JP2019168460A - Measuring method of liquid component on substrate, and substrate processing apparatus - Google Patents

Abstract

To provide a measuring method of a liquid component on a substrate capable of measuring on the spot, the amount of a component existing on the substrate, while processing the substrate.SOLUTION: In a measuring method of a liquid component on a substrate, process liquid S is supplied onto a rotating substrate W, and an infrared ray IR is irradiated to a liquid film F of the process liquid formed on the substrate upper surface during supply of the process liquid and/or after supply stop, and reflected light is received, and a present amount of one or more components contained in the process liquid film is measured from absorbance at a prescribed wavelength.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for 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, cleaning, rinsing, drying, and the like are performed by supplying a processing liquid to the surface of a substrate such as a semiconductor wafer while holding and rotating the substrate horizontally. At this time, if an unintended component remains on the substrate, it may cause a defect in a subsequent process. For example, the substance to be cleaned may remain because the cleaning process is insufficient. In recent years, a fine and high aspect ratio pattern is often formed on the wafer surface, and the water used for rinsing is difficult to be removed by a drying process using an organic solvent such as 2-propanol. Patterns may collapse due to large water remaining.

JP 2013-140881 A JP 2014-111262 A

  Measures are taken against such problems, such as supplying an excessive amount of processing liquid, increasing the processing time, and increasing the number of times of processing. However, there is a problem that the cost of waste liquid treatment increases as the amount of treatment liquid used increases.

  In order to efficiently perform substrate processing by reducing the amount of processing solution used, it is preferable to process the substrate while checking the amount of components to be noted, such as components that may remain, on the spot. By monitoring changes in the components of the cleaning liquid on the substrate during the cleaning process, or by monitoring the amount of water on the substrate during the drying process, the amount of processing liquid that is wasted can be reduced.

  The present invention has been made in consideration of the above, and it is an object of the present invention to provide a method for measuring a liquid component on a substrate, which can measure the amount of components present on the substrate in situ while processing the substrate. And In addition, it is an object of the present invention to provide a substrate processing apparatus for using such a method.

  In response to the above problems, the present invention measures the amount of components in the treatment liquid film on the substrate by the infrared absorption method.

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

  Here, the infrared ray means an infrared ray in a broad sense including a near infrared ray, an intermediate infrared ray, and a far infrared ray.

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

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

  As a result, even when the substrate surface is uneven and the substrate is not uniform in the circumferential direction of rotation, fluctuations in absorbance are averaged and measurement accuracy is improved.

  The liquid component measurement method on the substrate preferably measures the abundance of all the main components contained in the treatment liquid film from the absorbance at a predetermined wavelength, and adds them to the treatment liquid film thickness. calculate.

  Thereby, it is possible to monitor the change in the treatment liquid film thickness during the treatment liquid supply and / or after the supply is stopped. Since the film thickness is measured by the infrared absorption method, even if the substrate surface is uneven, it is not affected by this, and the film thickness averaged in the circumferential direction of the rotation of the substrate can be obtained.

  The measurement method of the liquid component on the substrate preferably includes the treatment liquid film thickness calculated from the absorbance or the treatment liquid film thickness measured by another method, and one or more contained in the treatment liquid film. The concentration of the component is calculated from the abundance of the component.

  Thereby, the concentration of the component to be noted 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. Further, the substrate can be a silicon semiconductor wafer.

  The treatment liquid may be a treatment liquid for etching, cleaning, rinsing, dehydrating or drying the substrate.

  The treatment liquid is water; functional water such as ozone water, radical water, electrolytic ionic water; organic solvent such as 2-propanol; ammonia hydrogen peroxide mixed solution, hydrochloric acid hydrogen peroxide mixed solution, sulfuric acid hydrogen peroxide mixed solution, From the group consisting of a mixed solution of hydrofluoric acid, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, buffered hydrofluoric acid, ammonia, hydrogen peroxide, hydrochloric acid, tetramethylammonium hydroxide (TMAH) and a mixture thereof with water Can be chosen.

