TW202226636A - Systems and fabrication methods for display panels with integrated micro-lens array - Google Patents

Abstract

Various embodiments include a display panel with an integrated micro-lens array. The display panel typically includes an array of mesas which includes an array of pixel light sources (e.g., LEDs) electrically coupled to corresponding pixel driver circuits (e.g., FETs). The array of micro-lenses is aligned to the mesas including the pixel light sources, and positioned to reduce the divergence of light produced by the pixel light sources. In some embodiments, the array of micro-lenses formed from a micro-lens material layer is formed directly on top of the mesas. The display panel may also include an integrated optical spacer formed from the same micro-lens material layer to maintain the positioning between the micro-lenses and pixel driver circuits.

Description

System and manufacturing method of display panel with integrated microlens array

The present invention relates generally to display devices, and more particularly to systems and methods of manufacture for display panels integrated with a microlens array.

Display technology is becoming more and more popular in today's commercial electronic devices. These display panels are widely used in fixed large screens such as Liquid Crystal Display TVs (LCD TVs) and Organic Light Emitting Diode TVs (OLED TVs) as well as in fixed large screens such as laptop personal computers, smart phones, tablet computers and wearable electronic devices in portable electronic devices. Much of the development of fixed large screens has been directed towards achieving a high viewing angle to accommodate multiple viewers and enable multiple viewers to see the screen from various angles. For example, various liquid crystal materials such as super twisted nematic (STN) and film-compensated super twisted nematic (FSTN) have been developed to achieve a large viewing angle for each pixel light source in a display panel.

However, most portable electronic devices are mainly designed for a single user, and the screen orientation of these portable devices should be adjusted to correspond to the best viewing angle of the user rather than to accommodate one of multiple viewers. angle. For example, a suitable viewing angle for a user may be perpendicular to the screen surface. In this case, most of the light emitted at a large viewing angle is wasted compared to a fixed large screen. In addition, large viewing angles can cause privacy concerns for portable electronic devices used in public areas.

Additionally, in conventional projection systems based on a passive imager device such as a liquid crystal display (LCD), digital mirror device (DMD), and liquid crystal on silicon (LCOS), the passive imager device itself does not emit light. Specifically, conventional projection systems operate by optically modulating collimated light emitted from a light source (ie, by transmission (eg, by an LCD panel) or reflection (eg, by a DMD) at the pixel level Panel) part of the light) to project the image. However, a portion of the light that is not transmitted or reflected is lost, which reduces the efficiency of the projection system. Furthermore, in order to provide collimated light, complex illumination optics are used to collect the divergent light emitted from the light source. These illumination optics not only make the system bulky, but also introduce additional optical losses into the system, which further affects the performance of the system. In a conventional projection system, typically less than 10% of the illumination light generated by the light source is used to form the projected image.

Light emitting diodes (LEDs) made of semiconductor materials can be used in monochrome or full-color displays. In current displays employing LEDs, the LEDs are typically used as light sources to provide light to be optically modulated by, for example, an LCD or DMD panel. That is, the light emitted by the LEDs does not form an image by itself. LED displays using LED panels comprising a plurality of LED modules as imager devices have also been studied. In such an LED display, the LED panel is a self-emissive imager device in which each pixel can include one LED module (monochromatic display) or a plurality of LED modules, each of the plurality of LED modules representing a primary color One of them (full color display). However, the light emitted by the LED modules is generated by spontaneous emission and is therefore not directional, resulting in a large divergence angle. The large divergence angle can cause various problems in an LED display. For example, due to the large divergence angle, the light emitted by the LED module may be more easily scattered and/or reflected in the LED display. This scattered/reflected light can illuminate other pixels, resulting in optical crosstalk between pixels, loss of sharpness, and loss of contrast.

There is a need for improved display designs that improve on conventional display systems, such as those described above, and help address the shortcomings of these conventional display systems. In particular, there is a need for display panels with reduced viewing angles to better protect user privacy and/or with reduced light waste to reduce power consumption and reduce light interference between pixels with better images.

Various embodiments include a display panel with an integrated microlens array. The display panel typically includes an array of pixel light sources (eg, LEDs, OLEDs) electrically coupled to corresponding pixel driver circuits (eg, FETs). The microlens array is aligned to the pixel light sources and positioned to reduce the divergence of light produced by the pixel light sources. The display panel may also include an integrated optical spacer to maintain alignment between the microlenses and the pixel driver circuits.

The microlens array reduces the divergence angle of the light generated by the pixel light sources and the usable viewing angle of the display panel. This in turn reduces power waste, increases brightness and/or better protects user privacy in public areas.

A display panel with an integrated microlens array can be fabricated using various fabrication methods, resulting in various device designs. In one aspect, the microlens array is fabricated directly as a mesa or protrusion of a substrate with pixel light sources. In some aspects, self-assembly, high temperature reflow, grayscale mask lithography, molding/imprinting/imprinting, and dry etch pattern transfer are techniques that can be used to fabricate microlens arrays.

Other aspects include components, devices, systems, improvements, methods, and processes, including methods of manufacture, applications, and other techniques related to any of the above.

In one aspect, a light-emitting pixel unit includes at least one mesa formed on a substrate. The light-emitting pixel unit also includes a microlens formed from at least a microlens layer covering a top of a top of the at least one mesa. In some embodiments, the material of the microlens layer is different from the material of the at least one mesa, and the microlens layer is in direct physical contact with the at least one mesa.

In some embodiments of the light-emitting pixel unit, the microlenses are individually formed around the top of the at least one mesa.

In some embodiments of the light-emitting pixel unit, a spacer is formed from the same microlens layer between the at least one mesa and the microlens.

In some embodiments of the light-emitting pixel unit, the spacer is no more than 1 micron thick.

In some embodiments of the light-emitting pixel unit, the material of the spacer is the same as the material of the microlens.

In some embodiments of the light-emitting pixel unit, the microlens is formed of a dielectric material.

In some embodiments of the light-emitting pixel unit, the dielectric material includes silicon oxide.

In some embodiments of the light-emitting pixel unit, the material of the microlenses is photoresist.

In some embodiments of the light-emitting pixel unit, the height of the microlenses is no more than 2 microns.

In some embodiments of the light-emitting pixel unit, the width of the microlenses is no more than 4 microns.

