Liquid component measuring device and liquid component measuring method

Abstract

To provide a liquid component measurement device capable of measuring the amounts of components in a treatment liquid on a substrate while treating the substrate and eliminating the effect of rippling of a treatment liquid surface.SOLUTION: A liquid component measurement device 20 is provided, comprising a light projection unit 23 configured to irradiate a treatment liquid S supplied onto a revolving substrate W with a light beam, a light reception unit 24 configured to receive light passing through the treatment liquid, a light measurement unit 25 configured to measure intensity of the received light, and a computation unit 26 configured to determine whether a value of the received light intensity is an abnormal value caused by rippling of a surface of the treatment liquid or not and derive abundance of one or more components contained in the treatment liquid according to a value of the received light intensity determined to be normal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for measuring components contained in a processing liquid on a substrate, such as a semiconductor wafer, in single-substrate processing of the substrate. [Background technology]

[0002] In the semiconductor industry, single-wafer processes involve holding semiconductor wafers horizontally and rotating them while applying processing solutions to their surfaces to perform processes such as etching and cleaning. The cleaning process consists of a rinsing process and a drying process. After the rinsing process, chemicals such as etching solutions are washed away with pure water, the pure water on the wafer is replaced with 2-propanol (IPA) in the drying process. If unintended components remain on the substrate during these processes, they can cause defects in subsequent processes. For example, insufficient rinsing can leave behind the materials being cleaned. Furthermore, residual water due to insufficient replacement of pure water with IPA can cause watermarks (drying marks). In recent years, fine, high-aspect-ratio patterns are often formed on wafer surfaces. Insufficient replacement with IPA can result in residual water, which has a high surface tension, causing the patterns to collapse.

[0003] To address this issue, excess processing liquid is supplied by increasing the amount or duration of the processing liquid supply. However, increasing the amount of processing liquid used increases the cost of waste liquid disposal. To reduce the amount of processing liquid used and efficiently process substrates, it is preferable to process substrates while checking the amounts of target components, such as components that may remain. By monitoring changes in the composition of water on the substrate during the rinsing process or by monitoring the progress of the replacement of pure water with IPA during the IPA drying process, the amount of processing liquid wasted can be reduced.

[0004] Patent Document 1 describes a method for measuring the amount of components present on a substrate in situ while processing the substrate. The method involves supplying a processing solution onto a rotating substrate, irradiating a liquid film of the processing solution formed on the substrate with infrared light, receiving reflected light, and measuring the amount of one or more components present in the processing solution film based on the absorbance at a predetermined wavelength. The method also describes that, in order to average out the effects of unevenness on the wafer surface, the measurement time for calculating absorbance is preferably a natural number multiple of the wafer rotation period. The examples describe the results of quantifying HO and IPA on a rotating silicon wafer while supplying an IPA-water mixture onto the wafer.

[0005] Patent Document 2 describes a substrate processing method that aims to effectively remove pure water from a substrate surface without wasting time or low-surface tension liquids such as IPA. This method involves supplying pure water to the substrate surface, followed by a low-surface tension liquid supply step, detecting the water concentration in the liquid on the substrate surface in parallel with the low-surface tension liquid supply step, and determining whether to terminate the low-surface tension liquid supply step based on the detected water concentration. The water concentration is detected by irradiating the liquid with light that passes through a prism in contact with the IPA liquid surface on the substrate, receiving the light that is multiplexed between the substrate and the prism with a light receiving unit, and then based on the intensity of the received light. This allows the light to pass through the liquid multiple times, effectively attenuating light of a specific wavelength due to the water in the liquid, thereby enabling accurate detection of the water concentration in the liquid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-070669 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-218402 Summary of the Invention [Problem to be solved by the invention]

[0007] When performing absorption analysis on a dynamic (non-stationary) liquid, it is common to calculate absorbance by integrating the received light intensity over a certain period of time. This averages out the effects of various scattering factors and reduces the variability in the measured value. Patent Document 1 also describes, as mentioned above, averaging out the effects of unevenness on the wafer surface by setting the measurement time for calculating absorbance to a natural number multiple of the wafer rotation period. However, even when measuring the amounts of components in the processing liquid using the method described in Patent Document 1, the variability in the measured value becomes large, making it sometimes difficult to determine whether the replacement of pure water with IPA is complete.

[0008] The inventors conducted experiments by changing the integration time of the received light intensity and discovered that undulation of the processing liquid surface had a significant effect on the variability of the measured values. Therefore, it was thought that when the undulation of the processing liquid surface increased due to conditions such as the rotation speed of the substrate and the supply speed of the processing liquid, the variability of the measured values ​​increased even when the method of Patent Document 1 was used.

