A method of forming a gallium nitride device and a gallium nitride device

Abstract

The application relates to the technical field of semiconductor manufacturing, in particular to a gallium nitride device forming method and a gallium nitride device. The gallium nitride device forming method provided by the application comprises the following steps: providing a to-be-etched substrate; the to-be-etched substrate at least comprises a substrate layer, a first conductive type gallium nitride layer, a quantum well layer and a second conductive type gallium nitride layer which are arranged in a laminated mode; dry etching the to-be-etched substrate; under an etching gas environment, an inductively coupled plasma etching is performed to form an etching groove in the to-be-etched substrate, so that the to-be-etched substrate forms a preliminary etching device; wherein the chemical corrosion and the physical bombardment jointly act; damage is repaired; under a repairing gas environment, the inductively coupled plasma etching is performed to form a target etching device from the preliminary etching device; and the chemical corrosion plays a leading role. The application can solve the problem that the dry etching of the gallium nitride device causes damage to the product structure sidewall, aggravates the sidewall defects and leads to the increase of the non-radiation recombination probability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a gallium nitride device forming method and a gallium nitride device. BACKGROUND

[0002] With the development of display technology, LED display technology is ushering in a leapfrog development, and the new generation display technology represented by Mirco-LED (micro light emitting diode) technology has become a typical representative.

[0003] The growing demand for mobile displays is driving the adoption of micro-pixels in next-generation display technologies. This shift from traditional liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) to Micro LED technology has significant advantages, including higher resolution, reduced energy consumption, longer lifespan, higher brightness, and faster response time. In particular, gallium nitride (GaN)-based Micro LEDs have emerged as a key technology in display technology and visible light communication (VLC) research. However, as chip size decreases, particularly in ultra-small chips critical for high-definition displays, the decline in efficiency poses a significant challenge to the commercial viability of Micro LEDs. In traditional top-down LED fabrication processes, dry etching using inductively coupled plasma (ICP) is primarily used, which can cause plasma-related damage to the device sidewalls. As device size shrinks, this damage becomes more pronounced due to the increased perimeter-to-area ratio, exacerbating the size effect. Sidewall damage increases the Shockley-Read-Hall (SRH) recombination rate, significantly reducing internal quantum efficiency and increasing peak current density, which adversely affects display performance. Historically, methods involving wet etching and deposition of passivation layers have been used to mitigate these negative effects. In particular, the use of wet etching after dry etching has been shown to significantly reduce non-radiative recombination defects, which is one of the most direct and effective strategies to alleviate etching damage and minimize size-related effects. However, alkaline wet etching lacks uniformity and has limited compatibility with nitride semiconductor processes, potentially posing potential risks to other functional layers, leading to reduced chip yield. Additionally, wet etching increases sidewall roughness and dangling bond density in nitride LEDs, reducing chip reliability. Recently, atomic layer etching and neutral beam etching have shown promise due to their low damage characteristics. Unfortunately, these methods have extremely low etching rates and are costly, limiting their scalability and practical application in future display technologies. While early strategies focused on mitigating sidewall damage effects in Micro LED devices, previous research primarily analyzed this damage from the perspective of final device performance, largely ignoring potential mechanisms and physical models. Therefore, to effectively advance Micro LED technology towards large-scale commercialization, there is an urgent need to understand the form and impact of sidewall damage. This insight must be combined with the development of compatible industrial strategies to effectively minimize surface defects, thereby fully realizing the full potential of Micro LED technology.

[0004] In the preparation process of the Mirco-LED device, the preparation of the film layer needs to be etched to form the required shape. Dry etching is a mainstream processing technology for forming the required shape of the film layer of the Mirco-LED device. In particular, the device of gallium nitride material. Compared with other processing technologies such as wet etching, dry etching technology has many advantages such as good macroscopic morphology of product structure side wall, high etching rate, high selectivity and high anisotropy. However, dry etching can also cause damage to the product structure side wall, aggravate the side wall defects, increase the probability of non-radiative recombination, and thus reduce the luminous efficiency. With the development of LED display technology, the size of the light emitting chip is becoming smaller and smaller, and this defect will be further amplified.

[0005] Therefore, a solution is needed to solve the problem that dry etching of gallium nitride devices can cause damage to the product structure side wall, aggravate the side wall defects, and increase the probability of non-radiative recombination. SUMMARY

[0006] Therefore, the present application provides a gallium nitride device forming method and a gallium nitride device to solve the problem that dry etching of gallium nitride devices can cause damage to the product structure side wall, aggravate the side wall defects, and increase the probability of non-radiative recombination.

