Frequency sweeping control method, frequency sweeping control apparatus, and semiconductor process device

Abstract

The present disclosure relates to the technical field of semiconductor process devices. Provided are a frequency sweeping control method, a frequency sweeping control apparatus, and semiconductor process device. The frequency sweeping control apparatus of the present disclosure comprises: an impedance measurement unit, which is configured to be connected between a matcher and a radio-frequency power source, so as to acquire the impedance value of the current load impedance at the rear end of the radio-frequency power source; a data processing unit, which is configured to obtain, on the basis of the impedance value of the current load impedance acquired by the impedance measurement unit, the operating voltage of the radio-frequency power source and the impedance value of the radio-frequency power source, a frequency point corresponding to the maximum power that can be obtained by a reaction chamber; and a control unit, which is configured to use, as an initial scanning frequency point of the radio-frequency power source, the frequency point corresponding to the maximum power that can be obtained by the reaction chamber, and control the radio-frequency power source to be turned on. In the present disclosure, on the basis of the value of the current load impedance at the rear end of a radio-frequency power source, a frequency point corresponding to the maximum power obtained in a chamber under a current process condition can be obtained, thereby reducing the risk of ignition failure.

Description

Frequency sweep control method and device, semiconductor process equipment Technical Field

[0001] This disclosure belongs to the field of semiconductor process equipment technology, specifically relating to a sweep frequency control method and sweep frequency control device, and semiconductor process equipment. Background Technology

[0002] With the rapid development of the integrated circuit manufacturing industry, capacitively coupled plasma (CCP) equipment has become one of the most widely used plasma generation devices. A typical CCP device integrates two parallel plate electrodes on its reaction chamber; one electrode is connected to the radio frequency (RF) power supply to excite and generate plasma, while the other is a ground electrode, forming a parallel plate capacitor. Reactive ion etching (RIE) equipment is a representative example of CCP equipment. During normal process operations, the wafer is transferred to an electrostatic chuck (ESC) by a robotic arm and fixed above the ESC by electrostatic adsorption, ensuring that the wafer's position does not deviate during processes such as ventilation and evacuation within the reaction chamber. Process gases are uniformly introduced into the reaction chamber through a showerhead (SHD), and the RF power output from the RF power supply is fed into the ESC through a matching converter, thereby exciting and generating plasma. Free radicals, electrons, and ions in the plasma bombard the wafer surface under the influence of electric and flow fields, resulting in chemical or physical reactions.

[0003] To achieve rapid ignition matching, an increasing number of etching devices are now using frequency sweep matching, which involves an RF power supply paired with a semi-fixed or fixed matcher, and then using a plasma etching machine. However, with a fixed matcher, the capacitor and inductor parameters within the matching network are not adjustable, relying entirely on frequency sweeping of the RF power supply for matching. This method results in a narrow matching range and high requirements for the downstream impedance. Therefore, most matching methods combine a semi-fixed matcher with an RF power supply. A semi-fixed matcher's matching network has only one adjustable capacitor, which, when paired with an RF power supply, provides a relatively wide matching range, suitable for capacitively coupled plasma etching applications.

[0004] Specifically, the working mode of the RF power supply's frequency sweep matching is shown in Figure 1. When an RF ON command is sent to the RF power supply, it will ignite at a fixed frequency. After ignition, it enters a coarse sweep state, quickly finding a frequency point where the reflected power is less than or equal to the coarse sweep reflection threshold (which can be set by the user, for example, 25W). After the coarse sweep, the RF power supply's frequency is fine-tuned within a small range. When a frequency point where the reflected power is less than or equal to the fine sweep reflection threshold (which can be set by the user, for example, 3-5W) is found, the frequency sweep will be fixed at the current frequency point, thus completing the frequency sweep matching. During the RF power supply's frequency sweep, the matching capacitor position is fixed. Therefore, the ignition of the reaction chamber depends on the RF power supply, requiring it to be at a suitable starting frequency to complete the ignition within the reaction chamber. Under different process conditions, the capacitance formed by the two parallel plate electrodes in the reaction chamber of the capacitively coupled plasma device is different, that is, the impedance value of the impedance element is different. Therefore, different starting frequencies are required to complete ignition in the reaction chamber. Thus, providing a power supply that can be set to a suitable starting frequency according to the current process conditions of the reaction chamber to ensure that ignition can be completed in the reaction chamber is an urgent technical problem to be solved. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art, and provides a frequency sweep control method and device, and semiconductor process equipment.

[0006] This disclosure provides a frequency sweep control device for use in semiconductor process equipment; wherein the frequency sweep control device includes:

[0007] An impedance measurement unit is configured to be connected between the matching unit and the RF power supply to obtain the impedance value of the current load impedance at the RF power supply back end.

