CN115347101A - Micro light-emitting diode structure - Google Patents

Abstract

The invention provides a micro light-emitting diode structure which comprises an epitaxial structure, a first insulating layer and a second insulating layer. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The first type semiconductor layer, the light emitting layer and the first portion of the second type semiconductor layer constitute a mesa. The platform has a top surface and a first side surface. The second portion of the second-type semiconductor layer is recessed with respect to the mesa to form a mesa surface. The second portion of the second-type semiconductor layer has a second side surface. The first insulating layer covers the platform surface from the top surface of the platform along the first side surface and exposes the second side surface. The second insulating layer directly covers the second side surface, wherein the thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50.

Description

micro light emitting diode structure

technical field

The invention relates to a light emitting structure, in particular to a micro light emitting diode structure.

Background technique

In the prior art, the main manufacturing process of micro light emitting diodes is carried out on the epitaxial substrate. After the manufacturing process is completed, the epitaxial substrate is removed and transferred to a temporary carrier substrate. In the above-mentioned process, an insulating layer (thickness ranging from about 0.5 micron to 1 micron) will be formed on the surface of the micro-LED structure for electrical passivation, and the insulating layer will start from the top surface of the micro-LED structure along its The surrounding surface extends to cover the surface of the epitaxial substrate. However, since the insulating layer has a certain thickness, when the laser lift-off (Laser Lift-Off, LLO) process is performed to remove the epitaxial substrate, it is easy to cause the epitaxial insulating layer to remain on the surrounding surface of the micro light emitting diode after stripping, thereby affecting the transfer Detrimental effects on subsequent processes.

Contents of the invention

The present invention is directed to a micro light emitting diode structure, which solves the problem in the prior art that the epitaxial insulating layer remains on the surrounding surface of the stripped micro light emitting diode, and can have better structural reliability, while taking into account the luminous efficiency, The overall process yield can be improved.

According to an embodiment of the present invention, the micro LED structure includes an epitaxial structure, a first insulating layer and a second insulating layer. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The light emitting layer is located between the first type semiconductor layer and the second type semiconductor layer. The first type semiconductor layer, the light emitting layer and the first part of the second type semiconductor layer constitute a platform. The platform has a top surface and a first side surface. The second portion of the second-type semiconductor layer is recessed relative to the platform to form a platform surface. The second portion of the second type semiconductor layer has a second side surface. The platform surface is located between the first side surface and the second side surface. The first insulation layer covers from the top surface of the platform to the platform surface along the first side surface, and exposes the second side surface. The second insulating layer directly covers the second side surface, wherein a thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50.

According to an embodiment of the present invention, the micro LED structure includes an epitaxial structure, a first insulating layer and a second insulating layer. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The light emitting layer is located between the first type semiconductor layer and the second type semiconductor layer. The first type semiconductor layer, the light emitting layer and the first part of the second type semiconductor layer constitute a platform. The platform has a top surface and a first side surface. The second portion of the second-type semiconductor layer is recessed relative to the platform to form a platform surface. The second portion of the second type semiconductor layer has a second side surface. The platform surface is located between the first side surface and the second side surface. The first insulating layer directly covers the platform from the top surface of the platform along the first side surface and exposes the second side surface, wherein the first insulating layer covering the first side surface forms a continuous surface with the second side surface. The second insulating layer is disposed on the first insulating layer and directly covers the continuous surface, wherein the first insulating layer is in direct contact with the second insulating layer.

Based on the above, in the design of the micro light emitting diode structure of the present invention, the first insulating layer covers from the top surface of the platform to the platform surface along the first side surface, and exposes the second part of the second part of the second type semiconductor layer. side surface, and the second insulating layer directly covers the second side surface, wherein the thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50. That is to say, the thicker first insulating layer will not extend to the substrate, which can solve the problem in the prior art that the epitaxial insulating layer remains on the surrounding surface of the stripped micro light emitting diode, while the thinner and directly covering the The second insulating layer on the second side surface can passivate the second side surface to improve luminous efficiency. Therefore, the micro light emitting diode structure of the present invention can have better structural reliability and luminous efficiency, while improving the overall process yield.

