WO2016110027A1 - 针对脉冲射频电源的阻抗匹配方法及装置 - Google Patents

针对脉冲射频电源的阻抗匹配方法及装置 Download PDF

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Publication number
WO2016110027A1
WO2016110027A1 PCT/CN2015/077779 CN2015077779W WO2016110027A1 WO 2016110027 A1 WO2016110027 A1 WO 2016110027A1 CN 2015077779 W CN2015077779 W CN 2015077779W WO 2016110027 A1 WO2016110027 A1 WO 2016110027A1
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Prior art keywords
matching
impedance
current
impedance matching
reflection coefficient
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PCT/CN2015/077779
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English (en)
French (fr)
Inventor
成晓阳
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Beijing NMC Co Ltd
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Beijing NMC Co Ltd
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Priority to JP2017553291A priority Critical patent/JP6619818B2/ja
Priority to KR1020177022097A priority patent/KR101902427B1/ko
Priority to US15/538,903 priority patent/US10643822B2/en
Priority to SG11201705228PA priority patent/SG11201705228PA/en
Publication of WO2016110027A1 publication Critical patent/WO2016110027A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082—Radio frequency generated discharge
    • H01J37/32174—Circuits specially adapted for controlling the RF discharge
    • H01J37/32183—Matching circuits
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082—Radio frequency generated discharge
    • H01J37/32137—Radio frequency generated discharge controlling of the discharge by modulation of energy
    • H01J37/32146—Amplitude modulation, includes pulsing
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/38—Impedance-matching networks
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/38—Impedance-matching networks
    • H03H7/40—Automatic matching of load impedance to source impedance
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P95/00—Generic processes or apparatus for manufacture or treatments not covered by the other groups of this subclass
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H2242/00—Auxiliary systems
    • H05H2242/20—Power circuits
    • H05H2242/26—Matching networks

Definitions

  • the invention belongs to the technical field of semiconductor device manufacturing, and in particular relates to an impedance matching method and device for a pulsed radio frequency power source.
  • the semiconductor processing equipment is usually applied to the reaction chamber of the high vacuum environment by the RF energy provided by the RF power source to excite the process gas in the reaction chamber to form a plasma containing a large amount of electrons, ions, excited atoms, molecules and Active particles, such as free radicals, that physically and/or chemically react with the surface of the wafer exposed to the plasma to complete etching, deposition, or other processes on the wafer.
  • RF energy provided by the RF power source to excite the process gas in the reaction chamber to form a plasma containing a large amount of electrons, ions, excited atoms, molecules and Active particles, such as free radicals, that physically and/or chemically react with the surface of the wafer exposed to the plasma to complete etching, deposition, or other processes on the wafer.
  • Active particles such as free radicals
  • the key factor that restricts the development of pulsed RF power supply as a plasma excitation source is its impedance matching technology.
  • Impedance matching is to match the load impedance of the pulsed RF power supply with the characteristic impedance (typically 50 ohms).
  • the pulse frequency of a common pulsed RF power supply ranges from 100 to 100 kHz, and the duty cycle ranges from 10 to 90%. Therefore, the width of each pulse period is only a few milliseconds, and the existing impedance adjustment based on mechanical adjustment is used. It is difficult for the device to achieve impedance matching within a few milliseconds, resulting in low matching accuracy and high reflected power of the pulsed RF power supply (typically 20%), resulting in poor utilization of the pulsed RF power supply.
  • the impedance matching apparatus 10 includes a control unit 11, an execution unit 12, and a matching network 13.
  • the pulsed RF power source 14 has a frequency sweep function and sends its pulse synchronization signal to the control unit 11, such as a pulse synchronization signal.
  • the pulsed RF power source 14 is modulated with a radio frequency power signal during a high level period, and no radio frequency power signal is modulated during a low level period.
  • the matching network 13 is provided with an impedance adjustable component; the pulsed RF power source 14 automatically performs sweep matching at a high level (ie, automatically adjusts to a pulse frequency of a maximum power output according to a load impedance of the pulsed RF power source 14); the control unit 11
  • the pulse synchronization signal acquires the current pulse frequency of the pulsed RF power source 14 in real time at a high level of each pulse period, and calculates the pulsed RF power source 14 according to the current pulse frequency, the circuit configuration of the matching network 13, and the current position of the impedance tunable component.
  • the control unit 12 is normally adjusted to adjust the position of the impedance tunable element to adjust the load impedance of the pulsed RF power source 14 for impedance matching.
  • FIG. 3 is a schematic view showing the structure of a conventional impedance matching device for a reaction chamber.
  • an induction coil 21 is disposed above the top of the reaction chamber 20.
  • the induction coil 21 is electrically connected to the first RF power source 23 through the first impedance matching device 22; and is disposed at the bottom portion of the reaction chamber 20 for carrying
  • the electrostatic chuck 24 of the wafer S is electrically connected to the second RF power source 26 through the second impedance matching device 25, wherein the first RF power source 23 adopts a continuous wave signal output mode, that is, the first RF power source 23 is continuous.
  • the RF power signal is output;
  • the second RF power source 26 is a pulsed RF power source, the frequency of the RF power signal is 13.56 MHz, the frequency of the pulse synchronization signal is 100 Hz, the duty ratio is 90%, and the second impedance matching device 25 is as shown in FIG. Impedance matching device.
  • FIG. 4 is a schematic diagram of the matching state of the second impedance matching device 25 at different time points of the impedance matching process.
  • the first pulse period during the high level period, the pulsed RF power source 26 starts the automatic frequency sweep matching, and is always in the "matching" state, that is, the impedance matching is not achieved;
  • the control unit 11 performs impedance matching by adjusting the position of the impedance tunable element by the control execution unit 12.
  • Second pulse period during the high level period, the pulsed RF power source 26 starts automatic frequency sweep matching, elapsed time T, from the "matching" state to the "matching" state, that is, the impedance matching is never implemented to achieve impedance matching; in the low level period, the matching position is kept unchanged.
  • the matching process of the third pulse period and the subsequent pulse period is similar to the matching process of the second pulse period, and will not be described herein.
  • FIG. 5 is a trajectory of impedance change of the load impedance of the second RF power source represented by the Smith chart during its impedance matching process.
  • the center point of the Smith chart represents a matched resistance value (50 ohms), and the position of the most center point is called the impedance matching point.
  • the impedance matching process is actually the movement process of the load impedance from the edge position of the chart toward its most central position. The motion process is embodied as sequentially experiencing the impedance region 1, the impedance region 2, and the impedance region. 3 and impedance zone 4.
  • the load impedance is the impedance caused by the interference signal, and is represented as an impedance region 1 outside the circle on the Smith chart.
  • the current load impedance is initially in the impedance region 2, and the impedance value is about 6 ⁇ - 86 °, at which time the pulsed RF power source 26
  • the priming in the reaction chamber is not realized; as the pulsed RF power source 26 automatically sweeps the frequency match, the current load impedance gradually moves from the impedance region 2 to the impedance matching position, but still does not move to the impedance matching point; in the first pulse period During the low period, impedance matching is not performed.
  • the load impedance is located in the impedance region 4 outside the Smith circle, and the signal impedance is coupled to the induction coil 21.
  • the load impedance at the beginning is moved in the impedance region 2 toward the impedance matching point
  • the unexcited impedance region of a certain distance makes the initial RF power supply 26 not illuminate.
  • the pulsed RF power source 26 automatically sweeps and matches, the current load impedance moves to the impedance zone 3, and the impedance value is about 40 ⁇ 25 °.
  • impedance matching is basically achieved; at low level, the load impedance is also located in the impedance region 4.
  • the movement process of the load impedance corresponding to the third pulse period and the subsequent pulse period is similar to the movement process of the load impedance corresponding to the second pulse period, and details are not described herein again.
  • the impedance matching of the pulsed RF power source by using the above existing impedance matching device often has the following technical problems: since the function of the pulsed RF power source in the process is to excite the process gas in the reaction chamber to form a plasma, And the load impedance of the pulsed RF power supply is different when the reaction chamber is lit up and the impedance matching is achieved. Therefore, after the first impedance matching is performed, the pulsed RF power supply needs to be realized first in the high period of each subsequent pulse period.
  • the reaction chamber illuminates to achieve impedance matching, that is, in the high-level period of each subsequent pulse period, in order to achieve the priming of the process gas, the load impedance obtained from the previous pulse period is required to match the load impedance value.
  • the load impedance After adjusting to the priming load impedance value, after the fading is performed, the load impedance needs to be matched by the automatic frequency sweep matching process such as shown in FIG. 4 and FIG. 5 until the load impedance value at the time of matching is reached. That is to say, the existing impedance matching device needs to perform a long automatic sweep matching time T in the high level period of each subsequent pulse period to achieve impedance matching, so the matching efficiency is low, resulting in poor process stability. And the utilization of pulsed RF power is low.
  • the invention aims to solve the technical problems existing in the prior art, and provides an impedance matching device and a semiconductor processing device, which can quickly realize impedance matching for a pulsed RF power source, thereby improving process stability and pulsed RF power supply. Utilization of RF energy.
  • the present invention provides an impedance matching method for a pulsed RF power supply, the impedance matching method comprising the following steps: a coarse adjustment step: adjusting according to a current load impedance to make a current reflection coefficient
  • the coarse adjustment step comprises the following steps:
  • Step 1 determining in real time whether the current reflection coefficient
  • Step 2 Perform the coarse adjustment step in real time according to the current load impedance; return to step 1.
  • the step of the coarse adjustment further includes: determining whether the current high-level period of the pulse period when the matching is not implemented, and if yes, performing the coarse adjustment step; otherwise, maintaining the current position unchanged.
  • the pulsed RF power source when determining that the current period of the pulse period is not at the time of the unrealized matching, adopts the frequency sweep mode for automatic impedance matching.
  • the step of fine tuning further includes: when the impedance matching is implemented, saving the matching position.
  • the switching step includes: after the first implementation of the impedance matching, switching from the rising position to the matching position in the high level period of each subsequent pulse period, and the self-matching position in the low period of each subsequent pulse period. Switch to the starting position.
