SEMICONDUCTOR LIGHT-EMITTING DEVICE

A semiconductor light-emitting device includes a bonding substrate, a multi-layered metal unit, and a semiconductor lighting unit. The bonding substrate includes an upper surface and a lower surface opposite to the upper surface. The multi-layered metal unit is disposed on the upper surface of the bonding substrate such that an exposed region of the upper surface of the bonding substrate is exposed from the multi-layered metal unit. The semiconductor lighting unit is disposed on the multi-layered metal unit opposite to the bonding substrate. A method for manufacturing the semiconductor light-emitting device is also disclosed.

FIELD

The disclosure relates to a light-emitting device, and more particularly to a semiconductor light-emitting device with improved light-emitting efficiency and reliability.

BACKGROUND

In order to obtain a light-emitting diode (LED) chip with a high brightness, a high power or a high heat radiation rate, a conventional LED epitaxial structure grown on a growth substrate is transferred to a transferring substrate that includes a metal reflection layer or a metal bonding layer, and the growth substrate is then removed by a chemical wet etching process or a laser lift-off (LLO) process. Next, the transferred LED epitaxial structure disposed on the metal reflection layer or the metal bonding layer is partially etched to form a cutting channel. Afterwards, such LED epitaxial structure is cut along the cutting channel using a dicing saw or a laser beam, so as to obtain a plurality of the LED chips.

However, since use of the dicing saw might enlarge an area of the cutting channel, the resultant LED chips might be susceptible to damage (e.g., collapse). Application of the laser beam for cutting the LED epitaxial structure seems to be more promising than that of the dicing saw since the laser beam allows the separated LED chips to have a flat breaking surface and a relatively narrow cutting channel. However, a large amount of burnt metal impurities would be generated when the laser beam focuses on the metal reflection layer or the metal bonding layer during the cutting process. Such burnt metal impurities would sputter on a sidewall of an light-emitting layer of the LED chips, resulting in an electrical leakage of the light-emitting layer and a decreased brightness due to light emitted from the light-emitting layer being absorbed by such burnt metal impurities.

SUMMARY

An object of the disclosure is to provide a semiconductor light-emitting device that can alleviate at least one of the drawbacks of the prior art.

According to the disclosure, the semiconductor light-emitting device includes a bonding substrate, a multi-layered metal unit, and a semiconductor lighting unit.

The bonding substrate includes an upper surface and a lower surface opposite to the upper surface.

The multi-layered metal unit is disposed on the upper surface of the bonding substrate such that an exposed region of the upper surface of the bonding substrate is exposed from the multi-layered metal unit.

The semiconductor lighting unit is disposed on the multi-layered metal unit opposite to the bonding substrate.

Another object of the disclosure is to provide a method for manufacturing at least one semiconductor light-emitting device that can alleviate or eliminate at least one of the drawbacks of the prior art.

According to the disclosure, the method includes the following steps (a) to (d).

In step (a), a semiconductor light-emitting structure is provided and includes a bonding substrate, a multi-layered metal unit, and a semiconductor lighting unit. The bonding substrate has an upper surface and a lower surface opposite to the upper surface. The multi-layered metal unit is disposed on the upper surface of the bonding substrate. The semiconductor lighting unit is disposed on the multi-layered metal unit opposite to the bonding substrate.

In step (b), a portion of the semiconductor lighting unit is removed to form a first recess structure on the multi-layered metal unit.

In step (c), a portion of the multi-layered metal unit is removed along the first recess structure to form a second recess structure that extends through the multi-layered metal unit to expose an exposed region of the bonding substrate.

In step (d), the bonding substrate is diced along the exposed region of the bonding substrate, so as to obtain the semiconductor light-emitting device from the semiconductor light-emitting structure.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, a first embodiment of a semiconductor light-emitting device according to the present disclosure includes a bonding substrate2, a multi-layered metal unit3, and a semiconductor lighting unit5.

