CN111326409B - Laser lift-off method and epitaxial structure of light-emitting diode devices on sapphire substrate - Google Patents

Abstract

The invention provides a laser lift-off method and an epitaxial structure of a light-emitting diode device on a sapphire substrate, which solves the problem of low product yield caused by shock waves in the process of laser lift-off of the sapphire substrate in the prior art. The laser lift-off method includes growing a sacrificial layer on a sapphire substrate, the sacrificial layer including a nitride-based semiconductor layer; implanting ions into the sacrificial layer, the ions are reducing ions, which are generated by combining with electrons in the nitride-based semiconductor layer when heated gas; growing the epitaxial structure of the light emitting diode device on the surface of the sacrificial layer; irradiating the sacrificial layer through the sapphire substrate with a laser to decompose it, so as to separate the sapphire substrate and the epitaxial structure of the light emitting diode device.

Description

Laser lift-off method and epitaxial structure of light-emitting diode devices on sapphire substrate

technical field

The invention relates to the technical field of preparation of light-emitting diodes, in particular to a laser lift-off method and an epitaxial structure of a light-emitting diode device on a sapphire substrate using the method for substrate lift-off.

Background technique

During the preparation of light-emitting diodes, it is usually necessary to remove the sapphire substrate by using laser lift-off technology, so as to transfer the epitaxial structure of the light-emitting diode device to the target substrate. When the laser is irradiated, a shock wave will be generated at the peeling interface, and the shock wave will generate a GP-level shock pressure, which will cause cracks in the epitaxial structure of the light-emitting diode device, resulting in product failure and lower product yield.

Contents of the invention

In view of this, the embodiments of the present invention are dedicated to providing a laser lift-off method and an epitaxial structure of a light-emitting diode device on a sapphire substrate, so as to solve the problem of low product yield caused by shock waves during laser lift-off of a sapphire substrate in the prior art.

One aspect of the present invention provides a laser lift-off method, comprising: growing a sacrificial layer on a sapphire substrate, the sacrificial layer including a nitride-based semiconductor layer; implanting ions into the sacrificial layer, the ions are reducing ions, and heated with nitrogen Combination of electrons in the chemical semiconductor layer to generate gas; grow the epitaxial structure of the light-emitting diode device on the surface of the sacrificial layer; irradiate the sacrificial layer with a laser through the sapphire substrate to decompose it, so as to separate the sapphire substrate and the epitaxial structure of the light-emitting diode device .

Optionally, implanting ions into the sacrificial layer includes: uniformly implanting ions into the sacrificial layer, so that the concentration of ions in the sacrificial layer is the same.

Optionally, the implanted ion concentration is 1×10 ¹⁵ -1×10 ¹⁸ Ions/cm ² .

Optionally, implanting ions into the sacrificial layer includes: the sacrificial layer includes alternately arranged first regions and second regions; respectively implanting ions into the first regions and the second regions using a mask, so that the ion concentration in the first region is high The ion concentration in the second region.

Optionally, growing the epitaxial structure of the light emitting diode device on the surface of the sacrificial layer includes: growing the epitaxial structure of the light emitting diode device on the surface of the second region of the sacrificial layer.

Optionally, implanting ions into the sacrificial layer includes: implanting ions into the sacrificial layer according to a predetermined depth, so as to form a contact layer and an ion implantation layer stacked one above the other.

Optionally, the nitride-based semiconductor layer includes a gallium nitride layer or an aluminum nitride layer.

Optionally, the ions include hydrogen ions, ammonia ions, argon ions.

According to another aspect of the present invention, there is also provided an epitaxial structure of a light emitting diode device on a sapphire substrate, comprising: a sapphire substrate; an epitaxial structure of a light emitting diode device grown on the sapphire substrate; and a sacrificial layer located on the sapphire substrate Between the bottom and the epitaxial structure of the light-emitting diode device, there are implanted ions, which are reducing ions, which are heated and combined with electrons in the nitride-based semiconductor layer to form gas.

Optionally, the concentrations of ions in the sacrificial layers are the same.

Optionally, the sacrificial layer includes a first region and a second region arranged at intervals, and the ion concentrations of the first region and the second region are different.

