JPWO2016104433A1 - Method and apparatus for measuring silicon concentration or etching selectivity - Google Patents

Abstract

A silicon concentration measuring method and measuring apparatus capable of continuously measuring the silicon concentration in an etching solution in-line are provided. Further, the present invention provides a silicon concentration measurement sensor head that is used in the measurement method and is less likely to be affected by a fixed state of a crystal resonator or a temperature difference between the sensor head and an etching solution. An etching selectivity measuring method and a measuring apparatus capable of measuring a silicon nitride film / silicon oxide film etching rate ratio in a continuous manner in a precise manner with a practical method are provided. A quartz crystal resonator 11 coated with a silicon oxide film to be brought into contact with the etching solution 25 of the substrate processing apparatus 26, a frequency detecting means 21 for detecting the oscillation frequency while vibrating the quartz crystal resonator 11, and a change rate of the oscillation frequency. And a calculation means 24 for calculating the silicon concentration in the etching solution 25.

Description

  The present invention relates to a silicon concentration measuring method and measuring apparatus for measuring a silicon concentration when etching a semiconductor wafer or the like, and a silicon concentration measuring sensor head used for the method, and more particularly to a substrate processing apparatus. In particular, it is useful as a technique for measuring the silicon concentration.

In addition, the present invention uses such a silicon concentration measurement method, and the ratio of the etching rates of a silicon nitride film (Si ₃ N ₄ or the like) and a silicon oxide film (SiO ₂ ) when a semiconductor wafer or the like is etched. In particular, the present invention is useful as a technique for continuously measuring an in-line selection ratio in-line with respect to a wafer processing apparatus.

  When a silicon nitride film is etched with a phosphoric acid solution in a semiconductor wafer process, a silicon oxide film is generally present on the wafer surface as an insulating film having a device structure in addition to the silicon nitride film. In that case, it is generally required that only the silicon nitride film is etched, and the silicon oxide film is hardly etched by the treatment liquid. In other words, the abnormal etching of the silicon oxide film causes problems such as device performance degradation or failure to function as a device. In any case, it is important to control the selection ratio, which is the ratio of the etching rates of the silicon nitride film and the silicon oxide film.

  It is known that the silicon nitride film and silicon oxide film are etched by water in a phosphoric acid solution, and the silicon oxide film is etched by phosphoric acid in a phosphoric acid solution as a mechanism by which the silicon nitride film and silicon oxide film are etched by a high temperature phosphoric acid solution. Yes. Further, the silicon concentration in the phosphoric acid solution changes during the etching, which affects the etching rate of the silicon oxide film.

  On the other hand, in order to measure the etching rate, a crystal resonator is coated with a material to be measured, the measurement material coated on the crystal resonator is brought into contact with an etching solution, and the material to be measured is determined from a change in vibration frequency of the crystal resonator. An etching rate evaluation method for quantitatively evaluating the etching rate in real time is known (see, for example, Patent Document 1). Further, this document discloses the use of a silicon oxide film as a material to be measured.

Japanese Patent Laid-Open No. 10-92789

  However, when the silicon nitride film is etched with a phosphoric acid solution, the silicon oxide film is also etched as described above, and the silicon concentration in the etching solution gradually increases. Therefore, the silicon concentration is controlled in controlling the etching selectivity. It is necessary to control. For this reason, as in the evaluation method described in Patent Document 1, even if the etching rate of the silicon oxide film can be known, the silicon concentration cannot be measured. Therefore, the etching selectivity depending on the silicon concentration is accurately controlled. There was a problem that it was difficult. However, since it is difficult to use a spectroscopic analysis method or the like, there has been no method for measuring the silicon concentration in the etching solution in-line in real time.

  On the other hand, the conventional QCM (quartz crystal microbalance method) sensor with a quartz resonator coated with the material to be measured does not fully consider the corrosion resistance against the etching solution, so it is durable when used in the etching solution. There was a problem that became low. For this reason, there is a need for a sensor head structure in which only the crystal resonator is brought into contact with the etching solution.

  However, the measurement accuracy varies depending on how the crystal unit is fixed to the sensor head, and the temperature of the crystal unit is not stable due to the temperature difference between the sensor head and the etchant. There has been concern about problems caused by breakage of the crystal unit.

  By the way, for the purpose of measuring the selectivity of treatment with phosphoric acid, the technique described in Patent Document 1 is used for etching a silicon nitride film and a silicon oxide film, respectively, and the silicon nitride film and the silicon oxide film are etched together. Since the etching rate of the silicon nitride film is faster than that of the silicon oxide film, it is not a practical method because it is necessary to frequently replace the quartz resonator covering the silicon nitride film. In addition, this method has a problem in that it must be practically divided into two measurement cells, and the measurement system becomes complicated, large, and high in cost.

  On the other hand, assuming that the etching rate of the silicon nitride film is constant, a method of calculating the selection ratio with the etching rate of the silicon oxide film is also conceivable. However, the etching rate of the silicon nitride film is a function of the temperature and concentration of the etching solution. In the semiconductor wafer process, since the temperature and the concentration change every moment, the accuracy of the calculated selectivity is insufficient. The etching rate of the silicon oxide film is also a function of the temperature and concentration of phosphoric acid and the silicon concentration in the phosphoric acid solution.

  Therefore, an object of the present invention is to provide a silicon concentration measuring method and measuring apparatus capable of continuously measuring the silicon concentration in an etching solution in-line. Another object of the present invention is to use a silicon concentration measurement method that can continuously measure the silicon concentration in an etching solution in-line, and it is affected by the fixed state of the crystal unit and the temperature difference between the sensor head and the etching solution. An object of the present invention is to provide a sensor head for measuring silicon concentration which is difficult.

  Another object of the present invention is to provide an etching selectivity ratio that can be measured in a continuous and in-line manner with high accuracy by a practical method, in the ratio of etching rate of silicon nitride film / silicon oxide film treated with phosphoric acid. It is to provide a measuring method and a measuring apparatus.

The above object can be achieved by the present invention as described below.
That is, the silicon concentration measuring method of the present invention includes a step of contacting a silicon oxide film coated on a crystal resonator with an etching solution of a substrate processing apparatus, detecting a vibration frequency while vibrating the crystal resonator, and the vibration. And a step of calculating a silicon concentration in the etching solution based on a frequency change rate.

  According to the silicon concentration measuring method of the present invention, the etching state of the silicon oxide film can be continuously quantified in-line by the step of detecting the vibration frequency, and the correlation between the change rate of the vibration frequency and the silicon concentration. Based on the above, the silicon concentration can be calculated in real time by the step of calculating the silicon concentration in the etching solution. At that time, the correlation between the silicon concentration and the change rate of the vibration frequency is influenced by the temperature of the etching solution, and the correlation at the temperature is used while controlling the temperature constant or measuring the temperature. Thus, the silicon concentration can be calculated with high accuracy. As a result, it is possible to provide a silicon concentration measuring method that can continuously measure the silicon concentration in the etching solution in-line.

  In the case where the temperature of the etching solution is not controlled to be constant, the method further includes a step of measuring the temperature of the etching solution, and in the step of calculating the silicon concentration in the etching solution, the temperature of the etching solution and the change of the vibration frequency It is preferable to calculate the silicon concentration in the etching solution based on the speed.