[0009] According to the method described in Patent Document 2, the prism is brought into contact with the processing liquid, so there is a possibility that undulations on the processing liquid surface will not affect the measurement values. However, the method of Patent Document 2 has the problem that it is difficult to control the position of the prism so that it does not collide with the substrate, because the substrate is rotated at high speed while the prism is brought close to the processing liquid film thickness of several tens to several hundreds of μm.

[0010] The present invention has been made in consideration of the above, and has an object to provide a liquid component measuring device or method that can measure the amount of components in a processing liquid on a substrate while processing the substrate, and that can eliminate the influence of rippling on the processing liquid surface. [Means for solving the problem]

[0011] The liquid component measuring device of the present invention comprises a light projecting unit that irradiates a light beam toward a treatment liquid supplied onto a rotating substrate, a light receiving unit that receives the light that has passed through the treatment liquid, a photometric unit that measures the intensity of the received light, and a calculation unit that determines whether the value of the intensity of the received light is an abnormal value caused by rippling of the surface of the treatment liquid, and calculates the amount of one or more components present in the treatment liquid based on the value of the intensity of the received light that is determined not to be an abnormal value.

[0012] Here, the abundance of a component is a concept that includes both the absolute amount, such as the mass of the component, and the relative amount, such as the concentration of the component in the treatment liquid.

[0013] The liquid component measuring method of the present invention comprises the steps of irradiating a light beam toward a treatment liquid supplied onto a rotating substrate, receiving the light that has passed through the treatment liquid, measuring the intensity of the received light, and determining whether the received light intensity or the absorbance value calculated from the received light intensity is an abnormal value, and calculating the amount of one or more components present in the treatment liquid based on the received light intensity or the absorbance value that is determined not to be an abnormal value. [Effects of the Invention]

[0014] According to the liquid component measuring device or liquid component measuring method of the present invention, it is determined whether the measured received light intensity is fluctuating due to the influence of undulations on the surface of the processing liquid on the substrate, and the amount of the component present is calculated based on the value of the received light intensity that is determined to be not an abnormal value, so that the influence of undulations on the surface of the processing liquid can be eliminated and the amount of the component present can be determined. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams illustrating the configuration and usage of a liquid component measuring device according to an embodiment. [Figure 2] 10A and 10B are diagrams illustrating an example of the structure of a probe that functions as both a light projecting unit and a light receiving unit. [Figure 3] 3A is a diagram showing an example of the internal structure of the photometry unit, and FIG. 3B is a view taken along the arrow AA in FIG. 3A. [Figure 4]FIG. 10 is a diagram for explaining variations in received light intensity. [Figure 5] FIG. 10 is a diagram for explaining variations in received light intensity. [Figure 6] FIG. 10 is a diagram for explaining variations in received light intensity. [Figure 7] FIG. 10 is a diagram showing an example of a frequency distribution of absorbance. [Figure 8] FIG. 10 is a diagram showing the relationship between the tolerance for absorbance and the sample size. [Figure 9] FIG. 1 is a graph showing the transition of IPA concentration in an example. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the liquid component measuring device and liquid component measuring method of the present invention will be described using a silicon wafer cleaning process as an example.

[0017] Referring to FIG. 1, a single-wafer substrate processing apparatus 10 includes a turntable 11 that rotates a wafer W horizontally or at a desired angle, and nozzles 12 that supply a processing liquid S onto the wafer. A plurality of nozzles 12 are provided for each type of processing liquid, and each is connected to a processing liquid supply source (not shown) by a pipe 13. The nozzles 12 are movable in the radial direction from the center to the outer edge of the wafer. When the processing liquid S is supplied to the upper surface of the wafer W while it is rotating, the processing liquid moves toward the outer edge of the wafer due to centrifugal force, forming a processing liquid film F with a thickness that balances the amount of movement and the amount of supply. When the supply of the processing liquid is stopped, the processing liquid is discharged from the outer edge of the wafer, and the processing liquid film decreases in thickness and eventually disappears.

[0018] The type of treatment liquid is not particularly limited, and examples thereof include water; functional water such as ozone water, radical water, and electrolytic ion water; organic solvents such as IPA; ammonia-hydrogen peroxide 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, tetramethylammonium hydroxide, and mixtures of these with water.

