Plasma treatment method and plasma treatment apparatus

Abstract

The monitoring accuracy of the plasma generated by supplying pulsed power is improved. [Solution] The plasma processing method includes steps (A) to (C). Step (A) involves supplying pulsed power from an energy source into a processing vessel to generate plasma. Step (B) involves calculating at least one of the following values: the average value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level, based on sensor data of pulsed power at multiple levels, including a first level indicating the plasma off-level and a second level indicating the plasma discharge level, and multiple pulse times maintained at each of the multiple levels. Step (C) involves determining whether the plasma is normal or abnormal using at least one of these values ​​and a preset threshold value.

Description

Technical Field

[0001] The present disclosure relates to a plasma processing method and a plasma processing apparatus.

Background Art

[0002] For example, Patent Document 1 discloses "providing a sensor insertion hole in each microwave radiation mechanism, inserting an electric field sensor or a plasma emission sensor into the sensor insertion hole, and grasping the value of the power of the microwave radiated from the surface wave plasma generation antenna of one microwave radiation mechanism, or the presence or absence of plasma ignition (lighting) in one microwave radiation mechanism".

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a plasma processing method and a plasma processing apparatus capable of enhancing the monitoring accuracy of plasma generated by the supply of pulsed power.

Means for Solving the Problems

[0005] One aspect of this disclosure provides a plasma processing method. The plasma processing method includes steps (A) to (C). Step (A) involves supplying pulsed power from an energy source into a processing vessel to generate plasma. Step (B) involves calculating at least one of the following values: the mean value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level, based on sensor data of pulsed power at multiple levels, including a first level indicating the plasma off-level and a second level indicating the plasma discharge level, and multiple pulse times maintained at each of the multiple levels. Step (C) involves determining whether the plasma is normal or abnormal using at least one of these values ​​and a preset threshold value. [Effects of the Invention]

[0006] According to this disclosure, the monitoring accuracy of plasma generated by supplying pulsed power can be improved. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to the first embodiment. [Figure 2] Figure 2 shows an example of a microwave plasma source. [Figure 3] Figure 3 is a cross-sectional view taken along the line AA in Figure 1. [Figure 4] Figure 4 shows an example of a monitoring system. [Figure 5] Figure 5 shows an example of pulsed power. [Figure 6] Figure 6 is a flowchart showing an example of data reading and calculation processing in a plasma processing method according to one embodiment. [Figure 7] Figure 7 shows an example of data read using the plasma processing method. [Figure 8] Figure 8 is a flowchart showing an example of the calculation process when the pulse is off. [Figure 9]Figure 9 is a flowchart showing an example of the calculation process when there is no pulse discharge. [Figure 10] Figure 10 is a flowchart showing an example of the calculation process during pulsed discharge. [Figure 11] Figure 11 is a flowchart showing an example of a determination process in a plasma processing method according to one embodiment. [Figure 12] Figure 12 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to the second embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the disclosed plasma processing method and plasma processing apparatus will be described in detail below with reference to the drawings. Note that these embodiments do not limit the plasma processing method and plasma processing apparatus described herein, and the following embodiments can be appropriately combined within the scope that does not contradict the configurations and processing contents of the disclosure.

[0009] Furthermore, the diagrams referenced below are schematic representations for illustrative purposes. Therefore, details may be omitted, and the dimensional proportions may not necessarily match those of reality.

[0010] [First Embodiment] A plasma processing apparatus according to the first embodiment of this disclosure will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to the first embodiment. Figure 2 is a diagram showing an example of a microwave plasma source.

[0011] The plasma processing apparatus 100 shown in Figure 1 comprises a processing vessel 101, a mounting base 102, a gas supply source 103, an exhaust device 104, a microwave plasma source 105, and a control unit 106. The processing vessel 101 is a bottomed cylindrical shape made of a metal material such as aluminum, providing a cylindrical processing space S inside, with an open top. The processing vessel 101 has a plate-shaped top wall portion 111 and a bottom wall portion 113, and side wall portions 112 connecting them.

[0012] The mounting stage 102 is on which the substrate W is placed. The substrate W is not particularly limited as long as it is subjected to plasma processing, but examples include semiconductor wafers and glass substrates. The gas supply source 103 supplies processing gas into the processing container 101. The exhaust device 104 exhausts the processing container 101. The microwave plasma source 105 is installed above the processing container 101 and introduces microwaves of 300 MHz to 3 THz to generate plasma inside the processing container 101. The microwave plasma source 105 supplies pulsed microwave power into the processing container 101. Hereinafter, pulsed microwave power or pulsed high-frequency power will also be referred to as "pulsed power". Pulsed power consists of a pulse-on time and a pulse-off time, and the pulse-on time and pulse-off time constitute one period of the pulse. The reciprocal of the time of one period is the pulse frequency, and pulse frequencies from 1 Hz to 50 kHz are set. Also, the duty cycle is obtained by dividing the pulse-on time by one period of the pulse, and duty cycles from 1 to 99% are set. The average value of the high-frequency power during the pulse-on time becomes the set value of the pulse power.

[0013] The plasma processing apparatus 100 is an example of a device that has a microwave plasma source 105, generates plasma using pulsed microwave power output from the microwave plasma source 105, and performs plasma processing on a substrate. However, the plasma processing apparatus 100 is not limited to this, and plasma may be generated using high frequencies in the RF (Radio Frequency) band of several kHz to 30 MHz, or the VHF (Very High Frequency) band of 30 MHz to 300 MHz. The plasma processing apparatus 100 may be a device that performs plasma processing such as film deposition or etching on a substrate.

[0014] The top wall portion 111 is disposed at the upper opening of the processing vessel 101. The top wall portion 111 has a plurality of openings for fitting the microwave radiation mechanism 143 of the microwave plasma source 105. The side wall portion 112 has a loading / unloading port 114 for loading and unloading the substrate W between the processing vessel 101 and an adjacent transfer chamber (not shown). The loading / unloading port 114 is configured to be opened and closed by a gate valve 115. The exhaust device 104 is provided in an exhaust pipe 116 connected to the bottom wall portion 113, and exhausts the inside of the processing vessel 101 through the exhaust pipe 116. Thereby, the exhaust device 104 controls the pressure inside the processing vessel 101.

