Substrate processing apparatus and parameter acquisition method

Abstract

The present application relates to a substrate processing apparatus and a parameter acquisition method for improving the control accuracy of the temperature of a heater. The substrate processing apparatus includes a heater resistor, a digital filter that filters at least one of a detection voltage and a detection current, the detection voltage being a digital voltage value detected by setting a voltage applied to the heater resistor, the detection current being detected by converting a voltage calculated from the heater resistor and a current flowing through the heater resistor into a digital voltage value, and a control unit that controls the temperature of the heater resistor using the detection voltage and the detection current filtered by the digital filter.

Description

Technical Field

[0001] This disclosure relates to a substrate processing apparatus and a parameter acquisition method. Background Technology

[0002] It is known to perform heater temperature control in a substrate processing apparatus (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-212670 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides a technique for improving the control accuracy of heater temperature.

[0008] Solution for solving the problem

[0009] One aspect of the substrate processing apparatus disclosed herein includes: a heater resistor; a digital filter that filters at least one of a detection voltage and a detection current, the detection voltage being a digital voltage value detected by setting a voltage applied to the heater resistor, the detection current being detected by converting a voltage calculated based on the heater resistor and the current flowing through the heater resistor into a digital voltage value; and a control unit that uses the detection voltage and detection current, at least one of which has been filtered by the digital filter, to control the temperature of the heater resistor.

[0010] The effects of the invention

[0011] According to this disclosure, the accuracy of heater temperature control is improved. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating an example of the general structure of a substrate processing apparatus according to an embodiment.

[0013] Figure 2 An example of a top view showing an electrostatic chuck.

[0014] Figure 3 This is a diagram showing an example of the outline structure of the heater control unit and the heater.

[0015] Figure 4 This is a diagram showing an example of a voltage waveform.

[0016] Figure 5 This is a diagram showing an example of a voltage waveform.

[0017] Figure 6 This is a diagram showing an example of a current waveform.

[0018] Figure 7 This is a diagram showing an example of a current waveform.

[0019] Figure 8 An example of a block diagram representing a digital filter.

[0020] Figure 9 This is a diagram illustrating an example of the schematic structure of a digital filter.

[0021] Figure 10 This is a graph illustrating an example of the relationship between the division ratio and the cutoff frequency.

[0022] Figure 11 This is a diagram showing an example of the outline structure of a digital filter and control unit.

[0023] Figure 12 This is a diagram showing an example of the outline structure of a digital filter and control unit.

[0024] Figure 13 This is a flowchart illustrating an example of a parameter acquisition method involved in an implementation method.

[0025] Figure 14 An example of a block diagram representing a digital filter.

[0026] Figure 15 An example of a block diagram representing a digital filter.

[0027] Figure 16 An example of a block diagram representing a digital filter.

[0028] Explanation of reference numerals in the attached figures

[0029] 1: Substrate processing apparatus; 25: Electrostatic chuck; 31: DC power supply; 35: First high-frequency power supply; 36: Second high-frequency power supply; 55: Variable DC power supply; 70: Heater control unit; 71: AC power supply; 72: Switch; 75: Digital filter; 751: Digital filter; 752: Digital filter; 753: Digital filter; 76: Control unit; 77: Calculation unit; 78: Comparison control unit; 253: Heater; 253a: Heater resistor. Detailed Implementation

[0030] Hereinafter, embodiments of the substrate processing apparatus and parameter acquisition method disclosed in this application will be described in detail with reference to the accompanying drawings. However, the disclosed substrate processing apparatus and parameter acquisition method are not intended to be limited by these embodiments.

[0031] When controlling the heater temperature in a substrate processing apparatus, the resistance value of the heater resistor is sometimes calculated. This is because there is a certain relationship between the heater temperature and the heater resistance; the heater temperature can be determined based on the heater resistance value. To calculate the resistance value, the voltage applied to the heater resistor and the current flowing through it are detected. In this case, if the detected voltage and current contain noise, the accuracy of heater temperature control decreases. Therefore, a technique to improve the accuracy of heater temperature control is desired.

[0032] The embodiments of the disclosed substrate processing apparatus and parameter acquisition method will now be described in detail based on the accompanying drawings. Furthermore, the disclosed technology is not limited by the following embodiments. Additionally, the various embodiments can be appropriately combined without contradiction.

[0033] Figure 1 This is a diagram illustrating an example of the general structure of the substrate processing apparatus according to the embodiment. The structure of the substrate processing apparatus 1 will now be described.

[0034] The substrate processing apparatus 1 includes a chamber 10, an exhaust device 16, and a gate valve 17. Figure 1 The diagram shows a cross-section of chamber 10. In this example, chamber 10 includes a bottom wall 11 and side walls 12, and has a generally cylindrical shape. The material of chamber 10 is, for example, aluminum. The inner surfaces of chamber 10 (the inner surfaces of the bottom wall 11 and / or the side walls 12) may be covered with an anodized coating. The space within chamber 10 used for processing the substrate (wafer W in this example) is illustrated as a processing space PS. The processing space PS is isolated from the external atmosphere by chamber 10. An exhaust port 13 connected to an exhaust device 16 is formed on the bottom wall 11 of chamber 10. The exhaust device 16 discharges gas from the processing space PS through the exhaust port 13 to depressurize the processing space PS to a predetermined vacuum level. An opening 14 connected to a gate valve 17 is formed on the side wall 12 of chamber 10. The gate valve 17 is used to open and close the opening 14.

[0035] The substrate processing apparatus 1 includes a mounting stage 20. The mounting stage 20 is disposed below the processing space PS within the chamber 10. The mounting stage 20 includes an insulating plate 21, an inner wall member 22, a support stage 23, a substrate 24, an electrostatic chuck 25, and an edge ring 26.

