Patent Application
20210214834
Embodiments of the disclosure relate to formation of electronic devices on substrates utilizing fine patterned shadow masks. In particular, embodiments disclosed herein relate to a method and apparatus for a fine patterned metal mask utilized in the manufacture of organic light emitting diodes (OLEDs).
In the manufacture of flat panel displays for television screens, cell phone displays, computer monitors, and the like, OLEDs have attracted attention. OLEDs are a special type of light-emitting diodes in which a light-emissive layer comprises a plurality of thin films of certain organic compounds. OLEDs can also be used for general space illumination. The range of colors, brightness, and viewing angle possible with OLED displays are greater than those of traditional displays because OLED pixels emit light directly and do not require a back light. Therefore, the energy consumption of OLED displays is considerably less than that of traditional displays. Further, the fact that OLEDs can be manufactured onto flexible substrates opens the door to new applications such as roll-up displays or even displays embedded in flexible media.
Current OLED manufacturing requires evaporation of organic materials and deposition of metals on a substrate utilizing a plurality of patterned shadow masks. Temperatures during evaporation and/or deposition require the material of the masks to be made of a material having a low coefficient of thermal expansion (CTE). The low CTE prevents or minimizes movement of the mask relative to the substrate. Thus, masks may be made from metallic materials having a low CTE. Typically, the masks are made by rolling a metallic sheet having a thickness of about 200 microns (μm) to about 1 millimeter to a desired thickness (e.g., about 20 μm to about 50 μm). A photoresist is formed on the rolled metal sheet in a desired pattern and exposed to light in a photolithography process. Then, the rolled metal sheet having the pattern formed by photolithography is then chemically etched to create fine openings therein.
However, the conventional mask forming processes have limitations. For example, etch accuracy becomes more difficult with increasing resolution requirements. Additionally, substrate surface area is constantly increasing in order to increase yield and/or make larger displays, and the masks may not be large enough to cover the substrate. This is due to the limited availability of sheet sizes for the low CTE material, and, even after rolling, fails to have a surface area that is sufficient. Further, increased resolution of the fine patterns requires thinner sheets. However, rolling and handling of sheets with a thickness of less than 30 μm is difficult. Additionally, electroformed sheets are not sufficiently flat which is at least partially due to accumulation of internal stresses from the electroforming process.
Therefore, there is a need for an improved fine metal shadow mask and method for making the fine metal shadow mask.
Embodiments of the disclosure provide methods and apparatus for a fine patterned shadow mask for organic light emitting diode manufacture.
In one embodiment, a shadow mask is provided and includes a frame made of a metallic material, and one or more mask patterns coupled to the frame, the one or more mask patterns comprising a metal having a coefficient of thermal expansion less than or equal to about 14 microns/meter/degrees Celsius and having a plurality of openings formed therein, the metal having a thickness of about 5 microns to about 50 microns and having borders formed therein each defining a fine opening having a recessed surface formed on a substrate contact surface thereof, wherein each of the one or more mask patterns have a flatness of less than about 150 microns across a surface area of about 70,000 square millimeters.
In another embodiment, a mask sheet pattern is provided. The mask sheet pattern is formed by preparing a mandrel comprising a material having a coefficient of thermal expansion less than or equal to about 7 microns/meter/degrees Celsius with a conductive material formed thereon, providing a photoresist material onto the mandrel, the photoresist having a plurality of openings formed therein exposing at least a portion of the conductive material, the photoresist material comprising a pattern of volumes, each of the volumes having a major dimension of about 5 microns to about 20 microns, exposing the mandrel to an electrolytic bath to form a plurality of second metal structures that surround the first metal structures in the openings in an electrodeposition process, separating the mask sheet pattern from the mandrel, and annealing the mask sheet pattern after the separating.
In another embodiment, a method for forming a mask sheet is provided. The method includes preparing a mandrel comprising a metal material or a glass material with a metal layer formed thereon. A first photoresist material is applied to the metal material or layer and patterned to form a first pattern area having first openings formed therein exposing portions of the metal material or layer. A second photoresist material is applied over the first photoresist material remaining in the pattern area, and the second photoresist material is patterned to form a second pattern area having second openings formed therein exposing portions of the metal material or layer. A first metal structure is then electrodeposited in each of the second openings. The second photoresist material may then be removed, and a second metal structure is electrodeposited onto the first metal structure. The first and second metal structures may then be separated from the mandrel and form borders of fine openings in the mask where organic material is patterned onto a substrate to form sub-pixel active areas. The first and second metal structures may have a coefficient of thermal expansion less than or equal to about 13 microns/meter/degrees Celsius.