According to the laser lift-off method and the epitaxial structure of the light-emitting diode device on the sapphire substrate provided by the present invention, by implanting ions in the sacrificial layer, the strength of the sacrificial layer is reduced, so that the sacrificial layer is more likely to undergo a decomposition reaction under laser irradiation, so that it can be used The lower-intensity laser is used for peeling, that is, the intensity threshold of the laser is reduced, which can reduce the damage caused by the shock wave generated during the laser peeling process and improve the product yield.

Description of drawings

FIG. 1 is a flowchart of a laser lift-off method provided by an embodiment of the present invention.

2a-2d are schematic diagrams of device structures sequentially formed during the laser lift-off process according to the method shown in FIG. 1 provided by an embodiment of the present invention.

FIG. 3 is a flowchart of a laser lift-off method provided by another embodiment of the present invention.

4a-4b are schematic diagrams of the device structure formed when the laser lift-off process is performed according to the method shown in FIG. 3 according to an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

FIG. 1 is a flowchart of a laser lift-off method provided by an embodiment of the present invention. As shown in Figure 1, the laser lift-off method 100 includes:

Step S110, growing a sacrificial layer on the sapphire substrate, the sacrificial layer including a nitride-based semiconductor layer.

The nitride-based semiconductor layer refers to a semiconductor film layer that can undergo a decomposition reaction to generate nitrogen gas under laser irradiation, such as a gallium nitride layer or an aluminum nitride layer.

Step S120 , implanting ions into the sacrificial layer, the ions are reducing ions, which are heated and combine with electrons in the nitride-based semiconductor layer to generate gas.

The ions here can be, for example, hydrogen ions, ammonia ions, argon ions, or any other rare gas ions.

Step S130, growing an epitaxial structure of a light emitting diode device on the surface of the sacrificial layer. The light-emitting diode device epitaxial structure includes an n-type gallium nitride layer, an active layer, a p-type gallium nitride layer, and a contact layer between the sacrificial layer and the n-type gallium nitride layer stacked in sequence.

Step S140 , irradiating the sacrificial layer with a laser through the sapphire substrate to decompose it, so as to separate the sapphire substrate and the epitaxial structure of the light emitting diode device.

The sapphire substrate and the sacrificial layer have different absorption efficiencies for laser light. Therefore, there must be a certain wavelength of laser light that can penetrate the substrate without any impact on it (that is, the substrate is transparent to the laser light of this specific wavelength. ), but it can cause the sacrificial layer to undergo a decomposition reaction. For example, the sacrificial layer of the nitride-based semiconductor material can be decomposed to generate nitrogen gas under the irradiation of the laser of this specific wavelength, thereby realizing the separation between the sapphire substrate and the epitaxial structure of the light-emitting diode device. .

Such as the bandgap energy of sapphire substrate 11 is 9.9eV, when the material of sacrificial layer 12 is gallium nitride, because the bandgap energy of gallium nitride is 3.39eV, can utilize photon energy at this moment to be 5eV (between sapphire substrate Between the bottom and the gallium nitride), the laser with a wavelength of 248nm passes through the sapphire substrate 11 to irradiate the gallium nitride layer, so that the gallium nitride layer undergoes a decomposition reaction, thereby realizing the peeling off of the sapphire substrate 11 . When the material of the sacrificial layer 12 is gallium nitride, the bandgap energy of aluminum nitride is 6.1eV. At this time, the photon energy can be 6.4eV (between the sapphire substrate and the gallium nitride layer), and the wavelength is 193nm. The laser irradiates the aluminum nitride layer, so that the aluminum nitride layer undergoes a decomposition reaction, thereby realizing the peeling off of the sapphire substrate 11 .

According to the laser lift-off method provided in this embodiment, by implanting ions in the sacrificial layer, when the laser irradiates the sacrificial layer, once the ions are heated, they will combine with electrons in the nitride-based semiconductor layer to generate gas overflow, thereby A microcavity structure is formed in the layer. In this case, on the one hand, the stable structure of the nitride-based semiconductor layer is destroyed because the ions absorb the electrons in the nitride-based semiconductor layer; on the other hand, the generation of the microcavity structure makes the nitride-based semiconductor structure loose, The combination of the two factors makes the strength of the nitride-based semiconductor layer relatively lower, that is, the strength of the sacrificial layer is reduced.