Description of drawings

1 is a schematic cross-sectional view of a micro light emitting diode structure according to an embodiment of the present invention;

2 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

3 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

4 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

5 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

6 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

7 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

8 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

9 is a schematic cross-sectional view of a micro light emitting diode structure according to another embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention.

Explanation of reference signs

100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h, 100i, 100j: micro light emitting diode structure;

101: substrate;

110: epitaxy structure;

112: the first type semiconductor layer;

114: light-emitting layer;

116: the second type semiconductor layer;

117: first part;

119: the second part;

120a, 120d: the first insulating layer;

122: first opening;

124: second opening;

130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j: second insulating layer;

131, 133, 135: film layer;

132e, 132f: the third opening;

134e, 134f: the fourth opening;

140a, 140e, 140f, 140h: first electrodes;

150a, 150d, 150e, 150f, 150h: second electrodes;

160: current distribution layer;

170: through hole;

B: bottom surface;

CS: continuous surface;

D: platform surface;

G: distance;

H: height;

M: platform;

P: plane;

S1: first side surface;

S2, S2': the second side surface;

T, T1, T2: thickness;

U: top surface.

Detailed ways

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used in the drawings and description to refer to the same or like parts.

FIG. 1 is a schematic cross-sectional view of a micro LED structure according to an embodiment of the present invention. Please refer to FIG. 1 , in the present embodiment, the micro LED structure 100 a includes an epitaxial structure 110 , a first insulating layer 120 a and a second insulating layer 130 a. The epitaxial structure 110 can be configured on the substrate 101, and the epitaxial structure 110 includes a first-type semiconductor layer 112, a light-emitting layer 114, and a second-type semiconductor layer 116, wherein the light-emitting layer 114 is located between the first-type semiconductor layer 112 and the second-type semiconductor layer 116. between the semiconductor layers 116 . The first type semiconductor layer 112 , the light emitting layer 114 and the first portion 117 of the second type semiconductor layer 116 constitute the platform M. The platform M has a top surface U and a first side surface S1 , wherein the extension direction of the top surface U may be perpendicular to the extension direction of the first side surface S1 . The second portion 119 of the second-type semiconductor layer 116 is recessed relative to the platform M to form a platform D, and the second portion 119 of the second-type semiconductor layer 116 has a second side surface S2, wherein the extending direction of the platform D can be vertical in the extending direction of the second side surface S2. The platform surface D is located between the first side surface S1 and the second side surface S2 , and the platform surface D can be parallel to the top surface U. The first insulating layer 120 a covers from the top surface U of the platform M to the platform surface D along the first side surface S1 , and exposes the second side surface S2 . The second insulating layer 130 a directly covers the second side surface S2 , wherein a thickness ratio of the first insulating layer 120 a to the second insulating layer 130 a is between 10 and 50. That is to say, the first insulating layer 120a in this embodiment does not cover the second side surface S2, and the second side surface S2 is only directly covered by the second insulating layer 130a.

Furthermore, in this embodiment, the first-type semiconductor layer 112 is, for example, a P-type semiconductor layer, and the light-emitting layer 114 is, for example, a multiple quantum well (Multi Quantum Well, MWQ) structure, and the second-type semiconductor layer 116 is, for example, It is an N-type semiconductor layer, but not limited thereto. Moreover, the micro LED structure 100a of this embodiment further includes a current distribution layer 160 disposed between the first insulating layer 120a and the first-type semiconductor layer 112, wherein the current distribution layer 160 and the first-type semiconductor layer 112 form an ohmic touch. Here, the current distribution layer 160 directly contacts the top surface U of the platform M, and the orthographic projection of the current distribution layer 160 on the top surface U may be equal to the top surface U, but not limited thereto. The material of the current distribution layer 160 can be, for example, indium tin oxide, indium oxide, tin oxide, aluminum zinc oxide, cadmium tin oxide, antimony tin oxide, zinc oxide or a combination of the above materials. Here, the thickness of the platform M plus the thickness of the current distribution layer 160 is a height H, wherein the height H is smaller than the thickness T of the second portion 119 of the second-type semiconductor layer 116 . Here, the height H is, for example, 1 micron to 2 microns, and the thickness T is, for example, 3 microns to 5 microns.