[0008] The data processing unit is configured to obtain the frequency point corresponding to the maximum power that the reaction chamber can obtain based on the impedance value of the current load impedance obtained by the impedance measurement unit, the operating voltage of the radio frequency power supply, and the impedance value of the radio frequency power supply.

[0009] The control unit is configured to use the frequency point corresponding to the maximum power that the reaction chamber can acquire as the initial scanning frequency point of the radio frequency power supply, and to control the radio frequency power supply to turn on.

[0010] In some examples, the impedance measurement unit includes: a signal acquisition module, a signal processing module, and an impedance calculation module;

[0011] The signal acquisition module is configured to acquire the voltage and current signals of the transmission cable of the radio frequency power supply.

[0012] The signal processing module is configured to process the voltage signal and the current signal acquired by the signal acquisition module to obtain a voltage amplitude signal, a current amplitude signal, and a phase difference signal.

[0013] The impedance calculation module is configured to calculate the impedance value of the current load impedance based on the voltage amplitude signal, the current amplitude signal, and the phase difference signal processed by the signal processing module.

[0014] In some examples, the signal acquisition module includes a first acquisition module for acquiring the voltage signal and a second acquisition module for acquiring the current signal;

[0015] The first acquisition module is configured to acquire the voltage signal of the transmission cable of the radio frequency power supply by using a voltage divider method;

[0016] The second acquisition module is configured to acquire the current signal of the transmission cable of the radio frequency power supply by means of current inductance combined with resistance.

[0017] In some examples, the first acquisition module includes a circuit composed of capacitive elements; and / or, the second acquisition module includes a circuit composed of inductors and resistors.

[0018] This disclosure provides a frequency sweep control method for an RF power supply, using any of the frequency sweep control devices described above, wherein the control method includes:

[0019] Obtain the current load impedance value at the RF power supply back end;

[0020] Based on the impedance value of the current load impedance, the operating voltage of the radio frequency power supply, and the impedance value of the radio frequency power supply, the frequency point corresponding to the maximum power that the reaction chamber can obtain is obtained.

[0021] The frequency point corresponding to the maximum power that the reaction chamber can obtain is used as the initial scanning frequency point of the radio frequency power supply, and the radio frequency power supply is controlled to be turned on.

[0022] In some examples, the step of obtaining the impedance value of the current load impedance of the RF power supply backend includes:

[0023] The voltage and current signals of the transmission cable of the radio frequency power supply are collected;

[0024] The voltage signal and the current signal are processed to obtain a voltage amplitude signal, a current amplitude signal, and a phase difference signal;

[0025] The impedance value of the current load impedance is calculated based on the voltage amplitude signal, the current amplitude signal, and the phase difference signal.

[0026] In some examples, the step of acquiring the voltage and current signals of the transmission cable of the radio frequency power supply includes:

[0027] The voltage signal of the RF power supply transmission cable is acquired by voltage division, and the current signal of the RF power supply transmission cable is acquired by current inductance combined with resistance.

[0028] This disclosure provides a semiconductor process apparatus, including a reaction chamber, a radio frequency (RF) power supply, and a matching unit; the RF unit is connected to the matching unit, and the matching unit is connected to the reaction chamber; wherein...

[0029] The semiconductor process equipment further includes a frequency sweep control device, which employs any of the frequency sweep control devices described above, and the impedance measurement unit of the frequency sweep control device is connected between the matching unit and the RF power supply.

[0030] In some examples, the semiconductor process apparatus further includes a bias power supply electrically connected to the reaction chamber via the matching unit and configured to provide a bias voltage to the reaction chamber.

[0031] In some examples, the matcher includes a first variable capacitor, a second variable capacitor, a first fixed capacitor, a second fixed capacitor, a first inductor, and a second inductor;

[0032] The first plate of the first variable capacitor is connected to the impedance measurement unit, and the second plate of the first variable capacitor is connected to the reference electrode; the first plate of the second variable capacitor is connected to the bias power supply, and the second plate of the second variable capacitor is connected to the reference electrode.

[0033] The first end of the first inductor is connected to the first plate of the first variable capacitor, the second end of the first inductor is connected to the first plate of the first fixed capacitor, and the second plate of the first fixed capacitor is connected to the second end of the second inductor and the reaction chamber; the first plate of the second fixed capacitor is connected to the first plate of the second variable capacitor, and the second plate of the second fixed capacitor is connected to the first end of the second inductor.

[0034] In some examples, the impedance measurement unit is electrically connected to the matching unit via a transmission cable; the transmission cable is a coaxial cable.

