Mass transfer of micro structures using adhesives

Mass transfer of micro structures are effected from one substrate to another using adhesives. In the context of an integrated micro LED display, a micro LED array is fabricated on a native substrate and corresponding CMOS pixel drivers are fabricated on a separate substrate. The micro LED substrate (e.g., sapphire) and the CMOS substrate (e.g., silicon) may be incompatible. For example, they may have different thermal coefficients of expansion which make it difficult to bond the micro LEDs to the pixel driver circuitry. The micro LED array is transferred to an intermediate substrate (e.g., silicon) by use of an adhesive. This intermediate substrate may be used in a process of bonding the micro LED array to the array of pixel drivers. The intermediate substrate is separated from the micro LED array by releasing the adhesive.

BACKGROUND

1. Technical Field

This disclosure relates generally to methods for fabricating semiconductor devices, including integrated multi-color micro LED display panels.

2. Description of Related Art

Active matrix liquid-crystal displays (LCD) and organic light emitting diode (OLED) displays combined with thin-film transistor (TFT) technology are becoming increasingly popular in today's commercial electronic devices. These displays are widely used in laptop personal computers, smartphones and personal digital assistants. Millions of pixels together create an image on a display. The TFTs act as switches to individually turn each pixel on and off, rendering the pixel light or dark, which allows for convenient and efficient control of each pixel and of the entire display.

However, conventional LCD displays suffer from low light efficiency, causing high power consumption and limited battery operation time. While active-matrix organic light-emitting diode (AMOLED) display panels generally consume less power than LCD panels, an AMOLED display panel can still be the dominant power consumer in battery-operated devices. To extend battery life, it is desirable to reduce the power consumption of the display panel.

Conventional inorganic semiconductor light emitting diodes (LEDs) have demonstrated superior light efficiency, which makes active matrix LED displays more desirable for battery operated electronics. Arrays of driver circuitry and lighting-emitting diodes (LEDs) are used to control millions of pixels, rendering images on the display. Both single-color display panels and full-color display panels can be manufactured according to a variety of fabrication methods.

However, the integration of thousands or even millions of micro LEDs with a pixel driver circuit array is quite challenging. Various fabrication methods have been proposed. In one approach, control circuitry is fabricated on one substrate and micro LEDs are fabricated on a separate substrate. The micro LEDs are picked and placed one or a few at a time onto the substrate with the control circuitry. However, this fabrication process is inefficient and costly.

In another approach, the entire micro LED array with its original substrate is aligned and bonded to the control circuitry using metal bonding. The substrate on which the micro LEDs is fabricated remains in the final product, which may cause light cross-talk. Additionally, the thermal mismatch between the two different substrates generates stress at the bonding interface, which can cause reliability issues. Furthermore, multi-color display panels typically require more micro LEDs and different color micro LEDs grown on different substrate materials, compared with single-color display panels, thus making the traditional manufacturing process even more complicated and inefficient.

As a result, there is a need for better manufacturing methods, both for micro LED displays as well as other types of semiconductor devices with micro structures.

SUMMARY

The present disclosure overcomes the limitations of the prior art by providing mass transfer of micro structures from one substrate to another using adhesives. In the context of an integrated micro LED display, a micro LED array is fabricated on a native substrate and corresponding CMOS pixel drivers are fabricated on a separate substrate. The micro LED substrate (e.g., sapphire) and the CMOS substrate (e.g., silicon) may be incompatible. For example, they may have different thermal coefficients of expansion which make it difficult to bond the micro LEDs to the pixel driver circuitry while both are still on their original substrates. Accordingly, the micro LED array is transferred to an intermediate substrate (e.g., silicon) by use of an adhesive. This intermediate substrate may be used in a process of bonding the micro LED array to the array of pixel drivers. The intermediate substrate is then separated from the micro LED array by releasing the adhesive.

