Separable multilayer gan substrate and method for separating the same, and method for manufacturing semiconductor chip

Abstract

The application discloses a separation method of a separable multi-layer GaN substrate. The separable multi-layer GaN substrate is immersed in an etching solution, so that a nitride sacrificial layer is immersed in the etching solution; a light source is provided, the light source irradiates a light beam to the separable multi-layer GaN substrate, the light beam forms a light spot on the nitride sacrificial layer through the GaN base layer; the light spot is moved, so that a moving track of the light spot meets the requirement of approaching from the edge to the center of the nitride sacrificial layer; wherein the light of the light source has an energy greater than the band gap of the nitride sacrificial layer and smaller than the band gap of the GaN base layer and the GaN functional layer, and the moving speed of the light spot meets the requirement that a nitride sacrificial layer region irradiated by the light spot can be etched by the etching solution. The GaN base layer after separation can be repeatedly used, and the manufacturing cost of a GaN device is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a multilayer GaN substrate and a manufacturing method thereof, and a manufacturing method of a semiconductor chip. BACKGROUND

[0002] GaN is a core and key material of the third generation semiconductor industry, has extremely high electro-optical conversion efficiency, low power consumption and other excellent performances, and is a core and foundation of future new generation of optoelectronic, power electronic and high-frequency microelectronic.

[0003] At present, the mainstream method for preparing self-supporting GaN substrate is hydride vapor phase epitaxy (HVPE), all reactions of which are carried out in a quartz tube of an HVPE device, and the reaction device is divided into two different temperature zones.

[0004] Firstly, the metal Ga is placed in the 850℃ temperature zone of the quartz tube, the substrate is placed in the 1050℃ temperature zone, and then the ammonia NH3 and hydrogen chloride gas HCl as reactants are introduced into the 850℃ temperature zone from the left end of the quartz tube, and the following chemical reaction occurs in this zone:

[0005] 2Ga(l)+2HCl(g)=2GaCl(g)+H2(g) (1-1)

[0006] The obtained reactant GaCl gas is guided into the 1050℃ high temperature zone by mixing a proper amount of H2 in N2 as a carrier gas, and reacts with NH3:

[0007] GaCl(g)+NH3(g)=GaN(s)+HCl(g)+H2(g) (1-2)

[0008] The two reactions generate GaN material, which constitutes the growth mechanism of HVPE epitaxial GaN. For different metal doping, the HCl gas is divided into two paths, one path reacts with gallium, and the other path reacts with doping metals (magnesium, iron, manganese, germanium, indium) to obtain a doping source, or SiH4 gas is used to realize silicon doping.

[0009] GaN thick film is epitaxially grown on a heterogeneous substrate by the HVPE device, and then self-supporting GaN substrate is obtained after substrate separation, shape processing, grinding and polishing. Since the growth process is a CVD reaction process, the utilization rate of raw materials is very low, and therefore the manufacturing cost of self-supporting GaN substrate is relatively high.

[0010] Secondly, the self-supporting GaN substrate is generally used for manufacturing high electron mobility transistors (HEMT), metal oxide semiconductor field effect transistors (MOSFET), blue-green light lasers (LD). The process generally adopts a metal organic vapor phase epitaxy method (MOCVD) to epitaxially grow a device structure on the self-supporting GaN substrate, and then prepares a required chip through electrode preparation, substrate thinning, and splitting processes. The process generally thins the 300-400 μm thick self-supporting GaN substrate to about 100 μm and then splits the substrate into chips.

[0011] The above process grinds away 200-300 μm thickness of the self-supporting GaN substrate, which is a significant waste in terms of manufacturing cost.

[0012] Therefore, it has become an industry choice to realize the reuse of the GaN substrate. However, the existing GaN substrate reuse technology mostly uses an electrochemical etching process, which has the following problems:

[0013] Firstly, the electrochemical etching process must be connected to an electrode by windowing the substrate, which is not only complex in process, but also destructive to the substrate itself;

[0014] Secondly, the gallium nitride is anisotropic, which causes the electrochemical etching to be anisotropic. If the etching selectivity is not controlled well, the upper and lower GaN layers will also be etched, resulting in damage to the substrate.