[0015] The mounting table 102 is made of a disk-shaped ceramic and is supported on the bottom wall portion 113 by a ceramic support member 120 via an insulating member 121. A guide ring 181 for guiding the substrate W is provided at the outer edge portion of the mounting table 102. A heater 182 and an electrode 184 are embedded inside the mounting table 102. The heater 182 heats the substrate W via the mounting table 102 by being supplied with power from a heater power source 183. A high-frequency bias for drawing ions into the mounting table 102 is applied to the electrode 184 from a high-frequency bias power source 122. Note that the high-frequency bias power source 122 may not be provided depending on the characteristics of the plasma processing.

[0016] The gas supply source 103 is connected to a plurality of gas introduction nozzles 123 via a gas supply pipe 125. The gas introduction nozzles 123 are fitted into openings formed in the top wall portion 111 of the processing vessel 101. The gas supply source 103 supplies a processing gas into the processing vessel 101 from the plurality of gas introduction nozzles 123.

[0017] The microwave plasma source 105 includes a microwave output unit 130, an antenna unit 140, and a dielectric 200. The microwave output unit 130 generates microwaves, distributes them to a plurality of paths, and outputs them. The antenna unit 140 introduces microwaves into the processing vessel 101 through the dielectric 200.

[0018] As shown in Figure 2, the microwave output unit 130 includes a microwave power supply 131, a microwave oscillator 132, an amplifier 133, and a distributor 134. The microwave output unit 130 is an example of an energy source that supplies pulsed power into the processing container 101. The microwave oscillator 132 is solid-state and, for example, oscillates microwaves at 915 MHz (e.g., PLL oscillation). Note that the microwave frequency is not limited to 915 MHz, but can be 2.45 GHz, 8.35 GHz, 5.8 GHz, 1.98 GHz, etc., in the range of 700 MHz to 10 GHz. However, the microwave frequency may be in the range of 300 MHz to 3 THz. The amplifier 133 amplifies the microwaves oscillated by the microwave oscillator 132. The distributor 134 distributes the microwaves amplified by the amplifier 133 to multiple paths. The distributor 134 distributes the microwaves while matching the impedance of the input and output sides. Furthermore, the microwave output unit 130 allows for adjustment of the microwave frequency, power, bandwidth, and other parameters.

[0019] The antenna unit 140 includes a plurality of antenna modules 141. Each of the plurality of antenna modules 141 introduces microwaves distributed by the distributor 134 into the processing container 101. The configuration of all of the plurality of antenna modules 141 is identical. Each antenna module 141 has an amplifier section 142 that mainly amplifies and outputs the distributed microwaves, and a microwave radiation mechanism 143 that radiates the microwaves output from the amplifier section 142 into the processing container 101.

[0020] The amplifier section 142 includes a phase shifter 145, a variable gain amplifier 146, a main amplifier 147, and an isolator 148. The phase shifter 145 changes the phase of the microwave. The variable gain amplifier 146 adjusts the power level of the microwave input to the main amplifier 147. The main amplifier 147 is configured as a solid-state amplifier. The isolator 148 isolates the reflected microwave that is reflected by the antenna section of the microwave radiation mechanism 143 and heads toward the main amplifier 147.

[0021] As shown in Figure 1, the microwave radiation mechanism 143 has a coaxially arranged outer conductor 144a and inner conductor 144b, and a tuner 149. The space between the outer conductor 144a and the inner conductor 144b is a microwave transmission path. The tuner 149 matches the impedance of the load to the characteristic impedance of the microwave output unit 130. Microwaves are radiated into the space inside the processing container 101 via the dielectric 200. Plasma is generated from the processing gas by the energy of the pulsed power of the microwaves, which are repeatedly switched on and off.

[0022] The control unit 106 processes computer-executable instructions to be executed by the plasma processing apparatus 100. The control unit 106 may be configured to control each element of the plasma processing apparatus 100 to perform various processes. In one embodiment, part or all of the control unit 106 may be included in the plasma processing apparatus 100. The control unit 106 may include a processing unit, a storage unit, and a communication interface (none of which are shown). The control unit 106 is implemented, for example, by a computer. The processing unit may be configured to perform various control operations by reading a program from the storage unit and executing the read program. This program may be stored in the storage unit in advance, or it may be obtained via a medium when needed. The obtained program is stored in the storage unit and read from the storage unit and executed by the processing unit. The medium may be various storage media readable by a computer, or it may be a communication line connected to a communication interface. The processing unit may be a CPU (Central Processing Unit). The storage unit 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 communicates with the plasma processing device 100 via a communication line such as a LAN (Local Area Network).

[0023] Figure 3 is a cross-sectional view taken along the line AA in Figure 1. As shown in Figure 3, there are seven microwave radiation mechanisms 143, one of which is located in the center of the top wall 111, with the other six microwave radiation mechanisms 143 arranged around it. These seven microwave radiation mechanisms 143 are arranged so that adjacent microwave radiation mechanisms 143 are equally spaced. Multiple gas introduction nozzles 123 are arranged to surround the central microwave radiation mechanism 143. Note that the number of microwave radiation mechanisms 143 is not limited to seven.

[0024] Near each of the seven microwave radiation mechanisms 143, a sensor insertion hole is provided that penetrates the top wall portion 111 in the thickness direction. An electric field sensor 151 is inserted into the sensor insertion hole. The electric field sensor 151 may also be inserted into the sensor insertion hole via a cylindrical metal reflector (not shown).

[0025] The electric field sensor 151 may be in the form of a coaxial cable, with its tip being a monopole antenna. The electric field sensor 151 is positioned near the location where microwave pulse power is radiated into the processing container 101. The tip of the electric field sensor 151 faces the back surface of the top wall portion 111 that is irradiated with microwaves, and is in contact with the plasma via the top wall portion 111, so that the microwaves radiated from the dielectric 200 into the processing container 101 can be directly monitored.

