Universal Alignment Adapter

In a shadow mask tensioning method and apparatus, a shadow mask supported by a support frame is positioned between a shadow mask frame and a set of actuators with a portion of the shadow mask extending across a gap between the support frame and the shadow mask frame. Under the control of a programmed controller, the set of actuators is caused to simultaneously displace numerous, spaced locations of the portion of the shadow mask into the gap to align alignment apertures of the shadow mask to predetermined positons in fields of view of cameras positioned to observe the alignment apertures. The shadow mask is then affixed to the shadow mask frame.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to the field of thin film electronic devices fabricated by additive manufacturing methods. In particular, the present invention is directed to a shadow mask used for patterning materials such as metals, oxides, and OLED compounds.

Description of Related Art

There is currently great interest in additive manufacturing methods for fabrication of thin film devices. Such methods would offer an alternative to established methods such as photolithography. Investigating alternatives to photolithography is of interest because photolithography requires significant facility floor space, requires numerous complex steps per patterned feature, and produces significant toxic chemical waste.

It is known in the art of additive manufacturing to employ the method of shadow masking. Shadow masking involves placing a substrate in close proximity or contact with a shadow mask that includes numerous formed apertures. Subsequently, material is deposited through the apertures, yielding the desired pattern on the substrate. Most often several shadow masks are required to produce a desired thin film device. Thus, it is necessary to precisely align the series of shadow masks with reference points on the substrate.

Typically, thin film devices require features to be accurately located within no more than a few micrometers of their specified location. Current alignment methods are capable of accurately placing the center of the shadow mask within less than 1 μm of its desired location. However, the shadow mask typically contains features over a significant area, hereinafter referred to as the “array.” Therefore, the size of the array must be controlled very precisely if the features of several masks are to be placed within their specified areas.

Because of the desired patterned feature sizes (typically >100 μm), the shadow mask is typically made of a thin metal foil less than 100 μm thick. Such a thin material does not have the structural integrity to be easily and safely handled on its own. Additionally, the shadow mask will be subject to elevated temperature during the deposition process and it is desired that the apertures of the array remain at constant locations during the thermal cycling. Therefore, tensioning the shadow mask and mounting the shadow mask to a rigid frame allows the shadow mask to be easily and safely handled while being robust to temperature changes.

Heretofore, heat was used to tension the shadow mask before it was attached to the frame. In this method, the frame is made of a low coefficient of thermal expansion alloy, such as invar. The frame and shadow mask are heated to a temperature where the array grows, via thermal expansion, to the proper size and an adhesive bonds the shadow mask to the frame. As the assembly cools, the shadow mask contracts more than the frame resulting in a tensioned shadow mask. This method of thermal tensioning does work but it has limitations and requires significant skill of the fabricator.

One limitation of thermal tensioning is that heat causes the shadow mask to expand proportionally in all directions. This method would be sufficient if all pre-mounted shadow masks are dimensionally accurate to the micrometer level. However, shadow masks often do not start with correct proportions. In an example, a shadow mask may require more stretch in a horizontal direction than in a vertical direction. The best course of action for mounting this shadow mask using thermal tensioning is to select a mounting temperature that splits the difference between the two desired dimensions. This introduces dimensional inaccuracies to the array of this shadow mask which could cause the shadow mask to become unusable. Therefore, the inability to adjust shadow mask dimensions independently is a limitation of thermal stretching.

When shadow masks are mounted via thermal tensioning, the selected mounting temperature should be higher than the maximum temperature realized at the shadow mask during deposition. When this is done the patterned features are generally observed to remain in their starting locations over the course of the thermal cycling of the deposition. According to observations, this starting location is the “cold” or room temperature dimension of the shadow mask. This differs from the mounting, “hot,” dimension of the shadow mask. When the shadow mask cools from the mounting temperature and becomes tensioned, the array changes in dimension. This process is somewhat repeatable in that shadow masks with the same aperture pattern tend to deform in the same fashion when transitioning from hot to cold states. However, achieving acceptable shadow mask mounting results requires collecting extensive data on the behavior of shadow masks and significant decision making from the fabricator. Further, transition from hot to cold can result in bowing of the array, a problem that cannot be directly addressed in the thermal tensioning process.

Including an elevated temperature within the mounting process also adds further complications. Introducing an environment of elevated and adjustable temperature greatly complicates the task of making the accurate micrometer scale measurements that are required for a precise shadow mask. Additionally, since it is continually desired to mount shadow masks at increasingly high temperatures, ease of handling and even operator safety become a concern.

