JP6522915B2 - Method of measuring liquid component on substrate and substrate processing apparatus - Google Patents

Description

  The present invention relates to a method of measuring a liquid component on a substrate such as a semiconductor wafer and a substrate processing apparatus for using the method.

  In a single wafer process or the like in the semiconductor industry, processing such as cleaning, rinsing and drying is performed by supplying a processing solution to the surface of a substrate such as a semiconductor wafer while holding the substrate horizontally and the like and rotating it. At this time, if an unintended component remains on the substrate, it causes a defect in a later process. For example, the substance to be cleaned may remain due to insufficient cleaning treatment. Further, in recent years, a pattern having a fine and high aspect ratio is often formed on the wafer surface, and the water used for the rinse is difficult to be removed even by the drying process using an organic solvent such as 2-propanol and the like. The pattern may collapse due to the large water remaining.

JP, 2013-140881, A JP, 2014-112652, A

  In order to cope with such a problem, measures such as excessive supply of the treatment liquid, prolongation of the treatment time, and increase of the number of treatments are taken. However, there has been a problem that the cost of waste liquid treatment increases as the amount of treatment solution used increases.

  In order to perform substrate processing efficiently by reducing the amount of processing liquid used, it is preferable to process the substrate while confirming the amount of the component to be focused on, such as a component that is likely to be residual, on the spot. By monitoring changes in the composition of the cleaning solution on the substrate during the cleaning process or monitoring the amount of water on the substrate during the drying process, the amount of processing solution that is wasted can be reduced.

  The present invention has been made in consideration of the above problems, and it is an object of the present invention to provide a method of measuring a liquid component on a substrate capable of measuring the amount of components present on the substrate in situ while processing the substrate. I assume. Another object of the present invention is to provide a substrate processing apparatus for using such a method.

  In order to solve the above-mentioned problems, the present invention measures the amount of components in the treatment liquid film on the substrate by an infrared absorption method.

  Specifically, in the method of measuring a liquid component on a substrate according to the present invention, the processing liquid is supplied onto a rotating substrate, and the processing liquid is formed on the upper surface of the substrate during and / or after supply stop of the processing liquid. The liquid film of the treatment liquid is irradiated with infrared light to receive the reflected light, and the abundance of one or more components contained in the treatment liquid film is measured from the absorbance at a predetermined wavelength.

  Here, infrared rays mean infrared rays in a broad sense, including near infrared rays, middle infrared rays, and far infrared rays.

  By this method, the substrate can be processed while monitoring the amount present on the substrate for the component to be focused on. As a result, for example, the amount of processing solution used can be reduced.

  Preferably, the absorbance is determined for a measurement time longer than the rotation period of the substrate.

  As a result, even if the substrate is not uniform in the circumferential direction of rotation due to unevenness or the like on the substrate surface, fluctuations in absorbance are averaged, and measurement accuracy is improved.

  Preferably, the method of measuring the liquid component on the substrate measures the abundance of each of the main components contained in the treatment liquid film from the absorbance at a predetermined wavelength, and adds the total amount to measure the film thickness of the treatment liquid. calculate.

  Thereby, it is possible to monitor the change in the film thickness of the processing liquid during and / or after the supply of the processing liquid is stopped. Since the film thickness is measured by the infrared absorption method, even when there is unevenness on the substrate surface, the film thickness averaged in the circumferential direction of the rotation of the substrate can be obtained without being affected by the unevenness.

  Preferably, the method of measuring the liquid component on the substrate is one or more of the processing liquid film thickness calculated from the absorbance or the processing liquid film thickness measured by another method, and one or more of the processing liquid films. The concentration of the component is calculated from the amount of the component present.

  Thereby, the concentration of the component to be focused on in the treatment liquid film can be known.

  The substrate may be a semiconductor wafer, a glass wafer, a crystal wafer or a ceramic wafer. Furthermore, the substrate can be a silicon semiconductor wafer.

  The processing solution may be a processing solution for etching, cleaning, rinsing, dehydration or drying of a substrate.

  The treatment liquid is water; functional water such as ozone water, radical water, electrolytic ion water; organic solvents such as 2-propanol; ammonia hydrogen peroxide mixed liquid, hydrochloric acid hydrogen peroxide mixed liquid, sulfuric acid hydrogen peroxide mixed liquid, From the group consisting of nitric acid hydrofluoric acid mixed solution, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, buffered hydrofluoric acid, ammonia, hydrogen peroxide, hydrochloric acid, tetramethyl ammonium hydroxide (TMAH), and mixed solutions of these with water; It can be chosen.

The component whose abundance is to be measured can be H ₂ O. At this time, preferably, the predetermined wavelength for measuring H ₂ O is an absorption peak wavelength of an OH group in the vicinity of 1460 nm. In addition, when the component to be measured is H ₂ O, the treatment liquid can be 2-propanol or a mixture of 2-propanol and water.

  Preferably, the infrared light includes light of at least a wavelength of 1350 to 1720 nm.

