Method for manufacturing recycled substrate and laminate structure

Abstract

To provide a new recycled technology for substrates used as growth base substrates for group III nitrides.SOLUTION: A method for manufacturing a recycled substrate comprises: (a) a process for preparing a substrate on which a layer composed of group III nitrides is deposited on the main surface; and (b) a process for supplying halogen-containing gas to the substrate to etch away the layer, in the process (b), monitor light is irradiated to the substrate and the change in reflectance of the monitor light is measured.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a regeneration substrate and a method for manufacturing a laminated structure.

Background Art

[0002] Group III nitrides such as gallium nitride (GaN) are used as materials for manufacturing semiconductor devices such as light-emitting elements and transistors. As a growth substrate for epitaxially growing Group III nitrides, a sapphire substrate, a silicon carbide (SiC) substrate, or the like is used.

[0003] Due to various circumstances, there may be cases where it is desired to regenerate a growth substrate that has once been used for the growth of Group III nitrides so that it can be used again for the growth of Group III nitrides (for example, for the regeneration of a sapphire substrate, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One object of the present invention is to provide a novel regeneration technique for a substrate used as a growth substrate for Group III nitrides.

Means for Solving the Problems

[0006] According to one aspect of the present invention, (a) preparing a substrate having a layer composed of a Group III nitride deposited on a main surface; and (b) supplying a halogen-containing gas to the substrate to etch and remove the layer. In the above (b), a method for manufacturing a reproduction substrate that irradiates a monitor light onto the substrate and measures a change in the reflectance of the monitor light is provided.

[0007] According to another aspect of the present invention, (a) A step of preparing a substrate having a layer composed of a group III nitride deposited on a main surface; (b) A step of supplying a halogen-containing gas to the substrate and etching and removing the layer; (c) A step of growing crystals on the main surface from which the group III nitride has been removed, and in the above (b), a method for manufacturing a laminated structure that irradiates a monitor light onto the substrate and measures a change in the reflectance of the monitor light is provided.

Advantages of the Invention

[0008] A novel regeneration technique for a substrate used as a growth underlayer substrate for a group III nitride is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiment for Carrying Out the Invention

[0010] <One Embodiment> A method for manufacturing a reproduction substrate according to an embodiment of the present invention will be described. The method for manufacturing a reproduction substrate according to the present embodiment includes a step of preparing a substrate having a layer made of a group III nitride deposited on the main surface, and a step of supplying a halogen-containing gas to the substrate to etch and remove the layer. In the step of etching and removing the layer, the substrate is irradiated with monitor light, and a change in the reflectance of the monitor light is measured.

[0011] Here, the group III nitride preferably contains indium (In), aluminum (Al), or gallium (Ga) as a group III element, and In x Al y Ga (1-x-y) It is represented by the composition formula of N(0≦x≦1, 0≦y≦1, x + y≦1).

[0012] FIGS. 1(a) to 2(b) are schematic views showing the flow of the reproduction process of the substrate 10. FIG. 3 is a timing chart of temperature and gas supply in the reproduction process of the substrate 10. FIG. 1(a) is a schematic view showing a step of preparing a substrate 10 (laminated structure 100) having a layer 20 made of a group III nitride deposited on the main surface 11. The substrate 10 is typically prepared in the form of a laminated structure 100 having a substrate 10 and a layer 20 made of a group III nitride epitaxially grown on the main surface 11 of the substrate 10.

[0013] The substrate 10 is made of a material different from the group-III nitride, and is made of a material that is less likely to be etched by a halogen-containing gas compared to the group-III nitride constituting the layer 20 when the layer 20 is etched and removed. Specifically, as the substrate 10, a silicon carbide (SiC) substrate, a diamond (C) substrate, etc. are used. In the present embodiment, hereinafter, an aspect of using an SiC substrate as the substrate 10 will be exemplified.

[0014] The main surface 11 is the upper surface of the substrate 10 and is a flat surface. In the present embodiment, the term "main surface" related to the substrate 10 means the upper surface of the substrate 10 (the surface that is the growth base of the layer 20), not the crystal growth surface of the layer 20 (the outermost surface of the stacked structure 100).

[0015] The layer 20 is typically formed over the entire main surface 11 of the substrate 10. The structure of the layer 20 is not particularly limited, and may be a single-layer structure, a stacked structure including a plurality of layers, or may have irregularities for forming a semiconductor element. The layer 20 may include, for example, a GaN layer, and in an aspect including a GaN layer, a buffer layer (for example, an AlN layer) may be included between the substrate 10 and the GaN layer. The thickness of the layer 20 is, for example, 100 nm or more and 5000 nm or less.

[0016] FIG. 1(b) is a schematic diagram showing a step of carrying the stacked structure 100 into the processing apparatus 200 and performing a pretreatment prior to the process of etching and removing the layer 20. In the present embodiment, a film-forming apparatus capable of performing a process of growing a group-III nitride on the substrate 10 is used as the processing apparatus 200 that performs a process of etching and removing the layer 20 to regenerate the substrate 10. For example, a metalorganic vapor phase epitaxy (MOVPE) apparatus is used.

[0017] As the processing apparatus 200, either a hot-wall type or a cold-wall type may be used. However, from the viewpoint of sufficiently increasing the processing temperature of various processes in the following regeneration process and further enhancing the effects of the present embodiment, it is preferable to use a cold-wall type processing apparatus 200. Hereinafter, the cold-wall type processing apparatus 200 will be exemplified.

[0018] A susceptor 220 is provided in a processing container 210 of a processing apparatus 200. A stacked structure 100 is placed on the susceptor 220. The susceptor 220 has a heater 230, and the heater 230 heats the stacked structure 100 to a predetermined processing temperature. A gas supply mechanism 240 supplies a processing gas 250 used for each process into the processing container 210.

