JP2002168892A - Characteristic measurement method for directional coupler, directional combiner using the method and plasma processor thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the error included in directionality and degree of coupling, obtain it with complex number and clarify the phase relationship between the directionality and the degree of coupling. SOLUTION: By using an impedance terminator of (n) kinds or more (n>=3) generating a reflection wave, a progressive wave voltage Vs and a reflection wave voltage Vr and the phase relationship between output voltages vs and vr of the directional coupler and that between Vs and Vr are known. So the reflectivity Γ (=Vr/Vs) in the directional coupler and the input impedance in the directional coupler is calculated and the impedance Zp of a reaction vessel can be monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the direction and coupling of a directional coupler, a directional coupler for measuring the direction and coupling by the measuring method, and a directional coupler. The present invention relates to a device provided, particularly a plasma processing apparatus for performing impedance monitoring.

[0002]

2. Description of the Related Art In recent years, semiconductor manufacturing apparatuses, such as RIE and plasma CVD, for performing desired processing on a sample using plasma have been widely used. This type of semiconductor manufacturing equipment includes V
Although a power source having a frequency in the HF or UHF band is sometimes used, mainly 13.56 MHz or 2.56 GHz
Is used. In order to control the power from such a high-frequency power supply, semiconductor manufacturing equipment includes:
The traveling wave incident into the device from the power supply and the reflected wave reflected from the semiconductor manufacturing device are measured by a directional coupler,
A power monitoring device is provided for monitoring the power consumption of the device based on the measurement result.

FIG. 5 shows a schematic configuration of a power monitoring apparatus for performing power monitoring using a directional coupler.

This power monitoring device has an oscillator 1 for oscillating high-frequency oscillating power, and a reaction vessel 9 for performing a reaction such as a plasma process using the oscillating power from the oscillator 1. Between 9, the circulator 10, the directional coupler 2, and the phase difference measuring device 8,
The components are provided in order from the oscillator 1 to the reaction vessel 9 via the transmission line 4. In addition, the circulator 10 includes
Non-reflection termination 5 that does not generate reflected waves via transmission line 4
Is connected.

The oscillating power oscillated by the oscillator 1 becomes a traveling wave and travels through the transmission line 4 through the circulator 10, the directional coupler 2, and the phase difference measuring device 8 in order, and Incident on.

[0006] The traveling wave incident on the reaction vessel 9 is consumed for processing of plasma or the like, but a part thereof becomes a reflected wave and is transmitted through the transmission line 4 to the phase difference measuring device 8 and the directionality. The light is reflected by the coupler 2.

The circulator 10 transmits the traveling wave power oscillated from the oscillator 1 to the directional coupler 2, and transmits the reflected wave power transmitted from the directional coupler 2 to the non-reflection terminal 5.

The directional coupler 2 measures the power of the traveling wave and the reflected wave by measuring the output voltage picked up from the traveling wave from the oscillator 1 and the reflected wave from the reaction vessel 9.

From the directional coupler 2 to the circulator 10
The reflected wave that has propagated through the transmission line 4
And is consumed at the non-reflection end 5.

In such a power monitoring apparatus, the ratio of the reflected wave reflected from the reaction vessel 9 to the traveling wave incident on the reaction vessel 9, that is, the reflectance depends on the input impedance of the reaction vessel 9. I have. Therefore, the amplitude of the traveling wave and the reflected wave is measured by the directional coupler 2, and at the same time, the phase difference between the traveling wave and the reflected wave is measured by the phase difference measuring device 8, and the reflectance is determined based on the amplitude and the phase difference. If so, the input impedance of the reaction vessel 9 is monitored.

At this time, the directional coupler 2 measures the amplitude of the traveling wave and the reflected wave, and measures the phase difference between the traveling wave and the reflected wave by the phase difference measuring device 8 to perform impedance monitoring. However, only the directional coupler 2 can monitor only the traveling wave power and the reflected wave power. This is because the degree of coupling and the directionality indicating the relationship between the traveling wave and the reflected wave propagating in the directional coupler 2 and the output signal of the directional coupler 2 are indicated by real numbers, and the amplitudes of the traveling wave and the reflected wave are shown. This is because you can only get it.

Next, a method of measuring the directivity and the degree of coupling based on the traveling wave and the reflected wave of the directional coupler in the prior art will be described.

The directional coupler 2 picks up a traveling wave output signal that depends only on the traveling wave and a reflected wave signal that depends only on the reflected wave, of the traveling wave and the reflected wave propagating therein.

However, in practice, the traveling wave output signal, which should depend only on the traveling wave, slightly includes the influence of the reflected wave, and the reflected wave output signal, which should depend on only the reflected wave, does not. Also include the effect of traveling waves.