The component whose abundance is 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. When the component to be measured is H ₂ O, the treatment liquid can be 2-propanol or a mixed liquid of 2-propanol and water.

  Preferably, the infrared rays include light having a wavelength of at least 1350 to 1720 nm.

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

  Preferably, the infrared ray has an incident angle to the treatment liquid film equal to or close to a gas constituting an atmosphere at the time of measurement of the liquid component on the substrate and a polarization angle (Brewster angle) with respect to the treatment liquid. It is irradiated so that it becomes. The infrared rays irradiate only P-polarized light or receive only the P-polarized component of the reflected light.

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

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

  As a result, the intensity of the received infrared light is less affected by surface deflection due to warping or rotation of the substrate, thus improving measurement accuracy.

  The device that receives the reflected light may be an infrared camera.

  Thereby, since the measurement area on the substrate can be made wider, even when the substrate surface has irregularities, the influence is averaged and the measurement accuracy is improved.

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

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

  The substrate processing apparatus of the present invention includes a substrate rotating unit that holds and rotates a substrate, a processing liquid supply unit that supplies a processing liquid onto the substrate, an infrared irradiation unit that irradiates the substrate with infrared rays, Infrared light receiving means for receiving the reflected light, photometric means for detecting the received infrared light, and calculating means for obtaining the absorbance at a predetermined wavelength and calculating the abundance of the predetermined component corresponding to the predetermined wavelength.

  With this configuration, the amount of processing liquid used can be reduced by processing the substrate while monitoring the amount of the component to be noted existing on the substrate.

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

1 is a schematic diagram showing a first embodiment of a substrate processing apparatus of the present invention. It is an example of an infrared absorption spectrum. It is a figure for demonstrating the influence of the surface unevenness | corrugation 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 demonstrating 2nd Embodiment of the substrate processing apparatus of this invention. It is a figure for demonstrating 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 1st Embodiment of this invention are demonstrated based on FIGS.

  In FIG. 1, the substrate processing apparatus 10 of this embodiment is a single wafer type semiconductor wafer processing apparatus. The substrate processing apparatus 10 includes a rotary table 11 that rotates while holding the wafer W horizontally or at a desired angle, and a nozzle 12 that supplies a processing liquid S onto the wafer. The substrate processing apparatus further includes a light projecting 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 processing liquid moves toward the peripheral edge of the wafer by centrifugal force, and forms a liquid film F having a thickness that balances the movement amount and the supply amount. When the supply of the processing liquid is stopped, the processing liquid is discharged from the peripheral edge portion of the wafer, and the processing liquid film disappears with a decrease in film thickness. In addition, after the supply of the processing liquid is stopped, the supply is resumed after a certain time, and the same processing may be repeatedly performed. Such processing is performed, for example, for various development, cleaning, rinsing, and drying (moisture removal) of the wafer.

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

  Each substance has its own absorption spectrum. The calculation unit 19 can obtain the absorbance at a predetermined wavelength corresponding to the component to be measured from the infrared absorption spectrum, and can calculate the amount of the component.

As an example, FIG. 2 shows an absorption spectrum when pure water, 2-propanol (50 wt%)-water (50 wt%) mixed solution, and 2-propanol are irradiated with infrared rays. In the figure, the horizontal axis represents the wavelength of light, and the vertical axis represents absorbance, which is an arbitrary unit. In the vicinity of the wavelength of 1460 nm, an absorption peak due to the OH bond of H ₂ O is observed. Near the wavelength of 1690 nm, two absorption peaks due to the CH bond of 2-propanol are observed. Therefore, when measuring H ₂ O, attention should be paid to the absorbance at the absorption peak wavelength of the OH group around 1460 nm. Note that the vicinity of 1460 nm is an overtone of the stretching vibration of the OH group, and the vicinity of 1690 nm is a harmonic of the stretching vibration of the CH group.

