JP2023027532A - Flow rate control method and flow rate control system - Google Patents

Abstract

To appropriately control the flow rate of a process gas that is used in substrate processing.SOLUTION: Provided is a process gas flow rate control method using a flow rate control system, the flow rate control system comprising a flow rate controller, a first valve, a second valve and a pressure sensor, the flow rate control method including a gas supply log data acquisition step, a computation step and a control step. In the gas supply log data acquisition step, a flow rate monitor value and a pressure value are acquired. In the computation step, the flow rate monitor value and the pressure value are compared and each delay signal is changed so as to shorten or extend each delay time. Then, the gas supply log data acquisition step is re-executed, or each delay signal is recorded, and the flow rate of the process gas is controlled in the control step using each delay signal having been recorded.SELECTED DRAWING: Figure 6

Description

The present disclosure relates to flow control methods and flow control systems.

Patent Literature 1 discloses a gas supply system capable of measuring the flow rate. The gas supply system includes a flow controller for controlling the flow rate of the gas, and a pressure detector and a temperature detector for detecting the temperature and pressure in the flow path surrounded by the first, second, and third shutoff valves. By applying Boyle's law to the open state and closed state of the third shutoff valve, the volume of the flow path surrounded by the volume measuring tank and the first, second, and third shutoff valves is demand. Further, arithmetic control for calculating the flow rate of the flow rate controller is performed using the channel volume and the detected values of the pressure detector and the temperature detector.

U.S. Patent Application Publication No. 2019/017855

A technique according to the present disclosure appropriately controls the flow rate of a processing gas used for substrate processing.

One aspect of the present disclosure is a process gas flow control method using a flow control system, wherein the flow control system includes a flow controller, a first valve provided upstream of the flow controller, and a second valve provided downstream of the flow rate controller; and a pressure sensor provided downstream of the first valve. and, in the gas supply log data acquisition step, a flow controller is provided with an opening signal for the first valve, a first delay signal for determining a first delay time, and the second valve. and a second delay signal that determines a second delay time, and then the flow rate controller so that the flow rate of the process gas becomes the set flow rate. a flow rate control start signal for starting flow rate control in is transmitted, and from the start to the end of the gas supply log data acquisition step, a flow rate monitor value indicating the flow rate in the flow rate controller, a pressure value in the pressure sensor, is obtained, and in the calculation step, the flow rate monitor value and the pressure value are compared, and if the first profile is detected before the rise time of the flow rate monitor value, the first delay time or changing the first delay signal or the second delay signal so as to shorten or extend the second delay time, and executing the gas supply log data acquisition step again; When comparing the flow rate monitor value and the pressure value, the first profile is not detected before the rise time of the flow rate monitor value and the second profile is detected after the rise time of the flow rate monitor value records the first delay signal and the second delay signal used in the gas supply log data acquisition step when acquiring the flow rate monitor value and the pressure value, and terminates the calculation step; In the control step, when the first profile is not detected before the rise time of the flow rate monitor value in the calculation step and the second profile is detected after the rise time of the flow rate monitor value, the recording The flow rate of the process gas is controlled using the first delay signal and the second delay signal.

According to the present disclosure, it is possible to appropriately control the flow rate of the processing gas used for substrate processing.

FIG. 5 is a comparison diagram of changes over time in an OES acquired value and a flow rate monitor value after the start of flow rate control. 1 is an explanatory diagram showing a configuration example of a plasma processing system according to an embodiment; FIG. 1 is a cross-sectional view showing a configuration example of a plasma processing apparatus according to an embodiment; FIG. 4 is a schematic diagram schematically showing the details of the configuration of the gas supply unit according to the embodiment; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a system diagram which shows the outline of a structure of the flow control system concerning embodiment. It is a flow chart showing an outline of a flow rate control method concerning an embodiment. FIG. 5 is a comparison diagram of changes over time in a flow rate monitor value and a pressure value after the start of flow rate control. FIG. 10 is a comparison diagram of changes over time in the flow rate monitor value and the pressure value after the start of flow rate control;

2. Description of the Related Art In plasma processing of a semiconductor substrate (hereinafter referred to as "substrate") in a plasma processing apparatus, various processing gases are supplied to a plasma processing chamber containing the substrate. A flow rate controller for controlling the flow rate of the processing gas is used to supply the processing gas. The flow controller controls the flow rate of the process gas whose flow rate is to be controlled. It also monitors the current flow rate of the flowing processing gas and outputs the flow rate monitor value. The control unit that controls the plasma processing apparatus transmits a flow rate setting signal to the flow rate controller as a control signal for setting the processing gas flowing through the flow rate controller to a desired flow rate (hereinafter referred to as a set flow rate). Control the gas flow. Also, based on the flow monitor value sent from the flow controller, the controllability of the flow is confirmed.

