JP3785996B2 - Plasma etching apparatus and semiconductor device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the production how a plasma etching apparatus and a semi-conductor device having a high-frequency power source.
[0002]
[Prior art]
In recent years, there has been a remarkable improvement in the degree of integration of semiconductor devices. However, as the degree of integration increases, the process margin in manufacturing semiconductor devices is becoming narrower. Semiconductor devices are made by numerous manufacturing processes and manufacturing equipment. For this reason, it is a big problem that the yield of the semiconductor device varies due to the difference between the manufacturing apparatuses and the equipment difference of the manufacturing apparatuses.
[0003]
FIG. 13 is a schematic view showing a conventional plasma etching apparatus. In FIG. 13, an upper electrode 2 and a lower electrode 3 are provided inside a reaction chamber 1, and a wafer 4 that is a semiconductor substrate is placed on the lower electrode 3. The process gas is introduced into the reaction chamber 1 through a flow meter (not shown). The gas pressure inside the reaction chamber 1 is measured by a pressure gauge 5 and controlled by a control device 8 so that the reaction chamber 1 becomes a predetermined pressure by a pressure adjusting valve 7 attached between the exhaust pump 6 and the reaction chamber 1. To do.
[0004]
Thereafter, high frequency power is applied between the upper electrode 2 and the lower electrode 3 from the high frequency power source 9 to generate plasma. The high-frequency power is matched by the matching unit 10 and supplied to the high-frequency application electrode composed of the upper electrode 2 and the lower electrode 3, but the reflected wave of the plasma reaching the wafer 4 is reduced as much as possible, in other words, the maximum power can be supplied. Thus, the impedance of the matching unit 10 is changed. These series of operations are performed by the control device 8.
[0005]
The high frequency power is measured by inserting the power sensor 11 between the matching unit 10 and the high frequency power source 9 and can be confirmed by the power meter 12. However, since the high frequency power is measured between the matching unit 10 and the high frequency power source 9, the high frequency power is matched. The loss in the vessel 10 is not considered. Therefore, the net amount of power entered from the lower electrode 3 cannot be measured. In addition, such power measurement is non-periodic measurement only at the time of start-up, and it cannot detect fluctuations in high-frequency power accompanying process fluctuations, equipment fluctuations caused by parts replacement or maintenance.
[0006]
[Problems to be solved by the invention]
In the conventional plasma etching apparatus, even if the impedance of the reaction chamber 1 changes, the control device 8 automatically adjusts the impedance of the matching unit 10 so as to follow the change so that the supplied high-frequency power is maximized. There was a problem that process yields and differences between apparatuses could not be detected, and the manufacturing yield of semiconductor devices varied.
[0007]
The present invention solves this problem, and plasma etching that prevents the semiconductor device manufacturing yield from fluctuating by directly measuring, analyzing, and adjusting the impedance applied to the semiconductor device even when the impedance of the reaction chamber 1 changes. An object of the present invention is to provide an apparatus, a method for manufacturing a semiconductor device using the same, and a method for monitoring a plasma etching apparatus.
[0008]
[Means for Solving the Problems]
The plasma etching apparatus of the present invention includes a high-frequency power source, a matching unit connected to the high-frequency power source, a current and a voltage applied to the high-frequency applying electrode between the matching unit and a high-frequency applying electrode in a reaction chamber, and A detecting means for detecting a phase difference is provided.
[0009]
By providing detection means between the matching unit and the high-frequency application electrode in the reaction chamber, it is possible to detect the current and voltage applied to the high-frequency application electrode accompanying the change in the impedance of the reaction chamber 1 and the phase difference thereof.
[0010]
In addition, the plasma etching apparatus of the present invention further includes a first control unit that analyzes a signal from the detection unit.
[0011]
By analyzing the signal from the detection means by the first control means, the impedance applied to the high frequency application electrode can be adjusted.
[0012]
In the plasma etching apparatus of the present invention, the second control means for controlling the plasma generation in the reaction chamber and the first control means are connected, and the current and voltage and their levels with time are synchronized with the plasma generation. It is characterized by detecting a phase difference.
[0013]
In addition, the plasma etching apparatus of the present invention is characterized in that the impedance and its harmonic component are calculated using Fourier transform.
[0014]
As a result, it is possible to automatically adjust the supply high-frequency power so as to maximize, excluding the influence of the harmonic component.