[0026] Figure 4 shows an example of a monitoring system. Figure 5 shows an example of pulse power. The monitoring system has a detection circuit 152 that detects signals from electric field sensors 151. The detection circuit 152 is connected to N electric field sensors 151 (in this embodiment, N=7, with the electric field sensors 151 corresponding to the microwave radiation mechanism 143) via a multiplexer 150. Based on a selection signal received from the control unit 106, the multiplexer 150 selects one electric field sensor 151 from the N electric field sensors 151 and inputs the sensor data detected by the selected electric field sensor 151 to the detection circuit 152.

[0027] The detection circuit 152 includes a bandpass filter 153, a variable attenuator 154, a detector 155, and an ADC 156. The bandpass filter 153 allows signals in a specific frequency band output by the microwave output unit 130 to pass through the sensor data detected by the electric field sensor 151. The variable attenuator 154 attenuates the level (amplitude) of the signals in the specific frequency band that have passed through the bandpass filter 153. The variable attenuator 154 controls the amount of attenuation to be variable. The detector 155 samples the input signal at a preset sampling rate.

[0028] When the sensor data from the electric field sensor 151 indicates a current value, the current value flowing through the electric field sensor 151 is proportional to the electric field, but the power passing through the top wall section 111 is proportional to the square of the electric field. Therefore, the square of the current value detected by the electric field sensor 151 is proportional to the power. Accordingly, the detector 155 calculates the pulse power level from the sampled sensor data and outputs the sensor data, including the pulse power level, to the ADC 156. The ADC 156 converts the input analog signal into a digital signal and transmits it to the control unit 106 as sensor data from the electric field sensor 151.

[0029] Figure 5(a) shows an example of sensor data from the electric field sensor 151 measured when the microwave output unit 130 supplies pulse power with a pulse-modulated pulse frequency of 10 kHz and a duty cycle of 40%. The microwave repeats a pulse-on time of 40 μs and a pulse-off time of 60 μs with a period of 100 μs. The duty cycle is determined by the following formula. Duty(%) = (Pulse-on time / (Pulse-on time + Pulse-off time)) × 100

[0030] Figure 5(b) shows the pulse power for one cycle output from the microwave output unit 130. Figure 5(c) shows the sensor data for one cycle detected by the electric field sensor 151 corresponding to the pulse power shown in Figure 5(b). In Figure 5(c), the sensor data is denoted as LEF. The power level of LEF detected during the pulse-off time is 0. The power level of LEF detected during the pulse-on time is a binary value consisting of the power level detected during the pulse-non-discharge time that appears at the beginning of the pulse-on time, and the power level detected during the pulse-discharge time after the pulse-non-discharge time has elapsed. The power level detected during the pulse-non-discharge time is the power level when the plasma is not ignited (when plasma is not being generated). The power level detected during the pulse-discharge time is the power level when the plasma is ignited (when plasma is being generated), so the difference in electric field strength is large and it is binary. Immediately after the start of the pulse-on time, the microwave reflection wave is large and becomes the pulse-non-discharge time. For this reason, the pulse-discharge time during which plasma is actually being generated may not coincide with the pulse-on time. In this case, there is a time lag between the microwave pulse being turned on and the plasma actually being generated. This time lag corresponds to the pulse non-discharge time.

[0031] Therefore, the plasma processing apparatus 100 monitors this time difference in real time using the electric field sensor 151. The pulse off time and pulse on time shown in Figure 5(b) are set in a recipe stored in the memory unit and controlled by the control unit 106.

[0032] Corresponding to the pulse off time in Figure 5(b), the LEF power level detected during the pulse off time in Figure 5(c) indicates the plasma off-level. Corresponding to the pulse on time in Figure 5(b), the LEF power levels detected during the pulse non-discharge time and pulse discharge time in Figure 5(c) indicate the plasma non-discharge level and plasma discharge level. At the plasma off-level and plasma non-discharge levels, plasma is either not generated or not ignited. At the plasma discharge level, plasma is ignited and generated by discharge.

[0033] The electric field sensor 151 detects sensor data at multiple levels, including a first level and a second level. Furthermore, the sensor data may also include a third level. The plasma off-level is an example of the "first level." The plasma discharge level is an example of the "second level." The plasma non-discharge level is an example of the "third level."

[0034] These three levels, in absolute value, are smallest at the first level, then the third level, and finally the second level. The first level is 0 or an approximate value of 0. The third level has a value between the first and second levels.

[0035] The first level pulse time is the time during which the first level is maintained and is the pulse-off time. The first level pulse time is calculated, for example, by multiplying the number of sensor data samples taken while the power level is continuously maintained at the first level by the first level time. However, it is not limited to this; if the sensor data includes the detection time, the first level pulse time may also be calculated from the detection time included in the sensor data while the power level is continuously maintained at the first level. The second level pulse time is the time during which the second level is maintained and is the plasma discharge time. The third level pulse time is the time during which the third level is maintained and is the plasma non-discharge time. The second level pulse time and the third level pulse time may also be calculated, for example, by the same calculation method as the first pulse time. The first level pulse time and the second level pulse time are greater than 0, and the third level pulse time is greater than or equal to 0.

[0036] [Plasma treatment method] Next, the data reading and calculation process for a plasma processing method according to one embodiment will be described with reference to Figures 6 and 7. Figure 6 is a flowchart showing an example of the data reading and calculation process in a plasma processing method according to one embodiment. Figure 7 is a diagram showing an example of data read by the plasma processing method.

[0037] In the following explanation, the variable n0 indicates the status of the power level detected by the electric field sensor 151. As shown in Figure 5(c), when n0 is 0, it indicates a pulse-off status; when n0 is 1, it indicates a pulse-non-discharge status; and when n0 is 2, it indicates a pulse-discharge status. The variable k indicates the sampling number of the sensor data. The variable i indicates the number of sensor data read consecutively while the status of n0 is the same, and the variable j indicates the number of pulses, which is the number of repetitions of pulse power, where one period of pulse power, in which multiple levels are periodically repeated, is defined as one pulse. PT(n0,j) indicates the pulse time, and PL(n0,j) indicates the power level. Of the pulse time, PT(0,j) is the pulse-off time, PT(1,j) is the pulse-non-discharge time, and PT(2,j) is the pulse-discharge time. Of the power levels, PL(0,j) is the pulse-off level, PL(1,j) is the pulse-non-discharge level, and PL(2,j) is the pulse-discharge level.