[0035] In the frequency sweep control device and method and semiconductor process equipment provided in the embodiments of this disclosure, the frequency point corresponding to the maximum power obtained in the cavity under the current process conditions can be obtained based on the current load impedance value of the RF power supply back end, which is the optimal frequency point, instead of using a fixed frequency sweep point, thereby reducing the risk of ignition failure. In addition, using the optimal frequency point obtained according to the current process conditions for frequency sweep ignition can achieve the purpose of ignition when only the RF power supply power is applied, avoiding the use of bias power supply for auxiliary ignition, avoiding the risk of cavity arcing, and increasing the process utilization window. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the working principle of the RF power supply frequency sweep.

[0037] Figure 2 is a structural diagram of an exemplary CCP device.

[0038] Figure 3 is a structural diagram of the sweep frequency control device of this disclosure applied to a CCP device.

[0039] Figure 4 is a block diagram of a sweep frequency control device according to an embodiment of the present disclosure.

[0040] Figure 5 is a schematic diagram of the equivalent impedance element at the back end of the RF power supply of the sweep frequency control device of this disclosure applied to a CCP device.

[0041] Figure 6 is an equivalent circuit diagram of the sweep frequency control device of this disclosure applied to a CCP device, at the RF power supply back end.

[0042] Figure 7 is a block diagram of the impedance measurement unit of the sweep frequency control device according to an embodiment of the present disclosure.

[0043] Figure 8 is a schematic diagram of the voltage and current signals acquired by the signal acquisition module of the sweep frequency control device according to an embodiment of the present disclosure.

[0044] Figure 9 is a flowchart of the frequency sweep control method of the radio frequency power supply according to an embodiment of the present disclosure.

[0045] Figure 10 is a flowchart of step S1 of the frequency sweep control method of the radio frequency power supply according to an embodiment of the present disclosure. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “including,” “comprising,” or “containing,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0048] Figure 2 is a structural diagram of an exemplary CCP device; as shown in Figure 2, the capacitively coupled plasma (CCP) device includes a reaction chamber, a matching unit, a bias power supply (LF, with frequencies typically 13.56MHz, 2MHz, 400kHz, etc.) and a radio frequency power supply (HF, with frequencies typically 60MHz, 40.68MHz, 27.12MHz, etc.).

[0049] The reaction chamber includes an inlet pipe 1, an inlet flow equalizer 2, a machine housing 3, a back plate 4, an up ground ring 5, an inner liner 6, a substrate 7, an edge ring 8 (HER; hot edge ring), a focusing ring 9, an isolation ring 10, a grounding ring 11, a ceramic base 12, an electrostatic chuck 13, and an electrostatic chuck interface plate 14. The inlet flow equalizer 2 is made of semiconductor material. The inner liner 6, located outside the UGR5, is also made of semiconductor material and primarily serves to confine the plasma. The edge ring 8, being an HER, is mainly made of semiconductor material and can improve plasma distribution and adjust the electric field uniformity. The focusing ring 9 can be made of quartz. The isolation ring 10 can be made of quartz ring or ceramic.

[0050] During the process, a robotic arm transfers the wafer 18 onto the electrostatic chuck 13. Process gases are uniformly introduced into the reaction chamber through the inlet pipe 1 and the inlet flow equalizer 2. The radio frequency power supply 17 transmits radio frequency power to the reaction chamber through the matching unit 19, the feed post 15, the electrostatic chuck interface plate 14, and the electrostatic chuck 13, completing ignition and generating plasma. The bias power supply 16 provides the ion energy for the plasma. The substrate 7 has a grid structure. Through the substrate 7, a dry pump can remove gases and byproducts from the reaction chamber, ensuring stable gas pressure inside the chamber during the process. In addition, the substrate 7 meets certain aspect ratio requirements to ensure plasma annihilation.

[0051] In related technologies, the initial ignition frequency of the RF power supply 17 is typically set to a default 60MHz (intermediate frequency). However, when dealing with processes with significant impedance differences, such as oxygen (O2) at a controlled voltage of 300mT and a flow rate of 800sccm (without a wafer), and argon (Ar) at a controlled voltage of 60mT and a flow rate of 500sccm (with a bare silicon wafer), experience has shown that the optimal frequencies for these two processes are 62.5MHz and 57MHz, respectively. The impedance frequencies of these processes are close to their limits, located at the two ends of the RF power supply 17's sweep frequency range, significantly different from the default initial ignition frequency of 60MHz. If ignition is performed using these optimal frequencies under these process conditions, setting the RF power supply 17 to 200W for ignition results in 100-120W of energy fed into the reaction chamber. This maximizes the bias voltage at wafer 18, sufficient to excite the gas and generate plasma, ensuring successful ignition. When using the default ignition frequency of 60MHz and setting the power of RF power supply 17 to 200W for ignition, the power fed into the reaction chamber is only 10-20W. The bias voltage generated at this low power is insufficient to excite the gas to generate plasma, which increases the probability of ignition failure. This is especially true for electronegative gases (O2) that are difficult to ignite, as they require even higher power. If the ignition start frequency is not the optimal frequency, the probability of ignition failure will increase significantly, resulting in total reflection and other issues during the process.

