TWI756384B - Method and process for mass transfer of micro-leds - Google Patents

Abstract

A method of forming a micro-LED device or display is provided. The method includes transferring a plurality of micro-LED material wafers onto a handling substrate. The method includes transferring a subset of the plurality of micro-LEDs from the handling substrate to a display backplane. The subset of transferred micro-LEDs includes at least one micro-LED from each of the plurality of micro-LED material wafers. The area defined by the perimeter of the handling substrate is greater than or is equal to the area defined by a perimeter of the display backplane. A large percentage of the total number of micro-LEDs needed for the display are transferred in a single step. The micro-LEDs may be formed by etching the micro-LED material from multiple wafers while supported by the handling substrate.

Description

Method and process for mass transfer of micro LEDs

CROSS-REFERENCE TO RELATED APPLICATIONS: This application claims priority under Section 28 of the Patent Act to US Provisional Application No. 62/472,121 filed on March 16, 2017, which is hereby relied upon and incorporated herein The contents of this US provisional application are incorporated by reference. The disclosure pertains generally to the field of micro-LED (micro-LED) device fabrication, and in particular to processes for mass-transferring micro-LEDs to devices, such as display backplanes.

In general, micro LED material is grown on a growth substrate such as sapphire. The micro LED material is then etched (usually while on the growth substrate) to form the micro LED. In order to utilize the micro LEDs in applications such as display applications, the micro LEDs are transferred to the display backplane. Efficiently transporting micro-LEDs, especially for large-area displays, has proven difficult due to the tight placement of micro-LEDs after etching, and the need for sparse placement on the display backplane.

One specific embodiment of the disclosure is related to a method of forming a micro LED display. The method includes transferring a plurality of wafers of micro LED material onto a first major surface of a handle substrate. A first area is defined by the perimeter of the first major surface of the handle substrate, and a plurality of micro LEDs are formed from each of the wafers of micro LED material. The method includes transferring a subset of the plurality of micro-LEDs from the handle substrate to a first major surface of a display backplane having electrical contacts coupled to each of the transferred plurality of micro-LEDs. The transferred subset of micro LEDs includes at least one micro LED from each of the plurality of wafers of micro LED material and has a first area equal to or greater than a second area defined by the perimeter of the first major surface of the display backplane.

Additional embodiments of the disclosure relate to a method of forming an LED device having a total of m micro LEDs arranged in an array on a selectively conductive substrate and having an average spacing pitch p ₂ . The method includes supporting a densely packed array of micro LEDs on a first major surface of a non-conductive support substrate. The closely spaced array of micro-LEDs has an evenly spaced pitch p ₁ , where p ₂ ≥ 10* p ₁ . The method includes moving the non-conductive support substrate such that the closely packed array of micro LEDs is positioned relative to the first major surface of the selectively conductive substrate. While the non-conductive support substrate is positioned such that the closely packed array of micro LEDs is positioned relative to the first major surface of the selectively conductive substrate, the method includes releasing a set of n non-contiguous micro LEDs from the closely packed array of the support substrate LEDs onto conductive substrates where n ≥ 0.05*m.

Additional embodiments of the disclosure are related to micro LED support devices. Micro LED supports contain glass or glass ceramic substrates. The glass or glass-ceramic substrate comprises: a first major surface; a second major surface opposite the first major surface; at least 50 mol% _SiO2 ; a width greater than 200 mm; and a length greater than 200 mm. The micro-LED support device includes an array of at least 10 layers of micro-LED material bonded to the first major surface of the glass or glass-ceramic substrate, and each layer of micro-LED material is formed as a closely packed array of micro-LEDs. The densely packed array of micro-LEDs contains an average spacing pitch of less than or equal to 100 μm, and the width of each micro-LED is less than or equal to 100 μm. The total number of micro LEDs supported by the glass substrate is greater than ten million.

The following detailed description will set forth additional features and advantages that will be apparent to those of ordinary skill in the relevant technical field from the description, or, to those of ordinary skill in the relevant technical field by implementation These features and advantages will be appreciated in part from the specific embodiments described in this specification and claimed scope (and by the accompanying drawings).

It is to be understood that both the foregoing general description and the following detailed description are exemplary only and are intended to provide an overview or framework for understanding the nature and character of the claimed scope.

Additional drawings are included to provide a further understanding of this specification, and are incorporated into and constitute a part of this specification. The drawings illustrate one or more specific embodiments, and together with the description serve to explain the principles and operation of the specific embodiments.

Referring generally to the drawings, various specific embodiments of systems and methods for forming micro LED display backplanes are illustrated. In various embodiments, the systems and methods discussed herein are used to populate a micro LED backplane and utilize a relatively small number of steps to transfer all required micro LEDs onto a display backplane. Micro LEDs are typically formed by etching individual micro LEDs from the deposited/grown micro LED material into a highly compact array while the micro LED material is supported by a growth substrate, such as a sapphire growth substrate. The micro-LEDs etched are very small (e.g., less than 100 µm in size, some as small as 12.5 µm x 12.5 µm, or even smaller), and the pitch (i.e., pitch) of adjoining micro-LEDs in the as-formed state is also very small (eg pitch less than 100 µm, less than 15 µm, or even smaller).

