.

  In one embodiment, the process chamber includes a substrate support disposed within the body of the process chamber, one or more motion alignment elements for supporting the mask, and a substrate supported on the mask and substrate support. A visualization system arranged to detect alignment of the first light source having a ring shape and a second light source adapted to direct light through the center of the first light source; A lens is disposed between the first light source and the camera, the camera being directed through the center of the first light source and adapted to capture an image through the lens.

  In one embodiment, a method of processing a substrate includes positioning the substrate on a substrate support in a processing chamber, wherein the substrate is positioned near a mask, and using a camera of a visualization system, A process of aligning the substrate with respect to the mask, the process of which the mask was previously subject to refurbishment, and the process of operating the camera vertically to focus the camera on the mask. The change in the vertical distance of the camera includes a step corresponding to a change in the position or thickness of the mask due to the modification, and a step of placing the mask on the substrate.

  For a better understanding of the above configuration of the present disclosure, a more detailed description of the present disclosure, briefly summarized above, may be made by reference to the embodiments. Some of the embodiments are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings depict only exemplary embodiments and that the present disclosure may include other equally effective embodiments and therefore should not be construed to limit the scope of the present disclosure. is there.

It is a schematic sectional drawing of the chemical vapor deposition apparatus by one Embodiment. 1B is an enlarged schematic view of a portion of the apparatus shown in FIG. 1A. FIG. 1 is a schematic diagram of a visualization system, according to one embodiment. FIG. 2B is a top view of a portion of the visualization system shown in FIG. 2A. FIG. 1 is a schematic isometric view of a mask and alignment system according to one embodiment. FIG. It is a bottom view of the shadow frame by one Embodiment. FIG. 5 is a flow diagram of a method for aligning a mask. ~ The fragmentary figure of the mask at the time of alignment operation is shown. ~ 2 shows a graph of measurement reproducibility using the vision system of the present disclosure. Fig. 4 shows a graph of focus measurement performed by the visualization system of the present disclosure.

  For ease of understanding, identical reference numerals are used where possible to designate identical elements that are common to the drawings. It is understood that elements and configurations of one embodiment may be advantageously incorporated into other embodiments without further reference.

Detailed description

  The present disclosure relates generally to an apparatus and method for aligning a mask with respect to a substrate. In one embodiment, the visualization system used for alignment includes a dual light source. The dual light source includes a first light source for viewing an alignment mark on the substrate and a second light source for viewing a mask opening or other alignment mark on the mask. In order to facilitate alignment of the mask with respect to the substrate, the first and second light sources can be switched. The visualization system is also operable in the z-axis direction for the focus of the visualization system while the mask is being imaged, thereby causing the original to be due to mask modifications or other factors that affect mask dimensions. Or it facilitates the determination of the displacement of the mask from the standard position.

  FIG. 1 is a schematic cross-sectional view of a chemical vapor deposition (CVD) apparatus 100 according to an embodiment. The apparatus 100 includes a chamber body 102 having an opening 104 through one or more walls, into which one or more substrates 106 and masks 108 can be inserted. The substrate 106 is placed on a substrate support 110 that faces the diffuser 112 during processing. The diffuser 112 has one or more openings 114 formed through the diffuser 112 to allow process gas to enter a process space 116 defined between the diffuser 112 and the substrate 106. .

  For processing, the mask 108 is first inserted into the apparatus 100 through the opening 104 and placed over a plurality of motion alignment elements 118A-118D (two shown). Thereafter, the substrate 106 is inserted through the opening 104 and placed on a plurality of lift pins 120 extending through the substrate support 110. Thereafter, the substrate support 110 is raised and contacts the substrate 106, and the substrate 106 is placed on the substrate support 110.

  Once the substrate 106 is placed on the substrate support 110, one or more visualization systems 122 determine whether the mask 108 is properly aligned on the substrate 106. If the mask 108 is not properly aligned, one or more actuators 124 of the alignment system 396 (shown in FIG. 3) move one or more motion alignment elements 118A-118D to adjust the position of the mask 108. To do. Thereafter, the one or more visualization systems 122 recheck the alignment of the mask 108.

