CN101217096B

CN101217096B - A quick RF automatic impedance matching method

Info

Publication number: CN101217096B
Application number: CN2007100632232A
Authority: CN
Inventors: 武晔
Original assignee: Beijing North Microelectronics Co Ltd
Current assignee: Beijing North Microelectronics Co Ltd
Priority date: 2007-01-04
Filing date: 2007-01-04
Publication date: 2010-09-08
Anticipated expiration: 2027-01-04
Also published as: CN101217096A

Abstract

The invention relates to the technical field of radio frequency transmission, in particular to a rapid RF automatic impedance matching method. The rapid RF automatic impedance matching method which is provided by the invention adopts at least two different proportion coefficients and the sizes of dead zones so as to allow the position of an impedance to be near to the matching point. When the position of the impedance is further away from the matching point, the larger proportion coefficients k1, k2 and the dead zones Delta Z, Delta Theta are selected so as to ensure the rapid entrance in the dead zones; when the position of the impedance is at the vicinity of the matching point, the proportion coefficients k1, k2 and the dead zones Delta Z, Delta Theta are reduced correspondingly so as to ensure the precision of matching. The invention solves the problems that the system is easy to generate the over-shooting when the fixed proportion coefficients are larger, and the impedance point is caused to oscillate at the vicinity of the matching points; that the system matching speed is slow and the matching time is long when the fixed proportion coefficients are smaller. At the same time, the method also solves the problem of oscillation phenomenon because the system matching precision is poor when the fixed dead zones are larger, and the system is not easy to match when the fixed dead zones are smaller, thus improving the precision and stability of the system matching.

Description

A kind of quick RF automatic impedance matching method

Technical field

The present invention relates to the radio frequency transmission technical field, relate in particular to a kind of method of quick RF automatic impedance coupling.

Background technology

In typical R F plasma producing apparatus, the RF generator of constant output impedance (being generally 50 Ω) produces the RF ripple of fixed frequency (being generally 13.56MHz), provide RF power to plasma chamber, to excite the plasma that is used for etching or other technologies.In general, the constant output impedance of the impedance of the nonlinear load of plasma chamber and RF generator is also unequal, so between RF generator and plasma chamber, have serious impedance mismatching, make to have bigger reflection power on the RF transmission line, the power that the RF generator produces can't all flow to plasma chamber.For addressing this problem, must between RF generator and plasma chamber, insert mould value/phase angle detector and impedance matching network.The former is used to detect relevant parameters such as voltage on the RF transmission line, electric current, forward power, backward power, and goes out modulus of impedance value error signal and the impedance angle error signal relevant with matching network input impedance according to these calculation of parameter.The latter comprises in order to realize match control method analog control circuit or digitial controller and in order to regulate the actuator of matching network input impedance.Wherein, controller is responsible for by certain control method, providing the control signal of control executing mechanism according to modulus of impedance value error signal and impedance angle error signal.Two variable impedance elements are arranged in the actuator, regulate their value according to control signal, thereby make the input impedance of matching network equal the constant output impedance of RF generator, the two reaches coupling.At this moment, the transmitting power on the RF transmission line is zero, and the power that the RF generator produces has all flowed to plasma chamber.

With L type matching network shown in Figure 1 is example, and traditional automatic impedance matching method often adopts the aspect ratio adjusting method of digital ratio equation coefficient and single The dead time, utilizes and the relevant error signal of matching network input impedance mould value | Z| _ErrorRegulate shunt capacitance C1, proportionality coefficient is k ₁0.Utilize error signal θ with distribution network input impedance phase angular dependence (-dance) _ErrorRegulate series capacitance C2, proportionality coefficient is k ₂＞0.When matching network input impedance mould value | Z|＞50 Ω and | Z| _Error＞Δ Z＞0 o'clock, the location variation that drives the stepping motor M1 of vacuum capacitance C1 rotation is Δ P ₁=k ₁* | Z| _Error＞0, the C1 value increases, otherwise C1 reduces.When the worth error theta of the mould of matching network input impedance _Error＞0 and θ _Error＞Δ θ＞0 o'clock, the location variation that drives the stepping motor M2 of vacuum capacitance C2 rotation is Δ P ₂=k ₂* θ _Error＞0, the C2 value increases, otherwise C2 reduces.Regulate C1, C2 simultaneously, up to | Z| _ErrorAnd θ _ErrorFall into dead band separately, promptly-Δ Z＜| Z| _Error＜Δ Z ,-Δ θ＜θ _Error＜Δ θ, at this moment | Z| ≈ 50 Ω, θ ≈ 0, network reaches coupling.

