Film thickness sensor and film thickness real-time monitoring system

Abstract

The utility model discloses a film thickness sensor and film thickness real -time monitoring system, this film thickness sensor includes circuit board, support block and crystal oscillator probe, crystal oscillator probe includes support outer ring, support inner ring in the support outer ring is established and is embedded in the crystal oscillator piece of support inner ring and support outer ring, and the bottom of crystal oscillator piece is electrically connected with circuit board through conducting spring, support outer ring is opposite sputtering cathode and sets up, is used to collect the free electron of plasma in the cavity in magnetron sputtering process, to form voltage between rotating ground base station, carries out self -power supply. The utility model removes the cooling pipeline in traditional crystal oscillator probe, forms the film thickness sensor in the application, fundamentally eliminates the redundant connection structure, makes the volume smaller, can carry out multipoint arrangement monitoring, need not external line and external power, so can move along with base station, tracks the real -time change of film thickness, simultaneously through wireless mode, the crystal oscillator frequency is transmitted to receiving terminal, can realize film thickness real -time monitoring.

Description

Technical Field

[0001] This utility model relates to the field of thin film thickness testing technology, specifically to a film thickness sensor and a real-time film thickness monitoring system. Background Technology

[0002] Thin film thickness measurement is a crucial step in fields such as semiconductor manufacturing, optical coating, biosensors, and materials science. Whether it's physical vapor deposition (PVD), chemical vapor deposition (CVD), or plasma etching processes, precise control and real-time monitoring of thin film thickness are essential for ensuring device performance and improving process yield.

[0003] When performing magnetron sputtering in a vacuum chamber, it is often necessary to monitor the film thickness in real time. Traditional crystal oscillator film thickness testers require an external wired power supply to power the crystal oscillator probe (i.e., film thickness sensor) inside the chamber, and vacuum electrodes need to be designed and installed on the chamber, which is costly. At the same time, traditional crystal oscillator probes are large in size due to the presence of cooling pipes, often limiting the monitoring space to fixed-point testing, and they cannot move with the substrate or track real-time changes in film thickness. Utility Model Content

[0004] Based on this, the purpose of this utility model is to provide a film thickness sensor and a real-time film thickness monitoring system. Through optimized design, the size of the film thickness sensor is reduced, and it can be deployed for monitoring at multiple points without the need for an external power supply. It can move with the base and track real-time changes in film thickness.

[0005] In the first aspect, the present invention provides a film thickness sensor, which is installed in a vacuum chamber and includes a circuit board mounted on a rotating grounding base, a support block connected to the circuit board and covering the surface of the circuit board, and a crystal oscillator probe. The crystal oscillator probe includes a support outer ring fastened to the support block, a support inner ring disposed in the support outer ring, and a crystal oscillator chip embedded in the support inner ring and the support outer ring. The bottom of the crystal oscillator chip is electrically connected to the circuit board via a conductive spring. The supporting outer ring is positioned directly opposite the sputtering cathode and is used to collect free electrons from the plasma within the cavity during magnetron sputtering, thereby forming a voltage with the rotating grounding base for self-powering.

[0006] Preferably, the supporting outer ring is made of aluminum alloy or copper.

[0007] Preferably, the circuit board is provided with a first step-down module, a second step-down module, an oscillator module, a frequency divider module and a main control module that are electrically connected in sequence; The power input terminal of the first step-down module is electrically connected to the supporting outer ring, and the output terminal is connected to the second step-down module, the oscillator module and the frequency divider module respectively, for converting the input voltage into 5V voltage; The output of the second step-down module is connected to the oscillator module and the main control module respectively, and is used to convert 5V voltage to 3.3V voltage; The oscillator module is used to generate a high-frequency oscillation signal from the vibration of the crystal oscillator and transmit the high-frequency oscillation signal to the frequency divider module; The frequency division module is used to convert the high-frequency oscillation signal into a low-frequency signal and transmit the low-frequency signal to the main control module; The main control module is used to calculate the frequency value based on the received low-frequency signal and transmit the frequency value to the receiving terminal wirelessly.