In particular, as shown in FIG. 1, the first insulating layer 120a directly covers the platform surface D, that is, the platform surface D only contacts the first insulating layer 120a, and covers the first insulating layer 120a and the second side surface of the first side surface S1. S2 forms a continuous surface CS. Viewed from a cross section, the continuous surface CS is a straight line, for example, a straight line extending along the normal direction of the substrate 101 , but not limited thereto. The second insulating layer 130a directly covers the first insulating layer 120a on the continuous surface CS, and extends along the continuous surface CS to cover the first insulating layer 120a on the platform surface D and the top surface U, wherein the thickness of the second insulating layer 130a is T2 less than the thickness T1 of the first insulating layer 120a. Here, the thickness T1 of the first insulating layer 120 a is, for example, between 0.5 micrometers and 1 micrometer, and the thickness T2 of the second insulating layer 130 a is, for example, between 20 nanometers and 50 nanometers. On the platform M and the platform surface D, the first insulating layer 120a and the second insulating layer 130a are arranged conformally, which means that the total thickness of the insulating layer is the thickness T1 of the first insulating layer 120a plus the thickness of the second insulating layer 130a T2, and on the second side surface S2, the total thickness of the insulating layer only has the thickness T2 of the second insulating layer 130a.

Furthermore, in this embodiment, the material of the first insulating layer 120a is substantially different from the material of the second insulating layer 130a. In one embodiment, the first insulating layer 120 a may be, for example, a physically deposited film layer, and the second insulating layer 130 a may be, for example, a chemically deposited film layer. The above-mentioned physical property means that the target material (target) has not undergone a chemical reaction, and the raw material is directly formed on the target by means of external force, etc.; while the chemical property means that the target material reacts in a chemical gas or on the target surface to form different compounds. and accumulate into a film. In one embodiment, the first insulating layer 120a and the second insulating layer 130a can be a single-layer film or a multi-layer film respectively. In one embodiment, the first insulating layer 120a can be, for example, a distributed Bragg reflection film layer formed by sputtering deposition (Sputtering) overlapping silicon dioxide (SiO ₂ )/titanium dioxide (TiO ₂ ), while the second insulating layer 120a The layer 130a can be, for example, aluminum oxide (Al ₂ O ₃ ) or hafnium dioxide (HfO ₂ ) coated by atomic layer deposition (Atomic Layer Deposition, ALD), or two layers of coated film by chemical vapor deposition (Chemical vapor deposition, CVD). Silicon Oxide (SiO ₂ )/Silicon Nitride (Si _X N _X ). When the second insulating layer 130a is formed by atomic layer deposition or chemical vapor deposition, it can have better step coverage on the second side surface S2, wherein the process temperature of the second insulating layer 130a can be slightly higher. at the process temperature of the first insulating layer 120a. In one embodiment, the density of the second insulating layer 130a may be higher than that of the first insulating layer 120a due to different manufacturing processes and material selection.

As shown in FIG. 1, the thicker first insulating layer 120a of this embodiment directly covers the surrounding surfaces (ie, the first side surface S1) of the first-type semiconductor layer 112, the light-emitting layer 114, and the second-type semiconductor layer 116. , to ensure the effect of electrical passivation. Furthermore, the second portion 119 of the second-type semiconductor layer 116 only directly covers the thinner second insulating layer 130a, so when the laser lift-off (LLO) process is performed, the second insulating layer (not shown) deposited on the substrate out) will be vaporized or broken, so the second insulating layer 130a will not remain at the bottom of the second part 119. Here, the setting of the first insulating layer 120a not only has the effect of electrical isolation, but also has the effect of vertically reflecting the light of the light-emitting layer 114 to the light-emitting surface; and the thinner second insulating layer 130a directly covers the The second side surface S2, therefore, the disposition of the second insulating layer 130a can passivate the second side surface S2 to reduce non-radiative recombination defects, thereby improving the luminous efficiency of the micro LED structure 100a. In short, the micro light-emitting diode structure 100a of this embodiment has both the thicker first insulating layer 120a and the thinner second insulating layer 130a directly contacting the first insulating layer 120a, which can take into account both structural reliability and Transfer yield.