  • the present invention also provides an impedance matching apparatus for a pulsed RF power source for matching load impedance and characteristic impedance of a pulsed RF power source.
  • the device includes: a coarse adjustment unit, a fine adjustment unit, and a switching unit, wherein: the coarse adjustment unit is configured to adjust a current reflection coefficient
  • the device further includes: a control module, a reflection coefficient determination module, and a calculation module, wherein: the calculation module is configured to calculate a current load impedance and a current reflection coefficient
  • Reflection coefficient judgment mode The block is configured to determine whether the current reflection coefficient
  • the control module is configured to trigger the coarse adjustment unit when receiving the first identification signal sent by the reflection coefficient determination module; and receive the transmission by the reflection coefficient determination module The fine tuning unit is triggered when the second identification signal is used.
  • the coarse adjustment unit includes a tunable capacitor and/or a tunable inductor, wherein: the coarse adjustment unit adjusts the tunable capacitor and/or may be adjusted in real time according to a current load impedance sent by the calculation module. Adjust the position of the inductor to adjust the current reflection coefficient
  • the trimming unit comprises a fixed capacitor and/or a fixed inductor and an on-off switch connected in series therewith, wherein: the trimming unit controls the on/off switch to be turned on or in real time according to a current load impedance sent by the calculation module Disconnect to achieve impedance matching, and set the current state of the on/off switch to match the on-off state.
  • the device further includes: a pulse period judging module, configured to determine whether a current period of a pulse period when the matching is not currently performed, and if so, triggering the coarse adjustment unit; otherwise, maintaining the current position unchanged.
  • a pulse period judging module configured to determine whether a current period of a pulse period when the matching is not currently performed, and if so, triggering the coarse adjustment unit; otherwise, maintaining the current position unchanged.
  • the device further includes: a storage module, configured to save the matching position when the fine tuning unit implements impedance matching according to a current load impedance real-time adjustment.
  • the switching unit is configured to switch from a rising position to a matching position in a high-level period of each subsequent pulse period after the first impedance matching is performed, and a self-matching position in a low-level period of each subsequent pulse period. Switch to the starting position.
  • the impedance matching method for the pulsed RF power supply provided by the invention first adjusts according to the current load impedance by means of the coarse adjustment step, so that the current reflection coefficient
  • the matching time of each subsequent pulse period is the switching time of the priming position and the matching position, which is compared with the matching time of each subsequent pulse period in the prior art.
  • the long automatic sweep frequency and repeated adjustment of the load impedance to achieve matching time can improve the matching rate, thereby improving the stability of the process and the utilization of the pulsed RF power supply.
  • the impedance matching device for the pulsed RF power supply provided by the invention adjusts the current reflection coefficient
  • Matching different pulse periods of subsequent pulse periods switching between the rising position and the matching position, specifically, switching from the initial position to the matching position in the high level period of the subsequent pulse period, in the low period of the subsequent pulse period
  • the self-matching position is switched to the priming position, so as to ensure that the high-level period of the next pulse period can directly achieve priming, and then the re-matching can be achieved by switching the priming position to the matching position, so each subsequent pulse period is
  • the matching time is the switching time of the priming position and the matching position, which is related to each pulse in the prior art.
  • Matching time period is longer automatic sweep, iteratively adjusting the load impedance matching is achieved compared to the time, rate matching can be improved, which can improve the stability and efficiency of a process pulsed RF power.
  • 1 is a schematic block diagram of an existing impedance matching device
  • FIG. 2 is a waveform diagram of a pulse synchronization signal of a pulsed RF power supply
  • FIG. 3 is a schematic structural view of a reaction chamber to which an existing impedance matching device is applied;
  • FIG. 4 is a schematic diagram of a matching state of a second impedance matching device at different time points of the impedance matching process
  • FIG. 5 is a trajectory diagram corresponding to a load impedance of a second RF power source corresponding to a Smith chart during impedance matching
  • FIG. 6 is a flowchart of a method for impedance matching of a pulsed RF power supply according to a first embodiment of the present invention
  • FIG. 7 is a schematic block diagram of an impedance matching apparatus for a pulsed RF power supply according to a second embodiment of the present invention.
  • Figure 8 is a schematic view of the coarse adjustment unit and the fine adjustment unit of Figure 7;
  • Figure 9 is a flow chart showing the operation of the impedance matching device shown in Figure 7;
  • FIG. 10 is a schematic diagram of matching states of impedance matching devices at different time points for performing impedance matching in the case where the current reflection coefficient
  • Figure 11 is a trajectory diagram of the load impedance of the pulsed RF power supply corresponding to the Smith circle during its impedance matching
  • FIG. 12 is a schematic diagram of matching states of impedance matching devices at different time points for performing impedance matching in the case where the current reflection coefficient
  • FIG. 6 is a flowchart of a method for impedance matching of a pulsed radio frequency power supply according to a first embodiment of the present invention.
  • a pulsed RF power supply according to a first embodiment of the present invention is provided.
  • the impedance matching method is used to match the load impedance of the pulsed RF power source and the characteristic impedance (for example, 50 ⁇ ), and the impedance matching method includes the following steps:
  • Coarse adjustment step adjust according to the current load impedance so that the current reflection coefficient
  • is the ratio of the reflected voltage wave to the incident voltage wave at the load impedance point.
  • refers to the load impedance when the pulsed RF power source achieves the priming of the reaction chamber.
  • For a certain process, the load impedance and reflection coefficient of the pulsed RF power supply when the reaction chamber is ignited are set to a fixed value; however, due to different process chamber pressure, process gas and other parameters to the pulsed RF The power supply has a certain influence on the priming of the reaction chamber. Therefore, the load impedance and reflection coefficient of the pulsed RF power supply in the process chamber during the different process are often different.
  • FIG. 5 is further illustrated here.
  • the impedance region 2 is a load impedance value when the process gas is not ignited at the beginning of the high-level period, and the impedance region 3 is achieved after the process gas is stabilized and the high-level period is realized.
  • the purpose of the coarse adjustment step in the present invention is to find a load impedance value close to the impedance matching state, that is, the current reflection coefficient
  • the current load impedance value gradually approaches the load impedance value at the matching state, that is, the current load impedance value gradually moves from the range of the impedance region 2 in FIG. 5 to the range of the impedance region 3.
  • the current load impedance value is the load impedance value at the moment of the process gas priming, so the position of each component in the current state is set as the priming position, Impedance matching has not yet been achieved.
  • Fine-tuning step keep the starting position unchanged, adjust in real time according to the current load impedance to achieve impedance matching, and set the current position as the matching position.
  • the steps of the lifting position are kept unchanged, and the fine adjustment step is performed. Then, until the load impedance value at the time of impedance matching is found, that is, the current load impedance value is in the impedance region 3 in FIG. 5, and the position of each component at this time is saved as the matching position.
  • the present invention obtains two positions, namely the starting position and the matching position, while completing the first impedance matching of the current pulsed RF power source.
  • Switching step after the first impedance matching is performed, switching between the starting position and the matching position in different pulse periods (ie, the high level period and the low level period) in subsequent pulse periods to achieve different pulse periods Impedance matching under. Specifically, in each pulse period after the first impedance matching, in the initial stage of the high level period, the components are in the priming position to make the process gas illuminate; and then the components are switched from the priming position state to the matching position state. , to achieve impedance matching.
  • pulse periods ie, the high level period and the low level period
  • the pulsed RF power source can realize the process gas priming; after that, at the matching position, at this time
  • the pulsed RF power supply can achieve impedance matching. Therefore, in the switching step, in the high-level period of each subsequent pulse period after the first impedance matching is realized, it is no longer necessary to repeatedly match the load impedance by the automatic sweeping as described in the prior art, and Impedance matching is achieved only by switching from the rising position to the matching position; and in the low period of each subsequent pulse period, the components can be switched from the matching position to the starting position, which ensures high power in the next pulse period.
  • the matching time is the switching time from the start position to the matching position in the high level period of each subsequent pulse period after impedance matching is first implemented, and the so-called matching time refers to the conversion from the unmatched state. The time taken to match the state of this matching process. Comparing the prior art and the embodiment of the present invention, it can be seen that in each subsequent pulse period after the first impedance matching is implemented, the prior art achieves matching by performing automatic sweeping for a long time and repeatedly adjusting the load impedance, so the matching is performed.
  • the time is longer; in the embodiment of the present invention, it is not necessary to repeatedly adjust the load impedance, but only the components are switched from the rising position to the matching position to achieve matching, so
  • the short matching time and high matching efficiency can improve the stability of the process and the utilization of the pulsed RF power supply.
  • the coarse adjustment step includes the following steps:
  • step S1 it is determined in real time whether the current reflection coefficient
  • step S2 the coarse adjustment step is performed in real time according to the current load impedance; and the process returns to step S1.
  • step S1 and step S2 real-time judgment and adjustment can be realized until the current reflection coefficient
  • the method further comprises: determining whether the current high level period of the pulse period when the matching is not implemented, and if yes, performing the coarse adjustment step; otherwise, the current low period of the pulse period, maintaining the current position constant.
  • the impedance matching method provided in this embodiment performs the coarse adjustment step only in the high level period of the pulse period when the matching is not currently performed, and does not operate in the low level period, which is low in the prior art.
  • the "blind adjustment" can be avoided, thereby avoiding the occurrence of overshoot, thereby improving the impedance matching for the first time. Matching efficiency.
  • the pulsed RF power source adopts the frequency sweeping mode for automatic impedance matching, that is, the pulsed RF power source automatically adjusts its pulse frequency for matching, which can not only The matching efficiency is further improved, and the matching accuracy can be improved.
  • the method further includes: saving the matching position when performing impedance matching.
  • FIG. 7 is a schematic block diagram of an impedance matching apparatus for a pulsed RF power supply according to a second embodiment of the present invention.
  • the impedance matching device is used to match the load impedance of the pulsed RF power source and the characteristic impedance (for example, 50 ⁇ ).