In confirming the controllability of the flow rate, it is preferable to establish a correlation between the flow rate monitor value of the process gas to be controlled in the flow controller and the amount of the process gas present in the plasma processing chamber. If correlated, the amount of process gas actually supplied to the plasma processing chamber can be controlled based on the flow monitor values.

The present inventors have compared the changes over time in the amount of process gas present in the plasma processing chamber with the flow rate monitor values, and obtained a comparison chart such as FIG. The amount of processing gas present was obtained by an optical emission spectrometer (OES) that observes internal plasma emission from the side wall of the plasma processing chamber. In FIG. 1, the OES acquired value sharply increased after the transmission of the process gas flow start signal S1 (densely hatched portion in FIG. 1). This indicates a rapid increase in the amount of process gas present in the plasma processing chamber. At this time, the flow rate monitor value in the flow controller indicated that the flow rate did not increase when the amount of process gas present increased rapidly. After that, when a flow rate control start signal was sent to the flow rate controller, the OES acquired value increased stably (the sparsely hatched portion in FIG. 1). This indicates a steady increase in the amount of process gas present. At this time the flow rate monitor indicated that the flow rate had increased. Therefore, the results of the comparison in FIG. 1 show that the actual amount of process gas present detected by the OES in the plasma processing chamber correlates with the monitored flow rate value detected by the flow controller, especially immediately after the start of flow control. showed no.

As a result of the comparison of FIG. 1, the inventors of the present invention have come to recognize the problem that the flow monitor value in the flow controller and the abundance in the plasma processing chamber may not be correlated. This lack of correlation means that the flow rate monitor value does not necessarily reflect the amount of process gas actually supplied to the plasma processing chamber. In this case, it may not be possible to appropriately control the flow rate of the processing gas actually supplied to the plasma processing chamber, depending on the control of the processing gas based on the flow rate monitor value.

In view of the above problems, the technology according to the present disclosure appropriately controls the flow rate of the processing gas supplied to the plasma processing chamber. Specifically, the correlation between the actual amount of processing gas present in the plasma processing apparatus and the flow rate monitor value detected by the flow rate controller is improved, and the controllability of the flow rate based on the flow rate monitor value is improved.

A plasma processing system having a flow rate control system according to the present embodiment and a flow rate control method using the flow rate control system will be described below with reference to the drawings. In this specification, elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

<Plasma processing system>
In one embodiment, the plasma processing system 1 includes a plasma processing device 2 and a controller 3 as shown in FIG. The plasma processing apparatus 2 includes a plasma processing chamber 10 , a substrate support section 11 and a plasma generation section 12 . Plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas inlet for supplying at least one process gas to the plasma processing space and at least one gas outlet for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply section 20, which will be described later, and the gas discharge port is connected to an exhaust system 40, which will be described later. The substrate support 11 is arranged in the plasma processing space and has a substrate support surface for supporting the substrate.

The plasma generator 12 is configured to generate plasma from at least one processing gas supplied within the plasma processing space. Plasma formed in the plasma processing space includes capacitively coupled plasma (CCP: Capacitively Coupled Plasma), inductively coupled plasma (ICP: Inductively Coupled Plasma), ECR plasma (Electron-Cyclotron-resonance plasma), helicon wave excited plasma (HWP: Helicon Wave Plasma), surface wave plasma (SWP: Surface Wave Plasma), or the like. Also, various types of plasma generators may be used, including alternating current (AC) plasma generators and direct current (DC) plasma generators. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency within the range of 100 kHz to 10 GHz. Accordingly, AC signals include RF (Radio Frequency) signals and microwave signals. In one embodiment, the RF signal has a frequency within the range of 200 kHz-150 MHz.

Controller 3 processes computer-executable instructions that cause plasma processing apparatus 2 to perform the various steps described in this disclosure. Controller 3 may be configured to control elements of plasma processing apparatus 2 to perform the various processes described herein. In one embodiment, part or all of the controller 3 may be included in the plasma processing apparatus 2 . The control unit 3 may include, for example, a computer 3a. The computer 3a may include, for example, a processing unit (CPU: Central Processing Unit) 3a1, a storage unit 3a2, and a communication interface 3a3. The processing unit 3a1 can be configured to perform various control operations based on programs stored in the storage unit 3a2. The storage unit 3a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 2 via a communication line such as a LAN (Local Area Network).

<Plasma processing device>
Next, a configuration example of a capacitively coupled plasma processing apparatus 2 as an example of the plasma processing apparatus 2 described above will be described. FIG. 3 is a vertical sectional view showing the outline of the configuration of the plasma processing apparatus 2. As shown in FIG.

