JP4069298B2 - Generation method of high-frequency plasma - Google Patents

Description

  The present invention relates to a high-frequency plasma apparatus having a tapped antenna used in plasma application processes such as film deposition, etching, plasma implantation, and the like, and a plasma generator for space propulsion.

Plasma generation using high frequency includes capacitively coupled plasma, inductively coupled plasma (hereinafter also referred to as ICP), helicon wave plasma, and the like.
FIG. 27 is a diagram schematically showing a capacitively coupled plasma generator 70 used for thin film deposition and etching. A high-frequency application electrode 72 and a ground electrode 73 which are two parallel plate electrodes are disposed in a chamber 71 in which a reactive gas is sealed, and a high-frequency oscillator 74 is applied to generate plasma 75. One end of the high-frequency oscillator 74 is connected to the high-frequency application electrode 72 via the matching unit 76 and the DC blocking capacitor 77, and the other end is connected to the ground electrode 73 and grounded. When the plasma 75 is regarded as a dielectric, the parallel plate electrodes 72 and 73 are called capacitor-coupled plasma because they are in the shape of capacitors. This plasma is generated by electric discharge generated by the electric field formed on the parallel plate electrodes. In a typical discharge state, the gas pressure is 10 to 1000 Pa, the electrode interval is 1 to ¹⁰ cm, the high frequency power is about 100 to 1000 W, and the plasma density is 1 × 10 ¹⁶ m ⁻³ (1 × 10 ¹⁰ cm ⁻³ ). It is a grade (refer nonpatent literature 1).

In recent years, inductively coupled plasma (ICP) has been used as a semiconductor processing apparatus in order to increase the density of plasma. FIG. 28 is a diagram schematically showing an inductively coupled plasma generator 80 used in the plasma processing apparatus. When high-frequency power is applied from a high-frequency oscillator 83 to a wound helical antenna coil 82 formed from the top to the bottom along the outer periphery of the reaction chamber 81 having a hemispherical quartz container, plasma is generated. . One end of the high-frequency oscillator 83 is connected to the helical antenna coil upper part 82a via the matching unit 84, and the other end is connected to the helical antenna coil lower part 82b and grounded. The reaction chamber 81 is evacuated by an exhaust system 86 through a vacuum exhaust port 85. The gas is introduced from the gas introduction system 87 into the shower head above the reaction chamber 81 through the gas introduction port 88. A stage 91 for placing the wafer 90 is installed in the lower part of the reaction chamber 81, and this stage 91 is grounded.
The inductively coupled plasma device 80 is discharged by a magnetic field generated by an antenna current. That is, the time change of the magnetic field induces an electric field according to Faraday's law of electromagnetic induction, and electrons are accelerated by this electric field to maintain the plasma discharge. Here, as an antenna for magnetic field discharge, a spiral antenna having a spiral shape is also used in addition to a cylindrical helical antenna. The plasma obtained by the inductively coupled plasma apparatus has a plasma density of 10 ¹⁷ to 10 ¹⁸ m ⁻³ , an electron temperature of 2 to 4 eV, and a diameter of about 30 cm. A large-diameter and high-density plasma can be easily obtained in a wide pressure range (1 to 40 Pa) (see Non-Patent Document 1 and Patent Document 1).

Recently, in order to increase the plasma density, if a high-frequency current sufficiently lower than the electron cyclotron frequency is passed through the antenna in a magnetic field, electrons can play a leading role even at low pressure due to clockwise circular polarization that travels in the plasma. It can generate high-density plasma and is called helicon wave plasma.
FIG. 29 is a diagram schematically illustrating an example of a helicon wave plasma apparatus. The helicon wave plasma apparatus 100 includes a reaction chamber 102 having a quartz tube 101, a helicon wave excitation high-frequency oscillator 103, a saddle antenna 104, an electromagnet 105, a permanent magnet 106, and a stage 108 on which a substrate 107 is placed. , And a substrate bias high-frequency oscillator 109. A magnetic field formed by the electromagnet 105 and the permanent magnet 106 is indicated by B. When high frequency power from a high frequency oscillator is applied to the saddle antenna 104 wound around the quartz tube 101, the magnetic field is excited and the helicon wave plasma 110 is excited. Here, the high-frequency power becomes wave energy in the plasma 110, and individual electrons are accelerated or attenuated by the electric field of the wave, and finally the kinetic energy of the electrons is increased to maintain the plasma 110. .
The plasma obtained by the helicon wave plasma apparatus 100 has a quartz tube 101 diameter of 10 cm, a magnetic field generated by a helicon wave excitation electromagnet of 0.01 T (Tesla), that is, 100 G (Gauss), and a high frequency oscillator 103 for helicon wave excitation. A plasma density of 10 ¹⁸ to 10 ¹⁹ m ⁻³ is obtained at a pressure of 1 to 5 Pa using .56 MHz and 1 kW (see Non-Patent Document 1).

  ICP in the presence of a helicon wave or a magnetic field provides a higher density plasma than capacitively coupled plasma, but the conventional helicon wave plasma is wound around an insulating container such as a small radius quartz tube. However, there is a drawback that a large area and large volume plasma cannot be obtained.

Recently, the present inventors have reported a high-frequency plasma apparatus using ICP and a helicon wave in which a spiral antenna, which is partially used in inductively coupled plasma, is installed at the container end. In a cylindrical reaction chamber having a diameter of about 45 cm and a length of 170 cm, helicon wave plasma of Ar (argon) gas (8.5 mTorr) is obtained. The volume of the high-frequency plasma is about 0.27 m ³ which is several times larger than the high-frequency plasma reported from other places. At this time, the frequency of the high-frequency oscillator is 7 MHz, the output power is 100 W to 2 kW, and a value of 1 × 10 ¹⁰ to 1 × 10 ¹³ cm ⁻³ is obtained as the plasma density (see, for example, Non-Patent Documents 2 and 3). ).

JP-A-7-302694 (FIGS. 1 and 3) Edited by Hideo Sakurai, Kazuyuki Oe, “Plasma Electronics”, Ohm Co., Ltd., August 25, 2000 (2000), Chapter 6 S. Shinohara, S. Takechi and Y. Kawai, "Effects of the Axial Magnetic Field and Faraday Shield on the Characteristics of RF Produced Plasma Using a Spiral Antenna", Jpn. J. Appl. Phys., 1996, Vol.35 Pt .1, No.8, pp. 4503-4508 Shunjiro Shinohara, “Recent Topics on High-Density Plasma Production Using Helicon Waves”, Journal of Plasma and Fusion Research, January 2002, Vol. 78, No. 1, pp.5-18

  In high-frequency plasma devices such as conventional inductively coupled plasma devices and helicon wave plasma devices, when trying to increase the size of the plasma, for example, in order to make the plasma density distribution in the axial direction of the plasma flat and uniform, There is a problem that the optimum magnetic field configuration has not been clarified as to how to apply the magnetic field applied to the helical antenna unit and the magnetic field in the plasma container.

  In addition, when ICP or helicon wave plasma is applied to the manufacture of a semiconductor device or a liquid crystal display device, the plasma density is increased and the uniformity within the surface on which the substrate is placed is required. However, there is a problem that the control method for the radial plasma density distribution in the plane perpendicular to the axial direction in the plasma vessel on which the substrate is placed (hereinafter referred to as the radial direction) is not clear. is there.

  In addition, when a spiral antenna or the like that excites high-frequency plasma is enlarged, the real part of the antenna impedance is very low resistance, whereas the inductance of the imaginary part increases, so that the supply voltage increases. In particular, there is a problem that impedance matching is difficult to obtain in a high frequency region.

  As described above, in the high-frequency plasma apparatus using ICP or helicon wave plasma, there is no known high-frequency plasma apparatus taking into consideration the increase in the size of plasma and the plasma density distribution in the radial direction.

In view of the above problems, and an object thereof is to provide a high frequency plasma generating method according to the tapped antenna capable of controlling the plasma density distribution in the size and radial direction of the plasma.

