JP3249193B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus for performing a predetermined process for forming a semiconductor device on a sample such as a wafer using a so-called helicon plasma excited by a helicon wave.

[0002]

2. Description of the Related Art FIG. 18 shows, for example, U.S. Pat.
229 shows a conventional helicon plasma processing apparatus disclosed in Japanese Patent Publication No. 229/229.

As shown in FIG. 18, a cylindrical plasma generating chamber 2 is set in a vacuum state and made of an electrically insulating material.
30 and a cylindrical processing chamber 231 in which the sample 300 is placed at the center thereof are connected in cascade. The pipe 233 is connected. A high-frequency coupling antenna 240 is fixedly provided on an outer peripheral portion of the plasma generation chamber 230, and a magnetic field generator for generating a DC magnetic field B in the axial direction of the plasma generation chamber 230 is provided on the outer peripheral portion of the antenna 240. A solenoid coil 250 is provided. The antenna 240 includes a circular upper ring portion 241 and a circular lower ring portion 242.

Here, the upper ring portion 241 and the lower ring portion 2
A high-frequency signal output from the high-frequency power supply 210 is applied to both ends of the upper ring portion 241 and both ends of the lower ring portion 242 via the impedance matching unit 211 and the coaxial cable 212 so as to be excited in opposite phases to each other. Upon input, the antenna 240 is excited. At this time, the high-frequency signal is combined with and penetrates the plasma generated inside the plasma generation chamber 230, whereby the high-frequency electromagnetic wave is converted into a helicon wave (Whistler wave) by the magnetic field in the axial direction inside the generated plasma. By propagating energy in electrons by propagating in Whistler mode along B and attenuating Landau to promote ionization,
Generates high-density plasma.

The density ne _e [cm ^-3 ] of the plasma generated in the helicon plasma processing apparatus is as follows: (a) The angular frequency ω of the high-frequency signal is the ion cyclotron angular frequency ω
a first approximation condition that is sufficiently higher than ci and sufficiently lower than the electron cyclotron angular frequency ωce;
(B) As is well known, using an approximate expression under the second approximate condition that the diameter of the generated plasma is relatively small,
It can be expressed by the following equation 1.

[0006]

[Number 1] _{n e = (190 · B 0} ) × 10 14 / (r a · f · λ) [cm -3] Here, B _0: magnetic flux density of the DC magnetic field [kG], r _a: cylindrical Radius of the plasma generation chamber 230 corresponding to the radius of the plasma [cm], f: frequency of high frequency signal [MHz],
λ: wavelength of helicon wave [cm].

Accordingly, the wavelength λ of the helicon wave to be excited is
Is expressed by Equation 2 from Equation 1 below.

[Number 2] _{λ = (190 · B 0)} / (r a · f · n e × 10 -14) [cm]

By forming the antenna 240 having the excitation wavelength λ given by the above equation 2, it is possible to generate plasma. Further, as is apparent from Equation 1, the density of the generated plasma is determined by the magnetic flux density B ₀ of the applied DC magnetic field, the radius r _a of the plasma generation chamber 230,
Since the frequency is determined by the frequency f of the applied high-frequency signal and the wavelength λ of the helicon wave corresponding to the antenna length of the antenna 240, when the overall size of the plasma processing apparatus is determined, the generated plasma Cannot easily be increased in density. In addition, these parameters B
_0, when r _a, f, the value of λ is fixed, there is a problem that can not be changed according to the type of processing to be executed a density of the plasma being the generation.

In the conventional helicon plasma processing apparatus, when the type of the reaction gas is changed, for example, to change the type of the process, the density of the plasma for the process changes. Changes in wavelength. On the other hand, since the high-frequency coupling antenna 240 is fixedly provided, the degree of coupling between the generated plasma and the high frequency is reduced. As a result, the high-frequency power is not efficiently absorbed by the plasma, and the generated plasma is not absorbed. However, there is a problem that the stability of the resin is reduced.

Further, in the conventional helicon plasma processing apparatus, a half of the wavelength λ calculated by the above equation (2) is used.
Since it is necessary to hold two ring antennas at an interval of the length, there is a problem that the device becomes large.

A first object of the present invention is to solve the above problems, and to generate a high-density plasma more uniformly and stably on the surface of a sample to be treated as compared with the conventional example. An object of the present invention is to provide a plasma processing apparatus.

A second object of the present invention is to provide a helicon plasma processing apparatus which can be reduced in size and weight as compared with the conventional example.

Further, a third object of the present invention is to generate a high-density plasma uniformly and stably on the surface of a sample to be treated, as compared with the conventional example, and to generate a plasma. It is an object of the present invention to provide a helicon plasma processing apparatus capable of controlling the density of a helicon plasma to a predetermined value.

[0014]

The inventor of the present invention has proposed an antenna 240 for a conventional helicon plasma processing apparatus.
Has the above-described shape, so that each of the ring portions 241,
In accordance with Lenz's law, a high-frequency signal passed through 42 rotates the angle of rotation around the axis of the cylindrical plasma generating chamber 230 on a plane parallel to the bottom surface of the cylindrical plasma generating chamber 230 (θ direction: hereafter referred to as the angle). It is noted that only an electric field (rotational direction) is generated. However, in practice, the electric field pattern of the helicon wave in the fundamental mode in which the value m corresponding to the Bessel function represented by the electric field amplitude is 0 is shown in FIG. Excited plasma (Helicon wave)
Excited Plasmas) "Applied Physics, 6th
Vol. 7, No. 7, pp 711-717, see FIG. 1 of July 1992), not only the rotation axis direction but also a radial direction from the axis of the plasma generation chamber 230 to the side surface (ra direction: hereinafter). , Radial direction) also has an electric field component, which is considerably different from an electric field induced by a high-frequency signal input to the antenna 240. That is, it is considered that the difference between the induced electric field and the electric field of the helicon wave propagating in the plasma is one of the causes of the instability of the generated plasma.

In view of the above, the present inventor has invented the following helicon plasma processing apparatus.

The plasma processing apparatus according to the present invention is directed to a plasma processing apparatus for performing a predetermined process on a sample by generating helicon plasma in a cylindrical plasma processing chamber whose inside is set to a vacuum state. Magnetic field generating means for generating a DC magnetic field in a direction toward the sample inside the chamber, and a first high-frequency electric field having a direction from the center of the cylindrical shape of the plasma processing chamber toward the outer periphery of the cylinder,
A second rotation direction generated using the first high-frequency signal and having an angular rotation direction in which the angle changes and rotates on a plane parallel to the bottom surface of the cylinder around the axis of the cylinder of the plasma processing chamber. Electric field generating means for generating a high-frequency electric field by using a second high-frequency signal having a predetermined phase difference with respect to the first high-frequency signal, thereby generating an electric field substantially equal to the electric field of the helicon wave; And an electric field generating means for generating at least three loop antennas which are concentric with the center of the cylindrical axis of the plasma processing chamber and are provided at a predetermined distance from each other, and generate the first and second high-frequency signals. And a first high-frequency signal generated by the signal generating means is applied between two loop antennas located at both ends of the at least three loop antennas. On the other hand, signal applying means for applying the second high-frequency signal generated by the signal generating means to both ends of one of the at least three loop antennas located at the center is provided. And

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

In the plasma processing apparatus according to the present invention, for example, a reaction gas necessary for performing a predetermined process for forming a semiconductor device flows into the plasma processing chamber, while a reaction gas necessary for performing a predetermined process is formed inside the plasma processing chamber. Is set to a predetermined vacuum state. Here, the magnetic field generating means generates a DC magnetic field in a direction toward the sample inside the plasma processing chamber, while the electric field generating means moves from the center of the cylindrical shape of the plasma processing chamber to the outer periphery of the cylindrical shape. A first high-frequency electric field having a direction toward the plasma processing chamber is generated using the first high-frequency signal, and the angle changes on a plane parallel to the bottom surface of the cylinder around the axis of the cylinder of the plasma processing chamber. By generating a second high-frequency electric field having an angular rotation direction that rotates by using a second high-frequency signal having a predetermined phase difference with respect to the first high-frequency signal,
An electric field substantially equal to the electric field of the helicon wave is generated.