Plasma processing apparatus 2 includes plasma processing chamber 10 , gas supply 20 , power supply 30 and exhaust system 40 . Also, the plasma processing apparatus 2 includes a substrate support section 11 and a gas introduction section. The gas introduction is configured to introduce at least one process gas into the plasma processing chamber 10 . The gas introduction section includes a showerhead 13 . A substrate support 11 is positioned within the plasma processing chamber 10 . The showerhead 13 is arranged above the substrate support 11 . In one embodiment, showerhead 13 forms at least a portion of the ceiling of plasma processing chamber 10 . The plasma processing chamber 10 has a plasma processing space 10 s defined by a showerhead 13 , side walls 10 a of the plasma processing chamber 10 and a substrate support 11 . Side wall 10a is grounded. The showerhead 13 and substrate support 11 are electrically insulated from the plasma processing chamber 10 housing.

The substrate support portion 11 includes a body portion 111 and a ring assembly 112 . The body portion 111 has a central region (substrate support surface) 111 a for supporting the substrate (wafer) W and an annular region (ring support surface) 111 b for supporting the ring assembly 112 . The annular region 111b of the body portion 111 surrounds the central region 111a of the body portion 111 in plan view. The substrate W is arranged on the central region 111 a of the main body 111 , and the ring assembly 112 is arranged on the annular region 111 b of the main body 111 so as to surround the substrate W on the central region 111 a of the main body 111 . In one embodiment, body portion 111 includes a base and an electrostatic chuck. The base includes an electrically conductive member. The conductive member of the base functions as a lower electrode. An electrostatic chuck is arranged on the base. The upper surface of the electrostatic chuck has a substrate support surface 111a. Ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Also, although not shown, the substrate supporter 11 may include a temperature control module configured to control at least one of the electrostatic chuck, the ring assembly 112, and the substrate to a target temperature. The temperature control module may include heaters, heat transfer media, flow paths, or combinations thereof. A heat transfer fluid, such as brine or gas, flows through the channel. Further, the substrate support section 11 may include a heat transfer gas supply section configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface 111a.

The showerhead 13 is configured to introduce at least one processing gas from the gas supply 20 into the plasma processing space 10s. The showerhead 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas introduction ports 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s through a plurality of gas introduction ports 13c. Showerhead 13 also includes a conductive member. A conductive member of the showerhead 13 functions as an upper electrode. In addition to the showerhead 13, the gas introduction part may include one or more side gas injectors (SGI: Side Gas Injectors) attached to one or more openings formed in the side wall 10a.

Gas supply 20 may include at least one gas source 21 and at least one flow controller 22 . In one embodiment, gas supply 20 is configured to supply at least one process gas from respective gas sources 21 through respective flow controllers 22 to showerhead 13 . Each flow controller 22 may include, for example, a mass flow controller or a pressure controlled flow controller 22 . Additionally, gas supply 20 may include at least one flow modulation device 23 that modulates or pulses the flow of at least one process gas based on a signal from controller 3 . Each flow controller 22 has a flow controller 24 . The flow controller 24 is configured to be able to control the flow controller 22 based on a signal from the controller 3 and control the flow rate of the processing gas flowing therethrough. Further, the flow control unit 24 is configured to monitor the flow rate of the processing gas currently flowing in the flow control device 22 and transmit the flow monitor value FM to the control unit 3 .

A pressure sensor 26 is provided downstream of the gas supply unit 20 . Pressure sensor 26 is configured to be able to measure the pressure of the process gas downstream of gas source 21 and flow controller 22 . When the gas supply unit 20 is provided with a plurality of gas sources 21 and flow rate controllers 22, one pressure sensor 26 is provided in a confluence channel 27 where the pipes forming these channels join. The pressure value measured by the pressure sensor 26 is configured to be able to be transmitted to the control unit 3 . In this specification, "upstream" or "downstream" of a component means "upstream" or "downstream" in the flow direction of the processing gas. Specifically, upstream refers to the gas supply 20 side of the component, and downstream refers to the plasma processing chamber 10 side of the component.

Power supply 30 includes an RF power supply 31 coupled to plasma processing chamber 10 via at least one impedance match circuit. RF power supply 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to conductive members of substrate support 11 and/or conductive members of showerhead 13 . be done. Thereby, plasma is formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least part of the plasma generator 12 . Further, by supplying the bias RF signal to the conductive member of the substrate supporting portion 11, a bias potential is generated in the substrate W, and ion components in the formed plasma can be drawn into the substrate W. FIG.