[0015]
In addition, the plasma etching apparatus of the present invention is characterized by comprising a calculation means for calculating the electron density from the current and voltage detected by the detection means.
[0016]
As a result, the electron density of the plasma etching apparatus can be managed and adjusted.
[0017]
A method of manufacturing a semiconductor device using a plasma etching apparatus of the present invention includes a step of placing a semiconductor substrate to be etched on a lower electrode in a reaction chamber, a pressure in the reaction chamber, and an upper electrode and a lower portion. A step of generating plasma by a high-frequency power source between high-frequency applied electrodes made of electrodes, and a detecting means for connecting a current and a voltage applied to the lower electrode on which the semiconductor substrate is placed and a phase difference thereof to the lower electrode And a detecting step.
[0018]
According to the manufacturing method described above, since the supply high-frequency power at the lower electrode on which the semiconductor substrate is directly mounted is viewed, process fluctuations and differences between devices can be detected and the supply high-frequency power can be adjusted to the maximum. Thereby, fluctuations in the manufacturing yield of the semiconductor device can be prevented.
[0019]
In addition, the monitoring method of the plasma etching apparatus of the present invention includes a high-frequency detecting device connected between a matching unit connected to a high-frequency power source and a high-frequency application electrode in the reaction chamber in synchronization with generation of plasma in the reaction chamber. It is characterized in that the current and voltage applied to the application electrode and the phase difference thereof are detected over time to check the change in etching characteristics.
[0020]
With this configuration, the high-frequency power at the high-frequency application electrode can be monitored over time in synchronization with the generation of plasma, so that the plasma state in the reaction chamber and the supplied high-frequency power can be adjusted.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a schematic view showing a plasma etching apparatus according to a first embodiment of the present invention. The same configurations as those in the schematic diagram of the plasma etching apparatus shown in FIG. 13 are denoted by the same reference numerals, and detailed configurations are omitted. In the plasma etching apparatus of the present invention, a current-voltage phase difference sensor 21 is attached between the lower electrode 3 and the high-frequency power matching unit 20 in the high-frequency application electrode composed of the upper electrode 2 and the lower electrode 3 in the reaction chamber 1. Thus, the current and voltage actually supplied to the plasma etching apparatus and the phase difference thereof can be directly measured by the current voltage phase difference sensor 21 which is a detecting means without including the loss in the matching unit 20, and the current voltage phase difference meter 22 can be measured. It can be confirmed with. Thereby, the electric energy supplied to the plasma etching apparatus can be detected.
[0022]
Further, the current-voltage phase difference sensor 21 has a sub-line coupled to the main line (not shown), and measures the current flowing through the main line by measuring the induced current induced in the sub-line. To do. In other words, the current flowing in the main line is not directly measured, but the induced current induced in the sub-line is measured. Therefore, the loss in the current-voltage phase difference sensor 21 need not be considered. Furthermore, the phase difference can be measured from the measured current and voltage. Accordingly, it is possible to measure the current and the applied voltage flowing into the lower electrode 3, and thus the wafer 4 that is the semiconductor substrate to be etched, placed on the lower electrode 3, and to measure the plasma impedance.
[0023]
(Second embodiment)
FIG. 2 is a schematic view showing a plasma etching apparatus according to the second embodiment of the present invention. A control device 23 is connected to the current voltage phase difference sensor 21 and the current voltage phase difference meter 22 with respect to the plasma etching apparatus according to the first embodiment. By adding the control device 23, the harmonic component of the current, voltage, and impedance value can be quantitatively extracted by performing Fourier transform on the measurement data of the electric energy measured by the current-voltage phase difference sensor 21. Further, not only numerical data but also a signal waveform with respect to time can be observed from the signal from the actual current / voltage phase difference sensor 21. It should be noted that the fluctuation of the impedance of the reaction chamber 1 due to the attachment of the control device 23 to this portion hardly affects.
[0024]
The harmonic components of current, voltage and impedance values are considered sensitive to process variations. This is because the harmonic components of the current, voltage, and impedance value reflect the state of the sheath formed on the wafer 4, and the energy of ions incident on the wafer 4 is changed by this sheath. Therefore, process fluctuations can be sensed by the harmonic components of the current, voltage and impedance values extracted by the control device 23, and as a result, adjustments to the impedance fluctuations can be made. In addition, the plasma state in the reaction chamber 1 can be adjusted.