Here, the direct current magnetic field generated by the magnetic field generating means causes a collision separation phenomenon due to a thermal motion of gas molecules existing in the plasma processing chamber and an ionization phenomenon caused by, for example, irradiation of light or cosmic rays. After the initial ions are generated, the electrons and ions existing in the magnetic field in the plasma processing chamber perform a so-called Larmor motion, which rotates clockwise and counterclockwise around the magnetic field lines, respectively. Further, for the generated magnetic field, a first high-frequency electric field having a direction from the center of the cylindrical shape of the plasma processing chamber toward the outer periphery of the cylindrical shape, and the center of the first high-frequency electric field having the center of the cylindrical shape of the plasma processing chamber. And a second high-frequency electric field having an angular rotation direction in which the angle changes and rotates on a plane parallel to the bottom surface of the cylinder.
Therefore, electrons and ions are caused by the E × B drift effect in a direction perpendicular to both the electric field and the magnetic field, that is, in the first high-frequency electric field, in the angular rotation direction, and in the second high-frequency electric field. If so, the plasma processing chamber moves while rotating in a direction from the center of the cylindrical axis of the plasma processing chamber toward the outer periphery of the cylinder.

As a result, impact ionization due to the α action of the electrons and secondary electron emission due to the γ action generated by the incidence of ions on the plurality of electric field generating means are repeated, and the plasma state is developed. Here, when the frequency corresponding to the angular velocity of the generated rotating electric field is high, γ
Even if no action occurs, the ionization phenomenon is promoted. Therefore, since the initial electrons move while rotating as described above, the probability of the initial electrons colliding with the neutral particles increases, so that the collision ionization phenomenon easily occurs. As a result, generation and maintenance of plasma are facilitated even in a low pressure state of, for example, about 10 ⁻³ Torr.

The electromagnetic wave including the electric field generated by the electric field generating means can propagate in the plasma without being shielded on the plasma surface when the DC magnetic field exists. In other words, the electromagnetic wave penetrates into the plasma, propagates in a direction parallel to the magnetic field, and attenuates Landau while giving energy to electrons.
The helicon wave described in the section of the related art is basically a right-handed polarized electromagnetic wave that turns an electromagnetic field clockwise with respect to the direction of a magnetic field. Therefore, in the present invention, it is possible to generate an electric field substantially equal to the electric field mode of the helicon wave excited in the plasma generation chamber in the direction of the DC magnetic field, that is, in the direction toward the sample. The helicon wave can be effectively excited in the generated plasma. Therefore, the Helicon wave gives energy to the electrons in the plasma by Landau damping, whereby a high-density plasma can be generated. In other words, the electrons in the plasma absorb energy by the electric field in the direction of propagation of the helicon wave propagating in the plasma, and further contribute to the ionization phenomenon. Therefore, the density of the plasma must be higher than that of the conventional device. Can be.

As described above, the plasma generated by the electric field consisting of the magnetic field and the first and second high-frequency electric fields is transported in the direction of the magnetic field lines of the magnetic field, and then is substantially perpendicular to the surface of the sample. Incident in the direction.

[0029]

[0030]

Further, in the plasma processing apparatus according to the present invention, the electric field generating means may include at least three loop antennas which are concentric with the center of the cylindrical axis of the plasma processing chamber and are provided at a predetermined distance from each other. When,
A signal generating means for generating the first and second high-frequency signals, and a first high-frequency signal generated by the signal generating means, the signal being generated by two loop antennas located at both ends of the at least three loop antennas. While applying
Signal applying means for applying the second high-frequency signal generated by the signal generating means to both ends of one of the at least three loop antennas located at the center. Thus, the electric field generating means
A first high-frequency electric field having a direction from the axial center of the cylindrical shape of the plasma processing chamber toward the outer periphery of the cylindrical shape; and a first high-frequency electric field having a direction centered on the axial center of the cylindrical shape of the plasma processing chamber. By generating a second high-frequency electric field having an angular rotation direction in which the angle changes and rotating using a first and a second high-frequency signal having a predetermined phase difference with each other, the electric field of the helicon wave is substantially reduced. And generate a substantially equal electric field.

[0032]

[0033]

[0034]

[0035]

[0036]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment according to the present invention.
FIG. 2 is a perspective view of a helicon plasma processing apparatus according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view taken along line AA ′ of the plasma processing apparatus of FIG. In addition, although the solenoid coil 21 for magnetic field generation is provided over 360 degrees of the outer peripheral part of the plasma generation chamber 10, in FIG. 1, only a 180 ° portion is shown in order to clearly illustrate other devices. .
This is the same in FIGS. 7, 8, 12 and 16 below.

In the plasma processing apparatus of this embodiment, a circular ring-shaped loop antenna LA is provided on the outer peripheral portion of the cylindrical plasma generating chamber 10 whose inside is set to a vacuum state so as to surround the outer peripheral portion of the plasma generating chamber 10. Of the two high-frequency signals having a phase difference φ substantially equal to π / 2, a first signal voltage V1 is applied to both ends of the loop antenna LA, and a second signal voltage V2 is FIG. 1 shows that the helicon wave is effectively excited by applying the voltage between the loop antenna LA and the ground potential.
In addition to generating an electric field substantially equal to the electric field of the helicon wave in the mode of m = 0 shown in FIG. 9, a solenoid coil 21 for generating a magnetic field is provided on the outer peripheral portion of the loop antenna LA, and By applying a predetermined DC voltage, the sample 30 is parallel to the axial direction of the plasma generation chamber 10 (hereinafter, referred to as the Z-axis direction).
A DC magnetic field B is generated in a direction toward zero, thereby generating plasma by being excited by the helicon wave, and causing the plasma to be applied to the upper surface of the sample 300 placed in the plasma processing chamber 11 following the generation chamber 10. Irradiation.

In the helicon plasma processing apparatus of this embodiment, the outer peripheral portion of the plasma generation chamber 10 is
At the position in the Z-axis direction between the loop antenna LA and the plasma processing chamber 11, the microwave signal radiated from the transmitting horn antenna AN 1 passes through the center axis of the plasma generating chamber 10 and faces the transmitting side so as to face each other. Horn antenna A
N1 and a receiving horn antenna AN2 are provided, and the density of the generated plasma is calculated using the method of the microwave interferometer based on the microwave signal received by the receiving horn antenna AN2. It is characterized in that the phase difference φ is changed so as to effectively excite the helicon wave based on the density of the plasma.

