A radio frequency power control method and plasma processing device

Abstract

The present invention provides a radio frequency power control method, wherein a plasma reaction device comprises a plurality of inductively coupled coils, and the radio frequency power of a radio frequency power source is distributed to the first to Mth coils of the inductively coupled coils through a matching network, so that plasma is generated in a vacuum reaction chamber of the plasma reaction device, and the control method comprises: synchronizing the output clock signal of the radio frequency power source; detecting the i-th current signal of the i-th coil, and converting the i-th current signal into a corresponding i-th pulse direct current signal; calculating the corresponding i-th current feedback value after processing the i-th pulse direct current signal according to the output clock signal; and adjusting the radio frequency power distributed to the i-th coil according to the i-th current feedback value; wherein i∈[1,M]. The present invention also provides a plasma processing device. The present invention can accurately control the radio frequency power applied to all coils, and is not limited by the output mode of the radio frequency power source.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a radio frequency power control method and a plasma processing device. Background Art

[0002] The inductively coupled (ICP) plasma reaction device includes multiple inductively coupled coils. Multiple coils can be arranged in a single inductively coupled coil. By controlling the power allocated to the multiple coils by the radio frequency power source, the plasma energy coupled to the reaction chamber is controlled, thereby controlling the etching speed of the wafer W. However, the coils in the inductively coupled coils will produce an inductive effect under the action of the current, thereby generating heat, which inevitably causes the radio frequency power applied to the coil to be lost, and this loss is difficult to measure. Therefore, it is difficult to accurately control the etching speed of the wafer W by controlling the power applied to each coil. Furthermore, since the ICP plasma reaction device includes a large number of coils, the power of each coil must be accurately controlled at the same time, and the control complexity is large.

[0003] In addition, in some processes, the RF power output by the RF power source is a pulse output, and it is difficult to detect the working status of the RF circuits in which the multiple coils in the inductively coupled coil are located under each pulse using traditional methods.

[0004] Therefore, how to accurately control the power allocated to each coil of each inductively coupled coil to ensure the stable operation of the ICP etching equipment is a problem that needs to be solved urgently. Summary of the invention

[0005] The object of the present invention is to provide a radio frequency power control method and a plasma processing device, which can accurately control the power allocated to multiple coils of the inductively coupled coil, thereby accurately compensating for the energy loss in the radio frequency circuit, ensuring the processing rate of the wafer, and ensuring the stable operation of the plasma processing device.

[0006] In order to achieve the above object, the present invention provides a radio frequency power control method, wherein a plasma reaction device comprises a plasma reaction chamber, a plurality of inductively coupled coils are arranged above the reaction chamber, and radio frequency power of a radio frequency power source is distributed to the first to Mth coils of the inductively coupled coils through a matching network, so that plasma is generated in the reaction chamber, and the radio frequency power control method further comprises:

[0007] An output clock signal of a synchronous radio frequency power source;

[0008] Detecting an i-th current signal of an i-th coil;

[0009] Converting the i-th current signal into a corresponding i-th pulse DC signal;

[0010] Processing the i-th pulse DC signal according to the output clock signal and calculating the corresponding i-th current feedback value;

[0011] The RF power allocated to the i-th coil is adjusted according to the i-th current feedback value; wherein i∈[1,M].

[0012] Preferably, the output clock signal of the synchronous RF power source includes: the output clock signal of the RF power source is synchronized according to the output power of the RF power source: when the RF power source outputs RF power, the output clock signal is at a high level; when the RF power source does not output RF power, the output clock signal is at a low level.

[0013] Preferably, the output clock signal of the synchronous RF power source includes: the output clock signal of the RF power source is synchronized according to the output power of the RF power source: when the RF power source outputs a first power, the output clock signal is at a high level; when the RF power source outputs a second power, the output clock signal is at a low level; the first power is greater than the second power.

[0014] Preferably, the corresponding i-th pulse DC signal is obtained by rectifying and filtering the i-th current signal, i∈[1,M].

[0015] Preferably, when the RF power source outputs RF power, the i-th pulse DC signal is sampled; the number of sampling times within a single clock cycle of the output clock signal is N times, and the sampling signals S i,1 ~S i,N ; Discard the sampled signal S i,1 ~S i,p and S i,q ~S i,N , realizing denoising of the sampling signal of the i-th pulse DC signal; wherein 1<p<q<N, p, q are respectively the first and second calibration values ​​corresponding to the reaction chamber process; the sampling signal of the i-th pulse DC signal that is retained is stored in real time according to the sampling time sequence; i∈[1,M].