  When the mask 108 is properly aligned on the substrate 106, the mask 108 is lowered onto the substrate 106 and then the substrate support 110 is raised over the stem 126 until the shadow frame 128 contacts the mask 108. The shadow frame 128 is placed in the chamber body 102 on a shelf 130 that extends from one or more inner walls of the chamber body 102 before being placed on the mask 108. The substrate support 110 continues to rise until the substrate 106, the mask 108, and the shadow frame 128 are placed in a processing position opposite the diffuser 112. Thereafter, process gas is delivered from one or more gas sources 132 through openings formed in the backing plate 134 while bias is supplied to the diffuser 112.

  In order to properly align the mask 108 on the substrate 106, the visualization system 122 works by directing light from a plurality of light sources (shown in FIG. 3) toward the substrate 106 and the mask 108. The illumination of the mask 108 and the substrate 106 facilitates alignment of an alignment mark 138 (eg, a reference mark) formed on the substrate 106 with respect to the opening 140 formed through the mask 108. Viewing the alignment mark 138 through the substrate support 110, one or more visualization systems 122 will see the shadow frame 128 in addition to the boundary of the opening 140 in the mask 108. The shadow frame 128 and the mask 108 can be made from anodized aluminum. However, since anodized aluminum is gray, one or more visualization systems 122 may have difficulty viewing alignment mark 138 relative to shadow frame 128 and mask 108. Accordingly, the visualization system 122 can be modified to clearly see the alignment mark 138, mask opening 140, and shadow frame 128 during the alignment operation, as further described with reference to FIG.

  FIG. 1B is an enlarged schematic view of a portion of the apparatus 100 shown in FIG. 1A. As shown in FIG. 1B, the substrate support 110 includes a first set of through openings that accommodate the lift pins 120 and a second set of openings through which alignment elements 118A-118D extend. The opening 136 is also present at a position corresponding to where the alignment visualization system 122 operates. The alignment visualization system 122 can be located external to the device 100 and can utilize one or more visualization elements (eg, cameras, lighting elements, lenses, and / or windows for viewing inside the device). Should be understood. The alignment visualization system 122 passes through the opening 136 formed in the substrate support 110, through the substrate 106, through the opening 140 formed in the mask 108, and at the alignment position 144 on the shadow frame 128. , By directing a plurality of light sources in the direction indicated by arrow “A”. The alignment visualization system 122 facilitates positioning the alignment mark 138 at the center in the opening 140 formed through the mask 108 by performing one or more measurements and position corrections.

  FIG. 2A is a schematic diagram of a visualization system 122 according to one embodiment. Visualization system 122 includes an optical system 250 coupled to a support 251. The optical system 250 includes a first light source 252a (for example, a ring light) disposed at a first end of the optical system 250. The second light source 252b (eg, a spotlight) is positioned to direct light through the central opening 295 in the first light source 252a. In one example, the second light source 252b is disposed perpendicular to the main tube 253 of the optical system 250, and is directed through the first light source 252a via the housing 293 disposed concentrically within the first light source 252a. It is done. The second light source 252b is coupled to the main tube 253 with an optical housing 254 optionally including one or more lenses or mirrors 290 therein and directs light through the central opening of the first light source 252a. Each of the first light source 252a and the second light source 252b may be a light emitting diode (LED) that generates white light.

  The main tube 253 includes a lens 291 (for example, a telecentric lens) housed in the proximity of the optical housing 254 between the optical housing 254 and the camera 255. In one example, camera 255 is a 2MP camera used to capture an image of substrate 106 and mask 108 (shown in figure 108) to facilitate alignment of substrate 106 with respect to mask 108. . Images captured by camera 255 can be sent via link 256 to a control unit (not shown). The control unit processes the captured image to determine an appropriate modification of the position of the substrate 106 and / or mask 108, eg, one or more actuators 124 and one or more motion alignment elements 118A- 118D is used to facilitate proper alignment.