In one embodiment, the RF power supply 31 includes a first RF generator 31a and a second RF generator 31b. The first RF generator 31a is coupled to the conductive member of the substrate support 11 and/or the conductive member of the showerhead 13 via at least one impedance matching circuit to provide a source RF signal for plasma generation (source RF electrical power). In one embodiment, the source RF signal has a frequency within the range of 13 MHz to 150 MHz. In one embodiment, the first RF generator 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are provided to conductive members of the substrate support 11 and/or conductive members of the showerhead 13 . The second RF generator 31b is coupled to the conductive member of the substrate support 11 via at least one impedance matching circuit and configured to generate a bias RF signal (bias RF power). In one embodiment, the bias RF signal has a lower frequency than the source RF signal. In one embodiment, the bias RF signal has a frequency within the range of 400 kHz to 13.56 MHz. In one embodiment, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. One or more bias RF signals generated are provided to the conductive members of the substrate support 11 . Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

Power supply 30 may also include a DC power supply 32 coupled to plasma processing chamber 10 . The DC power supply 32 includes a first DC generator 32a and a second DC generator 32b. In one embodiment, the first DC generator 32a is connected to a conductive member of the substrate support 11 and configured to generate the first DC signal. The generated first DC signal is applied to the conductive member of substrate support 11 . In one embodiment, the first DC signal may be applied to other electrodes, such as electrodes in an electrostatic chuck. In one embodiment, the second DC generator 32b is connected to the conductive member of the showerhead 13 and configured to generate the second DC signal. The generated second DC signal is applied to the conductive members of showerhead 13 . In various embodiments, the first and second DC signals may be pulsed. Note that the first and second DC generators 32a and 32b may be provided in addition to the RF power supply 31, and the first DC generator 32a may be provided instead of the second RF generator 31b. good.

The exhaust system 40 may be connected to a gas outlet 10e provided at the bottom of the plasma processing chamber 10, for example. Exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve regulates the pressure in the plasma processing space 10s. Vacuum pumps may include turbomolecular pumps, dry pumps, or combinations thereof.

Here, details of the configuration of the gas supply unit will be described with reference to FIG. 4 . FIG. 4 is a schematic diagram schematically showing the details of the configuration of the gas supply unit 20. As shown in FIG.

In one embodiment, the gas supply unit 20 includes multiple gas sources 21 and multiple flow controllers 22 connected thereto, as shown in FIG. Each flow controller 22 includes a flow controller 24 , a flow path 120 through which process gas passes, a control valve 122 , and a resistor (orifice) 124 . The flow path 120 has a first valve 126 at the end facing the gas source 21 and a second valve 128 at the end facing the plasma processing chamber 10 . Further, the flow path 120 includes a first flow path 130 which is a portion sandwiched between the control valve 122 and the resistor 124, and a second flow path 132 which is a portion sandwiched between the resistor 124 and the second valve 128. have First flow path 130 includes primary pressure sensor 134 and second flow path 132 includes secondary pressure sensor 136 . The primary pressure sensor 134 and the secondary pressure sensor 136 obtain the pressures of the first flow path 130 and the second flow path 132 respectively, and input the respective pressure values to the flow control section 24 . The flow rate control unit 24 controls the opening and closing of the control valve 122 based on the input difference between the pressures of the first flow path 130 and the pressure of the second flow path 132 and a set flow rate value FS, which will be described later. . Alternatively, the flow controller 24 controls the flow rate passing through the flow controller 22 by controlling the opening of the control valve 122 . The flow control unit 24 also monitors the current flow rate passing through the flow controller 22 and transmits a flow monitor value FM to the control unit 3 .

<Flow rate control system>
Next, an overview of the configuration of a flow control system 200 capable of controlling the flow rate of the processing gas in the plasma processing system 1 will be described with reference to FIG. FIG. 5 is a schematic diagram showing the configuration of a flow rate control system 200 that controls the flow rate of the processing gas in the plasma processing system 1. As shown in FIG.

In FIG. 5, the control unit 3 sends a flow start signal SO, which is a command to start the flow of the processing gas, and a flow end signal, which is a command to stop the flow of the processing gas, to the flow rate modulation device 23. Send SC. The flow modulation device 23 generates a first opening signal SO1 for opening the first valve 126, a second opening signal SO2 for opening the second valve 128, and a third valve 202 based on the flow start signal SO. A third opening signal SO3 to open is sent to each valve. In addition, the flow modulation device generates a first closing signal SC1 for closing the first valve 126, a second closing signal SC2 for closing the second valve 128, and a third valve 202 based on the flow termination signal SC. A third closing signal SC3 is sent to each valve to close the . In one embodiment, first valve 126, second valve 128, and third valve 202 can be air operated valves. In this case, it may be connected to the flow modulating device 23 via any air circuit. Additionally, the flow modulating device 23 may include solenoid valves that control the air supply to each valve. In this case, the transmission of the first to third opening signals SO1, SO2, SO3 and the first to third closing signals SC1, SC2, SC3 is performed by controlling the air supply by opening and closing the solenoid valves. good too. The controller 3 also transmits a flow control start signal FCS1 and a flow control end signal FCS2 to the flow controllers of the flow controllers 22 .