  Absorbance is expressed by A = αLC according to Lambert-Beer law. Here, A represents the absorbance, α represents the extinction coefficient, L represents the optical path length, and C represents the concentration. The amount of the component present on the wafer is proportional to LC. If the extinction coefficient α of the component is known, the LC value can also be obtained from the above formula. However, since the extinction coefficient changes due to the influence of coexisting components, a calibration curve is created by measuring using a film with a known thickness under conditions close to the actual processing conditions. It is preferable to calculate the LC value based on this.

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

  In this way, it is possible to confirm whether or not the processing has been performed reliably by monitoring the abundance in the processing liquid film for the component to be noted.

  The actual processing liquid film thickness on the wafer W can be calculated by obtaining virtual film thicknesses for all the main components contained in the liquid film F and adding them up. Here, the main component refers to a component that, if ignored, affects the calculated film thickness value. Therefore, in the measurement of the processing liquid film thickness, if measurement error is taken into consideration, it is not necessary to include a component having a small content in the processing liquid film thickness such as impurities and additives. If you want to measure the concentration of components with low content, use the virtual film thickness value for the abundance of components with low content and use the formula of virtual film thickness value / treatment liquid film thickness. The concentration can be calculated even for components with a small amount.

  In the present embodiment, the film thickness of the processing liquid is obtained by the infrared absorption method, so that it is not affected by unevenness 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, a value obtained by averaging the thickness of the liquid film F on the upper surface can be obtained. This is an advantage not found in film thickness measurement by optical interferometry.

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

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

  Monitoring the concentration of a component can be beneficial in the following cases: When it is desired to monitor the cleaning power of the cleaning liquid, the concentration (relative value) in the cleaning liquid is more important than the abundance (absolute value) of the active ingredient for cleaning. 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 so that light having a wavelength according to the purpose can be irradiated. In addition, the light receiving unit 16, the optical fiber 17, and the photometric unit 18 are designed to receive light having a wavelength according to the purpose and to be able to perform spectroscopy.

  The light source 13 preferably generates light in a continuous wavelength range. This is because it is possible to deal with many components simply by changing the setting of the calculation unit. Even when the component to be measured is determined, the absorption peak wavelength may be shifted depending on the coexisting surrounding substances. Therefore, measurement with higher accuracy is possible by using continuous wavelengths. A commercially available light source such as a halogen tungsten lamp can be used as such a light source.

  The light generated by the light source 13 may have a single wavelength. For example, a wavelength tunable laser may be used, or an absorption peak wavelength of a target component may be selectively extracted 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 order to use a single wavelength, an interference filter that is a band-pass filter may be installed in the light projecting unit 15 to project a desired wavelength.

  The light projecting unit 15 preferably includes a collimator and can project a parallel light beam. However, the light projecting unit 15 may be a light beam condensed on the wafer surface in order to ensure the brightness of the optical system. The position at which the wafer W is irradiated with infrared rays is not particularly limited. Further, during irradiation with infrared rays, the irradiation position may be fixed without moving, or the irradiation position may be moved in the radial direction of the wafer rotation. If measurement is performed by moving the irradiation position in the radial direction of rotation, the measurement data profile on the entire wafer surface can be measured, and the amount of variation on the entire wafer surface can be acquired and used as a process management index.

  The light receiving unit 16 is preferably arranged so as to receive infrared specularly reflected light emitted from the light projecting unit. However, the specular reflection angle may be intentionally removed to receive diffusely reflected light. In this case, there is an effect of mitigating the influence of light interference of the wafer pattern and the liquid film.

