Film thickness sensor

Abstract

To more accurately correct the temperature change of a film thickness sensor using a vibrator.SOLUTION: The film thickness sensor includes a film thickness measurement unit 100 and a temperature measurement unit 104. The temperature measurement unit 104 includes a sound wave propagation unit 105 and a sound speed measurement unit 106. The temperature measurement unit 104 measures the temperature of the environment in which the vibrator 101 is disposed based on the sound speed of the ultrasonic wave propagating through the vibrator 101. The film thickness measurement part 100 corrects the measurement result of the thickness of the thin film by using the temperature measured by the temperature measurement part 104.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film thickness sensor. [Background technology]

[0002] A film thickness sensor is known for use in film deposition equipment used in the manufacture of semiconductor devices. This film thickness sensor is composed of an oscillator made of a piezoelectric material and senses the amount of film (film thickness) deposited in the film deposition equipment. When a film is deposited on the oscillator and its mass changes, the resonant frequency changes. Therefore, by relating this change in resonant frequency to the change in deposited film thickness, a film thickness sensor can be used.

[0003] When the piezoelectric material used in a film thickness sensor is quartz, it is called a QCM (Quartz Crystal Microbalance), but it is not limited to quartz; other piezoelectric materials such as LiTaO3, LiNbO3, or AlN may also be used. This type of film thickness sensor's resonant frequency changes with temperature, so various measures are taken to ensure frequency stability against temperature.

[0004] For example, there are configurations that use an AT-Cut quartz crystal resonator, which has excellent temperature stability of the resonant frequency, or that store the film thickness sensor in a thermostatic chamber or place a heater nearby to keep the temperature around the film thickness sensor constant. Another configuration uses a temperature sensor to measure the surrounding temperature and provides a temperature compensation circuit that reduces frequency fluctuations due to temperature changes. Another configuration has been proposed in which a sensor with the same configuration is provided together with the film thickness sensor to cancel out changes in the resonant frequency due solely to temperature changes (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-033195 Summary of the Invention [Problem to be solved by the invention]

[0006] Placing the film thickness sensor in a thermostatic chamber or maintaining a constant temperature around the film thickness sensor using a heater placed near the film thickness sensor can greatly contribute to the temperature stability of the frequency. However, in a film deposition environment, the introduction of source gases and trace amounts of adsorbed and desorbed matter can cause sudden changes in the heat conduction state, resulting in temperature changes. It is difficult to compensate for such temperature changes that occur in a short period of time using heater control.

[0007] In addition, AT-Cut quartz crystal units exhibit excellent frequency temperature stability compared to other cut angles and other materials, but they exhibit temperature variations of approximately 30 ppm.

[0008] Furthermore, although a configuration that includes a temperature compensation circuit, such as a temperature-compensated crystal oscillator, is useful, the temperature changes of the temperature sensor and the film thickness sensor do not necessarily coincide due to differences in thermal conduction, and therefore it is difficult to say that this sufficiently compensates for frequency changes due to temperature changes.

[0009] In addition, a configuration is known in which a temperature sensor separate from the one used for film deposition sensing is installed within the same substrate, but the temperature sensor is installed at a position away from the film deposition sensor and is covered to prevent adhesion of foreign matter. As a result, the ambient environment and conditions of the sensor used for film deposition sensing are significantly different, and it is difficult to say that sufficient temperature compensation is achieved.

[0010] As described above, the conventional technology has a problem in that it is not possible to accurately correct the temperature change of a film thickness sensor using an oscillator.

[0011] The present invention has been made to solve the above problems, and has as its object to more accurately correct temperature changes in a film thickness sensor using an oscillator. [Means for solving the problem]

[0012] The film thickness sensor of the present invention comprises a vibrator, a first electrode and a second electrode formed facing each other across the vibrator, a film thickness measuring unit that measures the thickness of a thin film formed by deposits accumulated on the vibrator, and a temperature measuring unit that measures the temperature of the environment in which the vibrator is placed based on the sound speed of ultrasonic waves propagating through the object, and the film thickness measuring unit performs temperature compensation using the temperature measured by the temperature measuring unit.

