JP2020118698A - 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, a substrate such as a semiconductor wafer is held horizontally and rotated, and a treatment liquid is supplied to the surface thereof to perform treatments such as cleaning, rinsing, and drying. At this time, if an unintended component remains on the substrate, it may cause a defect in a post process. For example, the substance to be cleaned may remain due to insufficient cleaning treatment. Further, 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 remove even by a drying treatment using an organic solvent such as 2-propanol, so that surface tension Patterns may collapse due to large amounts of residual water.

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

Countermeasures against such problems have been taken, such as supplying an excessive amount of treatment liquid, lengthening the treatment time, and increasing the number of treatments. However, there is a problem that the cost of waste liquid treatment increases as the amount of treatment liquid used increases.

In order to perform the substrate processing efficiently by reducing the amount of the processing liquid used, it is preferable to process the substrate while confirming the amount of the component of interest, such as a component that may remain, on the spot. By monitoring changes in the components of the cleaning liquid on the substrate during the cleaning process and monitoring the amount of water on the substrate during the drying process, it is possible to reduce the amount of wasted processing liquid.

The present invention has been made in view 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 the component present on the substrate in situ while processing the substrate. And At the same time, it is an object to provide a substrate processing apparatus for using such a method.

With respect to the above problems, the present invention measures the amount of components in a processing liquid film on a substrate by an infrared absorption method.

Specifically, the method for measuring a liquid component on a substrate according to the present invention comprises supplying a treatment liquid onto a rotating substrate, and forming the treatment liquid on the upper surface of the substrate during and/or after stopping the supply of the treatment liquid. The liquid film of the treatment liquid is irradiated with infrared rays to receive 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, intermediate infrared rays, and far infrared rays.

By this method, the substrate can be processed while monitoring the amount of the component of interest 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 cycle of the substrate.

As a result, even if the substrate is uneven in the circumferential direction of rotation due to the unevenness of the substrate surface, variations in the absorbance are averaged, and the measurement accuracy is improved.

The method for measuring the liquid component on the substrate is preferably, for all the main components contained in the treatment liquid film, the abundance is measured from the absorbance at each predetermined wavelength, and the treatment liquid film thickness is obtained by summing them. calculate.

This makes it possible to monitor the change in the film thickness of the processing liquid during and/or after the supply of the processing liquid. Since the film thickness is measured by the infrared absorption method, even if there is unevenness on the surface of the substrate, it is not affected and it is possible to obtain a film thickness that is averaged in the circumferential direction of rotation of the substrate.

The method for measuring the liquid component on the substrate is preferably the treatment liquid film thickness calculated from the absorbance or the treatment liquid film thickness measured by another method, and one or more of the treatment liquid films contained in the treatment liquid film. The concentration of the component is calculated from the existing amount of the component.

Thereby, the concentration of the component of interest 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 ion water; organic solvent such as 2-propanol; ammonia hydrogen peroxide mixture, hydrochloric acid hydrogen peroxide mixture, sulfuric acid hydrogen peroxide mixture, Nitric-hydrofluoric acid mixture, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, buffered hydrofluoric acid, ammonia, hydrogen peroxide, hydrochloric acid, tetramethylammonium hydroxide (TMAH) and a mixture of these with water; Can be chosen.

The component whose abundance is measured may 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 near 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 before the process of supplying the processing liquid. At this time, the treatment liquid may be 2-propanol, and the component whose existing amount is measured may be H ₂ O.

Preferably, the infrared rays have an angle of incidence on the treatment liquid film that is equal to or close to a polarization angle (Brewster angle) with respect to the gas and the treatment liquid forming the atmosphere when measuring the liquid component on the substrate. It is irradiated so that. Then, the infrared ray irradiates only P-polarized light or receives only P-polarized component of reflected light.

This makes it possible to eliminate the reflection of infrared rays on the surface of the treatment liquid film and the interference due to multiple reflection at the liquid film interface. As a result, fluctuations in the intensity of infrared light received due to differences in liquid film thickness are suppressed, and measurement accuracy is improved.

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

As a result, the intensity of the received infrared light is less likely to be affected by surface warpage due to the warp or rotation of the substrate, which improves the measurement accuracy.

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

As a result, the measurement region on the substrate can be made wider, so that even if there is unevenness on the substrate surface, the effect is averaged and the measurement accuracy is improved.

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

This makes it possible to confirm the distribution of the processing liquid film thickness from the central portion to the peripheral portion of the substrate.