In some embodiments of the light emitting pixel unit, on the substrate, the at least one mesa is located in a mesa array matrix, and the microlenses are located in a microlens array matrix placed according to the placement of the mesa array.

In some embodiments of the light-emitting pixel unit, the top of the at least one mesa is flat and the microlens is hemispherical in shape.

In some embodiments of the light-emitting pixel unit, the at least one mesa includes at least one light-emitting device.

In some embodiments of the light-emitting pixel unit, the light-emitting device includes a PN junction.

In another aspect, a method of fabricating a light emitting pixel unit includes: providing a substrate; forming at least one mesa on the substrate; and depositing a layer of microlens material directly on at least a top of the at least one mesa. In certain embodiments, the layer of microlens material conforms to a shape of the at least one mesa and has a hemispherical shape on the at least one mesa.

In certain embodiments of the method of fabricating a light emitting pixel unit, the layer of microlens material is deposited by a chemical vapor deposition technique.

In certain embodiments of the method of fabricating a light-emitting pixel unit, certain parameters of the chemical vapor deposition technique used to deposit the layer of microlens material include: power is 0 W to 1000 W, pressure is 100 mTorr to 2000 mTorr, temperature 23°C to 500°C, gas flow rate 0 sccm to 3000 sccm, and time 1 hour to 3 hours.

In certain embodiments of the method of fabricating a light-emitting pixel unit, the layer of microlens material is composed of a dielectric material.

In some embodiments, the method of fabricating a light-emitting pixel unit further comprises: patterning the layer of microlens material to expose an electrode region of the substrate.

In some embodiments of the method of fabricating a light-emitting pixel unit, patterning further comprises: forming a mask on the surface of the microlens material; patterning the mask through a photolithography process, whereby the Openings are formed in the mask and the layer of microlens material is exposed over the electrode region of the at least one mesa; and with the mask in place, the portions of the layer of microlens material exposed by the openings are etched.

In certain embodiments of the method of fabricating a light-emitting pixel unit, the etching is a wet etching method.

In yet another aspect, a method of fabricating a light emitting pixel unit includes: providing a substrate; forming at least one mesa on the substrate; and depositing a layer of microlens material directly on at least a top of the at least one mesa. In certain embodiments, the layer of microlens material covers the top of the at least one mesa and the top surface of the microlens material is flat. In certain embodiments, the method of fabricating a light emitting pixel unit further comprises patterning the layer of microlens material from the top down, whereby the layer of microlens material is formed without penetrating the layer of microlens material form at least a hemisphere. In certain embodiments, the hemisphere is placed over the at least one table.

In certain embodiments, the method of fabricating a light-emitting pixel unit further comprises: depositing a mask layer on the surface of the microlens material layer; patterning the mask layer to form a hemisphere in the mask layer patterning; and using the hemisphere pattern as a mask, etching the layer of microlens material to form hemispheres in the layer of microlens material.

In certain embodiments of the method of fabricating a light emitting pixel unit, after etching the layer of microlens material, the top surface of the at least one mesa is exposed without etching through the layer of microlens material, whereby the at least one mesa is A spacer is formed on the top.

In certain embodiments of the method of fabricating a light emitting pixel unit, the layer of microlens material is deposited by spin coating.

In certain embodiments of the method of fabricating a light-emitting pixel unit, the mask layer is patterned first by a photolithography process and then by a reflow process.

In some embodiments of the method of fabricating a light emitting pixel unit, the layer of microlens material is etched by a photolithography process.

In certain embodiments, the method of fabricating a light emitting pixel unit further comprises: after forming the at least one mesa and before depositing the layer of microlens material, forming in the patterning process A marking layer of the marking of the lens material layer.

In some embodiments, the method of fabricating a light-emitting pixel unit further comprises: after patterning the layer of microlens material, patterning the layer of microlens material to expose an electrode region of the substrate.

The designs of the display devices and systems disclosed herein utilize the direct formation of microlenses on top of the mesas on the substrate by utilizing the shape of the microlens material to conform to the shape of the mesas, thereby greatly reducing the steps of microlens fabrication and Improve the efficiency of display panel structure formation. Furthermore, the fabrication of these display systems can reliably and efficiently pattern microlens structures without using or maintaining additional substrates. The reduced viewing angle and reduced light interference improve the light emission efficiency, resolution and overall performance of the display system. Therefore, implementing a display system with a microlens array can better satisfy augmented reality (AR) and virtual reality (VR), head-up displays (HUD), mobile device displays, wearable devices, compared to using conventional displays Display requirements for monitors, high-definition projectors and in-vehicle monitors.

Note that the various embodiments set forth above may be combined with any other embodiments set forth herein. The features and advantages set forth in the specification are not all-inclusive, and in particular, numerous additional features and advantages will become apparent to those skilled in the art in view of the drawings, the description, and the scope of the patent application. Furthermore, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to describe or limit the inventive subject matter.

Numerous details are set forth herein in order to provide a thorough understanding of one of the example embodiments illustrated in the accompanying drawings. However, certain embodiments may be practiced without numerous specific details, and the scope of the patentable scope is limited only by the features and aspects specifically recited in the patentable scope. Furthermore, well-known procedures, components and materials have not been described in detail so as not to unnecessarily obscure the relevant aspects of the embodiments described herein.

As discussed above, in some instances, LED modules have a large divergence angle, which can lead to various problems, such as those discussed in the background section. In addition, in a projection system using an LED array having a plurality of LED modules as a self-emissive imager device, a projection lens or a projection lens group is required to project the image generated by the LED array, and the projection lens can has a finite numerical aperture. Therefore, due to the large divergence angle of the LED modules, only a portion of the light emitted by the LED modules can be collected by the projection lens. This reduces the brightness and/or increases power consumption of LED-based projection systems.

Embodiments consistent with the present invention include an integrated display panel as a self-emissive imager device that includes a substrate having an array of pixel driver circuits, a mesa (which may include LEDs, for example) formed over the substrate module) array and a microlens array formed over the mesa array, and embodiments consistent with the present invention include methods of making the display panel. The display panel and the projection systems based on the display panel combine the light source, image forming function and beam collimation function into a single monolithic device and can overcome the disadvantages of conventional projection systems.