The spacing between adjacent micro-LEDs of the display backplane is typically many times greater than the spacing between adjacent micro-LEDs in the state formed on the growth substrate. Efficient transfer of micro-LEDs from a compact state to a sparse state on the display backplane after etching is a major challenge for the development of large-area micro-LED devices (or displays). Most prior art transfer methods require hundreds of individual transfer steps to fill large display backplanes (eg, displays with dimensions greater than about 300 mm x 300 mm (or larger)).

As discussed herein, the systems and methods discussed herein achieve sparse backplane fill with a relatively low number of transfer steps (eg, 20 steps or less, and 12 transfer steps in certain embodiments, and 12 transfer steps in other embodiments) Example for 4 transfer steps). As will be discussed in more detail below, the high-efficiency backplane fill systems and methods discussed herein involve bonding microLED material from a bulk growth wafer into an array (eg, tiled) on a large process substrate. ), the large processing substrate is the same size (or larger) as the display backplane.

With the micro LED material from multiple wafers supported by the handle substrate, the micro LED material is etched into micro LED arrays. Applicants believe that by etching micro-LEDs from multiple wafers at a time while their micro-LED material is supported by the backplane, it will allow micro-LEDs to have very low levels of pitch variation across the processed substrate ( At least compared to processes in which the micro-LEDs are etched on a growth substrate, and then transferred to a co-processing substrate after etching). This process produces a handle substrate that supports a tightly packed array of micro LEDs that is as large (or possibly larger) as the display backplane.

Next, the micro-LED large support processing substrate is aligned with the display backplane, and a large number of non-contiguous micro-LEDs are released (eg, via a laser) from the support substrate onto the display backplane. To provide a sparse micro LED fill on the display backplane, non-adjacent microLEDs from the handle substrate, spaced apart from each other by the desired display backplane pitch, are released from the handle substrate and bonded to the display backplane.

Thus, in this particular embodiment, a very large number of micro-LEDs (eg, at least 5% of the total number of micro-LEDs used in the display) are deposited onto the display backplane in a single transfer step. As will be appreciated, most micro-LED displays comprise groups of micro-LEDs comprising red micro-LEDs, blue micro-LEDs and green micro-LEDs at each location on the display backplane, and in this particular case In an embodiment, the transfer is performed at least once from a different process substrate for each microLED color to form a fully filled display backplane.

In certain embodiments, Applicants believe that micro LED wafers can be bonded to a handle substrate such that spaces or gaps in the form of blank rows and columns are formed between adjacent wafers on the handle substrate, and that these gaps are larger than the formed micro-LED wafers. LED pitch. As will be discussed below, in this particular embodiment, the systems and methods discussed herein include filling a handle substrate with additional micro LEDs that are used to fill "gap" on the display backplane, which The seed gap is caused by the rows of inter-wafer gaps on the main processing substrate. In this particular embodiment, however, the total number of LED transfer steps required is less than 20, and may be 12 in particular: one main transfer for each of the three colors of micro-LEDs, and one column transfer for each of the three colors of micro-LEDs In the gap-fill transfer, one row gap-fill transfer is performed for the micro-LEDs of the three colors respectively, and an intersection gap-fill transfer is performed for the micro-LEDs of the three colors respectively. Even in embodiments that address the inter-wafer gap on the processing substrate, the display backplane can be filled in fewer than 20 steps, compared to the hundreds of transfer steps of a typical backplane fill process.

Referring to Figures 1-10, a method for efficiently filling a display backplane is illustrated. As illustrated in FIG. 1 , a plurality (eg, at least 10, at least 30, at least 100) micro LED wafers 10 are bonded, bonded or transferred to a handle substrate 12 . As illustrated in FIG. 1 , the outer surface of each micro LED wafer 10 is bonded to the first major surface 14 of the handle substrate 12 . In certain embodiments, each micro LED wafer 10 includes a layer 16 of micro LED material (eg, GaN for blue and green micro LEDs and InP for red micro LEDs) supported on a growth substrate 18 . In this embodiment, the micro LED material layer 16 of each wafer is bonded (eg, through an adhesive material) to the first major surface 14 of the handle substrate. As illustrated in FIG. 2, after bonding to the handle substrate 12, each growth substrate 18 is released (eg, via a laser release process represented by arrows 19, or an alternative method (such as grinding and polishing)), each microscopic A layer 16 of LED material is bonded to the handle substrate 12 from each of the micro LED wafers 10 .

It should be appreciated that, for illustration, Figure 1 illustrates the removal of growth substrate 18 from micro LED material layer 16 in one step. In some embodiments, however, the growth substrate 18 may be removed after the micro LED material layer 16 of the growth substrate 18 is adhered to the handle substrate 12 and before attaching the next adjoining micro LED material layer 16 . In this particular embodiment, applicants believe that by prior to attaching the adjoining layer 16 of micro LED material With the growth substrate 18 removed, the gaps between adjoining micro LED material layers 16 can be formed to be very small (about 1 mm).

