Method and device for eliminating edge defects of gallium nitride crystal

Abstract

The invention provides a device and a method for eliminating edge defects of gallium nitride crystals. The eliminating device comprises a bearing device for bearing the gallium nitride crystals, a constant-temperature electrolytic bath for accommodating electrolyte and an electrolysis system, the gallium nitride crystal and the bearing device are submerged by the electrolyte; the electrolysis system comprises a power supply, an anode connected with the power supply and a cathode connected with the power supply, the anode is electrically contacted with the gallium nitride crystal, the cathode is electrically contacted with the electrolyte, and the power supply, the anode, the gallium nitride crystal, the electrolyte and the cathode form an electrolysis loop; the power supply supplies power to the anode and the cathode respectively so as to carry out specific corrosion on an abnormal growth region at the edge of the gallium nitride crystal, and the abnormal growth region contains defects. According to the method, the abnormal growth region containing defects at the edge of the gallium nitride crystal formed based on epitaxial growth can be accurately removed, and the risk of wafer cracking is avoided while the quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of compound semiconductor devices, and in particular to a method and device for eliminating edge defects of gallium nitride crystals. Background Art

[0002] Ginseng Figure 1 As shown in FIG. 1 , in a gallium nitride crystal grown based on an epitaxial process (e.g., HVPE), during the crystal growth process, the edge portion is in more complete contact with the growth environment, and impurities (e.g., oxygen impurities) are more likely to be deposited at the edge. At the same time, during the epitaxial growth process, due to the influence of factors such as the temperature gradient and concentration gradient at the edge, the diffusion and deposition rates of impurities at the edge change, resulting in a higher concentration of impurities at the edge than at the center of the gallium nitride crystal 11, which leads to the following: Figure 1 The edge 111 of the gallium nitride crystal 11 shown shows an abnormal growth region 12. The abnormal growth region 12 contains a large amount of impurities such as oxygen, which significantly affects the electrical properties and material stability of semiconductor devices made from the gallium nitride crystal and causes device failure.

[0003] At the same time, due to the lattice discontinuity and boundary effects at the edge 111 of the gallium nitride crystal 11, stress is further concentrated at the edge 111. The greater the thickness of the abnormal growth region 12, the greater the stress difference within it. Factors such as uneven epitaxial growth rates and impurities generate stress within the gallium nitride crystal 11. This stress accumulates during crystal growth and is more likely to concentrate at the edge 111 of the gallium nitride crystal, resulting in greater internal stress in the abnormal growth region 12.

[0004] Prior art typically uses mechanical polishing or grinding to remove the abnormal growth region 12. Due to the high stress in the abnormal growth region 12, mechanical polishing or grinding is highly susceptible to cracking, resulting in a low yield of the gallium nitride crystal 11. Furthermore, while prior art also utilizes wet etching to remove the abnormal growth region 12, the geometry and stress distribution of the edge 111 of the gallium nitride crystal 11 differ from the stress distribution within the abnormal growth region 12, and the concentration gradient and temperature gradient of the etching solution at the edge 111 may vary, resulting in deviations between the actual etching rate and removal effect and the expected etching rate and removal effect. Furthermore, due to the anisotropic nature of the gallium nitride crystal 11, the wet etching process used in prior art can result in inconsistent etching levels at different locations along the edge 111 of the gallium nitride crystal 11, making it difficult to precisely control the etching depth and extent. This can lead to over-etching of some areas while under-etching others, resulting in incomplete removal of the abnormal growth region 12 or the removal of part of the gallium nitride crystal 11. Therefore, whether the existing technology adopts mechanical polishing or mechanical grinding, or wet etching, it is impossible to accurately remove the abnormal growth region 12, and thus the abnormal growth region 12 formed at the edge 111 of the finally obtained gallium nitride crystal 11 cannot be accurately removed, resulting in the deposition of impurities such as oxygen impurities at the edge 111 of the gallium nitride crystal 11, and there is a risk of the gallium nitride crystal 11 cracking due to stress after the abnormal growth region 12 is removed.

[0005] In view of this, it is necessary to improve the existing methods for eliminating defects on the edges of gallium nitride crystals formed by epitaxial growth to solve the above-mentioned problems. It should be noted that the above introduction to the background technology is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and to facilitate the understanding of those skilled in the art. It should not be assumed that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present invention. Summary of the Invention

[0006] The present invention aims to disclose a method for eliminating defects at the edge of a gallium nitride crystal and a device for eliminating defects at the edge of a gallium nitride crystal based on the method, so as to solve the aforementioned technical problems. In particular, the present invention aims to achieve precise removal of abnormal growth areas containing defects at the edge of a gallium nitride crystal formed by epitaxial growth, while simultaneously preventing the gallium nitride crystal from cracking.

[0007] As a first aspect of the present invention, in order to achieve one of the above-mentioned objectives, the present invention provides a device for eliminating edge defects of a gallium nitride crystal, comprising:

[0008] A supporting device for the gallium nitride crystal, a constant-temperature electrolytic cell containing the electrolyte, and an electrolysis system;

[0009] The electrolyte submerges the gallium nitride crystal and the supporting device;

[0010] The electrolysis system includes a power supply, an anode connected to the power supply, and a cathode connected to the power supply. The anode electrically contacts the gallium nitride crystal, and the cathode electrically contacts the electrolyte. The power supply, the anode, the gallium nitride crystal, the electrolyte, and the cathode form an electrolysis circuit. The power supply supplies power to the anode and the cathode respectively to specifically corrode an abnormal growth area at the edge of the gallium nitride crystal, where the abnormal growth area contains defects.