At this time, the dependence of the traveling wave output signal on the traveling wave and the dependence of the reflected wave output signal on the reflected wave are referred to as a coupling degree. Conversely, the dependence of the traveling wave output signal on the reflected wave, The dependence of the reflected wave output signal on the traveling wave is called directionality, and is generally expressed as follows. Assuming that the traveling wave output signal is vs, the reflected wave output signal is vr, the traveling wave voltage is Vs, and the reflected wave voltage is Vr, the traveling wave output signal vs and the reflected wave output signal vr are expressed by the following equation (1). Is represented by

[0016]

(Equation 1) In the equation (1), k ₁₁ , k ₁₂ , k ₂₁ , and k ₂₂ are constants called coupling characteristic values of the directional coupler 2, respectively. Specifically, k ₁₁ is the coupling degree of the traveling wave pickup unit of the directional coupler 2, k ₁₂ / k ₁₁ represents the direction of the traveling wave pickup section, k ₂₂ is the coupling degree of the reflected wave pickup unit, k ₂₁ / k ₂₂ indicates the directionality of the reflected wave pickup unit.

Next, a method for determining the direction and the degree of coupling of the directional coupler 2 will be described with reference to FIG.

The directional coupler 2 has an input terminal 2a connected to the oscillator 1, and an output terminal 2b connected to an arbitrary load.
And a four-hole circuit having a reflected wave pickup unit 2c for picking up reflected wave power reflected from the load and a traveling wave pickup unit 2d for picking up traveling wave power. The reflected wave pickup 2c and the traveling wave pickup 2d are connected to an absorption resistor (not shown).

In such a directional coupler 2, when the output terminal 2 b is connected to a non-reflection terminal which does not generate a reflected wave, and a voltage is applied to the input terminal 2 a by the oscillator 1, the reflection appearing in the directional coupler 2 is generated. The waves become very small.

At this time, the traveling wave power is Pi, the reflected wave power is Pr, and the power generated in the traveling wave pickup unit 2d is P.
i ′, the power generated in the reflected wave pickup unit 2c is Pr ′
Then, the degree of coupling C of the traveling wave pickup unit 2d is defined by the following equation (2).

[0021]

(Equation 2) The degree of directional coupling (hereinafter, abbreviated as directionality) D of the reflected wave pickup unit 2c is defined by the following equation (3).

[0022]

(Equation 3) When the equations (2) and (3) are modified, the following equations (4) and (5) are obtained.

[0023]

(Equation 4)

[0024]

(Equation 5) In the expression (4), 10 ^{−C / 10} is | k ₁₁ | ^{2 in the} expression (1).
In equation (5), 10 ^{−D / 10} 10 ^{−C / 10} is
This corresponds to | k ₂₁ | ² in the equation (1).

Contrary to such a configuration, the input terminal 2a is connected to a non-reflection terminal, the output terminal 2b is connected to the oscillator 1, and the traveling wave pickup 2d and the reflected wave pickup 2c pick up. By measuring the voltage, the directionality of the traveling wave pickup unit 2d and the degree of coupling of the reflected wave pickup unit 2c can be obtained.

[0026]

However, even when the non-reflection terminal 5 which is assumed to generate no reflected wave is connected to the directional coupler 2, actually the directional coupler 2 has There is a slight reflected wave. For this reason, even in the above-described methods of measuring the degree of coupling and the directivity, an error due to the presence of a reflected wave is included.

The coupling degree and direction of each of the traveling wave pickup unit 2d and the reflected wave pickup unit 2c are as follows:
Since they are measured separately, the phase relationship between the traveling wave and the reflected wave inside the directional coupler 2 is unknown.

An error caused by the presence of a reflected wave inside the directional coupler 2 will be verified with reference to FIGS.

FIG. 7 is a schematic diagram showing a configuration for measuring the degree of coupling of the traveling wave pickup unit 2d of the directional coupler 2 according to the prior art. FIG. 8 is a schematic diagram showing a configuration for measuring the directionality of the traveling wave pickup unit 2d according to the related art.

7 and 8, the same components as those in FIGS. 5 and 6 are denoted by the same reference numerals. Directional coupler 2
The oscilloscope 11 for monitoring the voltage of the traveling wave pickup 2d and the voltage of the oscillator 1 is connected to the traveling wave pickup 2d.

Here, the output impedance of the oscillator 1, the characteristic impedance of the transmission line 4, the characteristic impedance of the directional coupler 2, and the input impedance of the non-reflection terminal 5 all have the same value. For example, if the output impedance of the oscillator 1 is 50Ω, which is usually used, the transmission line 4 and the directional coupler 2 and the reflectionless termination 5
The impedance is adjusted to be 50Ω or the impedance is adjusted to 50Ω.

In order to measure the directionality and the coupling degree, as described above, the directionality and the coupling degree of the traveling wave pickup unit 2d and the directionality and the coupling degree of the reflected wave pickup unit 2c are individually measured. Is done.

First, a method of measuring the degree of coupling of the traveling wave pickup unit 2d will be described.