Other aspects include components, devices, systems, improvements, methods, processes, applications, computer readable mediums, and other technologies related to any of the above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples primarily use an integrated micro LED display in which array(s) of GaN micro LEDs are attached to CMOS pixel drivers by eutectic bonding, but these are just examples and the techniques described are not limited to this particular application. Examples of micro LEDs include GaN based UV/blue/green micro LEDs, AlInGaP based red/orange micro LEDs, and GaAs or InP based infrared (IR) micro LEDs. Additional examples of micro LEDs and other micro structures are described in U.S. patent application Ser. No. 15/135,217 “Semiconductor Devices with Integrated Thin-Film Transistor Circuitry”, Ser. No. 15/269,954 “Making Semiconductor Devices with Alignment Bonding and Substrate Removal”, Ser. No. 15/269,956 “Display Panels with Integrated Micro Lens Array”, Ser. No. 15/272,410 “Manufacturing Display Panels with Integrated Micro Lens Array”, and Ser. No. 15/701,450 “Multi-Color Micro-LED Array Light Source”. All of the foregoing are incorporated by reference in their entirety. The concepts described herein can also be used to mass transfer other micro structures and devices, such as VCSELs (vertical cavity surface-emitting lasers), laser diodes, photodetectors, MEMS and power devices. Besides eutectic bonding, electrically conductive bonding of micro LEDs to the driver circuitry can also be achieved using adhesives with electrically conductive particles immersed in the adhesive.

FIG. 1Ais a circuit diagram of a pixel for an integrated micro LED display, according to one embodiment. The pixel includes a pixel driver and micro LED140. In this example, the pixel driver includes two transistors and one capacitor130, with one transistor being a control transistor120and the other being a driving transistor110. The control transistor120is configured with its gate connected to a scan signal bus line150, its one source/drain connected to a data signal bus line170, and the other drain/source connected to the storage capacitor130and to the gate of the driving transistor110. One source/drain of the driving transistor110is connected to a voltage supply Vdd, and the other drain/source is connected to the p-electrode of the micro LED140. The n-electrode of the micro LED140is connected to the capacitor130and to ground. In this example, when the scan signal150opens the gate of the control transistor120, the data signal170charges the storage capacitor130and sets the driving transistor110's gate voltage, which controls the current flow through the micro LED140. The storage capacitor130here is used to maintain the gate voltage of the driving transistor110, thus maintaining the current flowing through the micro LED140during the time that the scan signal150is setting other pixels.

The pixel drivers for the integrated micro LED display typically are fabricated on one substrate, as shown inFIG. 1B. The micro LEDs are fabricated on a different substrate, as shown inFIG. 1C. The integrated micro LED display is created by integrating the micro LEDs with their corresponding pixel drivers, which as described below is achieved using a mass transfer process using adhesives and intermediate substrates.

FIG. 1Bis a cross-sectional view of a CMOS die with an array of pixel drivers fabricated on a silicon substrate, according to one embodiment. InFIG. 1B, an array of individual driver circuits110are fabricated on the CMOS substrate102. The driver circuits110are labeled with suffixes R,G,B, because they correspond to red, green and blue pixels. In this example, comparing toFIG. 1A, only the driving transistor110of each pixel driver circuit is shown inFIG. 1Bfor clarity. The driving transistor110is a CMOS driver circuit with its source117connected to a contact116that will be bonded to the corresponding micro LED. In alternative embodiments not shown, the driver circuitry can also be TFT circuitry on glass or flexible substrate.

For clarity,FIG. 1Bshows only six driver circuits110labeled with110R,110G and110B, which corresponds to red micro LEDs, green micro LEDs and blue micro LEDs, as described below. It should be understood that the driver circuitry can include a different number of driver circuits. In a fully programmable display panel, the micro LEDs and driver circuits are arranged in arrays to form an array of individually addressable pixels, preferably color pixels. In alternate embodiments, the display panel may have a more limited programmability and the pixels may be arranged in different geometries. In addition, there does not have to be a one to one correspondence between driver circuits and micro LEDs. For example, there could be two or more micro LEDs connected to the same pixel driver output to create redundancy, so that if one of the micro LEDs fails, the remaining micro LEDs could still light the pixel.

Returning toFIG. 1B, the driver circuitry100is fabricated as follows. The CMOS substrate102is the substrate on which the array of individual driver circuits110is fabricated. In one embodiment, the substrate102is a Si substrate. In another embodiment, the supporting substrate102is a transparent substrate, for example, a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, sapphire or flexible substrates.