  • the impedance matching device includes a coarse adjustment unit, a fine adjustment unit, and a switching unit. Wherein, the coarse adjustment unit is used to adjust according to the current load impedance, so that the current reflection coefficient
  • of the pulsed RF power supply is the ratio of the reflected voltage wave to the incident voltage wave of the load impedance point, and the radiance reflection coefficient
  • the load impedance and reflection coefficient of the pulsed RF power supply when the reaction chamber is ignited are set to a fixed value; however, due to different process chamber pressure, process gas and other parameters to the pulsed RF The power supply has a certain influence on the priming of the reaction chamber. Therefore, the load impedance and reflection coefficient of the pulsed RF power supply in the process chamber during the different process are often different.
  • the fine adjustment unit is used to keep the starting position unchanged when the current reflection coefficient
  • the switching unit is configured to switch between the starting position and the matching position in different pulse periods of the subsequent same pulse period (ie, the high level period and the low level period) after the first impedance matching is implemented to achieve different pulse periods. Impedance matching under.
  • the pulsed RF power source can achieve the process gas priming; after that, at the matching position, the pulsed RF The power supply can achieve impedance matching.
  • the switching unit in the high-level period of each subsequent pulse period after impedance matching is realized for the first time, it is no longer necessary to repeatedly match the load impedance by the automatic sweeping as described in the prior art, and only Impedance matching is required to switch from the rising position to the matching position, and the low-level period of each subsequent pulse period after impedance matching for the first time can be switched from the matching position to the starting position, which can be guaranteed in the next pulse period.
  • the high-level period directly achieves the germination, and then the self-lighting position is switched to the matching position to directly re-match.
  • the matching time is the switching time from the start position to the matching position in the high level period of each subsequent pulse period after impedance matching is first implemented, and the so-called matching time refers to the conversion from the unmatched state. The time taken to match the state of this matching process.
  • the prior art achieves matching because of long-time automatic frequency sweep and repeated adjustment of load impedance, so the matching time is long.
  • the impedance matching device further includes a control module, a calculation module, and a determination module.
  • the calculation module is configured to calculate the current load resistance of the pulsed RF power source and the current reflection coefficient
  • the reflection coefficient judging module is configured to determine whether the current reflection coefficient
  • the second identification signal is, for example, a low level “0”.
  • the control module is configured to trigger the coarse adjustment unit when receiving the first identification signal; and trigger the fine adjustment unit when receiving the second identification signal.
  • the coarse adjustment unit includes a tunable capacitor and/or a tunable inductor.
  • the coarse adjustment unit adjusts the tunable capacitor and/or the tunable inductor in real time according to the current load impedance sent by the calculation module.
  • is adjusted to be no greater than the radiance reflection coefficient
  • the coarse adjustment unit also includes a motor, etc., and the motor can be a stepping motor. As shown in FIG.
  • the coarse adjustment unit in this embodiment includes adjustable capacitors C1 and C2; the drive motor M1 is connected to the adjustment terminal of the adjustable capacitor C1 for adjusting the adjustable capacitor C1; and the drive motor M2 is The regulating terminal of the capacitor C2 is connected for adjusting the adjustable capacitor C2.
  • the trimming unit includes a fixed capacitor and/or a fixed inductor and an on-off switch connected in series therewith. As shown in FIG. 8, the trimming unit includes two branches, one of which includes a series-connected on-off switch K1 and a fixed capacitor C11. The other branch includes a series of on/off switch K2 and fixed power Capacitor C12, on/off switches K1 and K2 include electronic switches such as diodes or relays. In this case, the trimming unit controls the on/off switches (K1 and K2) to be turned on or off in real time according to the current load impedance sent from the calculation module to achieve impedance matching, and to perform on/off during impedance matching.
  • the states of the switches are set to match the on-off state (also referred to as "matching position"). For example, if the on-off switch K1 is turned on and K2 is turned off when impedance matching is achieved, the on-off state (matching position) is matched. K2 is turned off for the on/off switch K1.
  • the impedance matching apparatus further includes a storage module, where the storage module is configured to save the matching position when the fine adjustment unit realizes the impedance matching according to the current load impedance real-time adjustment, and specifically, the pass of the on/off switch K1 and K2 is saved. Broken state.
  • the impedance matching device further includes a pulse period judging module, wherein the pulse period judging module is configured to determine whether the current period is a high level period of the pulse period when the matching is not implemented, and if so, triggering the coarse adjustment unit; otherwise Keep the current position unchanged, that is, C1, C2, K1, and K2 each maintain the same position. It can be seen that the impedance matching device provided in this embodiment triggers the coarse adjustment unit when the impedance matching is not implemented for the first time, and does not operate if it is currently in the low level period.
  • the "blind adjustment" can be avoided in the low-level period according to the load impedance control actuator adjusting the impedance adjustable element at the last time point of the high-level period. Therefore, overshoot can be avoided, and the matching efficiency of impedance matching for the first time can be improved.
  • the pulsed RF power source has an automatic frequency sweep mode for performing automatic impedance matching when the current impedance is not detected for the first time, and automatically adjusting the pulse frequency thereof. Make a match. It can be understood that the automatic frequency sweep matching by the pulsed RF power source at the high level of the pulse period can not only further improve the matching efficiency, but also improve the matching precision.
  • the load impedance is the impedance caused by the interference signal, and is represented as an impedance area A outside the circle on the Smith chart.
  • the pulsed RF power After the pulsed RF power is turned on, it sends the pulse synchronization signal to the pulse period judgment module, and the pulse period judgment module determines in real time whether it is the high level period of the first pulse period.
  • the pulse period judging module judges that the current period is the high level period of the first pulse period, and the pulse radio frequency power source performs automatic frequency sweep matching; and the calculation module starts to calculate the current load impedance and the current reflection coefficient
  • the reflection coefficient judgment module determines the current reflection coefficient from the calculation module in real time
  • the coarse adjustment unit is triggered to adjust the adjustable capacitances C1 and C2 in real time according to the current load impedance from the calculation module, that is, the matching is performed by "motor matching mode", in which the pulsed radio frequency is used.
  • the load impedance of the power source moves from the unexposed impedance region (not shown in FIG. 11) to the matching impedance region C, and, in the matching process K1 and K2 are off switch, without the operation in the initial off state.
  • the pulse period judging module judges in real time that the current low period of the first pulse period, the current position of the adjustable capacitors C1 and C2 is kept unchanged, waiting for the next pulse period, so as to be in the next pulse period.
  • the high level period continues to move toward the impedance matching area C.
  • the load impedance of the pulsed RF power source is located in the impedance zone D, which is the impedance of the induction coil coupling signal.
  • the pulsed RF power supply performs automatic frequency sweep matching; and the calculation module starts to calculate the current load impedance and the current reflection coefficient
  • To the reflection coefficient judging module if the reflection coefficient judging module judges in real time in the time period T2 that the current reflection coefficient
  • the load impedance continues to move to the impedance matching area C; the reflection coefficient judging module judges that the current reflection coefficient
  • the reflection coefficient judging module sends the control module to the control module.
  • the control module triggers the fine adjustment unit when receiving the second identification signal “0”, so that the current positions of the adjustable capacitors C1 and C2 (ie, the starting position) remain unchanged, and
  • the on/off switch K1 and K2 are turned on or off in real time, that is, the matching is performed by the "switch matching mode", and the on-off response time T3 of the on-off switches K1 and K2 is That is, the switching time is implemented to achieve impedance matching.
  • the current load impedance rapidly moves from the impedance region B to the impedance matching region C near the impedance matching point through the on-off response time T3.
  • the pulse frequency RF power is automatically swept.
  • the load impedance is shifted to the impedance matching point; and, when the "switch matching mode" is used for impedance matching, the memory module saves the current on-off state of the on/off switches K1 and K2 as a matching on-off state.
  • the pulse period judging module judges in real time that the current low period period is the second pulse period, although the high level period has achieved impedance matching, it is necessary to perform impedance matching again for the next pulse period, and therefore, the adjustable capacitor C1 is maintained. And the starting position of C2 is unchanged, so that the on/off switches K1 and K2 are switched from the matched on-off state to the initial on-off state.
  • the load impedance of the pulsed RF power source is located in the impedance region D, which is coupled to the induction coil. Signal impedance.
  • the pulse radio frequency power source automatically sweeps the frequency matching, and the calculation module calculates the current load impedance and the current reflection coefficient in real time, and sends the current load impedance to the coarse adjustment unit.
  • the reflection coefficient judging module judges from the calculation
  • is not greater than the radiance reflection coefficient
  • the control module when receiving the second identification signal "0", the control module triggers the fine adjustment unit to keep the starting position of the adjustable capacitors C1 and C2 unchanged, and directly controls the switching of the on/off switches K1 and K2 from the initial on/off state.
  • impedance matching is achieved through the switching time T3 of the on/off switches K1 and K2, and the load impedance is fast from the impedance region B over time T3. Move to the impedance matching area C near the impedance matching point, and achieve the load impedance at the impedance matching point by automatic sweep matching of the pulsed RF power supply.
  • the pulse period judging module judges that the current low period period of the third pulse period, although the high level period has achieved impedance matching, it needs to perform impedance matching again for the next pulse period, and therefore, the adjustable capacitor is continuously maintained.
  • the starting positions of C1 and C2 are unchanged, so that the on/off switches K1 and K2 are switched from the on-off state to the on-off state.
  • the load impedance of the pulsed RF power source is located in the impedance region D, which is the induction.
  • the coil couples the signal impedance.
  • the case of the high-level and low-level periods of the fourth pulse period and each subsequent pulse period is the same as the case of the high-level period and the low-level period of the third pulse period, and the law is maintained until the end of the process.
  • the load impedance is located in the impedance region A outside the Smith circle, which is the impedance caused by the interference signal.
  • the pulsed RF power After the pulsed RF power is turned on, it sends a pulse synchronization signal to the pulse period judgment module, and the pulse period is judged.
  • the module determines in real time whether it is currently a high level period of the first pulse period.