[0013] In one configuration example of the above film thickness sensor, the temperature measurement unit includes an acoustic wave propagation unit formed with one end in contact with the temperature measurement area of ​​the vibrator surrounding the arrangement area of ​​the first electrode, and an acoustic velocity measurement unit formed at one end of the acoustic wave propagation unit and including an excitation unit made of a piezoelectric material and a third electrode and a fourth electrode formed on either side of the excitation unit, and which measures the acoustic velocity of ultrasonic waves propagating in the thickness direction of the vibrator.

[0014] In one configuration example of the above film thickness sensor, the temperature measurement unit includes an ultrasonic wave generating unit formed in contact with the temperature measurement area of ​​the vibrator surrounding the arrangement area of ​​the first electrode, and generating ultrasonic waves of a frequency different from the resonant frequency of the vibrator, and a temperature measurement circuit that causes the ultrasonic wave generating unit to generate ultrasonic waves and then detects the generated ultrasonic waves using the first electrode, thereby measuring the sound speed of the ultrasonic waves propagating through the vibrator between the ultrasonic wave generating unit and the first electrode, and determining the temperature from the measured sound speed.

[0015] In one example configuration of the above film thickness sensor, the film thickness measurement unit is arranged inside a thin film formation chamber of a thin film formation apparatus for forming a thin film from a deposit, and the temperature measurement unit is arranged around a fixing unit that fixes a wafer on which a thin film is to be formed, which is arranged inside the thin film formation chamber, and is equipped with an ultrasonic wave generation unit that applies ultrasonic waves to the back surface of the wafer fixed to the fixing unit, an ultrasonic wave receiving unit that is arranged on the fixing unit, and a temperature measurement circuit that generates ultrasonic waves in the ultrasonic wave generation unit and then detects the generated ultrasonic waves with the ultrasonic wave receiving unit, thereby measuring the sound speed of the ultrasonic waves propagating through the wafer between the ultrasonic wave generation unit and the ultrasonic wave receiving unit, and determines the temperature from the measured sound speed. [Effects of the Invention]

[0016] As described above, according to the present invention, the temperature of the film thickness measuring section is compensated for using the temperature measured by the temperature measuring section, which measures the temperature of the environment in which the vibrator is placed based on the sound speed of ultrasonic waves propagating through an object, so that temperature changes in the film thickness sensor using a vibrator can be corrected more accurately. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing the configuration of a film thickness sensor according to a first embodiment of the present invention. [Figure 2A] FIG. 2A is an explanatory diagram for explaining temperature measurement based on the sound speed of ultrasonic waves propagating through an object. [Figure 2B] FIG. 2B is an explanatory diagram for explaining temperature measurement based on the sound speed of ultrasonic waves propagating through an object. [Figure 2C] FIG. 2C is an explanatory diagram for explaining temperature measurement based on the sound speed of ultrasonic waves propagating through an object. [Figure 3] FIG. 3 is a diagram showing the configuration of a film thickness sensor according to the second embodiment of the present invention. [Figure 4] FIG. 4 is a plan view showing the configuration of a film thickness sensor according to the second embodiment of the present invention. [Figure 5] FIG. 5 is a plan view showing a partial configuration of a film thickness sensor according to the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] A film thickness sensor according to an embodiment of the present invention will be described below.

[0019] [Embodiment 1] First, a film thickness sensor according to a first embodiment of the present invention will be described with reference to Fig. 1. This film thickness sensor includes a film thickness measuring unit 100 and a temperature measuring unit 104.

[0020] Film thickness measurement unit 100 includes oscillator 101 and first and second electrodes 102 and 103 formed facing each other across oscillator 101. Oscillator 101 can be made of, for example, an AT-cut quartz crystal substrate. The thickness and electrode shape of oscillator 101 can be designed so that it resonates at, for example, 6 MHz.

