Light emitting device and method of forming the same

Abstract

The present disclosure provides a light emitting device and a method of forming the same. The light emitting device includes a substrate; a plurality of light emitting diode dies on the substrate; a first reflective layer on the light emitting diode dies, wherein the first reflective layer is configured to reflect an emission light band from the light emitting diode dies; and a second reflective layer on the first reflective layer, wherein the second reflective layer is configured to reflect a laser light band, wherein a wavelength of the laser light band is less than 420 nm.

Description

Technical Field

[0001] This disclosure relates to a light-emitting device and a method for forming the same, and more particularly to a light-emitting device including a reflective layer and a method for forming the same. Background Technology

[0002] Light-emitting diodes (LEDs) are light-emitting devices that emit light when a voltage is applied. Nitride LEDs are commonly used as semiconductor optical elements that produce blue or green light. Considering the lattice matching of the compound, nitride semiconductor materials are typically grown on a sapphire substrate, and then the electrode structure is formed to create the nitride LED. However, sapphire substrates have high hardness, low thermal conductivity, and low electrical conductivity, which not only causes electrostatic problems but is also a major factor limiting heat dissipation in traditional upright LED chips. Furthermore, in traditional upright LED structures, the electrodes block some light, reducing luminous efficiency. Therefore, the flip-chip structure of LEDs has gradually been developed.

[0003] Currently, the common LED flip-chip technology involves flipping the fabricated LED chip and then soldering it onto a packaging substrate. Because the chip is flipped, the heat conduction path can be directly conducted from the semiconductor layer to the packaging substrate, avoiding the problem of poor heat dissipation in sapphire substrates. Furthermore, traditionally, during flip-chip technology, an array of LED chips is formed through a series of processes, using a pick-up head to select or transfer chips from one carrier to another. However, traditional processes may encounter some challenges. For example, the edge length of micro-LED chips is smaller than the minimum size limit of the pick-up head, making it impossible to effectively pick up LED chips. Also, the miniaturization of chip size means a massive increase in the number of chips that can be formed from a wafer of the same size. The traditional one-to-one pick-up method cannot meet the demand for mass transfer of LED chips, leading to a decrease in LED yield.

[0004] In the evolution of mass transfer LED chip technology, in order to meet the demand for high efficiency and achieve high production capacity, selective laser lift-off (selective LLO) technology is used to replace the traditional process. Summary of the Invention

[0005] According to some embodiments of this disclosure, a light-emitting device is provided. The light-emitting device includes a substrate; a plurality of light-emitting diode (LED) chips on the substrate; a first reflective layer on the LED chips, wherein the first reflective layer is used to reflect emitted light wavelengths from the LED chips; and a second reflective layer on the first reflective layer, wherein the second reflective layer is used to reflect laser wavelengths, wherein the wavelength of the laser wavelength is less than 420 nm.

[0006] According to some embodiments of this disclosure, a light-emitting device is provided. The light-emitting device includes a carrier plate; a plurality of light-emitting diode (LED) chips spaced apart on the carrier plate, wherein each LED chip includes a pair of electrodes facing the carrier plate; and a plurality of colloids covering the electrodes between the carrier plate and the LED chips, wherein the upper surface of the carrier plate is exposed between the LED chips.

[0007] According to some embodiments of the present disclosure, a light-emitting device is provided. The light-emitting device includes a carrier plate; a light-emitting diode (LED) die on the carrier plate, wherein the LED die includes a pair of electrodes remotely disposed from the carrier plate; an adhesive layer between the carrier plate and the LED die; and an colloid above the LED die, wherein the electrodes are exposed in the colloid.

[0008] According to some embodiments of this disclosure, a method for forming a light-emitting device is provided. The method includes providing a substrate having a plurality of spaced-apart light-emitting diode (LED) chips, each LED chip having a pair of electrodes on its front side away from the substrate; bonding a first carrier plate to the front side of the LED chips using an adhesive, wherein the electrodes face the first carrier plate; removing the substrate from the back side of the LED chips; removing a portion of the adhesive between the LED chips, such that the upper surface of the first carrier plate is exposed between the LED chips; bonding a second carrier plate to the back side of the LED chips using an adhesive layer; removing the first carrier plate from the front side of at least one LED chip, such that at least one LED chip is adhered to the second carrier plate; removing a portion of the adhesive on at least one LED chip on the second carrier plate, exposing the electrodes; bonding a back plate to the exposed electrodes on at least one LED chip; and removing the second carrier plate and the adhesive layer from the back side of at least one LED chip.

[0009] The following embodiments are described in detail with reference to the accompanying drawings. Attached Figure Description

[0010] A more comprehensive understanding of the embodiments of the present invention will be achieved by reading the following detailed description and examples in conjunction with the accompanying drawings, wherein:

[0011] Figure 1 A cross-sectional view of the light-emitting device is shown according to an embodiment of the present disclosure.