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, and Infrared light receiving means for receiving the reflected light of, the photometric means for detecting the received infrared light, and an arithmetic means for obtaining the absorbance at a predetermined wavelength and calculating the abundance of a predetermined component corresponding to the predetermined wavelength.

With this configuration, it is possible to reduce the amount of the processing liquid used by processing the substrate while monitoring the amount of the component of interest 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 existing 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 unevenness of a board|substrate. It is a figure for explaining the influence of interference by the processing liquid film on a substrate. It is a figure for demonstrating the 2nd Embodiment of the substrate processing apparatus of this invention. It is a figure for demonstrating the 3rd Embodiment of the substrate processing apparatus of this invention. 3 is an experimental result according to the first embodiment of the present invention. 3 is an experimental result according to the first embodiment of the present invention. It is an experimental result about the influence of interference by the processing liquid film on the substrate. It is an experimental result about the influence of interference by the processing liquid film on the substrate.

The apparatus and method according to the first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, the 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 at a horizontal or desired angle, and a nozzle 12 for supplying the processing liquid S onto the wafer. The substrate processing apparatus further includes a light projecting unit 15 connected to the infrared light source 13 by the optical fiber 14, a light receiving unit 16, a light measuring unit 18 connected by the light receiving unit and the optical fiber 17, and an arithmetic unit 19 electrically connected to the light measuring 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 due to the centrifugal force, and forms a liquid film F having a film thickness in which the movement amount and the supply amount are balanced. When the supply of the treatment liquid is stopped, the treatment liquid is discharged from the peripheral portion of the wafer, the treatment liquid film is reduced in thickness, and disappears in time. In addition, after the supply of the processing liquid is stopped, the supply may be restarted after a while, and the same processing may be repeated. Such processing is performed, for example, for various types of development, cleaning, rinsing, and drying (water removal) of the wafer.

The infrared IR is emitted from the light projecting unit 15 toward the wafer W. The reflected light from the wafer is received by the light receiving unit 16. At this time, when the infrared rays pass through the processing liquid film F on the wafer, a part of the infrared rays is absorbed by various components contained in the liquid film. The received infrared rays are separated 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 calculate the amount of the component.

FIG. 2 shows absorption spectra of pure water, 2-propanol (50% by weight)-water (50% by weight) mixed solution, and 2-propanol irradiated with infrared rays as an example. In the figure, the horizontal axis represents the wavelength of light and the vertical axis represents the absorbance in arbitrary units. An absorption peak due to the OH bond of H ₂ O is recognized near the wavelength of 1460 nm. Two absorption peaks due to the CH bond of 2-propanol are observed near the wavelength of 1690 nm. Therefore, when it is desired to measure H ₂ O, it suffices to focus on the absorbance at the absorption peak wavelength of the OH group near about 1460 nm. Note that the vicinity of 1460 nm is the overtone of the stretching vibration of the OH group, and the vicinity of 1690 nm is the overtone of the stretching vibration of the CH group.

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

The existing amount of the component on the wafer W can be expressed in various formats. For example, the absorbance A may be used as it is. Further, it is also possible to assume a virtual thin film consisting only of the component and express it by its film thickness (hereinafter referred to as “virtual film thickness”). Each of these is an index of the absolute amount of the component present on the wafer.

As described above, by monitoring the amount of the component of interest in the treatment liquid film, it is possible to confirm whether or not the treatment is performed reliably.

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 together. Here, the main component means a component that affects the calculated value of the film thickness when it is ignored. Therefore, when the measurement error is taken into consideration, it is not necessary to include the components such as impurities and additives having a small content in the treatment liquid film thickness in the treatment liquid film thickness measurement. In addition, when it is desired to measure the concentration of a component having a small content, the virtual film thickness value for the existing amount of the component having a small content is used, and the virtual film thickness value/treatment liquid film thickness is used to determine the content. It is possible to calculate the concentration of even a small amount of a component.

In the present embodiment, since the treatment liquid film thickness is obtained by the infrared absorption method, the surface roughness of the wafer W is not affected. As shown in FIG. 3, even if the surface of the wafer W has irregularities 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.

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

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

By monitoring the concentration of a component, there is real benefit in the following cases: When it is desired to monitor the detergency of the cleaning liquid, the concentration (relative value) in the cleaning liquid is more important than the existing amount (absolute value) of the active ingredient for cleaning. For example, in the hydrofluoric acid cleaning treatment, 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 emitted. Further, the light receiving unit 16, the optical fiber 17, and the photometric unit 18 are designed to be capable of receiving light having a wavelength according to the purpose and separating the light.