[0008] Preferably, the first step-down module includes a first step-down chip, the power input terminal of the first step-down chip is grounded, and a fifth capacitor and a sixth capacitor are connected in parallel with the negative power supply; The SW pin of the first step-down chip is connected in series with the first inductor, the second resistor, the fifth resistor, and the seventh resistor and then connected to the negative power supply. The second capacitor is connected between the SW pin and the bootstrap pin of the first step-down chip. The two ends of the fifth resistor are connected in parallel with the seventh capacitor. The feedback pin of the first step-down chip is connected between the fifth resistor and the seventh resistor. It also includes a third and a fourth capacitor connected in parallel, with one end connected between the second resistor and the first inductor, and the other end connected to the negative power supply.

[0009] Preferably, the second step-down module includes a second step-down chip, the power input terminal of the second step-down chip is connected between the second resistor and the first inductor, and is connected in series with the ninth capacitor and then connected to the negative power supply; The output terminal of the second step-down chip is connected in series with the eleventh capacitor and then connected to the negative power supply.

[0010] Preferably, the oscillator module includes a transistor and an inverter; The collector of the transistor is connected between the second resistor and the first inductor; The base of the transistor is connected to the conductive spring, and the collector of the transistor is connected through the ninth resistor. It is also connected in series with the twelfth and tenth capacitors and then connected to the negative power supply. The emitter of the transistor is connected between the twelfth capacitor and the tenth capacitor, and is also connected to the signal input terminal of the inverter through the sixth resistor; The signal input terminal of the inverter is connected in series with the twelfth resistor and then connected to the negative power supply. The power supply input terminal is connected to the output terminal of the second step-down chip, and the signal output terminal of the inverter is connected to the frequency divider module.

[0011] Preferably, the frequency division module includes a first counter chip and a second counter chip; The power supply pin of the first counter chip is connected between the second resistor and the first inductor, and is connected in series with the eighth capacitor to the negative power supply. The input pin of the first counter chip is connected to the signal output terminal of the inverter. The power supply pin of the second counter chip is connected between the second resistor and the first inductor, and the input pin of the second counter chip is connected to the output pin of the first counter chip. The output pin of the second counter chip is connected in series with the tenth and eleventh resistors and then connected to the negative power supply. The node between the tenth and eleventh resistors is connected to the signal input terminal of the main control module.

[0012] Secondly, this utility model provides a real-time film thickness monitoring system, including a film thickness sensor disposed inside a vacuum cavity and a receiving terminal disposed outside the vacuum cavity, wherein the film thickness sensor is the aforementioned film thickness sensor.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: First, during the coating process, the plasma density inside the cavity is high, which can form a self-powered power source to provide power without the need for external wiring or external power supplies, thus making installation simpler. Second, since the energy provided by the self-powered power supply is relatively low, an ultra-low power circuit structure is adopted to achieve real-time film thickness monitoring through a simple circuit structure. Third, since the temperature is relatively low during the coating process, the film thickness sensor in this application is formed by removing the cooling pipes in the traditional crystal oscillator probe, which fundamentally eliminates redundant connection structures, realizes the three-dimensional spatial overlap of circuit layout and sensing structure, greatly compresses the ineffective space, and makes the size smaller, allowing for multi-point monitoring. Fourth, since no external wiring or power supply is required, it can move with the base and track the real-time changes in film thickness. At the same time, the crystal oscillator frequency is transmitted to the receiving terminal wirelessly, enabling real-time monitoring of film thickness. Fifth, this application only requires optimizing the structure of the film thickness sensor, without the need for customizing the vacuum chamber, thus saving costs. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure inside the vacuum chamber during the coating process in this utility model. Figure 2 This is a schematic diagram of the film thickness sensor in this utility model; Figure 3 This is an exploded view of the film thickness sensor in this utility model; Figure 4 This is a schematic diagram of the circuit connections of each module on the circuit board in this utility model; Figure 5 The frequency-time curve of the crystal oscillator measured at 300W during the coating process of this utility model; Figure 6 When coating this utility model, the film thickness was photographed using a 300W ultra-high resolution field emission scanning electron microscope; Figure 7 The frequency-time curve of the crystal oscillator measured at 350W during the coating process of this utility model; Figure 8 When coating this utility model, the film thickness was photographed using a 350W ultra-high resolution field emission scanning electron microscope; Figure 9 The frequency-time curve of the crystal oscillator measured at 400W during the coating process of this utility model; Figure 10 When coating this utility model, the film thickness was photographed using a 400W ultra-high resolution field emission scanning electron microscope.