[0012] Figure 2A cross-sectional view of a light-emitting diode chip is shown according to an embodiment of the present disclosure.

[0013] Figures 3A to 3D The present disclosure illustrates cross-sectional views of various intermediate stages in the formation of a light-emitting diode (LED) die, based on some embodiments thereof.

[0014] Figures 4A to 4D The diagram illustrates cross-sectional views of reflective layers of different types and / or different contours, according to various embodiments of the present disclosure.

[0015] Figure 5 This is a cross-sectional view illustrating a light-emitting diode die having a light-emitting layer, according to an embodiment of the present disclosure.

[0016] Figure 6 This is a cross-sectional view of a light-emitting diode die having a barrier film formed, according to an embodiment of the present disclosure.

[0017] Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 , Figure 16 , Figure 17 , Figure 18 and Figure 19 The present disclosure illustrates cross-sectional views of various intermediate stages in the mass transfer of light-emitting diode (LED) chips, based on some embodiments thereof.

[0018] The reference numerals in the attached figures are explained as follows:

[0019] 10, 20, 30: Light-emitting devices

[0020] 102: Substrate

[0021] 102a: Roughened surface

[0022] 104: Light Emitting Diode Chip

[0023] 104a: Roughened surface

[0024] 106: First reflective layer

[0025] 108: Second reflective layer

[0026] 111: Hole

[0027] 112a, 112b: Electrodes

[0028] 113: Laser ablation process

[0029] 114: First adhesive layer

[0030] 115: Second adhesive layer

[0031] 116: Laser ablation process

[0032] 117: Roughening process

[0033] 117a: Roughened surface

[0034] 118: Semiconductor layer

[0035] 119: Emissive Layer

[0036] 120: Platform Structure Detailed Implementation

[0037] The following describes a light-emitting device and a method for forming the same according to embodiments of this disclosure. However, it should be understood that this disclosure provides many suitable inventive concepts that can be implemented in a wide range of specific contexts. The specific embodiments disclosed are only for illustrating the making and use of the invention by specific methods and are not intended to limit the scope of the invention. Furthermore, the same reference numerals are used in the drawings and descriptions of the embodiments of this disclosure to denote the same or similar components.

[0038] Furthermore, this disclosure provides numerous embodiments or examples for implementing different elements of the provided subject matter. Specific examples of each element and its configuration are described below to simplify the description of embodiments of the invention. Of course, these are merely examples and are not intended to limit the embodiments of the invention. For instance, if the description refers to a first element formed on a second element, it may include embodiments where the first and second elements are in direct contact, or embodiments where an additional element is formed between the first and second elements such that they are not in direct contact.

[0039] Furthermore, spatially relative terms may be used, such as "below," "under," "lower," "above," "higher," etc., to facilitate the description of the relationship between one or more components or features in the diagram. Spatially relative terms are used to include different orientations of the device in use or operation, as well as the orientations described in the diagram. When the device is turned to different orientations (rotated 90 degrees or other orientations), the spatially relative adjectives used will also be interpreted according to the orientation after the turn.

[0040] According to some embodiments of this disclosure, the light-emitting device includes a first reflective layer and a second reflective layer. The first reflective layer is disposed on the light-emitting diode (LED) chip, and the second reflective layer is disposed on the first reflective layer. In the mass transfer process used in existing light-emitting devices, when selective laser lift-off (SLO) technology is used, the high temperature of the laser may damage the LED chip, thus reducing the yield of the LED chip and affecting the performance of the light-emitting device. To solve the above problems, the light-emitting device provided in the embodiments of this disclosure, by providing a double reflective layer on the LED chip, not only can the external quantum efficiency (EQE) of the LED chip be improved, but the laser used by the selective laser lift-off (SLO) technology can also be reflected, preventing minor damage to the LED chip.

[0041] Figure 1 A cross-sectional schematic diagram of the light-emitting device 10 according to an embodiment of this disclosure is shown. Figure 1 In this embodiment, the light-emitting device 10 includes a substrate 102 and a plurality of light-emitting diode (LED) chips 104 spaced apart on the substrate 102. For simplicity, only three LED chips 104 are shown in the figure, but this disclosure is not limited thereto. Each LED chip 104 has a first electrode 112a (e.g., a positive electrode) and a second electrode 112b (e.g., a negative electrode). In some embodiments, the first electrode 112a is a negative electrode and the second electrode 112b is a positive electrode. The first electrode 112a and the second electrode 112b are disposed on the same side of the LED chip 104 away from the substrate 102 (which may be referred to as the front side). In some embodiments, the substrate 102 may be a sapphire substrate, a silicon substrate, a silicon carbide substrate, or a ceramic substrate. The LED chips 104 may be LED chips that emit blue, red, or green light.