  That is, as shown in FIG. 8, it was found that the change rate of the vibration frequency is different when the silicon concentration is different, but both are highly correlated. The rate of change of the vibration frequency is proportional to the etching rate (etching rate) of the silicon oxide film based on the principle of QCM described in detail later. In addition, as shown in FIG. 3, the etching rate of the silicon oxide film and the silicon concentration show a high correlation when the temperature of the etching solution and the phosphoric acid concentration are constant, but the correlation also changes when the temperature is different. To do. As described above, the present invention uses the high correlation between the change rate of the vibration frequency and the silicon concentration in the etching solution, and excludes the temperature effect by controlling the temperature of the etching solution to be constant or the influence of the temperature. By taking this into consideration, the silicon concentration in the etching solution can be continuously measured in-line.

  In the above, the method further includes the step of measuring the phosphoric acid concentration in the etching solution, and the step of calculating the silicon concentration in the etching solution is based on the temperature of the etching solution, the phosphoric acid concentration, and the change rate of the vibration frequency. It is preferable to calculate the silicon concentration in the etching solution. The correlation between the silicon concentration and the change rate of the vibration frequency (in other words, the etching rate of the silicon oxide film) is also affected by the phosphoric acid concentration in the etching solution. In particular, when the phosphoric acid concentration in the etching solution changes, the silicon concentration can be calculated with higher accuracy by using the correlation in the phosphoric acid concentration while measuring the phosphoric acid concentration. If there is a difference between the temperature of the etching solution in the etching treatment tank and the temperature of the etching solution in the vibration frequency detection means, a correction means may be provided separately.

  Moreover, it is preferable to calculate the etching rate of the silicon oxide film based on the change rate of the vibration frequency. The etching rate of the silicon oxide film can be easily calculated based on the change rate of the vibration frequency based on the principle of QCM, which will be described in detail later, and the silicon oxide film is etched by continuously measuring this inline. It can be used for controlling the speed and the selectivity with respect to the etching speed of the silicon nitride film.

  In addition, it is preferable to use a sensor head that holds the crystal resonator in a liquid-tight manner with a seal member that presses the periphery of the crystal resonator and heats the crystal resonator with a heating unit. As described above, the structure in which the crystal unit is held in a liquid-tight manner by the seal member reduces the influence of the fixed state of the crystal unit, and the sensor unit is heated by heating the crystal unit by heating means. The temperature difference of the etching solution is reduced, and the influence of the temperature change of the crystal resonator is less likely to occur, and the silicon concentration can be measured with higher accuracy.

  On the other hand, the silicon concentration measuring apparatus according to the present invention includes a quartz resonator coated with a silicon oxide film that is brought into contact with an etching solution of a substrate processing apparatus, and a frequency detector that detects a vibration frequency while vibrating the quartz resonator. And calculating means for calculating the silicon concentration in the etching solution based on the etching rate of the silicon oxide film calculated from the change in the vibration frequency of the crystal resonator and the change rate in the vibration frequency. And

  According to the silicon concentration measuring apparatus of the present invention, the etching state of the silicon oxide film can be continuously quantified in-line by the crystal resonator and the frequency detecting means, and the change rate of the vibration frequency and the silicon concentration can be determined. Based on the correlation, the silicon concentration can be calculated in real time by the calculation means for calculating the silicon concentration in the etching solution. At that time, the correlation between the silicon concentration and the change rate of the vibration frequency is affected by the temperature of the etching solution, but the correlation at that temperature is controlled while the temperature is controlled to be constant or measured by a temperature measuring means. Can be used to calculate the silicon concentration with high accuracy. As a result, it is possible to provide a silicon concentration measuring device capable of continuously measuring the silicon concentration in the etching solution in-line.

  In the case where the temperature of the etching solution is not controlled to be constant, it further includes a temperature measuring unit that measures the temperature of the etching solution, and the calculation unit is based on the temperature of the etching solution and the change rate of the vibration frequency, It is preferable to calculate the silicon concentration in the etching solution.

  In the above, it further includes a concentration measuring means for measuring the phosphoric acid concentration in the etching solution, and the computing means is based on the temperature of the etching solution and the change rate of the phosphoric acid concentration and the vibration frequency in the etching solution. It is preferable to calculate the silicon concentration. The correlation between the silicon concentration and the etching rate of the silicon oxide film is also influenced by the phosphoric acid concentration in the etching solution. While measuring this with the concentration measuring means for measuring the phosphoric acid concentration, By utilizing the correlation, the silicon concentration can be calculated with higher accuracy.

  Moreover, it is preferable that the said calculating means includes the calculation which calculates the etching rate of the said silicon oxide film based on the change rate of the said vibration frequency. The etching rate of the silicon oxide film can be easily calculated based on the change rate of the vibration frequency based on the principle of QCM, which will be described later in detail. This can be used for controlling the etching rate selectivity of the silicon film.

  It is preferable that the sensor further includes a sensor head that holds the crystal resonator in a liquid-tight manner with a seal member that presses the periphery of the crystal resonator and heats the crystal resonator with a heating unit. As described above, the structure in which the crystal unit is held in a liquid-tight manner by the seal member reduces the influence of the fixed state of the crystal unit, and the sensor unit is heated by heating the crystal unit by heating means. The temperature difference of the etching solution is reduced, and the influence of the temperature change of the crystal resonator is less likely to occur, and the silicon concentration can be measured with higher accuracy.

  On the other hand, a sensor head for measuring a silicon concentration according to the present invention includes a crystal resonator coated with a silicon oxide film, a seal member that presses the periphery of the crystal resonator to hold the crystal resonator in a liquid-tight state, and the crystal And heating means for heating the vibrator.

  According to the sensor head for measuring the silicon concentration of the present invention, the influence (measurement error) due to the fixed state of the crystal unit is reduced by the structure in which the crystal unit is held in a liquid-tight manner by the seal member, and the crystal unit is heated by the heating unit. By heating the vibrator, the temperature difference between the sensor head and the etching solution is reduced, and the influence of temperature change of the crystal vibrator is less likely to occur, and the silicon concentration can be measured with higher accuracy.

  In the above, an internal space that communicates with the outside only through a communication path inside the crystal unit, and a valve member that is provided in the communication path and closes the communication path when liquid flows into the internal space. It is preferable. With this configuration, when the internal space expands due to heating of the sensor head, air can be discharged through the communication path, and when the crystal unit is damaged and the etching liquid flows into the internal space of the sensor head The problem at the time of breakage can be avoided by closing the communication path with the valve member.

  On the other hand, in the method for measuring the etching selectivity of the present invention, the etching rate of the silicon oxide film is determined from the change in the vibration frequency of the crystal resonator while the silicon oxide film coated on the crystal resonator is brought into contact with the etching solution of the substrate processing apparatus. The silicon nitride film / oxide is calculated based on the step of calculating continuously, the step of calculating the etching rate of the silicon nitride film of the etching solution, and the calculated etching rate of the silicon oxide film and the etching rate of the silicon nitride film. And a step of continuously calculating a ratio of etching rates of the silicon film.

  According to the method for measuring the etching selectivity of the present invention, the etching rate of the silicon oxide film and the silicon nitride film is increased by the step of continuously calculating the etching rate of the silicon oxide film and the step of calculating the etching rate of the silicon nitride film. It is possible to quantify continuously and accurately in-line. For this reason, the selection ratio can be continuously measured with high accuracy in-line by the step of continuously calculating the etching rate ratio.

  At this time, in the step of calculating the etching rate of the silicon nitride film, the etching rate of the silicon nitride film is continuously calculated from the measured concentration and / or temperature while measuring the concentration and / or temperature of the etching solution. It is preferable. When the etching rate of the silicon nitride film is continuously calculated from the concentration and temperature of the etching solution based on the correlation between the etching rate and the etching rate, there is no need to replace the crystal unit and silicon nitride is highly accurate. The etching rate of the film can be calculated. As a result, it is possible to provide an etching selectivity measurement method capable of measuring the etching rate ratio of the silicon nitride film / silicon oxide film continuously in-line with high accuracy by a practical method.