[0021] The film thickness measuring unit 100 measures the thickness of a thin film formed by deposits deposited on the oscillator 101 (for example, on the first electrode 102). The film thickness measuring unit 100 also corrects (temperature compensates for) the measurement result of the thin film thickness using the temperature measured by the temperature measuring unit 104. Although not shown, the film thickness measuring unit 100 includes a measurement circuit that applies an excitation signal to the first electrode 102 and the second electrode 103, measures a change in the resonant frequency of the oscillator 101, and measures the thickness of the thin film deposited on the oscillator 101 based on the measured change in the resonant frequency. The excitation signal can be applied using, for example, a Colpitts-type oscillation circuit. This measurement circuit corrects (temperature compensates for) the measurement result of the thickness using the temperature measured by the temperature measuring unit 104.

[0022] The temperature measuring unit 104 measures the temperature of the environment in which the vibrator 101 is placed based on the sound speed of ultrasonic waves propagating through the object (vibrator 101). In the first embodiment, the temperature measuring unit 104 includes an acoustic wave propagating unit 105 and an acoustic speed measuring unit 106. One end of the acoustic wave propagating unit 105 is formed in contact with (joined to) the temperature measurement region of the vibrator 101 around the region where the first electrode 102 is placed. The acoustic wave propagating unit 105 can be made of sapphire, for example, and formed in a rod shape.

[0023] The sound velocity measuring unit 106 includes an excitation unit 107 made of a piezoelectric material such as AlN, and a third electrode 108 and a fourth electrode 109 formed on either side of the excitation unit 107. The sound velocity measuring unit 106 is formed at one end of the sound wave propagating unit 105, and measures the sound velocity of ultrasonic waves propagating in the thickness direction of the vibrator 101.

[0024] It is known that when ultrasonic vibrations are applied to an object from the outside, the applied vibrations propagate at a speed based on the physical properties (elastic constant, density, temperature, etc.) and shape of the object, known as the ultrasonic propagation velocity. Assuming that the physical properties of vibrator 101 do not change except for temperature, it is possible to measure the temperature change of vibrator 101 by measuring the ultrasonic propagation velocity propagating through vibrator 101 and capturing that change (Japanese Patent Laid-Open Publication No. 2008-070340).

[0025] When a predetermined signal is applied to the third electrode 108 and the fourth electrode 109, the excitation unit 107 generates an ultrasonic wave due to the inverse piezoelectric effect. This ultrasonic wave propagates to the transducer 101 via the sound wave propagation unit 105 and the junction between the sound wave propagation unit 105 and the transducer 101. A portion of the propagated ultrasonic wave is reflected at the junction toward the sound speed measurement unit 106 (first reflected wave 121), and a portion propagates through the transducer 101 and is reflected by the surface of the transducer 101 on which the second electrode 103 is formed (second reflected wave 122), returning to the sound speed measurement unit 106. The two main reflected waves (first reflected wave 121 and second reflected wave 122) that have returned to the sound speed measurement unit 106 are extracted as electrical signals due to the piezoelectric effect.

[0026] By using the difference information between the first reflected wave 121 and the second reflected wave 122 described above, it is possible to detect the temperature change of the transducer 101. The ultrasonic propagation speed of the excitation unit 107, the sound wave propagation unit 105, and the transducer 101 in the sound speed measurement unit 106 changes depending on the ambient temperature environment.

[0027] By observing the difference between the time it takes for the first reflected wave 121 to return to the sound speed measurement section 106 and the time it takes for the second reflected wave 122 to return to the sound speed measurement section 106, the influence of the change in the sound speed in the excitation section 107 and the sound wave propagation section 105 can be eliminated, and only the time Δt12 for the transducer 101 to travel back and forth in the thickness direction can be obtained (FIG. 2A).

[0028] If the thickness of the oscillator 101 is known, the speed of sound propagating through the oscillator 101 can be determined. Furthermore, if the temperature dependency of the sound waves propagating through the oscillator 101 is known, the temperature of the oscillator 101 can be determined from the determined sound speed. Note that if only the change in the differential time of the reflected wave is observed and the relative temperature change status can be obtained, this can provide sufficient information for monitoring the film formation process. Furthermore, if the temperature dependency of the sound wave speed is a linear curve, the relative temperature change can be obtained by multiplying the time change in the differential by a linear temperature coefficient.