[0007] The present application provides a gallium nitride device forming method, comprising the following steps: providing a to-be-etched substrate; the to-be-etched substrate at least comprises a substrate layer, a first conductive type gallium nitride layer, a quantum well layer and a second conductive type gallium nitride layer arranged in layers; the first conductive type gallium nitride layer and the second conductive type gallium nitride layer are opposite in conductive type; dry etching the to-be-etched substrate; in the etching gas environment, by inductively coupled plasma etching, forming an etching groove in the to-be-etched substrate, so as to form a preliminary etching device of the to-be-etched substrate; the etching groove extends from the second conductive type gallium nitride layer to the substrate layer, penetrates the quantum well layer, and the groove bottom penetrates into the first conductive type gallium nitride layer; damage repair; in the repair gas environment, by inductively coupled plasma etching, the preliminary etching device is formed into a target etching device. In the process of damage repair, the etching rate is less than the etching rate in the process of dry etching the to-be-etched substrate.

[0008] In one aspect of the present application, in the damage repair step, the following steps are included: forming a second etching mask on the side of the second conductive type gallium nitride layer away from the substrate layer, the second etching mask exposes the etching groove; in the inductively coupled plasma etching machine, the repair gas is introduced into the process chamber, and the second etching mask is used as a mask to inductively coupled plasma etch the preliminary etching device; the second etching mask is removed to form the target etching device.

[0009] In one aspect of the present application, in the step of repairing the damage, the repair gas comprises Cl2; the flow rate of the repair gas is 50sccm-110sccm.

[0010] In one aspect of the present application, in the step of repairing the damage, the process conditions further comprise: the plasma source power is 100W-400W; the bias power is 10W-50W; the direct current bias is 20V-60V; the pressure in the process chamber is 1mT-10mT; the temperature of the chiller is -10℃-10℃; the material of the second etching mask comprises SiO2, SiN, metal or photoresist.

[0011] In one aspect of the present application, in the step of dry etching the substrate to be etched, the step comprises: forming an initial first etching mask on the side of the second conductivity type gallium nitride layer away from the substrate layer; patterning the initial first etching mask to form a first etching mask; the surface of the second conductivity type gallium nitride layer exposed by the first etching mask; in an inductively coupled plasma etching machine, the etching gas is introduced into the process chamber, and the first etching mask is used as a mask to inductively couple plasma to etch the substrate to be etched; and removing the first etching mask to form the preliminary etching device.

[0012] In one aspect of the present application, in the step of dry etching the substrate to be etched, the etching gas comprises a main etching gas and an auxiliary etching gas; the main etching gas comprises Cl2, and the flow rate of the main etching gas is 20sccm-80sccm; the auxiliary etching gas comprises BCl3, Ar, N2 or He; the flow rate of the auxiliary etching gas is 10sccm-40sccm;

[0013] In one aspect of the present application, in the step of repairing the damage, the process conditions further comprise: the plasma source power is 300W-800W; the bias power is 100W-200W, and the plasma source bias power is less than half of the plasma source power; the direct current bias is 100V-200V; the pressure in the process chamber is 1mT-10mT; the temperature of the chiller is -10℃-10℃; the material of the first etching mask comprises SiO2, SiN, metal or photoresist.

[0014] In one aspect of the present application, the method for forming a gallium nitride device further comprises the step of: using a purge gas to purge the target etching device to remove residual etching gas and repair gas; in the step of purging the target etching device, a plurality of purge cycles are included; each purge cycle includes two purge stages; the two purge stages comprise: a first stage of continuously introducing the repair gas into the process chamber and a second stage of continuously evacuating.

[0015] In one aspect of the present application, the number of repetitions of the purging cycle is 8 to 12 times; the first stage time is 2s to 4s; and the second stage time is 2s to 4s.

[0016] The present application also provides a gallium nitride device formed by the gallium nitride device forming method.

