TWI720178B - Fine metal mask for producing organic light-emitting diodes - Google Patents

Abstract

The embodiments described herein generally relate to the formation of low tension fine metal masks for electro-optic devices. The low tension fine metal mask has a frame. The frame has a plurality of apertures. The low tension fine metal mask has a plurality of mask units. Each mask unit has a having a plurality of openings. Each metal mask unit is coupled to the frame in a manner that maintains a tension across the mask unit of about less than about 0.4 kgf/cm.

Description

Fine metal mask for the production of organic light-emitting diodes

The embodiments disclosed herein generally involve the production of electro-optical devices. More specifically, the embodiments disclosed herein generally involve forming a fine metal mask.

For many reasons, electro-optical devices using organic materials are becoming more and more needed. Many of the materials used to make such devices are relatively cheap, so organic electro-optical devices have the potential to exceed the cost advantages of inorganic devices. Likewise, the inherent properties of organic materials (such as their flexibility) may be advantageous for specific applications (such as for deposition or formation on flexible substrates). Examples of organic electro-optical devices include organic light-emitting devices (OLED), organic photoelectric crystals, organic photovoltaic cells, and organic light detectors.

For OLEDs, organic materials are considered to have performance advantages compared to traditional materials. For example, the wavelength at which the organic light-emitting layer emits light can usually be easily tuned with a suitable dopant. When voltage is applied to the device, the OLED utilizes a thin organic film that emits light. OLED is becoming an increasingly interesting technology for applications such as flat panel displays, lighting and backlighting.

Before and during the evaporative deposition of the OLED material, a fine metal mask (FMM) is used to define the deposition area on the substrate. Mask manufacturing issues, mask materials, small differences from batch to batch, and temperature changes during deposition can cause the FFM to be misaligned on the substrate. So far, these small temperature changes and changes during processing have limited the use of FMM for evaporation patterning to relatively small substrates and relatively large defined features.

One solution is to align the photomask with the substrate very accurately, keep the deposition temperature as low and constant as possible during processing, use a photomask material with a low coefficient of thermal expansion, and place the photomask under tension. This deposition technique has been carried out for many years and has reached its limit in terms of feature density (that is, the number of features that can be formed in a region).

Another possible solution is small mask scanning (SMS). SMS involves the use of a photomask that is smaller than the entire substrate or display; and scanned relative to the substrate, whereby the photomask is used to deposit stripes of red, green, and blue (RGB) materials. This technique has many problems because a gap must be maintained between the substrate and the photomask during deposition, which leads to cross-contamination between emitting RGB materials. In addition, SMS may have defects due to scratches, which is due to the desire to keep the gap as small as possible during scanning to avoid the cross-contamination described above.

Therefore, there is a continuing need for improved photomasks and photomask technology for forming electro-optical devices.

The embodiments described herein generally involve the formation of low tension fine metal masks for electro-optical devices. The low tension fine metal mask has a frame. The frame has a plurality of holes. The low-tension fine metal mask has a plurality of mask units. Each mask unit has a plurality of openings. Each metal mask unit is coupled to the frame in a manner to maintain a tension of approximately less than about 0.4 kgf/cm (such as 0.1 kgf/cm) across the mask unit.

In another embodiment, a photomask assembly is disclosed. The mask assembly has a main body. The main body has a frame and a plurality of supports, and holes are formed on at least one side of the frame. The size of the mask unit is suitable for the hole and engages with the hole. The photomask unit has a fine metal photomask, and the fine metal photomask has a plurality of openings. The fine metal mask is set in the frame and is under low tension.

In yet another embodiment, a method for forming a fine metal mask assembly is disclosed. The method begins with the preparation of a substrate formed of a silicon-metal hybrid material. Through the silicon layer of the silicon-metal hybrid material, a through hole is formed in the gap of the metal layer. The through hole has a side wall formed at a first angle. A second angle is formed on the sidewall of the metal layer. The substrate is cut into a shape suitable for forming the mask unit. The photomask unit is then coupled to the fine metal photomask assembly, wherein the tension across the photomask unit is less than about 0.4kgf/cm.