In order to achieve the above object, the high frequency plasma generation method of the present invention includes a reaction chamber into which a gas that becomes high frequency plasma is introduced, a magnet that is provided outside the reaction chamber and applies a magnetic field, and an end of the reaction chamber A high-frequency plasma apparatus comprising a tapped antenna for generating plasma and a high-frequency oscillator for applying high-frequency power to the antenna, the magnet is composed of a main magnet and a sub-magnet, and the sub-magnet is the end of the reaction chamber The magnetic field formed in the reaction chamber is a uniform magnetic field, a divergent magnetic field, a converging magnetic field, a cusp magnetic field, or a combination of two or more of these magnetic fields, and a magnet is used in the axial direction of the reaction chamber. Is flattened at the center portion thereof, and the frequency f of the high-frequency power is changed to the electron cyclotron frequency f1 determined by the magnetic field in the vicinity of the tapped antenna and the center portion of the reaction chamber. Against the electron cyclotron frequency f2 determined by the magnetic field B2 to be applied, and f <f1 / 10 and f2 / 10, and the high frequency 10 times higher than the ion cyclotron frequency by gas component as a plasma, a high frequency plasma The helicon wave plasma is generated, and the plasma density distribution in the axial direction of the reaction chamber is flattened at the central portion in the axial direction where the magnetic flux density distribution is flat.
The high-frequency plasma generation method of the present invention may be performed using a high-frequency plasma apparatus having a tapped antenna including a stage on which a substrate is placed in a reaction chamber.
In the magnetic flux density distribution in the axial direction of the reaction chamber, preferably, the magnetic fields at both ends thereof are made lower than the central portion.
Preferably, the secondary magnet is an electromagnet, and the plasma density distribution in the axial direction of the reaction chamber is changed by the current of the electromagnet. The secondary magnet may be an electromagnet, and the plasma density distribution in the radial direction of the reaction chamber may be changed by the electric current of the electromagnet.
The plasma density distribution in the radial direction of the reaction chamber is preferably changed depending on the tap position of the tapped antenna, or is changed depending on the feeding potential of the tapped antenna. The maximum value of the plasma density is 1 × 10 ⁹ cm ⁻³ or more.
When a stage on which a substrate is placed is provided in the reaction chamber, preferably, a bias high-frequency oscillator is connected to the stage to control the substrate bias.
According to this configuration, the magnetic field is formed by any one or a combination of a uniform magnetic field, a divergent magnetic field, a converging magnetic field, and a cusp magnetic field, and plasma excitation is performed by a tapped antenna to generate a high-frequency plasma composed of a helicon wave having a large volume. It is possible to generate helicon wave plasma that can control the plasma density distribution in the radial direction with good uniformity. In addition, if the frequency of the high frequency oscillator is selected as described above, a helicon wave plasma having a large volume can be generated, and a helicon wave plasma having a uniform plasma density distribution in the radial direction can be generated. it can.

According to the present invention, in a high-frequency plasma apparatus having a tapped antenna, the volume of a high-frequency plasma composed of generated helicon waves is increased by controlling the magnetic field configuration applied from the outside and selecting the tap of the tapped antenna. It is possible to provide an excellent method of generating high-frequency plasma that can control the plasma density distribution in the radial direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram schematically showing a configuration of a first embodiment of a high-frequency plasma apparatus 20 having a tapped antenna according to the present invention. A high-frequency plasma apparatus 20 having a tapped antenna includes a reaction chamber 1 in which a gas having a predetermined pressure is introduced to generate plasma, and a window 2 made of quartz or the like disposed at a predetermined position on the left end of the reaction tube 1 in FIG. A magnet 3 disposed outside the reaction chamber 1, a plasma generating tapped antenna 4 disposed in contact with the window, and a high frequency oscillator 5 for supplying high frequency power to the tapped antenna 4. Consists of Reference numeral 10 in the figure indicates high-frequency plasma generated by ICP or helicon wave plasma.

  Discharge gas introduction devices 7 and vacuum exhaust devices 8 are provided at the left and right ends of the reaction chamber 1, respectively. The plasma discharge gas introduction device 7 includes a discharge gas cylinder, a mass flow controller for adjusting a gas flow rate, a pressure gauge for pressure measurement, and the like. The vacuum evacuation device 8 is composed of a vacuum pump composed of a valve for opening and closing, an oil rotary pump, a turbo molecular pump, a vacuum gauge, etc., and evacuates the reaction chamber 1 before introducing the discharge gas. The vacuum evacuation device 8 may be used for controlling the introduction pressure of the discharge gas after introducing the discharge gas.

  The magnet 3 is made of, for example, an electromagnet or a permanent magnet. In order to optimize the magnetic field, the magnet 3 is preferably composed of a plurality of magnets, for example, a main magnet 3a and a sub magnet 3b. When the magnet is an electromagnet, for example, the windings of the main magnet 3a and the submagnet 3b are wound around the reaction chamber 1 in the same direction. The electromagnet 3 is excited by a DC power source and applies a magnetic field distribution (magnetic field configuration) described later to the reaction chamber 1.

As an example of the tapped antenna 4, a tapped spiral antenna or the like can be used. Hereinafter, a tapped spiral antenna will be described as an example.
The tapped spiral antenna 4 is basically disposed at the end along the magnetic field. That is, the normal direction may be parallel to the magnetic field lines (see the Z direction in FIG. 1) with respect to the antenna surface. As shown in the figure, the tapped spiral antenna 4 may be placed outside the reaction chamber 1 through a window 2 such as a quartz plate, or may be placed at the left end of the reaction chamber 1. In this case, it is desirable to provide an insulator around the tapped spiral antenna 4 or install a Faraday shield so that the electric field component of the tapped spiral antenna does not occur. Such a tapped spiral antenna 4 is connected to a high-frequency oscillator 5 via a matching unit 6.
Here, the spiral antenna 4 with a tap may be wound in a round shape or a rectangular shape in a spiral shape on a plane. It may be a staggered or ladder type. The outer diameter size of the tapped spiral antenna may be designed according to the plasma size and the applied magnetic field configuration. The tapped spiral antenna 4 is made of, for example, a copper tube. Although not shown, when the spiral antenna 4 with a tap is composed of a copper pipe, it is preferable to cool the pipe by circulating a cooling water inside the pipe. It is necessary to lengthen the insulating cooling pipe connected to the tapping spiral antenna 4 and the cooling pipe that is also used as a tapping spiral antenna 4 so as not to affect the water supply point due to the high voltage due to the high frequency of the antenna. The insulator pipe may be wound around the spiral antenna 4 with a tap or the matching unit 6 several times, for example, about 10 m.

  The operation of the magnet 3, the high-frequency oscillator 5, the gas introduction device 7, the vacuum evacuation device 8, and the like constituting the high-frequency plasma device 20 having the tapped antenna of the present invention may be controlled by the control device 9. The control device 9 is composed of, for example, a personal computer, and receives signals from a vacuum gauge provided in the reaction chamber 1, a probe for detecting each parameter of plasma, a so-called Langmuir probe, a magnetic field sensor, and the like. You can control the element.

The feature of the present invention is to use a tapped spiral antenna so that an efficient magnetic field configuration and a radial plasma density distribution can be controlled in order to obtain a large volume plasma in a high-frequency plasma apparatus. explain in detail.
Conventionally, an efficient magnetic field configuration has not been known, and the present inventors have found various types of magnetic field configurations and antennas in a high-frequency plasma apparatus and analyzed the plasma.
FIG. 2 is a diagram showing an example of a magnetic flux density distribution generated in the reaction chamber by the electromagnet used in the high-frequency plasma apparatus having the tapped antenna of the present invention. In FIG. 2, the horizontal axis represents the distance in the Z-axis direction in the central axis of the cylindrical reaction chamber, and the vertical axis represents the magnetic flux density. In the XYZ coordinates shown in FIG. 1, Z = 0 on the horizontal axis is the installation location of the spiral antenna at the left end of the reaction chamber in FIG. 1, and Z = L indicates the right end of the reaction chamber.
In the high frequency plasma apparatus of the present invention, the magnetic flux density distribution gradually increases from B1 to B2 from Z = 0 to Z = L1, the central portion (L1 to L2) in the axial direction is substantially flat, and the value is B2. The magnetic flux density gradually decreases from B2 to B3 from Z = L2 to Z = L, and the magnetic flux density of B3 when Z = L.