[0025]
In the case of an equivalent circuit, the plasma can be represented by resistance, and the sheaths of the upper electrode 2 and the lower electrode 3 can be represented by capacitance. In addition, a diode added in parallel with these capacitors can be considered. However, nonlinear effects such as harmonic components do not appear only with a linear element of resistance and capacitance. That is, the nonlinear effect reflects the state of the sheath.
[0026]
(Third embodiment)
FIG. 3 is a schematic view showing a plasma etching apparatus according to the third embodiment of the present invention. Reaction of the plasma etching apparatus with respect to the plasma etching apparatus according to the second embodiment, the control apparatus 23 for controlling the current / voltage phase difference sensor 21 and the current / voltage phase difference meter 22 for measuring the current / voltage / phase difference, and the plasma etching apparatus. By connecting a high-frequency power source 9 for applying high-frequency power to the pressure of the chamber 1 and a high-frequency application electrode and a control device 8 for controlling the matching unit 20 by signal lines, an on signal and an off signal for operating and not operating the plasma etching apparatus are connected. Can be imported. Accordingly, the current and voltage supplied to the plasma etching apparatus and the phase difference thereof can be automatically measured by the current / voltage phase difference sensor 21 in synchronization with the main body of the plasma etching apparatus.
[0027]
According to the measurement result of the current-voltage phase difference sensor 21, the control device 8 analyzes the process variation, senses the process variation, feeds back to the control device 23, adjusts the applied power by the high-frequency power source 9, and the pressure in the reaction chamber 1 The plasma state in the reaction chamber 1 can be controlled by the adjustment.
[0028]
(Fourth embodiment)
FIG. 4 is a schematic view showing a plasma etching apparatus according to the fourth embodiment of the present invention. An arithmetic unit 24 is further connected to the current / voltage phase difference sensor 21 for measuring the current / voltage / phase difference and the control unit 23 of the current / voltage phase difference meter 22 to the plasma etching apparatus of the third embodiment. . Thereby, it can calculate by the program etc. which the user set.
[0029]
Here, a case where the electron density is derived from the plasma impedance value will be described. The current density J in the bulk plasma is expressed by the following formula.
[0030]
J = [n _e e ² / {m _e (ν _e + iω)} + iωε ₀ ] E ………… (1)
= [{n _e e ² (ν _e -iω)} / {m _e (ν _e ² + ω ² )} + iωε ₀ ] E ………… (2)
Here, _ne is the electron density, _me is the static mass of the electron, ν _e is the collision frequency between the electron and neutral particles, ω is the angular frequency, ε ₀ is the dielectric constant of vacuum, E is the electric field strength, and i is Imaginary unit. Where ν _e >> ω, so
J = [(n _e e ² / m _e v _e ² ) (v _e -iω) + iωε ₀ ] E (3)
It becomes. Further, assuming that the electrode area is A and the distance between the electrodes is L, the current value I = JA and the voltage V = EL, so the bulk impedance Z is Z = V / I and is as follows.
[0031]
Z = L / [A {(n _e ² / m _e v _e ² ) (v _e -iω) + iωε ₀ }] ………… (4)
= (L / A) {Bν _e / C + iωB / C-iωε ₀ / C} ………… (5)
Here, put a ^{_{B = n e e 2 / m}} e ν e 2, C = (Bν e) 2 + ω 2 (ε 0 -B) 2.
[0032]
In the above equation (5), the real part of the first item represents the bulk resistance value, the imaginary part of the second item represents the inductance due to the inertia of the electrons, and the third item represents the bulk capacitance. Therefore, the bulk resistance value R _b is as shown in Equation (6).
[0033]
R _b = LBν _e / AC (6)
Further, the formula (6) is ^{_{1»ω 2 (ε 0 -B) 2}} / (Bν e) 2 So, the bulk resistance value R _b is represented by the formula (7), seen to be inversely proportional to the electron density n _e .
[0034]
R _b ≒ L m _e ν _e / A n _e e ² (7)
Therefore, the electron density _ne is obtained by measuring the bulk resistance value R _b from the equation (7). By executing the above calculation by the arithmetic unit 24, it is possible to manage the electron density change of the plasma etching apparatus. It calculates the bulk resistance value from the current and voltage and phase difference measured by the current-voltage phase difference sensor 21, then over time to calculate the electron density n _e by the programmed arithmetic unit 24, the electron density n as a result The change of _e can be recognized as the change of the plasma state of the plasma etching apparatus. Thereby, the arithmetic unit 24 is connected to the control unit 8 of the manufacturing apparatus via the control unit 23, and monitoring over time is possible, and the control unit is based on information fed back with respect to changes in the plasma state. Control is performed so as to obtain an optimal plasma state at 8.
