A real-time load impedance detection and fast matching method

Abstract

The present invention discloses a real-time load impedance detection and fast matching method. First, a voltage amplitude and phase detection module and a capacitance adjustment module are connected to an L-type impedance matching network. The voltage amplitude and phase detection module is used to measure the voltages at different positions of the L-type impedance matching network, and the capacitance adjustment module is used to adjust the capacitance value of the adjustable capacitor in the L-type impedance matching network. Then, the impedance value of the load is calculated from the real-time detection values of the voltage amplitude and phase detection module, and then the input impedance value and voltage reflection coefficient at the input end are calculated in sequence. Finally, the voltage reflection coefficient at the input end is compared with a set threshold. When it is greater than the threshold, the capacitance value required for the adjustable capacitor in the L-type impedance matching network is calculated and the adjustable capacitor is adjusted; otherwise, no adjustment is made. The present invention quickly adjusts the impedance matching network according to the load impedance value, realizes the matching of the load impedance, and reduces the loss of reflected power.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency impedance matching, and specifically to a method for real-time load impedance detection and rapid matching. Background Art

[0002] Radio frequency power supplies are widely used in fields such as plasma heating and semiconductor processes. Generally, such applications require a stable feed-in of radio frequency power. However, in reality, since the load connected to the radio frequency power supply is usually a plasma, due to the constantly changing state of the plasma and its non-linear effects, the equivalent load impedance value is not constant and fluctuates within a large range. The change in load impedance results in a large mismatch between the radio frequency power supply and the load, and a large part of the power entering the load is reflected back to the radio frequency power supply. On the one hand, the changing power entering the load causes instability in the process state; on the other hand, the reflected power causes power waste, and the large reflected power entering the radio frequency power supply may also damage the radio frequency power supply. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for real-time load impedance detection and rapid matching, which can quickly adjust the impedance matching network according to the load impedance value to achieve the matching of the load impedance and reduce the loss of reflected power.

[0004] The technical solution of the present invention is as follows:

[0005] A method for real-time load impedance detection and rapid matching specifically includes the following steps:

[0006] (1) Connect a voltage amplitude and phase detection module and a capacitance adjustment module to the L-type impedance matching network. The voltage amplitude and phase detection module includes a first voltage detection unit and a second voltage detection unit. One end of the first voltage detection unit is connected to the input end of the L-type impedance matching network and the other end is grounded. One end of the second voltage detection unit is connected to the output end of the L-type impedance matching network and the other end is grounded. The output end of the L-type impedance matching network is connected to the load, and the input end is connected to the radio frequency power supply; the capacitance adjustment module is used to adjust the capacitance value of the adjustable capacitor in the L-type impedance matching network;

[0007] (2) Calculate the impedance value of the load from the voltage amplitude and phase detected in real time by the voltage amplitude and phase detection module, then calculate the input impedance value at the input end from the impedance value of the load, and then calculate the voltage reflection coefficient at the input end from the input impedance value at the input end;

[0008] (3) Compare the voltage reflection coefficient at the input end with a set threshold: When the voltage reflection coefficient is greater than the threshold, calculate the capacitance value required for the adjustable capacitor in the L-type impedance matching network, and adjust the adjustable capacitor in the L-type impedance matching network to the required capacitance value through the capacitance adjustment module; when the voltage reflection coefficient is less than the threshold, keep the capacitance value of the adjustable capacitor unchanged.

[0009] The L-type impedance matching network includes a first adjustable capacitor, a second adjustable capacitor, and a first inductor. The first adjustable capacitor is connected in parallel to the input end of the L-type impedance matching network. The first inductor and the second adjustable capacitor are connected in series between the input end and the output end of the L-type impedance matching network. The capacitance adjustment module includes a first capacitance adjustment component for adjusting the capacitance value of the first adjustable capacitor and a second capacitance adjustment component for adjusting the capacitance value of the second adjustable capacitor.

[0010] The first voltage detection unit and the second voltage detection unit are equivalent to two third capacitors and fourth capacitors connected in parallel to ground. One end of the third capacitor is connected to the input end of the L-type impedance matching network and the other end is grounded. One end of the fourth capacitor is connected to the output end of the L-type impedance matching network and the other end is grounded.

