JPH10185960A - High frequency signal detection probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To collectively detect high frequency voltage, and amperage on a transmission line, their waveform, phase angle between voltage and current, direct current component, higher harmonic component, etc., by containing a voltage detector and a current detector in the case. SOLUTION: A transmission terminal 2 provided with a transmission line 5 in a case 1 is connected through the toroidal coil 6 of a current detector 16 to the opposite side transmission terminal 3. The detection signal of the current detector 16 is output externally from a current signal terminal 9 through a current signal line 10 and the voltage between the transmission lines 4 and 5 is detected in between a voltage measuring point P and an earth terminal 8. This voltage is divided by low resistors R1 and R2 and capacitors C1 and C2 in a voltage detector 15 and its output is given to the voltage signal line 11 from a voltage signal terminal 7. By this constitution, simultaneous detection of waveform of voltage and current at the same point and time and detection of phase angle between voltage and current become possible. Also, load power, load impedance, current component in high frequency voltage, higher harmonic content, etc., in the waveform can be calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a high-frequency voltage and a waveform of a high-frequency power applied from a transmission line to a reactor of a plasma etching apparatus during an IC manufacturing process.
High-frequency current and its waveform, phase angle between voltage and current,
The present invention relates to a probe which is integrally formed in a simple and easy-to-use form for the purpose of detecting a DC component in a high-frequency voltage, a harmonic component in a voltage waveform, and a harmonic component in a current waveform. These detected signals can be converted into data by using measuring instruments such as an oscilloscope, a detector, a recorder, a DC voltmeter, a phase meter, and a spectrum analyzer as necessary.

[0002]

2. Description of the Related Art Conventionally, an oscilloscope has been commonly used for measuring a high frequency voltage because of its wide frequency band and simplicity. In the measurement of high-frequency current, it is generally considered that either a toroidal coil is used as a current transformer or a low resistance is inserted in series with a load to convert the current to a voltage and measure with an oscilloscope due to the limitation of the frequency band. .

[0003]

In the prior art, high-frequency voltage and high-frequency current are detected individually on the transmission line. Therefore, in general, a detection circuit must be arranged and wired each time necessary for measurement, which is disadvantageous from the viewpoint of simplicity.
Due to the short wavelength of the wave to be measured, slight deviation or inclination of the measurement position may be greatly affected by the reproducibility of the detection signal, and the detection signal may become unstable due to an induction failure depending on the wiring method. Was. In addition, the detection device must be exposed to the air, and the danger of handling high-frequency high-frequency power cannot be ignored. The present invention has been made to solve such a problem.

[0004]

The gist of the present invention is that the voltage detector 15 and the current detector 16 shown in FIG. 1 are rationally combined in the case 1 and have a new function which is generated in principle. An object of the present invention is to provide a product and to provide a new technology for a method of detecting and measuring electric information on a transmission line, which has been a problem in many cases. A transmission line terminal 2 is attached to the case 1, to which one end of a pair of transmission lines, that is, an end of the transmission line 5 is connected. The transmission line 5 penetrates through the toroidal coil of the current detector inside the case 1 and reaches the transmission line terminal 3 on the opposite side. A current detection signal obtained by the toroidal coil is led out through a current signal terminal 9 to a current signal line 10. On the other hand, the voltage between the transmission lines 4 and 5 is detected as a potential between the voltage measuring point P conducted on the transmission line near the toroidal coil and the ground terminal. At this time, as shown in FIG. 2, the transmission line 4 is connected to one end of the load and is grounded. Therefore, the ground wire 17 drawn from the ground terminal 8 is connected to the ground point of the load. The high-frequency voltage detected in this manner is divided by a resistance voltage divider composed of low resistances R ₁ , R ₂ and capacitors C ₁ , C ₂ in the voltage detector 15, and the output is supplied from a voltage signal terminal 7 to a voltage signal terminal 7. It is led to the signal line 11. Now, if the damping ratio due to resistance is K, Voltage V Tosureba detected voltage signal V _E of the detection points converted if to preset the V E ₌ KV Therefore K is very easy. C ₁ and C ₂ are phase compensation capacitors, and are used to keep the attenuation ratio K constant regardless of the frequency. A resistor R in the current detector 16 in FIG. 1 is a damping resistor for suppressing resonance between the toroidal coil and the stray capacity. When configured as described above as a means for solving the problems, a function having a principle of novelty appears due to a combination effect thereof. These notable effects are listed below. (A) Voltage waveforms and current waveforms at the same point and at the same time can be detected simultaneously without time delay. Conventionally, this method has a difficulty in operation using a single detector. However, in the probe of the present invention, the opposite detectors 15 and 16 are mechanically and firmly fixed inside the case 1 and do not cause positional aging. Therefore, even if the mounting position of the case 1 on the transmission line is changed, good synchronism between the voltage signal and the current signal can be maintained. Observation or measurement of these waveforms can be performed with a normal two-phenomenon oscilloscope. (B) If the voltage waveform and the current waveform can be respectively detected by the term (a), the phase angle between the voltage and the current can be detected. This is a novel function that cannot be performed by a conventional single-function detector. (C) If the phase angle is known, the load power can be calculated. (D) Once the phase angle is determined, the impedance of the load is also determined. (E) Since a resistance voltage divider is used, a DC component included in the high-frequency voltage can also be detected. (F) Since the waveform measurement can be performed by the item (a), all the individual electrical information of the voltage and current signals can be obtained. That is, in addition to the term (b), for example, the harmonic component content, frequency, period, rise and fall of the waveform, duty cycle, pulse width, modulation degree, time interval, and the like are included. (G) Even if the probe of the present invention is attached, the effect on the load is negligibly small and does not affect the operation of the load at all. (H) It has a very compact configuration, is easy to install in narrow places, is convenient, and may be installed for a long time. In summary, the high-frequency signal probe of the present invention has only a total of three signal lines including the ground line 17 as a detection signal output, forms a small box-shaped object that does not require a power supply, and is located at an arbitrary position on the transmission line. It can be said that it is a new device that can be installed and can easily detect a lot of electrical information at the same point and the same time.