[0016] Preferably, the processing of the i-th pulse DC signal comprises: when the RF power source outputs the first power, sampling the i-th pulse DC signal; the number of sampling times in a single clock cycle of the output clock signal is N times, and the sampling signal S is obtained in sequence i,1 ~S i,N ; Discard the sampled signal S i,1 ~S i,p and S i,q ~S i,N, realizing denoising of the sampling signal of the i-th pulse DC signal; wherein 1<p<q<N, p, q are respectively the first and second calibration values ​​corresponding to the reaction chamber process; the sampling signal of the i-th pulse DC signal that is retained is stored in real time according to the sampling time sequence; i∈[1,M].

[0017] Preferably, the processing of the i-th pulse DC signal comprises: when the RF power source outputs the second power, sampling the i-th pulse DC signal; the number of sampling times in a single clock cycle of the output clock signal is N times, and the sampling signal S is obtained in sequence i,1 ~S i,N ; Discard the sampled signal S i,1 ~S i,p and S i,q ~S i,N , realize denoising of the sampling signal of the i-th pulse DC signal; wherein 1<p<q<N, p and q are the first and second calibration values ​​corresponding to the reaction chamber process respectively; the sampling signal of the i-th pulse DC signal is stored in real time according to the sampling time sequence; i∈[1,M]. .

[0018] Preferably, the calculation of the corresponding i-th current feedback value includes:

[0019] The average value of the stored sampling signal of the ith pulse DC signal is obtained to obtain the ith current feedback value fk at the current moment. i,t :

[0020]

[0021] Among them, m is a preset natural number, t is the current time, s iK is the sampling signal of the most recently stored ith pulse DC signal; s ik is the sampling signal of the i-th pulse DC signal stored for the kth time, i∈[1,M].

[0022] The RF power control method also includes setting the first to Mth variable capacitors in the inductive coupling coil; wherein the i-th variable capacitor is set at the front end of the i-th coil and is connected in series with the i-th coil to form an i-th branch; the first branch to the M-th branch are all connected in parallel; by adjusting the RF power output by the RF power source and adjusting any one or more of the first to Mth variable capacitors, the i-th current feedback value reaches the set i-th current standard feedback value, thereby adjusting the RF power allocated to the i-th coil; i∈[1,M].

[0023] The RF power control method further comprises: when the i-th current feedback value reaches the set i-th current standard feedback value, the capacitance value of the i-th variable capacitor is C i ;make If there are at least two pulse DC signals in the first to Mth pulse DC signals, and the phase difference between the two pulse DC signals exceeds the set phase difference threshold, the capacitance values ​​of the first to Mth variable capacitors are simultaneously reduced while maintaining α i,j unchanged, achieving that the phase difference is lower than the phase difference threshold; i,j∈[1,M].

[0024] The RF power control method further includes establishing a signal calibration table, the signal calibration table includes a plurality of triplets, the triplets include: a reaction chamber process code, and the first and second calibration values ​​corresponding to the reaction chamber process; and obtaining the first and second calibration values ​​by searching the signal calibration table.

[0025] The present invention also provides a plasma processing device, which is used in the radio frequency power control method of the present invention, and includes a plasma reaction chamber and a plurality of inductively coupled coils. A base for placing a wafer is provided at the bottom of the plasma reaction chamber, and the base serves as a lower electrode of the plasma reaction chamber. The radio frequency power of the radio frequency power source is distributed to the first to Mth coils of the inductively coupled coils through a matching network, so that plasma is generated in the plasma reaction chamber. The plasma processing device also includes:

[0026] A plurality of current sensors, used for detecting first to M-th coil current signals corresponding to the first to M-th coils, the first to M-th coils respectively corresponding to different current sensors;

[0027] A rectification-filtering-phase detection module, used to obtain the output clock signal of the RF power source, convert the i-th coil current signal into the corresponding i-th pulse DC signal, and obtain the phase difference between the first to M-th pulse DC signals; i∈[1,M];

[0028] The signal processing unit processes the i-th pulse DC signal according to the output clock signal, calculates the corresponding i-th current feedback value, and adjusts the RF power allocated to the first to M-th coils according to the i-th current feedback value and the phase difference.

[0029] Preferably, the inductive coupling coil is further provided with first to Mth variable capacitors; the i-th variable capacitor is arranged at the front end of the i-th coil and is connected in series with the i-th coil to form an i-th branch; the first branch to the M-th branch are connected in parallel; the RF power and any one or more of the first to M-th variable capacitors are adjusted through the signal processing unit so that the i-th current feedback value reaches the set i-th current standard feedback value, thereby adjusting the RF power allocated to the first to M-th coils; i∈[1,M].