The embodiments disclosed herein generally involve fine metal masks. A fine metal mask refers to a mask that can be used during the deposition of materials on a substrate. A fine metal mask can be used to form features that have a pattern resolution smaller than the entire active (light-emitting) area of the substrate. Generally, the fine metal mask has a certain size, and the size is the level of the size of a part of the sub-pixel (usually one color) to be disposed on the substrate. Therefore, fine metal photomasks are generally used to deposit the emission layer of organic devices, where the different colors of the display are respectively deposited through the fine metal photomask and designed to allow deposition only on a part of the active OLED present in the display ( For example, a fine metal mask that only deposits a red emission layer, another fine metal mask that only deposits a green emission layer, etc.).

The fine metal mask can be formed from a silicon-metal hybrid material using micromachining (MEMS) or plasma processing to achieve a mask pattern with an accuracy of about 1 micron. In addition, during the deposition process, both the substrate and the fine metal mask can be heated, and therefore both the substrate and the fine metal mask expand to a certain extent. When the substrate and the fine metal mask expand, the alignment of the fine metal mask relative to the substrate must be maintained to achieve high accuracy and high resolution. For example, a fine metal mask can achieve a pixel-per-inch (PPI) resolution greater than 600 PPI, such as pixels between about 800 PPI and about 1200 PPI on next-generation and large substrates. By positioning the fine metal mask in the rigid frame without tensioning the fine metal mask, the fine metal mask can be aligned with the substrate without shifting or deformation during the processing process. The embodiments disclosed herein are described more clearly below with reference to the drawings.

FIG. 1 depicts a schematic diagram of a part of the processing chamber 100 with the fine metal mask assembly 130. The processing chamber 100 may be a processing chamber suitable for use with the embodiments described below. In one embodiment, the processing chamber 100 may be a chamber available from AKT America, a subsidiary of Applied Materials, Inc., Santa Clara, California. It should be understood that the embodiments discussed herein can be implemented in other chambers (including those sold by other manufacturers).

The substrate 102 may be positioned in the processing chamber 100 in relation to an electrostatic chuck (not shown). The substrate 102 may be a substrate suitable for forming an organic light emitting diode (OLED) thereon. In addition, the substrate 102 may be a flexible material. The OLED may be composed of an organic material layer located between two electrodes (anode and cathode), all of which are deposited on the substrate 102. In one embodiment, the substrate 102 consists essentially of glass. The substrate may have a wide range of dimensions (eg, length, width, shape, thickness, etc.). In one embodiment, the substrate 102 is about 1 meter long and 1 meter wide. In this embodiment, the substrate 102 is depicted as having a cathode 104 formed on the lower surface 103. The cathode 104 may include indium tin oxide (ITO). In other embodiments, the cathode 104 is discontinuous and is formed on the substrate 102 in combination with the formation of an OLED layer (not shown).

The source 108 is positioned adjacent to the substrate 102 and the cathode 104. Generally, the source 108 may be a source boat or other container or reservoir capable of generating vapor of the organic material 110. The vapor of the organic material 110 may be configured to deposit further layers on the cathode 104, such as an emissive layer, a hole transport layer, a color changing layer, or a further layer (not shown) required or desired for forming an OLED structure. In one embodiment, the source 108 generates vapor of the organic material 110 to form a white emission layer (not shown) on the cathode 104 and a color changing layer on the white emission layer. In another embodiment, the source 108 generates vapor of the organic material 110 to form a color emissive layer (not shown) on the cathode 104. One or more additional layers may be formed on the cathode 104, such as an electron transport layer (not shown).

The fine metal mask assembly 130 is located between the substrate 102 and the source 108. It should be understood that the fine metal mask assembly 130 is not drawn to scale, and compared with related structures, may be smaller or larger in length, width, or height than shown. The fine metal mask assembly 130 includes a fine metal mask 106 and a frame 112. The fine metal mask 106 may be positioned in the frame 112. The fine metal mask 106 may be at least partially composed of one or more magnetic or non-magnetic metals. For example, the fine metal mask can be formed of a silicon-metal hybrid material. Suitable materials for the fine metal mask 106 or its components include (but are not limited to) silicon-nickel hybrid materials, INVAR (64FeNi), ASTM5 grade titanium (Ti-6Al-4V), titanium, aluminum, molybdenum, copper, 440 Stainless steel, HASTELLOY® alloy C-276, nickel, chromium molybdenum steel, 304 stainless steel, other iron-containing compositions, or combinations thereof. The frame 112 may be composed of a material similar to that of the fine metal mask 106. In one embodiment, the frame 112 is composed of INVAR.