Further, in FIG. 5, the flow control unit 24 sequentially transmits the monitored flow rate monitor value FM to the control unit 3 . The pressure sensor 26 also sequentially transmits the measured pressure value PS to the control unit 3 . Sequential transmission refers to acquisition and transmission of the flow rate monitor value FM and the pressure value PS at desired intervals during the execution of the flow rate control method MT, which will be described later.

<Flow rate control method>
Next, a processing gas flow rate control method MT in the plasma processing system 1 having the flow rate control system 200 configured as described above will be described with reference to FIG. FIG. 6 is a flowchart showing an outline of the flow rate control method MT according to this embodiment. As shown in FIG. 6, the flow rate control method MT includes steps ST10 to ST20 for acquiring gas supply log data, steps ST30 to ST32 for performing calculations based on the acquired gas supply log data, and and a step ST40 of controlling the flow rate.

First, the process of acquiring gas supply log data will be described. In step ST10, gas supply log data is acquired for any one flow rate controller 22 from start to finish. The gas supply log data refers to the flow rate monitor value FM acquired by the flow rate control section 24 of the one flow rate controller 22 and the pressure value PS acquired by the pressure sensor 26 in the combined flow path 27 . Specifically, the gas supply log data is acquired by the flow control unit 24 and the pressure sensor 26 respectively acquiring the flow rate monitor value FM and the pressure value PS at desired intervals and sequentially transmitting them to the control unit 3. be done.

In step ST11, the control unit 3 sends a flow start signal SO to the flow modulation device, thereby starting flow of the desired processing gas. The flow start signal SO consists of a first opening signal SO1 for opening the first valve 126, a second opening signal SO2 for opening the second valve 128, and a third opening signal SO2 for opening the third valve 202. It includes an opening signal SO3 and a first delay signal DL1 that determines a first delay time DT1 from the opening of the first valve 126 to the opening of the second valve 128.

In step ST12, the flow rate modulation device 23 moves the first valve 126 upstream of the one flow rate controller 22 based on the first opening signal SO1 and the third opening signal SO3 included in the flow start signal SO. and the third valve 202 are opened.

In step ST13, the flow modulation device closes the second valve 128 downstream of the one flow controller 22 after a first delay time DT1 based on the first delay signal DL1 included in the flow start signal SO. open the

At step ST14, the controller 3 transmits a flow rate control start signal FCS1 to the flow rate controller 24 of the one flow rate controller 22 described above. The flow control start signal FCS1 consists of a second delay signal DL2 that determines a second delay time DT2 from when each valve is opened until the start of flow control, and a desired signal to flow through the one flow controller 22. and a set flow value signal for setting the flow rate (set flow value FS).

In step ST15, the flow control unit 24 operates the control valve 122 so that the flow reaches the set flow value FS after the second delay time DT2 based on the second delay signal DL2 included in the flow control start signal FCS1. Control opening and closing. After that, the flow of the processing gas is continued for an arbitrary time.

In step ST16, the control unit 3 sends a flow termination signal SC to the flow rate modulation device 23 to terminate the flow of the desired processing gas. The flow termination signal SC includes a first closing signal SC1 closing the first valve 126, a second closing signal SC2 closing the second valve 128, and a third closing signal SC2 closing the third valve 202. It includes a closing signal SC3 and a third delay signal DL3 that determines a third delay time DT3 from closing the second valve 128 to closing the first valve 126. FIG.

In step ST17, the flow modulation device 23 controls the second valve upstream of the one flow controller 22 based on the first closing signal SC1 and the second closing signal SC2 included in the flow end signal SC. 128 and the third valve 202 is closed.

In step ST18, the flow modulation device 23 closes the first valve downstream of the one flow controller 22 after a third delay time DT3 based on the third delay signal DL3 included in the flow end signal SC. 126 is closed.

At step ST19, the controller 3 transmits a flow rate control end signal FCS2 to the flow rate controller 24 of the one flow rate controller 22 described above. The flow control termination signal FCS2 includes a fourth delay signal DL4 that determines a fourth delay time DT4 from closing of each valve to termination of flow control.

In step ST20, the flow control unit 24 closes the control valve 122 after the fourth delay time DT4 based on the fourth delay signal DL4 included in the flow control end signal FCS2, and ends the flow control. After the flow rate control ends, the acquisition of the gas supply log data ends.

Here, the gas supply log data obtained in steps ST10 to ST20 and transmitted to the control unit 3, that is, the flow rate monitor value FM and the pressure value PS will be described.