[0011] As a further improvement of the present invention, the voltage between the anode and the cathode is 80-150 VDC, and the current between the anode and the cathode is 5-20 mA;

[0012] and / or, the electrolyte is maintained at a constant temperature of 30 to 55° C.;

[0013] And / or, the gallium nitride crystal is a non-doped crystal;

[0014] And / or, after the power supply is started, defects in the abnormal growth area undergo an oxidation-reduction reaction with the electrolyte to be specifically corroded until the abnormal growth area is completely corroded.

[0015] As a further improvement of the present invention, the electrolyte is selected from a weak acid solution, a salt solution or a buffer solution; the weak acid solution includes oxalic acid, acetic acid, phosphoric acid, boric acid or nitrous acid, the concentration of the weak acid solution is 0.8~1.2 mol / L, and the pH value of the weak acid solution is 1~2.

[0016] As a further improvement of the present invention, the supporting device includes a support plate for supporting the gallium nitride crystal;

[0017] Alternatively, the supporting device includes a supporting plate for supporting the gallium nitride crystal, and a movable pressing assembly for movably pressing the top surface and / or side surfaces of the gallium nitride crystal, and the supporting plate and the movable pressing assembly jointly clamp the gallium nitride crystal.

[0018] As a further improvement of the present invention, the movable pressing assembly includes: a retaining member movably connected to the support plate, a pressing member penetrated by the retaining member and connected to the support plate, and a buffer member formed on the side of the pressing member facing the gallium nitride crystal, the buffer member pressing the top surface and / or side surface of the gallium nitride crystal.

[0019] As a further improvement of the present invention,

[0020] The size of the gallium nitride crystal is greater than 2 inches;

[0021] And / or, the defects include oxygen impurities, the concentration of the oxygen impurities in the abnormal growth region is greater than the concentration of the oxygen impurities in the remaining region of the gallium nitride crystal that does not include the abnormal growth region; the carrier concentration caused by the oxygen impurities in the abnormal growth region reaches 10 19 / cm 3 ;

[0022] And / or, the stress of the abnormal growth region is greater than the stress of the remaining region of the gallium nitride crystal excluding the abnormal growth region.

[0023] As a second aspect of the present invention, and based on the same inventive concept, the present invention further provides a method for eliminating edge defects of a gallium nitride crystal, comprising the following steps:

[0024] placing a gallium nitride crystal having an abnormal growth region on an edge on a supporting device, wherein the abnormal growth region contains defects;

[0025] Submerging the gallium nitride crystal and the supporting device in the electrolyte of a constant temperature electrolytic tank;

[0026] Electrically contacting the anode with the gallium nitride crystal and the cathode with the electrolyte, respectively establishing electrical connections between the anode and the cathode and a power source; wherein the power source, the anode, the gallium nitride crystal, the electrolyte, and the cathode form an electrolysis circuit;

[0027] The power supply is used to supply power to the anode and the cathode respectively, so as to specifically erode the abnormal growth area at the edge of the gallium nitride crystal.

[0028] As a further improvement of the present invention, the elimination method further includes:

[0029] The electrolyte in the constant temperature electrolytic tank is heated to a preset temperature and maintained at a constant temperature; the power supply is activated to specifically corrode the abnormal growth region at the edge of the gallium nitride crystal submerged in the electrolyte; wherein the preset temperature is 30 to 55° C., and defects in the abnormal growth region undergo an oxidation-reduction reaction with the electrolyte, thereby being specifically corroded until the abnormal growth region is completely corroded;

[0030] and / or, the voltage between the anode and the cathode is 80-150 VDC, and the current between the anode and the cathode is 5-20 mA;

[0031] And / or, the gallium nitride crystal is a non-doped crystal;

[0032] And / or, the electrolyte is selected from a weak acid solution, a salt solution or a buffer solution; the weak acid solution includes oxalic acid, acetic acid, phosphoric acid, boric acid or nitrous acid, the concentration of the weak acid solution is 0.8-1.2 mol / L, and the pH value of the weak acid solution is 1-2.

[0033] As a further improvement of the present invention, the elimination method further includes:

[0034] The voltage and / or the current output by the power supply are selectively changed to change the etching rate for specifically etching the abnormal growth area.

[0035] As a third aspect of the present invention, and based on the same inventive concept, a gallium nitride crystal is prepared by using the method for eliminating edge defects of a gallium nitride crystal as described in any of the aforementioned inventions.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In the present invention, since the abnormal growth region containing defects at the edge of the gallium nitride crystal has a different doping concentration of impurities such as oxygen impurities compared to the undoped gallium nitride crystal, the abnormal growth region at the edge of the gallium nitride crystal can be specifically corroded through an electrolytic circuit. After the abnormal growth region is completely corroded, the undoped gallium nitride crystal will not be corroded, thereby achieving precise removal of the abnormal growth region containing defects at the edge of the gallium nitride crystal formed based on epitaxial growth. At the same time, the present invention avoids damage to the gallium nitride crystal caused by mechanical polishing or mechanical grinding, and can effectively eliminate the abnormal growth region containing defects at the edge of the gallium nitride crystal while obtaining a crack-free gallium nitride crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 FIG4 is a cross-sectional view showing an abnormal growth region at the edge of a gallium nitride crystal in an example of forming a gallium nitride crystal based on HVPE epitaxial growth;

[0039] Figure 2 For the present invention Figure 1 An overall schematic diagram of a device for eliminating defects contained in an abnormal growth region at the edge of a gallium nitride crystal;

[0040] Figure 3 is a cross-sectional view of the supporting device;

