JPH0869895A - Electron injection type plasma generating device - Google Patents

Abstract

PURPOSE: To increase the density of plasma generated by a continuous electron injection, improve the production efficiency of a radical and ion, and quicken a film-forming speed in plasma CVD. CONSTITUTION: A microwave is incident onto a magnetic field to produce plasma by cyclotron resonance. This device is provided with a microwave waveguide 21 for introducing a microwave into a plasma production chamber 1, electromagnetic coils 23 and 25 for generating a magnetic field in a direction orthogonal to the propagation direction of the microwave in the plasma production chamber 1, and an electron injecting means 43 for injecting an electron, in the form of an electron beam having energy in a direction same as the direction of the magnetic field by electromagnetic coils 23 and 25, to the magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron injection type plasma generator, and more particularly to an electron injection type plasma generator used as a plasma source in a plasma CVD apparatus or the like.

[0002]

2. Description of the Related Art As a plasma CVD apparatus, an ECR plasma CVD apparatus as shown in FIG. 3 has been conventionally known. This ECR plasma CVD apparatus includes a cylindrical plasma generation container 3 that constitutes a plasma generation chamber 1,
It has a cylindrical film forming container 7 that constitutes the film forming chamber 5, and both are vertically connected in an electrically insulated state by an insulator 9.

A predetermined voltage is applied to the plasma generating container 3 by a power source 11 connected thereto, while the film forming container 7 is at ground potential due to ground connection.

A cooling water passage 13 is formed in the plasma generating container 3, and a cooling water supply pipe 15 is provided in the cooling water passage 13.
More cooling water is supplied.

A microwave introduction window 19 hermetically shielded by a quartz glass plate 17 is formed on the upper surface of the plasma generation container 3, and a microwave waveguide 21 is connected to the microwave introduction window 19. The waveguide 21 is supplied with a microwave of 2.45 GHz from a microwave generation source (not shown), and introduces the microwave into the plasma generation chamber 1 through the microwave introduction window 19.

The electromagnetic coils 23 and 25 are fixedly arranged in two stages, upper and lower, outside the plasma generating container 3. The electromagnetic coils 23 and 25 are mirror magnetic fields (magnetic fields) for confining the plasma having a magnetic flux density of 875 Gauss in the plasma generation chamber 1, particularly in the area (magnetic field area) A directly below the quartz glass plate 17.
To form.

The plasma generation chamber 1 has a plasma generation chamber 1
A gas introduction pipe 27 for supplying O ₂ gas is connected inside, and an L-shaped pipe 29 for blowing O ₂ gas toward the magnetic field region A is provided in the plasma generation chamber 1.

Between the plasma generating chamber 1 and the film forming chamber 5,
A microwave shield plate 31 having a large number of through holes and an annular lead electrode 33 having a ground potential are provided.

At the center of the film forming chamber 5, there is arranged a sample table 35 on which the wafer W is fixedly mounted by an electrostatic chuck or the like. A gas introducing pipe 37 for supplying a reaction gas such as SiH ₄ required for film formation into the film forming chamber 5 is connected to the film forming container 7, and a plurality of exhaust ports are provided at the bottom of the film forming container 7. 39 are provided in the same phase, that is, axisymmetric with respect to the center of the container. An exhaust device (not shown) is connected to the exhaust port 39.

Next, the operation of the above-mentioned ECR plasma CVD apparatus will be described by taking the case of forming a SiO ₂ film on the wafer W as an example.

First, while the plasma generating chamber 1 and the film forming chamber 5 are evacuated, the quartz glass plate 17 is irradiated with microwaves of 2.45 GHz from the waveguide 21. This microwave passes through the quartz glass plate 17 and is introduced into the plasma generation chamber 1. O ₂ gas is supplied into the plasma generation chamber 1 by the gas introduction pipe 27 to energize the electromagnetic coils 23 and 25, and the magnetic coils 23 and 25 generate a magnetic flux of 875 Gauss in the region A in the plasma generation chamber 1. Form a mirror field of density.