[0017] The present application has the following advantages:

[0018] The gallium nitride device forming method provided by the present application first etches a to-be-etched substrate in an etching gas environment by inductively coupled plasma etching to obtain a preliminary etched device; and then continues inductively coupled plasma etching in a repair gas environment. In the repair gas environment, the inductively coupled plasma etching is slowed down, which can effectively remove the damage layer formed in the etching step, obtain a surface with relatively lower roughness, make the surface of the device after etching and repair have better properties, and obtain a device surface with good shape, thereby reducing the defects of the sidewall and preventing the probability of non-radiative recombination from becoming larger. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0020] Figure 1 A partial structure schematic diagram of a gallium nitride device etched by a dry etching method;

[0021] Figure 2 A flowchart of the gallium nitride device forming method of an embodiment of the present application;

[0022] Figure 3 A partial structure schematic diagram of a to-be-etched substrate in the process of the gallium nitride device forming method of an embodiment of the present application;

[0023] Figure 4 A device state schematic diagram of forming an initial first etching mask in the process of the gallium nitride device forming method of an embodiment of the present application;

[0024] Figure 5 A device state schematic diagram of forming a first etching mask in the process of the gallium nitride device forming method of an embodiment of the present application;

[0025] Figure 6Schematic diagram of a device state in which a preliminary etching device is formed during a method for forming a gallium nitride device according to an embodiment of the present invention;

[0026] Figure 7 Schematic diagram of a device state in which a target etched device is formed during a method for forming a gallium nitride device according to an embodiment of the present invention;

[0027] Figure 8 A schematic diagram of a partial structure of a gallium nitride device formed by a method for forming a gallium nitride device according to an embodiment of the present invention;

[0028] Figure 9 is a graph showing the variation of DC bias voltage with increasing process gas flux in a method for forming a gallium nitride device according to an embodiment of the present invention;

[0029] Figure 10 This is a graph showing the variation of DC bias voltage with increasing plasma source power in a method for forming a gallium nitride device according to an embodiment of the present invention;

[0030] Figure 11 is a graph showing the increase in photoluminescence intensity (PL) as plasma source power increases in a method for forming a gallium nitride device according to an embodiment of the present invention;

[0031] Figure 12 A graph showing the variation of DC bias voltage with increasing bias power in a method for forming a gallium nitride device according to an embodiment of the present invention;

[0032] Figure 13 FIG. 1 is a graph showing the variation of the DC bias voltage with increasing chamber pressure in a method for forming a gallium nitride device according to an embodiment of the present invention.

[0033] Figure 14a An electron microscope image of the local morphology of a gallium nitride device formed by a gallium nitride device forming method according to an embodiment of the present invention before a damage repair step is performed;

[0034] Figure 14b for Figure 14a A magnified view of the local edge of the device;

[0035] Figure 14c This is an electron microscope image of the local morphology of a gallium nitride device formed by a gallium nitride device forming method according to an embodiment of the present invention after a damage repair step.

[0036] Description of reference numerals:

[0037] 100 - substrate layer; 200 - first conductivity type gallium nitride layer; 300 - quantum well layer; 400 - second conductivity type quantum well layer; 500 - initial first etching mask; 510 - first etching mask; 520 - second etching mask; damaged layer 600; A - etching gas; B - repair gas. DETAILED DESCRIPTION

[0038] Reference Figure 1 A method for dry etching a gallium nitride device, and a gallium nitride device after etching, as shown in the figure, include a substrate layer 100, a first conductive type gallium nitride layer 200, a quantum well layer 300, and a second conductive type gallium nitride layer 400 arranged in layers; the first conductive type gallium nitride layer and the second conductive type gallium nitride layer are opposite in conductive type. After dry etching, an etching groove is formed from the second conductive type gallium nitride layer 400 to the substrate layer 100, penetrating the quantum well layer 300, and the groove bottom reaches the first conductive type gallium nitride layer 200. As shown in the figure, the gallium nitride device after etching leaves a damage layer 600 on the surface of the etching groove. The inventor found that the damage layer 600 is naturally formed during the etching process due to the corrosion of the dry etching gas on the gallium nitride; the damage layer 600 causes sidewall damage of the device, which aggravates the sidewall defects and increases the non-radiative recombination probability.

[0039] To solve the problem that dry etching of a gallium nitride device causes damage to the sidewall of the product structure, aggravates the sidewall defects, and increases the non-radiative recombination probability, the present application provides a gallium nitride device forming method and a gallium nitride device.

[0040] The gallium nitride device forming method provided by the present application includes the following steps: providing a to-be-etched substrate; the to-be-etched substrate at least includes a substrate layer, a first conductive type gallium nitride layer, a quantum well layer, and a second conductive type gallium nitride layer arranged in layers; the first conductive type gallium nitride layer and the second conductive type gallium nitride layer are opposite in conductive type; dry etching the to-be-etched substrate; in an etching gas environment, an etching groove is formed on the to-be-etched substrate by inductively coupled plasma etching, so as to form a preliminary etching device; the etching groove extends from the second conductive type gallium nitride layer to the substrate layer, penetrates the quantum well layer, and the groove bottom reaches the first conductive type gallium nitride layer; damage repair; in a repair gas environment, the preliminary etching device is formed into a target etching device by inductively coupled plasma etching.

