TWI878168B - System for real-time measurement of film thickness using acoustic wave elements - Google Patents

Abstract

A system for measuring film thickness in real time using an acoustic wave element comprises at least one carrier having a film having a film thickness; at least one acoustic wave unit disposed around the carrier and detecting changes in the film thickness in real time to generate a harmonic frequency; and a computing unit receiving and processing the harmonic frequency generated by the acoustic wave element detection. The calculation unit obtains at least one two-dimensional coordinate system of the film thickness frequency before correction from the value of [film thickness-resonance frequency], and also obtains at least one two-dimensional coordinate system of temperature frequency compensation from the value of [chamber temperature-resonance frequency]; the calculation unit then calculates the two-dimensional coordinate system of the film thickness frequency before correction and the two-dimensional coordinate system of temperature frequency compensation to obtain a three-dimensional coordinate system for film thickness measurement, for interpolation search to obtain the film thickness during measurement, and can detect and feedback the film thickness in real time with high accuracy, thereby improving the coating yield.

Description

System for real-time measurement of film thickness using acoustic wave elements

This invention is related to film thickness measurement, and in particular to a system that uses acoustic wave components to measure film thickness in real time.

When coating a film on a wafer carrier, for example, it is necessary to adjust various operating parameters according to the thickness of the coating, and the thickness of the coating is also used for the calculation of other data. The acoustic wave elements commonly used for measuring coating thickness include Surface Acoustic Wave (SAW), Film Bulk Acoustic Resonator (FBAR), Bulk Acoustic Waves-Solidly Mounted Resonator (BAW-SMR), etc., which use the detected resonant frequency to convert the thickness of the coating. However, as the coating thickness increases or the cavity temperature rises during coating, the detected resonant frequency is affected, resulting in a large deviation between the coating thickness converted by the resonant frequency and the actual coating thickness. To prevent the chamber temperature from affecting the accuracy of the measured resonant frequency, the industry only performs film thickness measurement and resonant frequency data collection after the film coating is completed and the wafer carrier and acoustic wave device have cooled down. However, offline measurement must be repeatedly performed in a state where the chamber is vacuumed after breaking the vacuum and then evacuating the vacuum. In addition to wasting extra time, it is also impossible to know the changes in the film thickness during the coating process in real time to make corresponding operational adjustments immediately. Moreover, after stopping the coating and restarting it, there is a connection error between the new and old film layers, resulting in a reduction in the coating yield and the need to scrap and start over.

In addition, some conventional techniques use a temperature compensation layer (such as SiO ₂ ) on the acoustic wave element to compensate for the temperature change of the acoustic wave element during the coating process. However, this method can only reduce the interference of temperature on the resonant frequency, and still cannot continuously detect the change of the coating thickness during the coating process. Moreover, this conventional technique only considers the impact of temperature change on the resonant frequency, and does not include the change of the resonant frequency caused by the increase of the coating thickness into the variable comparison to calculate the accurate coating thickness. It can be seen that the conventional technique neither has the function of real-time monitoring of the coating thickness change, nor can it provide an accurate resonant frequency to convert to obtain the accurate coating thickness.

In view of this, how to solve the above-mentioned problem is the primary subject that the present invention intends to solve.

The main purpose of the present invention is to provide a system for real-time measurement of film thickness using an acoustic wave element. A pre-corrected film thickness frequency two-dimensional coordinate system consisting of film thickness and resonant frequency, and a temperature-frequency compensation two-dimensional coordinate system consisting of temperature and resonant frequency are used to form a film thickness measurement three-dimensional coordinate system including the corresponding values of cavity temperature, film thickness and resonant frequency. By interpolating and searching the cavity temperature and resonant frequency obtained by real-time measurement in the film thickness measurement three-dimensional coordinate system, a three-dimensional coordinate of (cavity temperature-resonant frequency-film thickness) can be obtained, thereby obtaining the film thickness in real time. Not only can the film thickness change be detected in real time to adjust the operating parameters, but also the film thickness-related values can be quickly obtained, shortening the measurement time.