The reduction in the strength of the sacrificial layer further makes the sacrificial layer more prone to decomposition reactions under the irradiation of laser light, so that the laser with lower intensity can be used for peeling, that is, the intensity threshold of the laser is reduced, and the damage caused by the shock waves generated during the laser peeling process can be reduced. Damage, improve product yield.

2a-2d are schematic diagrams of device structures sequentially formed during the laser lift-off process according to the method shown in FIG. 1 provided by an embodiment of the present invention.

According to step S110 , referring to FIG. 2 a , first a sacrificial layer is grown on the sapphire substrate 11 , and the sacrificial layer is a gallium nitride sacrificial layer 12 .

According to step S120, referring to FIG. 2b, ions are implanted into the gallium nitride sacrificial layer 12, and the ions are hydrogen ions.

According to step S130 , referring to FIG. 2 c , an epitaxial structure 13 of a light emitting diode device is grown on the surface of the gallium nitride sacrificial layer 12 .

Specifically, growing the light-emitting diode device epitaxial structure 13 on the surface of the gallium nitride sacrificial layer 12 may include: sequentially growing a contact layer 131, an n-type gallium nitride layer, an active layer, a p-type nitrogen oxide layer on the surface of the gallium nitride sacrificial layer 12 gallium nitride layer; then etch the isolation groove 132 on the surface of the p-type gallium nitride layer to expose the sacrificial layer 12, so as to form the light-emitting diode device epitaxial structures 13 arranged at intervals; finally, on the top surface of the light-emitting diode device epitaxial structure 13 and A passivation layer 134, such as a silicon nitride layer, is deposited on the side. The passivation layer 134 is used to provide a closed working environment for the epitaxial structure of the light emitting diode device, and isolate it from the surrounding acid and alkali environment, water molecules, oxygen, etc. .

According to step S140, referring to FIG. 2d, the surface of the sapphire substrate 11 is scanned with a laser, and the laser penetrates the sapphire substrate 11 to irradiate the gallium nitride sacrificial layer 12 to decompose it, so that the sapphire substrate 11 and the light-emitting diode The device epitaxial structure 13 is separated.

According to the laser lift-off method provided in this embodiment, hydrogen ions are implanted into the gallium nitride sacrificial layer 12. When the laser irradiates the gallium nitride sacrificial layer 12, once the hydrogen ions are heated, they will combine with the hydrogen ions in the gallium nitride sacrificial layer 12. The electrons combine to generate hydrogen gas overflow, thereby forming a microcavity structure in the sacrificial layer. In this case, on the one hand, the stable structure of the GaN sacrificial layer 12 is destroyed due to hydrogen ions absorbing the electrons in the GaN sacrificial layer 12; on the other hand, the generation of the microcavity structure makes the GaN sacrificial layer 12 The structure becomes loose, and the combined effect of the two factors makes the strength of the gallium nitride sacrificial layer 12 relatively lower. The reduction in the strength of the sacrificial layer further makes the sacrificial layer more prone to decomposition reactions under the irradiation of laser light, so that the laser with lower intensity can be used for peeling, that is, the intensity threshold of the laser is reduced, and the damage caused by the shock waves generated during the laser peeling process can be reduced. Damage, improve product yield.

In one embodiment, referring to FIG. 2c, when the sacrificial layer 12 and the contact layer 131 in the epitaxial structure 13 of the LED device are film layers of the same material, for example, the materials of the sacrificial layer 12 and the contact layer 131 are both gallium nitride. , in this case, the sacrificial layer 12 and the contact layer 131 can be prepared at one time.

Specifically, step S120 and step S130 are implemented together as follows: firstly, ions are implanted into the sacrificial layer 12 according to a predetermined depth to form a contact layer 131 and an ion implantation layer stacked up and down, and the ion implantation layer is the laser lift-off process. secondly, an n-type gallium nitride layer, an active layer, and a p-type gallium nitride layer are sequentially prepared on the contact layer 131; thirdly, the light-emitting diode device epitaxial structure 13 is finally formed according to the subsequent preparation process of step S130.

In this way, the ion implantation layer (equivalent to the sacrificial layer 12 ) and the contact layer 131 can be prepared at one time, and the step of depositing the contact layer 131 in the process of preparing the epitaxial structure 13 of the light emitting diode device is omitted.