[0015] Thirdly, the GaN substrate is prone to introducing stress during the epitaxial device structure process, especially during the epitaxial process of blue-green light lasers. The anisotropic electrochemical etching causes the etching result to be not circumferentially symmetric, thereby causing the residual stress to be asymmetric, which will cause the upper and lower GaN layers to be cracked after etching, especially the upper GaN functional layer. SUMMARY

[0016] Therefore, the purpose of the present application is to provide a separation method for separating a multi-layer GaN substrate, which can actively control the etching direction when the GaN substrate is peeled off by inducing the etching direction, thereby solving the defects in the prior art.

[0017] To achieve the above-mentioned purpose, the present application provides a separation method for separating a multi-layer GaN substrate, which includes a GaN base layer, a nitride sacrificial layer located on the GaN base layer, and a GaN functional layer located on the nitride sacrificial layer. The separation method includes:

[0018] immersing the multi-layer GaN substrate in an etching liquid so that the nitride sacrificial layer is immersed in the etching liquid;

[0019] A light source is provided to irradiate a light beam to the separable multi-layer GaN substrate, the light beam forms a light spot on the nitride sacrificial layer through the GaN base layer;

[0020] The light spot is moved so that the moving track of the light spot meets the requirement of moving from the edge to the center of the nitride sacrificial layer;

[0021] The light source has light with energy greater than the band gap of the nitride sacrificial layer and less than the band gap of the GaN base layer and GaN functional layer, and the moving speed of the light spot meets the requirement that the area of the nitride sacrificial layer irradiated by the light spot can be corroded by the etching liquid.

[0022] Preferably, the light spot is a block light spot, and the moving track of the light spot is a spiral track moving from the periphery to the center and covering the whole area of the nitride sacrificial layer.

[0023] Preferably, the light spot is a ring light spot, and the moving track of the light spot is gradually shrinking from the outside to the inside and covering the whole area of the nitride sacrificial layer.

[0024] Preferably, the GaN base layer, GaN functional layer and nitride sacrificial layer are doped with different types and / or concentrations of impurities, so that the band gap of the nitride sacrificial layer is at least 0.9 eV different from the band gap of the GaN base layer and GaN functional layer.

[0025] Preferably, the nitride sacrificial layer is doped with In to form an InGaN or InAlN layer, the doping content of the doped In is greater than 20%, and the band gap of the doped nitride sacrificial layer is less than 2.5 eV.

[0026] Preferably, the GaN base layer is undoped, the GaN functional layer is doped with silicon or germanium, and the band gap of the GaN base layer and GaN functional layer is greater than or equal to 3.4 eV.

[0027] Preferably, the thickness of the GaN base layer is not less than 200 μm, and the dislocation density is not greater than 1x10 6 cm -2 .

[0028] According to the purpose of the present application, a separable multi-layer GaN substrate is also provided, which comprises a GaN base layer, a nitride sacrificial layer located on the GaN base layer, and a GaN functional layer located on the nitride sacrificial layer, and the band gap of the nitride sacrificial layer is less than the band gap of the GaN base layer and the GaN functional layer.

[0029] Preferably, the GaN base layer, GaN functional layer and nitride sacrificial layer are doped with different types and / or concentrations of impurities, so that the band gap of the nitride sacrificial layer is at least 0.9 eV less than the band gap of the GaN base layer and GaN functional layer.

[0030] Preferably, the nitride sacrificial layer is doped with In to form an InGaN or InAlN layer, and the doping content of In is greater than 20%, and the band gap of the doped nitride sacrificial layer is less than 2.5eV.

[0031] Preferably, the GaN base layer is undoped, and the GaN functional layer is doped with Si or Ge, and the band gap of the GaN base layer and the GaN functional layer is greater than or equal to 3.4eV.

[0032] According to the purpose of the present application, a semiconductor chip manufacturing method is also provided,

[0033] A separable multi-layer GaN substrate is provided as described above.

[0034] A device structure epitaxial layer is epitaxially grown on the GaN functional layer of the multi-layer GaN substrate by MOCVD process.

[0035] The separable multi-layer GaN substrate is separated by the separation method of the separable multi-layer GaN substrate as described above, and the GaN functional layer provided with the device structure epitaxial layer is separated from the GaN base layer.

[0036] The GaN functional layer after separation is cracked according to the pattern distribution of the device structure epitaxial layer, and a semiconductor chip is obtained.

[0037] Preferably, the device structure epitaxial layer is one of high electron mobility transistor, metal oxide semiconductor field effect transistor, blue laser, and green laser.