The oscillation voltage V oscillated from the oscillator 1 is transmitted to the directional coupler 2 via the transmission line 4, passes through the directional coupler 2 as a traveling wave voltage Vs, and
Is transmitted to Traveling wave voltage Vs reaching non-reflection terminal 5
Are mostly consumed at the non-reflection terminal 5, but a part is reflected as the reflected wave voltage Vr. Although this reflected wave voltage Vr is slight, it is again reflected as a reflected wave on the transmission line 4.
And returns to the directional coupler 2. Therefore, a traveling wave and a slight reflected wave are mixed in the directional coupler 2.

The traveling wave voltage Vs, the reflected wave voltage Vr, and the voltage V oscillated by the oscillator 1 are expressed by the following equations (6) to (8) in consideration of the phase.

[0036]

(Equation 6)

[0037]

(Equation 7)

[0038]

(Equation 8) In this case, the output signal vs picked up by the traveling wave pickup unit 2d is expressed by the following expression (1) by the above expression (1).

[0039]

(Equation 9) Binding of the traveling wave pickup section 2d, in the equation (9), since represented by k _11, binding of the traveling wave pickup unit 2d, the next deformed for k ₁₁ (9) (1
0).

[0040]

(Equation 10) Here, since there is almost no loss in the transmission line 4, it can be approximated to | V / Vs | ≒ 1. Further, since the reflected wave voltage Vr is very small compared to the traveling wave voltage Vs, it can be approximated to | Vr / Vs | ≒ 0. Therefore, the degree of coupling k ₁₁ of the traveling wave pickup unit 2d is obtained as in the following equation (11), and the oscilloscope 11 monitors only the absolute value of the complex number.

[0041]

[Equation 11] As can be seen by comparing Equations (10) and (11), the degree of coupling determined by the prior art expressed by Equation (11) is negligible, although the reflected wave is present, albeit slightly. Contains an error in principle, and only its absolute value is known.

Next, the directionality of the traveling wave pickup unit 2d will be described.

As shown in FIG. 8, the non-reflective terminal 5 is connected to the input terminal 2a of the directional coupler 2, and the oscillator 1 is connected to the output terminal 2b. An oscilloscope 11 is connected to the traveling wave pickup unit 2d. Assuming that the output voltage of the oscillator 1 is V ', the traveling wave voltage inside the directional coupler is Vs', the reflected wave voltage is Vr ', and the output voltage detected by the traveling wave pickup unit 2d is vs', the following (12) ) Is obtained.

[0044]

(Equation 12) Therefore, the following equation (13) is obtained from the equation (12).

[0045]

(Equation 13) In the equation (13), | V ′ / Vs ′ | ≒ 1, | V
r ′ / Vs ′ | ≒ 0, the amplitude | vs ′ of the output voltage vs ′ of the traveling wave pickup unit 2d.
And the amplitude | V ′ | of the output voltage of the oscillator 1, the following equation (14) is obtained.

[0046]

[Equation 14] Therefore, the (14)
| K ₁₂ | of the equation is monitored, and equation (11) and (1)
The absolute value | k ₁₂ | / | k ₁₁ | of the complex number of the directivity of the traveling wave pickup unit 2d is determined by the expression 4).

As can be seen from a comparison between the expressions (13) and (14), the reflected wave which is actually present, albeit slightly, is neglected. The directionality includes an error in principle, and only its absolute value is known.

Also, the degree of coupling and directionality of the reflected wave pickup unit 2c can be obtained by the following equations (15) and (16) based on the same concept.

[0049]

(Equation 15)

[0050]

(Equation 16) The procedure of the method for measuring the degree of coupling and directionality will be described with reference to FIG.

First, the oscillator 1 is connected to the input section 2a of the directional coupler 2, and the non-reflection terminal 5 is connected to the output section 2b, to obtain the configuration shown in FIG.

The oscillation voltage V is applied from the oscillator 1, and the output voltage vs of the traveling wave pickup unit 2d and the output voltage vr of the reflected wave pickup unit 2c are measured (Step S2,
Step S3).

| K ₁₁ | is calculated from the above equation (11) (step S4), and | k ₂₁ | is calculated from the above equation (15) (step S5).

Next, the non-reflection terminal 5 is connected to the input terminal 2a of the directional coupler 2, and the oscillator 1 is connected to the output terminal 2b, thereby obtaining the configuration shown in FIG. 8 (step S6).

The oscillation voltage V 'is applied from the oscillator 1, and the output voltage vs' of the traveling wave pickup 2d and the output voltage vr' of the reflected wave pickup 2c are measured (steps S7 and S8).

| K ₁₂ | is calculated from the above equation (14) (step S9), and | k ₂₂ | is calculated from the above equation (16) (step S10).

Then, the calculated | k ₁₁ |, | k ₁₂ |
| K ₂₁ |, | k ₂₂ |
The degree of coupling | k ₁₁ | and directionality | k ₁₂ | / | k ₁₁ | of d and the degree of coupling | k ₂₂ | and directionality | k ₂₂ | / | k ₂₁ | of the reflected wave pickup unit 2c are calculated.

