Evaluation method for heteroepitaxial substrate

Abstract

To provide a novel evaluation method that can evaluate the thickness of a heteroepitaxial layer of a heteroepitaxial substrate without destruction in a short time in the wide range regardless of whether light can transmit the heteroepitaxial substrate.SOLUTION: An evaluation method for a heteroepitaxial substrate including a heteroepitaxial layer on a surface of a substrate includes irradiating the heteroepitaxial substrate with laser light, acquiring Raman spectrum by Raman spectroscopy, obtaining Raman signal intensity (ISub) of the substrate and Raman signal intensity (IEpi) of the heteroepitaxial layer from the Raman spectrum, and evaluating the thickness of the heteroepitaxial layer on the basis of the ISub and the IEpi.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating a heteroepitaxial substrate. [Background technology]

[0002] Large-diameter SiC and GaN substrates are required for power devices and high-frequency devices. Heteroepitaxial growth techniques have been investigated as a method for achieving this increase in diameter (see, for example, Patent Documents 1 and 2). These patent documents also disclose that heteroepitaxial layers can be grown on large-diameter substrates, such as those with a diameter of 300 mm, by selecting the appropriate reactor type.

[0003] However, the formation of heteroepitaxial layers requires determining the optimum growth conditions while checking the film thickness, and so far, the thickness of heteroepitaxial layers has been evaluated by cross-sectional TEM from the surface of the heteroepitaxial substrate.

[0004] Furthermore, Patent Document 3 discloses a wavelength selection method for selecting the wavelength of illumination light used in measuring the thickness of a thin film, in which illumination light of different wavelengths is irradiated onto a plurality of samples in which thin films of different film quality states and film thicknesses are formed on a substrate, and evaluation values ​​relating to the amount of light transmitted when irradiated with illumination light of each wavelength are measured, and based on the measurement results, a film thickness characteristic indicating the correlation between film thickness in each film quality state and the evaluation value is created for each wavelength, and a wavelength is selected for each film thickness characteristic in which the measurement difference in evaluation value depending on the film quality state is within a predetermined range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-045163 [Patent Document 2] Patent Publication No. 2021-020819 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-203090 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the cross-sectional TEM from the surface of a heteroepitaxial substrate that has been used to evaluate film thickness is a so-called destructive test that destroys the substrate, which has the problem that the evaluation requires a long time including the destructive work, and only local analysis of the destroyed area is possible.

[0007] Furthermore, the method of using transmitted light when irradiated with illumination light as shown in Patent Document 3 is more desirable than cross-sectional TEM in that it allows non-destructive evaluation, but has the problem that it cannot be used for heteroepitaxial substrates that do not transmit light.

[0008] The present invention has been made to solve the above problems, and aims to provide a new evaluation method that can evaluate the film thickness of a heteroepitaxial layer of a heteroepitaxial substrate non-destructively, quickly, and over a wide range, regardless of whether light can pass through the heteroepitaxial substrate. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a method for evaluating a heteroepitaxial substrate, which is a method for evaluating a heteroepitaxial substrate having a heteroepitaxial layer on a surface of the substrate, comprising: irradiating the heteroepitaxial substrate with laser light; obtaining a Raman spectrum by Raman spectroscopy; and determining the Raman signal intensity (I Sub ) and the Raman signal intensity (I Epi ) and calculate the above I Sub and the aforementioned I Epi The method is characterized in that the thickness of the heteroepitaxial layer is evaluated based on the following:

[0010] In this method, Raman spectroscopy is used, so the Raman spectrum is obtained using the Raman scattered light scattered in the direction of irradiation, rather than the transmitted light of the laser light irradiated on the heteroepitaxial substrate, and the I obtained from the Raman spectrum Sub and I Epi Since the thickness of the heteroepitaxial layer is evaluated based on this, whether light can pass through the heteroepitaxial substrate or not is irrelevant, and the thickness can be evaluated non-destructively. Furthermore, since it is non-destructive, there is no need for time spent on destructive work, and since the measurement is performed using the response of laser light, the thickness can be evaluated in a short time. Furthermore, since laser light is irradiated, the irradiation position can be easily changed, and it is possible to evaluate the thickness by changing the irradiation position from the center to the edge of the heteroepitaxial substrate, for example, and the thickness can be evaluated over a wide range.