[0030] Preferably, the processing includes: sampling and denoising.

[0031] Preferably, the signal processing unit further includes a storage module for storing a signal calibration table; the signal calibration table includes a plurality of triplets, the triplets including: a reaction chamber process code, a first calibration value corresponding to the reaction chamber process code, and a second calibration value; the first calibration value and the second calibration value are used to shield a plurality of sampling signals of the i-th pulse DC signal, so as to realize denoising of the sampling signals of the i-th pulse DC signal;

[0032] The storage module is also used to store the sampling signal of the ith pulse DC signal after denoising, the ith current feedback value, the ith current standard feedback value, and the phase difference threshold.

[0033] Preferably, the plasma processing device further comprises a graphical user interface communicatively connected to the signal processing unit, for inputting the reaction chamber process code into the signal processing unit and displaying the first to Mth current feedback values ​​calculated by the signal processing unit.

[0034] Preferably, the signal processing unit is a logic programmable circuit.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) The present invention can accurately control the power allocated to each coil of the inductively coupled coil, thereby accurately compensating for the energy loss in the radio frequency circuit, ensuring the processing rate of the wafer, and ensuring the stable operation of the plasma processing device;

[0037] 2) The present invention can be applied to RF power sources with various output modes, and is not limited by the output mode and output waveform of the RF power source;

[0038] 3) The present invention collects the current signal of each coil and uses it to feed back the RF power allocated to the coil through rectification and filtering; and controls the collection of the current signal according to the output clock signal of the RF power source, and does not collect the current signal when the output clock signal of the RF power source is at a low level, thereby ensuring the validity of the feedback data and being able to continuously provide a stable feedback signal for the RF power source;

[0039] 4) The present invention also shields the rising edge and falling edge of the pulse DC signal, so the control of the power allocated to the coil is more accurate;

[0040] 5) The present invention uses a logic programmable circuit as a signal processing unit to calculate the current feedback value of each coil, which has the advantages of fast calculation speed, strong processing capability, resistance to external interference, and the built-in feedback value calculation algorithm is easy to expand according to different processes in the reaction chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are an embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0042] Figure 1 It is a schematic diagram of the structure of a plasma processing device in the prior art;

[0043] Figure 2 A schematic diagram of the structure of a plasma processing device according to an embodiment of the present invention;

[0044] Figure 3 A flow chart of a radio frequency power control method according to an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of an output voltage waveform of a radio frequency power source, an output clock signal of the radio frequency power source, a first pulsed DC signal, and a first current feedback value output by a signal processing unit in Embodiment 1;

[0046] Figure 5 This is a schematic diagram of an output clock signal of the radio frequency power source when the radio frequency power source alternately outputs the first power and the second power in Embodiment 1;

[0047] Figure 6 This is a schematic diagram of the connection relationship between the current sensor and the variable capacitor in the first embodiment. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Inductively coupled plasma (ICP) reactor Figure 1 As shown, it includes a vacuum reaction chamber 100, which includes a roughly cylindrical reaction chamber side wall 101 made of metal material, and an opening 102 is provided on the reaction chamber side wall for accommodating the entry and exit of wafers. An insulating window 117 is provided above the reaction chamber side wall 101, and an inductive coupling coil 115 is provided above the insulating window 117. A radio frequency power source 118 applies radio frequency voltage to multiple coils of the inductive coupling coil 115 through a radio frequency matching network 116.

[0050] A liner 120 is arranged inside the reaction chamber to protect the inner wall of the reaction chamber from being corroded by plasma. A gas injection port 103 is arranged at one end of the side wall of the reaction chamber near the insulating window to inject the reaction gas into the vacuum reaction chamber 100. The RF power of the RF power source 118 drives the inductive coupling coil 115 to generate a strong high-frequency alternating magnetic field, so that the low-pressure reaction gas in the reaction chamber is ionized to generate plasma. A base 110 is arranged at the downstream position of the vacuum reaction chamber 100, and an electrostatic suction cup 112 is arranged on the base 110. The electrostatic suction cup 112 is used to generate electrostatic suction to achieve support and fixation of the wafer W to be processed during the process. The plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules and free radicals. The above-mentioned active particles can undergo various physical and chemical reactions with the surface of the wafer W to be processed, so that the morphology of the surface of the wafer W changes, that is, the etching process is completed. A bias RF power source 150 applies a bias RF voltage to the base through a RF matching network 152 to control the bombardment direction of charged particles in the plasma. An exhaust pump 140 is also provided below the vacuum reaction chamber 100 to exhaust the reaction byproducts from the vacuum reaction chamber and maintain the vacuum environment of the reaction chamber.