In certain embodiments, the handle substrate 12 has an adhesive that is initially uncured and then cured once the micro-LED material layer 16 contacts the adhesive. In one embodiment, the adhesive is, for example, an ultraviolet (UV) curing adhesive, and the ultraviolet light is passed through the processing substrate 12 to cure the adhesive. Selective removal of microLEDs, discussed in more detail below, can be achieved by using a laser to heat the adhesive to a liquid-like state at the location of the microLEDs to be released to achieve selective release of individual microLEDs. The heat from the laser can also be used to heat the solder (discussed below) on the display backplane, which is then cooled and frozen, so that the micro LEDs are bonded to the display backplane and can be released from the handle substrate 12 .

Referring to FIGS. 1-3 , the micro LED wafer 10 is bonded along both the width dimension and the length dimension (in the orientation shown) such that the LED material 16 from the micro LED wafer 10 is in the process substrate 12 arrays or imbricate arrangements). As best illustrated in FIG. 3, after removal of the growth substrate 18, a plurality of layers 16 of micro LED material from the micro LED wafer 10 are disposed on an array or overlay along the first major surface 14 of the handle substrate 12. in a tiled pattern.

As shown in FIG. 3, the processing substrate 12 has a width dimension W1 and a length L1. As shown in FIGS. 1 and 3, the processing substrate 12 is considerably larger than the micro LED wafers 10, so that the plurality of micro LED wafers 10 (and the micro LED material layers 16 of the plurality of micro LED wafers 10) fit in the Processing substrates within the perimeter of 12. In such embodiments, the handle substrate has a perimeter 2W1+2L1, and in certain embodiments 2W1+2L1 is greater than 3 times the length of the outermost perimeter of the micro LED wafer 10, specifically greater than 5 times, more specifically more than 10 times. Similarly, as shown in FIG. 3 , the area of the first major surface 14 of the handle substrate 12 is at least 10 times larger than the area of each micro-LED material layer 16 . These dimensional differences as described allow for the support of micro-LED material layers 16 from multiple micro-LED wafers 10 by a single handle substrate 12, such as, for example, a monolithic, continuously connected single sheet of material (or Groups of these sheets connected together to form a single process substrate). It should be appreciated that, for illustration, Figure 3 shows 20 layers of micro LED material 16 bonded to the handle substrate 12, and in many applications (where the handle substrate 12 is configured to fill a large display backplane (eg, a 50-inch display, 65 inch displays, 75 inch displays, etc.) or multiple display backplanes), the handle substrate 12 is as large (or larger) as the display backplane, and contains sufficient layer 16 of micro LED material to fill the area of the first major surface 14 .

In certain embodiments, the handle substrate 12 is sized to fill a relatively large display backplane with a small number of micro-LED transfer steps. In certain embodiments, W1 and or L1 may be at least 200 mm, at least 300 mm, at least 700 mm, at least 1270 mm, at least 1650 mm, at least 1900 mm, at least 2200 mm, and the like. In these specific embodiments, the area of the first major surface 14 of the handle substrate 12 is greater than 300 cm ² , greater than 1000 cm ² , greater than 5000 cm ² , greater than 1000 cm ² , and the like.

In certain embodiments, the handle substrate 12 is a non-conductive support substrate and does not include electrical connections for powering the micro LEDs (as would be present on the display backplane). In various embodiments, the handle substrate 12 is a sheet of glass or glass-ceramic material. In some such embodiments, the material of the handle substrate 12 is at least 50 mol % SiO ₂ , and in certain embodiments between 67 mol % and 70 mol % SiO ₂ . In certain embodiments, the processing substrate 12 may be Eagle XG glass supplied by Corning Incorporated.

In various embodiments, in addition to having a large perimeter and area, the handle substrate 12 can be relatively thin and light to facilitate in-process handling as discussed herein. As illustrated in FIG. 2 , the handle substrate 12 has a second major surface 26 opposite the first major surface 14 . The handle substrate 12 has a thickness T1 defined between the first major surface 14 and the second major surface 26 . In certain specific embodiments, T1 is between 0.25 mm and 1 mm.

As shown in FIG. 3 , in some embodiments, the micro LED wafer 10 is disposed on the processing substrate 12 , resulting in a plurality of horizontally oriented gap columns 20 , a plurality of vertically oriented gap rows 22 , and a plurality of gap columns 20 A plurality of intersecting gaps 24 where the gap row 22 intersects. In some embodiments, Applicants believe that due to the size of the micro LED wafer 10, and/or constraints imposed by the bonding and release processes used to bond the micro LED material layer 16 to the handle substrate 12, each The proximity of the micro LED wafers 10 to each other when bonded to the handle substrate 12 may be limited. This confinement creates gap columns 20 , gap rows 22 , and intersection gaps 24 between adjoining regions of the micro LED material layer 16 .