[0015] Explanation of key component symbols: 11-Film thickness sensor; 111-Circuit board; 112-Support block; 113-Crystal oscillator probe; 1131-Support outer ring; 1132-Crystal oscillator plate; 114-Conductive spring; 12-Receiver terminal; 13-Rotating grounding base.

[0016] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this utility model. Detailed Implementation

[0017] The following description is intended to disclose the present invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0018] Please see Figures 1 to 3 The real-time film thickness monitoring system provided in one embodiment of the present invention includes a film thickness sensor 11 disposed inside a vacuum cavity and a receiving terminal 12 disposed outside the vacuum cavity.

[0019] Please see Figures 1 to 3The film thickness sensor 11 is installed in a vacuum chamber and includes a circuit board 111 mounted on a rotating grounding base 13, a support block 112 connected to the circuit board 111 and covering the surface of the circuit board 111 (to prevent the circuit board 111 from being contaminated in the vacuum chamber), and a crystal oscillator probe 113. The crystal oscillator probe 113 includes a support outer ring 1131 that is fastened and installed in the support block 112, a support inner ring disposed in the support outer ring 1131, and a crystal oscillator chip 1132 embedded in the support inner ring and the support outer ring 1131. The bottom of the crystal oscillator chip 1132 is electrically connected to the circuit board 111 through a conductive spring 114 (to enhance connection stability). The outer supporting ring 1131 is positioned directly opposite the sputtering cathode and is used to collect free electrons from the plasma within the cavity during magnetron sputtering, thereby forming a voltage with the rotating grounding base 13 for self-powering.

[0020] It should be noted that during the coating process, the high plasma density within the vacuum chamber allows for the formation of a self-powered power source, eliminating the need for external wiring and power supplies, thus simplifying installation. Since the self-powered power source provides relatively low energy, an ultra-low power circuit structure is employed, enabling real-time film thickness monitoring through a simple circuit design. Because the temperature is relatively low during the coating process, the cooling pipes in traditional crystal oscillator probes are removed to form the film thickness sensor of this application, fundamentally eliminating redundant connection structures. This achieves three-dimensional spatial overlap between the circuit layout and the sensing structure, significantly reducing ineffective space and resulting in a smaller size, allowing for multi-point monitoring. Furthermore, replacing the cathode electron collecting element in the prior art with the supporting outer ring also reduces the size of the film thickness sensor.

[0021] In a preferred embodiment of this utility model, the supporting outer ring is made of aluminum alloy or copper, or other conductive materials.

[0022] In a preferred embodiment of this utility model, the surface of the circuit board is covered with a heat-resistant stabilizing layer, which is made of polytetrafluoroethylene or silicone sealant.

[0023] Please see Figures 2 to 4 In a preferred embodiment of the present invention, the circuit board is provided with a first step-down module, a second step-down module, an oscillator module, a frequency divider module and a main control module that are electrically connected in sequence. The power input terminal of the first step-down module is electrically connected to the supporting outer ring, and the output terminal is connected to the second step-down module, the oscillator module and the frequency divider module respectively, for converting the input voltage into 5V voltage; The output of the second step-down module is connected to the oscillator module and the main control module respectively, and is used to convert 5V voltage to 3.3V voltage; The oscillator module is used to generate a high-frequency oscillation signal from the vibration of the crystal oscillator and transmit the high-frequency oscillation signal to the frequency divider module; The frequency division module is used to convert the high-frequency oscillation signal into a low-frequency signal and transmit the low-frequency signal to the main control module; The main control module is used to calculate the frequency value based on the received low-frequency signal and transmit the frequency value to the receiving terminal wirelessly.