The bonding substrate2includes an upper surface21, a lower surface22opposite to the upper surface21, and a side surface23interconnecting the upper surface21and the lower surface22. A portion of the side surface23may be formed with a concave-convex structure231which may be formed from continuous or discontinuous explosion points generated by a laser cutting process as described below. In certain embodiments, the concave-convex structure231is located at a position that is relatively near one of the upper surface21and the lower surface22of the bonding substrate2, or at a center region of the side surface23of the bonding substrate2. In other embodiments, the concave-convex structure231extends to one of the upper surface21and the lower surface22of the bonding substrate2. A distance from the upper surface21to the concave-convex structure231may be one third to half of a distance from the upper surface to the lower surface22. The concave-convex structure231may have a roughness greater than that of the remaining region of the side surface23of the bonding substrate2. The bonding substrate2may be made of a non-metallic material, e.g., a semiconductor material. In certain embodiments, the bonding substrate2is an electrically conductive substrate that is configured to absorb a laser radiation during the laser cutting process. Examples of the electrically conductive substrate may include, but are not limited to, a nitride-based substrate, a silicon (Si) substrate (e.g., p-type silicon or n-type silicon substrate), and a silicon carbide (SiC) substrate.

The multi-layered metal unit3is disposed on the upper surface21of the bonding substrate2such that an exposed region211of the upper surface21of the bonding substrate2is exposed from the multi-layered metal unit3. That is, the multi-layered metal unit3and the bonding substrate2cooperate to form a stage structure (i.e., the exposed region211). The exposed region211of the upper surface21may have a width ranging from 2 μm to 10 μm, such as from 3 μm to 6 μm. The multi-layered metal unit3may include one of a bonding layer, a metal reflection layer, an ohmic contact layer, a blocking layer, and combinations thereof.

The bonding layer is disposed on the bonding substrate2for bonding the multi-layered metal unit3to the bonding substrate2. The bonding layer may be made of a metallic material (such as Au) that can electrically and mechanically connect to the bonding substrate2.

The ohmic contact layer is configured to form ohmic contact with the bonding substrate2. The ohmic contact layer may be made of a metallic material such as Au, Ti, and Al.

The metal reflection layer is configured to reflect a light emitted from, the semiconductor lighting unit5back thereto, and may include a conductive material with a high reflective index (e.g., at least 80%) to the light. For example, the metal reflection layer may include a metallic material such as a metal (e.g., Al, Au, or Ag) and a metal alloy thereof. In certain embodiments, the metal reflection layer is made of Au and has a predetermined thickness. The metal reflection layer and the ohmic contact layer may be made of an identical material.

The blocking layer is configured to prevent diffusion of metal atoms of the metal reflection layer into the semiconductor lighting unit5. The blocking layer may be made of a metallic material (e.g., Ti or Pt).

The semiconductor lighting unit5is disposed on the multi-layered metal unit3opposite to the bonding substrate2. In certain embodiments, the semiconductor lighting unit5is disposed on a portion of the multi-layered metal unit3, such that an exposed portion of the multi-layered metal unit3is exposed from the semiconductor lighting unit5. That is, the multi-layered metal unit3and the semiconductor lighting unit5cooperate to form another stage structure (i.e., the exposed portion of the multi-layered metal unit3) which may have a width ranging from 1.5 μm to 10 μm, such as from 3 μm to 8 μm. An area of a projection of the semiconductor lighting unit5on the bonding substrate2may be at least 50% (such as at least 70%, at least 80%, etc.) of an area of the upper surface21of the bonding substrate2.

The semiconductor lighting unit5may include a first-type contact layer and a second-type contact layer (not shown in the figures), and a light-emitting element51disposed between the first-type contact layer and the second-type contact layer. The term “first-type” refers to being doped with a first type dopant, and the term “second-type” refers to being doped with a second type dopant that is opposite in conductivity to the first type dopant. For instance, the first type dopant may be a p-type dopant, and the second type dopant may be an n-type dopant, and vice versa.

Each of the light-emitting element51, the first-type contact layer and the second-type contact layer may be made of a group III-V semiconductor material such as a binary semiconductor material (e.g., gallium arsenide (GaAs)-based material, gallium phosphide (GaP)-based material, or indium phosphide (InP)-based material), a ternary semiconductor material (e.g., indium gallium arsenide (InGaAs)-based material, indium gallium phosphide (InGaP)-based material, or aluminium gallium arsenide (AlGaAs)-based material), and a quaternary semiconductor compound (e.g., aluminium gallium indium phosphide (AlGaInP) -based material). The light-emitting element51may include a p-type cladding layer made of p-type AlGaInP-based material, an n-type cladding layer made of n-type AlGaInP-based material, and an active layer that is disposed between the p-type and n-type cladding layers, that is configured to emit a light having a predetermined wavelength, and that is made of an undoped AlGaInP-based material. The semiconductor lighting unit5may be first grown on a growth substrate made of a gallium arsenide (GaAs)-based material, and is then transferred to the bonding substrate2.