FIG. 7 is a comparison diagram in which the data of changes over time of the flow rate monitor value FM and the pressure value PS are superimposed and compared, with time on the horizontal axis and flow rate or pressure on the vertical axis. FIG. 7 also includes changes over time in the set flow rate value FS. A solid line indicates the pressure value PS, a dotted line indicates the set flow rate value FS, and a dashed line indicates the flow rate monitor value FM. In FIG. 7, the data of changes in the pressure value PS over time is referred to as a pressure profile. In addition, the portion including the peak in the pressure profile immediately after the start of flow rate control (the densely hatched portion in FIG. 7) is the first profile PF1, and the portion including the steady pressure value PS (the sparsely hatched portion in FIG. 7 part) is called the second profile PF2.

In steps ST11 to ST13, when each valve is opened, the pressure value PS shows a peak and forms a first profile PF1. Next, when flow rate control is started in steps ST14 and ST15, the pressure value PS rises stably to form a second profile PF2. Further, when the flow rate control is started, the flow rate monitor value FM increases from zero. Hereinafter, in this specification, the rise of the flow rate monitor value FM from 0 is referred to as rising, and the moment of rise from 0 is referred to as rising time. In steps ST16 to ST19, when each valve is closed, the pressure value PS decreases. Next, when the flow rate control ends in steps ST19 and ST20, the flow rate monitor value FM decreases.

Returning to FIG. 6, the step ST30 of performing calculations based on the gas supply log data will now be described. Step ST30 is executed following steps ST10 to ST20 for obtaining gas supply log data.

In step ST30, the control unit 3 converts the data on changes over time of the flow rate monitor value FM and the pressure value PS acquired in steps ST10 to ST20 to a first profile of the pressure value PS before the rise time of the flow rate monitor value FM. Perform an operation to see if PF1 is detected.

In step ST31, when the first profile PF1 of the pressure value PS is detected before the rise time of the flow rate monitor value FM in step ST30, the control unit 3 sets the first to fourth delay times DT1 and DT2. , DT3 and DT4, the first to fourth delay signals DL1, DL2, DL3 and DL4 are changed. Then, the control unit 3 uses the changed first to fourth delay signals DL1, DL2, DL3, and DL4 to execute steps ST10 to ST20 and ST30 again.

In step ST32, the control unit 3 determines that the first profile PF1 of the pressure value PS is not detected before the rise time of the flow rate monitor value FM in step ST30, and the second profile PF1 is detected after the rise time of the flow rate monitor value FM. When only PF2 is detected, the first to fourth delay signals DL1, DL2, DL3, and DL4 used for acquiring the gas supply log data in steps ST10 to ST20 are recorded.

Here, when the first profile PF1 of the pressure value PS is not detected before the rise time of the flow rate monitor value FM in step ST32, and only the second profile PF2 is detected after the rise time of the flow rate monitor value FM. Specifically, it refers to the case where a pressure profile as shown in FIG. 8 is detected.

Next, step ST40 for controlling the flow rate in plasma processing will be described. Step ST40 is performed when the plasma processing system 1 is used to perform plasma processing on the wafer after performing steps ST10 to ST20 and ST30 to ST32. In step ST40, when the processing gas is supplied to the plasma processing chamber 10 using the one flow rate controller 22, the first to fourth delay signals DL1, DL2, DL3, and DL4 recorded in step ST32 are included. The flow start signal SO, the flow rate control start signal FCS1, the flow end signal SC, and the flow rate control end signal FCS2 are used to control the start and end of flow of the processing gas and the flow rate of the processing gas.

Next, the reason for configuring the flow rate control method according to the present embodiment as described above will be described.

As described above, the present inventors have used OES to confirm changes over time in the amount of process gas present in the plasma processing chamber 10 and have found that this may not correlate with the monitored flow rate FM in the flow controller 22. confirmed. As a result of intensive studies by the inventors of the present invention, when the pressure sensor 26 is provided downstream of the flow controller 22 and the data of the temporal change of the pressure value PS is acquired, the data of the temporal change of the pressure value PS and the OES It was found that there is a good correlation with the data on the change in the abundance of the process gas over time obtained by Specifically, regarding the abundance of the processing gas in the plasma processing chamber 10 obtained by OES, when the abundance of the processing gas rapidly increases as shown in FIG. It has been found that a first profile PF1 is detected in the pressure profile corresponding to . Accordingly, the present inventors assume that in the flow rate control method MT according to the present embodiment, the pressure profile of the pressure sensor 26 substantially indicates the amount of processing gas present in the plasma processing chamber 10, and the pressure value of the pressure sensor 26 is We have found that it is possible to compare PS with the flow monitor value FM.

As a result of further investigation by the present inventors, the following reason was assumed as the reason for the lack of correlation between the existing amount of the processing gas obtained by the OES and the flow rate monitor value FM in the conventional flow rate control. In the flow controller 22 as shown in FIG. 4, when the flow rate control is finished after a given flow rate, the second valve 128 is first closed, and after the third delay time DT3 has passed, the first valve 128 is closed. Valve 126 is closed. At this time, the processing gas may remain in the flow path 120 of the flow controller 22 sandwiched between the first valve 126 and the second valve 128 . Hereinafter, the remaining processing gas will be referred to as residual gas.