As shown in FIGS. 1 and 2, for example, an electrically insulating material such as alumina or quartz glass is connected to the bottom of a cylindrical plasma generating chamber 10 so as to allow air to flow therethrough. A plasma processing chamber 11 made of an electrically insulating material and having a larger diameter than the plasma generation chamber 10 is connected. A sample support 30 made of an electrically insulating material is fixed to a bottom surface of the plasma processing chamber 11,
A bias voltage application electrode 31 is formed on the sample support table 30, and a sample 300, for example, a wafer of a semiconductor device, is mounted on the electrode 31 so that the surface thereof is perpendicular to the Z axis. Here, the high-frequency bias signal generator 33 whose one output terminal is grounded is connected to the capacitor 32.
By applying a bias AC signal, such as a high-frequency signal, to the electrode 31 via the electrode and controlling the voltage of the signal, the amount and energy of the ions in the generated plasma incident on the sample 300 are controlled. Thereby, for example, when a semiconductor device is formed, more precise processing can be performed.

Further, on the upper surface of the plasma generation chamber 10,
Gas cylinders 13a and 13b for storing a predetermined reaction gas are connected via a reaction gas transport pipe 12a, a valve 15, and variable leaks 14a and 14b, respectively.
And a vacuum adjusting valve 16 via a pressure adjusting valve 16.

1 and FIG. 2 on the outer periphery of the plasma generation chamber 10, a circular ring-shaped loop antenna LA is provided along the outer periphery of the plasma generation chamber 10. Surround, loop antenna L
The center of A is provided so as to be concentric with the axial center of the plasma generation chamber 10 and the surface of the loop antenna LA is parallel to the bottom surface of the plasma generation chamber 10.

As shown in FIGS. 1 and 2, the transmitting horn antenna AN1 is located at the outer peripheral portion of the plasma generating chamber 10 in the Z-axis direction between the loop antenna LA and the plasma processing chamber 11. A transmitting horn antenna AN1 and a receiving horn antenna AN2 are provided such that microwave signals radiated from the antenna pass through the center axis of the plasma generation chamber 10 and face each other. Further, a solenoid coil 21 for generating a magnetic field is provided on an outer peripheral portion of the loop antenna LA.
It is provided so as to surround the outer peripheral portion of the plasma generation chamber 10. A loop antenna LA is attached to the solenoid coil 21.
By applying a predetermined DC voltage necessary to generate a DC magnetic field having a magnetic flux density greater than the magnetic flux density of the magnetic field at which the electron cyclotron frequency is equal to the frequency of the high-frequency signal applied in the Z-axis direction, the plasma is generated. In the chamber 10 and the plasma processing chamber 11, a DC magnetic field B is generated in a direction parallel to the Z axis and toward the sample 300.

Further, in order to effectively excite the helicon wave in the plasma generation chamber 10 and generate an electric field close to the helicon wave in the mode of m = 0 shown in FIG. A signal of the sum of two high-frequency signals having a phase difference φ different from each other by approximately π / 2 is applied from a power supply circuit 600 described below.

FIG. 3 is a circuit diagram of the power supply circuit 600 of the helicon plasma processing apparatus shown in FIGS. As shown in FIG. 3, generated by the reference high-frequency signal generator 50,
For example, a sine-wave reference high-frequency signal having a frequency of 13.56 MHz is applied to the primary side of the high-frequency transformer T2 while being applied to the primary side of the high-frequency transformer T1. One end on the secondary side of the high-frequency transformer T2 is provided with a variable phase shifter 61 in which the phase shift amount φ is controlled by the controller 100, and impedance matching for performing impedance matching between the variable phase shifter 61 and the high-frequency transformer T1. Is connected to the center tap on the secondary side of the high-frequency transformer T1 via the switch 52, and the other end on the secondary side of the high-frequency transformer T2 is grounded.
Further, both ends on the secondary side of the high frequency transformer T1 are connected to both ends of the loop antenna LA via an impedance matching device 51 for performing impedance matching between the high frequency transformer T1 and the loop antenna LA. In this embodiment, it is assumed that the high-frequency transformers T1 and T2 each have a voltage ratio of 1: 1 and that the voltage does not change even in the impedance matching devices 51 and 52.

In the power supply circuit 600 configured as described above, the signal voltage of the reference high-frequency signal is set to V1, and the signal voltage at the output terminal of the impedance matching unit 52 is set to V1.
Assuming that the signal voltage is 2, the signal voltage of the high-frequency signal output from the secondary side of the high-frequency transformer T1 via the impedance matching device 51 is a signal voltage in which the signal voltage V2 is superimposed on the signal voltage V1 with reference to the ground potential. . Here, in the initial state, the signal voltages V1 and V2 have a phase difference φ equal to π / 2, as shown in FIG.
Further, the phase difference φ is controlled by the controller 100 based on the density of the generated plasma as described later in detail.

V1 = sin (ωt + π / 2)

## EQU4 ## V2 = sin (ωt)

In the power supply circuit 600, of the two signal voltages V1 and V2, the first signal voltage V1 is applied to both ends of the loop antenna LA, and the second signal voltage V2 is applied when the signal voltage V1 is zero. At some point, the signal voltage V2 is applied between the loop antenna LA and the ground potential so that the signal voltage V2 becomes maximum or minimum, and the electric field of the helicon wave in the mode of m = 0 shown in FIG. 19 is substantially reduced. An equal electric field is generated, which effectively excites the helicon wave. That is, the angle changes on a plane parallel to the bottom surface of the cylindrical plasma generation chamber 10 around the axis of the cylindrical plasma generation chamber 10 according to Lenz's law by the high frequency signal applied to the loop antenna LA by applying the signal voltage V1. While generating an electric field E1 having a rotating angular rotation direction (θ direction) and changing at the angular frequency ω of the high-frequency signal, the signal voltage V
2 has a radial direction (r direction) from the axis of the plasma generation chamber 10 to the side surface and has an angular frequency ω of the high-frequency signal due to the high-frequency signal excited between the loop antenna LA and the ground potential by applying A changing electric field E2 is generated.

For example, when ωt = 0, π, the absolute value of the signal voltage V1 becomes maximum while the signal voltage V2 becomes 0, as shown in FIG. 4, so that (a) and (e) of FIG. As shown, the absolute value of the electric field E1 is maximum, while the electric field E2 is zero. At this time, only the combined electric field E is generated in the direction of the angle rotation, and the combined electric field E is not generated in the Z-axis direction and the r direction parallel to the DC magnetic field B.

When ωt = π / 2, 3π / 2, the absolute value of the signal voltage V2 becomes the maximum while the signal voltage V1 becomes 0 as shown in FIG. 4, so that (c) of FIG. ,
As shown in (g), while the absolute value of the electric field E2 becomes maximum, the electric field E1 becomes zero. At this time, as the electric field E, only the electric field in the Z axis direction and the r direction is generated, and the combined electric field E in the angle rotation direction is not generated.

Further, ωt = π / 4, 3π / 4, 5π /
At 4,7π / 4, both signal voltages V1 and V2 have predetermined values as shown in FIG.
As shown in (d), (f), and (h), a combined electric field of the electric field E1 in the angular rotation direction and the electric field E2 in the Z-axis direction and the r direction is obtained.

Thus, the combined electric field E of these electric fields E1 and E2 on the plane of the loop antenna LA is, as shown in FIG. 5, an electric field substantially equal to the electric field of the helicon wave in the mode of m = 0. By generating the combined electric field E, the helicon wave in the plasma generation chamber 10 can be effectively excited.

FIG. 6 is a block diagram showing a microwave interferometer section and a control section of the helicon plasma processing apparatus of this embodiment. In this embodiment, the density of the plasma generated using the method of the microwave interferometer is calculated, and the helicon wave is synchronized with the composite electric field E generated by the high-frequency signal based on the calculated density of the plasma. The phase difference φ between the signal voltages V1 and V2, which is the phase shift amount of the variable phase shifter 61 in FIG.

