WO2013011705A1

WO2013011705A1 - Processing method of substrate for semiconductor elements

Info

Publication number: WO2013011705A1
Application number: PCT/JP2012/051899
Authority: WO
Inventors: Kouichi Inoue; Norihito Shibuya
Original assignee: Sintokogio, Ltd.
Priority date: 2011-07-21
Filing date: 2012-01-23
Publication date: 2013-01-24
Also published as: TWI545623B; CN103430281B; JP5716834B2; CN103430281A; TW201306092A; KR20140050604A; KR101883520B1; JP2014522731A

Abstract

To provide a processing method of a substrate for semiconductor elements, for applying blast processing to a substrate having a first surface and a second surface opposite to the first surface. The processing method includes a step of applying the blast processing to the second surface opposite to the first surface on which a compound semiconductor film is formed or is to be formed.

Description

DESCRIPTION

Title of Invention

PROCESSING METHOD OF SUBSTRATE FOR SEMICONDUCTOR ELEMENTS

Technical Field

[0001] The present invention relates to a processing method of a substrate for semiconductor elements.

Background Art

[0002] Conventionally, in a manufacturing process of light-emitting diodes, a light-emitting layer made of a GaN-based compound semiconductor is formed by epitaxial crystal growth on a mirror-finished main surface of a substrate formed of a material such as sapphire, and then electrodes are formed on the epitaxially grown wafer. The epitaxial growth (EPI growth) process includes steps, such as a step of forming a film on a substrate while heating the substrate, and a step of cooling the substrate to normal temperature after the film-forming step. For this reason, when the substrate is cooled after the film-forming step, a warp (distortion) projecting to the side of the GaN-based compound semiconductor occurs due to a difference in the linear expansion coefficient between the substrate and the GaN-based compound semiconductor. To cope with this, Patent Literature 1 discloses a technique to correct the warp. In this method, a large-sized press apparatus capable of applying pressure of 4.9x10⁴ Pa to 4.9 10⁶ Pa is used.

Citation List

Patent Literature [0003]

[Patent Literature 1] Japanese Patent Laid-Open Publication No. 2003-128499

Summary of Invention

Technical Problem

[0004] In the method described in Patent Literature 1, a press mechanism needs to be provided in an MOCVD apparatus for epitaxial growth. Further, according to a market trend toward mass production, the size of the substrate used in the manufacturing process tends to be further increased from the two-inch size to the four-inch size in future.

For this reason, it will become more important to suppress occurrence of breakage and cracks in the substrate at the time of pressing the substrate. In this technical field, there are demands for a semiconductor manufacturing method which is efficient and suitable for mass production, and a method which can correct a warp of the substrate for semiconductor elements at low cost.

Solution to Problem

[0005] A processing method of a substrate for semiconductor elements, according to an aspect of the present invention, is a processing method of a substrate for semiconductor elements, for applying blast processing to a substrate having a first surface and a second surface opposite to the first surface, and is featured by including a step of applying the blast processing to the second surface opposite to the first surface on which a compound semiconductor film is formed or the compound semiconductor film is to be formed.

Advantageous Effects of Invention [0006] With the processing method of a substrate for semiconductor elements, according to the aspect of the present invention, it is possible to provide a method which is efficient and suitable for mass production and which corrects a warp of a substrate for semiconductors.

Brief Description of Drawings

[0007]

[Figure 1] Figure 1 is a flow chart of an example according to an embodiment of the present invention.

[Figure 2] Figure 2 is a schematic view showing a measuring method according to the embodiment.

[Figure 3] Figure 3 is a schematic view showing an evaluation method according to the embodiment.

[Figure 4] Figure 4 is a schematic view showing a trajectory of relative movement of a blast iiozzle and a substrate at the time when blast processing according to the embodiment is performed.

[Figure 5] Figure 5 is a schematic view showing a principle for correcting distortion of a wafer by the blast processing according to the embodiment.

[Figure 6] Figure 6 is a flow chart showing a method according to another embodiment.

[Figure 7] Figure 7 is a flow chart showing a method according to still another embodiment.

