Patent ID: 12211957

DETAILED DESCRIPTION

Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.

It should be noted that, the formation of a first component over or on a second component in the description below may include embodiments in which the first and second components are formed in direct contact, and may also include embodiments in which additional components may be formed between the first and second components, such that the first and second components may not be in direct contact.

Referring toFIG.3, a first embodiment of a flip-chip light-emitting diode (LED) according to the present disclosure includes a transparent substrate001, a transparent bonding layer002, a first conductivity type semiconductor layer003, a light-emitting layer004, a second conductivity type semiconductor layer005, a first transparent dielectric layer007, a second transparent dielectric layer006, a distributed Bragg reflector (DBR) structure008, a third transparent dielectric layer009, and two electrodes010,011.

The transparent substrate001may be made of a material selected from the group consisting of sapphire, glass, gallium phosphide (GaP), or combinations thereof. In this embodiment, the transparent substrate001is made of sapphire. The transparent substrate001may have a thickness ranging from 30 μm to 100 μm. Each of top and bottom surfaces of the transparent substrate001may be a roughened surface or a flat surface.

The transparent bonding layer002is disposed between the transparent substrate001and the first conductivity type semiconductor layer003, and is used to bond the transparent substrate001to the first conductivity type semiconductor layer003. The transparent bonding layer002may be made of silicon oxide (SiO2), and may have a thickness ranging from 1 μm to 5 μm. In some embodiments, the transparent bonding layer002may be deposited on a surface of the first conductivity type semiconductor layer003using electron beam evaporation. When the surface of the transparent substrate001is flat, the transparent bonding layer002may be optionally deposited on a surface of the transparent substrate001; in contrast, when the surface of the transparent substrate001is roughened, the deposition of the transparent bonding layer002thereon is required. The transparent bonding layer002may be subjected to a polishing treatment, so as to have a roughness lower than 1 nm. The polished transparent bonding layer002on a surface of the first conductivity type semiconductor layer003may be subjected to an activation treatment followed by bonding to the transparent substrate001or a polished and activated transparent bonding layer of the transparent substrate001. The bonding between the polished transparent bonding layer002and the transparent substrate001may be formed at a high temperature and a high pressure.

The first conductivity type semiconductor layer003is disposed on the transparent bonding layer002opposite to the transparent substrate001. The light-emitting layer004is disposed on the first conductivity type semiconductor layer003opposite to the transparent bonding layer002. The second conductivity type semiconductor layer005is disposed on the light-emitting layer004opposite to the first conductivity type semiconductor layer003. In this embodiment, the first conductivity type semiconductor layer003is made of GaP, the light-emitting layer004has an emission wavelength (λ) of 630 nm, and the second conductivity type semiconductor layer005is made of aluminum gallium indium phosphide (AlGaInP).

In this embodiment, portions of the light-emitting layer004and the second conductivity type semiconductor layer005are etched, such that a portion of the first conductivity type semiconductor layer003is exposed from the light-emitting layer004and the second conductivity type semiconductor layer005, and is electrically connected to the electrode010as described hereinafter.

The first transparent dielectric layer007is disposed on the second conductivity type semiconductor layer005opposite to the light-emitting layer004. The first transparent dielectric layer007may be formed using plasma enhanced chemical vapor deposition (PECVD). The first transparent dielectric layer007may be made of SiO2, silicon oxynitride (SiNxOy), or a combination thereof. In this embodiment, the first transparent dielectric layer007is made of SiO2, and the refractive index of the first transparent dielectric layer007is 1.45. The first transparent dielectric layer007may have a thickness greater than λ/2n1, wherein n1is a refractive index of the first transparent dielectric layer007. In this embodiment, the first transparent dielectric layer007may have a thickness ranging from 1.8 μm to 2.2 μm.

The second transparent dielectric layer006is disposed between the first transparent dielectric layer007and the second conductivity type semiconductor layer005. The second transparent dielectric layer006may be deposited on the second conductivity type semiconductor layer005using PECVD. The second transparent dielectric layer006may be made of silicon nitride (SiNx), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), or combinations thereof. The second transparent dielectric layer006may have a thickness of mλ/4n2, wherein m is an odd number, n2is a refractive index of the second transparent dielectric layer006, and n2is greater than n1(the refractive index of the first transparent dielectric layer007). In this embodiment, the second transparent dielectric layer006is made of SiNx, the refractive index of the second transparent dielectric layer006is 1.96, and the thickness of the second transparent dielectric layer006is 78 nm. The refractive index n2(e.g., 1.96) of the second transparent dielectric layer006may be greater than that of the first transparent dielectric layer007(e.g., 1.45), and lower than that of the second conductivity type semiconductor layer005(e.g., 3.29). In some embodiments, each of the first transparent dielectric layer007and the second transparent dielectric layer006may have a density greater than that of the DBR structure008.

Since the thickness of the first transparent dielectric layer007is relatively large, a variation in the thickness of the first transparent dielectric layer007may range from −10% to 10% according to production control standard. Such variation in the thickness of the first transparent dielectric layer007may be about 200 nm, which is greater than λ/4n1(108 nm in this embodiment), and adversely affects the reflectance of the DBR structure008as described hereinafter and production stability of the flip-chip LEDs.