  • the pulse period judging module judges in real time that the current period is the high level period of the first pulse period, and the pulse radio frequency power source performs automatic frequency sweep matching; and the calculation module starts to calculate the current load impedance and the current reflection coefficient
  • the current load impedance is sent to the coarse adjustment unit and the fine adjustment unit, and the current reflection coefficient
  • the pulse period judging module judges in the real time that the current low period period is the first pulse period, then although impedance matching has been achieved in the high level period, impedance matching needs to be performed again in the next pulse period, therefore, Keeping the positions of the adjustable capacitors C1 and C2 unchanged, the on/off switches K1 and K2 are switched from the matched on-off state to the initial on-off state. Moreover, during the low level period, the load impedance of the pulsed RF power source is located in the impedance region D, which is the impedance of the induction coil coupling signal.
  • the pulse radio frequency power supply automatically sweeps the frequency matching, and the calculation module calculates the current load impedance and the current reflection coefficient
  • the reflection coefficient judging module directly judges that the current reflection coefficient
  • the reflection coefficient judging module sends a second identification signal “0” to the control module, and the control module triggers fine adjustment when receiving the second identification signal “0”.
  • the unit keeps the starting positions of the adjustable capacitors C1 and C2 unchanged, and directly controls the on/off switches K1 and K2 to switch from the initial on-off state to the matching on-off state, and achieve impedance matching through the switching time T3 of the on/off switches K1 and K2.
  • the load impedance rapidly moves from the impedance region B to the impedance matching region C near the impedance matching point after the switching time T3, and the load impedance is located at the impedance matching point by the automatic frequency sweep matching of the pulsed RF power source.
  • the pulse period judging module judges that the current period is the low period of the second pulse period, then although the high level period has achieved impedance matching, the impedance matching needs to be performed again in the next pulse period, and therefore, the adjustable capacitor is continuously maintained.
  • the positions of C1 and C2 are unchanged, and the on/off switches K1 and K2 are switched from the matched on-off state to the initial on-off state.
  • the load impedance of the pulsed RF power supply is located in the impedance region D, which is the induction coil coupling signal. impedance.
  • the case of the high-level and low-level periods of the third pulse period and each subsequent pulse period is the same as the case of the high-level and low-level periods of the second pulse period, and the law is maintained until the end of the process.
  • FIG. 10 and FIG. 12 Comparing FIG. 4, FIG. 10 and FIG. 12, it can be seen that the prior art shown in FIG. 4 needs to perform a long time T to achieve impedance matching after each impedance cycle is performed for the first time; FIG. 10 and FIG.
  • the impedance matching after the impedance matching is performed for the first time, the impedance matching can be achieved only after the switching time or the on-off response time T3 for each subsequent pulse period, and T3 ⁇ T, which can be seen, the embodiment of the present invention It can improve the matching efficiency of pulsed RF power supply.
  • the circuit structure of the matching network of the impedance matching device is L-shaped.
  • the present invention is not limited to this, in practical applications, matching the power of the network
  • the road structure may also include an inverted L type, a T type, or a ⁇ type.
  • the trimming unit in this embodiment includes a fixed capacitor and/or a fixed inductor and an on-off switch connected in series
  • the on-off position and the matching position are realized by the on and off of the on-off switch. Switching between, but the present invention is not limited thereto. In practical applications, other methods can be used to quickly switch between the starting position and the matching position.