At least one of the components whose abundance is to be measured may be a component derived from the liquid supplied onto the substrate prior to the process of supplying the processing liquid. At this time, the treatment liquid may be 2-propanol, and the component whose amount is to be measured may be H ₂ O.

  Preferably, the infrared light has an angle of incidence on the processing liquid film equal to or close to a polarization angle (Bluester's angle) with respect to the gas forming the atmosphere at the time of measurement of the liquid component on the substrate and the processing liquid. It is irradiated to become. Then, the infrared light emits only P-polarized light, or receives only the P-polarized component of the reflected light.

  Thereby, the reflection of infrared light on the surface of the treatment liquid film can be eliminated, and the interference due to the multiple reflection at the liquid film interface can be eliminated. As a result, fluctuations in the intensity of infrared rays received due to the difference in liquid film thickness are suppressed, and measurement accuracy is improved.

  Preferably, after the first reflection light from the substrate is reflected in the opposite direction by the corner cube, the infrared light is received by the reflection light reflected again by the substrate.

  As a result, the intensity of the received infrared light is less likely to be affected by the warpage due to the warpage or rotation of the substrate, so that the measurement accuracy is improved.

  The device for receiving the reflected light may be an infrared camera.

  As a result, the measurement area on the substrate can be made wider, so that the influence is averaged even if there are irregularities on the substrate surface, etc., and the measurement accuracy is improved.

  The infrared light may be irradiated while moving the incident position in the radial direction of the rotation of the substrate.

  Thereby, the distribution of the processing liquid film thickness from the central portion to the peripheral portion of the substrate can be confirmed.

  The substrate processing apparatus according to the present invention comprises a substrate rotating unit for holding and rotating a substrate, a processing liquid supply unit for supplying a processing liquid onto the substrate, an infrared irradiation unit for irradiating the substrate with infrared light, and the substrate The infrared light receiving means for receiving the reflected light, the photometric means for detecting the received infrared light, and the arithmetic means for obtaining the absorbance at a predetermined wavelength and calculating the abundance of the predetermined component corresponding to the predetermined wavelength.

  According to this configuration, the amount of processing solution used can be reduced by processing the substrate while monitoring the amount of the component to be focused on the substrate.

  According to the method of measuring a liquid component on a substrate or the substrate processing apparatus of the present invention, the amount of the component present on the substrate can be measured in situ while processing the substrate.

It is a schematic diagram which shows 1st Embodiment of the substrate processing apparatus of this invention. It is an example of an infrared absorption spectrum. It is a figure for demonstrating the influence of the surface asperity of a board | substrate. It is a figure for demonstrating the influence of the interference by the process liquid film on a board | substrate. It is a figure for describing 2nd Embodiment of the substrate processing apparatus of this invention. It is a figure for describing 3rd Embodiment of the substrate processing apparatus of this invention. It is an experimental result by the 1st Embodiment of this invention. It is an experimental result by the 1st Embodiment of this invention. It is an experimental result about the influence of the interference by the process liquid film on a board | substrate. It is an experimental result about the influence of the interference by the process liquid film on a board | substrate.

  The apparatus and method of the first embodiment of the present invention will be described based on FIGS.

  In FIG. 1, a substrate processing apparatus 10 of the present embodiment is a single wafer type semiconductor wafer processing apparatus. The substrate processing apparatus 10 has a rotary table 11 for holding and rotating the wafer W horizontally or at a desired angle, and a nozzle 12 for supplying the processing solution S on the wafer. The substrate processing apparatus further includes a light emitting unit 15 connected by the infrared light source 13 and the optical fiber 14, a light receiving unit 16, a photometric unit 18 connected by the light receiving unit and the optical fiber 17, and an arithmetic unit 19 electrically connected to the photometric unit. Have. Details of the configuration of the optical system will be described later.

  When the processing liquid S is supplied to the upper surface of the wafer W while rotating the wafer W, the processing liquid moves toward the peripheral portion of the wafer by centrifugal force, and forms a liquid film F having a thickness such that the amount of movement and the amount of supply balance. When the supply of the processing liquid is stopped, the processing liquid is discharged from the peripheral portion of the wafer, and the processing liquid film reduces its film thickness and disappears in a short time. In addition, after the supply of the processing liquid is stopped, the supply may be resumed after a while, and the same processing may be repeated. Such processing is performed, for example, for various development, cleaning, rinsing and drying (water removal) of the wafer.

  Infrared light IR is emitted from the light emitter 15 toward the wafer W. Reflected light from the wafer is received by the light receiving unit 16. At this time, when the infrared light passes through the processing liquid film F on the wafer, a part of the infrared light is absorbed by various components contained in the liquid film. The received infrared light is dispersed and detected by the photometry unit 18, and the data is sent to the calculation unit 19.

  The substances each have a unique absorption spectrum. The calculation unit 19 can calculate the amount of the component from the absorption spectrum of infrared light by obtaining the absorbance at a predetermined wavelength according to the component to be measured.