[0019] The liquid component measuring device 20 of this embodiment includes a light source 21, a probe 22, a photometric unit 25, and a calculation unit 27. The probe 22 is disposed above the wafer W inside the substrate processing apparatus 10, and in this embodiment, serves as both a light-projecting unit 23 that irradiates light toward the wafer W and a light-receiving unit 24 that receives reflected light that has passed through the processing liquid on the wafer. In the following, the probe 22 may be referred to as the light-projecting unit 23 in the description of light projection, and the probe 22 may be referred to as the light-receiving unit 24 in the description of light reception. The light source 21, the photometric unit 25, and the calculation unit 27 are disposed outside the substrate processing apparatus. The light-projecting unit 23 is connected to the light source 21, and the light-receiving unit 24 is connected to the photometric unit 25 by an optical fiber 28. The photometric unit 25 is composed of one or more photometers 26. The photometric unit 25 and the calculation unit 27 are electrically connected.

[0020] The light source 21 emits light including the absorption peak wavelength of the component to be measured (hereinafter referred to as the "specific component"). The light source 21 preferably generates light in a continuous wavelength range. This is because it can accommodate the measurement of many types of specific components. Even if the specific component is determined, the amount of that component present can be determined with higher accuracy by measuring absorption at multiple wavelengths, as will be described later. The light source 21 preferably includes near-infrared light, and more preferably includes wavelengths in the range of 1350 to 1720 nm, where the absorption peak wavelengths of HO and IPA exist. The light source 21 may be equipped with a lamp combined with an optical filter to cut out wavelengths unnecessary for measurement. For example, a commercially available lamp such as a halogen tungsten lamp can be used as the light source.

[0021] 2, probe 22 functions as both a light projecting unit 23 that projects light beam B onto a processing liquid film F on wafer W and a light receiving unit 24 that receives light reflected through the processing liquid. Probe 22 has a single optical path P inside its housing. Light introduced from one end of the probe (the right end in FIG. 2) through optical fiber 28 travels horizontally toward the left side of FIG. 2, is collimated by lens 31, is reflected downward by mirror 32, passes through lens 33, and is irradiated vertically toward wafer W. The light beam that passes through processing liquid film F on the wafer and is reflected by wafer W passes through lens 33 and travels inside the probe, then follows optical path P in reverse and is guided to optical fiber 28.

[0022] The light-projecting unit 23 and the light-receiving unit 24 may be provided separately. When the light-projecting unit and the light-receiving unit are provided separately, the angle of incidence onto the processing liquid film F can be selected. For example, by setting the angle of incidence at the Brewster angle and irradiating P-polarized light, reflection on the processing liquid surface can be suppressed. On the other hand, as shown in Figure 2, if the light-projecting unit and the light-receiving unit are combined and the light beam is irradiated perpendicularly onto the wafer, it becomes easier to control the distance between the probe and the wafer. Furthermore, if the optical path P is L-shaped as shown in Figure 2, the height of the probe can be lowered, which has the advantage of making it easier to install within the substrate processing apparatus 10.

[0023] The probe 22 is movable in the radial direction above the wafer W from the center to the outer edge of the wafer, thereby making it possible to measure the components in the processing liquid film at any position on the wafer.

[0024] The light received by the light receiving unit 24 is branched midway through the optical fiber 28 and guided to the photometric unit 25. An optical filter may be provided at the entrance of the photometric unit to cut out wavelengths unnecessary for measurement. The photometric unit may separate the light to determine the intensity of received light at a predetermined wavelength, or may use an interference filter or the like to extract light of a predetermined wavelength and measure the intensity of the received light. The photometric unit amplifies an electrical signal corresponding to the measured intensity of received light, if necessary, and outputs it to the calculation unit 27.

[0025] The photometry unit 25 may measure the received light intensity at one absorption peak wavelength of the specific component, but preferably measures the received light intensity at multiple wavelengths. The absorption wavelength of a specific component may overlap with the absorption wavelength range of other components, and by considering the ratio of light absorption at multiple wavelengths, the amount of the specific component can be determined with higher accuracy. Note that when the photometry unit measures the received light intensity at multiple wavelengths, it is not necessary for each of the multiple wavelengths to be the absorption peak wavelength of the specific component; it is sufficient that one of the wavelengths is included in the absorption bandwidth of the specific component.

[0026] When the photometry unit 25 measures the received light intensity at multiple wavelengths, the number of wavelengths for measuring the received light intensity is preferably 4 or more, more preferably 8 or more. This is because the greater the number of wavelengths, the higher the accuracy when calculating the abundance of a characteristic component from multiple received light intensities using the least squares method or the like. On the other hand, the number of wavelengths for measuring the received light intensity is not particularly limited, but is preferably 256 or less, more preferably 128 or less, and even more preferably 64 or less. This is because even if the number of wavelengths is increased more than necessary, the effect of improving accuracy relative to the cost is small.

[0027] When photometering unit 25 measures the intensity of received light at multiple wavelengths, the photometering unit may be configured using multiple photometers capable of measuring the intensity of received light at one wavelength, or may be configured using one or more photometers capable of measuring the intensity of received light at multiple wavelengths. For example, in Figure 1, photometering unit 25 is made up of two photometers 26, which are connected to branched optical fiber 28 and arranged in parallel.