The fine metal mask 106 may have a size and shape that allows covering at least a part of the substrate. In one embodiment, the length of the fine metal mask 106 is from 1 meter and 1.5 meters, and the height is from 750 mm to 925 mm. The fine metal mask 106 may have a thickness of less than 80 microns, such as about 40 microns or about 20 microns. In one embodiment, the fine metal mask 106 has a thickness of less than 40 microns.

The fine metal mask 106 is positioned in the processing chamber 100. The processing chamber is evacuated, where the temperature is stable and ready to receive the substrate 102. The substrate 102 can then be brought into the processing chamber 100 and the alignment marks on the fine metal mask 106 can be aligned with corresponding features on the substrate 102.

In order to better understand and appreciate the fine metal photomask 106, the fine metal photomask assembly 130 will be discussed first with respect to the traditional fine metal photomask 206. FIG. 2 depicts a top view of a conventional fine metal mask 206, which is set in the fine metal mask assembly 130, and is suitable for use in the processing chamber 100 of FIG. 1. The traditional fine metal mask 206 is connected to the frame 112. In one example, the conventional fine metal mask 206 uses micro-actuators 214 to attach to the frame 112. In another example, the traditional fine metal mask 206 is stretched and welded to the frame 112.

The traditional fine metal mask 206 is stretched, or the alternative micro-actuator 214 applies force to align and/or stretch the traditional fine metal mask 206. The mask opening 216 and the frame opening 218 are depicted as holes in the traditional fine metal mask 206 and frame 112, respectively. However, other connections may be used, such as hooks or bolts to attach the microactuator 214, or welding the microactuator 214 to the frame 112, a traditional fine metal mask 206, or both. In operation, the conventional fine metal mask 206 is tensioned so that the conventional fine metal mask 206 and the pattern defining features 220 reach the final desired size and position relative to the substrate 102. For example, the fine metal mask 206 may be generally tensioned in the range of about 0.7 to about 0.9 kgf/cm. Then, the fine metal mask assembly 130 will be loaded into the processing chamber 100.

The conventional fine metal mask 206 may include a size of about 750 mm×650 mm, which is tensioned to more than 0.8 kgf/cm in one or more sizes. The larger size used for the traditional fine metal mask 206 includes about 920mm×about 730mm, GEN 6 half-cut (about 1500mm×about 900mm).

The conventional fine metal mask 206 is formed of a piece of low thermal expansion metal sheet, which is stretched and then attached to a heavy frame in a stretched state. A heavy frame is usually required to maintain the high stretch, that is, tension, of the fine metal mask, and can be on the order of thousands of pounds. For example, a traditional fine metal mask 206 with 16 actuators can be formed by INVAR, which has a coefficient of thermal expansion (CTE) of 1.3 μm/m° C., a yield strength of 70 ksi, and a Young's modulus of 21500 ksi. When the temperature rises to 50°C, the thermal expansion is 162.5 μm. The strain and stress that need to be corrected for expansion is 0.0065%, and each of the 16 actuators is required to use 27.1 pounds of force. Similarly, a fine metal mask (FMM) can be formed by: Ti-6Al-4V, the force required for each actuator is 137.5 pounds; titanium, the force required for each actuator is 144.8 pounds; Al, for each actuator The force required for the actuator is 222.8 pounds; for molybdenum titanium, the force required for each actuator is 248.3 pounds; for copper, the force required for each actuator is 254.2 pounds; for stainless steel, the force required for each actuator is 286.6 pounds; HASTELLOY® , The force required for each actuator is 322.2 pounds; for nickel, the force required for each actuator is 347.3 pounds; and for chrome-molybdenum steel, the force required for each actuator is 351.7 pounds. However, the tension applied to the traditional fine metal mask 206 limits the resolution and causes the offset and deflection of the mask at high temperatures. Therefore, the traditional fine metal mask provides a poor guideline for high resolution and larger scalability.

