Adjusting method, control device and system of bias voltage, and semiconductor process equipment

Abstract

The invention provides a bias voltage adjusting method, a bias voltage control device, a bias voltage control system and semiconductor process equipment. The adjusting method comprises the following steps: acquiring an actual bias voltage of a lower electrode of semiconductor process equipment when a lower electrode radio frequency power supply outputs according to reference power, and recording the actual bias voltage as a first actual bias voltage; when the first actual bias voltage is stable, obtaining the precision of the first actual bias voltage; and when the precision of the first actual bias voltage meets a first target precision range, determining the precision of the lower electrode radio frequency power supply based on the output power of the lower electrode radio frequency power supply at the current moment, the first actual bias voltage at the current moment and the first actual bias voltages at two moments closest to the current moment. And controlling the lower electrode radio frequency power supply to output according to the second target output power.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of semiconductor technology, and particularly relates to a bias voltage adjustment method, a control device and system, and a semiconductor process equipment. BACKGROUND

[0002] In the related art, a semiconductor process equipment includes a process chamber, an upper electrode and a lower electrode. The upper electrode is arranged at the top of the process chamber and is used to load an upper radio frequency signal in a semiconductor process to excite a process gas delivered into the process chamber to generate plasma. The lower electrode includes an electrostatic chuck, which is arranged at the bottom of the process chamber and is used to adsorb and fix a wafer in the semiconductor process and can load a lower radio frequency signal to attract the plasma in the process chamber to act on the wafer.

[0003] In recent years, with the continuous development of integrated circuits, the industry has increasingly high requirements for the integration of integrated circuits, and needs to improve the performance and performance of integrated circuits by reducing the etching size of semiconductor devices. Inductively coupled plasma equipment (ICP) and capacitively coupled plasma equipment (CCP) are widely used in the field of microelectronic processing due to their advantages of high selectivity, high anisotropy and high etching rate. However, traditional continuous wave radio frequency source etching cannot meet the requirements of 20nm and below etching processes. Compared with continuous wave discharge, pulse discharge can not only obtain more extensive and independent control of plasma parameters, but also effectively reduce the damage to the sample surface caused by plasma, such as physical damage caused by continuous high-energy ion bombardment and radiation damage caused by vacuum ultraviolet photons. And, by modulating the pulse discharge, a higher aspect ratio, greater etching selectivity, less plasma-induced surface damage, greater etching yield, etc. can be obtained. At the same time, for high-voltage pulse processes with short process time, the lower electrode bias voltage requires faster adjustment speed. In view of the foregoing, there is a need for a method of controlling the lower electrode bias voltage to increase the level of control of plasma ion energy. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art, and provides a method for adjusting the bias voltage of a lower electrode, which is applied to a semiconductor process equipment, and is characterized in that the adjustment method comprises:

[0005] acquiring the actual bias voltage of the lower electrode of the semiconductor process equipment when the lower electrode radio frequency power source outputs according to the reference power, denoted as the first actual bias voltage;

[0006] when the first actual bias voltage reaches a stable state, acquiring the precision of the first actual bias voltage;

[0007] When the accuracy of the first actual bias voltage meets a first target accuracy range, the lower electrode RF power source is controlled to output at a second target output power based on the output power of the lower electrode RF power source at the current time, the first actual bias voltage at the current time, and the first actual bias voltages at the two most recent times before the current time.

[0008] In some embodiments, the adjusting method further includes:

[0009] When the accuracy of the first actual bias voltage meets a second target accuracy range, the lower electrode RF power source is controlled to output at a first target output power based on the output power of the lower electrode RF power source at the current time, the first actual bias voltage at the current time, and a target bias voltage, and an actual bias voltage at the current time is obtained, denoted as a second actual bias voltage; the first target accuracy range is higher than the second target accuracy range; and,

[0010] When the second actual bias voltage reaches stability, the accuracy of the second actual bias voltage is obtained.

[0011] When the accuracy of the second actual bias voltage meets the first target accuracy range, the lower electrode RF power source is controlled to output at a second target output power based on the output power of the lower electrode RF power source at the current time, the second actual bias voltage at the current time, and the second actual bias voltages at the two most recent times before the current time.

[0012] The embodiments of the present disclosure also provide an adjusting method of a lower electrode bias voltage, applied to a semiconductor process equipment, characterized in that the adjusting method includes:

[0013] An actual bias voltage of a lower electrode of the semiconductor process equipment when a lower electrode RF power source outputs at a reference power is obtained, denoted as a first actual bias voltage.

[0014] When the first actual bias voltage reaches stability, the lower electrode RF power source is controlled to output at a first target output power based on the output power of the lower electrode RF power source at the current time, the first actual bias voltage at the current time, and a target bias voltage, and an actual bias voltage at the current time is obtained, denoted as a second actual bias voltage.

[0015] When the second actual bias voltage reaches stability, the accuracy of the second actual bias voltage is obtained.

[0016] When the accuracy of the second actual bias voltage meets the first target accuracy range, the output power of the lower electrode radio frequency power supply at the current time, the second actual bias voltage at the current time, and the second actual bias voltages at the two most recent times before the current time are used to control the lower electrode radio frequency power supply to output at a second target output power.

[0017] In some embodiments, the adjusting method further comprises:

[0018] The second target output power is used as the output power of the lower electrode radio frequency power supply at the current time, and the lower electrode radio frequency power supply is controlled to output to the lower electrode.

[0019] An actual bias voltage of the lower electrode at the current time is obtained, denoted as a third actual bias voltage.

[0020] The accuracy of the third actual bias voltage is obtained.

[0021] It is determined whether the accuracy of the third actual bias voltage meets a third target accuracy range; the third target accuracy range is higher than the first target accuracy range.

[0022] If the accuracy of the third actual bias voltage meets the third target accuracy range, the radio frequency power supply is controlled to output at the current output frequency.

[0023] In some embodiments, the adjusting method further comprises:

[0024] If the accuracy of the third actual bias voltage does not meet the third target accuracy range, the output power of the lower electrode radio frequency power supply is adjusted based on the second target output power, the third actual bias voltage at the current time, and the third actual bias voltages at the two most recent times before the current time, and the step of obtaining the actual bias voltage of the lower electrode at the current time is returned to until the accuracy of the third actual bias voltage meets the third target accuracy range.