[0041] Figure 4 This is a schematic structural diagram of a supporting device included in a device for eliminating edge defects of a gallium nitride crystal according to the present invention;

[0042] Figure 5 for Figure 2A schematic diagram of a liquid replenishing device provided in a device for eliminating edge defects of a gallium nitride crystal according to the present invention is shown;

[0043] Figure 6 For the Figure 4 A cross-sectional view of an example taken along the AA axis;

[0044] Figure 7 For the Figure 4 A cross-sectional view taken along line AA in another embodiment;

[0045] Figure 8 For the Figure 4 A cross-sectional view taken along line AA in another embodiment;

[0046] Figure 9 This is an overall flow chart of a method for eliminating edge defects of a gallium nitride crystal according to the present invention;

[0047] Figure 10 This is a local SEM image of an abnormal growth area containing defects at the edge of a GaN crystal.

[0048] Figure 11 A local SEM image of the gallium nitride crystal at the edge of which the defect-containing abnormal growth region is specifically etched using a gallium nitride crystal edge defect elimination method of the present invention to completely peel off the gallium nitride crystal at the abnormal growth region. DETAILED DESCRIPTION

[0049] The present invention is described in detail below with reference to the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in this field based on these embodiments are all within the scope of protection of the present invention.

[0050] Ginseng Figures 2 to 5 A specific embodiment of a device 100 for eliminating edge defects of a gallium nitride crystal (hereinafter referred to as “elimination device 100 ”) of the present invention is shown.

[0051] The treatment object of the elimination device 100 may be a gallium nitride crystal 10, which may further include a gallium nitride crystal formed by epitaxial growth along a Ga polarity plane or an N polarity plane. The gallium nitride crystal 10 includes an undoped gallium nitride crystal 11 and an abnormal growth region 12 located on its side. Figure 1The direction indicated by the arrow 1 can be the direction of epitaxial growth along the Ga polarity plane or the direction of epitaxial growth along the N polarity plane. The abnormal growth area 12 to be removed is formed in a ring shape on the side of the gallium nitride crystal 11. Gallium nitride crystals can also be prepared by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), hydrothermal method and other routes. The elimination device 100 uses the technical solutions included in the elimination method in the following embodiment to eliminate the abnormal growth area 12. Figure 1 The gallium nitride crystal 10 having an abnormal growth region 12 containing defects at its edge is specifically etched to precisely remove the abnormal growth region 12 to form a non-doped gallium nitride crystal 11 , thereby avoiding undesirable excessive etching of the gallium nitride crystal 11 .

[0052] The elimination device 100 includes a support device 20 for supporting a gallium nitride crystal 10, a constant-temperature electrolytic tank 30 containing an electrolyte 31, and an electrolysis system. The electrolyte 31 submerges the gallium nitride crystal 10 and the support device 20. The electrolysis system includes a power supply 50, an anode 51 connected to the power supply 50, and a cathode 52 connected to the power supply 50. The anode 51 is in electrical contact with the gallium nitride crystal 10, and the cathode 52 is in electrical contact with the electrolyte 31. The power supply 50, the anode 51, the gallium nitride crystal 10, the electrolyte 31, and the cathode 52 form an electrolysis circuit. The power supply 50 supplies power to the anode 51 and cathode 52, respectively, to specifically etch the abnormal growth region 12 at the edge 111 of the gallium nitride crystal 10, which contains defects.

[0053] Furthermore, impurities such as oxygen impurities and / or internal stress in the abnormal growth region 12 are considered defects in the present invention. Defects can also be considered as one or more point defects such as vacancies, interstitials, tilted grain boundaries, grain boundaries, holes, pores, pits, and cracks, which can cause various defects in the mechanical or electrical properties of the gallium nitride crystal 10. Furthermore, after the power supply 50 is activated, the defects in the abnormal growth region 12 undergo a redox reaction with the electrolyte 31, causing specific corrosion until the abnormal growth region 12 is completely corroded.

[0054] In short, combined Figure 1As shown, the support device 20 of the present invention supports the gallium nitride crystal 10, which is connected to the electrolysis circuit. The electrolyte 31, acting as an electrolyte, exhibits strong chemical activity at the interface between the carriers formed by oxygen impurities and the electrolyte 31 when a power source 50 applies a preset voltage and current. This causes defects in the abnormal growth region 12 caused by impurities such as oxygen impurities to undergo redox reactions with the electrolyte 31. Consequently, the combined effects of the weakly acidic electrolyte 31 and the direct current cause specific corrosion based on electrochemical corrosion. Once the abnormal growth region 12 is completely etched away, the impurity-free gallium nitride crystal 11 is exposed. Because the carrier concentration in the inner gallium nitride crystal 11, which contains no oxygen impurities or has a low impurity concentration, is low or almost zero, when the specific corrosion process reaches the edge 111, the charge transfer on the surface of the gallium nitride crystal 11 is significantly hindered, as the gallium nitride crystal 11 contains no defects or has a very low and almost negligible defect rate. This causes the electrochemical reaction to cease, and the combined effects of the direct current and the electrolyte 31 prevent the gallium nitride crystal 11 without defects from being corroded by the electrolyte 31 and the electrolysis circuit. Therefore, the present elimination device 100 can preferentially remove the abnormal growth region 12, and this is a specific corrosion removal method, without causing excessive corrosion to the gallium nitride crystal 11 without defects.