[0029] If the time when the sound wave is emitted by the excitation unit 107 is T=0, and the times when the first reflected wave 121 and the second reflected wave 122 are detected by the sound velocity measurement unit 106 are t1 and t2, respectively, the relationship between these times is shown in FIG. 2A. The propagation time Δt12 of the sound wave propagating back and forth within the vibrator 101 is Δt12=t2-t1. The sound wave propagating through the film-thickness vibrator 101 changes with temperature. By monitoring Δt12, which changes with changes in the sound velocity, it is possible to observe temperature changes in the vibrator 101. Note that the sound velocity of the excitation unit 107 and the sound wave propagation unit 105 is also affected by temperature, but this effect acts in the same way on the first reflected wave 121 and the second reflected wave 122, so Δt12 depends only on the temperature change of the vibrator 101. If the thickness d of the transducer 101 is known, the sound velocity (or the amount of change in sound velocity) at a certain moment can be calculated by 2d / Δt12.

[0030] If the temperature coefficient of vibrator 101 (the gradient of the change in sound speed with respect to temperature) is known, the amount of change in temperature can be determined from the amount of change in sound speed. If the temperature dependency of vibrator 101 (horizontal axis: temperature, vertical axis: sound speed) is known, the absolute value of the sound speed at a certain moment can be determined. Even if the physical properties of vibrator 101, such as the thickness and temperature coefficient, are unknown, it is possible to determine the temperature from Δt12 by measuring Δt12 at multiple temperatures and determining the correlation equation between Δt12 and temperature.

[0031] Next, we will explain how to correct thickness measurement results (temperature compensation) in the film thickness measurement unit 100 by removing the effect of temperature from changes in the resonant frequency. Generally, the resonant frequency of the oscillator 101 is temperature dependent. The frequency-temperature characteristics of the oscillator 101 are determined in advance. This temperature characteristic can be used to determine the resonant frequency of the oscillator 101 (before film formation) at each temperature. Next, consider a case where the resonant frequencies of the oscillator 101 before and after film formation in a film formation apparatus in which the film thickness measurement unit 100 is installed are f1 and f2, respectively. The frequency change from f1 to f2 includes frequency changes due to the adsorption and desorption of the film formation substance to and from the oscillator 101 and frequency changes due to temperature changes in the film formation environment, including the oscillator 101.

[0032] Because Δt12 is measured before and after film formation, the temperatures TA and TB of the oscillator 101 before and after film formation can be easily calculated. The frequencies fA and fB at temperatures TA and TB are derived from the frequency-temperature characteristics of the oscillator 101. From the above, the frequency change of the oscillator 101 before and after film formation, excluding the influence of temperature changes, can be calculated from (f2 - f1) - (fA - fB).

[0033] The sound wave sent from the sound velocity measurement unit 106 (excitation unit 107) can also be a chirp wave (FIG. 2B). Similarly, if the signal applied to the excitation unit 107 is a chirp signal, the amount of change in the resonant frequency can be calculated excluding the influence of temperature changes (FIG. 2C).

[0034] Two IF signal frequency components can be obtained from the input chirp wave and the chirp signals reflected from one surface and the other surface of the oscillator 101 (Figure 2C). By observing the difference in this IF signal frequency, it is possible to capture changes in the speed of sound within the oscillator 101. Simply observe the change in the difference frequency of the IF signal, and observe the difference and the amount of change between the time when the IF signal due to the first reflected wave appears and the time when the IF signal due to the second reflected wave appears. This difference time can be multiplied by a temperature coefficient to convert it into a relative change in speed of sound. In addition, the absolute value of the speed of sound can be calculated using the thickness of the oscillator 101, and the absolute value of the temperature of the oscillator 101 can be calculated from the absolute value of the speed of sound.

[0035] It should be noted that Δt12 can be monitored at all times, not just before and after film formation, and the resonance frequency of the oscillator 101 can be constantly corrected (to remove the influence of temperature).