[0041] The gallium nitride device provided by the present application is manufactured by using the gallium nitride device forming method provided by the present application.

[0042] The technical solutions of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application. In the description of the present application, it should be noted that the terms "first", "second", "third" are only used for description purposes, and cannot be understood as indicating or implying relative importance.

[0043] Embodiment 1

[0044] Reference Figure 2 , and Figures 3-8 The embodiment provides a gallium nitride device forming method, comprising the following steps:

[0045] A to-be-etched substrate is provided; the to-be-etched substrate comprises at least the following layers which are arranged in sequence: a substrate layer 100, a first-conductivity-type gallium nitride layer 200, a quantum well layer 300 and a second-conductivity-type gallium nitride layer 400.

[0046] The first-conductivity-type gallium nitride layer 200 and the second-conductivity-type gallium nitride layer 400 are opposite in conductivity type; for example, in different embodiments, when the first-conductivity-type gallium nitride layer 200 is a P-type doped semiconductor layer, the second-conductivity-type gallium nitride layer 400 is an N-type doped semiconductor layer; conversely, when the first-conductivity-type gallium nitride layer 200 is an N-type doped semiconductor layer, the second-conductivity-type gallium nitride layer 400 is a P-type doped semiconductor layer. In the embodiment, the first-conductivity-type gallium nitride layer 200 is an N-type doped semiconductor layer, and the second-conductivity-type gallium nitride layer 400 is a P-type doped semiconductor layer.

[0047] The to-be-etched substrate is dry-etched; an etching groove is formed in the to-be-etched substrate by inductively coupled plasma etching in an etching gas A environment, so that a preliminary etching device is formed in the to-be-etched substrate; the etching groove extends from the second-conductivity-type gallium nitride layer 400 to the substrate layer 100, penetrates through the quantum well layer 300, and the groove bottom reaches the first-conductivity-type gallium nitride layer 200.

[0048] Damage repair; the preliminary etching device is formed into a target etching device by inductively coupled plasma etching in a repair gas B environment.

[0049] In the process of damage repair, the etching rate is less than the etching rate in the process of dry-etching the to-be-etched substrate.

[0050] The method for forming a gallium nitride device provided by the embodiment first etches a to-be-etched substrate in an etching gas A environment through inductively coupled plasma etching to obtain a preliminary etched device; and then continues inductively coupled plasma etching in a repair gas B environment. The inductively coupled plasma etching is slowed down, which can effectively remove the damage layer formed in the etching step, obtain a surface with relatively lower roughness, and make the surface of the device after etching and repair have better properties, so that a device surface with good shape can be obtained, thereby reducing defects of the sidewall and preventing the probability of non-radiative recombination from being large.

[0051] Further, referring to Figure 7 In the embodiment, the damage repair step includes the following steps:

[0052] A second etching mask 520 is formed on the side of the second conductive type gallium nitride layer 400 away from the substrate layer, and the second etching mask 520 exposes the etching groove;

[0053] In the inductively coupled plasma etching machine, the repair gas B is introduced into the process chamber, and the preliminary etched device is inductively coupled plasma etched with the second etching mask 520 as a mask.

[0054] Then, referring to Figure 8 , the second etching mask 520 is removed to form the target etched device.

[0055] In this way, the second conductive type gallium nitride layer 400 is covered by the second etching mask 520, and the etching groove is exposed, so that the inductively coupled plasma etching process in the repair gas B environment only occurs on the etching groove, and the damage layer 600 (position reference Figure 1 ) on the sidewall and the bottom of the etching groove is accurately etched, which can effectively etch and remove the damage layer 600 and prevent the residual etching gas A from further corroding the second conductive type gallium nitride layer 400 in the subsequent process, thereby avoiding further deepening of the damage layer 600.

[0056] Further, in the embodiment, the damage repair step includes the following steps:

[0057] The repair gas includes Cl2;

[0058] The flow rate of the repair gas B is 50sccm-110sccm.

[0059] In the repair stage, in order to slow down the corrosion of the second conductive type gallium nitride layer 400, the inductively coupled plasma etching process is dominated by gas chemical corrosion, so that the gas environment in the process only contains Cl2.