In addition, please refer to FIG. 1 again, the micro LED structure 100a of this embodiment further includes a first electrode 140a and a second electrode 150a. The first electrode 140 a is electrically connected to the first-type semiconductor layer 112 . The second electrode 150 a is electrically connected to the second-type semiconductor layer 116 , wherein the first electrode 140 a and part of the second electrode 150 a are located on the same plane P. In more detail, the first insulating layer 120a and the second insulating layer 130a expose the first-type semiconductor layer 112 on the top surface U to form the first opening 122, and expose the second part of the second-type semiconductor layer 116 on the platform surface D. 119 to form a second opening 124 . The first electrode 140a is disposed in the first opening 122 and extends to the second insulating layer 130a. The second electrode 150 a is disposed on the second insulating layer 130 a and extends into the second opening 124 . Since the second insulating layer 130a is conformally disposed on the platform M and the platform surface D with the first insulating layer 120a, the second insulating layer 130a also exposes the current distribution layer 160 exposed by the first opening 122 and the second insulating layer 130a. The second portion 119 of the second-type semiconductor layer 116 exposed by the opening 124 .

Since the first insulating layer 120a covers from the top surface U of the platform M to the platform surface D along the first side surface S1, and exposes the second side surface S2 of the second portion 119 of the second-type semiconductor layer 116, that is to say , the first insulating layer 120a does not extend to the substrate 101 , thus solving the problem in the prior art that the epitaxial insulating layer remains on the surrounding surface of the stripped micro-LEDs, so as to avoid adverse effects on the subsequent transfer process. In addition, the thickness ratio of the first insulating layer 120a to the second insulating layer 130a is between 10 and 50, which means that the thicker first insulating layer 120a mainly covers the sidewall of the light-emitting layer 114; The second insulating layer 120a on the surface S2 has a significantly thinner thickness, which can passivate the second side surface S2 to improve luminous efficiency, and will not affect the subsequent transfer step of the micro LED structure 100a.

It must be noted here that the following embodiments use the component numbers and partial content of the previous embodiments, wherein the same numbers are used to denote the same or similar components, and descriptions of the same technical content are omitted. For the description of omitted parts, reference may be made to the foregoing embodiments, and the following embodiments will not be repeated.

FIG. 2 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 2 at the same time. The micro light emitting diode structure 100b of this embodiment is similar to the micro light emitting diode structure 100a of FIG. The position of the second opening 124 seals the first insulating layer 120 a and part of the current distribution layer 160 to protect the first insulating layer 120 a. Figure 2 schematically shows that the second insulating layer 130 closes the first insulating layer 120a at the position of the first opening 122, and in other not shown embodiments, the second insulating layer 130 may also be located at the second opening. The first insulating layer 120a is enclosed at a location at 124 . At this time, the first electrode 140a only contacts the current distribution layer 160 and the second insulating layer 140a, but does not contact the first insulating layer 120a.

FIG. 3 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 3 at the same time. The micro light emitting diode structure 100c of this embodiment is similar to the micro light emitting diode structure 100a of FIG. At the position of the second opening 124, a distance G is retracted relative to the first insulating layer 120a to expose part of the first insulating layer 120a, that is, to expose more contact area of the current distribution layer 160 to the first electrode 140a. Contact, may have a better ohmic contact. FIG. 3 schematically shows that the second insulating layer 130c is retracted by a distance G relative to the first insulating layer 120a at the position of the first opening 122, and in other not shown embodiments, the second insulating layer 130c can also be placed The position of the second opening 124 is retracted by a distance G relative to the first insulating layer 120a, so that the second portion 119 of the second-type semiconductor layer 116 (or another current distribution layer not shown) can be completely exposed to the second opening. 124 to achieve better ohmic contact with the second electrode 150a. Here, the orthographic projection of the second insulating layer 130 c on the epitaxial structure 110 does not overlap with the orthographic projection of the connecting surface of the first electrode 140 a and the current distribution layer 160 on the epitaxial structure 110 .