[0011] The thickness of the heteroepitaxial layer was evaluated in advance using another heteroepitaxial substrate. Sub and I Epi The relationship between the ratio of I and the thickness of the heteroepitaxial layer is determined in advance, and the I obtained from the Raman spectrum is Sub and the aforementioned I Epi It is preferable to apply the ratio of the above to the relational expression to determine the thickness of the heteroepitaxial layer.

[0012] If you prepare such a relational expression in advance, I Sub and I Epi By simply finding the ratio and substituting it into the relational expression, the film thickness of the heteroepitaxial layer on the heteroepitaxial substrate can be evaluated reliably, non-destructively, in a short time, and over a wide range.

[0013] In addition, when obtaining a Raman spectrum by the Raman spectroscopy, Epi It is preferable to adjust the focus so that the value is maximized.

[0014] By adjusting the focus in this way, I Epiis the Raman signal intensity of the heteroepitaxial layer, which is generally thinner than the substrate, it is possible to focus on the heteroepitaxial layer and accurately determine the signal intensity without missing any of the heteroepitaxial layers, and it is possible to accurately evaluate the film thickness even for thin heteroepitaxial layers.

[0015] It is also preferable to adjust the wavelength of the laser light depending on the film thickness of the heteroepitaxial layer and the material that constitutes the heteroepitaxial layer.

[0016] By making such adjustments, it is possible to irradiate the heteroepitaxial layer with laser light of an appropriate wavelength depending on the film thickness of the heteroepitaxial layer and the material that constitutes the heteroepitaxial layer, thereby enabling the film thickness of the heteroepitaxial layer to be evaluated with greater accuracy.

[0017] The heteroepitaxial layer is preferably made of 3C-SiC single crystal or Ge single crystal.

[0018] By using such a heteroepitaxial layer, the thickness of the heteroepitaxial layer on the heteroepitaxial substrate can be evaluated reliably, non-destructively, in a short time, and over a wide range. [Effects of the Invention]

[0019] In the evaluation method of the heteroepitaxial substrate of the present invention, Raman spectroscopy is used, so that the Raman spectrum is obtained using Raman scattered light scattered in the direction of irradiation, rather than transmitted light of laser light irradiated onto the heteroepitaxial substrate, and I obtained from the Raman spectrum Sub and I EpiSince the thickness of the heteroepitaxial layer is evaluated based on this, whether light can pass through the heteroepitaxial substrate or not is irrelevant, and the thickness can be evaluated non-destructively. Furthermore, since it is non-destructive, there is no need for time spent on destructive work, and since the measurement is performed using the response of laser light, the thickness can be evaluated in a short time. Furthermore, since laser light is irradiated, the irradiation position can be easily changed, and it is possible to evaluate the thickness by changing the irradiation position from the center to the edge of the heteroepitaxial substrate, for example, and the thickness can be evaluated over a wide range. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of Raman spectrum acquisition by Raman spectroscopy in one embodiment of the present invention. [Figure 2] FIG. 1 is a correlation diagram between IEpi / ISub and the film thickness of a heteroepitaxial layer in Examples 1 to 3. [Figure 3] FIG. 10 is a correlation diagram between IEpi / ISub and the film thickness of the heteroepitaxial layer in Examples 4 to 6. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below, but the present invention is not limited thereto.

[0022] As described above, there has been a need to provide a new evaluation method that can evaluate the film thickness of a heteroepitaxial layer of a heteroepitaxial substrate nondestructively, quickly, and over a wide range, regardless of whether light can pass through the heteroepitaxial substrate.

[0023] The present inventors have conducted extensive research into the above-mentioned problems, and have focused on Raman scattered light rather than transmitted light when a heteroepitaxial substrate is irradiated with laser light. Sub ) and the Raman signal intensity (I Epi The present inventors have found a method for evaluating the film thickness of a heteroepitaxial layer based on the above-mentioned method, and have completed the present invention.