[0055] Furthermore, the elimination device 100 of this embodiment can avoid the technical issues of inconsistent or indiscriminate etching of different portions of the gallium nitride crystal 11, such as the edge 111 and normal growth region, using conventional wet etching processes. It can distinguish between normal growth regions and abnormal growth regions 12, thereby achieving specific etching of the abnormal growth regions 12. The elimination device and subsequent elimination method disclosed herein, which implement specific etching of the abnormal growth regions 12, are distinct from existing wet etching devices / processes.

[0056] Specifically, in the abnormal growth region 12 formed by epitaxial growth based on the deposition process at the edge 111 of the gallium nitride crystal 11, due to defects caused by impurities such as oxygen impurities in the abnormal growth region 12, the free carrier concentration at random positions in the abnormal growth region 12 is abnormally high, while the free carrier concentration in the normal growth region is abnormally low, resulting in the presence of free charges in the abnormal growth region 12. Since the traditional wet etching process is insensitive to electron concentration and requires the use of photoresist, the traditional wet etching process has the disadvantages of complex process and high cost. In particular, the traditional wet etching process will generate bubbles during the etching process of the abnormal growth region 12. The bubbles adhere to the surface of the abnormal growth region 12, causing the etching to terminate, thereby affecting the etching effect of the wet etching on the abnormal growth region 12. In addition, conventional wet etching processes have a natural isotropic nature, and therefore cannot distinguish between undoped (or low oxygen impurity concentration) gallium nitride crystals 11 (i.e., normal growth regions) and abnormal growth regions 12 doped with impurities such as oxygen impurities, thereby causing undesirable corrosion of the top surface 101 and bottom surface 102 of the normal growth regions, which is unacceptable. The elimination device 100 of this embodiment and the elimination methods disclosed in subsequent embodiments require the participation of charge to achieve specific corrosion of the abnormal growth regions 12. Therefore, the regions with high free carrier concentrations (i.e., abnormal growth regions 12) have a fast corrosion rate, while the normal growth regions with low or almost zero electron concentrations have a very slow corrosion rate and are hardly corroded.

[0057] The normal growth region of the gallium nitride crystal 11 grows from the (0001) plane. Since GaN on the (0001) plane repel oxygen impurities, the concentration of oxygen impurities and other impurities in the normal growth region is very low and almost zero. The lateral growth region, on the other hand, grows based on the (10-11) semipolar plane. The incorporation efficiency of oxygen impurities on the (10-11) semipolar plane is very high, forming an abnormal growth region 12 rich in oxygen impurities. Oxygen impurities occupy the nitrogen atomic position in GaN. Oxygen atoms have 6 electrons outside their nuclei, while nitrogen atoms have 5 electrons outside their nuclei. Therefore, when oxygen atoms occupy the nitrogen atomic position, they donate an electron, exhibiting the properties of shallow-level donor impurities, resulting in an increase in the carrier concentration in the oxygen-doped GaN. The high carrier concentration promotes electrochemical corrosion reactions and increases the rate of electrochemical corrosion. Therefore, the abnormal growth region 12 at the edge 111 of the gallium nitride crystal 11 is susceptible to specific corrosion. Therefore, the elimination device 100 in this embodiment and the elimination method disclosed in its subsequent embodiments are selective for electrochemical corrosion of areas with high electron concentration and areas with low electron concentration, thereby specifically etching and removing the high carrier concentration areas growing laterally at the edges, while having almost no corrosion effect on the gallium nitride crystals 11 in the normal growth area.

[0058] In one embodiment, the size of the gallium nitride crystal 10 is greater than 2 inches. The defects include oxygen impurities or other defects that can cause high carriers, such as gallium oxide or metal impurities. The concentration of oxygen impurities in the abnormal growth region 12 is greater than the concentration of oxygen impurities in the remaining region of the gallium nitride crystal that does not contain the abnormal growth region 12 (i.e., the gallium nitride crystal 11); the carrier concentration caused by oxygen impurities in the abnormal growth region 12 reaches 10 19 / cm 3 The stress in the abnormal growth region 12 is greater than the stress in the remaining region of the gallium nitride crystal 10 that does not include the abnormal growth region 12, that is, Figure 1 The stress of the non-doped gallium nitride crystal 11 is reduced. The aforementioned oxygen impurities include oxygen impurities with a valence of -2 or +2, and the metal elements in the compound (eg, gallium oxide) forming the oxygen impurities include but are not limited to gallium.

[0059] In another embodiment, the electrolyte 31 is selected from a weak acid solution, a salt solution or a buffer solution. The weak acid solution includes oxalic acid, acetic acid, phosphoric acid, boric acid or nitrous acid, which can generate free hydrogen ions (H + ) or other weak acids, with a weak acid solution concentration of 0.8 to 1.2 mol / L (e.g., 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, or 1.2 mol / L), and a weak acid solution pH of 1 to 2 (e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2). Alkaline solutions or strong acid solutions are not suitable for use as electrolyte 31.

[0060] In another embodiment, in conjunction with reference to Figure 2 and Figure 3 , Figure 3 A specific embodiment of a support device 20 is shown. The support device 20 includes a support plate 21 that supports the gallium nitride crystal 10. The end 511 of the anode 51 contacts the top surface 101 of the gallium nitride crystal 10, and the end 521 of the cathode 52 is submerged in the electrolyte 31. The positive (+) terminal of the power supply 50 is electrically connected to the anode 51, and the negative (-) terminal of the power supply 50 is electrically connected to the cathode 52.

[0061] Optionally, the support plate 21 may be in other shapes as long as it can support the gallium nitride crystal 10. Of course, multiple support plates such as the support plate 21 may be provided in one constant temperature electrolytic cell 30. Figure 3 The supporting device 20 shown is connected to the electrolysis system simultaneously with multiple gallium nitride crystals 10 located on the supporting device 20 to simultaneously perform specific etching on the abnormal growth regions 12 contained in the multiple gallium nitride crystals 10.