The absorption spectrum when infrared rays are irradiated to FIG. 2 as an example to a pure water, 2-propanol (50 weight%)-water (50 weight%) liquid mixture, and 2-propanol is shown. The horizontal axis of the figure is the wavelength of light, and the vertical axis is the absorbance in arbitrary units. In the vicinity of the wavelength 1460 nm, a peak of absorption due to the OH bond of H ₂ O is observed. In the vicinity of a wavelength of 1690 nm, two absorption peaks attributed to CH bond of 2-propanol are observed. Therefore, when it is desired to measure H ₂ O, attention should be paid to the absorbance at the absorption peak wavelength of OH group around about 1460 nm. The vicinity of 1460 nm is an overtone of the stretching vibration of the OH group, and the vicinity of 1690 nm is an overtone of the stretching vibration of the CH group.

  The absorbance is represented by A = α LC, according to Lambert-Beer's law. Here, A represents the absorbance, α represents the absorption coefficient, L represents the optical path length, and C represents the concentration. The amount of this component present on the wafer is proportional to LC. If the extinction coefficient α of the component is known, the value of LC can also be determined from the above equation. However, since the extinction coefficient changes under the influence of coexisting components, etc., measurement is performed using a film with a known thickness under conditions close to actual processing conditions, and a calibration curve is created, and the calibration curve is It is preferable to calculate the value of LC based on it.

  The abundance of the component on the wafer W can be expressed in various forms. For example, absorbance A may be used as it is. In addition, a virtual thin film made only of the component may be assumed, and the thin film may be represented by the film thickness (hereinafter referred to as “virtual film thickness”). All of these are indicators of the absolute amount of the component present on the wafer.

  As described above, by monitoring the abundance of the component to be focused on in the treatment liquid film, it is possible to confirm whether the treatment has been reliably performed or has been reliably performed.

  The actual film thickness of the processing liquid on the wafer W can be calculated by calculating the virtual film thickness for all the main components contained in the liquid film F and adding them together. Here, the main component refers to a component that affects the value of the calculated film thickness if it is ignored. Therefore, in consideration of the measurement error, it is not necessary to include the component having a small content in the film thickness of the treatment liquid, such as an impurity or an additive, in the treatment liquid film thickness measurement. When it is desired to measure the concentration of a component having a small content, the content is calculated by the equation of virtual film thickness value / treatment liquid film thickness using a hypothetical film thickness value with respect to the abundance of the component having a small content. Concentrations can be calculated even with small amounts of components.

  In the present embodiment, since the film thickness of the processing liquid is determined by the infrared absorption method, it is not affected by the unevenness or the like on the surface of the wafer W. As shown in FIG. 3, even when the surface of the wafer W is uneven due to patterning or the like, it is possible to obtain an averaged value of the thickness of the liquid film F on the upper surface thereof. This is an advantage not found in film thickness measurement by optical interferometry.

  Thus, the condition of the treatment liquid film can be monitored by obtaining the film thickness of the treatment liquid. Also, for example, when the presence or absence of a liquid film is confirmed and repeated processing is performed, there is an advantage that the supply stop time of the processing liquid can be shortened.

  Further, if the actual film thickness of the treatment liquid film is known, the concentration of the component contained in the treatment liquid film can be known from the film thickness and the hypothetical film thickness, that is, the existing amount of a certain component. Here, as described above, the film thickness calculated from the absorbance by the infrared absorption method can be used as the actual film thickness of the treatment liquid film. Alternatively, a film thickness obtained by a method other than the infrared absorption method can be used as an actual film thickness of the treatment liquid film. For example, if the film thickness can be measured by an optical interference method, the film thickness measured by that method may be used.

  By monitoring the concentration of a certain component, there are benefits in the following cases. When it is desired to monitor the cleaning power of the washing solution, the concentration (relative value) in the washing solution is more important than the amount (absolute value) of the active ingredient of the washing. For example, in the hydrofluoric acid cleaning process, the cleaning power can be monitored by monitoring the concentration of F ions in the liquid film on the wafer surface.

  In FIG. 1, the light source 13, the optical fiber 14, and the light projecting unit 15 are designed such that light of a wavelength according to the purpose can be emitted. Further, the light receiving unit 16, the optical fiber 17, and the photometric unit 18 are designed to be capable of receiving light of a wavelength according to the purpose and capable of being dispersed.

  The light source 13 preferably generates light in a continuous wavelength range. Thereby, it is possible to cope with many components only by changing the setting of the arithmetic unit. In addition, even when the component to be measured is determined, the absorption peak wavelength may be shifted depending on the coexisting surrounding materials, so that it is possible to perform measurement with higher accuracy by using a continuous wavelength. As such a light source, commercially available ones such as a halogen tungsten lamp can be used.