  When viewed from the tapped spiral antenna 4 at the left end of the reaction chamber 1, the magnetic flux density distribution shown in FIG. 2 is a divergent magnetic field from Z = 0 to Z = L1, a uniform magnetic field from Z = L1 to Z = L2, and Z = It can be said that L2 to Z = L are combinations of convergent magnetic fields. Such a magnetic field can be formed by any one of a uniform magnetic field, a divergent magnetic field, a converging magnetic field, and a cusp magnetic field. Further, this magnetic field may be formed, for example, with the vicinity of the spiral antenna 4 as a diverging magnetic field or a converging magnetic field and the other part as a uniform magnetic field. Therefore, the magnetic field may be formed from a combination of two or more of a uniform magnetic field, a divergent magnetic field, a converging magnetic field, and a cusp magnetic field.

FIG. 3 is a diagram schematically illustrating a magnetic field in the Z direction, which is (a) a uniform magnetic field, (b) a divergent magnetic field, (c) a converging magnetic field, and (d) a cusp magnetic field, respectively. As shown, the uniform magnetic field is the same as the magnetic field in the Z direction. In the divergent magnetic field, the magnetic field in the Z direction increases, and in the convergent magnetic field, the magnetic field in the Z direction decreases. The cusp magnetic field is a combination of a divergent magnetic field and a converging magnetic field, and is a magnetic field having a maximum value in the vicinity of the spatial antenna 4.
When the magnet 3 is an electromagnet, a desired magnetic field configuration can be obtained by changing the number of windings of the main electromagnet 3a and the sub electromagnet 3b, the winding interval, and the magnitude of the direct current to be energized. In order to obtain a desired magnetic field configuration, the direction of the direct current applied to each other is changed when the polarities of the main magnet 3a and the submagnet 3b using permanent magnets are changed, or when the directions of the main electromagnet 3a and the subelectromagnet 3b are the same. A cusp magnetic field generated in the opposite direction may be used.

Next, selection of the magnetic field strength and the frequency f of the high frequency oscillator will be described.
As an example, the strength of the magnetic field in the high-frequency plasma apparatus having the tapped antenna of the present invention is selected so as to be a high frequency in a region sufficiently larger than the ion cyclotron frequency and sufficiently smaller than the electron cyclotron frequency. That is, taking the magnetic field distribution of FIG. 2 as an example, the frequency f of the high-frequency power is determined by the electron cyclotron frequency f1 determined by the magnetic field in the vicinity of the tapped spiral antenna 4 and the electron determined by the magnetic field B2 applied to the central portion of the reaction chamber 1. For the cyclotron frequency f2, f is set lower than f1 and f2 (f <f1, f2), and higher than the ion cyclotron frequency due to the plasma gas component. As a specific example, the frequency of the high-frequency oscillator 5 needs to be 10 times or more the ion cyclotron frequency and 1/10 or less than the electron cyclotron frequencies f1 and f2.

On the other hand, the applied magnetic flux density B (Gauss) and the electron cyclotron frequency f _c (MHz) have a relationship of f _c = 2.80 × B.
As an example, in the magnetic field distribution of FIG. 2, the frequency f of the high-frequency oscillator 5 is set to a value sufficiently lower than the electron cyclotron frequency determined by the magnetic field B1 in the vicinity of the tapped spiral antenna 4 and the magnetic field B2 of the flat portion. High frequency plasma such as helicon wave plasma can be excited efficiently.
Here, for example, when B1 is 30 and 60 gauss, f _c is 84 MHz and 168 MHz, respectively. Therefore, in order to excite plasma efficiently, f of the high-frequency oscillator is about 1 / of these f _c. The value of 10 is preferably 10 MHz or less. Further, when the frequency f of the high-frequency oscillator 5 is set to 10 MHz, for example, it is desirable to apply a magnetic field having an electron cyclotron frequency of 100 MHz or more to the magnetic field B1 near the spiral antenna. At this time, the f _c in the case where the B2 of the flat portion and 100, 150, 200 gauss, respectively, 280 MHz, 420 MHz, since the 560 MHz, f of the high frequency oscillator 5, in the example about 10 MHz, F«f _c , and the helicon wave plasma can be excited efficiently.

Next, a description will be given of a method for reducing the inductance of the tapped spiral antenna in order to obtain high volume high frequency plasma in the high frequency plasma apparatus having the tapped antenna of the present invention.
FIG. 4 is a diagram showing the shape of the tapped spiral antenna 4. As shown in the plan view of FIG. 4A, the high frequency oscillator 5 is connected to the ends 4a and 4b of the four-turn spiral antenna 4 with a tap through a matching circuit. Furthermore, the tap 4c of the spiral antenna with a tap is installed for every half turn. The tap 4c can be made of a thin copper plate with a terminal. The tap 4c can be adjusted to an arbitrary number of turns by being slidably mounted in addition to being arranged at a fixed position.

  Thus, the tapped spiral antenna 4 can supply power at an arbitrary position. For example, power can be supplied by connecting the full turn, only the inside, only the outside, only the middle, or the outside and the inside. They can also be connected in series or parallel. Thereby, since coupling with plasma, inductance, and radial density distribution can be controlled, high-frequency power can be efficiently excited from the tapped antenna 4 to the gas in the reaction chamber 1.

  At this time, the impedance of the tapped spiral antenna 4 has a low resistance in the real part, whereas the imaginary part becomes an inductance component due to the winding of the tapped spiral antenna 4 and the frequency of the high frequency oscillator 5 is f. It has a size of 2πfL. As the impedance component of the tapped spiral antenna 4 is smaller, impedance matching with a high-frequency oscillator described later becomes easier. However, if the diameter of the reaction chamber 1 is increased as described above, the inductance of the tapped spiral antenna 4 increases. As a result, sufficient high frequency power cannot be supplied to the plasma.

As shown in FIG. 1, the tapped spiral antenna used in the high-frequency plasma apparatus having the tapped antenna of the present invention is coupled to the window 2 at the left end of the cylindrical reaction chamber 1. In order to increase the volume of the high-frequency plasma, there are a case where the axial direction of the reaction chamber is lengthened and a case where the cross section of the cylinder is enlarged. When the cross section of the cylinder is enlarged, ICP and helicon wave plasma cannot be generated efficiently unless the tapped spiral antenna 4 is enlarged to some extent according to the diameter of the cylinder.
4 (b) and 4 (c) are cross-sectional views showing the configuration of the winding of the tapped spiral antenna 4 for reducing the inductance of the tapped spiral antenna 4, and FIG. 4 (b) shows two copper wires. (C) shows an example in which the inductance is reduced by using the tube 12 as one winding and the flat copper tube 13 as one winding. Further, as a method of reducing the influence of the inductance component of the tapped spiral antenna 4, the frequency f of the high frequency oscillator may be reduced.

Next, the matching between the tapped spiral antenna and the high frequency oscillator in the high frequency plasma apparatus having the tapped antenna of the present invention will be described.
Since the impedance of a commercially available high-frequency oscillator is usually 50Ω or 75Ω, if a spiral antenna with a tap is directly connected to the high-frequency oscillator, impedance mismatch occurs. Therefore, a matching circuit 6 is inserted between the antenna and the high-frequency oscillator to insert the impedance. It is necessary to be consistent. Here, since the real part of the impedance in the case of the tapped spiral antenna is low, basically, a circuit that uses a matching circuit for converting from low impedance to high impedance of 50Ω and cancels L to convert impedance is preferable.

FIG. 5 is a diagram showing an example of a matching circuit for a spiral antenna used in a high-frequency plasma apparatus having a tapped antenna according to the present invention, FIG. 5 (a) is a split tank circuit, and FIG. 5 (b) is a π match circuit. It is. In the figure, the output impedance of the high-frequency oscillator 5 is Z ₀ , and the tapped spiral antenna 4 is shown as a series circuit of R and L. The split tank circuit shown in FIG. 5A includes two variable capacitors C1 and C2 (14, 15), and the π match circuit shown in FIG. 5B includes two variable capacitors C3 and C4 (16, 17). And an inductance Lp18.
Here, as for the matching condition of the split tank circuit of FIG. 5A, when the angular frequency of the high frequency oscillator is ω, C1 and C2 are given by the following equations (1) and (2).
C1 = 1 / Z ₀ * 1 / ω * ((Z ₀ / R) −1) ^0.5 (1)
C2 = 1 / ω * 1 / (− (R * (Z ₀ −R)) ^0.5 + ωL) (2)
Further, if necessary, a DC blocking capacitor having a sufficiently low capacitive impedance at the frequency f of the high-frequency oscillator 5 may be connected in series to the high-voltage side and the low-voltage side to perform DC cut. Thereby, the high frequency power can be more efficiently excited from the tapped antenna 4 to the gas in the reaction chamber 1.