[0038] Preferably, the thickness of the GaN functional layer is not sufficient for the GaN functional layer to be used as a self-supporting substrate, and a support substrate for support is bonded to the GaN functional layer of the epitaxial device structure, and the support substrate is separated from the GaN functional layer before cracking.

[0039] Compared with the prior art, the present application has the following advantages:

[0040] 1. By special doping of the nitride sacrificial layer, the band gap of the nitride sacrificial layer is much smaller than that of the upper and lower GaN layers, so that the photo-enhanced chemical corrosion reaction has selectivity, and the directional corrosion is realized without damaging the upper and lower GaN layers, which provides the feasibility for peeling.

[0041] 2. During the photo-assisted electrochemical corrosion, photo-generated carriers can be continuously generated, the required current density is relatively small, and by controlling the irradiation position of the light source, directional and selective corrosion can be realized.

[0042] 3、The GaN base layer thickness is not less than 200 μm, which can effectively overcome the cracking in the chemical etching process of the GaN base layer, and also can effectively overcome the cracking in the grinding and polishing process of the GaN base layer.

[0043] 4、The dislocation density of the GaN base layer is not more than 1x10 6 cm -2 , which can relieve the cracking in the chemical etching or grinding and polishing process of the GaN base layer, and greatly improve the service life of the device after epitaxy, especially the blue-green laser. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0045] Figure 1 is a schematic diagram of a multi-layer GaN substrate of the present application;

[0046] Figure 2 is a flow chart of the manufacturing method of the multi-layer GaN substrate of the present application;

[0047] Figure 3 is a flow chart of the separation method of the separable multi-layer GaN substrate of the present application.

[0048] Figure 4 is a spot trajectory schematic diagram in an embodiment;

[0049] Figure 5 is a spot trajectory schematic diagram in another embodiment;

[0050] Figure 6 is a flow chart of the method of manufacturing a semiconductor chip using the multi-layer GaN substrate of the present application DETAILED DESCRIPTION

[0051] The present application will be described in detail below in combination with the embodiments, but it should be noted that these embodiments are not a limitation of the present application, and equivalent changes or substitutions of the function, method or structure made by those skilled in the art according to these embodiments are within the protection scope of the present application.

[0052] Please refer to Figure 1 , Figure 1The application is a multi-layer GaN substrate 10, which comprises a GaN base layer 11, a nitride sacrificial layer 12 on the GaN base layer 11, and a GaN functional layer 13 on the nitride sacrificial layer 12. The GaN base layer 11 serves as the base layer of the whole substrate 10, and provides self-supporting effect for the nitride sacrificial layer 12 and the GaN functional layer 13. The nitride sacrificial layer 12 is used as an intermediate separation layer. When it is needed to separate the GaN functional layer 13 from the GaN base layer 11, the nitride sacrificial layer 12 can be removed by modification or etching, so that the GaN functional layer 13 can be peeled off from the GaN base layer 11. The GaN functional layer 13 is used as the substrate of a semiconductor device / chip, and the subsequent semiconductor device or chip is manufactured.

[0053] In particular, in the application, when the GaN functional layer 13 is separated from the GaN base layer 11, a photo-enhanced electrochemical etching process is used to perform the separation step, considering the yield and implementability of the separation process. The technical principle is as follows:

[0054] When a semiconductor material absorbs photon energy, electrons and holes are excited. The generation of holes makes the semiconductor material more easily oxidized, and the electrons can be consumed in the reduction process of the oxidizing agent. Therefore, by this property, the chemical properties of the semiconductor material can be changed by light irradiation, so that the semiconductor material is more easily involved in certain chemical reactions. In this case, by selecting a suitable band gap of the sacrificial layer and a light source, the energy of the photon is greater than the band gap of the sacrificial layer and less than the band gap of the GaN base layer and the functional layer (2.5 < hv < 3.4 eV). In this case, the GaN base layer and the functional layer do not absorb photons, but the nitride sacrificial layer strongly absorbs photons. At this time, electrons and holes are excited in the nitride sacrificial layer. The holes help the oxidation reaction of the nitride sacrificial layer, and the excess electrons are consumed by the reduction process of the oxidizing agent. Selecting a laser with a relatively high energy density as the light source is beneficial to enhance the generation of holes on the surface of the nitride sacrificial layer and improve the etching efficiency.