[0019] The processing apparatus 200 according to the present embodiment is also a film forming apparatus, and as an apparatus preferably provided in the film forming apparatus, a reflected light monitor 260 is provided. The reflected light monitor 260 in the film forming apparatus (see FIG. 6) irradiates a monitor light 261 onto a substrate 10a during the growth of the group III nitride, and measures various physical properties of the growing group III nitride (layer 20a) by detecting the reflected light. The reflected light monitor 260 typically measures at least one of the film thickness and the growth rate of the growing group III nitride based on interference caused by the thickness of the growing group III nitride. As the reflected light monitor 260, a known reflected light monitor provided in the film forming apparatus may be used.

[0020] After the stacked structure 100 is carried into the processing container 210, as a pretreatment prior to the process of etching and removing the layer 20, a step of annealing the substrate 10 in a reducing atmosphere is performed. Specifically, for example, the temperature is raised in a hydrogen gas (H2 gas) atmosphere to perform hydrogen annealing (see the period P1 in FIG. 3). In the annealing process, the processing temperature is, for example, 900°C or higher and 1300°C or lower, and the processing time is, for example, 10 seconds or longer and 600 seconds or shorter.

[0021] By the annealing process, an oxide film (such as a natural oxide film) formed on the surface of the layer 20 can be removed, and the removal of the group III nitride performed thereafter can proceed surely and efficiently.

[0022] FIG. 2(a) is a schematic diagram showing a process of supplying a halogen-containing gas to the substrate 10 and etching and removing the layer 20. Specifically, for example, chlorine gas (Cl2 gas) is used as the halogen-containing gas, and dry etching of the layer 20 is performed under predetermined processing conditions (see period P2 in FIG. 3). In the process of etching and removing the layer 20, the processing temperature is, for example, 800° C. or higher and 1100° C. or lower (preferably 800° C. or higher and 1000° C. or lower), and the processing time is, for example, 120 seconds or longer and 720 seconds or shorter. As the atmospheric gas, for example, nitrogen gas (N2 gas) is used.

[0023] In the process of etching and removing the layer 20, by removing the entire thickness of the layer 20, the entire main surface 11 of the substrate 10 is exposed. In this example where the substrate 10 is made of SiC, silicon (Si) is desorbed from the exposed main surface 11 by removing the layer 20, and a Si-deficient region 12 is formed on the main surface 11 (preferably over the entire area of the main surface 11). It is understood that SiC constituting the exposed main surface 11 reacts with the halogen-containing gas, and silicon halide gas is generated, so that Si is desorbed and the Si-deficient region 12 is formed. The carbon (C) remaining in the Si-deficient region 12 may be graphitized.

[0024] The etching and removing process is preferably performed under conditions capable of forming the Si-deficient region 12 over the entire area of the main surface 11. These conditions include, for example, the processing temperature, the processing time, and the like. For example, by setting the processing temperature to a temperature of 800° C. or higher and 1100° C. or higher (preferably 800° C. or higher and 1000° C. or lower) as described above, it becomes possible to form the Si-deficient region 12 over substantially the entire area of the main surface 11 (for example, an area of 90% or more).

[0025] From the viewpoint of suitably performing the etching and removal of the layer 20 (III-nitride) and the formation of the Si-deficient region 12, as the halogen-containing gas, at least any one gas selected from the group consisting of F2 gas, Cl2 gas, Br2 gas, I2 gas, NF3 gas, ClF3 gas, HF gas, HCl gas, HBr gas, and HI gas may be used.

[0026] In this embodiment, by using the reflected light monitor 260, the end point of the process of etching and removing the layer 20 is detected. Specifically, in the step of etching and removing the layer 20, the substrate 10 is irradiated with the monitor light 261, the change in the reflectance of the monitor light 261 is measured, and based on the change in the reflectance of the monitor light 261, the end point of the process of etching and removing the layer 20 is detected. After detecting the end point, the supply of the halogen-containing gas to the substrate 10 is stopped.

[0027] The monitor light 261 irradiated onto the substrate 10 is reflected from the surface of the layer 20 when the layer 20 remains on the substrate 10, and is reflected from the main surface 11 of the substrate 10 when the layer 20 is removed from the substrate 10. More specifically, as the etching and removing process of the layer 20 progresses, when the entire main surface 11 of the substrate 10 (the entire surface of the portion of the measurement position 262) is covered with the layer 20, the monitor light 261 is reflected only from the surface of the layer 20. When a part of the main surface 11 of the substrate 10 is exposed and a part of the layer 20 remains (in a state where the island-shaped remaining layer 20 and the exposed main surface 11 of the substrate 10 are mixed in the plane), the monitor light 261 is reflected from both the surface of the layer 20 and the main surface 11 of the substrate 10. When the layer 20 is completely removed from the substrate 10 (in a state where the main surface 11 of the substrate 10 is completely exposed), the monitor light 261 is reflected only from the main surface 11 of the substrate 10.

[0028] FIG. 4 is a graph showing an example of the change in the reflectance of the monitor light 261. The right graph in FIG. 4 is a graph of the change in the reflectance of the monitor light 261 in an experimental example in which the layer 20 is etched and removed. In this experimental example, light with a wavelength of 405 nm is used as the monitor light 261. The reflectance measured in the etching and removing process of the layer 20 is understood to reflect the surface roughness of the layer 20 (or the main surface 11 of the substrate 10), and the surface of the layer 20 (or the main surface 11 of the substrate 10) is evaluated such that the higher the reflectance of the monitor light 261, the flatter it is, and the lower the reflectance, the rougher it is. Hereinafter, the reflectance of the monitor light 261 is simply referred to as the reflectance.

[0029] Time t1 is the start time of introducing the halogen-containing gas into the processing container 210. The surface of layer 20 at time t1, that is, before the start of etching, is a relatively flat surface formed by epitaxial growth, and shows a flatness of about 0.4 (0.3 or more) as the reflectance in the measurement of this example.