[0062] In another embodiment, Figures 3 and 4As shown, the support plate 21 may be annular to support the bottom surface 102 of the gallium nitride crystal 10 and completely expose the side surface 121. The support plate 21 forms a circular exposed area 200 to establish an electron movement path for the electrolysis circuit through the circular exposed area 200 and the electrolyte 31. The abnormal growth area 12 between the side surface 121 and the edge 111 is exposed to hydrogen ions (H + ) and direct current, an oxidation-reduction reaction occurs, generating water or other soluble compounds, thereby accelerating the corrosion of the abnormal growth region 12. At the same time, due to the extremely high oxygen impurity content in the abnormal growth region 12, the electrode potential on the crystal surface is changed, making it easier for the abnormal growth region 12 to undergo an oxidation reaction with the electrolyte 31, further accelerating the corrosion process. As a result, the abnormal growth region 12 with a high oxygen impurity content is preferentially removed, thereby achieving specific corrosion. In another embodiment, the voltage between the anode 51 and the cathode 52 is 80-150 VDC, for example, 80 VDC, 90 VDC, 100 VDC, 110 VDC, 120 VDC, 130 VDC, 140 VDC or 150 VDC; the current between the anode 51 and the cathode 52 is 5-20 mA, for example, 5 mA, 6 mA, 7 mA, 8 mA, 9 mA, 10 mA, 11 mA, 12 mA, 13 mA, 14 mA, 15 mA, 16 mA, 17 mA, 18 mA, 19 mA or 20 mA.

[0063] Optionally, the voltage and / or current output by the power supply 50 may be selectively changed to change the corrosion rate of the abnormal growth region 12. For example, in the initial stage of the specific corrosion, the power supply 50 outputs a higher voltage and a larger current to accelerate the corrosion rate, and before the abnormal growth region 12 is completely etched away, the voltage and current are reduced stepwise or linearly.

[0064] In another embodiment, the electrolyte 31 is maintained at a constant temperature of 30 to 55°C. By setting the temperature of the electrolyte 31 to a preset temperature higher than room temperature, the thermal motion speed of the molecules in the electrolyte 31 can be accelerated, and the collision probability between the reactants (i.e., the electrolyte 31 and the compounds contained in the abnormal growth region 12) can be increased, thereby increasing the chemical reaction rate, which is conducive to accelerating the reaction rate of specific corrosion. Generally, the constant temperature of the electrolyte 31 cannot exceed 55°C to avoid excessive reaction in the reaction area where the electrolyte 31 contacts the abnormal growth region 12, thereby improving the controllability of the specific corrosion process. At the same time, by maintaining the electrolyte 31 in the constant temperature electrolytic cell 30 at a constant temperature, the temperature of each position in contact with the abnormal growth region 12 and the electrolyte 31 is kept consistent, thereby ensuring the uniformity of the temperature distribution, and making the reaction rate of the specific corrosion of the electrolyte 31 and each area of ​​the abnormal growth region 12 consistent, thereby ensuring the uniformity of the corrosion process from the side 121 to the edge 111. Figure 2 As shown, to ensure that the electrolyte 31 is in a constant temperature state, the constant temperature electrolytic cell 30 can be partially immersed in the aqueous solution 41 of the water bath heating device 40, and the aqueous solution 41 can be heated and kept at a constant temperature by any heating device (not shown) in the prior art, so that the temperature of the electrolyte 31 is maintained at a constant temperature of a preset temperature. Alternatively, the entire specific corrosion reaction process can be divided into several reaction stages according to the needs of the reaction process, and a higher constant temperature is maintained in the early stage of the reaction, and a lower constant temperature is maintained in the later stage of the reaction, and the temperature of the electrolyte 31 in multiple reaction stages is higher than room temperature. The room temperature referred to in each embodiment of the present invention defaults to 23°C.

[0065] In another embodiment, the gallium nitride crystal is an undoped crystal.

[0066] Usually, along Figure 1 At the top and bottom surfaces 101 and 102 of the epitaxially grown GaN crystal 10 in the direction of arrow 1, impurities in the growth environment are less likely to deposit on the top and bottom surfaces 101 and 102 due to lattice discontinuities and boundary effects during GaN epitaxial growth, as well as the lower contact area of ​​the growth environment relative to the edge 111. Consequently, the carrier concentrations due to, for example, oxygen impurities on the top and bottom surfaces 101 and 102 of the GaN crystal 10 are much lower than the carrier concentrations in the abnormal growth region 12 at the edge 111. During the specific etching process, the electrolyte 31 barely reacts with the undoped GaN crystal at the top and bottom surfaces 101 and 102, but only specifically etches the abnormal growth region 12. The reaction terminates at the edge 111 due to the rapid decrease in carrier concentration.

[0067] In other embodiments, Figure 5As shown, since the electrolyte 31 is consumed during the specific corrosion process, in order to ensure that the reaction rate remains stable, the elimination device 100 also includes a liquid replenishing device.

[0068] The rehydration device includes an inlet pipe 32, a rehydration pump 33 connected to the inlet pipe 32, a discharge pipe 34, and a discharge pump 35 connected to the discharge pipe 34. The inhydration pump 33 and the discharge pump 35 are controlled by an external control device, such as a single-chip microcomputer (not shown), which controls the activation and operation of the inhydration pump 33 and the discharge pump 35. The inlet pipe 32 replenishes new electrolyte 31 into the constant-temperature electrolytic cell 30, and the discharge pipe 34 removes the electrolyte 31 from the constant-temperature electrolytic cell 30 to ensure that the temperature of the electrolyte 31 remains constant at 30 to 55°C. The concentration of the weak acid solution constituting the electrolyte 31 also remains within a constant set range of 0.8 to 1.2 mol / L and a pH of 1 to 2.