The coupling degree and directionality of the traveling wave pickup unit 2d obtained in this way are based on the fact that reflected waves exist in principle, although the reflected waves actually exist are neglected. Contains errors. Also, the coupling degree and directionality, which are originally complex numbers, can be obtained only by the absolute value of the complex number.

Further, since the coupling degree and directionality of the traveling wave pickup unit 2d and the reflected wave pickup unit 2c are calculated separately, the phase relationship between the traveling wave pickup unit 2d and the reflected wave pickup unit 2c is unknown.

For the reasons described above, the directional coupler 2
Cannot accurately determine the reflectance Γ at each of the pickup units 2c and 2d. Therefore, since the impedance obtained based on the reflectance な い that cannot be obtained precisely is not precise, there is a problem that monitoring using the directional coupler 2 is not precise.

The present invention has been made in view of the above problems, and reduces the influence of an error included in the coupling degree and the directionality. Further, the coupling degree and the directionality can be obtained by a complex number so that both can be obtained. It is an object of the present invention to provide a method for measuring the degree of coupling and direction of a traveling wave and a reflected wave capable of clarifying a phase relationship and a plasma processing apparatus using the method.

[0062]

In order to solve the above-mentioned problems, a first aspect of the present invention is to connect an output terminal of a power supply to an input terminal of a directional coupler, and connect an output terminal of the directional coupler to impedance termination. Directional coupler connected to the input end of the directional coupler and measuring the output signal of the directional coupler according to the electromagnetic wave propagating inside the directional coupler to measure the degree of coupling and directionality of the directional coupler A method for measuring characteristics of a coupler, wherein an impedance terminator that generates a reflected wave is used as the impedance terminator.

The output terminal of the power supply is connected to a directional coupler.
To the input of the directional coupler, and connect the output of the
Connected to the input terminal of the impedance terminator,
Of n types (n ≧ 3) that generate reflected waves
Termination using an impedance terminator, impedance Zp_iTo
Connect the i-th (1 ≦ i ≦ n) impedance terminator
At the pickup of a directional coupler when it is deflected
率 Rate_iAnd the oscillation voltage of the power supply is V_iOf the directional coupler
Output voltage amplitude of row wave pickup | vf_i| And reflected wave
Pickup output voltage amplitude | vr_i| And each other's phase
Difference (Arg [vf_i] -Arg [vr_i]) And
Measure, Zin_i= (| Vr_i| / | Vf _i|) Exp
[Arg [vr_i] -Arg [vf_i]] Constant
And the traveling wave of the directional coupler
Pickup coupling degree k₁₁, Direction k₁₂/ K₁₁, Reflected wave
Pickup coupling degree k_{twenty one}, Direction k_{twenty two}/ K_{twenty one}Using
And k ₁₂’= K₁₂/ K₁₁, K_{twenty one}’= K_{twenty one}/ K₁₁, K_{twenty two}’
= K_{twenty two}/ K₁₁= (K_{twenty two}/ K_{twenty one}) × (k_{twenty one}/ K₁₁), Q_i
= -Zin_i-Zin_iΓ_ik₁₂’+ K_{twenty one}’+ K_{twenty two}’Γ_iTo
Define, Σ | Q_i|^TwoK that minimizes₁₂’, K_{twenty one}’,
k_{twenty two}’And k₁₁= | Vf_i
| / ｛| V_i|| 1 + k₁₂’Γ_iStep of calculating |｝
And

According to a third aspect of the present invention, in the method for measuring the characteristics of the directional coupler according to the first or second aspect, the impedance terminator is constituted by a capacity using gas as a medium.

The directional coupler according to the fourth aspect is the first to third aspects.
The directionality and the degree of bonding are measured by any of the methods described in 1. above.

According to a fifth aspect of the present invention, there is provided the plasma processing apparatus of the fourth aspect.
And a directional coupler described in (1).

[0067]

Embodiments of the present invention will be described below with reference to the drawings. (Method of Measuring Directivity and Degree of Coupling of Directional Coupler) FIG.
FIG. 1 is a schematic configuration diagram showing a schematic configuration for implementing a method for measuring the direction and coupling degree of a directional coupler according to the present invention.

The device shown in FIG. 1 has an oscillator 21 for oscillating an oscillating voltage, and this oscillator 21 is connected to a circulator 22 via a transmission line 26a. The circulator 22 is connected to an input 23a of the directional coupler 23 via a transmission line 26b. The output 23 b of the directional coupler 23 is connected to a known impedance 24 via a transmission line 27. The directional coupler 23 includes a traveling wave pickup unit Pf that picks up a traveling wave voltage Vf of the traveling wave propagating in the directional coupler 23 and a reflected wave of a reflected wave propagating in the directional coupler 23. And a reflected wave pickup section Pr for picking up the voltage Vr. Each pickup part Pf and P
The output voltages vf and vr picked up by r are connected to the output terminals A and B of the oscilloscope 25, respectively.