Those skilled in the art can understand that in this case, the thickness of the gallium nitride layer deposited on the sapphire substrate 11 should be the sum of the thicknesses of the sacrificial layer 12 and the gallium nitride contact layer 131 .

In one embodiment, as shown in FIG. 2 b , implanting ions into the sacrificial layer 12 according to step S120 includes: uniformly implanting ions into the sacrificial layer 12 so that the concentration of ions in the sacrificial layer 12 is the same. In this case, a constant-intensity laser can be used to scan at a constant speed to peel off the sapphire substrate 11 , which is easy for industrialization.

Considering that when the implanted ion concentration is too high, too many microcavities are formed, and the sapphire substrate will fall off directly during subsequent heating, which cannot provide support for the subsequent light-emitting diode device epitaxial structure 13; when the implanted ion concentration is too low, the formed If there are too few microcavities, the effect of lowering the laser threshold cannot be achieved. Therefore, in one embodiment, the implanted ion concentration is 1×10 ¹⁵ -1×10 ¹⁸ Ions/cm ² (Ions/cm ² represents the number of ions distributed on an area per square centimeter), so that the support can be satisfied at the same time. role and lower threshold requirements.

FIG. 3 is a flowchart of a laser lift-off method provided by another embodiment of the present invention. Comparing FIG. 1 and FIG. 3 , it can be seen that the difference between the laser lift-off method 300 provided in this embodiment and the laser lift-off method 100 shown in FIG. 1 lies only in the second step. The second step in this embodiment, that is, step S320 includes: the sacrificial layer includes first regions and second regions arranged alternately, and a mask is used to respectively implant ions into the first regions and the second regions, so that the first regions and the second regions The ion concentration of the second region is different.

By implanting ions of different concentrations in the alternately arranged first and second regions, for example, the ion concentration of the first region is higher than that of the second region, and the second region has a lower ion concentration than the first region due to the low ion concentration of the second region. The area is more difficult to decompose. In this case, it can be irradiated with a laser whose intensity is just enough to decompose the first area, and the second area will not be completely decomposed by irradiation, thereby retaining the cavity structure, which can be used for The gas shock wave generated in the decomposition process of the first region is buffered, thereby reducing the damage of the gas shock wave to the epitaxial structure of the light-emitting diode device. At the same time, the gas shock wave will further peel off the second region, so that the sapphire substrate in the second region is completely peeled off, that is to say, the sapphire substrate in the second region is peeled off by laser irradiation and gas shock in sequence.

According to the laser lift-off method provided in this embodiment, on the one hand, by implanting ions in the sacrificial layer, the laser intensity threshold is reduced. The principle for realizing this effect can refer to the analysis process of the laser lift-off method 100 shown in FIG. 1; on the other hand, By implanting ions with different concentrations in the adjacent area of the sacrificial layer, the damage to the epitaxial structure of the light-emitting diode device by the shock wave generated in the laser lift-off process is reduced, and the product yield is improved.

4a-4b are schematic diagrams of the device structure formed when the laser lift-off process is performed according to the method shown in FIG. 3 according to an embodiment of the present invention.

Referring to FIG. 4 a , first, according to step S310 , a sacrificial layer is grown on a sapphire substrate 41 , and the sacrificial layer is a gallium nitride sacrificial layer 42 . Then, according to step S320, the gallium nitride sacrificial layer 42 is divided into alternately arranged first regions 421 and second regions 422, and a mask is used to implant hydrogen ions into the first regions 421 and the second regions 422, so that the first The hydrogen ion concentration of a region 421 is higher than that of the second region 422 .

Referring to FIG. 4 b , according to step S330 , a light emitting diode device epitaxial structure 43 is grown on the surface of the second region 422 of the gallium nitride sacrificial layer 42 .