In another embodiment, a method for forming a mask sheet is provided. The method includes preparing a mandrel comprising a metal material or a glass material with a metal layer formed thereon, exposing the mandrel to an electrolytic bath to form a plurality of first metal structures in the openings in a first electrodeposition process, exposing the mandrel to an electrolytic bath to form a plurality of second metal structures that surround the first metal structures in the openings in a second electrodeposition process, and separating the mask sheet from the mandrel, and annealing the mask sheet after the separating.
In another embodiment, a method for forming a shadow mask is provided and includes preparing a mandrel comprising a conductive material and having a coefficient of thermal expansion less than or equal to about 7 microns/meter/degrees Celsius, depositing a photoresist material onto the mandrel in a pattern having a plurality of openings formed therein exposing at least a portion of the conductive material, wherein the pattern of includes a plurality of volumes, each of the volumes having a major dimension of about 5 microns to about 20 microns, placing the mandrel into an electrolytic bath comprising a material having a coefficient of thermal expansion less than or equal to about 14 microns/meter/degrees Celsius, and electroforming a plurality of borders in the openings of the mandrel.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, 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 disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. It is contemplated that elements and/or process steps of one embodiment may be beneficially incorporated in other embodiments without additional recitation.
Embodiments of the disclosure provide methods and apparatus for a fine metal mask that may be used as a shadow mask in the manufacture of organic light emitting diodes (OLED's). For example, a fine metal mask that is utilized in a vacuum evaporation or deposition process where multiple layers of thin films are deposited on the substrate. As an example, the thin films may form a portion of a display or displays on the substrate comprising OLED's. The thin films may be derived from organic materials utilized in the fabrication of OLED displays. The substrate may be made of glass, plastic, metal foil, or other material suitable for electronic device formation. Embodiments disclosed herein may be practiced in chambers and/or systems available from AKT, Inc., a division of Applied Materials, Inc., of Santa Clara, Calif. Embodiments disclosed herein may also be practiced in chambers and/or systems from other manufacturers.
Although not shown, the OLED device 100 may also include one or more hole injection layers as well as one or more electron transporting layers disposed between the electrodes 125 and 130 and the organic material layers 120. Additionally, while not shown, the OLED device 100 may include a film layer for white light generation. The film layer for white light generation may be a film in the organic material layers 120 and/or a filter sandwiched within the OLED device 100. The OLED device 100 may form a single pixel as is known in the art. The organic material layers 120, and the film layer for white light generation (when used), as well as the electrodes 125 and 130, may be formed using a fine metal mask as described herein.
The pattern areas 205 as well as the frame 210 may be made of a material having a low coefficient of thermal expansion (CTE) which resists movement of the fine openings 215 during temperature changes. Examples of materials having a low CTE include nickel (Ni), molybdenum (Mo), titanium (Ti), chromium (Cr), tungsten (W), tantalum (Ta), vanadium (V), alloys thereof and combinations thereof, as well as alloys of iron (Fe) and Ni, among other low CTE materials. The low CTE material maintains dimensional stability in the fine metal mask 200 which provides accuracy of the deposited materials. Low CTE materials or metals as described herein may be a CTE of less than or equal to about 15 microns/meter/degrees Celsius, such as less than or equal to about 14 microns/meter/degrees Celsius, for example less than or equal to about 13 microns/meter/degrees Celsius.
The mandrel 305 may be a metallic material having a coefficient of thermal expansion less than or equal to about 7 microns/meter/degrees Celsius. Examples include nickel, nickel alloys, nickel:cobalt alloys, among others. In some embodiments, the mandrel 305 may be an ultra-low CTE material including Fe:Ni alloys and Fe:Ni:Co alloys, which may include metals marketed under the trade names INVAR® (Fe:Ni 36), SUPER INVAR 32-5®, among others. Alternatively, the mandrel 305 may be a glass material coated with a thin conductive metal layer, such as copper (Cu), on the side where the fine metal mask sheet 300 is to be formed.
A thickness 312 of the mandrel 305 may be about 0.1 millimeters (mm) to about 10 mm. A thickness 313 of the first dielectric material 310 may be about 0.1 microns (μm) to about 2 μm. In some embodiments, the thickness 313 of the first dielectric material 310 is used to form the structure of the fine openings 215 in the fine metal mask sheet 300. The first dielectric material 310 may be deposited by various means such as plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), inkjet printing, evaporation, spin coating, slot-die coating, blade coating, transfer printing, or combinations thereof, as well as other deposition methods.
