CN112151355A - Manufacturing method of gallium nitride self-supporting substrate - Google Patents

Abstract

The invention provides a method for manufacturing a gallium nitride self-supporting substrate, which comprises the following steps: 1) forming a gallium nitride template layer on a sapphire substrate; 2) epitaxially growing a first gallium nitride layer for the first time; 3) separating the sapphire substrate from the gallium nitride template layer to obtain a thin gallium nitride self-supporting substrate; 4) removing the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate; 5) epitaxially growing a second gallium nitride layer for the second time to obtain a thick gallium nitride self-supporting substrate; 6) and polishing, trimming and chamfering the thick self-supporting substrate to obtain the final gallium nitride self-supporting substrate. According to the invention, after the first epitaxy, the bottom layer part with the worst crystal quality is removed, and the second epitaxy is carried out after the removal, so that the dislocation density can be effectively reduced in the process of the second epitaxy thickening, the stress of the gallium nitride self-supporting substrate is reduced, the cracking rate in the process of the second epitaxy thickening is reduced, and the overall manufacturing yield of the self-supporting substrate is improved.

Description

Manufacturing method of gallium nitride self-supporting substrate

technical field

The invention belongs to the field of semiconductor material manufacturing, and in particular relates to a manufacturing method of a gallium nitride self-supporting substrate.

Background technique

At the end of the 20th century, in order to realize the preparation of electronic power devices with excellent performance such as high frequency, high efficiency and high power, the third-generation wide-bandgap semiconductor materials represented by gallium nitride accelerated the development process. Due to its excellent properties, gallium nitride (GaN) can be widely studied and used in the preparation of semiconductor devices that work under other special conditions, such as high-power and high-frequency devices. The crystal quality of the GaN epitaxial layer is the fundamental guarantee for the realization of high-performance GaN-based devices. The use of GaN single crystal substrate to realize homoepitaxy is the main way to improve the crystal quality of GaN epitaxial layer and GaN-based devices.

At present, the preparation technology of gallium nitride self-supporting substrate has become one of the biggest obstacles on its way forward. -offTechnique) separates the gallium nitride film from the sapphire, thereby obtaining a self-supporting gallium nitride substrate. In the process of epitaxial growth of gallium nitride, there is stress in the epitaxial film, and the thickness of the gallium nitride film grown on sapphire can only be less than 400 microns due to the stress, and it is easy to crack if grown too thick. The thickness of the supporting GaN substrate is too thin to be ground and polished to obtain the desired epitaxial surface.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for manufacturing a gallium nitride self-supporting substrate, which is used to solve the problem of cracks caused by large residual stress in the epitaxy process in the prior art, and improve the overall production yield.

In order to achieve the above purpose and other related purposes, the present invention provides a method for manufacturing a gallium nitride self-supporting substrate, the manufacturing method comprising the steps of: 1) providing a sapphire substrate, and forming gallium nitride on the sapphire substrate template layer; 2) epitaxially growing a first gallium nitride layer on the gallium nitride template layer for the first time; 3) using a laser lift-off process to separate the sapphire substrate from the gallium nitride template layer to obtain a thin gallium nitride self-supporting substrate; 4) removing the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate; 5) on the thin gallium nitride self-supporting substrate obtained in step 4) for a second time Epitaxially growing a second gallium nitride layer to obtain a thick gallium nitride self-supporting substrate; 6) polishing the thick self-supporting substrate to obtain a final gallium nitride self-supporting substrate.

Optionally, step 1) utilizes a metal organic chemical vapor deposition process to deposit the gallium nitride template layer, and the thickness of the gallium nitride template layer is between 2 microns and 10 microns.

Optionally, in step 2) the first epitaxial growth is performed on the gallium nitride template layer by a hydride vapor phase epitaxy process to form the first gallium nitride layer, and the first gallium nitride layer is The thickness is between 250 microns and 400 microns.

Optionally, step 4) removes the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate by using a physical method or a chemical method, and the thickness of the removed bottom layer part is between 25 microns and 150 microns. between.