As shown in FIG. 6, the microwave signal generator 80 generates a microwave signal having a frequency sufficiently higher than the frequency of the high-frequency signal, for example, a frequency of 34 GHz, and converts the microwave signal into a variable attenuator. 81, a main transmission line 82a and an auxiliary transmission line 82b electromagnetically coupled to the main transmission line 82a.
To the transmission horn antenna AN1 via the main transmission line 82a of the directional coupler 82 having here,
The sub transmission line 82b of the directional coupler 82 is connected to the main transmission line 8
2a, a part of the microwave signal transmitted to the variable attenuator 84 and the variable phase shifter 8 are detected.
5 and a variable attenuator 86 to output the signal to a sub transmission line 87b of a directional coupler 87 having a main transmission line 87a and a sub transmission line 87b. The transmitting horn antenna AN1 passes the input microwave signal through the plasma generated in the plasma generating chamber 10 as indicated by an arrow MA, and receives the horn antenna AN2 provided opposite to the horn antenna AN1. Radiate. The receiving horn antenna AN2 outputs the received microwave signal to the main transmission line 87a of the directional coupler 87 via the variable attenuator 83. Further, the directional coupler 87 detects a part of the microwave signal input to the sub transmission line 87b, and converts the detected part of the microwave signal and the microwave signal input to the main transmission line 87a. The mixing causes interference between the electromagnetic waves of the respective signals, and outputs the mixed microwave signal to the diode detector 88. Further, the diode detector 88 detects the input microwave signal and outputs a detection current to the current detector 89. In response, the current detector 89 generates an analog voltage signal proportional to the detected current value. Then, via an analog / digital converter (A / D converter) 90,
It outputs to the controller 100 as a digital voltage signal.

When the plasma is not generated in the plasma generation chamber 10, the microwave signal input to the main transmission line 87a and the microwave signal input to the sub transmission line 87b are converted by the directional coupler 87. Main transmission line 8
At the output end of 7a, a variable phase shifter 8
5, the phase shift amount is adjusted. Next, when the plasma is generated in the plasma generation chamber 10, the directional coupler 87 mixes the microwave signal that has passed through the plasma with the microwave signal that is a reference signal that does not pass through the plasma. Interference is generated between two electromagnetic waves of the microwave signal, and the amount of the DC component after mixing is detected as a phase difference Δθ. As is well known, the phase difference Δθ [rad] is proportional to a value obtained by integrating the density of the plasma included in the microwave path. Therefore, the density n _e of the generated plasma [cm ^-3], the approximation that the refractive index of the plasma in the range of density n _e of the plasma is sufficiently smaller than the cut-off density n _ce is proportional to the density of electrons Under the conditions, it can be expressed by the following equation 5, as is known.

[0055]

N _e = 118 · (ωm / 2π) · Δθ / 2r _a where ωm: angular frequency [Hz] of the microwave signal generated by the microwave signal generator 80, 2r _a : microwave signal Is the thickness of the plasma passing therethrough, that is, the diameter [cm] of the cylinder of the plasma generation chamber 10. Further, the frequency of the microwave signal generated by the microwave signal generator 80 is preferably set to a sufficiently high frequency of at least three times the cutoff frequency corresponding to the electron density of the plasma to be measured. Note that the electron density obtained from Equation 5 is the amount of an average value averaged over time and space.

From the above equation (5), when the phase difference Δθ increases,
The plasma density _ne increases. If the density n _e of the plasma is greater than the predetermined set value n _e s, may be longer wavelength λ of helicon waves than the number 1, therefore, the plasma density n _e is made smaller the phase difference Δθ the can be made closer to the set value n _e s. Using this principle, the controller 100 performs control processing as follows.

The controller 100 calculates the phase difference Δθ using a predetermined conversion equation based on the voltage of the input digital voltage signal, and then uses the equation 5 to calculate the plasma density n based on the calculated phase difference Δθ. Calculate _e . On the other hand, the operator sets the density n _{es of the} plasma to be set on the keyboard 1.
01 to the controller 100. Then
The controller 100 calculates the calculated plasma density _ne.
Smaller but larger than the density n _e s of to be set plasma to reduce the phase difference φ of the variable phase shifter 61, whereas, than the density n _e s of to be set calculated plasma density n _e is plasma For example, the variable phase shifter 61 is controlled so that the phase difference φ of the variable phase shifter 61 is increased. Thereby, the density of the plasma generated in the plasma generation chamber 10 can be controlled to be set to the density n _{es of} the plasma input by the operator. In addition, the above control can control the coupling between the wave of the helicon wave and the electric field by the high-frequency signal to be in an optimum state, thereby generating a plasma with higher density and more stability than the conventional example. Can be. Therefore, when the generated plasma is used for predetermined processing of a semiconductor device or the like, there is an advantage that the processing can be performed more stably.

In the plasma processing apparatus configured as described above, for example, a reaction gas necessary for performing a predetermined process for forming a semiconductor device is supplied from the gas cylinders 13a and 13b through the variable leaks 14a and 14b. Is mixed and generated at a predetermined mixing ratio, and the generated mixed gas 500 flows into the plasma generation chamber 10 and the plasma processing chamber 11 via the valve 15 and the reaction gas transport pipe 12a. On the other hand, pump 17
Is driven, the gas 510 in the plasma generation chamber 10 and the plasma processing chamber 11 is exhausted to the pump 17 through the exhaust pipe 12 b and the pressure adjustment valve 16, and by using the pressure adjustment valve 16, The inside of the plasma processing chamber 11 is set to a predetermined vacuum state. In the present embodiment, preferably, 10 ⁻³ Torr
The following states are set.

The generated combined electric field E causes initial electrons and initial electrons due to a collision separation phenomenon due to thermal motion of gas molecules existing in the plasma generation chamber 10 and an ionization phenomenon caused by, for example, irradiation of light or cosmic rays. After the ions are generated, electrons and ions existing in the combined electric field E for helicon wave excitation in the plasma generation chamber 10 are combined with the combined electric field E.
Vibrates at an angular frequency ω in the direction of, and a trapping phenomenon occurs, and electrons repeat the α action while reciprocating in the plasma generation chamber 10. Therefore, even if the loop antenna LA is placed outside the plasma generation chamber 10, Even when the loop antenna LA is covered with an electrical insulator, a discharge phenomenon occurs. Preferably, by mounting the loop antenna LA outside the plasma generation chamber 10 as in the present embodiment, it is possible to generate plasma free from contamination of the loop antenna LA with the constituent materials, that is, completely free of impurities.

As shown in FIGS. 1 and 2, a DC magnetic field B is generated in the Z-axis direction which is parallel to the axial direction of the cylinder of the plasma generation chamber 10, so that electrons and ions respectively move right and left around the magnetic field lines. A helical motion called a so-called Larmor motion is performed in the clockwise and counterclockwise directions. Further, as described above, since the high-frequency combined electric field E that effectively excites the helicon wave is generated, the initial electrons are perpendicular to both the applied combined electric field E and the magnetic field B by the E × B drift effect. Move while rotating in different directions. As a result, the probability that the initial electrons collide with the neutral particles increases, so that the impact ionization phenomenon is likely to occur. As a result, generation and maintenance of plasma are facilitated even in a low pressure state of, for example, about 10 ⁻³ Torr.