[0060] Referring to Figure 9 , Figure 9The curve shows that the direct current bias is low between 40 sccm and 120 sccm, and the lower the direct current bias, the smaller the damage. Considering the error range and the redundancy of the operation process, the flux of the repair gas B in the repair process is selected to be 50 sccm to 110 sccm. If the flux of the repair gas B is lower than 50 sccm, the gas may not be dissociated, and the process may not be performed. In addition, the plasma energy may be too low to effectively remove the etching damage layer. If the flux of the repair gas B is higher than 110 sccm, the plasma energy may be too high, thereby causing new damage. Therefore, by selecting the gas flux in the range of 50 sccm to 110 sccm, a balance can be achieved between effectively removing the damage and avoiding increasing new damage.

[0061] Further, in the embodiment, the process conditions in the damage repair step further include:

[0062] The plasma source power is 100 W to 400 W.

[0063] Reference Figure 10 , Figure 10 The curve is a curve of the direct current bias changing with the increase of the plasma source power. It is generally believed that under the premise that other conditions remain unchanged, the lower the source power, the lower the bombardment of the plasma on the material of the device to be etched. However, the method takes into account the collision between ions, and a window of the minimum direct current bias is obtained through experiments, as shown in Figure 10 By observing the overall curve, the direct current bias is the lowest when the source power is 400 W, so the window is around 400 W. The reason for selecting the interval of <400 W is that the larger the source power, the larger the ion energy. Under the premise that the direct current bias is not much different, the larger the ion energy, the greater the damage to the material. Therefore, in the selection of this parameter, the Figure 11 The photoluminescence (PL) test is used to further narrow the window of the source power. It is generally believed that the lower the direct current bias, the smaller the etching damage to the material. However, the size of the source power determines the size of the energy carried by the ions after the process gas is dissociated. Even if the direct current bias is at the lowest value, a larger source power will still cause etching damage. Finally, the photoluminescence (PL) test is performed on the sample after etching, as shown in Figure 11 The balance point between the low direct current bias and the low source power is found, and a relatively ideal plasma source power is obtained.

[0064] The bias power is 10W-50W. The DC bias is 20V-60V. During the plasma etching process, a negative DC voltage is formed on the surface of the electrode (wafer) due to the difference in mobility between electrons and ions. Specifically, the mass of an electron is much smaller than that of an ion, so under the action of a radio frequency electric field, electrons can quickly move to the surface of the electrode to accumulate, resulting in a negative charge on the surface of the electrode, and finally forming a negative DC bias between the electrode and the plasma, which is referred to as the DC bias in this article.

[0065] Reference Figure 12 , Figure 12 is a curve graph of the DC bias changing with the increase of the bias power. The size of the DC bias is proportional to the size of the bias power. In theory, the lower the bias power, the lower the bias power required. As can be seen from the curve, the DC bias is proportional to the bias power, so it is desirable to choose a lower bias power. Therefore, by choosing a bias power in the range of 10W-50W, a balance can be achieved between ensuring the operation of the process equipment and avoiding the adverse effects of excessively high voltage on the equipment.

[0066] The pressure in the process chamber is 1mT-10mT.

[0067] Reference Figure 13 , Figure 13 is a curve graph of the DC bias changing with the increase of the chamber pressure. As Figure 13 indicated, within a certain range of gas flux, the lower the pressure, the lower the DC bias, so by choosing a pressure in the range of 1mT-10mT, a lower DC bias can be selected, thereby causing less damage to the gallium nitride of the second conductive type gallium nitride layer 400. If it is lower than 1mT, the pressure is too low, which may cause the process gas to be unable to dissociate, and the equipment cannot work; if it is higher than 10mT, the pressure is too high, which will affect the uniformity. Therefore, by choosing a pressure in the range of 1mT-10mT, a balance can be achieved between ensuring the dissociation of the process gas and ensuring the uniformity.

[0068] The cooler temperature is -10℃-10℃.

[0069] The material of the second etching mask includes SiO2, SiN, metal or photoresist.

[0070] Further, in the embodiment, the step of dry etching the substrate to be etched includes the following steps:

[0071] Reference Figure 4 , an initial first etching mask 500 is formed on the side of the second conductive type gallium nitride layer 400 away from the substrate layer 100;

[0072] Reference Figure 5, the initial first etching mask 500 is patterned to form a first etching mask 510; the first etching mask 510 exposes a part of the surface of the second-conductivity-type gallium nitride layer 400;

[0073] Reference Figure 6 In an inductively coupled plasma etching machine, the first etching mask 510 is used as a mask to etch the substrate to be etched in the etching gas A environment; in this process, an etching groove is formed, and a damage layer 600 is naturally formed on the surface of the etching groove;

[0074] Figure 6 The first etching mask 510 is removed to form the preliminary etching device.