As illustrated in FIG. 3 , the gap columns 20 , the gap rows 22 , and the intersection gaps 24 are relatively large compared to the dimensions of the micro LED material layer 16 , and are very large compared to the dimensions of the micro LEDs to be formed from the micro LED material layer 16 . Big. In various embodiments, the gap columns 20 and the gap rows 22 generally have a gap size, shown as G1. In certain embodiments, G1 is greater than 0.5 mm, specifically between 0.5 mm and 1.5 mm, and more specifically about 1 mm. It should be appreciated that the gap dimension G1 is exaggerated in Figure 3 for ease of explanation. As an example, the dimensions of the micro-LED material layer will typically be on the order of about 100 mm, and in such an embodiment, at least 90% (specifically at least 95%, and more specifically at least 95%, and more specifically at least 95%, and more specifically the surface area of the substrate 12 is processed) is at least 99% occupied by the micro LED material layer 16 . As will be explained in more detail below with respect to FIG. 10, the various display backplane filling methods discussed herein utilize three additional process substrates for each color of microLED to fill the display backplane corresponding to the gap columns 20 and 20. Space for gap row 22 and intersection gap 24 .

4, once the growth substrate 18 is removed, leaving the layer of micro LED material 16 supported by the handle substrate 12, the micro LEDs 30 are formed from the plurality of layers of micro LED material 16 on the handle substrate 12. As illustrated in FIG. 4 , the micro LEDs 30 are formed from multiple layers of micro LED material 16 while being supported by the handle substrate 12 , and in certain embodiments, from all of the micro LEDs while being supported on the handle substrate 12 Material layer 16 forms all micro LEDs 30 .

In certain embodiments, by etching all of the micro LED material while the micro LED material layer 16 is supported by the handle substrate 12 The material layer 16 is formed to form a plurality of micro LEDs 30 to form the micro LEDs 30 . In some embodiments, etching to form the micro LEDs 30 includes applying a photoresist coating to all of the micro LED material layers 16 while the micro LED material layers 16 are supported on the first major surface 14 of the handle substrate 12 .

It will be appreciated that the micro LED material layer 16 from each micro LED wafer 10 illustrated in Figure 4 is etched into 16 micro LEDs for ease of drawing. However, the exact number of micro LEDs 30 formed from each micro LED material layer 16 will depend on the size of the micro LED wafer 10 and the final size of each micro LED 30, each micro LED material layer 16 forming a large number of micro LEDs LED 30. In certain embodiments, each micro LED material layer 16 forms more than one million micro LEDs 30, at least ten million micro LEDs 30, at least thirty million micro LEDs 30, and the like. Thus, in various embodiments, each handle substrate 12 may support more than ten million micro LEDs, more than 100 million micro LEDs, more than 500 million micro LEDs, more than 800 million micro LEDs, and so on.

4, the number of micro LEDs 30 formed from each micro LED material layer 16 depends on the size of each micro LED 30 (shown as W2), the size of each micro LED material layer 16 (shown as W3), and the pitch spacing between adjacent micro LEDs 30 within each micro LED material layer 16 (shown as P1). In various embodiments, W2 is less than or equal to 100 μm and P1 is less than or equal to 100 μm. In various embodiments, W3 is between 50mm and 150mm, and more specifically about 100mm. In some embodiments, the micro The LEDs 30 may be very small or closely packed micro LEDs. In particular, in some embodiments, the micro LEDs 30 may be rectangular and have dimensions of about 11.5 x 11.5 m, and in some such embodiments, a pitch P1 of about 12.5 μm. In some embodiments, W2 can be as small as 5 μm.

Referring to FIGS. 5-9, one or more display backplanes 40 are illustrated with the handle substrate 12 filled. Figure 5 illustrates the substrate 12 being processed with additional micro LED material 16 areas etched into the micro LEDs 30 to illustrate display backplane fill using the systems and methods discussed herein. For ease of illustration, FIG. 5 illustrates the gap columns 20 and the gap rows 22 as lines.

In general, referring to FIG. 6 , a selectively conductive substrate, such as an insulating substrate with conductive traces (shown as display backplane 40 ), is configured to receive and support micro LEDs 30 in display applications support device. In certain applications, the display backplane 40 is a support device that includes one or more conductive layers/elements and electrical contacts that will be coupled to each of the conductive layers/components and electrical contacts transferred to the display backplane 40 . A tiny LED 30.

Referring to FIGS. 6 and 7 , the handle substrate 12 is moved and positioned so that the micro LEDs 30 face the first major surface 42 of the display backplane 40 . As will be appreciated, the desired micro LED spacing pitch P2 on the display backplane 40 is greater than the etched, spacing pitch P1 of the micro LEDs 30 on the handle substrate 12 in the tightly etched state. Referring to FIG. 7, the larger micro-LED spacing pitch required to accommodate the display backplane 40 P2, transfer the subset of micro LEDs 30 from the processing substrate 12 (eg, via selective laser release) to the display backplane 40. As illustrated in FIG. 7, the desired spacing pitch on the display backplane 40 is accommodated by transferring the non-adjacent micro-LEDs 44 on the substrate 12 spaced apart from each other by the desired backplane pitch P2.