  • each branch The circuit may include a plurality of capacitors and/or inductors and a plurality of on-off switches connected in series to change the reactance value of the trimming unit by means of a combination of the respective on-off and closed states.
  • the impedance matching apparatus does not limit the radio frequency of the pulsed radio frequency power source 30, for example, the radio frequency is 400 kHz, 2 MHz, 3 MHz, 27 MHz, 40 MHz, or 60 MHz, etc.; and the pulsed RF power source 30
  • the pulse frequency and the pulse duty ratio are also not limited.
  • the pulse frequency can be within 1 MHz, and the pulse duty ratio can take any value less than one.

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Abstract

一种针对脉冲射频电源的阻抗匹配方法及装置。该阻抗匹配方法包括以下步骤：粗调步骤：根据当前负载阻抗进行调节，使当前反射系数|Г|不大于起辉反射系数|Гt|，并设置当前位置为起辉位置；微调步骤：保持起辉位置不变，根据当前负载阻抗实时调节实现阻抗匹配，并设置当前位置为匹配位置；切换步骤：在首次实现阻抗匹配后，在后续的各脉冲周期中的不同脉冲时段，在起辉位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。该阻抗匹配方法及装置可以提高脉冲射频电源的匹配速率，从而可以提高工艺的稳定性和脉冲射频电源的利用率。

Description

针对脉冲射频电源的阻抗匹配方法及装置 技术领域
本发明属于半导体设备制造技术领域，具体涉及一种针对脉冲射频电源的阻抗匹配方法及装置。
背景技术
半导体加工设备通常借助射频电源提供的射频能量施加至高真空环境的反应腔室内，来将反应腔室内的工艺气体激发形成等离子体，等离子体中含有大量的电子、离子、激发态的原子、分子和自由基等活性粒子，该活性粒子与暴露在等离子体环境中的晶圆表面发生物理和/或化学反应，从而完成晶圆的刻蚀、沉积或者其他工艺。随着集成电路的进一步发展，现有的技术无法满足22nm及以下尺寸刻蚀工艺的要求，为此，采用脉冲射频电源作为等离子体激发源，以减小连续波射频能量带来的等离子体诱导损伤、增大工艺调节手段和工艺窗口。目前，制约脉冲射频电源作为等离子体激发源发展的关键因素为其阻抗匹配技术，阻抗匹配也就是使脉冲射频电源的负载阻抗和特征阻抗(一般为50欧姆)相匹配。常见的脉冲射频电源的脉冲频率范围在100～100kHz，占空比范围在10～90％，因此，每个脉冲周期的宽度仅几毫秒，而采用现有的以机械调节方式为主的阻抗匹配装置很难在该几毫秒内实现阻抗匹配，造成匹配精度低，脉冲射频电源的反射功率高(一般为20％)，从而造成脉冲射频电源的利用率差。
为此，现有技术中采用如图1所示的阻抗匹配装置，其以电子调节方式为主，机械调节方式为辅。请参阅图1，该阻抗匹配装置10包括控制单元11、执行单元12和匹配网络13。其中，脉冲射频电源14具有扫频功能，并向控制单元11发送其脉冲同步信号，脉冲同步信号如 图2所示，脉冲射频电源14在高电平时段调制有射频功率信号，在低电平时段未调制有射频功率信号。匹配网络13中设置有阻抗可调元件；脉冲射频电源14在高电平自动进行扫频匹配(即，根据脉冲射频电源14的负载阻抗自动调节到功率输出最大的脉冲频率)；控制单元11根据脉冲同步信号在每个脉冲周期的高电平时实时获取脉冲射频电源14的当前脉冲频率，并根据当前脉冲频率、匹配网络13的电路结构和其阻抗可调元件的当前位置计算脉冲射频电源14的当前负载阻抗，判断当前负载阻抗与其特征阻抗是否匹配，若是，则在当前脉冲周期的低电平时保持阻抗可调元件的当前位置，即保持匹配位置；若否，则在当前脉冲周期的低电平时控制执行单元12调节阻抗可调元件的位置，以调节脉冲射频电源14的负载阻抗来进行阻抗匹配。
图3为反应腔室应用现有的阻抗匹配装置的结构示意图。请参阅图3，反应腔室20的顶部上方设置有感应线圈21，感应线圈21通过第一阻抗匹配装置22与第一射频电源23电连接；在反应腔室20内的底部区域设置有用于承载晶片S的静电卡盘24，静电卡盘24通过第二阻抗匹配装置25与第二射频电源26电连接，其中，第一射频电源23采用连续波信号输出方式，即，第一射频电源23连续输出射频功率信号；第二射频电源26为脉冲射频电源，其射频功率信号的频率为13.56MHz，脉冲同步信号的频率100Hz，占空比为90％，第二阻抗匹配装置25采用图1所示的阻抗匹配装置。
在上述情况下，图4为第二阻抗匹配装置25在阻抗匹配过程的不同时间点的匹配状态的示意图。请参阅图4，具体地，第一脉冲周期：在高电平时段，脉冲射频电源26开始自动扫频匹配，且一直处于“匹配中”状态，即，未能实现阻抗匹配；在低电平时段，控制单元11通过控制执行单元12调节阻抗可调元件的位置进行阻抗匹配。第二脉冲周期：在高电平时段，脉冲射频电源26开始自动扫频匹配，经过时间 T，由“匹配中”状态变化至“匹配”状态，即，从未实现阻抗匹配变化到实现阻抗匹配；在低电平时段，保持匹配位置不变。第三脉冲周期和后续的脉冲周期的匹配过程与第二脉冲周期的匹配过程类似，在此不再赘述。
对应地，图5为用Smith圆图表示的第二射频电源的负载阻抗在其阻抗匹配过程中的阻抗变化轨迹。请参阅图5，Smith圆图的最中心点代表一个已匹配的电阻数值(50欧姆)，该最中心点所在位置称之为阻抗匹配点。在该Smith圆图上，阻抗匹配过程实际上为负载阻抗自该圆图的边缘位置朝向其最中心位置的运动过程，该运动过程具体体现为顺次经历阻抗区1、阻抗区2、阻抗区3和阻抗区4。
其中，脉冲射频电源26未开启时，其负载阻抗为干扰信号引起的阻抗，在Smith圆图上表示为圆圈外的阻抗区1。脉冲射频电源26开启后，在阻抗匹配过程的第一脉冲周期中的高电平时段，当前负载阻抗刚开始时处于阻抗区2，阻抗值约为6∠-86°，此时脉冲射频电源26未实现反应腔室内的起辉；随着脉冲射频电源26自动扫频匹配，当前负载阻抗自阻抗区2逐渐向阻抗匹配位置移动，但仍未移动至阻抗匹配点；在第一脉冲周期中的低电平时段，不进行阻抗匹配，此时负载阻抗位于Smith圆外的阻抗区4，为感应线圈21耦合信号阻抗。在阻抗匹配过程的第二脉冲周期：在高电平时段，由于在第一脉冲周期的低电平时段对阻抗可调元件进行调节，使得刚开始时负载阻抗位于阻抗区2朝向阻抗匹配点移动了一定距离的未起辉阻抗区，使得刚开始脉冲射频电源26未实现起辉，随着脉冲射频电源26自动扫频匹配，当前负载阻抗移动至阻抗区3，阻抗值约为40∠25°，此时，基本实现阻抗匹配；在低电平时，负载阻抗同样位于阻抗区4。第三脉冲周期和后续的脉冲周期对应的负载阻抗的移动过程与第二脉冲周期对应的负载阻抗的移动过程相类似，在此不再赘述。
在实际应用中，采用上述现有的阻抗匹配装置对脉冲射频电源进行阻抗匹配往往会存在以下技术问题：由于脉冲射频电源在工艺过程中的作用是将反应腔室内的工艺气体激发形成等离子体，并且脉冲射频电源的负载阻抗在反应腔室起辉时和实现阻抗匹配时不同，因此，在首次实现阻抗匹配之后，在后续的每个脉冲周期的高电平时段，脉冲射频电源都需要先实现反应腔室起辉再实现阻抗匹配，即，在后续的每个脉冲周期的高电平时段，为了实现工艺气体的起辉，需要将负载阻抗由前一个脉冲周期时所获得的匹配负载阻抗值调整至起辉负载阻抗值，待起辉后，又需要通过诸如前述图4和图5所示的自动扫频匹配过程对负载阻抗进行匹配，直至达到实现匹配时的负载阻抗值。也就是说，采用现有的阻抗匹配装置在后续的每个脉冲周期的高电平时段需要经过较长的自动扫频匹配时间T才能实现阻抗匹配，因而匹配效率低，从而造成工艺的稳定性差和脉冲射频电源的利用率低。
因此，目前亟需一种针对脉冲射频电源能够快速实现阻抗匹配的阻抗匹配方法及装置。
发明内容
本发明旨在解决现有技术中存在的技术问题，提供了一种阻抗匹配装置及半导体加工设备，可以快速地实现针对脉冲射频电源的阻抗匹配，从而可以提高工艺的稳定性和脉冲射频电源的射频能量的利用率。
为解决现有技术中存在的技术问题，本发明提供一种针对脉冲射频电源的阻抗匹配方法，该阻抗匹配方法包括下列步骤：粗调步骤：根据当前负载阻抗进行调节，使当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前位置为起辉位置；微调步骤：保持所述起辉位置不变，根据当前负载阻抗实时调节而实现阻抗匹配，并设置当前位置为匹配位置；切换步骤：在首次实现阻抗匹配后，在后续的各脉冲周期中的不同脉冲时段，在所述起辉 位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。
其中，所述粗调步骤包括下列步骤：
步骤1，实时判断当前反射系数|Γ|是否不大于起辉反射系数|Γt|，若是，执行步骤2；否则，执行所述微调步骤；
步骤2，根据当前负载阻抗实时执行所述粗调步骤；返回步骤1。
其中，所述粗调步骤之前还包括：判断当前是否处于未实现匹配时的脉冲周期的高电平时段，若是，执行所述粗调步骤；否则，保持当前位置不变。
其中，在判断当前处于未实现匹配时的脉冲周期的高电平时段时，所述脉冲射频电源采用扫频模式进行自动阻抗匹配。
其中，所述微调步骤中还包括：在实现阻抗匹配时，保存所述匹配位置。
其中，所述切换步骤包括：在首次实现阻抗匹配后，在后续的各脉冲周期的高电平时段自起辉位置切换至匹配位置，以及在后续的各脉冲周期的低电平时段自匹配位置切换至起辉位置。
作为另一个方面，本发明还提供一种针对脉冲射频电源的阻抗匹配装置，用于实现脉冲射频电源的负载阻抗和特征阻抗相匹配。所述装置包括：粗调单元、微调单元以及切换单元，其中：所述粗调单元，用于根据当前负载阻抗调节当前反射系数|Γ|，使其不大于起辉反射系数|Γt|，并设置当前位置为起辉位置；所述微调单元，用于在当前反射系数|Γ|不大于起辉反射系数|Γt|时，保持所述起辉位置不变，根据当前负载阻抗实时调节实现阻抗匹配，并设置当前位置为匹配位置；所述切换单元，用于在首次实现阻抗匹配后，在后续的各脉冲周期的不同脉冲时段，在所述起辉位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。