[0075] Further, in the embodiment, in the step of dry etching the substrate to be etched,

[0076] The etching gas includes a main etching gas and an auxiliary etching gas;

[0077] The main etching gas includes Cl 2。

[0078] The flow rate of the main etching gas is 20-80sccm.

[0079] The auxiliary etching gas includes BCl3, Ar, N2 or He.

[0080] The flow rate of the auxiliary etching gas is 10-40sccm.

[0081] The material of the first etching mask 510 includes SiO2, SiN, metal or photoresist.

[0082] In the dry etching process, the main purpose is to form an etching groove with a target size and structure, so fast and accurate etching is required. Therefore, the etching gas A is selected to include a main etching gas and an auxiliary etching gas. If the flow rate of the corresponding gas is too low, the plasma density will be affected, thereby affecting the etching rate of the damage layer, and a longer repair time may be required to achieve the same effect, which prolongs the process time. If the flow rate is too high, the equipment may not work because it exceeds the range of the flow meter. The selection of the main etching gas and the auxiliary etching gas and the corresponding parameter range can balance the relatively short process time and meet the working conditions of the equipment.

[0083] Further, in the embodiment, in the step of damage repair, the process conditions further include:

[0084] The plasma source power is 300-800W;

[0085] The bias power is 100W-200W, and the plasma source bias power is less than half of the plasma source power;

[0086] The direct current bias is 100V-200V.

[0087] The pressure in the process chamber is 1mT-10mT.

[0088] The cooler temperature is -10℃-10℃.

[0089] The material of the first etching mask includes SiO2, SiN, metal or photoresist.

[0090] Further, in the embodiment, the method for forming a gallium nitride device further comprises the following steps:

[0091] The target etching device is purged using a purge gas to remove residual etching gas A and repair gas B.

[0092] By removing the etching gas A and repair gas B involved in the surface of the target device through the purge gas, further corrosion of the gallium nitride by the gas in the subsequent process can be prevented, damage can be avoided, and the shape of the surface of the target etching device can be ensured.

[0093] The step of purging the target etching device includes a plurality of purge cycles; each purge cycle includes two purge stages.

[0094] The two purge stages include a first stage of continuously introducing the repair gas into the process chamber and a second stage of continuously evacuating. By multiple purge cycles and the first and second stages in each purge cycle, a relatively good device topography effect can be achieved.

[0095] Further, in the embodiment, the number of repetitions of the purge cycle is 8-12 times; the first stage time is 2-4 seconds; and the second stage time is 2-4 seconds. If the number of repetitions is too small, the purge may not be complete, resulting in residual process gas or by-products on the device surface that cannot be completely removed, thereby continuing to corrode the device after the process is completed. If the number of repetitions is too large, although it will not affect the device, it will cause waste of production capacity. Therefore, the number of repetitions of the purge cycle is in the range of 8-12 times, which can balance between completely removing the device surface and avoiding waste of production capacity.

[0096] To further illustrate the method for forming a gallium nitride device of the present application, a specific implementation process is provided as follows:

[0097] The device used in the process is an inductively coupled plasma etching machine. The device has independent control function of source radio frequency power and bias radio frequency power; the process gas flow is controlled by mass flow meter; the pressure cavity is controlled by molecular pump and mechanical pump; the sample is controlled by back helium system and cold water machine; the direct current bias can be read through software interface.

[0098] As shown in Figure 3 , a substrate to be etched is provided. In the process, the substrate to be etched is a gallium nitride epitaxial wafer, which includes a substrate layer 100, a first conductive type gallium nitride layer 200, a quantum well layer 300, and a second conductive type gallium nitride layer 400. The first conductive type gallium nitride layer 200 is an N-type doped semiconductor layer; the second conductive type gallium nitride layer 400 is a P-type doped semiconductor layer.

[0099] As shown in Figure 4 , an initial first etching mask 500 is formed on the surface of the gallium nitride epitaxial wafer. The material of the initial first etching mask 500 is SiO2.

[0100] As shown in Figure 5 , the initial first etching mask 500 is patterned by using photolithography and etching technology, so that the gallium nitride epitaxial material that needs to be etched to form an etching groove is exposed. After this step, the first etching mask 510 with etching blocking pattern is formed on the surface of the epitaxial material.

[0101] As shown in Figure 6 , the dry etching step is the main etching step in the gallium nitride forming method, which aims to etch the substrate to be etched to a target depth to form an etching groove and define the etching topography.