Again, to reduce or minimize the number of transfer steps required, the area of the first major surface 14 of the processing substrate 12 is greater than or equal to the area of the first major surface 42 of the display backplane 40 . Thus, because the handle substrate 12 is as large (or larger) as the display backplane 40, one of the micro LEDs 30 on the handle substrate 12 will face on the display backplane 40 in the facing arrangement illustrated in FIGS. most or all of the desired LED positions. Thus, the selective release of each non-adjacent micro-LED 30 spaced from one another by display pitch P2 forms a transferred micro-LED 44 on display backplane 40 with pitch P2. In this way, most (or all) of the display backplane 40 is filled as desired with micro LEDs 30 from a single transfer step.

Referring to Figures 7 and 8, the transfer of the micro LEDs 30 from the process substrate 12 is illustrated in greater detail. A subset of the micro LEDs 30 are released from the processing substrate 12, forming a partially filled substrate 46 with an ordered pattern of spaces 48 that were released to become the transferred micro LEDs 44 on the display backplane 40. The micro LEDs 30 are occupied. As illustrated in FIG. 9 , the transferred micro-LEDs 44 on the display backplane 40 are a mirror image of the spaces 48 vacated by the transfer of the micro-LEDs from the handle substrate 12 .

Additionally, as illustrated in Figures 7-9, at least one micro LED 30 from each micro LED material layer 16 is transferred to the display The backplane 40, and in this particular embodiment, because only a subset of the micro LEDs 30 transferred from the handle substrate 12 has filled the display backplane 40, the handle substrate 12 can be used to populate multiple display backplanes. For example, FIGS. 7-9 illustrate micro LEDs 30 that are 25% transferred from each micro LED material layer 16 , and thus handle substrate 12 can be used to fill four display backplanes 40 . However, as previously mentioned, each micro LED material layer 16 will typically contain millions of micro LEDs 30, and because the ratio of P2 to P1 will be very large, only one of the total number of LEDs will be transferred from the handle substrate 12 in each transfer step A small portion to the display backplane 40 (eg, less than 5% of micro-LEDs 30, less than 3% of micro-LEDs 30, less than 1% of micro-LEDs 30, etc.). Thus, each handle substrate 12 can be used in multiple transfer steps for multiple display backplanes 40 to fill a large number of display backplanes.

As will be appreciated, since many display backplanes 40 include 3 micro LEDs at each LED location (one red, one blue and one green, see Figure 12), for Figures 7-9 The process in question will be repeated with three different substrates, each with microLEDs in one of three colors. Additionally, in certain embodiments, the process includes a fill-in sequence of the processing substrates to account for the size and space occupied by the micro LEDs 30 . For example, in one embodiment, a complete handle substrate 12 with green micro LEDs, as illustrated in FIG. 7, may not be positioned relative to the display backplane 40 that has been filled with blue micro LEDs, due to the complete handle substrate 12 Interference between the micro-LEDs on the display backplane 40 and the blue micro-LEDs that already exist on the display backplane 40 . Thus in this particular embodiment, the blue micro LEDs 30 are already present on the display backplane 40 When on, use partially filled green micro LEDs to carry the processing substrate 12 . Thus, some display backplanes 40 may first be filled with green micro LEDs to provide partial fill-in process substrate 12 to fill those display backplanes 40 that have received blue micro LEDs first, and some display backplanes 40 may first be filled with green micro LEDs Filled with blue micro LEDs 30 to provide partially filled blue handle substrates 12 to fill those substrates that had previously received green micro LEDs.

In some embodiments, the thickness of the material forming the red micro-LEDs (eg, for the height of the handle substrate 12) is greater than the material height of the blue micro-LEDs or the green micro-LEDs. Thus in this particular embodiment, filling the display backplane 40 with the red micro LEDs 30 first (or as a second fill) will interfere with the back of the subsequent green or blue micro LEDs 30 because of the greater height plate filling. Thus in this particular embodiment, in the various methods discussed herein, the red micro LEDs 30 are filled after all of the green and blue micro LEDs 30 have been filled on the display backplane 40 .

0.05 * m、n

0.1 * m、n

0.2 * m、或n

0.3 * m。因此，如圖示，即使利用具有間隙列20、間隙行22與交會間隙24的基板，針對第5圖至第9圖所說明的製程，允許由每一轉移步驟，轉移顯示器背板40所需的最終LED數量的非常大的部分。 Thus, with reference to Figures 5-9, the processes discussed herein allow the formation of LED devices, such as a display device, having a total of m micro-LEDs arranged in an array on the display backplane 40 with an average Spacing pitch P2. The micro LEDs 30 are supported in a closely packed array on the handle substrate 12, the array having an evenly spaced pitch P1. In various embodiments, P2 is 10 times greater than P1, and more specifically, P2 is 30 times greater than P1. In this particular embodiment, a large portion of the total m micro-LEDs of the display backplane 40 are transferred in a single step. In various embodiments, in each release step, n micro-LEDs 30 are released, forming released micro-LEDs 44 on the display backplane 40 . In certain specific embodiments, the plurality (n) of transferred micro-LEDs 30 transferred in a single transfer step follow one or more of the following relationships: n

0.05 * m , n

0.1 * m , n

0.2 * m , or n

0.3 * m . Thus, as shown, even with a substrate having gap columns 20, gap rows 22, and intersecting gaps 24, the process illustrated in FIGS. 5-9 allows for each transfer step to transfer the display backplane 40 required for transfer a very large portion of the final LED count.