  The light generated by the light source 13 may have a single wavelength. For example, it may be a wavelength variable laser, or may be one that selectively extracts the absorption peak wavelength of the target component using an interference filter or the like. The merit of using a single wavelength is that the later calculation processing is simplified and the calculation speed can be increased. In addition, in order to use a single wavelength, the interference filter which is a band pass filter may be installed in the light projection part 15, and a desired wavelength may be projected.

  The light projector 15 is preferably provided with a collimator to be able to emit parallel rays, but may be rays collected on the wafer surface in order to ensure the brightness of the optical system. The position to which the wafer W is irradiated with the infrared light is not particularly limited. Moreover, while irradiating infrared rays, the irradiation position may be fixed without moving, or the irradiation position may be moved in the radial direction of the rotation of the wafer. If the irradiation position is moved in the radial direction of rotation for measurement, the measurement data profile over the entire surface of the wafer can be measured, and the variation over the entire surface of the wafer can be obtained and used as a process control index.

  The light receiving unit 16 is preferably disposed so as to be able to receive the specularly reflected light of infrared light emitted from the light projecting unit, but may intentionally receive the diffusely reflected light by intentionally removing the specular reflection angle. In this case, the effect of light interference of the wafer pattern and liquid film can be mitigated.

  The photometry unit 18 splits the infrared light guided from the light receiving unit 16 by the optical fiber 17 as needed, detects it, converts it into an electric signal, and performs processing such as amplification as needed. The structure of the photometry unit 18 is not particularly limited, and a known one such as a dispersion type spectrophotometer using a diffraction grating or the like, or a non-dispersion type spectrophotometer such as a Fourier transform infrared spectrometer can be used. When light of a specific wavelength is projected from the light projecting unit 15, the light separating unit in the light measuring unit is unnecessary.

  The arithmetic unit 19 calculates the absorption spectrum and the absorbance at a predetermined wavelength based on the electric signal from the photometry unit 18, and performs averaging processing by integrating the absorbance or creates a frequency distribution within a unit time to obtain a median value. The (median value) is determined, and processing is performed to suppress variations in the measurement data. Thereafter, virtual film thickness value calculation, concentration calculation and the like are performed.

  The wavelength of infrared IR needs to be a wavelength which a substrate reflects. A semiconductor is transparent to light of energy less than its band gap. However, even for such long wavelength light, practically sufficient reflection is often obtained because the refractive index of the semiconductor is generally large. For example, in the case of a silicon wafer, sufficient reflectance can be obtained with light of 1950 nm or less.

When using infrared radiation in a continuous wavelength range, the wavelength range needs to include the wavelength absorbed by the component to be measured. For example, to measure H ₂ O and 2-propanol, preferably, light in a wavelength range including 1350 to 1720 nm is irradiated. In order to analyze other practically important components, light in a wavelength range including more preferably 900 to 1950 nm, still more preferably 800 to 2600 nm is irradiated.

The arrangement of the light projector 15 and the light receiver 16 is preferably configured such that the incident angle of infrared light on the processing liquid film is equal to or close to the polarization angle, and only P-polarized light is It is preferable to use for measurement. In FIG. 4A, when the infrared rays IR are reflected on the surface of the processing liquid film F and the surface of the wafer W, interference occurs due to multiple reflection, and the reflected light intensity vibrates due to the film thickness, which causes a measurement error. This phenomenon is particularly noticeable in the process of decreasing the liquid film thickness after the treatment liquid supply is stopped. On the other hand, in FIG. 4B, by using the polarization angle θ _B and P polarization, reflection on the surface of the processing liquid film is eliminated, and interference due to multiple reflection does not occur.

The polarization angle θ _B is also called Brewster's angle. The polarization angle is an angle at which the reflectance of light of a polarization component (P-polarized light) having an electric field vector parallel to the plane of incidence becomes zero when light is incident on the surface of the transparent body, tan θ _B = n ₂ / n ₁ Determined by Here, θ _B is a polarization angle, n ₂ is a refractive index of the transmission medium, and n ₁ is a refractive index of the incident medium. Therefore, in the present embodiment, the polarization angle may be determined by using the gas constituting the atmosphere when performing the measurement as the incident side medium and the treatment liquid as the transmission side medium. For example, the refractive index _{n 1} of nitrogen 1, if the refractive index _{n 2} in the aqueous wavelength 800~1600nm and from 1.33 to 1.31, the polarization angle when the light in dilute aqueous solution from the nitrogen atmosphere enters theta _B Is about 53 degrees.

  In order to use only P-polarized light for measurement, only P-polarized light is irradiated, or only P-polarized light component of reflected light is received. In the former case, a polarizer may be provided on the front surface of the light projection unit 15 and only P-polarized light may be irradiated. In the latter case, a polarizer may be provided on the front surface of the light receiving unit 16 to receive only the light of the P polarization component.