[0042] Figure 2 It is drawn Figure 1 Detailed cross-sectional structure of the light-emitting diode chip 104. Figure 2 In this design, a first reflective layer 106 is disposed on the light-emitting diode (LED) chip 104, and a second reflective layer 108 is further disposed on the first reflective layer 106. The first reflective layer 106 is used to reflect the light emitted by the LED chip 104, increasing the external quantum efficiency (EQE). The second reflective layer 108 is used to reflect the laser used in the selective laser lift-off (SLO) technique during the subsequent batch transfer of the LED chips 104, preventing thermal damage to the LED chips caused by the laser. In some embodiments, the first electrode 112a and the second electrode 112b pass through the second reflective layer 108 and are in electrical contact with the LED chip 104, as shown in the figure. The fabrication process for forming the first reflective layer 106 and the second reflective layer 108 will be described in more detail later.

[0043] Figures 3A to 3D This is a cross-sectional view illustrating various intermediate stages in the formation of the light-emitting diode die 104 according to various embodiments of the present disclosure. (Refer to...) Figure 3A An epitaxial semiconductor layer 118 is deposited on a semiconductor substrate 102. In some embodiments, before depositing the epitaxial semiconductor layer 118, a roughening process may be performed on the semiconductor substrate 102 to form a periodic roughened surface 102a. In some embodiments, a patterned substrate is formed using a patterned sapphire substrate (PSS) technique to increase light extraction efficiency. For example, a patterned substrate can be formed by a lithography process and an etching process. In the lithography process, a photoresist layer (not shown) is first applied to the semiconductor substrate 102 by, for example, spin coating. Then, the photoresist layer is exposed according to a pattern mask and developed to form a periodic pattern in the photoresist layer. The photoresist layer with a periodic pattern can be used as an etching mask to pattern the semiconductor substrate 102. A portion of the surface of the semiconductor substrate 102 is then protected using the patterned photoresist layer, while the etching process forms recesses into the surface of the semiconductor substrate 102 in the unprotected areas, thus leaving the periodic roughened surface 102a. Finally, the photoresist layer is removed, for example by ashing. In some embodiments, the periodically roughened surface 102a is formed using dry etching, such as reactive ion etching (RIE), wet etching, or a combination thereof.

[0044] It should be noted that the roughening process here is optional and can be omitted or the light-emitting diode die 104 can be roughened in subsequent processes (detailed later). In some embodiments, the epitaxial semiconductor layer 118 includes a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer formed on the substrate 102 in sequence. For example, the first-type semiconductor layer and the second-type semiconductor layer can be different types of semiconductor materials. For example, the first-type semiconductor layer is gallium nitride (n-GaN) with n-type conductivity, and the second-type semiconductor layer is gallium nitride (p-GaN) with p-type conductivity, and they can also be interchanged. Other III-V group compounds can be used, such as: indium nitride (InN), aluminum nitride (AlN), indium gallium nitride (InxGa(1-x)N), aluminum gallium nitride (AlxGa(1-x)N), or aluminum indium gallium nitride (AlxInyGa(1-x-y)N), etc., where 0 < x ≤ 1, 0 < y ≤ 1, and 0 ≤ x + y ≤ 1. The light-emitting layer 119 can have a multiple quantum well structure (MQW) composed of semiconductor materials. The light-emitting layer can include other suitable light-emitting materials, but is not limited thereto. In one embodiment, the method of forming the epitaxial semiconductor layer 118 can include an epitaxial growth process, such as chemical vapor deposition (CVD), metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), liquid phase epitaxy (LPE), or other suitable chemical vapor deposition methods.

[0045] Refer back to Figure 3A , then, a patterned mesa structure 120 is formed on the epitaxial semiconductor layer 118. Through the patterning process, the range of the components to be formed next is defined. The above patterning process can include photolithography and etching processes, similar to the aforementioned patterning process, and will not be elaborated here.