[0005]

FIG. 2 shows a specific example in which the terminal voltage and load current of a load to which high-frequency power is supplied by the transmission lines 4 and 5 are detected. The high-frequency signal detection probe of the present invention is connected between the impedance matching device and the load by the transmission lines 4 and 5, and the wiring distance between the transmission line terminal 3 and the load terminal is made as small as possible. This is to prevent an error in detecting the phase angle. Power is supplied to the load via the impedance matching device. At this time, the circuit constant of the matching unit is adjusted so that the reflected wave from the input of the impedance matching unit is minimized so that the load impedance and the power supply output impedance are matched. The position where the probe of the present invention is inserted is the most sensitive to this matching condition. However, the shape, size, structure,
As a result of optimizing the arrangement and the like experimentally, it has been found that the effect on the load impedance and the load can be ignored in practical use. This is the case, for example, when measuring the plasma current generated in the reactor during the plasma etching process during IC manufacturing described below, a resistor with a low resistance value is inserted in series between the impedance matching device and the reactor as a current detecting element. In some cases, the use of a signal detection probe has no effect on the use of a signal detection probe, which is one of the most important issues in probe configuration. In order to measure the signal output with the high frequency signal detection probe of the present invention, it is convenient to use an oscilloscope, a detector and a DC voltmeter. In the oscilloscope, both the voltage detection signal and the current detection signal are detected as a voltage signal waveform, and the V
_{A PP} value or a _VP value is obtained. To record on a recorder, this voltage waveform is rectified by a detector to obtain a _VP value. Using the resistive divider as shown in Figure 1, the voltage V between the transmission lines 4 and 5 because the attenuation factor K is found is K times the detected voltage signal V _E. The load current is measured in the same manner, and the voltage value obtained by multiplying the current signal output V ₁ volt by a constant N is converted to a current value. The constant N is determined experimentally in advance.

[0006]

【Example】

Embodiment 1 Embodiment 1 will be described below with reference to FIG. (A) An input coaxial connector is attached to the metal case 1 as the transmission line terminal 2. Similarly, an output coaxial connector is attached as the transmission line terminal 3. (B) A small coaxial connector is mounted as the voltage signal terminal 7 and a small coaxial connector is similarly mounted as the current signal terminal 9. (C) The printed circuit board in which the voltage detector 15 and the current detector 16 are combined is stored in the case 1 and the terminals 2, 3,
7 and 9 are fixed by soldering and are electrically connected at the same time. (D) Close the lid 12. The first embodiment has an integral structure as described above, and is a system applied as a feature of the configuration when the transmission line is a coaxial cable. In addition, since the coaxial cable is used, since the braided wire is shared with the ground wire to connect to the load, no ground terminal is provided. Also, since this probe is a shield type, it has a feature that it is difficult to pick up induced noise from outside.

Embodiment 2 Embodiment 2 is configured as shown in FIG. (A) A square hole is made in the side surface of the plastic case 1 and copper bands are penetrated therethrough as the transmission line terminals 2 and 3 so that the toroidal coil can operate as a current detecting element. (B) A small coaxial connector is attached as each of the voltage signal terminal 7 and the current signal terminal 9. (C) A ground terminal 8 having an appropriate structure is provided. (D) A printed circuit board in which the voltage detector 15 and the current detector 16 are combined is housed in the case 1 and wiring and soldering are performed. (E) Close the lid 13 to form an integral structure. Embodiment 2 is a probe suitable for a split line type transmission line as described above.