Here, the characteristic impedance of the directional coupler 23 is Z ₀ , the propagation constant is γ (= α + jβ), and the characteristic impedance and the propagation constant of the transmission lines 26 and 27 are the same as those of the directional coupler 23. Similarly, it has a characteristic impedance Z ₀ and a propagation constant γ. The impedance value of the known impedance 24 is Zp, and the electrical length from the known impedance 24 to each of the pickup units Pf and Pr of the directional coupler 23 is L.

The oscillating voltage V oscillated from the oscillator 21 is transmitted as a traveling wave to the transmission line 26, the circulator 22, the directional coupler 23, and the transmission line 27, and enters the known impedance 24. The traveling wave that has entered the known impedance 24 is partially or wholly reflected, and propagates as a reflected wave traveling in a direction opposite to the traveling wave to the transmission line 27, the directional coupler 23, the transmission line 26b, and the circulator 22. Then, the signal is transmitted to the dummy load 28 by the circulator 22 via the transmission line 26c.
At 8 all power is consumed.

In this case, the output voltages Vf and Vr of the traveling wave and the reflected wave in the directional coupler 23 and the impedance Zp of the known wave 24 and the traveling wave and the reflected wave are defined by the high frequency distribution constant theory. , The following equation (17) exists.

[0072]

[Equation 17] Γ indicates the reflectance at the directional coupler 23,
The reflectivity Γ varies according to the value of the impedance Zp of the known impedance 24, as shown in Expression (17). Assuming that the output voltages picked up by the respective pickup units Pf and Pr and output from the respective pickup units Pf and Pr are vf and vr, the output voltages vf and vr are respectively expressed by the following equations (18). You.

[0073]

(Equation 18) In the equation (18), k ₁₁ , k ₁₂ , k ₂₁ , and k ₂₂ indicate coupling characteristic values of the directional coupler 23, respectively. This binding characteristic value k ₁₁ to k _22, each pickup Pf and Pr
Since the output voltages vf and vr and the traveling wave voltage Vf and the reflected wave voltage Vr are complex numbers including phase information, k ₁₁
~k ₂₂ also becomes complex, respectively.

Here, a constant Zin obtained from the amplitude ratio and the phase difference between the output voltages vf and vr of the pickup units Pf and Pr is defined as in the following equation (19).

[0075]

[Equation 19] In the equation (19), | vr | / | vf | is the amplitude ratio of the output voltage, Exp [Arg (vr) -Arg (v
f)] indicates a phase difference.

The constant Zin can be expressed by the following equation (20) using the equation (18).

[0077]

(Equation 20) From the equation (19), the following equations (21) and (22) are defined.

[0078]

(Equation 21)

[0079]

(Equation 22) Equations (21) and (22) above represent the directional coupler 23
, K ₁₁ to k ₂₂ , the reflectance に お け る at each of the pickup units Pf and Pr, and the output voltage ratio Zin of each of the pickup units Pf and Pr.

Therefore, once the coupling characteristic values k _{11 to} k _{21 of} the directional coupler 23 are calculated, the output voltages vf and vr of the pickup units Pf and Pr are monitored by the oscilloscope 25, and Zin (= vr
/ Vf) is calculated. Zi calculated in this way
Based on n, k ₁₂ ′, k ₂₁ ′, and k ₂₂ ′, the output impedance of the directional coupler 23 is calculated.

Here, since k ₁₂ ′, k ₂₁ ′ and k ₂₂ ′ are complex numbers, these k ₁₂ ′, k ₂₁ ′ and k ₂₂ ′ can be expressed as in the following equation (23). (x ₁₂ '~x _22'
Is a real number).

[0082]

(Equation 23) Then, by setting various impedance values Zpi (i = 1 to n) to the known impedance 24, the output voltages vfi and vri for various reflectances Γi are monitored by the oscilloscope 25 and substituted into the equation (23). Gives the following equation (24).

[0083]

(Equation 24) Since each of the constants Re [Zin] and the like and x ₁₂ ′ to y ₂₂ ′ are real numbers, three different known impedances Zp ₁ , Zp ₂ , and Zp ₃ are set in the known impedance 24, and the respective output voltage ratios Zin = vr / vf measured, solving 6-way linear system, it is possible to obtain each x ₁₂ '~y _22'.

Further, in consideration of the measurement error of the output voltages vf and vr, the output voltages vfn and vrn for n kinds (n> 3) of known impedances Zpn are measured for the known impedance 24, and the following equation (25) is obtained. Therefore, the re-probability values of k ₁₂ ′ to k ₂₂ ′ can be determined by the least square method.

[0085]

(Equation 25) Further, from the ratio between the output voltage V of the oscillator 1 and the output voltage vf of the directional coupler 23, as shown in the following equation (26),
It is also possible to determine the pickup constants k _11.

[0086]

(Equation 26) However, k _11, either calculated by selecting one of i as i = 1 to n, calculate the k ₁₁ for all i, or calculate the average may be either.