其中，所述装置还包括：控制模块、反射系数判断模块和计算模块，其中：所述计算模块，用于在实时计算出所述脉冲射频电源的当前负载阻抗和当前反射系数|Γ|，并将当前负载阻抗发送至所述粗调单元和所述微调单元，以及将当前反射系数|Γ|发送至所述反射系数判断模块。所述反射系数判断模 块，用于判断当前反射系数|Γ|是否不大于起辉反射系数|Γt|，若是，向所述控制模块发送第一标识信号；否则，向所述控制模块发送第二标识信号。所述控制模块，用于在接收到由所述反射系数判断模块发送而来的所述第一标识信号时，触发所述粗调单元；以及在接收到由所述反射系数判断模块发送而来的所述第二标识信号时，触发所述微调单元。
其中，所述粗调单元包括可调电容和/或可调电感，其中：所述粗调单元，根据由所述计算模块发送而来的当前负载阻抗实时调节所述可调电容和/或可调电感的位置，以调节当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前可调电容和/或可调电感的位置为起辉位置。
其中，所述微调单元包括固定电容和/或固定电感以及与其串接的通断开关，其中：所述微调单元根据由计算模块发送而来的当前负载阻抗实时控制所述通断开关接通或断开以实现阻抗匹配，并设置当前所述通断开关的状态为匹配通断状态。
其中，所述装置还包括：脉冲周期判断模块，用于判断当前是否处于未实现匹配时的脉冲周期的高电平时段，若是，触发所述粗调单元；否则，保持当前位置不变。
其中，所述装置还包括：存储模块，用于在所述微调单元根据当前负载阻抗实时调节而实现阻抗匹配时，保存所述匹配位置。
其中，所述切换单元用于在首次实现阻抗匹配后，在后续的各脉冲周期的高电平时段自起辉位置切换至匹配位置，以及在后续的各脉冲周期的低电平时段自匹配位置切换至起辉位置。
本发明具有下述有益效果：
本发明提供的针对脉冲射频电源的阻抗匹配方法，先借助粗调步骤，根据当前负载阻抗进行调节，使当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前位置为起辉位置；再借助微调步骤，保持起辉位置不变，根据当前负载阻抗实时调节实现阻抗匹配，并设置当前位置为 匹配位置；最后借助切换步骤，在首次实现阻抗匹配后，在后续的各脉冲周期中的不同脉冲时段，在起辉位置和匹配位置进行切换，具体地，在后续各脉冲周期的高电平时段，自初始位置切换至匹配位置；在后续各脉冲周期的低电平时段，自匹配位置切换至起辉位置，以此保证下一个脉冲周期的高电平时段直接能够实现起辉，再通过起辉位置切换至匹配位置可实现重新匹配，因此，后续的每个脉冲周期的匹配时间为起辉位置和匹配位置的切换时间，这与现有技术中后续的每个脉冲周期的匹配时间为较长的自动扫频、反复调节负载阻抗而实现匹配的时间相比，可以提高匹配速率，从而可以提高工艺的稳定性和脉冲射频电源的利用率。
本发明提供的针对脉冲射频电源的阻抗匹配装置，借助粗调单元根据当前负载阻抗调节当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前位置为起辉位置；微调单元在当前反射系数|Γ|不大于起辉反射系数|Γt|时，保持起辉位置不变，根据当前负载阻抗实时调节实现阻抗匹配，并设置当前位置为匹配位置，以及，切换单元在首次实现阻抗匹配后续的各脉冲周期的不同脉冲时段，在起辉位置和匹配位置进行切换，具体地，在后续脉冲周期的高电平时段自初始位置切换至匹配位置，在后续脉冲周期的低电平时段自匹配位置切换至起辉位置，以此保证下一个脉冲周期的高电平时段直接能够实现起辉，再通过起辉位置切换至匹配位置可实现重新匹配，因此，后续的每个脉冲周期的匹配时间为起辉位置和匹配位置的切换时间，这与现有技术中后续的每个脉冲周期的匹配时间为较长的自动扫频、反复调节负载阻抗而实现匹配的时间相比，可以提高匹配速率，从而可以提高工艺的稳定性和脉冲射频电源的利用率。
附图说明
图1为应用现有的阻抗匹配装置的原理框图；
图2为脉冲射频电源的脉冲同步信号的波形图；
图3为应用现有的阻抗匹配装置的反应腔室的结构示意图；
图4为第二阻抗匹配装置在阻抗匹配过程的不同时间点的匹配状态的示意图；
图5为第二射频电源的负载阻抗在其阻抗匹配过程中对应在Smith圆图上的轨迹图；
图6为本发明第一实施例提供的针对脉冲射频电源的阻抗匹配方法的流程图；
图7为本发明第二实施例提供的针对脉冲射频电源的阻抗匹配装置的原理框图；
图8为图7中粗调单元和微调单元的示意图；
图9为图7所示的阻抗匹配装置的工作流程图；
图10为阻抗匹配装置在当前反射系数|Γ|大于起辉反射系数|Γt|的情况下进行阻抗匹配的不同时间点的匹配状态示意图；
图11为脉冲射频电源的负载阻抗在其阻抗匹配过程中对应在Smith圆的轨迹图；以及
图12为阻抗匹配装置在当前反射系数|Γ|不大于起辉反射系数|Γt|的情况下进行阻抗匹配的不同时间点的匹配状态示意图。
具体实施方式
为使本领域的技术人员更好地理解本发明的技术方案，下面结合附图对本发明提供的针对脉冲射频电源的阻抗匹配方法及装置进行详细描述。
图6为本发明第一实施例提供的针对脉冲射频电源的阻抗匹配方法的流程图。请参阅图6，本发明第一实施例提供的针对脉冲射频电源 的阻抗匹配方法，用于实现脉冲射频电源的负载阻抗和特征阻抗(例如，可以为50Ω)相匹配，该阻抗匹配方法包括下列步骤：
粗调步骤：根据当前负载阻抗进行调节，使当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前位置为起辉位置。
脉冲射频电源的反射系数|Γ|的物理意义为其负载阻抗点的反射电压波和入射电压波之比，起辉反射系数|Γt|是指脉冲射频电源实现反应腔室起辉时的负载阻抗对应的反射系数|Γ|。对于某一工艺过程而言，实现反应腔室起辉时的脉冲射频电源的负载阻抗和反射系数|Γ|为定值；但是，由于不同工艺过程的腔室压力、工艺气体等参数对脉冲射频电源实现反应腔室起辉具有一定的影响，因此，脉冲射频电源在不同工艺过程中实现反应腔室起辉时的负载阻抗和反射系数|Γ|往往不同。
此处需要对图5进行进一步说明，图5中阻抗区2为高电平时段开始时工艺气体未起辉时的负载阻抗值，阻抗区3为工艺气体起辉稳定后且高电平时段实现基本匹配时的负载阻抗值，在阻抗区2和阻抗区3之间必然存在处于该高电平时段且工艺气体起辉瞬间时的负载阻抗值(图中未标出)，该负载阻抗值接近于阻抗区3。
因此，本发明中粗调步骤的目的就是找到接近于阻抗匹配状态时的负载阻抗值，即在当前反射系数|Γ|由大于起辉反射系数|Γt|向等于起辉反射系数|Γt|的缩小过程中，当前负载阻抗值逐渐接近于匹配状态时的负载阻抗值，即当前负载阻抗值逐步由图5中阻抗区2的范围向阻抗区3的范围移动。规定在当前反射系数|Γ|不大于起辉反射系数|Γt|时，当前的负载阻抗值为工艺气体起辉瞬间的负载阻抗值，因此设置当前状态下各部件的位置为起辉位置，此时还没有实现阻抗匹配。
微调步骤：保持起辉位置不变，根据当前负载阻抗实时进行调节，以实现阻抗匹配，并设置当前位置为匹配位置。
在粗调步骤后，保持起辉位置的各部件不变的基础上，进行微调步 骤，直至找到阻抗匹配时的负载阻抗值，即，使当前负载阻抗值处于图5中的阻抗区3，并保存此时各部件的位置为匹配位置。
上述两个步骤之后，本发明获得了两个位置，即起辉位置和匹配位置，同时完成了对当前脉冲射频电源的首次阻抗匹配。
切换步骤：在首次实现阻抗匹配后，在后续的各脉冲周期中的不同脉冲时段(即，高电平时段和低电平时段)，在起辉位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。具体地，在首次阻抗匹配后的每一脉冲周期中，在高电平时段的初期，各部件处于起辉位置，使工艺气体起辉；而后使各部件自起辉位置状态切换至匹配位置状态，实现阻抗匹配。
由上可知，在位于起辉位置时，当前反射系数|Γ|不大于起辉反射系数|Γt|，此时，脉冲射频电源可以实现工艺气体起辉；之后，在位于匹配位置时，此时，脉冲射频电源可以实现阻抗匹配。因此，在切换步骤中，在首次实现阻抗匹配后的各个后续脉冲周期的高电平时段，不再需要像现有技术中所述的那样通过自动扫频反复调节负载阻抗而进行反复匹配，而只需自起辉位置切换至匹配位置而实现阻抗匹配；并且在后续各脉冲周期的低电平时段，可以将各部件自匹配位置切换至起辉位置，这可以保证在下一个脉冲周期的高电平时段直接实现起辉，再通过自起辉位置切换至匹配位置就可直接重新实现匹配。因此，在本实施例中，在首次实现阻抗匹配后的各个后续脉冲周期的高电平时段，匹配时间为由起辉位置切换至匹配位置的切换时间，所谓匹配时间是指自未匹配状态变换为匹配状态这一匹配过程所用的时间。比较现有技术和本发明实施例可以看出，在首次实现阻抗匹配后的各个后续脉冲周期中，现有技术由于要进行较长时间的自动扫频、反复调节负载阻抗而实现匹配，因此匹配时间较长；而在本发明实施例中，无需进行反复调节负载阻抗，而是仅需将各部件自起辉位置切换至匹配位置而实现匹配，因此 匹配时间短、匹配效率高，因而可以提高工艺的稳定性和脉冲射频电源的利用率。
具体地，在本实施例中，粗调步骤，包括下列步骤：
步骤S1，实时判断当前反射系数|Γ|是否不大于起辉反射系数|Γt|，若是，执行步骤S2；否则，执行微调步骤。
步骤S2，根据当前负载阻抗实时执行粗调步骤；返回步骤S1。
通过步骤S1和步骤S2，可以实现实时判断和调节，直至当前反射系数|Γ|不大于起辉反射系数|Γt|。
优选地，粗调步骤之前，还包括：判断当前是否处于未实现匹配时的脉冲周期的高电平时段，若是，执行粗调步骤；否则，当前为脉冲周期的低电平时段，保持当前位置不变。由此可知，本实施例提供的阻抗匹配方法仅在当前处于未实现匹配时的脉冲周期的高电平时段进行粗调步骤，在低电平时段不动作，这与现有技术中在低电平时段根据高电平时段的最后一个时间点的负载阻抗控制执行机构调节阻抗可调元件相比，可以避免进行“盲调”，因而可以避免发生超调现象，从而可以提高首次实现阻抗匹配的匹配效率。
进一步优选地，在判断当前处于未实现匹配时的脉冲周期的高电平时段时，脉冲射频电源采用扫频模式进行自动阻抗匹配，即，脉冲射频电源自动调节其脉冲频率进行匹配，这不仅可以进一步提高匹配效率，而且可以提高匹配精度。
并且，在微调步骤中，还包括：在实现阻抗匹配时，保存匹配位置。