For example, when a high-frequency combined electric field E is applied to plasma in the absence of any DC magnetic field B, the high-frequency angular frequency ω of the combined electric field becomes equal to the electron plasma frequency ωpe
When (≒ 10 ⁴ ( _ne ) ^1/2 Hz (where _ne is the density of electrons)) or less, the high-frequency synthetic electric field E is shielded by the collective motion of electrons on the surface of the plasma. The combined electric field E cannot penetrate into the plasma. However, when a DC magnetic field B is applied to the plasma by the solenoid coil 21, the movement of the electrons is restricted, so that an electromagnetic wave having a low frequency can also propagate in the plasma. For example, when a magnetic field B of 4.9 Gs or more is applied, the angular frequency ω of the applied high frequency signal is sufficiently lower than the electron cyclotron angular frequency ωce and sufficiently higher than the ion cyclotron angular frequency ωci. When the first approximation condition described above is satisfied, for example, when the frequency of the angular frequency ω is 13.56 MHz, the electromagnetic wave of the high-frequency signal can propagate in the plasma. In other words, when a magnetic field B of 4.9 Gs or more is applied in the Z-axis direction, the applied high frequency signal electromagnetic wave having a frequency of 13.56 MHz penetrates the plasma and propagates in a direction parallel to the DC magnetic field B. Then, Landau damps while giving energy to the electrons. Therefore, the electrons in the plasma absorb energy by the electric field of the electromagnetic wave propagating in the plasma, and further contribute to the ionization phenomenon. For example, the density of the plasma should be higher than that of the conventional helicon plasma processing apparatus. Can be.

In this embodiment, in order to effectively excite the helicon wave, the mode of the electric field of the helicon wave generated in the plasma generation chamber 10 (in this embodiment, the basic mode of m = 0) ), And the electric field structure is set to be substantially the same. Actually, since there is a boundary of a discharge tube, which is an outer peripheral wall of the plasma generation chamber 10, it does not propagate as a pure transverse wave (electromagnetic wave), and the DC magnetic field B
Is a hybrid wave having an electric field component in the direction along. Therefore, the Helicon wave gives energy to the electrons in the plasma by Landau damping, whereby a high-density plasma can be generated.

As described above, the DC magnetic field B and the plasma generated by the high-frequency combined electric field E are transported in the direction of the lines of magnetic force of the DC magnetic field B, that is, in the Z-axis direction. Incident in a substantially perpendicular direction.

In this embodiment, unlike the conventional magnetron plasma processing apparatus, the plasma is transported by the generated magnetic field B without confining the plasma, so that the plasma is uniformly applied to the sample 300. Can be.

In this embodiment, the plasma generation chamber 10
The electric field induced inside is closer to the helicon wave actually propagating in the plasma than in the case of applying an electric field only in the angular rotation direction as in the conventional helicon plasma processing apparatus, so that the plasma is effectively And more stable helicon plasma can be obtained. Thereby, processing for forming a semiconductor device and the like can be performed more stably.

The loop antenna LA of the present embodiment has one
The two ring portions 241,
242 can be miniaturized as compared with the conventional helicon plasma processing apparatus. Furthermore, since there is one loop antenna LA, a mismatch between the antenna distance and the wavelength of the helicon wave due to a change in plasma density does not occur. Therefore, even if the applied high-frequency signal changes from low power to high power, a plasma having a higher density can be generated more stably as compared with the conventional example.

In this embodiment, the density of the plasma generated in the plasma generation chamber 10 is measured by the microwave interferometer shown in FIG. 6, and the level of the high-frequency signal is determined based on the measured density of the plasma. By controlling the phase difference φ, the density of the plasma can be controlled to a predetermined value by controlling the coupling with the wave of the helicon wave in the plasma to an optimum state.

FIG. 7 is a perspective view of a helicon plasma processing apparatus which is a modification of the first embodiment according to the present invention.
, The same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.

As shown in FIG. 7, two loop antennas LA1 and LA2 are provided on the outer peripheral portion of the plasma generation chamber 10 at intervals of a distance L0 in the Z-axis direction which are close to each other, as compared with the first embodiment. The signal voltage V1 of the high-frequency signal generated by the power supply circuit 600 may be applied to both ends of the loop antenna LA1, while the signal voltage V2 may be applied between one end of the loop antenna LA2 and the ground potential. Here, the distance L0 is preferably a distance having a length sufficiently equal to zero.
With the above-described configuration, the device according to the modification has the same operation and effect as the first embodiment.

<Second Embodiment> FIG. 8 shows a second embodiment according to the present invention.
FIG. 9 is a perspective view of a helicon plasma processing apparatus according to an embodiment of the present invention. In FIG. 8, the same components as those in FIGS. 1, 2 and 7 are denoted by the same reference numerals.

The helicon plasma processing apparatus according to the second embodiment differs from the first embodiment in the following points. (A) Three circular ring-shaped loop antennas LA1, LA2, and LA3 are arranged on the outer peripheral portion of the plasma generation chamber 10 in the Z-axis direction in the order of LA1, LA3, and LA2 and between the loop antennas LA1 and LA3. An axial distance L1 and a Z-axis distance L2 between the loop antennas LA3 and LA2.
Are λ / 8 (where λ is the wavelength of the helicon wave under predetermined conditions), and the plasma generation chamber 10
And two high-frequency signals having a phase difference φ substantially equal to π / 2 generated by a power supply circuit 610 to be described later. The first signal voltage V1 of the voltages V1 and V2 is applied between the loop antenna LA1 and the loop antenna LA2, each of which is electrically closed, and the second signal voltage V2 is applied to both ends of the loop antenna LA3. Generating an electric field that is substantially equal to the electric field of the helicon wave in the m = 0 mode illustrated in FIG. 19 so that the application effectively excites the helicon wave. (B) Two solenoid coils 21 and 22 for generating a magnetic field are provided on the outer peripheral portions of the loop antennas LA1, LA2 and LA3, and a predetermined DC voltage is applied to the solenoid coils 21 and 22 to form the plasma generating chamber 10. DC magnetic field B in a direction parallel to the Z-axis direction and
To generate.

FIG. 9 is a circuit diagram of the power supply circuit 610 of the helicon plasma processing apparatus of FIG. 8, and in FIG. 9, the same components as those of FIG. 3 are denoted by the same reference numerals.

As shown in FIG. 9, for example, a frequency of 13.56 MH generated by the reference high-frequency signal generator 50.
The reference high-frequency signal of the sine wave of z is applied to the primary side of the high-frequency transformer T1 and to the primary side of the high-frequency transformer T2. Both ends on the secondary side of the high-frequency transformer T1 are connected to the high-frequency transformer T1 and the loop antenna LA, respectively.
1 and LA2 are connected to closed loop antennas LA1 and LA2, respectively, via an impedance matching unit 51 for performing impedance matching between the loop antennas LA1 and LA2. One end on the secondary side of the high-frequency transformer T2 is connected to one end on the primary side of the high-frequency transformer T3 via a variable phase shifter 61 whose phase shift amount is controlled by the controller 100. The other end and the other end on the primary side of the high-frequency transformer T3 are grounded. Further, the secondary side of the high-frequency transformer T3 is connected to both ends of the loop antenna LA3 via an impedance matching device 52 for performing impedance matching between the high-frequency transformer T3 and the loop antenna LA3. In this embodiment, the high-frequency transformers T1, T
2 and T3 each have a one-to-one voltage ratio, and it is assumed that the voltage does not change even in the impedance matching devices 51 and 52.

Here, in the initial state, the respective signal voltages V1 and V2 are mutually π / 2 as shown in the following equations (6) and (7).
, And the phase difference φ is controlled by the controller 100 based on the density of the generated plasma, as described in detail below. The setting of the initial state of each of the signal voltages V1 and V2 is performed in the same manner as the signal voltage V1 in the first embodiment for convenience of explanation.
And V2 are switched.