[0052] To address the aforementioned risk of ignition failure, related technologies employ a bias power supply 16 to transmit 200W of power to the reaction chamber simultaneously with the RF power supply 17 for ignition, assisting in the process. While the higher voltage of the bias power supply facilitates plasma excitation and ignition, this introduces several problems: First, during the initial ignition stage, the gas pressure in the reaction chamber is unstable. Applying a high bias voltage through the bias power supply at this time results in a very high bias voltage on the wafer 18 on the electrostatic chuck 13. The unstable gas pressure in the reaction chamber during this initial stage increases the risk of arcing, leading to greater losses. Second, if the subsequent process requires a lower bias voltage, the bias power supply 16 is not needed to reduce damage. Applying a bias power supply during the ignition stage may cause abnormal wafer demo morphology.

[0053] To address the aforementioned problems, this disclosure provides a frequency sweep control device 20, applied in semiconductor process equipment, such as a CCP device. This disclosure only uses the application of the frequency sweep control device 20 in a CCP device as an example for illustration. Figure 3 is a structural diagram of the frequency sweep control device applied in a CCP device according to an embodiment of this disclosure; Figure 4 is a block diagram of the frequency sweep control device according to an embodiment of this disclosure. As shown in Figures 3 and 4, the frequency sweep control device 20 is used to control the frequency sweep of the RF power supply 17. Specifically, the frequency sweep control device 20 includes an impedance measurement unit 201, a data processing unit 202, and a control unit 203. When the frequency sweep control device 20 is applied in a semiconductor process equipment, the impedance measurement unit 201 is connected between the RF power supply 17 and the matching unit 19, and is configured to acquire the impedance value of the current load impedance of the downstream end of the RF power supply 17, that is, to acquire the impedance value of the current load impedance of the matching unit 19 and the reaction chamber. The data processing unit 202 is connected to the impedance measurement unit 201 and is configured to obtain the frequency point corresponding to the maximum power that the reaction chamber can obtain based on the impedance value of the current load impedance obtained by the impedance measurement unit 201, the operating voltage of the RF power supply 17, and the impedance value of the RF power supply 17. The control unit 203 is connected to the data processing unit 202 and is configured to use the frequency point corresponding to the maximum power that the reaction chamber can obtain as the initial scanning frequency point of the RF power supply 17 and control the RF power supply 17 to turn on.

[0054] In the frequency sweep control device 20 of this disclosure embodiment, the frequency point corresponding to the maximum power obtained in the cavity under the current process conditions can be obtained based on the current load impedance value of the RF power supply 17, which is the optimal frequency point, instead of using a fixed frequency sweep point, thereby reducing the risk of ignition failure. In addition, using the optimal frequency point obtained according to the current process conditions for frequency sweep ignition can achieve the purpose of ignition by only loading the RF power supply 17, avoiding the use of bias power supply for auxiliary ignition, avoiding the risk of cavity arcing, and increasing the process utilization window.

[0055] To better understand why the sweep frequency control device 20 in this embodiment of the present disclosure can ensure successful ignition inside the reaction chamber by determining the frequency point based on the current load impedance value at the back end of the RF power supply 17, the following is a detailed explanation.

[0056] Referring again to Figure 3, since the semiconductor process equipment includes not only the RF power supply 17 but also the bias power supply, in this case, the matching unit 19 can be a dual-frequency fixed matching unit. This matching unit 19 includes two matching branches: a first matching branch for connecting the RF power supply 17 to the reaction chamber, and a second matching branch for connecting the bias power supply 16 to the reaction chamber. In one example, the first matching branch consists of a first variable capacitor C1, a first fixed capacitor C2, and a first inductor L1; the second matching branch consists of a second variable capacitor C7, a second fixed capacitor C8, and a second inductor L2. Specifically, the first plate of the first variable capacitor C1 is connected to the impedance measurement unit 201, and the second plate of the first variable capacitor C1 is connected to the reference electrode; the first plate of the second variable capacitor C7 is connected to the bias power supply 16, and the second plate of the second variable capacitor C7 is connected to the reference electrode; the first end of the first inductor L1 is connected to the first plate of the first variable capacitor C1, the second end of the first inductor L1 is connected to the first plate of the first fixed capacitor C2, the second plate of the first fixed capacitor C2 is connected to the second end of the second inductor L2 and the reaction chamber; the first plate of the second fixed capacitor C2 is connected to the first plate of the second variable capacitor C8, and the second plate of the second fixed capacitor C8 is connected to the first end of the second inductor L2.