  The photometry unit 18 spectrally separates infrared light guided by the optical fiber 17 from the light receiving unit 16 as necessary, detects and converts it into an electrical signal, and performs processing such as amplification as necessary. The structure of the photometry unit 18 is not particularly limited, and a known one such as a dispersive spectrophotometer using a diffraction grating or the like, or a non-dispersive spectrophotometer such as a Fourier transform infrared spectrophotometer can be used. When light having a specific wavelength is projected from the light projecting unit 15, a spectroscopic unit in the photometric unit is not necessary.

  The calculation unit 19 calculates the absorption spectrum and the absorbance at a predetermined wavelength based on the electrical signal from the photometry unit 18, averages the absorbance by integration, or creates a frequency distribution within a unit time to obtain a median value (Median) is obtained and processing for suppressing variation in measurement data is performed. Thereafter, virtual film thickness value calculation, concentration calculation, and the like are performed.

  The wavelength of the infrared IR needs to be a wavelength reflected by the substrate. A semiconductor is transparent to light of energy smaller than its band gap. However, even for such long-wavelength light, since the refractive index of a semiconductor is generally large, sufficient practical reflection is often obtained. For example, in the case of a silicon wafer, sufficient reflectance was obtained if the light was 1950 nm or less.

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

The arrangement of the light projecting unit 15 and the light receiving unit 16 is preferably configured such that the incident angle of the infrared ray to the treatment liquid film is equal to or close to the polarization angle, and only P-polarized light is emitted. It is preferable to use for measurement. In FIG. 4A, when the infrared IR is 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 depending on the film thickness, which causes a measurement error. This phenomenon appears particularly remarkably in the process in which the liquid film thickness decreases after the supply of the processing liquid is stopped. On the other hand, in FIG. 4B, by using the polarization angle θ _B and P-polarized light, there is no reflection on the surface of the treatment liquid film, and interference due to multiple reflection does not occur.

The polarization angle θ _B is also called a Brewster 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 incident surface is 0 when light is incident on the transparent surface, and tan θ _B = n ₂ / n ₁ , Determined by. Here, θ _B is the polarization angle, n ₂ is the refractive index of the transmission side medium, and n ₁ is the refractive index of the incident side medium. Therefore, in the present embodiment, the polarization angle may be obtained by using the gas constituting the atmosphere when performing the measurement as the incident side medium and the processing liquid as the transmission side medium. For example, if the refractive index n _{1 of} nitrogen is 1, and the refractive index n ₂ at a wavelength of water of 800 to 1600 nm is 1.33 to 1.31, the polarization angle θ _B when light enters the dilute aqueous solution from the nitrogen atmosphere Is about 53 degrees.

  In order to use only P-polarized light for measurement, only P-polarized light is irradiated or only the P-polarized component of the reflected light is received. In the former case, a polarizer may be provided on the front surface of the light projecting unit 15 to irradiate only P-polarized light. 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-polarized component.

Since the polarization angle θ _B depends on the refractive index of the incident-side gas and the transmission-side treatment liquid, strictly speaking, the polarization angle θ _B varies depending on the type of gas constituting the atmosphere, the type and concentration of the treatment liquid, and the like. On the other hand, you may adjust arrangement | positioning of the light projection part 15 and the light-receiving part 16 according to a process liquid. In addition, since the refractive index of gas and aqueous solution does not differ greatly even if the components differ, even if the arrangement of the light projecting part and the light receiving part is fixed in accordance with the typical process, it is sufficient for other processes. Is often obtained. For example, if the incident angle is in the range of the polarization angle of −12 degrees to the polarization angle of +6 degrees, a sufficient effect can be obtained.