[0011] The impedance value of the load is calculated from the voltage amplitude and phase detected in real time by the voltage amplitude and phase detection module. The calculation process is shown in Equation (1) below:

[0012] (1);

[0013] In Equation (1), is the impedance value of the load, represents the voltage value detected in real time by the first voltage detection unit, represents the voltage value detected in real time by the second voltage detection unit, represents the imaginary unit, is the angular frequency, represents the capacitance value of the first adjustable capacitor, represents the capacitance value of the second adjustable capacitor, represents the inductance value of the first inductor;

[0014] The and are calculated by Equation (2) below:

[0015] (2);

[0016] In Equation (2), represents the amplitude value detected in real time by the first voltage detection unit, represents the The amplitude value, represents the phase value detected in real time by the first voltage detection unit, represents the phase value detected in real time by the second voltage detection unit.

[0017] The input impedance value of the input end calculated from the impedance value of the load. The calculation process is shown in the following formula (3):

[0018] (3);

[0019] In formula (3), represents the input impedance value of the input end, represents the sum of the impedance values of the second adjustable capacitor, the first inductor and the load, represents the imaginary unit, is the angular frequency, represents the capacitance value of the first adjustable capacitor, represents the capacitance value of the second adjustable capacitor, represents the inductance value of the first inductor.

[0020] The voltage reflection coefficient of the input end calculated from the input impedance value of the input end. The calculation process is shown in the following formula (4):

[0021] (4);

[0022] In formula (4), represents the voltage reflection coefficient of the input end; represents the characteristic impedance.

[0023] The capacitance value required for the adjustable capacitor in the L-type impedance matching network is calculated. Specifically, the capacitance values required for the first adjustable capacitor and the second adjustable capacitor in the L-type impedance matching network are calculated by the following formula (5) and :

[0024] (5);

[0025] In formula (5), represents the real part of the load impedance, represents the imaginary part of the load impedance, is the angular frequency, represents the inductance value of the first inductor, represents the real part of the impedance of the RF power supply.

[0026] Advantages of the present invention:

[0027] (1). The present invention is provided with a voltage amplitude and phase detection module to collect the voltage amplitude and phase information at the input and output ends of the impedance matching network. The phases of the two voltages are relative values, thus canceling out the extra errors introduced due to the defects in the acquisition accuracy. Compared with the method of simultaneously measuring voltage and current by the vector voltammetry method, the difficulty of circuit design is reduced, and the result is more accurate.

[0028] (2). The present invention quickly calculates the load impedance value based on the voltages collected by the voltage amplitude and phase detection module, and then calculates the matching network and adjusts the value of the adjustable capacitance element to achieve the matching of the load impedance, reduce the reflection power loss, with a simple circuit structure and high load impedance measurement accuracy, and can be used in an automatic impedance matching system. Description of the Drawings

[0029] Figure 1 is the equivalent circuit diagram composed of the L-type impedance matching network, voltage amplitude and phase detection module, and capacitance adjustment module of the present invention.

[0030] Figure 2 is the circuit diagram of the L-type impedance matching network of the present invention connected between the RF power supply and the load. Detailed Embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] A real-time load impedance detection and rapid matching method specifically includes the following steps:

[0033] (1). See Figure 1 and Figure 2 , connect the voltage amplitude and phase detection module and the capacitance adjustment module to the L-type impedance matching network. The L-type impedance matching network includes a first adjustable capacitor C1, a second adjustable capacitor C2, and a first inductor L1. The first adjustable capacitor C1 is connected in parallel with the input end P1 of the L-type impedance matching network. The first inductor L1 and the second adjustable capacitor C2 are connected in series between the input end P1 and the output end P2 of the L-type impedance matching network. The input end P1 of the L-type impedance matching network is connected to the RF power supply RFPS, and the output end P2 is connected to the load ZL.