图7为本发明第二实施例提供的针对脉冲射频电源的阻抗匹配装置的原理框图。请参阅图7，该阻抗匹配装置用于实现脉冲射频电源的负载阻抗和特征阻抗(例如可以为50Ω)相匹配。该阻抗匹配装置包括粗调单元、微调单元和切换单元。其中，粗调单元用于根据当前负载阻抗进行调节，使当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置 当前位置为起辉位置。其中，脉冲射频电源的反射系数|Γ|的物理意义为其负载阻抗点的反射电压波和入射电压波之比，起辉反射系数|Γt|是指脉冲射频电源实现反应腔室起辉时的负载阻抗对应的反射系数|Γ|。对于某一工艺过程而言，实现反应腔室起辉时的脉冲射频电源的负载阻抗和反射系数|Γ|为定值；但是，由于不同工艺过程的腔室压力、工艺气体等参数对脉冲射频电源实现反应腔室起辉具有一定的影响，因此，脉冲射频电源在不同工艺过程中实现反应腔室起辉时的负载阻抗和反射系数|Γ|往往不同。
微调单元用于在当前反射系数|Γ|不大于起辉反射系数|Γt|时，保持起辉位置不变，根据当前负载阻抗实时进行调节，以实现阻抗匹配，并设置当前位置为匹配位置。
切换单元用于在首次实现阻抗匹配后，在后续的同一脉冲周期的不同脉冲时段(即，高电平时段和低电平时段)，在起辉位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。
由上可知，在位于起辉位置时，当前反射系数|Γ|不大于起辉反射系数|Γt|，此时，脉冲射频电源可以实现工艺气体起辉；之后，在位于匹配位置时，脉冲射频电源可以实现阻抗匹配。因此，借助切换单元，在首次实现阻抗匹配后的各个后续脉冲周期的高电平时段，不再需要像现有技术中所述的那样通过自动扫频反复调节负载阻抗而进行反复匹配，而只需自起辉位置切换至匹配位置而实现阻抗匹配，并且在首次实现阻抗匹配后的各个后续脉冲周期的低电平时段，可以自匹配位置切换至起辉位置，这可以保证在下一个脉冲周期的高电平时段直接实现起辉，再通过自起辉位置切换至匹配位置就可直接重新实现匹配。因此，在本实施例中，在首次实现阻抗匹配后的各个后续脉冲周期的高电平时段，匹配时间为由起辉位置切换至匹配位置的切换时间，所谓匹配时间是指自未匹配状态变换为匹配状态这一匹配过程所用的时间。比较现有 技术和本发明实施例可以看出，在首次实现阻抗匹配后的各个后续脉冲周期中，现有技术由于要进行较长时间的自动扫频、反复调节负载阻抗而实现匹配，因此匹配时间较长；而在本发明实施例中，无需进行反复调节负载阻抗，而是仅需将各部件自起辉位置切换至匹配位置而实现匹配，因此匹配时间短、匹配效率高，因而可以提高工艺的稳定性和脉冲射频电源的利用率。
在本实施例中，阻抗匹配装置还包括控制模块、计算模块和判断模块。其中，计算模块用于实时计算出脉冲射频电源的当前负载阻和当前反射系数|Γ|，并将当前负载阻抗发送至粗调单元和微调单元，以及将当前反射系数|Γ|发送至反射系数判断模块。反射系数判断模块用于判断当前反射系数|Γ|是否不大于起辉反射系数|Γt|，若是，向控制模块发送第一标识信号，例如为高电平“1”；否则，向控制模块发送第二标识信号，例如为低电平“0”。控制模块用于在接收到第一标识信号时，触发粗调单元；以及在接收到第二标识信号时，触发微调单元。
其中，粗调单元包括可调电容和/或可调电感，在这种情况下，粗调单元根据由计算模块发送而来的当前负载阻抗实时调节可调电容和/或可调电感，将当前反射系数|Γ|调节至不大于起辉反射系数|Γt|，以使工艺气体起辉，并将当前可调电容和/或可调电感的位置设置为起辉位置。为了对可调电容和/或可调电感进行调节，粗调单元还包括电机等，电机可以为步进电机。如图8所示，本实施例中的粗调单元包括可调电容C1和C2；驱动电机M1与可调电容C1的调节端连接，用于对可调电容C1进行调节；驱动电机M2与可调电容C2的调节端连接，用于对可调电容C2进行调节。
微调单元包括固定电容和/或固定电感以及与其串接的通断开关，如图8所示，微调单元包括两个支路，其中一个支路包括串接的通断开关K1和固定电容C11，另一个支路包括串接的通断开关K2和固定电 容C12，通断开关K1和K2包括二极管或继电器等电子开关。在这种情况下，微调单元根据由计算模块发送而来的当前负载阻抗而实时控制通断开关(K1和K2)接通或断开，以实现阻抗匹配，并将实现阻抗匹配时的通断开关(K1和K2)的状态设置为匹配通断状态(也称为“匹配位置”)，例如，若实现阻抗匹配时通断开关K1接通K2断开，则匹配通断状态(匹配位置)为通断开关K1接通K2断开。
另外，本实施例提供的阻抗匹配装置还包括存储模块，存储模块用于在微调单元根据当前负载阻抗实时调节而实现阻抗匹配时，保存匹配位置，具体地，保存通断开关K1和K2的通断状态。
优选地，在本实施例中，阻抗匹配装置还包括脉冲周期判断模块，脉冲周期判断模块用于判断当前是否处于未实现匹配时的脉冲周期的高电平时段，若是，触发粗调单元；否则，保持当前位置不变，即，C1、C2、K1和K2各自保持位置不变。由此可知，本实施例提供的阻抗匹配装置在尚未首次实现阻抗匹配时，若当前处于高电平时段时，则触发粗调单元；若当前处于低电平时段，则不动作。这与现有技术中在尚未首次实现阻抗匹配时，在低电平时段根据高电平时段的最后一个时间点的负载阻抗控制执行机构调节阻抗可调元件相比，可以避免进行“盲调”，因而可以避免发生超调现象，从而可以提高首次实现阻抗匹配的匹配效率。
另外，在本实施例中，脉冲射频电源具有自动扫频模式，用以在尚未首次实现阻抗匹配时进行当前是否处于高电平时段的判断时，进行自动阻抗匹配，即，自动调节其脉冲频率进行匹配。可以理解，借助脉冲射频电源在脉冲周期的高电平时进行自动扫频匹配，不仅可以进一步提高匹配效率，还可以提高匹配精度。
下面通过实验验证本实施例提供的阻抗匹配装置是如何提高阻抗匹配速率的。本实验采用图3所示的反应腔室，其中的第二阻抗匹配装 置应用本发明上述实施例提供的阻抗匹配装置，其他参数与现有技术相同。
在上述情况下，若刚开始匹配的当前反射系数|Γ|大于起辉反射系数|Γt|，则结合图9、图10和图11进行说明。
如图9、图10和图11所示，在脉冲射频电源未开启时，其负载阻抗为干扰信号引起的阻抗，在Smith圆图上表示为圆圈外的阻抗区A。在脉冲射频电源开启后，其将脉冲同步信号发送至脉冲周期判断模块，脉冲周期判断模块实时判断当前是否为第一脉冲周期的高电平时段。一方面，脉冲周期判断模块判断出当前为第一脉冲周期高电平时段，则脉冲射频电源进行自动扫频匹配；并且，计算模块开始实时计算当前负载阻抗和当前反射系数|Γ|，并将当前负载阻抗发送至粗调单元和微调单元，将当前反射系数|Γ|发送至反射系数判断模块，在整个高电平时段T1内，反射系数判断模块实时判断出来自计算模块的当前反射系数|Γ|大于起辉反射系数|Γt|，则说明反应腔室内的工艺气体未实现起辉，该反射系数判断模块向控制模块发送第一标识信号“1”，控制模块在接收到该第一标识信号“1”时，触发粗调单元，使其根据来自计算模块的当前负载阻抗而实时调节可调电容C1和C2，即，采用“电机匹配模式”进行匹配，在该匹配过程中，脉冲射频电源的负载阻抗自未起辉阻抗区(图11中未示出)向匹配阻抗区C移动，并且，在该匹配过程中，通断开关K1和K2不动作而位于初始通断状态。
另一方面，若脉冲周期判断模块实时判断出当前为第一脉冲周期的低电平时段，则保持可调电容C1和C2的当前位置不变，等待下一个脉冲周期，以便在下一个脉冲周期的高电平时段继续向阻抗匹配区C移动。此时，脉冲射频电源的负载阻抗位于阻抗区D，为感应线圈耦合信号阻抗。
若脉冲周期判断模块判断出当前为第二脉冲周期的高电平时段，则 脉冲射频电源进行自动扫频匹配；并且，计算模块开始实时计算当前负载阻抗和当前反射系数|Γ|，并将当前负载阻抗发送至粗调单元和微调单元，以及将当前反射系数|Γ|发送至反射系数判断模块，若反射系数判断模块在时间段T2内实时判断出来自计算模块的当前反射系数|Γ|大于起辉反射系数|Γt|，则说明反应腔室未实现起辉，且反射系数判断模块向控制模块发送第一标识信号“1”，控制模块在接收到来自判断模块发送而来的第一标识信号“1”时，触发粗调单元，采用“电机匹配模式”继续进行匹配，负载阻抗继续向阻抗匹配区C移动；反射系数判断模块在时间点t2判断来自计算模块的当前反射系数|Γ|不大于起辉反射系数|Γt|，则说明反应腔室实现起辉，此时，当前负载阻抗移动至实现反应腔室起辉所对应的阻抗区B，反射系数判断模块向控制模块发送第二标识信号“0”，控制模块在接收到该第二标识信号“0”时，触发微调单元，于是可调电容C1和C2的当前位置(即，起辉位置)保持不变，而是根据由计算模块发送而来的当前负载阻抗实时控制通断开关K1和K2接通或断开，即采用“开关匹配模式”进行匹配，经过通断开关K1和K2的通断响应时间T3(即，切换时间)而实现阻抗匹配，此时，当前负载阻抗经过通断响应时间T3快速地自阻抗区B移动至阻抗匹配点附近的阻抗匹配区C，此时，由于脉冲射频电源自动扫频匹配而实现负载阻抗移动至阻抗匹配点；并且，在采用“开关匹配模式”实现阻抗匹配时，存储模块将通断开关K1和K2的当前通断状态保存为匹配通断状态。
当脉冲周期判断模块实时判断当前为第二脉冲周期的低电平时段时，虽然其高电平时段已实现阻抗匹配，但需要对下一个脉冲周期重新进行阻抗匹配，因此，保持可调电容C1和C2的起辉位置不变，使通断开关K1和K2自匹配通断状态切换至初始通断状态，在该低电平时段，脉冲射频电源的负载阻抗位于阻抗区D，为感应线圈耦合信号阻抗。
当脉冲周期判断模块判断出当前为第三脉冲周期的高电平时段时，脉冲射频电源自动扫频匹配，计算模块实时计算当前负载阻抗和当前反射系数，并将当前负载阻抗发送至粗调单元和微调单元，以及将当前反射系数发送至反射系数判断模块，由于可调电容C1和C2处于起辉位置，通断开关K1和K2位于初始通断状态，因此，反射系数判断模块判断出来自计算模块的当前反射系数|Γ|不大于起辉反射系数|Γt|，此时，说明反应腔室已实现起辉，负载阻抗位于阻抗区B，反射系数判断模块向控制模块发送第二标识信号“0”，控制模块在接收到该第二标识信号“0”时，触发微调单元，保持可调电容C1和C2的起辉位置不变，直接控制通断开关K1和K2自初始通断状态切换至匹配通断状态，经过通断开关K1和K2的切换时间T3实现阻抗匹配，负载阻抗经过时间T3快速地自阻抗区B移动至阻抗匹配点附近的阻抗匹配区C，并通过脉冲射频电源自动扫频匹配实现负载阻抗位于阻抗匹配点。
当脉冲周期判断模块判断出当前为第三脉冲周期的低电平时段时，虽然其高电平时段已实现阻抗匹配，但需要对下一个脉冲周期重新进行阻抗匹配，因此，继续保持可调电容C1和C2的起辉位置不变，使通断开关K1和K2自匹配通断状态切换至起辉通断状态，在该低电平时段，脉冲射频电源的负载阻抗位于阻抗区D，为感应线圈耦合信号阻抗。