Since the polarization angle θ _B depends on the refractive index of the gas on the incident side and the treatment liquid on the transmission side, it strictly depends on the type of gas constituting the atmosphere, the type and concentration of the treatment liquid, and the like. On the other hand, the arrangement of the light emitter 15 and the light receiver 16 may be adjusted according to the processing liquid. In addition, the refractive index of the gas or aqueous solution does not differ significantly even if the components differ, so even if the arrangement of the light emitting unit and the light receiving unit is fixed according to the typical process, the effect is sufficient for other processes. Is often obtained. For example, if the incident angle is in the range of polarization angle of −12 degrees to polarization angle of +6 degrees, sufficient effects can be obtained.

  Next, a preferable range will be described with respect to the measurement time of absorbance. When the photometry unit 18 detects the received infrared light, the detection time of one detection (for example, the exposure time of the photodiode) is usually several milliseconds to several tens of milliseconds. The absorbance can be obtained by integrating one or more detection results in the arithmetic unit 19. Here, when the surface is not uniform because the wafer W has irregularities or the like, the film thickness of the processing liquid varies depending on the position on the wafer, and the measurement value varies when the measurement position on the wafer changes with the rotation. It will be. Therefore, it is preferable that the measurement time for the calculation unit 19 to calculate the absorbance be longer than the rotation period of the wafer. As a result, since the wafer makes one rotation or more within the measurement time, the influence is averaged even if the film thickness of the processing liquid is not uniform. More preferably, the measurement time of absorbance is a natural number multiple of the rotation period of the wafer. As a result, since the influence of the unevenness is averaged with the same weight over the entire circumferential direction of the rotation of the wafer, the measurement variation is further reduced.

  The measuring method of the liquid component on the substrate and the substrate processing apparatus of the present embodiment are applicable to various processing and processing solutions. For example, phosphoric acid solution in nitride film etching process; diluted hydrofluoric acid and buffered hydrofluoric acid in oxide film etching process; various acid-based chemical solutions in cobalt etching process; sulfuric acid hydrogen peroxide mixed solution in various cleaning processes, ammonia hydrogen peroxide Functional liquid such as mixed liquid, hydrochloric acid hydrogen peroxide mixed liquid, ozone water, radical water and electrolytic ion water; pure water in rinse treatment; 2-propanol in dry treatment; measurement with treatment liquid such as TMAH it can. In these processes, the success or failure directly affects the failure rate in the subsequent steps, so the merit of applying the present invention is great.

  Further, the treatment liquid may be supplied while gradually changing the composition during supply.

  The measuring method of the liquid component on the board | substrate of this embodiment and the component to which a substrate processing apparatus is applicable are not specifically limited. The amount of the components in each of the above-mentioned processing solutions can be measured.

Among other things, applying the present invention to confirm the amount of H ₂ O present during drying treatment with 2-propanol is particularly advantageous. In the semiconductor manufacturing process, after performing some wet processing, rinsing with pure water and drying processing with 2-propanol or the like are necessarily performed. Also, as described above, if water remains after the drying process, it causes a big problem. The H ₂ O may be contained as an impurity or the like in 2-propanol used in the drying process, or may be one in which one used in the previous stage of the rinsing process remains. In particular, since water tends to remain after rinse processing on a wafer subjected to patterning with a large aspect ratio, H ₂ derived from pure water used in rinse processing during drying processing with 2-propanol which is a subsequent step The merit of checking the abundance of O is great.

The absorption peak for measuring the amount of H ₂ O is present in the vicinity of 1200 nm, in the vicinity of 1900 nm, and in the vicinity of 2600 nm, in addition to the vicinity of 1460 nm described above. The absorption peak near 1200 nm has a small absorption coefficient. The absorption peaks near 1900 nm and 2600 nm have large absorption coefficients, but the reflectance of the silicon wafer decreases, and as a result, the measured absorbance decreases. Therefore, it is preferable to use an absorption peak around 1460 nm for the measurement of H ₂ O.

  Next, a second embodiment of the present invention will be described based on FIG. The present embodiment is characterized in that an infrared camera is used for the light receiving unit.

  In FIG. 5, in the present embodiment, infrared rays IR are emitted from the light emitting unit 22 to a wider range on the wafer W, and the regions irradiated with the infrared rays are imaged by the three infrared cameras 23. The infrared camera 23 transmits the photographed image data to the arithmetic unit 19 as an electric signal. That is, the infrared camera of the present embodiment has the functions of the light receiving unit and the light measuring unit of the first embodiment. As a result, since measurement can be performed on a wider area on the wafer, measurement variations due to non-uniformity of the wafer surface are averaged, and measurement accuracy is improved.

  When one infrared camera is used as the infrared camera 23, an imaging device such as an RGB camera in the visible light region preferably has sensitivity to infrared rays of three or more wavelengths in the infrared region is preferably used in this embodiment. Because of the arbitraryness of the measurement wavelength value and the number, a plurality of cameras in which band pass filters having different transmission wavelengths are installed at the incident position to the infrared camera are adopted. At this time, the position of the image from each camera is matched in the calculating part 19, and the light absorbency in the said position can be calculated | required by taking the difference of the brightness of the pixel corresponding to the same position. The baseline of the absorption spectrum may fluctuate due to various factors, and when the absorbance is determined by one camera, this effect is strongly influenced. By using two or more infrared cameras with different wavelength sensitivity characteristics, even if the baseline of the absorption spectrum fluctuates, the influence thereof can be suppressed, so that the measurement accuracy is improved.