[0025] In some embodiments, the adjusting method further comprises: at the power-on time of the semiconductor process equipment, a corresponding reference power is obtained based on the process performed by the semiconductor process equipment, and the lower electrode radio frequency power supply is controlled to output at the reference power.

[0026] In some embodiments, the adjusting method further comprises: the first target output power is calculated by the following formula (1):

[0027]

[0028] P_feedback1 = K0 * (V_target - V_current) + P_current, wherein P_feedback1 is the first target output power; P_current is the output power of the lower electrode radio frequency power supply at the current time; V_target is the target bias voltage; V_current is the actual bias voltage of the lower electrode at the current time; K0 is a proportional adjustment coefficient, used to represent the relationship between the difference between the target bias voltage and the actual bias voltage and the target bias voltage.

[0029] In some embodiments, the adjustment method further comprises: calculating the second target output power by the following formula (2):

[0030]

[0031] P_feedback2 = K1 * (V_target - V_current) + K2 * (V_target - V_current) + P_current, wherein P_feedback2 is the second target output power; P_current is the output power of the lower electrode radio frequency power supply at the current time; AV(current) is the difference between the actual bias voltage of the lower electrode at the current time and the actual bias voltage of the lower electrode at the previous time; AV(current-1) is the difference between the actual bias voltage of the lower electrode at the previous time and the actual bias voltage of the lower electrode at the time before the previous time; K1 is a gain coefficient, used to represent the relationship between the output power of the lower electrode radio frequency power supply and the actual bias voltage of the lower electrode; K2 is a time constant integral coefficient, used to represent the relationship between the sampling time and the response time constant; a is a nonlinear parameter quadratic coefficient, b is a linear parameter coefficient, and a and b are both used to represent the adjustment speed. P T

[0032] In some embodiments, the adjustment method further comprises: before calculating the second target output power by the formula (2), calculating the linear parameter coefficient b by the following formula (3), and obtaining the nonlinear parameter quadratic coefficient a:

[0033]

[0034] V_target = Vref * (P_max - P_current) / P_max, wherein V_target is the target bias voltage; P_max is the maximum output power of the lower electrode radio frequency power supply; Vref is a reference voltage; max

[0035] In some embodiments, the linear parameter coefficient b has a value range of [1, 80].

[0036] In some embodiments, the gain coefficient K1 has a value range of [0.005, 0.1], and the time constant integral coefficient K2 has a value range of [0.00015, 0.0003]. P T ​​​​​

[0037] The embodiment of the present disclosure further provides a control device, comprising a controller and a memory; the memory stores a computer program, and the computer program is executed by the controller to realize the adjusting method in the above embodiment.

[0038] The embodiment of the present disclosure further provides a control system applied to a semiconductor process equipment, characterized in that the control system comprises a voltage acquisition device and the control device in the above embodiment.

[0039] The voltage acquisition device is configured to acquire the bias voltage of the lower electrode of the semiconductor process equipment to obtain an actual bias voltage.

[0040] The control device is configured to acquire the actual bias voltage acquired by the voltage acquisition device and control the power output of the lower electrode radio frequency power supply of the semiconductor process equipment.

[0041] In some embodiments, the voltage acquisition device comprises an acquisition unit and a signal processing unit.

[0042] The acquisition unit is configured to acquire the bias voltage of the lower electrode to obtain an initial bias voltage.

[0043] The signal processing unit is configured to process the initial bias voltage to obtain the actual bias voltage.

[0044] In some embodiments, the control system further comprises a signal synchronization control device configured to control the lower electrode radio frequency power supply and the voltage acquisition device to work synchronously.

[0045] The embodiment of the present disclosure further provides a semiconductor process equipment comprising a process chamber, an upper electrode, a lower electrode, an upper electrode radio frequency power supply, a lower electrode radio frequency power supply and a control system; characterized in that the control system adopts the control system in the above embodiment.

[0046] In the adjustment method of the present application, the controller first controls the lower electrode RF power supply to start working at a reference power through the first stage of adjustment, taking the reference power as the starting point of the subsequent adjustment, which can greatly shorten the adjustment time and improve the adjustment speed. Then, the controller successively adjusts the output power of the lower electrode RF power supply through the second and third stages of adjustment, or, based on the accuracy of the lower electrode bias voltage when the lower electrode RF power supply outputs at the reference power, the controller adjusts the output power through the third stage of fine adjustment alone or successively through the second stage of coarse adjustment and the third stage of fine adjustment. Both of these two adjustment methods gradually improve the accuracy of the bias voltage of the lower electrode under the premise of ensuring that the working environment is stable enough, and finally make the accuracy of the bias voltage reach the target accuracy range. The adjustment method of the present application can greatly improve the adjustment speed of the bias voltage, and further improve the response speed of the process equipment, meeting the demand of high-power pulse process for voltage control speed. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 A structural schematic diagram of a semiconductor process equipment is provided for the embodiments of the present disclosure.

[0048] Figure 2 A flowchart of a control method for controlling the bias voltage of a lower electrode is provided.

[0049] Figure 3 A structural schematic diagram of a semiconductor process equipment is provided for the embodiments of the present disclosure.

[0050] Figure 4 A structural schematic diagram of a controller is provided for the embodiments of the present disclosure.

[0051] Figure 5 A flowchart of the first example of the adjustment method provided for the embodiments of the present disclosure.

[0052] Figure 6 A flowchart of the second example of the adjustment method provided for the embodiments of the present disclosure.

[0053] Figure 7 A control effect diagram of adjusting the bias voltage by using the adjustment method shown in Figure 5 A control effect diagram of adjusting the bias voltage by using the control method shown in

[0054] Figure 8 A control effect diagram of adjusting the bias voltage by using the control method shown in Figures 1-2 A control effect diagram of adjusting the bias voltage by using the control method shown in DETAILED DESCRIPTION

[0055] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be described in further detail below in conjunction with the drawings and specific embodiments.