The driver circuits110form individual pixel drivers to drive micro LEDs that will be bonded to the driver circuits, as described below. In the example shown inFIG. 1B, a driver circuit110is a CMOS driver circuit that includes a source117, a drain118and a gate119. The source117is further connected to an electrode that contacts the bonding contact116. The drain118is connected to an external voltage supply via a Vdd contact115. In alternate embodiments, the position of the drain118R and the source117R can be switched depending on the channel type of the driver circuit110R (e.g., n-channel or p-channel FET).

An insulating dielectric layer113is formed to electrically separate the Vdd contact115, the gate119and the electrode from the source117. A ground contact114is also formed within each pixel driver, to which the corresponding micro LED will be connected. The micro LED will contact the bonding contact116on one side and the ground contact114on the other side. In alternative embodiments not shown, the driver circuitry can include driver circuits other than CMOS driver circuits. As one example, the driver circuitry may include thin-film transistor (TFT) driver circuits. As another example, the driver circuitry can use III-V compound semiconductors.

As more fully described below, a bonding contact116is formed for each driver circuit110on top of the insulating dielectric layer113to make contact with a bonding contact of a corresponding micro LED, enabling the driver circuit110to be electrically coupled to the micro LED. The bonding contact116is an ohmic contact, for example a metal contact.

FIG. 1Cis a cross-sectional view of a micro LED die with an array of red micro LEDs140R fabricated on a GaAs substrate142R. In other embodiments, the micro LEDs can be blue or green micro LEDs and the substrate can be a sapphire, SiC or Si substrate. The micro LEDs140preferably are 20 microns or smaller in size. In one embodiment, the micro LEDs140R are arranged in an array on the substrate142R to form a fully programmable display panel with individually addressable pixels after the micro LEDs are integrated onto the CMOS die shown inFIG. 1B. For clarity,FIG. 1Cshows only two micro LEDs140R fabricated on the substrate142R. It should be understood that the micro LED die can include a different number of micro LEDs, and that multiple die can be used, for example different die for red, green and blue micro LEDs.

The micro LEDs140R are epitaxially grown on the substrate142R. A passivation layer143R is formed to electrically isolate individual micro LEDs140R on the micro LED die, and a bonding layer is formed on top of the micro LEDs, in which case for each of the micro LEDs, a bonding contact146R is formed to electrically coupled to a corresponding driver circuit110R as described above inFIG. 1B.

InFIG. 1C, the micro LEDs140R are red micro LEDs. In alternative embodiments not shown, a micro LED die including ultraviolet (UV) micro LEDs covered with phosphor layers or nano-particles can also be used to form a full-color micro LED display. Single-color micro LED display panels can also be fabricated. Alternately, same color micro LEDs with different color phosphors or nano-particles may be used to fabricate a multi-color display.

Micro LEDs typically have a pair of contacts, one to the p-layer and one to the p-layer of the micro LED. In the embodiment ofFIG. 1C, only one contact of the pair is connected via the bonding process. In this example, the bonding contact146is connected to the p-layer of the micro LED.

FIGS. 2-9illustrate various examples for bonding the micro LED arrays with the pixel driver arrays. These are based on mass transfer of the micro LED arrays to intermediate substrates using adhesives. For example, the micro LED arrays may be transferred to a carrier substrate that is more thermally compatible with the CMOS substrate. If the bonding process occurs at an elevated temperature, different thermal coefficients of expansion may prevent bonding of the arrays of micro LEDs and pixel drivers while they are still on their native substrates due to misalignment or internal stresses caused by the different rates of thermal expansion. However, these problems can be overcome by first transferring the micro LED array to an intermediate substrate that has a more compatible thermal coefficient of expansion.

For example, the CMOS pixel drivers typically are fabricated on a silicon substrate, but GaN-based micro LEDs may be grown on a sapphire substrate. Thermal mismatch between silicon and sapphire makes it difficult to bond an array of micro LEDs to an array of pixel drivers with an acceptable transfer yield. Instead, the Ga-based micro LEDs may first be mass transferred to an intermediate silicon substrate and then bonded to the array of pixel drivers.

FIGS. 2A-2Fare cross-sectional views illustrating fabrication of an integrated micro LED display panel by a single flip mass transfer adhesive process, according to one embodiment.FIG. 2Ashows an array of GaN micro LEDs240fabricated on a native sapphire substrate242. The micro LED array240is to be attached to a corresponding array of pixel drivers on a CMOS substrate (seeFIG. 2E). The transfer is effected by mass transfer of the micro LED array240to an intermediate substrate250using an adhesive. In this example, the intermediate substrate250is silicon, to match the thermal expansion of the substrate with the CMOS circuitry.