[0038] [Data loading and calculation processing] In the data reading and calculation process shown in Figure 6, the control unit 106 controls the initialization of the above variables, the reading of sensor data, and the calculation of statistical values ​​such as the average value. The control unit 106 executes the process shown in Figure 6 continuously or periodically to acquire sensor data sampled from the detection circuit 152.

[0039] (Step S200: Variable initialization) In step S200, the control unit 106 initializes the variables. Specifically, the control unit 106 sets each of the variables k, i, j, and n0 to 0.

[0040] (Step S201: Pulse power control determination) Next, in step S201, the control unit 106 determines whether the supply of pulsed microwave power from the microwave output unit 130 to the processing container 101 is being controlled. If the control unit 106 determines that the supply of pulsed power is not being controlled, it repeats the process from steps S200 to S201. If it determines that the supply of pulsed power is being controlled, it proceeds to step S202. The process of supplying pulsed power from the microwave output unit 130 to the processing container 101 to generate plasma is an example of the process in (A).

[0041] (Step S202: Reading sensor data) Next, in step S202, the control unit 106 reads the sampled sensor data, LEF(k).

[0042] (Step S203: State determination) Next, in step S203, the control unit 106 determines the status of n0. If n0 is 0, the control unit 106 proceeds to step S204 and executes the calculation process for pulse-off as shown in Figure 8. If n0 is 1, the control unit 106 proceeds to step S205 and executes the calculation process for non-pulse discharge as shown in Figure 9. If n0 is 2, the control unit 106 proceeds to step S206 and executes the calculation process for pulse discharge as shown in Figure 10.

[0043] (Step S204: Calculation when pulse is off) In step S204, the control unit 106 performs calculation processing for the pulse-off level and pulse-off time. Figure 8 is a flowchart showing an example of the calculation process during pulse-off.

[0044] In the calculation process when the pulse is off, as shown in Figure 8, in step S210, the control unit 106 determines whether the read LEF(k) is equal to 0. If the control unit 106 determines that LEF(k) is equal to 0, it proceeds to step S211, adds 1 to both variables k and i, and returns to step S201 in Figure 6.

[0045] In step S201, if the control unit 106 determines that pulse power supply control is being performed, it proceeds to step S202 and reads LEF(k). Next, in step S203, while n0 is 0, the control unit 106 executes the calculation process for when the pulse is off in step S204. In step S210, while it is determined that LEF(k) is 0, the control unit 106 repeats the processes of steps S201 to S204 in Figure 6 and S210 to S211 in Figure 8.

[0046] In step S210, if the control unit 106 determines that LEF(k) is not 0, it proceeds to step S212, sets the variable i to pulse off time PT(0, j), and stores pulse off time PT(0, j) in the memory unit. At this point, the variable i is the number of sensor data read consecutively while the value of n0 is 0. The control unit 106 may also store the value obtained by multiplying the variable i by the sampling time as the actual pulse off time PT(0, j).

[0047] Next, in step S213, the control unit 106 sets the pulse-off level PL(0, j) to the value of LEF(k-1) read immediately before LEF(k). In Figure 7, the horizontal axis represents time, and the vertical axis represents the power level of the LEF. At this point, the control unit 106 stores the pulse-off time PT(0, 0) and pulse-off level PL(0, 0) for the pulse-off state (n0=0) from the i LEFs that have been read into the memory unit.

[0048] Next, in step S214, the control unit 106 adds 1 to variable k, sets variable i to 0, adds 1 to variable n0, and returns to step S201 in Figure 6. At this point, n0 is 1, indicating a pulse non-discharge status. Therefore, the control unit 106 proceeds from S201 to S203 to step S205.

[0049] (Step S205: Calculation when pulses are not discharged) In step S205, the control unit 106 performs calculation processing for the power level and pulse non-discharge time during pulse non-discharge. Figure 9 is a flowchart showing an example of the calculation processing during pulse non-discharge.

[0050] In the calculation process during non-pulsed discharge shown in Figure 9, in step S220, the control unit 106 determines whether LEF(k) is equal to LEF(k-1) read immediately before. If the control unit 106 determines that LEF(k) is equal to LEF(k-1), it proceeds to step S221 and adds 1 to both variables k and i. However, the determination process in step S220 is not limited to this; for example, if LEF(k) is within ±5% of LEF(k-1), it may be determined that LEF(k) is equal to LEF(k-1). Note that the range in which LEF(k) is determined to be equal to LEF(k-1) is not limited to ±5% of LEF(k-1).

[0051] Next, in step S222, the control unit 106 sets the value of LEF(k) to P(i), stores P(i) in the memory unit, and then returns to step S201 in Figure 6.

[0052] In step S201, if the control unit 106 determines that pulse power supply control is being performed, it proceeds to step S202 and reads LEF(k). Next, in step S203, while n0 is 1, the control unit 106 executes the calculation process for non-pulse discharge in step S205. In step S220, while it is determined that LEF(k) is equal to LEF(k-1), the control unit 106 repeats the processes of steps S201 to S203 and S205 in Figure 6 and S220 to S222 in Figure 9.

[0053] In step S220, if the control unit 106 determines that LEF(k) is different from LEF(k-1), it proceeds to step S223, sets the variable i to pulse non-discharge time PT(1, j), and stores pulse non-discharge time PT(1, j) in the memory unit. At this point, the variable i is the number of sensor data read consecutively while the value of n0 is 1. The control unit 106 may also store the value obtained by multiplying the variable i by the sampling time as the actual pulse non-discharge time PT(1, j).

[0054] Next, in step S224, the control unit 106 calculates the average value of the power level per unit time when pulses are not discharged using the following equation (1), and stores it in the memory unit as the pulse non-discharge level PL(1, j). PL(1, j)=ΣP(i) / PT(1, j) (1)

[0055] At this point, as shown in Figure 7, the control unit 106 calculates the pulse non-discharge time PT(1, 0) and pulse non-discharge level PL(1, 0) when the pulse non-discharge state (n0=1) from the most recently read i LEFs.