[0056] Unless otherwise defined, technical terms and scientific terms used in the present application shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "a", "an", "one", "this", and the like, as used in the present application, do not denote number restriction, but refer to a single or multiple. The terms "include", "comprise", "have", and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a list of steps or modules (units) is not limited to the listed steps or units, but can further include other steps or units not listed, or can further include other steps or units inherent to such a process, method, product, or device. The terms "connect", "connected", "couple", and the like, are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The term "multiple" refers to two or more. The term "and / or" describes the association relationship between the associated objects, which means that there can be three relationships, for example, "A and / or B" can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects. The terms "first", "second", "third", and the like, are only used to distinguish similar objects, and do not represent a specific order of the objects. "Up", "down", "left", "right", and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0057] Figure 1 A structural schematic diagram of a semiconductor process equipment is provided for the embodiments of the present disclosure. The semiconductor process equipment can include an inductively coupled plasma (ICP) or a capacitively coupled plasma (CCP), Figure 1 The semiconductor process equipment in the present application is described and illustrated only by taking ICP as an example.

[0058] Referring to Figure 1The semiconductor processing equipment includes an upper electrode radio frequency power supply 1, an inductive coupling coil 2, a processing chamber 3, a lower electrode 4, a lower electrode radio frequency power supply 5, and a bias voltage adjusting device 01. The inductive coupling coil 2 is arranged at the top of the processing chamber 3, and the lower electrode 4 is arranged at the bottom of the processing chamber 3. When the upper electrode radio frequency power supply 1 loads an upper radio frequency signal to the inductive coupling coil 2, the inductive coupling coil 2 generates an electromagnetic field under excitation, and a process gas in the processing chamber 3 is decomposed to generate plasma under the action of the electromagnetic field. The lower electrode radio frequency power supply 5 provides a lower radio frequency signal for the lower electrode 4, and the bias voltage of the lower electrode 4 attracts the plasma in the processing chamber 3 to act on a wafer 10 arranged on the lower electrode 4, and then completes the semiconductor process procedures such as cleaning, surface modification, etching, and deposition. For example, the lower electrode 4 can include an electrostatic chuck to clamp the wafer 10. The bias voltage adjusting device 01 includes an analog signal detector 001, a signal processing unit 002, and a controller 003.

[0059] In the process of executing the semiconductor process by the semiconductor processing equipment, plasma of active particles such as electrons, ions, excited atoms, molecules, and free radicals needs to be generated under the excitation of the upper electrode radio frequency power supply 1. At the same time, because electrons are lighter than positive ions, the number of electrons falling on the surface of the wafer 10 is more than the number of positive ions, so a direct current bias voltage can be formed on the surface of the wafer 10. The greater the plasma density, the greater the direct current bias voltage. In order to increase the direct current bias voltage, the energy of the active particles such as positively charged ions can be increased by increasing the radio frequency power of the lower electrode radio frequency power supply 5.

[0060] The size of the direct current bias voltage of the lower electrode 4 reflects some parameter states of the plasma. If the size of the direct current bias voltage changes, it indicates that the state of the plasma in the reaction chamber changes, which needs to be adjusted to avoid affecting the plasma process. When the radio frequency power output by the lower electrode radio frequency power supply 5 is constant, the direct current bias voltage on the surface of the wafer 10 is relatively stable, and the analog signal of the direct current bias voltage on the surface of the wafer 10 can be directly collected to monitor the direct current bias voltage on the surface of the wafer. However, in some processes, the radio frequency power output by the lower electrode radio frequency power supply 5 is a pulse wave, so the direct current bias voltage on the surface of the wafer will change with the change of the radio frequency power pulse, and a complex pulse wave is also formed. The collected direct current bias voltage signal will be mixed with a large amount of noise and contain signal rising and falling edges. Some processes will appear overshoot in the process of rising and falling of the direct current bias voltage signal, and some processes will appear a slope in the process of rising and falling of the direct current bias voltage signal, so the collected direct current bias voltage signal is not an ideal square wave signal. If the radio frequency power output by the bias radio frequency power supply is directly fed back according to the collected direct current bias voltage signal, a large error will be caused.

[0061] Figure 2For a flowchart of an existing control method for controlling the bias voltage of an electrode, refer to Figures 1-2 The control method includes the following steps S101-S103.

[0062] S101, the analog signal detector 001 detects the DC bias voltage signal on the surface of the wafer 10.

[0063] S102, the signal processing unit 002 acquires the output clock signal of the lower electrode RF power supply 5, determines the output mode of the lower electrode RF power supply 5 according to the output clock signal (determines whether the signal output by the lower electrode RF power supply 5 is a continuous wave or a pulse wave), and calculates the feedback value after sampling, filtering and denoising the detected DC bias voltage signal according to the output clock signal and the output mode.

[0064] S103, the controller 003 adjusts the output power of the lower electrode RF power supply 5 according to the feedback value. For example, when the feedback value is lower than a preset first threshold, the lower electrode RF power supply 5 is driven to increase its output power; when the feedback value is higher than a preset second threshold, the lower electrode RF power supply 5 is driven to decrease its output power. The second threshold is greater than the first threshold.

[0065] In the control method shown in Figures 1-2 , the feedback value of the lower electrode RF power supply 5 is calculated by the logic programmable circuit as the signal processing unit 002, and the output power of the lower electrode RF power supply 5 is controlled by comparing the feedback value with the preset first threshold and second threshold in the controller 003. That is, the output power of the lower electrode RF power supply 5 and the power value fed back by the signal processing unit 002 both need to be transferred to the power supply after being relayed in the controller 003, resulting in slow adjustment speed and long adjustment period.