[0046] Refer to Figure 3BA first reflective layer 106 is formed on the platform structure 120. The first reflective layer 106 has a high reflectivity, for example, greater than 90%, for the light-emitting band of the light-emitting diode chip 104, to reflect the light-emitting band of the light-emitting diode chip 104 and increase the external quantum efficiency (EQE). In some embodiments, the first reflective layer 106 may be a Bragg reflector. In one embodiment, the Bragg reflector may include a periodic structure composed of alternating layers of two materials with different refractive indices, or a dielectric waveguide with a periodic variation in effective refractive index. In one embodiment, the material of the Bragg reflector may include an insulator. For example, the material of the Bragg reflector may include silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum oxide (Ta2O5), aluminum oxide (Al2O3), or silicon nitride (Si3N4), but is not limited thereto. The thickness of each layer is related to the wavelength of the incident light. When the product of the refractive index and the optical thickness of each layer is equal to one-quarter of the wavelength of the incident light, constructive interference occurs because the optical path difference between the incident and reflected light is exactly an integer multiple of the wavelength of the incident light (nλ, n = 1, 2, 3…). The light cannot penetrate the Bragg reflector layer. Based on the above principle and material properties, the light emitted by the LED chip 104 is reflected, increasing the external quantum efficiency (EQE). In one embodiment, the higher the number of Bragg reflector layers, the more pronounced the light reflection. In some embodiments, the thickness of the first reflective layer 106 can be controlled within the range of 0.1 μm to 4 μm, for example, 0.6 μm to 2 μm.

[0047] Next, a second reflective layer 108 is formed on the first reflective layer 106. The second reflective layer 108 has a high reflectivity, for example, greater than 90%, for the selective laser lift-off (SLO) laser used subsequently in the batch transfer of the LED chips 104. Therefore, the second reflective layer 108 can reflect the SLO laser used subsequently, preventing thermal damage to the LED chips caused by the laser. In some embodiments, the second reflective layer 108 can be a Bragg reflective layer, using a different thickness than the aforementioned Bragg reflective layer 106. In some embodiments, the material of the second reflective layer 108 can be similar to the material of the Bragg reflective layer 106. In some embodiments, the material of the second reflective layer 108 can be exactly the same as the material of the Bragg reflective layer 106, reducing process complexity. In some embodiments, the material of the second reflective layer 108 can be different from the material of the Bragg reflective layer 106, depending on the design requirements of the light-emitting device. In some embodiments, a higher number of layers in the second reflective layer 108 results in better reflection and improved yield of the light-emitting device. In some embodiments, the thickness of the second reflective layer 108 can be controlled within the range of 0.1 μm to 4 μm, for example, 0.6 μm to 2 μm. In some embodiments, the thickness of the second reflective layer 108 is less than the thickness of the first reflective layer 106.

[0048] Then, the first reflective layer 106 and the second reflective layer 108 are patterned to form recesses 111 that penetrate the first reflective layer 106 and the second reflective layer 108, exposing portions of the epitaxial semiconductor layer 118, such as... Figure 3B As shown. The recess 111 will be used subsequently to form the electrodes of the light-emitting diode chip. The patterning process can use a similar patterning process as described above, which will not be elaborated here.

[0049] Reference Figure 3C The epitaxial semiconductor layer 118 is etched to form the individually spaced light-emitting diode chips 104. The etching process may include dry etching, such as reactive ion etching (RIE), wet etching, or a combination thereof.

[0050] Reference Figure 3DA first electrode 112a and a second electrode 112b are formed passing through the first reflective layer 106 and the second reflective layer 108 and are in solid contact with the light-emitting diode die 104. In some embodiments, the materials of the first electrode 112a and the second electrode 112b may include metals or metal alloys. For example, the metal materials of the first electrode 112a and the second electrode 112b may include copper (Cu), aluminum (Al), indium (In), tin (Sn), gold (Au), platinum (Pt), zinc (Zn), silver (Ag), titanium (Ti), nickel (Ni), or combinations thereof, but are not limited thereto. In some embodiments, the first electrode 112a and the second electrode 112b may be formed using chemical vapor deposition (CVD), including low-pressure chemical vapor deposition (LPCVD) and plasma chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or other suitable deposition processes. Subsequently, the electrode layers are patterned using lithography and etching processes, such as... Figure 3D As shown. For example, a patterning process similar to that described above can be used, which will not be elaborated here.

[0051] Reference Figures 4A-4D According to various embodiments of this disclosure, cross-sectional views are shown illustrating reflective layers of different types and / or different contours. Figure 4A In some embodiments, both the first reflective layer 106 and the second reflective layer 108 are Bragg reflective layers. The first reflective layer 106 can reflect light emitted from the front side (the side with electrodes) of the LED chip 104, increasing the external quantum efficiency (EQE). The second reflective layer 108 can reflect the laser used in the selective laser lift-off (SLO) technique subsequently used during the mass transfer of the LED chips 104, preventing thermal damage to the LED chips caused by the laser. Furthermore, the first reflective layer 106 and the second reflective layer 108 can extend towards the substrate, covering most of the sidewalls of the LED chip 104. The extended portion of the first reflective layer 106 can reflect light emitted from the LED chip 104 to the left and right sides, thereby increasing the external quantum efficiency (EQE). The extended portion of the second reflective layer 108 can reflect the laser used in the selective laser lift-off (SLO) technique subsequently used during the mass transfer of the LED chips 104, such as... Figure 4B , Figure 4CAs shown. In some embodiments, the sidewalls of the second reflective layer 108 are aligned with the exposed sidewalls of the LED die 104, which can preserve a thicker first reflective layer 106 and second reflective layer 108, increasing external quantum efficiency (EQE) and enhancing the reflection of laser light subsequently used in selective laser lift-off (SLO) technology during batch transfer. Alternatively, in some embodiments, the sidewalls of the second reflective layer 108 can be recessed within the sidewalls of the LED die 104, such as... Figure 4C As shown, this reduces process complexity and eliminates the need for additional steps to align the sidewalls of the second reflective layer 108 with the exposed sidewalls of the LED chip 104.