[0057] Figure 5 is a schematic diagram of the equivalent impedance elements at the back end of the RF power supply of the sweep frequency control device according to an embodiment of this disclosure applied to a CCP device. Referring to Figure 5, under the current process conditions, the feed post 15 is equivalent to an inductor L2, and the wafer 18, the reaction gas in the reaction chamber, the inlet flow equalizer 2, and the isolation ring 10 are equivalent to capacitors C3, C4, C5, and C6, respectively. The values ​​of L2, C5, and C6 are related to the structure of the reaction chamber, and L2, C5, and C6 are fixed values. C3 and C4 are related to the wafer 18 and the reaction gas in the reaction chamber, respectively; therefore, the values ​​of C3 and C4 are different under different process conditions.

[0058] Based on the above analysis, the equivalent circuit diagram of the RF power supply 17 and the first matching branch of the matching unit 19 connected thereto, as well as the reaction chamber, is shown in Figure 6. The load value of the back-end impedance load of the RF power supply 17 is ZL.

[0059] Where X1 is the equivalent load value of C2, L1 and L2; X2 is the equivalent load value of C1; X3 is the equivalent load value of C3, C4 and C5; and X4 is the equivalent load value of C6.

[0060] Where ω = 2πf, f is the frequency of RF power supply 17, and the impedance of RF power supply 17 is: Z S =R S +X S

[0061] For the equivalent circuit in Figure 5, the voltage of the load at the back end of the RF power supply 17 is:

[0062] V L =Z L ×I L ;in,

[0063] In the static state, the total power received by the downstream load of RF power supply 17 is:

[0064] From formula (6), we can see that V S With Z S The output voltage and internal resistance of RF power supply 17 are known parameters. Under static conditions, the power received by the load downstream of RF power supply 17 and the impedance Z of the load downstream of RF power supply 17 are also known parameters. L Strong correlation. As can be seen from formulas (1) to (5), the power obtained by the chamber load is different for different sweep frequencies. By calculation, the frequency point f1 corresponding to the maximum power obtained by the load at the back end of the RF power supply 17 can be found. When igniting, the initial frequency point of the RF power supply 17 is set to f1 to ensure that the maximum power can be obtained in the reaction chamber, which makes it easier to excite the plasma and achieve the purpose of ignition.

[0065] In some examples, Figure 7 is a block diagram of the impedance measurement unit of the sweep frequency control device according to an embodiment of the present disclosure. As shown in Figure 7, the impedance measurement unit 201 of this embodiment may specifically include a signal acquisition module 2011, a signal processing module 2012, and an impedance calculation module 2013. The signal acquisition module 2011 is configured to acquire the voltage and current signals of the transmission cable of the RF power supply 17. The signal processing module 2012 is configured to process the voltage and current signals acquired by the signal acquisition module 2011 to obtain a voltage amplitude signal, a current amplitude signal, and a phase difference signal. The impedance calculation module 2013 is configured to calculate the impedance value of the current load impedance based on the voltage amplitude signal, current amplitude signal, and phase difference signal obtained by the signal processing module 2012.

[0066] In some examples, the transmission line connecting the signal acquisition module 2011 and the matching unit 19 can specifically be a coaxial cable (i.e., a cable line). The signal acquisition module 2011 can include a first acquisition module for acquiring voltage signals and a second acquisition module for acquiring current signals. The first acquisition module can be a voltage divider circuit, which can acquire the voltage wave on the transmission cable to obtain the voltage signal by voltage division. The second acquisition module can be a circuit combining current inductance and resistance, which acquires the current wave on the transmission cable to obtain the aforementioned current signal by combining current inductance and resistance. Figure 8 is a schematic diagram of the signal acquisition module 2011 of the sweep frequency control device 20 of this disclosure acquiring voltage and current signals; as shown in Figure 8, the voltage divider circuit in the signal acquisition module 2011 consists of two capacitor elements, and the current inductance and resistance circuit consists of an inductor and a resistor.

[0067] In some examples, the signal processing module 2012 can specifically rectify the waveforms of the voltage and current signals in forward and reverse directions respectively to obtain DC information of the voltage and current waves. From this DC information, the voltage amplitude signal and current amplitude signal are obtained. Simultaneously, the waveforms of the voltage and current signals are compared using zero-crossing comparators to obtain their respective pulse signals. These pulse signals are then passed through a phase detector or phase detection circuit to obtain the phase difference. This phase difference is then biased and calibrated so that when the output impedance of the RF power supply 17 equals the standard output impedance (e.g., 50Ω), the phase difference is 0V. Finally, the phase difference signal is output through an amplification circuit. The phase difference signal obtained through zero-crossing comparator processing can reduce the influence of waveform distortion, harmonics, and other factors, thereby improving the measurement accuracy of the phase difference signal.

[0068] In some examples, the impedance calculation module 2013 integrates an I / O interface module, which is used to receive voltage amplitude signals, current amplitude signals and phase difference signals, and after calculating the impedance value of the current load impedance, sends it to the data processing unit 202.