The electrons in the plasma generation chamber 1 vibrate at the electron cyclotron frequency due to the mirror magnetic field. The frequency is 2.45 GHz in the magnetic field area A of 875 Gauss.
As a result, in the magnetic field region A, the frequency due to the magnetic field and the frequency due to the microwave match, a resonance phenomenon occurs, and high-density plasma is generated.

The microwaves introduced into the plasma generation chamber 1 from the waveguide 21 are almost reflected by the plasma in the magnetic field region A, and part of them are transmitted. The transmitted microwave is reflected by the microwave shield plate 31 and does not enter the film forming chamber 5.

Ions, electrons and neutral particles in the plasma generated in the plasma generation chamber 1 are supplied into the film formation chamber 5 through the microwave shield plate 31 and the extraction electrode 33. The electrons enter the film forming chamber 5 along the divergent magnetic field formed in the film forming chamber 5 while performing the cyclotron motion. At this time, the electrons lose the energy represented by the product of the kinetic energy in the plasma generation chamber 1 and the decrease in the magnetic field strength due to the divergent magnetic field.

In the film forming chamber 5, a gas introducing pipe 37 is used for S
A reaction gas such as iH ₄ is supplied, and the ions, electrons, and neutral particles from the plasma generation chamber 1 react with the reaction gas in the film formation chamber 5, are decomposed, and are deposited on the wafer W. .

The reaction gas not used for film formation on the wafer W is exhausted from the exhaust port 39 to the outside of the device by the exhaust device.

[0017]

The film formation rate in the above-mentioned ECR plasma CVD apparatus is about 1000 angstrom / minute, which is very slow, and it takes a long time to deposit a thick film on the order of microns.

By the way, ions, gas molecules, radicals, etc. in the plasma generation process have a very large mass as compared with electrons, hardly move, and are substantially stationary between ions, gas molecules, radicals, etc. A model is established in which electrons are oscillated by cyclotron and ionization is carried out with a probability corresponding to the ionization cross section of each gas molecule, and electron cyclotron resonance is generated in the ECR plasma generator to enhance gas ionization efficiency and heat ECR plasma. It is known that the electrons mainly contribute to the high density.

In view of this, it has been considered that the electron beam is incident on the magnetic field region A to inject the electrons into the magnetic field region A to increase the amount of electrons in the magnetic field region A.

However, when an electron beam is made to enter the plasma generating chamber 1 of the apparatus shown in FIG. 3 from the lateral direction (horizontal horizontal direction in FIG. 3), the incident direction of the electron beam and the direction of the magnetic field applied to the plasma. And are orthogonal, and the following problem occurs. That is, the electron beam receives a Lorentz force under the influence of the magnetic field, and the Lorentz force acts in a direction orthogonal to both the direction of the electron beam and the direction of the magnetic field, so that the electron beam is deflected. This Lorentz force increases as the energy of the electron beam increases. For example, an electron beam accelerated by a voltage of 10 KV is deflected in a magnetic field of 875 Gauss with a radius of curvature of about 33 mm.

In order to avoid this problem, it is conceivable that the electron beam injection and the ECR plasma generation are performed alternately. However, in this case, the following problems occur.

(1) Since it takes a certain time from when the electromagnetic coil is energized until a required magnetic field is formed, plasma is generated in a transient state before the required magnetic field is formed, There is a possibility that the cyclotron resonance phenomenon cannot be realized reliably. (2) Since the filament, which is the electron beam source, must be periodically operated, and a current is intermittently applied to the filament every short time, the filament is easily broken,
The life of the filament is very short. (3) In order to repeatedly turn on / off the microwave power source,
The microwave power supply has a very short life. (4) A large electric power is required at the time of plasma formation as compared with the case of continuously holding the plasma. (5) In order to solve the above-mentioned four problems, if the frequency at which the incidence of the electron beam and the generation of the ECR plasma are alternately made small, the effect of electron injection by the electron beam is reduced.