[0055] According to the above principle, in the present application, by doping a first doping element in the nitride sacrificial layer 12, the first doping element makes the nitride sacrificial layer 12 have a band gap different from the GaN base layer 11 and the GaN functional layer 13, so that the nitride sacrificial layer 12 is etched at a rate faster than the GaN base layer and the GaN functional layer in a photo-enhanced chemical etching process. In this way, when peeling is needed, the entire substrate is immersed in a chemical etching liquid for a photo-enhanced chemical etching reaction. Since the nitride sacrificial layer 12 is designed to have a smaller band gap, it can strongly absorb light sources with longer wavelengths that the GaN base layer and the GaN functional layer cannot absorb, thereby generating a large number of photo-generated carriers in the nitride sacrificial layer 12. Therefore, the nitride sacrificial layer 12 will concentrate most of the photo-generated carriers, forming a faster chemical etching, so that the nitride sacrificial layer 12 can form a directional reaction in the photo-enhanced chemical etching process compared with the upper and lower GaN layers. The photo-enhanced chemical etching is selective, so that the nitride sacrificial layer 12 can be removed without damaging the upper and lower GaN layers.

[0056] In an embodiment, the GaN base layer 11 uses a non-doped GaN single crystal layer, the nitride sacrificial layer 12 uses a combined layer of InGaN and InAlN, and the GaN functional layer 13 uses a silicon-doped or germanium-doped GaN single crystal layer. In this way, the band gap of the nitride sacrificial layer 12 can be less than 2.5eV, and the band gap of the GaN base layer 11 and the GaN functional layer 13 is greater than or equal to 3.4eV, so that the nitride sacrificial layer 12 located in the middle forms a clear band gap difference between the upper and lower GaN layers.

[0057] According to the above material selection and modification target, in an embodiment, a high-intensity green light or red light source with a wavelength greater than 413nm is used for irradiation, so that the nitride sacrificial layer 12 is excited to generate a large number of holes and electrons, while the GaN base layer 11 and the GaN functional layer 13 remain unchanged, thereby achieving the effect of accelerating the chemical reaction etching of the nitride sacrificial layer 12.

[0058] In an embodiment, the oxidizing agent can be selected from K2S2O8 and potassium bisulfate complex salt PMS, and the specific chemical equation is as follows:

[0059] GaN + photon → GaN + e - + h +

[0060] 2 GaN + 6 h + + 6 OH - → Ga2O3 + 3 H2O + N2

[0061] 52O8 2- + 2 e - → 2 SO42-

[0062] Further, different layers have different thicknesses based on different functions. The nitride sacrificial layer 12 cannot be too thin and needs to be etched as soon as possible, and its thickness is preferably not less than 5 μm, otherwise it is difficult for the electrolyte to enter. The GaN base layer 11 needs to be repeatedly used, and in particular, during peeling, in order to ensure that it does not break due to stress, the thickness is preferably set to be greater than 200 μm, and the GaN functional layer 13 not only needs to consider its own strength problem, but also needs to be determined according to the future needs of semiconductor device production. Generally, the thickness of the GaN functional layer 13 should be greater than 100 μm. In this way, the total thickness of the formed multilayer GaN substrate is not less than 300 μm.

[0063] Therefore, the GaN base layer 11 needs to be set to a certain thickness to control its strength, and the specific reasons are as follows:

[0064] (1) The GaN base layer 11 is surface planarized and epitaxial polished by grinding and polishing, and surface planarization needs to use diamond powder to grind the GaN surface under pressure.

[0065] (2) The etching process is a process of expanding from the edge to the middle, and as the separation proceeds, the changing geometry of the nitride sacrificial layer 12 causes a constantly changing stress between the GaN base layer 11 and the GaN functional layer 13.