[0030] After time t1, as layer 20 is etched by the halogen-containing gas, the surface of layer 20 becomes rough, and accordingly, the reflectance decreases. The surface of layer 20 after the start of etching reaches a roughness of 0.2 or less, and further reaches a roughness of 0.1 or less as the reflectance in the measurement of this example.

[0031] The reflectance of the monitor light 261 turns upward after reaching the minimum value (about 0.02). The reason why the reflectance turns upward is understood to be that as the etching of layer 20 progresses, the main surface 11 of the substrate 10 begins to be exposed, and the exposed area of the main surface 11 expands, so that the flatness of the surface reflecting the monitor light 261 increases.

[0032] The reflectance that has turned upward reaches the maximum value RM at time t2. This is understood to be because at time t2, the removal of layer 20 is completed and the main surface 11 of the substrate 10 is completely exposed. After time t2, when the reflectance becomes constant (for example, the change range of the reflectance is ±0.01 or less), it is determined that the reflectance has reached the maximum value. In this way, it is detected that layer 20 has been completely removed, that is, the process of etching and removing layer 20 has reached the end point.

[0033] The main surface 11 of the substrate 10 is provided as a flat surface compared with the surface of layer 20 at the time when it becomes the roughest with the etching of layer 20, and it can be said that the maximum value RM of the reflectance corresponds to the flatness of the main surface 11. The main surface 11 of the substrate 10 shows a flatness exceeding 0.5 (0.3 or more, 0.4 or more) as the reflectance in the measurement of this example.

[0034] The left graph in FIG. 4 is a graph of the change in reflectance of the monitoring light 261 in an experimental example in which a group-III nitride is grown on a growth substrate similar to the substrate 10. Up to time t4, it is the period during which the growth substrate is heated to the growth processing temperature of the group-III nitride, and from time t4 to time t5, it is the period during which the group-III nitride is grown.

[0035] Time t3 indicates the point in time when the temperature of the growth substrate before the growth of the group-III nitride becomes equal to the etching removal processing temperature of the layer 20. It can be seen that the reflectance RM at time t2 in the right graph (etching removal processing) is equal to the reflectance at time t3 in the left graph (group-III nitride growth). That is, it can be seen that the reflectance RM is equal to the reflectance of the main surface 11 of the substrate 10 at the etching removal processing temperature of the layer 20, and it can be seen that the layer 20 is completely removed at time t2 and the entire surface of the main surface 11 of the substrate 10 is exposed.

[0036] Thus, in the present embodiment, based on the behavior that the reflectance of the monitoring light 261 once decreases and then increases as the layer 20 is etched and removed, the end point of the process of etching and removing the layer 20 is detected. Thereby, compared with a behavior in which the reflectance changes monotonically (increases monotonically), for example, from time t1 to time t2, the change in reflectance becomes prominent, and the determination of the end point detection based on the change in reflectance can be made more clearly.

[0037] In order to temporarily decrease the reflectance with etching, the process of etching and removing the layer 20 is performed under conditions such that the surface of the layer 20 becomes rough as the layer 20 is etched and removed. In order to roughen the surface of the layer 20, preferably, for example, the concentration of the halogen-containing gas in the processing gas in the etching removal process of the layer 20 is set to 0.01% or more (preferably 0.1% or more, more preferably 1.0% or more). Note that the upper limit of the halogen-containing gas concentration is, for example, 10% or less (preferably 5% or less, more preferably 3% or less). In order to roughen the surface of the layer 20, preferably, for example, before performing the etching removal process of the layer 20 using the halogen-containing gas, the above-described pretreatment (annealing in a reducing atmosphere of the substrate 10) is performed.

[0038] Note that, as described above, in this example where the substrate 10 is made of SiC, since the main surface 11 is exposed to a halogen-containing gas, the Si-deficient region 12 is formed on the main surface 11, so the exposed main surface 11 may be in a state where the Si-deficient region 12 is formed. According to the findings obtained by the inventor of the present application, the flatness of the main surface 11 is not particularly changed by the formation of the Si-deficient region 12.

[0039] At the time t2 when the reflectance reaches the maximum value RM, that is, when the entire main surface 11 is exposed, it is considered that the reaction for forming the Si-deficient region 12 is almost completed. However, from the viewpoint of making the reaction for forming the Si-deficient region 12 more reliable, the supply of the halogen-containing gas does not have to be terminated immediately after the time t2, and it may be continued for a certain period (for example, about 360 seconds) after passing the time t2.

[0040] FIG. 2(b) is a schematic diagram showing a process of supplying a hydrogen-containing gas to the substrate 10 from which the layer 20 (III-nitride) has been removed and modifying the main surface 11. Specifically, for example, ammonia gas (NH3 gas) is used as the hydrogen-containing gas, and the main surface 11 is modified under predetermined processing conditions (see the period P3 in FIG. 3). In the modification treatment of the main surface 11, the treatment temperature is, for example, 900°C or higher and 1200°C or lower (preferably 1100°C or higher and 1200°C or lower), and the treatment time is, for example, 150 seconds or more and 600 seconds or less. As the atmosphere gas, for example, N2 gas or H2 gas is used. The treatment temperature in the modification treatment of the main surface 11 is preferably relatively high and higher than the treatment temperature in the etching removal treatment of the layer 20. Note that the atmosphere gas may be switched so that N2 gas is first used and then H2 gas is used. By terminating the treatment in an H2 gas atmosphere, the modification of the main surface 11 (the purification of SiC constituting the main surface 11) can be performed more preferably.

[0041] In this example where the substrate 10 is made of SiC, by modifying the main surface 11, the C component is desorbed from the Si-deficient region 12, and the Si-deficient region 12 is removed from the main surface 11 (preferably from the entire area of the main surface 11). It is understood that C contained in the Si-deficient region 12 on the main surface 11 reacts with the hydrogen-containing gas to generate a hydrocarbon gas, and C is desorbed, thereby removing the Si-deficient region 12.