FIG. 4 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 4 at the same time. The micro LED structure 100d of this embodiment is similar to the micro LED structure 100a of FIG. 170 , passing through the current distribution layer 160 , the first-type semiconductor layer 112 , the light-emitting layer 114 and part of the second-type semiconductor layer 116 . The first insulating layer 120d further extends to cover the inner wall of the through hole 170 , and the second electrode 150d extends in the through hole 170 and is electrically connected to the second-type semiconductor layer 116 . At this time, because the second insulating layer 130d directly contacts and conforms to the first insulating layer 120d , at the second opening 124 , the second insulating layer 130d also extends into the through hole 170 .

FIG. 5 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 5 at the same time. The micro light emitting diode structure 100e of this embodiment is similar to the micro light emitting diode structure 100a of FIG. Part of the second insulating layer 130e does not directly contact the first insulating layer 120a. In detail, the first electrode 140e and the second electrode 150e are located between the first insulating layer 120a and the second insulating layer 130e, which means that the first electrode 140e and the second electrode 150e connect the first insulating layer 120a and the second insulating layer 130e are spaced apart, which can reduce/avoid the chance of short circuit between the first electrode 140e and the second electrode 150e caused by subsequent solder bump overflow. The second insulating layer 130e is formed after the formation of the first electrode 140e and the second electrode 150e, so the second insulating layer 130e can define the third opening 132e exposing the first electrode 140e and exposing the second electrode 140e through patterned etching. The fourth opening 134e of the electrode 150e facilitates subsequent solder bumps to be electrically connected to the first electrode 140e and the second electrode 150e respectively through the third opening 132e and the fourth opening 134e. Here, the micro LED structure 100e may be, for example, a red micro LED structure.

FIG. 6 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 4 and FIG. 6 at the same time. The micro light emitting diode structure 100f of this embodiment is similar to the micro light emitting diode structure 100d of FIG. A portion of the second insulating layer 130f does not directly contact the first insulating layer 120d. In detail, the first electrode 140f and the second electrode 150f are located between the first insulating layer 120d and the second insulating layer 130f, which means that the first electrode 140f and the second electrode 150f connect the first insulating layer 120d and the second insulating layer 130f are spaced apart, which can reduce/avoid the chance of short circuit between the first electrode 140f and the second electrode 150f caused by subsequent solder bump overflow. In the embodiment of FIG. 6, since the second insulating layer 130f is formed after the formation of the first electrode 140f and the second electrode 150f, the second insulating layer 130f does not extend into the through hole 170, and has exposed first The third opening 132f of the electrode 140f and the fourth opening 134f exposing the second electrode 150f, so that subsequent solder bumps can pass through the third opening 132f and the fourth opening 134f to be electrically connected to the first electrode 140f and the second electrode 150f respectively. connect. In other words, the second insulating layer 130f exposes the first electrode 140f and the second electrode 150f at the positions of the first opening 122 and the second opening 124 respectively. Here, the micro LED structure 100f may be, for example, a red micro LED structure.

