Micro light-emitting diode chip, micro light-emitting diode chip transfer substrate, micro light-emitting diode display, and xr glasses

Abstract

Provided is a micro light-emitting diode chip having a blue-emitting AlGaInN light-emitting diode structure (B), a green-emitting AlGaInN light-emitting diode structure (G), and a red-emitting AlGaInN light-emitting diode structure (R) on an n-type GaN layer (11), these AlGaInN light-emitting diode structures having: an insulating film (12) having at least one opening (12a) provided on the n-type GaN layer; GaN layers (13) each in a truncated pyramid shape provided on the n-type GaN layer in the portion of the opening; light-emitting layers (14-16) provided along a top surface and a side surface of this GaN layer; a p-type GaN layer (17) provided to cover the light-emitting layers; a p-side electrode (19) on the p-type GaN layer; and an n-side electrode (20) on the n-type GaN layer.

Description

Micro light-emitting diode chip, micro light-emitting diode chip transfer substrate, micro light-emitting diode display, and XR glasses

[0001] The present invention relates to a micro light-emitting diode chip, a substrate for transferring the micro light-emitting diode chip, a micro light-emitting diode display, and XR (Cross Reality) glasses.

[0002] Micro light-emitting diode (LED) displays can achieve brightness far superior to that of liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays, and are expected to be applied to XR glasses, large-screen TVs, etc. However, due to the extremely high manufacturing costs, although commercialization has been achieved, the high product price has prevented them from being widely adopted.

[0003] To reduce the cost of microLED displays, chip sizes must be scaled down to the order of a few micrometers. Therefore, technologies must be introduced to mitigate the decline in luminous efficiency associated with miniaturization. The primary reason for this decline in luminous efficiency is the significant number of defects that arise in the cross section during chip separation. Holes and electrons reside most abundantly in the active layer, which has the smallest bandgap. Light is emitted when they combine with each other and emit photons with an energy appropriate for the bandgap. The presence of many defects in the active layer increases the proportion of holes and electrons that are trapped by the defects and do not contribute to luminescence. On average, holes and electrons (especially electrons) can travel several micrometers within the active layer before combining with their carrier counterparts (holes). As chips become smaller and the width of the active layer becomes smaller, the proportion of holes and electrons that are captured by defects on the sidewalls of the active layer and lost increases dramatically compared to the proportion that combines. Therefore, as chip sizes become smaller, such as a few micrometers, the luminous efficiency also decreases dramatically. If the decrease in the light-emitting efficiency of the LED can be prevented even when the chip is miniaturized, the light-emitting area of ​​the LED required to ensure brightness can be reduced, leading to a reduction in material costs.

[0004] Regarding the transfer of micro-LED chips, remarkable technological advances have been made in recent years, such as improvements in transfer speed and transfer yield. However, the reality is that there are still many issues that have not been overcome, such as the complexity of the process when transferring three types of chips, each emitting red (R), green (G), and blue (B), onto one pixel, the difficulty of measuring and repairing the characteristics of micro-LED chips on the order of a few micrometers, the difficulty of selecting defective chips due to the difficulty of chip measurement, and the low manufacturing yield caused by the inclusion of a small number of defective micro-LED chips.

[0005] Recently, proposals have been made to simplify the manufacturing process by growing GaN nanorods to form micro-LED chips of three colors (RGB) on the same substrate, and active research is being conducted on this topic (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1). However, it is difficult to ensure uniformity / reproducibility of the rod height and wavelength when growing GaN nanorods, and stable production is an issue.

[0006] Furthermore, due to vigorous research by various research institutes, the efficiency of InGaN-based red LEDs grown on flat C-plane GaN has recently improved, and it is expected that full-color displays will be realized using only GaN-based LEDs without wavelength conversion (see, for example, Non-Patent Document 2).

[0007] However, despite rising expectations, no technology has emerged that can solve all of the above issues at once, such as improving manufacturing yields, and the reality is that low prices for micro LED displays have yet to be realized. Therefore, there is a need for a technology that simultaneously achieves high manufacturing yields, simplifies the manufacturing process by integrating RGB, and addresses efficiency reductions due to sidewall damage.

[0008] Patent No. 5547076 Patent No. 5687731

[0009] [Retrieved June 9, 2023], Internet <URL: https: / / shingi.jst.go.jp / pdf / 2018 / 2018_kisoken2_1.pdf > [Retrieved June 9, 2023], Internet <URL: https: / / www.wavefront.co.jp / CAE / MOVPE-database / exp5.html>

[0010] Therefore, the problem to be solved by the present invention is to provide a micro light-emitting diode chip that is capable of emitting RGB light with a single chip and that can achieve high light-emitting efficiency even when miniaturized, a micro light-emitting diode chip transfer substrate that allows a large number of these micro light-emitting diode chips to be easily transferred, a high-performance micro light-emitting diode display that uses this micro light-emitting diode chip, and high-performance XR glasses that use this micro light-emitting diode display.

[0011] In order to achieve the above object, the present invention provides a light emitting diode (LED) having at least one blue-emitting AlGaInN-based light emitting diode structure, at least one green-emitting AlGaInN-based light emitting diode structure, and at least one red-emitting AlGaInN-based light emitting diode structure on an n-type GaN layer, wherein the blue-emitting AlGaInN-based light emitting diode structure, the green-emitting AlGaInN-based light emitting diode structure, and the red-emitting AlGaInN-based light emitting diode structure each have an insulating film having at least one opening provided on the n-type GaN layer, a truncated polygonal pyramid-shaped GaN layer provided on the n-type GaN layer in a portion of the insulating film that is exposed to the opening, a light emitting layer provided along an upper surface and a side surface of the truncated polygonal pyramid-shaped GaN layer, a p-type GaN layer provided so as to cover the light emitting layer, one or a plurality of p-side electrodes that are separated from one another provided on the upper surface of the p-type GaN layer, and at least one n-side electrode provided on a portion of the n-type GaN layer where the truncated polygonal pyramid-shaped GaN layer is not provided, The number of the blue light emitting AlGaInN-based light emitting diode structures, the green light emitting AlGaInN-based light emitting diode structures, and the red light emitting AlGaInN-based light emitting diode structures included in the entire micro light emitting diode chip is N b , N g and N r the number of p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p When Np ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2.

[0012] The shape of the truncated pyramidal GaN layer may be various and is not particularly limited. For example, the truncated pyramidal GaN layer may be a hexagonal pyramid, a hexagonal pyramid elongated in one direction, or an octagonal pyramid. The GaN layer may be undoped or n-type.

[0013] The shape of the openings in the insulating film is selected as needed, and may be a polygon similar to or similar to the frustum-shaped GaN layer, or may be a shape other than a polygon, such as a circle. The arrangement of the openings in the insulating film is also selected as needed. The insulating film is selected as needed, and may be, for example, an oxide film (SiO 2 film, etc.), nitride film (Si 3 N 4 film, etc.), oxynitride film (SiON film, etc.), titanium oxide film (TiO 2 Preferably, a portion of the n-type GaN layer is formed by lateral growth, and the opening in the insulating film is formed on the portion of the n-type GaN layer formed by the lateral growth. This makes it possible to significantly reduce the threading dislocation density of the truncated polygonal pyramidal GaN layer provided on the n-type GaN layer in the opening portion of the insulating film, thereby suppressing a decrease in light emission efficiency due to non-radiative recombination at the threading dislocation portion propagating from the truncated polygonal pyramidal GaN layer to the light-emitting layer, and suppressing leakage current due to threading dislocations.

[0014] For example, the thickness of the p-type GaN layer above the top surface of the truncated pyramidal GaN layer may be selected to be smaller than the thickness of the p-type GaN layer above the side surface of the truncated pyramidal GaN layer (thickness measured along a direction perpendicular to the top surface of the truncated pyramidal GaN layer), so that light is emitted mainly from the light-emitting layer on the top surface of the truncated pyramidal GaN layer. Conversely, the thickness of the p-type GaN layer above the side surface of the truncated pyramidal GaN layer may be selected to be smaller than the thickness of the p-type GaN layer above the top surface of the truncated pyramidal GaN layer, so that light is emitted mainly from the light-emitting layer on the side surface of the truncated pyramidal GaN layer.