[0051] Usually, the inductive coupling coil 115 may include multiple coils (recorded as the first to Mth coils). By controlling the RF power applied to the coil, the plasma concentration in the reaction chamber is controlled, and then the processing speed of the wafer is controlled. In some processes, the RF power required to be allocated to each coil is different. In particular, for the inductive coupling coil 115 including three or more coils, the power set for each coil is further increased. The complexity of control. On the other hand, the coil will generate heat due to the inductance effect under the action of the current, which will inevitably cause the RF power applied to the coil to be lost, and the loss is difficult to measure. Furthermore, when the RF power source in the process is a pulsed output, it is difficult to detect the working state of each coil in its respective RF circuit in each pulse cycle. If the RF power is configured for each coil only according to the preset standard, it is usually impossible to make the plasma concentration in the reaction chamber reach the ideal state, and thus the processing speed of the wafer in the reaction chamber cannot meet the actual needs.

[0052] The present invention provides a radio frequency power control method, which performs feedback control on the radio frequency power distributed in the coil by collecting the current of the coil, and is not affected by the output mode of the radio frequency power source, thus well ensuring the stability of the process in the reaction chamber.

[0053] like Figure 3 As shown, the radio frequency power control method comprises the steps of:

[0054] S101, output clock signal of synchronous radio frequency power source;

[0055] S102, detecting the i-th current signal of the i-th coil;

[0056] S103, converting the i-th current signal into a corresponding i-th pulse DC signal;

[0057] S104, processing the i-th pulse DC signal according to the output clock signal and calculating the corresponding i-th current feedback value;

[0058] S105 , adjusting the radio frequency power allocated to the i th coil according to the i th current feedback value; wherein i∈[1,M].

[0059] Embodiment 1

[0060] like Figure 6 As shown, in this embodiment, the inductively coupled coil of the plasma reaction device includes two coils, namely a first coil and a second coil connected in parallel.

[0061] like Figure 4 As shown, in step S101 of this embodiment, the output clock signal of the RF power source is synchronized, including: synchronizing the output clock signal of the RF power source according to the output power of the RF power source: when the RF power source outputs RF power, the output clock signal is at a high level; when the RF power source does not output RF power, the output clock signal is at a low level. The output voltage waveform of the RF power source is as follows: Figure 4 When the RF power source outputs RF power (the output power of the biased RF power source is 800W at this time), the output clock signal is at a high level; when the biased RF power source does not output RF power (the output power of the RF power source is 0W at this time), the output clock signal is at a low level. The output clock signal waveform is shown in FIG. Figure 4 As shown in waveform 2.

[0062] In this embodiment, the output clock signal includes a high level and a low level, and it is determined that the output mode of the radio frequency power source is a pulse wave. Figure 4 The sinusoidal pulse wave in the figure is only an example, and the present invention can be applied to a radio frequency power source with any pulse waveform, such as a rectangular pulse wave, a triangular pulse wave, etc.

[0063] In step S102 of this embodiment, the first coil and the second coil are both provided with copper pillars (not shown in the figure) for introducing current, and two clamp current sensors are respectively mounted on the copper pillars of the first and second coils to measure the first and second current signals through electromagnetic induction.

[0064] In step S103 of this embodiment, the first and second current signals are converted into corresponding first and second pulse DC signals by rectification and filtering. Figure 4As shown in waveform 3 in FIG. Obviously, the first pulse DC signal includes a rising edge and a falling edge corresponding to the high level of the output clock signal.

[0065] In step S104 of this embodiment, processing the first and second pulse DC signals includes:

[0066] The first and second pulsed DC signals are sampled when the RF power source outputs RF power (when the output clock signal is at a high level), because the plasma in the reaction chamber is in an activated state at this time. When the RF power source does not output RF power (when the output clock signal is at a low level), the first and second pulsed DC signals are not sampled.