[0024] Please see Figures 2 to 4 In a preferred embodiment of the present invention, the first step-down module includes a first step-down chip, the power input terminal of the first step-down chip is grounded, and a fifth capacitor and a sixth capacitor are connected in parallel with the negative power supply. It should be noted that in this embodiment, the first step-down chip is a TI TPS54302. The SW pin of the first step-down chip is connected in series with the first inductor, the second resistor, the fifth resistor, and the seventh resistor and then connected to the negative power supply. The second capacitor is connected between the SW pin and the bootstrap pin of the first step-down chip. The two ends of the fifth resistor are connected in parallel with the seventh capacitor. The feedback pin of the first step-down chip is connected between the fifth resistor and the seventh resistor and is used to adjust the output voltage. It also includes a third and a fourth capacitor connected in parallel, with one end connected between the second resistor and the first inductor, and the other end connected to the negative power supply.

[0025] Please see Figures 2 to 4 In a preferred embodiment of the present invention, the second step-down module includes a second step-down chip, the power input terminal of the second step-down chip is connected between the second resistor and the first inductor, and is connected in series with the ninth capacitor and then connected to the negative power supply. It should be noted that in this embodiment, the second step-down chip is a linear regulator, model MICRONEME6206A33; the output terminal of the second step-down chip is connected in series with the eleventh capacitor and then connected to the negative power supply.

[0026] Please see Figures 2 to 4 In a preferred embodiment of this utility model, the oscillator module includes a transistor and an inverter; It should be noted that in this embodiment, the oscillator is a Colpitts oscillator. It is understood that in other embodiments, the oscillation circuit can be a bridge oscillator circuit, a Hartley oscillator circuit, etc.

[0027] The collector of the transistor is connected between the second resistor and the first inductor; The base of the transistor is connected to the conductive spring, and the collector of the transistor is connected through the ninth resistor. It is also connected in series with the twelfth and tenth capacitors and then connected to the negative power supply. The emitter of the transistor is connected between the twelfth capacitor and the tenth capacitor, and is also connected to the signal input terminal of the inverter through the sixth resistor; It should be noted that, in this embodiment, the inverter is model TI SN74AUP1G14DBVR.

[0028] The signal input terminal of the inverter is connected in series with the twelfth resistor and then connected to the negative power supply. The power supply input terminal is connected to the output terminal of the second step-down chip. The signal output terminal of the inverter is connected to the frequency divider module to avoid counting interference caused by oscillation signal distortion.

[0029] Please see Figures 2 to 4 In a preferred embodiment of this utility model, the frequency division module includes a first counter chip and a second counter chip; It should be noted that in this embodiment, both the first counter chip and the second counter chip are TI SN74HC4040. The power supply pin of the first counter chip is connected between the second resistor and the first inductor, and is connected in series with the eighth capacitor to the negative power supply. The input pin of the first counter chip is connected to the signal output terminal of the inverter. The power supply pin of the second counter chip is connected between the second resistor and the first inductor, and the input pin of the second counter chip is connected to the output pin of the first counter chip. The output pin of the second counter chip is connected in series with the tenth and eleventh resistors and then connected to the negative power supply. The node between the tenth and eleventh resistors is connected to the signal input terminal of the main control module to convert the high-frequency signal into a low-frequency signal and improve the frequency identification accuracy.