  In the above, when calculating the ratio of the etching rates, it is preferable to include an arithmetic process for converting the etching rate of the silicon oxide film coated on the crystal resonator into the etching rate of the silicon oxide film formed on the substrate. When the silicon oxide film coated on the crystal resonator is different from the silicon oxide film formed on the substrate, the etching rate is also different. Etching selectivity can be measured.

  Further, it is preferable that a silicon oxide film is formed on the crystal resonator by sputtering. By forming by sputtering, a uniform silicon oxide film can be formed at low cost, and the etching speed can be increased, so that the measurement sensitivity of the etching selectivity can be increased. Note that other film forming methods may be used as long as a uniform silicon oxide film can be formed at low cost. For example, PVD such as vapor deposition, chemical vapor deposition (CVD) (thermal CVD, plasma CVD, photo CVD, etc.), organic Silicon material may be applied and fired.

  Moreover, it is preferable to calculate the silicon concentration in the etching solution from the calculated etching rate of the silicon oxide film. When etching a silicon nitride film with a phosphoric acid solution, the silicon oxide film is also etched, and the silicon concentration in the etching solution gradually increases. Therefore, the silicon concentration is measured and controlled in controlling the etching selection ratio. This is because it is effective.

  On the other hand, the etching selectivity measuring apparatus according to the present invention includes a quartz resonator coated with a silicon oxide film to be brought into contact with an etching solution of a substrate processing apparatus, and a frequency detection means for detecting a vibration frequency while vibrating the quartz resonator. And the ratio of the etching rate of the silicon nitride film / silicon oxide film is continuously calculated based on the etching rate of the silicon oxide film and the etching rate of the silicon nitride film calculated from the vibration frequency change of the crystal resonator And an arithmetic means.

  According to the etching selectivity measuring apparatus of the present invention, the etching state of the silicon oxide film can be continuously quantified in-line by the crystal resonator and the frequency detecting means, and the etching rate of the silicon nitride film is It can be quantified from the concentration and temperature controlled to be constant, or from the concentration and temperature measured by the concentration measuring means and the temperature measuring means. For this reason, the selection ratio can be continuously measured with high accuracy in-line by continuously calculating the ratio of the etching rates by the calculation means.

  At this time, the apparatus further includes at least one of a concentration measuring unit that measures the concentration of the etching solution and a temperature measuring unit that measures the temperature of the etching solution, and the calculation unit includes an oxidation calculated from a change in vibration frequency of the crystal resonator. Based on the etching rate of the silicon film and the etching rate of the silicon nitride film calculated from the measured concentration and / or temperature of the etching solution, the ratio of the etching rate of the silicon nitride film / silicon oxide film is continuously set. It is preferable to calculate. When the etching rate of the silicon nitride film is continuously calculated from the concentration and temperature of the etching solution based on the correlation between the etching rate and the etching rate, there is no need to replace the crystal unit, and the accuracy is high. The etching rate of the silicon nitride film can be calculated by a compact and inexpensive system. As a result, it is possible to provide an etching selectivity measuring apparatus capable of measuring the etching rate ratio of the silicon nitride film / silicon oxide film continuously in-line with high accuracy and with a practical method. If there is a difference between the temperature of the etching solution in the etching treatment tank and the temperature of the etching solution in the vibration frequency detection means, a correction means may be provided separately.

  In the above, the calculation means performs calculation processing for converting the etching rate of the silicon oxide film coated on the crystal resonator into the etching rate of the silicon oxide film formed on the substrate when calculating the ratio of the etching rates. It is preferable to include. When the silicon oxide film coated on the crystal resonator is different from the silicon oxide film formed on the substrate, the etching rate is also different. Etching selectivity can be measured.

  Further, it is preferable for the above reason that a silicon oxide film is formed on the crystal resonator by sputtering. It is preferable for the above reason that the calculation means further performs a calculation process for calculating the silicon concentration in the etching solution from the calculated etching rate of the silicon oxide film.

  Furthermore, it is preferable that the sensor further includes a sensor head that holds the crystal resonator in a liquid-tight manner by a seal member that presses the periphery of the crystal resonator and heats the crystal resonator by heat transfer from a heating unit. As described above, the structure in which the crystal unit is held in a liquid-tight manner by the seal member reduces the influence of the fixed state of the crystal unit, and the crystal unit is heated by heat transfer from the heating unit. The temperature difference between the sensor head and the etching solution becomes small, and the influence of the temperature change of the crystal resonator is less likely to occur, and the silicon concentration can be measured with higher accuracy.

  In that case, the inside of the crystal unit is provided with an internal space that communicates with the outside only through the communication path, and a valve member that is provided in the communication path and closes the communication path when liquid flows into the internal space. It is preferable. With this configuration, when the internal space expands due to heating of the sensor head, air can be discharged through the communication path, and when the crystal unit is damaged and the etching liquid flows into the internal space of the sensor head The problem at the time of breakage can be avoided by closing the communication path with the valve member.

The schematic block diagram which shows an example of the measuring apparatus of the silicon concentration of this invention The schematic block diagram which shows an example of the measuring apparatus of the etching selectivity of this invention Sectional drawing which shows an example of the principal part of the measuring apparatus of the silicon concentration of this invention Sectional drawing which shows an example of the sensor head for silicon concentration measurement of this invention Sectional drawing which shows the decomposition | disassembly state of an example of the sensor head for silicon concentration measurement of this invention Graph showing silicon wafers deposited with silicon oxide immersed in a phosphoric acid solution and etched, changing the silicon concentration and phosphoric acid temperature, and measuring the etching rate The flowchart which shows an example of the data processing in a calculating means Sectional drawing which shows the other example of the principal part of the measuring apparatus of the silicon concentration of this invention The top view which shows the other example of the principal part of the measuring apparatus of the silicon concentration of this invention The schematic block diagram which shows the other example of the measuring apparatus of the silicon concentration of this invention Etching the silicon oxide film coated on the crystal unit while changing the silicon concentration in the phosphoric acid etching solution (temperature 150 ° C., phosphoric acid concentration 87% by weight), and measuring the amount of change in vibration frequency while vibrating the crystal unit Graph showing the results A graph showing the difference in the change over time in the frequency of the crystal unit (QCM), the phosphoric acid temperature, and the temperature of the crystal unit depending on whether the sensor head is preheated or not. The graph which shows the relationship between the phosphoric acid density | concentration and the etching rate of a silicon nitride film in different temperature (150 degreeC, 160 degreeC, 170 degreeC).

(Silicon concentration measuring device)
As shown in FIG. 1A, a silicon concentration measuring apparatus according to the present invention includes a crystal resonator 11 coated with a silicon oxide film to be brought into contact with an etching solution 25 of a substrate processing apparatus 26 such as a wafer processing apparatus, and the crystal resonator 11. And vibration frequency detecting means 21 for detecting the vibration frequency. In the present embodiment, an example in which the measurement container 10 is provided in the circulation pipe 27 and the crystal unit 11 is brought into contact with the etching solution 25 inside the measurement container 10 is shown.