其中，θ表示光线在膜层131、133、135等各层介质中入射到另一膜层的入射角度，n表示膜层的折射率，m表示任一正整数，λ表示发光层的发光波长。依据上述，膜厚d系取决于所选材料的折射率、以及针对微型发光二极管的出光角度范围的控制需求，并可借由上述薄膜干涉原理以实验方式来调整膜层131、133、135的厚度。由于薄膜干涉属于既有的光学知识，故此处不再深入说明。较佳地，每一膜层131、133、135的厚度可介于发光层114的发光波长的1/4倍至1/2倍之间，可改变微型发光二极管结构100g内部反射的路径，以减少光在内部的反射损耗。值得一提的是，于另一未示出的实施例中，亦可以是第一绝缘层为分布式布拉格反射膜层，或者是，第一绝缘层与第二绝缘层分别为分布式布拉格反射膜层，其中第一绝缘层中的膜层厚度可不同于第二绝缘层中的膜层厚度，上述仍属于本发明所欲保护的范围。FIG. 7 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 7 at the same time. The micro light emitting diode structure 100g of this embodiment is similar to the micro light emitting diode structure 100a of FIG. At least one of the layers 130g is a DBR layer. Here, the second insulating layer 130g is a distributed Bragg reflection film layer, which includes a plurality of film layers 131, 133, 135 stacked alternately and with different refractive indices, which can enlarge the critical angle of internal reflection and increase the light extraction of the light-emitting surface. . The film layers 131 , 133 , and 135 can be oxide layers or nitride layers respectively, but not limited thereto. The thickness of the film layer is designed according to different requirements. In detail, according to the thin film interference formula, the film thickness d meets: 2n _film dcos(θ)=mλ under constructive interference; and when the design requirement of the distributed Bragg reflection film layer is In the case of destructive interference, it means that the reflected light in the film layer is designed to have a phase difference (the case of phase inversion is not discussed here), then the film thickness d at this time conforms to

Among them, θ represents the angle of incidence of light incident on another film layer in each layer of medium such as film layers 131, 133, 135, n represents the refractive index of the film layer, m represents any positive integer, and λ represents the emission wavelength of the light-emitting layer . According to the above, the film thickness d depends on the refractive index of the selected material and the control requirements for the range of light emission angles of the micro-LEDs, and the thickness of the film layers 131, 133, 135 can be adjusted experimentally by using the above-mentioned thin film interference principle. thickness. Since thin-film interference belongs to the existing optical knowledge, it will not be described in depth here. Preferably, the thickness of each film layer 131, 133, 135 can be between 1/4 time and 1/2 time of the light emitting wavelength of the light emitting layer 114, which can change the internal reflection path of the micro light emitting diode structure 100g, so as to Reduce the reflection loss of light in the interior. It is worth mentioning that, in another unshown embodiment, the first insulating layer may also be a distributed Bragg reflection layer, or the first insulating layer and the second insulating layer may be distributed Bragg reflection layers respectively. The thickness of the film layer in the first insulating layer may be different from the thickness of the film layer in the second insulating layer, the above still belongs to the protection scope of the present invention.

FIG. 8 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 4 and FIG. 8 at the same time. The micro light emitting diode structure 100h of this embodiment is similar to the micro light emitting diode structure 100d of FIG. An insulating layer 120d. In detail, the second portion 119 of the second-type semiconductor layer 116 further has a bottom surface B opposite to the platform surface D, wherein the bottom surface B can be parallel to the platform surface D, and the second side surface S2 can vertically connect the platform surface D and the bottom surface B . The second insulating layer 130h extends from the second side surface S2 and directly covers the bottom surface B, and the second insulating layer 130h does not overlap and does not contact the first insulating layer 120d. At this time, the first insulating layer 120d and the second insulating layer 130h surround the peripheral surface of the epitaxial structure 110, and there is only the first insulating layer 120d on the platform M and the platform D, and the second insulating layer 116 of the second type Only the second insulating layer 130h is formed on the bottom surface B and the second side surface S2 of the portion 119 . The first electrode 140h directly contacts the first insulating layer 120d and the current distribution layer 160 , and the second electrode 150h directly contacts the first insulating layer 120d and the second-type semiconductor layer 116 exposed by the through hole 170 .

FIG. 9 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 8 and FIG. 9 at the same time. The micro light emitting diode structure 100i of this embodiment is similar to the micro light emitting diode structure 100h of FIG. The first insulating layer 120d on the first side surface S1 is flush with the first insulating layer 120d on the top surface U of the platform M, so on the first side surface S1, the first insulating layer 120d and the second insulating layer 130i direct contact.