[0069] This disclosure also provides a frequency sweep control method, which is applied to the frequency sweep control device 20 provided in this disclosure embodiment. FIG9 is a flowchart of the frequency sweep control method of the radio frequency power supply in this disclosure embodiment; as shown in FIG9, the frequency sweep control method may specifically include the following steps:

[0070] S1. Acquire the current load impedance value of the back end of the RF power supply 17, that is, obtain the current load impedance value of the reaction chamber and the matching unit 19.

[0071] In some examples, step S1 can specifically employ the impedance measurement unit 201 described above to acquire the impedance value of the current load impedance at the downstream end of the RF power supply 17. Figure 10 is a flowchart of step S1 of the RF power supply sweep frequency control method according to an embodiment of this disclosure; as shown in Figure 10, when the impedance measurement unit 201 is composed of a signal acquisition module 2011, a signal processing module 2012, and an impedance calculation module 2013, step S1 may include the following steps:

[0072] S11. Collect the voltage and current signals of the transmission cable of the radio frequency power supply 17.

[0073] In some examples, step S11 may include acquiring the voltage and current signals of the transmission cable of the RF power supply 17 through the signal acquisition module 2011. For example, the voltage signal can be obtained by acquiring the voltage wave of the transmission cable using a voltage divider; the current signal can be obtained by acquiring the current wave of the transmission cable using a current inductor combined with a resistor. That is, the signal acquisition module 2011 may integrate a first acquisition module and a second acquisition module. The first acquisition module may be a voltage divider circuit, and the second acquisition module may be a circuit of current inductor combined with a resistor, as shown in Figure 8.

[0074] S12. Process the voltage and current signals to obtain voltage amplitude signals, current amplitude signals, and phase difference signals.

[0075] In some examples, step S12 may include processing the voltage and current signals using the signal processing module 2012 to obtain voltage amplitude signals, current amplitude signals, and phase difference signals. For example, the signal processing module may specifically rectify the waveforms of the voltage and current signals in both forward and reverse directions to obtain DC information for the voltage and current waves, thus obtaining voltage amplitude signals and current amplitude signals. Simultaneously, the waveforms of the voltage and current signals are compared using zero-crossing comparators to obtain their respective pulse signals. These pulse signals are then processed by a phase detector or phase detection circuit to obtain the phase difference. The phase difference is then biased and calibrated so that when the output impedance of the RF power supply 17 equals the standard output impedance (e.g., 50Ω), the phase difference is 0V. Finally, the phase difference signal is output through an amplification circuit. The phase difference signal obtained through zero-crossing comparator processing can reduce the influence of waveform distortion, harmonics, and other factors, improving the measurement accuracy of the phase difference signal.

[0076] S13. Calculate the impedance value of the current load impedance based on the voltage amplitude signal, current amplitude signal, and phase difference signal.

[0077] In some examples, step S13 may include using an impedance calculation module 2013 to calculate the impedance value of the current load impedance using a preset impedance calculation algorithm and based on the voltage amplitude signal, current amplitude signal, and phase difference signal.

[0078] S2. Based on the current load impedance value, the operating voltage of the RF power supply 17, and the impedance value of the RF power supply 17, obtain the frequency point corresponding to the maximum power that the reaction chamber can obtain.

[0079] In some examples, step S2 may include using data processing unit 202 to obtain the frequency point corresponding to the maximum power that the reaction chamber can obtain, based on the impedance value of the load impedance of the back end of the RF power supply 17, the operating voltage of the RF power supply 17, and the impedance value of the RF power supply 17 obtained in step S1. The operating voltage and impedance value of the RF power supply 17 are fixed values ​​and can be pre-stored in data processing unit 202. The maximum power obtained by the current load impedance of the RF power supply 17 can be calculated using the above calculation formulas (1)-(6). The power magnitude is related to the frequency sweep, so the frequency point corresponding to the maximum power obtained by the current load impedance of the RF power supply 17 can be obtained. For example, if the data processing unit 202 stores the correspondence between power and frequency sweep, then when calculating the maximum power obtained by the current load impedance, the frequency sweep corresponding to that power can be directly obtained based on the correspondence between power and frequency sweep. Of course, data processing unit 202 can also obtain the frequency sweep corresponding to the calculated maximum power obtained by the current load impedance using a preset algorithm.

[0080] S3. The frequency point corresponding to the maximum power that the reaction chamber can obtain is used as the initial scanning frequency point of the RF power supply 17, and the RF power supply 17 is turned on.

[0081] In some examples, step S3 may include obtaining the frequency point corresponding to the maximum power obtained by the current load impedance of the back end of the RF power supply 17 obtained in step S2, using the frequency point corresponding to the maximum power that the reaction chamber can obtain as the initial scanning frequency point of the RF power supply 17, and controlling the RF power supply 17 to start the frequency sweep matching operation.