  The etching solution 25 may be of any type as long as the etching rate of the silicon oxide film changes according to the silicon concentration. For example, a mixed solution of phosphoric acid and a diluted solution such as water, or a diluted solution of sulfuric acid and water, etc. Examples thereof include a mixed solution with a liquid, hydrofluoric acid, buffered hydrofluoric acid and the like. In this embodiment, an example in which a silicon nitride film is etched by immersing a substrate (for example, a silicon wafer for semiconductor, not shown) using a high-temperature mixed solution of phosphoric acid and water is shown.

  The quartz oscillator 11 is covered with a silicon oxide film, but a silicon oxide film can be formed on one or both of the electrodes provided on the surface of a flat plate-like quartz plate. In the present embodiment, an example in which the crystal resonator 11 is held by the sensor head 12 and a silicon oxide film is formed on one of the electrodes is shown.

  The silicon oxide film can be formed by sputtering, reactive sputtering, vacuum deposition, or the like. However, by forming the silicon oxide film by sputtering, the etching rate can be increased, and the detection sensitivity of the etching rate can be improved. it can. If a uniform silicon oxide film can be formed at low cost, other film forming methods may be used. For example, chemical vapor deposition (CVD) (thermal CVD, plasma CVD, photo CVD, etc.), application of organic silicon material, It may be fired.

  The formation of the silicon oxide film can be performed up to a thickness of 500 nm. When the etching rate of the silicon oxide film is about 0.25 nm / min, if it is used for 10 minutes, it is used for measurement about 200 times. be able to. The quartz crystal resonator 11 covered with the silicon oxide film is replaced according to the consumption level of the silicon oxide film.

  In the present invention, the etching rate of the silicon oxide film can be measured using the principle of QCM (quartz crystal microbalance method). The QCM is a mass sensor that measures the amount of adhesion using the property that the resonance frequency changes according to the mass of the substance adhering to the surface of the crystal unit 11. As shown in FIG. 2A, the crystal unit 11 is preferably held by a sensor head 12 inside the measurement container 10. The measurement container 10 including the sensor head 12 will be described in detail later.

  The frequency detector 21 is electrically connected to the crystal unit 11 and detects the vibration frequency while vibrating the crystal unit 11. Various types of QCM sensors are commercially available, and an oscillation circuit that vibrates the QCM sensor and a measuring device for performing mass measurement using the QCM sensor are also commercially available. These apparatuses utilize the principle of QCM, and Japanese Patent Application Laid-Open No. 10-92789 and Japanese Translation of PCT International Application No. 2002-500828 disclose examples applied to the measurement of the etching rate.

  The quartz crystal resonator 11 using the QCM principle can calculate the mass change amount of the adhered substance from the change in the vibration frequency, as shown in the following Zawelbray equation. Therefore, by measuring the change amount of the vibration frequency at a predetermined time interval, this mass change amount per unit time, that is, the etching rate can be obtained. Further, from this equation, it can be understood that the change rate of the vibration frequency and the etching rate are in a proportional relationship.

As shown in FIG. 1A, the silicon concentration measuring apparatus of the present invention preferably includes means for controlling the temperature of the etching solution 25 to be constant or temperature measuring means 22 for measuring the temperature. The temperature measuring means 22 includes a temperature sensor 22a, and a thermocouple, a resistance temperature detector, or the like is used as the temperature sensor 22a.
As a method for controlling the temperature and concentration of the etching solution to be constant, a method described in the item of the prior art in JP-A-11-154665 can be cited. For example, when the etching solution is a phosphoric acid aqueous solution, use a heating device having a heater power equal to or higher than the boiling point of the phosphoric acid aqueous solution, and control the amount of pure water input so that the temperature of the phosphoric acid aqueous solution maintains the boiling temperature while continuing heating. Thus, the temperature and phosphoric acid concentration of the phosphoric acid aqueous solution are kept constant.

  In addition, the silicon concentration measuring device of the present invention is provided with a calculating means 24, which calculates the silicon concentration in the etching liquid 25 based on the temperature of the etching liquid 25 and the change rate of the vibration frequency. calculate. At that time, the correlation between the change rate of the vibration frequency and the silicon concentration can be used (see FIG. 8). However, the etching rate of the silicon oxide film calculated from the change of the vibration frequency of the crystal resonator 11 and the silicon concentration It is also possible to calculate the silicon concentration in the etching solution 25 based on the correlation with the etching rate of the silicon oxide film. As the correlation used at this time, a correlation considering at least the temperature of the etching solution 25 is used.

  FIG. 3 is a graph showing the results of etching by immersing a silicon wafer on which silicon oxide is deposited in phosphoric acid (aqueous solution having a phosphoric acid concentration of 87.4% by weight), changing the silicon concentration and the phosphoric acid temperature, and measuring the etching rate. It is. As this result shows, the silicon concentration and the etching rate of the silicon oxide film have a high correlation, and the correlation differs depending on the temperature of the etching solution 25.

  The graph of FIG. 3 shows the measurement results when the phosphoric acid concentration is 87.4% by weight. When the phosphoric acid concentration is changed, the silicon concentration at the temperature of the etching solution 25 and the silicon oxide film at each phosphoric acid concentration are shown. The correlation with the etching rate is different.

  Therefore, in the present invention, in particular, when the phosphoric acid concentration in the etching solution 25 changes, it is preferable to use a correlation that takes into account the phosphoric acid concentration in addition to the temperature of the etching solution 25. For this reason, in this invention, it is preferable to further contain the density | concentration measurement means 23 which measures the phosphoric acid density | concentration in etching liquid. In the present embodiment, an example in which the concentration measuring unit 23 includes a measurement cell 23a and the measurement cell 23a is provided in the circulation pipe 27 is shown. The concentration measuring means 23 will be described in detail later.

  Therefore, in the present embodiment, the calculation means 24 is based on the correlation between the silicon concentration at the temperature and the phosphoric acid concentration of the etching solution 25 and the change rate of the vibration frequency (or the etching rate of the silicon oxide film). An example of calculating the silicon concentration is shown.

  As the calculation means 24, a microcomputer, a personal computer, or the like can be used, and the above calculation can be performed using the correlation data 24a stored in the storage device. As the correlation data 24a, a function obtained by formulating the correlation as shown in FIG. 3 can be used. Such a function is set according to the temperature of the etching solution 25 and the phosphoric acid concentration. Further, from the graph as shown in FIG. 8, the correlation between the silicon concentration and the change rate of the vibration frequency is obtained, and a function obtained by formulating this can be used.

  The calculation by the calculation means 24 is executed according to the computer program, for example, according to the flow shown in FIG. In this example, the calculation means 24 fetches sampling data at a fixed time interval and calculates.

  In step S1, a time standby for performing the following steps S2 to S5 is performed in accordance with a preset sampling time interval. For example, 60 to 600 seconds are set as the sampling time interval.

  In step S2, the frequency is sampled by the frequency detection means 21. The frequency detection means 21 outputs a frequency and a value corresponding to the frequency, but it is also possible to calculate and output the mass of the adhered substance. By outputting such values at regular time intervals, the calculation means 25 can determine the rate of change of the vibration frequency per unit time and / or the etching rate.

  In step S3, temperature sampling is performed by the temperature measuring means 22. The temperature measuring means 22 outputs a temperature and a value corresponding to the temperature. By outputting such values at regular time intervals, the correlation data 24a corresponding to the temperature at that time can be taken into the computing means 25.

  In step S4, the phosphoric acid concentration is sampled by the concentration measuring means 23. The concentration measuring means 23 outputs a phosphoric acid concentration and a value corresponding to this. By outputting such values at regular time intervals, the correlation data 24a corresponding to the phosphoric acid concentration at that time can be taken into the computing means 25.