第四脉冲周期和后续的每个脉冲周期的高电平和低电平时段的情况均与第三脉冲周期高电平时段和低电平时段的情况相同，维持该规律直至工艺结束。
若刚开始匹配的当前反射系数|Γ|不大于起辉反射系数|Γt|，则结合图9、图11和图12进行说明。
如图9、图11和图12所示，在脉冲射频电源未开启时，其负载阻抗位于Smith圆外的阻抗区A，为干扰信号引起的阻抗。在脉冲射频电源开启后，其将脉冲同步信号发送至脉冲周期判断模块，脉冲周期判断 模块实时判断当前是否为第一脉冲周期的高电平时段。一方面，脉冲周期判断模块实时判断出当前为第一脉冲周期高电平时段，则脉冲射频电源进行自动扫频匹配；并且，计算模块开始实时计算当前负载阻抗和当前反射系数|Γ|，将当前负载阻抗发送至粗调单元和微调单元，并将当前反射系数|Γ|发送至反射系数判断模块，反射系数判断模块在时间点t2判断出当前反射系数|Γ|不大于起辉反射系数|Γt|，则说明时间点t2时反应腔室已实现起辉，当前负载阻抗位于阻抗区B，反射系数判断模块向控制模块发送第二标识信号“0”，控制模块在接收到该第二标识信号“0”时，触发微调单元，保持可调电容C1和C2的起辉位置(即，初始位置)不变，根据由计算模块发送而来的当前负载阻抗实时控制通断开关K1和K2接通或断开，即，采用“开关匹配模式”进行匹配，经过通断开关K1和K2的通断响应时间T3实现阻抗匹配，此时，负载阻抗经过时间T3快速地自阻抗区B移动至阻抗匹配点附近的阻抗匹配区C，并通过脉冲射频电源自动扫频匹配实现负载阻抗位于阻抗匹配点；并且，在采用“开关匹配模式”实现阻抗匹配时，存储模块保存通断开关K1和K2的当前通断状态为匹配通断状态。
另一方面，若脉冲周期判断模块实时判断出当前为第一脉冲周期的低电平时段，那么，虽然在高电平时段已实现阻抗匹配，但需要在下一个脉冲周期重新进行阻抗匹配，因此，保持可调电容C1和C2的位置不变，使通断开关K1和K2自匹配通断状态切换至初始通断状态。并且，在该低电平时段，脉冲射频电源的负载阻抗位于阻抗区D，为感应线圈耦合信号阻抗。
若脉冲周期判断模块判断出当前为第二脉冲周期的高电平时段，则脉冲射频电源自动扫频匹配，并且，计算模块实时计算当前负载阻抗和当前反射系数|Γ|，并将当前负载阻抗发送至粗调单元和微调单元，以及将当前反射系数|Γ|发送至反射系数判断模块，由于可调电容C1和 C2处于起辉位置，通断开关K1和K2位于初始通断状态，因此，反射系数判断模块直接判断出来自计算模块的当前反射系数|Γ|不大于起辉反射系数|Γt|，此时，说明反应腔室已实现起辉，且负载阻抗位于阻抗区B，反射系数判断模块向控制模块发送第二标识信号“0”，控制模块在接收到该第二标识信号“0”时，触发微调单元，保持可调电容C1和C2的起辉位置不变，直接控制通断开关K1和K2自初始通断状态切换至匹配通断状态，经过通断开关K1和K2的切换时间T3实现阻抗匹配，负载阻抗经过切换时间T3快速地自阻抗区B移动至阻抗匹配点附近的阻抗匹配区C，并通过脉冲射频电源自动扫频匹配实现负载阻抗位于阻抗匹配点。
若脉冲周期判断模块判断出当前为第二脉冲周期的低电平时段，那么，虽然其高电平时段已实现阻抗匹配，但需要在下一个脉冲周期重新进行阻抗匹配，因此，继续保持可调电容C1和C2的位置不变，使通断开关K1和K2自匹配通断状态切换至初始通断状态，在该低电平时段，脉冲射频电源的负载阻抗位于阻抗区D，为感应线圈耦合信号阻抗。
第三脉冲周期和后续的每个脉冲周期的高电平和低电平时段的情况均与第二脉冲周期的高电平和低电平时段的情况相同，维持该规律直至工艺结束。
对比图4、图10和图12可以看出，图4所示现有技术在首次实现阻抗匹配之后，后续的每个脉冲周期需要经过较长的时间T才能实现阻抗匹配；而图10和图12所示本发明实施例在首次实现阻抗匹配之后，后续的每个脉冲周期仅需要经过切换时间或通断响应时间T3就可实现阻抗匹配，且T3＜T，由此可见，本发明实施例可以提高脉冲射频电源的匹配效率。
需要说明的是，在本实施例中，阻抗匹配装置的匹配网络的电路结构为L型。但是，本发明并不局限于此，在实际应用中，匹配网络的电 路结构还可以包括倒L型、T型或者π型等。
还需要说明的是，尽管本实施例中微调单元包括固定电容和/或固定电感以及与之串接的通断开关，且通过通断开关的接通和断开实现在起辉位置和匹配位置之间的切换，但是，本发明并不局限于此，在实际应用中，还可以采用其他方式快速地在起辉位置和匹配位置进行切换。进一步地，尽管本实施例中微调单元的两个分支中分别接入了一个固定电容及与之串接的一个通断开关，但是本发明并不局限于此，在实际应用中，每一个支路可以包括多个电容和/或电感及多个与之串联的通断开关，借助于各个通断开关闭合状态的组合而改变微调单元的电抗数值。
另外需要说明的是，本实施例提供的阻抗匹配装置对脉冲射频电源30的射频频率并不限制，例如，射频频率为400KHz、2MHz、3MHz、27MHz、40MHz或者60MHz等；且对脉冲射频电源30的脉冲频率和脉冲占空比也不作限制，例如，脉冲频率可以在1MHz以内，脉冲占空比可以取小于1的任意值。
可以理解的是，以上实施方式仅仅是为了说明本发明的原理而采用的示例性实施方式，然而本发明并不局限于此。对于本领域内的普通技术人员而言，在不脱离本发明的原理和实质的情况下，可以做出各种变型和改进，这些变型和改进也视为本发明的保护范围。

Claims (13)

  1. 一种针对脉冲射频电源的阻抗匹配方法，其特征在于，所述阻抗匹配方法，包括下列步骤：
    粗调步骤：根据当前负载阻抗进行调节，使当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前位置为起辉位置；
    微调步骤：保持所述起辉位置不变，根据当前负载阻抗实时调节而实现阻抗匹配，并设置当前位置为匹配位置；
    切换步骤：在首次实现阻抗匹配后，在后续的各脉冲周期中的不同脉冲时段，在所述起辉位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。
  2. 根据权利要求1所述的针对脉冲射频电源的阻抗匹配方法，其特征在于，所述粗调步骤，包括下列步骤：
    步骤1，实时判断当前反射系数|Γ|是否不大于起辉反射系数|Γt|，若是，执行步骤2；否则，执行所述微调步骤；
    步骤2，根据当前负载阻抗实时执行所述粗调步骤；返回步骤1。
  3. 根据权利要求1所述的针对脉冲射频电源的阻抗匹配方法，其特征在于，所述粗调步骤之前，还包括：
    判断当前是否处于未实现匹配时的脉冲周期的高电平时段，若是，执行所述粗调步骤；否则，保持当前位置不变。
  4. 根据权利要求3所述的针对脉冲射频电源的阻抗匹配方法，其特征在于，在判断当前处于未实现匹配时的脉冲周期的高电平时段时，所述脉冲射频电源采用扫频模式进行自动阻抗匹配。
  5. 根据权利要求1所述的针对脉冲射频电源的阻抗匹配方法，其特征在于，所述微调步骤中，还包括：
    在实现阻抗匹配时，保存所述匹配位置。
  6. 根据权利要求1所述的针对脉冲射频电源的阻抗匹配方法，其特征在于，所述切换步骤，包括：
    在首次实现阻抗匹配后，在后续的各脉冲周期的高电平时段自起辉位置切换至匹配位置，以及在后续的各脉冲周期的低电平时段自匹配位置切换至起辉位置。
  7. 一种针对脉冲射频电源的阻抗匹配装置，用于实现脉冲射频电源的负载阻抗和特征阻抗相匹配，其特征在于，所述装置包括：粗调单元、微调单元以及切换单元，其中：
    所述粗调单元，用于根据当前负载阻抗调节当前反射系数|Γ|，使其不大于起辉反射系数|Γt|，并设置当前位置为起辉位置；
    所述微调单元，用于在当前反射系数|Γ|不大于起辉反射系数|Γt|时，保持所述起辉位置不变，根据当前负载阻抗实时调节实现阻抗匹配，并设置当前位置为匹配位置；
    所述切换单元，用于在首次实现阻抗匹配后，在后续的各脉冲周期的不同脉冲时段，在所述起辉位置和匹配位置进行切换，以实现不同脉冲周期下的阻抗匹配。
  8. 根据权利要求7所述的针对脉冲射频电源的阻抗匹配装置，其特征在于，所述装置还包括：控制模块、反射系数判断模块和计算模块，其中：
    所述计算模块，用于在实时计算出所述脉冲射频电源的当前负载阻抗和当前反射系数|Γ|，并将当前负载阻抗发送至所述粗调单元和所述微调单元，以及将当前反射系数|Γ|发送至所述反射系数判断模块；
    所述反射系数判断模块，用于判断当前反射系数|Γ|是否不大于起辉反射系数|Γt|，若是，向所述控制模块发送第一标识信号；否则，向所述控制模块发送第二标识信号；
    所述控制模块，用于在接收到由所述反射系数判断模块发送而来的所述第一标识信号时，触发所述粗调单元；以及在接收到由所述反射系数判断模块发送而来的所述第二标识信号时，触发所述微调单元。
  9. 根据权利要求8所述的针对脉冲射频电源的阻抗匹配装置，其特征在于，所述粗调单元包括可调电容和/或可调电感，其中：
    所述粗调单元，根据由所述计算模块发送而来的当前负载阻抗实时调节所述可调电容和/或可调电感的位置，以调节当前反射系数|Γ|不大于起辉反射系数|Γt|，并设置当前可调电容和/或可调电感的位置为起辉位置。
  10. 根据权利要求8所述的针对脉冲射频电源的阻抗匹配装置，其特征在于，所述微调单元包括固定电容和/或固定电感以及与其串接的通断开关，其中：
    所述微调单元根据由计算模块发送而来的当前负载阻抗实时控制所述通断开关接通或断开以实现阻抗匹配，并设置当前所述通断开关的状态为匹配通断状态。
  11. 根据权利要求7所述的针对脉冲射频电源的阻抗匹配装置，其特征在于，所述装置还包括：
    脉冲周期判断模块，用于判断当前是否处于未实现匹配时的脉冲周期的高电平时段，若是，触发所述粗调单元；否则，保持当前位置不变。
  12. 根据权利要求7所述的针对脉冲射频电源的阻抗匹配装置，其特征在于，所述装置，还包括：
    存储模块，用于在所述微调单元根据当前负载阻抗实时调节而实现阻抗匹配时，保存所述匹配位置。
  13. 根据权利要求7所述的针对脉冲射频电源的阻抗匹配装置，其特征在于，所述切换单元，用于在首次实现阻抗匹配后，在后续的各脉冲周期的高电平时段自起辉位置切换至匹配位置，以及在后续的各脉冲周期的低电平时段自匹配位置切换至起辉位置。
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