[0035]
Conventionally, the electron density n _e was measured by inserting a like rungs mu Ah probes were generated in the reaction chamber plasma, in this case, can not be accurately measured by the deposition film on the probe surface is adhered In addition, there are many problems such as metal contamination such as tungsten by the probe and the fact that the vacuum has to be broken in order to attach it, making it difficult to use in actual mass production sites. According to the monitoring method in the embodiment of the present invention, all these problems can be solved.
[0036]
Next, an actual case, in particular, a case where a deposited film is formed on the surface of the reaction chamber and the plasma changes will be described. Conventionally, semiconductor devices have been manufactured with elements such as oxygen, phosphorus, arsenic, boron, nitrogen, and aluminum using silicon as the main raw material, but new technologies have been developed in the process of overcoming various technical issues such as reduction in integration and power consumption. Some of these technologies use elements other than conventional elements. For example, there is a technique using copper as a wiring material in addition to aluminum.
[0037]
FIG. 5 shows a state of the plasma etching apparatus for specifically explaining a case where deposits adhere to the wall surface of the reaction chamber 1, using FIG. 4 showing the plasma etching apparatus according to the fourth embodiment. FIG. When the wafer 4 placed on the lower electrode 3 is subjected to plasma etching, a reaction product is formed, and a low vapor pressure deposits as an adherent 25 on the wall surface of the reaction chamber 1.
[0038]
Among the reaction products, when a silicon nitride film or silicon oxide film on a metal such as aluminum or copper is etched, a part of the metal is etched and sputtered by ion bombardment during overetching. Depending on the aspect ratio of the pattern, the metal scatters into the reaction chamber 1 if the aspect ratio is small. When the scattered metal accumulates on the wall surface of the reaction chamber 1, it affects the plasma and changes the etching characteristics on the wafer 4.
[0039]
Here, the silicon nitride film on the copper wiring will be described.
[0040]
FIG. 6 is a semiconductor substrate to be etched in FIG. 5 and shows a cross-sectional structure of the wafer 4 in the process of removing the silicon nitride film on the copper wiring. In FIG. 6, a silicon nitride film 31 is formed on the surface of a silicon substrate 30 which is a semiconductor substrate, a copper wiring 32 is formed on the silicon nitride film 31, and a silicon nitride film 33 is formed thereon with a thickness of 200 nm. Has been. In order to etch the silicon nitride film 33, a resist film 34 is selectively formed on the silicon nitride film 33 with a thickness of 1200 nm.
[0041]
The result of etching the wafer 4 with copper shown in FIG. 6 and examining the change in etching characteristics will be described. FIG. 7 is a characteristic diagram showing etching characteristics of various insulating films such as a silicon nitride film or a silicon oxide film and a resist film on the copper wiring 32 formed on the wafer 4. The horizontal axis represents the etching time of the wafer with copper, and the vertical axis represents the etching rate of each insulating film.
[0042]
It is known that when copper is etched for about 300 seconds, a deposit containing copper having a surface concentration on the wafer of 10 ¹⁰ / cm ² to 10 ¹¹ / cm ² adheres to the reaction chamber wall surface. With this level of copper, the etching rate (SiN rate) of the silicon nitride film decreases to less than half of 400 nm / min compared to 1000 nm / min at the start of etching when the etching time of copper is about 100 seconds. On the other hand, the etching rate (SiO ₂ rate) of the silicon oxide film is approximately doubled. On the other hand, the etching rate (PR1 rate) of the resist film on the silicon nitride film and the etching rate (PR2 rate) of the resist film on the silicon oxide film hardly change regardless of the etching time of copper.
[0043]
This is because CF ₂ radicals are decomposed by the catalytic effect of copper to become CF radicals and fluorine radicals. When the CF radical becomes dominant, a fluorocarbon layer is easily formed because there is no oxygen on the surface of the silicon nitride film. However, since there is no oxygen, the fluorocarbon layer does not decompose. This slows the etching rate. On the other hand, since the silicon oxide film contains oxygen, the fluorocarbon layer formed on the surface is decomposed and can be converted into volatile products such as SiO ₂ and CO ₂ . Thereby, since the fluorocarbon layer can be generated and decomposed smoothly, the etching rate is increased. In other words, in the case of a silicon nitride film, it is in a reaction-controlled state, and the etching rate is slowed down by forming a fluorocarbon layer, and the silicon oxide film is in a supply-controlled state, and the fluorocarbon layer is formed in the top. It is considered that the etching rate is increased.