Referring to FIG. 10 , in embodiments in which the processing substrate 12 includes gap columns 20 , gap rows 22 , and intersecting gaps 24 , additional transfer steps may be required to fill corresponding gaps formed on the display backplane 40 . As illustrated in FIG. 10 , the transfer of the micro LEDs from the handle substrate 12 creates gaps on the display backplane 40 corresponding to the gap columns 20 , the gap rows 22 and the intersection gaps 24 on the handle substrate 12 . In particular, after initial transfer from handle substrate 12 , display backplane 40 includes gap columns 50 corresponding to substrate gap columns 20 , gap rows 52 corresponding to substrate gap rows 22 , and gap intersections corresponding to substrate intersection gaps 24 point 54. As will be appreciated, because the handle substrate 12 includes the gap columns 20 , the gap rows 22 , and the intersection gap 24 , when the micro LEDs are released from the handle substrate 12 , there are no LED gap columns 20 , gap rows 22 , and intersection gap 24 regions There is no way to transfer the LEDs to the opposing display backplane 40 segment, resulting in corresponding backplane gap columns 50 , gap rows 52 and gap intersections 54 .

As illustrated in FIG. 10, the size of the gap columns 50, the gap rows 52 and the gap intersection points 54 is larger than the desired pitch P2 on the display backplane 40. Furthermore, before the gap filling transfer step, the gap columns 50, the gap rows 54 are The dimensions of 52 and gap intersection 54 result in an uneven distribution of micro-LEDs 44 on display backplane 40 . To eliminate these gaps and non-uniformities, three additional process substrates are provided, shown as substrates 60 , 62 and 64 . Substrates 60 , 62 and 64 are formed in the same manner and have the same settings as previously described for processing substrate 12 . However, when substrates 60, 62, and 64 are aligned with display backplane 40 (similar to the manner illustrated in Figure 7), only selected spaced-apart micro LEDs 30 are released to fill gap columns 50, gap rows 52, and gaps Rendezvous point 54. As illustrated in Figure 10, the substrate 60 is the "intersection point" substrate, and the selected micro LEDs (identified as number 1) are released onto the display backplane 40 to fill all gaps in the display backplane 40 at the intersection points 54 . Substrate 62 is the "row" substrate and releases selected micro LEDs (identified as number 2 ) onto display backplane 40 to fill gap row 50 . Substrate 64 is the "row" substrate and releases selected micro LEDs (identified as number 3) onto display backplane 40 to fill gap row 52. In certain embodiments, gap intersections 54 are filled before gap columns 50 or gap rows 52 .

Thus, as illustrated in Figure 10, in this particular embodiment, all micro-LEDs of a given color are filled onto the display backplane 40 by four transfers, one from the "intersection" substrate 60 and one from the "row" substrate 62 , once from the “row” substrate 64 and once from the process substrate 12 . In certain embodiments, the transfer from the "meeting" substrate 60 is performed first, and the last It is then transferred from the handle substrate 12 to fill the display backplane 40 . In this particular embodiment, a total of 12 transfers are required to completely fill the display backplane 40 because four transfers are repeated for each of the three colors of microLEDs.

As previously mentioned, FIGS. 5-10 illustrate that the pitch P1 on the process substrate 12 , substrates 60 , 62 and 64 is only one-half the pitch P2 on the display backplane 40 for ease of drawing. FIGS. 11 and 12 illustrate examples of typical values for the pitch difference between the etched micro LEDs 30 and the display backplane 40 . In this specific embodiment, the pitch P1 of the micro LEDs 30 on the processing substrate 12 is 12.5 μm, and the pitch P2 of the micro LEDs on the display backplane 40 is 375 μm. Thus in this example, one out of every 30 micro LEDs 30 on the handle substrate 12 is transferred to the display backplane 40 to provide a display backplane pitch of 375 μm.

In addition, as an example, FIG. 12 illustrates that each LED group 70 includes three micro LEDs. In one embodiment, each LED group 70 includes a blue micro-LED 72 , a green micro-LED 74 and a red micro-LED 76 . In another embodiment, each LED group 70 may include three LEDs of the same color, and in such an embodiment, the display backplane 40 may be used in conjunction with a color conversion device to form the final display device.

In addition to the processing and efficiency advantages discussed above, the methods described herein may provide other advantages over other micro LED etching and transfer methods. For example, it has been observed that stress from lattice mismatch is released during etching on the growth substrate. Lateral displacement of the micro LEDs during release from the growth wafer was observed. Applicants hypothesize that lateral displacement of the micro-LEDs can be reduced or avoided by etching the micro-LEDs 30 on the handle substrate 12 as discussed herein, rather than on the growth substrate.