[0066] The applicant has obtained the following important results through long-term technical development: the thickness of the GaN base layer 11 is set to be greater than 200 μm, which can effectively overcome the cracking of the GaN base layer 11, and the specific values are shown in Table 1. In addition, the applicant also found that the dislocation density is set to be not greater than 1 x 10 6 cm -2 , which can effectively alleviate the probability of cracking of the GaN base layer 11. The physical mechanism here can be as follows: dislocation is a kind of linear defect, and since the GaN epitaxial process is all heteroepitaxy, there is a difference between the hetero-substrate and GaN in lattice constant and thermal expansion coefficient (lattice mismatch and thermal mismatch), resulting in a large number of defects (edge dislocations, screw dislocations, mixed dislocations) in the epitaxial GaN substrate, mainly in the form of mixed dislocations. The edge dislocations or mixed dislocations will directly cause stress in the GaN substrate at the micro level (the deviation value of the E2(high) peak of a single dislocation in the micro test Raman spectrum is 0.05 cm -1 , and the stress caused is about 11.9 MPa, see Non-Patent Literature 1). Therefore, by controlling the thickness of the GaN base layer 11, the cracking during chemical etching or grinding and polishing can be solved; at the same time, by controlling the dislocation density, the stress can be improved, thereby improving the probability of cracking during chemical etching or grinding and polishing.

[0067]

[0068]

[0069] Table 1, the influence of GaN-based layer thickness and dislocation density on grinding and polishing and the occurrence of cracks in separation.

[0070] Reference non-patent document:

[0071] [1] Kokubo, N., Tsunooka, Y., Fujie, F., Ohara, J., Hara, K., Onda, S., Yamada, H., Shimizu, M., Harada, S., Tagawa, M., Ujihara, T., Detection of edge component of threading dislocations in GaN by Raman spectroscopy. Applied Physics Express, 2018, 11(6), 061002.

[0072] More importantly, the applicant found that the dislocation density has an important improvement on the life of high-power GaN-based devices (blue or green laser). See Table 2 for details. Since dislocations are linear defects that can penetrate to the device surface, and dislocation edges can accumulate impurities, dislocations are leakage channels, and the leakage characteristics of leakage channels are enhanced in high-power density devices under long-term use conditions, leading to device failure. Therefore, setting the dislocation density to be not more than 1x10 6 cm -2 Not only can it alleviate the cracking that occurs during chemical etching or grinding and polishing of the GaN-based layer, but it also greatly improves the life of the device after epitaxy.

[0073]

[0074] Table 2, the influence of GaN-based layer dislocation density on the life of a blue laser.

[0075] The multi-layer GaN substrate 10 of the present application can strip the bottom GaN layer for support after the semiconductor device or chip is made, which not only reduces the thinning process of the GaN substrate, but also allows the stripped GaN-based layer 11 to be reused, greatly reducing the cost.

[0076] Please refer to Figure 2 , Figure 2 is a flow chart of the manufacturing method of the multi-layer GaN substrate of the present application, as shown in the figure, the manufacturing method comprises the following steps:

[0077] S1, providing a substrate, growing a GaN base layer on the substrate, making the thickness of the GaN base layer at least greater than 200 μm, and peeling off the GaN base layer from the substrate. Specifically comprising the following steps:

[0078] S11, growing a GaN thick film of a certain thickness on the substrate by HVPE method. The substrate can be selected from GaN template, or hetero-substrate such as sapphire, silicon carbide, silicon, etc. Preferably, the GaN template is grown by metal organic chemical vapor deposition system (MOCVD) on sapphire to a thickness of > 2 μm.

[0079] S12, separating the substrate from the GaN thick film, which can be achieved by laser peeling, mechanical grinding, chemical etching, etc. Preferably, laser peeling is used.

[0080] S13, processing the separated GaN thick film into a circular shape with a reference edge and a diameter of no less than 50 mm, then planar grinding to achieve surface planarization, and then surface polishing, thereby obtaining a GaN base layer with a thickness of 200 μm or more.

[0081] S2, growing a nitride sacrificial layer on the GaN base layer, the thickness of the nitride sacrificial layer being no less than 5 μm, and doping the nitride sacrificial layer with a first doping impurity, so that the band gap of the nitride sacrificial layer is less than 2.5 eV. Specifically, growing an InGaN sacrificial layer with a thickness of no less than 5 μm on the GaN base layer by MOCVD to form a new self-supporting GaN substrate. The band gap of the sacrificial layer is set to be less than 2.5 eV.