[0067] In this embodiment, the etching process is carried out in the reaction chamber, the output frequency of the RF power source is 1 MHz, and the sampling frequency is 100 MHz. That is, within the high level duration of a single clock cycle of the output clock signal, the sampling times are 100 times, and the sampling signals S are obtained in sequence from the first and second pulsed DC signals. 1,1 ~S 1，100 , S 2,1 ~S 2，100 . Obtain the first calibration value i=10 and the second calibration value j=10 corresponding to the reaction chamber process. Figure 4 As shown, the first pulse DC signal, i.e. the sampling signal S 1,1 ~S 1，10 and S 1,90 ~S 1，100 (i.e. the first 10 and the last 10 sampling signals), and the sampling signal S of the second pulse DC signal is discarded 2,1 ~S 2，10 and S 2,90 ~S 2，100 , realizing denoising of the first and second pulse DC signals obtained by sampling (removing the sampling signals of the rising edge and the falling edge).

[0068] The first and second calibration values ​​can be found from a pre-established signal calibration table. The signal calibration table includes a number of triplets, and the triplets include: a reaction chamber process code, and the first and second calibration values ​​corresponding to the reaction chamber process; the first and second calibration values ​​are obtained by searching the signal calibration table. In this embodiment, the process code of the etching process is set to 0001, and a triplet of "0001, 10, 10" is established and put into the signal calibration table.

[0069] During the high level duration of each clock cycle of the output clock signal, the first and second pulse DC signals are subjected to the same sampling steps, and the retained sampling signals of the first and second pulse DC signals are stored in real time according to the sampling time sequence.

[0070] In step S104 of this embodiment, calculating the first and second current feedback values ​​includes:

[0071] The first and second current feedback values ​​fk at the current moment are obtained by averaging the sampled signals of the first and second pulsed DC signals stored. 1,t , fk 2,t :

[0072]

[0073] Among them, t is the current time, s 1,K 、s 2,K is the sampling signal of the first and second pulse DC signals stored most recently; 1,k 、s 2,k is the sampling signal of the first and second pulse DC signals stored for the kth time. In this embodiment, 50 sampling signals are used to calculate the feedback value at one time, which is only an example and should not be used as a limitation of the present invention. The waveform of the first current feedback value is as follows Figure 4 As shown in waveform 4.

[0074] In the present invention, a plurality of variable capacitors are arranged in the inductive coupling coil, and one variable capacitor corresponds to one coil of the inductive coupling coil. The variable capacitor is arranged at the front end of the corresponding coil and is connected in series with the coil. Figure 6 As shown, in this embodiment, two variable capacitors 235 are provided, which are the first variable capacitor and the second variable capacitor corresponding to the first coil and the second coil respectively; by adjusting the RF power output by the RF power source, adjusting any one or more of the first variable capacitor and the second variable capacitor, the first and second current feedback values ​​reach the set first and second current standard feedback values, so as to adjust the RF power allocated to the first and second coils. In this embodiment, by increasing the RF power output by the RF power source, the first and second current feedback values ​​are increased; by increasing the capacitance value of the first variable capacitor, the first current feedback value is increased; by increasing the capacitance value of the second variable capacitor, the second current feedback value is increased.

[0075] When the first and second current feedback values ​​reach the set first and second current standard feedback values, the capacitance values ​​of the first variable capacitor and the second variable capacitor are C1 and C2, respectively. At this time, the amplitudes of the first and second pulse DC signals have reached the predetermined standard, but the phase difference between the first and second pulse DC signals may still exceed the set phase difference threshold. If the phase difference between the first and second pulse DC signals exceeds the set phase difference threshold, the capacitance values ​​of the first and second variable capacitors are reduced while maintaining α 1,2 The phase difference between the first and second pulse DC signals remains unchanged, so that the phase difference between the first and second pulse DC signals is lower than the phase difference threshold.

[0076] Embodiment 2

[0077] like Figure 5 As shown, in this embodiment, the RF power source sequentially outputs the first power or the second power. When the RF power source outputs the first power (800W), the output clock signal is at a high level; when the RF power source outputs the second power (400W), the output clock signal is at a low level; it is obvious that the first power is greater than the second power.

[0078] In this embodiment, when the RF power source outputs the first power, the first and second pulse DC signals are sampled, and the number of sampling times is 50 times within the high level duration of a single clock cycle of the output clock signal.

[0079] In this embodiment, the sampling signals of the first and second pulsed DC signals are denoised, the first and second feedback values ​​are calculated, and the RF power allocated to the first and second coils is adjusted in the same manner as in the first embodiment.

[0080] Embodiment 3

[0081] In this embodiment, the RF power source sequentially outputs the first power or the second power, and the first power is greater than the second power. In this embodiment, according to process requirements, when the RF power source outputs the second power, the first and second pulsed DC signals are sampled, and the remaining steps are the same as those in the second embodiment.