[0028] Referring to FIG. 3, light introduced from optical fiber 28 into photometer 26 is collimated by lens 41 and the like, passes through bandpass filter (BPF) 44, and reaches photodetector 45. A light-opaque partition 42 is provided in the optical path, and holes 43 of the same shape and area are formed in partition 42 in a rotational symmetry around optical axis X. A BPF is disposed to cover each hole 43, and a photodetector 45 is disposed behind the BPF. Each BPF transmits light of a different wavelength, which is the absorption wavelength of a characteristic component. In FIG. 3, four pairs of BPFs 44 and photodetectors 45 are disposed at positions with four-fold rotational symmetry around optical axis X. Each pair of BPFs 44, holes 43, and photodetectors 45 is disposed rotationally symmetrically with respect to the optical axis, and therefore, the distance from the optical axis is equal for each pair, and the intensity of light incident on each BPF is equal.

[0029] The number of pairs of BPF 44 and photodetector 45 included in one photometer 26 is not particularly limited, but is preferably 3 or 4. This is because it allows more light with high intensity to be utilized that is closer to the optical axis X. Furthermore, by providing multiple photometers 26 in parallel as necessary, the photometering unit 25 can measure the received light intensity at multiple desired wavelengths.

[0030] When the photometry unit 25 measures the received light intensity at multiple wavelengths, it is possible to measure the received light intensity using a single photodetector while switching between BPFs that transmit light of each wavelength. However, a higher sampling rate can be achieved by providing multiple pairs of BPF 44 and photodetector 45 and measuring the received light intensity at multiple wavelengths simultaneously.

[0031] The sampling rate at which the photometry unit 25 measures the intensity of received light must be high enough to distinguish fluctuations in the intensity of received light due to rippling of the surface of the processing liquid. Details of the sampling rate will be described in the explanation of the liquid component measurement method and in the examples.

[0032] The calculation unit 27 receives the received light intensity as an electrical signal from the photometry unit 25, and performs various calculations such as determining whether or not the received light intensity is affected by undulations on the surface of the liquid being treated, determining whether the received light intensity is normal or abnormal, calculating the absorbance from the received light intensity, calculating the amount of a specific component present, etc. Specific examples of the calculations will be described in the explanation of the liquid component measurement method and in the examples.

[0033] Next, the liquid component measuring method of this embodiment will be described.

[0034] When processing liquid S is supplied to the upper surface of wafer W while it is being rotated, the processing liquid moves toward the peripheral edge of the wafer due to centrifugal force, forming a processing liquid film F on the wafer. Light beam B is irradiated onto this processing liquid film from light projecting unit 23. The light beam passes through the processing liquid, is reflected by the wafer surface, is received by light receiving unit 24, and is sent to photometry unit 25 via optical fiber 28.

[0035] The photometry unit 25 measures the intensity of the received light and sends an electrical signal corresponding to the intensity of the received light to the calculation unit 27. At this time, the frequency at which the intensity of the received light is measured once and sent to the calculation unit is the sampling rate. The sampling rate needs to be high enough to be able to distinguish fluctuations in the intensity of the received light due to rippling of the processing liquid surface. Because rippling of the processing liquid surface moves at high speed from the center to the periphery of the wafer W, if the sampling rate is slow, the influence of rippling of the processing liquid surface is smoothed out, making it difficult to distinguish whether or not there has been a fluctuation in the intensity of the received light due to rippling of the processing liquid surface.

[0036] The inventors conducted experiments in which the sampling rate of the received light intensity was varied under conditions of different substrate rotation speeds and different processing liquid supply speeds. The results showed that, in order to distinguish fluctuations in the received light intensity due to undulations on the processing liquid surface, a sampling rate of 400 times / second or more is preferable, and 750 times / second or more is even more preferable. However, there is no particular upper limit to the sampling rate. Since many commercially available photodetectors have sampling time intervals of a few micrometers, the sampling rate is preferably 100,000 times / second or less. Furthermore, the sampling rate is more preferably 10,000 times / second or less. A higher sampling rate offers no particular benefit, and would increase costs by providing the processing unit 27 with high-speed processing capabilities.