[0024] That is, the method for evaluating a heteroepitaxial substrate of the present invention is a method for evaluating a heteroepitaxial substrate having a heteroepitaxial layer on a surface of a substrate, the method comprising: irradiating the heteroepitaxial substrate with laser light; obtaining a Raman spectrum by Raman spectroscopy; and determining the Raman signal intensity (I Sub ) and the Raman signal intensity (I Epi ) and calculate the above I Sub and the aforementioned I Epi The method is characterized in that the thickness of the heteroepitaxial layer is evaluated based on the following:

[0025] Hereinafter, one embodiment of the heteroepitaxial substrate evaluation method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

[0026] (1)I Epi / I Sub Derivation of the relation between the thickness of the heteroepitaxial layer and

[0027] Figure 1 is a schematic diagram of Raman spectrum acquisition using Raman spectroscopy.

[0028] First, a plurality of heteroepitaxial substrates 1 are prepared, each having a heteroepitaxial layer on the surface of the substrate and having a heteroepitaxial layer with a different thickness.

[0029] Next, as shown in FIG. 1, laser light 3 is irradiated from laser 2 onto the surfaces of heteroepitaxial substrates 1 with different film thicknesses, and Raman spectra are obtained by Raman spectroscopy. More specifically, Raman scattered light 4 generated by irradiation with laser light 3 is dispersed by a spectrometer 5, which may be, for example, a diffraction grating, and detected for each wavelength by a CCD detector 6, for example, for example, for example, for example, and the signal obtained by the CCD detector 6 is converted by a PC 7, for example, for example, for example, for example, for example, for example, for example, for example, into Raman spectra attributable to the substrate and heteroepitaxial layer. From the obtained Raman spectra, the Raman signal intensity (I) of the substrate is calculated. Sub) and the Raman signal intensity (I Epi ) is found.

[0030] In addition, in Raman spectroscopy, although not particularly limited, an objective lens 8 may be used.

[0031] At this time, as the thickness of the heteroepitaxial layer increases, the Raman signal intensity (I Epi In this case, the intensity of the laser light penetrating the substrate decreases, so the Raman signal intensity (I Sub ) versus the Raman signal intensity (I Epi ) increases. Therefore, I Sub and I Epi Based on this, the thickness of the heteroepitaxial layer can be evaluated.

[0032] In this method, Raman spectroscopy is used, so that the Raman spectrum is obtained using Raman scattered light 4 scattered in the direction of irradiation, rather than the transmitted light of the laser light 3 irradiated onto the heteroepitaxial substrate 1, and I obtained from the Raman spectrum Sub and I Epi Since the thickness of the heteroepitaxial layer is evaluated based on this, whether or not light can pass through the heteroepitaxial substrate 1 is irrelevant, and the thickness can be evaluated non-destructively. Furthermore, since it is a non-destructive method, there is no need for time spent on destructive work, and since it uses the response of laser light, measurement is extremely fast, allowing the thickness to be evaluated in a short time. Furthermore, since laser light is irradiated, the irradiation position can be easily changed, and it is possible to evaluate the thickness by changing the irradiation position from the center to the edge of the heteroepitaxial substrate 1, for example, and the thickness can be evaluated over a wide range.

[0033] Here, I Sub and I Epi The evaluation of the thickness of the heteroepitaxial layer based on this method is not particularly limited, but can be performed, for example, by the following method. Epi / I Sub For example, multiple measurements can be taken at 10 points for each film thickness, and the average value and standard deviation can be calculated. Epi / I Sub and the film thickness of the heteroepitaxial layer can be derived.

[0034] Here, if the thickness of the heteroepitaxial layer of the prepared heteroepitaxial substrate is known, that value may be used as the thickness of the heteroepitaxial layer for deriving the relational expression. However, in order to prevent individual variations, it is preferable to use the above-mentioned method. Epi / I Sub It is more preferable to calculate the film thickness by performing a cross-sectional TEM at the position where the laser is irradiated on the film for which the thickness is found.

[0035] The following describes, but is not limited to, the procedure for creating a relational expression based on Lambert's law (the absorbance of a substance at a specific wavelength is proportional to the thickness of the absorbing layer of the substance).