Have automatic impedance matching method now in adjustment process, proportionality coefficient k ₁, k ₂Remain unchanged.When | Z| _ErrorAnd θ _ErrorWhen big, the impedance position is far away apart from match point, bigger k ₁, k ₂Can make the impedance position close to match point with fast speeds, along with the impedance position is close to match point, | Z| _ErrorAnd θ _ErrorAlso reduce thereupon, at this moment, same k ₁, k ₂Can cause system overshoot, " missing " dead band, thus cause impedance point near the dead band, " to be paced up and down ", system produces concussion.In like manner, less k ₁, k ₂Though can be at | Z| _ErrorAnd θ _ErrorLess seasonal system stability, but work as | Z| _ErrorAnd θ _ErrorWhen big, can cause matching speed slower, increase match time.

Existing automatic impedance matching method is in adjustment process, and dead band size delta Z, Δ θ also remain unchanged.If it is excessive that the dead band is selected, promptly Δ Z, Δ θ are excessive, and system can't reach needed matching precision.If but the dead band selection is too small, promptly Δ Z, Δ θ are too small, though can guarantee system accuracy, can cause the increase of motor number of revolutions, the degree of wear to strengthen, thereby cause reduce useful life.

In addition, because the selection of the size in dead band and proportionality coefficient has certain relation, select the bad system that may cause to mate.So single proportionality coefficient and dead band are difficult for solving simultaneously problems such as matching speed, matching precision, system overshoot, concussion and motor rotation number of times be too much.

Summary of the invention

The purpose of this invention is to provide a kind of automatic impedance matching method of RF fast, adopt at least two different proportionality coefficients and dead band size to make impedance position match points close, when choosing, bigger proportionality coefficient and bigger dead band cooperate, and less proportionality coefficient cooperates with less dead band.When far away, select bigger proportionality coefficient k1, k2 and dead band Δ Z, Δ θ, apart from match point in the impedance position to guarantee to enter fast the dead band; When the impedance position was near match point, corresponding proportionality coefficient k1, k2 and dead band Δ Z, the Δ θ of reducing was to guarantee matching precision.

Wherein, utilize and the relevant error signal of matching network input impedance mould value | Z| _ErrorRegulate shunt capacitance C1, utilize error signal θ with matching network input impedance phase angular dependence (-dance) _ErrorRegulate series capacitance C2; In the impedance position apart from match point when far away, | Z| _ErrorAnd θ _ErrorBigger, otherwise, | Z| _ErrorAnd θ _ErrorLess.

Preferably, when adopting two proportionality coefficients and two The dead time, with the relevant error signal of matching network input impedance mould value | Z| _ErrorProportionality coefficient be k ₁₁, k ₁₂And k ₁₁＞k ₁₂, its dead band size is Δ Z ₁, Δ Z ₂And Δ Z ₁＞Δ Z ₂＞0; When | Z| _Error＞Δ Z ₁The time, the location variation that drives the stepping motor M1 of shunt capacitance C1 rotation is Δ P ₁=k ₁₁* | Z| _Error＞0, the C1 value increases with fast speeds; When | Z| _Error＜-Δ Z ₁The time, the location variation that drives the stepping motor M1 of shunt capacitance C1 rotation is Δ P ₁=k ₁₁* | Z| _Error＜0, the C1 value reduces with fast speeds; As Δ Z ₂＜|| Z| _Error|＜Δ Z ₁The time, | Z| _ErrorFall into dead band 1, proportionality coefficient switches to k ₁₂If Δ Z ₁＞| Z| _Error＞Δ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error＞0, C1 increases with slower speed; If-Δ Z ₁＜| Z| _Error＜-Δ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error＜0, C1 reduces with slower speed; Up to-Δ Z ₂＜| Z| _Error＜Δ Z ₂The time, | Z| _ErrorFall into dead band 2, motor shuts down.

In addition, use θ _ErrorThe method of adjusting series capacitance C2 and adjusting C1's | Z| _ErrorMethod identical.