To achieve the above-mentioned purpose, the present invention provides a system for real-time measurement of film thickness using an acoustic wave element, the system comprising:

At least one carrier, a surface of which is coated with a thin film having a film thickness;

At least one acoustic wave element is disposed around the carrier to detect the change of the film thickness in real time and generate a harmonic frequency;

A computing unit, used for receiving and processing the resonant frequency generated by the acoustic wave element detection;

When the film is continuously deposited on the surface of the carrier, the surface of the acoustic wave element is also deposited with the same film to detect the thickness change of the film in real time. The resonant frequency generated by the acoustic wave element decreases as the thickness of the film increases. Under a fixed temperature condition, the calculation unit generates at least one two-dimensional coordinate system of the film thickness frequency before correction through the correspondence of the measured values of [film thickness-resonant frequency];

When the cavity temperature continues to rise, the temperature of the acoustic wave element rises accordingly, and the resonance frequency generated by the acoustic wave element detecting the film thickness in real time decreases as the temperature rises. Under the condition of a fixed film thickness, the calculation unit generates at least one temperature-frequency compensation two-dimensional coordinate system through the correspondence of the measured values of [cavity temperature-resonance frequency];

The calculation unit further generates a three-dimensional coordinate system for measuring film thickness by comprehensively calculating the two-dimensional coordinate systems of the film thickness frequency before correction and the two-dimensional coordinate systems of the temperature frequency compensation, and obtains three-dimensional coordinates including the corresponding values of the cavity temperature, the film thickness and the resonant frequency. When the acoustic wave element detects the film thickness, the detected resonant frequency value and the cavity temperature can be interpolated and searched in the three-dimensional coordinate system for measuring film thickness, and a three-dimensional coordinate value of [cavity temperature-film thickness-resonant frequency] can be obtained, and the corresponding film thickness can be obtained. The cavity temperature and the resonant frequency can be intermittently measured during the coating process to achieve the effect of measuring the film thickness in real time.

Preferably, the resonant frequency of the acoustic wave element is between 1 GHz and 10 GHz.

Preferably, when the acoustic wave element detects the change in the film thickness of the carrier in real time, the resonant frequency of the acoustic wave element changes between 1 KHz and 20 MHz for every 1 nm increase in the film thickness.

Preferably, the system is suitable for a carrier coating environment with a temperature variation range of 0°C to 150°C and a film thickness range of 1nm to 1000nm.

Preferably, the carriers face a coating source, and a plurality of baffles are provided between the coating source and the carriers. The baffles communicate with the computing unit, and the relative positions between the baffles and the carrier are controlled to change according to the film thickness detected in real time by the computing unit to adjust the uniformity of the coating of the carrier by the coating source.

Preferably, when the coating process of the carriers is completed and the etching process is started, the acoustic wave elements also cooperate with the calculation unit to measure the film thickness in real time to adjust the film etching depth.

Preferably, a plurality of acoustic wave elements are arranged in array around each carrier, and a MEMS (Micro Electro Mechanical Systems) switch element is provided corresponding to each acoustic wave element, so that the MEMS switch elements are arranged in an array, and the corresponding acoustic wave element is operated or closed by turning on and off the MEMS switches.

Preferably, each of the carriers is placed in a deposition area correspondingly, or the deposition area is arranged close to the periphery of the carrier, and the surface area of each MEMS switch element corresponding to one side of the acoustic wave element is larger than the resonant effective area of the acoustic wave element, so as to completely shield the resonant effective area of the acoustic wave element and then control the operation of the acoustic wave element.

Preferably, the system for measuring film thickness in real time comprises the following operating steps when the carrier is coated:

Step 1: each acoustic wave element is also disposed at different distances from a film source to collect resonant frequencies of different environmental conditions;

Step 2, the calculation unit receives the resonant frequency and calculates a film thickness deposition rate by operating the real-time film thickness measurement system, and transmits the film thickness deposition rate data back to a control system;

Step 3, the control system adjusts the shielding area, shielding angle and shielding distance of each shielding plate to the coating source;

Step 4: repeat step 2 and determine whether the target film thickness deposition rate is reached. If not, repeat step 3; if reached, proceed to step 5.