[0036] Both the insulating plate 21 and the inner wall member 22 are insulating, used to insulate the rest of the stage 20 relative to the chamber 10. The insulating plate 21 is disposed on the bottom wall 11 of the chamber 10. The insulating plate 21 has a disc shape. The inner wall member 22 is disposed on the edge of the insulating plate 21 and on the insulating plate 21. The inner wall member 22 has a cylindrical shape. The material of the inner wall member 22 is, for example, quartz.

[0037] The support platform 23 and the substrate 24 are disposed on the inner side of the inner wall member 22. The support platform 23 is conductive and is disposed on the insulating plate 21. The substrate 24 is disposed on the support platform 23. The material of the substrate 24 is, for example, aluminum. A refrigerant circulation path 24a connected to the cooling device 33 described later is provided inside the substrate 24.

[0038] An electrostatic chuck 25 is disposed on a substrate 24. The electrostatic chuck 25 includes a body 251, electrodes 252, and a plurality of heaters 253. The body 251 is insulating. The electrodes 252 and heaters 253 are embedded within the body 251. In this example, the electrostatic chuck 25 includes a plurality of heaters 253. A heat transfer gas supply path 25a is formed in the electrostatic chuck 25 to reach the upper surface of the electrostatic chuck 25. See also... Figure 2 To illustrate the electrostatic chuck 25 and multiple heaters 253.

[0039] Figure 2 This is an example of a top view of an electrostatic chuck. The upper surface of the electrostatic chuck 25 is divided into multiple regions 25d. In this example, it is divided into three parts radially and eight parts circumferentially. However, the method of division is not particularly limited. Each heater of the multiple heaters 253 is embedded in its corresponding region 25d. When AC power from AC power source 71 is supplied to the heaters 253, the heaters 253 heat the electrostatic chuck 25 with the corresponding region 25d as the center.

[0040] return Figure 1 The edge ring 26 is disposed on the inner wall member 22 and the substrate 24 such that an electrostatic chuck 25 is included on the inner side of the edge ring 26. The edge ring 26 is formed, for example, from monocrystalline silicon.

[0041] The substrate processing apparatus 1 includes a DC power supply 31, a cooling device 33, and a heat transfer gas supply unit 34. The DC power supply 31 applies a DC voltage to the electrodes 252 of the electrostatic chuck 25. The cooling device 33 cools the refrigerant to a predetermined temperature and circulates the refrigerant in the refrigerant circulation path 24a. The heat transfer gas supply unit 34 supplies heat transfer gas (e.g., He gas) between the substrate (in this example, the wafer W) and the electrostatic chuck 25 via the heat transfer gas supply path 25a.

[0042] The substrate processing apparatus 1 includes a plurality of heater control units 70. Each heater control unit of the plurality of heater control units 70 is respectively provided corresponding to each heater of the plurality of heaters 253. Power from an AC power supply 71 is supplied to the heaters 253. The AC power supply 71 can be, for example, a commercial power supply (RMS value of approximately 200V, frequency of 60Hz, etc.). Referring to the following text... Figure 3 The details of the heater control unit 70 and the heater 253 are further illustrated in the accompanying drawings.

[0043] The substrate processing apparatus 1 includes a first high-frequency power supply 35 and a second high-frequency power supply 36. The first high-frequency power supply 35 supplies high-frequency power at a first frequency (e.g., 100MHz) to the substrate 24 via a first matching unit 37. The second high-frequency power supply 36 supplies high-frequency power at a second frequency (e.g., 13MHz) lower than the first frequency to the substrate 24 via a second matching unit 38.

[0044] The substrate processing apparatus 1 includes a spray head 40. The spray head 40 is disposed above the mounting stage 20 in the processing space PS such that the lower surface of the spray head 40 faces the mounting stage 20 and the plane of the lower surface of the spray head 40 is substantially parallel to the plane of the upper surface of the mounting stage 20.

[0045] The spray head 40 includes an insulating component 41, a main body 42, and an upper top plate 43.

[0046] An insulating member 41 insulates the other parts of the spray head 40 relative to the chamber 10. The insulating member 41 is supported on the upper part of the chamber 10. The main body 42 is conductive and is supported on the insulating member 41. The main body 42 is made of, for example, aluminum, and its surface can be anodized. The main body 42 and the substrate 24 serve as the upper electrode and the lower electrode (a pair of electrodes). An upper top plate 43 is disposed on the lower part of the main body 42 and is supported on the main body 42 in a manner that allows it to be easily attached and detached from the main body 42. The upper top plate 43 is made of, for example, a silicon-containing material such as quartz.

[0047] A gas diffusion chamber 42a, a gas inlet 42b, and a gas outlet 42c are formed in the main body 42. The gas diffusion chamber 42a is formed inside the main body 42. The gas inlet 42b is formed in the main body 42 at an upper position than the gas diffusion chamber 42a, and the gas inlet 42b communicates with the gas diffusion chamber 42a. A plurality of gas outlets 42c are formed in the main body 42 at a position above the top plate 43 of the gas diffusion chamber 42a, and the plurality of gas outlets 42c communicate with the gas diffusion chamber 42a.

[0048] Multiple gas inlets 43c are formed in the upper top plate 43. The multiple gas inlets 43c are formed in such a way that they penetrate the upper surface and the lower surface of the upper top plate 43, and the multiple gas inlets 43c are respectively connected to multiple gas outlets 42c.

[0049] The substrate processing apparatus 1 includes a processing gas supply source 51, a valve 52, and a mass flow controller 53 (MFC).

[0050] The processing gas supply source 51 is connected to the gas inlet 42b of the main body 42 of the spray head 40 via a piping 54.

