JP4792267B2 - Surface state measuring method and apparatus - Google Patents

Description

  The present invention relates to a surface state measuring method and apparatus for measuring a surface state of a substrate to be measured by an infrared multiple internal reflection method.

  Knowing the surface condition such as organic contamination of a substrate such as a semiconductor wafer is very important for ensuring the yield and quality reliability of devices manufactured using these substrates. For example, organic contamination on the surface of a semiconductor wafer is known to cause film formation abnormalities and an increase in interface resistance in the manufacturing process.

  As measurement methods for detecting such organic contamination on the substrate surface, there are known thermal desorption GC / MS (Gas Chromatography / Mass Spectroscopy), APIMS (Atmospheric Pressure Ionization Mass Spectroscopy), SIMS (Secondary Ion Mass Spectroscopy) and the like. ing. However, these measurement methods cannot directly observe a large substrate such as a wafer having a diameter exceeding 300 mm that will be developed in the future, require a vacuum atmosphere, have a low throughput, and have a molecule to be measured by heating. It was not suitable for in-situ measurement at the manufacturing site due to the change in properties of the material.

  In addition, an apparatus for measuring organic contamination by Fourier spectroscopy of infrared rays that pass through a substrate to be measured such as a semiconductor wafer has been released by the US company Nicole. However, in this apparatus, since organic contamination is detected by analyzing the absorption by the organic substance adhering to the surface of the infrared substrate that passes through the substrate to be measured only once, the signal-to-noise ratio (S / S) of the detection system of the apparatus is detected. N ratio) was poor, and the detection sensitivity of organic contamination was low.

  From this point of view, the inventors of the present application have proposed a method of measuring the surface state of a substrate such as a semiconductor wafer by infrared multiple internal reflection (see, for example, Patent Document 1).

  Detection of contaminants by the infrared multiple internal reflection method will be described with reference to FIG. FIG. 5 (a) is a diagram for explaining the principle of the surface state measurement method by the conventional infrared multiple internal reflection method, and FIGS. 5 (b) to 5 (d) are reference spectra in the conventional infrared multiple internal reflection method, respectively. It is the schematic which shows the example of a sample spectrum and an absorbance spectrum.

  As shown in FIG. 5A, when infrared rays are incident on one end of the wafer 100 at a specific incident angle, the infrared rays propagate through the wafer 100 while repeating internal reflection on both surfaces. At this time, if the frequency component of the light (evanescent light) that bleeds when infrared light is reflected on the surface of the semiconductor wafer 100 matches the molecular vibration frequency of the organic contaminant attached to the surface of the wafer 100, resonance absorption is performed. Therefore, by analyzing the measured multiple internal reflection spectrum, the type and amount of organic contaminants adhering to the surface of the wafer 100 can be specified. In this method, since the infrared rays repeatedly and repeatedly reflected inside the wafer 100, that is, the infrared rays accumulating information of organic contaminants attached to the surface are spectrally analyzed, the S / N ratio is improved and the detection sensitivity can be increased. . Further, it is possible to measure organic contaminants adhering to the surface of the wafer 100 in a non-contact / non-destructive manner.

  In order to quantify the adhesion amount of contaminants on the wafer surface by the infrared multiple internal reflection method, it is necessary to obtain an absorbance spectrum. The absorbance spectrum can be obtained by the following procedure.

First, a multiple internal reflection spectrum is measured for a reference wafer such as a wafer having a clean surface, and is set as a reference spectrum S ₀ (ν).

Next, a multiple internal reflection spectrum is measured for the wafer whose surface state is to be measured, and is defined as a sample spectrum S ₁ (ν).

Next, an absorbance spectrum A (ν) = − log ₁₀ {S ₁ (ν) / S ₀ (ν)} is obtained from the reference spectrum S ₀ (ν) and the sample spectrum S ₀ (ν).

The amount of contaminants attached can be quantified based on the magnitude of the absorption peak observed in the absorbance spectrum A (ν) thus obtained from the background level.
Japanese Patent No. 3261362

  In the conventional surface state measurement method using the infrared multiple internal reflection method, in order to detect a contaminant based on the absorbance spectrum, the amount of the contaminant attached needs to change between the reference spectrum and the sample spectrum. That is, when there is no change in the amount of contaminants adhered between the substrate on which the reference spectrum is measured and the substrate whose surface state is to be measured, no change appears in the absorbance spectrum. For this reason, there is a case where there are contaminants that cannot be detected despite being attached to the substrate surface.