The first dielectric material 310 may be patterned utilizing known photolithography techniques. For example, the first dielectric material 310 may be exposed to electromagnetic energy 315 (shown in
In
In
After formation of the positive pattern 320, the mask pattern 302 on the mandrel 305 may be placed in an electrolytic bath (not shown). The bath includes a material with a low CTE metal dissolved therein. Examples of materials having a low CTE include molybdenum (Mo), titanium (Ti), chromium (Cr), tungsten (W), tantalum (Ta), vanadium (V), alloys thereof and combinations thereof, as well as alloys of iron (Fe) and nickel (Ni), alloys of iron (Fe), nickel (Ni) and cobalt (Co), among other low CTE materials. Examples of Fe:Ni alloys and Fe:Ni:Co alloys may include metals marketed under the trade names INVAR® (Fe:Ni 36), SUPER INVAR 32-5®, among others. According to electroforming techniques, an electrical bias is provided between the mandrel 305 and the low CTE metal in the bath. As shown in
In
In
Sidewalls 360 of the borders 355 may form an angle α of about 45 degrees to about 55 degrees, such as about 50 degrees. The term “about” may be defined as +/−3 degrees to +/−5 degrees. Volumes 365 may also be formed in the fine openings 215 that are defined by the borders 355. In some embodiments, the taper angle α of the borders 355 also effects uniformity of deposition by shadowing the organic material (deposited in the sub-pixel active area 135 of the OLED device 100 of
In some embodiments, shown in
After the fine metal mask sheet 300 is formed, the fine metal mask sheet 300 is subjected to one embodiment of an annealing process according to relieve internal stresses in the fine metal mask sheet 300. In one example of the annealing process includes placing the fine metal mask sheet 300 in a furnace or an oven and heated in a first heating process for a first time period. The first heating process heats the fine metal mask sheet 300 to a first temperature that is about 800 degrees Celsius to about 900 degrees Celsius. The first time period is about 30 minutes. After the first heating process, a first cooling process is performed on the fine metal mask sheet 300 during a second time period. The first cooling process is configured to cool the fine metal mask sheet 300 down to about 300 degrees Celsius (e.g., a second temperature). Water may be used to cool down the fine metal mask sheet 300. After the first cooling process, a second heating process is performed on the fine metal mask sheet 300 that heats the fine metal mask sheet 300 to a third temperature during a third time period. The third temperature is about 300 degrees Celsius and the third time period is about 3 hours. After the fine metal mask sheet 300 is heated in the second heating process, the fine metal mask sheet 300 is cooled in a second cooling process. The second cooling process is performed in a fourth time period that cools the fine metal mask sheet 300 to about 300 degrees Celsius (e.g., a fourth temperature). Air may be used to cool down the fine metal mask sheet 300. After the second cooling process is completed, the fine metal mask sheet 300 undergoes a third heating process where the fine metal mask sheet 300 is heated during a fifth time period to a fifth temperature. The fifth temperature is about 100 degrees Celsius and the fifth time period is about 48 hours. After the third heating process is completed, the fine metal mask sheet 300 is cooled to a sixth temperature in a third cooling process in a sixth time period. The sixth temperature is about ambient temperature or room temperature (e.g., about 70 degrees Celsius). Air may be used to cool down the fine metal mask sheet 300. A plurality of fine metal mask sheets 300 may be produced to enable fabrication of the fine metal mask 200 by tensioning and welding the plurality of fine metal mask sheets 300 to the frame 210 of
In another embodiment of an annealing process includes placing the fine metal mask sheet 300 in a furnace or an oven and heated in a first heating process for a first time period. The first heating process heats the fine metal mask sheet 300 to a first temperature that is about 800 degrees Celsius to about 900 degrees Celsius. The first time period is about 6 hours. After the first heating process, a first cooling process is performed on the fine metal mask sheet 300 during a second time period. The first cooling process is configured to cool the fine metal mask sheet 300 down to about 550 degrees Celsius (e.g., a second temperature) that is maintained for the second time period. The second time period is about 4 hours. After the first cooling process, a second cooling process is performed on the fine metal mask sheet 300 that cools the fine metal mask sheet 300 to a third temperature of about 300 degrees Celsius during a third time period. The third time period is about 3 hours. The third temperature is maintained during the third time period. After the fine metal mask sheet 300 is cooled in the second cooling process, the fine metal mask sheet 300 is cooled in a third cooling process. The third cooling process is performed in a fourth time period that cools the fine metal mask sheet 300 to about 100 degrees Celsius (e.g., a fourth temperature). The fourth time period is about 2 hours. The fourth temperature is maintained during the fourth time period. A plurality of fine metal mask sheets 300 may be produced to enable fabrication of the fine metal mask 200 by tensioning and welding the plurality of fine metal mask sheets 300 to the frame 210 of
The annealing process as described above relieves internal stresses in the fine metal mask sheet 300. The annealing process also improves flatness of the fine metal mask sheet 300. The annealing process may also positively impact the physical strength and/or the CTE of the fine metal mask sheet 300. For example, the heat treatment provided by the annealing process as described herein re-orders the crystal structure of the fine metal mask sheet 300 which may increase the strength of the fine metal mask sheet 300 as well as reduce the CTE of the fine metal mask sheet 300.