Description of Embodiments

[0008] In the following, embodiments according to the present invention will be described. A method according to an embodiment of the present invention is a warp correction method using blast processing which is applied to a substrate made of a material, such as sapphire, at the time when light-emitting diode (LED) elements, and the like, are manufactured. In this method, a warp is corrected by using blast processing which is applied to a substrate for semiconductor elements at the time when LED elements or LD elements are manufactured. For example, this method may include: a step of making a substrate; a step of performing a step of forming a compound semiconductor film on the substrate; a step of applying blast processing to the surface of the substrate, the surface being opposite to the mirror surface on which the compound semiconductor film is formed; and a step of forming LED electrodes or LD electrodes on the surface being opposite to the surface subjected to the blast processing and then cutting the substrate into LED elements or LD elements.

[0009] Here, in the embodiment, the LED element means, for example, an InGaN-based high luminance LED. As the other LED elements, there are an AlGaNlnP-based high luminance LED, a GaP-based high luminance LED, a GaAs-based high luminance LED, and the like. The LED means a light-emitting diode which emits light at the time when electricity is supplied thereto and which is used for large area illumination, and the like. Further, the LD means a laser diode which emits laser light at the time when electricity is thereto and which is used as a light source for communication and an optical disk.

[0010] The substrate means a substrate which is made by slicing an ingot of a single-crystal of sapphire, SiC, GaAS, GaP, GaAlAs, or the like, and which can be subjected to epitaxial growth. This substrate is, for example, a substrate for semiconductor elements and has a first surface and a second surface opposite to the first surface. A compound semiconductor film is formed on the first surface. The second surface may have a surface roughness larger than the surface roughness of the first surface. The both surfaces of the substrate may be polished. The blast processing means processing in which a workpiece is processed in such a manner that a mixture of abrasive grains and compressed air is ejected as a solid-air two-phase flow by using a rectangular nozzle or a round nozzle, and that the grains of the solid-air two-phase flow are made to collide with the workpiece. In the present embodiment, the workpiece was processed while being scanned (scan processing method).

[0011] The mirror surface of the sapphire substrate means a surface having surface roughness of about 1 to 5 A Ra. The GaN-based compound semiconductor film means a film which is formed on the mirror surface side of the substrate by using a gas phase growth method or a liquid phase growth method. Forming an LED electrode or an LD electrode means forming a transparent electrode, a pad electrode, a protective film, and the like, on the compound semiconductor film formed on the substrate. For example, a GaN-based compound semiconductor film is formed. The element means an LED chip or an

LD chip on which the electrode is formed. Cutting means cutting the substrate into chips having a standard size by using a method using a laser, a blade, or a blast, or the like.

[0012] In the following, a processing method according to an embodiment will be described with reference to the accompanying drawings. Figure 1 shows a flow chart of a warp correction method using blast processing which is applied to a substrate at the time of manufacturing LED elements or LD elements. In Figure 1, the processing method includes: a step (S10) of making a substrate; a step (SI 2) of performing a step of forming a compound semiconductor film on the substrate; a step (SI 4) of applying blast processing to the surface opposite to the mirror surface on which the compound semiconductor film is formed; and a step (SI 6) of forming LED electrodes or LD electrodes on the surface being opposite to the surface which the blast processing is applied, and then cutting the substrate into LED elements or LD elements. Note that, in the following, a case of forming a GaN-based compound semiconductor film will be described as an example in consideration of the ease of description and understanding.

[0013] First, a substrate is made (S10). For example, a substrate, which is made of sapphire and which has a size of 4 inches and a thickness of 0.65 mm, is made. Next, a film is formed on the substrate (S12). For example, a GaN-based compound semiconductor film is formed. Next, a blast processing step is performed (S14). Here, the blast processing is performed, for example, under the following conditions (Table 1) in order to apply the blast processing to the entire surface of the substrate, the entire surface being opposite to the surface on which the GaN-based compound semiconductor film is formed.

[Table 1]

[0014] The conditions shown in Table 1 represent, as an example, a case where a rectangular nozzle having a nozzle size of 15 mm x 4.8 mm is used. However, a round nozzle having a nozzle diameter of q>8 mm, or the like, may also be used. Further, the conditions shown in Table 1 represent, as an example, a case where the blast processing is applied to the entire surface of a sapphire substrate by using a scan processing method. Thereby, stress is applied to the entire wafer, so that the warp of the wafer is corrected. Note that, when the uniformity of surface roughness of the surface subjected to the blast processing is not needed, the blast processing needs not necessarily be applied to the entire wafer surface. For example, stress may also be applied by performing the ejection at a fixed portion, such as the center portion of the sapphire substrate.