[0052] Furthermore, in other embodiments, the first reflective layer 106 can be a metal layer to reflect the light emitted by the LED chip 104, thereby increasing the external quantum efficiency (EQE), such as... Figure 4D As shown. In some embodiments, the material of the first reflective layer 106 includes metals, such as silver (Ag), aluminum (Al), and gold (Au). In some embodiments, the first reflective layer 106 may have a thickness of approximately to approximately The first reflective layer 106 can be formed using chemical vapor deposition (CVD), including low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or other suitable deposition processes. Notably, when the first reflective layer 106 is a metal layer, it can be deposited directly after the formation of the epitaxial semiconductor layer 118, followed by etching of the metal layer and the epitaxial semiconductor layer 118 to form the platform structure 120 and a patterned first reflective layer 106 on the upper surface of the platform structure 120. Next, a patterned second reflective layer 108 is formed on the first reflective layer 106, using a patterning process similar to that described above. The patterned second reflective layer 108 exposes a portion of the first reflective layer 106 and a portion of the epitaxial semiconductor layer 118. Finally, a first electrode 112a is formed to contact the epitaxial semiconductor layer 118, and a second electrode 112b is formed to contact the first reflective layer 106, as shown below. Figure 4D As shown. To simplify the illustration, the process cross-sectional view of the embodiment only illustrates one configuration of the light-emitting diode chip 104 and the first reflective layer 106, but it could be any other configuration. Figures 4A-4D Any one of them.

[0053] Reference Figure 5According to some embodiments of this disclosure, the first reflective layer 106 laterally covers the light-emitting layer 119. The bottommost end of the first reflective layer 106 extending into the sidewall may be lower than or equal to the bottom surface of the light-emitting layer 119, which can reflect the light emitted by the light-emitting layer 119 to the left and right sides, thereby increasing the external quantum efficiency (EQE) of the light-emitting diode chip 104.

[0054] Reference Figure 6 According to other embodiments of this disclosure, before and / or after the deposition of the first reflective layer, barrier films 110a and / or 110b may be formed on the light-emitting diode die 104 and / or on the second reflective layer 108 as needed. The barrier films 110a and 110b are used to cover the surfaces of the first reflective layer 106 and the second reflective layer 108, protecting them from damage caused by external substances such as moisture or oxygen, and filling defects caused during the deposition of the reflective layers to prevent leakage current and increase reliability. In some embodiments, the barrier films 110a and 110b may each comprise inorganic materials, such as dielectric materials (e.g., SiO2, Al2O3, or Si3N4). In some embodiments, the barrier films 110a and 110b may be multilayer barrier films, applied to the surfaces of the first reflective layer 106 and / or the second reflective layer 108 by coating or lamination. In some embodiments, the thicknesses of the barrier films 110a and 110b are greater than 10 nm and less than 500 nm, respectively.

[0055] Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 and Figure 16 The present disclosure provides cross-sectional views illustrating various intermediate stages in the mass transfer of the light-emitting diode die 104, based on some embodiments thereof.

[0056] Reference Figure 7First, a carrier plate 202 is provided, and the carrier plate 202 has a first adhesive layer 114 (also referred to as an adhesive). In some embodiments, the material of the carrier plate 202 may include a plastic substrate, a glass substrate, a silicon substrate, or a sapphire substrate, or other suitable materials, but is not limited thereto. In some embodiments, the first adhesive layer 114 may be a UV adhesive that reacts with the laser used subsequently. In some embodiments, the first adhesive layer 114 decomposes after absorbing the laser used, causing the light-emitting diode chip 104 to peel off from the first adhesive layer 114. In some embodiments, the wavelength of the laser used is less than 420 nm, for example, wavelengths of 248, 260, 280, 355 nm, etc., but is not limited thereto.