Specifically, for example, the following can be implemented. Each camera incorporates a band pass filter that matches the infrared wavelength that you want to capture with each camera. When there are three cameras, the wavelength sensed by the first camera is taken as the measurement wavelength λ ₁ , the wavelength sensed by the second camera as the reference wavelength λ ₂ , and the wavelength sensed by the third camera as the reference wavelength λ ₃ . Here, measurement wavelength lambda ₁ is the absorption peak wavelength due to the measurement components desired. Reference wavelength lambda ₂ is a somewhat shorter than the measurement wavelength is the wavelength that is not affected by absorption by the component. Reference wavelength lambda ₃ is a slightly longer wavelength than the measurement wavelength is the wavelength that is not affected by absorption by the component. The absorbance A (λ ₁ ) measured by the first camera, which is the absorbance of the component in question, is subject to baseline fluctuations in the absorption spectrum. Therefore, this is corrected by subtracting the absorbances A (λ ₂ ) and A (λ ₃ ) at the reference wavelengths of the second and third cameras from the absorbance A (λ ₁ ) of the first camera. The corrected absorbance is
A (λ ₁ )-{A (λ ₂ ) + A (λ ₃ )} / 2
It is determined by Since the second term of this equation reflects the fluctuation of the baseline of the absorption spectrum, the absorbance of the component can be determined more accurately.

When there are two cameras, either one of A (λ ₂ ) or A (λ ₃ ) may be used as the reference wavelength.

  Next, a third embodiment of the present invention will be described based on FIG.

  In FIG. 6, in the present embodiment, a corner cube 21 is provided in the optical system. A corner cube is a device in which three plane mirrors are combined at right angles to each other with a mirror surface inside to form a cube apex type. Light incident on the inside of the corner cube returns in the opposite direction parallel to the incident light. The infrared radiation IR emitted from the light emitting unit 15 toward the liquid film F is reflected by the wafer W for the first time to reach the corner cube 21, reflected in the opposite direction by the corner cube, and reflected again by the wafer Light is received by the light receiving unit 16.

  When the wafer W is warped or a surface deviation due to rotation occurs, the direction in which the first reflected light travels from the wafer changes. If the traveling direction of the reflected light is largely deviated from the center of the light receiving unit, the intensity of the received infrared light is reduced, which causes a measurement error. According to the present embodiment, the light reflected from the corner cube returns to be parallel to the incident light, so that the light reflected again by the wafer W is parallel to the light emitted from the light projection unit 15 even if there is a surface deviation or the like. Return to the light projection unit. Therefore, light does not largely deviate from the light receiving unit.

  When the corner cube 21 is used, it is necessary to guide the reflected light returning toward the light emitting unit 15 to the light receiving unit 16. This can be realized by integrating the light emitting unit 15 and the light receiving unit 16 using a coaxial probe, as shown in FIG. In addition, reflected light can be separated and guided to the light receiving unit using a half mirror or the like.

  Next, the method of measuring a liquid component on a substrate of the present invention will be described in more detail based on experimental results.

The experiment was performed using the apparatus described in the first embodiment. As a light source, a tungsten lamp (15 W) is used, and after the light source, an interference filter is incorporated and dispersed. The sensor used InGaAs (indium gallium arsenide) type. While rotating a non-patterned silicon wafer with a diameter of 150 mm at 300 rpm, 2-propanol (hereinafter abbreviated as "IPA") or a mixed solution of IPA and water was dropped at the center of the wafer from the nozzle at 23 mL / min. . The infrared light was irradiated at 1 cm inside the wafer outer peripheral edge at an incident angle of 53 degrees in a wavelength range of about 900 to 1950 nm, and a polarizer was provided in front of the light projection part to utilize only the P polarization component. The reflected light was received to obtain an infrared absorption spectrum, and the amount of H ₂ O was measured from the absorbance at around 1460 nm, and the amount of IPA was measured from the absorbance at around 1690 nm. Thirty detections were integrated per measurement, and the measurement time was about 1.07 seconds. The determination of H ₂ O and IPA was carried out by changing the concentration of the IPA-water mixed solution under the same conditions and performing an experiment, measuring the thickness of the liquid film by an optical interference method, and creating a calibration curve.

The experimental results are shown in FIG. The vertical axis of the figure represents absorbance (arbitrary unit). The horizontal axis of the figure represents the passage of time, and one scale represents 20 measurements and 21.4 seconds. In this experiment, dropping IPA on the wafer for about 1 minute was repeated three times with time. The liquid film thickness during IPA dropping was about 60 μm. When a liquid film was formed by dropping, the absorbance by IPA increased. On the other hand, the absorbance by H ₂ O was almost zero.