[0036] As described above, according to the first embodiment, it is possible to obtain the change in the resonant frequency of the vibrator due to the adsorption and desorption of deposits that accumulate (adsorb) on the vibrator, excluding (or taking into account) the influence of temperature changes. According to the first embodiment, it is possible to more accurately correct the temperature change of a film thickness sensor that uses a vibrator. Furthermore, according to the first embodiment, since the temperature measurement unit captures the temperature change of the vibrator itself, the delay time of the temperature change required for heat conduction is small, and the temperature change of the vibrator can be detected in real time with high accuracy. Note that the delay time associated with signal processing such as Fourier transform can be measured and corrected in advance to obtain a more accurate arrival time.

[0037] [Embodiment 2] Second Embodiment Next, a film thickness sensor according to a second embodiment of the present invention will be described with reference to Fig. 3. This film thickness sensor includes a film thickness measuring unit 100 and a temperature measuring unit 104a.

[0038] The film thickness measuring unit 100 includes an oscillator 101, and a first electrode 102 and a second electrode 103 formed facing each other with the oscillator 101 sandwiched between them. The film thickness measuring unit 100 measures the thickness of a thin film formed by deposits deposited on the oscillator 101 (for example, on the first electrode 102). The film thickness measuring unit 100 also performs temperature compensation using a temperature measured by a temperature measuring unit 104.

[0039] The film thickness measuring unit 100 includes a film thickness measuring circuit 111 that applies an excitation signal to the first electrode 102 and the second electrode 103, measures a change in the resonant frequency of the vibrator 101, and measures the thickness of the thin film deposited on the vibrator based on the measured change in the resonant frequency. In addition, the film thickness measuring circuit 111 performs temperature compensation using the temperature measured by the temperature measuring unit 104.

[0040] The temperature measuring unit 104a measures the temperature of the environment in which the transducer 101 is placed based on the sound speed of the ultrasonic waves propagating through the object (the transducer 101). In the second embodiment, the temperature measuring unit 104a includes an ultrasonic wave generating unit 110 and a temperature measuring circuit 112.

[0041] The ultrasonic wave generating unit 110 is formed in contact with the temperature measurement region of the vibrator 101 around the region where the first electrode 102 is arranged, and generates ultrasonic waves at a frequency different from the resonant frequency of the vibrator 101. The ultrasonic wave generating unit 110 can be provided at multiple locations on the vibrator 101, for example, as shown in FIG. 4. As shown in FIG. 4, by providing the ultrasonic wave generating units 110 at multiple locations surrounding the first electrode 102, ultrasonic waves are generated sequentially from the ultrasonic wave generating units 110 at the multiple locations, and the arrival time of each ultrasonic wave is processed. In this way, the temperature distribution of the entire vibrator 101 can be observed.

[0042] The ultrasonic wave generating unit 110 can be configured, for example, from a piezoelectric transducer. The ultrasonic wave generating unit 110 can also be configured from an electrostatic actuator, a magnetic actuator, a voice coil, a pneumatic or hydraulic cylinder, a motor, an electromagnetic solenoid, or a composite mechanism of a shape memory alloy and a heater. The ultrasonic wave generating unit 110 can also be configured from an electrostatic chuck or a vacuum chuck that secures the vibrator 101. By turning these chuck mechanisms on and off in pulses or bursts, or by turning them on and off based on a modulation signal, ultrasonic waves can be generated by mechanical vibrations caused by the vibrator 101 repeatedly adsorbing and detaching from the fixed portion.

[0043] The temperature measurement circuit 112 generates ultrasonic waves in the ultrasonic generating unit 110, and then detects the generated ultrasonic waves using the first electrode 102, thereby measuring the speed of sound of the ultrasonic waves propagating through the vibrator 101 between the ultrasonic generating unit 110 and the first electrode 102, and calculates the temperature from the measured speed of sound.