For example, the contamination 2 that shows absorption when measuring the sample spectrum S ₁ (ν) shown in FIG. 5C does not show absorption when measuring the reference spectrum S ₀ (ν) shown in FIG. Therefore, this contamination 2 can be detected in the absorbance spectrum A (ν) shown in FIG.

On the other hand, the contamination 1 shows the same infrared absorption even when measuring the reference spectrum S ₀ (ν) shown in FIG. In this case, the absorbance due to contamination 1 is apparently zero in the absorbance spectrum A (ν). Therefore, as shown in FIG. 5D, the contamination 1 cannot be detected in the absorbance spectrum A (ν).

  As described above, in the conventional surface state measurement method using the infrared multiple internal reflection method, there is a case where there is a contaminant that cannot be detected from the absorbance spectrum even though the contaminant is attached on the wafer surface.

  Further, in the conventional surface state measurement method using the infrared multiple internal reflection method, it is necessary to measure the reference spectrum on a substrate different from the substrate whose surface state is to be measured or a state having a different surface state. As a result, the measurement of the surface state of the substrate has been complicated.

  From such a background, for the surface state measurement method by infrared multiple internal reflection method, it is possible to detect a substance adhering to the surface without measuring the reference spectrum for a separate substrate etc., and to quantify the amount of adhesion. Establishment is required.

  An object of the present invention is to measure the surface state of a substrate by infrared multiple internal reflection method, so that a substance adhering to the surface of the substrate can be reliably detected and the surface state can be easily measured. To provide a state measurement method and apparatus.

  The above object is to detect infrared rays emitted from the substrate to be measured after the infrared rays are incident on the substrate to be measured, multiple reflections inside the substrate to be measured, and analyzing the detected infrared rays. In the surface state measuring method for measuring the surface state, the first infrared ray and the second infrared ray, each having a different number of multiple reflections inside the substrate to be measured, are detected, respectively, and the first infrared ray and the second infrared ray are detected. This is achieved by a surface state measurement method characterized by identifying the type of chemical substance adhering to the substrate to be measured and / or quantifying the amount of the chemical substance adhering based on the infrared analysis result.

  Further, in the above surface state measurement method, infrared light is incident at a predetermined incident angle on the end surface of the measured substrate from a position having a first inclination with respect to the measured substrate plane. An infrared ray emitted from the substrate to be measured after multiple reflection is detected as the first infrared ray, and a second larger than the first inclination with respect to the plane of the substrate to be measured at the end surface of the substrate to be measured. An infrared ray may be incident at a predetermined incident angle from a position having an inclination, and the infrared ray emitted from the substrate to be measured after multiple reflection within the substrate to be measured may be detected as the second infrared ray.

  Further, in the above surface state measurement method, the outer peripheral portion of the substrate to be measured has a first inclined surface having a first inclination angle with respect to the plane of the substrate to be measured, and the first inclination angle. A second inclined surface having a small second inclination angle is formed, and infrared rays are incident substantially perpendicularly to the first inclined surface, and after being subjected to multiple reflections within the measured substrate, the measured object Infrared light emitted from the substrate is detected as the first infrared light, and the infrared light is incident substantially perpendicular to the second inclined surface, and after multiple reflection inside the measured substrate, is emitted from the measured substrate. Infrared rays may be detected as the second infrared ray.

  Further, in the above surface state measurement method, a reference spectrum is measured by spectroscopically analyzing the first infrared ray, a sample spectrum is measured by spectroscopically analyzing the second infrared ray, and the reference spectrum and Based on the sample spectrum, the type of the chemical substance attached on the substrate to be measured may be identified and / or the amount of the chemical substance attached may be quantified.

  Further, the object is to provide infrared incident means for making infrared rays incident on the measurement substrate, infrared detection means for detecting infrared rays emitted from the measurement substrate after multiple reflection inside the measurement substrate, and the infrared detection means. A surface state measuring device having surface state measuring means for measuring the surface state of the substrate to be measured based on the infrared rays detected by the infrared detecting device, wherein the infrared detecting means performs multiple reflections inside the substrate to be measured. First and second infrared rays having different numbers of times are detected, respectively, and the surface state measuring means adheres to the substrate to be measured based on the detection results of the first and second infrared rays. This is achieved by a surface state measuring device characterized by identifying the kind of chemical substance and / or quantifying the amount of the chemical substance deposited.