  Next, a preferable range for the absorbance measurement time will be described. When the photometry unit 18 detects the received infrared ray, the detection time for one detection (for example, the exposure time of the photodiode) is usually several milliseconds to several tens of milliseconds. The absorbance is obtained by integrating the detection results of one time or a plurality of times by the calculation unit 19. Here, when the surface of the wafer W is not uniform due to irregularities or the like, the film thickness of the processing solution varies depending on the position on the wafer. Therefore, if the measurement position on the wafer changes with rotation, the measurement value varies. It will be. Therefore, it is preferable that the measurement time for the calculation unit 19 to calculate the absorbance is longer than the rotation period of the wafer. Thereby, since the wafer is rotated one or more times within the measurement time, the influence is averaged even if the treatment liquid film thickness is not uniform. Further, the absorbance measurement time is more preferably a natural number times the wafer rotation period. Thereby, since the influence of unevenness | corrugation is averaged with the same weight over the perimeter of the circumferential direction of rotation of a wafer, measurement dispersion | variation is reduced more.

  The method for measuring a liquid component on a substrate and the substrate processing apparatus of the present embodiment can be applied to various processing and processing liquids. For example, phosphoric acid solution in nitride film etching process; dilute hydrofluoric acid in buffered film etching process, buffered hydrofluoric acid; various acid chemicals in cobalt etching process; sulfuric acid hydrogen peroxide mixed solution in various cleaning processes, ammonia hydrogen peroxide It is possible to perform measurement on functional water 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; TMAH, etc. it can. These treatments have a great merit in applying the present invention because success or failure directly affects a defect rate in a subsequent process.

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

  The component to which the method for measuring a liquid component on the substrate and the substrate processing apparatus of the present embodiment can be applied is not particularly limited. The abundance can be measured with respect to the components in the treatment liquids.

In particular, it is particularly advantageous to apply the present invention to confirm the abundance of H ₂ O during the drying treatment with 2-propanol. This is because in the semiconductor manufacturing process, after performing some kind of wet treatment, rinsing with pure water and drying treatment with 2-propanol or the like are always performed. Further, as described above, if water remains after the drying treatment, a big problem occurs. This H ₂ O may be contained as an impurity or the like in 2-propanol used in the drying treatment, or may remain from that used in the previous rinsing treatment. In particular, since water is likely to remain after the rinsing process in a finely patterned wafer having a high aspect ratio, H ₂ derived from pure water used in the rinsing process during the subsequent drying process using 2-propanol. The merit of confirming the abundance of O is great.

The absorption peak for measuring the amount of H ₂ O exists in the vicinity of 1200 nm, 1900 nm, and 2600 nm in addition to the vicinity of 1460 nm. The absorption peak near 1200 nm has a small absorption coefficient. The absorption peaks near 1900 nm and 2600 nm have a large absorption coefficient, but the reflectivity of the silicon wafer decreases, resulting in a lower measured absorbance. Therefore, it is preferable to use an absorption peak near 1460 nm for the measurement of H ₂ O.

  Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is characterized in that an infrared camera is used for the light receiving unit.

  In FIG. 5, in the present embodiment, infrared light IR is irradiated to a wider range on the wafer W from the light projecting unit 22, and a region irradiated with the infrared light is imaged by three infrared cameras 23. The infrared camera 23 transmits the captured image data to the calculation unit 19 as an electrical signal. That is, the infrared camera of the present embodiment also functions as the light receiving unit and the photometric unit of the first embodiment. As a result, since measurement can be performed on a wider area on the wafer, measurement variations caused by non-uniformity on the wafer surface are averaged, and measurement accuracy is improved.

  As the infrared camera 23, when one infrared camera is used, an image pickup device that is sensitive to infrared rays having three or more wavelengths in the infrared region, such as an RGB camera in the visible light region, is preferably used. Because of the arbitrary measurement wavelength value and number, we adopted multiple cameras with bandpass filters with different transmission wavelengths at the incident points on the infrared camera. At this time, the computing unit 19 aligns the positions of the images from the respective cameras, and obtains the absorbance at the position by taking the difference in brightness of the pixels corresponding to the same position. The baseline of the absorption spectrum may fluctuate due to various factors, and when the absorbance is obtained with one camera, this influence is strongly influenced. By using two or more infrared cameras having different wavelength sensitivity characteristics, even if the baseline of the absorption spectrum fluctuates, the influence can be suppressed, so that the measurement accuracy is improved.