Heretofore, tensioning of a shadow mask and mounting of the tension shadow mask to a rigid frame was performed manually. As would be appreciated by one of ordinary skill in the art, such manual process is time consuming and has the potential for the introduction of human error. Moreover, this prior art manual method is time consuming and may not be consistent when mounting and tensioning a number of different shadow masks to a like number of different shadow mask frames in a production environment where a used shadow mask that is coated with deposition material is replaced with a fresh, uncoated tensioned shadow mask.

SUMMARY OF THE INVENTION

Various preferred and non-limiting examples will now be described as set forth in the following numbered clauses:

Clause 1: A shadow mask tensioning method comprises: (a) providing a shadow mask supported by a support frame; (b) following step (a), positioning the shadow mask supported by a support frame between a shadow mask frame and a set of actuators with a portion of the shadow mask extending across a gap between the support frame and the shadow mask frame; (c) following step (b), causing the set of actuators to simultaneously displace numerous, spaced locations of the portion of the shadow mask into the gap; and (d) following step (c), affixing the shadow mask to the shadow mask frame.

Clause 2: The method of clause 1, further including: a plurality of alignment apertures in the shadow mask; providing cameras to view the plurality of alignment apertures; and step (c) includes causing the set of actuators to displace the numerous, spaced locations of the portion of the shadow mask into the gap to align the plurality of alignment apertures to predetermined positons in fields of view of the cameras.

Clause 3: The method of clause 1 or 2, wherein step (c) occurs automatically under the control of a programmed controller.

Clause 4: The method of any one of clauses 1-3, wherein each camera is positioned with at least one alignment aperture in the field of view of the camera.

Clause 5: The method of any one of clauses 1-4, further including providing a light source for: projecting light onto a side of the shadow mask that faces the cameras; or passing light through the plurality of alignment apertures to the cameras.

Clause 6: The method of any one of clauses 1-5, further including: (e) following step (d), separating the shadow mask affixed to the shadow mask frame from the support frame.

Clause 7: The method of any one of clauses 1-6, wherein step (e) includes cutting the portion of the shadow mask extending across the gap.

Clause 8: The method of any one of clauses 1-7, wherein the gap and the portion of the shadow mask surround the shadow mask frame.

Clause 9: A shadow mask tensioning apparatus comprises: means for supporting a shadow mask that includes alignment apertures with a portion of the shadow mask in alignment with a gap; a plurality of cameras each of which is positioned to observe in a field of view of said camera at least one alignment aperture of the shadow mask; and means for individually displacing numerous, spaced locations of the portion of the shadow mask into the gap simultaneously based on the positions of the alignment apertures in the fields of view of the cameras.

Clause 10: The apparatus of clause 9, wherein the means for supporting includes a shadow mask frame surrounded in spaced relation by a support frame defining the gap.

Clause 11: The apparatus of clause 9 or 10, wherein the gap surrounds the shadow mask frame.

Clause 12: The apparatus of any one of clauses 9-11, further including a light source positioned to: project light on a side of the shadow mask that faces the cameras; or pass light through the alignment apertures to the cameras.

Clause 13: The apparatus of any one of clauses 9-12, wherein the plurality of cameras and the means for individually displacing are positioned on opposite sides of the shadow mask.

Clause 14: The apparatus of any one of clauses 9-13, wherein the alignment apertures are positioned to an inside or an outside of the shadow mask frame.

Clause 15: The apparatus of any one of clauses 9-14, wherein the means for individually displacing includes a plurality of actuators operating under the control of a programmed controller.

Clause 16: The apparatus of any one of clauses 9-15, wherein the controller is operative for controlling the plurality of actuators to move the at least one alignment aperture in the field of view of each camera to a predetermined positon in said field of view.

Clause 17: The apparatus of any one of clauses 9-16, wherein each actuator includes a piston or plunger that extends to displace one of the locations of the portion of the shadow mask.

Clause 18: The apparatus of any one of clauses 9-17, wherein each actuator is a servomotor.

Clause 19: The apparatus of any one of clauses 9-18, wherein the alignment apertures are positioned in an apertures section of the shadow mask.

DESCRIPTION OF THE INVENTION

The following examples will be described with reference to the accompanying figures where like reference numbers correspond to like or functionally equivalent elements.

In an example, an apparatus for tensioning a shadow mask for thin film deposition is shown schematically inFIG. 1, which is a section taken along lines I-I inFIG. 2, and which is also shown inFIG. 2, which is a section taken along lines II-II inFIG. 1.FIGS. 1 and 2are schematic drawings of an example shadow mask tensioning apparatus.