  Further, in the surface state measuring apparatus, when detecting the first infrared ray, the infrared ray incident means is at a position having a first inclination with respect to the plane of the measured substrate at an end surface of the measured substrate. Infrared rays are incident at a predetermined incident angle, and the infrared detector is configured to receive infrared rays that are incident from a position having the first inclination and are emitted from the substrate to be measured after multiple reflection inside the substrate to be measured. When detecting the second infrared ray, the infrared incident means detects a second infrared ray larger than the first inclination with respect to the measured substrate plane at the end surface of the measured substrate. Infrared light is incident at a predetermined incident angle from a position having an inclination, and the infrared detection means is incident from a position having the second inclination, and is subjected to multiple reflection inside the substrate to be measured. The infrared rays emitted from the measured substrate may be detected as the second infrared after.

  In the above surface condition measuring apparatus, the outer peripheral portion of the substrate to be measured has a first inclined surface having a first inclination angle with respect to the plane of the substrate to be measured, and the first inclination angle. A second inclined surface having a small second inclination angle is formed, and when detecting the first infrared ray, the infrared incident means transmits the infrared ray substantially perpendicularly to the first inclined surface. The infrared detecting means is incident substantially perpendicularly to the first inclined surface, and infrared rays emitted from the substrate to be measured after being multiple-reflected inside the substrate to be measured are used as the first infrared rays. When detecting and detecting the second infrared ray, the infrared ray incident means enters the infrared ray substantially perpendicularly to the second inclined surface, and the infrared ray detecting means is applied to the second inclined surface. In the substrate to be measured. In the infrared rays emitted from the measured substrate may be detected as the second infrared after multiple reflections.

  According to the present invention, infrared rays are incident on the inside of the substrate to be measured, the infrared rays emitted from the substrate to be measured after multiple reflection inside the substrate to be measured are detected, and the surface of the substrate to be measured is analyzed by analyzing the detected infrared rays. In the surface state measurement method for measuring the state of the first and second infrared rays, the first infrared ray and the second infrared ray having different numbers of multiple reflections inside the substrate to be measured are detected, and the first infrared ray and the second infrared ray are analyzed. The type of chemical substance adhering to the substrate to be measured is identified and / or the amount of the chemical substance adhering is quantified, so that the substance adhering to the surface of the substrate to be measured can be detected reliably and easily. The surface state can be measured.

[Principle of the present invention]
In the surface state measuring method according to the present invention, infrared rays are incident on a substrate such as a wafer whose surface state is to be measured under conditions where the number of internal reflections is different, multiple internal reflection spectra are measured for each condition, and the number of internal reflections is small. The main feature is to obtain an absorbance spectrum using a multiple reflection spectrum as a reference spectrum and a sample spectrum having a large number of internal reflections. As a result, it is possible to detect all contaminants having absorption in the infrared wavelength region used as the probe light and quantify the amount of adhesion.

  Hereinafter, the principle of the surface state measuring method according to the present invention will be described with reference to FIG. FIG. 1A is a diagram for explaining the measurement principle of the surface state measuring method according to the present invention, and FIGS. 1B to 1D are reference spectra, sample spectra, and absorbance spectra in the surface state measuring method according to the present invention, respectively. It is the schematic which shows the example of.

When light having an intensity of ₁₀ is incident on a substance having a thickness d and an extinction coefficient per unit length, the transmitted light intensity I transmitted through the substance is expressed by the following equation according to Lambert's law. Is done.

I = I ₀ exp (−αd) (1)
Even in the case where infrared rays are multiple-reflected inside the wafer, the above equation can be extended and applied on the assumption that absorption corresponding to a certain optical path length is received by one reflection. The absorption coefficient of the contaminants adhering to the wafer surface alpha, when the equivalent optical path length and d _e, infrared attenuation in the internal reflections once is expressed by the following equation.

I = I ₀ exp (−αd _e ) (2)
Therefore, the internal reflectance R of infrared rays is
R = I / I ₀ = exp (−αd _e ) (3)
It becomes.

  Here, in the case of absorption due to a very small amount of contamination such as organic contamination of a silicon wafer, it is considered that the absorption caused by one internal reflection is very small. Therefore, equation (3) can be approximated as follows.

R = 1−αd _e (4)
When reflection is repeated R times inside the wafer,
R ^N = (1−αd _e ) ^N (5)
It is expressed. Equation (5) can also be approximated as follows when the absorption is small, that is, when αd _e << 1.

R ^N = 1−Nαd _e (6)
The absorption of infrared rays that are reflected multiple times inside the wafer is proportional to the number of reflections, and transmitted light I attenuated by N internal reflections is expressed by the following equation.

I = (1-R ^N ) I ₀ = Nαd _e I ₀ (7)
Therefore, the absorbance A of infrared rays reflected by multiple internal reflections can be defined by the following equation using the incident light intensity I ₀ and the transmitted light intensity I.