[0030] In a preferred embodiment of this utility model, the monitoring method of the real-time film thickness monitoring system includes the following steps: Step S11: During the magnetron sputtering process, the oscillator module generates a high-frequency oscillation signal from the vibration of the crystal oscillator and transmits the high-frequency oscillation signal to the frequency divider module. Step S12: The frequency division module converts the received high-frequency oscillation signal into a low-frequency signal and transmits the low-frequency signal to the main control module. Step S13: The main control module calculates the frequency value based on the received low-frequency signal and transmits the frequency value to the receiving terminal wirelessly. In step S14, the receiving terminal first calculates the frequency change based on the received frequency value, then calculates the mass change using the Sauerbrey formula, and finally calculates the film thickness based on the relationship between mass, density, area, and thickness.

[0031] Furthermore, the receiving terminal 300 can be a mobile phone, computer, tablet, or smart TV. The wireless transmission method used in this invention is Bluetooth Low Energy (BLE), and the main control chip supports BLE; the signal is transmitted to the receiving terminal 300 via Bluetooth. It is understood that in other embodiments, the wireless transmission method can also be Wi-Fi, ZigBee, infrared, or laser, in addition to Bluetooth.

[0032] It should be noted that in this invention, the frequency variation of the crystal oscillator conforms to the Sauerbrey formula:

[0033] In the formula, The fundamental frequency of the crystal oscillator is (). The density of quartz crystals, Let A be the shear modulus of the quartz crystal, and A be the area of ​​a circular crystal oscillator with a diameter of 8 mm. This represents the mass increment of the material rigidly attached to the electrode surface. This is the change in resonant frequency caused by the increase in the mass of the material on the electrode surface. (The change in frequency is related to...) The change in mass can be calculated. Given that the thin film material is chromium, its density... It is 7.15 g / cm 3 The change in film thickness can then be calculated. : .

[0034] In this embodiment, chromium is selected as the target material, and a pulsed DC power supply is used for sputtering with a power of 30-450W, a duty cycle of 20-90%, and a frequency of 20kHz. The flow rate of the inert gas is 20-100 sccm. Real-time monitoring of the thickness change during the magnetron sputtering process includes the following steps: Step 1: Write a program to the main control chip to achieve the following functions: use the input capture function of the timer to measure the period of the low-frequency signal, convert it back to the crystal oscillator frequency, and then transmit it to the terminal via Bluetooth.

[0035] Step 2: Reference Figure 1 The testing system is installed inside the vacuum chamber; Step 3: Close the chamber door and evacuate to 5×10⁻⁶. -3The base was rotated to face the target, and argon gas was introduced at 30 sccm. The process vacuum levels were 0.48 Pa, 0.40 Pa, and 0.38 Pa, respectively. The power supply was turned on, with the duty cycle set to 90% and the power outputs set to 300 W, 350 W, and 400 W, respectively. Real-time monitoring was used for testing. Step 4: Receive Bluetooth data using the receiving terminal and process the data by plotting curves; Step 5: Take ultra-high resolution field emission scanning electron microscope images of the cross-section of the coated sample and measure the film thickness.

[0036] Example 1, please refer to Figure 5 and Figure 6 The initial frequency under 300W operating conditions is 5998523.6Hz, and the termination frequency is 5796008Hz. The frequency change... The mass increment is 202515.6 Hz, obtained using the Sauerbrey formula. The value is 1.25 mg. The change in film thickness was calculated. It is 3.46 μm, as measured. h The value is 3.47 μm, with an error rate of 0.3%. Please refer to [link / reference]. Figure 5 The data transmitted via Bluetooth to the receiving terminal includes the frequency of the crystal oscillator at different times. Based on this, a crystal oscillator frequency-time curve is plotted with the horizontal axis representing the time span (s) and the vertical axis representing the crystal oscillator frequency (kHz). Figure 5 As can be seen, the frequency of the crystal oscillator decreases over time. After fitting, the frequency change at 300W is 52.18Hz / s (i.e., Figure 5 The slope of the straight line in the figure is constant, indicating that the coating process is stable. Based on the relationship between speed, time and thickness, the coating rate can be calculated to be 0.89 nm / s.