Optionally, the removal rate of the bottom portion of the thin gallium nitride self-supporting substrate with the worst crystal quality is between 20 microns/hour and 100 microns/hour.

Optionally, the physical method includes one of laser ablation removal and plasma etching, and the chemical method includes one of phosphoric acid etching and alkali etching.

Optionally, the laser used in the laser ablation includes one of a gas laser, a solid-state laser and a semiconductor laser.

Optionally, the laser power is 2-15W.

Optionally, the etching gas selected for the plasma etching includes Cl ₂ and BCl ₃ .

Optionally, before performing the chemical method to remove the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate, it also includes forming a corrosion protection on the upper surface of the thin gallium nitride self-supporting substrate layer steps.

Optionally, step 5) uses a hydride vapor phase epitaxy process to perform a second epitaxial growth on the thin gallium nitride self-supporting substrate to form the second gallium nitride layer, the second gallium nitride layer The thickness is between 400 microns and 1000 microns.

Optionally, step 6) using grinding and polishing equipment to polish the thick self-supporting substrate multiple times, and then perform edge trimming and chamfering treatment to obtain a final gallium nitride self-supporting substrate, the final nitrogen The thickness of the gallium nitride free-standing substrate ranges from 300 microns to 1000 microns.

As mentioned above, the manufacturing method of the gallium nitride self-supporting substrate of the present invention has the following beneficial effects:

In the method for manufacturing a gallium nitride self-supporting substrate of the present invention, after the first epitaxy, the bottom layer with the worst crystal quality is removed by an optimized removal method, and the second epitaxy is performed after the removal. The dislocation density is effectively reduced during the second epitaxial thickening process, thereby reducing the stress of the gallium nitride self-supporting substrate, reducing the split rate during the second epitaxial thickening process, and improving the overall production yield of the self-supporting substrate.

By configuring the epitaxial thickness and removal thickness in each step, the present invention can further reduce the dislocation density and stress in the self-supporting substrate, and manufacture a gallium nitride self-supporting substrate suitable for industrial production. The field of manufacturing has broad application prospects.

Description of drawings

1 to 6 are schematic structural diagrams of each step of the manufacturing method of the gallium nitride self-supporting substrate according to Embodiment 1 of the present invention.

FIGS. 7 to 12 are schematic structural diagrams of each step of the manufacturing method of the gallium nitride self-supporting substrate according to Embodiment 2 of the present invention.

13 to 18 are schematic structural diagrams of each step of the manufacturing method of the gallium nitride self-supporting substrate according to Embodiment 3 of the present invention.

FIGS. 19 to 24 are schematic structural diagrams of each step of the manufacturing method of the gallium nitride self-supporting substrate according to Embodiment 4 of the present invention.

Component label description

101 Sapphire substrate

102 GaN template layer

103 Lower layer of the first gallium nitride layer

1031 The bottom part of the lower layer

1032 Top part of lower layer

104 Upper layer of the first gallium nitride layer

105 Second Gallium Nitride Layer

301 Acid Resistant Photoresist

302 Alkali Resistant Photoresist

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

When describing the embodiments of the present invention in detail, for the convenience of explanation, the cross-sectional views showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the protection scope of the present invention. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in the actual production.

For convenience of description, spatially relative terms such as "below," "below," "below," "below," "above," "on," etc. may be used herein to describe an element shown in the figures or The relationship of a feature to other components or features. It will be understood that these spatially relative terms are intended to encompass other directions of the device in use or operation than those depicted in the figures. In addition, when a layer is referred to as being 'between' two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

In the context of this application, descriptions of structures where a first feature is "on" a second feature can include embodiments in which the first and second features are formed in direct contact, and can also include further features formed over the first and second features. Embodiments between the second features such that the first and second features may not be in direct contact.