Next, the procedure of the method for measuring the degree of coupling according to the present embodiment will be described with reference to FIG.

First, the oscillator 21, the circulator 22,
The directional coupler 23, the oscilloscope 25, the dummy load 28, and the transmission lines 26 and 27 are arranged as shown in FIG. 1 (Step S1).

Next, the first known impedance 24 of the n pieces is connected to the output terminal 23b of the directional coupler 23 (step S2).

[0090] Then, by (17), to calculate the reflectivity gamma _1. The oscillating power is oscillated from the oscillator 21, and the output voltages vf and vr output to the respective pickup units Pf and Pr of the directional coupler 23 are monitored by the oscilloscope 25.
It calculates the n ₁ (step S3).

Thereafter, the second known input is connected to the directional coupler 3.
Connect the impedance 24 and reflectivity Γ _TwoCalculate the direction
Output voltage v of each pickup section Pf and Pr of coupler 3
Monitor f and vr with oscilloscope 25
And the output voltage ratio Zin_TwoIs calculated. Perform this operation n times
(N ≧ 2)
3) (Step S4).

[0092] By the above, each of the output voltage is measured by repeating n times vf _i and vr _i, and the output voltage ratio Zi
The n _i and the reflectance gamma _i and the impedance Zp _i (1 ≦ _i ≦
n), k by the least square method according to the equation (25).
_{12 / k 11, k 21 /} k 11, the most probable value of k ₂₂ / k ₁₁ is calculated in complex (step S5).

Further, based on the output voltage V of the oscillator 21 and the output voltage vf output by the traveling wave pickup unit Pf of the directional coupler 23, the degree of coupling of the traveling wave pickup unit Pf is calculated based on the equation (26). | K ₁₁ | is calculated (step S6).

As described above, in the present embodiment, since the directional coupler 23 is calculated without ignoring the reflected wave, the error caused by ignoring the reflected wave is calculated. Is not included, and the accuracy of the directionality and the coupling degree is improved. Further, the directionality and the degree of connection can be obtained by complex numbers.

Here, the measurement accuracy of the coupling characteristic value obtained as a complex number is determined by the accuracy of the impedance value Zp of the known impedance 24 and the accuracy of the output voltages vf and vr of the pickup units Pf and Pr. When real resistance, capacitance, and inductance are formed by using a substance such as a metal, a semiconductor, an insulator, or a dielectric as the known impedance 24, a measurement error of the resistivity, the dielectric constant, and the like of the substance such as a metal becomes the known impedance 24. Impedance value Zp
And the measurement accuracy of the coupling characteristic value decreases.

Therefore, it is desirable to use gas as the medium for the known impedance 24. If gas is used as the medium, the relative permittivity ε of the dielectric constituting the capacitor
r can be set to εr = 1.0, and the accuracy of the impedance Zp of the known impedance 24 can be further improved.

In this embodiment, since the coupling characteristic value is calculated simultaneously and is calculated as a complex number, not only the amplitude of the traveling wave and the reflected wave but also the phase relationship between the traveling wave and the reflected wave is obtained. Can be.

As described above, it is possible to accurately monitor the impedance of the reaction vessel for performing the plasma processing or the like. (Plasma Processing Apparatus with Directional Coupler) A plasma processing apparatus with a directional coupler according to the method for measuring the directivity and the coupling degree will be described.

FIG. 2 is a schematic configuration diagram of a plasma processing apparatus 30 having a directional coupler.

The plasma processing apparatus 30 includes a matching device portion 31, a directional coupler portion 32 connected to one end of the matching device portion 31, and a directional coupler portion 32 connected to the other end of the directional coupler portion 32. And a reaction vessel portion 33 provided.

The matching device portion 31 includes a coaxial line 41 composed of a cylindrical outer conductor 41b having an outer diameter D, and a center conductor 41a having an outer diameter d disposed coaxially with the axis of the outer conductor 41b. have. A box 42 is provided on the side of the end of the coaxial line 41 on the side of the directional coupler portion 32, and the box 42 communicates with the center conductor 41 a through the outer conductor 41 b of the coaxial line 41. And
A variable capacitance 43 for changing the capacitance in the outer conductor 41 b of the coaxial line 41 is provided in the box 42. Box 4
A connector 44 connected to the variable capacitor 43 in the box 42 is provided outside the box 2.

In the outer conductor 41b of the coaxial line 41, a movable short-circuit end 45 movably arranged is provided along the axial direction. The movable short-circuit end 45 is moved in the axial direction by a handle 46 provided at the end of the coaxial line 41. The movement of the movable short-circuit end 45 adjusts the input impedance to the plasma processing apparatus 30.