[0015] Note that, as a blasting machine, for example, MICROBLASTER MB-1 (manufactured by Sintokogio, Ltd.) can be adopted. For example, a suction type flat nozzle that is a rectangular nozzle can be adopted as the nozzle for the blast processing.

[0016] Further, the surface roughness (arithmetic average roughness Ra) of the surface subjected to the blast processing may be in a range of, for example, 0.01 to 5.0 um Ra, Thereby, the warp can be corrected without significantly changing the surface roughness before and after the blast processing. Further, it may be more preferred that the surface roughness of the surface subjected to the blast processing is in a range of 0.5 to 5.0 μπι Ra. In order to obtain the surface roughness in the range of 0.5 to 5.0 um Ra, the blast processing may be performed, for example, under the blasting conditions shown in Table 2.

[Table 2] Abrasive WA#600

Ejection amount 200 g/min

Ejection pressure 0.2 MPa

Nozzle traverse speed 100 mm/sec

Nozzle feed pitch 20 mmP

Ejection distance 100 mm

Ejection angle Perpendicular to substrate

The number of times of scan 1 pass

Ejection time 21 sec

Here, the abrasive is the material included the abrasive micro grain sizes of JIS (Japanese Industrial Standards) R6001.

[0017] The blasting conditions shown in Table 2 are examples. The warp amount of the sapphire substrate is changed according to the size and thickness of the sapphire substrate and further according to the conditions under which the GaN-based compound semiconductor film is formed. For this reason, each of the blasting conditions may be arbitrarily changed according to the warp amount of the sapphire substrate to be corrected.

[0018] Further, in the blast processing, optimum conditions are selected according to the hardness of abrasive, the ejection speed, the coverage (the density of material ejected to the substrate, the density being associated with the ejection amount), and the like. As for the abrasive, for example, an example, in which alumina abrasive grains expressed by a chemical formula of A1₂0₃ are used as the abrasive, is shown in Table 2. However, any material may be used as long as the material can give stress to the substrate. The hardness of the material may also be suitably selected as long as the material having the selected hardness can apply give to the substrate. [0019] The size of the abrasive preferably has an average particle diameter of 25 to 70 um. In the case where the average particle diameter of the abrasive is more than 70 um, the surface of the substrate is roughened. In the case where the average particle diameter of the abrasive is less than 25 um, there is a possibility that, even when the ejection pressure is increased, since the collision energy of the grains applied to the substrate is insufficient, the warp of the substrate cannot be corrected to a desired curvature radius.

[0020] Further, the ejection speed is determined by the kind of abrasive, the ejection pressure, the ejection amount, and the like. Here, the ejection pressure may be set in a range of 0.2 MPa to 0.4 MPa. In the case where the ejection pressure is more than 0.4 MPa, since the processing energy becomes excessive, breakage and cracks may occur in the substrate. In the case where the ejection pressure is less than 0.2 MPa, since stress applied to the substrate becomes small, the processing time required to correct the warp of the substrate may be increased. Further, the ejection amount may be set in a range of 100 g/min to 400 g/min. This is because, when the ejection amount is less than 100 g/min, the processing time required to fill the coverage is increased. When the ejection amount is more than 400 g/min, there is a possibility that, since the coverage is filled in a short time, the warp of the substrate cannot be corrected to a desired curvature radius.

[0021] Further, the coverage is an indicator similar to the density of material ejected to the substrate, and is influenced by the kind of abrasive, the ejection amount, the ejection time, the nozzle traverse speed, the nozzle feed pitch, the ejection angle, and the like. From the above, when alumina abrasive grains are adopted, the abrasive may have an average particle diameter in a range of 25 um to 70 um. The ejection pressure may be set in a range of 0.2 MPa to 0.5 MPa, and more preferably set in a range of 0.2 MPa to 0.4 MPa. The ejection amount may be set in a range of 100 g/min to 400 g/min, and more preferably set in a range of 200 g/min to 400 g/min. Under the above-described conditions, the blast processing can be performed at a high speed of about 20 seconds for one scan by using the above-described blasting machine.