1 is a cross-sectional view of an exemplary display panel 100 integrated with a microlens array 120 in accordance with certain embodiments. In FIG. 1 , the finished display panel 100 includes a lensless display panel 110 (ie, without a microlens array) and a microlens array 120 . Display panel 100 includes an individual mesa array 102 within each individual pixel, such as shown at pixel 112P. In some embodiments, the mesa array 102 is formed on the substrate 130 . In some embodiments, the substrate is a semiconductor substrate. In certain embodiments, each of the pixels 112P further includes a pixel driver circuit (not shown in FIG. 1 ) and a corresponding pixel light source 112S within the respective mesas 102M. The microlenses 122M within the microlens array 120 cover at least the tops of the mesas 102M. In some embodiments, the microlenses 122M directly cover and touch the mesa 102M. In some embodiments, the microlenses 122M conform to the shape of the mesas 102M and form a hemisphere on the mesas 102M. For example, microlenses are formed on the top and outside of mesas 102M. In certain embodiments, the composition of the microlens array 120 is different from the composition of the mesa 102M. In certain embodiments, the tops of the mesas 102M are generally flat and the microlenses 122M are generally hemispherical in shape. In some embodiments, the mesa 102M is a circular platform. In some embodiments, the microlenses 122M do not touch after they are formed on top of the mesas 102M.

In some embodiments, the microlens array 120 is made of a dielectric material such as silicon oxide. In some embodiments, the dielectric material is a transparent oxide, such as silicon nitride, silicon carbide, aluminum oxide, or the like. In some embodiments, the microlens array 120 is made of photoresist. In some embodiments, the height of the microlenses 122M is no more than 2 microns. In some embodiments, the height of the microlenses 122M is no more than 1 micron. In some embodiments, the height of the microlenses 122M is no more than 0.5 microns. In some embodiments, the width of the microlenses 122M is no more than 4 microns. In some embodiments, the width of the microlenses 122M is no more than 3 microns. In some embodiments, the width of the microlenses 122M is no more than 2 microns. In some embodiments, the width of the microlenses 122M is no more than 1 micron. In some embodiments, the ratio of width to height of microlenses 122M is greater than two.

Each pixel light source 112S is electrically coupled to and driven by the pixel driver circuit. The pixel light sources 112S are individually controllable. A microlens array 120 is formed over the lensless display panel 110, with the microlenses 122M aligned to the corresponding mesas 102 (not separately shown in FIG. 1 ) containing the pixel light sources 112S. For the purposes of this disclosure, terms such as "above" and "top" mean that light travels in a direction away from pixel light source 112A and toward the viewer. The mesa array 102 including the pixel light sources 112S, the pixel driver circuit array (not shown) and the microlens array are all integrated on a common substrate 130 . In some embodiments, each of the pixel light sources 112S includes a PN node plane.

For clarity, FIG. 1 shows only three individual pixels 112P in display panel 100, each of which includes one pixel light source 112S corresponding to a single microlens 122M. It should be understood that a full display panel 100 will include an array of individual pixels 112P and an array of microlenses 122M. Additionally, a one-to-one correspondence between microlenses 122M and mesas 102M containing pixel light sources 112S is unnecessary, as is a one-to-one correspondence between pixel driver circuits (not shown) and pixel light sources. A pixel light source can also be made from a plurality of individual light elements (eg, LEDs connected in parallel). In some embodiments, one microlens 122M may cover several mesas 102M.

The pixel light sources 112S generate light for the display panel 100 . Different types of pixel light sources 112S can be used, for example, a micro LED array comprising an array of individual micro LEDs, a micro OLED array comprising an array of individual micro OLEDs, or a micro LCD comprising an array of individual micro LCDs array. Note that in LCD arrays, a "pixel light source" is actually modulated from light generated by a backlight or elsewhere (as opposed to electrically generating light), but will still be referred to herein as a pixel light source unless otherwise stated. In one embodiment, each individual pixel light source 112S includes a single light element. In another embodiment, each individual pixel light source 112S includes multiple light elements, eg, LEDs coupled in parallel.

In FIG. 1, the microlens array 120 includes an array of individual microlenses 122M, and each microlens is aligned to a corresponding pixel light source 112S. Individual microlenses 122M have positive optical power and are positioned to reduce the divergence or viewing angle of light emitted from corresponding pixel light sources 112S (as shown by light rays 116-118 in FIG. 1). Light ray 116 represents the edge of the light beam emitted from pixel light source 112S, which has a relatively wide original divergence angle 126 . In one embodiment, the original angle 126 is greater than 60 degrees. The microlens 122M bends the light so that the new edge light ray 118 now has a reduced divergence angle 128 . In one embodiment, the reduced angle 128 is less than 30 degrees. The microlenses 122M in the microlens array 120 are generally the same. Examples of microlenses include spherical microlenses, aspherical microlenses, Frenaline microlenses, and cylindrical microlenses.

The microlens array 120 generally has a flat side and a curved side. In FIG. 1, the bottom of the microlens 122M is the flat side, and the top of the microlens 122M is the curved side. Typical shapes for the base of each microlens 122M include circle, square, rectangle and hexagon. Individual microlenses 122M may be the same or different in shape, curvature, optical power, size, mount, spacing, and the like. In the example of FIG. 1, the circular base of the microlens 122M has the same width as the individual pixels 112P, but has a smaller area because the microlens base is circular and the individual pixels 112P are square. In some embodiments, the area of the microlens base is larger than the area of the pixel light source 112S.

In some embodiments, an optical spacer 140 is formed between the lensless display panel 110 and the microlens array 120 . In some embodiments, an optical spacer 140 is formed between the mesa array 102 and the microlens array 120 .

Optical spacer 140 is an optically transparent layer formed to maintain the position of microlens array 120 relative to pixel light source array 112S. Optical spacers 140 may be made of various materials that are transparent at the wavelengths emitted from pixel light sources 112 . Exemplary transparent materials for optical spacers 140 include polymers, dielectrics, and semiconductors. The material used to make the optical spacer 140 may be the same or different from the material used to make the microlens array 120 . In certain embodiments in which the microlenses 122M are formed to conform to the shape of the mesas 102M, the optical spacer layer 140 may be formed with the microlenses 122M in the same process with the same material. In certain embodiments, the optical spacer layer 140 may be formed under the microlenses 122M with the same material in the same process. In some embodiments, the height of the mesa 102M is greater than, the same as, or less than the thickness of the optical spacer 140 as measured from the bottom of the substrate 130 .