A = -log ₁₀ (I / I ₀ )
= -Log ₁₀ (Nαd _e ) (8)
According to the equation (7) thus obtained, it can be seen that the absorbance due to multiple internal reflections increases as the number N of internal reflections increases.

  Therefore, if multiple internal reflection spectra with different numbers of internal reflections are measured on the same substrate, a spectrum with a small number of internal reflections is used as a reference spectrum, and a spectrum with a large number of internal reflections is used as a sample spectrum, the reference spectrum and sample spectrum are Infrared absorption by the same pollutant will not be the same. Therefore, if an absorbance spectrum is obtained from both spectra, there is no contaminant that has an apparent absorbance of zero. Thereby, a contaminant can be reliably detected based on an absorbance spectrum.

  The surface state measurement method according to the present invention makes it possible to detect all contaminants having absorption in the infrared wavelength region used as probe light based on the above-described knowledge.

  In the surface state measurement method according to the present invention, two multiple internal reflection spectra having different numbers of internal reflections are measured for a wafer whose surface state is to be measured. For this purpose, with respect to the wafer whose surface state is to be measured, infrared rays having different incident angles are incident from the wafer end faces having different tilt angles.

  When measuring a multiple reflection spectrum with a small number of internal reflections, for example, as shown in FIG. 1 (a), the light beam 1 is made substantially perpendicular to the end surface from the end surface having a large inclination angle 1 with respect to the wafer 10 plane. Incident.

  On the other hand, when measuring a multiple internal reflection spectrum having a large number of internal reflections, the light beam 2 is incident substantially perpendicularly to the end surface from an end surface having an inclination angle 2 smaller than the inclination angle 1 with respect to the wafer 10 plane.

  Thus, among the infrared rays incident on the wafer 10, the light beam 1 can be set so that the number of internal reflections is small, and the light beam 2 is set to have a large number of internal reflections.

  The multiple internal reflection spectra obtained for the light rays 1 and 2 shown in FIG. 1A are both measured for the same wafer 10. Therefore, on both spectra, absorption by the same pollutant is observed in the same wave number region. However, since the number of internal reflections is different, the infrared absorption amount by the same contaminant is not the same.

  FIG. 1B is a schematic diagram showing a multiple internal reflection spectrum measured for the light beam 1, and FIG. 1C is a schematic diagram showing a multiple internal reflection spectrum measured for the light beam 2. As shown in the figure, both the spectrum obtained with respect to the light beam 1 and the spectrum obtained with respect to the light beam 2 exhibit absorption due to contamination 1 and contamination 2. However, the spectrum obtained for the light beam 2 has a higher number of infrared internal reflections than the spectrum obtained for the light beam 1. For this reason, the amount of infrared absorption due to contamination 1 and contamination 2 is greater when observed in the spectrum obtained for light 2.

  Therefore, an absorbance spectrum is obtained using a multiple reflection spectrum with a small number of internal reflections as a reference spectrum and a multiple reflection spectrum with a large number of internal reflections as a sample spectrum. Thereby, the infrared absorption amount by the same contaminant does not become the same at the time of a reference spectrum measurement and the time of a sample spectrum measurement conventionally. Therefore, it is possible to detect all contaminants having absorption in the infrared wavelength region used as the probe light by the absorbance spectrum.

FIG. 1C shows an absorbance spectrum A (ν) obtained by using the spectrum shown in FIG. 1B as the reference spectrum S ₀ (ν) and the spectrum shown in FIG. 1C as the sample spectrum S ₁ (ν). FIG. As shown, both contamination 1 and contamination 2 can be detected in the absorbance spectrum A (ν).

  Further, in order to quantify the amount of contaminants attached, an absorbance spectrum is obtained from a multiple reflection spectrum having a different number of internal reflections as described above for a wafer to which a specific contaminant having a known concentration is attached. A relationship between the concentration of the contaminant and the absorbance is prepared in advance as a calibration curve from the absorption peak observed in the absorbance spectrum obtained for the contaminant having a known concentration. Based on this calibration curve, the amount of contaminants attached can be quantified from the absorbance spectrum obtained for the wafer whose surface state is to be measured.

[First Embodiment]
A surface state measuring method and apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a schematic view showing the structure of the surface state measuring apparatus according to the present embodiment, and FIG. 3 is a top view of the wafer to be measured in the surface state measuring method according to the present embodiment.