Conventional masks are made of multiple mask sheets (that are not annealed as described herein) are not sufficiently flat. A conventional mask has, as one example, a surface area of about 1500 mm×about 925 mm, and includes about 20 mask sheets. Each of the 20 mask sheets include dimensions of about 75 mm×about 925 mm, and each sheet may include a flatness (measured by laser scanning) of about 600-700 μm. However, the fine metal mask 200 as described herein has a flatness of less than about 150 μm with the same surface area (e.g., about 70,000 square millimeters) after the annealing process as described above.
Embodiments described herein particularly relate to deposition of materials, for example. for display manufacturing on large area substrates. The substrates in the manufacturing system 500 may be moved throughout the manufacturing system 500 on carriers that may support one or more substrates at edges thereof, by electrostatic attraction, or combinations thereof. According to some embodiments, large area substrates or carriers supporting one or more substrates, for example large area carriers, may have a size of at least 0.174 m2. Typically, the size of the carrier can be about 0.6 square meters to about 8 square meters, more typically about 2 square meters to about 9 square meters or even up to 12 square meters. Typically, the rectangular area, in which the substrates are supported and for which the holding arrangements, apparatuses, and methods according to embodiments described herein are provided, are carriers having sizes for large area substrates as described herein. For instance, a large area carrier, which would correspond to an area of a single large area substrate, can be GEN 5, which corresponds to about a 1.4 square meter substrate (1.1 m×1.3 m), GEN 7.5, which corresponds to about a 4.29 square meter substrate (1.95 m×2.2 m), GEN 8.5, which corresponds to about a 5.7 square meter substrate (2.2 m×2.5 m), or even GEN 10, which corresponds to about an 8.7 square meter substrate (2.85 m×3.05 m). Even larger generations, such as GEN 11 and GEN 12 and corresponding substrate areas can similarly be implemented. The fine metal mask 200 as described herein may be sized accordingly.
According to typical embodiments, substrates may be made from any material suitable for material deposition. For instance, the substrate may be made from a material selected from the group consisting of glass (for instance soda-lime glass, borosilicate glass etc.), metal, polymer, ceramic, compound materials, carbon fiber materials or any other material or combination of materials which can be coated by a deposition process.
The manufacturing system 500 shown in
In
At least a portion of the deposition chambers 524 include one or more of the fine metal mask 200 as described herein (not shown). Each of the deposition chambers 524 also include a deposition source 420 (only one is shown) to deposit film layers on at least one substrate 405. In some embodiments, the deposition source 420 comprises an evaporation module and a crucible. In further embodiments, the deposition source 420 may be movable in the direction indicated by arrows in order to deposit a film on two substrates 405 supported on a respective carrier (not shown). Deposition is performed on the substrates 405 as the substrates 405 are in a vertical orientation or a substantially vertical orientation with a respective patterned mask between the deposition source 420 and each substrate 405. Each of the patterned masks include at least a first opening as described above. The first opening may be utilized to deposit a portion of a film layer outside of a pattern area of the patterned mask as described in detail above.
Alignment units 528 can be provided at the deposition chambers 524 for aligning substrates relative to the respective patterned mask. According to yet further embodiments, vacuum maintenance chambers 530 can be connected to the deposition chambers 524, for example via gate valve 532. The vacuum maintenance chambers 530 allow for maintenance of deposition sources in the manufacturing system 500.