The example shadow mask tensioning apparatus includes a frame2that supports a camera array4and a piston array assembly6in spaced relation defining a gap8therebetween. Frame2supports a platform10which, in use, is configured to support a shadow mask frame12on a side of platform10opposite camera array4. Frame2is also configured to support a replaceable cartridge assembly14comprised of a shadow mask16supported on its periphery by a support frame18. In an example, the periphery shadow mask16can be affixed to support frame18in any suitable and/or desirable manner, e.g., fasteners44.

As seen best inFIGS. 1 and 2, when replaceable cartridge assembly14is mounted on frame2, shadow mask frame12is positioned under, and either spaced from or in contact with, the downward facing side of shadow mask16and a portion of shadow mask16extends across a gap46between shadow mask frame12and support frame18.

Support frame18can be a metal frame to which shadow mask16is attached. Support frame18facilitates shadow mask16being easily handled and fixed in position when tensioned to a desired dimension.

As shown inFIG. 2, shadow mask16can be comprised of a square or rectangular, thin metal foil with an array of apertures20which can be formed in a central portion of shadow mask16. WhileFIG. 2shows a single aperture20, it is to be appreciated that aperture20inFIG. 2is representative of one or more apertures in a desired pattern.

Shadow mask16also includes a plurality of small alignment holes or apertures22. In an example, each alignment aperture22can be a50un diameter hole. However, this is not to be construed in a limiting sense. As shown inFIG. 2, each alignment aperture22can be positioned about an interior of shadow mask frame12(shown in phantom inFIG. 2), for example, within the apertures20section of shadow mask16. However, this is not to be construed in a limiting sense since it is envisioned that one or more alignment apertures can, also or alternatively, be positioned about an exterior of shadow mask frame12.

Camera array4includes a plurality of cameras24supported by frame2. In an example, each camera24is positioned and oriented such that when shadow mask16and camera array4are in the position shown inFIG. 1, each camera24observes an area that includes at least one of the alignment apertures22. Isolated views of cartridge assembly14(including shadow mask16supported by support frame18) and camera array4including a plurality of cameras24are shown inFIGS. 3 and 4, respectively.

An isolated view of a single camera24of camera array4having a field of view26that observes an area in which at least a single alignment aperture22resides is shown inFIG. 5.FIG. 5also shows an alignment mark28in the field of view26of camera24. Alignment mark28does not exist physically but resides in a memory of controller30(FIG. 1) which is programmed and operative under the control of non-transitory computer readable program code (software) in a manner to tension shadow mask16(in a manner to be described hereinafter) to move alignment aperture22to the position represented by alignment mark28inFIG. 5. In other words, alignment mark28is representative of a predetermined, desired position in the field of view of camera24to which it is desired to move alignment aperture22. One skilled in the art will recognize that, based on the position and orientation thereof, the field of view26of each camera24and the location of each alignment aperture22in said field of view26can be the same or different and that the position to which each alignment aperture22is moved in the field of view26of each camera24, which position is represented by alignment mark28inFIG. 5, can also be different.

In an example, each field of view26of each camera24can observe an area having1, or2, or more alignment apertures22and an alignment mark28can be associated with a subset of said alignment apertures22in said field of view26. In an example, there can be a one-to-one correspondence between each alignment aperture22and an alignment mark28, e.g., as shown inFIG. 5. In another example, each alignment mark28can be associated with two or more alignment apertures22, e.g., position the alignment mark28between the two or more alignment apertures22. In yet another example, each alignment aperture22can be associated with two or more alignment marks28, e.g., position the alignment aperture22between the two or more alignment marks28. However, these examples are not to be construed in a limiting sense.

Referring now toFIGS. 1, 2, and 6, the latter of which is a view taken along lines VI-VI in Fig,1, piston array assembly6includes a plurality actuators32, each of which includes a piston or plunger34. Operating under the control of controller30, each actuator32can cause its piston34to move between a position where the distal end36of said piston34is spaced from shadow mask16(as shown by the solid lines of pistons34inFIG. 1) to a position in contact with a portion of shadow mask16(as shown by the dashed lines of pistons34inFIG. 1). In an example, each actuator can be a servomotor. In an example, controller30operating under the control of the non-transitory computer readable program code (software) can control the force applied by each actuator32individually on shadow mask16, the amount of displacement of the portion of shadow mask16contacted by said actuator32, or both.

Piston array assembly6includes a piston support frame38which is supported by frame2in a manner whereupon the distal ends36of pistons34of actuators32face the surface of shadow mask16opposite camera array4.

Finally, in an example, depending on the amount of ambient light, an optional light source40can be positioned to a side of piston array assembly6opposite camera array4. However, the positioning of optional light source40is not to be construed in a limiting sense since it is envisioned that optional light source40can alternatively be positioned to project light onto a side of shadow mask16that faces camera array4. For the purpose of the following example, it will be assumed that optional light source40is present and is positioned as shown inFIG. 1.