[0042] The modification treatment of the main surface 11 is preferably performed under conditions that enable the removal of the Si-deficient region 12 from the entire area of the main surface 11. Such conditions include, for example, the treatment temperature, treatment time, etc. For example, as described above, the treatment temperature in the modification treatment of the main surface 11 is set to a temperature higher than the treatment temperature in the etching removal treatment of the layer 20, and is a temperature of 900 °C or higher and 1200 °C or higher (preferably 1100 °C or higher and 1200 °C or lower), so that the Si-deficient region 12 can be removed from substantially the entire area of the main surface 11 (for example, an area of 90% or more).

[0043] From the viewpoint of suitably removing the Si-deficient region 12, as the hydrogen-containing gas, at least any one gas selected from the group consisting of H2 gas, NH3 gas, N2H2 gas, N2H4 gas, and N3H8 gas may be used.

[0044] By removing the Si-deficient region 12 by the treatment for modifying the main surface 11, a regenerated substrate 10a having a clean main surface 11 made of SiC is obtained. Then, the temperature of the regenerated substrate 10a is lowered to a predetermined temperature. In this embodiment, as described above, the regeneration of the substrate 10, that is, the production of the regenerated substrate 10a is performed.

[0045] The process of removing the layer 20 (Fig. 2(a)) and the process of modifying the main surface 11 (Fig. 2(b)) are performed continuously within the same processing container 210 (without taking out the substrate 10 from the processing container 210 and exposing it to the atmosphere midway). Thereby, it becomes possible to improve the productivity of the regenerated substrate 10a. Also, it becomes possible to avoid contamination of the regenerated substrate 10a due to exposure to the atmosphere or the like. Note that it is also preferable to perform the annealing process (Fig. 1(b)), which is a pretreatment, and the process of removing the layer 20 (Fig. 2(a)) continuously within the same processing container 210.

[0046] After growing a group III nitride on a substrate 10 which is a new SiC substrate, a test of regenerating it by the method of this embodiment was conducted. The thickness of the new substrate 10 was 0.4935 mm (analysis error ±0.0003 mm), and the thickness of the regenerated substrate 10a was 0.4936 mm (analysis error ±0.0003 mm). The thickness of the regenerated substrate 10a was substantially equivalent to the thickness of the new substrate 10.

[0047] In the method for regenerating the substrate 10 according to this embodiment, in this way, it is possible to regenerate the substrate 10 while suppressing a decrease in the thickness of the substrate 10 due to the regeneration process as compared with the conventional regeneration method such as polishing. Note that in this embodiment, an Si-deficient region 12 is generated and removed on the main surface 11 of the substrate 10, but the variation in the thickness of the substrate 10 accompanying the removal of the Si-deficient region 12 remains at a level far smaller than the analysis error of the thickness measurement of the substrate 10.

[0048] Also, on a substrate 10 which is a SiC substrate, growing and then removing a group-III nitride (specifically, a stack of a high electron mobility transistor structure) under the same conditions was repeated 18 times (i.e., 18 regenerations were performed) starting from a new substrate 10 by the method of this embodiment. The film thickness and Al composition of the AlGaN barrier layer grown on the new substrate 10 were 21.3 nm and 0.277, respectively, and the film thickness of the GaN cap layer was 3.4 nm. The film thickness and Al composition of the AlGaN barrier layer obtained by growth in 18 regenerations were values within the ranges of 21.1 nm to 21.6 nm and 0.271 to 0.276, respectively, and the film thickness of the GaN cap layer was a value within the range of 3.3 nm to 3.5 nm. Thus, according to the method of this embodiment, even if regeneration is repeated, the growth of the group-III nitride can be performed substantially similarly, and a regenerated substrate 10a of a certain quality can be obtained repeatedly.

[0049] As described above, the method for manufacturing a regenerated substrate according to this embodiment includes a step of preparing a substrate having a layer composed of a group-III nitride deposited on a main surface, and a step of supplying a halogen-containing gas to the substrate and etching and removing the layer. In the step of etching and removing the layer, monitor light is irradiated on the substrate, and a change in the reflectance of the monitor light is measured.

[0050] During the progress of the etching and removing process of the layer composed of the group-III nitride, by measuring the reflectance of the monitor light irradiated on the substrate, it becomes possible to grasp in-situ and in real time the progress of the etching and removing process (such as the etching end point).

[0051] The method for manufacturing a regenerated substrate according to this embodiment also detects the end point of the process of etching and removing the layer based on the change in the reflectance of the monitor light in the step of etching and removing the layer. And after detecting the end point, the supply of the halogen-containing gas to the substrate is stopped.

[0052] Based on the change in the reflectivity of the monitor light irradiated on the substrate, it can be confirmed that the group III nitride has been removed, so the end point of etching can be detected more reliably. Since the supply of the halogen-containing gas is prevented from being stopped during the removal of the group III nitride, the removal of the group III nitride can be performed reliably.

[0053] In addition, the method for manufacturing a regenerated substrate according to the present embodiment may be performed by using a film-forming apparatus capable of growing a group III nitride as a processing apparatus for etching and removing a layer composed of the group III nitride. Further, the measurement of the change in reflectivity during the etching and removal process of the layer may be performed by using a reflected light monitor provided in the film-forming apparatus. Thereby, it is not necessary to separately prepare another apparatus for performing the regeneration process of the substrate.

[0054] The reflected light monitor in the film-forming apparatus is used as an apparatus for measuring at least one of the film thickness and the growth rate of the growing group III nitride based on the interference caused by the thickness of the growing group III nitride. When used during the etching and removal process of the group III nitride, the usage mode of the reflected light monitor is different from the usage mode (measurement of film thickness or growth rate) when used during the growth of the group III nitride, and it is a usage mode of measuring the reflectivity of the monitor light as a physical property value corresponding to the surface roughness of the surface of the layer composed of the group III nitride and the main surface of the substrate.