The DBR structure008is disposed on the first transparent dielectric layer007opposite to the second transparent dielectric layer006. The DBR structure008may be deposited on the first transparent dielectric layer007using plasma-assisted electron beam evaporation or magnetron sputtering. The DBR structure008includes plural sets of a first light-transmissive layer and a second light-transmissive layer stacked on each other (not shown), and a refractive index of the first light-transmissive layer is greater than that of the second light-transmissive layer. The first light-transmissive layer may be made of TiO2, Ta2O5, or a combination thereof. The second light-transmissive layer may be made of SiO2, magnesium fluoride (MgF2), aluminum oxide (Al2O3), or combinations thereof. A total set number of the first light-transmissive layer and the second light-transmissive layer may range from 3 to 10. In this embodiment, the first light-transmissive layer is made of TiO2and has a thickness of 68 nm, the second light-transmissive layer is made of SiO2and has a thickness of 108 nm, and the total set number of the first light-transmissive layer and the second light-transmissive layer is 5. In some embodiments, the DBR structure008includes a contact layer (not shown) in contact with the first transparent dielectric layer007, and the contact layer has a refractive index greater than that of the first transparent dielectric layer007and is made of TiO2, Ta2O5, or a combination thereof. In this embodiment, the contact layer of the DBR structure008in contact with the first transparent dielectric layer007is made of TiO2, and has a thickness of λ/4n0(nc: a refractive index of the contact layer).

In this embodiment, by having the second transparent dielectric layer006, the first transparent dielectric layer007, the second transparent dielectric layer006, and the second conductivity type semiconductor layer005cooperate to form an anti-reflective coating structure, such that a light emitted from the light-emitting layer004is directed out of the first transparent dielectric layer007, and enters into the DBR structure008, preventing the reflectance of the DBR structure008from being adversely affected by the variation in the thickness of the first transparent dielectric layer007, as shown inFIG.4. The second transparent dielectric layer006fully covers the second conductivity type semiconductor layer005, the light-emitting layer004, and the first conductivity type semiconductor layer003. The first transparent dielectric layer007covers the second transparent dielectric layer006, to thereby insulate the first conductivity type semiconductor layer003, the light-emitting layer004, and the second conductivity type semiconductor layer005. In such case, after etching, exposed sidewalls of the second conductivity type semiconductor layer005and the light-emitting layer004are also covered by the second transparent dielectric layer006.

The third transparent dielectric layer009is disposed on the DBR structure008opposite to the first transparent dielectric layer007. The third transparent dielectric layer009may be formed using plasma-assisted electron beam evaporation or magnetron sputtering. The third transparent dielectric layer009has a refractive index greater than that of a distal layer of the DBR structure008in contact with the third transparent dielectric layer009and distal from the first transparent dielectric layer007. The distal layer of the DBR structure008in contact with the third transparent dielectric layer009may be made of SiO2. The third transparent dielectric layer009is made of SiNx, TiO2, Ta2O5, or combinations thereof. The third transparent dielectric layer009may have a thickness ranging from kλ/4n3to (k+1)λ/4n3, wherein n3is a refractive index of the third transparent dielectric layer009, and k is an odd number. In this embodiment, the third transparent dielectric layer009is made of TiO2, has a refractive index of 2.28, and has a thickness of 95 nm. Another contact layer (i.e., the distal layer) of the DBR structure008in contact with the third transparent dielectric layer009is SiO2.

With the third transparent dielectric layer009having the refractive index greater than that of the air, a light directed out of the DBR structure008and transmitted to an interface between the third transparent dielectric layer009and the air may be effectively reflected. Since the refractive index of the distal layer of the DBR structure008in contact with the third transparent dielectric layer009is lower than that of the third transparent dielectric layer009, such distal layer of the DBR structure008, the third transparent dielectric layer009, and the electrodes010,011in contact with the third transparent dielectric layer009may cooperate to form an anti-reflective coating structure, which will adversely affect reflection of light at the electrodes010,011. In order to avoid formation of the abovementioned anti-reflective coating structure, the thickness of the third transparent dielectric layer009may be increased (e.g., greater than λ/4n3), thereby increasing reflection of light transmitted to the electrodes010,011, and the interface between the third transparent dielectric layer009and the air, as shown inFIG.5.

The electrodes010,011are disposed on the DBR structure008, and are spaced apart from each other. In this embodiment, the flip-chip light-emitting diode may further include two through holes021,022that are spaced apart from each other, and that penetrate through the third transparent dielectric layer009, the DBR structure008, the first transparent dielectric layer007and the second transparent dielectric layer006to terminate at the first conductivity type semiconductor layer003and the second conductivity type semiconductor layer005, respectively. The electrodes010,011are electrically connected to the first conductivity type semiconductor layer003and the second conductivity type semiconductor layer005through the through holes021,022, respectively. The through holes021,022may be formed using well-known techniques such as photolithography and dry etching. Each of the electrodes010,011may be formed as a multi-layered metal structure. In some embodiments, each of the electrodes010,011may have a contact layer that is in contact with the third transparent dielectric layer009and that is made of aluminum (Al), gold (Au), platinum (Pt), silver (Ag), or combinations thereof. A surface of the contact layer of the electrodes010,011is in contact with the DBR structure008, and acts as a reflector.