[0044]
The catalytic effect of copper will be described based on changes in the emission intensity of fluorine, argon and oxygen. FIG. 8 is a characteristic diagram showing the change in the emission intensity of each element with respect to the etching time of the silicon nitride film 33 on copper on the wafer 4. FIG. 8A shows the change in the emission intensity of fluorine, FIG. 8B shows the change in the emission intensity of argon, and FIG. 8C shows the change in the emission intensity of oxygen. FIG. 8A shows that the etching time of copper becomes long, that is, the concentration of fluorine increases when copper adheres to the reaction chamber wall surface.
[0045]
This indicates that fluorine is generated as a result of the decomposition of the CF ₂ radical by the catalytic effect of copper. FIG. 8B also shows that the emission intensity of argon increases with the release of copper. This is because electrons are captured by copper and the dissociation of argon proceeds to maintain the electron density. The increase in the emission intensity of oxygen shown in FIG. 8C is the same as in the case of argon.
[0046]
In such a phenomenon that copper adheres to the reaction chamber wall surface, the etching characteristics change as described above. The results of simultaneous measurement of the current-voltage phase difference will be described below.
[0047]
FIG. 9 is a characteristic diagram of the current value flowing into the wafer with respect to the etching time of the silicon nitride film on copper on the wafer. 9A shows the fundamental wave of the current value, FIG. 9B shows the first harmonic, FIG. 9C shows the second harmonic, FIG. 9D shows the third harmonic, FIG. e) shows the fourth harmonic. The current value increases from the fundamental wave and from the first harmonic to the third harmonic with the release of copper. This is considered to reflect an increase in plasma density. The fourth harmonic has almost no change, and the detection sensitivity of the reaction chamber state is small.
[0048]
FIG. 10 is a characteristic diagram of a voltage value applied to the wafer with respect to the etching time of the silicon nitride film on copper on the wafer. 10A shows the fundamental wave of the voltage, FIG. 10B shows the first harmonic, FIG. 10C shows the second harmonic, FIG. 10D shows the third harmonic, and FIG. ) Indicates the fourth harmonic. The fundamental wave of the voltage becomes smaller when copper is scattered in the reaction chamber. This reflects the increase in plasma density.
[0049]
FIG. 11 is a characteristic diagram of the impedance value at the wafer with respect to the etching time of the silicon nitride film on copper on the wafer. 11A shows the fundamental wave of the impedance value, FIG. 11B shows the first harmonic, FIG. 11C shows the second harmonic, FIG. 11D shows the third harmonic, 11 (e) represents the fourth harmonic. The impedance value also tends to decrease when copper is scattered in the reaction chamber, reflecting the increase in plasma density.
[0050]
When the impedance value is represented on the Smith chart, it can be seen that the impedance movement of the fundamental wave has a decrease in resistance value and an additional capacitance component.
[0051]
As can be seen from FIGS. 9, 10, and 11, the etching state in the plasma state can be monitored by measuring the current, voltage, or impedance at any time by the monitoring method shown in the present invention. Optimal control is possible.
[0052]
FIG. 12 shows the etching rate variation in the process of decreasing the concentration of copper adhering to the reaction chamber surface with respect to the etching time by performing dummy discharge in the silicon dummy wafer.
[0053]
In the above description, the case where the opening area for copper is large has been described, but it goes without saying that the same can be said when copper is released into the reaction chamber even when the opening area is small as in the case of damascene etching. Absent.
[0054]
Moreover, although it demonstrated as what controls the plasma state of a plasma etching apparatus automatically with a control apparatus based on the monitoring result, it is needless to say that it may be manual.
[0055]
【The invention's effect】
In the plasma etching apparatus of the present invention, detection means for detecting current and voltage and its phase difference is inserted between a high-frequency applying electrode in a reaction chamber for performing an etching process on a semiconductor substrate and a matching unit connected to a high-frequency power source. Therefore, it is possible to detect process fluctuations on the semiconductor substrate based on the change in the reaction chamber by directly measuring the current and voltage applied to the high frequency application electrode and the phase difference without including the loss in the matching unit. it can. Further, by linking with the control means for controlling the plasma generation in the reaction chamber, it becomes possible to detect the current and voltage at the high frequency application electrode and the phase difference in synchronization with the plasma generation, and based on the detection result. In addition, it is possible to control the plasma state for optimization.