FIG. 8 shows the concentration (% by weight) of H ₂ O. FIG. 8A is created from the same data as FIG. FIGS. 8B and 8C show the results of experiments in which a mixture of IPA (94% by weight) -water (6% by weight) and IPA (91% by weight) -water (9% by weight) was dropped, respectively. H 2 _O concentration, which was determined by infrared absorption method, in which the virtual thickness of H 2 _O, divided by the sum of the virtual thickness of the virtual thickness and IPA of H 2 _O. From FIG. 8, it was confirmed that the H ₂ O concentration in the treatment liquid can be measured.

The standard deviations of the measurement data in the experiments of FIGS. 7 and 8 were 0.36 to 0.77 μm for the H ₂ O hypothetical film thickness and 0.62 to 1.22% for the H ₂ O concentration. Since the H ₂ O concentration is obtained by dividing the film thickness of H ₂ O by the total film thickness, the standard deviation is larger.

  Although this measurement accuracy is appropriate as a simple experimental device, there is still room for improvement. The inventors of the present invention have observed that the causes of measurement error in these experiments are mainly the uneven discharge of the processing liquid from the nozzles and the surface deviation due to the rotation of the wafer. These can be improved by mechanical improvements of the feed system and the rotary system, respectively. Further, as described in the third embodiment, the influence of the upset can be further reduced by using a corner cube.

Here, it is examined whether or not it is possible to measure components such as H ₂ O in the process of gradually decreasing the film thickness after the supply of IPA is stopped. From FIG. 7, the IPA liquid film on the wafer disappears about 5 seconds after the stop of the supply of IPA. Since the rotation period of the wafer in this experiment was 0.2 seconds, the wafer rotated about 25 times before the liquid film disappeared. Although the measurement time of this experiment was about 1 second, the measurement time can be further shortened by increasing the processing speed of the operation unit while taking the above-mentioned measures to improve the measurement accuracy. Assuming that the measurement time is 0.2 seconds, about 20 or more measurements can be made even in the process of decreasing the film thickness. Therefore, it is sufficiently possible to observe changes in the amount of H ₂ O etc. while the film thickness is decreasing.

  Next, experiments were conducted to confirm the effects of using the polarization angle and the P polarization. In this experiment, about 30 mL of IPA was dropped on the wafer without rotating the wafer, and the change in absorbance during the process of disappearance of the IPA liquid film by evaporation was measured. FIG. 9 shows the results of an experiment conducted without controlling the polarization of the irradiation light, and FIG. 10 shows the results of an experiment in which a polarizer is provided in front of the light emitting section and only the P polarization component is irradiated. For convenience, the figure shows the time change of the absorbance at 1300 nm, 1500 nm and 1700 nm. The vertical axis of the figure is the absorbance (arbitrary unit), and the horizontal axis represents the passage of time, and one division represents 10 seconds with 20 measurements.

  The absorbance in FIG. 9 rises when a liquid film is formed by IPA dripping, rapidly decreases when the film thickness decreases due to IPA spreading, and gradually decreases to about 0.2 as the film thickness decreases due to evaporation. It dropped sharply when the IPA film disappeared and returned to 0 when the wafer was completely dried. From FIG. 9, it was observed that the absorbance vibrated by interference as the IPA film thickness approaches 0. Although the reason why the absorbance decreases to only about 0.2 during the film thickness reduction is not clear, it is considered to be an offset due to reflection and scattering on the surface of the IPA film.

  The absorbance in FIG. 10 rises when a liquid film is formed by IPA dripping, decreases rapidly as the film thickness decreases as IPA spreads, and gradually decreases to about -0.04 as the film thickness decreases due to evaporation. It dropped and rose sharply when the IPA film disappeared and returned to 0 when the wafer was completely dried. In FIG. 10, even if the IPA film thickness approaches 0, no vibration of absorbance due to interference was observed. The reason why the absorbance decreases to about -0.04 during the film thickness reduction is not clear, but is considered to be due to the change in reflectance due to the presence or absence of the IPA film.

  From the results in FIG. 9 and FIG. 10, by using infrared light incident at an angle close to the polarization angle and using only P-polarized light, the measurement accuracy is significantly improved for a liquid film having a small film thickness. It could be confirmed.

  The present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the technical idea thereof.

  For example, the substrate is not limited to a silicon wafer, and may be a silicon carbide, a compound semiconductor such as gallium arsenide, or a crystal wafer such as sapphire. The substrate may be a glass substrate for a flat panel display, or may be a ceramic wafer for producing an electronic component or the like. In any of these substrates, the success or failure of the treatment with the treatment liquid greatly affects the defect rate of the product, so the effect of applying the present invention is large.