It should be noted that the diagrams provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the diagrams only show the components related to the present invention rather than the number, shape and the number of components in the actual implementation. For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

During the epitaxial growth of gallium nitride, stress exists in the epitaxial film, and the stress is mainly lattice mismatch stress and thermal mismatch stress. The lattice mismatch stress is mainly caused by the mismatch of the lattice constants of the sapphire substrate and the gallium nitride crystal; the thermal mismatch stress is mainly due to the different thermal expansion coefficients of the two, and the gallium nitride epitaxial wafer is above 800 ℃ Grown at high temperature, after the growth is completed and the temperature is lowered, the lattice shrinkage ratio of the two is very different, thus causing the lattices to restrain each other. Stress causes the thickness of the gallium nitride film grown on sapphire to be less than 400 microns, and it is easy to crack if grown too thick, so the thickness of the self-supporting gallium nitride substrate obtained after laser lift-off is too thin, which is not enough for grinding and polishing to obtain the desired epitaxial surface. To this end, it is necessary to continue epitaxial thickening growth to a sufficient thickness (usually more than 800 microns) on the self-supporting gallium nitride substrate after laser lift-off. In the process of thickening growth, some "growth stress" will inevitably be introduced. The dislocation density is the highest at the interface of sapphire and gallium nitride, and the further to the gallium nitride grown later, the lower the dislocation density inside, so that from the interface of sapphire and gallium nitride to the surface of the finally grown gallium nitride will be There is a gradient of dislocation density. The study found that as the growth thickness of gallium nitride increases, the dislocation density becomes more and more difficult to reduce. The dislocation density within 100 microns above the interface between sapphire and gallium nitride decreases much faster than that of gallium nitride grown later. This means that the dislocation density gradient within 100 microns above the sapphire and gallium nitride interface is much larger than the dislocation density of the later grown gallium nitride. The larger dislocation density within 100 microns above the sapphire and gallium nitride interface means that the residual stress in this layer of gallium nitride is relatively large, which limits the final growth thickness of gallium nitride, and if the growth is too thick, it will crack.

In order to solve the above problems, the present invention provides a method for fabricating a gallium nitride self-supporting substrate, the fabrication method comprising the steps of:

Step 1), providing a sapphire substrate, and forming a gallium nitride template layer on the sapphire substrate; for example, using a metal organic chemical vapor deposition process to deposit the gallium nitride template layer, the thickness of the gallium nitride template layer between 2 microns and 10 microns.

Step 2), growing a first gallium nitride layer on the gallium nitride template layer for the first time; for example, the first epitaxy can be performed on the gallium nitride template layer by a hydride vapor phase epitaxy process growing to form the first gallium nitride layer, and the thickness of the first gallium nitride layer is between 250 microns and 400 microns.

Step 3), using a laser lift-off process to separate the sapphire substrate from the gallium nitride template layer to obtain a thin gallium nitride self-supporting substrate.

Step 4), remove the bottom layer with the worst crystal quality in the thin gallium nitride self-supporting substrate, and the bottom layer with the worst crystal quality is the thin gallium nitride self-supporting substrate with the highest dislocation density part, which may comprise the gallium nitride template layer and part of the first gallium nitride layer, by removing the bottom part of the worst crystal quality, the remaining thin gallium nitride self-supporting substrate can be greatly reduced Therefore, the stress of the gallium nitride self-supporting substrate can be reduced during the second epitaxial thickening process, and the split rate of the second epitaxial thickening process can be reduced.

As an example, a physical method or a chemical method can be used to remove the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate, and the thickness of the removed bottom layer part is between 25 microns and 150 microns. The removal rate of the bottom portion of the thin gallium nitride self-supporting substrate with the worst crystal quality is between 20 micrometers/hour and 100 micrometers/hour. The physical method includes one of laser ablation removal and plasma etching. The laser used in the laser ablation includes one of a gas laser, a solid-state laser and a semiconductor laser. More preferably, the laser power can be selected from the group consisting of: 2-15W. The etching gases selected for the plasma etching include Cl ₂ and BCl ₃ . The chemical method includes one of phosphoric acid etching and alkali etching, and before the chemical method is performed to remove the bottom layer with the worst crystal quality in the thin gallium nitride self-supporting substrate, the method also includes nitriding the thin gallium nitride self-supporting substrate. The step of forming a corrosion protection layer on the upper surface of the gallium self-supporting substrate.