[0051] A mass flow controller 53 is located midway through piping 54. A valve 52 is located between the mass flow controller 53 and the gas inlet 42b in piping 54. The amount of processed gas supplied from the processed gas supply source 51 to the gas inlet 42b is adjusted by opening and closing the valve 52.

[0052] The substrate processing apparatus 1 includes a variable DC power supply 55, a low-pass filter 56 (LPF), and a switch 57. The variable DC power supply 55 is electrically connected to the main body 42 of the spray head 40 via a circuit 58. The low-pass filter 56 and the switch 57 are located midway through the circuit 58. The DC voltage applied to the spray head 40 is switched by opening and closing the switch 57.

[0053] The substrate processing apparatus 1 includes a ring magnet 61. The ring magnet 61 is used to generate a magnetic field in the region between the spray head 40 and the stage 20 in the processing space PS. The ring magnet 61 is arranged concentrically with the chamber 10, with the chamber 10 included inside the ring magnet 61. The ring magnet 61 is supported in the chamber 10 in a rotatable manner via a rotating mechanism (not shown). The ring magnet 61 is formed, for example, of a permanent magnet.

[0054] The substrate processing apparatus 1 includes a deposition shield 62, a deposition shield 63, and a conductive member 64. The deposition shield 62 prevents etching byproducts (deposits) from adhering to the inner peripheral surface of the sidewall 12 of the chamber 10. The deposition shield 62 is configured to cover the inner peripheral surface of the sidewall 12 of the chamber 10 and is supported in the chamber 10 in a manner detachable from the chamber 10. The deposition shield 63 prevents etching byproducts from adhering to the outer peripheral surface of the inner wall member 22. The deposition shield 63 is configured to cover the outer peripheral surface of the inner wall member 22. The conductive member 64 suppresses abnormal discharge within the chamber 10. The conductive member 64 is configured in the processing space PS such that its height is approximately the same as the height of the wafer W placed on the electrostatic chuck 25, and is supported by the deposition shield 62. The conductive member 64 is electrically grounded.

[0055] The substrate processing apparatus 1 includes a control device 5. The control device 5 performs overall control of the substrate processing apparatus 1 by controlling the various structures of the substrate processing apparatus 1. The control device 5 is implemented, for example, by a computer, which is configured to include a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc.

[0056] The operation of substrate processing (plasma etching) performed by the substrate processing apparatus 1 described above will be explained in summary. The opening 14 is opened by controlling the gate valve 17. The wafer W is moved into the processing space PS through the opening 14 and placed on the stage 20. A DC voltage is applied to the electrode 252 by the DC power supply 31, and the wafer W is held in place by the electrostatic chuck 25 by Coulomb force. The opening 14 is closed by controlling the gate valve 17. The processing space PS is evacuated by controlling the exhaust device 16 to achieve a predetermined vacuum level. A predetermined amount of processing gas is supplied from the processing gas supply source 51 to the gas inlet 42b by controlling the valve 52. The processing gas is also sprayed into the processing space PS of the chamber 10 through multiple gas outlets 42c and gas inlets 43c.

[0057] Heat transfer gas is supplied to the heat transfer gas supply path 25a (between the electrostatic chuck 25 and the wafer W) by controlling the heat transfer gas supply unit 34. The electrostatic chuck 25 is cooled by circulating refrigerant, cooled to a predetermined temperature, in the refrigerant circulation path 24a by controlling the cooling device 33. The temperature of the heater 253 is controlled by the heater control unit 70 to achieve the target temperature (set temperature).

[0058] High-frequency power is supplied to the substrate 24 of the stage 20 by controlling the first high-frequency power supply 35 and the second high-frequency power supply 36. Plasma is generated in the region between the stage 20 and the spray head 40 in the processing space PS. A predetermined DC voltage is applied to the spray head 40 from the variable DC power supply 55 by controlling the variable DC power supply 55 and the switch 57. The wafer W is etched by the plasma generated in the processing space PS. The plasma is, for example, CCP (Capacitively Coupled Plasma), ICP (Inductively Coupled Plasma), Radial Line Slot Antenna, ECR (Electron Cyclotron Resonance Plasma), HWP (Helicon Wave Plasma), etc.

[0059] After etching wafer W, the supply of high-frequency power to the substrate 24 of the stage 20 is stopped by controlling the first high-frequency power supply 35 and the second high-frequency power supply 36. The application of DC voltage to the spray head 40 is stopped by controlling the variable DC power supply 55 and the switch 57. The opening 14 is opened by controlling the gate valve 17. The electrostatic chuck 25 is released from holding wafer W by controlling the DC power supply 31. Wafer W is removed from the processing space PS of the chamber 10 via the opening 14. In plasma etching, the temperature of wafer W is appropriately adjusted to a predetermined temperature, and etching is performed.

[0060] Furthermore, the heater control unit 70 and the heater 253 will be described. Hereinafter, one group of the plurality of heater control units 70 and heaters 253 will be described, but the same description can be given for other groups of heater control units 70 and heaters 253.

[0061] Figure 3 This diagram illustrates an example of the general structure of the heater control unit and the heater. The heater control unit 70 is electrically connected between the AC power supply 71 and the heater 253. The heater 253 includes a heater resistor 253a. The heater resistor 253a is heated by applied power (the voltage applied to the heater resistor 253a and the current flowing through the heater resistor 253a). The heater control unit 70 uses power from the AC power supply 71 to heat the heater resistor 253a. The main power path from the AC power supply 71 to the heater resistor 253a is illustrated as the power line PL. The resistance value and temperature of the heater resistor 253a are illustrated as the heater resistance value R and the heater temperature T, respectively. The heater resistance value R is, for example, 40 Ω. In this case, when an AC voltage of 200 V is applied to the heater resistor 253a, an AC current of 5 A flows through the heater resistor 253a. In this disclosure, the heater temperature T is treated as the same temperature as the heater 253.