[0082] In the frequency sweep control method of this disclosure embodiment, the frequency point corresponding to the maximum power obtained in the reaction chamber under the current process conditions can be calculated based on the current load impedance value of the RF power supply 17, which is the optimal frequency point, instead of using a fixed frequency sweep point, thereby reducing the risk of ignition failure. In addition, using the optimal frequency point obtained under the current process conditions for frequency sweep ignition can achieve the purpose of ignition by only loading the power of the RF power supply 17, avoiding the use of bias power supply for auxiliary ignition, avoiding the risk of chamber arcing, and increasing the process utilization window.

[0083] This disclosure also provides a semiconductor process apparatus, specifically the CCP device described above. The semiconductor process apparatus includes a reaction chamber, an RF power supply 17, a matching unit 19, and a sweep frequency control device 20. The sweep frequency control device 20 is the sweep frequency control device 20 described above. The RF unit is connected to the matching unit 19, and the matching unit 19 is connected to the reaction chamber; the impedance measurement unit 201 of the sweep frequency control device 20 is connected between the matching unit 19 and the RF power supply 17.

[0084] In the semiconductor process equipment of this disclosure embodiment, since the semiconductor process equipment includes the above-mentioned sweep frequency control device 20, the sweep frequency control device 20 can determine the frequency point corresponding to the maximum power obtained in the cavity under the current process conditions, i.e., the optimal frequency point, based on the current load impedance value of the downstream of the RF power supply 17, instead of using a fixed sweep frequency point, thereby reducing the risk of ignition failure. In addition, using the optimal frequency point obtained according to the current process conditions for sweep frequency ignition can achieve the purpose of ignition by only loading the power of the RF power supply 17, avoiding the use of bias power supply for auxiliary ignition, avoiding the risk of cavity arcing, and increasing the process utilization window.

[0085] Referring again to Figure 2, the semiconductor process equipment includes not only an RF power supply 17 but also a bias power supply 16. The bias power supply 16 is electrically connected to the reaction chamber via a matching adapter 19 and is configured to provide a bias voltage to the reaction chamber. In this case, the matching adapter 19 can be a dual-band fixed matching adapter 19, which includes two matching branches: a first matching branch for connecting the RF power supply 17 to the reaction chamber, and a second matching branch for connecting the bias power supply 16 to the reaction chamber. In one example, the first matching branch consists of a first variable capacitor, a first fixed capacitor, and a first inductor; the second matching branch consists of a second variable capacitor, a second fixed capacitor, and a second inductor. In this configuration, the first plate of the first variable capacitor is connected to the impedance measurement unit 201, and the second plate of the first variable capacitor is connected to the reference electrode; the first plate of the second variable capacitor is connected to the bias power supply 16, and the second plate of the second variable capacitor is connected to the reference electrode; the first end of the first inductor is connected to the first plate of the first variable capacitor, the second end of the first inductor is connected to the first plate of the first fixed capacitor, the second plate of the first fixed capacitor is connected to the second end of the second inductor and the reaction chamber; the first plate of the second fixed capacitor is connected to the first plate of the second variable capacitor, and the second plate of the second fixed capacitor is connected to the first end of the second inductor.

[0086] In some examples, the impedance measurement unit 201 is electrically connected to the matching unit 19 via a transmission cable; the transmission cable is a coaxial cable (i.e., a cable line). When the impedance measurement unit 201 includes a signal acquisition module 2011, a signal processing module 2012, and an impedance calculation module 2013, the signal acquisition module 2011 is connected to the matching unit 19 via a coaxial cable.

[0087] It should be noted that when the impedance measurement unit 201 is used to obtain the impedance value of the current load impedance at the back end of the RF power supply 17, the current load impedance value obtained at this time includes not only the impedance values ​​of the matching unit 19 and the reaction chamber, but also the impedance value of the coaxial cable. However, since the impedance value of the coaxial cable has a very small impact on the current load impedance value obtained, it can be ignored.

[0088] In summary, in the frequency sweep control device 20 and frequency sweep control method and semiconductor process equipment provided in the embodiments of this disclosure, the frequency point corresponding to the maximum power obtained in the cavity under the current process conditions can be obtained based on the current load impedance value of the RF power supply 17, which is the optimal frequency point, instead of using a fixed frequency sweep point. This reduces the risk of ignition failure. In addition, using the optimal frequency point obtained under the current process conditions for frequency sweep ignition can achieve the purpose of ignition by only loading the RF power supply 17, avoiding the use of bias power supply for auxiliary ignition, avoiding the risk of cavity arcing, and increasing the process utilization window.