[0044] The sound waves generated by the ultrasonic generator 110 propagate through the transducer 101, reach the first electrode 102, and are sent to the temperature measurement circuit 112. The temperature measurement circuit 112 constantly monitors the first electrode 102 and converts the obtained signal from a time signal to a frequency signal using a fast Fourier transform. By differentiating the excitation frequency of the transducer 101 in the film thickness measurement unit 100 from the frequency of the ultrasonic waves generated by the ultrasonic generator 110, the time it takes for the ultrasonic waves sent from the ultrasonic generator 110 to reach the first electrode 102 can be obtained. Since changes in this arrival time depend on changes in the temperature of the transducer 101, it is possible to capture temperature changes in the transducer 101 relatively.

[0045] If the temperature coefficient of the sound wave propagating through the vibrator 101 is known, the relative change in the sound velocity can be determined, and if the distance between the ultrasonic wave generating unit 110 and the first electrode 102 is known, the absolute value of the sound velocity can be determined. Furthermore, if the temperature dependency of the sound wave propagating through the vibrator 101 is known, the absolute temperature of the vibrator 101 can be determined from the determined sound velocity. Using the temperature of the vibrator 101 determined in this manner, the film thickness measuring unit 100 temperature compensates (corrects) the measurement results of the thickness of the thin film deposited on the vibrator 101.

[0046] As described above, according to the second embodiment, it is possible to obtain the change in the resonant frequency of the vibrator due to the adsorption and desorption of deposits that accumulate (adsorb) on the vibrator, excluding (or taking into account) the effect of temperature changes. According to the second embodiment, it is possible to more accurately correct the temperature change of a film thickness sensor that uses a vibrator. Furthermore, according to the second embodiment, since the temperature measurement unit captures the temperature change of the vibrator itself, the delay time of the temperature change required for heat conduction is small, and the temperature change of the vibrator can be detected in real time with high accuracy. Note that the delay time associated with signal processing such as Fourier transform can be measured and corrected in advance to obtain a more accurate arrival time.

[0047] [Embodiment 3] Next, a film thickness sensor according to a second embodiment of the present invention will be described with reference to Fig. 5. This film thickness sensor includes a film thickness measurement unit (not shown) and a temperature measurement unit 104b. The film thickness measurement unit is disposed in a thin film formation chamber (not shown) of a thin film formation apparatus (not shown) for forming a thin film from a deposit. The film thickness measurement unit is the same as that of the first embodiment described above, and details thereof will be omitted.

[0048] The temperature measuring unit 104 b includes a fixing unit 131 , an ultrasonic wave generating unit 132 , and an ultrasonic wave receiving unit 133 .

[0049] The holding unit 131 is disposed inside the thin film formation chamber and holds a wafer (not shown) on which a thin film is to be formed. The ultrasonic wave generating unit 132 is disposed around the holding unit 131 and applies ultrasonic waves to the backside of the wafer held on the holding unit 131. For example, the ultrasonic wave generating units 132 can be provided at multiple locations on the holding unit 131. The ultrasonic wave generating units 132 can be configured from an electrostatic chuck or a vacuum chuck that holds the wafer to the holding unit 131. By turning these chuck mechanisms on and off in pulses or bursts, or by turning them on and off based on a modulated signal, ultrasonic waves can be generated by mechanical vibrations caused by the vibrator 101 repeatedly adsorbing and desorbing from the holding unit 131.

[0050] The ultrasonic wave receiving unit 133 can be disposed in the center of the fixed part 131. The ultrasonic wave receiving unit 133 can be composed of, for example, a receiving piezoelectric element and a transfer rod. The tip of the transfer rod is disposed so as to contact the vicinity of the center of the wafer fixed to the fixed part 131. The transfer rod can be provided with an appropriate buffer mechanism to prevent the wafer from being damaged. Furthermore, the location of the ultrasonic wave receiving unit 133 is not limited to the center of the fixed part 131 (wafer) and can be disposed in other positions, and ultrasonic wave receiving units 133 can be provided in multiple locations.