[0015] The p-side electrode may be at least partially transparent, allowing light from the light-emitting layer to be extracted to the outside through this transparent portion, or may be made of a material containing a highly reflective metal layer such as Ag, allowing light from the light-emitting layer to be extracted to the outside mainly from the n-side (for example, in the case of flip-chip mounting in which the p-side electrode (p-type layer) is on the mounting substrate side). The n-side electrode is provided on the n-type GaN layer in a portion where the truncated pyramidal GaN layer is not provided, and is typically provided so as to contact the n-type GaN layer through an opening provided in an insulating film provided on the n-type GaN layer.

[0016] The blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure typically have an InGaN-based light-emitting layer, but by controlling the growth conditions of the light-emitting layer, it is possible to emit blue light (for example, a wavelength of 440 nm to 470 nm), green light (for example, a wavelength of 515 nm to 545 nm), or red light (for example, a wavelength of 605 nm to 655 nm).

[0017] The chip size of the micro light-emitting diode chip is selected as needed, but is generally 20 μm × 20 μm or less, typically 10 μm × 10 μm or less, most typically 5 μm × 5 μm or less, and typically 0.5 μm × 0.5 μm or more. The thickness of the micro light-emitting diode chip is also selected as needed, but is typically 1 μm to 6 μm. The micro light-emitting diode chip is preferably formed by crystal growth of semiconductor layers constituting a light-emitting diode structure on a substrate, followed by separation of the substrate from the semiconductor layers. The overall shape of the micro light-emitting diode chip is selected as needed, but is not particularly limited, and is typically square or rectangular. The side surfaces of the micro light-emitting diode chip are formed so that the upper surface of the GaN layer, which is a light-emitting layer provided along the upper and side surfaces of the polygonal truncated pyramidal GaN layer, is not exposed to the side surfaces. In this way, even if defects exist on the side surfaces formed by chipping when the semiconductor layers constituting the light-emitting diode structure are separated by dry etching such as RIE after crystal growth of the semiconductor layers on the substrate, the defects have almost no effect on the light emission because they are located sufficiently far from the light-emitting layer on the upper surface of the truncated polygonal pyramidal GaN layer where light emission mainly occurs. When one micro light-emitting diode chip has multiple truncated polygonal pyramidal GaN layers, the side surfaces of the micro light-emitting diode chip are formed so that the upper surface portion of at least one or more of the light-emitting layers provided along the upper and side surfaces of the truncated polygonal pyramidal GaN layers is not exposed on the side surfaces.

[0018] In this micro light-emitting diode chip, the number N of blue-emitting AlGaInN-based light-emitting diode structures is b , the number N of green-emitting AlGaInN-based light-emitting diode structures g , the number N of red-emitting AlGaInN-based light-emitting diode structures r , the number N of p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure p is N p ×N b ≧2, Np ×N g ≧2, N p ×N r Any selection may be made as long as it satisfies the condition ≧2. For example, p ×N b ≧3, N p ×N g ≧3, N p ×N r ≧3. For example, N p If =1, then N b ≧2, N g ≧2, N r ≧2, so for example, N b , N g , N r can be 2, 3 or 4. b = 1, N g = 1, N r If = 1, then N p ≧2.

[0019] The present invention also provides a semiconductor device comprising: an n-type GaN layer provided on a substrate; and chip regions each including at least one blue-emitting AlGaInN-based light-emitting diode structure, at least one green-emitting AlGaInN-based light-emitting diode structure, and at least one red-emitting AlGaInN-based light-emitting diode structure, arranged in a two-dimensional array on the n-type GaN layer; and the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure each comprising: an insulating film having at least one opening provided on the n-type GaN layer; a polygonal truncated pyramidal GaN layer provided on the n-type GaN layer in the opening portion of the insulating film; a light-emitting layer provided along the upper surface and side surfaces of the polygonal truncated pyramidal GaN layer; a p-type GaN layer provided so as to cover the light-emitting layer; and one or a plurality of p-side electrodes provided on the upper surface of the p-type GaN layer, the p-type GaN layer being separated from each other. and at least one n-side electrode provided on the n-type GaN layer in a portion where the polygonal truncated pyramidal GaN layer is not provided, and the number of the blue light emitting AlGaInN based light emitting diode structures, the green light emitting AlGaInN based light emitting diode structures, and the red light emitting AlGaInN based light emitting diode structures included in the entire chip region is set to N. b , N g and N r the number of p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p When N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2, and the chip region is defined by a separation groove separating the n-type GaN layer.

[0020] The substrate is not particularly limited as long as it allows for the growth of AlGaInN-based semiconductors (especially C-plane growth), and examples include a sapphire substrate, a Si substrate, etc. In the invention of this micro light-emitting diode chip transfer substrate, the matters described in relation to the above-mentioned invention of the micro light-emitting diode chip apply, unless otherwise stated and are inconsistent with the nature of the invention.

[0021] The present invention also provides a light emitting diode device comprising: a display unit on which a plurality of micro light emitting diode chips are mounted in a two-dimensional array; a drive circuit unit in which a plurality of drive circuits that can be controlled and driven independently of one another are provided in a two-dimensional array; and a wiring circuit that wires the display unit and the drive circuit unit, wherein the micro light emitting diode chip has at least one blue light emitting AlGaInN based light emitting diode structure, at least one green light emitting AlGaInN based light emitting diode structure, and at least one red light emitting AlGaInN based light emitting diode structure on an n-type GaN layer, and the blue light emitting AlGaInN based light emitting diode structure, the green light emitting AlGaInN based light emitting diode structure, and the red light emitting AlGaInN based light emitting diode structure each have an insulating film having at least one opening provided on the n-type GaN layer; a polygonal truncated pyramidal GaN layer provided on the n-type GaN layer in the opening portion of the insulating film; and a light emitting layer provided along the top surface and side surfaces of the polygonal truncated pyramidal GaN layer. a p-type GaN layer provided so as to cover the light-emitting layer, one or a plurality of p-side electrodes provided on an upper surface of the p-type GaN layer, and at least one n-side electrode provided on the n-type GaN layer in a portion where the polygonal truncated pyramidal shaped GaN layer is not provided, and the number of the blue light-emitting AlGaInN-based light-emitting diode structures, the green light-emitting AlGaInN-based light-emitting diode structures, and the red light-emitting AlGaInN-based light-emitting diode structures included in the entire micro light-emitting diode chip is N b , N g and N r the number of p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p When N p ×N b ≧2, N p ×N g ≧2, N p ×N r The micro light emitting diode display is a micro light emitting diode chip with a capacitance of ≧2.

[0022] This micro light-emitting diode display can be used as a color display because the micro light-emitting diode chips can emit light in three colors: red, green, and blue (RGB). This micro light-emitting diode display can be driven by any of a passive matrix, an active matrix, a pulse-width modulation (PWM), and the like. In a PWM-driven color display, for example, the micro light-emitting diode chips can be transferred onto an IC substrate incorporating a PWM drive circuit. In a typical example of this micro light-emitting diode display, multiple p-side electrodes are provided separately for each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure, and at least one n-side electrode is provided. Each micro light-emitting diode chip has its p-side electrode electrically connected to a plurality of branch wirings branched from a first main wiring connected to the drive circuit of the drive circuit unit via wiring in the wiring circuit, and its n-side electrode electrically connected to a second main wiring connected to the drive circuit of the drive circuit unit via wiring in the wiring circuit. In the invention of this micro light-emitting diode display, the matters described in relation to the invention of the micro light-emitting diode chip above are applicable except for the above, unless they are contrary to the nature of the invention.

[0023] The present invention also provides a display comprising: a display unit on which a plurality of micro light-emitting diode chips are mounted in a two-dimensional array; a drive circuit board on which a plurality of drive circuits that can be controlled and driven independently of one another are provided in a two-dimensional array; and a flexible printed circuit that connects the display unit and the drive circuit board; and the micro light-emitting diode chip has at least one blue-emitting AlGaInN-based light-emitting diode structure, at least one green-emitting AlGaInN-based light-emitting diode structure, and at least one red-emitting AlGaInN-based light-emitting diode structure on an n-type GaN layer, and the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure each have an insulating film having at least one opening provided on the n-type GaN layer; a polygonal truncated pyramidal GaN layer provided on the n-type GaN layer in the opening portion of the insulating film; and a light-emitting layer provided along the top surface and side surfaces of the polygonal truncated pyramidal GaN layer. a p-type GaN layer provided so as to cover the light-emitting layer, one or a plurality of p-side electrodes provided on an upper surface of the p-type GaN layer, and at least one n-side electrode provided on the n-type GaN layer in a portion where the polygonal truncated pyramidal shaped GaN layer is not provided, and the number of the blue light-emitting AlGaInN-based light-emitting diode structures, the green light-emitting AlGaInN-based light-emitting diode structures, and the red light-emitting AlGaInN-based light-emitting diode structures included in the entire micro light-emitting diode chip is N b , N g and N r the number of p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p When N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2, a micro light-emitting diode chip, XR Glass.