[0057] In some embodiments, the first adhesive layer 114 can be deposited on the carrier plate 202 by spin coating. Then, Figure 1 The first electrode 112a and the second electrode 112b of the semiconductor device 10 are bonded to a first adhesive layer 114 on the carrier plate 202. In some embodiments, the first adhesive layer 114 is squeezed into the gap between the light-emitting diode chips 104, adheres to a portion of the sidewall of the light-emitting diode chips 104, covers the first electrode 112a and the second electrode 112b, but does not directly contact the substrate 102, such as... Figure 7 As shown. In some embodiments, the first adhesive layer 114 covers 100% of the top surface and more than 80% of the side surface of the light-emitting diode die 104. In other embodiments, the first adhesive layer 114 may be attached to the entire top and side surfaces of the light-emitting diode die 104, directly contacting the substrate 102 (not shown).

[0058] Reference Figure 8 The substrate 102 is removed by a fully laser lift-off (LLO) process 113 to transfer all light-emitting diode (LED) chips 104 to the carrier plate 202. In some embodiments, the fully laser lift-off (LLO) process 113 is applied from the surface of the substrate 102 to remove the substrate 102. In some embodiments, the wavelength of the laser used in the fully laser lift-off (LLO) process 113 is below 420 nm, for example, wavelengths of 248, 260, 280, 355 nm, etc., but not limited thereto. In some embodiments, the material of the LED chips 104 can completely absorb the laser used in the fully laser lift-off (LLO) process, thereby avoiding damage to the LED chips 104 caused by the laser. For example, in embodiments where the LED chips 104 include a III-V compound (e.g., gallium nitride), the III-V compound can completely absorb the laser at the interface with the substrate 202, preventing laser damage to the LED chips 104 and improving the yield of the light-emitting device.

[0059] Reference Figure 9 In some embodiments, since the substrate 102 has a patterned periodic surface 102a, the light-emitting diode chip 104 also has a periodic roughened surface 104a at the interface with the substrate 102. After the laser lift-off process, the periodic roughened surface 104a of the light-emitting diode chip 104 can be exposed to increase the light extraction efficiency of the light-emitting diode chip 104.

[0060] Reference Figure 10 In other embodiments, after removing the substrate 102, a roughened surface 117a may be formed on the exposed surface of the LED chip 104 through a roughening process 117 as needed, to increase the light extraction efficiency of the LED chip 104. In some embodiments, the roughened surface 117a may include semiconductor materials and / or polymers. For example, a light-transmitting layer (not shown) may optionally be formed on the periodically roughened surface of the LED chip 104. The light-transmitting layer may include polymers such as silicone or resin, and may be formed by molding, glue-filling, or other suitable processes. The roughening process 117 is then performed on the light-transmitting layer to form the periodically roughened surface 117a, by means such as sandblasting or surface etching. In some embodiments, the surface roughness of the roughened surface 117a may be in the range of 0.1 μm to 3 μm, for example, 0.2 μm to 2 μm, but is not limited thereto.

[0061] Reference Figure 11 This forms a light-emitting device 20. (Continued) Figure 9 The first adhesive layer 114 between the sidewalls of the LED chips 104 is etched to expose the upper surface 202a of the carrier 202, separating each LED chip 104 to facilitate subsequent selective transfer of the LED chips 104. This reduces difficulties in selective transfer caused by the first adhesive layer 114 remaining between each LED chip 104. The etching process may include dry etching such as reactive ion etching (RIE), wet etching, or a combination thereof.

[0062] Reference Figure 12 , continuing Figure 11A second carrier plate 302 is provided, and the second carrier plate 302 has a second adhesive layer 115. In some embodiments, the material of the second carrier plate 302 may include a plastic substrate, a glass substrate, a silicon substrate, or a sapphire substrate, or other suitable materials, but is not limited thereto. In some embodiments, the second adhesive layer 115 may be a polymeric material and an elastomeric material, such as an elastomeric elastic polymer material. In some embodiments, the elastomeric elastic polymer material may include a polysiloxane material, such as polydimethylsiloxane (PDMS). In some embodiments, the second adhesive layer 115 may be deposited by spin coating. Then, Figure 11 The back side (the side away from the electrode) of the light-emitting device 20 is bonded to the second adhesive layer 115 on the second carrier plate 302, as shown in the figure. Figure 12 As shown.

[0063] Reference Figure 13 , continuing Figure 12 The LED chip 104 is selectively transferred to the second carrier plate 302. The LED chip 104 is then selectively peeled off from the first carrier plate 202 by performing a selective laser lift-off (LLO) process 116 on the electrode side of the LED chip 104 to be transferred. In some embodiments, the laser used in the selective laser lift-off (LLO) process 116 has a wavelength below 420 nm, for example, wavelengths of 248, 260, 280, 355 nm, etc., but not limited to these. In some embodiments, the first adhesive layer 114 cannot completely absorb the laser used in the selective laser lift-off process 116. To avoid damage to the LED chip 104 caused by the high temperature of the laser, a second reflective layer 108 on the LED chip 104 can reflect the laser used in the selective laser lift-off process 116, reducing the impact of the high temperature of the laser on the LED chip 104 and increasing the yield of batch transfers.