[0037] Conventionally, when performing absorption analysis on dynamic liquids, it has been common to calculate absorbance by integrating the received light intensity over a certain period of time to average out the effects of various scattering factors and reduce variation in measurement values. Even when measuring and displaying liquid components in real time, a sampling interval of approximately 0.1 to 0.5 seconds is sufficient for "real-time" monitoring, as long as the measurement results are displayed at intervals of approximately 0.1 to 0.5 seconds. When using a charge-type photodetector, the received light intensity is sometimes sampled once every several milliseconds to several tens of milliseconds and sent to a calculation unit to prevent overflow of the photodetector. Even in this case, the calculation unit calculates absorbance by integrating the received light intensity over a period of approximately 0.1 to 0.5 seconds. In contrast, the present embodiment uses the received light intensity measured at a higher sampling rate to determine whether the measured received light intensity is affected by rippling of the liquid surface.

[0038] Furthermore, it is preferable that the sampling by the photometry unit 25 is synchronized with the rotation of the turntable 11 of the substrate processing apparatus 10. This allows the received light intensity to be measured at the same position or in the same range for each rotation of the wafer W. To synchronize the sampling with the rotation of the substrate, a signal synchronized with the rotation may be sent from the substrate processing apparatus 10 to the liquid component measuring apparatus 20. Furthermore, when the rotation speed is changed during wafer processing, the sampling rate may be changed in accordance with the rotation speed of the wafer within a range that allows for discrimination of fluctuations in the received light intensity due to rippling of the processing liquid surface.

[0039] The calculation unit 27, which receives the received light intensity from the photometry unit 25, performs two main tasks: one is to calculate the amount of a specific component present based on the received received light intensity, and the other is to determine whether the received received light intensity is an abnormal value that has fluctuated due to the influence of rippling on the surface of the treatment liquid.

[0040] First, the method by which the calculation unit 27 calculates the abundance of a specific component will be described.

[0041] The absorbance A is A=-log(I / I0) (Equation 1) Here, I is the measured light intensity, and I0 is the light intensity when no specific component is present. I0 can be measured in advance. The absorbance A is given by the Beer-Lambert law as follows: A = αLC (Equation 2) Here, α is the absorption coefficient of the specific component, L is the optical path length, and C is the concentration of the specific component. C corresponds to the abundance (relative amount) of the specific component, and LC corresponds to the abundance (absolute amount) of the specific component.

[0042] When calculating the amount of a specific component from the intensity of received light at one absorption peak wavelength, if the absorption coefficient α of the specific component is known, the absolute amount LC of the specific component can be determined using the above equations 1 and 2. If the absorption coefficient α of the specific component is not known, a calibration curve can be created from measurement results using a liquid film of known thickness under conditions similar to the actual processing conditions, and the absolute amount LC of the specific component can be calculated based on the calibration curve. Furthermore, if the processing liquid film thickness is measured simultaneously as needed, the concentration C of the specific component in the processing liquid film can be calculated using the above equation 2, with the optical path length L set to approximately twice the liquid film thickness, taking into account reflections at each interface.

[0043] When calculating the amount of a specific component from the received light intensity at multiple wavelengths, the amount of the specific component can be determined by least squares or the like based on a group of absorbance data measured in advance while varying the amount of the specific component. Furthermore, when there are multiple specific components to be measured, if there is a group of absorbance data measured in advance while varying the amount of each component, the amount of each component can be determined by multivariate analysis using principal component regression or partial least squares regression. Furthermore, if there is a group of absorbance data measured in advance while varying the liquid film thickness and the concentration of the specific component, the thickness of the treatment liquid film and the concentration of the specific component in the treatment liquid can be simultaneously determined by multivariate analysis using the liquid film thickness and the concentration as independent variables.

[0044] The amount of a specific component (LC or C) is preferably calculated based on multiple received light intensities received during a specified period. As with conventional methods, this is to reduce the variability in the measurement values ​​by averaging out the effects of various scattering factors such as wafer surface irregularities. The period during which the amount of a specific component is calculated once is called the "accumulation period." The accumulation period is preferably 0.05 seconds or more, and more preferably 0.1 seconds or more. On the other hand, when the amount of a specific component is calculated in real time, The integration period is set to match the display interval for monitoring the specific component in real time, and is preferably 0.5 seconds or less, more preferably 0.25 seconds or less, and particularly preferably 0.1 seconds or less. For each integration period, calculation unit 27 integrates the received light intensities measured by and received from photometry unit 25 during that integration period to calculate the amount of the specific component present.

[0045] In parallel with calculating the abundance of a specific component, or prior to calculating the abundance of a specific component, the calculation unit 27 determines whether the received light intensity is an abnormal value affected by fluctuations in the surface ripple of the processing liquid. Whether the received light intensity is affected by ripples in the processing liquid can be determined by examining the variation in the received light intensity received during a predetermined period. For example, the calculation unit calculates the median of the received light intensity received during an integration period. If there is a received light intensity whose difference from the median exceeds a predetermined value, the calculation unit can determine that the received light intensity is an abnormal value affected by ripples in the processing liquid, and that the received light intensity measured during that integration period contains an abnormal value. Alternatively, the calculation unit may calculate absorbance from the received light intensity each time it receives it from the photometry unit and determine whether or not there is an effect of ripples in the processing liquid based on the variation in absorbance. Based on the variation in absorbance, it is preferable because it is easier to identify abnormal values ​​affected by ripples in the processing liquid.