[0066] In view of this, the present disclosure provides a control system and two kinds of adjustment methods for the bias voltage of the lower electrode, all of which are applied to semiconductor process equipment. Figure 3 A structural schematic diagram of a semiconductor process equipment provided by an embodiment of the present disclosure is provided; Figure 4 A structural schematic diagram of a controller provided by an embodiment of the present disclosure is provided; Figure 5 A flowchart of an adjustment method for the bias voltage of a lower electrode provided by an embodiment of the present disclosure is provided; Figure 6 A flowchart of another adjustment method for the bias voltage of a lower electrode provided by an embodiment of the present disclosure is provided. Refer to Figure 3 , the semiconductor process equipment includes an upper electrode RF power supply 1, an inductive coupling coil 2, a process chamber 3, a lower electrode 4, a lower electrode RF power supply 5 and a control system 6. Among them, the upper electrode RF power supply 1, the inductive coupling coil 2, the process chamber 3, the lower electrode 4, the lower electrode RF power supply 5 and Figure 1The structure and function of the control system 6 in the semiconductor processing equipment 1 are the same as those in the prior art, and will not be described here. The control system 6 comprises a voltage acquisition device 61 and a control device 62. The voltage acquisition device 61 comprises an acquisition unit 611 and a signal processing unit 612. The control device 62 comprises a memory 621 and a controller 622. The memory stores a computer program. The controller is configured to execute the computer program. When the computer program is executed by the controller, the above-mentioned adjustment method of the bias voltage of the lower electrode is implemented.

[0067] Before introducing the specific adjustment method, it needs to be explained that in the embodiments of the present disclosure, the bias voltage of the lower electrode 4 is mainly adjusted by adjusting the output power of the lower electrode radio frequency power supply 5. The working frequency of the lower electrode radio frequency power supply 5 includes but is not limited to 13.56 MHz, 2 MHz and 40 MHz. The parameter for measuring the adjustment result (i.e. whether the working environment of the semiconductor processing equipment is stable) is the accuracy SD of the bias voltage of the lower electrode 4, which is calculated by the controller 622. The actual bias voltage used by the controller 622 in the accuracy calculation is obtained by the voltage acquisition device 61 periodically acquiring the bias voltage of the lower electrode 4, and the acquisition period can be 1 ms, for example. Specifically, the acquisition unit 611 in the voltage acquisition device 61 is configured to periodically acquire the bias voltage of the lower electrode 4 to obtain an initial bias voltage. The signal processing unit 612 is configured to digitally process and filter the initial bias voltage to finally obtain the actual bias voltage.

[0068] The calculation formula of the accuracy SD is: Vtarget target is a target bias voltage, which is a preset voltage value and can be obtained through previous process experience. When the bias voltage of the lower electrode 4 is the target bias voltage, it indicates that the process equipment is in the best working state. Generally, different processes correspond to different target bias voltages, for example, the target bias voltage corresponding to a certain etching process is 780 V. current is the actual bias voltage at the current time acquired by the voltage acquisition device 61, that is, the accuracy SD of the bias voltage of the lower electrode 4 at each time needs to be calculated by the controller 622 according to the corresponding actual bias voltage. It can be understood that the voltage acquisition device 61 needs to acquire the bias voltage of the lower electrode 4 all the time, and the controller 622 also needs to calculate the accuracy of the bias voltage of the lower electrode 4 all the time during the entire process (i.e. from power-on to power-off of the semiconductor processing equipment). The period of the accuracy calculation by the controller 622 can be the same as or greater than the acquisition period of the voltage acquisition device 61.

[0069] Further, as shown in FIG. 2, the control device 62 further comprises a memory 621 and a controller 622. The memory 621 stores a computer program. The controller 622 is configured to execute the computer program. When the computer program is executed by the controller 622, the above-mentioned adjustment method of the bias voltage of the lower electrode is implemented. Figure 4As shown, the controller 622 includes a precision calculation unit 6220, a judgment unit 6221, a first calculation unit 6222, a second calculation unit 6223, and a power control unit 6224. The precision calculation unit 6220 is configured to receive the actual bias voltage collected by the voltage collection device 61 and calculate the precision SD at the corresponding time. The judgment unit 6221 is configured to determine which target precision range the precision SD is in. Here, three target precision ranges are exemplarily set in the embodiment of the present disclosure, i.e., a first target precision range (1%-3%), a second target precision range (greater than 3%), and a third target precision range (less than 1%). The first target precision range is higher than the second target precision range, and the third target precision range is higher than the first target precision range. It should be noted that "higher" here refers to the comparison of precision, and high precision is manifested as a small value, for example, 1% precision is higher than 3% precision. It can be understood that the number of target precision ranges and the boundary values of adjacent target precision ranges can be set differently according to needs, and the present disclosure does not limit this. The first calculation unit 6222 and the second calculation unit 6223 are respectively configured to calculate the output power of the lower electrode radio frequency power supply 5 when the precision SD is in different target precision ranges, and the power control unit 6224 is configured to control the lower electrode radio frequency power supply 5 to work according to the output power calculated by the first calculation unit 6222 or the second calculation unit 6223, so as to adjust the bias voltage of the lower electrode 4.

[0070] Next, the method for adjusting the bias voltage of the lower electrode provided by the present disclosure is introduced.

[0071] First example

[0072] Figure 5 The flow chart of the adjusting method of the first example provided by the embodiment of the present disclosure is as follows. Figure 5 As shown, the adjusting method includes the following first to third stages.

[0073] In the first stage, at the power-on time of the semiconductor process equipment, the controller 622 reads the corresponding reference power from the preset relationship according to the process currently performed by the semiconductor process equipment, and controls the lower electrode radio frequency power supply 5 to output according to the reference power. The preset relationship stores the corresponding relationship between different processes and different reference powers. Different processes correspond to different reference powers, which can be obtained from previous process experience.

[0074] Afterwards, the voltage collection device 61 collects the bias voltage of the lower electrode 4 to obtain the actual bias voltage at the current time, denoted as the first actual bias voltage, and transmits the first actual bias voltage to the precision calculation unit 6220. It should be noted that, in order to distinguish the actual bias voltage at different times, the actual bias voltage corresponding to the reference power output of the lower electrode RF power source 5 is denoted as the first bias voltage, the actual bias voltage corresponding to the first target output power of the lower electrode RF power source 5 is denoted as the second actual bias voltage, and the actual bias voltage corresponding to the second target output power of the lower electrode RF power source 5 is denoted as the third actual bias voltage (the first target output power and the second target output power will be described in detail later). Afterwards, the precision calculation unit 6220 calculates the precision SD of the bias voltage based on the first actual bias voltage and the target bias voltage.