Specifically, for example, it can be carried out as follows. Each camera incorporates a bandpass filter that matches the infrared wavelength that the camera wants to capture. In the case of three cameras, the wavelength sensed by the first camera is the measurement wavelength λ ₁ , the wavelength sensed by the second camera is the reference wavelength λ ₂ , and the wavelength sensed by the third camera is the reference wavelength λ ₃ . Here, the measurement wavelength λ ₁ is the absorption peak wavelength due to the component to be measured. The reference wavelength λ ₂ is a wavelength that is slightly shorter than the measurement wavelength and is not affected by absorption by the component. The reference wavelength λ ₃ is a wavelength that is slightly longer than the measurement wavelength and is not affected by absorption by the component. The absorbance A (λ ₁ ) measured by the first camera is the absorbance of the component, but is affected by fluctuations in the baseline of the absorption spectrum. Therefore, this is corrected by subtracting the absorbances A (λ ₂ ) and A (λ ₃ ) at the reference wavelengths by the second and third cameras from the absorbance A (λ ₁ ) by the first camera. The corrected absorbance is
A (λ ₁ ) − {A (λ ₂ ) + A (λ ₃ )} / 2
Is required. 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.

If there are two cameras, either 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 with reference to FIG.

  In FIG. 6, in this embodiment, the optical system has a corner cube 21. The corner cube is a device in which three plane mirrors are combined at right angles to each other with the mirror surface inward to form a vertex shape of a cube. The light incident on the inside of the corner cube returns to the reverse method in parallel with the incident light. The infrared IR irradiated from the light projecting unit 15 toward the liquid film F is reflected at the wafer W for the first time, reaches the corner cube 21, is reflected in the opposite direction by the corner cube, and is reflected again at the wafer. Light is received by the light receiving unit 16.

  When the wafer W is warped or a surface blur occurs due to rotation, the direction in which the first reflected light travels from the wafer changes. If the traveling direction of the reflected light deviates greatly from the center of the light receiving unit, the intensity of the received infrared light is reduced, causing a measurement error. According to the present embodiment, since the reflected light from the corner cube returns in parallel with the incident light, the light reflected again by the wafer W is parallel to the light irradiated from the light projecting unit 15 even if there is a surface blur or the like. Then return to the floodlight. Therefore, the light does not greatly 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 projecting unit 15 to the light receiving unit 16. As shown in FIG. 6, this can be realized by integrating the light projecting unit 15 and the light receiving unit 16 using a coaxial probe. Further, the reflected light can be separated and guided to the light receiving unit using a half mirror or the like.

  Next, the method for measuring the liquid component on the 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. Note that a tungsten lamp (15 W) is used as the light source, and an interference filter is incorporated after the light source to perform spectroscopy. The sensor was an InGaAs (indium gallium arsenide) type. While rotating an unpatterned silicon wafer having a diameter of 150 mm at 300 rpm, 2-propanol (hereinafter abbreviated as “IPA”) or a mixed solution of IPA and water was dropped from the nozzle onto the center of the wafer at 23 mL / min. . Infrared rays had a wavelength range of about 900 to 1950 nm, an incident angle of 53 degrees, was irradiated 1 cm inward from the outer periphery of the wafer, a polarizer was provided in front of the light projecting unit, and only the P-polarized component was used. The reflected light was received to obtain an infrared absorption spectrum, and the abundance of H ₂ O was measured from the absorbance near 1460 nm, and the abundance of IPA was measured from the absorbance near 1690 nm. 30 detections were integrated per measurement, and the measurement time was about 1.07 seconds. H ₂ O and IPA were quantified under the same conditions by changing the concentration of the IPA-water mixture, measuring the thickness of the liquid film by optical interference, and creating a calibration curve.