Residual gas is released the next time control is initiated using the flow controller 22 . Specifically, it is discharged into the combined channel 27 when the first valve 126 and the second valve 128 are opened. That is, the reason why the amount of the processing gas existing in the plasma processing chamber 10 increased rapidly immediately after the start of flow rate control and the reason why the first pressure profile PF1 was detected was that the residual gas in the flow rate controller 22 was discharged. It seems that it is due to the result. On the other hand, when the first valve 126 and the second valve 128 are opened, the flow control start signal FCS1 is not sent to the flow control unit 24 of the flow controller 22, and the flow controller 22 no process gas is flowing. Therefore, the flow monitor value FM in the flow controller 24 becomes zero. That is, residual gas released immediately after the first valve 126 and the second valve 128 are opened is not detected by the flow controller 24 of the flow controller 22 . Therefore, the process gas remains in the flow controller 22 at the end of flow control, and the residual gas is released when control is next started using the same flow controller 22, and the release of the residual gas is controlled by the flow controller. It is considered that there is no correlation between the pressure profile and the flow rate monitor value FM because the flow rate control unit 24 of 22 cannot detect it.

In contrast, according to the flow rate control method MT, when the flow rate is controlled by the flow rate controller 22, control is performed so that the first profile PF1 is not detected or the first profile PF1 is minimized. can be done. Specifically, for the gas supply log data, when the first profile PF1 of the pressure value PS is detected before the rise time of the flow rate monitor value FM in step ST30, the first to fourth profile PF1 in step ST31. The first to fourth delay signals DL1, DL2, DL3 and DL4 are changed so as to shorten the delay times DT1, DT2, DT3 and DT4. As a result, residual gas can be prevented from remaining between the first valve 126 and the second valve 128, and the influence of the residual gas can be included in the flow rate monitor value FM. In particular, by shortening the third delay time DT3, the time from closing the second valve 128 to closing the first valve 126 is shortened, so the amount of process gas flowing into the flow controller 22 during that time is reduced. can be reduced, and the residual gas can be suppressed accordingly. Further, by shortening the first delay time DT1 and the second delay time DT2, it is possible to shorten the time from the opening of each valve to the start of flow rate control, and even if residual gas is released, Its effect can be included in the flow monitor value FM.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The embodiments described above may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

Note that the following configuration also belongs to the technical scope of the present disclosure. For example, in the above embodiment, each delay signal is changed so as to shorten each delay time when the first profile PF1 is detected, but the present invention is not limited to this. Each delay signal may be changed to extend each delay time so that the first profile PF1 can be suppressed.

Further, the influence of the residual gas may occur when valves that open and close by opening and closing signals are provided upstream and downstream of the flow rate controller 22 to be controlled. The flow rate control method MT according to the present embodiment is effective when the influence of the residual gas is occurring. Therefore, in the above embodiment, the flow rate control method MT is applied to the pressure control type flow rate controller 22, but the present invention is not limited to this. For example, even for a thermal flow controller 22, the effects of residual gas can be suppressed by shortening or extending the first to fourth delay signals when opening and closing valves upstream and downstream of the flow controller 22. can be done.

Also, in order to reduce the influence of residual gas and improve the correlation between the pressure value PS and the flow rate monitor value FM, synchronized control of opening and closing operations of each valve is important. By the way, the opening and closing operation of a pneumatically driven valve, which is generally used, tends to cause variations due to errors in control speed and differences in response speed among individual valves, which is disadvantageous for tuning control. Therefore, for the first to third valves in the above embodiment, in order to further improve the synchronized control of valve opening/closing operations, electromagnetic opening/closing valves that are directly operated by electric signals can be used. Specifically, by using electromagnetic opening and closing valves, it is possible to control the opening and closing of each valve more precisely, thereby further reducing the influence of residual gas and improving the correlation between the pressure value PS and the flow rate monitor value FM. can be improved.

In order to reduce the influence of the residual gas and improve the correlation between the pressure value PS and the flow monitor value FM, the volume of the flow path 120 in the flow controller 22 in which the residual gas can remain can be minimized. It is valid. Thus, to minimize the volume of flow path 120, for example, flow controller 22 and first valve 126 and second valve 128 can be integrally provided. According to this, for example, of the flow path 120, the portion of the flow path 120 excluding the first flow path 130 and the second flow path 132, such as the portion sandwiched between the first valve 126 and the control valve 122, Shortening is possible, thus minimizing volume.