[0055] The technique of measuring the change in the reflectivity of the monitor light as described above can be preferably used even when performing substrate regeneration other than the exemplified SiC substrate. In the regeneration of the SiC substrate, the above-described embodiment has the following characteristics.

[0056] In the step of removing the group III nitride from the main surface of the substrate, a Si-deficient region is formed on the main surface, and in the step of modifying the main surface, the Si-deficient region is removed from the main surface. The Si-deficient region is preferably formed over the entire main surface and removed from the entire main surface.

[0057] The regeneration of the substrate can be carried out by dry etching as in the present embodiment, rather than by polishing or wet etching methods, which makes it possible to improve the productivity in manufacturing the regenerated substrate. However, according to the intensive research of the inventors of the present application, simply performing dry etching to remove the group III nitride may reduce the quality of the crystal to be epitaxially grown on the regenerated substrate (for example, the number of defects appearing on the crystal surface increases). When performing dry etching using a halogen-containing gas, Si may desorb from the main surface of the SiC substrate exposed by the removal of the group III nitride, and as a result, a "Si-deficient region" containing graphene or the like may be generated on the main surface. This Si-deficient region is considered to be a factor that degrades the quality of the crystal epitaxially grown on the main surface of the regenerated substrate.

[0058] On the other hand, according to the intensive research of the inventors of the present application, the state of the new main surface (refreshed main surface) obtained through the formation and removal of the Si-deficient region is compared with the state of the main surface that has not undergone this process, that is, the original main surface state considered to contain SiC crystals damaged in the processing steps during substrate manufacturing. It has been found that the crystal quality is improved and it is suitable as a growth substrate for epitaxial growth.

[0059] According to the present embodiment, in the step of removing the group III nitride from the main surface of the substrate, a Si-deficient region is intentionally formed on the main surface of the SiC substrate, and then in the step of modifying the main surface, the Si-deficient region is removed from the main surface, making it possible to obtain a high-quality regenerated substrate.

[0060] The processing apparatus 200 according to the present embodiment is also a film-forming apparatus, and a growth process of group III nitride may be performed prior to the regeneration process of the substrate 10. As shown in FIG. 1(b), due to the growth process, deposits 270 containing group III nitride may adhere to the inner wall of the processing container 210 at the time of starting the regeneration process of the substrate 10. The deposits 270 may adhere over the entire inner wall of the processing container 210, but here, for simplicity of illustration, the deposits 270 are shown as one granular shape.

[0061] To remove deposits containing group-III nitrides, that is, to clean the processing chamber of a film forming apparatus, generally, a cleaning process of supplying a halogen-containing gas into the processing chamber is performed. As shown in Fig. 2(a), in the present embodiment, the process of etching and removing the layer 20 (III group nitride) from the main surface 11 of the substrate 10 supplies a halogen-containing gas into the processing chamber 210, so it also functions as a cleaning process and has the effect of removing the deposits 270 adhering to the inner wall of the processing chamber 210.

[0062] Therefore, it can be said that the step of etching and removing the layer 20 (and the step of modifying the main surface 11) is performed in parallel with the step of cleaning the inside of the processing chamber 210. Note that the processing conditions for the process of etching and removing the layer 20 do not have to be optimal as the processing conditions for the process of cleaning the inside of the processing chamber 210. In order to make the effect of the cleaning process more reliable, the step of etching and removing the layer 20 (and the step of modifying the main surface 11) and (under processing conditions suitable for cleaning, additionally, before or after the step of etching and removing the layer 20), the step of cleaning the inside of the processing chamber 210 may be performed continuously.

[0063] By performing the step of etching and removing the layer 20 (and the step of modifying the main surface 11) and the step of cleaning the inside of the processing chamber 210 in parallel or continuously, it becomes possible to improve their respective productivity. In addition, halogen-containing gases, electric power, etc. can be effectively utilized, and it becomes possible to reduce these processing costs.

[0064] In a film deposition apparatus for growing a group III nitride, originally, cleaning inside the processing chamber is performed by dry etching using a halogen-containing gas. Therefore, the method for manufacturing a regenerated substrate according to this embodiment can be easily performed using the film deposition apparatus, and by using the film deposition apparatus, it is not necessary to use another processing apparatus for performing the regeneration process of the substrate. Further, by using the film deposition apparatus to perform the method for manufacturing a regenerated substrate according to this embodiment, an effect of cleaning the inside of the processing chamber of the film deposition apparatus can also be obtained.

[0065] <Modification example> Next, a modification example of the above-described embodiment will be described. In this modification example, a mode of simultaneously performing the regeneration process of a plurality of substrates 10, particularly, a mode of measuring the change in reflectance during the etching removal process of the layer 20 for a plurality of substrates 10 will be described. In the step of preparing the substrates, a plurality of substrates 10 on which the layer 20 is deposited are prepared.

[0066] FIG. 5(a) is a schematic diagram showing a susceptor 220 on which a plurality of substrates 10 according to this modification example are placed, and a measurement position 262 of the monitor light 261, and FIG. 5(b) is a schematic diagram showing the vicinity of the measurement position 262.

[0067] The susceptor 220 of this modification example holds a plurality of substrates 10 so as to revolve and rotate. Specifically, the centers of the plurality of substrates 10 are arranged on a circumference (revolution orbit) 222 centered on the revolution rotation center 221 (arranged in the circumferential direction of revolution). Each (circular-shaped) substrate 10 has its center as the rotation center 223 of rotation. Each substrate 10 revolves as the susceptor 220 rotates (moves in the revolution direction 224), and rotates while revolving (moves in the rotation direction 225). The measurement position 262 of the monitor light 261 is arranged at a predetermined position on the circumference 222 (that is, on the circumference centered on the revolution rotation center 221 and having a radius from the revolution rotation center 221 to the rotation center 223 of rotation).