[1] Surface State Measuring Device First, the surface state measuring device according to the present embodiment will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 2, a wafer 14 on which a surface state on which a plurality of end faces having a predetermined inclination angle are formed is to be measured is mounted on a substrate mounting base 10.

  In the vicinity of the outer peripheral portion of the wafer 14, an incident optical system 18 is provided that injects infrared light into the wafer 14 at a predetermined incident angle from an end surface having a predetermined inclination angle.

  The incident optical system 18 includes an infrared light source that emits infrared light as probe light, and a reflecting mirror and a concave mirror that collect the infrared light emitted from the infrared light source and make the infrared light enter the wafer from the wafer end surface. ing. In FIG. 1, an infrared light source, a reflecting mirror, and a concave mirror are omitted.

  In the vicinity of the outer peripheral portion of the wafer 14 facing the outer peripheral portion of the wafer 14 provided with the incident optical system 18 in the vicinity, infrared rays emitted from the end surface facing the end surface on which infrared rays are incident after being subjected to multiple reflection inside the wafer 14 are detected. An infrared analysis device 20 for performing spectral analysis is provided.

  The infrared analyzer 20 is connected to an arithmetic unit (not shown) for identifying the type of chemical substance adhering to the surface of the wafer 14 and calculating the concentration based on the analysis result.

  Next, each component of the surface state measuring apparatus according to the present embodiment and the wafer 14 whose surface state is to be measured will be described in detail.

(A) Wafer 14
As shown in FIG. 3, the wafer 14 whose surface state is to be measured is formed with end faces having the same inclination angle with respect to the plane of the wafer 14 at the opposing outer peripheral portions. A plurality of sets of such end faces are formed, and the inclination angles of the sets of end faces provided on the outer peripheral portion of the wafer 14 are different from each other. In FIG. 3, for example, the inclination angle 1> the inclination angle 2> the inclination angle 3> the inclination angle 4 is set.

  By making infrared rays enter the wafer 14 from the end faces with different inclination angles at a predetermined incident angle, multiple internal reflection spectra with different numbers of infrared internal reflections can be measured for the same wafer 14.

(B) Board mounting base 12
The substrate mounting table 12 mounts a wafer 14 and provides a surface state measurement. The substrate mounting table 12 includes a position adjusting mechanism that moves or rotates the mounted wafer 14 in a horizontal plane. Thereby, infrared light can be incident on the inside of the wafer 14 from the arbitrary end surface formed on the wafer 14 by the incident optical system 18.

(C) Incident optical system 18 (infrared light source, reflecting mirror, concave mirror)
As the infrared light source, a light source that emits infrared rays in the 2 to 25 μm band corresponding to the molecular vibrations of organic molecules can be applied. For example, it is possible to use, as a light source, heat rays generated by applying current to silicon carbide (SiC) or nichrome wire as a filament. A light source using SiC, such as a SiC glover lamp, emits infrared rays in the 1.1 to 25 μm band and is characterized in that it is not burned even when used in the air.

  The reflecting mirror and the concave mirror are for introducing from the end face of the wafer 14 so as to collect the infrared rays emitted from the infrared light source and to multiplexly reflect the infrared rays inside the wafer 14.

  In addition, the incident optical system 18 includes an angle adjustment mechanism that adjusts the angle at which infrared rays are introduced into the end face of the wafer 14. Thereby, infrared rays can be incident on the inside of the end surface of the wafer 14 having a predetermined inclination angle at a predetermined incident angle.

(D) Infrared analyzer 20
As the infrared analysis device 20, for example, an FTIR device including an infrared detector such as nitrogen-cooled InSb can be used. The infrared analyzer 20 detects infrared rays emitted from the end face of the wafer 14, and generates a multiple internal reflection spectrum by performing Fourier spectroscopy on the detected infrared rays.

  The FTIR apparatus used as the infrared analyzing apparatus 20 performs infrared spectral analysis by, for example, a Fourier transform spectroscopy mechanism based on a two-beam interferometer (Michelson interferometer). Alternatively, an infrared spectrometer using a diffraction grating (grating) may be used instead of the FTIR apparatus.

  The infrared analyzer 20 can detect infrared rays according to the emission angle of infrared rays emitted from the end face of the wafer 14.

(E) Arithmetic Device The measurement data of the multiple internal reflection spectrum obtained by the infrared analysis device 20 is sent to the arithmetic device, where the chemical substance adhering to the surface of the wafer 14 is identified and the amount is calculated.

  The arithmetic unit obtains an absorbance spectrum from multiple internal reflection spectra that are measured for the same wafer 14 and have different numbers of internal reflections.