[0082] The present invention also provides a plasma processing device, which is used in the radio frequency power control method of the present invention. Figure 2 As shown, the plasma processing device includes a vacuum reaction chamber 200, and the vacuum reaction chamber includes a roughly cylindrical reaction chamber side wall 201 made of metal material, and an opening 102 is provided on the reaction chamber side wall for accommodating the entry and exit of wafers. An insulating window 217 is provided above the reaction chamber side wall 201, and an inductive coupling coil 215 is provided above the insulating window 217. The RF power source 218 applies RF voltage to multiple coils 230 (referred to as the first to Mth coils) of the inductive coupling coil 215 through the RF matching network 216. The inductive coupling coil 215 is provided with the first to Mth variable capacitors; the i-th variable capacitor is provided at the front end of the i-th coil, and is connected in series with the i-th coil to form the i-th branch, where i∈[1,M]. The first branch to the M-th branch are connected in parallel; by adjusting the RF power, any one or more of the first to M-th variable capacitors, the i-th current feedback value reaches the set i-th current standard feedback value, thereby adjusting the RF power allocated to the first to M-th circles. When M=2, as Figure 6 As shown, the two variable capacitors 235 are respectively connected to the corresponding two coils 230 .

[0083] A liner 220 is also provided inside the reaction chamber to protect the inner wall of the reaction chamber from being corroded by the plasma. A gas injection port 203 is provided at one end of the side wall of the reaction chamber near the insulating window to inject the reaction gas into the vacuum reaction chamber 200. A base 210 is provided at the downstream position of the vacuum reaction chamber 200, and an electrostatic chuck 212 is provided on the base 210. A bias RF power source 250 applies a bias RF voltage to the base through an RF matching network 252 to control the bombardment direction of charged particles in the plasma. An exhaust pump 240 is also provided below the vacuum reaction chamber 200 to discharge the reaction byproducts from the vacuum reaction chamber and maintain the vacuum environment of the reaction chamber.

[0084] like Figure 2 , Figure 6 As shown, the plasma processing device of the present invention further includes: a plurality of current sensors 231 , a rectification-filtering-phase detection module 232 , a signal processing unit 233 , and a graphical user interface 234 .

[0085] A plurality of current sensors 231, used to detect first to M-th coil current signals corresponding to the first to M-th coils, the first to M-th coils respectively corresponding to different current sensors 231;

[0086] The rectification-filtering-phase detection module 232 is used to obtain the output clock signal of the RF power source, convert the i-th coil current signal into the corresponding i-th pulse DC signal through rectification and filtering, and obtain the phase difference between the first to M-th pulse DC signals through phase detection; i∈[1,M];

[0087] The signal processing unit 233 is a logic programmable circuit. The signal processing unit 233 samples the i-th pulse DC signal according to the output clock signal, removes noise, and calculates the corresponding i-th current feedback value; the signal processing unit 233 also adjusts the RF power of the RF power source, any one or more of the first to M-th variable capacitors, according to the i-th current feedback value and the phase difference, so that the i-th current feedback value reaches the set i-th current standard feedback value, thereby adjusting the RF power distributed to the first to M-th coils. i∈[1,M].

[0088] The signal processing unit 233 also includes a storage module (not shown in the figure) for storing a signal calibration table; the signal calibration table includes a plurality of triplets, the triplets including: a reaction chamber process code, a first calibration value and a second calibration value corresponding to the reaction chamber process code; the first calibration value and the second calibration value are used to shield a plurality of sampling signals of the i-th pulse DC signal to achieve denoising of the sampling signal of the i-th pulse DC signal. The first calibration value and the second calibration value can be obtained through experiments. The storage module is also used to store the sampling signal of the i-th pulse DC signal after denoising, the i-th current feedback value, the i-th current standard feedback value, and the phase difference threshold.

[0089] The graphical user interface 234 is communicatively connected to the signal processing unit 233 , and is used to input the reaction chamber process code to the signal processing unit 233 and display the first to Mth current feedback values ​​calculated by the signal processing unit 233 .

[0090] The present invention adjusts the RF power allocated to the coil 230 by collecting the current signal and phase difference of the coil 230, and has more advantages in complex RF circuits. The present invention shields the pulse DC signal corresponding to the low level of the output clock signal, and also shields the rising edge and falling edge of the pulse DC signal, and can continuously provide a stable and effective feedback signal for the RF power source, so that the RF power allocated to the coil 230 is more accurate.