The thickness of the optical spacers 140 is designed to maintain the proper spacing between the microlens array 120 and the pixel light source array 112S. As an example, for an optical spacer that maintains an optical separation between the pixel light source and the microlens (which is more than a focal length of the microlens), an image of a single pixel is formed at a particular distance. As another example, a reduced divergence/viewing angle is achieved for an optical spacer that maintains an optical separation between the pixel light source and the microlens that is less than a focal length of the microlens. The amount of divergence/view angle reduction also depends in part on the thickness of the optical spacer 140 as measured from the top surface of the mesa 102M. In some embodiments, the thickness of the spacers 140 is no more than 1 micron as measured from the top surface of the mesa 102M. In certain embodiments, the thickness of the optical spacer 140 is no more than 0.5 microns as measured from the top surface of the mesa 102M. In certain embodiments, the thickness of the optical spacer 140 is no more than 0.2 microns as measured from the top surface of the mesa 102M. In some embodiments, the thickness of the optical spacer 140 is about 1 micron as measured from the top surface of the mesa 102M. In some embodiments, the material of the optical spacers 140 is the same as the material of the microlens array 120 .

In some embodiments, a brightness enhancement effect is achieved by integrating a microlens array into the display panel. In some instances, the brightness with the microlens array is 4 times as bright as without the microlens array in the direction normal to the display surface due to the light concentration effect of the microlens. In alternative embodiments, the brightness enhancement factor may vary according to different designs of the microlens array and optical spacers. For example, a factor greater than 8 can be achieved.

2A-2B are top views of exemplary monochrome display panels integrated with a spherical microlens array in accordance with certain embodiments. More specifically, FIG. 2A is a top view of an example monochrome display panel 200 having a square array configuration of pixels, and FIG. 2B illustrates an example single color display panel 200 of a triangular and a hexagonal array configuration of pixels. A top view of the color display panel 250. As an example, an embodiment of a triangular array configuration 230 and an embodiment of a hexagonal array configuration 235 are shown in FIG. 2B. Both display panels 200, 250 include an array of microlenses 210, 260, a mesa array including pixel light sources 220, 270 below the microlens 210, and optional optical spacers formed between the microlens array and the mesa array 240, 290. Each individual microlens is aligned to a mesa containing an individual pixel light source. In more detail, the display panel 200 having a square matrix configuration includes an array of individual microlenses 210, a corresponding mesa array including pixel light sources 220, and an optional optical spacer 240 therebetween, and has a triangular matrix or a hexagonal configuration. The display panel 250 includes an array of individual microlenses 260 , a corresponding mesa array including pixel light sources 270 , and an optional optical spacer 290 therebetween. In both the display panels 200 and 250, the pixel light sources are all monochromatic pixel light sources that generate light of the same color, for example, monochromatic LEDs forming a monochromatic display panel.

In FIGS. 2A to 2B , the individual microlenses 210 and 260 corresponding to the display panels 200 and 250 are configured as spherical microlenses in a square, triangular or hexagonal matrix. In alternative embodiments, the microlenses may have a non-spherical shape. The microlenses can also be configured in other matrix configurations, such as a rectangular matrix configuration or an octagonal matrix configuration or a combination of geometric matrix configurations.

3A-3B are top views of exemplary multi-color display panels integrated with a spherical microlens array in accordance with certain embodiments. More specifically, FIG. 3A is a top view of an example multicolor display panel 300 having a square array configuration of pixels, and FIG. 3B is an example multicolor display panel 350 having a triangular array configuration of pixels Top view. Both display panels 300, 350 include a microlens array 310, 360, a mesa array including pixel light sources 320, 370, and an optional optical spacer 340, 390 formed between the microlens array and the pixel light source array , and each microlens is aligned with a corresponding mesa including the individual pixel light source.

In more detail, the display panel 300 having a square matrix configuration includes an array of individual microlenses 310 , a corresponding mesa array including pixel light sources 320 , and an optional optical spacer 340 therebetween. Unlike the monochrome display panels 200, 250 shown in FIGS. 2A-2B, the pixel light source array in display panel 300 includes pixel light sources associated with different emission wavelengths, resulting in a multicolor display panel. For example, pixel light source 320R produces red light and the corresponding microlens 310R is aligned to the red pixel light source, pixel light source 320G produces green light and the corresponding microlens 310G is aligned to the green pixel light source, and pixel light source 320B produces blue light and corresponds to the microlens 310B is aligned to the blue pixel light source. In one embodiment, several pixel light sources 320 of different colors are grouped together at a specific ratio to form an RGB full-color pixel. For example, several pixel light sources 320 of different colors are grouped together in a triangular, rectangular or hexagonal matrix configuration. For example, in one common design, red pixel light sources 320R, green pixel light sources 320G, and blue pixel light sources 320B are grouped in a ratio of 1:2:1 to form a single full light source having a 2x2 square light source configuration Color pixel 330.

In FIGS. 3A to 3B , the respective microlenses 310 and 360 corresponding to the display panels 300 and 350 are spherical microlenses. In alternative embodiments, the microlenses may have a non-spherical shape. The microlenses can also be configured in other matrix configurations, such as a rectangular matrix configuration or a hexagonal matrix configuration.

The display panel 350 having a triangular matrix configuration also includes an array of individual microlenses 360, a corresponding mesa array including pixel light sources 370 and an optical spacer 390 therebetween, and the pixel light sources 370 are also associated with different emission wavelengths to provide different light color. For example, pixel light source 370R emits red light and the corresponding microlens 360R is aligned to the red pixel light source, pixel light source 370G emits green light and the corresponding microlens 360G is aligned to the green pixel light source, and pixel light source 370B emits blue light and corresponds to the microlens 360B is aligned to the blue pixel light source. In this example, red pixel light sources 320R, green pixel light sources 320G, and blue pixel light sources 320B are grouped in a ratio of 1:1:1 to form a single full-color pixel 380 having a triangular light source configuration. In some embodiments, an array of cylindrical microlenses can be formed on top of the mesas.