The directional coupler portion 32 has a center conductor 51a having an outer diameter d which is concentric with the center conductor 41a of the coaxial line 41 of the matching device portion 31, and a center conductor 51b of the coaxial line 41 which is concentric. It has a directional coupler 51 having an outer conductor 51b having an outer diameter D which is integrated and continuous. On the side of the directional coupler 51, a traveling wave pickup unit Ps for picking up traveling wave power, and a reflected wave pickup unit Ph arranged at a position facing the traveling wave pickup unit Ps for picking up reflected wave power. Are provided.

The outer diameter d of the reaction vessel portion 33 is integrally connected concentrically with the center conductor 51 a of the directional coupler 51.
Center conductor 61a. The center conductor 61a is arranged along the axis of a cylindrical reaction vessel 61 having a cylindrical inside 61b having the same diameter as the inner diameter of the outer conductor 51b of the directional coupler 51. Tip 61c of center conductor 61a
Is a mounting surface of a sample to be subjected to plasma processing, and a gap adjusting device 62 for adjusting a gap in a space on the sample surface where the plasma processing is performed is provided opposite to the tip portion 61c. A reaction gas inlet 63 for introducing a reaction gas is formed on a side portion of the reaction container 61. A partition 64 is provided at the end of the reaction vessel 61 on the side of the directional coupler portion 32 so that the reaction gas introduced from the reaction gas inlet 63 does not flow out to the directional coupler 51.

Here, the distance from the variable capacitor 43 of the matching device portion 31 to the movable short-circuit end 45 is LB, and the reaction in which the plasma P is generated from the traveling wave pickup portion Ps and the reflected wave pickup portion Ph of the directional coupler 51. Container 61
The electrical distance between the center conductor 61a and the tip 61c of the
Let p.

The coaxial line 41 of the matching unit 31 and the directional coupler 51 of the directional coupler 32
The reaction vessel 61 of the reaction vessel portion 33 as a whole forms a coaxial line composed of a center conductor having an outer diameter d and an outer conductor having an outer diameter D, and its characteristic impedance is Z ₀ , and its propagation constant is γ. I do. The coaxial line as a whole is formed by a tip 61 of a center conductor 61a of a reaction vessel 61 for generating plasma P.
This is a coaxial resonator in which the plasma processing section c is a capacitor and the movable short-circuit end 45 of the matching device section 31 is short-circuited.

Next, the operation of the plasma processing apparatus 30 having the above configuration will be described.

First, the capacitance C of the variable capacitor 43 and the length LB of the coaxial line 41 of the matching device portion 31 are set to the handle 46 so that the input impedance Zin to the plasma processing device 30 matches (50 + 0j) [Ω]. Adjust.

After the adjustment, an external power supply (not shown) is connected to the connector 44, and a high-frequency voltage having a frequency f [Hz] is applied to the matching device portion 31.

The high-frequency voltage introduced into the plasma processing apparatus 30 passes through a directional coupler 51, and passes through a coaxial line having a length of Lp.
Is transmitted to

A reaction gas is introduced from a reaction gas inlet 63 of the reaction vessel 61, and the tip 61c of the center conductor 61a is introduced.
The reactive species are generated by the plasma P generated by the high-frequency voltage transmitted to the sample, and the plasma processing is performed on the sample placed on the tip 61c of the center conductor 61a.

While the sample is being subjected to plasma processing,
The traveling wave pickup unit Ps of the directional coupler 51 picks up the output voltage vs from the traveling wave voltage Vs, and the reflected wave pickup unit Ph outputs the output voltage v from the reflected wave voltage Vh.
Pick up h. Each pickup part Ps and Ph
The output voltages vs and vh can be expressed by the following equation (27) using the traveling wave voltage Vs and the reflected wave voltage Vh, as in the above equation (20).

[0113]

[Equation 27] Further, each pickup unit Ps and Ps of the directional coupler 51
h and the impedance Zp of the tip 61c of the center conductor 61a of the reaction vessel 61,
The following equation (28) is obtained based on the electrical distance Lp between the tip 61c of the first part 1a and the directional coupler 61.

[0114]

[Equation 28] Then, a capacity using air as a medium is formed at the end 61c of the center conductor 61a, and the capacity of the reaction vessel 61 is changed to various values by the gap adjusting device 62 to change the impedance Zp of the reaction vessel 61. The amplitude ratio vs / vh of the output voltages vs, vh of the respective pickup units Ps and Ph.
And the phase difference (Arg [vh] −Arg [vs]) were measured, and using the above-described equations (17) to (25),
k ₁₂ ′, k ₂₁ ′, and k ₂₂ ′ are calculated, and the coupling degree and directionality are calculated.

Then, the reflectance Γ is calculated based on the calculated coupling degree and directionality, and the impedance of the reaction vessel 61 is monitored.

Here, actually, by adjusting the gap adjusting device 62, the pickup portion Ps, when the volume of the tip 61c formed by using air as a medium is changed,
The output voltage vs of Ph, the amplitude ratio vs / vh of vh, and the phase difference (Arg [vh] −Arg [vs]) are measured, and k ₁₂ ′, k ₂₁ ',
k ₂₂ ′ is calculated, and based on the calculated k ₁₂ ′ and the like, the impedance Zp
I asked. This impedance is shown in FIG.