The light source 13 preferably emits 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. Further, even if the component to be measured is fixed, the absorption peak wavelength may shift depending on the coexisting surrounding substances, so that it is possible to measure with higher accuracy by using continuous wavelengths. As such a light source, a commercially available one such as a halogen tungsten lamp can be used.

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 filter or the like may be used to selectively extract the absorption peak wavelength of the target component. The advantage of using a single wavelength is that the subsequent arithmetic processing becomes simple and the arithmetic speed can be increased. In addition, in order to use a single wavelength, an interference filter, which is a bandpass filter, may be installed in the light projecting unit 15 to project a desired wavelength.

The light projecting unit 15 is preferably provided with a collimator and capable of projecting a parallel light beam, but it may be a light beam focused on the wafer surface in order to secure the brightness of the optical system. The position of irradiating the wafer W with infrared rays is not particularly limited. Further, the irradiation position may be fixed without moving while the infrared rays are being irradiated, 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 on the entire surface of the wafer can be measured, and the variation amount on the entire surface of the wafer can be acquired and used as a process control index.

The light receiving unit 16 is preferably arranged so as to be able to receive the specular reflection light of the infrared light emitted from the light projecting unit, but the specular reflection angle may be intentionally removed to receive the diffuse reflection light. In this case, the effect of light interference of the wafer pattern and the liquid film is reduced.

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

The calculation unit 19 calculates the absorption spectrum and the absorbance at a predetermined wavelength based on the electric signal from the photometric unit 18, and also performs an averaging process by integrating the absorbance or creates a frequency distribution within a unit time to calculate a median value. The (median value) is obtained, and the process of suppressing the variation in the measurement data is performed. After that, the virtual film thickness value calculation, the concentration calculation, etc. are performed.

The wavelength of the infrared IR needs to be the wavelength reflected by the substrate. Semiconductors are transparent to light with energies smaller than their band gap. However, even for such long-wavelength light, since the semiconductor generally has a large refractive index, practically sufficient reflection is often obtained. For example, with a silicon wafer, sufficient reflectance was obtained with light of 1950 nm or less.

When using infrared rays in a continuous wavelength range, the wavelength range needs to include the wavelength absorbed by the 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 more preferably 900 to 1950 nm, and further preferably 800 to 2600 nm is irradiated.

The arrangement of the light projecting unit 15 and the light receiving unit 16 is preferably configured such that the incident angle of infrared rays on the treatment liquid film is equal to or close to the polarization angle, and only P-polarized light is emitted. It is preferably used 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, the reflected light intensity vibrates depending on the film thickness, and causes a measurement error. This phenomenon is particularly remarkable in the process of decreasing the liquid film thickness after stopping the supply of the processing liquid. On the other hand, in FIG. 4B, by utilizing the polarization angle θ _B and the P-polarized light, the reflection on the surface of the treatment liquid film disappears, and the interference due to the 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 incident surface is 0 when light is incident on the transparent body 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 forming the atmosphere when the measurement is performed as the incident side medium and the treatment liquid as the transmission side medium. For example, when the refractive index n _{1 of} nitrogen is 1, and the refractive index n ₂ of water at a wavelength 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.

To use only the P-polarized light for measurement, only the P-polarized light is emitted 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 P-polarized component light.

Since the polarization angle θ _B depends on the refractive index of the gas on the incident side or the processing liquid on the transmission side, strictly speaking, it varies depending on the type of gas forming the atmosphere, the type/concentration of the processing liquid, and the like. On the other hand, the arrangement of the light projecting unit 15 and the light receiving unit 16 may be adjusted according to the processing liquid. In addition, the refractive index of gas or aqueous solution does not make a big difference even if the components are different, so even if the placement of the light projecting unit and the light receiving unit is fixed according to typical processing, it is sufficient for other processing. Is often obtained. For example, when the incident angle is in the range of polarization angle −12 degrees to polarization angle +6 degrees, a sufficient effect can be obtained.

Next, a preferable range of the absorbance measurement time will be described. When the photometric unit 18 detects the received infrared rays, 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 accumulating 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 the unevenness of the wafer W, the film thickness of the processing liquid varies depending on the position on the wafer, and thus the measured value varies when the measuring position on the wafer changes with rotation. 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 cycle of the wafer. As a result, since the wafer makes one or more revolutions within the measurement time, even if the film thickness of the processing liquid is not uniform, the influence thereof is averaged. Further, it is more preferable that the measurement time of the absorbance be a natural number times the rotation period of the wafer. Thereby, the influence of the unevenness is averaged with the same weight over the entire circumference in the circumferential direction of the rotation of the wafer, so that the measurement variation is further reduced.