Unless explicitly stated otherwise, any method set forth herein should not be construed as requiring that its steps be performed in a particular order. Thus, if a method claim does not actually recite the order in which its steps are to be followed, or is not expressly stated in the claim or specification that the steps are limited to a particular order, no order is intended to be inferred. In addition, the article "a" as used herein is meant to include one or more elements or elements, and is not intended to be interpreted to mean only one.

It will be apparent to those skilled in the art of the present invention that various modifications and variations can be made in the disclosed embodiments without departing from the spirit and scope of the disclosed embodiments. As modifications, combinations, sub-combinations and variations of the disclosed embodiments that incorporate the spirit and substance of the disclosed embodiments may be contemplated by those skilled in the art of the invention, the disclosed embodiments should be construed as including Anything within the scope of the appended claims and their equivalents.

1: Selected Micro LED 1

2: Selected Micro LED 2

3: Selected Micro LED 3

10: Micro LED Wafer

12: Process the substrate

14: First main surface

16: Micro LED material layer

18: Growth substrate

19: Laser release process

20: Gap Column

22: Gap Row

24: Rendezvous Gap

26: Second main surface

30: Micro LEDs

40: Display backplane

42: First main surface

44: Non-Contiguous Micro LEDs

46: Partially fill the blank substrate

48: Space

50: Gap Column

52: Gap Row

54: Gap intersection point

60: Substrate

62: Substrate

64: Substrate

70: LED group

72: Blue Micro LED

74: Green Micro LED

76: Red Micro LED

P1: pitch

P2: pitch

T1: Thickness

G1: Gap size

W1: width dimension

W2: size

W3: Dimensions

L1: length

FIG. 1 is a schematic diagram of a micro LED wafer bonded to a handle substrate in accordance with an exemplary embodiment.

Figure 2 is a schematic illustration of removal of a growth substrate from a layer of micro LED material after bonding to a handle substrate in accordance with an exemplary embodiment.

Figure 3 is a schematic perspective view of a handle substrate supporting layers of micro LED material from multiple wafers prior to etching in accordance with an exemplary embodiment.

4 is a schematic perspective view of micro-LED material etched into micro-LEDs from multiple wafers while supported by a handle substrate, according to an exemplary embodiment.

5 is a schematic plan view of a handle substrate supporting etched micro LEDs from a plurality of wafer materials, in accordance with an exemplary embodiment.

FIG. 6 is a schematic diagram of the process substrate of FIG. 5 positioned adjacent to a display backplane, according to an exemplary embodiment.

Figure 7 shows selected non-contiguous micro-LEDs removed from a handle substrate and bonded to a display backplane, in accordance with an exemplary embodiment.

Figure 8 is a schematic plan view of a processed substrate after removal of selected non-adjacent micro LEDs, according to an exemplary embodiment.

9 is a schematic plan view of a display backplane after receiving selected non-contiguous micro LEDs from a processing substrate, according to an exemplary embodiment.

10 is a schematic plan view illustrating gap fill on a display backplane, according to an exemplary embodiment.

Figure 11 is an etched micro LED on a handle substrate with a fine pitch pitch according to an exemplary embodiment.

Figure 12 is a group of three micro LEDs on a display backplane with a large spacing pitch, according to an exemplary embodiment.

Domestic storage information (please note in the order of storage institution, date and number) None

Foreign deposit information (please note in the order of deposit country, institution, date and number) None

16‧‧‧Micro LED Material Layer

30‧‧‧Micro LED

P1‧‧‧Pitch

W2‧‧‧Dimensions

W3‧‧‧Dimensions

Claims (20)