Step 5: Fix the parameters of the baffle.

Preferably, in step 1, the temperature in the cavity is increased before coating and the resonant frequency generated by the acoustic wave element is tested. Coating measurement is performed after the resonant frequency is determined to be within a calibration range. During the coating measurement process, the change of the resonant frequency is detected and compared to see whether it exceeds the calibrated resonant frequency range to determine whether the acoustic wave element can operate normally.

The above-mentioned objects and advantages of the present invention can be more clearly understood from the following detailed description of the selected embodiments and the accompanying drawings.

As shown in FIG. 1 to FIG. 11 , a system for real-time measurement of film thickness using an acoustic wave element is provided in an embodiment of the present invention. The system includes at least one carrier, at least one acoustic wave element, and a calculation unit.

Please refer to FIG. 9. In this embodiment, three carriers are provided. An acoustic wave element is provided around each carrier to detect the change of the thickness of the film formed on the surface of the carrier during coating in real time and generate a resonant frequency. The resonant frequency of the acoustic wave element is between 1 GHz and 10 GHz. The acoustic wave element is one of Surface Acoustic Wave (SAW for short), Film Bulk Acoustic Resonator (FBAR for short), and Bulk Acoustic Waves-Solidly Mounted Resonator (BAW-SMR for short). The above acoustic wave elements all change in frequency with temperature changes. The acoustic wave element in this embodiment is FBAR.

As mentioned above, when the film is continuously deposited on the surface of the carrier, the surface of the acoustic wave element will also be deposited with the same film to detect the change of the film thickness in real time. The resonant frequency generated by the acoustic wave element decreases as the film thickness increases. It should be noted that the resonant frequency of the acoustic wave element changes between 1KHz and 20MHz for every 1nm increase in the film thickness. Under fixed temperature conditions, the calculation unit generates a two-dimensional coordinate system of the film thickness frequency before correction as shown in Figure 1 through the corresponding measurement value of [film thickness-resonant frequency]. The present invention measures the change of the resonant frequency as the film thickness increases under the conditions that the chamber temperature is stabilized at 25°C, 40°C, 50°C and 100°C respectively. The calculation unit obtains the measured values of [film thickness-resonant frequency] generated by different film thicknesses under 4 different temperature conditions by detecting, and then obtains the corresponding two-dimensional coordinate system of the film thickness frequency before correction.

Please refer to the curve shown in Figure 2, which is the relationship between the film thickness and the resonant frequency of the acoustic wave element with different resonant areas under the condition of cavity temperature of 25℃. The resonant areas of the acoustic wave element are ^6400um2 , ^10000um2 , ^14400um2 and ^25600um2 , and the film thickness is 0nm (i.e., uncoated), 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm and 50nm. The resonant frequency detected by the acoustic wave element gradually decreases as the coating thickness increases. From the two-dimensional coordinate system of film thickness frequency before correction, it can be seen that when the cavity temperature remains unchanged, the film thickness of the carrier increases, while the resonant frequency detected by the acoustic wave unit gradually decreases.

As the cavity temperature continues to rise, the temperature of the acoustic wave element rises accordingly. The resonance frequency generated by the acoustic wave element detecting the film thickness in real time decreases as the temperature rises. Under the condition of a fixed film thickness, the measurement value of [cavity temperature-resonance frequency] obtained by the calculation unit through detection corresponds to a temperature-frequency compensation two-dimensional coordinate system as shown in Figure 3. Furthermore, when the effective resonance area of the acoustic wave element is 6400 um ² In the present invention, when the carrier and the acoustic wave element have different film thicknesses of 0nm (i.e., uncoated), 5nm, 10nm, 15nm, 30nm, and 50nm, and the cavity temperature is respectively 25°C, 40°C, 50°C, and 100°C, the change of the resonant frequency as the temperature increases is measured and recorded. The calculation unit detects the four different temperatures corresponding to different film thicknesses. The measured values of [cavity temperature-resonance frequency] generated by the conditions are used to obtain the corresponding temperature-frequency compensation two-dimensional coordinate system, and the temperature-frequency compensation two-dimensional coordinate system before correction is summarized as shown in Figure 4. It can be seen from the temperature-frequency compensation two-dimensional coordinate system that under the condition that the thickness of the carrier film remains unchanged, the cavity temperature gradually increases, while the resonant frequency detected by the acoustic wave unit gradually decreases.