FIG. 3 shows a top view of a fine metal mask 106 according to an embodiment, which is set in a fine metal mask assembly 130 suitable for use in the processing chamber of FIG. 1. The fine metal mask 106 is not subject to the tension force used in the conventional fine metal mask 206 discussed above with respect to FIG. 2. The fine metal mask 106 may include a size of about 750 mm×650 mm, which is tensioned to less than about 0.4 kgf/cm in one or more dimensions, such as 0.1 kgf/cm or less. The larger size of the fine metal mask 106 includes about 920mm×about 730mm, GEN 6 half-cut (about 1500mm×about 900mm), and extends to even larger sizes, such as GEN 6 (about 1500mm×about 1800mm), GEN 8.5 ( About 2200mm×about 2500mm) and GEN 10 (about 2800mm×about 3200mm).

The frame 112 of the fine metal mask assembly 130 has a main body 352. The main body 352 can be made of INVAR (64FeNi), ASTM grade 5 titanium (Ti-6Al-4V), titanium, aluminum, molybdenum, copper, 440 stainless steel, HASTELLOY® alloy C-276, nickel, chromium molybdenum steel, 304 stainless steel, and other iron-containing The composition, or a combination thereof. The main body 352 has a housing 354. The housing 354 may be shaped as a ribbon having an inner portion 342 and an outer periphery 344. Examples of the band shape used for the housing 354 may include a circular ring shape, an elliptical ring shape, a rectangular ring shape, or other suitable polygonal band/ring shapes with a central hollow area.

The main body 352 may additionally have one or more supports 336. The main body 352 may also have a plurality of auxiliary supports 334. The support members 336 and 334 divide the inner part 342 of the housing 354 into a plurality of holes 332. The supports 336 and 334 may be integrated with the housing 354. For example, the hole 332 and the supporting members 336, 334 can be formed by removing material from the housing 354 or by an additional manufacturing process like 3D printing during the manufacturing of the housing 354, so that the housing 354 and the supporting members 336, 334 is formed by a solid uniform material sheet. Alternatively, the supports 336, 334 may be a single unit or separate members attached to the housing 354 when the main body 352 is formed. For example, the support members 336 and 334 can be welded, glued, fastened or attached to the housing 354 by other techniques, with or without tension. In one embodiment, the frame 112 has ten (10) holes 332. The holes 332 can be shaped as rectangles, squares, circles, triangles, pies or other suitable shapes. For example, ten holes 332 may have a substantially rectangular shape.

The mask unit 306 is configured to be disposed in the hole 332. The mask unit 306 may have an external support 308. The fine metal photomask 106 may be formed in the external support 308 or supported by the external support 308 to form the photomask unit 306. Alternatively, the photomask unit 306 may be formed by only the fine metal photomask 106. The mask unit 306 may be shaped to be held by the combination of the supports 336 and 334 and the housing 354. The outer support 308 may be substantially or partially aligned with one or more of the supports 336, 334 and the housing 354 forming the hole 332. One or more photomask units 306 may be configured to cover one of the holes 332. In one embodiment, each hole 332 has an individual mask unit 306. In another embodiment, each hole 332 has two or more mask units 306. In yet another embodiment, the hole 332 may include a plurality of mask units 306 disposed therein.

The fine metal mask 106 is provided in each mask unit 306. Suitable materials for the fine metal mask 106 or its components include (not limited to) silicon-metal mixtures such as silicon-nickel, INVAR 36 (64FeNi), ASTM grade 5 titanium (Ti-6Al-4V), titanium, aluminum, Molybdenum, copper, 440 stainless steel, HASTELLOY® alloy C-276, nickel, chromium molybdenum steel, 304 stainless steel, other iron-containing compositions, or combinations thereof.