4-5 show examples of different fabrication methods for forming a display panel integrated with a microlens array in accordance with various embodiments.

4 shows a flowchart of a method of manufacturing a light-emitting pixel unit on a display panel integrated with a microlens array, according to some embodiments. The operations (eg, steps) of method 400 corresponding to the embodiment illustrated in FIG. 1 may be performed.

The method 400 includes a step 402 of providing a substrate. For example, FIG. 1 shows a cross-sectional view of a substrate 130 . In some embodiments, the substrate 130 is a semiconductor substrate such as silicon. In some embodiments, the material of the substrate 130 is selected from Group II to Group III compounds, sapphire, aluminum oxide, gallium nitride, and the like.

Method 400 also includes a step 404 of forming at least one mesa on the substrate. In certain embodiments, the mesa has a steep-sided flat-topped protrusion from the substrate formed by existing semiconductor fabrication methods such as deposition, photolithography, and etching. In certain embodiments, the mesa may be in the shape of a rectangle, square, triangle, trapezoid, polygon, or the like. In some embodiments, the mesa includes at least one PN node. For example, FIG. 1 shows a cross-sectional view of a mesa 102M. Substrate 130 has included an integrated array of individual pixels 112P each having a corresponding pixel light source 112S within mesas 102M. In one embodiment, an array of pixel driver circuits (not shown) that control the corresponding array of pixel light sources is also integrated on the substrate 130 . The embodiment in FIG. 4 begins with this structure, which is referred to as the lensless display panel 110 as shown in FIG. 1 .

The method 400 further includes a step 406 of depositing a layer of microlens material directly on at least a top of a mesa and in direct physical contact with the mesa. In certain embodiments, as shown in FIG. 1 , the shape of the layer of microlens material conforms to the shape of the mesas 102M and forms a hemisphere on the mesas. In certain embodiments, the tops of the mesas 102M are generally flat and the shape of the formed microlenses 122M is generally hemispherical. In some embodiments, the layer of microlens material is deposited directly on the substrate by chemical vapor deposition (CVD) techniques. In some embodiments, the deposition parameters of the CVD process are: power from about 0 W to about 1000 W, pressure from about 100 mTorr to about 2000 mTorr, temperature from about 23°C to about 500°C, gas flow about 0 to about 3000 sccm (standard cubic centimeters per minute), and the time is about 1 hour to about 3 hours. In some embodiments, the material of the microlens material layer is a dielectric material such as silicon dioxide.

The method 400 further includes a step 408 of patterning the layer of microlens material to expose electrode regions (not shown in FIG. 1 ) of the substrate. In some embodiments, the step 408 of patterning the layer of microlens material includes an etching step. In some embodiments, the etching step includes the step of forming a mask on the surface of the microlens material. The etching step also includes the step of patterning the mask through a photolithography process thereby forming openings in the mask and exposing the layer of microlens material over the electrode regions of the mesas. The etching step further includes a step of etching the portion of the layer of microlens material exposed by the opening with the mask protection in place. In some embodiments, the exposed layer of microlens material is etched by a wet etch method.

5 shows a flowchart of a method of manufacturing a light-emitting pixel unit on a display panel integrated with a microlens array, according to some embodiments. The operations (eg, steps) of method 500 corresponding to the embodiment illustrated in FIG. 1 may be performed.

The method 500 includes a step 502 of providing a substrate. For example, FIG. 1 shows a cross-sectional view of a substrate 130 . In some embodiments, the substrate 130 is a semiconductor substrate such as silicon.

Method 500 also includes a step 504 of forming at least one mesa on the substrate. In certain embodiments, the mesa has a steep-sided flat-topped protrusion from the substrate formed by existing semiconductor fabrication methods such as deposition, photolithography, and etching. In certain embodiments, the mesa may be in the shape of a rectangle, square, triangle, trapezoid, polygon, or the like. In some embodiments, the mesa includes at least one PN node. For example, FIG. 1 shows a cross-sectional view of a mesa 102M. Substrate 130 has included an integrated array of individual pixels 112P each having a corresponding pixel light source 112S within mesas 102M. In one embodiment, an array of pixel driver circuits (not shown) that control the corresponding array of pixel light sources is also integrated on the substrate 130 . The embodiment in FIG. 5 begins with this structure, which is referred to as the lensless display panel 110 as shown in FIG. 1 .

In some embodiments, method 500 also includes an optional step 506 of forming a marker layer having markers for alignment to a layer of microlens material deposited in a later step. For example, the marking layer is formed to align cells of light-emitting pixels to a layer of microlens material to form microlenses at the center of the light-emitting pixels. In some embodiments, the marking layer is formed to align the mesas to a layer above it (particularly a layer of microlens material) to form microlenses on top of the mesas.

The method 500 further includes a step 508 of depositing a layer of microlens material directly on at least the top of a mesa. 6A-6B further illustrate a method of fabricating a display panel integrated with a microlens array using top-down pattern transfer, according to certain embodiments. In certain embodiments, the microlens material layer 645 covers the top of the mesa 602M, as shown in FIG. 6A, and the top surface of the microlens material layer 645 is flat. In some embodiments, a layer of microlens material 645 is deposited on top of the mesa array 602 by spin coating. In some embodiments, the material of the microlens material layer 645 is photoresist. In some embodiments, the material of the microlens material layer 645 is a dielectric material such as silicon oxide.

The method 500 further includes a step 510 of patterning the layer of microlens material from the top down, thereby forming at least hemispheres in the layer of microlens material (as shown in FIGS. 6A-6B ). In some embodiments, patterning is performed without penetrating through or etching to the bottom of the microlens material layer 645 . In some embodiments, a hemisphere of microlens 620 is placed on at least one mesa 602M.

In certain embodiments, step 510 further includes a first step of depositing a mask layer 630 (as shown in FIG. 6A ) on the surface of the layer 645 of microlens material.