The semiconductor lighting unit5may further include a current spreading layer52disposed between the light-emitting element51and the multi-layered metal unit3. The current spreading layer51may be made of p-type GaP, and is adapted for spreading current around the p-type cladding layer. In certain embodiments, the light-emitting element51may be disposed on a portion of the current spreading layer52, such that an exposed portion of the current spreading layer52is exposed from the light-emitting element51, i.e., forming a stage.

The second-type contact layer is formed on a light extraction surface of the light-emitting element51, i.e., a surface of the n-type cladding layer that is opposite to the active layer. In certain embodiments, in order to increase the light emitting efficiency of the semiconductor light-emitting device, two opposite surfaces of the light-emitting element51and/or a side surface of the light-emitting element51are formed with a concave-convex portion. The concave-convex portion may be covered with a transparent insulating film.

The semiconductor light-emitting device may further include a transparent insulating layer4that is disposed between the semiconductor lighting unit5and the multi-layered metal unit3, and that may be formed as one of a single layer structure and a multi-layered structure.

The semiconductor light-emitting device may further include, between the first-type contact layer and the metal reflection layer of the multi-layered metal unit3, a dielectric layer (i.e., an insulating film), and an ohmic contact portion that is disposed on a region free of the dielectric layer and that is configured to electrically connect the first-type contact layer to the metal reflection layer.

Specifically, the dielectric layer is formed with a through hole that is defined by a hole-defining wall and that extends from the first-type contact layer and the metal reflection layer. The ohmic contact portion is formed on the hole-defining wall to electrically connect the first-type contact layer to the metal reflection layer. The ohmic contact portion may be made of a metal (such as Au and Zn), or a metal alloy (e.g., AuZn alloy).

The dielectric layer may be formed as a single layer structure, i.e., an insulating film made of silicon dioxide (SiO2) or silicon nitride (Si3N4). Alternatively, the dielectric layer may be formed as a multi-layered insulating structure, which may include multiple insulating films having different refractive indices. For example, the insulating films of the multi-layered insulating structure may have refractive indices that gradually decrease in a direction away from the light extraction surface of the light-emitting element51and/or the side surface of the light-emitting element51. Alternatively, the multi-layered insulating structure may include multiple pairs of insulating films, each pair containing a first insulating film (such as silicon dioxide (SiO2) film) and a second insulating film (such as silicon nitride (Si3N4) film) having a refractive index different from that of the first insulating film. The first insulating films and the second insulating films in the multi-layered insulating structure may be alternately stacked. In certain embodiments, the multi-layered insulating structure is a distributed bragg reflector (DBR) structure that includes multiple pairs of films, each pair containing a SiO2film having a predetermined thickness and a titanium oxide (TiO2) film having a predetermined thickness, and the SiO2films and the TiO2films are alternately stacked.

The semiconductor light-emitting device further includes a front metal electrode6and a conductive metal layer1(or a backside metal electrode).

The front metal electrode6is disposed on the second-type contact layer of the semiconductor lighting unit5opposite to the light-emitting element51, and is adapted to be bonded to a pad electrode of a pad through a wire. There are no particular limitations on the shape of the front metal electrode6. For example, the front metal electrode6may be in a circle shape (seeFIG. 7b) or in a polygonal shape (e.g., hexagon). The front metal electrode6is made of a metallic material (e.g., Au, Ge, or Ni) so as to form an ohmic contact with the n-type contact layer. The pad electrode that is in contact with a surface of the front metal electrode6may be made of a metallic material such as Ti and Au.

The conductive metal layer1is disposed on the lower surface22of the bonding substrate2, and is electrically connected to the bonding substrate2. The conductive metal layer1may be made of a metallic material such as Ti and Au. In this embodiment, the conductive metal layer1is made of Au.

Referring toFIGS. 3 to 7b, a method for manufacturing at least one of the semiconductor light-emitting device according to a second embodiment of this disclosure includes the following consecutive steps S1to S4. The second embodiment is generally similar to the first embodiment, except that in the second embodiment, an area of a projection of the transparent insulating layer4on the bonding substrate is the same as an area of a projection of the multi-layered metal unit3on the bonding substrate2(seeFIG. 7a).

In step S1, a semiconductor light-emitting structure as shown inFIG. 3is provided. The semiconductor light-emitting structure includes the conductive metal layer1, and the bonding substrate2, the multi-layered metal unit3, the transparent insulating layer4, the semiconductor lighting unit5and at least one front metal electrode6that are sequentially disposed on the conductive metal layer1.