[0034] The voltage amplitude and phase detection module includes a first voltage detection unit and a second voltage detection unit. The first voltage detection unit and the second voltage detection unit are equivalent to two third capacitors C3 and fourth capacitors C4 connected in parallel to the ground. One end of the third capacitor C3 is connected to the input end P1 of the L-type impedance matching network, and the other end is grounded. One end of the fourth capacitor C4 is connected to the output end P2 of the L-type impedance matching network, and the other end is grounded;

[0035] The capacitance adjustment module includes a first capacitance adjustment component T1 for adjusting the capacitance value of the first adjustable capacitor and a second capacitance adjustment component T2 for adjusting the capacitance value of the second adjustable capacitor. The first capacitance adjustment component T1 and the second capacitance adjustment component T2 can be selected as stepping motors. The stepping motors drive the sliding ends of the first adjustable capacitor C1 and the second adjustable capacitor C2 to slide to achieve capacitance adjustment, or other adjustment structures can be used to achieve controllable adjustment of the capacitance values of the first adjustable capacitor C1 and the second adjustable capacitor C2;

[0036] Among them, the first inductor L1 can also be provided with multiple gears to increase the adjustment range of impedance matching;

[0037] (2) First, calculate the impedance value of the load from the voltage amplitude and phase detected in real time by the voltage amplitude and phase detection module. The calculation process is shown in the following formula (1):

[0038] (1);

[0039] In formula (1), is the impedance value of the load, represents the voltage value detected in real time by the first voltage detection unit, represents the voltage value detected in real time by the second voltage detection unit, represents the imaginary unit, is the angular frequency, represents the capacitance value of the first adjustable capacitor C1, represents the capacitance value of the second adjustable capacitor C2, represents the inductance value of the first inductor L1;

[0040] and are calculated from the following formula (2):

[0041] (2);

[0042] In formula (2), represents the amplitude value detected in real time by the first voltage detection unit, represents the amplitude value detected in real time by the second voltage detection unit, The phase value detected in real time by the first voltage detection unit , The phase value detected in real time by the second voltage detection unit ;

[0043] Then, the input impedance value of the input terminal P1 is calculated from the impedance value of the load ZL . The calculation process is shown in the following formula (3):

[0044] (3);

[0045] In formula (3), represents the input impedance value of the input terminal, represents the sum of the impedance values of the second adjustable capacitor C2, the first inductor L1 and the load ZL, represents the imaginary unit, is the angular frequency, represents the capacitance value of the first adjustable capacitor C1, represents the capacitance value of the second adjustable capacitor C2, represents the inductance value of the first inductor L1;

[0046] Then, the voltage reflection coefficient of the input terminal is calculated from the input impedance value of the input terminal P1 . The calculation process is shown in the following formula (4): (4);

[0047] In formula (4),

[0048] represents the voltage reflection coefficient of the input terminal P1; represents the characteristic impedance, and its value is 50Ω;

[0049] (3) Compare the voltage reflection coefficient of the input terminal with the set threshold value (1%): When the voltage reflection coefficient is greater than the threshold value, the capacitance values required for the first adjustable capacitor and the second adjustable capacitor in the L-type impedance matching network are calculated by the following formula (5), and the adjustable capacitors in the L-type impedance matching network are adjusted to the required capacitance values through the capacitance adjustment module; when the voltage reflection coefficient is less than the threshold value, the capacitance values of the adjustable capacitors remain unchanged.

[0050] Calculate the capacitance values required for the adjustable capacitors in the L-type impedance matching network. Specifically, the capacitances required for the first adjustable capacitor and the second adjustable capacitor in the L-type impedance matching network are calculated by the following formula (5) values and :

[0051] (5); ​

[0052] In Equation (5), represents the real part of the load impedance, represents the imaginary part of the load impedance, represents the capacitance value required for the first adjustable capacitor in the L-type impedance matching network, represents the capacitance value required for the second adjustable capacitor in the L-type impedance matching network, is the angular frequency, represents the inductance value of the first inductor, represents the real part of the RF power supply impedance.

[0053] Among them, Equation (5) is derived from the following steps:

[0054] When impedance matching is performed, for the ideal matching (i.e., no reflection) case, the output impedance of the L-type impedance matching network satisfies the following Equation (6):

[0055] (6);

[0056] In Equation (6), is the conjugate of the load impedance;

[0057] At the same time, since , ; among them, is the real part of the output impedance, is the imaginary part of the output impedance, is the real part of the load impedance, the imaginary part of the load impedance; thus, the following Equation (7) is obtained:

[0058] (7);

[0059] Then, substitute the expressions of the real part and the imaginary part of the output impedance, that is, Equation (6), into Equation (7), and Equation (5) is obtained;

[0060] (8);

[0061] Among them, the input impedance value and the RF power supply impedance are in a conjugate relationship, is the RF power supply impedance 's real part.