Next, the calculation unit further calculates the pre-corrected film thickness frequency two-dimensional coordinate system and the temperature frequency compensation coordinate system to generate a film thickness measurement three-dimensional coordinate system as shown in FIG. 5, and obtains a three-dimensional coordinate system including the corresponding values of the cavity temperature, film thickness and resonant frequency, so that when the acoustic wave element detects the film thickness, the detected resonant frequency and cavity temperature can be used in the film thickness measurement three-dimensional coordinate system. The system performs interpolation search to obtain a three-dimensional coordinate value of [chamber temperature-film thickness-resonance frequency], and the corresponding film thickness can be obtained. The chamber temperature and resonance frequency are measured intermittently during the coating process to achieve real-time measurement of film thickness. The system is suitable for carrier coating environments with a temperature variation range of 0℃~150℃ and a film thickness range of 1nm~1000nm.

As shown in FIG. 9 and FIG. 10 , the carriers 2 face a coating source 4, and the coating source 4 forms a thin film on the surface of the carrier 2 by sputtering the coating material. The coating method can be evaporation, sputtering or chemical vapor deposition. A plurality of baffles 5 are provided between the coating source 4 and the carriers 2. In this embodiment, three carriers 2 are arranged to face a coating source 4, and at least two baffles 5 that can swing left and right are provided between the coating source 4 and the carriers 2. The baffles 5 communicate with the calculation unit, and the calculation unit obtains the real-time film thickness in the film thickness measurement three-dimensional coordinate system according to the real-time detected cavity temperature and resonant frequency, and controls the change of the relative position between the baffles 5 and the carrier 2 according to the real-time film thickness to adjust the uniformity of the coating source on the carrier. In detail, the baffle 5 is used to adjust the plating rate of the plating source, and its blocking area for the plating source 4 or the carrier 2 is inversely proportional to the film thickness. When the film thickness is thicker and the mark is closer to the target set thickness, the plating rate should be slowed down. Therefore, the calculation unit controls the movement of the baffle 5 to increase the blocking area, adjust the blocking angle and the blocking distance, thereby reducing the plating rate and ensuring the uniformity of the carrier plating.

As further illustrated in FIG. 8 , the present invention has a plurality of acoustic wave elements 1 arranged in an array around each carrier 2, and each acoustic wave element 1 is provided with a corresponding MEMS (Micro Electro Mechanical Systems) switch element 3, so that the MEMS switch elements 3 are arranged in an array. Further, each of the carriers is placed in a deposition area correspondingly, and in other practicable embodiments, the deposition area can also be arranged close to the carrier. The surface area of one side of the acoustic wave element corresponding to each MEMS switch element is larger than the resonant effective area of the acoustic wave element so as to completely shield the acoustic wave element 1. The operation or shutdown of the corresponding acoustic wave element 1 is determined by turning on and off the MEMS switches 3. That is, when the MEMS switch 3 is turned on, the corresponding acoustic wave element 1 operates and generates a resonant frequency; if the MEMS switch 3 is closed, the corresponding acoustic wave element 1 is closed and stops operating, thereby realizing flexible adjustment of the corresponding operating acoustic wave element according to the number of carriers to be measured. During the film thickness measurement process, at least one acoustic wave element is turned on as a measurement group to monitor the change of the film thickness of the carrier, and another acoustic wave element can be turned on at different coating times and temperatures as a comparison group, and the harmonic frequency detected by the comparison group is compared with the data of the measurement group to determine whether there is a problem with the harmonic frequency detected by the measurement group. Alternatively, the accuracy of the acoustic wave element can be verified by turning on the comparison group after a period of time, such as 1000 hours.