10 substrate processing apparatus 11 rotating table (substrate rotating means)
12 Treatment liquid supply nozzle (treatment liquid supply means)
13 light source 14, 17 optical fiber 15, 22 light projection part (infrared irradiation means)
16 light receiver (infrared light receiver)
18 Photometric unit (photometric unit)
19 operation unit (operation means)
21 corner cube 23 infrared camera W wafer (substrate)
S treatment solution F treatment solution film IR infrared θ incident angle θ _B polarization angle (Bluester angle)

Claims (18)

Supply the processing solution onto the rotating substrate,
After feed during and / or stop of the supply of the treatment liquid, the infrared board from the light projecting portion to which the liquid film side is provided at a space of the substrate to the liquid film of the process liquid formed in the substrate top surface While moving the incident position in the radial direction of the rotation of the light source, the light reflected by the upper surface of the substrate is received by the light receiving unit provided on the liquid film side of the substrate with a space, Measuring the amount of one or more components contained in the treatment liquid film from the absorbance at
Method of measuring liquid component on substrate. The absorbance is determined for a measurement time longer than the rotation period of the substrate.
A method of measuring a liquid component on a substrate according to claim 1. The abundance of each of the main components contained in the treatment liquid film is measured from the absorbance at a predetermined wavelength, and the film thickness of the treatment liquid is calculated by adding them together.
A method of measuring a liquid component on a substrate according to claim 1 or 2. The concentration of the component is calculated from the thickness of the treatment liquid calculated from the absorbance or the thickness of the treatment liquid measured by another method, and the abundance of one or more components contained in the treatment liquid film. ,
The method of measuring a liquid component on a substrate according to any one of claims 1 to 3. The substrate is a semiconductor wafer, a glass wafer, a crystal wafer or a ceramic wafer.
The measuring method of the liquid component on the board | substrate as described in any one of Claims 1-4. The substrate is a silicon semiconductor wafer;
A method of measuring a liquid component on a substrate according to claim 5. The treatment liquid is a treatment liquid for etching, washing, rinsing, dehydration or drying of a substrate, water; functional water such as ozone water, radical water, electrolytic ion water; organic solvents such as 2-propanol; ammonia excess Hydrogen oxide mixed solution, hydrochloric acid hydrogen peroxide mixed solution, sulfuric acid hydrogen peroxide mixed solution, nitric acid hydrofluoric acid mixed solution, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, buffered hydrofluoric acid, ammonia, hydrogen peroxide, hydrochloric acid, hydroxylated water Selected from the group consisting of tetramethyl ammonium and a mixture of these with water;
A method of measuring a liquid component on a substrate according to any one of claims 1 to 6. The component whose abundance is to be measured is H ₂ O,
A method of measuring a liquid component on a substrate according to any one of claims 1 to 7. The predetermined wavelength is an absorption peak wavelength of an OH group near 1460 nm,
A method of measuring a liquid component on a substrate according to claim 8. The treatment liquid is 2-propanol or a mixture of 2-propanol and water,
A method of measuring a liquid component on a substrate according to claim 8 or 9. The infrared radiation includes light of at least a wavelength of 1350 to 1720 nm.
A method of measuring a liquid component on a substrate according to any one of claims 1 to 10. At least one of the components whose abundance is to be measured is a component derived from the liquid supplied onto the substrate at a stage prior to the process of supplying the processing liquid,
A method of measuring a liquid component on a substrate according to any one of claims 1 to 11. The treatment liquid is 2-propanol,
The component whose abundance is to be measured is H ₂ O,
A method of measuring a liquid component on a substrate according to claim 12. The infrared is
The light is irradiated so that the incident angle to the processing liquid film is equal to or close to the polarization angle with respect to the gas forming the atmosphere when measuring the liquid component on the substrate and the processing liquid,
Irradiate only P-polarized light or receive only P-polarized light component of reflected light,
A method of measuring a liquid component on a substrate according to any one of claims 1 to 13. In the infrared light, the first reflected light from the substrate is reflected by the corner cube in the opposite direction, and the reflected light reflected again by the substrate is received.
The method of measuring a liquid component on a substrate according to any one of claims 1 to 14. The device for receiving the reflected light is an infrared camera,
The method of measuring a liquid component on a substrate according to any one of claims 1 to 14. Using two or more infrared cameras having different wavelength sensitivity characteristics,
A method of measuring a liquid component on a substrate according to claim 16. Substrate rotating means for holding and rotating the substrate;
Treatment liquid supply means for supplying a treatment liquid onto the substrate;
An infrared irradiation means which is provided with a space on the liquid film side of the substrate and irradiates the liquid film of the processing liquid formed on the upper surface of the substrate with infrared rays while moving the incident position in the radial direction of the rotation of the substrate. When,
An infrared light receiving unit provided on the liquid film side of the substrate with a space, for receiving the reflected light reflected by the upper surface of the substrate;
Photometric means for detecting the received infrared light;
Calculating means for determining the absorbance at a predetermined wavelength and calculating the abundance of the predetermined component corresponding to the predetermined wavelength;
Substrate processing apparatus having:

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