[0024] In these XR glasses, the locations for mounting the display unit, drive circuit board, and flexible printed circuit are selected as needed and are not particularly limited, but for example, the display unit may be mounted on the inside surface of the windshield, the drive circuit board may be mounted on the ear hooks of the frame, and the flexible printed circuit may be mounted on the frame. XR (Cross Reality) glasses is a general term for glasses that use technologies such as VR (Virtual Reality), AR (Augmented Reality), MR (Mixed Reality), and SR (Substitutional Reality), technologies that combine these technologies (e.g., technologies that combine VR and AR), and technologies that are intermediate between these technologies (e.g., technologies positioned between AR and MR), and are video display devices that create a space that provides a simulated experience by fusing the real and virtual worlds. VR is a technology that allows you to experience a virtual world as if it were the real world, AR is a technology that projects a virtual world onto real space, MR is a technology that blends real space with virtual space, and SR is a technology that overlays past footage onto real space, making it appear as if past events are happening right in front of your eyes.

[0025] In a typical example of this XR glass, a plurality of p-side electrodes are provided separately for each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure, and at least one n-side electrode is provided, and each micro light-emitting diode chip is electrically connected to each of a plurality of branch wirings branched from a first main wiring connected to the drive circuit of the drive circuit board via the flexible printed circuit, and the n-side electrode is electrically connected to each of a second main wiring connected to the drive circuit of the drive circuit board via the flexible printed circuit. In this XR glass invention, the matters described in relation to the above micro light-emitting diode chip invention are valid, unless otherwise particularly contrary to the nature of the invention.

[0026] According to this invention, the micro light-emitting diode chip has a blue-emitting AlGaInN-based light-emitting diode structure, a green-emitting AlGaInN-based light-emitting diode structure, and a red-emitting AlGaInN-based light-emitting diode structure on an n-type GaN layer, so that one chip can emit blue, green, and red light. Moreover, in each light-emitting diode structure, a light-emitting layer is provided along the top and side surfaces of the polygonal truncated pyramidal GaN layer. Therefore, even if defects are present on the side surfaces of the micro light-emitting diode chip due to dry etching or the like, this has almost no effect on the light emission. Therefore, high light-emitting efficiency can be obtained even when miniaturized, and further, since the structure is simple, it can be easily manufactured.

[0027] This high-performance micro light-emitting diode chip can be used to realize a high-performance micro LED display, and this micro LED display can be used to realize high-performance XR glasses. Furthermore, by using a micro light-emitting diode chip transfer substrate having a blue-emitting AlGaInN-based light-emitting diode structure, a green-emitting AlGaInN-based light-emitting diode structure, and a red-emitting AlGaInN-based light-emitting diode structure on an n-type GaN layer in each chip region, it is possible to transfer, for example, millions to tens of millions of micro light-emitting diode chips to a mounting substrate at once, and to easily manufacture large-area or highly integrated micro LED displays.

[0028] Furthermore, according to the present invention, a single chip can emit blue, green, and red light, and has multiple electrodes or light-emitting diode structures for each emission wavelength, which are independently controllable. Therefore, even if inspection of individual chips (full inspection) is omitted and millions to tens of millions of micro light-emitting diode chips are transferred and assembled at once, pixels can be repaired by isolating the defective part by disconnecting the wiring, thereby ensuring a high manufacturing yield of micro LED displays.

[0029] FIG. 1 is a perspective view showing a micro LED chip according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view showing a micro LED chip according to the first embodiment of the present invention; FIG. 3 is a cross-sectional view showing a micro LED chip according to the first embodiment of the present invention; FIG. 4 is a plan view for explaining an example of a method for manufacturing a micro LED chip according to the first embodiment of the present invention; FIG. 5 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to the first embodiment of the present invention; FIG. 6 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to the first embodiment of the present invention; FIG. 7 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to the first embodiment of the present invention; FIG. 8 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to the first embodiment of the present invention; Fig. 1 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to a first embodiment of the present invention. Fig. 3 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to a first embodiment of the present invention. Fig. 4 is a cross-sectional view for explaining an example of a method for manufacturing a micro LED chip according to a first embodiment of the present invention. Fig. 5 is a cross-sectional view showing a micro LED chip transfer substrate according to a second embodiment of the present invention. Fig. 6 is a cross-sectional view for explaining a method for manufacturing a micro LED chip transfer substrate according to a second embodiment of the present invention.FIG. 1 is a cross-sectional view illustrating a method for manufacturing a micro LED chip transfer substrate according to a second embodiment of the present invention. FIG. 2 is a perspective view illustrating a micro LED chip according to a third embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a micro LED chip according to the third embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a micro LED chip according to the third embodiment of the present invention. FIG. 5 is a plan view illustrating a method for manufacturing a micro LED chip according to the third embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a method for manufacturing a micro LED chip according to the third embodiment of the present invention. FIG. 7 is a cross-sectional view illustrating a micro LED chip transfer substrate according to a fourth embodiment of the present invention. FIG. 8 is a perspective view illustrating XR glasses according to a fifth embodiment of the present invention. FIG. 9 is a plan view illustrating a display unit 300, a flexible printed circuit 400, and a printed circuit board 500 of XR glasses according to the fifth embodiment of the present invention. FIG. 10 is a plan view illustrating the display unit 300 of XR glasses according to the fifth embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating the display unit 300 of XR glasses according to the fifth embodiment of the present invention. Fig. 10 is a perspective view showing XR glasses according to a sixth embodiment of the present invention. Fig. 11 is a development view of a light engine 600 of XR glasses according to a sixth embodiment of the present invention. Fig. 12 is a plan view showing an LED array unit 610 of XR glasses according to a sixth embodiment of the present invention. Fig. 13 is a cross-sectional view showing an LED array unit 610 of XR glasses according to a sixth embodiment of the present invention. Fig. 14 is a cross-sectional view showing the configuration of a light engine 600 of XR glasses according to a seventh embodiment of the present invention.

[0030] Hereinafter, modes for carrying out the invention (hereinafter referred to as "embodiments") will be described.

[0031] 1A, 1B, and 1C show a micro LED chip 10 according to a first embodiment, where FIG. 1A is a perspective view, FIG. 1B is a cross-sectional view taken along line B-B in FIG. 1A, and FIG. 1C is a cross-sectional view taken along line CC in FIG. 1A. As shown in FIGS. 1A, 1B, and 1C, the micro LED chip 10 has a square or rectangular shape and includes a blue-emitting AlGaInN-based LED structure B, a green-emitting AlGaInN-based LED structure G, and a red-emitting AlGaInN-based LED structure R. In the micro LED chip 10, an insulating film 12 is provided on an n-type GaN layer 11. As already mentioned, the insulating film 12 is made of SiO 2 The thickness of the insulating film 12 is selected as required, but is, for example, 10 to 30 nm. The n-type GaN layer 11 is generally grown on a sapphire substrate or a Si substrate via a low-temperature buffer layer, but usually contains a large number of threading dislocations (10 8 ~10 10 pieces / cm 2 The threading dislocations can cause a decrease in light emission efficiency and electrical leakage. Therefore, it is preferable that the n-type GaN layer 11 is laterally grown by the conventionally known ELO (Epitaxial Lateral Overgrowth) method, and has a low threading dislocation density region (not shown) in part. The region of the n-type GaN layer 11 that corresponds to the seed (seed crystal) used for lateral growth and the region (meeting portion) where the layers laterally grown from adjacent seeds meet are high dislocation density regions (10 8 ~10 10 pieces / cm 2 The lateral growth region between these two regions is a low dislocation density region (10 6 ~10 7 pieces / cm 2 (To some extent).