[0068] In this modified example, while revolving each substrate 10 around the revolution center 221 and rotating it around the rotation center 223, a halogen-containing gas is simultaneously supplied to each substrate 10 to etch and remove the layer 20 of each substrate 10. Then, at the measurement position 262, each time each substrate 10 passes through the measurement position 262 as it revolves, the monitor light 261 is irradiated onto each substrate 10, thereby measuring the change in the reflectance of the monitor light 261 with respect to each substrate 10.

[0069] By revolving and rotating a plurality of substrates 10 while performing etching and removal of the layer 20, it is possible to suppress variations in the etching progress state between each substrate 10 and within the plane of each substrate 10. Furthermore, this modified example has the following advantages by performing measurement of the reflectance at the measurement position 262 while revolving and rotating a plurality of substrates 10 and performing etching and removal of the layer 20.

[0070] The period for one revolution of a single substrate 10 passing through the measurement position 262 as it revolves will be referred to as the measurement period (for one time). The radial direction and the circumferential direction with respect to the substrate 10 will simply be referred to as the radial direction and the circumferential direction, respectively, hereinafter. Also, the relative position in plan view on the substrate 10 at the measurement position 262 will simply be referred to as the measurement position 262 on the substrate 10 hereinafter. The measurement position 262 on the substrate 10 moves substantially in the radial direction as it revolves and also moves in the circumferential direction as it rotates during the measurement period (see Fig. 5(b)). Therefore, by controlling the revolution speed and the rotation speed, the measurement position 262 on the substrate 10 can be controlled in both the radial direction and the circumferential direction, and the measurement position 262 on the substrate 10 can be controlled to be arranged at a predetermined position within the plane of the substrate 10.

[0071] In this modified example, during one measurement period, the reflectance measurement may be performed not only once but also multiple times. That is, during one measurement period, the reflectance may be measured at a plurality of positions on the substrate 10. As a result, for example, the in-plane distribution of the reflectance (at least one of the radial distribution and the circumferential distribution) on the substrate 10 can be obtained, so that the etching removal of the layer 20 can be performed while confirming the uniformity of the etching progress situation in the plane. Thus, for example, it is also possible to obtain knowledge of the change in reflectance during one measurement period.

[0072] In this modified example, for each substrate 10, the change in the reflectance of the monitor light 261 is measured, and based on the change in the reflectance of the monitor light 261, the end point of the process of etching and removing the layer 20 can be detected. Preferably, after detecting the end point of the process of etching and removing the layer 20 for all the substrates 10, the supply of the halogen-containing gas to these substrates 10 is stopped. Thereby, for all of the plurality of substrates 10, it is possible to ensure the completion of the etching removal of the layer 20.

[0073] <Other modified examples> The process of etching and removing the layer 20 and the process of modifying the main surface 11 may be alternately performed a plurality of times. Specifically, for example, a period PL in which the period P2 (the process of removing the layer 20) and the period P3 (the process of modifying the main surface 11) in FIG. 3 are taken as a set may be repeated a plurality of times.

[0074] Although sufficient effects can be obtained by performing only once the process of etching and removing the layer 20 and the process of modifying the main surface 11, by repeating these, the effect of cleaning the main surface 11 of the substrate 10 can be further enhanced. In addition, by such repetition, the effect of cleaning the inside of the processing container 210 can also be further enhanced.

[0075] <Other embodiments> As another embodiment applying the method for manufacturing a reproduction substrate according to the above-described embodiment, a method for manufacturing a laminated structure will be described. The method for manufacturing a laminated structure according to this embodiment has a step of growing crystals on a main surface (that is, the main surface of the reproduction substrate) from which a layer made of a group III nitride has been etched away, in addition to the steps of the method for manufacturing a reproduction substrate described above. The crystals grown on the main surface of the reproduced substrate are preferably group III nitride crystals.

[0076] FIG. 6 is a schematic view showing a step of growing a new layer 20a (crystals) made of a group III nitride on the main surface 11 of the reproduction substrate 10a (the main surface 11 from which the layer 20 has been etched away). Here, a film forming apparatus is used as the processing apparatus 200 for performing the reproduction process of the substrate 10, and an embodiment in which the layer 20a is grown using the same processing apparatus 200 is illustrated.

[0077] For example, the processing apparatus 200 is a MOVPE apparatus, and the layer 20a is grown on the main surface 11 of the reproduction substrate 10a by MOVPE. The process of growing the layer 20a may be continuously performed in the same processing container 210 as the reproduction process of the substrate 10 (that is, the etching removal process of the layer 20 and the surface modification process of the main surface 11). In this way, a laminated structure 100a in which the layer 20a is laminated on the main surface 11 of the reproduction substrate 10a is manufactured.

[0078] According to this embodiment, a laminated structure 100a that can be used for a semiconductor device can be manufactured using the reproduction substrate 10a. Also in this application aspect, as described above, in the etching removal process of the layer 20 when obtaining the reproduction substrate 10a, by performing reflectance measurement, it becomes possible to grasp in-situ and in real time the progress of the etching removal process (such as the etching end point).

[0079] By performing the process of growing the layer 20a continuously in the same processing container 210 as the regeneration process of the substrate 10 (that is, performing it subsequent to the regeneration process), it becomes possible to improve the productivity when manufacturing the laminated structure 100a using the regenerated substrate 10a. Further, it is possible to avoid contamination of the regenerated substrate 10a due to exposure to the atmosphere or the like, and it becomes possible to enhance the performance and reliability of the semiconductor device manufactured using the laminated structure 100a.

[0080] <Preferred Embodiment of the Present Invention> Hereinafter, preferred embodiments of the present invention will be appended.