Step 5), a second epitaxial growth of a second gallium nitride layer on the thin gallium nitride self-supporting substrate obtained in step 4) to obtain a thick gallium nitride self-supporting substrate, for example, a hydride vapor phase epitaxy process can be used A second epitaxial growth is performed on the thin gallium nitride self-supporting substrate to form the second gallium nitride layer, and the thickness of the second gallium nitride layer is between 400 microns and 1000 microns.

Step 6), polishing the thick self-supporting substrate for several times to obtain a final gallium nitride self-supporting substrate. For example, grinding and polishing equipment can be used to polish the thick self-supporting substrate for many times, and then perform edge trimming and chamfering treatment to obtain the final gallium nitride self-supporting substrate, the final gallium nitride self-supporting substrate The thickness of the substrate ranges from 300 microns to 1000 microns.

Example 1

As shown in FIG. 1 to FIG. 6 , this embodiment provides a method for fabricating a gallium nitride self-supporting substrate, including the following steps:

As shown in FIG. 1 , step 1) is first performed, a sapphire substrate 101 is provided, and a 4-6 micron thick gallium nitride is epitaxially grown on the sapphire substrate 101 by using a metal organic chemical vapor deposition process MOCVD, as nitrogen for subsequent growth The gallium nitride template layer 102 .

As shown in FIG. 2 and FIG. 3 , then step 2) is performed, and a first gallium nitride layer with a total thickness of 250-400 μm is epitaxially epitaxially for the first time on the gallium nitride template layer 102 by a hydride vapor phase epitaxy process HVPE , the sapphire/gallium nitride composite substrate is obtained, and the first gallium nitride layer includes a lower layer 103 and an upper layer 104 .

As shown in FIG. 4 , step 3) is performed next, and laser lift-off (LLO for short) is performed: the sapphire/gallium nitride composite substrate is turned over so that the sapphire substrate 101 faces upward, and the sapphire substrate 101 faces upwards. The sapphire/gallium nitride interface is irradiated with a laser in an atmosphere to separate the sapphire substrate from the gallium nitride in the sapphire/gallium nitride composite substrate to obtain a thin gallium nitride self-supporting substrate, which includes a gallium nitride template layer 102 and the first gallium nitride layers 103 and 104 .

Wherein, the laser is one of a gas laser, a solid-state laser and a semiconductor laser, and the wavelength of the laser can be 355 nanometers or 266 nanometers.

As shown in FIG. 5, then proceed to step 4), using a laser to remove the part with the worst crystal quality in the thin gallium nitride self-supporting substrate obtained in 3), the removed part includes the gallium nitride layer template layer 102 and the first nitrogen The bottom layer portion 1031 of the lower layer 103 of the gallium nitride layer is removed with a total thickness of 25-150 microns, and the removal rate is between 20-100 microns/hour, for example, it can be 20 microns/hour, and the remaining part of the gallium nitride layer contains The top layer portion 1032 of the lower layer of the first gallium nitride layer and the upper layer 104 of the first gallium nitride layer, during this process, the gallium nitride template layer 102 is formed before the bottom layer portion 1031 of the lower layer 103 of the first gallium nitride layer. ablated. In this embodiment, a laser is used to remove the part with the worst crystal quality in the thin gallium nitride self-supporting substrate, which has the advantages of simple process, low process cost and high process efficiency.

Wherein, the laser is one of a gas laser, a solid-state laser and a semiconductor laser. The wavelength of the laser is less than or equal to 10.8 microns, and the power of the laser is 3.5W.

By removing the bottom part with the worst crystal quality, the stress in the remaining thin gallium nitride self-supporting substrate can be greatly reduced, so that the dislocation density and nitridation can be effectively reduced during the second epitaxial thickening process. The stress of the gallium self-supporting substrate reduces the splitting rate of the second epitaxial thickening process.