[0082] S3, growing a GaN functional layer on the nitride sacrificial layer, the thickness of the GaN functional layer being greater than 100 μm, and doping the GaN functional layer with a second impurity, so that the band gap of the GaN functional layer is greater than or equal to 3.4 eV. Specifically, growing a GaN single crystal layer with a thickness of 100 μm or more on the new self-supporting GaN substrate formed in step S2 by HVPE, and setting the doping impurity to be silicon doping, germanium doping, or a combination of silicon doping and germanium doping, so that the band gap of the GaN functional layer in direct contact with the nitride sacrificial layer is greater than or equal to 3.4 eV. Then, planar grinding is performed to achieve surface planarization, and surface polishing is performed, thereby obtaining a multilayer structure GaN substrate with a total thickness of no less than 300 μm.

[0083] Preferably, when the thickness of the GaN functional layer is not sufficient for the GaN functional layer to serve as a self-supporting substrate, such as less than 100 μm, a support substrate is bonded to the surface of the GaN functional layer at this time. When the thickness of the GaN functional layer is sufficient for the GaN functional layer to serve as a self-supporting substrate, the above process is not needed.

[0084] Please refer to Figure 3, Figure 3 is a flowchart of a separation method of a separable multi-layer GaN substrate according to the present application. As shown in the figure, the method comprises the following steps:

[0085] L1: immerse the separable multi-layer GaN substrate into a corrosion liquid, so that the nitride sacrificial layer is immersed in the corrosion liquid. In one embodiment, the corrosion liquid can be K2S2O8, potassium bisulfate composite salt PMS, which can react with the nitride sacrificial layer to corrode the nitride sacrificial layer.

[0086] L2: provide a light source, which irradiates a light beam to the separable multi-layer GaN substrate, and the light beam forms a light spot on the nitride sacrificial layer through the GaN base layer. The light source has an energy greater than the band gap of the nitride sacrificial layer and less than the band gap of the GaN base layer and the GaN functional layer. In one embodiment, the light source uses a high-intensity green or red light source with a wavelength greater than 413 nm. The light spot emitted by such light source can excite the nitride sacrificial layer to generate electrons and holes, so that the nitride sacrificial layer can more effectively react with the corrosion liquid to be etched.

[0087] L3: move the light spot so that the moving track of the light spot meets the requirement of moving from the edge to the center of the nitride sacrificial layer, and the moving speed of the light spot meets the requirement that the area of the nitride sacrificial layer irradiated by the light spot can be corroded by the corrosion liquid.

[0088] Please refer to Figure 4 In one embodiment, the light spot is a block-shaped light spot, and the moving track of the light spot is a spiral shape moving from the periphery to the center and covering the entire area of the nitride sacrificial layer. The movement of the light spot can be achieved by moving the light source as a whole, so that the path of the light spot on the substrate surface forms a projection relationship with the path of the light spot. Alternatively, the projection angle of the rotating light source can be set to meet the path requirement of the light spot.

[0089] Please refer to Figure 5 In another embodiment, the light spot is a ring-shaped light spot, and the moving track of the light spot gradually shrinks from the outside to the inside and covers the entire area of the nitride sacrificial layer. The light source design corresponding to this embodiment can be achieved by modulating the shape of the output light spot, such as using a ring-shaped light source, and then using a zoom optical path to achieve the path design. The projection optical path can also be used, such as using a spatial light modulating device such as DMD, LCOS, etc. to modulate the shape of the output light spot.

[0090] Please refer to Figure 6 , Figure 6 is a flowchart of a method for manufacturing a semiconductor chip using a multi-layer GaN substrate according to the present application. As shown in the figure, the manufacturing method comprises the following steps:

[0091] P1: providing a separable multi-layer GaN substrate of the present application;

[0092] P2: epitaxially growing a device structure epitaxial layer on the GaN functional layer of the multi-layer GaN substrate by a MOCVD process;

[0093] P3: separating the separable multi-layer GaN substrate by the separation method of the present application, so that the GaN functional layer provided with the device structure epitaxial layer is separated from the GaN base layer;

[0094] P4: dicing the separated GaN functional layer according to the pattern distribution of the device structure epitaxial layer to obtain semiconductor chips.

[0095] Further, when the thickness of the GaN functional layer is not sufficient for the GaN functional layer to serve as a self-supporting substrate, the method further comprises bonding a support substrate for supporting on the GaN functional layer of the epitaxial device structure, the support substrate having a certain mechanical strength to ensure that the GaN functional layer is not damaged during separation. The support substrate is separated from the GaN functional layer before dicing.

[0096] Further, the device structure epitaxial layer is a high electron mobility transistor, a metal oxide semiconductor field effect transistor, a blue laser, a green laser, etc.