[0032] Three elongated rectangular openings 12a, each having the same planar shape, are formed in the insulating film 12 at equal intervals and parallel to one another in a low-dislocation density region of the n-type GaN layer 11. The size of the openings 12a is selected as needed, but is, for example, (100 to 2000 nm) x (1 to 10 μm). A GaN layer 13, elongated in the longitudinal direction of the opening 12a and generally island-shaped, is provided on the n-type GaN layer 11 in the portion of each opening 12a so as to extend separately from one another on the insulating film 12. In this case, the GaN layer 13 has an octagonal truncated pyramid shape extending in the longitudinal direction of the opening 12a. The GaN layer 13 may be undoped or n-type. 1A and 1B , blue-emitting light-emitting layer 14 is provided in an island shape along the top and side (slope) surfaces of GaN layer 13 in the leftmost opening 12 a, green-emitting light-emitting layer 15 is provided in an island shape along the top and side (slope) surfaces of GaN layer 13 in the central opening 12 a, and red-emitting light-emitting layer 16 is provided in an island shape along the top and side (slope) surfaces of GaN layer 13 in the rightmost opening 12 a. P-type GaN layers 17 are provided separately from each other to cover light-emitting layers 14, 15, and 16, respectively. By appropriately selecting conditions such as temperature, growth rate, and pressure during crystal growth of p-type GaN layer 17, the lateral (horizontal) growth of p-type GaN layer 17 relative to the longitudinal (vertical) direction is promoted, and part or all of p-type GaN layer 17 above the top surface of GaN layer 13 and above the side (slope) surfaces of GaN layer 13 is flattened. Therefore, the thickness of the p-type GaN layer 17 above the top surface of the GaN layer 13 is smaller than the thickness of the p-type GaN layer 17 above the side surfaces (slope surfaces) of the GaN layer 13. Note that a p-type AlGaN layer or the like is often inserted between the light-emitting layers 14, 15, 16 and the p-type GaN layer 17, but illustration and description thereof are omitted.

[0033] The light-emitting layers 14, 15, and 16 may include, for example, In as a barrier layer. x Ga 1-x In as N layer and well layer y Ga 1-y In layers and N layers are alternately stacked. x Ga 1-x N / In y Ga 1-y The light-emitting layer 14 has an In multiple quantum well (MQW) structure (x<y, 0≦x<1, 0≦y<1). x Ga 1-x N / In y Ga 1-y The In composition ratios x and y of the N MQW structure are selected according to the emission wavelength of blue light. x Ga 1-x N / In y Ga 1-y The In composition ratios x and y of the N MQW structure are selected according to the emission wavelength of green light. x Ga 1-x N / In y Ga 1-y The In composition ratios x and y of the N MQW structure are selected according to the emission wavelength of red light. x Ga 1-x N layer and In y Ga 1-y It also varies depending on the growth conditions of the N layer. The In composition of the light-emitting layers 14, 15, and 16, which are formed in an octagonal pyramidal truncated shape following the octagonal pyramidal truncated GaN layer 13, is larger in the portion on the top surface of the GaN layer 13 than in the portion on the side surface of the GaN layer 13. This is because, compared to InGaN grown on the C-plane, which is a polar plane, InGaN grown on a nonpolar or semipolar plane has a tendency to have a lower In composition at the same temperature. Therefore, the band gap of the portions of the light-emitting layers 14, 15, and 16 on the side surface of the GaN layer 13 is larger than the band gap of the portion on the top surface of the GaN layer 13.

[0034] The n-type GaN layer 11, the GaN layer 13, the light-emitting layer 14, and the p-type GaN layer 17 in the leftmost opening 12a form a blue-emitting AlGaInN-based LED structure B, the n-type GaN layer 11, the GaN layer 13, the light-emitting layer 15, and the p-type GaN layer 17 in the central opening 12a form a green-emitting AlGaInN-based LED structure G, and the n-type GaN layer 11, the GaN layer 13, the light-emitting layer 16, and the p-type GaN layer 17 in the rightmost opening 12a form a red-emitting AlGaInN-based LED structure R.

[0035] An insulating film 18 is provided to cover each p-type GaN layer 17. The insulating film 18 has a plurality of (four in this example) circular openings 18a formed in a row at equal intervals along the longitudinal centerline of each p-type GaN layer 17. The diameter of the openings 18a is selected as needed, but is typically about the width (100 to 2000 nm) of the openings 18a. A plurality of (four in this example) p-side electrodes 19 are provided in a row, separated from one another, on the p-type GaN layer 17 along the longitudinal centerline through each opening 18a at positions corresponding to the light-emitting layers 14, 15, and 16. In this case, the number N of blue-emitting AlGaInN-based LED structures B is b , the number N of green-emitting AlGaInN-based LED structures G g and the number N of red-emitting AlGaInN-based LED structures R r is N b = N g = N r = 1, so the number N of p-side electrodes 19 p is N p ×N b ≧2, N p ×N g ≧2, N p ×N r Since ≧2, N p 1A, 1B and 1C are selected in a range that satisfies N p is selected as 4. The p-side electrode 19 is made of a multilayer film such as an ITO / Ag / Ti / Au film. Here, Ag is used to increase the light reflectivity of the p-side electrode 19 when extracting light from the n-type GaN layer 11 side of the micro LED chip 10. Here, the thicknesses of the ITO film, Ag film, Ti film, and Au film constituting the p-side electrode 19 are, for example, 50 nm, 100 nm, 20 nm, and 50 nm, respectively. A pair of elongated rectangular contact holes 12b are provided in a portion of the insulating film 12 away from the GaN layer 13, in a direction perpendicular to the extension direction of the GaN layer 13, parallel to the sides of the chip so as to sandwich the GaN layer 13. Two elongated rectangular n-side electrodes 20 are provided in contact with the n-type GaN layer 11 through these contact holes 12b. The n-side electrode 20 is made of a multilayer film such as a Ti / Al / Ti / Ni / Au film.

[0036] The n-type GaN layer 11, the light-emitting layers 14, 15, and 16, and the p-type GaN layer 17 typically have a C-plane orientation. The resistivities of the n-type GaN layer 11 and the GaN layer 13 are, for example, about 0.01 Ωcm, but are not limited to this. The resistivities of the light-emitting layers 14, 15, and 16 are, for example, about 0.1 to 0.3 Ωcm, but are not limited to this. The resistivity of the p-type GaN layer 17 is, for example, about 1 to 3 Ωcm, but are not limited to this. The thickness of the n-type GaN layer 11 is, for example, 1 to 5 μm, the thickness of the GaN layer 13 is, for example, 100 to 1500 nm, the thickness of the light-emitting layers 14, 15, and 16 is, for example, 30 to 100 nm, and the thickness of the portion of the p-type GaN layer 17 above the top surface of the GaN layer 13 is, for example, 100 to 200 nm, but are not limited to these. The total thickness of the n-type GaN layer 11, the GaN layer 13, the light-emitting layers 14, 15, and 16, and the p-type GaN layer 17 is, for example, 1.2 to 6.8 μm, but is not limited to this.

[0037] [Operation of Micro LED Chip] In this micro LED chip 10, blue light can be emitted by applying a forward bias between the p-electrode 19 and the n-electrode 20 in the blue-emitting AlGaInN-based LED structure B, green light can be emitted by applying a forward bias between the p-electrode 19 and the n-electrode 20 in the green-emitting AlGaInN-based LED structure G, and red light can be emitted by applying a forward bias between the p-electrode 19 and the n-electrode 20 in the red-emitting AlGaInN-based LED structure R. In this case, the n-type GaN layer 11 and the p-type GaN layer 17 are separated by the insulating film 12 except for the opening 12 a, so that leakage current during operation can be effectively suppressed. Furthermore, the thickness of the p-type GaN layer 17, which has a high resistivity, is smaller above the top surface of the GaN layer 13 than above the side surfaces (slope) of the GaN layer 13. Therefore, the current flowing between the p-side electrode 19 and the n-side electrode 20 mainly passes through the p-type GaN layer 17 above the top surface of the GaN layer 13, which has a lower resistance, and only a small amount of current passes through the p-type GaN layer 17 above the side surfaces of the GaN layer 13. Furthermore, the In composition ratios x and y of the MQW structure of light-emitting layers 14, 15, and 16 are smaller in the portions of light-emitting layers 14, 15, and 16 above the side surfaces of GaN layer 13 than in the portions above the top surface of GaN layer 13. Therefore, the band gap of light-emitting layers 14, 15, and 16 is smaller in the portions above the top surfaces of GaN layer 13 than in the portions above the side surfaces of GaN layer 13, but carriers (electrons and holes) tend to gather in light-emitting layers 14, 15, and 16 above the top surfaces of GaN layer 13, which have a smaller band gap. Thus, current flows between p-side electrode 19 and n-side electrode 20, causing light emission in light-emitting layers 14, 15, and 16. Light is emitted mainly from light-emitting layers 14, 15, and 16 above the top surfaces of GaN layer 13, and this light is extracted to the outside through n-type GaN layer 11.