Next, the procedure for causing plasma discharge by the high-frequency plasma apparatus 20 having the tapped antenna of the present invention will be described.
After the reaction chamber 1 is evacuated to a predetermined pressure by the evacuation device 8, a predetermined current is applied to the magnet 3 in order to apply a magnetic field as shown in FIG. This operation is not necessary when the magnet 3 is a permanent magnet. Next, in order to generate a high-frequency plasma, a gas having a predetermined pressure is introduced into the reaction chamber 1 from the gas introduction device 7 and is controlled together with the vacuum exhaust device 8 so as to have a constant pressure. Then, by supplying high frequency power from the high frequency oscillator 5 to the tapped spiral antenna 4 via the matching unit 6, the high frequency plasma 10 by ICP or helicon wave plasma can be generated.
Here, by changing the tap position of the tapped spiral antenna 4 and changing the number of turns, that is, the effective antenna length, the plasma density distribution in the radial direction of the generated plasma can be made variable. Further, ICP can be easily generated when the output power of the high-frequency oscillator 5 is low, and helicon wave plasma can be generated when the output power of the high-frequency oscillator 5 is high. In some cases, the transition from ICP to helicon wave plasma can be achieved only by increasing the output power of the high-frequency oscillator 5.

At this time, the introduced gas pressure and its flow rate may be selected according to the required high-frequency plasma process. When the gas pressure increases and the electron collision frequency (ions and neutral particles) becomes higher than the excitation frequency f of the high-frequency oscillator 5, the helicon wave plasma gradually shifts to an inductively coupled plasma in the presence of a magnetic field. In addition, when the gas pressure is low, the collision frequency with the neutral particles of electrons becomes small, making it difficult to generate plasma. When argon gas is used, helicon wave plasma can be generated at a typical pressure of about 0.1 mTorr to 100 mTorr. The output power of the high-frequency oscillator 5 may be applied according to the required plasma density, and the plasma density increases with this output power.
Thus, in the high-frequency plasma apparatus having the tapped antenna of the present invention, for example, the magnetic field configuration in the long axis direction of the cylindrical reaction chamber 1 is set so that the magnetic field in the vicinity of the tapped spiral antenna 4 is not zero. If the electron cyclotron frequency is 10 times as large as the frequency f of 5 and the electron cyclotron frequency in the maximum magnetic field at the axial center is sufficiently high, 30 times to several tens of times the frequency f of the high-frequency oscillator 5. Good.
According to this configuration, a large volume of high-frequency plasma can be efficiently generated by the magnetic field configuration generated by the magnet 3 provided outside the reaction tube 1. Moreover, the plasma density distribution in the radial direction can be made variable by changing the tap position of the spiral antenna 4 with a tap.

Next, a high-frequency plasma apparatus having a tapped antenna according to the second embodiment of the present invention will be described.
FIG. 6 is a diagram schematically showing the configuration of the second embodiment of the high-frequency plasma apparatus 30 having the tapped antenna of the present invention. The high-frequency plasma apparatus 30 is a high-frequency plasma apparatus that performs plasma etching or plasma deposition on a substrate 21 such as a Si substrate or a liquid crystal glass substrate having a relatively large diameter. As shown in the figure, the substrate 21 is configured by rotating the high-frequency plasma apparatus 20 of FIG. Other configurations are the same as those in FIG.
The stage 22 can be made of, for example, disc-shaped stainless steel. In order to prevent contamination of the substrate 21 by sputtering of the stage 22, the stage 22 may be covered with a quartz plate or the like. If necessary, the stage 22 may be cooled to prevent the substrate 21 from being overheated. Here, since the stage 22 is grounded, for example, outside the reaction chamber 1, when high-frequency plasma is generated by the high-frequency plasma apparatus 30 having a tapped antenna, the substrate 21 is caused by ions in the plasma. A DC voltage is generated by the so-called floating potential effect.

FIG. 7 is a diagram schematically showing a modification of the second embodiment of the present invention. The high-frequency plasma apparatus 35 having a tapped antenna is a high-frequency plasma apparatus that can control the bias voltage of the substrate 21. As shown in the figure, the stage 22 of the high-frequency plasma apparatus 35 having a tapped antenna has the same configuration as that shown in FIG. 6 except that it is grounded via a high-frequency bias oscillator 23.
Here, the frequency of the high-frequency bias oscillator 23 is set to a frequency that does not affect the high-frequency plasma 10 generated by the high-frequency oscillator 5, and the output power is appropriately adjusted, whereby the placement of the substrate 21. The potential of the stage 22 can be controlled to an arbitrary bias potential instead of the floating potential. For example, the frequency of the high frequency bias oscillator 23 may be about 1/10 to 1/100 of the frequency of the high frequency oscillator 5. As a result, in the high-frequency plasma apparatuses 30 and 35, the high-frequency plasma apparatus having a tapped antenna capable of processing the plasma process with high accuracy is realized by controlling the substrate potential to be a floating bias potential or an arbitrary bias potential. it can.

Next, a high frequency plasma apparatus having a tapped antenna according to a third embodiment of the present invention will be described.
FIG. 8 is a diagram schematically showing the configuration of the third exemplary embodiment of the present invention. The high-frequency plasma apparatus 40 having a tapped antenna can perform preionization by providing the electron generator 25 when high-frequency plasma discharge is difficult to ionize at low pressure, and can efficiently generate high-frequency plasma. The electron generator 25 for preliminary ionization is provided near the wall of the reaction chamber 1 that does not face the antenna at the left end of the reaction chamber 1. The electron generation heater 26 such as W (tungsten), a lead electrode 27, The heater heating power source 28 and the electronic drawing power source 29 are configured. The electron generator 25 has a structure that can be retracted to a preliminary chamber 1A provided at a predetermined location in the reaction chamber 1 except when the high-frequency plasma is activated. When a gas used for plasma contains a corrosive gas, it is desirable to provide such a spare chamber 1A. Other configurations are the same as those in FIG.

Here, in the method for generating a high-frequency plasma having a tapped antenna described in the first embodiment of the present invention, electrons are generated from the electron generator 25 after introducing a predetermined plasma gas in the reaction chamber 1. Then, by applying high frequency power from the high frequency oscillator 5, high frequency plasma such as ICP or helicon wave plasma can be easily generated in a low pressure gas. At this time, once the high-frequency plasma is generated, the discharge of the high-frequency plasma continues even if the electron generation portion 25 is stopped. The electron generator 25 is not only the high-frequency plasma apparatus 20 having the tapped antenna described in the first embodiment of the present invention, but also the high frequency having the tapped antenna described in the second embodiment of the present invention. The present invention can also be applied to the plasma devices 30 and 35.
By providing the electron generating means of this configuration, high-frequency plasma having a tapped antenna that can easily generate ICP or helicon wave high-frequency plasma with a high uniformity of plasma density distribution of large volume and radial distribution at low pressure. A device can be realized.

Next, Example 1 of the high-frequency plasma apparatus having the above-described tapped antenna of the present invention will be described.
The high-frequency plasma apparatus having a tapped antenna has the configuration shown in FIG. 1, and the cylindrical reaction chamber 1 has an outer diameter of 75 cm, an axial length of 486 cm, and a volume of about 2 m ³ . As the magnet 3, an electromagnet was used. The window 2 is made of quartz glass. As the tapped antenna 4, a spiral antenna having an outer diameter of 23 cm and 6 volumes was used, and the taps were both ends of the spiral antenna. The matching circuit 6 used a split tank circuit. The high frequency oscillator 5 has a frequency of 7 MHz and a maximum output of 1 kW. Here, the feeding of the high-frequency power was set so that the outer end 4b of the spiral antenna 4 was on the high potential side and the inner end 4a was on the low potential side (see FIG. 4A). In addition, the magnetic field sensor provided in the reaction chamber 1, a Langmuir probe, a window part, etc. measured the magnetic field, the plasma density, the spatial measurement of the magnetic field of excitation high frequency (7 MHz), the plasma emission, etc.