  In step S5, the correlation data 24a taken into the calculation means 25 is correlated with the temperature of the etching solution 25 and the change rate of the vibration frequency and / or the etching rate of the silicon oxide film at the time of the phosphoric acid concentration. Used as a relationship. Based on this correlation, the calculation means 25 calculates the silicon concentration in the etching solution 25 from the change rate of the vibration frequency and / or the etching rate.

  In step S6, the result obtained by the calculation means 25 in step S5 is output. The output form may be display on a display device, printing, or the like, but it may be output as an operation signal for controlling the silicon concentration, the etching rate, or the like. In that case, the silicon concentration, the etching rate, and values corresponding to these are output.

(Etching selectivity measurement device)
The etching selectivity measuring apparatus of the present invention measures the etching selectivity using the method for measuring the silicon concentration of the present invention as described above. As shown in FIG. 1B, the etching selectivity measuring apparatus of the present invention has a crystal resonator 11 coated with a silicon oxide film to be brought into contact with the etching solution 25 of the substrate processing apparatus 26, and vibrates the crystal resonator 11. And a frequency detection means 21 for detecting the vibration frequency. In the present embodiment, an example in which the measurement container 10 is provided in the circulation pipe 27 and the crystal unit 11 is brought into contact with the etching solution 25 inside the measurement container 10 is shown.

  The type of the etching solution 25 may be any as long as etching of the silicon nitride film and the silicon oxide film occurs. For example, a mixed solution of phosphoric acid and a diluted solution such as water, or a diluted solution such as sulfuric acid and water. A mixed liquid etc. are mentioned.

  As shown in FIG. 1B, the etching selectivity measuring apparatus of the present invention preferably includes a concentration measuring means 23 for measuring the phosphoric acid concentration in the etching solution. In the present embodiment, an example in which the concentration measuring unit 23 includes a measurement cell 23a and the measurement cell 23a is provided in the circulation pipe 27 is shown. The concentration measuring means 23 will be described in detail later.

  Moreover, it is preferable that the apparatus for measuring an etching selectivity of the present invention includes a temperature measuring unit 22 that measures the temperature of the etching solution 25. The temperature measuring means 22 includes a temperature sensor 22a, and a thermocouple, a resistance temperature detector, or the like is used as the temperature sensor 22a.

  In addition, the etching selectivity measurement apparatus of the present invention includes a calculation unit 24, and the calculation unit 24 measures the etching rate of the silicon oxide film calculated from the change in the vibration frequency of the quartz crystal resonator 11, and is measured or constant. On the basis of the etching rate of the silicon nitride film calculated from the concentration and temperature of the etching solution 25 controlled to the above, the ratio of the etching rate of the silicon nitride film / silicon oxide film is continuously calculated. At this time, it is preferable that the etching rate of the silicon nitride film is continuously calculated from the concentration and temperature of the etching solution 25 based on the correlation between the etching rate of the silicon nitride film and these. As a method for controlling the temperature and concentration of the etching solution to be constant, a method described in the item of the prior art in JP-A-11-154665 can be cited. For example, when the etching solution is a phosphoric acid aqueous solution, use a heating device having a heater power equal to or higher than the boiling point of the phosphoric acid aqueous solution, and control the amount of pure water input so that the temperature of the phosphoric acid aqueous solution maintains the boiling temperature while continuing heating. Thus, the temperature and phosphoric acid concentration of the phosphoric acid aqueous solution are kept constant.

  In the present invention, it is preferable to further perform calculation processing for calculating the silicon concentration in the etching solution 25 from the calculated etching rate of the silicon oxide film by the calculation means 24. However, the silicon concentration can also be calculated based on the correlation between the change rate of the vibration frequency and the silicon concentration.

  That is, as shown in FIG. 8, it was found that the change rate of the vibration frequency is different when the silicon concentration is different, but both are highly correlated. The change rate of the vibration frequency is proportional to the etching rate (etching rate) of the silicon oxide film based on the principle of QCM. In addition, as shown in FIG. 3, the etching rate of the silicon oxide film and the silicon concentration show a high correlation when the temperature of the etching solution and the phosphoric acid concentration are constant, but the correlation also changes when the temperature is different. To do. In this way, the present invention utilizes the high correlation between the change rate of the vibration frequency and the silicon concentration in the etching solution, and in this case, the influence of the temperature of the etching solution is taken into consideration, thereby Concentration can be measured continuously in-line.

  On the other hand, the silicon concentration in the etching solution 25 can be calculated based on the correlation between the etching rate of the silicon oxide film calculated from the change in the vibration frequency of the quartz crystal resonator 11 and the etching rate of the silicon concentration and the silicon oxide film. Is possible. As the correlation used at this time, a correlation considering at least the temperature of the etching solution 25 is used.

  As the calculation means 24, a microcomputer, a personal computer, or the like can be used, and the above calculation can be performed using the correlation data 24a stored in the storage device. The correlation data 24a includes correlation data for calculating the etching rate of the silicon nitride film and correlation data for calculating the silicon concentration in the etching solution 25.

  As correlation data for calculating the silicon concentration, a function obtained by formulating the correlation as shown in FIG. 3 and the like can be used. Such a function is set according to the temperature of the etching solution 25 and the phosphoric acid concentration. Further, from the graph as shown in FIG. 8, the correlation between the silicon concentration and the change rate of the vibration frequency is obtained, and a function obtained by formulating this can be used.

  As correlation data for calculating the etching rate of the silicon nitride film, a function obtained by formulating the correlation as shown in FIG. 10 can be used. FIG. 10 is a graph showing the relationship between the phosphoric acid concentration and the etching rate of the silicon nitride film at different temperatures (150 ° C., 160 ° C., and 170 ° C.). It can be understood that the etching rate of the silicon nitride film can be calculated based on the correlation with the etching rate of the film.

  The calculation by the calculation means 24 is executed according to the computer program, for example, according to the flow shown in FIG. In this example, the calculation means 24 fetches sampling data at a fixed time interval and calculates. The processing in each step S1 to S6 is as described above.

  In particular, in step S5, the correlation data 24a captured by the computing means 25 is used as a correlation for calculating the etching rate of the silicon nitride film from the concentration and temperature of the etching solution 25 at that time. Based on the calculated etching rate of the silicon nitride film and the etching rate of the silicon oxide film calculated as described above, the ratio of the etching rate of the silicon nitride film / silicon oxide film is continuously calculated. .

  Further, the correlation data 24a is used as a correlation between the temperature of the etching solution 25 and the change rate of the vibration frequency and / or the etching rate of the silicon oxide film at the temperature and the phosphoric acid concentration of the time. Based on this correlation, the calculation means 25 can calculate the silicon concentration in the etching solution 25 from the change rate of the vibration frequency and / or the etching rate.

  In the present invention, the calculation of the ratio of the etching rates may include a calculation process for converting the etching rate of the silicon oxide film coated on the crystal unit 11 into the etching rate of the silicon oxide film formed on the substrate. preferable. This arithmetic processing can be performed based on the correlation between the etching rate of the silicon oxide film obtained in advance and the etching rate of the silicon oxide film formed on the substrate. Since both are normally in a proportional relationship, a specific proportional constant can be used as the correlation.

  In step S6, the result obtained by the calculation means 25 in step S5 is output. The output form may be display by a display device, printing, or the like, but it may be output as an operation signal for controlling the etching selection ratio, silicon concentration, etching rate, and the like. In that case, an etching selection ratio, a silicon concentration, an etching rate, and values corresponding to these are output.