[0064] Reference Figure 14 , continuing Figure 13 Remove the first carrier plate 202 so that the LED chip 104 to be transferred leaves the first carrier plate 202 and adheres to the second adhesive layer 115, while the LED chip 104 that is not transferred remains on the first carrier plate 202 and leaves the second adhesive layer 115.

[0065] Reference Figure 15 This forms a light-emitting device 30. (Continued) Figure 14The first adhesive layer 114 on the LED chip 104 is etched to expose the bottom surface and part of the sidewalls of the first electrode 112a and the second electrode 112b of the LED chip 104, facilitating subsequent bonding processes so that the LED chip 104 can be electrically connected to the target backplane. In some embodiments, the etching process can be similar to the etching process previously used to etch the first adhesive layer. In some embodiments, the etching process can include other suitable processes. In some embodiments, the first adhesive layer 114 remains on the front side of the LED chip 104, covering part of the sidewalls of the first electrode 112a and the second electrode 112b, which can protect the LED chip 104 and part of the sidewalls of the first electrode 112a and the second electrode 112b. In some embodiments, while etching the first adhesive layer 114 of the LED chip 104, a portion of the second adhesive layer 115 between the LED chips 104 may also be etched, so that the second adhesive layer 115 between the LED chips 104 is thinned. This thinning prevents existing LED chips from accidentally adhering to the backplane during the transfer of LED chips to the backplane (detailed explanation will follow with reference to Figure 18). In some embodiments, the second adhesive layer 115 includes a second adhesive layer 115a located between the LED chips 104 and a second adhesive layer 115b in direct contact with the LED chips 104. It is noteworthy that the etching process described above etches the second adhesive layer 115a between the LED chips 104, while using the LED chips 104 as a hard mask to retain the second adhesive layer 115b in direct contact with the LED chips 104. Therefore, the thickness of the second adhesive layer 115a between the LED chips 104 is thinner than the thickness of the second adhesive layer 115b in direct contact with the LED chips 104. Consequently, in some embodiments, the second adhesive layer 115 has an irregular surface. In some embodiments, the thickness of the second adhesive layer 115a between the LED chips 104 is different from that of the second adhesive layer 115b in direct contact with the LED chips 104.

[0066] Reference Figure 16 , continuing Figure 15 A backplate 402 is provided, and a plurality of conductive components 412 are provided on the backplate 402. In some embodiments, the material of the backplate 402 may include a glass substrate or a plastic substrate or other suitable materials, but is not limited thereto. The conductive components 412 may be metal electrodes, and for example, the material of the conductive components 412 may include nickel (Ni), tin (Sn), indium (In), gold (Au), titanium (Ti), copper (Cu), or combinations thereof, but is not limited thereto. In some embodiments, the conductive components 412 may be pre-melted to have adhesive properties, or the conductive components 412 may further include solder or similar adhesive materials pre-embedded on the metal electrodes. Next, Figure 15The first electrode 112a and the second electrode 112b of the light-emitting device 30 are bonded to the conductive component 412 on the back plate 402. In some embodiments, the first electrode 112a and the second electrode 112b are electrically in contact with the conductive component 412, such as... Figure 16 As shown.

[0067] Reference Figure 17 , continuing Figure 16 Remove the second carrier plate 302 so that the LED chip 104 to be transferred leaves the second carrier plate 302 and is bonded to the conductive component 412 of the back plate 402, such as... Figure 17 As shown.

[0068] The batch transfer capability of this disclosure allows for the selective transfer of LED chips 104 to the target backplane 402 according to its design requirements. For example, firstly, spaced-apart LED chips 104 (e.g., blue LEDs) can be transferred to the target backplane 402, followed by the transfer of secondly spaced LED chips 105 (e.g., red LEDs) to the spaces on the target backplane 402. Figure 18 , Figure 19 As shown, the above description is merely an example and is not limited to this. More types of LED chips can be transferred to the target backplane 402 according to the design requirements of the backplane. Furthermore, as... Figure 18 As shown, since the thickness of the second adhesive layer 115a between the LED chips 104 is thinner than the thickness of the second adhesive layer 115b directly contacting the LED chips 104, the second adhesive layer 115a can be prevented from adhering to the LED chips 104 already transferred to the target backplane during subsequent transfer processes, thereby increasing process yield. Afterwards, the carrier board 302 is removed, resulting in... Figure 19 The backplane is shown. In some embodiments, the spacing between each LED die 104 can be changed according to the design requirements of the backplane. The batch transfer method disclosed herein can be applied not only to different types of LED dies 104, but also widely to the fields of batch transfer or mass transfer of various micro-semiconductor structures.