[0069] In addition, as a further preferred embodiment, an ultrasonic transducer (not shown) can be provided at the bottom of the water bath heating device 40 and connected to an ultrasonic generator (not shown) via a wire. The ultrasonic waves generated by the ultrasonic transducer further accelerate the reaction rate of specific corrosion between the electrolyte 31 and the abnormal growth region 12, and facilitate the stripping and discharge of corrosion byproducts of the specific corrosion. At the same time, since mechanical polishing or grinding is avoided to remove the abnormal growth region 12 at the edge 111 of the gallium nitride crystal 10, cracking caused by excessive internal stress in the abnormal growth region 12 when removing the abnormal growth region 12 is effectively avoided, thereby significantly reducing the risk of cracking in the resulting gallium nitride crystal 11, which is beneficial to the production and processing of the gallium nitride crystal 11.

[0070] Optionally, in an embodiment, the ultrasonic power may be 300W and the ultrasonic frequency may be 80 kHz. After the specific etching is completed, the gallium nitride crystal 11 is obtained and finally cleaned with deionized water. The gallium nitride crystal 11 is then blown dry with nitrogen or spin-dried to produce a gallium nitride crystal 11 whose edge 111 does not include the abnormal growth region 12.

[0071] In another embodiment, as a further improvement of the supporting device shown in the above embodiment, Figure 6 Another specific embodiment of the support device 20 is shown. In this embodiment, the support device 20 includes a support plate 21 and a movable holding assembly 22. The support plate 21 is used to support the gallium nitride crystal 10. The bottom surface 102 of the gallium nitride crystal 10 is in contact with and pressed against the annular top surface 211 of the support plate 21. The movable holding assembly 22 flexibly holds the top surface 101 of the gallium nitride crystal 10, so that the support plate 21 and the movable holding assembly 22 jointly clamp the gallium nitride crystal 10.

[0072] The movable holding assembly 22 includes a holding member 221, a retaining member 222, and a buffering member 223. The retaining member 222 is movably connected to the support plate 21. The holding member 222 penetrates the holding member 221 and connects to the support plate 21. The buffering member 223 is formed on the side of the holding member 221 facing the gallium nitride crystal 10, and the buffering member 223 only presses the top surface 101 of the gallium nitride crystal 10. Specifically, the retaining member 222 can be a screw, forming a fixing bolt 2221 that penetrates the holding member 221 and the support plate 21. The fixing bolt 2221 has an external thread (not shown). The buffering member 223 can be made of a corrosion-resistant material, such as polytetrafluoroethylene (PTFE) or other corrosion-resistant, flexible material, to prevent the buffering member 223 from breaking during contact with the abnormal growth region 12.

[0073] An annular gap is formed between the movable holding assembly 22 and the support plate 21 to hold the gallium nitride crystal 10. The annular gap has a height of h. The support plate 21 and the holding member 221 form internal threads (not shown) that are threadedly connected to the external threads of the fixing bolt 2221. This allows the retaining member 222 to be screwed into the holding member 221 and the support plate 21, where it compresses and holds the top surface 101 of the gallium nitride crystal 10 via the buffer 223, thereby preventing displacement of the gallium nitride crystal 10 during the specific etching process. After the specific etching is complete, the holding member 221 is rotated to increase the annular gap height, facilitating separation of the gallium nitride crystal 10 from the support assembly 20.

[0074] As an optional embodiment, the retaining member 222 can also be set to Figure 6 The spring (not shown) that vertically tensions the pressing member 221 and the support plate 21 against each other or any other component that can mechanically establish a stable annular gap between the pressing member 221 and the support plate 21 is shown.

[0075] In this embodiment, the buffer 223 prevents damage or cracking of the GaN crystal 10 due to compression during fixation. Furthermore, the buffer 223 compresses the top surface 101 of the GaN crystal 10, fully exposing the side surfaces 121 of the GaN crystal 10. This eliminates the need for secondary adjustment of the relative position between the GaN crystal 10 and the buffer 223 during the specific etching process.

[0076] In another embodiment, Figure 7 As shown, Figure 7 FIG. 2 shows another embodiment of a support device 20. The support device 20 includes a support plate 21 and a movable holding assembly 22. The support plate 21 is used to support the gallium nitride crystal 10. The movable holding assembly 22 movably holds the top surface 101 and side surfaces 121 of the gallium nitride crystal 10. The support plate 21 and the movable holding assembly 22 jointly clamp the gallium nitride crystal 10.

[0077] The movable pressing assembly 22 includes: a pressing member 221, a retaining member 222, and a buffer member 223a. The retaining member 222 is movably connected to the support plate 21. The pressing member 221 is penetrated by the retaining member 222 and connected to the support plate 21. The buffer member 223a is formed on the side of the pressing member 221 facing the gallium nitride crystal 10. The buffer member 223a is embedded in the inner side of the pressing member 221 facing the gallium nitride crystal 10. The buffer member 223a simultaneously presses the top surface 101 and the side surface 121 of the gallium nitride crystal 10, so that the gallium nitride crystal 10 is clamped by the support plate 21 and the movable pressing assembly 22.