[0056] Next, in step S225, the control unit 106 adds 1 to variable k, sets variable i to 0, adds 1 to variable n0, and returns to step S201 in Figure 6. At this point, n0 is 2, indicating the pulse discharge status. Therefore, the control unit 106 proceeds from S201 to S203 to step S206.

[0057] (Step S206: Calculation during pulsed discharge) In step S206, the control unit 106 performs calculation processing for the power level and pulse discharge time during pulse discharge. Figure 10 is a flowchart showing an example of the calculation process during pulse discharge.

[0058] In the calculation process during pulse discharge shown in Figure 10, in step S230, the control unit 106 determines whether LEF(k) is equal to LEF(k-1) which was read immediately before. If the control unit 106 determines that LEF(k) is equal to LEF(k-1), it proceeds to step S231 and adds 1 to both variables k and i. However, the determination process in step S230 is not limited to this; for example, if LEF(k) is within ±5% of LEF(k-1), it may be determined that LEF(k) is equal to LEF(k-1). Note that the range in which LEF(k) is determined to be equal to LEF(k-1) is not limited to ±5% of LEF(k-1).

[0059] Next, in step S232, the control unit 106 sets the value of LEF(k) to P(i), stores P(i) in the memory unit, and returns to step S201 in Figure 6.

[0060] In step S201, if the control unit 106 determines that pulse power supply control is being performed, it proceeds to step S202 and reads LEF(k). Next, in step S203, the control unit 106 executes the calculation process for pulse discharge in step S206 while n0 is 2. In step S230, while the control unit 106 determines that LEF(k) is equal to LEF(k-1), it repeats the processes of steps S201 to S203 and S206 in Figure 6 and S230 to S232 in Figure 10.

[0061] In step S230, if the control unit 106 determines that LEF(k) is different from LEF(k-1), it proceeds to step S233, sets the variable i to pulse discharge time PT(2, j), and stores pulse discharge time PT(2, j) in the memory unit. At this point, the variable i is the number of sensor data read consecutively while the value of n0 is 2. The control unit 106 may also store the value obtained by multiplying the variable i by the sampling time as the actual pulse discharge time PT(2, j).

[0062] Next, in step S234, the control unit 106 calculates the average value of the power level during pulse discharge per unit time using the following equation (2) and stores it in the memory unit as pulse discharge level PL(2, j). PL(2, j)=ΣP(i) / PT(2, j) (2)

[0063] At this point, as shown in Figure 7, the control unit 106 calculates the pulse discharge time PT(2, 0) and pulse discharge level PL(2, 0) for the pulse discharge state (n0=2) from the most recently read i LEFs.

[0064] Next, in step S235, the control unit 106 adds 1 to variable k, sets variables i and n0 to 0, adds 1 to variable j, and returns to step S201 in Figure 6. At this point, variable n0 is 0, indicating a pulse-off status. Therefore, the control unit 106 proceeds from S201 to S203 to step S204.

[0065] (Steps S204-S206: Repeated processing) The control unit 106 repeatedly executes the calculation process in step S204, the calculation process in step S205, and the calculation process in S206 in order, based on the value of the variable n0. By repeating the processes in steps S204 to S206, the control unit 106 stores the pulse times PT(0,1), PT(1,1), PT(2,1) and power levels PL(0,1), PL(1,1), PL(2,1) for the second cycle of pulse power shown in Figure 7 in the memory unit. The calculated pulse times PT and power levels PL are stored in the memory unit. The control unit 106 continues this repeated process for the third cycle and beyond, as shown in Figure 7. As a result, pulse times PT(0,2), PT(1,2), PT(2,2), PT(0,3)... and power levels PL(0,2), PL(1,2), PL(2,2), PL(0,3)... are accumulated in the memory unit.

[0066] [Decision Processing] Next, the determination process for a plasma processing method according to one embodiment will be described with reference to Figure 11. Figure 11 is a flowchart showing an example of the determination process in a plasma processing method according to one embodiment.

[0067] In the determination process shown in Figure 11, the control unit 106 determines whether the plasma is normal or abnormal by reading and using the data stored in the memory unit as a result of the calculation process shown in Figure 6.

[0068] (Step S300: Data reading) In step S300, the control unit 106 reads the data stored in the memory unit as a result of executing the process shown in Figure 6. The control unit 106 may read the pulse time PT and power level PL calculated based on the sensor data of pulse power with a preset number of pulses, with one period of pulse power, in which multiple levels are periodically repeated, being considered as one pulse. For example, when the number of pulses is set to "10", the control unit 106 reads the pulse times PT(0, j-9)~PT(0, j), PT(1, j-9)~PT(1, j), and PT(2, j-9)~PT(2, j). The control unit 106 also reads the power levels PL(0, j-9)~PL(0, j), PL(1, j-9)~PL(1, j), and PL(2, j-9)~PL(2, j).

[0069] (Step S301: Calculation of the average value) Next, in step S301, the control unit 106 calculates the average value of the pulse time PT and the average value of the power level PL. The control unit 106 sets the average value of the pulse off time PTa(0) to PT(0, j) obtained by dividing the sum of the pulse times PT(0, j-9) to PT(0, j) by the number of pulses. The control unit 106 also sets the average value of the pulse off level PLa(0) obtained by dividing the sum of the power levels PL(0, j-9) to PL(0, j) by the number of pulses. The control unit 106 also sets the average value of the pulse non-discharge time PTa(1) obtained by dividing the sum of the pulse times PT(1, j-9) to PT(1, j) by the number of pulses. The control unit 106 also sets the average value of the pulse non-discharge level PLa(1) obtained by dividing the sum of the power levels PL(1, j-9) to PL(1, j) by the number of pulses. Furthermore, the control unit 106 sets the average value of pulse discharge time PTa(2) to the value obtained by dividing the sum of pulse times PT(2, j-9) to PT(2, j) by the number of pulses. Also, the control unit 106 sets the average value of pulse discharge level PLa(2) to the value obtained by dividing the sum of power levels PL(2, j-9) to PL(2, j) by the number of pulses. Step S301 is an example of process (B).