In step S2, as shown inFIG. 4, a portion of the semiconductor lighting unit5is removed to form a first recess structure81on the multi-layered metal unit3.

To be specific, the semiconductor lighting unit5is subjected to a photolithography process which includes application of a photoresist layer on a surface of the semiconductor lighting unit5opposite to the bonding substrate2, light-exposure and development, etching treatment, and removal of the photoresist layer. The first recess structure81may extend through the semiconductor lighting unit5, and terminate at and expose the transparent insulating layer4. The etching treatment may be a dry etching process.

In step S3, as shown inFIG. 5, a portion of the multi-layered metal unit3is removed along the first recess structure81by, e.g. a photolithography process, to form a second recess structure82that extends through the multi-layered metal unit3so as to expose an exposed region of the bonding substrate2. The second recess structure82has a width that is greater than a width of the first recess structure81.

Specifically, the semiconductor lighting unit5(including a side wall of the first recess structure81) and a peripheral region of a bottom wall of the first recess structure81(i.e., a portion of the exposed transparent insulating layer4) are covered by a photoresist layer, so as to prevent the semiconductor lighting unit5from being etched and to avoid the loss of the light-emitting area in subsequent etching treatment. Then, the remaining portion of the first recess structure81(i.e., the uncovered portion of the transparent insulating layer4) and the multi-layered metal unit3are subjected to an etching treatment to expose the bonding substrate2. The etching treatment may include a dry etching process and/or a wet etching process depending on the materials to be removed. For example, the transparent insulating layer4and the current spreading layer52, if present, may be removed by a dry etching process. The multi-layered metal unit3may be removed by a wet etching process and a dry etching process. For instance, the metal reflection layer made of AuZn or Au is removed by the wet etching process, and the blocking layer made of Ti or Pt is removed by the dry etching process. By virtue of the etching treatment in this step which involves several etching processes as mentioned above, at least one of the multi-layered metal unit3, the transparent insulating layer4and the current spreading layer52(if present) may have an area that gradually changes (e.g., increase in size) in a direction towards the bonding substrate2. In one form, the multi-layered metal unit3is formed with an inclined side surface and has an area that gradually increases in a direction towards the bonding substrate2, and a projection of the transparent insulating layer4on the bonding substrate2is smaller than that of the multi-layered metal unit3(seeFIG. 6). With such structure, light emitted from a side surface of the semiconductor lighting unit5is capable of being reflected by the multi-layered metal unit3.

In step S4, the bonding substrate2is diced along the exposed region of the bonding substrate2, so as to obtain the semiconductor light-emitting device from the semiconductor light-emitting structure.

In this embodiment, step S4is implemented by a laser stealth dicing process. Specifically, as shown inFIGS. 7aand 7b, the bonding substrate2is first formed with a plurality of explosion points7corresponding in position to the exposed region of the upper surface21by focusing a laser beam inside the bonding substrate2. By virtue of adjusting the power of the laser beam, a distance from the upper surface21of the bonding substrate2to the explosion points7may be one third to half of a distance from the upper surface21to the lower surface22of the bonding substrate2. Next, the bonding substrate2of the semiconductor light-emitting structure is cut along the exposed region of the bonding substrate2to expose the explosion points7, so as to obtain the semiconductor light-emitting device from the semiconductor light-emitting structure. Since the explosion points7have decreased stress, the bonding substrate2may be formed with the concave-convex structure231at the side surface23which corresponds in position to the explosion points7.

In a variation of this embodiment, step S4is implemented by a laser scribing and breaking process, so as to reduce the area to be cut, thereby increasing an area of the light-emitting region and the light-emitting efficiency of the thus obtained semiconductor light-emitting device. Specifically, the exposed region of the bonding substrate2is first scribed using laser to form a recess that has a predetermined depth in the bonding substrate2. Next, the bonding substrate2is subjected to breaking using a saw along the recess, so as to obtain the semiconductor light-emitting device from the semiconductor light-emitting structure.

In summary, by virtue of forming the second recess structure82in the multi-layered metal unit3to expose the exposed region211of the upper surface21of the bonding substrate2therefrom, during the dicing step, the laser beam can be prevented from directly being focused on the multi-layered metal unit3, so as to avoid generation of burnt metal impurities that may sputter on the sidewall of the semiconductor lighting unit5. Therefore, electrical leakage of the semiconductor light-emitting device of this disclosure can be greatly reduced, so that light-emitting efficiency and stability of the semiconductor light-emitting device can be improved.