[0036] First, the symbols used in the relational expressions are defined. I Epi : Raman signal intensity of heteroepitaxial layer I Sub : Raman signal intensity of the substrate I0: Incident light intensity on the sample surface α Epi : Absorption coefficient of heteroepitaxial layer α Sub : absorption coefficient of the substrate d Epi :Heteroepitaxial layer thickness d Sub :Substrate film thickness A: The rate at which light penetrates from the heteroepitaxial layer to the substrate B: The rate at which light penetrates from the substrate into the heteroepitaxial layer E Epi : The ratio of Raman scattered light emitted to incident light in the heteroepitaxial layer E Sub : The ratio of Raman scattered light emitted from the substrate to the incident light

[0037] Next, based on Lambert's law, I Sub , I Epi is derived.

[0038]

number

[0039]

number

[0040] Next, I Sub and I Epi The intensity ratio is taken.

[0041]

number

[0042] Next, E Epi / (ABE Sub )=C.

[0043]

number

[0044] The calculated value (I Epi / I Sub Substituting the above, we get d Epi ) is closest to the experimental value, the final relationship can be determined.

[0045] If you prepare such a relational expression in advance, I Sub and I Epi By simply finding the ratio and substituting it into the relational expression, the film thickness of the heteroepitaxial layer on the heteroepitaxial substrate can be evaluated reliably, non-destructively, in a short time, and over a wide range.

[0046] The wavelength of the laser light can be, for example, 325 nm, but is not limited to this. However, since the penetration depth of the laser light varies depending on the wavelength and the material, it is preferable to adjust the wavelength of the laser light depending on the film thickness of the heteroepitaxial layer and the material constituting the heteroepitaxial layer, although this is not particularly limited.

[0047] By making such adjustments, it is possible to irradiate the heteroepitaxial layer with laser light of an appropriate wavelength depending on the film thickness of the heteroepitaxial layer and the material that constitutes the heteroepitaxial layer, thereby enabling the film thickness of the heteroepitaxial layer to be evaluated with greater accuracy.

[0048] The material constituting the substrate may be, for example, Si, but is not particularly limited as long as it is a material from which a Raman signal can be detected.

[0049] (2) Calculation of heteroepitaxial layer thickness

[0050] Although not particularly limited, a Raman spectroscopy-based device such as that shown in Figure 1, similar to that described in (1) above, is used to calculate the film thickness of a heteroepitaxial substrate, the thickness of which is unknown for the heteroepitaxial layer to be evaluated. Laser light 3 is irradiated onto the surface of the heteroepitaxial substrate 1, and the resulting Raman scattered light 4 is dispersed by a spectrometer 5 consisting of a diffraction grating and detected for each wavelength by a CCD detector 6. The signal obtained by the CCD detector 6 is converted by a PC 7 into Raman spectra of the substrate and heteroepitaxial layer. From the obtained Raman spectra, the Raman signal intensity (I Sub ) and the Raman signal intensity (I Epi ) is found.

[0051] Although not particularly limited, when obtaining a Raman spectrum by Raman spectroscopy, I Epi It is preferable to adjust the focus so that the value is maximized.

[0052] By adjusting the focus in this way, I Epiis the Raman signal intensity of the heteroepitaxial layer, which is generally thinner than the substrate, it is possible to focus on the heteroepitaxial layer and accurately determine the signal intensity without missing any of the heteroepitaxial layers, and it is possible to accurately evaluate the film thickness even for thin heteroepitaxial layers.

[0053] Next I Epi / I Sub Ask for.

[0054] Next, this value is calculated by (1) Epi / I Sub and the relational expression for the thickness of the heteroepitaxial layer (the final relational expression in which the value of C is also set), the thickness (calculated value) of the heteroepitaxial layer can be calculated.

[0055] Here, just to be sure, the usefulness of this relational expression was verified. For multiple heteroepitaxial substrates for which the thicknesses (calculated values) of the heteroepitaxial layers had been determined, cross-sectional TEM was performed at the laser irradiation position to calculate the actual thicknesses (experimental values). As a result, all calculated values ​​were within ±3σ of the experimental values, demonstrating that the thicknesses of the heteroepitaxial layers can be calculated with high accuracy by using the evaluation method of this embodiment.