FIGS. 2B-2Cillustrate transfer of the micro LED array from the original sapphire substrate242to the silicon carrier substrate250. InFIG. 2B, the micro LED array240and native substrate242are attached to the silicon substrate250by an adhesive260. Examples of adhesives include epoxy-based polymers such as SU-8, benzocyclobutene (BCB), polyimide, polybenzoxazole (PBO), silicone or thermal release coating. The adhesive could be photosensitive, in which case UV or other irradiation is used to cure the adhesive. Alternatively, thermal treatment may be used to cure the adhesive. Here, the carrier substrate250is silicon, but sapphire, glass, ceramic and polymer substrates are other example materials that can be used for carrier substrates.

InFIG. 2C, the native sapphire substrate242is removed from the micro LED array240. In this example, the substrate removal is achieved by laser irradiation. Other techniques such as wet chemical etching, dry etching or chemical mechanical polishing (CMP) could be used for substrate removal processes. For GaN micro LEDs on a transparent substrate such as sapphire, substrate removal may be done by laser irradiation. For GaN micro LEDs on a silicon substrate, substrate removal may be done by CMP followed by wet chemical etching or dry etching. For AlGaInP micro LEDs on a GaAs substrate, wet chemical etching is preferably used for substrate removal. After the substrate removal, the adhesive260between LEDs240may be recess etched to expose more of the sidewalls of the micro LEDs, thus providing more clearance in the spaces between the micro LEDs and facilitating easier separation of the micro LEDs from adhesive260and carrier substrate250after bonded to pixel driver die210.

InFIG. 2D, bonding contacts246are deposited on the micro LEDs240. InFIG. 2E, these bonding contacts246are bonded to the corresponding contacts216on the die210that includes the pixel drivers. For convenience, that die will be referred to as the CMOS die210. It uses a silicon substrate in this example. Because the carrier substrate250is also silicon, the two substrates expand and contract at the same rate during the thermal cycling of the bonding process.

InFIG. 2F, the carrier substrate250is separated from the micro LED array240by releasing the adhesive260. Due to the weak bonding between the micro LEDs240and the surrounding adhesive260, mechanical exfoliation is preferably used to separate the carrier substrate250and the adhesive260from the micro LEDs240. To ensure good transfer yield of micro LEDs240to the CMOS die210, the bonding strength between the micro LEDs240and adhesive260can be tailored by inserting a low adhesion layer between them, and by recess etching the adhesive260to expose the entire sidewall of the micro LEDs240to minimize the contact area between them. Other techniques such as laser irradiation, wet etching, or dry etching can also be used to remove the carrier substrate250and the adhesive260. After release, excessive adhesive remaining on the CMOS die210may be removed, for example by wet etching or dry etching. The device now includes an array of micro LEDs240bonded to an array of corresponding pixel drivers.

Mass transfer of micro LEDs from a donor substrate to an acceptor substrate is beneficial because many micro LEDs may be transferred in parallel. The examples described herein refer to die, but it should be understood that these techniques can be readily applied at the wafer-level to the die before they are singulated from the wafer.

FIGS. 3A-3Dshow microscopic images of micro LED arrays transferred onto carrier substrates and acceptor substrates.FIGS. 3A and 3Bshow the acceptor substrate with micro LEDs arranged regularly on top after the transfer process.FIGS. 3C and 3Dshow the carrier substrate after the transfer of micro LEDs.

FIGS. 4A-4Dshow application of the process shown inFIGS. 2A-2F, to fabricate full color micro LED displays which requires multiple mass transfers of red, green, and blue micro LEDs to the pixel driver circuits.FIG. 4Ashows the device at a step corresponding toFIG. 2E. The red micro LEDs140R have already been transferred from their native substrate to the silicon carrier substrate250R using adhesive260R. Bonding contacts146R have been added to the micro LEDs140R and the entire device has been eutectically bonded to the corresponding bonding contacts116R on the CMOS die containing the driver circuits110R. The substrate102for the CMOS circuitry is silicon.FIG. 4Bshows the device after removal of the carrier substrate250R by release of adhesive260R.

