JP2005209935A - Electric discharge detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric discharge detecting apparatus capable of surely detecting electric discharge generated in a chamber. <P>SOLUTION: The electric discharge detecting apparatus for detecting the electric discharge generated in the chamber 14 to which plasma is sealed includes a current probe 50 (detection means) for detecting a current signal appearing in a power feeding cable 40 for power required to generate the plasma, and an amplifier 70 (amplification means) for amplifying the detected current signal. An electromagnetic wave E generated in the chamber 14 is caught by the feeding cable 40 connected to an anode 24 and the current signal is generated in the feeding cable 40. The probe 50 detects the current signal, the amplifier 70 amplifies the current signal and thereafter a digital oscilloscope 80 displays the current. Thus, the electric discharge generated in the chamber 14 can surely be monitored independently of the frequency band of an electromagnetic wave. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a discharge detection apparatus for detecting a discharge generated inside a chamber such as a plasma etching apparatus.

  In a plasma etching apparatus, which is a kind of semiconductor manufacturing equipment, abnormal discharge phenomenon that occurs inside the chamber may be visually confirmed from the window of the chamber, and if the discharge energy is large, burning marks may be seen on the semiconductor wafer. There is also. This discharge phenomenon may break the insulation of a part or the whole region of the wafer, which causes a significant decrease in the productivity of the electronic device. Here, an example of a plasma etching apparatus is shown. However, since a discharge easily occurs even in a low electric field in a vacuum, the same discharge phenomenon occurs in an ion milling apparatus, an ion implantation apparatus, a sputtering apparatus for forming a metal film, and the like.

However, since the window portion of the chamber is generally small, the entire area in the chamber cannot be visually observed. In addition, since light emission due to discharge often disappears in a short spot, it may not be recognized visually. Further, in order to move the wafer charged during the plasma processing to the next stage, the back surface of the wafer is pushed up with metal pins, but the electrostatic discharge phenomenon that occurs at this point cannot be visually observed.
In recent years, as a technique for detecting the abnormal discharge phenomenon that occurs in the above-described chamber, an acoustic sensor is attached to the external wall surface of the plasma etching apparatus and monitoring is performed by the sound generated during discharge, or an AC voltage of about 13 MHz. A technique for monitoring by a change in the harmonic current of the source has been announced (see Non-Patent Document 1).
“Ultrasonic TECHNO 2002.5-6”, Nippon Kogyo Publishing Co., Ltd., p41-46

However, according to the technique for monitoring by the above-mentioned sound, since the discharge environment is close to vacuum, the sound wave may not reach the wall surface depending on the discharge position, and the discharge cannot always be detected. In addition, when using a harmonic current, there is a disadvantage that it is impossible to detect a phenomenon in which a high-frequency electrode plate is not directly discharged during operation, and it is impossible to detect a discharge phenomenon during conveyance other than a plasma state.
An object of the present invention is to provide a discharge detection device capable of accurately detecting a discharge in a chamber.

The present invention relates to a discharge detection device for detecting a discharge generated inside a chamber that encloses plasma, and is provided in a power supply path for generating the plasma in the chamber, and a current signal appearing in the power supply path And amplifying means for amplifying the current signal detected by the detecting means.
Here, since the discharge always involves the emission of electromagnetic waves, if the electromagnetic waves can be detected from the outside, the occurrence of discharge inside the chamber can be known. However, since the chamber is generally made of metal, the chamber basically has a structure in which electromagnetic waves do not leak outside. Therefore, the present invention focuses on a power supply path for generating plasma in the chamber, and captures a current signal due to electromagnetic waves in the chamber received by this power supply path. That is, according to the configuration of the present invention, an electromagnetic wave is captured using the feeding path protruding into the chamber as an antenna, and a current signal induced in the feeding path by the electromagnetic wave is monitored. Therefore, the occurrence of discharge in the chamber can be known from the current signal on the power supply path.

Moreover, in the above-described discharge detection device, the detection means includes, for example, a current probe that detects a magnetic field formed by the current signal. According to this configuration, the current signal on the power feeding path is detected via the magnetic field formed by the current signal on the power feeding path. Therefore, it is possible to effectively detect a current signal generated in the power feeding path without processing the power feeding path.
Furthermore, it is good also as a frequency identification means which identifies the frequency of the current signal amplified by the said amplifying means, and the said frequency identification means may identify the frequency of the said current signal by making 300 MHz into a threshold value, for example.

  According to the present invention, it is possible to directly detect an electromagnetic wave accompanying a discharge generated inside the chamber. Therefore, it becomes possible to detect the electromagnetic waves accompanying the discharge inside the chamber with high accuracy regardless of the frequency band.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an application example of a discharge detection device according to an embodiment of the present invention. In the figure, a chamber 14 constitutes a plasma dry etching apparatus, which is a kind of semiconductor manufacturing apparatus, in which an anode 24 on which a semiconductor wafer 22 as an object of dry etching processing is placed, and a gas G A cathode 26 also serving as a blowout port is accommodated. A high-frequency power source 28 provided outside the chamber 14 is connected to the anode 24.

  The gas G is introduced into the chamber from the inlet 32 at the upper end of the chamber I4, passes through the periphery of the wafer 22, and is discharged out of the chamber from the outlet 34 at the lower end of the chamber 14. A high-frequency voltage is applied to the anode 24 by the above-described high-frequency power supply 28 via the feeding cable 40, and a high-frequency electric field is formed between the anode 24 and the cathode 26. The power feeding cable 40 is composed of a coaxial cable having a low loss with respect to the high frequency power to be transmitted. The gas G is excited by an electric field formed between the anode 24 and the cathode 26 to form plasma, and the semiconductor wafer 22 is etched by the plasma. The window portion 12 provided on the outer wall of the chamber 14 is for an operator to observe the inside of the chamber from the outside, and is fitted with glass.