(Measurement method of silicon concentration)
The silicon concentration measuring method of the present invention can be preferably carried out using the silicon concentration measuring apparatus of the present invention as described above. That is, the method for measuring the silicon concentration of the present invention includes a step of contacting a silicon oxide film coated on the crystal resonator 11 with the etching solution 25 of the substrate processing apparatus and detecting the vibration frequency while vibrating the crystal resonator 11; And a step of calculating the silicon concentration in the etching solution 25 based on the change rate of the vibration frequency. In the above-described embodiment, the step of measuring the temperature of the etching solution 25 is further included, and the silicon concentration in the etching solution 25 is calculated based on the temperature of the etching solution 25 and the change rate of the vibration frequency.

  As described above, the step of calculating the etching rate of the silicon oxide film can be performed using the substrate processing apparatus 26, the crystal resonator 11, the frequency detecting means 21, and the calculating means 24 as shown in FIG. . Further, the step of measuring the temperature of the etching solution can be performed using the temperature measuring means 22. Furthermore, the step of calculating the silicon concentration can be performed using the calculation means 24 in the flow as shown in FIG.

  The present invention further includes a step of measuring the phosphoric acid concentration in the etching solution 25 as in the above-described embodiment, and in the step of calculating the silicon concentration in the etching solution 25, the temperature, phosphoric acid concentration and vibration of the etching solution 25 are calculated. It is preferable to calculate the silicon concentration in the etching solution 25 based on the frequency change rate. The step of measuring the phosphoric acid concentration can be performed using the concentration measuring means 23 for measuring the phosphoric acid concentration. Moreover, it is preferable to include the step of calculating the etching rate of the silicon oxide film based on the change rate of the vibration frequency. Furthermore, it is preferable to implement the silicon concentration measuring method of the present invention using the sensor head 12 of the present invention as described later.

(Measurement method of etching selectivity)
The method for measuring the etching selectivity of the present invention can be preferably carried out using the etching selectivity measuring apparatus of the present invention as described above. That is, the method for measuring the etching selectivity of the present invention etches the silicon oxide film from the change in the vibration frequency of the crystal unit 11 while bringing the silicon oxide film coated on the crystal unit 11 into contact with the etching solution 25 of the substrate processing apparatus. Based on the step of continuously calculating the rate, the step of continuously calculating the etching rate of the silicon nitride film of the etching solution 25, and the calculated etching rate of the silicon oxide film and the etching rate of the silicon nitride film, And a step of continuously calculating an etching rate ratio of the silicon nitride film / silicon oxide film. At this time, it is preferable to continuously calculate the etching rate of the silicon nitride film from the measured concentration and temperature while measuring the concentration and temperature of the etching solution 25.

  As described above, the step of calculating the etching rate of the silicon oxide film can be performed using the substrate processing apparatus 26, the crystal resonator 11, the frequency detecting means 21, and the calculating means 24 as shown in FIG. . Further, as described above, the step of calculating the etching rate of the silicon nitride film can be performed using the temperature measuring means 22, the concentration measuring means 23, and the calculating means 24 as shown in FIG. Further, the step of calculating the ratio of the etching rates and the step of calculating the silicon concentration can be performed using the calculation means 24 in the flow as shown in FIG.

  The present invention further includes a step of measuring the phosphoric acid concentration in the etching solution 25 as in the above-described embodiment, and in the step of calculating the silicon concentration in the etching solution 25, the temperature, phosphoric acid concentration and vibration of the etching solution 25 are calculated. It is preferable to calculate the silicon concentration in the etching solution 25 based on the frequency change rate. The step of measuring the phosphoric acid concentration can be performed using the concentration measuring means 23 for measuring the phosphoric acid concentration. Furthermore, the method for measuring the etching selectivity of the present invention is preferably carried out using a sensor head 12 as described later.

(Sensor head for silicon concentration measurement)
As shown in FIGS. 2A to 2C, the sensor head 12 used in the method for measuring the etching selectivity of the present invention includes a crystal resonator 11 coated with a silicon oxide film and a crystal by pressing the periphery of the crystal resonator 11. A seal member 13 that holds the vibrator 11 in a liquid-tight manner and a heating unit 14 that heats the quartz vibrator 11 by heat transfer are provided.

  As shown in FIG. 9, when the sensor head 12 is not preheated, the temperature of the crystal unit 11 is not stabilized due to the temperature difference between the sensor head 12 and the etching solution 25, and the frequency is not stabilized under the influence. On the other hand, when the sensor head 12 is preheated, the temperature difference between the sensor head 12 and the etching solution 25 becomes small, the temperature of the crystal unit 11 stabilizes quickly, and the frequency stabilizes early due to the influence. It has been found.

  By heating the crystal unit 11 by heat transfer from the heating means 14 in this way, the temperature difference between the sensor head 12 and the etching solution 25 is reduced, and the influence (measurement error) due to the temperature change of the crystal unit 11 occurs. It is difficult to measure the silicon concentration with higher accuracy.

  As shown in FIG. 2C, in the illustrated example, the seal member 13 includes an outer seal member 13a and an inner seal member 13b. The inner seal member 13b has an L-shaped cross section, and when the outer seal member 13a is fitted therein, the periphery of the crystal unit 11 is pressed by the outer seal member 13a and the inner seal member 13b. The The seal member 13 is formed of a corrosion-resistant material such as a fluororesin such as PTFE or fluororubber. In the present invention, it is preferably formed of a fluororesin such as PTFE or a perflo-based material having a high etching solution temperature and high heat resistance.

  Further, the seal member 13 is held by the frame member 15 when the inner seal member 13 b is fitted into the frame member 15. With this structure, the sensor unit 12 can be easily replaced without damaging the crystal unit 11. The frame member 15 is formed of a material such as a fluorine resin such as PTFE, a glass epoxy resin, FRP, CFRP, or glassy carbon.

  The frame member 15 is fitted and held in the sensor base 16. By making the frame member 15 and the sensor base 16 separable, when the crystal unit 11 is replaced, the entire frame member 15 can be safely replaced without being damaged. The sensor base 16 is made of a material such as fluororesin such as PTFE, glass epoxy resin, FRP, CFRP, or glassy carbon.

  The inner seal member 13b, the frame member 15, and the sensor base 16 are provided with a through hole 16a for allowing the pin 17 to pass therethrough. By penetrating the pin 17, the pin 17 can be electrically connected to the electrode terminal of the crystal unit 11.

  The heating means 14 is constituted by a surface heater or the like, and is fixed to the sensor head 12 by fastening the male screw portion 19d of the second hanging 19b to the female screw portion 19c of the first hanging 19a. The second handling 19b has a through-hole 19f for penetrating a pin or the like for electrical connection with the heating means 14. In this case, the surface heater or the like is preferably a heater such as a heat-resistant / chemical-resistant rubber or a heat-resistant / chemical-resistant film, such as a rubber heater or a Kapton heater.

  The sensor base 16 is fixed to the sensor head 12 by fastening the male threaded portion 18a of the nut member 18 to the female threaded portion 19e of the second hanging 19b. At that time, the seal member 13 that holds the crystal resonator 11 in a liquid-tight manner is in close contact with the inner surface of the first hanging 19 a and is fixed to the sensor head 12. The nut member 18 is made of a fluororesin such as PTFE or a material such as PEEK.

  Inside the nut member 18, a socket holder 31 having an insertion opening 31 a for the pin 17 is inserted. The insertion port 31a has an O-ring, and the pin 17 is inserted in a liquid-tight state and is electrically connected to the socket pin 31b. An O-ring is also held on the outer peripheral surface and the outer wall surface of the socket holder 31, so that liquid does not enter the sensor head 12.