[0037] Example 2, please refer to Figure 7 and Figure 8 The initial frequency of the 350W operating condition is 5996746.8Hz, and the termination frequency is 5741572Hz. Frequency variation... The mass increment is 255174.8 Hz, obtained from the Sauerbrey formula. The value is 1.57 mg. The change in film thickness was calculated. The measured value is 4.38 μm, and the actual measured value of h is also 4.38 μm. Please refer to [link / reference]. Figure 7 The data transmitted via Bluetooth to the receiving terminal includes the frequency of the crystal oscillator at different times. Based on this, a crystal oscillator frequency-time curve is plotted with the horizontal axis representing the time span (s) and the vertical axis representing the crystal oscillator frequency (kHz). Figure 7 As can be seen, the frequency of the crystal oscillator decreases over time. After fitting, the frequency change at 350W is 70.37Hz / s (i.e., Figure 7 The slope of the straight line is constant, indicating that the coating process is stable. Based on the relationship between speed, time and thickness, the coating rate can be calculated to be 1.20 nm / s.

[0038] Example 3, please refer to Figure 9 and Figure 10 The initial frequency under 400W operating conditions is 5994544.4Hz, and the termination frequency is 5648481.6Hz. The frequency change... The mass increment is 346062.8 Hz, obtained from the Sauerbrey formula. The value was 2.13 mg. The change in film thickness was calculated. The measured value was 5.98 μm, while the actual measured value was 5.99 μm, resulting in an error rate of 0.2%. Please refer to [link / reference]. Figure 9 The data transmitted via Bluetooth to the receiving terminal includes the frequency of the crystal oscillator at different times. Based on this, a crystal oscillator frequency-time curve is plotted with the horizontal axis representing the time span (s) and the vertical axis representing the crystal oscillator frequency (kHz). Figure 9 As can be seen, the frequency of the crystal oscillator decreases over time. After fitting, the frequency change at 400W is 85.37Hz / s (i.e., Figure 9 The slope of the straight line in the figure is constant, indicating that the coating process is stable. Based on the relationship between speed, time and thickness, the coating rate can be calculated to be 1.46 nm / s.

[0039] It should be noted that the film thickness resolution and sampling period of the real-time film thickness monitoring system provided by this utility model are mainly determined by the density of the material itself and the crystal oscillator frequency resolution of the system. The frequency resolution is determined by the timer and clock source frequency of the main control module. In this embodiment, the fundamental frequency of the crystal oscillator... The high-frequency clock source of the main control module The main control module's counter has a bit width of 32 bits, and the frequency divider module divides the high-frequency oscillation signal 20 times. Based on this, the film thickness resolution and sampling period of this system can be calculated.

[0040] The sampling period of this system is:

[0041] Calculate the overflow time of the 32-bit counter:

[0042] Therefore, the counter will not overflow.

[0043] Calculate the time resolution of a high-frequency clock source:

[0044] Calculate the resolution:

[0045] The frequency resolution of this system: .

[0046] Taking chromium as an example, the film thickness resolution of this system is: .

[0047] The above calculations show that the film thickness resolution is in the nanometer range (less than 1 nm) and the sampling period is in the second range (less than 1 s), indicating that the system has high resolution and high sampling rate, and can acquire high-fidelity detailed data in a very short sampling time.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A film thickness sensor, characterized in that, Installed inside a vacuum chamber, the device includes a circuit board mounted on a rotating grounding base, a support block connected to and covering the surface of the circuit board, and a crystal oscillator probe. The crystal oscillator probe includes a support outer ring fastened to the support block, a support inner ring disposed in the support outer ring, and a crystal oscillator chip embedded in the support inner ring and the support outer ring. The bottom of the crystal oscillator chip is electrically connected to the circuit board via a conductive spring. The supporting outer ring is positioned directly opposite the sputtering cathode and is used to collect free electrons from the plasma within the cavity during magnetron sputtering, thereby forming a voltage with the rotating grounding base for self-powering.