[0075] After the first actual bias voltage reaches stability within the first preset time, the judgment unit 6221 judges the precision SD of the first actual bias voltage. If the precision of the first actual bias voltage meets the third target precision range (greater than 3%), it enters the second stage; if the precision meets the first target precision range (1-3%), it enters the third stage; if the precision always meets the third target precision range (less than 1%), it indicates that the reference power at this time is highly matched with the impedance of the process chamber, and the controller 622 does not need to adjust the output power of the lower electrode RF power source 5, and only needs to maintain the continuous calculation and detection of the precision SD. Exemplarily, the first preset time can be 10-30 ms.

[0076] Here, the judgment condition for whether the first actual bias voltage is stable within the first preset time is to ensure the stability of the bias voltage. That is, if the bias voltage cannot continuously meet a certain target precision range within the first preset time, it indicates that the working environment in the process chamber is not stable enough, and the subsequent adjustment of the bias voltage may have errors, affecting the product yield. Only when the precision of the bias voltage remains stable within a certain time, is it meaningful to adjust the bias voltage. Similarly, the meanings of the second preset time and the third preset time in the following are the same as the first preset time, which are all to ensure the stability of the bias voltage.

[0077] Further, whether the bias voltage is stable at the first preset time can be measured according to the consistency of the bias voltage. Specifically, the consistency of the bias voltage is high means that the voltage variation amplitude of the bias voltage within the first preset time meets the first range, more specifically, the first range means that the amplitude fluctuation of the bias voltage is less than a certain preset value. Taking 20 ms as the first preset time for example, the voltage collecting device 61 collects the bias voltage of the lower electrode 4 for 20 times within 20 ms, and obtains 20 first actual bias voltages. Assuming that 1% of the average value of the 20 first actual bias voltages is the first preset value, if the difference between the maximum value and the minimum value of the 20 first actual bias voltages is less than the first preset value, it means that the consistency of the bias voltage is high, and the working environment is relatively stable; if the difference between the maximum value and the minimum value of the 20 first actual bias voltages is greater than the first preset value, it means that the consistency of the bias voltage is low, and the working environment is unstable, and the working environment needs to be checked. Of course, the first preset value can be designed differently according to the specific process, for example, in a strict process, the first preset value can be set to 0.5% or 0.1% of the average value of the 20 first actual bias voltages, and the present disclosure does not limit this.

[0078] By setting the first stage, the previous process experience can be applied to the adjustment process of the bias voltage, and the bias voltage is controlled to start adjusting from the reference voltage as the starting point, instead of starting from zero, so that the adjustment time can be greatly shortened, the adjustment speed can be improved, and the response speed of the equipment can be improved. It is verified by experiment that the duration of the first stage is about 0.1 s.

[0079] In the second stage, the first calculation unit 6222 obtains the first actual bias voltage at the current time from the voltage collecting device 61, and obtains the actual power at the current time from the lower electrode RF power supply 5, calculates the first target output power by the following formula (1), and then the power control unit 6224 controls the lower electrode RF power supply 5 to output according to the first target output power.

[0080]

[0081] Wherein, P_feedback1 is the first target output power; P_current is the output power of the lower electrode RF power supply at the current time; V_target is the target bias voltage; V_current is the first actual bias voltage at the current time; K0 is a proportional adjustment coefficient, used to represent the relationship between the difference between the target bias voltage and the first actual bias voltage and the target bias voltage, the greater the value of K0, the faster the adjustment speed, but a too large value may cause over-adjustment. Exemplarily, the value range of K0 is [1, 10].

[0082] Afterwards, the bias voltage of the lower electrode 4 is changed under the influence of the first target output power P_feedback1. At this time, the voltage collection device 61 collects the bias voltage of the lower electrode 4 to obtain an actual bias voltage, denoted as a second actual bias voltage, and transmits the second actual bias voltage to the precision calculation unit 6220. If the second actual bias voltage reaches stability within a second preset time (i.e., the voltage variation amplitude of the second actual bias voltage satisfies a second range), the precision calculation unit 6220 calculates the precision SD of the bias voltage at the current time based on the second actual bias voltage at the current time and the target bias voltage. If the second actual bias voltage has a large fluctuation within the second preset time, the first target output power is recalculated based on the second actual bias voltage at the time of the fluctuation and the output power of the lower electrode radio frequency power supply, and the power control unit 6224 controls the lower electrode radio frequency power supply 5 to output according to the new first target output power. This is repeated one or more times until the second actual bias voltage reaches stability within the second preset time. The second preset time has a value range of 30 ms to 50 ms. Here, the second range has a similar meaning to the first range, and the only difference is that the number of times of collecting the actual bias voltage is different when the second preset time is different from the first preset time.

[0083] After the second actual bias voltage reaches stability within the second preset time, the judging unit 6221 judges the precision SD of the second actual bias voltage. If the precision SD satisfies the first target precision range (1-3%), the third stage is entered. If the precision SD does not satisfy the first target precision range (1-3%), the second stage is re-executed, i.e., the first target output power is recalculated based on the second actual bias voltage at this time and the actual power, the power control unit 6224 controls the lower electrode radio frequency power supply 5 to output according to the new first target output power, if the precision satisfies the first target precision range (1-3%), the third stage is entered, and if the precision has a large fluctuation again within the second preset time, the second stage is executed again. This is repeated multiple times until the precision SD of the second actual bias voltage is stable within the first target precision range.

[0084] Through the adjustment of the second stage, the precision SD of the bias voltage of the lower electrode 4 can be stabilized within the first target precision range (1-3%). Through multiple experimental verifications, the duration of the second stage is 0.2 s to 0.3 s.

[0085] In the third stage, the second calculation unit 6223 obtains the second actual bias voltage at the current time, the last time, and the last time of the last time from the voltage collection device 61, and obtains the actual power at the current time from the lower electrode radio frequency power supply 5, and calculates the second target output power through the following formula (2), and then the power control unit 6224 controls the lower electrode radio frequency power supply 5 to output according to the second target output power.