  The sensor head main body 32 is provided with a female screw portion 32a, and the whole is fixed to the sensor head main body 32 by screwing the male screw portion 19d of the second hanging 19b. An O-ring is also held on the outer wall surface of the sensor head main body 32, which is in close contact with the inner wall surface of the first hanging 19a, resulting in a liquid-tight structure. The first hanging 19a, the second hanging 19b, and the socket holder 31 are made of a heat-resistant, chemical-resistant, and good heat-conductive material such as glassy carbon.

  As shown in FIG. 2B (not shown in FIG. 2C), the sensor head 12 includes an internal space 16b that communicates with the inside of the crystal unit 11 only through the communication path 16c, and an internal space 16b that is provided in the communication path 16c. It is preferable to include a valve member 16d that closes the communication path 16c when the liquid flows in.

  In the present embodiment, an example in which the valve member 16d is provided as a spherical floating body in the space where the diameter of the communication path 16c is expanded is shown. Since this floating body is usually located in the lower part of the expanded space, when the internal space 16b expands due to the heating of the sensor head 12, air can be discharged through the communication path 16c. In addition, when the crystal unit 11 is damaged and the etching solution 25 flows into the internal space 16b of the sensor head 12, the communication path 16c is blocked by a floating body, which is caused by corrosion generated by the chemical solution at the time of damage. Problems in the electric circuit can be avoided.

  As the floating body, a material having a specific gravity lighter than the etching solution 25 or a hollow ball shape can be used. Further, the boundary between the communication path 16c and the expanded space functions as a valve seat. In this invention, it may replace with such a floating body and may provide the valve member 16d which act | operates by the inflow pressure of a liquid and obstruct | occludes the communicating path 16c.

  As shown in FIG. 2A, the sensor head main body 32 is a container having an open side surface, and a first housing 19a and the like are provided on the side surface to form a sealed structure. The sensor head main body 32 is fixed to the measurement container 10 via the connecting portion 23 for passing the wiring 24, and thereby the sensor head 12 is provided inside the measurement container 10. The sensor head main body 32 is formed of a material such as a fluororesin such as PEEK or PTFE.

  As shown in FIG. 1, the measurement container 10 is provided in a circulation pipe 27 for the etching solution 25. The circulation pipe 27 is provided with a pump 27a for performing circulation. Thereby, the etching rate can be measured in more real time.

  The measurement container 10 is provided with an introduction portion 29 and a discharge portion 35 for the etching solution 25, and also includes an exhaust portion 36 for initial exhaust. In addition, thermocouple introduction portions 33 and 34 for temperature measurement and temperature control in the measurement container 10 are provided.

  Further, a rubber heater 26 for heating the inside is provided on the outer periphery of the container body 25, and a heat insulating material 27 is provided on the outer periphery thereof. The upper surface of the container body 25 is open, and the sensor head 12 is hermetically sealed by a lid body 28 attached via a connecting portion 23. The lid body 28 is fastened to the container body 25 by bolts or the like.

  Further, the crystal unit 11 preferably has a high vibration frequency up to about 30 MHz, so that various external noises enter the measurement system. The main noise includes a wide variety of noises such as those caused by electromagnetic waves from the outside and those caused by high temperature, temperature change, and flow of the etching solution 25 that is an electrolyte. For this reason, the above-mentioned member needs to be grounded as a conductor. For example, the first hanging 19a and the second hanging 19b may be glassy carbon as a conductor, but members such as the sensor head body 32 may be made of conductive fluororesin mixed with a conductor such as carbon fiber. CFRP (carbon resin reinforced plastic) or the like, and all exterior members constituting the sensor head 12 for measuring the silicon concentration may be made into a conductor and grounded. Further, the wiring between the silicon concentration measuring sensor head 12 and the frequency detecting means 21 is a coaxial cable that is resistant to external noise, which is further covered with a wiring coating on which a conductor is formed. It only has to be grounded. In this way, it is possible to prevent a wide variety of external noises from entering the measurement system, and it is possible to perform more accurate frequency measurement.

(Measuring means for phosphoric acid concentration)
The phosphoric acid concentration measuring means 23 is preferably a spectroscopic measuring means for measuring the concentration of the etching solution 25 by measuring the light absorption characteristics of the etching solution 25. Thereby, the phosphoric acid concentration in the etching solution 25 can be measured in-line in real time, and the silicon concentration can be calculated with higher accuracy by utilizing the correlation in the phosphoric acid concentration. The phosphoric acid concentration is also used for calculating the etching rate of the silicon nitride film.

  The light absorption characteristic of the etching solution 25 can be measured by the intensity value of the transmitted light. Specifically, the phosphoric acid solution to be measured is introduced into the light transmitting part of the measuring cell 25a, and light having a different wavelength with respect to the light transmitting part. Then, the intensity value of the transmitted light is measured, the absorbance is calculated from the intensity value, and the concentration of the acid in the phosphoric acid solution can be determined using the absorbance and the calibration curve equation.

  The calibration curve type is a method in which a sample of a phosphoric acid solution having a known concentration is introduced into a light transmission cell or the like, and light having a different wavelength in the infrared wavelength region is transmitted to the measurement cell 25a and the like, and the intensity value of the transmitted light is measured. By repeating this measurement for a plurality of samples and calculating the absorbance from the intensity values of the plurality of samples, a calibration curve equation between the absorbance and the acid concentration in the phosphoric acid solution can be obtained.

  Details of such spectroscopic phosphoric acid concentration measuring means are described in JP2013-51334A, JP2012-028580A, and the like, and the present invention is implemented using these. be able to.

[Another embodiment]
The present invention is not limited to the above-described embodiment, and the embodiment can be modified as follows.

  (1) In the above embodiment, the measurement container 10 is provided in the circulation pipe 27 of the substrate processing apparatus 26, and the crystal resonator 11 is brought into contact with the etching solution 25 therein. It is also possible to provide the measurement container 10 in the continuous waste liquid piping of the etching liquid 25 of the processing device 26.

  Further, as shown in FIGS. 5 to 6, a flow cell 38 may be provided in the pipe 37, and the crystal unit 11 may be brought into contact with the etching solution 25 therein. In that case, the sensor head 12 similar to that of the above-described embodiment is provided, but it is preferable that the flow cell 38 has a circular shape in plan view corresponding to the sensor head 12. Further, as shown in the figure, when the sensor head 12 is arranged so that the crystal resonator 11 is horizontal, the moving direction of the floating body that closes the communication path when the liquid flows into the internal space becomes vertical. In addition, it is preferable to form a space having an enlarged diameter.

  (2) In the above-described embodiment, the example using the sensor head for measuring the etching selectivity is shown. However, as shown in FIG. 7, the present invention can be implemented using a commercially available QCM sensor as it is. is there. In that case, the QCM sensor coated with the silicon oxide film can be immersed in the etching solution 25 as it is, or the temperature sensor 22a of the temperature measuring means 22 can be immersed in the etching solution 25 in the same manner.

  (3) The above embodiment further includes a concentration measuring means 23 for measuring the phosphoric acid concentration in the etching solution 25, and the computing means 24 is based on the temperature of the etching solution 25, the phosphoric acid concentration, and the change rate of the vibration frequency. In the present invention, the silicon concentration in the etching solution 25 is calculated. However, in the present invention, the measurement of the phosphoric acid concentration can be omitted when the silicon concentration is calculated. In that case, for example, a correlation using an average etching solution temperature may be used in the measurement period.