[0007]

In the transmission of high-frequency power, there is a case where it is particularly desired to know the state of the load strictly in real time. A good example of this is seen in the plasma etching process during IC manufacture.
Since the high-frequency signal detection probe of the present invention is a kind of diagnostic device developed for the purpose of stabilizing this process, it can be obtained as a result of an experimental test of the probe of the present invention prior to being actually employed in this process. The effect will be described. The high-frequency discharge phenomenon in the plasma reaction chamber is directly related to the type of gas used, its combination, pressure, the type and amount of labile products produced by the reaction, the dimensions of the reaction chamber and electrodes, their surface conditions, and the reaction time. By indirectly,
The amount of high frequency power applied, its waveform, voltage peak value, current peak value, its phase angle, the harmonic content of the voltage / current waveform, etc., or the circuit constant in the impedance matching device connected in the preceding stage The state greatly depends on the selection of the item. It is needless to say that in order to perform this operation efficiently and economically in the plasma etching process, it is essential to fully understand the above-mentioned various factors that are extremely complicated and mutually related. But,
Heretofore, there has been no satisfactory probe on the market for detecting such a large amount of electrical information in real time, simultaneously and continuously without affecting the running reaction process. The probe of the present invention not only satisfies all of these requirements, but also has the simplicity of being easily attached to a narrow portion of a device that is actually operating, and can cope with either a coaxial type or a stripline type. It also has general versatility that can be used for the majority of existing plasma etching apparatuses. Therefore, the probe of the present invention has great value as a new powerful plasma diagnostic apparatus or a monitor for a plasma reaction chamber. Hereinafter, several examples of uses and effects that apply these features are listed in a bulleted list. (A) Plasma process diagnostic monitor In particular, a single-wafer type plasma process apparatus continuously performs wafer processing, but uses the probe of the present invention, has no effect on the process result, and has a long time without heat generation of the probe itself. It was possible to monitor continuously for a stable period. Abnormalities during the process were determined based on the voltage-current waveform, voltage-current characteristics, etc., and the difference between normal and abnormal could be grasped reliably. (B) Abnormal plasma discharge detection monitor The plasma in the reaction chamber may cause a local small spark discharge for some reason, and the process itself may fail. Since the probe of the present invention enables real-time waveform observation with an oscilloscope, it can reliably detect high-speed phenomena such as spark discharge. As a result, abnormal discharge which is often overlooked was detected, which was useful for improving etching conditions. (C) End point detection monitor Conventionally, the end point of the etching process has been optically observed for the plasma spectrum. However, as a result of detecting the voltage-current characteristics of the plasma with the probe of the present invention, the end point detection monitor depends on the optical method. The end point could be easily detected. (D) Diagnosis monitor for plasma equipment differences In a factory, there are many plasma equipment used in the same process. Naturally, efficiency cannot be improved unless the characteristics of each model are uniform. As a result of detecting and comparing specific electrical characteristics using the probe of the present invention for this purpose, it was possible to reduce variations among devices so as to obtain good compatibility in all models. It can be easily inferred that the above-mentioned application examples are only a few application examples of the high-frequency signal detection probe of the present invention and have many more possibilities.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the configuration principle of the present invention.

FIG. 2 is an explanatory view showing how to use the present invention.

FIG. 3 is a six-sided view of a product showing the first embodiment of the present invention.

FIG. 4 is a six-sided view of a product showing Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2 Transmission line terminal 3 Transmission line terminal 4 Transmission line 5 Transmission line 6 Toroidal coil 7 Voltage signal terminal 8 Ground terminal 9 Current signal terminal 10 Current signal line 11 Voltage signal line 12 Lid 13 Lid 14 Mounting bracket 15 Voltage detector 16 Current detector 17 Ground wire

Claims (1)

[Claims] A transmission line terminal connected to a transmission line.
A voltage detector 15 and a current detector 16 are built in the case 1 in which the transmission line terminal 3 connected to the load is mounted, and a high-frequency voltage between the transmission line terminal 2 or 3 and the ground terminal 8 and its waveform are detected. Detecting the high-frequency current flowing between the transmission line terminals 2 and 3 and its waveform,
From the voltage signal terminal 7 and the current signal terminal 9 mounted on the case 1, the high-frequency voltage value and its waveform at the same point and the same time on this transmission line, the high-frequency current value and its waveform, the phase angle between the voltage and current, It is characterized by being able to simultaneously detect all the electrical information such as the DC component in the high-frequency voltage, the harmonic component in the voltage waveform, and the harmonic component in the current waveform, and output the signal at the same time. High frequency signal detection probe pursuing compactness and simplicity by structuring