[0086]

[0087] P_feedback2 = P_current + K * ΔV(current) + K * ΔV(current-1) + a * P_current2 + b * P_current P K is a gain coefficient, used to represent the relationship between the output power of the lower electrode radio frequency power supply and the lower electrode bias voltage; K T K is a time constant integral coefficient, used to represent the relationship between the sampling time and the response time constant; a is a nonlinear parameter quadratic coefficient, b is a linear parameter coefficient, and a and b are both used to represent the adjustment speed.

[0088] After that, the bias voltage of the lower electrode 4 changes under the influence of the second target output power P_feedback2. At this time, the voltage collection device 61 collects the bias voltage of the lower electrode 4 to obtain the actual bias voltage, denoted as the third actual bias voltage, and transmits the third actual bias voltage to the precision calculation unit 6220. If the third actual bias voltage reaches stability within a third preset time, the precision calculation unit 6220 calculates the bias voltage precision SD based on the third actual bias voltage and the target bias voltage at this moment. If the third actual bias voltage fluctuates greatly within the third preset time, the second target output power is recalculated based on the third actual bias voltage at the time of fluctuation and the output power of the lower electrode radio frequency power supply, and the power supply control unit 6224 controls the lower electrode radio frequency power supply 5 to output according to the new second target output power. This is repeated one or more times until the third actual bias voltage reaches stability within the third preset time. The value range of the third preset time is 30ms-50ms.

[0089] After the third actual bias voltage reaches stability within the third preset time, the judging unit 6221 judges the precision SD of the third actual bias voltage. If the precision meets the third target precision range (less than 1%), it indicates that the matching degree of the bias voltage with the process chamber at this time is high, and the working environment is stable, so the controller 622 does not need to adjust, and the continuous calculation and detection of the precision can be maintained. If the precision does not meet the third target precision range (less than 1%), the third stage is re-executed, that is, the second target output power is recalculated according to the third actual bias voltage at this moment and the third actual bias voltage at the two closest moments before this moment, and the actual power at this moment, and the power control unit 6224 controls the lower electrode radio frequency power source to output according to the new second target output power. Repeat this multiple times until the precision SD of the third actual bias voltage stabilizes within the third target precision range (less than 1%). It should be noted that, Figure 5 The adjustment method shown herein only exemplarily illustrates the adjustment process of the lower electrode bias voltage by the control device 62 when the semiconductor process equipment is powered on. In actual processes, the bias voltage may fluctuate at any time, and at this time, the adjustment process of the lower electrode bias voltage by the control device 62 can only include the second stage and the third stage, or only include the third stage.

[0090] Specifically, in the normal process, if the precision calculation unit 6220 detects that the precision of the bias voltage changes from the third target precision range (less than 1%) to the second target precision range (greater than 3%), the control device 62 sequentially executes the second stage and the third stage, and adjusts the output power of the lower electrode radio frequency power source 5 multiple times until the precision of the bias voltage of the lower electrode 4 meets the third target precision range. If the precision calculation unit 6220 detects that the precision of the bias voltage changes from the third target precision range (less than 1%) to the first target precision range (1-3%), the control device 62 directly executes the third stage, and adjusts the output power of the lower electrode radio frequency power source 5 one or more times until the precision of the lower electrode bias voltage meets the third target precision range (less than 1%).

[0091] Second example

[0092] Figure 6 The flow chart of the adjustment method of the second example provided by the embodiment of the present disclosure is shown in FIG. 6B. As shown in FIG. 6B, Figure 6 The same as the first example is that the adjustment method in the second example also includes the first to third stages, and different from the first example is that in the first stage of the second example, when the first actual bias voltage reaches stability within the first preset time, it directly enters the second stage, and the judging unit 6221 no longer judges the precision SD of the first actual bias voltage, so as to simplify the adjustment steps.

[0093] Specifically, referring to Figure 6The first stage in the second example includes: when the semiconductor process equipment is powered on, the controller 622 controls the lower electrode RF power supply 5 to output according to the reference power according to the process currently performed by the semiconductor process equipment.

[0094] Afterwards, the voltage acquisition device 61 acquires the bias voltage of the lower electrode 4 and obtains the actual bias voltage at the current moment, which is recorded as the first actual bias voltage. When the first actual bias voltage reaches stability within the first preset time, the second stage begins. For example, the first preset time can be 10ms to 30ms.

[0095] Afterwards, the controller 622 executes the second stage and the third stage in sequence. The second stage and the third stage here are exactly the same as those in the first example and will not be described again here.

[0096] In the first and second examples above, the controller first controls the lower electrode RF power supply to start working at the reference power through the first stage of adjustment, and uses the reference power as the starting point for subsequent adjustment, which can greatly shorten the adjustment time and improve the adjustment speed. Afterwards, the controller performs coarse and fine adjustments on the output power of the lower electrode RF power supply through the second and third stages of adjustment in turn (the second example), or, based on the accuracy of the lower electrode bias voltage when the lower electrode RF power supply outputs according to the reference power, the controller adjusts the output power through the third stage of fine adjustment alone or through the second stage of coarse adjustment and the third stage of fine adjustment in turn (the first example). Both of these adjustment methods can control the accuracy of the bias voltage of the lower electrode to gradually improve while ensuring that the working environment is sufficiently stable, and ultimately make the accuracy of the bias voltage reach the target accuracy range (i.e., the second target accuracy range in the above embodiment). After experimental verification, the bias voltage of the lower electrode is adjusted by the adjustment method of the present application, and the adjustment time to achieve an accuracy of the bias voltage of less than 1% is 0.5s, as shown in FIG. Figure 7 shown. Figure 8 To adopt Figures 1-2 The control method shown in FIG is used to adjust the bias voltage. Figure 8 It can be seen that under the same process conditions, the time required to adjust the bias voltage to an accuracy of less than 1% using the existing control method is 2.5s. Figures 7-8 It can be seen that the adjustment method of the present application can greatly improve the adjustment speed of the bias voltage, thereby improving the response speed of the process equipment and meeting the voltage control speed requirements of high-power pulse processes with short process time.