FIG. 7 shows the experimental results. The vertical axis in the figure represents absorbance (arbitrary unit). The horizontal axis of the figure represents the passage of time, with one scale representing 20 measurements and 21.4 seconds. In this experiment, dropping IPA on the wafer for about 1 minute was repeated three times over time. The liquid film thickness during the 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. FIG. 8B and FIG. 8C show the results of an experiment in which a mixed solution of IPA (94 wt%)-water (6 wt%) and IPA (91 wt%)-water (9 wt%) was dropped. 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 virtual 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 H ₂ O film thickness by the total film thickness, the standard deviation is larger.

  This measurement accuracy is reasonable for a simple experimental device, but there is room for further improvement. As a result of observations by the present inventors, the cause of the measurement error in these experiments is considered to be mainly the unevenness of the discharge of the processing liquid from the nozzles and the surface shake due to the rotation of the wafer. These can be improved by mechanical improvements of the supply system and the rotary system, respectively. Further, as described in the third embodiment, the influence of the surface shake can be further reduced by using the corner cube.

Here, it is examined whether components such as H ₂ O can be measured 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 supply of IPA is stopped. 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 taking the above measure for improving the measurement accuracy and increasing the processing speed of the calculation unit. If the measurement time is 0.2 seconds, about 20 times or more can be measured even in the process of decreasing the film thickness. Therefore, it is possible to observe a change in the abundance of H ₂ O and the like in the process of decreasing the film thickness.

  Next, an experiment for confirming the effect of using the polarization angle and the P-polarized light was performed. In this experiment, about 30 mL of IPA was dropped on the wafer without rotating the wafer, and the change in absorbance was measured in the process where the IPA liquid film disappeared by evaporation. FIG. 9 shows the result of an experiment conducted without controlling the polarization of the irradiation light, and FIG. 10 shows the result of an experiment in which a polarizer is provided in front of the light projecting unit and only the P-polarized light component is irradiated. In the figure, for the sake of convenience, changes with time in absorbance at 1300 nm, 1500 nm, and 1700 nm are shown. In the figure, the vertical axis represents absorbance (arbitrary unit), the horizontal axis represents time, and one scale represents 10 seconds in 20 measurements.

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

  The absorbance in FIG. 10 increases when a liquid film is formed by dropping IPA, rapidly decreases when the film thickness decreases due to spreading of IPA, and gradually decreases to about −0.04 as the film thickness decreases due to evaporation. When the IPA film disappeared, it rapidly increased, and when the wafer was completely dried, it returned to zero. In FIG. 10, even when 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 thought to be due to the change in reflectance depending on the presence or absence of the IPA film.

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

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

  For example, the substrate is not limited to a silicon wafer, and may be a compound semiconductor such as silicon carbide or gallium arsenide, or a crystal wafer such as sapphire. The substrate may be a glass substrate for a flat panel display, or a ceramic wafer for manufacturing electronic components and 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 that the effect of applying the present invention is great.

DESCRIPTION OF SYMBOLS 10 Substrate processing apparatus 11 Rotary table (Substrate rotating means)
12 Treatment liquid supply nozzle (treatment liquid supply means)
13 Light source 14, 17 Optical fiber 15, 22 Projection unit (infrared irradiation means)
16 Light receiving part (Infrared light receiving means)
18 Metering unit (Measuring means)
19 Calculation unit (calculation means)
21 Corner cube 23 Infrared camera W Wafer (substrate)
S Treatment liquid F Treatment liquid film IR Infrared θ Incident angle θ _B Polarization angle (Brewster angle)

Claims (18)