V1 = sin (ωt)

V2 = sin (ωt + π / 2)

In the power supply circuit 610, the first signal voltage V1 of the two signal voltages V1 and V2 is applied to the closed loop antennas LA1 and LA2, respectively, and the signal voltage V2 is applied to both ends of the loop antenna LA3. When applied, an electric field is generated which is substantially equal to the electric field of the helicon wave in the mode of m = 0 shown in FIG. 19, thereby effectively exciting the helicon wave. That is,
By applying the signal voltage V1 between the loop antennas LA1 and LA2, the antenna has a radial direction near the loop antenna LA1 (represented by an electric field E1 in FIG. 8) and a direction parallel to the Z-axis direction near the loop antenna LA3. While having a radial direction near the loop antenna LA2 (represented by an electric field E2 in FIG. 8) and generating an electric field that changes at the angular frequency ω of the high-frequency signal, the signal voltage V2 is applied to both ends of the loop antenna LA3. When the voltage is applied, the cylindrical plasma generating chamber 1 is formed according to Lenz's law by a high-frequency signal flowing through the loop antenna LA.
An electric field E3 having an angular rotation direction (θ direction) in which the angle changes and rotates on a plane parallel to the bottom surface around the 0 axis and changing at the angular frequency ω of the high-frequency signal is generated.

For example, when ωt = 0, π, the signal voltage V2
Of the electric field E3, while the absolute value of the electric field E3 becomes the maximum and the absolute value of the electric field E3 becomes the maximum as shown in FIGS. 10A and 11A. Is 0
Becomes At this time, an electric field E3 in the vicinity of the loop antenna LA3 is induced, and the electric field E3 induces an electric field in the loop antennas LA1 and LA2 having a smaller angle of rotation than the electric field E3. Therefore,
As a composite electric field E of these electric fields, only an electric field in the angle rotation direction is generated, and no composite electric field E is generated in the Z-axis direction parallel to the DC magnetic field B.

When ωt = π / 2, 3π / 2, the absolute value of the signal voltage V1 becomes maximum while the signal voltage V2 becomes 0, so that (c) of FIG. 10 and (c) of FIG. ), The absolute values of the electric fields E1 and E2 are maximized, while the electric field E3 is 0. At this time, an electric field E is generated only in the Z-axis direction in the direction from the loop antenna LA1 to the loop antenna LA2 via the loop antenna LA3 or in the opposite direction.

Further, ωt = π / 4, 3π / 4, 5π /
In the case of 4,7π / 4, both signal voltages V1 and V2 have predetermined values, so that (b), (d) in FIG.
As shown in (b) and (d) of FIG.
1 and a combined electric field of the electric field E2 in the Z-axis direction.

Thus, the combined electric field E of these electric fields E1 and E2 is an electric field substantially equal to the electric field of the helicon wave in the mode of m = 0, as shown in FIGS. By generating the combined electric field E, the helicon wave in the plasma generation chamber 10 can be effectively excited. Note that the combined electric field E generated in the second embodiment has the same shape near the loop antenna LA1 as in the first embodiment, and has the same shape near the loop antenna LA2, but is formed in the same order. Because of the opposite, the electromagnetic wave near the loop antenna LA1 propagates in the same direction as the DC magnetic field B, while the electromagnetic wave near the loop antenna LA2 propagates in the opposite direction to the DC magnetic field B. Therefore,
Compared to the first embodiment, the density of the plasma near the loop antenna LA3 in the center of the plasma generation chamber 10 can be increased, and the helicon wave can be more effectively excited.

The helicon plasma processing apparatus of the second embodiment configured as described above has the same functions and effects as the apparatus of the first embodiment, and further has the same effects as those of the first embodiment. Compared to this, a plasma having a higher density can be stably generated.

In the second embodiment, three loop antennas LA1 to LA3 are used. However, the present invention is not limited to this, and at least one loop antenna is provided between the loop antenna LA1 and the loop antenna LA3. An antenna is provided, and the loop antenna LA3 and the loop antenna L
At least one loop antenna may be provided between the antenna and A2, and a predetermined signal voltage may be applied to each of the loop antennas so as to be close to the electric field of the helicon wave in the mode of m = 0. Further, a loop antenna is provided above the loop antenna LA1 or below the loop antenna LA2, and the antenna configuration of the second embodiment is provided in multiple stages, and an electric field substantially equal to the electric field of the helicon wave is generated. Then, a signal voltage of a predetermined value for effectively exciting the helicon wave may be applied to each antenna.

<Third Embodiment> FIG. 12 is a perspective view of a helicon plasma processing apparatus according to a third embodiment of the present invention. In FIG. 12, FIG. 12, FIG. 7, FIG. The same components are denoted by the same reference numerals.

The helicon plasma processing apparatus according to the third embodiment differs from the first embodiment in the following points. (A) Two circular ring-shaped loop antennas LA1 and LA2 are provided on the outer periphery of the plasma generation chamber 10 in the Z-axis direction.
The interval L10 is λ / 4 (where λ is the wavelength of the helicon wave under predetermined conditions), and surrounds the outer peripheral portion of the plasma generation chamber 10 and is
And a power supply circuit 6 described later.
A first signal voltage V1 of two high-frequency signals having a phase difference .phi. Substantially equal to .pi. / 2, which is generated by the first signal voltage V1, and applied to both ends of the loop antenna LA1; Apply signal voltage V2 to loop antenna LA
2 to generate an electric field E in the direction of angular rotation in the vicinity of the loop antennas LA1 and LA2 so as to effectively excite the helicon wave by being applied to both ends of the loop antenna 2. (B) The outer circumference of the loop antennas LA1 and LA2 is
By providing a predetermined magnetic field generating solenoid coils 21 and 22 and applying a predetermined DC voltage to the solenoid coils 21 and 22, a DC magnetic field is generated in a direction parallel to the Z-axis direction of the plasma generation chamber 10 and toward the sample 300. Generating B.

FIG. 13 is a circuit diagram of a power supply circuit 620 of the helicon plasma processing apparatus shown in FIG. 12. In FIG. 13, the same components as those in FIGS. 3 and 9 are denoted by the same reference numerals.

The power supply circuit 620 of the third embodiment differs from the power supply circuit 610 shown in FIG. 9 in the following point. (A) The signal voltage V1 output from the impedance matching device 51 is applied to both ends of the loop antenna LA1. (B) The signal voltage V2 output from the impedance matching device 52 is applied to both ends of the loop antenna LA2.

Here, in the initial state, the signal voltages V1 and V2 are mutually π / 2 as shown in the following equations (8) and (9).
, And the phase difference φ is controlled by the controller 100 based on the density of the generated plasma, as described in detail below. The initial settings of the signal voltages V1 and V2 are set differently from those of the first and second embodiments for convenience of explanation.

V1 = sin (ωt−π / 4)

V2 = sin (ωt−3π / 4)

In the power supply circuit 620, the first signal voltage V1 of the two signal voltages V1 and V2 is applied to both ends of the loop antenna LA1, and the signal voltage V2 is applied to both ends of the loop antenna LA2. Generates an electric field close to the electric field of the helicon wave,
Effectively excites helicon waves. That is, by applying the signal voltage V1 to both ends of the loop antenna LA1, the antenna has an angular rotation direction near the loop antenna LA1 and the angular frequency ω of the high-frequency signal according to Lenz's law.
Generates an electric field E1 that varies with
By applying a signal voltage V2 to both ends of A2, an electric field E2 having an angular rotation direction near the loop antenna LA2 and changing at an angular frequency ω of a high-frequency signal is generated according to Lenz's law.