[0038] [Method for Manufacturing Micro LED Chip] An example of a method for manufacturing a micro LED chip will be described.

[0039] First, as shown in FIGS. 2A and 2B , an n-type GaN layer 11 is grown on a C-plane oriented sapphire substrate 30 by, for example, metalorganic chemical vapor deposition (MOCVD). Here, FIG. 2A is a plan view, and FIG. 2B is a cross-sectional view. The growth of the n-type GaN layer 11 is performed, for example, as follows, but is not limited to this. First, a GaN layer is epitaxially grown on the sapphire substrate 30 by MOCVD, and then a seed (not shown) is formed by patterning the GaN layer by a conventionally known method. Next, the n-type GaN layer 11 is grown from the seed by lateral overgrowth using ELO, a conventionally known MOCVD method. During this process, growth is stopped when an island-shaped n-type GaN layer 11 collides with an adjacent island-shaped n-type GaN layer 11. In some cases, the growth of adjacent island-shaped n-type GaN layers 11 may continue even after the collision between them, or the growth may be stopped before the n-type GaN layers 11 collide with each other by appropriately designing the seed position and the lateral growth distance. Next, SiO is deposited on the n-type GaN layer 11 by chemical vapor deposition (CVD), sputtering, vacuum deposition, or the like. 2 After forming an insulating film 12 such as a thin film, the insulating film 12 is patterned by a conventionally known method to form a long and narrow rectangular opening 12a in a portion where the blue light-emitting AlGaInN-based LED structure B is to be formed. The opening 12a is formed in a laterally grown region of the n-type GaN layer 11 that has a low threading dislocation density.

[0040] 3, the GaN layer 13 is grown in the shape of an octagonal pyramidal island in each opening 12a by ELO. In this case, GaN is first selectively grown on the surface of the n-type GaN layer 11 exposed in the opening 12a of the insulating film 12, and then grows laterally on the insulating film 12, thereby growing the GaN layer 13 on the insulating film 12. Next, In is grown on the island-shaped GaN layer 13 thus grown. x Ga 1-x N / In y Ga 1-y An N MQW structure light-emitting layer 14 is epitaxially grown. This blue-emitting light-emitting layer 14 can be grown by a conventionally known growth method. Typically, the In composition of the InGaN layer grown on the top surface (C-plane) of the GaN layer 13 is smaller than the In composition of the InGaN layer grown on the side surfaces (semi-polar planes). Subsequently, a p-type GaN layer 17 is epitaxially grown to cover the light-emitting layer 14. By adjusting growth conditions such as pressure and temperature, it is possible to form the p-type GaN layer 17 above the top surface of the GaN layer 13 so that its thickness is smaller than the p-type GaN layer 17 above the side surfaces of the GaN layer 13. The growth of the GaN layer 13, light-emitting layer 14, and p-type GaN layer 17 is performed consecutively in an MOCVD furnace.

[0041] Next, as shown in FIG. 4, SiO is deposited by, for example, vacuum deposition to cover the p-type GaN layer 17. 2 An insulating film 18 such as a film is formed.

[0042] Next, as shown in FIG. 5, the insulating film 12 is patterned by a conventionally known method to form a long and narrow rectangular opening 12a in the portion where the green light emitting AlGaInN based LED structure G is to be formed.

[0043] Next, as shown in FIG. 6, on the n-type GaN layer 11 exposed in the newly formed opening 12a, a GaN layer 13 and an In layer are formed in the same manner as in the portion where the blue light emitting AlGaInN based LED structure B is to be formed. x Ga 1-x N / In y Ga 1-y The light emitting layer 15 having an N MQW structure and the p-type GaN layer 17 are grown in this order. The green light emitting layer 15 can be grown by a conventionally known growth method.

[0044] Next, as shown in FIG. 7, SiO is deposited by, for example, vacuum deposition to cover the p-type GaN layer 17. 2 After forming the insulating film 18 such as a film, the insulating film 12 is patterned by a conventionally known method to form a long and narrow rectangular opening 12a in the portion where the red light emitting AlGaInN based LED structure R is to be formed.

[0045] Next, as shown in FIG. 8, on the n-type GaN layer 11 exposed in the newly formed opening 12a, a GaN layer 13 and an In layer are formed in the same manner as in the portion where the blue light emitting AlGaInN based LED structure B is to be formed. x Ga 1-x N / In y Ga 1-y The light-emitting layer 16 having an N MQW structure and the p-type GaN layer 17 are grown in this order. The red-emitting light-emitting layer 16 can be grown by a conventionally known growth method (see, for example, Non-Patent Document 2). Subsequently, SiO is grown by, for example, vacuum deposition so as to cover the p-type GaN layer 17. 2 An insulating film 18 such as a film is formed.

[0046] Next, as shown in FIG. 9 , circular contact holes 18 a are formed in the insulating film 18 above each of the blue-emitting AlGaInN-based LED structure B, the green-emitting AlGaInN-based LED structure G, and the red-emitting AlGaInN-based LED structure R, and the p-type GaN layer 17 is exposed inside the contact holes 18 a.

[0047] Next, as shown in FIGS. 10A and 10B , a p-side electrode 19 is formed to contact the p-type GaN layer 17 through the contact hole 18 a. Here, FIG. 10A is a plan view, and FIG. 10B is a cross-sectional view taken along line B-B in FIG. 10A . The p-side electrode 19 can be formed, for example, as follows: An ITO film, an Ag film, a Ti film, and an Au film are sequentially formed over the entire substrate surface by, for example, sputtering or vacuum deposition, and then these ITO, Ag, Ti, and Au films are patterned by etching or the like. Next, the insulating film 12 is patterned by a conventionally known method to form two parallel, elongated rectangular contact holes 12 b (see FIG. 1C ) for the n-side electrode so as to sandwich the entire blue-emitting AlGaInN-based LED structure B, the green-emitting AlGaInN-based LED structure G, and the red-emitting AlGaInN-based LED structure R from both sides. The n-type GaN layer 11 is exposed inside these contact holes 12 b. Next, an n-side electrode 20 having a long and narrow rectangular shape is formed so as to contact the n-type GaN layer 11 through each of the contact holes 12b. One or more n-side electrodes 20 are sufficient, and two are formed in the example shown in Figures 10A and 10B.

[0048] 11A and 11B, an etching mask (not shown) for chip separation is formed, and then the sapphire substrate 30 is etched in the vertical direction by RIE using this etching mask until it reaches the sapphire substrate 30. In this way, separation grooves 31 are formed.

[0049] Next, as shown in Figure 12, a secondary substrate 40 is prepared on which solder layers 41 are formed in the same arrangement pattern as the arrangement pattern of the p-side electrodes 19 and n-side electrodes 20 of a chip area selected from all chip areas (including the case where all chip areas are selected), and the solder layers 41 of this secondary substrate 40 are superimposed so that they correspond to the p-side electrodes 19 and n-side electrodes 20 of the sapphire substrate 30 formed up to the separation grooves 31 as shown in Figures 11A and 11B.

[0050] Next, as shown in FIG. 13 , a laser beam is irradiated from the backside of the sapphire substrate 30 onto all or selected chip regions, causing delamination at the interface between the n-type GaN layer 11 in the chip region and the sapphire substrate 30, separating the sapphire substrate 30 (laser lift-off). At the same time, the solder layer 41 in the portion corresponding to the chip region is melted by conduction of heat generated in the blue-emitting AlGaInN-based LED structure B, the green-emitting AlGaInN-based LED structure G, and the red-emitting AlGaInN-based LED structure R during laser beam irradiation. After the solder layer 41 cools and solidifies, the sapphire substrate 30 is separated from the secondary substrate 40. When irradiating only selected chip regions from the backside of the sapphire substrate 30 with a laser beam, the laser beam is irradiated using a predetermined mask (not shown) with openings only in the portions corresponding to the selected chip regions. Because the sapphire substrate 30 is transparent to visible light, it may be left as is without being peeled off.