[0070] (Step S302: Calculation of standard deviation) Next, in step S302, the control unit 106 calculates the standard deviation of the pulse time PT and the standard deviation of the power level PL. The control unit 106 calculates the standard deviation of the pulse off time PTv(0) based on the difference between each of PT(0, j-9) to PT(0, j) and the average value PTa(0). The control unit 106 also calculates the standard deviation of the pulse off level PLv(0) based on the difference between each of PL(0, j-9) to PL(0, j) and the average value PLa(0). The control unit 106 also calculates the standard deviation of the pulse non-discharge time PTv(1) based on the difference between each of PT(1, j-9) to PT(1, j) and the average value PTa(1). The control unit 106 also calculates the standard deviation of the pulse non-discharge level PLv(1) based on the difference between each of PL(1, j-9) to PL(1, j) and the average value PLa(1). Furthermore, the control unit 106 calculates the standard deviation of pulse discharge time PTv(2) based on the difference between each of PT(2, j-9) to PT(2, j) and the average value PTa(2). Also, the control unit 106 calculates the standard deviation of pulse discharge level PLv(2) based on the difference between each of PL(2, j-9) to PL(2, j) and the average value PLa(2). Step S302 is an example of process (B).

[0071] (Step S303: Output of monitoring results) Next, in step S303, the control unit 106 outputs the monitoring results from the electric field sensor 151. The control unit 106 may output at least one of the following values ​​as monitoring results: for example, the average value of the pulse discharge level PLa(2), the standard deviation of the pulse discharge time PTv(2), and the standard deviation of the pulse discharge level PLv(2).

[0072] The control unit 106 may output, for example, the average value PLa(2), the standard deviation PTv(2), and the standard deviation PLv(2), as well as the time of one cycle of pulse power and the duty cycle. In this case, the control unit 106 sets the sum of PTa(0), PTa(1), and PTa(2) as the time of one cycle. The control unit 106 also sets the duty cycle to the value obtained by dividing PTa(2) by the sum of PTa(0), PTa(1), and PTa(2).

[0073] (Step S304: Anomaly detection) Next, in step S304, the control unit 106 determines whether the plasma is normal or abnormal using at least one of the average value PLa(2) of the pulse discharge level, the standard deviation PTv(2) of the pulse discharge time, and the standard deviation PLv(2) of the pulse discharge level, and a preset threshold for each of these values. Step S304 is an example of the process of (C).

[0074] The control unit 106 may determine that the plasma is abnormal if it determines that at least one of the values ​​of the mean PLa(2), the standard deviation PTv(2), and the standard deviation PLv(2) deviates from the range indicated by the threshold for each of these values. For example, the control unit 106 may determine that the plasma is abnormal if it determines that at least one of the values ​​of the mean PLa(2), the standard deviation PTv(2), and the standard deviation PLv(2) deviates from the range of ±5% of the threshold for each value.

[0075] (Step S305: Warning Processing) If the plasma is determined to be abnormal in step S304, the process proceeds to step S305, and the control unit 106 issues a warning. Step S305 is an example of process (D). The control unit 106 may issue the warning by monitor display or by sound, or by at least one of the other. Step S305 may be omitted.

[0076] If the control unit 106 determines in step S304 that the plasma is abnormal, it may stop supplying pulsed microwave power. Stopping the supply of pulsed power is an example of step (E). For example, if the control unit 106 determines that at least one of the values ​​of the mean value PLa(2), the standard deviation PTv(2), and the standard deviation PLv(2) deviates from the range of ±6% of the threshold, it may stop supplying pulsed microwave power. If the control unit 106 determines that at least one of the values ​​of the mean value PLa(2), the standard deviation PTv(2), and the standard deviation PLv(2) deviates from the range of ±5% but is within the range of ±6% of the threshold, it may issue a warning but control the microwave not to stop.

[0077] When an abnormality in the plasma is detected in step S304, the control unit 106 may provide feedback control to at least one of the power level PL or pulse time PT based on the data read from the storage unit. This can improve the accuracy of the plasma processing of the substrate W.

[0078] For example, the control unit 106 may correct the pulse discharge level based on the data read from the storage unit and supply pulse power at the corrected pulse discharge level.

[0079] When an abnormality in the plasma is detected in step S304, the control unit 106 may correct the pulse discharge time based on the pulse non-discharge time, using the data read from the storage unit, and supply pulse power at the pulse discharge level to the corrected pulse discharge time.

[0080] For example, when processing an arbitrary number of pulses as a single unit of processing data, the control unit 106 may control the total pulse discharge time for the arbitrary number of pulses to match the planned total pulse on time for the arbitrary number of pulses. If these total times do not match, the control unit 106 may add or subtract any of the pulse discharge times for the arbitrary number of pulses based on the pulse non-discharge time so that the total pulse discharge time for the arbitrary number of pulses matches the total pulse on time for the arbitrary number of pulses. This allows the control unit 106 to supply pulse power at the planned plasma discharge level for the planned total pulse on time for the planned arbitrary number of pulses.

[0081] Furthermore, for example, the control unit 106 may control the pulse discharge time of the second pulse to match the planned pulse on time based on the pulse non-discharge time or pulse discharge time of the first pulse. If it determines that the pulse discharge time of the second pulse does not match the planned pulse on time, the control unit 106 may use feedback control to adjust the pulse discharge time of the second pulse based on the pulse non-discharge time of the first pulse so that these values ​​match. The control unit 106 may continue to control the pulse discharge time of the third pulse, fourth pulse, and so on, based on the pulse non-discharge time of the previous pulse.

[0082] Furthermore, for example, the control unit 106 may control the pulse discharge time of the first pulse to match the planned pulse on time based on the pulse non-discharge time or pulse discharge time. If it determines that the pulse discharge time of the first pulse does not match the planned pulse on time, the control unit 106 may use feedback control to adjust the pulse discharge time of the first pulse based on the pulse non-discharge time of the first pulse so that these values ​​match. The control unit 106 may continue this feedback control for the second pulse, the third pulse, and so on.