[0081] (Appended Note 1) (a) A step of preparing a substrate having a layer composed of a group III nitride deposited on a main surface; (b) A step of supplying a halogen-containing gas to the substrate and etching and removing the layer, and In the above (b), a method for manufacturing a regenerated substrate in which monitor light is irradiated on the substrate and a change in the reflectance of the monitor light is measured.

[0082] (Appended Note 2) In the above (b), based on the change in the reflectance of the monitor light, the end point of the process of etching and removing the layer is detected The method for manufacturing a regenerated substrate according to Appended Note 1.

[0083] (Appended Note 3) In the above (b), after detecting the end point, the supply of the halogen-containing gas to the substrate is stopped The method for manufacturing a regenerated substrate according to Appended Note 2.

[0084] (Appended Note 4) In the above (b), based on the behavior that the reflectance of the monitor light once decreases and then increases as the layer is etched and removed, the end point of the process of etching and removing the layer is detected The method for manufacturing a regenerated substrate according to Appended Note 2.

[0085] (Appended Note 5) In the above (b), based on the behavior that the reflectance of the monitor light once decreases and then increases as the layer is etched away, and maintains a constant value after reaching a predetermined reflectance, the end point of the process of etching away the layer is detected. The method for manufacturing a reproduction substrate according to Supplementary Note 2.

[0086] (Supplementary Note 6) In the above (b), a process of etching away the layer is performed under heating conditions. The predetermined reflectance is the reflectance of the main surface at the processing temperature of the process of etching away the layer. The method for manufacturing a reproduction substrate according to Supplementary Note 5.

[0087] (Supplementary Note 7) In the above (b), a process of etching away the layer is performed under conditions such that the surface roughness of the surface of the layer becomes coarser as the layer is etched away. The method for manufacturing a reproduction substrate according to Supplementary Note 1. Note that the surface of the layer is evaluated to be flatter as the reflectance of the monitor light is higher and rougher as the reflectance is lower. For example, when the surface roughness of the surface of the layer is represented by the reflectance when light with a wavelength of 405 nm is used as the monitor light, the surface roughness before the start of etching of the layer is preferably 0.3 or more in reflectance, and as the layer is etched, the surface roughness preferably reaches 0.2 or less in reflectance, more preferably 0.1 or less in reflectance.

[0088] (Supplementary Note 8) In the above (b), the halogen-containing gas concentration in the processing gas is set to 0.01% or more (preferably 0.1% or more, more preferably 1.0% or more). The method for manufacturing a reproduction substrate according to Supplementary Note 7. Note that the halogen-containing gas concentration is, for example, set to 10% or less (preferably 5% or less, more preferably 3% or less).

[0089] (Supplementary Note 9) Before performing the above (b), a step of annealing the substrate in a reducing atmosphere is included. The method for manufacturing a reproduction substrate according to Supplementary Note 7.

[0090] (Supplementary Note 10) The substrate is made of a material different from the group III nitride and is composed of a material that is less likely to be etched by the halogen-containing gas than the group III nitride. The main surface is flatter than the surface of the layer at the time when it becomes roughest as the layer is etched and removed. The method for manufacturing a reproduction substrate according to Supplementary Note 7. Note that the main surface of the substrate is evaluated to be flatter as the reflectance of the monitor light is higher and rougher as the reflectance is lower. For example, when the surface roughness of the main surface is expressed as the reflectance when light with a wavelength of 405 nm is used as the monitor light, it is preferably 0.3 or more, and more preferably 0.4 or more.

[0091] (Supplementary Note 11) In the step (b), a process of etching and removing the layer is performed in a processing chamber of a film forming apparatus capable of growing a group III nitride. The film forming apparatus includes a reflection light monitor that measures at least one of the film thickness and the growth rate of the growing group III nitride based on interference caused by the thickness of the growing group III nitride. In the step (b), the reflectance of the monitor light is measured using the reflection light monitor as a physical property value corresponding to the surface roughness of the surface of the layer and the main surface of the substrate. The method for manufacturing a reproduction substrate according to Supplementary Note 1.

[0092] (Supplementary Note 12) In the step (b), The substrate is revolved around a first rotation center and rotated around a second rotation center that is the center of the substrate while supplying the halogen-containing gas to the substrate to etch and remove the layer. At a measurement position arranged on a circumference centered on the first rotation center and with a radius from the first rotation center to the second rotation center, each time the substrate passes through the measurement position as it revolves, the monitor light is irradiated onto the substrate to measure the change in the reflectance of the monitor light with respect to the substrate. The method for manufacturing a reproduction substrate according to Supplementary Note 1.

[0093] (Supplementary Note 13) In the above (b), During the period for each time the substrate passes through the measurement position as it revolves, the reflectance is measured at a plurality of positions on the substrate. The method for manufacturing a reproduction substrate according to Supplementary Note 12.

[0094] (Supplementary Note 14) In the above (a), Prepare another substrate having another layer formed of a group III nitride deposited on the main surface. In the above (b), The center of the substrate and the center of the other substrate are arranged side by side in the circumferential direction of the revolution. While revolving the other substrate around the first rotation center and rotating the other substrate around a third rotation center which is the center of the other substrate, supply the halogen-containing gas to the other substrate to etch and remove the other layer. At the measurement position, each time the other substrate passes through the measurement position as it revolves, the monitor light is irradiated onto the other substrate to measure the change in the reflectance of the monitor light with respect to the other substrate. The method for manufacturing a reproduction substrate according to Supplementary Note 12.

[0095] (Supplementary Note 15) In the above (b), Based on the change in the reflectance of the monitor light, after detecting the end point of the process of etching and removing the layer on the substrate and the end point of the process of etching and removing the other layer on the other substrate, Stop the supply of the halogen-containing gas to the substrate and the other substrate. The method for manufacturing a playback substrate according to Supplementary Note 14.