[0062] A coil La, a coil Lb, and a capacitor C are connected between the heater control unit 70 and the heater resistor 253a. The coils La and Lb are connected in series to allow the current flowing through the power line PL to pass through. The capacitor C is connected in parallel to allow the current flowing through the power line PL to pass through. The coils La, Lb, and C allow alternating current to flow from the alternating current power source 71 to the heater 253, and reduce high-frequency noise flowing from the heater 253 side into the heater control unit 70.

[0063] The heater control unit 70 includes a switch 72, resistors 73a and 73b, an amplifier 73c, an analog-to-digital converter (ADC) 73d, resistors 74a and 74c, an ADC 74d, a digital filter 75, and a control unit 76. The heater control unit 70 can be a substrate (heater control substrate) on which these components are provided.

[0064] The switch 72 and resistor 74a in the heater control unit 70 are connected in series on the power line PL between the AC power supply 71 and the heater resistor 253a. Figure 3 A three-terminal bidirectional switch (two-way three-terminal thyristors) is used as switch 72. The resistance of resistor 74a is very small (e.g., about 100mΩ), and the voltage drop generated in resistor 74a is very small relative to the voltage of AC power supply 71. That is, when switch 72 is energized, a voltage corresponding to the voltage of AC power supply 71 is applied to heater resistor 253a. In addition, a current corresponding to the current from AC power supply 71 flows through heater resistor 253a.

[0065] During the energization period of the control switch 72, the heater control unit 70 aims to bring the temperature of the heater resistor 253a close to the set temperature. The energization period can be the energization period within half a cycle of the AC power supply 71 (e.g., 60Hz). By controlling the energization period of the control switch 72, the power supplied from the AC power supply 71 to the heater resistor 253a is controlled, thereby controlling the heater temperature T. In the control process, the heater resistance value R is calculated to monitor the heater temperature T. This is because the heater resistance value R changes with respect to the heater temperature T in a known manner.

[0066] The heater resistance value R is calculated based on the voltage applied to heater resistor 253a and the current flowing through heater resistor 253a. The voltage detected, set as the voltage applied to heater resistor 253a, is called the detected voltage V and is illustrated here. The current detected, set as the current flowing through heater resistor 253a, is called the detected current I and is illustrated here. The detected voltage V and detected current I can be digital voltage values ​​(voltage waveforms) detected over a fixed period. The minimum unit of the fixed period can be 1 / 2 cycle of AC power supply 71. In this case, the fixed period can be an integer multiple of 1 / 2 cycle of AC power supply 71.

[0067] The detected voltage V is achieved through resistors 73a and 73b, amplifier 73c, and AD converter 73d (voltage detection unit). Resistors 73a and 73b are connected in series to divide the voltage of AC power supply 71. The voltage obtained by this voltage division is extracted (detected) by amplifier 73c and converted into a digital voltage value by AD converter 73d. Resistors 73a, 73b, amplifier 73c, and AD converter 73d are designed to represent (calculate, etc.) digital voltage values ​​that correspond to the magnitude of the actual voltage generated across resistors 73a and 73b.

[0068] The current I is detected by resistor 74a, amplifier 74c, and AD converter 74d (current detection unit). A voltage corresponding to the magnitude of the current flowing through heater resistor 253a is generated across resistor 74a. This voltage is extracted (detected) by amplifier 74c and converted into a digital voltage value by AD converter 74d. Resistor 74a, amplifier 74c, and AD converter 74d are designed to represent (calculate, etc.) a digital voltage value corresponding to the magnitude of the actual current flowing through resistor 74a. That is, the current I is detected by converting the voltage calculated based on heater resistor 253a and the current flowing through heater resistor 253a into a digital voltage value.

[0069] Digital filter 75 filters the detection voltage V and detection current I. This is because a power supply, which could be a source of noise voltage and noise current (noise source), is electrically coupled to the heater resistor 253a, and these noise voltages and currents may be contained in the detection voltage V and detection current I. A power supply that could be a noise source is, for example, the one previously mentioned. Figure 1 The DC power supply 31, the first high-frequency power supply 35, the second high-frequency power supply 36, and the variable DC power supply 55 are described. However, in addition to these power supplies, various power supplies used in the substrate processing apparatus 1 can also become noise sources. For example, pulsed power supplies are sometimes used to improve the etching process. Through the capacitive coupling of such pulsed power supply with the heater resistor 253a, voltage noise and current noise are sometimes superimposed on the voltage applied to the heater resistor 253a and the current flowing through the heater resistor 253a (i.e., the detection voltage V and the detection current I). (Refer to...) Figures 4-7 This will be used to explain voltage noise and current noise.

[0070] Figure 4 and Figure 5 This is a graph showing an example of a voltage waveform. The horizontal axis of the graph represents time, and the vertical axis represents the instantaneous value of the voltage (V). Figure 4The example shows the waveform of the detected voltage V for half a cycle when the frequency is 60Hz and the effective value is 200V. Figure 5 shown in the Figure 4 A portion of the waveform after magnification. For example... Figure 5 As shown, the detection voltage V is a voltage with a noise voltage (a voltage at a higher frequency than 60Hz) superimposed on the signal voltage (a voltage at 60Hz). The signal voltage is from AC power supply 71, for example, from a commercial power supply (system voltage), and is therefore referred to as the signal voltage Vsys for illustration. The noise voltage is referred to as the noise voltage Vnoise for illustration. The signal voltage Vsys is equivalent to the voltage assuming that the noise voltage Vnoise is not present in the detection voltage V. The waveform of the detection voltage V is distorted relative to the waveform of the signal voltage Vsys by the amount of noise voltage Vnoise included. This distortion, for example, affects values ​​determined based on the voltage waveform (RMS value, etc.). For example, the RMS value increases by the value corresponding to the noise voltage Vnoise.