[0083] [Effects of the First Embodiment] As described above, the plasma processing method includes steps (A) to (C). Step (A) involves supplying pulsed power from an energy source into the processing vessel 101 to generate plasma. Step (B) involves calculating at least one of the following values ​​based on sensor data of multiple levels of pulsed power, including a pulsed off-level indicating the plasma off-level and a pulsed discharge level indicating the plasma discharge level, and multiple pulse times maintained at multiple levels: the average value of the pulsed discharge level, the standard deviation of the pulse time of the pulsed discharge level, and the standard deviation of the pulsed discharge level. Step (C) involves determining whether the plasma is normal or abnormal using at least one of these values ​​and a preset threshold for these values.

[0084] This improves the accuracy of monitoring the plasma generated by the supply of pulsed power. As a result, it becomes possible to accurately determine whether the plasma is normal or abnormal.

[0085] The multiple levels include a third level between the first and second levels, and the control unit 106 may perform steps (B) and (C) when the pulse time of the third level is greater than 0.

[0086] [Second Embodiment] Next, a plasma processing apparatus according to a second embodiment of the present disclosure will be described with reference to Figure 12. Figure 12 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to the second embodiment. The plasma processing apparatus 100A has a VHF power supply 11 and is an example of an apparatus that generates plasma using VHF pulse power output from the VHF power supply 11 and performs plasma processing on a substrate.

[0087] The plasma processing apparatus 100A comprises a processing vessel 1, a lid 2, and a mounting table 3. The processing vessel 1 is cylindrical with a bottom and an open top. The lid 2 is configured to seal the upper opening of the processing vessel 1. A processing chamber U is provided inside the processing vessel 1. The mounting table 3 is located inside the processing chamber U and on which the substrate W is placed. The substrate W is subjected to plasma processing.

[0088] The plasma processing apparatus 100A further includes an upper electrode 5 and a dielectric ring 7. The upper electrode 5 faces the mounting base 3. The upper electrode 5 is disc-shaped and has a metal shower plate structure.

[0089] The space enclosed by the upper electrode 5, the lid 2, and the processing container 1 constitutes a waveguide 9. The waveguide 9 is located along the upper electrode 5. High-frequency (VHF) power in the VHF band propagates through the waveguide 9. However, high-frequency power in the UHF band may also propagate through the waveguide 9.

[0090] Within the upper electrode 5, a diffusion chamber 5a and a plurality of gas holes 5b are formed. The plurality of gas holes 5b are through holes that penetrate the lower surface of the upper electrode 5 in order to connect the diffusion chamber 5a and the processing chamber U. The dielectric ring 7 is an annular member having an inner diameter slightly larger than the diameter of the upper electrode 5 and an outer diameter slightly smaller than the diameter of the inner surface of the processing container 1, and separates the vacuum space processing chamber U from the atmospheric space waveguide 9. The dielectric ring 7 is located between the upper electrode 5 and the processing container 1, at the end of the waveguide 9.

[0091] The cover 2 is disc-shaped with an opening in the center. The matching unit 10 is positioned on top of the plasma processing apparatus 100A to close the central opening of the cover 2. The matching unit 10 is connected to the upper electrode via a transmission line 8. The transmission line 8 may consist of a waveguide or coaxial cable capable of transmitting high-frequency power in the VHF or UHF band.

[0092] The VHF power supply 11 is electrically connected to the upper electrode 5 via the matching circuit 10 and the transmission line 8. The VHF power supply 11 outputs VHF and supplies VHF pulsed power into the processing container 1. The VHF power supply 11 is an example of an energy source that supplies pulsed power into the processing container 101. The matching circuit 10 has a matching circuit to match the impedance on the load side (upper electrode 5 side) of the VHF power supply 11 to the output impedance of the VHF power supply 11.

[0093] VHF waves propagate through the waveguide 9 via the matching unit 10 and transmission line 8, and are radiated into the processing chamber U via the dielectric ring 7. This supplies the processing chamber U with pulsed VHF power to generate plasma. The pulsed VHF power exhibits a periodic repetition of pulse-off and pulse-on times, as shown in Figure 5(b).

[0094] The plasma processing apparatus 100A further includes a gas supply source 16. The gas supply source 16 is connected to a gas supply pipe 17. The gas supply pipe 17 penetrates the cover 2, the waveguide 9, and the upper electrode 5, and communicates with the diffusion chamber 5a. The processing gas is supplied from the gas supply source 16, diffused in the diffusion chamber 5a via the gas supply pipe 17, and then supplied into the processing chamber U through a plurality of gas holes 5b.

[0095] The mounting platform 3 is electrically connected to the high-frequency power supply 12. The high-frequency power supply 12 applies a high-frequency bias voltage in the RF (Radio Frequency) band to the mounting platform 3, primarily for attracting ions from the plasma. The high-frequency power supply 12 can output continuous wave power or pulsed power. However, the high-frequency power supply 12 is not required.

[0096] A gas exhaust port 18 is formed at the bottom of the processing container 1. The gas exhaust port 18 is connected to an exhaust device 19. The exhaust device 19 exhausts the gas inside the processing chamber U to the outside through the gas exhaust port 18. The processing container 1 has an inlet / outlet (not shown) for loading and unloading substrates W to and from a transport chamber (not shown). The inlet / outlet is opened and closed by a gate valve (not shown).

[0097] The control unit 106' processes computer-executable instructions to be performed by the plasma processing apparatus 100A. The control unit 106' may be configured to control each element of the plasma processing apparatus 100A to perform various processes.

[0098] The plasma processing apparatus 100A has an electric field sensor 151'. The electric field sensor 151' is inserted from the outer surface of the processing vessel 1 through a through hole that penetrates the side wall of the processing vessel 1, and its tip contacts the dielectric ring 7. The electric field sensor 151' is positioned close to the plasma, corresponding to the position of the dielectric ring 7 from which VHF pulsed power is radiated. The electric field sensor 151' may have the same structure as the electric field sensor 151 according to the first embodiment.

[0099] When a processing gas is introduced into the processing container 1, and the pressure inside the processing chamber U is reduced to a level where plasma can be generated by the exhaust device 19, a VHF pulse power is introduced into the processing chamber U, and plasma is generated by the VHF pulse power. The electric field sensor 151' monitors this plasma.