FIG. 9 is a diagram showing a magnetic flux density distribution in the reaction chamber 1 formed by the magnet 3 of the first embodiment. When the current of the main magnet 3a is 50A, the current of the submagnet 3b is 0A, (b) is 10A, and (c) is 20A, respectively. In the figure, the horizontal axis indicates the axial length (m) of the reaction chamber, and the position of the tapped spiral antenna 4 is zero. The vertical axis represents the magnetic flux density (Gauss).
As shown in FIG. 9A, the magnetic flux density distribution formed when the main electromagnet 3a is 50A and the sub electromagnet 3b is 0A is about 10 Gauss near the tapped spiral antenna 4 (Z = 0), It is about 140 gauss at the flat part near the center and several gausses at the other end of the reaction chamber 1.
The magnetic flux density distribution formed when the main electromagnet 3a is 50A and the subelectromagnet 3b is 10A, as shown in FIG. 9 (b), the current is supplied to the submagnet 3b except for the case where the vicinity of the tapped spiral antenna 4 is 30 gauss. Almost the same as when not flowing, the flat portion near the center is about 140 gauss, and the other end of the reaction chamber is several gauss.
The magnetic flux density distribution formed when the main electromagnet 3a is 50A and the sub electromagnet 3b is 20A, as shown in FIG. 9C, except that the vicinity of the spiral antenna 4 with a tap is 50 gauss, The magnetic flux density distribution is the same as in FIG.

Next, generation of high-frequency plasma when the reaction chamber 1 is filled with Ar gas at a pressure of 2 mTorr will be described.
10 to 13 are diagrams showing the relationship between the output power of the high-frequency oscillator of Example 1 and the obtained plasma density. In the figure, the horizontal axis represents the high frequency power (W) that is the output power of the high frequency oscillator, and the vertical axis represents the plasma density (cm ⁻³ ). The current of the main electromagnet 3a is kept constant at 50A, and the current value of the sub electromagnet is changed. The current of the submagnet 3b is 0A, FIG. 11 is 5A, FIG. 12 is 10A, and FIG. In the figure, ● (black circle) indicates the plasma density at Z = 37 cm, ▲ (black triangle) indicates Z = 150 cm, and ■ (black square) indicates the plasma density at Z = 370 cm.
In either case, a so-called jump phenomenon has been observed in which the plasma density is improved as the output power of the high-frequency oscillator is increased.
As shown in FIG. 10, when the current of the secondary magnet 3b is 0 A, the plasma density jump occurs when the output power of the high-frequency oscillator 5 is about 70 W or more, and the plasma density is about 1 × 10 ¹² cm ⁻ at about 600 W. It turns out that it is ³ .

As shown in FIG. 11, when the current of the secondary magnet 3b is 5A, the plasma density increases rapidly when the output power of the high-frequency oscillator 5 is about 170 W or more, and the plasma density exceeds 1 × 10 ¹² cm ⁻³ at about 220 W. was gotten. At this time, the plasma density is maximum at Z = 150 cm in the vicinity of the center of the reaction chamber 1, but almost the same value is obtained at Z = 37 cm and Z = 370 cm, and the high-frequency plasma 10 having a very uniform density is obtained. Obtained.

As shown in FIG. 12, when the current of the secondary magnet 3b is 10 A, the plasma density increases rapidly when the output power of the high-frequency oscillator 5 is about 220 W or more, and exceeds 2 × 10 ¹² cm ⁻³ at about 300 W. Plasma density was obtained. At this time, the plasma density distribution in the Z direction was the same as when the current was 5A.

Furthermore, as shown in FIG. 13, when the current of the secondary magnet 3b is 15A, the plasma density increases rapidly when the output power of the high-frequency oscillator 5 is about 300 W or more, and is about 2 × 10 ¹² cm ⁻³ or more at about 390 W. Plasma density was obtained.
Here, the plasma density distribution and the excitation high frequency (7 MHz) magnetic field spatial measurement, etc., the plasma below the output power at which the jump phenomenon is observed is ICP, the plasma above the output power at which the jump phenomenon is observed is the helicon wave. It was estimated that the high-frequency plasma. Furthermore, before the jump phenomenon occurred, the plasma density continuously changed with respect to the high frequency power. Moreover, even after the jump phenomenon occurs, a high plasma density can be obtained as the high frequency power increases. In this case, since the change in the plasma density with an increase in the high-frequency power becomes large, it can be seen that accurate control of the high-frequency power is necessary to obtain a desired plasma density. The state before and after the jump can be easily determined by measuring the plasma density distribution, the spatial measurement of the excitation high frequency magnetic field, and the observation of the plasma emission intensity from the plasma observation window provided in the reaction chamber.

FIG. 14 is a diagram showing the relationship between the plasma density with respect to the current of the submagnet 3b shown in FIGS. 10 to 13 and the high-frequency power when the jump phenomenon occurs. In the figure, the horizontal axis indicates the current (A) of the secondary magnet 3b, and the vertical axis indicates the plasma density (cm ⁻³ ) and the high frequency power (W) when the jump phenomenon occurs. The current of the main electromagnet 3a is constant at 50A. In the figure, ○ (white circle) and ● (black circle) are Z = 37 cm, Δ (white triangle) and ▲ (black triangle) are Z = 150 cm, □ (white square) and ■ (black square) are Z = 370 cm. 2 shows the plasma density before and after the occurrence of the jump phenomenon and the high-frequency power when the jump occurs.
As is clear from the figure, the threshold high-frequency power when the jump phenomenon occurs increased with the increase of the secondary magnet current. It can also be seen that the plasma density before and after the jump phenomenon increases as the secondary magnet current increases.

FIG. 15 shows the plasma density distribution in the direction along the central axis of the Z axis in FIG. In the figure, the horizontal axis indicates the distance in the Z-axis direction (cm), and the vertical axis indicates the plasma density (1 × 10 ¹² cm ⁻³ ). Here, the secondary magnet current is 15 A, the output power of the high-frequency oscillator 5 is 390 W, and Z = 0 is the position of the spiral antenna 4. As shown in FIG. 15, it can be seen that the plasma density increases from the spiral antenna 4 toward the inside of the reaction chamber, and is constant at approximately Z = 50 cm or more. Although not shown, the other end of the reaction chamber shows a similar tendency. According to the measurement of the plasma density in the Z-axis direction, the plasma density distribution in the central part in the Z-axis direction was a flat plasma density distribution of about 350 cm out of the total length 486 cm of the reaction chamber 1.

FIG. 16 is a diagram showing the plasma density distribution in the radial direction in FIGS. The plasma density distribution is a measured value at Z = 150 cm. In FIG. 16, the horizontal axis indicates the radial distance (cm), and the vertical axis indicates the normalized plasma density normalized by the maximum value of the plasma density. Further, the current of the submagnet 3b is shown in the case where the black square in the figure is 0A, the black circle is 5A, the * is 10A, and the black triangle is 15A.
When no current is passed through the secondary magnet 3b, a plasma density of 4.4 × 10 ¹⁰ cm ⁻³ is obtained at a high frequency power of 42 W, and the half width in the radial direction of the plasma density at that time is about 22 cm. On the other hand, when the submagnet current was 5 A to 15 A, the output power of the high frequency oscillator 5 was 69 W to 168 W, and the maximum value of the plasma density was 5.9 to 9.9 × 10 ¹⁰ cm ⁻³ . At this time, the half width of the plasma density distribution was about 34 cm to 29 cm. From this it can be seen that the plasma density distribution in the radial direction changes as the secondary magnet current is increased from zero.