[0071] Figure 6 and Figure 7 This is a diagram illustrating an example of a current waveform. In Figure 6 The example shows a half-cycle current waveform with a frequency of 60Hz and an effective value of 200V. Figure 7 shown in the Figure 6 The current waveform is a magnified portion of the waveform. For example... Figure 7 As shown, the sensed current I is a current superimposed with a noise current on the signal current. The signal current is referred to as the signal current Isys for illustration. The noise current is referred to as the noise current Inoise for illustration. The signal current Isys corresponds to the current assuming that the sensed current I does not contain the noise current Inoise. The waveform of the sensed current I is distorted relative to the waveform of the signal current Isys by the amount of noise current Inoise included. This distortion, for example, affects values ​​determined based on the current waveform (RMS value, etc.). For example, the RMS value increases by the value corresponding to the noise current Inoise.

[0072] Here, the influence of noise voltage Vnoise on signal voltage Vsys is often different from the influence of noise current Inoise on signal current Isys. In this case, as shown in equation (1) below, the values ​​on the left and right sides are inconsistent.

[0073]

Number 1

[0074]

[0075] The inconsistency shown in Equation (1) above causes a decrease in the accuracy of calculating the heater resistance value R using the detection voltage V and the detection current I. Therefore, in this embodiment, the digital filter 75 filters the noise voltage Vnoise and the noise current Inoise in a manner that makes the value on the left side of Equation (1) close to (equal to) the value on the right side. (Refer to...) Figures 8-10 To explain the details of digital filter 75.

[0076] Figure 8 An example block diagram representing a digital filter. In this example, digital filter 75 includes digital filter 751 (first digital filter) and digital filter 752 (second digital filter).

[0077] Digital filter 751 is a low-pass filter used to attenuate the noise voltage Vnoise contained in the detection voltage V. The attenuation rate α, defined as the rate attenuation of the noise voltage Vnoise by digital filter 751, is illustrated. The attenuation rate α can be a value less than 1 (α ≤ 1.0).

[0078] Digital filter 752 is a low-pass filter used to attenuate the noise current Inoise contained in the detection current I. The attenuation rate β of the noise current Inoise caused by digital filter 752 is illustrated. The attenuation rate β can be a value less than 1 (attenuation rate β ≤ 1.0).

[0079] Here, refer to Figure 9 and Figure 10 This will provide an overview of digital filters.

[0080] Figure 9 This is a diagram illustrating an example of the general structure of a digital filter. The illustrated digital filter 80 filters the input voltage Vin and outputs it as the output voltage Vout. The digital filter 80 includes a frequency divider 81, a multiplier 83, and multiple taps 82. Furthermore, in... Figure 9 Only one tap 82 is marked, and tap 82 includes a delay unit 82a, a switch 82b, and an adder 82c.

[0081] Frequency divider 81 divides the provided clock CLK (e.g., 100MHz) by a division ratio A. The division ratio A can be arbitrarily selected. The divided clock CLK is supplied to the delay unit 82a of each of the multiple taps 82. When switch 82b is turned on (becomes in the on state), tap 82 is activated. By individually controlling the switch 82b of each of the multiple taps 82, the number of activated taps 82 can be arbitrarily selected. Taps 82 are activated sequentially starting from the tap closest to the input voltage Vin. The voltage obtained by applying a delay amount corresponding to the delay unit 82a of the activated tap Vin to the input voltage Vin is added by the adder 82c of the corresponding tap 82, and then multiplied by a predetermined number by the multiplier 83. When the number of taps is set to N, the predetermined number is, for example, 1 / (N+1). The output voltage Vout obtained in this way is the voltage obtained by filtering the input voltage Vin.

[0082] The filtering characteristics of digital filter 80 are adjusted by the division ratio A and the number of taps N. The filtering characteristics are, for example, the cutoff frequency (the frequency at which -3dB occurs). (See reference...) Figure 10 This needs to be explained.

[0083] Figure 10 This is a graph illustrating the relationship between the crossover ratio and the cutoff frequency. The horizontal axis of the graph represents the crossover ratio, and the vertical axis represents the cutoff frequency (kHz). In the graph, circles indicate the relationship between the crossover ratio and the cutoff frequency when the number of taps is 7. Quadrilaterals indicate the relationship when the number of taps is 15. According to... Figure 10 Understandably, the desired cutoff frequency can be obtained by changing the division ratio and / or the number of taps. For example, by setting the number of taps to 15 and the division ratio to 60, a cutoff frequency of approximately 50kHz can be obtained. In the case of analog filters, adjusting the cutoff frequency requires hardware design changes such as alterations to the constants of electronic components (component changes), but such changes are not necessary in digital filters. Therefore, the filtering characteristics can be flexibly varied.

[0084] Furthermore, the digital filter 80 described above is only one example of digital filters 751 and 752. Digital filters of various other structures can also be used as digital filters 751 and 752.

[0085] return Figure 8 The attenuation rate α of digital filter 751 and the attenuation rate β of digital filter 752 are further explained. The attenuation rate α and attenuation rate β are determined in a way that reduces the inconsistency of the above equation (1). That is, as shown in equation (2) below.

[0086]

Number 2

[0087]

[0088] In this case, the attenuation rate α and attenuation rate β are determined, for example, to satisfy the values ​​of the following equation (3).

[0089]

Number 3

[0090]

[0091] The attenuation rates α and β obtained as described above are attenuation rates that make the two sides of the above equation (1), namely the ratio of signal voltage Vsys to noise voltage Vnoise and the ratio of signal current Isys to noise current Inoise, close to each other (equal).