FIG. 10 is a schematic cross-sectional view of a micro LED structure according to another embodiment of the present invention. Please refer to FIG. 1 and FIG. 10 at the same time. The micro light emitting diode structure 100j of this embodiment is similar to the micro light emitting diode structure 100a of FIG. An insulating layer 120a, and the first insulating layer 120a covering the first side surface S1 is discontinuous with the second side surface S2'. In detail, the second portion 119 of the second-type semiconductor layer 116 further has a bottom surface B relative to the platform surface D, wherein the bottom surface B can be parallel to the platform surface D, and the second side surface S2' can be inclined to connect the platform surface D and the bottom surface b. That is to say, the second side surface S2' is inclined relative to the bottom surface B, which can increase light reflection, thereby increasing the light output. The second insulating layer 130j directly covers the second side surface S2' and the bottom surface B, and the second insulating layer 130j does not overlap and does not contact the first insulating layer 120a. At this time, the first insulating layer 120a and the second insulating layer 130j surround the peripheral surface of the epitaxial structure 110, and only the first insulating layer 120a is on the platform M and the platform D, and the second layer of the second-type semiconductor layer 116 The bottom surface B and the second side surface S2' of the portion 119 only have the second insulating layer 130j. The first electrode 140j directly contacts the first insulating layer 120a and the current distribution layer 160 , and the second electrode 150j directly contacts the first insulating layer 120a and the second-type semiconductor layer 116 exposed by the second opening 124 .

It is worth mentioning that the second insulating layers 130h, 130i, and 130j in the micro LED structures shown in FIGS. 8 to 10 extend from the bottom surface B toward the top surface U to cover them. In an actual manufacturing process, the second insulating layers 130h, 130i, 130j and the first insulating layers 120a, 120d may be formed at different stages respectively. In detail, the first insulating layers 120a, 120d are first formed in the process stage (chip on wafer) on the epitaxial wafer; and in the embodiment of FIG. 8 to FIG. 10, the second insulating layers 130h, 130i, 130j It is formed after the micro-LED structures 100h, 100i, 100j are flipped and transferred to a temporary carrier substrate, so they present a covering direction opposite to the first insulating layer 120a, 120d. In other words, during the process stage on the epitaxial wafer, only the first insulating layers 120a, 120d may be formed, leaving the second side surfaces S2, S2' exposed.

After the miniature light emitting diode structures 100h, 100i, 100j are reversed, according to different design purposes or different film-forming methods, the second insulating layers 130h, 130i, 130j can be implemented in various ways. For example, in FIG. 8, the second insulating layer 130h only extends to cover the platform surface D; and as shown in FIG. The first insulating layer 120d is flush with each other. In addition, for some embodiments such as FIG. 10 , the second insulating layer 130j formed after the transfer process can also better cover the inclined second side surface S2', ensuring that all of the micro light emitting diode structure 100j Surrounding surfaces are well insulated.

In this way, when the micro LED structures 100h, 100i, 100j are transferred, since the second insulating layer 130h, 130i, 130j has not been formed yet, the residual problem caused by incomplete laser lift-off can be completely avoided.

To sum up, in the design of the micro light emitting diode structure of the present invention, the first insulating layer covers from the top surface of the platform to the platform surface along the first side surface, and exposes the second part of the second type semiconductor layer. The second side surface, and the second insulating layer directly covers the second side surface, wherein the thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50. That is to say, the thicker first insulating layer will not extend to the substrate, which can solve the problem in the prior art that the epitaxial insulating layer remains on the surrounding surface of the stripped micro light emitting diode, while the thinner and directly covering the The second insulating layer on the second side surface can passivate the second side surface to improve luminous efficiency. Therefore, the micro LED structure of the present invention can have better structural reliability and luminous efficiency.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (15)