[0102] The main etching gas used in the main etching step is Cl2 with a flow rate of 50 sccm, and the auxiliary etching gas is BCl3 with a flow rate of 20 sccm. In this step, chemical corrosion and physical bombardment act together.

[0103] The plasma source power used in the main etching step is 500 W, and the bias power is 180 W. Generally, the bias power is set to be less than half of the source power.

[0104] The direct current bias in the main etching step process is 130 V.

[0105] The chamber pressure in the main etching step process is 3 mT.

[0106] The cooler temperature in the main etching step process is 0℃.

[0107] Then the first etching mask 510 is removed.

[0108] As shown in Figure 7As shown, the etch repair step aims to remove the damage layer 600 caused by the main etching step. This step also causes etch damage, but the damage is much smaller than the main etching step.

[0109] Before the etching step, the sample surface is purged after the end of the etch repair step and before the sample is transferred out of the vacuum chamber. The purpose is to remove the residual process gas between devices to prevent the gallium nitride material from continuing to erode after being transferred out of the device.

[0110] The repair gas used in the etch repair step is Cl2, with a flow rate of 50-110 sccm, and no auxiliary etching gas. Since physical bombardment is more likely to cause damage, this step is dominated by chemical corrosion. Since etch damage is mostly caused by physical bombardment, a chemical corrosion-dominated etch can reduce etch damage and obtain better device topography.

[0111] The plasma source power used in the etch repair step is 100-400 W, and the bias power is 10-50 W.

[0112] The direct current bias during the etch repair step process is controlled at 20-60 V.

[0113] The chamber pressure during the etch repair step process is 1-10 mT.

[0114] The chiller temperature during the etch repair step process is -10-10°C.

[0115] Finally, a purge process is performed to purge the target etched device after the damage repair step. The purge process is performed for 10 cycles, each cycle including two stages: the first stage is to continuously pass nitrogen for 3 seconds, and the second stage is to continuously pump vacuum for 3 seconds.

[0116] To demonstrate the actual effect of the embodiment, reference is made to Figures 14a-14c As shown in Figure 14a and Figure 14b , before the etch repair step, the edge of the device side / trench side layer structure of the device is not clear and has a large roughness, which is caused by etch damage. As shown in Figure 14c , after the etch repair step, the edge of the device side / trench side structure of the device is clear and has a small roughness, with good topography. Thus, it can be seen that after the method of embodiment 1 is formed, a device surface with good shape can be obtained, thereby reducing the defects of the sidewall and preventing the probability of non-radiative recombination from being large.

[0117] Specifically, a high-resolution transmission electron microscope (TEM) is used to study the MESA array before and after repair to investigate the effect of sidewall etch damage on the brightness of the "good area" of the chip and to verify the effect of the repair technology on the sidewall of the chip. As shown in Figure 14a ,Figure 14b As shown, the MESA edge prepared using conventional ICP technique shows significant changes in the sidewall etch region, approximately 50 nm inside, by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging. The multiple quantum wells (MQWs) of the LED epitaxial layer are blurred by the high-energy ion etching, and the originally clear and steep well-barrier interfaces disappear, and the element distribution of this functional layer becomes random. An amorphous layer of approximately 2 nm thick appears at the sidewall edge, indicating that the etching damage not only destroys the single-crystal integrity of the sidewall surface but also affects the depth of the lattice and element distribution of the light-emitting layer. This local sidewall morphology change weakens the carrier confinement capability of the MQW, thereby reducing the radiative recombination rate. Notably, the electron blocking layer (EBL) located above the quantum well also shows similar morphological damage as the MQWs, indicating that the integrity within a depth of 50 nm at the sidewall edge is damaged. This is the main reason for the sharp drop in sidewall brightness profile observed in the un-repaired chip. More critically, the damage to the EBL enhances the electron migration capability in this region, which dominates the leakage of a large number of carriers. The damaged EBL forms a low-resistance "parallel circuit" at the edge of the original diode configuration, attracting carriers away from the radiative recombination occurring in the good area. These carriers are directed to the sidewall region with high defect density, resulting in leakage current and non-radiative recombination. The reduced carrier blocking capability of the EBL and the lateral carrier concentration gradient of the chip work together to attract carriers that should have been radiatively recombined in the good area. This process explains the reason for the significant reduction in brightness of the good area observed in the chip brightness imaging.

[0118] Embodiment 2

[0119] The embodiment provides a gallium nitride device, which is manufactured by using the gallium nitride device forming method provided in the embodiment 1.