[0091] The present invention uses a logic programmable circuit as the signal processing unit 233, and calculates the feedback value of the bias RF power source according to the algorithm built into the signal processing unit 233. The algorithm is easy to expand according to different processes in the reaction chamber.

[0092] It should be emphasized that the present invention is not limited by the output mode of the radio frequency power source, and has a good effect on both continuous wave and pulse wave radio frequency power sources.

[0093] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A radio frequency power control method, wherein a plasma reaction device comprises a plasma reaction chamber, a plurality of inductively coupled coils are arranged above the reaction chamber, and the radio frequency power of a radio frequency power source is distributed to the plurality of coils of the inductively coupled coils through a matching network so that plasma is generated in the reaction chamber, wherein the plurality of coils are denoted as first to Mth coils, and characterized in that: The radio frequency power control method comprises: An output clock signal of a synchronous radio frequency power source; Detecting an i-th current signal of an i-th coil; Converting the i-th current signal into a corresponding i-th pulse DC signal; Processing the i-th pulse DC signal according to the output clock signal and calculating the corresponding i-th current feedback value; The processing includes sampling and denoising the i-th pulse DC signal; The output clock signal is at a high level and samples the i-th pulse DC signal; the denoising is implemented by removing the sampling signals at the rising and falling edges of the i-th pulse DC signal; and the i-th current feedback value is obtained by averaging the multiple sampled signals after being collected and denoised; adjusting the radio frequency power allocated to the i-th coil according to the i-th current feedback value; in i∈[1,M].

2. The radio frequency power control method according to claim 1, characterized in that: The output clock signal of the synchronous RF power source includes: an output clock signal of the RF power source synchronized according to the output power of the RF power source: when the RF power source outputs RF power, the output clock signal is at a high level; when the RF power source does not output RF power, the output clock signal is at a low level.

3. The radio frequency power control method according to claim 1, characterized in that: The output clock signal of the synchronous RF power source includes: the output clock signal of the RF power source is synchronized according to the output power of the RF power source: when the RF power source outputs a first power, the output clock signal is at a high level; when the RF power source outputs a second power, the output clock signal is at a low level; the first power is greater than the second power.

4. The radio frequency power control method according to claim 1, characterized in that: The corresponding i-th pulse DC signal is obtained by rectifying and filtering the i-th current signal, i∈[1,M].

5. The radio frequency power control method according to claim 2, characterized in that: The processing of the i-th pulse DC signal comprises: sampling the i-th pulse DC signal when the radio frequency power source outputs radio frequency power; The number of sampling times in a single clock cycle of the output clock signal is N times, and the sampling signal S is obtained in sequence i,1 ~S i,N ; Discard the sampled signal S i,1 ~S i,p and S i,q ~S i,N , realizing denoising of the sampling signal of the i-th pulse DC signal; Wherein 1<p<q<N, p, q are respectively the first and second calibration values ​​corresponding to the reaction chamber process; the sampled signal of the retained i-th pulse DC signal is stored in real time according to the sampling time sequence; i∈[1,M].

6. The radio frequency power control method according to claim 3, characterized in that: The processing of the i-th pulse DC signal comprises: when the RF power source outputs the first power, sampling the i-th pulse DC signal; the number of sampling times in a single clock cycle of the output clock signal is N times, and the sampling signal S is obtained in sequence i,1 ~S i,N ; Discard the sampled signal S i,1 ~S i,p and S i,q ~S i,N , realizing denoising of the sampling signal of the i-th pulse DC signal; Wherein 1<p<q<N, p, q are respectively the first and second calibration values ​​corresponding to the reaction chamber process; the sampled signal of the retained i-th pulse DC signal is stored in real time according to the sampling time sequence; i∈[1,M].

7. The radio frequency power control method according to claim 3, characterized in that: The processing of the i-th pulse DC signal comprises: when the radio frequency power source outputs the second power, sampling the i-th pulse DC signal; The number of sampling times in a single clock cycle of the output clock signal is N times, and the sampling signal S is obtained in sequence i,1 ~S i,N ; Discard the sampled signal S i,1 ~S i,p and S i,q ~S i,N , realizing denoising of the sampling signal of the i-th pulse DC signal; Wherein 1<p<q<N, p, q are respectively the first and second calibration values ​​corresponding to the reaction chamber process; the sampled signal of the retained i-th pulse DC signal is stored in real time according to the sampling time sequence; i∈[1,M].