The same high-frequency plasma apparatus as in Example 1 was used except that the tap of the spiral antenna 4 with taps was 6 taps and 3 taps on the outer peripheral side and 3 taps on the inner peripheral side were used. Here, the power supply to the spiral antenna 4 is such that the outer end 4b is on the high potential side and the inner end 4a is on the low potential side (see FIG. 4A).
17 and 18 are diagrams showing the relationship between the output power of the high-frequency oscillator and the obtained plasma density when using the spiral antenna with three taps on the outer peripheral side and the inner peripheral side in Example 2, respectively. is there. In the figure, the horizontal axis represents the output power (W) of the high-frequency oscillator, and the vertical axis represents the plasma density (× 10 ¹² cm ⁻³ ). The currents of the main electromagnet 3a and the sub electromagnet 3b are 50A and 15A, respectively. Ar gas pressures are 0.5 mTorr and 2 mTorr. In the figure, Δ (white triangle) indicates the plasma density at Z = 40 cm, ○ (white circle) indicates Z = 150 cm, and □ (white square) indicates the plasma density at Z = 320 cm.
When the tapped spiral antenna 4 provided with taps on the outer peripheral side 3 turns is used, as shown in FIG. 17, high-frequency plasma is generated from Ar gas pressure of 2 mTorr and high-frequency power of about 10 W. I understand. When the current of the secondary magnet 3b is 15A, a jump occurs at about 180W. Further, a plasma density of about 2 × 10 ¹¹ cm ⁻³ can be obtained at a high frequency power of about 200 W. It can be seen that, as in the first embodiment, when the current of the secondary magnet 3b is increased, the plasma density distribution increases and the jumping high-frequency power that changes from ICP to helicon wave plasma also increases. It can also be seen that when the Ar gas pressure is as low as 0.5 mTorr, the plasma density is lower than when the Ar gas pressure is 2 mTorr.

Also, in the case of FIG. 18 using the tapped spiral antenna 4 provided with taps on the inner volume 3 windings, high frequency plasma is generated from Ar gas pressure of 2 mTorr and high frequency power of about 10 W as in FIG. I understand that When the current of the secondary magnet 3b is 15A, a jump occurs at about 200W. Moreover, a plasma density of about 4 × 10 ¹¹ cm ⁻³ can be obtained at a high frequency power of about 300 W. As in the first embodiment, when the current of the secondary magnet 3b is increased, the plasma density distribution is increased and the jumping high-frequency power changing from ICP to helicon wave plasma is also increased. Further, when the Ar gas pressure is as low as 0.5 mTorr, the plasma density is low as compared with 2 mTorr, and when the current of the secondary magnet 3 b is 15 A, the ICP to the helicon wave plasma up to 800 W. It turns out that the jump which changes to does not occur. From this, it is understood that when the high frequency plasma is generated by the tap of the spiral antenna 4 with the tap on the outer peripheral side and the inner peripheral side of the three turns, the generated plasma density and the jumping high frequency power change. .

19 and 20 are diagrams showing the plasma density distribution in the radial direction in FIGS. 17 and 18. In the figure, the horizontal axis represents the radial distance (cm), and the vertical axis represents the plasma density (× 10 ¹² cm ⁻³ ). The plasma density distribution is a measured value at Z = 150 cm, and the Ar gas pressure indicates a case where ◯ (white circle) in the figure is 2 mTorr and ▲ (black triangle) is 0.5 mTorr, respectively.
As shown in FIG. 19, when a spiral antenna 4 with a tap provided on the outer peripheral side 3 turns is used, when the Ar gas pressure is 2 mTorr and the current of the secondary magnet 3b is 15 A, the high frequency power is changed from 179 W to 193 W. As a result, the plasma density increases from about 8 × 10 ¹⁰ cm ⁻³ to 3.1 × 10 ¹¹ cm ⁻³ and the plasma plasma density distribution changes. As the half width of the plasma density distribution at this time, when the high frequency power is changed from 179 W to 193 W, about 34 cm and 29 cm are obtained, respectively, and the plasma density distribution in the radial direction changes. The plasma density distribution in the radial direction was almost the same as that at 0.5 mTorr where the Ar gas pressure was low.

As shown in FIG. 20, when a tapped spiral antenna 4 provided with a tap on the inner peripheral side 3 turns is used, the Ar gas pressure is 2 mTorr, and the current of the secondary magnet 3b is 15 A, the high frequency power is changed from 87 W to 232 W. When it is changed, it can be seen that the plasma density increases from about 8 × 10 ¹⁰ cm ⁻³ to 4 × 10 ¹¹ cm ⁻³ and the plasma density distribution changes. The half-value width of the plasma density distribution at this time is about 34 cm to 24 cm when the high frequency power is changed from 87 W to 232 W, the plasma density distribution in the radial direction is changed, and the plasma density distribution is It can be controlled by tapping the spiral antenna. Further, it can be seen that the plasma density distribution in the radial direction has a wide range of uniformity when the Ar gas pressure is low at 0.5 mTorr.
As described above, when high-frequency plasma is generated using the tap of the spiral antenna 4 with a tap on the outer peripheral side and the inner peripheral side, the plasma density generated and the plasma density distribution in the radial direction are generated. Can be seen to change.

The same high-frequency plasma apparatus as in Example 1 was used except that the outer diameter of a spiral antenna with a tap as the antenna 4 was 43 cm and four turns were used. Here, the power supply to the spiral antenna 4 is such that the outer end 4b is on the high potential side and the inner end 4a is on the low potential side (see FIG. 4A).
FIG. 21 is a diagram showing the plasma density distribution in the radial direction in Example 3. FIG. In the figure, the horizontal axis represents the radial distance (cm) centered on 0 and the vertical axis represents the plasma density (cm ⁻³ ). The current of the main magnet 3a is 50A, and the current of the sub-magnet 3b is shown when the circle (white circle) in the figure is 0A and the circle (black circle) is 16A. The Ar gas pressure is 0.5 mTorr. When no current is passed through the secondary magnet 3b, a high-frequency power is 520 W, a plasma density of 1.7 × 10 ¹² cm ⁻³ is obtained, and the half-value width of the plasma density distribution is about 16 cm. On the other hand, when the sub-magnet current is 16 A, the high frequency power is 561 W, the plasma density of 8.5 × 10 ¹¹ cm ⁻³ is obtained, and the half width of the plasma density distribution is about 38 cm.
As described above, when the sub-magnet current is 16 A, the half width of the plasma density distribution becomes wider in the helicon wave plasma as the Ar gas pressure is lower and in the ICP plasma state. From this, it can be seen that the plasma density distribution in the radial direction is improved and the uniform region is expanded by increasing the sub-magnet current from 0 and increasing the magnetic field in the vicinity of the spiral antenna 4. This is because the convergence of the convergence distribution of the magnetic field in the vicinity of the spiral antenna 4 becomes weak and becomes close to a uniform distribution due to the increase in the current of the secondary magnet 3b.

As Example 4, the outer diameter is 43 cm as in Example 3, and the spiral antenna 4 with 4 turns is used, except that the outer circumference side 2 turns tap and the inner circumference side 2 turns tap are used, respectively. The same high-frequency plasma apparatus as in Example 1 was used. Here, the power supply to the spiral antenna 4 in the case of the outer peripheral side two-turn tap is set so that the outer end 4b is on the high potential side and the inner second turn tap 4c is on the low potential side (FIG. 4 ( a)). In addition, in the case of a tap of 2 turns on the inner peripheral side, the spiral antenna 4 is fed with the tap 4c of the second turn from the inner peripheral end 4a on the high potential side and the inner end 4a on the low potential side (FIG. 4). (See (a)).
FIG. 22 is a diagram showing a high-frequency plasma density distribution by radial helicon waves in Example 4. In the figure, the horizontal axis indicates the radial distance (cm) with 0 as the axis center, and the vertical axis indicates the plasma density (× 10 ¹² cm ⁻³ ). The current of the main magnet 3a is 50A, and the current of the sub magnet 3b is 16A. In the figure, □ (white square) is the case of using the tap on the inner peripheral side of the spiral antenna 4 with tapping, and △ (white triangle) is the case of using the tap on the outer peripheral side of 2 turns. (Black circle) is the case of the 4-turn spiral antenna shown for comparison. The current of the main magnet 3a is 50A, and the current of the sub magnet 3b is 16A. The Ar gas pressure is 0.5 mTorr, and the measurement point is Z = 150 cm.
When two taps on the inner circumferential side of the tapped spiral antenna 4 are used, a plasma density distribution having a maximum of 2.1 × 10 ¹¹ cm ⁻³ is obtained at a high frequency power of 374 W, and the plasma density distribution is obtained. The half width of was about 33 cm. On the other hand, when two taps on the outer peripheral side of the tapped spiral antenna 4 are used, a high-frequency power is 387 W, and a hollow plasma density distribution having a flat portion of a maximum of 3.3 × 10 ¹¹ cm ⁻³ is obtained. The half width of the plasma density distribution is about 41 cm. In addition, when the tapped spiral antenna 4 has four turns, the plasma density having a peak of 6 × 10 ¹¹ cm ⁻³ was obtained at a high frequency power of 555 W, and the half-value width of the plasma density distribution was about 41 cm. . From this, it can be seen that the helicon wave plasma density in the radial direction changes by changing the tap position of the tapped spiral antenna 4.