The fine metal mask 106 can be formed by electroforming process or MEMS technology, such as molding and electroplating, wet etching, dry etching, electrical discharge machining (EDM), thinning of silicon wafer by grinding and suitable for manufacturing Other technologies for small devices. The fine metal mask 106 may have a plurality of small openings 310. The small opening 310 is suitable for forming features such as devices or pixels on the surface of the substrate exposed to the fine metal mask 106. The opening 310 may have an area having a size between about 1 micrometer to about 100 micrometers (ie, about 0.001 millimeters to about 0.1 millimeters), such as about 25 micrometers. The small opening 310 in the fine metal mask may be adapted to form features at a density of 300 features per inch or greater, such as 800 features per inch or 1000 features per inch. For example, the fine metal mask 106 may have small openings 310 configured to produce between about 250 pixels per inch (PPI) and about 1200 PPI, such as between about 600 PPI and 900 PPI, such as about 800 PPI. The small openings 310 may have a size variation of less than about 1 micrometer (such as about 0.2 micrometers), and a pitch of less than about +/- 3 μm/160 mm distance (ie, a center-to-center distance between the small openings 310).

The plurality of photomask units 306 may be joined to the main body 352 when the fine metal photomask assembly 130 is formed. The joining with the main body 352 may be performed by welding (such as laser welding), gluing, such as by epoxy or acrylic, integrally formed with the main body 352 or by other suitable means. Perform the bonding of the fine metal mask 106 with the external support 308 or directly to any one of the main body 352 of the fine metal mask assembly 130, so that the fine metal mask 106 is under low tension, such as at about zero kg/cm and about 0.1 kg /cm between tension. The low tension of the mask unit 306 is formed without any substantial sagging, and has a flatness between 2 microns and about 5 microns. For example, bonding the fine metal mask 106 with epoxy resin at low temperature can prevent the deformation of the fine metal mask 106 due to temperature changes. In one embodiment, the mask unit 306 is bonded to the main body 352 of the fine metal mask assembly 130 with epoxy resin to form pixels on an area of about 900 mm to about 1500 mm with a density greater than about 800 PPI. The photomask unit 306 may have an alignment accuracy of about 1 micron to about 5 microns, that is, the actual position (compared to the designed position) accuracy of the photomask unit 306, the opening 310, the alignment mark (not shown), etc. Within about 1 micron.

Advantageously, the above-mentioned fine metal mask assembly 130 can be positioned in the processing chamber relative to the substrate. The fine metal mask assembly 130 may be aligned and positioned in conjunction with the substrate for deposition. The low tension of the fine metal mask 106 significantly prevents offset or deformation in the alignment of the fine metal mask assembly 130 and the substrate at high temperatures. Therefore, the low tension of the fine metal photomask 106 in the fine metal photomask assembly 130 can have a higher resolution and operate at a higher temperature than the conventional metal photomask shown and described in FIG. 2.

Another advantage is that the photomask unit 306 can be easily replaced by detaching or unbonding the photomask unit 306 from the main body 352 of the fine metal photomask assembly 130. When the photomask unit 306 becomes clogged, dirty, damaged, or worn, each photomask unit 306 can be replaced or repaired, thereby minimizing cost and operating downtime.

Figures 4A and 4B depict cross-sectional views for forming a low-tension fine metal mask. The diagram shows an opening 310. However, it should be understood that the fine metal mask 106 has a plurality of openings, and may have more than 250 openings per square inch or more.

The silicon layer 402 has a top surface 472. The silicon layer 402 may have a thickness between about 700 microns and about 40 microns, such as about 65 microns. Species The sub-layer 404 can be disposed on the silicon layer 402. The seed layer 404 may be titanium (Ti), copper (Cu) or other suitable materials. The metal layer 432 may be disposed on the seed layer 404. The metal layer 432 may be formed of nickel (Ni) or a nickel alloy, such as nickel-cobalt (NiCo) or other suitable materials.

The silicon layer 402 can be thinned, such as by etching in and around the opening 310, so that the silicon layer 402 is about 30 microns thick. For example, the thinning may be performed by chemically etching or grinding the bottom of the silicon layer 402 before etching the top surface 472. Alternatively, the silicon layer 402 may be bidirectionally chemically etched in a single step to perform the etching.