As shown in FIG. 6 , step 5) is performed next, and the thin gallium nitride self-supporting substrate obtained in 4) is turned over, and the second epitaxial growth 400 is performed on the upper layer 104 of the first gallium nitride layer by the hydride vapor phase epitaxy process HVPE. - 1000 micron thick second gallium nitride layer 105, resulting in a thick gallium nitride free-standing substrate.

Finally, step 6) is performed, and the thick self-supporting substrate obtained in step 5) is polished multiple times to a thickness of 300-1000 microns using a grinding and polishing equipment, and then edge trimming and chamfering are performed to obtain the final gallium nitride self-supporting substrate. end.

Example 2

As shown in FIGS. 7-12 , this embodiment provides a method for fabricating a gallium nitride self-supporting substrate, including the following steps:

As shown in FIG. 7 , step 1) is first performed, a sapphire substrate 101 is provided, and gallium nitride with a thickness of 4-6 microns is epitaxially grown on the sapphire substrate 101 by using the metal organic chemical vapor deposition process MOCVD to serve as nitrogen for subsequent growth The gallium nitride template layer 102 .

As shown in FIG. 8 and FIG. 9 , then step 2) is performed, and a first gallium nitride layer with a total thickness of 250-400 microns is epitaxially epitaxially for the first time on the gallium nitride template layer 102 by a hydride vapor phase epitaxy process HVPE , the sapphire/gallium nitride composite substrate is obtained, and the first gallium nitride layer includes a lower layer 103 and an upper layer 104 .

As shown in FIG. 10 , step 3) is performed next, and laser lift-off (LLO for short) is performed: the sapphire/gallium nitride composite substrate is turned over so that the sapphire substrate 101 faces upward, and the sapphire/gallium nitride composite substrate is turned upside down. The sapphire/gallium nitride interface is irradiated with a laser in an atmosphere to separate the sapphire substrate from the gallium nitride in the sapphire/gallium nitride composite substrate to obtain a thin gallium nitride self-supporting substrate, which includes a gallium nitride template layer 102 and the first gallium nitride layers 103 and 104 .

Wherein, the laser is one of a gas laser, a solid-state laser and a semiconductor laser, and the wavelength of the laser can be 355 nanometers or 266 nanometers.

As shown in FIG. 11 , proceed to step 4), using inductively coupled plasma etching (ICP etching) to completely remove the gallium nitride layer 103 with the worst crystal quality in the thin gallium nitride self-supporting substrate obtained in 3) The removal part includes the gallium nitride layer template layer 102 and the lower layer 103 of the first gallium nitride layer, the total thickness of the removal is 25-150 microns, and the removal rate is 20-100 microns/hour, for example, it can be 20 microns /hour, the remaining part of the gallium nitride layer is the upper layer 104 of the first gallium nitride layer. During this process, the gallium nitride template layer 102 is etched away before the lower layer 103 of the first gallium nitride layer. Wherein, in the ICP etching, Cl ₂ and BCl ₃ may be selected as etching gases. In this embodiment, inductively coupled plasma etching (ICP etching) is used to remove the part with the worst crystal quality in the thin gallium nitride self-supporting substrate, which has the advantages of high process precision and basically no residue.

By removing the bottom part with the worst crystal quality, the stress in the remaining thin gallium nitride self-supporting substrate can be greatly reduced, so that the dislocation density and nitridation can be effectively reduced during the second epitaxial thickening process. The stress of the gallium self-supporting substrate reduces the splitting rate of the second epitaxial thickening process.

As shown in FIG. 12, then step 5) is performed, the thin gallium nitride self-supporting substrate obtained in 4) is turned over, and the second epitaxial growth 400 is performed on the upper layer 104 of the first gallium nitride layer by the hydride vapor phase epitaxy process HVPE. - 700 micron thick second gallium nitride layer 105, resulting in a thick gallium nitride free-standing substrate.

Finally, step 6) is performed, and the thick self-supporting substrate obtained in step 5) is polished multiple times to a thickness of 300-1000 microns using a grinding and polishing equipment, and then edge trimming and chamfering are performed to obtain the final gallium nitride self-supporting substrate. end.