[0100] The detection circuit 152' has the same configuration as the detection circuit 152 shown in Figure 4. In the second embodiment, since there is only one electric field sensor 151', the multiplexer 150 shown in Figure 4 is not required, and the electric field sensor 151' is directly connected to the detection circuit 152'. However, in the second embodiment, multiple electric field sensors 151' may be arranged in the circumferential direction or in the thickness direction of the dielectric ring 7.

[0101] [Effects of the second embodiment] In the plasma processing apparatus 100A described above, the control unit 106' acquires sensor data from an electric field sensor 151' mounted in contact with a dielectric (dielectric ring 7) inside a vacuum vessel (processing vessel 1) that monitors the state of the plasma, and controls the plasma processing method described in Figures 6 and 11 in the first embodiment. This improves the accuracy of monitoring the plasma generated by supplying VHF pulsed power. As a result, it is possible to accurately determine whether the plasma is normal or abnormal.

[0102] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0103] Furthermore, the following additional information is disclosed regarding the above embodiments. <Note> (1) (A) A process of supplying pulsed power from an energy source into the processing vessel to generate plasma, (B) A step of calculating at least one of the following values ​​based on sensor data of the pulse power at multiple levels, including a first level indicating the off-level of the plasma and a second level indicating the discharge level of the plasma, and a plurality of pulse times maintained at each of the multiple levels: the mean value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level. (C) A step of determining whether the plasma is normal or abnormal using at least one of the above values ​​and a threshold value set in advance for the above value, A plasma treatment method, including the following. (2) The plurality of levels include a third level between the first level and the second level, The plasma processing method according to (1), wherein (B) and (C) are performed when the pulse time of the third level is greater than 0. (3) The plasma processing method according to (1) or (2), wherein, in (B) above, the sensor data of the pulse power is measured using an electric field sensor provided in the processing vessel. (4) The plasma processing method according to (3), wherein the electric field sensor is arranged in the processing container corresponding to the position where the pulsed power is radiated. (5) (D) A plasma processing method according to any one of (1) to (4) which issues a warning when an abnormality in the plasma is detected. (6) The plasma processing method according to (2), wherein when an abnormality in the plasma is detected, the second level is corrected and pulse power of the corrected second level is supplied. (7) The plasma processing method according to (2), wherein when an abnormality in the plasma is detected, the second level pulse time is corrected by the third level pulse time, and the second level pulse power is supplied to the corrected second level pulse time. (8) (E) The plasma processing method according to any one of (1) to (5), wherein when an abnormality in the plasma is detected, the supply of the pulsed power is stopped. (9) The plasma processing method according to any one of (1) to (8) above, wherein, in (B) above, one period of the pulse power in which the plurality of levels are periodically repeated is defined as one pulse, and based on sensor data of the pulse power for a preset number of pulses and a plurality of pulse times maintained for each of the plurality of levels, at least one of the values ​​of the mean of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level is calculated. (10) Processing container and An energy source that supplies pulsed power into the processing container, It has a control unit and The control unit, (A) A process of supplying pulsed power from an energy source into the processing vessel to generate plasma, (B) A step of calculating at least one of the following values ​​based on sensor data of the pulse power at multiple levels, including a first level indicating the off-level of the plasma and a second level indicating the discharge level of the plasma, and a plurality of pulse times maintained at each of the multiple levels: the mean value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level. (C) A plasma processing apparatus that controls a step of determining whether the plasma is normal or abnormal using at least one of the above values ​​and a threshold value set in advance for the above value. [Explanation of Symbols]

[0104] 11:VHF power supply 100, 100A: Plasma processing equipment 1. 101: Processing container 105: Microwave plasma source 106, 106': Control Unit 131: Microwave power supply 151, 151': Field sensor 152, 152': Detection circuit W: Circuit board

Claims

1. (A) A process of supplying pulsed power from an energy source into the processing container to generate plasma, (B) A step of calculating at least one of the following values ​​based on sensor data of the pulse power at a plurality of levels, including a first level indicating the off-level of the plasma and a second level indicating the discharge level of the plasma, and a plurality of pulse times maintained at each of the plurality of levels: the average value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level. (C) A step of determining whether the plasma is normal or abnormal using at least one of the above values ​​and a threshold value set in advance for the above value, A plasma treatment method, including the following.

2. The plurality of levels include a third level between the first level and the second level, The plasma processing method according to claim 1, wherein (B) and (C) are performed when the pulse time of the third level is greater than 0.

3. The plasma processing method according to claim 1, wherein, in (B) above, the sensor data of the pulse power is measured using an electric field sensor provided in the processing vessel.

4. The plasma processing method according to claim 3, wherein the electric field sensor is arranged in the processing container corresponding to the position where the pulsed power is radiated.

5. (D) The plasma processing method according to claim 1, wherein a warning is issued when an abnormality in the plasma is detected.

6. The plasma processing method according to claim 2, wherein when an abnormality in the plasma is detected, the second level is corrected and pulse power of the corrected second level is supplied.

7. The plasma processing method according to claim 2, wherein when an abnormality in the plasma is detected, the second level pulse time is corrected by the third level pulse time, and the second level pulse power is supplied to the corrected second level pulse time.

8. (E) The plasma processing method according to any one of claims 1 to 5, wherein when an abnormality in the plasma is detected, the supply of pulsed power is stopped.

9. The plasma processing method according to any one of claims 1 to 5, wherein in (B) above, one period of the pulse power in which the plurality of levels are periodically repeated is defined as one pulse, and based on sensor data of the pulse power for a preset number of pulses and a plurality of pulse times maintained for each of the plurality of levels, at least one of the values ​​of the average value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level is calculated.

10. Processing container and An energy source that supplies pulsed power into the processing container, It has a control unit and The control unit, (A) A process of supplying pulsed power from an energy source into the processing container to generate plasma, (B) A step of calculating at least one of the following values ​​based on sensor data of the pulse power at a plurality of levels, including a first level indicating the off-level of the plasma and a second level indicating the discharge level of the plasma, and a plurality of pulse times maintained at each of the plurality of levels: the average value of the second level, the standard deviation of the pulse time of the second level, and the standard deviation of the second level. (C) A plasma processing apparatus that controls a step of determining whether the plasma is normal or abnormal using at least one of the above values ​​and a threshold value set in advance for the above values.

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