In an example, camera array4, platform10, shadow mask frame12, shadow mask16, piston array assembly6, and light source40are positioned such that a subset of alignment apertures22can pass light42from light source40to a corresponding subset of cameras24. Herein, “subset” is a set consisting of elements of a given set that can be the same as the given set or smaller. Accordingly, the subset of alignment apertures22can include all or less than all of the alignment apertures22. Similarly, the subset of cameras24can include all or less than all of the cameras24.

In an example, there can be a one to one correspondence between a camera and a corresponding alignment aperture. However, this is not to be construed in a limiting sense since it is envisioned that any number of cameras24and any number of alignment apertures22can be utilized in the manner described hereinafter to tension shadow mask16. Hence, for example, shadow mask16can include a large number of apertures, with only a portion of said apertures22being utilized to pass light42to a corresponding number of cameras24positioned to receive light passing through said apertures22. Similarly, the number of cameras24is not to be construed in a limiting sense since it is envisioned that the number of cameras24used can be the same as, greater than, or equal to the number of alignment apertures22in shadow mask16.

Having thus described the tensioning apparatus shown inFIG. 1, the operation of said tensioning apparatus will now be described.

Prior to use of the tensioning apparatus shown inFIG. 1, cartridge assembly14(FIG. 3) is assembled. Specifically, shadow mask16is attached to support frame18in any suitable and/or desirable manner. Prior to installing cartridge assembly14onto frame2, shadow mask frame12is positioned on platform10. Fiducial features (not shown) can be provided on platform10, shadow mask frame12, or both to facilitate desired positioning of shadow mask frame12on platform10.

Next, cartridge assembly14is positioned on frame2with shadow mask16positioned between piston array assembly6and shadow mask frame12. Fiducial features (not shown) can be provided on support frame18, frame2, or both to facilitate accurate positioning of cartridge assembly14on frame2. In an example, the underside of shadow mask16can be in contact with the top side of shadow mask frame12. However, this is not to be construed in a limiting sense.

In an example, piston array assembly6is fixed in position on frame2prior to mounting shadow mask frame12and cartridge assembly14on frame2. However, this is not to be construed in a limiting sense since it is also envisioned that piston array assembly6can be mounted on frame2after installation of shadow mask frame12, cartridge assembly14, or both on frame2.

Prior to tensioning of shadow mask16, shadow mask16is held taut and planar by support frame18in the position shown by solid lines inFIG. 1.

When it is desired to tension shadow mask16, light source40is activated to output light42through alignment apertures22and controller30, operating under the control of the non-transitory computer readable program code, acquires the fields of view26of a subset of cameras24. For each thus acquired field of view, controller.30determines the current position of at least one alignment aperture22in said field of view26and further determines a distance46(FIG. 5) and direction between the current position of said alignment aperture22and a desired position (represented inFIG. 5by alignment mark28) of said alignment aperture22in field of view26. It is to be appreciated that alignment mark28inFIG. 5is only for the purpose of illustration and is not actually present in the field of view26of camera24. Rather, the position represented by alignment mark28(which is not present) in field of view26is programmed into a memory of controller30which is programmed to tension shadow mask16in the manner described next to move alignment aperture22in each field of view26to the desired position within said field of view26, which desired position in the field of view26is represented by alignment mark28inFIG. 5. In an example, the position represented by an alignment mark28can be a predetermined pixel or array of pixels in the field of view26of a camera24. Under the control of controller30, shadow mask16can be tensioned to move the alignment aperture22into alignment with the predetermined pixel or array of pixels in the field of view26.

In an example, once controller30has processed the images acquired from cameras24of the fields of view26of a subset of cameras24and has determined the distance and directions to move the alignment apertures22in said fields of view26, controller30causes a subset (all or less than all) of actuators32to extend their respective pistons34until the distal ends36come into contact with the top surface of shadow mask16. Thereafter, controller30controls each actuator32(e.g., a servomotor) to control the amount of force that the distal end36of the piston34of said actuator32applies to the portion of shadow mask16in contact with said distal end36, or the amount that the portion of shadow mask16in contact with said distal end36displaces, or both. In response to the displacement of shadow mask16by the distal end36of each actuator32into the gap46between shadow mask frame12and support frame18, tension is applied to shadow mask16. By selectively controlling the amount of force, or displacement, or both applied to shadow mask16by the subset of actuators32, the alignment apertures22can be moved to desired positions (e.g., move to the alignment marks28) within the fields of view of cameras24. Once the alignment apertures22have been moved to the desired positions (represented by alignment marks28) within the fields of view of cameras24, shadow mask16can be affixed to shadow mask frame12in any suitable and/or desirable manner, e.g., spot welding or adhesive48.