A method of forming a micro LED display, comprising the steps of: transferring a plurality of wafers of micro LED material onto a first main surface of a handle substrate, wherein a perimeter of the first main surface of the handle substrate defines a a first area in which a plurality of micro LEDs are formed from each of the wafers of micro LED material; and transferring a subset of the plurality of micro LEDs from the handle substrate to a first major surface of a display backplane , the display backplane has electrical contacts coupled to each of the plurality of transferred micro-LEDs, wherein a subset of the transferred micro-LEDs includes At least one micro LED, wherein the first area is greater than or equal to a second area defined by a perimeter of the first main surface of the display backplane. The method of claim 1, wherein the first area of the handle substrate is larger than a third area defined by a perimeter of one of the wafers of micro LED material. The method of claim 2, wherein the first area of the processing substrate is more than 10 times larger than the third area. The method of claim 1, wherein the step of transferring the subset of micro LEDs from the handle substrate to the display backplane further comprises the step of: moving the handle substrate such that the micro LEDs are positioned facing the display the first major surface of the backplane; and releasing n non-contiguous microLEDs from the handle substrate to the display while the handle substrate is positioned such that the microLEDs face the first major surface of the display backplate on the first major surface of the backplane, where n is greater than or equal to 5% of the total number of an LED to be supported by the display backplane. The method of claim 1, further comprising the step of etching all of the wafers of micro LED material while the wafers of micro LED material are supported by the processing substrate to form the plurality of micro LEDs . The method of claim 5, wherein etching comprises the step of applying and patterning a photoresist coating to the first major surface of a handle substrate while the wafers of micro LED material are supported on the All of these micro LED material on wafers. The method of claim 1, wherein the processing substrate is a glass material sheet or a glass ceramic material sheet, and the first area is at least 300 cm ² . The method of claim 1, wherein the processing substrate supports at least 10 micro LED wafers. The method of claim 1, wherein the wafers of micro LED material are positioned on the first major surface of the handle substrate such that a vertically oriented gap is located between each wafer of micro LED material and a horizontally adjacent micro LED between wafers of material, and a horizontally oriented gap is located between each wafer of micro LED material and a vertically adjacent wafer of micro LED material. The method of claim 9, further comprising the steps of: transferring a plurality of non-contiguous, spaced-apart micro-LEDs from a second processing substrate to the first major surface of the display backplane to the display backplane all of the areas in the vertical rows on; transferring a plurality of non-contiguous, spaced-apart micro-LEDs from a third processing substrate to the first major surface of the display backplane to all of the display backplanes an area within a vertical row; and transferring a plurality of non-contiguous, spaced-apart micro-LEDs from a fourth processing substrate to the first major surface of the display backplane to all the horizontal rows and verticals on the display backplane The area within the intersection between the lines. The method of claim 10, wherein the plurality of non-contiguous, spaced-apart micro LEDs are transferred from the fourth processing substrate prior to transferring the plurality of non-contiguous, spaced-apart micro LEDs from the second substrate or the third substrate to the display backplane Non-contiguous, spaced-apart micro LEDs to the first major surface of the display backplane to areas within the intersections. A method of forming a micro LED device comprising the steps of: bonding an unetched wafer of micro LED material to a first main surface of a handle substrate, wherein a length of the first main surface of the handle substrate is related to a At least one of the widths is greater than a length and width of the micro LED material wafers, so that a plurality of micro LED material wafers are located on a single processing substrate; and the micro LED material wafers are supported by the processing substrate. At the same time, the wafers of micro LED material are etched to form a micro LED array. The method of claim 12, wherein both the length and the width of the first major surface of the processing substrate are greater than a length and a width of the micro LED material wafers, wherein at least 10 micro LED wafers A circle is bonded to the first major surface of the handle substrate. A method of forming an LED device having a total of m micro LEDs arranged in an array on a selectively conductive substrate and having an average spacing pitch p ₂ , the method comprising the steps of : supporting on a first major surface of a non-conductive support substrate a closely packed micro LED array having an evenly spaced pitch p ₁ , where p ₂ ≥ 10* p ₁ ; moving the a non-conductive support substrate such that the closely spaced array of micro LEDs is positioned relative to a first major surface of the selectively conductive substrate; and the non-conductive support substrate is positioned such that the closely spaced array of micro LEDs is positioned To release a set of n non-contiguous micro-LEDs from the closely packed array of the support substrate onto the conductive substrate simultaneously with respect to the first major surface of the selectively conductive substrate, where n > 0.05* m . The method of claim 14, further comprising the step of forming the closely spaced array of micro LEDs, wherein the step of forming the closely spaced array of micro LEDs comprises the steps of: bonding at least 10 micro LED wafers to the non-conductive support substrate, each micro-LED wafer having a micro-LED material layer and a growth substrate; removing the growth from each micro-LED wafer after bonding the micro-LED wafer to the non-conductive support substrate a substrate; and while being supported by the non-conductive support substrate, and after removing the growth substrates, forming the closely packed micro LED array from the bonded layers of micro LED material. A micro-LED supporting device, comprising: a glass or glass-ceramic substrate, comprising: a first main surface; a second main surface opposite to the first main surface; at least 50 mol% SiO ₂ ; width; and a length greater than 200 mm; and an array of at least 10 micro-LED material layers bonded to the first major surface of the glass or glass-ceramic substrate, each micro-LED material layer formed as a tight An array of discharged micro LEDs comprising: an average spacing pitch of less than or equal to 100 µm; and each micro LED having a width of less than or equal to 100 µm; wherein the total number of micro LEDs supported by the glass substrate is greater than ten million indivual. The micro-LED support device of claim 16, wherein the array of micro-LED material layers comprises at least 30 micro-LED material layers bonded to the first major surface of the glass or glass-ceramic substrate, wherein the glass substrate supports micro-LED material layers The total number of LEDs is greater than 800 million. The micro LED support device of claim 16, wherein the glass or glass-ceramic substrate comprises an average thickness between the first and second major surfaces of between 0.25 mm and 1 mm, wherein the glass Or the glass-ceramic substrate contains between 67 and 70 mol % of SiO ₂ . The micro-LED support device of claim 16, further comprising: a plurality of length-oriented gaps between each layer of micro-LED material and a horizontally adjacent layer of micro-LED material; and a plurality of width-oriented gaps , located between each micro-LED material layer and the vertically adjacent micro-LED material layer. The micro LED support device of claim 16, wherein both the widths of the alignment gaps of equal length and the alignment gaps of equal widths are at least 0.5 mm.

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