[0097] The scheme of the present application will be described below through several embodiments. Specific Embodiment 1

[0099] The multi-layer structure GaN substrate of Embodiment 1 is as follows:

[0100] The lowest layer is a 250 μm undoped GaN single crystal layer, the middle layer is a 10 μm thick InGaN nitride sacrificial layer, and the upper layer is a 125 μm silicon-doped GaN single crystal layer.

[0101] The multi-layer structure GaN substrate is used to prepare a blue laser LD epitaxial structure by MOCVD. Then, by virtue of the characteristics that the band gap of the 10 μm thick InGaN sacrificial layer is less than 2.5 eV, and the band gap of the silicon-doped GaN single crystal layer and the undoped GaN single crystal layer is relatively large (3.4 eV), the entire 10 μm thick InGaN sacrificial layer is gradually etched from the edge to the center by a photo-enhanced chemical etching method. In this process, a high-intensity green or red light source with a wavelength greater than 413 nm (> 2.5 eV) is used for irradiation, so that directional irradiation light-assisted electrochemical etching can be achieved. Thus, the silicon-doped GaN single crystal layer and the blue laser epitaxial structure on the upper layer are separated from the undoped GaN single crystal layer, the undoped GaN single crystal layer can be reused, and finally a semiconductor chip array is prepared. Specific Embodiment 2

[0103] The bottom layer is a 250 μm undoped GaN single crystal layer, the middle layer is a 10 μm thick InAlN nitride sacrificial layer, and the top layer is a 125 μm silicon-doped GaN single crystal layer.

[0104] The GaN substrate of the multi-layer structure is used to prepare a blue laser LD epitaxial structure by MOCVD. Then, by using the characteristics that the band gap of the 10 μm thick InAlN sacrificial layer is less than 2.5 eV, the band gap of the silicon-doped GaN single crystal layer is relatively large (3.4 eV), and the band gap of the undoped GaN single crystal layer is relatively large (3.4 eV), the entire 10 μm thick InAlN sacrificial layer is gradually etched from the edge to the center by photo-enhanced chemical etching. In this process, high-intensity green or red light sources with a wavelength greater than 413 nm (> 2.5 eV) are used for irradiation, so that directional irradiation light-assisted electrochemical etching can be achieved. Thus, the silicon-doped GaN single crystal layer on the top and the blue laser epitaxial structure are separated from the undoped GaN single crystal layer, the undoped GaN single crystal layer can be reused, and finally a semiconductor chip array is prepared. Specific embodiment 3:

[0106] The bottom layer is a 250 μm undoped GaN single crystal layer, the middle layer is a 10 μm thick InGaN nitride sacrificial layer, and the top layer is a 50 μm germanium-doped GaN single crystal layer.

[0107] The GaN substrate of the multi-layer structure is used to prepare a blue laser LD epitaxial structure by MOCVD, and then bonded to a Si substrate. Then, by using the characteristics that the band gap of the 10 μm thick InGaN sacrificial layer is less than 2.5 eV, the band gap of the germanium-doped GaN single crystal layer is relatively large (3.4 eV), and the band gap of the undoped GaN single crystal layer is relatively large (3.4 eV), the entire 10 μm thick InGaN sacrificial layer is gradually etched from the edge to the center by photo-enhanced chemical etching. In this process, high-intensity green or red light sources with a wavelength greater than 413 nm (> 2.5 eV) are used for irradiation, so that directional irradiation light-assisted electrochemical etching can be achieved. Thus, the germanium-doped GaN single crystal layer on the top and the blue laser epitaxial structure and the Si substrate are separated from the undoped GaN single crystal layer, the undoped GaN single crystal layer can be reused, and finally the bonded Si substrate is removed to prepare a semiconductor chip array.

[0108] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0109] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made specifically within that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.