[0092] The cutoff frequency of digital filter 751 is set to the cutoff frequency of attenuation rate α, which satisfies the attenuation rate α and attenuation rate β in equation (2) or (3) above. The cutoff frequency of digital filter 752 is set to the cutoff frequency of attenuation rate β, which satisfies the attenuation rate α and attenuation rate β in equation (2) or (3) above. When the attenuation rate α and attenuation rate β are different, the cutoff frequencies of digital filter 751 and digital filter 752 are also different. Furthermore, either attenuation rate α or attenuation rate β can be 1.

[0093] The digital filter 75 is parameter-controlled so that digital filters 751 and 752 function as low-pass filters exhibiting the desired filtering characteristics. Parameters include, for example, the cutoff frequency mentioned above. Other examples of parameters are attenuation rate α and attenuation rate β. In addition to these parameters, various parameters that impart filtering characteristics to the digital filters can be used. For example, control device 5 ( Figure 1 The parameters can be stored in a reference manner. The control device 5 sets the filtering characteristics of digital filters 751 and 752 based on the parameters. For example, if it is a previously referenced... Figure 9 The structure of the digital filter 80 described herein allows the control device 5 to set the division ratio A and / or the number of taps N for obtaining the filtering characteristics represented by the parameters.

[0094] The parameters of digital filter 751 and digital filter 752 can be prepared individually based on the operating conditions of the power supply that could be a noise source, the degree of coupling between the power supply and heater resistor 253a, etc. (hereinafter referred to as "power supply operating conditions, etc."). In this case, parameters corresponding to the power supply operating conditions, etc., are set. Referring to the following text... Figure 13 This will explain how to obtain such parameters.

[0095] return Figure 3The detection voltage V and detection current I, obtained by filtering through digital filter 75, are input to control unit 76. Control unit 76 uses the detection voltage V and detection current I to control the heater temperature. Figure 3 The example shown is a calculation unit 77 and a comparison control unit 78 included in the control unit 76 as a structure for performing representative processing.

[0096] The calculation unit 77 uses the detected voltage V and detected current I obtained by filtering through the digital filter 75 to calculate the heater resistance value R. The heater resistance value R is obtained by dividing the detected voltage V by the detected current I (i.e., R = V ÷ I). In one embodiment, the calculation unit 77 uses the effective value of the detected voltage V and the effective value of the detected current I to calculate the heater resistance value R. For example, the effective value can be obtained based on the voltage waveform represented by the detected voltage V. For example, the effective value can be obtained based on the current waveform represented by the detected current I.

[0097] The calculation unit 77 calculates the heater temperature T based on the calculated heater resistance value R. For example, a polynomial can be prepared in advance for calculating the heater temperature T based on the heater resistance value R, and this polynomial can be used to calculate the heater temperature T. Alternatively, a data table can be prepared that describes the heater resistance value R in relation to the heater temperature T, and this data table can be used to calculate the heater temperature T. Furthermore, the range of the heater resistance value R that varies with the heater temperature T is very narrow (e.g., about 1%), and the calculation of the heater resistance value R is easily affected by interference such as noise. In this sense, improving the accuracy of the calculated heater resistance value R is crucial for improving the control accuracy of the heater temperature T.

[0098] The comparison control unit 78 compares the calculation result (heater resistance value R or heater temperature T) of the calculation unit 77 with the set value SV. The set value SV is the target temperature of the heater resistor 253a (or the heater resistance value), and is provided externally from the heater control unit 70, for example. The comparison result is, for example, the difference between the calculation result of the calculation unit 77 and the set value SV.

[0099] Furthermore, the comparison control unit 78 controls the switch 72 based on the comparison result. For example, the comparison control unit 78 controls the on-time of the switch 72 to reduce the difference expressed by the comparison result. In this example, the switch 72 is a three-terminal bidirectional switch, so the comparison control unit 78 generates a gate trigger voltage VGT for controlling the on-time and supplies it to the three-terminal bidirectional switch.

[0100] As described above, the control unit 76 uses the detection voltage V and the detection current I to control the heater temperature T.

[0101] The aforementioned digital filter 75 and control unit 76 (calculation unit 77 and comparison control unit 78) are implemented, for example, using an FPGA (Field Programmable Gate Array) or a CPU (Central Processing Unit). See reference. Figure 11 and Figure 12 Let me illustrate with a few examples.

[0102] Figure 11 and Figure 12 This is a diagram illustrating an example of the outline structure of a digital filter and control unit. Figure 11 In the example shown, the digital filter 75, the calculation unit 77, and the comparison control unit 78 (a component of the control unit 76) are implemented by an FPGA. Figure 12 In the example shown, the digital filter 75 and the calculation unit 77 are implemented by an FPGA, and the comparison control unit 78 is implemented by a CPU.

[0103] Next, refer to Figure 13 Here is an example of how to obtain the parameters (cutoff frequency, etc.) of the digital filter 751 and digital filter 752 mentioned above.

[0104] Figure 13 This is a flowchart illustrating an example of a parameter acquisition method according to an embodiment. This process is performed, for example, using a substrate processing apparatus 1.

[0105] In step S1, the power supply and heater are activated. For example, the power supply, which can be a noise source as described so far, is activated under the same conditions as when the wafer W is actually processed in the substrate processing apparatus 1. Similarly, the heater 253 is activated to heat the substrate.

[0106] In step S2, noise is measured. For example, in the previous reference... Figure 3 The noise voltage Vnoise is measured at the detection point of the described detection voltage V (resistor 73a, etc.). The noise current Inoise is measured at the detection point of the detection current I (resistor 74a, etc.). Alternatively, the noise voltage Vnoise is measured, for example, based on the digital voltage value obtained by conversion via AD converter 73d. The noise current Inoise is measured based on the digital current value obtained by conversion via AD converter 74d.