[0046] Incidentally, abnormal values ​​caused by malfunctions of the device, such as abnormal values ​​caused by the lamp of the light source 21 not being lit or by a break in the optical fiber 28, can also be detected by conventional assumed devices, and it is preferable that they can also be detected by the liquid component measuring device of this embodiment.

[0047] Next, two methods for calculating the abundance of a specific component by the calculation unit 27 will be described, which differ in the method for selecting received light intensity data to be used in the calculation.

[0048] The first method by the calculation unit 27 is to calculate the abundance of a specific component using all of the received light intensities received during a certain integration period, while simultaneously determining whether or not each received light intensity is affected by rippling of the treatment liquid surface.

[0049] The calculation unit 27 may calculate the absorbance or the amount of a specific component each time it receives a received light intensity and obtain an average during the integration period, or may integrate the received light intensities measured during the integration period and obtain the absorbance or the amount of a specific component from the integrated value. At the same time, the calculation unit 27 determines whether the received light intensity is an abnormal value affected by rippling of the treatment liquid surface.

[0050] This method allows us to determine whether the calculated amount of a specific component is affected by ripples on the processing liquid surface, and the measurement results can be used to control wafer processing conditions. For example, in the drying process following the rinsing process, the IPA supply time is set to be long to ensure that the pure water on the wafer is replaced with IPA. However, if the calculated amount of IPA is stable over multiple cumulative periods and it is determined that the amount is not affected by ripples on the processing liquid surface, the IPA supply can be stopped immediately to shorten the drying process time. On the other hand, if the calculated amount of IPA is stable over multiple cumulative periods but it is determined that the amount is affected by ripples on the processing liquid surface, the IPA supply can be continued for a predetermined amount of time to allow for further drying.

[0051] The second method by the calculation unit 27 is to determine whether or not each received light intensity received during a certain integration period is an abnormal value affected by wavyness on the treatment liquid surface, and to calculate the abundance of the specific component using only the received light intensity determined not to be an abnormal value. This makes it possible to determine the abundance of the specific component while eliminating the influence of wavyness on the treatment liquid surface. Details of this method will be described later based on experimental results. [Example]

[0052] First, an example of measurement of the received light intensity in a preliminary experiment will be shown.

[0053] In the preliminary experiment, a 200 mm diameter unpatterned silicon wafer was rotated at 500 rpm. Pure water was supplied to the center of the wafer at 1.0 L / min. Light from a 15 W tungsten lamp was projected perpendicularly onto the wafer surface from a probe (light projector) 50 mm from the wafer center. The reflected light was received by a probe (light receiver), and the received light intensity was measured by a photometer. The photometer consisted of three parallel-arranged optical fibers branched into three sets of bandpass filters and photodetectors (InGaAs). The received light intensity was measured at nine wavelengths in the near-infrared range at a sampling rate of 1000 times per second. The absorbance A was calculated using Equation 1, where I was the measured received light intensity and I0 was the received light intensity without water supply.

[0054] Figure 4 shows the absorbance calculated from the received light intensity at a wavelength of 1300 nm. Figure 4 plots the received light intensity over one second, i.e., 1000 times. In Figure 4, the absorbance fluctuates widely, with occasionally extremely high values ​​observed. This confirms that the fluctuations in the received light intensity due to rippling of the treatment liquid surface are not simply due to changes in the thickness of the treatment liquid film, but are due to the scattering of light irradiated by the treatment liquid, resulting in a decrease in the amount of light returning to the light receiving element. Furthermore, it was confirmed that, at a sampling rate of 1000 times per second, it was possible to distinguish fluctuations in the received light intensity due to rippling of the treatment liquid surface.

[0055] Figures 5 and 6 show the absorbance calculated after integrating the received light intensity two or three times in the experiment shown in Figure 4. Figures 5 and 6 correspond to the results when the sampling rates were 500 times / second and 333 times / second, respectively. Comparing Figures 4 to 6, it can be seen that while it is possible to determine the effect of rippling on the treatment liquid surface on the received light intensity in Figures 4 and 5, it is not easy in Figure 6. From this, it was determined that the sampling rate for measuring the received light intensity should preferably be 400 times / second or higher, and even more preferably 750 times / second or higher.