This method is applicable to the matching network of two variable impedance elements of L type network, T type network or pin network.Alternative described stepping motor of also available servomotor and air electric capacity and described electric capacity are as the actuator of this method.

This method is applicable to the matching network of two variable impedance elements of L type network, T type network or pin network.Alternative described stepping motor of also available servomotor and air electric capacity and vacuum variable electric capacity are as the actuator of this method.

Method of the present invention solved the fixed proportion coefficient when big system be easy to generate " overshoot ", cause impedance point near matched position, to be shaken; Hour system matches speed is slow for the fixed proportion coefficient, the problem that match time is long.Simultaneously, this method has also solved system matches low precision when fixedly the dead band is big; Fixedly the dead band hour, system is difficult for coupling, causes the problem of reforming phenomena, has improved speed, precision and the stability of system matches.

Description of drawings

Fig. 1 is a L type matching network schematic diagram traditional in the prior art;

Fig. 2 adopts the method flow diagram of pair proportionality coefficients and two The dead time for the present invention.

Embodiment

Following examples are used to illustrate the present invention, but are not used for limiting the scope of the invention.

The present invention adopts a plurality of (two or more) different proportionality coefficient and dead band size, in the impedance position apart from match point when far away, promptly | Z| _ErrorAnd θ _ErrorWhen big, select bigger proportionality coefficient k ₁, k ₂With dead band Δ Z, Δ θ, enter the dead band fast with the assurance system, and reduce the motor rotation number of times.When the impedance position is near match point, suitably reduce proportionality coefficient k ₁, k ₂With dead band Δ Z, Δ θ, to guarantee the matching precision and the stability of system.

To adopt pair proportionality coefficients and the method for two The dead time is example, and its flow process as shown in Figure 2.With the relevant error signal of matching network input impedance mould value | Z| _ErrorProportionality coefficient be k ₁₁, k ₁₂And k ₁₁K ₁₂, its dead band size is Δ Z ₁, Δ Z ₂And Δ Z ₁Δ Z ₂0.Error signal θ with matching network input impedance phase angular dependence (-dance) _ErrorProportionality coefficient be k ₂₁, k ₂₂And k ₂₁K ₂₂, its dead band size is Δ θ ₁, Δ θ ₂And Δ θ ₁Δ θ ₂0.

To regulate C1 | Z| _ErrorBe example.When | Z| _ErrorΔ Z ₁The time, the location variation that drives the stepping motor M1 of vacuum capacitance C1 rotation is Δ P ₁=k ₁₁* | Z| _Error0, the C1 value increases with fast speeds; When | Z| _Error＜-Δ Z ₁The time, the location variation that drives the stepping motor M1 of vacuum capacitance C1 rotation is Δ P ₁=k ₁₁* | Z| _Error＜0, the C1 value reduces with fast speeds.

When | Z| _ErrorFallen into dead band 1, i.e. Δ Z ₂＜|| Z| _Error|＜Δ Z ₁The time, proportionality coefficient switches to k ₁₂If Δ Z ₁| Z| _ErrrΔ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error0, C1 increases with slower speed; If-Δ Z ₁＜| Z| _Error＜-Δ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error＜0, C1 reduces with slower speed.

Up to | Z| _ErrorFallen into dead band 2, promptly-Δ Z ₂＜| Z| _Error＜Δ Z ₂The time, we just think | Z|=50 Ω makes Δ P ₁=0, motor shuts down.

Use θ _ErrorThe reason of regulating vacuum capacitance C2 is the same.

Provide according to mould value/phase angle detector | Z| _ErrorAnd θ _Error, adjust C1 and C2 simultaneously.Mould value/phase angle detector whenever provides one group | Z| _ErrorAnd θ _ErrorValue, C1 and C2 just change once thereupon.Up to | Z| _ErrorAnd θ _ErrorAll fall into dead band 2 separately, we just think | Z|=50 Ω and θ=0, system reaches coupling, motor M 1 and M2 all shut down.At this moment, mould value/phase angle detector still constantly detects the relevant parameter on the RF transmission line, in case error signal | and Z| _ErrorAnd θ _ErrorThe scope that exceeds dead band 2 is then readjusted C1 and C2 according to the method described above, reaches coupling again up to system.