For example, when ωt = π / 4, 5π / 4, the absolute value of the signal voltage V1 becomes maximum while the signal voltage V2 becomes 0, so that FIG. 14 (b) and FIG. 15 (b) As shown in the figure, while the absolute value of the electric field E1 is maximum, the electric field E2
Becomes 0. At this time, only the electric field E1 in the angle rotation direction is generated near the loop antenna LA1.

When ωt = 3π / 4, 7π / 4,
While the absolute value of the signal voltage V2 is maximized, the signal voltage V1 is
Becomes 0, so that the absolute value of the electric field E2 becomes maximum as shown in FIG. 14 (d) and FIG.
1 becomes 0. At this time, only the electric field E2 in the angular rotation direction is generated near the loop antenna LA2.

Further, ωt = 0, π / 2, π, 3π / 2
At the time of π, both signal voltages V1 and V2 have a predetermined value, so that FIGS. 14 (a) and (c) and FIGS.
As shown in (c), each loop antenna LA1, LA2
, Electric fields E1 and E2 in the angle rotation direction are generated.

Here, the phase difference φ between the signal voltage V1 and the signal voltage V2 is determined by the operator by inputting the density of the plasma generated in the plasma generation chamber 10 as in the first embodiment. It was can be controlled so as to set the plasma density n _e s. In addition, the above control can control the coupling between the wave of the helicon wave and the electric field by the high-frequency signal to be in an optimum state, thereby generating a plasma with higher density and more stability than the conventional example. Can be. Therefore, when the generated plasma is used for predetermined processing of a semiconductor device or the like, there is an advantage that the processing can be performed more stably.

FIG. 16 is a perspective view of a helicon plasma processing apparatus which is a modification of the third embodiment according to the present invention, and is the same as FIG. 1, FIG. 2, FIG. 7, FIG. 8, and FIG. Are given the same reference numerals. FIG. 17 shows the power supply circuit 6 of the helicon plasma processing apparatus shown in FIG.
30 is the circuit diagram of FIG. 17, and in FIG. 17, the same components as those in FIGS. 3, 9, and 13 are denoted by the same reference numerals.

The modification of the third embodiment is different from the third embodiment in that the power supply circuit 63 differs from the power supply circuit 620.
It is characterized in that each of the loop antennas LA1, LA2 is excited using the signal voltages V1, V2 supplied from 0.

Power supply circuit 630 is configured as follows. As shown in FIG. 17, for example, a sine-wave reference high-frequency signal having a frequency of 13.56 MHz generated by the reference high-frequency signal generator 50 includes high-frequency transformers T1, T2,
Applied to each primary side of T4. In addition, high-frequency transformer T
2 is connected to one end on the primary side of the high-frequency transformer T3 via a variable phase shifter 62 whose phase shift amount φ1 is controlled by the controller 100a, and is connected to the other end on the secondary side of the high-frequency transformer T2. The other end of the primary side of the high-frequency transformer T3 is grounded. Furthermore, a high-frequency transformer T4
Is connected to one end on the primary side of the high-frequency transformer T5 via a variable phase shifter 63 whose phase shift amount φ2 is controlled by the controller 100a.
4 and the other end of the high-frequency transformer T5 on the primary side are both grounded.

One end on the secondary side of the high-frequency transformer T5 is connected to the center tap on the secondary side of the high-frequency transformer T1,
The other end on the secondary side of the high-frequency transformer T5 is a high-frequency transformer T
3 is connected to the center tap on the secondary side. Further, both ends on the secondary side of the high frequency transformer T1 are connected to the high frequency transformer T1.
1 is connected to both ends of the loop antenna LA1 via an impedance matching unit 51 for performing impedance matching between the loop antenna LA1 and the high-frequency transformer T3.
Are connected to both ends of the loop antenna LA2 via an impedance matching unit 52 for performing impedance matching between the high-frequency transformer T3 and the loop antenna LA2.

Here, the signal voltage V1 output from the impedance matching device 51 is applied to the loop antenna LA1, while the signal voltage V2 output from the impedance matching device 52 is applied to the loop antenna LA2. The controller 100a controls each phase shift amount φ1 of the variable phase shifters 62 and 63 so that the phase difference between the signal voltages V1 and V2 is controlled similarly to the phase difference φ of the first embodiment or the second embodiment. , Φ
2 is controlled.

The helicon plasma processing apparatus according to the modification of the third embodiment configured as described above has the same operation and effect as the apparatus according to the third embodiment, and is different from the apparatus according to the third embodiment. Then, an electric field parallel to the DC magnetic field B is generated, and the generated combined electric field becomes equivalent to the electric field of the helicon wave, so that the helicon wave can be more effectively excited.

<Other Embodiments> Although a loop antenna is used in the above embodiments, the present invention is not limited to this, and a conductor plate or a conductive film is attached to the outer peripheral portion of the plasma generation chamber 10 as a loop antenna. Alternatively, it may be formed. Further, although the cylindrical plasma generation chamber 10 and the plasma processing chamber 11 are used, the present invention is not limited to this, and another cylindrical shape such as a rectangular cylindrical shape may be used.

[0099] In the above embodiments, based on the measured plasma density n _e, but by controlling the density of the plasma by controlling the phase difference φ of the high-frequency signal,
The present invention is not limited to this, as the number 1 is clear, based on the measured plasma density n _e, the phase difference phi,
Frequency f or the angular frequency ω of the RF signals, and may control the plasma density n _e by varying at least one of the magnetic flux density of the DC magnetic field B applied.

Further, another solenoid coil is provided on the outer peripheral portion of the DC magnetic field B generated below the plasma processing chamber 11 and the other solenoid coil has the same polarity as the solenoid coils 21 and 22. DC voltage is applied at the same current value. Thereby, the solenoid coil 2
The so-called mirror magnetic field is generated by converging the magnetic flux that has been diverged by only the solenoid coils 1 and 22 by the solenoid coil 25. Thereby, the incident angle of the plasma incident on the upper surface of the sample 300 becomes vertical over substantially the whole of the sample 300, and the plasma processing apparatus can be applied to the anisotropic etching process.

Further, it may be set so that a mirror magnetic field is formed by controlling a current value applied to the solenoid coils 21 and 22.

In the above embodiments, a high-frequency signal is used, but the present invention is not limited to this, and an AC signal including a low-frequency signal may be used.

In the above embodiments, the electrode 31 and the bias signal generator 33 are provided, but the present invention is not limited to this, and the electrode 31 and the bias signal generator 33 may not be provided.

In the above embodiment, the density of the plasma generated is detected by using the method of the microwave interferometer. However, the present invention is not limited to this, and the electrostatic probe is inserted into the plasma generation chamber 10. A known electrostatic probe method for measuring the density of plasma generated by the above method may be used.

In the above embodiment, the loop antenna L
Although A and LA1 to LA3 are provided on the outer peripheral portion of the plasma generation chamber 10, the present invention is not limited to this, and may be provided in the plasma generation chamber 10. Also, the magnetic field generating solenoid coils 21 and 22 may be provided in the plasma generation chamber 10. Further, in the present embodiment, the plasma generation chamber 10
And the plasma processing chamber 11 are separated, but the present invention is not limited to this, and each of the chambers 10 and 11 may be configured by one chamber.

In the above embodiment, the plasma processing chamber 1
Although 1 is formed of an electrical insulator, it may be formed of a conductive material such as a metal. In this case, preferably, a non-magnetic metal such as aluminum, which does not affect the DC magnetic field generated by the solenoid coils 21 and 22, is used.