[0078] An annular gap is formed between the movable pressing assembly 22 and the support plate 21 to clamp the gallium nitride crystal 10 , and the annular gap height is h′, and the annular gap height h′ is smaller than the annular gap height h, so as to adapt to the specific etching treatment of the gallium nitride crystal 10 with a smaller thickness.

[0079] It is worth mentioning that Figure 7 The disclosed supporting device 20 and Figure 6 The other technical solutions included in the supporting device 20 shown are the same and will not be described again here.

[0080] In other embodiments, Figure 8 As shown, Figure 8 FIG2 shows another embodiment of a supporting device 20. The supporting device 20 includes a support plate 21 and a movable pressing assembly 22. The support plate 21 is used to support the gallium nitride crystal 10. The movable pressing assembly 22 movably presses the side surface 121 of the gallium nitride crystal 10. The support plate 21 and the movable pressing assembly 22 jointly clamp the gallium nitride crystal 10.

[0081] The movable pressing assembly 22 includes a pressing member 221, a retaining member 222, and a buffer member 223b. The retaining member 222 is movably connected to the support plate 21. The pressing member 221 is penetrated by the retaining member 222 and connected to the support plate 21. The buffer member 223b is formed on the side of the pressing member 221 facing the gallium nitride crystal 10. The buffer member 223b only presses the side surface 121 of the gallium nitride crystal 10. The cross-section of the buffer member 223b can be a right-angled triangle. By pressing the side surface 121 of the gallium nitride crystal 10 at a right angle, the side surface 121 of the gallium nitride crystal 10 is exposed to the greatest extent.

[0082] It is worth mentioning that Figure 8 The disclosed supporting device 20 and Figure 6 or Figure 7 The other technical solutions included in the supporting device 20 shown are the same and will not be described again here.

[0083] It should be pointed out that for Figures 6 to 8The various supporting devices 20 shown and the various elimination devices 100 including different supporting devices 20, the holding member 221 and the buffer member 223 (or buffer member 223a or buffer member 223b) can be either continuously arranged integral annular components or non-continuously arranged independent components arranged in an annular manner, so that the buffer member 223 (or buffer member 223a or buffer member 223b) can movably press the top surface 101 and / or side surface 121 of the gallium nitride crystal 10.

[0084] Based on the technical solutions contained in the multiple embodiments of the elimination device 100 disclosed above, the present invention also discloses a method for eliminating edge defects of gallium nitride crystals (hereinafter referred to as "elimination method"). The elimination method adopts the elimination device in any of the above embodiments. Specifically, Figure 9 As shown, the elimination method includes the following steps S1 to S4.

[0085] Step S1: placing a gallium nitride crystal 10 having an abnormal growth region 12 at its edge 111 on a supporting device 20 , wherein the abnormal growth region 12 contains defects.

[0086] The supporting device 20 can be Figure 3 、 Figure 6 、 Figure 7 or Figure 8 Any of the ones shown.

[0087] Step S2 : Submerge the gallium nitride crystal 10 and the supporting device 20 in the electrolyte 31 of the constant temperature electrolytic tank 30 .

[0088] Step S3: Electrically contact the anode 51 with the gallium nitride crystal 10 and the cathode 52 with the electrolyte 31, establishing electrical connections between the anode 51, the cathode 52, and the power supply 50. The power supply 50, the anode 51, the gallium nitride crystal 10, the electrolyte 31, and the cathode 52 form an electrolysis circuit.

[0089] In step S4 , the power supply 50 is used to supply power to the anode 51 and the cathode 52 respectively, so as to specifically etch the abnormal growth region 12 at the edge 111 of the gallium nitride crystal 10 .

[0090] The above-mentioned elimination method also includes: heating the electrolyte 31 in the constant temperature electrolytic tank 30 to a preset temperature and maintaining the constant temperature; starting the power supply 50 to specifically corrode the abnormal growth region 12 at the edge 111 of the gallium nitride crystal 10 submerged in the electrolyte 31; wherein the preset temperature is 30-55°C, and the defects in the abnormal growth region 12 undergo an oxidation-reduction reaction with the electrolyte 31, thereby being specifically corroded until the abnormal growth region 12 is completely corroded.

[0091] Furthermore, the voltage between the anode 51 and the cathode 52 is 80-150 VDC, and the current between the anode 51 and the cathode 52 is 5-20 mA.

[0092] Furthermore, the gallium nitride crystal 11 is a non-doped crystal. The electrolyte 31 is selected from a weak acid solution, a salt solution or a buffer solution.

[0093] Furthermore, the weak acid solution includes oxalic acid, acetic acid, phosphoric acid, boric acid or nitrous acid, the concentration of the weak acid solution is 0.8-1.2 mol / L, and the pH value of the weak acid solution is 1-2.

[0094] The elimination method disclosed in this embodiment further includes: in step S4, selectively changing the voltage and / or current output by the power supply 50 to change the corrosion rate of the abnormal growth region 12. For example, in the initial stage of the specific corrosion, the power supply 50 outputs a higher voltage and a larger current to accelerate the corrosion rate, and before the abnormal growth region 12 is completely etched away, the voltage and current are reduced stepwise or linearly.

[0095] In one embodiment, after the abnormal growth region 12 is completely etched, the gallium nitride crystal 11 is cleaned with deionized water, and then the gallium nitride crystal 11 is blown dry with nitrogen or spin-dried to obtain a gallium nitride crystal 11 whose edge 111 does not include the abnormal growth region 12.

[0096] Finally, Figure 10 and Figure 11 As shown, the aforementioned elimination method completely etches the abnormal growth region 12 at the edge 111 of the inner gallium nitride crystal 11 without causing corrosion to the inner gallium nitride crystal 11. This achieves specific etching, precisely controls the etching depth and range, and avoids excessive corrosion in certain areas. As a result, the resulting gallium nitride crystal 11 exhibits a continuous distribution of grains on both the surface and within, without any cracks.