Example 3

As shown in FIGS. 13-18 , this embodiment provides a method for fabricating a gallium nitride self-supporting substrate, including the following steps:

As shown in FIG. 13 , step 1) is first performed, a sapphire substrate 101 is provided, and 4-6 μm thick gallium nitride is epitaxially grown on the sapphire substrate 101 by using the metal organic chemical vapor deposition process MOCVD, as the nitrogen for subsequent growth The gallium nitride template layer 102 .

As shown in FIG. 14 and FIG. 15 , step 2) is performed, and a first gallium nitride layer with a total thickness of 250-400 microns is epitaxially epitaxially for the first time on the gallium nitride template layer 102 by a hydride vapor phase epitaxy process HVPE , the sapphire/gallium nitride composite substrate is obtained, and the first gallium nitride layer includes a lower layer 103 and an upper layer 104 .

As shown in FIG. 16 , step 3) is performed next, and laser lift-off (LLO for short) is performed: the sapphire/gallium nitride composite substrate is turned over so that the sapphire substrate 101 faces upwards, and the sapphire substrate 101 faces upwards. The sapphire/gallium nitride interface is irradiated with a laser in an atmosphere to separate the sapphire substrate from the gallium nitride in the sapphire/gallium nitride composite substrate to obtain a thin gallium nitride self-supporting substrate, which includes a gallium nitride template layer 102 and the first gallium nitride layers 103 and 104 .

Wherein, the laser is one of a gas laser, a solid-state laser and a semiconductor laser, and the wavelength of the laser can be 355 nanometers or 266 nanometers.

As shown in FIG. 17, then proceed to step 4), spin-coating a certain thickness of acid-resistant photoresist 301 on the surface of the gallium nitride layer 104 of the thin gallium nitride self-supporting substrate, and develop it as a whole, as shown in FIG. 17 In order to prevent this surface from being affected by the subsequent chemical etching process, for example, the photoresist 301 can be positive or negative, and the thickness is greater than 2 microns to ensure its protective effect. Then, the thin composite substrate is immersed in a hot phosphoric acid solution to remove the part with the worst crystal quality. The removed part includes the template layer 102 of the gallium nitride layer and the lower layer 103 of the first gallium nitride layer, and the total thickness removed is 25-150 microns , the removal rate is between 20-100 μm/hour, for example, it can be 50 μm/hour, and the remaining part of the gallium nitride layer is the upper layer 104 of the first gallium nitride layer. During this process, the gallium nitride template layer 102 is etched away prior to the lower layer 103 of the first gallium nitride layer. Wherein, the temperature of the hot phosphoric acid is greater than 100°C, and the mass concentration is 70-90%. In this embodiment, the hot phosphoric acid solution is used to remove the part with the worst crystal quality, which has a very efficient removal rate and can greatly improve the overall process efficiency.

By removing the bottom part with the worst crystal quality, the stress in the remaining thin gallium nitride self-supporting substrate can be greatly reduced, so that the dislocation density and nitridation can be effectively reduced during the second epitaxial thickening process. The stress of the gallium self-supporting substrate reduces the splitting rate of the second epitaxial thickening process.

As shown in FIG. 18, then proceed to step 5), remove the photoresist 301 on the surface of the thin gallium nitride self-supporting substrate obtained in step 4), clean it, and then use the hydride vapor phase epitaxy process HVPE on the first nitrogen A second gallium nitride layer 105 with a thickness of 400-700 microns is epitaxially grown on the upper layer 104 of the gallium nitride layer to obtain a thick gallium nitride self-supporting substrate.

Finally, step 6) is performed, and the thick self-supporting substrate obtained in step 5) is polished multiple times to a thickness of 300-550 microns using a grinding and polishing equipment, and then trimming and chamfering are performed to obtain the final gallium nitride self-supporting substrate. end.