[0056] Although not particularly limited, it is preferable that the heteroepitaxial layer be made of 3C-SiC single crystal or Ge single crystal.

[0057] By using such a heteroepitaxial layer, the thickness of the heteroepitaxial layer on the heteroepitaxial substrate can be evaluated reliably, non-destructively, in a short time, and over a wide range, as will be further described in the following examples.

[0058] As described above, the method for evaluating a heteroepitaxial substrate of this embodiment can evaluate the film thickness of the heteroepitaxial layer of a heteroepitaxial substrate non-destructively, quickly, and over a wide range, regardless of whether light can pass through the heteroepitaxial substrate.

[0059] Since the film thickness can be evaluated non-destructively and over the entire surface of the substrate, it is possible to determine the film thickness of the entire substrate, for example. [Example]

[0060] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples.

[0061] [Examples 1 to 3, Comparative Examples 1 to 3] The heteroepitaxial layer is a 3C-SiC single crystal

[0062] (1)I Epi / I Sub and the thickness of the heteroepitaxial layer (3C-SiC single crystal)

[0063] First, one heteroepitaxial substrate was used, in which 3C-SiC single crystals with thicknesses of 50, 70, 95, 165, and 270 nm were heteroepitaxially grown on a 300 mm diameter Si single crystal substrate. The thicknesses of the 3C-SiC single crystals, which were the heteroepitaxial layers, were estimated separately by cross-sectional TEM.

[0064] Next, I Epi / I Sub The relationship between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer was investigated. Epi / I Sub The correlation diagram between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer is shown in Figure 1. The error bars in the figure indicate ±3σ. Based on the data examined, fitting was performed using a relational expression based on Lambert's law, and by setting C = 0.001, the calculated value calculated from the relational expression and the experimental value were the closest values, and I in Equation 1 below was obtained. Epi / I Sub The relation between the thickness of the heteroepitaxial layer and the α Sub is the absorption coefficient of Si, α Epi is the absorption coefficient of 3C-SiC, d Sub is the Si film thickness, d Epi indicates the film thickness of 3C-SiC.

[0065] Here IEpi / I Sub The calculated values ​​calculated from the relational expression between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer were within ±3σ of the experimental values.

number

[0066] The wavelength of the laser light in this example was 325 nm. The laser Raman microscope used for Raman spectroscopy was a Nanophoton Laser Raman microscope (RAMANdrive UV-VIS-NIR-SHK), and the measurement conditions were: excitation wavelength: 325 nm, diffraction grating: 3600 gr / mm, resolution: 1.8 cm. -1 It was decided.

[0067] (2) Calculation of the thickness of the heteroepitaxial layer (3C-SiC single crystal)

[0068] A laser beam was irradiated onto the surface near the center of a heteroepitaxial substrate of 3C-SiC single crystal with an unknown film thickness. The resulting Raman scattered light was dispersed using a diffraction grating and detected by wavelength using a CCD detector. The signal obtained by the CCD detector was then converted by a PC into a Raman spectrum resulting from the LO mode (longitudinal optical mode) of Si and 3C-SiC.

[0069] The focus was adjusted to maximize the signal intensity of the 3C-SiC LO mode, and the Raman signals resulting from the Si and 3C-SiC LO modes were observed. Epi / I Sub Calculate the I obtained in (1) above. Epi / I Sub The film thickness of the 3C-SiC single crystal was derived from the relational expression (Equation 1) between the thickness of the heteroepitaxial layer and the thickness of the 3C-SiC single crystal. Epi / I Sub are different, 0.012, 0.025, and 0.074.

[0070] Furthermore, as comparative examples, the film thickness of the 3C-SiC single crystal was measured and verified by cross-sectional TEM observation, which involves destruction.Epi / I Sub and for 0.012, 0.025, and 0.074.

[0071] Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1.

[0072] [Table 1]

[0073] From Table 1, Examples 1 to 3 (I Epi / I Sub The thickness of the 3C-SiC single crystal calculated from the relational expression between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer is roughly consistent with the thickness measured by cross-sectional TEM observation in Comparative Examples 1 to 3. Therefore, it was demonstrated that the thickness of the 3C-SiC single crystal can be evaluated non-destructively in Examples 1 to 3, whereas Comparative Examples 1 to 3 are destructive because they are based on conventional methods.