[0097] In some embodiments, the controller includes not only the precision calculation unit 6220, the determination unit 6221, the first calculation unit 6222, the second calculation unit 6223, and the power control unit 6224 described above, but also a coefficient acquisition unit 6225 for acquiring the nonlinear parameter quadratic coefficient a, the linear parameter coefficient b, the gain coefficient K P and the time constant integral coefficient K T .

[0098] Specifically, the coefficient acquisition unit 6225 can calculate the linear parameter coefficient b by the following formula (3), and the nonlinear parameter quadratic coefficient a has a value range of

[0099]

[0100] where V_target is the target bias voltage; P max is the maximum output power of the lower electrode radio frequency power supply 5; and Vref is the reference voltage, which is unique for each semiconductor process equipment.

[0101] After multiple debugging and optimization, the value range of the linear parameter coefficient b is [1, 80], and the value range of the nonlinear parameter quadratic coefficient a is [0.01, 0.8]. It should be noted that the values of the nonlinear parameter quadratic coefficient a and the linear parameter coefficient b are related to the target bias voltage. The greater the target bias voltage, the greater the values of a and b.

[0102] The gain coefficient K P and the time constant integral coefficient K T can be calculated through multiple experiments. Specifically, the coefficient acquisition unit 6225 acquires the gain coefficient K P and the time constant integral coefficient K T by the following process: recording the output power of the lower electrode radio frequency power supply 5, the bias voltage of the lower electrode 4, and the response time constant T τ under different process conditions, and then calculating a plurality of initial gain parameters K i under different process conditions by the following formula (4), calculating the gain coefficient K P by the following formula (5), and calculating the time constant integral coefficient K T by the following formula (6). It should be noted that the response time constant T τ is the time required for the lower electrode radio frequency power supply 5 to start outputting to the bias voltage of the lower electrode 4 reaching a stable state.

[0103] The process conditions include the gas pressure in the process chamber 3 and the output power of the upper electrode RF power source 1, that is, the coefficient acquisition unit 6225 first records a plurality of sets of output power P of the lower electrode RF power source 1 when the process chamber 3 is at different gas pressures and the output power of the upper electrode RF power source 1 is at different conditions 下i , the bias voltage V of the lower electrode 4 i , and the response time constant T τ The initial gain parameters K under a plurality of different processes are calculated by the following formula (2) i , i is an integer from 1 to N, N is the number of experiments, and therefore N is an integer greater than 1.

[0104]

[0105] In formula (4), k is a proportional coefficient, and the value of k affects the speed of adjustment. The larger the value of k, the faster the adjustment speed. In order to prevent overshoot during adjustment, the value of k is in the range of 1≤k≤10, and preferably, the value of k is in the range of 3≤k≤10.

[0106] After obtaining a plurality of initial gain parameters K i , the coefficient acquisition unit 6225 calculates the gain coefficient K i after averaging a plurality of initial gain parameters K P by the following formula (5).

[0107]

[0108] After obtaining the gain coefficient K P , the coefficient acquisition unit 6225 obtains the time constant integral coefficient K T by the following formula (6).

[0109]

[0110] In formula (6), T is the sampling time length, T τ is the response time constant. K T mainly determines the adjustment accuracy and stability during adjustment, and K T is too large or too small, which affects the stability of adjustment. Its size needs to be matched with the system response time to better stabilize the adjustment. In an actual example, the system response time, i.e., the response time constant T τ is between 30-50 ms, and therefore the sampling time length T is set to 1 ms, and at this time K T is about 1 / 50 to 1 / 30 of the size of K P . After multiple debugging and optimization, the gain coefficient K Pthe value range of K is [0.005, 0.1] T the value range of K is [0.00015, 0.0003].

[0111] In some examples, as shown in Figure 3 In addition to the voltage acquisition device 61 and the controller 62, the control system 6 also includes a signal synchronization control device 63, which is configured to control the lower electrode RF power supply 5 and the voltage acquisition device 61 to start working at the same time, so as to improve the synchronization of the signal.

[0112] With reference back to Figure 3 In addition to the upper electrode RF power supply 1, the upper electrode 2, the process chamber 3, the lower electrode 4, the lower electrode RF power supply 5 and the control system 6, the semiconductor process equipment also includes an upper electrode matcher 8 and a lower electrode matcher 9. The upper electrode matcher 8 is configured to control the impedance matching between the upper electrode RF power supply 1 and the upper electrode 2. The lower electrode matcher 9 is configured to control the impedance matching between the lower electrode RF power supply 5 and the lower electrode 4.

[0113] In some examples, the semiconductor process equipment also includes a spectrometer 7 and a dielectric window 11. The spectrometer 7 can acquire the luminous intensity of the plasma in the process chamber 3 through the observation window arranged on the sidewall of the process chamber 3, so as to ensure the accuracy of the process and the product quality. The dielectric window 11 allows the transmission of RF energy from the RF power supply to the process chamber 3, excites the process gas to form plasma, so as to carry out semiconductor processing such as etching, deposition, etc. At the same time, the dielectric window 11 can isolate the process chamber 3 from the external environment, prevent the process materials such as plasma from leaking to the outside, and at the same time protect the RF power supply from the harsh environment in the process chamber.

[0114] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. A method for adjusting the bias voltage of a lower electrode, applied to semiconductor process equipment, characterized in that: The adjustment method comprises: Obtaining an actual bias voltage of the lower electrode of the semiconductor process equipment when the lower electrode radio frequency power supply outputs a reference power, and recording the voltage as a first actual bias voltage; When the first actual bias voltage reaches stability, obtaining an accuracy of the first actual bias voltage; When the accuracy of the first actual bias voltage meets the first target accuracy range, the lower electrode RF power supply is controlled to output according to the second target output power based on the output power of the lower electrode RF power supply at the current moment, the first actual bias voltage at the current moment, and the first actual bias voltages at the two moments most recent before the current moment.