Step 510 also includes a second step of patterning the mask layer 630 to form a hemispherical pattern in the mask layer 630 . In some examples, the mask layer 630 is patterned first by a photolithography process and then by a reflow process. In certain embodiments, photopolymer mask layer 630 is patterned into isolated cells 640, as shown in FIG. 6A as dashed rectangular cells, in preparation for forming a hemispherical pattern. As an example, isolated cells 640 are patterned and formed via a photolithography process. The patterned photopolymer mask layer 650 with the isolated cells 640 is then shaped into a hemispherical pattern 660 using a high temperature reflow process. In one method, isolated cells 640 are formed into isolated hemispherical patterns 660 via high temperature reflow. In some embodiments, the isolated hemispherical pattern 660 of a pixel is not in direct physical contact with a hemispherical pattern of an adjacent pixel. In some embodiments, the hemispherical pattern 660 of one pixel contacts the hemispherical pattern of an adjacent pixel only at the bottom of the hemispherical pattern 660 . The patterned photopolymer mask layer 650 is heated to a temperature above the melting point of the polymer material for a specified time. After the polymer material has melted into a liquefied state, the surface tension of the liquefied material will cause it to assume a shape with a smoothly curved surface. For a cell with a circular base of a radius R (when the height of the cell is 2R/3), a hemispherical shape/pattern will be formed after the reflow process. 6A shows a display panel integrated with an array of hemisphere patterns 660 after completion of the high temperature reflow process. In certain embodiments, the hemispherical pattern in the mask layer may be formed by other fabrication methods including the fabrication method for microlenses described in method 400 . In certain other embodiments, grayscale mask photolithographic exposure may be used to form the hemispherical pattern in the mask layer. In certain other embodiments, the hemispherical pattern in the mask layer can be formed via a molding/imprinting process.

Step 510 further includes a third step of etching the microlens material layer 645 using the hemisphere pattern 660 as a mask to form hemispheres in the microlens material layer 645 . In some examples, the microlens material layer 645 is etched by a photolithography process. In some examples, the microlens material layer 645 is etched by a dry etch, such as a plasma etch process 635 (as shown in FIG. 6A). In some embodiments, after the microlens material layer 645 is etched, the top surfaces of the mesas 602M are not etched through the microlens material layer 645 (as shown in FIGS. 6A-6B ), thereby forming over the mesas 602M A spacer 670 on top or covering the top of mesa 602M (as shown in Figure 6B).

The method 500 further includes a step 512 of patterning the layer of microlens material to expose electrode regions (not shown in FIG. 6B ) of the substrate. In some embodiments, the step 512 of patterning the layer of microlens material includes an etching step. In some embodiments, the etching step includes the step of forming a mask on the surface of the microlens material. The etching step also includes a step of patterning the mask through a photolithography process whereby openings are formed in the mask and a layer of microlens material is exposed over the electrode regions of the mesas. The etching step further includes the step of etching the exposed layer of microlens material with mask protection. In some embodiments, the exposed layer of microlens material is etched by a wet etch method. In some embodiments, the opening for an electrode is positioned outside the display array area.

As set forth above, Figures 1, 4, 5, 6A, and 6B show various fabrication methods for forming a display panel integrated with a microlens array. It should be understood that these examples are merely examples and other fabrication techniques may also be used.

Although the detailed description contains numerous specific details, these should not be construed as limiting the scope of the invention, but merely as illustrating various examples and aspects of the invention. It should be understood that the scope of the present invention includes other embodiments not discussed in detail above. For example, microlenses with differently shaped mounts can also be used, such as square mounts or other polygonal mounts. Those skilled in the art will appreciate the configuration, operation and details of the methods and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims. Various other modifications, changes, and changes are apparent. Accordingly, the scope of the present invention should be determined by the appended claims and their legal equivalents.

Additional embodiments also include various subgroups of the above embodiments, including Figures 1, 2A, 2B, 3A, 3B, 4, 5, The embodiment shown in Figures 6A and 6B.

FIG. 7 is a top view of a micro LED display panel 700 according to some embodiments. The display panel 700 includes a data interface 710 , a control module 720 and a pixel area 750 . Data interface 710 receives data defining the image to be displayed. The source and format of this data will vary depending on the application. The control module 720 receives the incoming data and converts it into a format suitable for driving the pixels in the display panel. Control module 720 may include: digital logic and/or state machines for converting from the received format to the format appropriate for pixel area 750; shift registers or other types of buffers and memory for Store and transfer data; digital-to-analog converters and level shifters; and scan controllers that include timing circuitry.

Pixel area 750 includes an array of mesas (not shown separately from LEDs 734 in FIG. 7) containing pixels. The pixels include micro LEDs, such as a single-color or multi-color LED 734, integrated with a pixel driver, for example as described above. An array of microlenses (not shown separately from LEDs 734 in Figure 7) covers the top of the mesa array. In this example, display panel 700 is a color RGB display panel. It contains red, green and blue pixels. Within each pixel, LEDs 734 are controlled by a pixel driver. According to the previously shown embodiment, the pixel is in contact with a supply voltage (not shown) and ground via a ground pad 736, and is also in contact with a control signal. Although not shown in Figure 7, the p-electrode of LED 734 is electrically connected to the output of the drive transistor. LED current drive signal connection (between p-electrode of LED and output of pixel driver), ground connection (between n-electrode and system ground), supply voltage Vdd connection (between pixel driver's gate) according to various embodiments source and system Vdd) and control signal connections. Any of the microlens arrays disclosed herein can be implemented with micro LED display panel 700 .

FIG. 7 is only a representative diagram. Other designs will become apparent. For example, the colors do not have to be red, green and blue. It also does not have to be configured in columns or stripes. As an example, in addition to a square pixel matrix configuration shown in FIG. 7 , a hexagonal pixel matrix configuration may also be used to form display panel 700 .

In some applications, a fully programmable rectangular pixel array is not necessary. Other display panel designs with various shapes and displays can also be formed using the device structures described herein. Examples of one class are special applications, including signage and automobiles. For example, a plurality of pixels can be configured in the shape of a star or a spiral to form a display panel, and different patterns on the display panel can be created by turning LEDs on and off. Another special example is automotive headlights and smart lighting devices, where specific pixels are grouped together to form various illumination patterns and each group of LED pixels can be turned on or off or otherwise adjusted by individual pixel drivers.

Even the lateral device configuration within each pixel can vary. In Figures 1, 6A and 6B, the LEDs and pixel drivers are arranged vertically, that is, each LED is on top of the corresponding pixel driver circuit. Other configurations are also possible. For example, pixel drivers can also be located "behind", "before" or "beside" the LEDs.