[0056] The inventors also conducted preliminary experiments in which the rotation speed of the silicon wafer was varied in the range of 100 to 1000 rpm and the supply rate of pure water was varied in the range of 0.1 to 1.0 L / min, and similar results were obtained from these experiments as the preferred range of the sampling rate.

[0057] Furthermore, a reasonably fast sampling rate is required to calculate the amount of a specific component in real time. Whether or not the received light intensity is affected by rippling of the treatment liquid surface is determined by observing the variation in the received light intensity received over a predetermined period. In order to meet the requirements for real-time measurement, the integration period is preferably 0.5 seconds or less, more preferably 0.25 seconds or less, and particularly preferably 0.1 seconds or less, and it is necessary to measure a certain number of received light intensities during this integration period.

[0058] As in the preliminary experiment described above, the absorbance was calculated from the measured light intensity at a silicon wafer rotation speed of 300 rpm, a pure water supply rate of 1 L / min, and a sampling rate of 1000 times / sec. Figure 7 shows the absorbance over 1 second at 1450 nm, where the absorption by HO is significant and the absorbance varies widely. The standard deviation of the data in Figure 7 was 0.15.

[0059] The relationship between the allowable error δ and the sample size n is as follows: δ=zσ / √(n) (Equation 3) where z is a constant, for example, 1.96 for a 95% confidence interval or 2.63 for a 99% confidence interval, σ is the standard deviation, and √(n) is the square root of the sample size n. Figure 8 is a graph showing the relationship between the sample size n and the allowable error δ in Equation 3. Figure 8 shows that in order to reduce the allowable error δ to a certain extent, the sample size n needs to be 50 or more, and more stably, 100 or more.

[0060] From the above calculations, it was found that, for example, when the integration period for calculating the abundance of a specific component in real time is set to 0.1 seconds, in order to determine whether the received light intensity is an abnormal value affected by rippling of the treatment liquid surface based on the variation in the received light intensity within the integration period, preferably 50 or more, more preferably 100 or more pieces of received light intensity data per 0.1 seconds are required in relation to the allowable error. From these results, it is preferable that the sampling rate for measuring the received light intensity is 500 times / second or more, and even more preferably 1000 times / second or more.

[0061] Next, an embodiment of the present invention will be described.

[0062] In the experiment, a 200 mm diameter unpatterned silicon wafer was rotated at 1000 rpm. Pure water was supplied to the center of the wafer at 50 mL / min for 18 seconds, after which the supply of pure water was stopped and IPA was supplied at 50 mL / min for approximately 20 seconds. Light from a tungsten lamp (15 W) was projected perpendicularly onto the wafer surface from a probe (light-emitting unit) 50 mm from the wafer center. The reflected light was received by a probe (light-receiving unit), and the received light intensity was measured by a photometer. The photometer consisted of three parallel units, each equipped with a branched optical fiber, three sets of band-pass filters (BPFs), and a photodetector (InGaAs). The received light intensity at nine near-infrared wavelengths was measured at a sampling rate of 1000 times per second. The measured light intensity was judged to be an abnormal value due to rippling of the processing liquid surface. For light intensities that were judged not to be abnormal, a multivariate analysis was performed using a group of absorbance data previously measured with different liquid film thicknesses and IPA-water mixture ratios, with an integration period of 0.1 seconds, to determine the IPA concentration in the processing liquid on the wafer.

[0063] The abnormal values ​​were determined as follows: absorbance was calculated from 100 received light intensities for each integration period, and the 10 smallest data values ​​were unconditionally determined to be abnormal and excluded. The smallest value among the remaining 90 was then determined to be a normal absorbance value and used as the reference value. The reference value is a value that is considered to be a normal value with great certainty, and it is acceptable for the excluded 10 data to contain normal values.

[0064] Next, the reference value + 0.2 was used as a threshold, and among the 90 absorbance data, data exceeding the threshold were determined to be abnormal values, and data below the threshold were left as normal values. The threshold may be set in advance to a fixed value, for example, the maximum expected absorbance, or, as in this example, may be set according to the reference value and a predetermined calculation formula.

[0065] The determination of whether a value is abnormal can also be performed by other methods. For example, based on a histogram of absorbance, values ​​that fall outside a predetermined range including the median value can be determined to be abnormal.

[0066] In this embodiment, the absorbance was calculated each time the received light intensity was measured, and a determination was made as to whether the calculated absorbance was an abnormal value, but since there is a one-to-one correspondence between absorbance and received light intensity, it is also possible to determine whether the received light intensity is an abnormal value. However, it should be noted that the magnitudes of the absorbance and received light intensity are reversed.