[0022] Note that, after the substrate is sliced from a single crystal of sapphire, both the sliced surfaces of the sapphire substrate may also be polished. The surface roughness of the polished surfaces is, for example, as follows (Table 3).

[Table 3]

[0023] The surface roughness in the table is as an example, and the surface roughness before the film formation can be changed according to the condition of the polishing step after the substrate is made by the slicing step, and according to the condition at the time when the GaN-based compound semiconductor film is formed.

[0024] However, the front and back surfaces of the substrate may have a difference in the surface roughness after the substrate is formed by the slicing step and is polished by the polishing step. This is because a surface subjected to mirror polishing is necessary to form a uniform and thin film at the time of epitaxial growth. On the other hand, after the electrode forming step, the back surface is subjected to a step referred to as BGP (Back Grinding Polish) to reduce the thickness of the substrate to about 0.1 mm, and hence the back surface of the substrate need not be polished to a mirror surface at the time of the polishing step after the substrate is made by the slicing step.

[0025] Further, when the surface of the substrate which have large surface roughness is subjected to the blast processing, a warp of the substrate can be corrected without giving damage to the mirror surface of the substrate which surface is subjected to epitaxial growth. Hence, it may be to provide beforehand a difference in the surface roughness between the surface and the back surface of the substrate. This is because, when the surface roughness of the back surface is the same as the surface roughness of the surface polished into the mirror surface, the polishing step needs to be additionally performed, and after the additional polishing step, an additional blasting step needs to be further performed. Further, when a difference in the surface roughness between the surface and the back surface of the substrate is provided beforehand, an advantage is obtained that a warp of the substrate can be corrected without giving damage to the mirror surface of the substrate which surface is subjected to epitaxial growth.

[0026] Note that, in the measurement of the warp amount before and after the blast processing of the sapphire substrate, for example, a surface roughness meter SURFCOM HOOD (manufactured by Tokyo Seimitsu Co., Ltd.) can be used. An example of a measurement range is shown in Figure 2. The measurement range is, for example, a range surrounded by a rectangle having a side of L = 97 mm. The effect of warp correction before and after the blast processing can be confirmed in such a manner that the warp amount is measured by this method in the two directions before and after the blast processing, and that the average value of the warp amount is obtained and then the warp amount is converted to a curvature radius.

[0027] Figure 3 is a schematic view showing an evaluation method. The warp amount Ah is a difference between a maximum height and a minimum height on the surface of the sapphire substrate. The warp amount Ah is represented by a plus value when the surface is convex, while the warp amount Ah is represented by a minus value when the surface is concave. The curvature radius R can be converted from the warp amount Ah. The relationship between the curvature radius R and the warp amount Ah is shown in Figure 3. Note that the apparatus and method for measuring the surface roughness is not limited to those described above.

[0028] At the time of the blast processing, the blast processing is performed, for example, in such a manner that the nozzle is scanned while the side of the GaN-based compound semiconductor film is fixed by suction negative pressure applied by using a suction jig. Figure 4 is a schematic view showing a trajectory of relative movement between the blast nozzle and the substrate at the time of the blast processing according to the present invention. In the embodiment, the blast processing may be performed by scanning from SI to S2 under the conditions of the nozzle traverse speed: 100 mm/sec, the nozzle feed pitch: P = 20 mm, and the number of times of scans: 1 pass. Further, a method in which the nozzle is scanned is described in the above. However, a method may also be adopted in which the side of the suction jig for fixing the sapphire substrate is scanned, and in which the nozzle is fixed. Further, the blast processing may also be performed by performing the scanning operation in such a manner that the nozzle is moved along one axis while the suction jig is moved in the direction orthogonal to the moving direction of the nozzle. In short, any scanning means can be used only as long as the scan processing is applied to the sapphire wafer by moving the wafer and the nozzle relative to each other.

[0029] Figure 5 is a schematic view showing a principle for correcting distortion of a wafer by the blast processing according to the embodiment. Note that, in the following, a case where the blast processing is applied after the formation of a GaN-based compound semiconductor film is described. In Figure 5, an abrasive F is ejected from a nozzle N to a sapphire wafer W which is warped due to the formation of a film of GaN-based compound semiconductor G As a result, the warp of the sapphire wafer W warped due to the formation of the film of GaN-based compound semiconductor G is corrected in the state where the GaN-based compound semiconductor Gf is held on the sapphire wafer Wf.