Different types of display panels can be manufactured. For example, the resolution of a display panel may typically range from 8×8 to 3840×2160. Common display resolutions include QVGA with 320×240 resolution and an aspect ratio of 4:3, XGA with 1024×768 resolution and an aspect ratio of 4:3, 1280×720 resolution and 16:9 One aspect ratio D, FHD with 1920x1080 resolution and 16:9 aspect ratio, UHD with 3840x2160 resolution and 16:9 aspect ratio, and 4K with 4096x2160 resolution. Various pixel sizes can also exist, ranging from sub-micron and sub-sub-micron to 10 mm and above. The size of the overall display area can also vary widely, ranging from as small as tens of microns or less diagonally up to thousands of inches or more.

Different applications will also have different requirements for optical brightness and viewing angles. Example applications include direct view display screens, light engines for home/office projectors and portable electronic devices such as smartphones, laptops, wearable electronic devices, AR and VR glasses, and retinal projection. Power consumption can range from as low as a few milliwatts for retina projectors to as high as several kilowatts for large-screen outdoor displays, projectors, and smart car headlights. In terms of frame rate, due to the fast response (nanoseconds) of inorganic LEDs, the frame rate can be as high as KHz or even MHz for small resolutions.

Additional embodiments also include various subgroups of the above embodiments, including Figures 1, 2A, 2B, 3A, 3B, 4, 5, The embodiment shown in FIGS. 6A , 6B and 7 .

Although the detailed description contains numerous specific details, these should not be construed as limiting the scope of the invention, but merely as illustrating various examples and aspects of the invention. It should be understood that the scope of the present invention includes other embodiments not discussed in detail above. For example, the methods set forth above can be applied to integrate functional devices other than LEDs and OLEDs with control circuitry other than pixel drivers. Examples of non-LED devices include vertical cavity surface emitting lasers (VCSELs), photodetectors, microelectromechanical systems (MEMS), silicon photonics devices, power electronic devices, and distributed feedback lasers (DFBs). Examples of other control circuitry include current drivers, voltage drivers, transimpedance amplifiers, and logic circuits.

The foregoing descriptions of the disclosed embodiments are provided to enable those skilled in the art to make or use the embodiments set forth herein and variations thereof. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the subject matter disclosed herein. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the scope of the appended claims and the principles and novel features disclosed herein.

Features of the present invention may be implemented in, using, or by means of a computer program product, such as instructions stored thereon/wherein may be used to program a processing system to perform any of the features presented herein A storage medium(s) of one or a computer-readable storage medium. The storage medium may include, but is not limited to, high speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices , optical disc storage devices, flash memory devices or other non-volatile solid state storage devices. Memory optionally includes one or more storage devices remote from the CPU. A memory, or alternatively a non-volatile memory device within a memory, includes a non-transitory computer-readable storage medium.

Stored on any machine-readable medium(s), the features of the present invention may be incorporated into software and/or firmware for controlling the hardware of a processing system and enabling a processing system to utilize the results of the present invention Interact with other agencies. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments/containers.

It will be understood that, although the terms "first," "second," etc. may be used herein to describe various elements or steps, these elements or steps should not be limited by these terms. These terms are only used to distinguish one element or step from another element or step.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the claims. As used in the description of the embodiments and the appended claims, the singular forms "a (a, an)" and "the (the)" are also intended to include the plural forms unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" and/or "includes" when used in this specification designate the presence of stated features, integers, steps, operations, elements and/or components, but do not exclude the presence or Add one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, depending on the context, the term "if, then..." can be interpreted to mean "when a stated precondition is true" or "based on a stated precondition being true" or "response to Determining that a stated precondition is true" or "in accordance with a determination that a stated precondition is true" or "in response to detecting that a stated precondition is true". Similarly, depending on context, the phrase "if it is determined that [a stated precondition is true], then..." or "if [a stated precondition is true], then..." or "when [a stated precondition is true]..." The condition is true] can be interpreted to mean "based on a determination that the stated precondition is true" or "in response to a determination that the stated precondition is true" or "based on a determination that the stated precondition is true" or "Based on detecting that the stated prerequisite is true" or "in response to detecting that the stated prerequisite is true".

For purposes of explanation, the foregoing description has been set forth with reference to specific embodiments. However, the illustrative discussions are not intended to be exhaustive or to limit the scope of the claims to the precise forms disclosed. Numerous modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of operation and practical application, to thereby enable those skilled in the art to best utilize the invention and various embodiments.

100: display panel/finished display panel/full display panel 102: Individual Countertop Arrays / Countertop Arrays / Countertops 102M: Countertop 110: Lensless display panel 112P: Pixel 112S: Pixel light source/light source/pixel light source array 116: Ray of Light 118: Ray of Light/New Edge Ray of Light 120: Micro lens array 122M: Micro lens 126: Primitive Divergence Angle / Primitive Angle 128: Reduced Divergence Angle / Reduced Angle 130: Substrate 140: Optical Spacer/Optical Spacer Layer 200: Monochrome display panel/display panel 210: Micro lens 220: pixel light source 230: Triangular array configuration 235: Hexagon Array Configuration 240: Optical Spacer 250: Monochrome display panel/display panel 260: Micro lens 270: pixel light source 290: Optical Spacer 300: Multicolor Display Panel/Display Panel 310B: Micro lens 310G: Micro lens 310R: Micro lens 320B: pixel light source/blue pixel light source 320G: pixel light source/green pixel light source 320R: pixel light source/red pixel light source 330: full color pixels 340: Optical Spacer 350: Multicolor Display Panel / Display Panel 360B: Micro lens 360G: Micro lens 360R: Micro lens 370B: Pixel light source 370G: pixel light source 370R: Pixel light source 380: full color pixels 390: Optical Spacer 400: Method 402: Step 404: Step 406: Step 408: Step 500: Method 502: Step 504: Step 506: Steps 508: Steps 510: Steps 512: Steps 602: Countertop Array 602M: Countertop 620: Micro lens 630: mask layer/photopolymer mask layer 635: Plasma Etching Process 640: Isolated unit 645: Micro lens material layer 650: Patterned photopolymer mask layer 660: Hemisphere pattern 670: Spacer 700: Micro LED Display Panel/Display Panel 710: Data Interface 720: Control Module 734: Light Emitting Diode 736: Ground Pad 750: Pixel area

In order that the present invention may be understood in greater detail, reference may be made to a more specific description of the features of various embodiments, some of which are illustrated in the accompanying drawings. However, the drawings illustrate only relevant features of the invention and are therefore not to be regarded as limiting, as the description may allow for other effective features.