The process is repeated for green and blue micro LEDs.FIG. 4Cshows attachment of the green micro LEDs140G to the CMOS die. The green micro LEDs140G have been transferred from their native substrate to the silicon carrier substrate250G using adhesive260G. Bonding contacts246G have been added to the micro LEDs140G and the array has been eutectically bonded to the corresponding bonding contacts116G on the CMOS die containing the driver circuits110G.

Note that in this case, there must be space between the green micro LEDs140G to allow for the existing red micro LEDs140R. If the adhesive260G originally extends between the green micro LEDs140G, it may be etched or otherwise removed to create space between the green micro LEDs140G. More generally, material between the micro LEDs140G, including the adhesive and the substrate, may be removed to increase the vertical clearance in the areas between the micro LEDs140G. Additional layers may also be added between the micro LEDs140G and the substrate250G or the thickness of the adhesive260G may be increased to further increase the height of the micro LEDs140G above the substrate250G.

FIG. 4Dshows the integrated micro LED display after integration of red, green and blue micro LEDs140.

Once red, green, blue micro LEDs are transferred to the pixel driver die, electrical connection is formed between the top semiconductor layer of micro LEDs and the common electrode of the pixel driver die.FIG. 5is a top view of an example micro LED display panel, according to one embodiment. The display panel includes a data interface510, a control module520and a pixel region540. The data interface510receives data defining the image to be displayed. The source(s) and format of this data will vary depending on the application. The control module520receives the incoming data and converts it to a form suitable to drive the pixels in the display panel. The control module520may include digital logic and/or state machines to convert from the received format to one appropriate for the pixel region540, shift registers or other types of buffers and memory to store and transfer the data, digital-to-analog converters and level shifters, and scan controllers including clocking circuitry.

The pixel region540includes an array of pixels. The pixels include micro LEDs534monolithically integrated with pixel drivers, for example as described above or in the following figures. In this example, the display panel is a color RGB display panel. It includes red, green and blue pixels, arranged in columns. Columns532R are red pixels, columns532G are green pixels and columns532B are blue pixels. Within each pixel, a micro LED534is controlled by a pixel driver. The pixel makes contact to a supply voltage (not shown) and ground via a ground pad536, and also to a control signal, according to the embodiments shown previously. Although not shown inFIG. 5, the p-electrode of micro LED and the output of the driving transistor are positioned underneath the micro LED534, and they are electrically connected by bonding metal. The micro LED current driving signal connection (between p-electrode of micro LED and output of the pixel driver), ground connection (between n-electrode and system ground), the Vdd connection (between source of the pixel driver and system Vdd), and the control signal connection to the gate of the pixel driver are made in accordance with various embodiments described previously.

FIG. 5is merely a representative figure. Other designs will be apparent. For example, the colors do not have to be red, green and blue, and there do not have to be equal numbers of each color pixel. They also do not have to be arranged in columns or stripes. A set of four color pixels could be arranged as a 2×2 square, for example. As one example, apart from the arrangement of a square matrix of pixels shown inFIG. 5, an arrangement of hexagonal matrix of pixels can also be used to form the display panel.

In some applications, a fully programmable rectangular array of pixels is not necessary. Other designs of display panels with a variety of shapes and displays may also be formed using the device structures described herein. One class of examples is specialty applications, including signage and automotive. For example, multiple pixels may be arranged in the shape of a star or a spiral to form a display panel, and different patterns on the display panel can be produced by turning on and off the micro LEDs. Another specialty example is automobile headlights and smart lighting, where certain pixels are grouped together to form various illumination shapes and each group of micro LED pixels can be turned on or off or otherwise adjusted by individual pixel drivers.

Different types of display panels can be fabricated. For example, the resolution of a display panel can range typically from 8×8 to 4096×2160. 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, HD with 1280×720 resolution and an aspect ratio of 16:9, FHD with 1920×1080 resolution and an aspect ratio of 16:9, UHD with 3840×2160 resolution and an aspect ratio of 16:9, and 4K with 4096×2160 resolution. There can also be a wide variety of pixel sizes, ranging from sub-micron and below to 10 mm and above. The size of the overall display region can also vary widely, ranging from diagonals as small as tens of microns or less up to hundreds of inches or more.