[0030] Table 4 shows an example of measurement results when the abrasive, the ejection amount, the ejection pressure, and the warp amount after EPI step are changed.

[Table 4] Warp amount after Warp amount

Ejection Ejection Curvature

EPI step (before after blast

Abrasive amount pressure radius blast processing) processing

[g min] [MPa] [m]

[um] [um]

Substrate 1 WA#600 200 0.3 83 32 36.8

Substrate 2 WA#400 200 0.3 103 35 33.6

Substrate 3 WA#400 200 0.4 132 29 40.6

Substrate 4 WA#320 400 0.3 125 23 51.1

Substrate 5 WA#240 400 0.5 210 20 58.8

As the abrasive, alumina abrasive grains (White Alundum)

WA#240 to WA #600 (manufactured by Sintokogio, Ltd.), that is, alumina abrasive grains having an average particle diameter of 25 um to 70 μιη were used. Here, the abrasive is the material included the abrasive micro grain sizes of JIS (Japanese Industrial Standards) R6001.

Further, an ejection pressure of 0.3 MPa to 0.5 MPa was used. The warp amount in an area of 97 mm x 97 mm of a 4-inch (φΙΟΟ mm) substrate (wafer) W after the EPI step was varied in a range of 83 um to 210 um. However, after the blast processing, the warp amount was corrected to 40 um or less (35 um to 20 um). Note that the curvature radius converted from the warp amount was 30 m or more. Further, in the case where the inch size of the wafer is increased in future, the warp amount of a wafer as a whole may become 40 um or more. Even in this case, the warp amount is acceptable as long as, when the warp amount is converted to a warp amount of the 4-inch (φΙΟΟ mm) wafer, the converted warp amount is 40 um or less. In this range of the warp amount, there is an advantage that, in the subsequent process, the yield in laser processing for cutting the substrate into chips is improved.

[0031] Returning to Figure 1, when the blast processing step is completed, the processing is shifted to the electrode forming step (SI 6). In the electrode forming step, a transparent electrode, a pad electrode, a protective film, and the like, are formed on the compound semiconductor film formed on the wafer. When the electrode forming step is completed, the processing is shifted to the element cutting step (SI 8). In the element cutting step, the substrate is cut into chips having a standard size. When the step of S 18 is completed, the method shown in Figure 1 is ended.

[0032] As is apparent from the above description, according to the embodiment of the present invention, the warp caused at the time of the formation of the GaN-based compound semiconductor film can be corrected by performing the blast processing after the formation of the GaN-based compound semiconductor film.

[0033] Note that the embodiment described above shows an example of the processing method according to the present invention. The processing method according to the present invention is not limited to the processing method according to the above-described embodiment. For example, in another embodiment, when the blast processing is performed before the formation of the compound semiconductor film, it is also possible to correct a warp caused at the time of the formation of the GaN-based compound semiconductor film. The flow chart of this example is shown in Figure 6. The flow chart shown in Figure 6 is substantially the same as the flow chart shown in Figure 1, and the processing of each of S20, S26 and S28 corresponds to the processing of each of S10, S16 and SI 8. That is, in Figure 6, the film forming step (S24) is performed after the blast processing step (S22).

[0034] As is apparent from the above description, when the blast processing is performed before or after the formation of the GaN-based compound semiconductor film, it is possible to correct a warp caused at the time of the formation of the GaN-based compound semiconductor film.

[0035] However, when the blast processing is performed before the formation of the GaN-based compound semiconductor film, the phenomenon, in which the mirror surface side of the substrate is warped into a convex shape at the time of the formation of the GaN-based compound semiconductor film, can be offset by forming beforehand the mirror surface side of the substrate in a concave shape. However, when the mirror surface side of the substrate is formed in a concave shape beforehand, film formation variation may occur depending on the way of heating by a heat source at the time of the formation of the GaN-based compound semiconductor film. Therefore, it is preferred that the blast processing is performed after the formation of the

GaN-based compound semiconductor film.