The method for measuring a liquid component on a substrate and the substrate processing apparatus of this embodiment can be applied to various kinds of processing and processing liquids. For example, phosphoric acid solution in nitride film etching treatment; dilute hydrofluoric acid and buffered hydrofluoric acid in oxide film etching treatment; various acid chemicals in cobalt etching treatment; sulfuric acid/hydrogen peroxide mixture solution in various cleaning treatments, ammonia hydrogen peroxide Measurements can be performed on mixed solutions, hydrochloric acid/hydrogen peroxide mixed solutions, functional water such as ozone water, radical water and electrolytic ion water; pure water during rinse treatment; 2-propanol during drying treatment; and treatment liquids such as TMAH. it can. The success or failure of these treatments directly affects the defective rate in the post-process, and therefore the merit of applying the present invention is great.

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

The component applicable to the method for measuring a liquid component on a substrate and the substrate processing apparatus of this embodiment is not particularly limited. The abundance of the components in each treatment liquid can be measured.

Above all, applying the present invention to confirm the amount of H ₂ O present during the drying treatment with 2-propanol is particularly advantageous. 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 in 2-propanol used in the drying process as impurities or the like, or may be the one used in the rinsing process which is the previous step. In particular, since water is likely to remain after the rinse treatment in a fine patterned wafer having a large aspect ratio, H ₂ derived from pure water used in the rinse treatment during the subsequent drying treatment with 2-propanol is performed. The merit of confirming the existing amount of O is great.

The absorption peak for measuring the amount of H ₂ O exists near 1200 nm, around 1900 nm, and around 2600 nm, in addition to around 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 a large absorption coefficient, but the reflectance of the silicon wafer is small, and the resulting absorbance is small. Therefore, it is preferable to use the absorption peak near 1460 nm for the measurement of H ₂ O.

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

In FIG. 5, in the present embodiment, the infrared light IR is irradiated from the light projecting unit 22 to a wider area on the wafer W, and the area irradiated with the infrared light is captured by the three infrared cameras 23. The infrared camera 23 transmits the captured 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 photometry unit of the first embodiment. As a result, since it is possible to measure a wider area on the wafer, the measurement variations due to the non-uniformity of the wafer surface are averaged and the measurement accuracy is improved.

When one infrared camera is used as the infrared camera 23, an image sensor 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, but in the present embodiment, Because of the arbitrariness of the measurement wavelength value and the number, we adopted a plurality of cameras with bandpass filters with different transmission wavelengths at the incident points on the infrared camera. At this time, in the calculation unit 19, the positions of the images from the cameras are aligned, and the difference in the brightness of the pixels corresponding to the same position is taken to obtain the absorbance at that position. The baseline of the absorption spectrum may fluctuate due to various factors, and if the absorbance is obtained with one camera, it is strongly affected by this. By using two or more infrared cameras having different wavelength sensitivity characteristics, even if the baseline of the absorption spectrum changes, its influence can be suppressed, so that the measurement accuracy is improved.

Specifically, for example, it can be implemented as follows. Each camera incorporates a bandpass filter that matches the infrared wavelengths that it wants to image. When the number of cameras is three, the wavelength detected by the first camera is the wavelength λ ₁ for measuring the absorbance, the wavelength detected by the second camera is the reference wavelength λ ₂ , and the wavelength detected by the third camera is the reference wavelength λ ₃ . Here, the measurement wavelength λ ₁ is the absorption peak wavelength of the component to be measured. The reference wavelength λ ₂ is a wavelength that is slightly shorter than the measurement wavelength and is a wavelength that 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 a 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 relevant component, is affected by the fluctuation of 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 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
Required by. Since the second term of this equation reflects the change in the baseline of the absorption spectrum, the absorbance of the component can be obtained more accurately.

When 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 based on FIG.

In FIG. 6, in the present embodiment, the optical system has a corner cube 21. A corner cube is a device in which three plane mirrors are combined at right angles to each other with their mirror surfaces inside and are in the shape of a cube vertex. Light incident on the inside of the corner cube returns in the reverse direction parallel to the incident light. The infrared light IR radiated from the light projecting unit 15 toward the liquid film F is reflected by 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 by the wafer. The light is received by the light receiving unit 16.