[0097] The elimination method of the present invention is implemented by using the elimination device disclosed in any of the above specific embodiments. The specific technical solution of the elimination device is shown in the above embodiments and will not be repeated here.

[0098] Finally, based on the technical concepts contained in the embodiments of the aforementioned elimination method and / or elimination device, the present invention also discloses a gallium nitride crystal, which is prepared using the gallium nitride crystal edge defect elimination method as described in any of the aforementioned embodiments.

[0099] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0101] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A device for eliminating edge defects of gallium nitride crystals, characterized in that: include: A supporting device for the gallium nitride crystal, a constant-temperature electrolytic cell containing the electrolyte, and an electrolysis system; The electrolyte submerges the gallium nitride crystal and the supporting device; The electrolysis system includes a power supply, an anode connected to the power supply, and a cathode connected to the power supply. The anode electrically contacts the gallium nitride crystal, and the cathode electrically contacts the electrolyte. The power supply, the anode, the gallium nitride crystal, the electrolyte, and the cathode form an electrolysis circuit. The power supply supplies power to the anode and the cathode respectively to specifically corrode an abnormal growth area at the edge of the gallium nitride crystal, where the abnormal growth area contains defects.

2. The elimination device according to claim 1, characterized in that The voltage between the anode and the cathode is 80-150 VDC, and the current between the anode and the cathode is 5-20 mA; and / or, the electrolyte is maintained at a constant temperature of 30 to 55° C.; And / or, the gallium nitride crystal is a non-doped crystal; And / or, after the power supply is started, defects in the abnormal growth area undergo an oxidation-reduction reaction with the electrolyte to be specifically corroded until the abnormal growth area is completely corroded.

3. The elimination device according to claim 2, characterized in that The electrolyte is selected from a weak acid solution, a salt solution or a buffer solution; the weak acid solution includes oxalic acid, acetic acid, phosphoric acid, boric acid or nitrous acid, the concentration of the weak acid solution is 0.8-1.2 mol / L, and the pH value of the weak acid solution is 1-2.

4. The elimination device according to any one of claims 1 to 3, characterized in that The supporting device includes a support plate for supporting the gallium nitride crystal; Alternatively, the supporting device includes a supporting plate for supporting the gallium nitride crystal, and a movable pressing assembly for movably pressing the top surface and / or side surfaces of the gallium nitride crystal, and the supporting plate and the movable pressing assembly jointly clamp the gallium nitride crystal.

5. The elimination device according to claim 4, characterized in that: The movable pressing assembly includes: a retaining member movably connected to the support plate, a pressing member penetrated by the retaining member and connected to the support plate, and a buffer formed on the side of the pressing member facing the gallium nitride crystal, wherein the buffer presses the top surface and / or side surface of the gallium nitride crystal.

6. The elimination device according to claim 1, characterized in that The size of the gallium nitride crystal is greater than 2 inches; And / or, the defects include oxygen impurities, the concentration of the oxygen impurities in the abnormal growth region is greater than the concentration of the oxygen impurities in the remaining region of the gallium nitride crystal that does not include the abnormal growth region; the carrier concentration caused by the oxygen impurities in the abnormal growth region reaches 10 19 / cm 3 ; And / or, the stress of the abnormal growth region is greater than the stress of the remaining region of the gallium nitride crystal excluding the abnormal growth region.

7. A method for eliminating edge defects of gallium nitride crystals, characterized in that: The following steps are involved: placing a gallium nitride crystal having an abnormal growth region on an edge on a supporting device, wherein the abnormal growth region contains defects; Submerging the gallium nitride crystal and the supporting device in the electrolyte of a constant temperature electrolytic tank; Electrically contacting the anode with the gallium nitride crystal and the cathode with the electrolyte, respectively establishing electrical connections between the anode and the cathode and a power source; wherein the power source, the anode, the gallium nitride crystal, the electrolyte, and the cathode form an electrolysis circuit; The power supply is used to supply power to the anode and the cathode respectively, so as to specifically erode the abnormal growth area at the edge of the gallium nitride crystal.

8. The elimination method according to claim 7, characterized in that: The elimination method further comprises: The electrolyte in the constant temperature electrolytic tank is heated to a preset temperature and maintained at a constant temperature; the power supply is activated to specifically corrode the abnormal growth region at the edge of the gallium nitride crystal submerged in the electrolyte; wherein the preset temperature is 30 to 55° C., and defects in the abnormal growth region undergo an oxidation-reduction reaction with the electrolyte, thereby being specifically corroded until the abnormal growth region is completely corroded; and / or, the voltage between the anode and the cathode is 80-150 VDC, and the current between the anode and the cathode is 5-20 mA; And / or, the gallium nitride crystal is a non-doped crystal; And / or, the electrolyte is selected from a weak acid solution, a salt solution or a buffer solution; the weak acid solution includes oxalic acid, acetic acid, phosphoric acid, boric acid or nitrous acid, the concentration of the weak acid solution is 0.8-1.2 mol / L, and the pH value of the weak acid solution is 1-2.

9. The elimination method according to claim 7, characterized in that: The elimination method further comprises: The voltage and / or the current output by the power supply are selectively changed to change the etching rate for specifically etching the abnormal growth area.

10. A gallium nitride crystal, characterized in that: The gallium nitride crystal is prepared by the method for eliminating edge defects of the gallium nitride crystal according to any one of claims 7 to 9.

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