[0089] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A frequency sweep control device, applied in semiconductor process equipment; characterized in that, The frequency sweep control device includes: An impedance measurement unit is configured to be connected between the matching unit and the RF power supply to obtain the impedance value of the current load impedance at the RF power supply back end. The data processing unit is configured to obtain the frequency point corresponding to the maximum power that the reaction chamber can obtain based on the impedance value of the current load impedance obtained by the impedance measurement unit, the operating voltage of the radio frequency power supply, and the impedance value of the radio frequency power supply. The control unit is configured to use the frequency point corresponding to the maximum power that the reaction chamber can acquire as the initial scanning frequency point of the radio frequency power supply, and to control the radio frequency power supply to turn on.

2. The frequency sweep control device according to claim 1, characterized in that, The impedance measurement unit includes: a signal acquisition module, a signal processing module, and an impedance calculation module; The signal acquisition module is configured to acquire the voltage and current signals of the transmission cable of the radio frequency power supply. The signal processing module is configured to process the voltage signal and the current signal acquired by the signal acquisition module to obtain a voltage amplitude signal, a current amplitude signal, and a phase difference signal. The impedance calculation module is configured to calculate the impedance value of the current load impedance based on the voltage amplitude signal, the current amplitude signal, and the phase difference signal processed by the signal processing module.

3. The frequency sweep control device according to claim 2, characterized in that, The signal acquisition module includes a first acquisition module for acquiring the voltage signal and a second acquisition module for acquiring the current signal; The first acquisition module is configured to acquire the voltage signal of the transmission cable of the radio frequency power supply by using a voltage divider method; The second acquisition module is configured to acquire the current signal of the transmission cable of the radio frequency power supply by means of current inductance combined with resistance.

4. The frequency sweep control device according to claim 3, characterized in that, The first acquisition module includes a circuit composed of capacitors; and / or, the second acquisition module includes a circuit composed of inductors and resistors.

5. A frequency sweep control method for an RF power supply, using the frequency sweep control device according to any one of claims 1-4, characterized in that, The frequency sweep control method includes: Obtain the current load impedance value at the RF power supply back end; Based on the impedance value of the current load impedance, the operating voltage of the radio frequency power supply, and the impedance value of the radio frequency power supply, the frequency point corresponding to the maximum power that the reaction chamber can obtain is obtained. The frequency point corresponding to the maximum power that the reaction chamber can obtain is used as the initial scanning frequency point of the radio frequency power supply, and the radio frequency power supply is controlled to be turned on.

6. The frequency sweep control method according to claim 5, characterized in that, The step of obtaining the impedance value of the current load impedance of the RF power supply backend includes: The voltage and current signals of the transmission cable of the radio frequency power supply are collected; The voltage signal and the current signal are processed to obtain a voltage amplitude signal, a current amplitude signal, and a phase difference signal; The impedance value of the current load impedance is calculated based on the voltage amplitude signal, the current amplitude signal, and the phase difference signal.

7. The frequency sweep control method according to claim 6, characterized in that, The steps of acquiring the voltage and current signals of the transmission cable of the radio frequency power supply include: The voltage signal of the RF power supply transmission cable is acquired by voltage division, and the current signal of the RF power supply transmission cable is acquired by current inductance combined with resistance.

8. A semiconductor process apparatus comprising a reaction chamber, a radio frequency (RF) power supply, and a matching unit; wherein the RF unit is connected to the matching unit, and the matching unit is connected to the reaction chamber; characterized in that, The semiconductor process equipment further includes a frequency sweep control device, which is the frequency sweep control device according to any one of claims 1-4, and the impedance measurement unit of the frequency sweep control device is connected between the matching unit and the RF power supply.

9. The semiconductor process equipment according to claim 8, characterized in that, Also includes: A bias power supply, which is electrically connected to the reaction chamber via the matching unit, is configured to provide a bias voltage to the reaction chamber.

10. The semiconductor process equipment according to claim 9, characterized in that, The matching unit includes a first variable capacitor, a second variable capacitor, a first fixed capacitor, a second fixed capacitor, a first inductor, and a second inductor; The first plate of the first variable capacitor is connected to the impedance measurement unit, and the second plate of the first variable capacitor is connected to the reference electrode. The first plate of the second variable capacitor is connected to the bias power supply, and the second plate of the second variable capacitor is connected to the reference electrode. The first end of the first inductor is connected to the first plate of the first variable capacitor, the second end of the first inductor is connected to the first plate of the first fixed capacitor, and the second plate of the first fixed capacitor is connected to the second end of the second inductor and the reaction chamber; the first plate of the second fixed capacitor is connected to the first plate of the second variable capacitor, and the second plate of the second fixed capacitor is connected to the first end of the second inductor.

11. The semiconductor process equipment according to claim 9, characterized in that, The impedance measurement unit and the matching unit are electrically connected via a transmission cable; the transmission cable is a coaxial cable.

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