Different applications will also have different requirements for optical brightness. Example application include direct viewing display screens, light engines for home/office projectors and portable electronics such as smart phones, laptops, wearable electronics, and retinal projections. The power consumption can vary from as low as a few milliwatts for retinal projectors to as high as kilowatts for large screen outdoor displays, projectors, and smart automobile headlights. In terms of frame rate, due to the fast response (nano seconds) of inorganic micro LEDs, the frame rate can be as high as KHz, or even MHz for small resolutions.

The example ofFIG. 2is a “single transfer” or “single flip” process. The micro LED array is transferred once to a carrier substrate, with the orientation of the LEDs flipped during transfer. For most widely used epi wafers in the LED industry, the top epi-layer is p-type semiconductor, such as p-GaN for blue/green LEDs and p-GaP for red LEDs. After the single transfer process to the carrier substrate with adhesive and removal of the epi-substrate, the polarity of the micro LEDs is flipped with the top top epi-layer being n-type semiconductor. However, the transfer process can be repeated to control the polarity of the micro LEDs' top surface.FIGS. 6A-6Dare an example of a “double transfer” or “double flip” process. InFIG. 6A, the micro LED array640has already been transferred to a first carrier substrate651using adhesive661. Rather than attaching the micro LEDs to the CMOS die, it is instead transferred to a second carrier substrate652and then attached to the CMOS die, as shown inFIGS. 6B-6D. This might be done because the micro LEDs640are not oriented correctly inFIG. 6A. That is, the unexposed side of the micro LEDs640may be the side to be bonded to the CMOS die. Therefore, the micro LEDs640are flipped once before bonding to reorient them.

InFIG. 6B, the micro LED array plus carrier substrate651are attached to a second carrier substrate652using additional adhesive662. As shown inFIG. 6C, the first carrier substrate651is separated from the micro LED array by releasing the adhesive661, leaving the micro LED array640supported by the second carrier substrate652. Note that the micro LED array inFIG. 6Cis upside down compared to its orientation inFIG. 6A.

As shown inFIG. 6D, bonding contacts646are added, and the micro LED array supported by substrate652is bonded to corresponding contacts616on the CMOS die610. The carrier substrate652is then separated from the micro LED array640by releasing the adhesive662. InFIG. 6D, the micro LEDs640are “upside down” compared to the micro LEDs240in the single flip process ofFIG. 2F.

FIG. 7shows an example where the adhesive has two layers761and762. For example, these may be two different adhesives. This may be used to facilitate separation of the carrier substrate750from the micro LED array640and CMOS die710. For example, the interface between the two adhesive layers761,762may be designed to facilitate separation. Alternatively, the adhesive layer761may facilitate selective wet etching or laser irradiation if the adhesive layer762is not amenable to these techniques. The residual adhesive layer762may then be removed by dry etching, for example.

FIGS. 8A-8Bshow an example where the micro LEDs have additional structure when they are mass transferred. InFIG. 8A, p- and n-electrodes to the micro LED840are already formed while the micro LED is still supported by the native sapphire substrate842. The micro LED array840with electrodes is transferred to a silicon carrier substrate850using the double flip process described previously. The result is shown inFIG. 8B. This can then be bonded to the CMOS die. Alternately, it can be attached to the CMOS die using an adhesive with conductive particles that form electrical connections between the micro LED electrodes and the corresponding devices on the CMOS die.

FIGS. 9A-9Cshow an example where not all of the micro LEDs are released at once.FIG. 9Ashows a micro LED array940after transfer to a carrier silicon substrate950using adhesive960. Bonding contacts946have already been deposited. This is similar to the structure inFIG. 2D. However, as shown inFIGS. 9B and 9C, only every third micro LED940is bonded to the CMOS die910. After this process, the carrier substrate950contains additional micro LEDs940which may then be bonded to other CMOS die.

Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples. It should be appreciated that the scope of the disclosure includes other embodiments not discussed in detail above. For example, the bonding pad metals can be Au/Sn, Au/In, or In/Pd. As another example, the bonding pads on the CMOS die910and red, green, and blue micro LED template (FIG. 9A) can be arranged such that only a selected portion of the red/green/blue micro LEDs on the red/green/blue template are bonded to their designated red/green/blue pixels. The rest of the micro LEDs on the same template do not bond to any pad on the CMOS die910. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope as defined in the appended claims. Therefore, the scope of the invention should be determined by the appended claims and their legal equivalents.