1 is a cross-sectional view of an exemplary display panel integrated with a microlens array in accordance with certain embodiments.

2A is a top view of an exemplary monochrome display panel having a square array configuration of pixels in accordance with certain embodiments.

2B is a top view of an example monochrome display panel illustrating a triangular and a hexagonal array configuration of pixels, according to an embodiment.

3A is a top view of an example multicolor display panel having a square array configuration of pixels in accordance with certain embodiments.

3B is a top view of an example multicolor display panel having a triangular array configuration of pixels in accordance with certain embodiments.

4 shows a flowchart of a method of manufacturing a light-emitting pixel unit on a display panel integrated with a microlens array, according to some embodiments.

5 shows a flowchart of a method of manufacturing a light-emitting pixel unit on a display panel integrated with a microlens array, according to some embodiments.

6A shows a method of fabricating a display panel integrated with a microlens array using top-down pattern transfer according to certain embodiments.

6B shows a method of fabricating a display panel integrated with a microlens array using bottom-up pattern transfer according to certain embodiments.

7 is a top view of a micro LED display panel according to some embodiments.

In accordance with common practice, the various features illustrated in the drawings may not necessarily be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. Additionally, some of the figures may not depict all of the components of a given system, method, or apparatus. Finally, similar reference numerals may be used to designate similar features in the specification and drawings.

100: display panel/finished display panel/full display panel

102: Individual Countertop Arrays / Countertop Arrays / Countertops

102M: Countertop

110: Lensless display panel

112P: Pixel

112S: Pixel light source/light source/pixel light source array

116: Ray of Light

118: Ray of Light/New Edge Ray of Light

120: Micro lens array

122M: Micro lens

126: Primitive Divergence Angle / Primitive Angle

128: Reduced Divergence Angle / Reduced Angle

130: Substrate

140: Optical Spacer/Optical Spacer Layer

Claims (23)

A light-emitting pixel unit, comprising: at least one mesa formed on a substrate; and a microlens formed from a microlens layer covering at least a top of the at least one mesa; in: The material of the microlens layer is different from the material of the at least one mesa, and The microlens layer is in direct physical contact with the at least one mesa. The light-emitting pixel unit of claim 1, wherein the microlenses are individually formed around the top of the at least one mesa. The light-emitting pixel unit of claim 1, wherein a spacer is formed from the same microlens layer between the at least one mesa and the microlens. The light-emitting pixel unit of claim 3, wherein the material of the spacer is the same as the material of the microlens. The light-emitting pixel unit of claim 1, wherein the microlens is formed of a dielectric material. The light-emitting pixel unit of claim 1, wherein the material of the microlens is a photoresist. The light-emitting pixel unit of claim 1, wherein the height of the microlens is no more than 2 microns. The light-emitting pixel unit of claim 1, wherein the width of the microlens is no more than 4 microns. The light-emitting pixel unit of claim 1, wherein, on the substrate, the at least one mesa is located in a mesa array matrix, and the microlenses are located in a microlens array matrix placed according to the placement of the mesa array. The light-emitting pixel unit of claim 1, wherein the top of the at least one mesa is flat, and the shape of the microlens is a hemisphere. The light-emitting pixel unit of claim 1, wherein the at least one mesa comprises at least one light-emitting device. A method of manufacturing a light-emitting pixel unit, comprising: providing a substrate; forming at least one mesa on the substrate; and A layer of microlens material is deposited directly on top of at least one of the at least one mesas, wherein the layer of microlens material conforms to a shape of one of the at least one mesas and has a hemispherical shape on the at least one mesa. The method of manufacturing a light-emitting pixel unit of claim 12, wherein the layer of microlens material is deposited by a chemical vapor deposition technique. The method of manufacturing a light-emitting pixel unit of claim 12, further comprising: patterning the microlens material layer to expose an electrode region of the substrate. The method of manufacturing a light-emitting pixel unit of claim 14, wherein the patterning further comprises: forming a mask on the surface of the microlens material; patterning the mask through a photolithography process, thereby forming openings in the mask and exposing the layer of microlens material over the electrode region of the at least one mesa; and With the mask protection in place, the portions of the layer of microlens material exposed by the openings are etched. The method of manufacturing a light-emitting pixel unit of claim 15, wherein the etching is a wet etching method. A method of manufacturing a light-emitting pixel unit, comprising: providing a substrate; forming at least one mesa on the substrate; depositing a layer of microlens material directly on at least a top of the at least one mesa, wherein the layer of microlens material covers the top of the at least one mesa and the top surface of the microlens material is flat; and The layer of microlens material is patterned from the top down, thereby forming at least a hemisphere in the layer of microlens material without penetrating the layer of microlens material, wherein the hemisphere is placed over the at least one mesa. A method of fabricating a light-emitting pixel unit as claimed in claim 17, wherein the layer of microlens material is deposited by spin coating. The method of fabricating a light-emitting pixel unit of claim 17, further comprising: after forming the at least one mesa and before depositing the layer of microlens material, forming in the patterning process a method for aligning to the microlens A marking layer of the marking of the material layer. The method of manufacturing a light-emitting pixel unit of claim 17, further comprising: after patterning the microlens material layer, patterning the microlens material layer to expose an electrode region of the substrate. The method for manufacturing a light-emitting pixel unit of claim 17, further comprising: depositing a mask layer on the surface of the microlens material layer; patterning the mask layer to form a hemispherical pattern in the mask layer; and Using the hemisphere pattern as a mask, the layer of microlens material is etched to form hemispheres in the layer of microlens material. The method of manufacturing a light-emitting pixel unit of claim 21, wherein after etching the layer of microlens material, the top surface of the at least one mesa is not etched through the layer of microlens material, whereby the top surface of the at least one mesa is not etched through. A spacer is formed on the top. The method of manufacturing a light-emitting pixel unit of claim 21, wherein the mask layer is patterned first by a photolithography process and then by a reflow process.

Images