2. The adjustment method according to claim 1, characterized in that: The adjustment method further comprises: When the accuracy of the first actual bias voltage meets the second target accuracy range, based on the output power of the lower electrode RF power supply at the current moment, the first actual bias voltage at the current moment, and the target bias voltage, the lower electrode RF power supply is controlled to output according to the first target output power, and the actual bias voltage at the current moment is obtained, which is recorded as the second actual bias voltage; the first target accuracy range is higher than the second target accuracy range; and When the second actual bias voltage reaches stability, obtaining an accuracy of the second actual bias voltage; When the accuracy of the second actual bias voltage meets the first target accuracy range, the lower electrode RF power supply is controlled to output according to the second target output power based on the output power of the lower electrode RF power supply at the current moment, the second actual bias voltage at the current moment, and the second actual bias voltages at the two moments most recent before the current moment.

3. A method for adjusting the bias voltage of a lower electrode, applied to semiconductor process equipment, characterized in that: The adjustment method comprises: Obtaining an actual bias voltage of the lower electrode of the semiconductor process equipment when the lower electrode radio frequency power supply outputs a reference power, and recording the voltage as a first actual bias voltage; When the first actual bias voltage reaches stability, based on the output power of the lower electrode RF power supply at the current moment, the first actual bias voltage at the current moment, and the target bias voltage, controlling the lower electrode RF power supply to output according to the first target output power, and obtaining the actual bias voltage at the current moment, which is recorded as a second actual bias voltage; When the second actual bias voltage reaches stability, obtaining an accuracy of the second actual bias voltage; When the accuracy of the second actual bias voltage meets the first target accuracy range, the lower electrode RF power supply is controlled to output according to the second target output power based on the output power of the lower electrode RF power supply at the current moment, the second actual bias voltage at the current moment, and the second actual bias voltages at the two moments most recent before the current moment.

4. The adjustment method according to any one of claims 1 to 3, characterized in that: The adjustment method further comprises: Using the second target output power as the output power of the lower electrode radio frequency power supply at the current moment, and controlling the lower electrode radio frequency power supply to output power to the lower electrode; Obtaining the actual bias voltage of the lower electrode at the current moment, recorded as a third actual bias voltage; Obtaining an accuracy of the third actual bias voltage; Determining whether the accuracy of the third actual bias voltage is within a third target accuracy range; the third target accuracy range is higher than the first target accuracy range; If the accuracy of the third actual bias voltage meets the third target accuracy range, the RF power supply is controlled to output according to the current output frequency.

5. The adjustment method according to claim 4, characterized in that: The adjustment method further comprises: If the accuracy of the third actual bias voltage does not meet the third target accuracy range, the output power of the lower electrode RF power supply is adjusted based on the second target output power, the third actual bias voltage at the current moment, and the third actual bias voltage at the two moments most recent before the current moment, and the step of obtaining the actual bias voltage of the lower electrode at the current moment is returned until the accuracy of the third actual bias voltage meets the third target accuracy range.

6. The adjustment method according to claim 1 or 3, characterized in that: The adjustment method further includes: when the semiconductor process equipment is powered on, obtaining a corresponding reference power based on the process performed by the semiconductor process equipment, and controlling the lower electrode RF power supply to output according to the reference power.

7. The adjustment method according to claim 2 or 3, characterized in that: The adjustment method further includes: calculating the first target output power by the following formula (1); Among them, P_feedback1 is the first target output power; P_current is the output power of the lower electrode RF power supply at the current moment; V_target is the target bias voltage; V_current is the actual bias voltage of the lower electrode at the current moment; K0 is the proportional adjustment coefficient, which is used to characterize the relationship between the difference between the target bias voltage and the actual bias voltage and the target bias voltage.

8. The adjustment method according to claim 1 or 3, characterized in that: The adjustment method further includes: calculating the second target output power by the following formula (2); Wherein, P_feedback2 is the second target output power; P_current is the output power of the lower electrode RF power supply at the current moment; ΔV(current) is the difference between the actual bias voltage of the lower electrode at the current moment and the previous moment; ΔV(current-1) is the difference between the actual bias voltage of the lower electrode at the previous moment and the moment before the previous moment; K P is the gain coefficient, which is used to characterize the relationship between the output power of the lower electrode RF power supply and the actual bias voltage of the lower electrode; K T is the time constant integral coefficient, which is used to characterize the relationship between the sampling time and the response time constant; a is the quadratic coefficient of the nonlinear parameter, and b is the linear coefficient. Both a and b are used to characterize the adjustment speed.

9. The adjustment method according to claim 8, characterized in that: The adjustment method further includes: before calculating the second target output power by the formula (2), calculating the first-order parameter coefficient b by the following formula (3), and obtaining the second-order coefficient a of the nonlinear parameter; Wherein, V_target is the target bias voltage; P max is the maximum output power of the lower electrode RF power supply; Vref is the reference voltage; 10. The adjustment method according to claim 8, characterized in that: The value range of the primary parameter coefficient b is [1, 80].

11. The adjustment method according to claim 8, characterized in that: The gain coefficient K P The value range of is [0.005, 0.1], the time constant integral coefficient K T The value range is [0.00015, 0.0003].

12. A control device comprising a controller and a memory; the memory stores a computer program, and when the computer program is executed by the controller, the control method according to any one of claims 1 to 11 is implemented.

13. A control system, applied to semiconductor process equipment, characterized in that: The control system includes a voltage acquisition device and a control device as claimed in claim 12; The voltage acquisition device is configured to acquire the bias voltage of the lower electrode of the semiconductor process equipment to obtain an actual bias voltage; The control device is configured to obtain the actual bias voltage collected by the voltage collection device and control the power output of the lower electrode radio frequency power supply of the semiconductor process equipment.

14. The control system according to claim 13, characterized in that: The voltage acquisition device includes an acquisition unit and a signal processing unit; The acquisition unit is configured to acquire the bias voltage of the lower electrode to obtain an initial bias voltage; The signal processing unit is configured to process the initial bias voltage to obtain the actual bias voltage.

15. The control system according to claim 13, characterized in that: The control system further includes a signal synchronization control device configured to control the lower electrode radio frequency power supply and the voltage acquisition device to operate synchronously.

16. A semiconductor process equipment comprising a process chamber, an upper electrode, a lower electrode, a radio frequency power supply for the upper electrode, a radio frequency power supply for the lower electrode, and a control system; characterized in that: The control system adopts the control system according to any one of claims 13 to 15.

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