In addition, the curves shown in Figures 2, 6 and 7 are the relationship diagrams between the resonant area of the acoustic wave element, the thickness of the _SiO2 film layer and the resonant frequency. When the cavity temperature is 25°C and 40°C respectively, and the film thickness is 0nm (i.e., uncoated), 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm respectively, and the effective resonant area of the acoustic wave element is ^6400um2 , ^10000um2 , ^14400um2 , ^25600um2 , the resonant frequency detected by the acoustic wave element increases with the increase of the effective resonant area of the acoustic wave element, but decreases with the increase of the film thickness. The real-time film thickness measurement system can be fine-tuned by half-opening or partially opening the MEMS switch, and can also be used to correct the resonant frequency drift caused by temperature rise.

As shown in FIG. 11 , the system for real-time measurement of film thickness using an acoustic wave element of the present invention comprises the following operating steps when the carrier is coated:

In step 1, each acoustic wave element is also arranged at different distances from a coating source to collect the resonant frequency of different environmental conditions (such as cavity temperature); before coating, the temperature in the cavity is increased and the resonant frequency generated by the acoustic wave element is tested, and coating measurement is performed after the resonant frequency is judged to be within a calibration range, and during the coating measurement process, the change of the resonant frequency is detected and compared to see whether it exceeds the calibrated resonant frequency range, and it is judged whether the acoustic wave element is operating normally, and step 2 is performed after it is judged to be operating normally;

Step 2, the calculation unit receives the resonant frequency and calculates a film thickness deposition rate by operating the real-time film thickness measurement system, and transmits the film thickness deposition rate data back to a control system;

Step 3, the control system adjusts the shielding area, shielding angle and shielding distance of each shielding plate to the coating source;

Step 4: repeat step 2 and determine whether the target film thickness deposition rate is reached. If not, repeat step 3; if reached, proceed to step 5.

Step 5: Fix the parameters of the baffle.

The present invention can also be applied to etching operations after film coating is completed, using the principle that when the film thickness increases during film coating, the resonant frequency becomes lower, and when the film thickness decreases during film etching, the resonant frequency increases, and when the cavity temperature increases, the frequency decreases. After the film coating process of the carriers is completed, when the etching operation is performed, the acoustic wave elements also cooperate with the calculation unit to measure the film thickness in real time. The calculation unit obtains the film etching depth according to the increase in the resonant frequency, and then adjusts the film etching depth according to the process requirements.

From the above embodiments, it can be seen that the system for real-time measurement of film thickness using an acoustic wave element provided by the present invention can achieve the following improvement effects:

First, real-time detection and feedback of film thickness can improve the yield of film coating. The present invention constructs a three-dimensional coordinate system for film thickness calculation that includes chamber temperature, film thickness and resonant frequency. In actual use, it is only necessary to detect the chamber temperature and resonant frequency, and interpolate and search the above two data in the three-dimensional coordinate system for film thickness calculation to obtain accurate film thickness. The calculation efficiency is high, and the key parameter film thickness in the process is fed back in real time, which is beneficial for operators to adjust the operating parameters in time, ensure the uniformity of film coating, and improve the yield of film coating.

Second, it automatically compensates for the resonant frequency changes caused by the cavity temperature, and the results are highly accurate. Conventional technology uses a temperature compensation layer to compensate for the temperature changes of the cavity during film coating, but because the temperature compensation layer cannot be flexibly adjusted according to the actual production situation, the temperature changes it compensates for are not accurate. The three-dimensional coordinate system for film thickness calculation established by the present invention through a large amount of experimental data includes the corresponding resonant frequencies under different cavity temperature conditions. In the three-dimensional coordinate system for film thickness calculation, the resonant frequency is used to compensate for the actually measured resonant frequency, thereby obtaining an accurate film thickness.