  The optical system 250 is fixed to the support 251 via one or more clamps 257 (two are shown) coupled to the bracket 258. The bracket 258 is operable in the vertical direction along the rail 259 of the support 251. Actuation of the bracket 258 and the optical system 250 coupled thereto is accomplished via an actuator 260 (eg, a stepper motor, ball screw, or other suitable linear actuator operatively coupled to the bracket 258). An optional guide 297 is coupled to the rail 259 to facilitate movement along it. In one embodiment, it is understood that the guide may be omitted or formed integrally with the bracket 258. A sensor 298 (eg, an encoder) may be placed to monitor or sense the absolute or relative position of the guide 297 and / or bracket 258 along the rail 259 and the resulting position of the camera 255. In one example, sensor 298 may be coupled to actuator 260 as shown, but other sensor positions are also contemplated.

  FIG. 2B is a top view of a portion of the visualization system 122 shown in FIG. 2A. In particular, FIG. 2B is a top plan view of the first light source 252a and surrounds the extension of the main tube 253. Light from the second light source 252b (shown in FIG. 2B) can be emitted from an extension of the main tube 253 adjacent to the first light source 252a. In one example, the first light source 252a can include a bulb that is partially surrounded by a housing that is used to direct light to the substrate and mask.

  FIG. 3 is a schematic isometric view of the mask 108 and alignment system 396 according to one embodiment. As described above, the mask 108 is first inserted into the apparatus 100 using an end effector that places the mask 108 on one or more alignment elements 118A-118D. In the illustrated embodiment, alignment system 396 includes four alignment elements 118A-118D in addition to two actuators 124. It should be understood that the present invention is not limited to four alignment elements 118A-118D. Each alignment element 118A-118D is coupled to one or more actuators 124 that control the movement of alignment element 118A-118D.

  The alignment elements 118A-118D may not be identical. In one example, the two alignment elements 118A, 118D are XYZ alignment elements (ie, moveable via actuators in three different planes), and the other two alignment elements 118C, 118B are Z Motion alignment element (movement through an actuator only in one plane). Thus, all four alignment elements 118A-118D can move in a plane perpendicular to the deposition surface of the substrate 106, and only two alignment elements 118A, 118D move in a plane parallel to the deposition surface of the substrate 106. Is possible. In the embodiment shown in FIG. 4, the XYZ alignment elements 118A, 118D are not adjacent to each other, but rather are opposed to each other. Similarly, the Z alignment elements 118B, 118C are not adjacent to each other, but rather are opposed to each other.

  FIG. 4 is a bottom view of the shadow frame 128 according to an embodiment. To accommodate the visualization system 122 (shown in FIG. 1A), the shadow frame 128 has an alignment position 144 that corresponds to where the light from each visualization system 122 illuminates. Alignment position 144 is a portion of shadow frame 128 that is not anodized aluminum. The remaining portion of the shadow frame 128 is anodized aluminum. Although four alignment positions 144 are shown, it should be understood that more or fewer alignment positions 144 can exist. There is sufficient contrast between the mark 138 on the substrate 106 and the alignment position 144 on the shadow frame 128 to ensure that the visualization system 122 can effectively visualize the mark 138 on the substrate 106. Additionally, there is sufficient contrast between the anodized portions of the shadow frame 128 and the alignment position 144 so that the visualization system 122 can distinguish these portions of the shadow frame. The alignment position 144 may have a solid, non-anodized aluminum, which will have a bright silver appearance rather than the gray of anodized aluminum. Optionally, alignment position 144 can include a ceramic material that is inserted into shadow frame 128 so that alignment position 144 has a white appearance for alignment purposes. When the visualization system 122 is in operation, the alignment position 144 improves contrast relative to the anodized shadow frame 128.

  In conventional systems, alignment problems occur when the substrate alignment mark 138 is positioned outside the opening of the mask 108 relative to the field of view of the visualization system 122. In particular, the alignment mark 138 lacks contrast with the anodized aluminum of the mask 108 or shadow frame 128, which makes it difficult to identify the alignment mark 138. In general, conventional systems that use only a single light source during the alignment operation cannot detect or visualize the alignment mark 138 when placed outside the area of the opening 140. Thus, as the visualization system 122 looks for the alignment mark 138, throughput (efficiency) is reduced, which may include moving the mask 108 randomly relative to the substrate 106 until the alignment mark 138 appears in the opening 140. There is sex.