Example 4

As shown in FIGS. 19-24 , this embodiment provides a method for fabricating a gallium nitride self-supporting substrate, including the following steps:

As shown in FIG. 19 , step 1) is first performed, a sapphire substrate 101 is provided, and 4-6 μm thick gallium nitride is epitaxially grown on the sapphire substrate 101 by using the metal organic chemical vapor deposition process MOCVD, as nitrogen for subsequent growth The gallium nitride template layer 102 .

As shown in FIG. 20 and FIG. 21 , then step 2) is performed, and a first gallium nitride layer with a total thickness of 250-400 μm is epitaxially epitaxially for the first time on the gallium nitride template layer 102 by a hydride vapor phase epitaxy process HVPE , the sapphire/gallium nitride composite substrate is obtained, and the first gallium nitride layer includes a lower layer 103 and an upper layer 104 .

As shown in FIG. 22 , step 3) is performed next, and laser lift-off (LLO for short) is performed: the sapphire/gallium nitride composite substrate is turned over so that the sapphire substrate 101 faces upward, and the sapphire/gallium nitride composite substrate is turned upside down. The sapphire/gallium nitride interface is irradiated with a laser in an atmosphere to separate the sapphire substrate from the gallium nitride in the sapphire/gallium nitride composite substrate to obtain a thin gallium nitride self-supporting substrate, which includes a gallium nitride template layer 102 and the first gallium nitride layers 103 and 104 .

Wherein, the laser is one of a gas laser, a solid-state laser and a semiconductor laser, and the wavelength of the laser can be 355 nanometers or 266 nanometers.

By removing the bottom part with the worst crystal quality, the stress in the remaining thin gallium nitride self-supporting substrate can be greatly reduced, so that the dislocation density and nitridation can be effectively reduced during the second epitaxial thickening process. The stress of the gallium self-supporting substrate reduces the splitting rate of the second epitaxial thickening process.

As shown in FIG. 23, then proceed to step 4), spin coating a certain thickness of alkali-resistant photoresist 301 on the surface of the gallium nitride layer 104 of the thin gallium nitride self-supporting substrate, and develop it as a whole, as shown in FIG. 23 As shown, so that this surface is not affected by the subsequent chemical etching process, for example, the photoresist 301 can be a positive photoresist or a negative photoresist, and the thickness is greater than 2 microns to ensure its protective effect. Then, the thin composite substrate is immersed in potassium hydroxide solution to remove the part with the worst crystal quality. The removed part includes the template layer 102 of the gallium nitride layer and the lower layer 103 of the first gallium nitride layer, and the total thickness removed is 25-150 microns, the removal rate is between 20-100 microns/hour, for example, it can be 50 microns/hour, and the remaining part of the gallium nitride layer is the upper layer 104 of the first gallium nitride layer. During this process, the gallium nitride template Layer 102 is etched away prior to the underlying layer 103 of the first gallium nitride layer. Wherein, the temperature of the potassium hydroxide is greater than 60°C, and the molar concentration is 1-3 mol/L. In this embodiment, potassium hydroxide solution is used to remove the part with the worst crystal quality, which has a very efficient removal rate and can greatly improve the overall process efficiency.

As shown in FIG. 24, then proceed to step 5), remove the photoresist 301 on the surface of the thin gallium nitride self-supporting substrate obtained in step 4), clean it, and then use the hydride vapor phase epitaxy process HVPE on the first nitrogen A second gallium nitride layer 105 with a thickness of 400-1000 microns is epitaxially grown on the upper layer 104 of the gallium nitride layer to obtain a thick gallium nitride self-supporting substrate.

Finally, step 6) is performed, and the thick self-supporting substrate obtained in step 5) is polished multiple times to a thickness of 300-1000 microns using a grinding and polishing equipment, and then edge trimming and chamfering are performed to obtain the final gallium nitride self-supporting substrate. end.