[0036] In this way, the manufacturing process, in which LED elements or LD elements are manufactured, is designed such that the blast processing is performed before or after the GaN-based compound semiconductor film is formed on the substrate. Thereby, the curvature radius of a warp of the substrate caused at the time of the formation of the GaN-based compound semiconductor film can be increased to 30 m or more.

[0037] Note that, before or after the polishing step, or after the blasting step, or in an interval between formation of electrodes, or the like, it is preferred to add a washing step to wash and remove impurities, such as oil and fat content, oxide, and processing waste, which are generated in the polishing step, the blasting step, and the electrode forming step. Figure 7 shows an example of the processing method in which the washing step is added. The flow chart shown in Figure 7 is substantially the same as the flow chart shown in Figure 1, and the processing of S30 corresponds to the processing of S10 in Figure 1. Further, the processing of S36 to S40 corresponds to the processing of S12 to S16 in Figure 1, and the processing of S46 corresponds to the processing of S 18 in Figure 1. That is, the polishing process (S32 and S42) and the washing process (S34 and S44) are included in Figure 7.

[0038] In another embodiment, it is also possible that the blast processing is performed while the surface roughness is measured, and that the measured result is fed back to the blast processing. On the other hand, the measurement of the surface roughness need not be necessarily performed for all the substrates. When the processing conditions are determined, the measurement of the surface roughness is unnecessary in the ordinary step.

Industrial Applicability

[0039] According to the embodiments and various aspects of the present invention, a warp of a substrate can be corrected at the time of manufacturing LED elements and LD elements, whereby in the subsequent process for cutting the substrate into respective elements by using a laser, it is possible to eliminate cutting failure due to focusing failure that is caused when the substrate is warped.

[0040] Further, according to the embodiments and various aspects of the present invention, it is also possible to reduce variation at the time of the formation of electrodes on the GaN-based compound semiconductor.

[0041] Further, according to the embodiments and various aspects of the present invention, at the time of applying the blast processing to the substrate, the blast processing is applied, by changing the blast processing conditions, to the surface opposite to the surface on which a GaN-based compound semiconductor film is formed. Thereby, the blasted surface of the substrate can be processed to have any surface roughness. As a result, in the case of an LED element or an LD element using, as the light emission side, the surface opposite to the surface on which the GaN-based compound semiconductor film is formed, the light diffusion property can be improved in correspondence with the wavelength of light emitted from the LED or the LD.

Reference Signs List

[0042] W, Wf Substrate (wafer), L Surface roughness measurement range, Ah Warp amount, R Curvature radius, N Blast nozzle, G, Gf Formed film

Claims

[Claim 1]

A processing method of a substrate for semiconductor elements, for applying blast processing to a substrate having a first surface and a second surface opposite to the first surface, the processing method comprising

a step of applying the blast processing to the second surface opposite to the first surface on which a compound semiconductor film is formed or is to be formed.

[Claim 2]

The processing method of a substrate for semiconductor elements, according to claim 1, further comprising:

a step of making a substrate;

a step of performing a step of forming the compound semiconductor film on the first surface of the substrate; and

a step of forming LED electrodes or LD electrodes on the first surface being opposite to the second surface subjected to the blast processing, and of cutting the substrate into LED elements or LD elements.

[Claim 3]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein, when the blast processing is applied to the substrate, the blast processing is applied to the entire surface of the second surface of the substrate.

[Claim 4]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein the surface subjected to the blast processing has a surface roughness in a range of 0.01 to 5.0 um Ra.

[Claim 5]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein a warp amount of the substrate subjected to the blast processing is in a range of -40 μηι or more to 40 um or less in an area of 97 mm x 97 mm of the substrate.

[Claim 6]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein the surface roughness of the second surface is larger than the surface roughness of the first surface.

[Claim 7]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein, in the blast processing, alumina abrasive grains having an average particle diameter in a range of 25 μιη to 70 μιη are used as the abrasive, the ejection pressure is set in a range of 0.2 MPa, to 0.5 MPa, and the ejection amount is set in a range of 100 g/min to 400 g/min.

[Claim 8]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein the substrate is a sapphire substrate.

[Claim 9]

The processing method of a substrate for semiconductor elements, according to claim 1 or 2, wherein the compound semiconductor film is made of a GaN-based compound.