  FIG. 5 is a flow diagram of a method 560 for aligning the mask. 6A-6D show partial views of the mask 108 during the alignment operation. For ease of explanation, FIGS. 5 and 6A to 6D will be described together. FIG. 6A is a partial view of the mask 108 having an opening 140 formed therein during illumination. Illumination occurs during operation 561 using a first light source, such as first light source 252a (shown in FIG. 2). As shown, the substrate alignment mark 138 (shown in dashed lines) is not aligned with the opening 140, and therefore is generally due to the lack of contrast between the anodized aluminum on the mask 108 and the alignment mark 138. Cannot be viewed using a single light source visualization system. The lack of contrast is due, at least in part, to the nature of the flood illumination of the single light source 252a. However, the opening 140 can be viewed using the first light source 252a.

  Embodiments of the present disclosure include an additional light source, such as a second light source 252b (shown in FIG. 2), to facilitate visualization of the alignment mark 138. Use of the second light source 252b occurs during operation 562. By using the second light source 252b, the alignment mark 138 can be seen even when the alignment mark 138 is not located in the opening 140 with respect to the visual field of the visualization system 122. The second light source 252b generally generates a “spotlight” or other focused or focused light beam to facilitate the visual contrast of the alignment mark 138 with respect to the mask. In particular, the light beam generated by the second light source 252b is collected more than the light beam generated by the first light source 252a, so that the second light source 252b is more uniform or consistent in the region near the opening 140. Generates a unique lighting pattern. As shown in FIG. 6B, the alignment mark 138 is not located in the opening 140 (not shown in FIG. 6B), however, the alignment mark is generated by the first light source 252a adjacent to the opening 140. The uniform illumination that is still visible to the mask 108. In general, it should be noted that utilization of the second light source 252b does not provide sufficient contrast of the opening 140 to the remainder of the mask 108.

  As is apparent from FIGS. 6A and 6B, the first and second light sources allow each of the opening 140 and the alignment mark 138 to be easily and reliably detected by the visualization system 122, respectively. During operation 563, the relative position of the opening 140 and the alignment mark 138 can be provided to the control unit, which subsequently adjusts the position of the substrate 106 and / or the mask 108 to the opening 140. On the other hand, the alignment mark 138 can be aligned. It will be appreciated that the first light source 252a and the second light source 252b can be repeatedly switched (eg, switched) repeatedly, multiple times, to facilitate alignment. In such embodiments, the first light source 252a can be used to determine the position of the opening 140, and subsequently the position of the alignment mark 138 can be determined by illumination of the second light source 252b. Thereafter, the position of the substrate 106 or the mask 108 can be changed before repeating the illumination of the first and second light sources, for example, as in operation 564. FIG. 6C shows the alignment mark 138 aligned in the opening 140 using the visualization system 122. Once the mask 108 is properly aligned on the substrate 106, the alignment elements 118 </ b> A- 118 </ b> D can lower the mask 108 onto the substrate 106.

  FIG. 6D shows the alignment of the mask 108 and the substrate alignment mark 138 additionally aligned to the alignment position 144 on the shadow frame 128. The alignment position 144 may be a ceramic button or ring located on the surface of the shadow frame 128, for example. Alignment of the alignment position 144 is facilitated by illumination from the first light source 252a. Since the alignment mark 138 is placed in the field of view through the opening 140, as shown in FIG. 6D, the alignment mark 138 can also be seen because it is illuminated by the first light source 252a, thus causing contrast problems. It should be noted that it does not exist. A separate alignment control of the shadow frame can be used for shadow frame alignment. Additionally or alternatively, the mask 108 and the substrate 106 can be aligned with respect to a fixed shadow frame. In such an embodiment, alignment to the shadow frame occurs simultaneously with operations 561-564.