[0069] It should be noted that this disclosure describes in general terms the process for batch transfer of light-emitting diode (LED) chips. Other processes and sequences can be used. For example, fewer or additional carriers can be used, different step sequences can be used, additional carriers can be formed and removed, and / or similar processes can be performed. Furthermore, different structures and steps can be used to form LED chips.

[0070] According to the embodiments provided in this disclosure, the light-emitting device includes a first reflective layer and a second reflective layer. The first reflective layer is on the light-emitting diode (LED) chip, and the second reflective layer is on the first reflective layer. By providing the first reflective layer on the LED chip, the first reflective layer can reflect the light emitted by the LED chip, improving the external quantum efficiency (EQE) of the LED chip, thereby increasing the light extraction efficiency of the light-emitting device. Furthermore, by providing the second reflective layer on the first reflective layer of the LED chip, the second reflective layer can reflect the laser used in the selective laser lift-off (SLO) process in the batch transfer process, reducing the impact of the high temperature of the laser on the LED chip, thereby increasing the yield of the batch transfer.

[0071] While some embodiments and advantages of the present invention have been described in detail, it should be understood that various modifications, substitutions, and refinements can be made without departing from the spirit and scope of the invention as defined by its protection scope. For example, those skilled in the art to which this invention pertains will readily understand that many components, functions, processes, and materials described herein can be altered without departing from the scope of the invention. Furthermore, the scope of this application is not limited to the specific embodiments of processes, machines, manufacturing, material composition, methods, and steps described in the specification. Those skilled in the art to which this invention pertains will readily understand from the present invention that any existing or future processes, machines, manufacturing, material composition, methods, or steps that can achieve substantially the same function or substantially the same result as the corresponding embodiments described herein can be used according to the embodiments of the present invention. Therefore, the protection scope of the present invention includes the aforementioned processes, machines, manufacturing, material composition, methods, or steps.

Claims

1. A method for forming a light-emitting device, comprising: A substrate is provided, wherein the substrate has a plurality of light-emitting diode (LED) chips spaced apart, wherein each LED chip has a pair of electrodes on its front side away from the substrate; A first carrier plate is bonded to the front side of the light-emitting diode chip via an colloid, wherein the electrode faces the first carrier plate; Remove the substrate from the back side of the light-emitting diode die; Remove a portion of the colloid between the LED chips, so that the upper surface of the first carrier is exposed between the LED chips; A second carrier plate is bonded to the back side of the light-emitting diode chip via an adhesive layer; The first carrier is removed from the front side of at least one light-emitting diode chip, and the at least one light-emitting diode chip is adhered to the second carrier. Remove a portion of the colloid on the at least one light-emitting diode die on the second carrier to expose the electrode; A backplate is bonded to the electrode exposed on the at least one light-emitting diode die; as well as The second carrier and the adhesive layer are removed from the back side of the at least one light-emitting diode die.

2. The method of forming a light-emitting device as claimed in claim 1, wherein removing the first carrier from the front side of the at least one light-emitting diode die includes a selective laser lift-off process.

3. The method for forming a light-emitting device as claimed in claim 2, wherein the light-emitting diode die further includes a reflective layer that reflects the laser used in the laser stripping process on the side near the electrode.

4. The method for forming a light-emitting device as claimed in claim 1, wherein when a first carrier plate is bonded to the front side of the light-emitting diode chip via a colloid, the colloid surrounds a portion of the sidewall of the light-emitting diode chip.

5. The method for forming a light-emitting device as claimed in claim 1 further includes removing a portion of the adhesive layer that is not adhered to the at least one light-emitting diode die.

6. The method for forming a light-emitting device as claimed in claim 1, after removing the substrate from the back side of the light-emitting diode die, further includes performing a roughening process on the surface of the light-emitting diode die to form a periodic roughened surface.

7. The method for forming a light-emitting device as claimed in claim 1, wherein the step of providing the light-emitting diode die further comprises: A semiconductor layer having multiple platforms is formed above the substrate; A first reflective layer and a second reflective layer are sequentially formed on the platform; Etching the semiconductor layer to form the light-emitting diode chips spaced apart from each other; and The electrode is formed on the second reflective layer and extends through the first reflective layer and the second reflective layer.

8. The method of forming a light-emitting device as claimed in claim 7, further comprising forming a barrier film below the first reflective layer or on the second reflective layer before or after forming a first reflective layer and a second reflective layer.

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