  (4) In the above embodiment, an example in which a silicon nitride film is etched with a phosphoric acid solution in a semiconductor wafer process has been described. However, in the present invention, a silicon oxide film is formed using hydrofluoric acid, buffered hydrofluoric acid, or the like. The same can be applied to the etching. That is, the etching rate and the silicon concentration in these etching solutions also have a certain correlation, which depends on the temperature of the etching solution. In that case, the concentration measuring means for measuring the phosphoric acid concentration is omitted.

  (5) In the above embodiment, in the step of calculating the etching rate of the silicon nitride film, the etching rate of the silicon nitride film is continuously calculated from the measured concentration and temperature while measuring the concentration and temperature of the etching solution. However, it is also possible to continuously calculate the etching rate of the silicon nitride film from the concentration and / or temperature of the etching solution while controlling the concentration and / or temperature of the etching solution to be constant. is there. As a method for controlling the concentration and / or temperature of the etching solution to be constant, in addition to a method using an indicating controller such as a temperature indicating controller (TIC), means for detecting the concentration and / or temperature of the etching solution, and a concentration And / or a method for operating the temperature and a control unit for operating the operating unit so that the detected value approaches the set value based on a detection signal from the detecting unit. As control of the control means, PID (proportional / integral / derivative) control, ON / OFF control, or the like is possible.

11 Crystal resonator 12 Sensor head (Sensor head for silicon concentration measurement)
DESCRIPTION OF SYMBOLS 13 Seal member 14 Heating means 16b Internal space 16c Communication path 16d Valve member 21 Frequency detection means 22 Temperature measurement means 23 Concentration measurement means 24 Calculation means 25 Etching solution

Claims (22)

A step of contacting a silicon oxide film coated on a crystal resonator with an etching solution of a substrate processing apparatus and detecting a vibration frequency while vibrating the crystal resonator;
Calculating the silicon concentration in the etchant based on the change rate of the vibration frequency;
Method for measuring silicon concentration containing Further comprising measuring the temperature of the etchant;
The silicon concentration measurement according to claim 1, wherein in the step of calculating the silicon concentration in the etching solution, the silicon concentration in the etching solution is calculated based on the temperature of the etching solution and the change rate of the vibration frequency. Method. Further comprising measuring a phosphoric acid concentration in the etching solution;
The step of calculating the silicon concentration in the etching solution calculates the silicon concentration in the etching solution based on the temperature of the etching solution, the phosphoric acid concentration, and the change rate of the vibration frequency. The measuring method of silicon concentration as described.   The method for measuring a silicon concentration according to claim 1, further comprising a step of calculating an etching rate of the silicon oxide film based on a change rate of the vibration frequency.   The silicon concentration according to any one of claims 1 to 4, wherein a sensor head that holds the crystal resonator in a liquid-tight manner by a sealing member that presses the periphery of the crystal resonator and heats the crystal resonator by a heating unit. Measuring method. A quartz resonator coated with a silicon oxide film to be in contact with an etching solution of a substrate processing apparatus;
A frequency detecting means for detecting a vibration frequency while vibrating the crystal resonator;
Calculation means for calculating the silicon concentration in the etching solution based on the change rate of the vibration frequency;
A silicon concentration measuring device. A temperature measuring means for measuring the temperature of the etching solution;
The silicon concentration measuring apparatus according to claim 6, wherein the calculation unit calculates a silicon concentration in the etching solution based on a temperature of the etching solution and a change speed of the vibration frequency. A concentration measuring means for measuring a phosphoric acid concentration in the etching solution;
The silicon concentration measuring apparatus according to claim 6 or 7, wherein the calculation means calculates the silicon concentration in the etching solution based on the temperature of the etching solution, the phosphoric acid concentration, and the change rate of the vibration frequency.   The silicon concentration measuring apparatus according to claim 6, wherein the calculation means includes a calculation for calculating an etching rate of the silicon oxide film based on a change rate of the vibration frequency.   10. The silicon according to claim 6, further comprising a sensor head that holds the crystal resonator in a liquid-tight manner by a sealing member that presses the periphery of the crystal resonator and that heats the crystal resonator by a heating unit. Concentration measuring device.   A silicon concentration measurement comprising: a quartz resonator coated with a silicon oxide film; a seal member that presses around the quartz resonator to hold the quartz resonator in a liquid-tight manner; and a heating unit that heats the quartz resonator Sensor head.   12. An internal space that communicates with the outside only through a communication path inside the crystal unit, and a valve member that is provided in the communication path and closes the communication path when liquid flows into the internal space. 2. A sensor head for measuring a silicon concentration according to 1. A step of continuously calculating an etching rate of the silicon oxide film from a change in vibration frequency of the crystal resonator while contacting the silicon oxide film coated on the crystal resonator with an etching solution of the substrate processing apparatus;
Calculating an etching rate of the silicon nitride film of the etchant;
A step of continuously calculating a silicon nitride film / silicon oxide film etching rate ratio based on the calculated etching rate of the silicon oxide film and the etching rate of the silicon nitride film;
A method for measuring an etching selectivity including:   The step of calculating the etching rate of the silicon nitride film continuously calculates the etching rate of the silicon nitride film from the measured concentration and / or temperature while measuring the concentration and / or temperature of the etching solution. 14. The method for measuring an etching selectivity according to 13.   15. The calculation method according to claim 13, further comprising an arithmetic process for converting an etching rate of the silicon oxide film coated on the crystal resonator into an etching rate of the silicon oxide film formed on the substrate when calculating the ratio of the etching rates. Method for measuring the etching selectivity.   The method for measuring an etching selectivity according to any one of claims 13 to 15, further comprising a step of calculating a silicon concentration in the etching solution from the calculated etching rate of the silicon oxide film. A quartz resonator coated with a silicon oxide film to be in contact with an etching solution of a substrate processing apparatus;
A frequency detecting means for detecting a vibration frequency while vibrating the crystal resonator;
Calculation means for continuously calculating the ratio of the silicon nitride film / silicon oxide film etching rate based on the etching rate of the silicon oxide film and the etching rate of the silicon nitride film calculated from the change in the vibration frequency of the crystal resonator When,
An etching selectivity measurement apparatus including: It further comprises at least one of a concentration measuring means for measuring the concentration of the etching solution and a temperature measuring means for measuring the temperature of the etching solution,
Based on the etching rate of the silicon oxide film calculated from the change in the vibration frequency of the crystal resonator and the etching rate of the silicon nitride film calculated from the measured concentration and / or temperature of the etching solution. The apparatus for measuring an etching selectivity according to claim 17, wherein the ratio of the etching rate of the silicon nitride film / silicon oxide film is continuously calculated.   The calculation means includes calculation processing for converting an etching rate of a silicon oxide film coated on a crystal resonator into an etching rate of a silicon oxide film formed on a substrate when calculating a ratio of etching rates. An apparatus for measuring an etching selectivity according to 17 or 18.   20. The etching selectivity measuring apparatus according to claim 17, wherein the arithmetic means further performs arithmetic processing for calculating a silicon concentration in the etching solution from the calculated etching rate of the silicon oxide film.   21. The sensor head according to any one of claims 17 to 20, further comprising: a sensor head that holds the crystal resonator in a liquid-tight manner by a seal member that presses the periphery of the crystal resonator and heats the crystal resonator by heat transfer from a heating unit. The apparatus for measuring the etching selectivity described in the above. The sensor head includes an internal space that communicates with the outside only through a communication path inside the crystal unit, and a valve member that is provided in the communication path and closes the communication path when liquid flows into the internal space. The apparatus for measuring an etching selectivity according to claim 21.

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