In FIG. 4A, a through hole 422 is formed in the silicon layer 402 as a part of forming the opening 310. The via 422 may have sidewalls that extend from the bottom surface 411 of the silicon layer 402 to the surface. The via 422 may be formed by anisotropic chemical etching (such as potassium hydroxide (KOH) etching) or other suitable techniques in the silicon layer 402. The etching rate can be controlled so that the width of the via 422 (such as the bottom width 408) becomes narrower as the depth 482 of the via 422 increases from the top surface 472 of the silicon layer 402. The sidewall of the through hole 422 extends at an angle 406 such that the opening of the through hole 422 at the top surface 472 is larger than the opening of the bottom surface 411 (ie, the bottom width 408). The angle 406 may be between about 40 degrees to about 60 degrees, such as about 54.7 degrees. The angle 406 can be precisely controlled by anisotropic etching, allowing the bottom width 408 to be maintained with an accuracy of about 1 micron, and the sidewall angle 406 to be maintained at about 54.7 degrees. The bottom width 408 of the through hole 422 may be about 38 microns. The width of the through hole 422 at the top surface may be about 94 microns. Therefore, the corresponding portion 409 of the bottom surface 411 adjacent to the bottom width 408 of the opening 310 may be about 28 microns.

In Figure 4B, the metal layer 432 is circular. The metal layer 432 can be rounded by grinding, etching or other suitable techniques. For example, iron trichloride (FeCl ₃ ) etching may be used to round the nickel material of the metal layer 432. The sidewalls 425 of the metal layer 432 can be similarly aligned with the sidewalls of the silicon wafer. That is, the sidewall 425 may be angled between about 40 degrees and about 50 degrees, such as about 54.7 degrees, to match the angle 406 of the sidewall of the silicon layer 402. Each opening for the through hole 422 corresponds to a small opening 310 (as shown in Figure 3) in the finished low tension fine metal mask. Therefore, the through holes 422 can be formed at an appropriate density to form a plurality of features in a substrate with a fine metal mask with a low tensile force. The silicon layer 402 can now be cut to fit in each photomask unit 306 to form a low tension fine metal photomask 106. The tension across the low tension fine metal mask 106 is less than about 0.4 kgf/cm. The low tension fine metal photomask 106 can be bonded and unbonded to the photomask assembly for use and replacement of the unit. For example, the low-tension fine metal mask 106 can be joined by epoxy resin at a temperature of about 25 degrees Celsius or room temperature.

Advantageously, the sidewalls 425 of the through holes 422 are angled to minimize shadows and promote evaporation performance. The silicon-metal hybrid material of the low-tension fine metal mask can be magnetically biased to the substrate for more stringent processing control. The silicon-metal hybrid material also enhances the durability of the low-tension fine metal mask. The materials and manufacturing methods used for the low tension fine metal masks allow higher density openings to be coupled with alignment accuracy of less than about 1 micron to form a feature density on the substrate with minimal skew.

Although the foregoing relates to embodiments of the present invention, other and additional embodiments of the present invention may be designed without departing from the basic scope of the present invention.

100: processing chamber

102: substrate

103: lower surface

104: cathode

106: Fine metal mask

108: Source

110: organic materials

112: Frame

130: Fine metal mask assembly

206: Fine metal mask

214: Micro Actuator

216: Mask opening

218: Frame opening

220: pattern defining features

306: Mask unit

308: external support

310: open

332: hole

334: Support

336: Support

342: internal part

344: Outer Perimeter

352: main body

354: Shell

401: Silicon layer

402: Silicon layer

404: Seed layer

406: angle

408: bottom width

409: part

411: bottom surface

422: Through hole

425: Sidewall

432: Metal layer

472: top surface

482: depth

Therefore, the way in which the above-mentioned features of the present invention can be understood in detail, and a more specific description of the present invention briefly summarized above can be obtained by referring to the examples (some examples are shown in the accompanying drawings) . However, it should be noted that the accompanying drawings only show typical embodiments of the present invention, and are not therefore considered as limiting the scope of the present invention, because the present invention may recognize other equally effective embodiments.

Figure 1 depicts a schematic view of a portion of a processing chamber with a photomask assembly.