  Once the substrate 106, mask 108, and shadow frame 128 are aligned, the height of the mask 108 can be determined and adjusted thereafter during operation 565, if necessary. During operation 565, the actuator 260 on the support 251 (shown in FIG. 2) causes the distance between the camera 255 (shown in FIG. 2) and the mask 108 until the mark 138 on the mask 108 is in focus with respect to the camera. Adjust. Since the camera 255 has a certain known focal length, once the camera 255 is in focus, the distance between the camera 155 and the mask 108 can be quickly and easily determined. Further, the sensor 296 facilitates the determination of the position of the camera 255 with respect to the fixed substrate 106 and, additionally, the distance of the mask 108 with respect to the fixed substrate 106. Accordingly, the distance of the mask 108 from the substrate 106 can be determined by the focus of the camera 255 on the mask 108. By determining the distance between the mask 108 and the substrate 106, the contact between the mask 108 and the substrate 106 when positioning the mask 108 can be more relaxed, thereby reducing accidental damage to the substrate 106. Become.

  Variations in the distance from the substrate 106 to the mask 108 may occur due to, for example, accumulation of deposited material on the mask 108 or, optionally, processing or modification of the mask 108. In one example, the mask 108 can be modified by removing the deposited material from the surface of the mask 108 (eg, via grinding, polishing, chemical etching). Removal of material from the mask 108 by modification or addition of material to the mask 108 by deposition moves the mask 108 relative to the camera 255. The movement of the mask 108 with respect to the camera 255 causes the mask 108 to be out of focus. However, as described above, the camera 255 can be refocused, and the distance that the camera 255 moves to refocus is equal to the change in mask height.

  During operation 565, the exact change in the relative distance between the mask 108 and the substrate 106 can be determined by finding the change in the distance of the camera 255 relative to the mask 108 by refocusing the camera 255. In one example, the change in distance may be about 200 micrometers or less. Determining the exact distance between the mask 108 and the substrate 106 facilitates a gentler contact between the mask 108 and the substrate 106 during mask placement, thus damaging the substrate 106 (eg, chipping the substrate surface). (Or scratching). It will be appreciated that operation 565 may be performed for each substrate, every few substrates, and the first substrate after mask 108 modification or replacement. After the mask height is adjusted in operation 565 and before a deposition process such as a CVD process, the mask 108 can be placed on the substrate 106 during operation 566.

  7A-7C show graphs of measurements using the visualization system of the present disclosure. FIG. 7A is a graph 780 illustrating 24 different measurements of the position of the alignment mark 138 using the visualization system 122 described herein. Measurement of alignment mark 138 resulted in a sigma value of 0.0808 micrometers on the x-axis and 0.0867 micrometers on the y-axis. FIG. 7B is a graph 781 showing 24 different measurements of the position of the mask opening 140 using the visualization system 122. Measurement of the mask opening 140 resulted in a sigma value of 0.1361 micrometers on the x-axis and 0.1837 micrometers on the y-axis. FIG. 7C is a graph 782 showing 24 different measurements of the position of the alignment position 144 on the shadow frame 128 using the visualization system 122. Measurement of alignment position 144 resulted in a sigma value of 1.4502 micrometers on the x-axis and 1.0417 micrometers on the y-axis. Therefore, by using the visualization system of the present disclosure, the substrate, the mask, and the shadow frame can be aligned quickly and accurately even when the alignment mark 138 of the substrate 106 is hidden by a part of the mask 108. .

  FIG. 8 shows a graph 788 of focus measurements performed by the visualization system 122 of the present disclosure. The camera 255 of the visualization system 122 moves both positive and negative in the z direction and identifies the peak of maximum focus as indicated by region 789. By determining the relative z position of the maximum focus, the visualization system and / or controller coupled thereto can modify the mask positioning to compensate for mask position changes due to mask modifications or other factors. . Accordingly, the movement of the mask is adjusted to compensate for changes in the distance from the mask to the substrate, thereby facilitating gentle contact between the mask 108 and the substrate 106 and placing the mask 108 on the substrate 106. In this case, damage to the substrate 106 can be reduced. Without adjusting the mask height, the absolute height of the mask 108 above the substrate 106 is not known, and when the mask 108 is placed on the substrate 106, for example, by not decelerating the movement of the mask 108. This can result in contact with excessive force. In one example, the mask position can be determined within a distance of about 25 micrometers or less using the embodiments described herein.