[0107]

As described above in detail, according to the plasma processing apparatus of the present invention, a helicon plasma is generated in a cylindrical plasma processing chamber in which the inside is set to a vacuum state, and a predetermined amount is applied to the sample. In a plasma processing apparatus for performing processing, a magnetic field generating means for generating a DC magnetic field in a direction toward the sample inside the plasma processing chamber, and a direction from an axial center of a cylindrical shape of the plasma processing chamber to an outer periphery of the cylinder. Generating a first high-frequency electric field using the first high-frequency signal, and rotating the plasma processing chamber with its angle changed on a plane parallel to the bottom surface of the cylinder around the axis of the cylinder of the plasma processing chamber. By generating a second high-frequency electric field having an angular rotation direction using a second high-frequency signal having a predetermined phase difference with respect to the first high-frequency signal, a helicon wave electric field is generated. And a field generation means for generating a qualitatively same field. Here, the electric field generating means includes at least three loop antennas that are concentric with the center of the cylindrical axis of the plasma processing chamber and that are provided at a predetermined distance from each other, and that the first and second high-frequency signals are connected to each other. A signal generating means for generating the signal, and applying the first high-frequency signal generated by the signal generating means between two loop antennas located at both ends of the at least three loop antennas; Signal applying means for applying the second high-frequency signal generated by the above to both ends of one of the at least three loop antennas located at the center.

Therefore, the helicon wave is effectively excited by an electric field close to the electric field mode of the helicon wave excited in the plasma processing chamber with respect to the direction of the DC magnetic field generated by the electric field generating means. Is propagated into the plasma by the magnetic field, so that the degree of vacuum is higher than that of the first conventional example, that is, the density of the plasma is significantly increased while the gas pressure in the plasma processing chamber is lowered. Can be. Further, for example, since the generated plasma is transported by the magnetic field without confining the plasma as in a conventional magnetron high-frequency plasma processing apparatus, the surface of the sample can be uniformly irradiated with the plasma. . Here, for example, if the direction of the magnetic field is set in a direction perpendicular to the surface of the sample, the sample can be irradiated with plasma in a direction exactly perpendicular to the sample. Accordingly, when the generated plasma is used for a predetermined process of a semiconductor device or the like, there is an advantage that the process can be performed more stably.

[0109]

[0110]

[0111]

[0112]

[Brief description of the drawings]

FIG. 1 is a perspective view of a helicon plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is an AA ′ of the helicon plasma processing apparatus of FIG. 1;
It is a longitudinal cross-sectional view about a line.

FIG. 3 is a circuit diagram of a power supply circuit of the helicon plasma processing apparatus of FIGS. 1 and 2;

FIG. 4 shows two signal voltages V1 and V2 applied to a loop antenna of the helicon plasma processing apparatus of FIGS. 1 and 2;
6 is a graph showing the waveform of FIG.

FIG. 5 shows each phase of the signal voltage (ωt = 0) in the loop antenna of the helicon plasma processing apparatus of FIGS. 1 and 2;
FIG. 7 is a perspective view showing an electric field E generated at ７7π / 4).

FIG. 6 is a block diagram showing a microwave interferometer unit and a control unit of the helicon plasma processing apparatus shown in FIGS. 1 and 2;

FIG. 7 is a perspective view of a helicon plasma processing apparatus which is a modification of the first embodiment according to the present invention.

FIG. 8 is a perspective view of a helicon plasma processing apparatus according to a second embodiment of the present invention.

9 is a circuit diagram of a power supply circuit of the helicon plasma processing apparatus of FIG.

10 shows each phase (ωt = 0 to 3) of a signal voltage in each loop antenna of the helicon plasma processing apparatus of FIG.
FIG. 4 is a perspective view showing an electric field E generated at (π / 4).

11 shows each phase (ωt = π to 7) of a signal voltage in each loop antenna of the helicon plasma processing apparatus of FIG.
FIG. 4 is a perspective view showing an electric field E generated at (π / 4).

FIG. 12 is a perspective view of a helicon plasma processing apparatus according to a third embodiment of the present invention.

13 is a circuit diagram of a power supply circuit of the helicon plasma processing apparatus of FIG.

14 shows each phase (ωt = 0 to ωt = 0) of a signal voltage in each loop antenna of the helicon plasma processing apparatus of FIG.
FIG. 3 is a perspective view showing an electric field E generated at 3π / 4).

FIG. 15 shows each phase of the signal voltage (ωt = π〜) in each loop antenna of the helicon plasma processing apparatus of FIG. 12;
FIG. 7 is a perspective view showing an electric field E generated at 7π / 4).

FIG. 16 is a perspective view of a helicon plasma processing apparatus which is a modification of the third embodiment according to the present invention.

17 is a circuit diagram of a power supply circuit of the helicon plasma processing apparatus of FIG.

FIG. 18 is a longitudinal sectional view of a conventional helicon plasma processing apparatus.

19 shows each phase (ωt = −π / 2, 0, ωt) of the signal voltage in the loop antenna of the plasma processing apparatus of FIG.
FIG. 3 is a perspective view showing an electric field E generated at (π / 2).

[Explanation of symbols]

 Reference Signs List 10: plasma generation chamber, 11: plasma processing chamber, 12a: reaction gas transport pipe, 12b: exhaust pipe, 21, 22: solenoid coil for generating magnetic field, 30: sample support table, 33: high frequency bias signal generator, 50: Reference high frequency signal generator, 61, 62, 63: variable phase shifter, 80: control microwave signal generator, 82, 87: directional coupler, 85: variable phase shifter, 88: diode detector, 89 ... current detector, 100, 100a ... controller, 300 ... sample, 600, 610, 620, 630 ... power supply circuit, LA, LA1, LA2, LA3 ... loop antenna, T1, T2, T3, T4, T5 ... high frequency transformer, E, E1, E2: electric field, B: DC magnetic field, AN1, AN2: horn antenna.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-185825 (JP, A) JP-A-3-64897 (JP, A) JP-A-4-167400 (JP, A) JP-A-3-167 68773 (JP, A) JP-A-4-160162 (JP, A) WO 92/142558 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 H05H 1 / 46

Claims (1)

(57) [Claims] 1. A plasma processing apparatus for performing a predetermined process on a sample by generating helicon plasma in a cylindrical plasma processing chamber whose interior is set to a vacuum state, wherein said sample is processed inside said plasma processing chamber. Magnetic field generating means for generating a DC magnetic field in a direction toward the first direction, and a first high-frequency electric field having a direction from the axial center of the cylindrical shape of the plasma processing chamber toward the outer periphery of the cylindrical shape is generated using the first high-frequency signal. And a second rotation direction having an angle of rotation in which the angle changes and rotates on a plane parallel to the bottom surface of the cylinder around the axis of the cylinder of the plasma processing chamber.
Electric field generating means for generating an electric field substantially equal to the electric field of the helicon wave by generating the high-frequency electric field using a second high-frequency signal having a predetermined phase difference with respect to the first high-frequency signal. Wherein the electric field generating means comprises: at least three loop antennas which are concentric with the center of the cylindrical axis of the plasma processing chamber and are provided at a predetermined distance from each other; A signal generating means for generating the signal; and applying the first high-frequency signal generated by the signal generating means between two loop antennas located at both ends of the at least three loop antennas. For applying the second high-frequency signal generated by the above to both ends of one of the at least three loop antennas located at the center. And a plasma processing apparatus.