  The type and calibration curve of the chemical substance adhering to the surface of the wafer 14 are separately stored in the storage unit of the arithmetic unit as a database, and the measurement data is quantified with reference to those databases.

In order to identify chemical substances adhering to the surface of the wafer 14, the wave numbers of infrared absorption due to various molecular vibrations of various substances are stored in a computing device as a database. For example, for each chemical substance, data of absorption wavenumbers by CH ₃ symmetric stretching vibration, CH ₃ asymmetric stretching vibration, CH ₂ symmetric stretching vibration, CH ₂ asymmetric stretching vibration, and the like are stored. When identifying a chemical substance, data on absorption wavenumbers caused by specific molecular vibrations is referenced from a database of absorption wavenumbers caused by various molecular vibrations.

  As described above, the surface state measurement apparatus according to the present embodiment can measure infrared multiple reflection spectra having different numbers of internal reflections by making infrared rays incident at a predetermined incident angle from the end face of the wafer 14 having a predetermined tilt angle. The main feature is that As a result, an absorbance spectrum can be obtained using a multiple internal reflection spectrum with a small number of internal reflections measured for the same wafer 14 as a reference spectrum, and therefore a contaminant having infrared absorption in the infrared wavelength region used as probe light. All of these can be detected and the amount of adhesion can be quantified.

  Furthermore, since it is not necessary to measure multiple internal reflection spectra for wafers having different surface states in order to measure the reference spectrum, the measurement can be simplified.

[2] Surface State Measuring Method Next, the surface state measuring method according to the present embodiment will be described with reference to FIG.

  In the surface state measurement method according to the present embodiment, multiple internal reflection spectra with different numbers of internal reflections are measured for the same wafer 14. The absorbance spectrum is obtained using the measured multiple reflection spectrum with a small number of internal reflections as a reference spectrum and the multiple reflection spectrum with a large number of internal reflections as a sample spectrum, and this is analyzed to identify and attach a chemical substance attached to the wafer 14. Quantify the amount.

  First, the wafer 14 whose surface state is to be measured is placed on the substrate mounting table 10.

  Next, first, a multiple reflection spectrum with a small number of internal reflections, that is, a reference spectrum is measured as follows.

  First, as an end face to which infrared rays are incident, for example, as shown in FIG. 3, an end face having a large inclination angle 1 with respect to the plane of the wafer 14 is selected from the end faces formed on the wafer 14. Further, the incident angle of the infrared rays by the incident optical system 18 is set so that the infrared rays can be incident substantially perpendicular to the end face of the wafer 14. Thereby, the incident angle can be set so that the infrared rays incident on the wafer 14 can be multiple-reflected within the wafer 14 a few times. In addition, the positional relationship between the substrate mounting base 10 and the infrared analysis device 20 is set so that infrared rays emitted from the end surface at the inclination angle 1 facing the end surface on which infrared rays are incident can be detected.

  Next, infrared light is incident on the inside of the wafer 14 from the end surface at the inclination angle 1 by the incident optical system 18.

  Infrared rays introduced into the wafer 14 propagate through the inside of the wafer 14 while being subjected to multiple reflections, and are then emitted from the end surface at an inclination angle 1 opposite to the end surface on which the infrared rays are incident.

  Next, infrared rays emitted from the end face after being subjected to multiple reflections inside the wafer 14 are detected by the infrared analyzer 20, and a multiple internal reflection spectrum is obtained based on the principle of Fourier transform spectroscopy.

  In this way, the multiple internal reflection spectrum measured by the infrared rays incident from the end face at the inclination angle 1 is stored in the arithmetic unit as the reference spectrum.

  Next, infrared rays are incident on the wafer 14 under the condition that the number of internal reflections is larger than that at the time of measuring the reference spectrum acquired for the wafer 14 as described above, and the multiple internal reflection spectrum is measured.

  First, as shown in FIG. 3, the positional relationship between the substrate mounting base 10 and the incident optical system 18 is set so that infrared light can be incident on the inside of the wafer 14 from an end surface having an inclination angle 2 smaller than the inclination angle 1. In addition, the positional relationship between the substrate mounting base 10 and the infrared analysis device 20 is set so that the infrared rays emitted from the end surface with the inclination angle 2 facing the end surface on which the infrared rays are incident can be detected.

  Thus, the measurement system is set so that the number of infrared internal reflections is greater than when the reference spectrum is measured.

  Next, infrared light is incident on the inside of the wafer 14 from the end surface at the inclination angle 2 by the incident optical system 18.

  Next, infrared rays emitted from the end face after being subjected to multiple reflections inside the wafer 14 are detected by the infrared analyzer 20, and the internal multiple reflection spectrum is measured in the same manner.