[0051] An on / off signal is sent to each of the ultrasonic wave generators 132 provided at multiple locations, and the sound waves generated by the ultrasonic wave generators 132 are received by the ultrasonic wave receivers 133. With this configuration, it is possible to detect the propagation time of the sound waves propagating through the wafer from the ultrasonic wave generators 132 to the ultrasonic wave receivers 133. From the propagation time of the sound waves, the speed of sound can be determined, as in the first embodiment described above. If another ultrasonic wave generator 132 exists between the ultrasonic wave generators 132 and the ultrasonic wave receivers 133, the speed of sound (arrival time, and ultimately the temperature) can be determined in order starting from the ultrasonic wave generators 132 closest to the ultrasonic wave receivers 133, thereby making it possible to obtain a detailed temperature distribution of a wafer such as a Si wafer.

[0052] For example, ultrasonic waves are generated by the ultrasonic generator 132, and then the generated ultrasonic waves are detected by the ultrasonic receiver 133, thereby measuring the speed of sound of the ultrasonic waves propagating through the wafer between the ultrasonic generator 132 and the ultrasonic receiver 133, and the temperature is calculated from the measured speed of sound, and the temperature distribution described above can be measured by the temperature measurement circuit. Based on the temperature distribution calculated in this way, the film thickness measurement unit corrects the thickness measurement results.

[0053] Here, the temperature measuring unit 104b including the fixing unit 131, the ultrasonic wave generating unit 132, and the ultrasonic wave receiving unit 133 is not limited to being used for correcting the temperature characteristics of the vibrator in the film thickness measuring unit. By using the temperature measuring unit 104b to measure the temperature distribution during film formation of a wafer placed in the thin film formation chamber of the thin film formation apparatus, it is possible to more accurately control, for example, the amount of source gas supplied to the thin film formation chamber.

[0054] For example, in semiconductor device manufacturing processes such as film formation and etching, controlling the wafer temperature is generally important, and measuring the wafer temperature distribution is crucial for this control. However, it is difficult to measure the wafer temperature without affecting the process. While techniques for measuring temperature using a radiation thermometer or the like are known, the film formation chamber in which the wafer is placed is very narrow, and due to equipment constraints, it is difficult to provide a window or the like, making it difficult to secure space for installing a radiation thermometer. In response to these issues, the temperature measurement unit 104b described above can accurately measure the temperature distribution without the above-mentioned constraints and limitations.

[0055] Although longitudinal waves are primarily used for the ultrasonic waves generated by the excitation unit, other waves such as transverse waves or a mixture of multiple modes can also be used. The material and length of the acoustic wave propagation unit can be designed appropriately, and the acoustic wave propagation unit can also be omitted. A low-volatility couplant material can be placed between the joint and the transducer, firmly connecting the transducer and the acoustic wave propagation unit. The couplant material can be water, inorganic or organic materials such as solder or wax that melt at a specified temperature, or magnetic fluid. When using magnetic fluid, a magnetic fluid retention mechanism consisting of a permanent magnet or other device can be installed.

[0056] In addition to using piezoelectric materials for the excitation unit as mentioned above, an Electro-Magnetic Acoustic Transducer (EMAT) can also be used. Mechanical excitation and detection mechanisms such as solenoid coils, and electrostatic excitation and detection mechanisms can also be used. Furthermore, it is not necessary for the excitation unit to perform ultrasonic excitation and detection as a single unit; excitation and detection can be performed by separate mechanisms (or separate physical phenomena), and the detection mechanism can even be separated and the detection unit can be provided on the bottom surface of the deposition sensor. In this case, the delay time is halved.

[0057] Since the film thickness sensor operates on the same principle as a general film thickness sensor that uses the piezoelectric effect, it can also be used as a QCM (Quartz Crystal Microbalance) sensor that measures the amount of adsorption and desorption of a specific substance by providing a sensitive layer on the electrode.

[0058] Furthermore, in the above description, the thickness of the vibrator, the linear expansion coefficient, the material constant, the relationship between temperature and sound velocity, the relationship between resonant frequency and temperature, etc. are required, but constants described in papers or scientific chronologies can be used. These values ​​can be determined in advance using standard samples, and values ​​measured on the actual sensor to be used can be used. Average data that takes manufacturing variations into account to some extent can also be used, and a statistically processed range of variation can be shown taking manufacturing deviations, etc. into account. Alternatively, the characteristics for each temperature can be measured in advance for each configuration to determine the correction coefficient.