FIG. 2 is a conventional technology, and depicts a top view of a fine metal mask provided in a mask assembly suitable for use in the processing chamber of FIG. 1.

Figure 3 shows a top view of a low tension fine metal photomask according to one embodiment, similarly provided in a photomask assembly suitable for use in the processing chamber of Figure 1.

Figures 4A and 4B depict cross-sectional views for forming a low-tension fine metal mask.

For ease of understanding, where possible, the same element symbols are used to denote the same elements that are commonly used in the drawings. It is envisaged that the elements and features of one embodiment can be advantageously incorporated into other embodiments without further description.

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106‧‧‧Fine metal mask

112‧‧‧Frame

130‧‧‧Fine metal mask assembly

306‧‧‧Mask unit

308‧‧‧External support

310‧‧‧Open

332‧‧‧hole

334‧‧‧Support

336‧‧‧Support

342‧‧‧Internal part

344‧‧‧Outer periphery

352‧‧‧Main body

354‧‧‧Shell

Claims (19)

A low-tension fine metal mask, comprising: a frame with a plurality of holes; and a plurality of fine metal mask units, each fine metal mask unit is arranged in a separate one of the holes, each fine metal light The mask unit has a plurality of openings, and each fine metal mask unit is coupled to the frame in a manner to maintain a sheet force of less than about 0.4 kgf/cm across the mask unit. The low-tension fine metal mask according to claim 1, wherein the openings have a density between about 250 per inch and 1200 per inch. The low-tension fine metal mask according to claim 1, wherein the openings in the mask unit have an alignment accuracy of about 1 micrometer with the substrate. The low-tension fine metal mask according to claim 1, wherein the openings have a plurality of side walls angled between about 40 degrees and about 60 degrees. The low-tension fine metal mask according to claim 1, wherein the tension across the mask unit is about 0.1 kgf/cm. A photomask assembly includes: a main body with a frame and a plurality of supporting members, and a plurality of holes are formed on at least one side of the frame; and A plurality of photomask units are adjusted in size to fit the hole, wherein the photomask unit includes: a fine metal photomask with a plurality of openings, and each photomask unit keeps the fine metal photomask having a size smaller than It is joined to each of the holes with a force of about 0.4kgf/cm. The photomask assembly according to claim 6, wherein the openings have a density between 600 per inch and 900 per inch. The photomask assembly according to claim 6, wherein the openings have a density of about 800 per inch. The photomask assembly according to claim 6, wherein the fine metal photomask is bonded to the frame by epoxy resin. The photomask assembly according to claim 6, wherein the openings have a plurality of side walls of about 54.7 degrees. The photomask assembly according to claim 6, wherein the fine metal photomask is formed of a silicon-nickel mixed material. A method for forming a fine metal mask assembly includes the following steps: preparing a substrate formed of a silicon-metal hybrid material; multiple gaps in a metal layer through a silicon layer of the silicon-metal hybrid material A through hole is formed therein, wherein the through hole has a plurality of sidewalls formed at a first angle; Forming a second angle on a side wall of the metal layer; cutting the substrate into a shape suitable for forming a photomask unit; and coupling the photomask unit to the fine metal photomask assembly, which spans The sheet force of the mask unit is less than about 0.4kgf/cm. The method according to claim 12, wherein the metal layer is one of nickel (Ni), nickel-cobalt alloy (NiCo), stainless steel, or nickel-iron alloy. The method of claim 12, wherein preparing the substrate further comprises the step of: performing anisotropic etching on the silicon-metal mixed material to a thickness of about 30 microns, wherein the first sidewalls of the silicon layer The angle is about 54.7 degrees. The method according to claim 12, wherein the coupling of the photomask unit to the fine metal photomask assembly is performed with an epoxy resin at a temperature of about 25 degrees Celsius. The low-tension fine metal mask according to claim 1, wherein the openings have a density between 600 per inch and 900 per inch. The low-tension fine metal mask according to claim 1, wherein the openings have a density of about 800 per inch. The low-tension fine metal mask according to claim 1, wherein the fine metal mask is joined to the frame by epoxy resin. The low-tension fine metal mask according to claim 1, wherein the fine metal mask is formed of a silicon-nickel mixed material.

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