[0120] The gallium nitride device provided in the embodiment is manufactured by the gallium nitride device forming method in the embodiment 1. First, the preliminary etching device is obtained by etching the etching substrate under the etching gas environment through inductively coupled plasma etching; and then, the inductively coupled plasma etching is continued under the repairing gas environment. The inductively coupled plasma etching is slowed down under the repairing gas environment, which can effectively remove the damage layer formed in the etching step, obtain a surface with relatively lower roughness, make the surface state of the device after etching and repairing better, and obtain a device surface with good shape, thereby reducing the defects of the sidewall and preventing the probability of non-radiative recombination from being large.

[0121] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and can not be enumerated. The obvious changes or variations derived from the above description are still within the protection scope of the present application.

Claims

1. A method for forming a gallium nitride device, characterized in that: The following steps are involved: Providing a substrate to be etched; the substrate to be etched comprises at least a stacked arrangement of: a substrate layer, a first conductivity type gallium nitride layer, a quantum well layer, and a second conductivity type gallium nitride layer; the first conductivity type gallium nitride layer and the second conductivity type gallium nitride layer have opposite conductivity types; dry etching the substrate to be etched; forming an etched groove in the substrate to be etched by inductively coupled plasma etching in an etching gas environment, so that the substrate to be etched forms a preliminary etched device; the etched groove extends from the second conductive type gallium nitride layer to the substrate layer, penetrates the quantum well layer, and the bottom of the groove extends deep into the first conductive type gallium nitride layer; wherein chemical etching and physical bombardment act together; Damage repair; in a repair gas environment, forming a target etched device from the preliminary etched device by inductively coupled plasma etching; wherein chemical etching plays a leading role; The damage repair step includes the following steps: forming a second etching mask on a side of the second conductive type gallium nitride layer away from the substrate layer, wherein the second etching mask exposes the etching groove; In an inductively coupled plasma etcher, the repair gas is introduced into a process chamber, and the preliminary etching device is etched by inductively coupled plasma using the second etching mask as a mask; removing the second etching mask to form the target etching device; The method for forming a gallium nitride device further comprises the following steps: Using a purge gas to purge the target etching device to remove residual etching gas and repair gas; The step of purging the target etching device includes a plurality of purging cycles; each of the purging cycles includes two purging stages; The two purge stages include: a first stage of continuously introducing the repair gas into the process chamber and a second stage of continuously evacuating the chamber.

2. The gallium nitride device forming method according to claim 1, characterized in that: In the damage repair step, the repair gas includes Cl2; The flow rate of the repair gas is 50 sccm~110 sccm.

3. The gallium nitride device forming method according to claim 1, characterized in that: In the damage repair step, the process conditions also include: Plasma source power is 100W~400W; Bias power is 10W~50W; DC bias voltage is 20V~60V; The pressure in the process chamber is 1mT~10mT; The cooler temperature is -10℃~10℃; The material of the second etching mask includes SiO2, SiN, metal or photoresist.

4. The method for forming a gallium nitride device according to claim 1, wherein: The step of dry etching the substrate to be etched includes the following steps: forming an initial first etching mask on a side of the second conductive type gallium nitride layer away from the substrate layer; Patterning the initial first etching mask to form a first etching mask; the first etching mask exposes a portion of the surface of the second conductive type gallium nitride layer; In an inductively coupled plasma etcher, the etching gas is introduced into a process chamber, and the substrate to be etched is etched by inductively coupled plasma using the first etching mask as a mask; The first etching mask is removed to form the preliminary etching device.

5. The method for forming a gallium nitride device according to claim 4, wherein: In the step of dry etching the substrate to be etched, the etching gas includes a main etching gas and an auxiliary etching gas; The main etching gas includes Cl2; The flow rate of the main etching gas is 20 sccm~80 sccm; The auxiliary etching gas includes BCl3, Ar, N2 or He; The flow rate of the auxiliary etching gas is 10 sccm~40 sccm; The material of the first etching mask includes SiO2, SiN, metal or photoresist.

6. The gallium nitride device forming method according to claim 5, characterized in that: In the damage repair step, the process conditions also include: Plasma source power is 300W~800W; The bias power is 100W to 200W, and the bias power of the plasma source is less than half of the plasma source power; DC bias voltage is 100V~200V; The pressure in the process chamber is 1mT~10mT; The cooler temperature is -10℃~10℃; The material of the first etching mask includes SiO2, SiN, metal or photoresist.

7. The method for forming a gallium nitride device according to claim 1, wherein: The purge cycle is repeated 8 to 12 times; The first stage lasts for 2s~4s; The second stage lasts for 2s to 4s.

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