[0056]
According to the method of manufacturing a semiconductor device using these plasma etching apparatuses, since the supply high-frequency power is observed at the lower electrode on which the semiconductor substrate is directly mounted, process fluctuations and differences between apparatuses are detected, and the supply high-frequency power is detected. The power can be adjusted to the maximum. Thereby, fluctuations in the manufacturing yield of the semiconductor device can be prevented.
[0057]
Further, according to the monitoring method of the plasma etching apparatus of the present invention, the high-frequency power at the direct high-frequency application electrode can be monitored over time in synchronization with the generation of plasma, so that the plasma state in the reaction chamber and the supplied high-frequency power can be adjusted. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing a plasma etching apparatus according to a first embodiment. FIG. 2 is a schematic view showing a plasma etching apparatus according to a second embodiment. FIG. 3 is a third embodiment. FIG. 4 is a schematic view showing a plasma etching apparatus according to a fourth embodiment. FIG. 5 is a schematic view of the plasma etching apparatus when deposits are attached to the wall of the reaction chamber. 6 is a diagram showing a cross-sectional structure of a wafer in a process of removing a silicon nitride film on a copper wiring. FIG. 7 is a characteristic diagram showing etching characteristics of various insulating films as copper increases. FIG. 8 is an etching of a silicon nitride film. FIG. 9 is a characteristic diagram of the light emission intensity of each element with respect to time. FIG. 9 is a characteristic diagram of a current value flowing into the wafer with respect to the etching time of the silicon nitride film. [Fig. 11] Characteristic diagram of the impedance value at the wafer with respect to the etching time of the silicon nitride film. [Fig. 12] Characteristic diagram of the etching rate as the copper decreases. [Fig. Schematic showing the plasma etching system
DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Upper electrode 3 Lower electrode 4 Wafer 5 Pressure gauge 6 Exhaust pump 7 Pressure adjustment valve 8 Control apparatus 9 High frequency power supply 20 Matching device 21 Current voltage phase difference sensor 22 Current voltage phase difference meter 23 Control apparatus 24 Calculation apparatus 30 Silicon Substrate 31 Silicon nitride film 32 Copper wiring 33 Silicon nitride film 34 Resist film

Claims (7)

A high frequency power supply,
A matching unit connected to the high-frequency power source;
A detecting means for detecting a current and a voltage applied to the high-frequency application electrode and a phase difference between the matching unit and the high-frequency application electrode in the reaction chamber;
The detection means is connected to a high frequency application electrode on which a wafer is installed,
The detection means includes a main line and a sub line coupled with the main line,
A plasma etching apparatus for measuring a current flowing in the main line by measuring an induced current induced in the sub line. 2. The plasma etching apparatus according to claim 1, further comprising first control means for analyzing a signal from the detection means. A second control means for controlling plasma generation in the reaction chamber and the first control means are connected, and current, voltage and phase difference are detected over time in synchronization with the plasma generation. The plasma etching apparatus according to claim 2. 4. The plasma etching apparatus according to claim 2, wherein the first control unit calculates a harmonic component of a current, a voltage, and a phase difference using Fourier transform. 5. 4. The plasma etching apparatus according to claim 2, wherein the first control means calculates an impedance and its harmonic component using Fourier transform. 6. The plasma etching apparatus according to claim 1, further comprising a calculation unit that calculates an electron density from the current and voltage detected by the detection unit. A step of placing the semiconductor substrate of the etching target on the lower electrode in the anti応室,
Controlling the pressure in the reaction chamber and generating plasma with a high-frequency power source between a high-frequency application electrode consisting of an upper electrode and the lower electrode;
A step of detecting current and voltage applied to the lower electrode on which the semiconductor substrate is placed and a phase difference thereof with a detecting means connected to the lower electrode,
The detection means is connected to a high frequency application electrode on which a wafer is installed,
The detection means includes a main line and a sub line coupled with the main line,
A method for manufacturing a semiconductor device, comprising: measuring an induced current induced in the sub line to measure a current flowing in the main line.

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