Third, the acoustic wave element can be flexibly selected; compared with the conventional technology, the present invention does not need to add a temperature compensation layer to the acoustic wave element before the film thickness detection of the carrier coating can be performed, so most of the acoustic wave elements are suitable for the present invention.

Fourth, it can be applied to film thickness detection in different processes; the present invention can be applied to real-time film thickness detection during coating and etching. When the coating process is completed, it can immediately switch to etching operation. The acoustic wave element of the present invention also cooperates with the calculation unit to detect the film thickness in real time. It uses the principle that the resonant frequency becomes lower when the film thickness increases during coating, and the resonant frequency increases when the film thickness decreases during etching, and the frequency decreases when the cavity temperature increases. The calculation unit obtains the film etching depth according to the increase in the resonant frequency, and then adjusts the film etching depth according to the process requirements.

However, what is described above is only a preferred embodiment of the present invention and should not be used to limit the scope of the present invention. In other words, all equivalent changes and modifications made within the scope of the patent application should still fall within the scope of the present invention.

In summary, those familiar with the art will be able to understand that the present invention can achieve the aforementioned purpose and is in compliance with the provisions of the Patent Law, and therefore can file an application in accordance with the law.

Acoustic wave element 1 Carrier 2 MEMS switch element 3 Coating source 4 Baffle 5

Figure 1 is a two-dimensional coordinate system diagram of the film thickness frequency before correction of the present invention. Figure 2 is a two-dimensional coordinate curve diagram of the film thickness-resonance frequency of the acoustic wave element with different resonant areas under 25°C conditions of the present invention. Figure 3 is a two-dimensional coordinate system diagram of temperature-frequency compensation of the present invention. Figure 4 is a two-dimensional coordinate system diagram of temperature-frequency compensation of the acoustic wave element with different film thicknesses of the present invention. Figure 5 is a three-dimensional coordinate system diagram of film thickness measurement of the present invention. Figure 6 is a two-dimensional coordinate curve diagram of the resonant area-resonance frequency of the acoustic wave element with different film thicknesses under 25°C conditions of the present invention. Figure 7 is a two-dimensional coordinate curve of the resonant area-resonant frequency of the acoustic wave element of the present invention at 40°C with different film thicknesses. Figure 8 is a schematic diagram of the position structure of the acoustic wave element and the MEMS switch element of the present invention. Figure 9 is a schematic diagram of the position structure of the coating source and the carrier of the present invention. Figure 10 is a block diagram of the connection relationship of each component of the present invention. Figure 11 is a schematic diagram of the process of film thickness monitoring and correction of the present invention.

Claims (10)