The current probe 50, the signal cable 60, the amplifier 70, and the digital oscilloscope 80 constitute a discharge detection device of the present invention that detects a discharge generated in the chamber 14. Here, the current probe 50 is for detecting a current signal generated in the power feeding cable 40, and is configured to be magnetically coupled to the power feeding cable 40 to detect the current signal, and uses a known technique. Can do.
The configuration of the current probe 50 is shown in FIG. The upper part of the figure is a perspective view, and the lower part of the figure is a sectional view. As shown in the upper part of the figure, the current probe 50 is formed in a substantially annular shape, and the skin portion 51 is made of a conductive metal member, and a slit 52 is formed along the inner periphery of the skin portion 51. A current probe 509 is attached to the power supply cable 40 so that the power supply cable 40 passes through the through hole of the current probe 50.

  Further, as shown in the lower part of the figure, a magnetic body 53 is provided inside the skin portion 51. That is, an annular magnetic body 53 is covered with a skin portion 51 made of a metal member, and a slit 52 is formed along the inner periphery of the skin portion 51. In the lower part of the figure, the inner conductor on one end side of the signal cable 60 is connected to the skin portion 51 corresponding to the upper end portion of the slit 52, and the outer conductor is connected to the skin portion 51 corresponding to the lower end portion of the slit 52. . The other end of the signal cable 60 is connected to the input portion of the amplifier 70, and the current signal detected by the current probe 50 is input to the amplifier 70 via the signal cable 60. A digital oscilloscope 80 is connected to the output section of the amplifier 70 so that the waveform of the output signal of the amplifier 70 can be observed.

Next, the operation of the discharge detection apparatus according to this embodiment will be described.
If a discharge occurs inside the chamber 14 during the processing of the semiconductor wafer 22, an electromagnetic wave E is generated along with this discharge. A part of the electromagnetic wave E enters the anode 24 in the chamber, and a current signal due to the electromagnetic wave E is generated in the internal conductor of the power supply cable 40 connected to the anode 24. When a current signal is generated in the inner conductor of the power supply cable 40, a current having a phase opposite to that of the current signal (hereinafter referred to as a reverse-phase current) is induced in the outer conductor of the power supply cable 40 after a certain delay time.

Here, when the length of the feeding cable 40 is 1 meter and the propagation speed of the electric signal is 300,000 km / s, the delay time when the electric signal propagates through the feeding cable 40 of 1 m is about 1 × 10 ^−9. Second. Accordingly, a delay time of about 1 × 10 ⁻⁹ seconds is generated from when a current signal is generated in the inner conductor of the power supply cable 40 until a reverse phase current appears in the outer conductor. During this time, a current signal exists only in the inner conductor of the power supply cable 40, and a state in which no reverse-phase current has yet occurred in the outer conductor occurs. In this state, since the magnetic field formed by the current signal reaches the current probe 50 without being attenuated by the reverse-phase current, the current signal is detected from this magnetic field.

  That is, in the lower part of FIG. 2, when a current signal appears in the feeding cable 40 that passes through the through hole of the current probe 50, a magnetic flux due to this current signal is generated inside the magnetic body 53. As a result, a current is induced between the upper end side of the slit 52 formed on the inner peripheral side of the skin portion 51 and the lower end side of the slit 52 through the skin portion 51, and this induced current is transmitted to the signal cable 60. The signal is supplied to the amplifier 70 via the amplifier 70, amplified by the amplifier 70, and then displayed on the digital oscilloscope 80. Thereby, the occurrence of the discharge is notified.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and design changes and the like within a scope not departing from the gist of the present invention are included in the present invention. For example, in the above-described embodiment, the current probe 50 is attached to the power supply cable 40 that supplies power to the anode 24 on which the wafer is placed. However, when power is supplied to the cathode 26 side, the current probe 50 is connected to the cathode side. A current probe may be attached to the feeder cable.

  Further, a filter having a frequency characteristic according to the type of discharge may be provided in the amplifier 70, whereby the frequency of the amplified current signal is identified, and the type of discharge is specified from the identified frequency. . In this case, if the frequency is identified using 300 MHz as a threshold, it is possible to effectively distinguish and notify low frequency discharge and high frequency discharge. In addition, although the current detected by the current probe 50 (induced current) is displayed on the digital oscilloscope 80, it may be notified by, for example, an alarm sound. Further, a filtering process may be performed on the current detected by the current probe 50 to cut out frequency components that become noise, or only specific frequency components related to discharge are selectively extracted. It may be amplified.

It is a block diagram which shows the structural example of the discharge detection apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the structure of the current probe which concerns on embodiment of this invention.

Explanation of symbols

12; window, 14; chamber, 22; semiconductor wafer, 24; anode, 25; electrostatic chuck, 26; cathode, 28; high-frequency voltage source, 32; inlet, 34; Current probe, 60; signal cable, 70; amplifier, 80; digital oscilloscope.

Claims (4)

A discharge detection device for detecting a discharge generated inside a chamber enclosing plasma,
Detection means for detecting a current signal that is provided in a power supply path for generating the plasma in the chamber and that appears in the power supply path;
Amplifying means for amplifying the current signal detected by the detecting means;
A discharge detection device comprising:   2. The discharge detection apparatus according to claim 1, wherein the detection unit includes a current probe that detects a magnetic field formed by the current signal.   The discharge detection device according to claim 1, further comprising a frequency identification unit that identifies a frequency of the current signal amplified by the amplification unit. 4. The discharge detection apparatus according to claim 3, wherein the frequency identification unit identifies the frequency of the current signal with a threshold of 300 MHz.

Images