[0074] [Examples 4 to 6, Comparative Examples 4 to 6] The heteroepitaxial layer is a Ge single crystal

[0075] (1)I Epi / I Sub Derivation of the relational expression between the thickness of the heteroepitaxial layer (Ge single crystal) and

[0076] First, we used one heteroepitaxial substrate each, in which Ge single crystals with thicknesses of 23, 45, 95, and 151 nm were heteroepitaxially grown on a 300 mm diameter Si single crystal substrate. The thicknesses of the Ge single crystals, which were the heteroepitaxial layers, were estimated separately using cross-sectional TEM.

[0077] Next, I Epi / I Sub The relationship between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer was investigated. Epi / I SubThe correlation diagram between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer is shown in Figure 1. The error bars in the figure indicate ±3σ. Based on the data examined, fitting was performed using a relational expression based on Lambert's law, and by setting C = 8.8, the calculated value calculated from the relational expression and the experimental value were the closest values, and I in Equation 2 below was obtained. Epi / I Sub The relation between the thickness of the heteroepitaxial layer and the α Sub is the absorption coefficient of Si, α Epi is the absorption coefficient of Ge, d Sub is the Si film thickness, d Epi indicates the thickness of the Ge film.

[0078] Here I Epi / I Sub The calculated values ​​calculated from the relational expression between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer were within ±3σ of the experimental values.

number

[0079] The wavelength of the laser light in this example is 785 nm. The laser Raman microscope used for Raman spectroscopy is a Nanophoton Laser Raman microscope (RAMANdrive UV-VIS-NIR-SHK), and the measurement conditions are excitation wavelength: 785 nm, diffraction grating: 600 gr / mm, resolution: 2 cm. -1 It was decided.

[0080] (2) Calculation of the thickness of the heteroepitaxial layer (Ge single crystal)

[0081] A laser beam was irradiated onto the surface near the center of a heteroepitaxial substrate of Ge single crystal with an unknown thickness. The resulting Raman scattered light was dispersed using a diffraction grating and detected by wavelength using a CCD detector. The signal obtained by the CCD detector was then converted into a Raman spectrum attributed to Si and Ge using a PC.

[0082] The focus was adjusted to maximize the signal intensity of Ge, and the Raman signals originating from Si and Ge were observed. Epi / ISub Calculate the I obtained in (1) above. Epi / I Sub The thickness of the Ge single crystal was derived from the relational expression (Equation 2) between the thickness of the heteroepitaxial layer and the thickness of the Ge single crystal. Epi / I Sub are different, 0.004, 0.102, and 0.403.

[0083] Furthermore, as comparative examples, the film thickness of the Ge single crystal was measured and verified by cross-sectional TEM observation, which involves destruction. Epi / I Sub and for 0.004, 0.102, and 0.403.

[0084] Examples 4 to 6 and Comparative Examples 4 to 6 are summarized in Table 2.

[0085] [Table 2]

[0086] From Table 2, Examples 4 to 6 (I Epi / I Sub The thickness of the Ge single crystal (calculated from the relational expression between the thickness of the heteroepitaxial layer and the thickness of the heteroepitaxial layer) roughly coincides with the thickness measured by cross-sectional TEM observation in Comparative Examples 4 to 6. Therefore, it was shown that the thickness of the Ge single crystal can be evaluated non-destructively in Examples 4 to 6, whereas Comparative Examples 4 to 6 are destructive because they are based on conventional methods.

[0087] As described above, Examples 1 to 6 have shown that, although not limited to this, the film thickness of a heteroepitaxial layer in a heteroepitaxial substrate can be evaluated non-destructively by constructing the heteroepitaxial layer from a 3C-SiC single crystal or a Ge single crystal.

[0088] Furthermore, Examples 1 to 6 showed that by adjusting the wavelength of the laser light (325 nm for 3C-SiC single crystal, 785 nm for Ge single crystal) depending on the thickness of the heteroepitaxial layer and the material constituting the heteroepitaxial layer (3C-SiC single crystal, Ge single crystal), it was possible to evaluate the thickness of the heteroepitaxial layer non-destructively and with high accuracy.