Because the distance of impedance position Distance Matching point means error signal | Z| _ErrorAnd θ _ErrorThe size of absolute value.So, when error is big, choose bigger proportionality coefficient and The dead time.Can guarantee that the impedance position is close to match point with fast speeds, enter dead band 1, both reduce match time, reduce the number of times of motor rotation again, prolong its life-span.Less when error, match point when but also not entering dead band 2, is chosen less proportionality coefficient and The dead time in dead band 1.Suitably slow down matching speed, both can reduce system overshoot, can guarantee matching precision again.And after the impedance position fell into dead band 2, if external disturbance is little, in a single day system broke away from matching status, less proportionality coefficient and The dead time also can guarantee system once more fast the coupling.

In addition, the proportionality coefficient and the The dead time of two (or more than two) can cooperatively interact when choosing, and find the best configuration that solves variety of issue.

Invention is to adopt mould value/phase angle detector measurement | Z| _ErrorAnd θ _Error, drive stepping motor rotation, the L type matching network that drives the vacuum variable capacitance variation is an example.But this method is not limited to this.Transducer in the matching network can be an arbitrary form, as long as can provide and the relevant error signal of matching network input impedance mould value | and Z| _ErrorWith with the error signal θ of matching network input impedance phase angular dependence (-dance) _Error, and | Z| _ErrorAnd θ _ErrorMeaning and invention identical the getting final product of being set forth.Actuator is also like this, is not limited to the form that stepping motor adds vacuum variable electric capacity, and the actuator that servomotor adds the air capacitive form is suitable for too.Variable element can use the inductance form even.Equally, this method is suitable for too for the matching network of two variable impedance elements such as T type network, pin network.

Simultaneously, the aspect ratio adjusting method of two proportionality coefficients and two The dead time has only been introduced in invention.But method is not limited to this, and plural proportionality coefficient and many The dead time also can realize with this method.Certainly, along with the increase of proportionality coefficient and The dead time quantity, the complexity of method also increases thereupon.

With the method that adopts three proportionality coefficients and three The dead time is example.With the relevant error signal of matching network input impedance mould value | Z| _ErrorProportionality coefficient be k ₁₁, k ₁₂, k ₁₃And k ₁₁K ₁₂K ₁₃, its dead band size is Δ Z ₁, Δ Z ₂, Δ Z ₃And Δ Z ₁Δ Z ₂Δ Z ₃0.Error signal θ with matching network input impedance phase angular dependence (-dance) _ErrorProportionality coefficient be k ₂₁, k ₂₂, k ₂₃And k ₂₁K ₂₂K ₂₃, its dead band size is Δ θ ₁, Δ θ ₂, Δ θ ₃And Δ θ ₁Δ θ ₂Δ θ ₃0.

When | Z| _ErrorFallen into dead band 1, i.e. Δ Z ₂＜|| Z| _Error|＜Δ Z ₁The time, proportionality coefficient switches to k ₁₂If Δ Z ₁| Z| _ErrorΔ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error0, C1 increases with slower speed; If-Δ Z ₁＜| Z| _Error＜-Δ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error＜0, C1 reduces with slower speed.

When | Z| _ErrorFallen into dead band 2, i.e. Δ Z ₃＜|| Z| _Error|＜Δ Z ₂The time, proportionality coefficient switches to k ₁₃If Δ Z ₂| Z| _ErrorΔ Z ₃, Δ P then ₁=k ₁₃* | Z| _Error0, C1 increases with extremely slow speed; If-Δ Z ₂＜| Z| _Error＜-Δ Z ₃, Δ P then ₁=k ₁₃* | Z| _Error＜0, C1 reduces with extremely slow speed

Up to | Z| _ErrorFallen into dead band 3, promptly-Δ Z ₃＜| Z| _Error＜Δ Z ₃The time, we just think | Z|=50 Ω makes Δ P ₁=0, motor shuts down.

Use θ _ErrorThe reason of regulating vacuum capacitance C2 is the same.

Provide according to mould value/phase angle detector | Z| _ErrorAnd θ _Error, adjust C1 and C2 simultaneously.Mould value/phase angle detector whenever provides one group | Z| _ErrorAnd θ _ErrorValue, C1 and C2 just change once thereupon.Up to | Z| _ErrorAnd θ _ErrorAll fall into dead band 3 separately, we just think | Z|=50 Ω and θ=0, system reaches coupling, motor M 1 and M2 all shut down.At this moment, mould value/phase angle detector still constantly detects the relevant parameter on the RF transmission line, in case error signal | and Z| _ErrorAnd θ _ErrorThe scope that exceeds dead band 3 is then readjusted C1 and C2 according to the method described above, reaches coupling again up to system.