FIG. 23 is a diagram showing a radial ICP high-frequency plasma density distribution in Example 4. In the figure, the horizontal axis indicates the radial distance (cm) with 0 as the axis center, and the vertical axis indicates the plasma density (× 10 ¹² cm ⁻³ ). In the figure, □ (white square) is a case where a tap of 2 turns on the inner circumference side of the spiral antenna 4 with a tap is used, and Δ (white triangle) is a case where a tap of 2 turns on the outer circumference side is used. The current, Ar gas pressure, and measurement points of the main magnet 3a and the sub magnet 3b are the same as those in FIG.
When two taps on the inner peripheral side of the tapped spiral antenna 4 are used, a plasma density distribution having a substantially flat peak with a high-frequency power of 209 W and a maximum plasma density of about 7 × 10 ¹⁰ cm ⁻³ is obtained. The half width of the plasma density distribution was about 45 cm. On the other hand, when two taps on the outer peripheral side of the spiral antenna 4 with a tap are used, the center of the flat part with a high frequency power of 195 W and a maximum plasma density of 3.5 × 10 ¹⁰ cm ⁻³ is slightly depressed. A plasma density is obtained, and the half width of the plasma density distribution is about 50 cm. Thereby, it turns out that the radial helicon wave plasma density and its half value width change by changing the position of the tap of the spiral antenna 4 with a tap and its feeding potential.

FIG. 24 is a diagram showing a high-frequency plasma density distribution by a helicon wave in the radial direction when power feeding is reversed when a tap of two turns on the inner peripheral side of the spiral antenna 4 with tap is used. In the figure, the horizontal axis represents the radial distance (cm) centered on 0 and the vertical axis represents the plasma density (× 10 ¹² cm ⁻³ ). In the figure, □ (white square) is the case where the innermost end 4a of the spiral antenna 4 with a tap is fed with a high potential, and Δ (white triangle) is low on the end 4a. The data of FIG. 22 in which the potential and the outer tap are set to a high potential are also shown. The current, Ar gas pressure, and measurement points of the main magnet 3a and the sub magnet 3b are the same as those in FIG. When the power supply is reversed and the inside is supplied with a high potential, a high-frequency power is 437 W, and a plasma density distribution having a maximum peak of 5.5 × 10 ¹¹ cm ⁻³ is obtained. It can be seen that the maximum plasma density is increased although the high frequency power is slightly high, and the half width of the plasma density distribution is almost the same. From this, it can be seen that the helicon wave plasma density in the radial direction changes by changing the tap position of the tapped spiral antenna 4 and its feeding potential.

FIG. 25 is a diagram showing the ICP high-frequency plasma density distribution in the radial direction when the feed is reversed when the tap on the inner circumferential side of the spiral antenna 4 with a tap of FIG. 23 is used. In the figure, the horizontal axis represents the radial distance (cm) centered on 0 and the vertical axis represents the plasma density (× 10 ¹² cm ⁻³ ). 23 (black square) in the figure is a case where the innermost end 4a of the tapped spiral antenna 4 is fed with a high potential, and □ (white square) is lower than the end 4a. It is the data of FIG. 23 which made the outer tap 4c a high electric potential. Further, the current of the main magnet 3a and the sub magnet 3b, the Ar gas pressure, and the measurement points are the same as those in FIG. When the power supply is reversed and the inner side is supplied with a high potential, a high-frequency power is 197 W, a plasma density distribution having a peak of 5 × 10 ¹⁰ cm ^-3 at the maximum is obtained, and the half width of the plasma density distribution is about 40 cm. It can be seen that the maximum plasma density and the half width of the plasma density distribution are reduced. From this, it can be seen that when the inside of the tapped spiral antenna 4 is set at a high potential, a plasma density distribution having a peak is obtained, and when the outside inside is set at a high potential, a relatively flat plasma density is obtained. Thus, it can be seen that the ICP plasma density in the radial direction and its half-value width change by changing the tap position of the spiral antenna 4 with a tap and its feeding potential.

Next, plasma discharge in which ICP and CCP (inductively coupled discharge) are mixed, which is plasma generated with high-frequency power lower than that of ICP high-frequency plasma, will be described.
FIG. 26 is a diagram illustrating a high-frequency plasma density distribution of a mixture of ICP and CCP in the radial direction when power feeding is reversed when a tap with two turns on the inner peripheral side of the tapped spiral antenna 4 is used. In the figure, the horizontal axis indicates the radial distance (cm) with 0 as the axis center, and the vertical axis indicates the plasma density (× 10 ¹² cm ⁻³ ). In the figure, ■ (black square) is the case where the innermost end 4a of the spiral antenna 4 with a tap is fed to a high potential, and □ (white square) is the end 4a at a low potential and the outer tap 4c is at a high potential. This is the case of potential. The high frequency power is 12W. Further, the current of the main magnet 3a and the sub magnet 3b, the Ar gas pressure, and the measurement points are the same as those in FIG.
When the inside is supplied with a high potential, a plasma density distribution having a maximum peak of 1.3 × 10 ¹⁰ cm ⁻³ is obtained, and the half-value width of the plasma density distribution is about 43 cm. On the other hand, when the outside is supplied with a high potential, a plasma density distribution having a substantially flat peak of 2 × 10 ¹⁰ cm ^{-3 at} the maximum is obtained, and the half width of the plasma density distribution is about 50 cm. From this, it can be seen that when the inside of the tapped spiral antenna 4 is set at a high potential, a plasma density distribution having a peak is obtained, and when the outside is set at a high potential, a relatively flat plasma density is obtained. Thus, it can be seen that by changing the tap position of the spiral antenna 4 with a tap and its feeding potential, the high-frequency plasma density mixed with ICP and CCP in the radial direction and its half-value width change.
In the above embodiment, the magnetic field distribution is changed by the main electromagnet 3a and the sub magnet current 3b. However, a desired magnetic field distribution may be realized by one electromagnet.

As described in the first to fourth embodiments, the high-frequency plasma having various plasma density distributions can be obtained by changing the magnetic field distribution, the high-frequency power, the shape of the tapped spiral antenna, the tap, and the way of supplying the feeding potential. Obtained.
From these examples, it can be seen that the plasma density distribution increases with increasing high frequency power. Further, the high-frequency power at which a so-called jump phenomenon that can be estimated to be helicon wave plasma from ICP changes the current of the secondary magnet 3b, that is, the magnetic field distribution, the structure of the tapped spiral antenna, and the high-frequency oscillator for plasma excitation. It turns out that it changes with electric power.
In the high-frequency plasma apparatus using the tapped antenna of the present invention, for example, by using a magnetic field configuration as shown in FIG. 8, a high-frequency plasma having a large volume of 2 m ³ has a plasma density of 1 × 10 ¹² cm ⁻³ . Was obtained with a low power of about 300 W. It can also be seen that the plasma density increases as the magnetic field intensity in the vicinity of the spiral antenna 4 increases, and the half-value width of the plasma density distribution in the radial direction can be controlled to be wide.

As described above, the high-frequency plasma volume having the tapped antenna obtained in the example is about 2 m ³ , and a high-frequency plasma having a volume about 7 times larger than the conventional example by the present inventors can be obtained. Also, the plasma density distribution in the radial direction can be controlled. Thereby, according to the high-frequency plasma apparatus having the tapped antenna of the present invention, it is possible to obtain high-frequency plasma by ICP or helicon wave that is controllable and has a good plasma density distribution in the radial direction.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. It is also clear that the shape of the magnet, reaction chamber, tapped antenna, etc. that give the desired magnetic field distribution can be designed as appropriate according to the purpose of the plasma.