[0089] It should be noted that the above Examples 1 to 6 only explained how the thickness of a heteroepitaxial layer can be evaluated nondestructively and with high accuracy, compared to Comparative Examples 1 to 6, which are conventional methods and therefore involve destruction. However, it is clear that the present invention has many other significant advantages, such as the fact that it can be applied to many substrates regardless of whether the heteroepitaxial substrate can transmit light because it uses Raman scattered light, that it is nondestructive and therefore does not require time spent on destructive work, and that it can be evaluated in a short time because it is measured with laser light, and that it can be evaluated over a wide range because the irradiation position of the laser light can be easily changed.

[0090] The present invention includes the following aspects. [1]: A method for evaluating a heteroepitaxial substrate having a heteroepitaxial layer on a surface of a substrate, comprising: irradiating the heteroepitaxial substrate with laser light; obtaining a Raman spectrum by Raman spectroscopy; and determining the Raman signal intensity (I Sub ) and the Raman signal intensity (I Epi ) and calculate the above I Sub and the aforementioned I Epi A method for evaluating a heteroepitaxial substrate, characterized in that the film thickness of the heteroepitaxial layer is evaluated based on the above formula. [2]: The thickness of the heteroepitaxial layer was evaluated in advance using another heteroepitaxial substrate. Sub and I Epi The relationship between the ratio of I and the thickness of the heteroepitaxial layer is determined in advance, and the I obtained from the Raman spectrum is Sub and the aforementioned I EpiThe method for evaluating a heteroepitaxial substrate according to [1] above, wherein the film thickness of the heteroepitaxial layer is determined by applying the ratio of [3]: When obtaining a Raman spectrum by the Raman spectroscopy, Epi The method for evaluating a heteroepitaxial substrate according to [1] or [2] above, wherein the focus is adjusted so that the value is maximized. [4]: A method for evaluating a heteroepitaxial substrate according to any one of [1] to [3] above, characterized in that the wavelength of the laser light is adjusted depending on the film thickness of the heteroepitaxial layer and the material constituting the heteroepitaxial layer. [5]: The method for evaluating a heteroepitaxial substrate according to any one of [1] to [4] above, wherein the heteroepitaxial layer is composed of a 3C-SiC single crystal or a Ge single crystal.

[0091] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0092] 1... heteroepitaxial substrate, 2... laser, 3... laser light, 4...Raman scattered light, 5...spectroscope, 6...CCD detector, 7...PC, 8...Objective lens.

Claims

1. A method for evaluating a heteroepitaxial substrate having a heteroepitaxial layer on a surface of a substrate, comprising: irradiating the heteroepitaxial substrate with laser light; obtaining a Raman spectrum by Raman spectroscopy; and determining a Raman signal intensity (I Ｓｕｂ ) and the Raman signal intensity (I Ｅｐｉ ) is obtained, and Ｓｕｂ and the aforementioned I Ｅｐｉ A method for evaluating a heteroepitaxial substrate, characterized in that the film thickness of the heteroepitaxial layer is evaluated based on the above formula.

2. The thickness of the heteroepitaxial layer was evaluated in advance using another heteroepitaxial substrate. Ｓｕｂ and I Ｅｐｉ and the film thickness of the heteroepitaxial layer, and Ｓｕｂ and the aforementioned I Ｅｐｉ 2. The method for evaluating a heteroepitaxial substrate according to claim 1, wherein the thickness of the heteroepitaxial layer is determined by applying the ratio of:

3. When obtaining a Raman spectrum by the Raman spectroscopy, Ｅｐｉ 3. The method for evaluating a heteroepitaxial substrate according to claim 1, wherein the focus is adjusted so that the value is maximized.

4. 2. The method for evaluating a heteroepitaxial substrate according to claim 1, wherein the wavelength of the laser light is adjusted depending on the film thickness of the heteroepitaxial layer and the material constituting the heteroepitaxial layer.

5. 5. The method for evaluating a heteroepitaxial substrate according to claim 1, wherein the heteroepitaxial layer is made of a 3C-SiC single crystal or a Ge single crystal.

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