As shown in
According to yet further embodiments, one or more of the transfer chambers 512A-512F are provided as a vacuum rotation module. The first track 534 and the second track 536 can be rotated at least 90 degrees, for example 90 degrees, 180 degrees or 360 degrees. The carriers, such as the carrier 415, moves linearly on the tracks 534 and 536. The carriers may be rotated in a position to be transferred into one of the deposition chambers 524 of the deposition apparatuses 514, or one of the other vacuum chambers described below. The transfer chambers 512A-512F are configured to rotate the vertically oriented carriers and/or substrates, wherein, for example, the tracks in the transfer chambers are rotated around a vertical rotation axis. This is indicated by the arrows in the transfer chambers 512A-512F of
According to some embodiments, the transfer chambers are vacuum rotation modules for rotation of a substrate under a pressure below 10 mbar. According to yet further embodiments, another track is provided within the two or more transfer chambers (512A-512F), wherein a carrier return track 540 is provided. According to typical embodiments, the carrier return track 540 can be provided between the first track 534 and second track 536. The carrier return track 540 allows for returning empty carriers from the further the exit vacuum swing module 516 to the vacuum swing module 508 under vacuum conditions. Returning the carriers under vacuum conditions and, optionally under controlled inert atmosphere (e.g. Ar, N2 or combinations thereof) reduces the carriers' exposure to ambient air. Contact with moisture can therefore be reduced or avoided. Thus, the outgassing of the carriers during manufacturing of the devices in the manufacturing system 500 can be reduced. This may improve the quality of the manufactured devices and/or the carriers can be in operation without being cleaned for an extended time period.
According to embodiments described herein, loading, treatment and processing of substrates, which may be conducted before the substrate is loaded into the vacuum swing module 508, is conducted while the substrate is horizontally oriented or essentially horizontally oriented. The manufacturing system 500 as shown in
The manufacturing system 500 shown in
According to yet further embodiments, the manufacturing system can include a carrier buffer 548. For example, the carrier buffer 548 can be connected to the first transfer chamber 512A, which is connected to the vacuum swing module 508 and/or the last transfer chamber, i.e. the sixth transfer chamber 512F. For example, the carrier buffer 548 can be connected to one of the transfer chambers, which is connected to one of the vacuum swing modules. Since the substrates are loaded and unloaded in the vacuum swing modules, it is beneficial if the carrier buffer 548 is provided close to a vacuum swing module. The carrier buffer 548 is configured to provide the storage for one or more, for example 5 to 30, carriers. The carriers in the buffer can be used during operation of the manufacturing system 500 in the event another carrier needs to be replaced, for example for maintenance, such as cleaning.
According to yet further embodiments, the manufacturing system can further include a mask shelf 550, i.e. a mask buffer. The mask shelf 550 is configured to provide storage for replacement patterned masks and/or masks, which need to be stored for specific deposition steps. According to methods of operating a manufacturing system 500, a mask can be transferred from the mask shelf 550 to a deposition apparatus 514 via the dual track transportation arrangement having the first track 534 and the second track 536. Thus, a mask in a deposition apparatus can be exchanged either for maintenance, such as cleaning, or for a variation of a deposition pattern without venting a deposition chamber 524, without venting a transfer chambers 512A-512F, and/or without exposing the mask to atmospheric conditions.
Embodiments of the fine metal mask 200 as described herein may be utilized in the manufacture of high resolution displays. The fine metal mask 200 as described herein may include sizes of about 750 mm×650 mm according to one embodiment. A fine metal mask of this size may be a full sheet (750 mm×650 mm) that is tensioned in two-dimensions. Alternatively, a fine metal mask of this size may be a series of strips that are tensioned in one-dimension to cover a 750 mm×650 mm area. Larger fine metal mask sizes include about 920 mm×about 730 mm, GEN 6 half-cut (about 1500 mm×about 900 mm), GEN 6 (about 1500 mm×about 1800 mm), GEN 8.5 (about 2200 mm×about 2500 mm) and GEN 10 (about 2800 mm×about 3200 mm). In at least the smaller sizes, a pitch tolerance between fine openings of the fine metal mask 200 or the fine metal mask sheets 300 as described herein may be about +/−3 μm per a 160 mm length.
Utilizing electroforming techniques in the manufacture of the fine metal mask 200 or the fine metal mask sheets 300 as described herein has a substantial advantage over conventional forming processes. Standard opening sizes in conventional masks may have a variation of about +/−2 um to 5 um which is due to variations of the chemical etching process when forming fine openings in the mask. In contrast, the mask pattern 302 as described herein are formed by photolithography techniques. Thus, variations in sizes of the fine openings are less than about 0.2 um. That provides an advantage as resolution increases Thus, the fine metal masks 200 or the fine metal mask sheets 300 as described herein may have more uniform opening size (due to the better control by photolithography techniques). The fine metal mask 200 as described herein may also have a very consistent mask-to-mask uniformity. The uniformity may be improved not only in opening size, but pitch accuracy, as well as other properties may be improved.
The fine metal masks 200 or the fine metal mask sheets 300 as described herein may be used to form the sub-pixel active areas 135 of the OLED device 100 shown in
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. Therefore, the scope of the present disclosure is determined by the claims that follow.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/092888 | 6/26/2018 | WO | 00 |