When the wafer W is warped or surface wobbling 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 significantly from the center of the light receiving portion, the intensity of the received infrared ray decreases, which causes 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 emitted from the light projecting unit 15 even if there is surface wobbling or the like. Then, it returns toward the light projecting section. Therefore, the light does not largely deviate from the light receiving portion.

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. This can be realized by integrating the light projecting unit 15 and the light receiving unit 16 using a coaxial probe as shown in FIG. Further, the reflected light can be separated and guided to the light receiving portion by 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 the experimental results.

The experiment was performed using the apparatus described in the first embodiment. In addition, a tungsten lamp (15 W) is used as a light source, and an interference filter is incorporated after the light source to perform spectral analysis. The sensor used 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 at 23 mL/min from the nozzle to the center of the wafer. .. Infrared rays were radiated in the wavelength range of about 900 to 1950 nm at an incident angle of 53 degrees to the inside of the outer edge of the wafer by 1 cm, and a polarizer was provided in front of the light projecting portion to use only the P polarized component. The reflected light was received to obtain an infrared absorption spectrum, and H ₂ O was measured from the absorbance near 1460 nm, and the IPA abundance was measured from the absorbance near 1690 nm. The detection was integrated 30 times for each measurement, and the measurement time was about 1.07 seconds. The quantification of H ₂ O and IPA was performed under the same conditions by changing the concentration of the IPA-water mixed solution, measuring the thickness of the liquid film by an optical interference method, and creating a calibration curve.

Experimental results are shown in FIG. 7. The vertical axis of the figure represents the 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 3 times with a time interval. The liquid film thickness during the dropping of IPA 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 are the results of the experiment in which the mixed solutions of IPA (94 wt %)-water (6 wt %) and IPA (91 wt %)-water (9 wt %) were 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 could be measured.

The standard deviation of the measurement data in the experiments of FIGS. 7 and 8 was 0.36 to 0.77 μm in the H ₂ O virtual film thickness and 0.62 to 1.22% in the H ₂ O concentration. The H ₂ O concentration has a larger standard deviation because the H ₂ O film thickness is divided by the total film thickness.

This measurement accuracy is reasonable for a simple experimental device, but there is room for further improvement. According to the observation by the present inventors, the causes of the measurement error in these experiments are considered to be mainly the unevenness of the ejection of the processing liquid from the nozzle and the surface wobbling due to the rotation of the wafer. These can be improved by mechanical modifications of the feed system and the rotary system, respectively. Further, as described in the third embodiment, the influence of surface wobbling 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 reducing the film thickness after the supply of IPA is stopped. From FIG. 7, the IPA liquid film on the wafer disappeared about 5 seconds after the supply of IPA was stopped. Since the rotation cycle 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-mentioned measure for improving the measurement accuracy and increasing the processing speed of the arithmetic unit. If the measurement time is 0.2 seconds, the measurement can be performed about 20 times or more even in the process of decreasing the film thickness. Therefore, it is sufficiently possible to observe the change in the abundance of H ₂ O and the like in the process of decreasing the film thickness.

Next, an experiment was conducted to confirm the effect of using the polarization angle and P-polarized light. 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 disappearing the IPA liquid film by evaporation was measured. FIG. 9 shows the result of an experiment performed without controlling the polarization of the irradiation light, and FIG. 10 shows the result of an experiment in which a polarizer was provided in front of the light projecting section and only the P-polarized component was irradiated. In the figure, the time change of the absorbance at 1300 nm, 1500 nm, and 1700 nm is shown for convenience. The vertical axis of the figure represents the absorbance (arbitrary unit), the horizontal axis represents the passage of 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, and rapidly decreases when the film thickness decreases due to the spread of IPA, and gradually decreases to about 0.2 as the film thickness decreases due to evaporation. Then, when the IPA film disappeared, it dropped sharply and returned to 0 when the wafer was completely dried. From FIG. 9, when the IPA film thickness approaches 0, it was observed that the absorbance vibrates due to interference. It is not clear why the absorbance decreases to only about 0.2 while the film thickness is decreasing, but it is considered to be offset due to reflection/scattering on the surface of the IPA film.

The absorbance of FIG. 10 rises when a liquid film is formed by IPA dropping, decreases rapidly when the film thickness decreases due to the spread of IPA, 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 when the IPA film thickness approaches 0, the oscillation of the absorbance due to the interference was not recognized. The reason why the absorbance decreases to about −0.04 while the film thickness is decreasing is not clear, but it is considered to be due to the change in reflectance depending on the presence or absence of the IPA film.