[0051] In this manner, the micro LED chips 10 are manufactured in a state where they are transferred to predetermined positions on the secondary substrate 40, as shown in Fig. 14. Fig. 14 shows, as an example, a case where every third micro LED chip 10 is transferred.

[0052] According to the above-mentioned manufacturing method, it is possible to independently optimize the crystal growth parameters (growth pressure, growth rate, temperature, flow rate, raw material supply ratio, etc.) of the AlGaInN crystal for each emission wavelength, and it is possible to grow under crystal growth conditions that realize maximum performance (luminous efficiency) for each emission wavelength. Because there are multiple crystal growth parameters, a manufacturing method that can independently optimize each for each wavelength is extremely advantageous for improving luminous efficiency.

[0053] As described above, according to the first embodiment, the light-emitting layers 14, 15, and 16 on the upper surface of the GaN layer 13, where light emission primarily occurs, are completely separated from the dry-etched portions used in forming the micro LED chip 10 and are therefore not affected by etching damage. Furthermore, due to the shape of the p-type GaN layer 17, the current flowing between the p-side electrode 19 and the n-side electrode 20 is concentrated in the light-emitting layers 14, 15, and 16 on the upper surface of the GaN layer 13, thereby maintaining a high electron-hole recombination probability in the light-emitting layers 14, 15, and 16 on the upper surface of the GaN layer 13, thereby achieving high light-emitting efficiency. Furthermore, the micro LED chip 10 can be easily and inexpensively manufactured using conventionally known techniques. Furthermore, the micro LED chip 10 has a blue-emitting AlGaInN-based LED structure B, a green-emitting AlGaInN-based LED structure G, and a red-emitting AlGaInN-based LED structure R on the n-type GaN layer 11, enabling blue, green, and red light emission from a single chip. A high-performance micro LED display can be realized using this high-performance micro LED chip 10, and high-performance XR glasses can be realized using this micro LED display. Furthermore, each of the blue-emitting AlGaInN-based LED structure B, the green-emitting AlGaInN-based LED structure G, and the red-emitting AlGaInN-based LED structure R of this micro LED chip 10 has four p-side electrodes 19, which can be controlled independently. Therefore, even if millions to tens of millions of micro LED chips are transferred and assembled at once without inspecting each individual chip (full inspection), pixels can be repaired by isolating defective parts due to broken wiring, thereby ensuring a high manufacturing yield of micro LED displays.

[0054] Second Embodiment [Micro LED Chip Transfer Substrate] Fig. 15 is a cross-sectional view showing a micro LED chip transfer substrate 100. As shown in Fig. 15, the micro LED chip transfer substrate 100 has a large number of chip regions surrounded by separation grooves 31 arranged in a two-dimensional array, as shown in Figs. 11A and 11B.

[0055] [Method for Manufacturing Micro LED Chip Transfer Substrate] The micro LED chip transfer substrate 100 can be manufactured by carrying out the method for manufacturing the micro LED chip according to the first embodiment up to the step of forming the separation grooves 31.

[0056] [Method of Using the Micro LED Chip Transfer Substrate] In the same manner as in the manufacturing method of the first embodiment, the micro LED chip transfer substrate 100 is bonded to the secondary substrate 40 as shown in FIG. 16A, and then a laser beam is irradiated to transfer the micro LED chip 10 to a predetermined position on the secondary substrate 40 as shown in FIG. 16B.

[0057] According to the second embodiment, by using the micro LED chip transfer substrate 100, a large number of micro LED chips 10 according to the first embodiment can be transferred onto the secondary substrate 40 at once.

[0058] 17A , 17B, and 17C show a micro LED chip 10 according to a third embodiment, with FIG. 17A being a perspective view, FIG. 17B being a cross-sectional view taken along line B-B in FIG. 17A , and FIG. 17C being a cross-sectional view taken along line C-C in FIG. 17A . As shown in FIGS. 17A , 17B, and 17C , in this micro LED chip 10, an insulating film 12 is provided on an n-type GaN layer 11. In this case, the insulating film 12 has a plurality of (four, for example) circular openings 12a formed in a row at equal intervals at positions corresponding to the elongated rectangular openings 12a in the first embodiment. Then, island-shaped hexagonal truncated pyramidal GaN layers 13 are formed on the n-type GaN layer 11 in the portions of the openings 12a. 2 The GaN layer 13 is provided so as to extend on the insulating film 12. In the portion where the blue-emitting AlGaInN-based LED structure B is to be formed, a light-emitting layer 14 is provided in an island shape along the upper surface and side surfaces (slope) of the GaN layer 13, a p-type GaN layer 17 is provided so as to cover the light-emitting layer 14, an insulating film 18 is provided so as to cover the p-type GaN layer 17, and a p-side electrode 19 is provided on the p-type GaN layer 17 through a contact hole 18 a provided in the insulating film 18. Similarly, in the portion where the green-emitting AlGaInN-based LED structure G is to be formed, a light-emitting layer 15 is provided in an island shape along the upper surface and side surfaces (slope) of the GaN layer 13, a p-type GaN layer 17 is provided so as to cover the light-emitting layer 15, an insulating film 18 is provided so as to cover the p-type GaN layer 17, and a p-side electrode 19 is provided on the p-type GaN layer 17 through a contact hole 18 a provided in the insulating film 18. In the portion where the red-emitting AlGaInN-based LED structure R is formed, a light-emitting layer 16 is provided in an island shape along the upper surface and side surfaces (slope) of the GaN layer 13, a p-type GaN layer 17 is provided to cover the light-emitting layer 16, an insulating film 18 is provided to cover the p-type GaN layer 17, and a p-side electrode 19 is provided on the p-type GaN layer 17 through a contact hole 18a provided in the insulating film 18. In this case, the N b = 4, green light emitting AlGaInN based LED structure G g = 4, red-emitting AlGaInN-based LED structure R r = 4, and the number of p-side electrodes 19 is N in all of the blue-emitting AlGaInN-based LED structure B, the green-emitting AlGaInN-based LED structure G, and the red-emitting AlGaInN-based LED structure R. p = 1, so N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2 is satisfied. In other respects, the micro LED chip 10 is similar to the micro LED chip 10 according to the first embodiment.

[0059] [Method of Manufacturing Micro LED Chips] First, as shown in Figures 18A and 18B, an n-type GaN layer 11 is grown on a sapphire substrate 30 in the same manner as in the manufacturing method of the first embodiment. An insulating film 12 is then formed thereon, and the insulating film 12 is then patterned to form circular openings 12a. Here, Figure 18A is a plan view, and Figure 18B is a cross-sectional view. Next, as shown in Figures 19A and 19B, the same process as in the manufacturing method of the first embodiment is carried out. Island-shaped hexagonal truncated pyramidal GaN layers 13 are grown on the n-type GaN layer 11 in the openings 12a of the insulating film 12, forming a blue-emitting AlGaInN-based LED structure B, a green-emitting AlGaInN-based LED structure G, and a red-emitting AlGaInN-based LED structure R. Finally, the resulting structures are transferred to a secondary substrate 40 to produce the desired micro LED chips 10. Here, Figure 19A is a plan view, and Figure 19B is a cross-sectional view.

[0060] According to the third embodiment, it is possible to obtain the same advantages as the first embodiment.

[0061] <Fourth embodiment> [Micro LED chip transfer substrate] Fig. 20 is a cross-sectional view showing a micro LED chip transfer substrate 100. As shown in Fig. 20, the micro LED chip transfer substrate 100 has a large number of chip regions surrounded by separation grooves 31 arranged in a two-dimensional array, as shown in Figs. 19A and 19B.

[0062] [Method for Manufacturing Micro LED Chip Transfer Substrate] The micro LED chip transfer substrate 100 can be manufactured by carrying out the method for manufacturing a micro LED chip according to the third embodiment up to the step of forming the separation grooves 31.