As mentioned above, the manufacturing method of the gallium nitride self-supporting substrate of the present invention has the following beneficial effects:

In the method for manufacturing a gallium nitride self-supporting substrate of the present invention, after the first epitaxy, the bottom layer with the worst crystal quality is removed, and after the removal, the second epitaxy is performed, and the second epitaxy can be thickened in the second epitaxy. In the process, the dislocation density is effectively reduced, thereby reducing the stress of the gallium nitride self-supporting substrate, reducing the split rate of the second epitaxial thickening process, and improving the overall production yield of the self-supporting substrate.

Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can make modifications or changes to the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (12)

1. a preparation method of gallium nitride self-supporting substrate, is characterized in that, described preparation method comprises the steps: 1) providing a sapphire substrate, and forming a gallium nitride template layer on the sapphire substrate; 2) epitaxially growing a first gallium nitride layer on the gallium nitride template layer for the first time; 3) using a laser lift-off process to separate the sapphire substrate from the gallium nitride template layer to obtain a thin gallium nitride self-supporting substrate; 4) removing the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate; 5) secondly epitaxially growing a second gallium nitride layer on the thin gallium nitride self-supporting substrate obtained in step 4) to obtain a thick gallium nitride self-supporting substrate; 6) Polishing the thick free-standing substrate to obtain the final gallium nitride free-standing substrate. 2. The method for manufacturing a gallium nitride self-supporting substrate according to claim 1, wherein step 1) utilizes a metal organic chemical vapor deposition process to deposit the gallium nitride template layer, the gallium nitride template layer The thickness is between 2 microns and 10 microns. 3. The method for manufacturing a gallium nitride self-supporting substrate according to claim 1, wherein step 2) adopts a hydride vapor phase epitaxy process to carry out the first epitaxial growth on the gallium nitride template layer , forming the first gallium nitride layer, and the thickness of the first gallium nitride layer is between 250 microns and 400 microns. 4. The method for making a gallium nitride self-supporting substrate according to claim 3, wherein step 4) adopts a physical method or a chemical method to remove the worst crystal quality in the thin gallium nitride self-supporting substrate The bottom layer portion, the thickness of the removed bottom layer portion is between 25 microns and 150 microns. 5. The method for manufacturing a gallium nitride self-supporting substrate according to claim 4, wherein the removal rate of the bottom layer with the worst crystal quality in the thin gallium nitride self-supporting substrate is between 20 microns /hour-100 microns/hour. 6 . The method for manufacturing a gallium nitride self-supporting substrate according to claim 4 , wherein the physical method comprises one of laser ablation removal and plasma etching, and the chemical method comprises phosphoric acid etching. 7 . And one of alkali corrosion. 7 . The method for manufacturing a gallium nitride self-supporting substrate according to claim 6 , wherein the laser used in the laser ablation comprises one of a gas laser, a solid-state laser and a semiconductor laser. 8 . 8 . The method for manufacturing a gallium nitride self-supporting substrate according to claim 7 , wherein the laser power is 2-15W. 9 . 9 . The method for fabricating a gallium nitride self-supporting substrate according to claim 6 , wherein the etching gas selected for the plasma etching comprises Cl ₂ and BCl ₃ . 10 . 10 . The method for manufacturing a gallium nitride self-supporting substrate according to claim 6 , wherein: before performing the chemical method to remove the bottom layer part with the worst crystal quality in the thin gallium nitride self-supporting substrate. 11 . and further comprising the step of forming a corrosion protection layer on the upper surface of the thin gallium nitride self-supporting substrate. 11 . The method for manufacturing a gallium nitride self-supporting substrate according to claim 1 , wherein in step 5) a second epitaxy is performed on the thin gallium nitride self-supporting substrate by a hydride vapor phase epitaxy process. 12 . growing to form the second gallium nitride layer, and the thickness of the second gallium nitride layer is between 400 microns and 1000 microns. 12. The method for producing a gallium nitride self-supporting substrate according to claim 11, wherein in step 6) the thick self-supporting substrate is polished multiple times by using a grinding and polishing device, and then edge trimming and pouring are performed. Corner processing to obtain a final gallium nitride free-standing substrate, the final gallium nitride free-standing substrate having a thickness ranging from 300 microns to 1000 microns.

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