1. A micro light-emitting diode structure, characterized in that, comprising: An epitaxial structure, including a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer, the light-emitting layer is located between the first-type semiconductor layer and the second-type semiconductor layer, and the first-type semiconductor layer , the light-emitting layer and the first part of the second-type semiconductor layer form a platform, the platform has a top surface and a first side surface, and the second part of the second-type semiconductor layer is recessed relative to the platform a platform is formed, and the second portion has a second side surface, the platform is located between the first side surface and the second side surface; a first insulating layer covering from the top surface of the platform to the platform surface along the first side surface and exposing the second side surface; and The second insulating layer directly covers the second side surface, wherein the thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50. 2. The micro light emitting diode structure according to claim 1, wherein the first insulating layer directly covers the platform surface, and the first insulating layer covering the first side surface and the first insulating layer cover the first side surface. The two side surfaces form a continuous surface. 3. The micro light emitting diode structure according to claim 2, wherein the second insulating layer directly covers the first insulating layer on the continuous surface, and extends along the continuous surface to cover the The platform surface and the first insulating layer on the top surface. 4. The micro light emitting diode structure according to claim 1, wherein the density of the second insulating layer is higher than that of the first insulating layer. 5 . The micro LED structure according to claim 1 , wherein the first insulating layer is a physically deposited film, and the second insulating layer is a chemically deposited film. 6 . The micro LED structure according to claim 1 , wherein the material of the first insulating layer is different from that of the second insulating layer. 7 . The micro LED structure according to claim 1 , wherein the thickness of the second insulating layer is between 20 nanometers and 50 nanometers. 8. The micro light emitting diode structure according to claim 1, wherein at least one of the first insulating layer and the second insulating layer is a distributed Bragg reflection film layer, and the distributed Bragg reflection The film layer includes multiple film layers stacked alternately and with different refractive indices, and the thickness of each of the multiple film layers is between 1/4 times and 1/2 times the light emitting wavelength of the light emitting layer. 9. The micro light emitting diode structure according to claim 1, wherein the first insulating layer and the second insulating layer expose the first type semiconductor layer on the top surface to form a first opening, And exposing the second part of the second type semiconductor layer on the platform surface to form a second opening, and the micro light emitting diode structure further includes: a first electrode disposed in the first opening and electrically connected to the first-type semiconductor layer; and The second electrode is disposed in the second opening and electrically connected to the second type semiconductor layer, wherein both the first electrode and the second electrode extend to the second insulating layer, and the The first electrode and part of the second electrode are located on the same plane. 10 . The micro LED structure according to claim 9 , wherein the second insulating layer seals the first insulating layer at the position of the first opening or the second opening. 11 . 11. The micro light emitting diode structure according to claim 9, wherein the second insulating layer shrinks inwardly relative to the first insulating layer at the position of the first opening or the second opening. distance. 12. The micro light emitting diode structure according to claim 9, wherein the first electrode and the second electrode are located between the first insulating layer and the second insulating layer, and the first insulating layer The two insulating layers respectively expose the first electrode and the second electrode at the positions of the first opening and the second opening. 13. The micro light-emitting diode structure according to claim 1, wherein the second part of the second-type semiconductor layer also has a bottom surface opposite to the platform surface, and the second side surface is connected to the The platform surface and the bottom surface, and the second insulating layer extends from the second side surface and directly covers the bottom surface. 14. The micro light emitting diode structure according to claim 13, wherein the second insulating layer covers the first insulating layer on the first side surface, and is in contact with the first insulating layer The top surface of the platform is flush. 15. A micro light emitting diode structure, characterized in that it comprises: An epitaxial structure, including a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer, the light-emitting layer is located between the first-type semiconductor layer and the second-type semiconductor layer, and the first-type semiconductor layer , the light-emitting layer and the first part of the second-type semiconductor layer form a platform, the platform has a top surface and a first side surface, and the second part of the second-type semiconductor layer is formed by being recessed relative to the platform a platform surface, and the second portion has a second side surface, the platform surface is located between the first side surface and the second side surface; The first insulating layer covers directly from the top surface of the platform to the platform surface along the first side surface, and exposes the second side surface, wherein all the parts covering the first side surface The first insulating layer forms a continuous surface with the second side surface; and The second insulating layer is disposed on the first insulating layer and directly covers the continuous surface, wherein the first insulating layer is in direct contact with the second insulating layer.

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