Referring toFIG.6, a second embodiment of the flip-chip LED according to the present disclosure is generally similar to the first embodiment, except for the following differences.

First, in the second embodiment, a distal layer of the DBR structure008distal from the first transparent dielectric layer007is made of TiO2having a high refractive index.

In addition, the flip-chip LED further includes a transparent conducting layer201which is disposed between the electrodes010,011and the DBR structure008and which has a refractive index lower than that of the distal layer of the DBR structure008distal from the first transparent dielectric layer007and in contact with the transparent conducting layer201. The transparent conducting layer201may be made of indium zinc oxide (IZO), indium tin oxide (ITO), aluminum zinc oxide (AZO) or combinations thereof, and may be formed by evaporation. The transparent conducting layer201may have a thickness of kλ/4n, wherein n is a refractive index of the transparent conducting layer201and k is an odd number. In this embodiment, the refractive index of the transparent conducting layer201is 2.0, and the thickness of the transparent conducting layer201is 79 nm. In addition, as described above in the first embodiment, each of the electrodes010,011may be formed as a multi-layered metal structure. In the second embodiment, each of the electrodes010,011may have a contact layer that is in contact with the transparent conducting layer201and that is made of Al, Au, Pt, Ag, or combinations thereof, so as to act as a reflector.

The distal layer of the DBR structure008, the transparent conducting layer201, and the electrodes010,011cooperate to form a reflector structure having a high reflectance.

Referring toFIG.7, a third embodiment of the flip-chip LED according to the present disclosure is generally similar to the first embodiment, except for the following differences.

First, in the third embodiment, the third transparent dielectric layer009has a refractive index lower than that of a distal layer (i.e., the contact layer) of the DBR structure008in contact with the third transparent dielectric layer009and distal from the first transparent dielectric layer007. The third transparent dielectric layer009may be made of SiO2, MgF2, Al2O3, and combinations thereof. In this embodiment, the third transparent dielectric layer009is made of SiO2, has a refractive index of 1.45, and has a thickness of λ/4n3(108 nm in this embodiment).

Second, a contact layer (not shown) of the DBR structure008in contact with the third transparent dielectric layer009is made of TiO2. Such contact layer of the DBR structure008is formed by evaporation at a high temperature of at least 300° C., followed by annealing for a time period ranging from 350 seconds to 500 seconds, so as to provide the contact layer (not shown) of the DBR structure008with an etching selectivity with respect to the third transparent dielectric layer009.

The third transparent dielectric layer009is disposed between the electrodes010,011and the DBR structure008. The formation of the third transparent dielectric layer009may involve depositing a transparent dielectric layer on the DBR structure008, forming the electrodes010,011, and then etching the transparent dielectric layer through the electrodes010,011that serve as masks to expose the DBR structure008, so as to form the third transparent dielectric layer009.

The DBR structure of the conventional flip-chip LED has fewer pairs of the first light-transmissive layer and the second light-transmissive layer stacked on each other, such that the spectral reflectance of the flip-chip LED might be adversely affected by a variation in the thickness of each layer of the flip-chip LED. Compared with the conventional flip-chip LED, the flip-chip LED of the present disclosure has the following advantages:

1. The first and second transparent dielectric layers can fully cover the second conductivity type semiconductor layer, the light-emitting layer, and the first conductivity type semiconductor layer, so as to prevent short-circuit caused by a solder paste being in contact with a semiconductor material of the flip-chip LED during packaging.
2. With the second transparent dielectric layer, the first transparent dielectric layer, the second transparent dielectric layer, and the second conductivity type semiconductor layer cooperate to form an anti-reflective coating structure, such that a light emitted from the light-emitting layer is directed out of the first transparent dielectric layer, and enters into the DBR structure, so as to prevent the reflectance of the flip-chip LED from being adversely affected by the variation in the thickness of the first transparent dielectric layer, thereby enlarging a process window for the flip-chip LED, and being conducive for providing stability of mass production of the flip-chip LED.
3. By increasing the thickness of the third transparent dielectric layer (e.g., greater than λ/4n3), the anti-reflective coating structure formed by the third transparent dielectric layer and the electrodes may be avoided, such that a light emitted from the light-emitting layer can be effectively reflected when transmitting to the electrodes and an interface between the DBR structure and the air.
4. With the transparent conducting layer disposed between the electrodes and the distal layer of the DBR structure distal from the first transparent dielectric layer, the distal layer of the DBR structure, the transparent conducting layer, and the electrodes cooperate to form a reflector structure without affecting reflection of a light transmitted to the interface the DBR structure and the air.

In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure.

While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.