Claims

1. A separation method of a separable multi-layer GaN substrate, the separable multi-layer GaN layer comprising a GaN base layer, a nitride sacrificial layer on the GaN base layer, and a GaN functional layer on the nitride sacrificial layer, characterized by, The separation method comprises: immersing the separable multi-layer GaN substrate into an etching solution so that the nitride sacrificial layer is immersed in the etching solution; providing a light source which irradiates a light beam to the separable multi-layer GaN substrate, the light beam forms a light spot on the nitride sacrificial layer through the GaN base layer; moving the light spot so that the moving track of the light spot meets the requirement of moving from the edge to the center of the nitride sacrificial layer; The light source has light with energy greater than the band gap of the nitride sacrificial layer and less than the band gap of the GaN-based layer and the GaN functional layer, and the moving speed of the light spot satisfies that the region of the nitride sacrificial layer irradiated by the light spot can be corroded by the etching liquid. The GaN-based layer has a thickness not less than 200 μm and a dislocation density not greater than 1x10 6 cm -2 .

2. The separation method of the separable multi-layer GaN substrate according to claim 1, characterized by: the light spot is a block light spot, and the moving track of the light spot is a spiral track which moves from the periphery to the center and covers the whole area of the nitride sacrificial layer.

3. The separation method of the separable multi-layer GaN substrate according to claim 1, characterized by: the light spot is a ring light spot, and the moving track of the light spot gradually shrinks from the outside to the inside and covers the whole area of the nitride sacrificial layer.

4. The separation method of the separable multi-layer GaN substrate according to claim 1, characterized by: The GaN base layer, GaN functional layer and nitride sacrificial layer are doped with different types and / or concentrations of impurities, so that the band gap of the nitride sacrificial layer is at least 1eV different from that of the GaN base layer and GaN functional layer.

5. The separation method of the separable multi-layer GaN substrate according to claim 1, characterized by: The nitride sacrificial layer is doped with element In to form an InGaN or InAlN layer, and the doping content of the element In is greater than 20%, and the band gap of the doped nitride sacrificial layer is less than 2.5eV.

6. The separation method of the separable multi-layer GaN substrate according to claim 1, characterized by: The GaN base layer is non-doped, the GaN functional layer is doped with silicon or germanium, and the band gap of the GaN base layer and GaN functional layer is greater than or equal to 3.4eV.

7. A separable multi-layer GaN substrate for use in the separation method of claim 1, comprising a GaN base layer, a nitride sacrificial layer on the GaN base layer, a GaN functional layer on the nitride sacrificial layer, characterized in that: The band gap of the nitride sacrificial layer is less than the band gap of the GaN-based layer and the GaN functional layer, the GaN-based layer has a thickness of not less than 200 μm and a dislocation density of not more than 1 x 10 6 cm -2 The nitride sacrificial layer is doped with In to form an InGaN or InAlN layer, the doping content of the doped In is greater than 20%, and the band gap of the doped nitride sacrificial layer is less than 2.5 eV.

8. The separable multi-layer GaN substrate of claim 7, wherein: The GaN base layer, GaN functional layer and nitride sacrificial layer are doped with different types and / or concentrations of impurities, so that the band gap of the nitride sacrificial layer is at least 0.9eV less than that of the GaN base layer and GaN functional layer.

9. The separable multi-layer GaN substrate of claim 7, wherein: The nitride sacrificial layer is doped with element In to form an InGaN or InAlN layer, and the doping content of the element In is greater than 20%, and the band gap of the doped nitride sacrificial layer is less than 2.5eV.

10. The separable multi-layer GaN substrate of claim 7, wherein: The GaN base layer is non-doped, the GaN functional layer is doped with silicon or germanium, and the band gap of the GaN base layer and GaN functional layer is greater than or equal to 3.4eV.

11. A semiconductor chip manufacturing method, characterized in that: providing the separable multi-layer GaN substrate according to any one of claims 7-10; epitaxially growing a device structure epitaxial layer on the GaN functional layer of the multi-layer GaN substrate by MOCVD process; separating the separable multi-layer GaN substrate by the separation method of the separable multi-layer GaN substrate according to any one of claims 1-6, so that the GaN functional layer provided with the device structure epitaxial layer is separated from the GaN base layer; breaking the separated GaN functional layer according to the pattern distribution of the device structure epitaxial layer to obtain a semiconductor chip.

12. The method of claim 11, wherein: The device structure epitaxial layer is one of high electron mobility transistor, metal oxide semiconductor field effect transistor, blue laser and green laser.

13. The method of claim 11, wherein: The thickness of the GaN functional layer is not sufficient for the GaN functional layer to be a self-supporting substrate, and the method further comprises bonding a support substrate for supporting on the GaN functional layer of the epitaxial device structure; and separating the support substrate from the GaN functional layer before breaking.

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