2. The film thickness sensor according to claim 1, characterized in that, The supporting outer ring is made of aluminum alloy or copper.

3. The film thickness sensor according to claim 1, characterized in that, The circuit board is sequentially provided with a first step-down module, a second step-down module, an oscillator module, a frequency divider module, and a main control module that are electrically connected to each other. The negative power supply of the circuit board is electrically connected to the outer supporting ring; The input terminal of the first step-down module is connected to the grounding base, and the output terminal is connected to the second step-down module, the oscillator module and the frequency divider module respectively, for converting the input voltage into 5V voltage; The output of the second step-down module is connected to the oscillator module and the main control module respectively, and is used to convert 5V voltage to 3.3V voltage; The oscillator module is used to start the crystal oscillator to oscillate, generate a high-frequency oscillation signal, and transmit the high-frequency oscillation signal to the frequency divider module; The frequency division module is used to convert the high-frequency oscillation signal into a low-frequency signal and transmit the low-frequency signal to the main control module; The main control module is used to calculate the frequency value based on the received low-frequency signal and transmit the frequency value to the receiving terminal wirelessly.

4. The film thickness sensor according to claim 3, characterized in that, The first step-down module includes a first step-down chip, the power input terminal of the first step-down chip is grounded, and a fifth capacitor and a sixth capacitor are connected in parallel with the negative power supply; The SW pin of the first step-down chip is connected in series with the first inductor, the second resistor, the fifth resistor, and the seventh resistor and then connected to the negative power supply. The second capacitor is connected between the SW pin and the bootstrap pin of the first step-down chip. The two ends of the fifth resistor are connected in parallel with the seventh capacitor. The feedback pin of the first step-down chip is connected between the fifth resistor and the seventh resistor. It also includes a third and a fourth capacitor connected in parallel, with one end connected between the second resistor and the first inductor, and the other end connected to the negative power supply.

5. The film thickness sensor according to claim 4, characterized in that, The second step-down module includes a second step-down chip, the power input terminal of which is connected between the second resistor and the first inductor, and is connected in series with the ninth capacitor and then connected to the negative power supply. The output terminal of the second step-down chip is connected in series with the eleventh capacitor and then connected to the negative power supply.

6. The film thickness sensor according to claim 5, characterized in that, The oscillator module includes a transistor and an inverter; The collector of the transistor is connected between the second resistor and the first inductor; The base of the transistor is connected to the conductive spring, and the collector of the transistor is connected through the ninth resistor. It is also connected in series with the twelfth and tenth capacitors and then connected to the negative power supply. The emitter of the transistor is connected between the twelfth capacitor and the tenth capacitor, and is also connected to the signal input terminal of the inverter through the sixth resistor; The signal input terminal of the inverter is connected in series with the twelfth resistor and then connected to the negative power supply. The power supply input terminal is connected to the output terminal of the second step-down chip, and the signal output terminal of the inverter is connected to the input terminal of the frequency divider module.

7. The film thickness sensor according to claim 6, characterized in that, The frequency division module includes a first counter chip and a second counter chip; The power supply pin of the first counter chip is connected between the second resistor and the first inductor, and is connected in series with the eighth capacitor to the negative power supply. The input pin of the first counter chip is connected to the signal output terminal of the inverter. The power supply pin of the second counter chip is connected between the second resistor and the first inductor, and the input pin of the second counter chip is connected to the output pin of the first counter chip. The output pin of the second counter chip is connected in series with the tenth and eleventh resistors and then connected to the negative power supply. The node between the tenth and eleventh resistors is connected to the signal input terminal of the main control module.

8. A real-time film thickness monitoring system, characterized in that, It includes a film thickness sensor disposed inside a vacuum cavity and a receiving terminal disposed outside the vacuum cavity, wherein the film thickness sensor is the film thickness sensor according to any one of claims 1 to 7.

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