Specifically, growing the light-emitting diode device epitaxial structure 43 on the surface of the gallium nitride sacrificial layer 42 may include: sequentially growing a contact layer, an n-type gallium nitride layer, an active layer, a p-type nitride oxide layer on the surface of the gallium nitride sacrificial layer 42 gallium layer; then, the isolation groove 432 is etched on the surface of the p-type gallium nitride layer corresponding to the first region 421 of the gallium nitride sacrificial layer 42 to expose the sacrificial layer 42, that is, the light-emitting diode device epitaxial structure 43 corresponds to the gallium nitride sacrificial layer 42 in the second region 422 with low ion concentration to form light-emitting diode device epitaxial structures 43 arranged at intervals; finally, a passivation layer 434, such as silicon nitride, is deposited on the top and side surfaces of the light-emitting diode device epitaxial structures 43 layer, the passivation layer 434 is used to provide a sealed working environment for the epitaxial structure 43 of the light emitting diode device, and isolate it from the surrounding acid and alkali environment, water molecules, oxygen and the like.

According to step S340, the surface of the sapphire substrate 41 is scanned with a laser, and the laser penetrates the sapphire substrate 41 to irradiate the gallium nitride sacrificial layer 42 to decompose it, so that the sapphire substrate 41 and the light-emitting diode device epitaxial structure 43 separate.

According to the laser lift-off method provided in this embodiment, since the region with low ion concentration can use the cavity to buffer the gas shock wave generated by laser irradiation, the light-emitting diode device epitaxial structure 43 is arranged in the gallium nitride sacrificial layer 42 so that the ion concentration is low The region can further reduce the shock wave damage to the epitaxial structure 43 of the light emitting diode device, thereby further improving the product yield.

The present invention also provides an epitaxial structure of a light emitting diode device on a sapphire substrate. As shown in FIG. , and a sacrificial layer 12 located between the sapphire substrate 11 and the epitaxial structure 13 of the light-emitting diode device, the sacrificial layer 12 includes implanted ions, the ions are reducing ions, which are generated by combining with electrons in the nitride-based semiconductor layer when heated gas.

In one embodiment, as shown in Figure 2c, the ion concentrations in the sacrificial layer 12 are the same.

In one embodiment, as shown in FIG. 4 b , the sacrificial layer 22 includes alternately arranged first regions 421 and second regions 422 , and the ion concentrations of the first regions 421 and the second regions 422 are different.

For the detailed description of the epitaxial structure of the light emitting diode device on the sapphire substrate provided by the present invention, reference may be made to the description process of the above method, which will not be repeated here.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (6)

1. A laser stripping method, characterized in that, comprising: growing a sacrificial layer on a sapphire substrate, the sacrificial layer including a nitride-based semiconductor layer; Implanting ions into the sacrificial layer, the ions are reducing ions, and are heated to combine with electrons in the nitride-based semiconductor layer to generate gas; growing an epitaxial structure of a light emitting diode device on the surface of the sacrificial layer; irradiating the sacrificial layer with a laser through the sapphire substrate to decompose it, so as to separate the sapphire substrate and the epitaxial structure of the light emitting diode device; Wherein, the sacrificial layer includes alternately arranged first regions and second regions; implanting ions in the sacrificial layer includes: using a mask to respectively implant ions into the first region and the second region, so that all The ion concentration of the first region is higher than the ion concentration of the second region. 2. The laser lift-off method according to claim 1, wherein growing an epitaxial structure of a light-emitting diode device on the surface of the sacrificial layer comprises: An epitaxial structure of a light emitting diode device is grown on the surface of the second region of the sacrificial layer. 3. The laser lift-off method according to claim 1, wherein implanting ions in the sacrificial layer comprises: Ions are implanted into the sacrificial layer according to a predetermined depth to form a contact layer and an ion implantation layer stacked one above the other. 4. The laser lift-off method according to any one of claims 1-3, wherein the nitride-based semiconductor layer comprises a gallium nitride layer or an aluminum nitride layer; and/or, The ions include hydrogen ions, ammonia ions, and argon ions. 5. A light-emitting diode device epitaxial structure on a sapphire substrate, characterized in that it comprises: Sapphire substrate; an epitaxial structure of a light emitting diode device grown on the sapphire substrate; and a sacrificial layer, the sacrificial layer is located between the sapphire substrate and the epitaxial structure of the light-emitting diode device, including implanted ions, the ions are reducing ions, which are generated by combining with electrons in the nitride-based semiconductor layer when heated gas, the sacrificial layer includes a first region and a second region arranged at intervals, and the ion concentrations of the first region and the second region are different. 6 . The epitaxial structure of a light emitting diode device on a sapphire substrate according to claim 5 , wherein the concentrations of the ions in the sacrificial layers are the same.

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