  The internal multiple reflection spectrum thus measured is stored in the arithmetic unit as a sample spectrum.

  Next, an absorbance spectrum is obtained from the measured reference spectrum and sample spectrum by an arithmetic device.

  Based on the obtained absorbance spectrum, the database or calibration curve stored in the memory arithmetic unit 30 is referred to identify the structure or type of the contaminant adhering to the surface of the wafer 14 and the amount of adhesion is calculated.

  Thus, the measurement of the surface state of the wafer 14 is completed.

  Thus, according to this embodiment, the multiple internal reflection spectrum with a small number of internal reflections measured for the wafer 14 whose surface state is to be measured is used as a reference spectrum, and the multiple internal reflection spectrum with a large number of internal reflections is used as a sample spectrum. Since the absorbance spectrum is obtained, all contaminants having absorption in the infrared wavelength region used as the probe light can be detected, and the amount of adhesion can be quantified.

  Further, it is not necessary to separately measure a multiple reflection spectrum as a reference spectrum for wafers having different surface states. Thereby, the measurement of the surface state by the infrared multiple internal reflection method can be simplified.

[Modified Embodiment]
The present invention is not limited to the above embodiment, and various modifications can be made.

  For example, in the above embodiment, the measurement of the surface state of the wafer is described, but the measurement of the surface state is not limited to the wafer. For example, it is possible to measure the surface state of a substrate that is transparent to infrared light, such as a glass substrate that forms a liquid crystal device.

  In the above embodiment, contaminants are measured as a measurement of the surface state. However, it is also possible to measure a chemical state such as a hydrogen termination state by hydrofluoric acid, a dry cleaning state, a wet cleaning state, or the like. .

  Further, in the above-described embodiment, the case where the wafer having the inclined surface having the predetermined inclination angle is measured has been described. However, the surface state measuring method according to the present invention is also applied to the wafer having no inclined surface having the predetermined inclination angle. Can be applied.

  For example, the present invention can be applied to a wafer having a curved end surface. A case where the surface state of a wafer having a curved end surface is measured by the surface state measuring method according to the present invention will be described with reference to FIG. FIG. 4 is a view for explaining an infrared incidence method for a wafer having a curved end surface, and shows a cross section near the outer periphery of the wafer.

  When infrared rays are incident on the end surface of the wafer 24 shown in FIG. 4, the number of multiple reflections inside the wafer 24 increases as the infrared rays are incident from a position where the inclination of the curved surface with respect to the plane of the wafer 24 is small, such as the light beam 1. On the other hand, the number of multiple reflections inside the wafer 24 is reduced as the infrared rays are incident from the position where the inclination of the curved surface with respect to the plane of the wafer 24 is large, like the light ray 2 at the same incident angle.

  Therefore, in the case of the wafer 24 having a curved end surface as shown in FIG. 4, a multiple reflection spectrum measured by incident infrared rays from a position with a large inclination with respect to the plane of the curved wafer 24 is used as a reference spectrum. In addition, a multiple internal reflection spectrum measured by incident infrared rays from a position with a small inclination at the same incident angle is taken as a sample spectrum. In the case shown in FIG. 4, the absorbance spectrum is obtained using the multiple internal reflection spectrum measured for light 2 as a reference spectrum and the multiple internal reflection spectrum measured for light 1 as a sample spectrum.

  Thus, an absorbance spectrum can be obtained from two multiple internal reflection spectra having different numbers of internal reflections. As a result, the wafer 24 having a curved end surface can detect all contaminants having absorption in the infrared wavelength region used as the probe light, as in the case of the above-described embodiment, and the amount of adhesion thereof. Can be quantified. Moreover, the surface state measuring method by the infrared multiple internal reflection method can be simplified.

It is a figure explaining the measurement principle of the surface state measuring method by this invention. It is the schematic which shows the structure of the surface state measuring apparatus by one Embodiment of this invention. It is a top view which shows the measuring object wafer in the surface state measuring method by one Embodiment of this invention. It is a figure explaining the incident method of the infrared rays in the surface state measuring method by the modification of one Embodiment of this invention. It is a figure explaining the surface state measuring method by the conventional infrared multiple internal reflection method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Wafer 12 ... Substrate mounting stage 14 ... Wafer 18 ... Incident optical system 20 ... Infrared analyzer 24 ... Wafer

Claims (7)