  Advantages of the present disclosure include quick and accurate alignment of the mask with respect to the substrate. The multiple light source vision system facilitates mask alignment even when substrate alignment marks are not present through openings in the mask. In addition, the z-axis autofocus of the disclosed vision system camera allows for the determination and compensation of changes in mask height with mask modifications. Thus, the mask can be placed more gently on the substrate and damage to the substrate can be minimized.

  While the above is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be created without departing from the basic scope thereof, the scope of which is as follows: It is determined based on the range.

Claims (15)

A visualization system, a first light source having a ring shape;
A second light source adapted to direct light through the center of the first light source;
A visualization system comprising a lens disposed between a first light source and a camera, the camera being directed through the center of the first light source and adapted to capture an image through the lens.   The visualization system according to claim 1, wherein the lens is a telecentric lens, the second light source is a spotlight, and the camera is coupled to a linear actuator.   The visualization system of claim 1, further comprising an optical housing housing a mirror or lens therein, the mirror or lens being adapted to direct light from the second light source. A process chamber,
A substrate support disposed within the body of the process chamber;
One or more motion alignment elements for supporting the mask;
A visualization system arranged to detect alignment of a substrate supported on a mask and a substrate support, the visualization system comprising:
A first light source having a ring shape;
A second light source adapted to direct light through the center of the first light source;
A process chamber including a lens disposed between the first light source and the camera, the camera including a visualization system that is directed through the center of the first light source and adapted to capture an image through the lens.   The process chamber of claim 4, wherein the lens is a telecentric lens, the second light source is a spotlight, and the camera is coupled to a linear actuator.   The process chamber of claim 4 including a shadow frame having a plurality of alignment positions for detection by a visualization system.   The process chamber of claim 4, wherein the substrate support includes a plurality of openings for directing the first light source and the second light source.   The process chamber of claim 4, wherein the first light source and the second light source are LEDs. A method of processing a substrate, comprising:
Positioning a substrate on a substrate support in a processing chamber, the substrate being positioned near a mask;
Directing the first light source to the substrate and the mask and determining the position of the alignment mark on the substrate;
Directing the second light source to the substrate and the mask and determining the position of the alignment opening of the mask;
Adjusting the position of the substrate or mask and aligning the alignment marks of the substrate with the alignment openings of the mask.   The method of claim 9, comprising repeating the orientation of the first light source, the orientation of the second light source, and adjustment.   10. The method of claim 9, including the step of placing a mask on the substrate, wherein the substrate support has a plurality of openings for directing the first light source and the second light source therethrough.   The method according to claim 9, further comprising the step of aligning the alignment mark on the substrate and the alignment opening of the mask with respect to the alignment position of the shadow frame. A method of processing a substrate, comprising:
Positioning a substrate on a substrate support in a processing chamber, the substrate being positioned near a mask;
A process of aligning the substrate with respect to the mask using the camera of the visualization system, wherein the mask was previously subject to refurbishment;
A step of vertically operating the camera to focus the camera on the mask, wherein the change in the vertical distance of the camera at the time of focusing corresponds to a change in the position or thickness of the mask due to the modification;
Placing the mask on the substrate. The process of aligning the substrate with respect to the mask
Directing the first light source to the substrate and the mask and determining the position of the alignment mark on the substrate;
Directing the second light source to the substrate and the mask and determining the position of the alignment opening of the mask;
14. The method of claim 13, wherein the position of the substrate or mask is adjusted to align the substrate alignment marks with respect to the mask alignment openings.   The method of claim 14, comprising aligning the alignment mark on the substrate and the alignment opening of the mask with respect to the alignment position of the shadow frame.