From the results of FIG. 9 and FIG. 10, it is possible to remarkably improve the measurement accuracy for a liquid film having a small film thickness by making infrared rays 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 can be made within the scope of the technical idea thereof.

For example, the substrate is not limited to a silicon wafer, but may be a compound semiconductor such as silicon carbide or gallium arsenide, or a crystal wafer such as sapphire. Further, the substrate may be a glass substrate for a flat panel display, or may be a ceramic wafer for manufacturing electronic parts and the like. In all of these substrates, the success or failure of the treatment with the treatment liquid has a great influence on the defective rate of the product, and therefore the effect of applying the present invention is great.

10 Substrate Processing Device 11 Rotating Table (Substrate Rotating Means)
12 Processing liquid supply nozzle (processing liquid supply means)
13 light sources 14 and 17 optical fibers 15 and 22 light projecting section (infrared irradiation means)
16 Light receiving part (infrared light receiving means)
18 Photometric unit (photometric means)
19 Calculation unit (calculation means)
21 corner cube 23 infrared camera W wafer (substrate)
S treatment liquid F treatment liquid film IR infrared ray θ incident angle θ _B polarization angle (Brewster angle)

Claims (18)

Supply the processing liquid on the rotating substrate,
During and/or after the supply of the processing liquid is stopped, the liquid film of the processing liquid formed on the upper surface of the substrate emits infrared rays from a light projecting unit provided on the liquid film side of the substrate with a space. Irradiating while moving the incident position in the radial direction of rotation, the reflected light reflected on the upper surface of the substrate is received by the light receiving portion provided on the liquid film side of the substrate with a space, and 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 liquid components on a substrate. The absorbance is obtained for a measurement time longer than the rotation cycle 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 each predetermined wavelength, 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 or 2. The concentration of the component is calculated from the treatment liquid film thickness calculated from the absorbance or the treatment liquid film thickness measured by another method, and the existing amount of one or more components contained in the treatment liquid film. ,
The method for measuring a liquid component on a substrate according to claim 1. The substrate is a semiconductor wafer, a glass wafer, a crystal wafer or a ceramic wafer,
The method for measuring a liquid component on a substrate according to claim 1. 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, dehydrating or drying the substrate, and water; functional water such as ozone water, radical water, electrolytic ion water; organic solvent such as 2-propanol; ammonia peroxide. Hydrogen oxide mixed solution, hydrochloric acid hydrogen peroxide mixed solution, sulfuric acid hydrogen peroxide mixed solution, nitric hydrofluoric acid mixed solution, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, buffered hydrofluoric acid, ammonia, hydrogen peroxide, hydrochloric acid, hydroxylated Selected from the group consisting of tetramethylammonium and a mixture thereof with water;
The method for measuring a liquid component on a substrate according to claim 1. The component whose abundance is measured is H ₂ O,
The method for measuring a liquid component on a substrate according to claim 1. 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 rays include light having a wavelength of at least 1350 to 1720 nm,
The method for measuring a liquid component on a substrate according to claim 1. At least one of the components whose abundance is measured is a component derived from the liquid supplied onto the substrate before the process of supplying the processing liquid,
The method for measuring a liquid component on a substrate according to claim 1. 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 rays are
The incident angle to the treatment liquid film is irradiated so as to be an angle equal to or close to a polarization angle with respect to the gas and the treatment liquid that constitute the atmosphere at the time of measuring the liquid component on the substrate,
Irradiate only P-polarized light, or receive only P-polarized component of reflected light,
The method for measuring a liquid component on a substrate according to claim 1. In the infrared ray, 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 method for measuring a liquid component on a substrate according to claim 1. A device for receiving the reflected light is an infrared camera,
The method for measuring a liquid component on a substrate according to claim 1. Using two or more infrared cameras having different wavelength sensitivity characteristics,
The method for measuring a liquid component on a substrate according to claim 16. A substrate rotating means for holding and rotating the substrate;
Processing liquid supply means for supplying the processing liquid onto the substrate,
Infrared irradiating means which is provided on the liquid film side of the substrate with a space in between 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 rotation of the substrate. When,
Infrared light receiving means provided on the liquid film side of the substrate with a space therebetween, and receiving the reflected light reflected on the upper surface of the substrate,
Photometric means for detecting the received infrared rays,
Calculating means for calculating the absorbance at a predetermined wavelength, and calculating the abundance of a predetermined component corresponding to the predetermined wavelength;
A substrate processing apparatus having.

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