[0067] Figure 9 shows the results of measuring the amount of IPA present on the wafer before and after switching the processing liquid from pure water to IPA. The horizontal axis represents the passage of time, and the vertical axis represents the IPA concentration. The open circles represent the IPA concentration calculated every 0.1 seconds based on absorbance values ​​that were determined to be normal. The closed circles are an index of the change in IPA concentration over time; in Figure 9, this is the absolute value of the difference between the maximum and minimum concentration values ​​of the previous five measurements. The index of the change in IPA amount over time can also be expressed as the first derivative of the amount present.

[0068] In Figure 9, while pure water is being supplied onto the wafer, both the IPA concentration and its change index (hereafter referred to as "fluctuation amount") are close to 0. When the supply of pure water is stopped and the supply of IPA is started at 18 seconds on the horizontal axis, both begin to rise. When the fluctuation amount exceeds the replacement threshold, it is determined that replacement has started (S). After the fluctuation amount exceeds the replacement threshold, if the fluctuation amount continuously falls within the stability range for the number of convergence judgment points, it is determined that replacement has been completed (E). The replacement threshold, stability range, and convergence judgment point are set to appropriate values ​​in advance. In Figure 7, the replacement threshold is 40%, the stability range is ±15%, and the convergence judgment point is 5 points.

[0069] From the measurement results in Figure 9, it can be determined that the replacement was completed approximately 1.4 seconds after the start of IPA supply. When the amount of IPA present is not measured in real time, the IPA supply time is often set to approximately 10 to 20 seconds to allow for some leeway. However, if it can be determined from the IPA concentration and fluctuations measured in real time that the replacement of water with IPA was completed in approximately 1.4 seconds, then by stopping the IPA supply at that point, it is possible to reduce the amount of IPA used and shorten the drying process time.

[0070] The present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the technical concept thereof.

[0071] 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 crystalline wafer such as sapphire. The substrate may also be a glass substrate for a flat panel display, or a ceramic wafer for manufacturing electronic components, etc. For all of these substrates, the success or failure of treatment with the treatment liquid significantly affects the product defect rate, so applying the present invention is highly effective. [Explanation of symbols]

[0072] 10. Substrate processing equipment 11 Rotating table 12 nozzles 13 Piping 20 Liquid component measuring device 21 Light source 22 probes 23 Light projector 24 Light receiving part 25 Photometry section 26 Photometer 27 Arithmetic section 28 Optical Fiber 31, 33 Lens 32 Mirror 41 Lens 42 Bulkhead 43 holes 44 Bandpass Filter 45 Photodetector B ray F Treatment liquid membrane P Optical path inside the probe S processing solution W wafer (substrate) X Optical axis of photometer

Claims

1. a light projecting unit that projects a light beam toward the processing liquid supplied onto the rotating substrate; a light receiving unit that receives light that has passed through the treatment liquid; a photometric unit for measuring the intensity of the received light; a calculation unit that calculates a histogram of the received light intensity obtained by multiple measurements, determines based on the histogram whether or not each of the received light intensity values ​​is an abnormal value caused by undulations on the liquid surface of the treatment liquid, and calculates the abundance of one or more components contained in the treatment liquid based on the received light intensity value that is determined not to be an abnormal value; and A liquid component measuring device having the same.

2. a light projecting unit that projects a light beam toward the processing liquid supplied onto the rotating substrate; a light receiving unit that receives light that has passed through the treatment liquid; a photometric unit for measuring the intensity of the received light; a calculation unit that calculates absorbance from the received light intensity each time the photometry unit measures the received light intensity, calculates a histogram of the absorbance obtained by multiple measurements, determines based on the histogram whether each absorbance value is an abnormal value caused by waviness on the liquid surface of the treatment liquid, and calculates the abundance of one or more components contained in the treatment liquid based on the absorbance value that is determined not to be an abnormal value; A liquid component measuring device having the same.

3. The photometry unit measures the received light intensity at a sampling rate of 400 times / second or more.

3. The liquid component measuring device according to claim 1 or 2.

4. The light includes near-infrared rays. The liquid component measuring device according to any one of claims 1 to 3.

5. The calculation unit calculates the abundance of the one or more components in real time. The liquid component measuring device according to any one of claims 1 to 4.

6. irradiating a light beam toward the treatment liquid supplied onto the rotating substrate; receiving light that has passed through the treatment liquid; measuring the intensity of the received light; a calculation step of calculating a histogram of the received light intensities obtained by multiple measurements or absorbances calculated from the received light intensities, determining based on the histogram whether or not each of the received light intensities or absorbance values ​​is an abnormal value caused by undulations on the liquid surface of the treatment liquid, and calculating the abundance of one or more components contained in the treatment liquid based on the received light intensities or absorbance values ​​determined not to be abnormal values; A liquid component measuring method comprising the steps of:

Images