[0096] (Supplementary Note 16) (a) A step of preparing a substrate having a layer composed of a group III nitride deposited on a main surface; (b) A step of supplying a halogen-containing gas to the substrate and etching away the layer; (c) A step of growing crystals on the main surface from which the layer has been etched away, and having: In the step (b), a method for manufacturing a laminate in which monitor light is irradiated onto the substrate and a change in the reflectance of the monitor light is measured.

[0097] (Supplementary Note 17) The steps (b) and (c) are continuously performed in the same processing container. The method for manufacturing a laminate according to Supplementary Note 16.

Explanation of Reference Numerals

[0098] 10... Substrate, 10a... Playback substrate, 11... Main surface, 12... Si-deficient region, 20, 20a... Layer (composed of a group III nitride), 100, 100a... Laminate, 200... Processing apparatus, 210... Processing container, 220... Susceptor, 221... Rotation center (of revolution), 222... Circumference (orbit of revolution), 223... Rotation center (of rotation), 224... Revolution direction, 225... Rotation direction, 230... Heater, 240... Gas supply mechanism, 250... Processing gas, 260... Reflective light monitor, 261... Monitor light, 262... Measurement position, 270... Deposit

Claims

1. (a) A step of preparing a substrate having a layer made of a group III nitride deposited on a main surface; (b) A step of supplying a halogen-containing gas to the substrate and etching away the layer, and having, In the step (b), a method for manufacturing a regenerated substrate in which monitor light is irradiated onto the substrate and a change in the reflectance of the monitor light is measured.

2. In the step (b), based on the change in the reflectance of the monitor light, the end point of the process of etching away the layer is detected The method for manufacturing a regenerated substrate according to claim 1.

3. In the step (b), after detecting the end point, the supply of the halogen-containing gas to the substrate is stopped The method for manufacturing a regenerated substrate according to claim 2.

4. In the step (b), based on the behavior that the reflectance of the monitor light once decreases and then increases as the layer is etched away, the end point of the process of etching away the layer is detected The method for manufacturing a regenerated substrate according to claim 2.

5. In the step (b), based on the behavior that the reflectance of the monitor light once decreases and then increases as the layer is etched away, and after reaching a predetermined reflectance, maintains a constant value, the end point of the process of etching away the layer is detected The method for manufacturing a regenerated substrate according to claim 2.

6. In the step (b), the process of etching away the layer is performed under heating conditions, The predetermined reflectance is the reflectance of the main surface at the processing temperature of the process of etching away the layer The method for manufacturing a regenerated substrate according to claim 5.

7. In the step (b), the process of etching away the layer is performed under conditions such that the surface roughness of the surface of the layer becomes rougher as the layer is etched away The method for manufacturing a regenerated substrate according to claim 1.

8. In the step (b), the concentration of the halogen-containing gas in the processing gas is set to 0.01% or more The method for manufacturing a regenerated substrate according to claim 7.

9. Before performing the step (b), a step of annealing the substrate in a reducing atmosphere is included The method for manufacturing a regenerated substrate according to claim 7.

10. The substrate is made of a material different from the group III nitride and is made of a material that is less likely to be etched by the halogen-containing gas than the group III nitride, The main surface is flatter than the surface of the layer at the time when the layer becomes roughest as the layer is etched away The method for manufacturing a regenerated substrate according to claim 7.

11. In the step (b), a process of etching and removing the layer is performed inside a processing chamber of a film deposition apparatus capable of growing a group-III nitride. The film deposition apparatus includes a reflection light monitor that measures at least one of the film thickness and the growth rate of the growing group-III nitride based on interference caused by the thickness of the growing group-III nitride. In the step (b), using the reflection light monitor, the reflectance of the monitor light is measured as a physical property value corresponding to the surface roughness of the surface of the layer and the main surface of the substrate. The method for manufacturing a regenerated substrate according to claim 1.

12. In the step (b), The substrate is revolved around a first rotation center and rotated around a second rotation center which is the center of the substrate, while supplying the halogen-containing gas to the substrate to etch and remove the layer. At a measurement position arranged on a circumference centered on the first rotation center and having a radius from the first rotation center to the second rotation center, each time the substrate passes through the measurement position as it revolves, the monitor light is irradiated onto the substrate to measure the change in the reflectance of the monitor light with respect to the substrate. The method for manufacturing a regenerated substrate according to claim 1.

13. In the step (b), During each period when the substrate passes through the measurement position as it revolves, the reflectance is measured at a plurality of positions on the substrate. The method for manufacturing a regenerated substrate according to claim 12.

14. In the step (a), Another substrate having another layer composed of a group-III nitride deposited on its main surface is prepared. In the step (b), The center of the substrate and the center of the other substrate are arranged side by side in the circumferential direction of the revolution. The other substrate is revolved around the first rotation center and rotated around a third rotation center which is the center of the other substrate, while supplying the halogen-containing gas to the other substrate to etch and remove the other layer. At the measurement position, each time the other substrate passes through the measurement position as it revolves, the monitor light is irradiated onto the other substrate to measure the change in the reflectance of the monitor light with respect to the other substrate. The method for manufacturing a regenerated substrate according to claim 12.

15. In the step (b), After detecting the end point of the process of etching and removing the layer on the substrate and the end point of the process of etching and removing the other layer on the other substrate based on the change in the reflectance of the monitor light, Stop the supply of the halogen-containing gas to the substrate and the other substrate The method for manufacturing a regenerated substrate according to claim 14

16. (a) A step of preparing a substrate having a layer composed of a group III nitride deposited on a main surface; (b) A step of supplying a halogen-containing gas to the substrate and etching and removing the layer; (c) A step of growing crystals on the main surface from which the layer has been etched and removed, and having, In the step (b), a method for manufacturing a laminated structure in which monitor light is irradiated onto the substrate and a change in the reflectance of the monitor light is measured

17. Perform the step (b) and the step (c) continuously in the same processing container The method for manufacturing a laminated structure according to claim 16

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