[0107] In step S3, parameters are calculated. For example, the cutoff frequencies of digital filter 751 and digital filter 752 are calculated. That is, the cutoff frequencies corresponding to the attenuation rate α that satisfies the above equation (2) or equation (3) and the cutoff frequencies corresponding to the attenuation rate β are calculated.

[0108] In step S4, parameters are stored. That is, the parameters calculated in the previous step S3 are stored. For example, the parameters are stored in a manner that can be referenced by the control device 5. The parameters are stored in a way that corresponds to the operating conditions of the power supply in the previous step S1.

[0109] After the processing in step S4 is completed, the flowchart processing ends.

[0110] For example, the parameters of digital filter 75 are obtained through the above process. The same process is repeated by changing the operating conditions of the power supply, thereby obtaining the parameters corresponding to the operating conditions of the power supply.

[0111] It should be considered that the embodiments described above are illustrative in all respects and not restrictive. The above embodiments can be implemented in various ways. The above embodiments can be omitted, substituted, or modified in various ways without departing from the claims and their spirit.

[0112] In the above embodiment, an example of providing two digital filters—a digital filter 751 configured for the detection voltage V and a digital filter 752 configured for the detection current I—was described. However, it is also possible to provide only one digital filter. (Refer to...) Figures 14-16 To illustrate this point.

[0113] Figures 14-16 An example of a block diagram representing a digital filter. Figure 14 The exemplified digital filter 75A is compared to the digital filter 75 ( Figure 8 The difference is that digital filter 752 is not included. In digital filter 75A, only the detected voltage V, which is filtered by digital filter 751, is filtered. In this case, the cutoff frequency of digital filter 751 corresponds to the attenuation rate α when the attenuation rate β is 1 in the above equation (2) or equation (3).

[0114] Figure 15 The exemplified digital filter 75B is compared to the digital filter 75 ( Figure 8 The difference is that digital filter 751 is not included. In digital filter 75B, only the detection current I is filtered by digital filter 752. In this case, the cutoff frequency of digital filter 752 corresponds to the attenuation rate β when the attenuation rate α is 1 in the above equation (2) or equation (3).

[0115] Figure 16The illustrated digital filter 75C includes a digital filter 753 and switches 753a, 753b, 753c, and 753d for switching the filtering target of the digital filter 753 between the detection voltage V and the detection current I. Switching switches 753a and 753b selects whether the digital filter 753 is used for the detection voltage V. Switching switches 753c and 753d selects whether the digital filter 753 is used for the detection current I. Each switch is controlled, for example, by a control device 5. The cutoff frequency of the digital filter 753 corresponds to the attenuation rate α when the attenuation rate β is 1 or the attenuation rate α when the attenuation rate α is 1 in the above equation (2) or equation (3).

[0116] In the above embodiment, an example was described using the effective value of the detection current I and the effective value of the detection voltage V to calculate the heater resistance value R. However, it is not limited to the effective value, and various factors that can be used to calculate the heater resistance value R can also be used.

[0117] In the above embodiments, an example was described where the voltage detection unit for detecting the detection voltage V is composed of resistors 73a and 73b, an amplifier 73c, and an AD converter 74d provided in the heater control unit 70. Similarly, an example was described where the current detection unit for detecting the detection current I is composed of resistors 74a, an amplifier 74c, and an AD converter 74d provided in the heater control unit 70. However, the structure is not limited to these configurations, and various structures capable of detecting both the detection voltage V and the detection current I can be used. Furthermore, the detection of the detection voltage V and the detection current I can be performed at all locations where the voltage applied to the heater resistor 253a and the current flowing through the heater resistor 253a can be detected.

[0118] In the above embodiment, an example of a three-terminal bidirectional switch being described is given for switch 72. However, it is not limited to a three-terminal bidirectional switch, and various devices capable of controlling the power supply to the heater resistor 253a can be used as switch 72.

[0119] In the above embodiment, an example of using a commercial power supply 71 was described. However, it is not limited to commercial power supplies, and various power supplies capable of supplying heating power to the heater resistor 253a can be used as the AC power supply 71.

[0120] In the above embodiment, an example was described where the heater 253 provided on the electrostatic chuck 25 was the object of control of the heater control unit 70. However, heaters provided in any part of the substrate processing apparatus 1 may be included in the objects of control of the heater control unit 70.

[0121] In the above embodiments, an example was described where the substrate processing apparatus 1 processes a semiconductor substrate such as a wafer W. However, the substrate processing apparatus 1 is not limited to semiconductor substrates. For example, liquid crystal substrates, organic EL substrates, etc., can also be processed by the substrate processing apparatus 1.

[0122] The substrate processing apparatus 1 described above is, for example, defined as follows: The substrate processing apparatus 1 includes a heater resistor 253a, a digital filter 75, and a control unit 76. The heater resistor 253a is a heater resistor electrically coupled to a power supply, which is a source of noise voltage Vnoise and noise current Inoise. The digital filter 75 filters at least one of the noise voltage Vnoise and noise current Inoise. The detection voltage V is a digital voltage value detected by setting the voltage applied to the heater resistor 253a. The detection current I is a detection current that is detected by converting the voltage calculated based on the heater resistor 253a and the current flowing through the heater resistor 253a into a digital voltage value. The control unit 76 uses the detection voltage V and the detection current I, which have been filtered by the digital filter 75, to control the heater temperature T of the heater resistor 253a.