In an example, controller30causes the subset (all or less than all) of actuators32to simultaneously displace multiple portions of shadow mask16in contact with the distal ends36of said actuators32at the same time. However, this is not to be construed in a limiting sense since it is envisioned that distal ends36of a first subset of actuators32can displace first portions of shadow mask16in contact therewith into a first part of gap46at a first time and the distal ends36of a second subset of actuators32can displace other portions of shadow mask16in contact therewith into a second part of gap46at a second, different time.

In the example shown inFIG. 5, the desired position is denoted by alignment mark28which, in an example, resides in a memory of controller30(e.g., as X×Y coordinate(s) of pixel(s) observed by camera24) and which does not actually appear in the field of view26. Because of alignment differences between cameras24of camera array4, each aperture22can be at a different position in the field of view26of each camera24. To account for this difference, the desired position (alignment mark28) in each field of view26where it is desired to move the corresponding alignment aperture22can be programmed into controller30. Once this programming is completed, because camera assembly4remains affixed to frame2, this programming of the desired position (alignment mark28) of each alignment aperture22can be utilized for tensioning any number of similar shadow mask16having the same arrangement/pattern of alignment apertures22.

The foregoing example assumes that it would be necessary for a subset of actuators32to press down and apply a force to and, hence, displace portions of shadow mask16around (on all four sides of) shadow mask frame12. However, this is not to be construed in a limiting sense since it is envisioned that a smaller subset of actuators32may only need to apply a force on corresponding portions of the shadow mask16on 1, 2 or 3 sides of shadow mask frame12in order to displace the portions of shadow mask16contacted by said smaller subset of actuators32to bring all of the alignment marks22in fields of view26of cameras24to the desired alignment positions (represented by alignment marks28) within said fields of view.

Once all of the desired alignment apertures22have been positioned at the desired alignment positions (represented by alignment marks28) within fields of view26of a subset of cameras24, shadow mask16is permanently affixed to shadow mask frame12via, for example, without limitation, spot welding or adhesive. Once the securing of tensioned shadow mask16to shadow mask frame12is complete, controller30can cause actuators32to withdraw pistons34from contact with shadow mask16. Thereafter, the portion of shadow mask16between shadow mask frame12and support frame18can be cut to separate shadow mask16affixed to shadow mask frame12from support frame18.

The example thus described herein has several advantages over the prior art. First, since tension within the shadow mask is created by (simultaneous or individual) adjustment at numerous locations around the perimeter of the shadow mask, there is significant flexibility in the shape of the metal foil that comprises the shadow mask, and, hence, the shape of the array of apertures represented by aperture20. Horizontal and vertical (X×Y) dimensions of the shadow mask and, hence, the array of apertures represented by aperture20can be adjusted separately.

Moreover, the use of camera array4and controller30in combination with alignment apertures22in shadow mask16facilitates accurate and automated tensioning of shadow mask16. Furthermore, frame2, including platform10, enables tensioning of a number of similar shadow masks16to a like number of similar shadow mask frames12in a quick and efficient manner. For example, once a first shadow mask16has been tensioned and secured to a first shadow mask frame12, said first shadow mask16and first shadow mask frame12can be removed from frame2and a second, similar shadow mask16can be tensioned and secured to a second, similar shadow mask frame12on frame2in the manner described above. This process can be repeated for any number of similar shadow masks and shadow mask frames.

As can be seen, disclosed herein a measurement system and method that can be used for rapidly and accurately aligning locations22on a work piece16to predetermined positions28. The measurement system and method can be used for rapidly and accurately aligning any number of like or similar work pieces. The measurement system and method can employ a camera at each location22to facilitate aligning said locations22to said predetermined positions28. Determination of how to adjust each work piece to align all of the locations22to the predetermined positions28can occur simultaneously or near simultaneously, e.g., within 10-100 milliseconds, since the cameras are stationary and do not need to move between locations22in operation of the system.

Total measurement time can be reduced over systems that use/move one or more cameras between multiple locations by a factor (F) of at least: F=# of measured locations÷time to take measurement of all locations.

Finally, because the cameras are rigidly attached to the frame and, hence, are stationary, repeatability error and angular errors of the cameras are avoided.

The foregoing example has been described with reference to the accompanying figures. Modifications and alterations will occur to others upon reading and understanding the foregoing example. Accordingly, the foregoing example is not to be construed as limiting the disclosure.