[0063] [Method of using the micro LED chip transfer substrate] In the same manner as the manufacturing method of the third embodiment, the micro LED chip transfer substrate 100 is bonded to the secondary substrate 40, and then the micro LED chip 10 is transferred to a predetermined position on the secondary substrate 40 by irradiating it with a laser beam.

[0064] According to the fourth embodiment, by using the micro LED chip transfer substrate 100, a large number of micro LED chips 10 according to the third embodiment can be transferred onto the secondary substrate 40 at once.

[0065] Fifth Embodiment [XR Glasses] FIG. 21 shows XR glasses according to a fifth embodiment. As shown in FIG. 21 , the XR glasses include a display unit 300, on the inner surface of the windshields 201 and 202, that face the pupils of the user's eyes when the user wears the XR glasses. The windshields 201 and 202 are typically made of glass or plastic, but may also have prescriptions for lenses for myopia or hyperopia, depending on the case. Because the distance between the display unit 300 and the pupils of the user's eyes when the user wears the XR glasses is as short as a dozen or so millimeters, at least one lens (not shown) for adjusting the focal length is attached between the pupils and the light-emitting surface of the display unit 300, adjusting the focus to focus on each pixel at a distance that is comfortable for the eyes. The lens may be a convex lens or Fresnel lens that covers the entire display unit 300, or a microlens may be provided for each pixel. Furthermore, the optical system may be configured using a single lens or a combination of multiple lenses. The display unit 300 is configured to be smaller than the windshield units 201 and 202. The display unit 300 is connected to a drive circuit board 550 (see FIG. 22) made of a Si-CMOS IC mounted on a printed circuit board 500 via a flexible printed circuit 400. The flexible printed circuit 400 and the printed circuit board 500 are mounted on a frame 203. The printed circuit board 500 is mounted in a state where it is wrapped around the ear hook portion of the frame 203. FIG. 22 shows an overall view of the display unit 300, the flexible printed circuit 400, and the printed circuit board 500.

[0066] Drive circuits 560, each composed of a CMOS circuit, are provided in a two-dimensional array on the drive circuit substrate 550. In Fig. 22, one pixel drive circuit is composed of three adjacent drive circuits 560, as indicated by dashed lines on the drive circuit substrate 550. The size of the drive circuit 560 is selected as needed and is not particularly limited, but is, for example, about 24 µm square.

[0067] Details of the display unit 300 are shown in FIG. 23A . FIGS. 23B and 23C are cross-sectional views taken along line B-B and line C-C in FIG. 23A , respectively. As shown in FIGS. 22 , 23A , 23B, and 23C , the display unit 300 has a large number of micro LED chips 10 arranged in a two-dimensional array, each having a blue-emitting AlGaInN-based LED structure B, a green-emitting AlGaInN-based LED structure G, and a red-emitting AlGaInN-based LED structure R (see FIGS. 1A , 1B, and 1C for details of the micro LED chips 10). Four branch wirings 712 branch out from a p-side wiring 711 connected to the drive circuit 560 of the drive circuit board 550 via a flexible printed circuit 400, per micro LED chip 10, and are connected to the four p-side electrodes 19 of the blue-emitting AlGaInN-based LED structure B, the green-emitting AlGaInN-based LED structure G, and the red-emitting AlGaInN-based LED structure R, respectively. Although not shown, a thin film fuse is provided midway along the branch wiring 712. When excessive current flows due to a leak defect in the p-side electrode 19, the thin film fuse melts, disconnecting the branch wiring 712. Similarly, branch wiring 722 branching from an n-side wiring 721 connected to the drive circuit 560 of the drive circuit board 550 via a flexible printed circuit 400 connects to the n-side electrodes 20 at both ends of the micro LED chip 10. The size of one pixel shown in FIG. 23A is, for example, 4.2 μm × 4.2 μm. This corresponds to a pixel density of 6000 ppi. If the chip size of the micro LED chip 10 is, for example, 1.6 μm × 1.6 μm, the aperture ratio is approximately 85%. The power supply (battery) and control circuit for the display unit 300 and the drive circuit board 550 are provided in the ear hooks and windshields 201 and 202 of the frame 203 of the XR glasses. The micro LED chip 10 can be easily mounted on the display unit 300 using the micro LED chip transfer substrate 100 according to the second embodiment.

[0068] The fifth embodiment offers the following advantages. The display unit 300 for XR glasses includes a blue-emitting AlGaInN-based LED structure B, a green-emitting AlGaInN-based LED structure G, and a red-emitting AlGaInN-based LED structure R. The micro LED chips 10 capable of emitting blue, green, and red light are arranged in a two-dimensional array. This allows the area of ​​the micro LED chips 10 per pixel of the display unit 300 to be significantly reduced, significantly increasing the aperture ratio of each pixel. Furthermore, pixel densities of several tens of thousands of pixels per inch (PPI) can be easily achieved. Furthermore, the micro LED chips 10 can be quickly and easily mounted using the micro LED chip transfer substrate 100. Furthermore, in these XR glasses, the printed circuit board 500 on which the drive circuit board 550 is mounted and the display unit 300 are connected to each other via the flexible printed circuit 400. Therefore, it is sufficient to fabricate the array of drive circuits 560 on the drive circuit board 550 at a lower density. As a result, high-performance XR glasses can be easily realized.

[0069] Sixth Embodiment [XR Glasses] Fig. 24 shows XR glasses according to a sixth embodiment. As shown in Fig. 24, these XR glasses have a light engine 600 wrapped around the ear loops of the frame 203. Fig. 25 shows an exploded view of the light engine 600. As shown in Fig. 25, the light engine 600 includes an LED array section 610, in which a large number of micro LED chips 10 are mounted in a two-dimensional array, and a drive circuit board 550, which is made of a Si-CMOS IC mounted on a printed circuit board 500, connected by a flexible printed circuit 400. Optical waveguides (not shown) are provided from the light-emitting section of the light engine 600 through the ear loops of the frame 203 to the inner surfaces of the portions of the windshields 201 and 202 that face the pupils of the user's eyes when the user wears the XR glasses. Light emitted from the micro LED chips 10 in the LED array unit 610 of the light engine 600 enters one end of a light waveguide via a lens (not shown), undergoes repeated total reflection within the light waveguide, and is emitted to the outside from the other end of the light waveguide, with the other end of this light waveguide constituting the display unit 300. In the LED array unit 610, the micro LED chips 10 are connected by simple matrix wiring consisting of p-side wiring 711 and n-side wiring 721 arranged vertically and horizontally. Details of the LED array unit 610 are shown in FIG. 26A. FIGS. 26B and 26C are cross-sectional views taken along lines B-B and C-C, respectively, of FIG. 26A. The micro LED chips 10 in the LED array unit 610 can be easily mounted using a micro LED chip transfer substrate 100.

[0070] According to the sixth embodiment, since an optical waveguide is used in the display unit 300, there is no need to ensure an aperture ratio, and the advantage is that the light engine 600 can be made compact by arranging the micro LED chips 10 at high density in the LED array unit 610.

[0071] Seventh Embodiment [XR Glasses] The XR glasses according to the seventh embodiment differ from the XR glasses according to the sixth embodiment in the configuration of the light engine 600. Figure 27 shows the light engine 600 used in the XR glasses according to the seventh embodiment.

[0072] In the first to sixth embodiments, the sapphire substrate 30 used in manufacturing the micro LED chip 10 is finally peeled off. However, because the sapphire substrate 30 is transparent to visible light, it can also be used without peeling. Therefore, in the seventh embodiment of XR Glass, after performing the steps up to the step of forming the separation grooves 31 on the sapphire substrate 30, the sapphire substrate 30 is polished from the backside to be thinned. For example, a 400 μm-thick sapphire substrate 30 is used, and this sapphire substrate 30 is thinned to a thickness of 100 μm or less, e.g., 80 μm. Next, the sapphire substrate 30 is cut to a size that includes the required number of pixels. As shown in FIG. 27, the cut sapphire substrate 30 of a predetermined size is bonded to a drive circuit board 550, which is composed of a Si-CMOS IC mounted on a printed circuit board 500, as a secondary substrate. The printed circuit board 500 and the drive circuit board 550 are bonded together with wires W. In this case, the LED array unit 610 is bonded to the drive circuit board 550. The printed circuit board 500 is connected to a power supply and a control circuit via wiring 502 connected to terminals 501. As in the sixth embodiment, light emitted from the micro LED chips 10 of the LED array unit 610 of the light engine 600 enters one end of the optical waveguide via a lens (not shown), undergoes repeated total reflection within the optical waveguide, and is emitted to the outside from the other end of the optical waveguide. The other end of this optical waveguide constitutes the display unit 300.