8. The radio frequency power control method according to any one of claims 5 to 7, characterized in that: The calculating the corresponding i-th current feedback value includes: The average value of the stored sampling signal of the ith pulse DC signal is obtained to obtain the ith current feedback value fk at the current moment. i,t : Among them, m is a preset natural number, t is the current time, s i,K is the sampling signal of the most recently stored ith pulse DC signal; s i,k is the sampling signal of the i-th pulse DC signal stored for the kth time, i∈[1,M].

9. The radio frequency power control method according to claim 1, wherein: It also includes setting the first to Mth variable capacitors in the inductive coupling coil; wherein the i-th variable capacitor is set at the front end of the i-th coil and is connected in series with the i-th coil to form the i-th branch; the first branch to the M-th branch are all connected in parallel; by adjusting the RF power output by the RF power source and adjusting any one or more of the first to the M-th variable capacitors, the i-th current feedback value reaches the set i-th current standard feedback value, thereby adjusting the RF power allocated to the i-th coil; i∈[1,M].

10. The radio frequency power control method according to claim 9, characterized in that: It also includes: when the i-th current feedback value reaches the set i-th current standard feedback value, the capacitance value of the i-th variable capacitor is C i ;make If there are at least two pulse DC signals in the first to Mth pulse DC signals, and the phase difference between the two pulse DC signals exceeds the set phase difference threshold, the capacitance values ​​of the first to Mth variable capacitors are simultaneously reduced while maintaining α i,j unchanged, achieving that the phase difference is lower than the phase difference threshold; i,j∈[1,M].

11. The radio frequency power control method according to any one of claims 5 to 7, characterized in that: It also includes establishing a signal calibration table, the signal calibration table includes a plurality of triplets, the triplets include: a reaction chamber process code, and the first and second calibration values ​​corresponding to the reaction chamber process; and obtaining the first and second calibration values ​​by searching the signal calibration table.

12. A plasma processing device, used in the RF power control method according to any one of claims 1 to 11, comprising a plasma reaction chamber and a plurality of inductively coupled coils, wherein a base for placing a wafer is provided at the bottom of the plasma reaction chamber, and the base serves as a lower electrode of the plasma reaction chamber, and the RF power of the RF power source is distributed to the first to Mth coils of the inductively coupled coils through a matching network, so that plasma is generated in the plasma reaction chamber, characterized in that: The plasma processing device further comprises: A plurality of current sensors, used for detecting first to M-th coil current signals corresponding to the first to M-th coils, the first to M-th coils respectively corresponding to different current sensors; A rectification-filtering-phase detection module, used for obtaining the output clock signal of the RF power source, converting the i-th coil current signal into the corresponding i-th pulse DC signal, and obtaining the phase difference between the first to M-th pulse DC signals; i∈[1,M]; The signal processing unit processes the i-th pulse DC signal according to the output clock signal, calculates the corresponding i-th current feedback value, and adjusts the RF power allocated to the first to M-th coils according to the i-th current feedback value and the phase difference.

13. The plasma processing apparatus according to claim 12, wherein: The inductive coupling coil is further provided with first to Mth variable capacitors; the i-th variable capacitor is provided at the front end of the i-th coil and is connected in series with the i-th coil to form an i-th branch; the first branch to the M-th branch are connected in parallel; the RF power and any one or more of the first to Mth variable capacitors are adjusted by the signal processing unit so that the i-th current feedback value reaches the set i-th current standard feedback value, thereby adjusting the RF power distributed to the first to M-th coils; i∈[1,M].

14. The plasma processing apparatus according to claim 12, wherein: The processing includes sampling and denoising.

15. The plasma processing apparatus according to claim 12, wherein: The signal processing unit further includes a storage module for storing a signal calibration table; the signal calibration table includes a plurality of triplets, the triplets including: a reaction chamber process code, a first calibration value corresponding to the reaction chamber process code, and a second calibration value; the first calibration value and the second calibration value are used to shield a plurality of sampling signals of the i-th pulse DC signal, so as to realize denoising of the sampling signals of the i-th pulse DC signal; The storage module is also used to store the sampling signal of the ith pulse DC signal after denoising, the ith current feedback value, the ith current standard feedback value, and the phase difference threshold.

16. The plasma processing apparatus according to claim 15, wherein: It also includes a graphical user interface that is communicatively connected to the signal processing unit and is used to input the reaction chamber process code into the signal processing unit and display the first to Mth current feedback values ​​calculated by the signal processing unit.

17. The plasma processing apparatus according to claim 12, wherein: The signal processing unit is a logic programmable circuit.

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