A system for measuring film thickness in real time using an acoustic wave element, the system comprising: At least one carrier, which is coated in a cavity, and a thin film is coated on its surface, and the thin film has a film thickness; At least one acoustic wave element, which is arranged around the carrier, is used to detect the change of the film thickness in real time and generate a harmonic frequency; A computing unit, which is used to receive and process the harmonic frequency generated by the acoustic wave element detection; When the film is continuously deposited on the surface of the carrier, the surface of the acoustic wave element will also be deposited with the same film to detect the thickness change of the film in real time. The resonant frequency generated by the acoustic wave element decreases as the thickness of the film increases. Under fixed temperature conditions, the calculation unit generates at least one two-dimensional coordinate system of the film thickness frequency before correction through the correspondence between the measured values of [film thickness-resonant frequency]; When the cavity temperature of the cavity continues to rise, the temperature of the acoustic wave element rises accordingly, and the resonance frequency generated by the real-time detection of the film thickness by the acoustic wave element decreases as the temperature rises. Under the condition of fixed film thickness, the calculation unit generates at least one temperature-frequency compensation two-dimensional coordinate system through the corresponding measurement value of [cavity temperature-resonance frequency]; The calculation unit further generates a three-dimensional coordinate system for measuring film thickness by comprehensively calculating the two-dimensional coordinate systems of film thickness frequency before correction and the two-dimensional coordinate systems of temperature frequency compensation. The three-dimensional coordinate system including the corresponding values of cavity temperature, film thickness and resonant frequency can be obtained. When the acoustic wave element detects the film thickness, the detected resonant frequency value and cavity temperature can be interpolated and searched in the three-dimensional coordinate system for measuring film thickness to obtain a three-dimensional coordinate value of [cavity temperature-film thickness-resonant frequency], and the corresponding film thickness can be obtained. The cavity temperature and resonant frequency can be intermittently measured during the coating process to achieve the effect of measuring film thickness in real time. A system for real-time measurement of film thickness using an acoustic wave element as described in claim 1, wherein the resonant frequency of the acoustic wave element is between 1 GHz and 10 GHz. A system for measuring film thickness in real time using an acoustic wave element as described in claim 1, wherein when the acoustic wave element detects changes in the film thickness of the carrier in real time, the resonant frequency of the acoustic wave element changes between 1 KHz and 20 MHz for every 1 nm increase in the film thickness. A system for real-time measurement of film thickness using an acoustic wave element as described in claim 1, wherein the system is applicable to a carrier coating environment with a temperature variation range of 0°C to 150°C and a film thickness range of 1nm to 1000nm. A system for real-time measurement of film thickness using an acoustic wave element as described in claim 1, wherein the carriers face a coating source, a plurality of baffles are provided between the coating source and the carriers, the baffles communicate with the computing unit, and the relative positions between the baffles and the carrier are controlled to change according to the film thickness detected in real time by the computing unit, so as to adjust the uniformity of coating the carrier by the coating source. As described in claim 1, the system uses acoustic wave elements to measure film thickness in real time, wherein, when the coating process of the carriers is completed and the etching process begins, the acoustic wave elements also cooperate with the calculation unit to measure the film thickness in real time to adjust the film etching depth. A system for real-time measurement of film thickness using acoustic wave elements as described in claim 1, wherein a plurality of acoustic wave elements are arranged in array around each carrier, and a MEMS (Micro Electro Mechanical Systems) switch element is provided corresponding to each acoustic wave element so that the MEMS switch elements are arranged in an array, and the corresponding acoustic wave element is operated or closed by turning the MEMS switches on and off. A system for real-time measurement of film thickness using acoustic wave elements as described in claim 7, wherein each carrier is placed in a deposition area correspondingly, or the deposition area is arranged close to the periphery of the carrier, and the surface area of each MEMS switch element corresponding to one side of the acoustic wave element is larger than the resonant effective area of the acoustic wave element, so as to completely cover the resonant effective area of the acoustic wave element and thereby control the operation of the acoustic wave element. A system for measuring film thickness in real time using an acoustic wave element as described in any one of claim 1 to claim 8, wherein the system for measuring film thickness in real time comprises the following operating steps when the carrier is coated: Step 1, each acoustic wave element is also respectively arranged at a different distance from a coating source to collect the resonant frequency of different environmental conditions; Step 2, the calculation unit receives the resonant frequency and calculates a film thickness deposition rate by operating the system for measuring film thickness in real time, and transmits the film thickness deposition rate data back to a control system; Step 3, the control system adjusts the shielding area, shielding angle and shielding distance of each baffle to the coating source; Step 4: Repeat step 2 and determine whether the target film thickness deposition rate is reached. If not, repeat step 3. If reached, proceed to step 5. Step 5: Fix the parameters of the baffle. As described in claim 9, a system for measuring film thickness in real time using an acoustic wave element, wherein in step 1, the temperature in the cavity is increased before coating and the resonant frequency generated by the acoustic wave element is tested, and coating measurement is performed after the resonant frequency is determined to be within a calibration range. During the coating measurement process, the change in the resonant frequency is detected and compared to see whether it exceeds the calibrated resonant frequency range, so as to determine whether the acoustic wave element can operate normally.