An infrared ray is incident inside the substrate to be measured, an infrared ray emitted from the substrate to be measured after multiple reflection within the substrate to be measured is detected, and the state of the surface of the substrate to be measured is analyzed by analyzing the detected infrared ray. In the surface state measurement method to measure,
A first infrared ray and a second infrared ray, each of which has a different number of times of multiple reflection inside the substrate to be measured, are respectively detected, and on the substrate to be measured based on the analysis result of the first infrared ray and the second infrared ray. A method for measuring a surface condition, characterized by identifying the type of chemical substance adhering to and / or quantifying the amount of adhering chemical substance. In the surface state measuring method according to claim 1,
At the end face of the substrate to be measured, infrared light is incident at a predetermined incident angle from a position having a first inclination with respect to the plane of the substrate to be measured, and is emitted from the substrate to be measured after multiple reflection inside the substrate to be measured. Detected infrared rays as the first infrared rays,
Infrared light is incident at the predetermined incident angle on the end surface of the measured substrate from a position having a second inclination larger than the first inclination with respect to the measured substrate plane, and is multiplexed inside the measured substrate. An infrared ray emitted from the substrate to be measured after being reflected is detected as the second infrared ray. In the surface state measuring method according to claim 1,
A first inclined surface having a first inclination angle with respect to the measurement substrate plane and a second inclination angle smaller than the first inclination angle are formed on the outer periphery of the measurement substrate. Are formed with an inclined surface,
An infrared ray is incident substantially perpendicularly to the first inclined surface, and an infrared ray emitted from the substrate to be measured after multiple reflection inside the substrate to be measured is detected as the first infrared ray,
An infrared ray is incident substantially perpendicularly to the second inclined surface, and an infrared ray emitted from the substrate to be measured after multiple reflection inside the substrate to be measured is detected as the second infrared ray. Surface state measurement method. In the surface state measuring method according to any one of claims 1 to 3,
By measuring the first infrared spectrum, a reference spectrum is measured,
Measuring the sample spectrum by spectroscopically analyzing the second infrared;
A method for measuring a surface condition, comprising: identifying a type of the chemical substance adhering to the substrate to be measured and / or quantifying the amount of the chemical substance adhering based on the reference spectrum and the sample spectrum. Infrared incident means for injecting infrared rays into the measurement substrate, infrared detection means for detecting infrared rays emitted from the measurement substrate after multiple reflection inside the measurement substrate, and infrared rays detected by the infrared detection means A surface state measuring device having surface state measuring means for measuring the surface state of the substrate to be measured,
The infrared detection means detects first infrared rays and second infrared rays each having a different number of multiple reflections inside the substrate to be measured;
The surface condition measuring means identifies the type of chemical substance adhering to the substrate to be measured and / or quantifies the amount of the chemical substance adhering based on the detection result of the first infrared ray and the second infrared ray. A surface condition measuring device characterized by comprising: In the surface state measuring apparatus according to claim 5,
When detecting the first infrared ray, the infrared ray incident means makes the infrared ray incident at a predetermined incident angle from a position having a first inclination with respect to the plane of the measured substrate at an end surface of the measured substrate. The infrared detecting means detects an infrared ray incident from a position having the first inclination and emitted from the substrate to be measured after multiple reflection inside the substrate to be measured as the first infrared ray,
When detecting the second infrared ray, the infrared ray incident means emits the infrared ray from a position having a second inclination larger than the first inclination with respect to the measurement target substrate plane at the end surface of the measurement target substrate. The incident light is incident at a predetermined incident angle, and the infrared detection means is incident from a position having the second inclination, and the infrared light emitted from the substrate to be measured after being multiple-reflected inside the substrate to be measured. A surface state measuring device characterized by detecting as infrared rays. In the surface state measuring apparatus according to claim 5,
A first inclined surface having a first inclination angle with respect to the measurement substrate plane and a second inclination angle smaller than the first inclination angle are formed on the outer periphery of the measurement substrate. Are formed with an inclined surface,
When detecting the first infrared ray, the infrared ray incident means enters the infrared ray substantially perpendicularly to the first inclined surface, and the infrared ray detecting means is substantially perpendicular to the first inclined surface. And detecting infrared rays emitted from the substrate to be measured after multiple reflection inside the substrate to be measured as the first infrared rays,
When detecting the second infrared ray, the infrared ray incident means enters the infrared ray substantially perpendicularly to the second inclined surface, and the infrared ray detecting means is substantially perpendicular to the second inclined surface. The surface state measuring apparatus is characterized in that an infrared ray that is incident on the substrate and is multiple-reflected inside the substrate to be measured and then emitted from the substrate to be measured is detected as the second infrared ray.

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