[0123] According to the substrate processing apparatus 1 described above, by using a digital filter 75 that allows for flexible variation of filtering characteristics, noise voltage Vnoise and noise current Inoise, which can be generated in various ways, can be filtered. Therefore, the calculation accuracy of the heater resistance value R and the control accuracy of the heater temperature T can be improved.

[0124] The digital filter 75 can filter at least one of the detection voltage V and the detection current I in such a way that the ratio of the signal voltage Vsys to the noise voltage Vnoise in the filtered detection voltage V is close to the ratio of the signal current Isys to the noise current Inoise. The signal voltage Vsys is the detection voltage V assuming the absence of noise voltage Vnoise. The signal current Isys is the detection current I assuming the absence of noise current Inoise. The digital filter 75 can be a low-pass filter that attenuates at least one of the noise voltage Vnoise and the noise current Inoise. The filtering characteristics of the digital filter 75 can be parameter-controlled, and the parameters of the digital filter 75 include a cutoff frequency. The heater resistor 253a is heated using power supplied from the AC power supply 71, and the heater control unit 70 calculates the heater resistance value R of the heater resistor 253a based on the effective value of the detection voltage V and the effective value of the detection current I. This reduces the influence of noise voltage Vnoise and noise current Inoise in the calculation of the heater resistance value R. The ability to control the heater temperature T based on the heater resistance value R is as explained above.

[0125] In the digital filter 75, the parameters of the digital filter 751 (first digital filter) set for the detection voltage V and the parameters of the digital filter 752 (second digital filter) set for the detection current I can be different. For example, by setting such parameters, even if the degree of influence of the noise voltage Vnoise on the detection voltage V is different from the degree of influence of the noise current Inoise on the detection current I, the influence of the noise voltage Vnoise and the noise current Inoise in the calculation of the heater resistance value R can be reduced.

[0126] A heater resistor 253a can be disposed on a mounting stage 20 of a substrate (e.g., wafer W). The heater resistor 253a can be embedded in an electrostatic chuck 25 included in the mounting stage 20. Thus, the temperature of the mounting stage 20 for supporting the substrate and the electrostatic chuck 25 for holding the substrate on the mounting stage 20 can be controlled.

[0127] Reference Figure 13 The parameter acquisition method described above is also an aspect of this disclosure. Specifically, the parameter acquisition method includes the following steps: a measurement step (step S2), measuring the noise voltage Vnoise and noise current Inoise generated in the heater resistor 253a used in the substrate processing apparatus 1; and an acquisition step (steps S3 and S4), using the measured noise voltage Vnoise and noise current Inoise to acquire the parameters of a digital filter 75 that filters at least one of the detection voltage V and the detection current I.

[0128] In the acquisition steps (steps S3 and S4), parameters of the digital filter 75 can be acquired, which filters at least one of the detection voltage V and the detection current I in such a way that the ratio of the signal voltage Vsys to the noise voltage Vnoise in the filtered detection voltage V is close to the ratio of the signal current Isys to the noise current Inoise. The parameters can be parameters (e.g., cutoff frequency) that enable the digital filter 75 to function as a low-pass filter that attenuates at least one of the noise voltage Vnoise and the noise current Inoise.

[0129] By using the parameters obtained as described above, the control accuracy of the heater temperature T can be improved, as explained so far.

Claims

1. A substrate processing apparatus comprising: Heater resistor; A digital filter that filters at least one of a detection voltage and a detection current, wherein the detection voltage is a digital voltage value detected by means of a voltage applied to the heater resistor, and the detection current is detected by converting a voltage calculated based on the heater resistor and the current flowing through the heater resistor into a digital voltage value; and The control unit uses at least one of the detected voltage and the detected current, filtered by the digital filter, to control the temperature of the heater resistor. The heater resistor is heated using electricity supplied from an AC power source. The control unit calculates the resistance value of the heater resistor based on the effective value of the detected voltage and the effective value of the detected current. The digital filter filters at least one of the detection voltage and the detection current in such a way that the ratio of the detection voltage to the noise voltage in the filtered detection voltage, assuming the absence of noise voltage, is close to the ratio of the detection current to the noise current in the filtered detection current, assuming the absence of noise current.

2. The substrate processing apparatus according to claim 1, characterized in that, The digital filter is a low-pass filter that attenuates at least one of the noise voltage and noise current.

3. The substrate processing apparatus according to claim 2, characterized in that, The filtering characteristics of the digital filter can be controlled by parameters, including the cutoff frequency.

4. The substrate processing apparatus according to claim 1 or 2, characterized in that, The digital filter includes a first digital filter for filtering the detected voltage and a second digital filter for filtering the detected current. The parameters of the first digital filter are different from those of the second digital filter.

5. The substrate processing apparatus according to claim 1 or 2, characterized in that, The heater resistor is disposed on the substrate mounting stage.

6. The substrate processing apparatus according to claim 5, characterized in that, The heater resistor is embedded in the electrostatic chuck included in the mounting stage.

7. A substrate processing apparatus comprising: Heater resistor; A digital filter that filters at least one of a detection voltage and a detection current, wherein the detection voltage is a digital voltage value detected by means of a voltage applied to the heater resistor, and the detection current is detected by converting a voltage calculated based on the heater resistor and the current flowing through the heater resistor into a digital voltage value; and The control unit uses at least one of the detected voltage and the detected current, filtered by the digital filter, to control the temperature of the heater resistor. The digital filter includes a first digital filter for filtering the detected voltage and a second digital filter for filtering the detected current. The parameters of the first digital filter are different from those of the second digital filter. The digital filter filters at least one of the detection voltage and the detection current in such a way that the ratio of the detection voltage to the noise voltage in the filtered detection voltage, assuming the absence of noise voltage, is close to the ratio of the detection current to the noise current in the filtered detection current, assuming the absence of noise current.

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