[0062] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A real-time load impedance detection and fast matching method, characterized in that: Specifically, it includes the following steps: (1) Connect a voltage amplitude and phase detection module and a capacitance adjustment module to the L-type impedance matching network. The voltage amplitude and phase detection module includes a first voltage detection unit and a second voltage detection unit. One end of the first voltage detection unit is connected to the input end of the L-type impedance matching network and the other end is grounded. One end of the second voltage detection unit is connected to the output end of the L-type impedance matching network and the other end is grounded. The output end of the L-type impedance matching network is connected to the load and the input end is connected to the RF power supply. The capacitance adjustment module is used to adjust the capacitance value of the adjustable capacitor in the L-type impedance matching network; (2) Calculate the impedance value of the load from the voltage amplitude and phase detected in real time by the voltage amplitude and phase detection module, then calculate the input impedance value of the input end from the impedance value of the load, and then calculate the voltage reflection coefficient of the input end from the input impedance value of the input end; (3) Compare the voltage reflection coefficient of the input end with a set threshold: when the voltage reflection coefficient is greater than the threshold, calculate the capacitance value required for the adjustable capacitor in the L-type impedance matching network, and adjust the adjustable capacitor in the L-type impedance matching network to the required capacitance value through the capacitance adjustment module; when the voltage reflection coefficient is less than the threshold, keep the capacitance value of the adjustable capacitor unchanged; The L-type impedance matching network includes a first adjustable capacitor, a second adjustable capacitor and a first inductor. The first adjustable capacitor is connected in parallel with the input end of the L-type impedance matching network. The first inductor and the second adjustable capacitor are connected in series between the input end and the output end of the L-type impedance matching network. The capacitance adjustment module includes a first capacitance adjustment component for adjusting the capacitance value of the first adjustable capacitor and a second capacitance adjustment component for adjusting the capacitance value of the second adjustable capacitor; The impedance value of the load is calculated from the voltage amplitude and phase detected in real time by the voltage amplitude and phase detection module. The calculation process is shown in the following formula (1): （1）； In formula (1), is the impedance value of the load, represents the voltage value detected in real time by the first voltage detection unit, represents the voltage value detected in real time by the second voltage detection unit, represents the imaginary unit, is the angular frequency, represents the capacitance value of the first adjustable capacitor, represents the capacitance value of the second adjustable capacitor, represents the inductance value of the first inductor; The described and is calculated by the following formula (2): （2）； In formula (2), represents the amplitude value of detected in real time by the first voltage detection unit, represents the amplitude value of detected in real time by the second voltage detection unit, represents the phase value of detected in real time by the first voltage detection unit, represents the phase value of detected in real time by the second voltage detection unit.

2. The real-time load impedance detection and fast matching method according to claim 1, wherein: The first voltage detection unit and the second voltage detection unit are equivalent to two third capacitors and fourth capacitors connected in parallel to ground. One end of the third capacitor is connected to the input end of the L-type impedance matching network and the other end is grounded. One end of the fourth capacitor is connected to the output end of the L-type impedance matching network and the other end is grounded.

3. A real-time load impedance detection and rapid matching method according to claim 1, characterized in that: The input impedance value of the input end is calculated from the impedance value of the load. The calculation process is shown in the following formula (3): （3）； In formula (3), represents the input impedance value of the input terminal, represents the sum of the impedance values of the second adjustable capacitor, the first inductor, and the load, represents the imaginary unit, is the angular frequency, represents the capacitance value of the first adjustable capacitor, represents the capacitance value of the second adjustable capacitor, represents the inductance value of the first inductor.

4. A real-time load impedance detection and fast matching method according to claim 3, characterized in that: The voltage reflection coefficient of the input end is calculated from the input impedance value of the input end. The calculation process is shown in the following formula (4): （4）； In formula (4), represents the voltage reflection coefficient at the input end; represents the characteristic impedance.

5. A real-time load impedance detection and fast matching method according to claim 4, characterized in that: The capacitance value required for the adjustable capacitor in the L-type impedance matching network is specifically calculated by the following formula (5) to obtain the capacitance values required for the first adjustable capacitor and the second adjustable capacitor in the L-type impedance matching network and : （5）； In formula (5), represents the real part of the load impedance, represents the imaginary part of the load impedance, is the angular frequency, represents the inductance value of the first inductor, represents the real part of the radio frequency power supply impedance.

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