It is a figure which shows typically the structure of 1st Embodiment of the high frequency plasma apparatus which has an antenna with a tap by this invention. It is a figure which shows an example of magnetic flux density distribution which arises in a reaction chamber with the electromagnet used for the high frequency plasma apparatus which has an antenna with a tap of this invention. It is a figure explaining the magnetic field of a Z direction typically, (a) is a uniform magnetic field, (b) is a divergent magnetic field, (c) is a convergence magnetic field, (d) is a cusp magnetic field, respectively. It is the top view and sectional drawing which show the shape of the spiral antenna with a tap. An example of a matching circuit for a tapped spiral antenna used in a high-frequency plasma apparatus having a tapped antenna of the present invention is shown, wherein (a) is a split tank circuit and (b) is a π match circuit. It is a figure which shows typically the structure of 2nd Embodiment of the high frequency plasma apparatus which has an antenna with a tap by this invention. It is a figure which shows typically the structure of the modification of 2nd Embodiment by this invention. It is a figure which shows typically the structure of 3rd Embodiment of the high frequency plasma apparatus which has an antenna with a tap by this invention. It is a figure which shows magnetic flux density distribution in the reaction chamber formed of a magnet. It is a figure which shows the relationship between the output power of a high frequency oscillator, and the plasma density obtained when the submagnet current is 0A. It is a figure which shows the relationship between the output power of a high frequency oscillator, and the plasma density obtained when the submagnet current is 5A. It is a figure which shows the relationship between the output power of a high frequency oscillator, and the plasma density obtained when the submagnet current is 10A. It is a figure which shows the relationship between the output power of a high frequency oscillator, and the plasma density obtained when the submagnet current is 15A. It is a figure which shows the relationship between the plasma density with respect to the electric current of the submagnet shown in FIGS. 10-13, and the high frequency electric power when a jump phenomenon arises. It is a figure which shows the plasma density distribution of the direction in alignment with the central axis of the Z-axis in FIG. It is a figure which shows the plasma density distribution of the radial direction in FIGS. It is a figure which shows the relationship between the output electric power of a high frequency oscillator when using the outer periphery side 3 volume | tapped spiral antenna, and the obtained plasma density. It is a figure which shows the relationship between the output electric power of a high frequency oscillator when using the inner periphery side 3 volume | tap spiral antenna, and the obtained plasma density. It is a figure which shows the plasma density distribution of the radial direction in FIG. It is a figure which shows the plasma density distribution of the radial direction in FIG. It is a figure which shows the plasma density distribution of the radial direction in Example 3. FIG. It is a figure which shows the high frequency plasma density distribution by the helicon wave of the radial direction in Example 4. FIG. It is a figure which shows ICP high frequency plasma density distribution of the radial direction in Example 4. FIG. It is a figure which shows the high frequency plasma density distribution by the helicon wave of a radial direction when electric power feeding is reversed when the tap of the inner peripheral side 2 turns of a spiral antenna with a tap is used. It is a figure which shows ICP high frequency plasma density distribution of radial direction when electric power feeding is reversed when the tap of the inner peripheral side 2 turns of the spiral antenna with a tap of FIG. 23 is used. It is a figure which shows the high frequency plasma density distribution of ICP and CCP of radial direction when electric power feeding is reversed when the tap of the inner peripheral side of a spiral antenna with a tap is used. It is a figure which shows typically the general capacitive coupling type plasma generator used for deposition and etching of a thin film. It is a figure which shows typically the general inductively coupled plasma generator used for the plasma processing apparatus. It is a figure which shows typically an example of the conventional helicon wave plasma apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Window 3 Magnet 3a Main magnet 3b Secondary magnet 4 Antenna with a tap (spiral antenna with a tap)
4a, 4b Taped spiral antenna end 4c Tap 5 High frequency oscillator 6 Matching device 7 Gas introduction device 8 Vacuum exhaust device 9 Control device 10 High frequency plasma 12, 13 Copper tubes 14, 15, 16, 17 Variable capacitance capacitor 18 Inductance 20, 30, 35, 40 High-frequency plasma apparatus 21 having a tapped antenna 21 Substrate 22 Stage 23 High-frequency bias oscillator 25 Electron generator 26 Electron generator heater 27 Extraction electrode 28 Heater heating power supply 29 Electronic extraction power supply

Claims (9)

A reaction chamber into which a gas to be a high frequency plasma is introduced, a magnet provided outside the reaction chamber for applying a magnetic field, a tapped antenna for plasma generation provided at an end of the reaction chamber, and a high frequency to the antenna A plasma generation method for a high-frequency plasma device comprising a high-frequency oscillator for applying power,
The magnet is composed of a main magnet and a submagnet, and the submagnet is arranged on the end side of the reaction chamber,
The magnetic field formed in the reaction chamber is a uniform magnetic field, a divergent magnetic field, a convergent magnetic field, a cusp magnetic field, or a combination of any two or more of the magnetic fields,
The magnetic flux density distribution in the axial direction of the reaction chamber is flattened at the center by the magnet,
The frequency f of the high frequency power is f <f1 / with respect to the electron cyclotron frequency f1 determined by the magnetic field near the tapped antenna and the electron cyclotron frequency f2 determined by the magnetic field B2 applied to the center of the reaction chamber. 10 and f2 / 10, and, as a high frequency 10 times higher than the ion cyclotron frequency by the gas component to be the plasma, by generating the helicon wave plasma comprising a high-frequency plasma,
A method for generating high-frequency plasma, characterized in that the plasma density distribution in the axial direction of the reaction chamber is flattened at a central portion in the axial direction where the magnetic flux density distribution is flat. A reaction chamber into which a gas to be a high frequency plasma is introduced, a magnet provided outside the reaction chamber for applying a magnetic field, a tapped antenna for plasma generation provided at an end of the reaction chamber, and a high frequency to the antenna A plasma forming method for a high-frequency plasma apparatus having a tapped antenna comprising a high-frequency oscillator for applying power and a stage on which a substrate is placed in the reaction chamber,
The magnet is composed of a main magnet and a submagnet, and the submagnet is arranged on the end side of the reaction chamber,
The magnetic field formed in the reaction chamber is a uniform magnetic field, a divergent magnetic field, a convergent magnetic field, a cusp magnetic field, or a combination of any two or more of the magnetic fields,
The magnetic flux density distribution in the axial direction of the reaction chamber is flattened at the center by the magnet,
The frequency f of the high frequency power is f <f1 / with respect to the electron cyclotron frequency f1 determined by the magnetic field near the tapped antenna and the electron cyclotron frequency f2 determined by the magnetic field B2 applied to the center of the reaction chamber. 10 and f2 / 10, and, as a high frequency 10 times higher than the ion cyclotron frequency by the gas component to be the plasma, by generating the helicon wave plasma comprising a high-frequency plasma,
A method of generating high-frequency plasma, characterized in that the plasma density distribution in the axial direction of the reaction chamber is flattened at a central portion in the axial direction where the flatness of the magnetic flux density distribution is flat. 3. The method of generating high-frequency plasma according to claim 1, wherein in the magnetic flux density distribution in the axial direction of the reaction chamber, the magnetic fields at both ends of the reaction chamber are made lower than the central portion. The method of generating high-frequency plasma according to claim 1 or 2 , wherein the sub-magnet is an electromagnet, and the plasma density distribution in the axial direction of the reaction chamber is changed by an electric current of the electromagnet. The method of generating high-frequency plasma according to claim 1 or 2 , wherein the sub-magnet is an electromagnet, and the plasma density distribution in the radial direction of the reaction chamber is changed by an electric current of the electromagnet. 3. The method of generating high-frequency plasma according to claim 1, wherein a plasma density distribution in a radial direction of the reaction chamber is changed depending on a tap position of the tapped antenna. The high-frequency plasma generation method according to claim 1 or 2 , wherein a plasma density distribution in a radial direction of the reaction chamber is changed by a feeding potential of the tapped antenna. 3. The method of generating high-frequency plasma according to claim 1, wherein the maximum value of the plasma density in the axial direction of the reaction chamber is 1 × 10 ⁹ cm ⁻³ or more. 3. The method of generating high-frequency plasma according to claim 2 , wherein a bias high-frequency oscillator is connected to the stage to control the bias of the substrate.

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