In addition, this method can adopt digitial controller, as realizations such as single-chip microcomputer, DSP, also can realize with the control circuit of simulation.When adopting digitial controller, mould value/phase angle detector can be provided | Z| _ErrorAnd θ _ErrorChange into digital quantity, compare itself and the size that is all the dead band of digital quantity then.If adopt analog control circuit to realize, can adopt comparator IC, relatively analog quantity | Z| _Error, θ _ErrorSize with Δ Z, Δ θ.

Though the present invention specifically illustrates and illustrates in conjunction with a preferred embodiment; but the personnel that are familiar with this technical field are appreciated that; wherein no matter still can make various changes in detail in form, this does not deviate from spirit of the present invention and scope of patent protection.

Claims

1. quick RF automatic impedance matching method, it is characterized in that: adopt at least two different proportionality coefficients and dead band size to make the impedance position close to match point, when choosing, bigger proportionality coefficient and bigger dead band cooperate, and less proportionality coefficient cooperates with less dead band; When far away, select bigger proportionality coefficient k1, k2 and dead band Δ Z, Δ θ, apart from match point in the impedance position to guarantee to enter fast the dead band; When the impedance position was near match point, corresponding proportionality coefficient k1, k2 and dead band Δ Z, the Δ θ of reducing was to guarantee matching precision; Δ Z is and the relevant error signal of matching network input impedance mould value | Z| _ErrorThe dead band, Δ θ is the error signal θ with matching network input impedance phase angular dependence (-dance) _ErrorThe dead band.

2. the quick RF automatic impedance matching method of stating as claim 1 is characterized in that: utilize and the relevant error signal of matching network input impedance mould value | Z| _ErrorRegulate shunt capacitance C1, utilize error signal θ with matching network input impedance phase angular dependence (-dance) _ErrorRegulate series capacitance C2; In the impedance position apart from match point when far away, | Z| _ErrorAnd θ _ErrorBigger, otherwise, | Z| _ErrorAnd θ _ErrorLess.

3. quick RF automatic impedance matching method as claimed in claim 2 is characterized in that:

When adopting two proportionality coefficients and two The dead time, with the relevant error signal of matching network input impedance mould value | Z| _ErrorProportionality coefficient be k ₁₁, k ₁₂And k ₁₁＞k ₁₂, its dead band size is Δ Z ₁, Δ Z ₂And Δ Z ₁＞Δ Z ₂＞0;

When | Z| _Error＞Δ Z ₁The time, the location variation that drives the stepping motor M1 of shunt capacitance C1 rotation is Δ P ₁=k ₁₁* | Z| _Error＞0, the C1 value increases with fast speeds; When | Z| _Error＜-Δ Z ₁The time, the location variation that drives the stepping motor M1 of shunt capacitance C1 rotation is Δ P ₁=k ₁₁* | Z| _Error＜0, the C1 value reduces with fast speeds;

As Δ Z ₂＜|| Z| _Error|＜Δ Z ₁The time, | Z| _ErrorFall into dead band 1, proportionality coefficient switches to k ₁₂If Δ Z ₁＞| Z| _Error＞Δ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error＞0, C1 increases with slower speed; If-Δ Z ₁＜| Z| _Error＜-Δ Z ₂, Δ P then ₁=k ₁₂* | Z| _Error＜0, C1 reduces with slower speed.

Up to-Δ Z ₂＜| Z| _Error＜Δ Z ₂The time, | Z| _ErrorFall into dead band 2, motor shuts down.

4. quick RF automatic impedance matching method as claimed in claim 3 is characterized in that using θ _ErrorThe method of adjusting series capacitance C2 and adjusting C1's | Z| _ErrorMethod identical.

5. as claim 3 or 4 described quick RF automatic impedance matching methods, it is characterized in that using servomotor and the alternative described stepping motor of air electric capacity and described electric capacity actuator as this method.

6. quick RF automatic impedance matching method as claimed in claim 2 is characterized in that this method is applicable to the matching network of two variable impedance elements of L type network, T type network or pin network.