Supply the processing liquid onto the rotating substrate,
During the supply of the processing liquid and / or after the supply is stopped, infrared rays are emitted from a light projecting portion provided on the liquid film side of the substrate with a space on the liquid film side of the substrate formed on the upper surface of the substrate. The reflected light reflected from the upper surface of the substrate is received by a light receiving unit provided with a space on the liquid film side of the substrate, and is irradiated at a predetermined wavelength. Measuring the abundance of one or more components contained in the treatment liquid film from the absorbance at
A method for measuring a liquid component on a substrate. The absorbance is determined for a measurement time longer than the rotation period of the substrate.
The method for measuring a liquid component on a substrate according to claim 1. For all the main components contained in the treatment liquid film, the abundance is measured from the absorbance at a predetermined wavelength, respectively, and the treatment liquid film thickness is calculated by summing these.
The method for measuring a liquid component on a substrate according to claim 1. The concentration of the component is calculated from the film thickness of the treatment liquid calculated from the absorbance or the film thickness of the treatment liquid measured by another method and the abundance of one or more components contained in the treatment liquid film. ,
The measuring method of the liquid component on the board | substrate as described in any one of Claims 1-3. 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;
The method for measuring a liquid component on a substrate according to claim 5. The treatment liquid is a treatment liquid for etching, cleaning, rinsing, dehydration or drying of the substrate, water; functional water such as ozone water, radical water, electrolytic ion water; organic solvent such as 2-propanol; Hydrogen oxide mixture, hydrochloric acid hydrogen peroxide mixture, sulfuric acid hydrogen peroxide mixture, nitric acid hydrofluoric acid mixture, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, buffered hydrofluoric acid, ammonia, hydrogen peroxide, hydrochloric acid, hydroxylation Selected from the group consisting of: tetramethylammonium and a mixture thereof with water;
The measuring method of the liquid component on the board | substrate as described in any one of Claims 1-6. The component whose abundance is measured is H ₂ O;
The measurement method of the liquid component on the board | substrate as described in any one of Claims 1-7. The predetermined wavelength is an absorption peak wavelength of an OH group near 1460 nm.
The method for measuring a liquid component on a substrate according to claim 8. The treatment liquid is 2-propanol or a mixed liquid of 2-propanol and water,
The method for measuring a liquid component on a substrate according to claim 8 or 9. The infrared ray includes light having a wavelength of at least 1350 to 1720 nm,
The measuring method of the liquid component on the board | substrate as described in any one of Claims 1-10. At least one of the components whose abundance is measured is a component derived from the liquid supplied onto the substrate in a stage prior to the process of supplying the processing liquid.
The measurement method of the liquid component on the board | substrate as described in any one of Claims 1-11. The treatment liquid is 2-propanol;
The component whose abundance is measured is H ₂ O;
The method for measuring a liquid component on a substrate according to claim 12. The infrared is
Irradiated so that the incident angle to the treatment liquid film is equal to or close to the polarization angle with respect to the gas constituting the atmosphere at the time of measuring the liquid component on the substrate and the treatment liquid,
Irradiate only P-polarized light, or receive only the P-polarized component of reflected light,
The measurement method of the liquid component on the board | substrate as described in any one of Claims 1-13. In the infrared, the first reflected light from the substrate is reflected in the opposite direction by the corner cube, and the reflected light reflected again by the substrate is received.
The measurement method of the liquid component on the board | substrate as described in any one of Claims 1-14. The device that receives the reflected light is an infrared camera,
The measurement method of the liquid component on the board | substrate as described in any one of Claims 1-14. Two or more infrared cameras having different wavelength sensitivity characteristics are used.
The method for 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;
Infrared irradiation means for irradiating infrared light onto the liquid film of the processing liquid formed on the substrate upper surface with a space provided on the liquid film side of the substrate while moving the incident position in the radial direction of rotation of the substrate When,
Infrared light receiving means provided on the liquid film side of the substrate with a space therebetween and receiving reflected light reflected from the upper surface of the substrate;
Photometric means for detecting the received infrared rays;
Calculating means for calculating absorbance at a predetermined wavelength, and calculating an abundance of a predetermined component corresponding to the predetermined wavelength;
A substrate processing apparatus.

Images