[0073] According to the seventh embodiment, it is possible to obtain the same advantages as those of the fifth and sixth embodiments.

[0074] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical concept of the present invention are possible.

[0075] For example, the numerical values, configurations, shapes, materials, methods, etc. given in the above-described embodiments are merely examples, and different numerical values, configurations, shapes, materials, methods, etc. may be used as needed.

[0076] REFERENCE SIGNS LIST 10 Vertical micro LED chip 11 n-type GaN layer 12 Insulating film 12a Opening 13 GaN layer 14, 15, 16 Light-emitting layer 17 p-type GaN layer 18 Insulating film 18a Contact hole 19 P-side electrode 20 N-side electrode 30 C-plane sapphire substrate 40 Secondary substrate 41 Solder layer B Blue-emitting AlGaInN-based LED structure G Green-emitting AlGaInN-based LED structure R Red-emitting AlGaInN-based LED structure

Claims

1. At least one blue-emitting AlGaInN-based light-emitting diode structure, at least one green-emitting AlGaInN-based light-emitting diode structure, and at least one red-emitting AlGaInN-based light-emitting diode structure are provided on an n-type GaN layer, and the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure each have an insulating film having at least one opening provided on the n-type GaN layer, a polygonal truncated pyramid-shaped GaN layer provided on the n-type GaN layer in a portion of the insulating film that is at the opening, a light-emitting layer provided along an upper surface and a side surface of the polygonal truncated pyramid-shaped GaN layer, a p-type GaN layer provided so as to cover the light-emitting layer, one or a plurality of p-side electrodes separated from each other provided on the upper surface of the p-type GaN layer, and at least one n-side electrode provided on a portion of the n-type GaN layer where the polygonal truncated pyramid-shaped GaN layer is not provided, The number of the blue light emitting AlGaInN based light emitting diode structures, the green light emitting AlGaInN based light emitting diode structures, and the red light emitting AlGaInN based light emitting diode structures included in the entire micro light emitting diode chip is N b , N g and N r The number of the p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p Then, N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2.

2. The micro light-emitting diode chip according to claim 1, wherein the thickness of the p-type GaN layer above the top surface of the truncated pyramidal GaN layer is smaller than the thickness of the p-type GaN layer above the side surface of the truncated pyramidal GaN layer, and light is emitted mainly from the light-emitting layer on the top surface of the truncated pyramidal GaN layer.

3. A chip region including at least one blue-emitting AlGaInN-based light-emitting diode structure, at least one green-emitting AlGaInN-based light-emitting diode structure, and at least one red-emitting AlGaInN-based light-emitting diode structure is arranged in a two-dimensional array on an n-type GaN layer provided on a substrate, and the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure each include an insulating film having at least one opening provided on the n-type GaN layer, a polygonal truncated pyramid-shaped GaN layer provided on the n-type GaN layer in the opening portion of the insulating film, a light-emitting layer provided along an upper surface and a side surface of the polygonal truncated pyramid-shaped GaN layer, a p-type GaN layer provided so as to cover the light-emitting layer, and one or a plurality of p-side electrodes separated from each other provided on the upper surface of the p-type GaN layer, and at least one n-side electrode provided on the n-type GaN layer in a portion where the polygonal pyramid-shaped GaN layer is not provided, and the number of the blue-emitting AlGaInN-based light-emitting diode structures, the green-emitting AlGaInN-based light-emitting diode structures, and the red-emitting AlGaInN-based light-emitting diode structures included in the entire chip region is set to N. b , N g and N r The number of the p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p Then, N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2, and the chip region is defined by a separation groove that separates the n-type GaN layer.

4. A display unit having a plurality of micro light-emitting diode chips mounted in a two-dimensional array; a drive circuit unit having a plurality of drive circuits arranged in a two-dimensional array, each of which can be controlled and driven independently of one another; and a wiring circuit for wiring the display unit and the drive circuit unit, wherein the micro light-emitting diode chip has at least one blue-emitting AlGaInN-based light-emitting diode structure, at least one green-emitting AlGaInN-based light-emitting diode structure, and at least one red-emitting AlGaInN-based light-emitting diode structure on an n-type GaN layer, and the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure each have an insulating film having at least one opening provided on the n-type GaN layer; a polygonal truncated pyramid-shaped GaN layer provided on the n-type GaN layer in a portion of the opening of the insulating film; a light-emitting layer provided along the upper and side surfaces of the polygonal truncated pyramid-shaped GaN layer; and a p-type GaN layer provided so as to cover the light-emitting layer. The micro light-emitting diode chip has one or a plurality of p-side electrodes provided on an upper surface of the p-type GaN layer, and at least one n-side electrode provided on the n-type GaN layer in a portion where the polygonal truncated GaN layer is not provided, and the number of the blue light-emitting AlGaInN-based light-emitting diode structures, the green light-emitting AlGaInN-based light-emitting diode structures, and the red light-emitting AlGaInN-based light-emitting diode structures included in the entire micro light-emitting diode chip is N. b , N g and N r The number of the p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p Then, N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2. The micro light-emitting diode display, wherein the micro light-emitting diode chip is 5. The micro light-emitting diode display according to claim 4, wherein a plurality of the p-side electrodes are provided separately for each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure and the red-emitting AlGaInN-based light-emitting diode structure, and at least one n-side electrode is provided, and each of the micro light-emitting diode chips is electrically connected to each of a plurality of branch wirings branched from a first main wiring connected to the drive circuit of the drive circuit section via wiring of the wiring circuit, and the n-side electrode is electrically connected to each of a plurality of branch wirings branched from a first main wiring connected to the drive circuit of the drive circuit section via wiring of the wiring circuit.

6. A display comprising: a display unit on which a plurality of micro light-emitting diode chips are mounted in a two-dimensional array; a drive circuit board on which a plurality of drive circuits capable of being controlled and driven independently of one another are provided in a two-dimensional array; and a flexible printed circuit for wiring the display unit and the drive circuit board; and the micro light-emitting diode chip comprises at least one blue-emitting AlGaInN-based light-emitting diode structure, at least one green-emitting AlGaInN-based light-emitting diode structure, and at least one red-emitting AlGaInN-based light-emitting diode structure on an n-type GaN layer, and the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure each comprise an insulating film having at least one opening provided on the n-type GaN layer; a polygonal truncated pyramidal GaN layer provided on the n-type GaN layer in a portion of the opening of the insulating film; and a light-emitting layer provided along an upper surface and a side surface of the polygonal truncated pyramidal GaN layer. a p-type GaN layer provided so as to cover the light emitting layer, one or a plurality of p-side electrodes provided on an upper surface of the p-type GaN layer, and at least one n-side electrode provided on the n-type GaN layer in a portion where the polygonal pyramid-shaped GaN layer is not provided, and the number of the blue light emitting AlGaInN-based light emitting diode structures, the green light emitting AlGaInN-based light emitting diode structures, and the red light emitting AlGaInN-based light emitting diode structures included in the entire micro light emitting diode chip is N b , N g and N r The number of the p-side electrodes provided on the upper surface of the p-type GaN layer of each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure, and the red-emitting AlGaInN-based light-emitting diode structure is N p Then, N p ×N b ≧2, N p ×N g ≧2, N p ×N r ≧2, the display unit is mounted on an inner surface of the windshield unit, the driving circuit board is mounted on an ear hook unit of the frame, and the flexible printed circuit is mounted on the frame.

7. The XR glasses according to claim 6, wherein a plurality of the p-side electrodes are provided separately for each of the blue-emitting AlGaInN-based light-emitting diode structure, the green-emitting AlGaInN-based light-emitting diode structure and the red-emitting AlGaInN-based light-emitting diode structure, and at least one n-side electrode is provided, and each of the micro light-emitting diode chips is electrically connected to each of a plurality of branch wirings branched from a first main wiring connected to the drive circuit of the drive circuit board via the flexible printed circuit, and the n-side electrode is electrically connected to each of the second main wiring connected to the drive circuit of the drive circuit board via the flexible printed circuit.

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