As can be seen from FIG. 3, the actual impedance Zp due to the capacity set in the reaction vessel 61 and the impedance Zp calculated from the output voltages vs, vh and k ₁₂ ′, k ₂₁ ′, k ₂₂ ′ are well. It was confirmed that the method of the present embodiment was accurate.

[0118]

As is clear from the above description, according to the present invention, the traveling wave voltage V inside the directional coupler is
s and the reflected wave voltage Vr, and the output voltage vs of the directional coupler
And the phase relationship between Vs and Vr, the reflectance 分 か る (= Vr /
Vs), the impedance in the directional coupler, and the input impedance Zp of the reaction vessel are calculated only by the directional coupler, and the impedance Zp of the reaction vessel can be monitored. This makes it possible to configure a plasma processing apparatus for detecting the end point of etching, and an apparatus for measuring plasma impedance.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for implementing the method for measuring the direction and coupling of a traveling wave and a reflected wave according to the present invention.

FIG. 2 is a schematic configuration diagram showing a plasma processing apparatus using the method for measuring the directionality and the degree of coupling according to the present invention.

FIG. 3 is a graph showing impedance calculated by a method for measuring the directionality and the degree of coupling.

FIG. 4 is a flowchart showing a procedure of a method for measuring the directionality and the coupling degree according to the present invention.

FIG. 5 is a schematic configuration diagram illustrating a configuration of a power monitoring device that performs power monitoring using a directional coupler.

FIG. 6 is a schematic diagram illustrating an outline of a directional coupler.

FIG. 7 is a schematic configuration diagram showing a configuration for measuring a coupling degree by a conventional method.

FIG. 8 is a schematic configuration diagram showing a configuration for measuring directionality by a conventional method.

FIG. 9 is a flowchart illustrating a procedure for measuring a direction and a coupling degree by a conventional method.

[Explanation of symbols]

 Reference Signs List 21 oscillator 22 circulator 23 directional coupler 24 known impedance 25 oscilloscope 26 transmission line 27 transmission line 28 dummy load Pf traveling wave pickup unit Pr reflected wave pickup unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Okuda 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Isamu Mori ▲ kura ▼ 8--16 private city, Katano-shi, Osaka No. 19 F term (reference) 2G028 AA01 BB10 BF00 CG15 CG19

Claims (5)

[Claims] An electromagnetic wave propagating inside the directional coupler, wherein an output terminal of the power supply is connected to an input terminal of the directional coupler, an output terminal of the directional coupler is connected to an input terminal of the impedance terminator. A characteristic measuring method of a directional coupler for measuring a coupling degree and a directional characteristic of the directional coupler by measuring an output signal of the directional coupler according to the following. A method for measuring characteristics of a directional coupler, comprising using an impedance terminator generated. 2. An output terminal of the power supply is connected to an input terminal of the directional coupler.
Connect the output end of the directional coupler to the impedance terminator
Connected to the input terminal of the
N kinds (n ≧ 3) impedance terminators that generate radiation
And impedance Zp_iI-th (1 ≦ i ≦ n) in
Pickup of a directional coupler when a impedance terminator is connected
Increase the reflectance in the up area_iAnd the oscillation voltage of the power supply is V_i
Output voltage swing of the traveling wave pickup of the directional coupler.
Width | vf_i| And the output voltage amplitude of the reflected wave pickup |
vr_i| And the phase difference (Arg [vf_i] -Arg
[Vr_i]) And Zin_i= (| Vr_i
| / | Vf _i|) Exp [Arg [vr_i] -Arg [v
f_iSteps for calculating constants represented by]
And the coupling k of the traveling wave pickup of the directional coupler₁₁,direction
Sex₁₂/ K₁₁, Reflected wave pickup coupling k_{twenty one},direction
Sex_{twenty two}/ K_{twenty one}Using k₁₂’= K₁₂/ K₁₁, K_{twenty one}’=
k_{twenty one}/ K₁₁, K_{twenty two}’= K_{twenty two}/ K₁₁= (K_{twenty two}/ K_{twenty one}) ×
(K_{twenty one}/ K₁₁), Q_i= -Zin_i-Zin_iΓ_ik₁₂’+
k_{twenty one}’+ K_{twenty two}’Γ_iAnd Σ | Q_i|^TwoMinimize
k₁₂’, K_{twenty one}’, K_{twenty two}’
And k₁₁= | Vf_i| / ｛| V_i|| 1 + k₁₂’Γ_iCalculate｝
Measuring the characteristics of the directional coupler.
Law. 3. The method for measuring characteristics of a directional coupler according to claim 1, wherein the impedance terminator is constituted by a capacitance using gas as a medium. 4. A directional coupler for measuring directionality and degree of coupling by the method according to claim 1. 5. A plasma processing apparatus comprising the directional coupler according to claim 4.