22 flow controller 26 pressure sensor 126 first valve 128 second valve MT flow control method SO1 first opening signal SO2 second opening signal SC1 first closing signal SC2 second closing signal FM flow monitor value PS Pressure value PF1 First profile PF2 Second profile DL1 First delay signal DL2 Second delay signal DL3 Third delay signal DL4 Fourth delay signal DT1 First delay time DT2 Second delay time DT3 Second Third delay time DT4 Fourth delay time

Claims (5)

A process gas flow control method using a flow control system, comprising:
The flow control system comprises a flow controller, a first valve provided upstream of the flow controller, a second valve provided downstream of the flow controller, and a valve provided downstream of the first valve. a pressure sensor configured to
The flow rate control method includes a gas supply log data acquisition step, a calculation step, and a control step,
In the gas supply log data acquisition step, the first valve opening signal for the flow controller, the first delay signal for determining the first delay time, the second valve opening signal, the second and a second delay signal that determines two delay times, followed by initiating flow rate control in the flow controller such that the flow rate of the process gas reaches a set flow rate. transmitting a flow rate control start signal, and acquiring a flow rate monitor value indicating a flow rate in the flow rate controller and a pressure value in the pressure sensor from the start to the end of the gas supply log data acquisition step;
In the calculation step, the flow rate monitor value and the pressure value are compared, and if the first profile is detected before the rise time of the flow rate monitor value, the first delay time or the second delay time changing the first delay signal or the second delay signal so as to shorten or extend the delay time, and executing the gas supply log data acquisition step again; or
In the calculating step, the flow rate monitor value and the pressure value are compared, the first profile is not detected before the rise time of the flow rate monitor value, and the second profile is detected after the rise time of the flow rate monitor value. is detected, the first delay signal and the second delay signal used in the gas supply log data acquisition step when acquiring the flow rate monitor value and the pressure value are recorded, and End the calculation process,
In the control step, when the first profile is not detected before the rise time of the flow rate monitor value in the calculation step and the second profile is detected after the rise time of the flow rate monitor value, the recording and controlling the flow rate of the process gas by using the first delay signal and the second delay signal. In the gas supply log data acquisition step, after transmitting the flow rate control start signal, the first valve closing signal, the third delay signal for determining the third delay time, and the transmitting an end-of-flow signal comprising a second valve closing signal and a fourth delay signal determining a fourth delay time;
In the calculating step, the flow rate monitor value and the pressure value are compared, and if the first profile is detected before the rise time of the flow rate monitor value, the third delay time and the change to shorten or extend the delay time of four, or compare the flow rate monitor value and the pressure value, the first profile is not detected before the rise time of the flow rate monitor value, and the flow rate When the second profile is detected after the rise time of the monitor value, further recording the third delay signal and the fourth delay signal,
2. The flow rate control method according to claim 1, wherein said control step further uses said third delay signal and said fourth delay signal. 3. The flow rate control method according to claim 1, wherein said first valve and said second valve are electromagnetic opening/closing valves. The flow rate control method according to any one of claims 1 to 3, wherein the flow rate controller, the first valve and the second valve are provided integrally. A flow rate control system for controlling the flow rate of a process gas, comprising:
a flow controller, a first valve provided upstream of the flow controller, a second valve provided downstream of the flow controller, a pressure sensor provided downstream of the first valve, and a control and
The control unit is configured to be able to execute a flow rate control method,
The flow rate control method includes a gas supply log data acquisition step, a calculation step, and a control step,
In the gas supply log data acquisition step, the first valve opening signal for the flow controller, the first delay signal for determining the first delay time, the second valve opening signal, the second and a second delay signal that determines two delay times, followed by initiating flow rate control in the flow controller such that the flow rate of the process gas reaches a set flow rate. transmitting a flow rate control start signal, and acquiring a flow rate monitor value indicating a flow rate in the flow rate controller and a pressure value in the pressure sensor from the start to the end of the gas supply log data acquisition step;
In the calculation step, the flow rate monitor value and the pressure value are compared, and if the first profile is detected before the rise time of the flow rate monitor value, the first delay time or the second delay time changing the first delay signal or the second delay signal so as to shorten or extend the delay time, and executing the gas supply log data acquisition step again; or
In the calculating step, the flow rate monitor value and the pressure value are compared, the first profile is not detected before the rise time of the flow rate monitor value, and the second profile is detected after the rise time of the flow rate monitor value. is detected, the first delay signal and the second delay signal used in the gas supply log data acquisition step when acquiring the flow rate monitor value and the pressure value are recorded, and End the calculation process,
In the control step, when the first profile is not detected before the rise time of the flow rate monitor value in the calculation step and the second profile is detected after the rise time of the flow rate monitor value, the recording A flow rate control system that controls the flow rate of the process gas using the first delay signal and the second delay signal obtained by the above method.

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