[0059] Furthermore, in the third embodiment, the chuck mechanism is not limited to an electrostatic chuck or vacuum chuck, and a separate mechanical excitation mechanism (piezoelectric or electrostatic) can also be used. The signal for operating the chuck mechanism is not limited to a single pulse, and any signal such as a burst wave, modulated wave, or chirp signal can be used. Furthermore, a heat conduction simulation of the wafer and chuck mechanism can be performed in advance, and the detailed temperature distribution of each part can be estimated based on the local temperatures.

[0060] To receive the sound waves, known amplifier circuits such as low-noise amplifiers can be used as appropriate. To measure the propagation time, known measurement techniques such as oscilloscopes and time-to-digital converters (TDCs) can be used. Chirp signal processing is based on the same principle as heterodyne detection. To remove measurement noise, known filters and lock-in detection techniques can be used.

[0061] As described above, according to the embodiment of the present invention, the temperature of the film thickness measuring unit is compensated for using the temperature measured by the temperature measuring unit, which measures the temperature of the environment in which the vibrator is placed based on the sound speed of ultrasonic waves propagating through the object, so that temperature changes in the film thickness sensor using the vibrator can be corrected more accurately.

[0062] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0063] 100...film thickness measurement section, 101...vibrator, 102...first electrode, 103...second electrode, 104...temperature measurement section, 105...sound wave propagation section, 106...sound speed measurement section, 107...excitation section, 108...third electrode, 109...fourth electrode, 121...first reflected wave, 122...second reflected wave.

Claims

1. a film thickness measuring unit including a vibrator and a first electrode and a second electrode formed facing each other across the vibrator, the film thickness measuring unit measuring the thickness of a thin film formed by deposits deposited on the vibrator; a temperature measurement unit that measures the temperature of the environment in which the transducer is placed based on the sound speed of ultrasonic waves propagating through an object; Equipped with The film thickness measuring unit is a film thickness sensor that performs temperature compensation using the temperature measured by the temperature measuring unit.

2. 2. The film thickness sensor according to claim 1, The temperature measurement unit an acoustic wave propagating portion having one end formed in contact with a temperature measurement region of the transducer surrounding an arrangement region of the first electrode; an excitation part made of a piezoelectric material, and a sound velocity measurement part formed at one end of the sound wave propagation part, the sound velocity measurement part including a third electrode and a fourth electrode formed on either side of the excitation part, the sound velocity measurement part measuring the sound velocity of an ultrasonic wave propagating in the thickness direction of the transducer; A film thickness sensor comprising:

3. 2. The film thickness sensor according to claim 1, The temperature measurement unit an ultrasonic wave generating unit formed in contact with a temperature measurement region of the vibrator around an arrangement region of the first electrode, the ultrasonic wave generating unit generating ultrasonic waves having a frequency different from a resonance frequency of the vibrator; a temperature measurement circuit that generates an ultrasonic wave in the ultrasonic generating unit, and then detects the generated ultrasonic wave using the first electrode, thereby measuring the speed of sound of the ultrasonic wave propagating through the transducer between the ultrasonic generating unit and the first electrode, and determines the temperature from the measured speed of sound; A film thickness sensor comprising:

4. 2. The film thickness sensor according to claim 1, the film thickness measurement unit is disposed within a thin film formation chamber of a thin film formation apparatus for forming a thin film from the deposit, The temperature measurement unit an ultrasonic wave generating unit that is disposed in the periphery of a fixing unit that fixes a wafer on which a thin film is to be formed, and that applies ultrasonic waves to the back surface of the wafer fixed to the fixing unit, and that is disposed inside the thin film forming chamber; an ultrasonic receiving unit disposed on the fixed portion; The ultrasonic wave generating unit generates ultrasonic waves, and then the ultrasonic wave receiving unit detects the generated ultrasonic waves, thereby measuring the sound speed of the ultrasonic waves propagating through the wafer between the ultrasonic wave generating unit and the ultrasonic wave receiving unit, and calculating the temperature from the measured sound speed, and a temperature measuring circuit. A film thickness sensor comprising:

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