The present invention has been made by paying attention to the above-mentioned problems, and the electron beam is continuously incident on the magnetic field for confining the plasma without alternately performing the electron beam incidence and the ECR plasma generation. And an electron injection type plasma generator capable of increasing the density of plasma generated by incidence of this electron beam, improving the generation efficiency of radicals and ions, and increasing the film formation rate in plasma CVD. Is intended.

[0024]

In order to achieve the above-mentioned object, an electron injection type plasma generator according to the present invention is an electron injection type plasma generation in which a microwave is injected into a magnetic field to generate plasma by cyclotron resonance. In the apparatus, a microwave waveguide that introduces microwaves into the plasma generation chamber, an electromagnetic coil that generates a magnetic field in the plasma generation chamber in a direction orthogonal to the propagation direction of the microwave, and the electromagnetic coil are in the same direction as the magnetic field. And an electron injection means for injecting electrons into the magnetic field in the form of an electron beam having energy.

The electron injection means in the electron injection type plasma generator according to the present invention comprises an electron beam linear introduction passage means extending in a direction orthogonal to a microwave propagation direction and opened at one end into the plasma generation chamber, An electron beam generator disposed at the other end of the electron beam linear introduction passage means,
It may be of a type having an accelerating electrode provided in the middle of the electron beam linear introduction passage means.

[0026]

According to the above construction, the electromagnetic coil generates a magnetic field in the plasma generation chamber in a direction orthogonal to the microwave propagation direction, and the magnetic field is in the same direction as the magnetic field by the electron injection means. By injecting electrons in the form of an energetic electron beam, the amount of electrons in the magnetic field increases, and as the amount of electrons increases, the density of plasma generated in the magnetic field region increases.

In this case, since the incident direction of the electron beam with respect to the magnetic field is the same as the direction of the magnetic field, the electron beam receives the Lorentz force and goes straight without being deflected, and the electron beam converges. Electrons are continuously and efficiently injected by an electron beam.

[0028]

Embodiments of the present invention will be described in detail below with reference to the drawings. In the embodiments of the present invention, the same components as those in the above-described conventional example are designated by the same reference numerals as those in the above-described conventional example, and the description thereof will be omitted.

FIG. 1 shows an embodiment in which the electron injection type plasma generator according to the present invention is applied as a plasma source of a plasma CVD apparatus.

The electromagnetic coils 23 and 25 are arranged symmetrically with respect to the center of the plasma production container 1 on both sides of the plasma production container 1. The electromagnetic coils 23 and 25 are energized in the same direction as each other to generate a region A in the plasma generation chamber 1.
In addition, a mirror magnetic field of 875 gauss is formed in a direction orthogonal to the microwave propagation direction of the waveguide 21.

An electron beam introducing tube portion 41 is provided on one side of the plasma generating container 3. The electron beam introducing pipe portion 41 penetrates the bobbin center space of the electromagnetic coil 25,
It extends in the direction orthogonal to the microwave propagation direction, in other words, in the same direction as the direction of the mirror magnetic field in the region A, and opens toward the region A of the plasma generation chamber 1. Although the opening position of the electron beam introducing tube portion 41 is the central portion of the plasma generation chamber 1, it may be eccentric.

One end of an electron beam linear conduit 45 of the electron injection device 43 is connected to the electron beam introducing tube portion 41 so as to communicate therewith. The electron beam linear conduit 45 is the electron beam introducing pipe section 4.
It extends in the same direction as 1. Here, the electron beam introduction tube portion 41 and the electron beam linear conduit 45 form an electron beam linear introduction passage means.

An exhaust pump 47 such as a turbo molecular pump and an auxiliary pump 49 such as a dry pump are connected to the electron beam linear conduit 45. The exhaust pump 47 and the auxiliary pump 49 serve to pump the electron beam linear conduit 45. The insides of 45 and the electron beam introducing tube section 41 are in a high vacuum state. The exhaust speed of the exhaust pump 47 may be about 550 l / sec.

An orifice 51 is provided near the opening end of the electron beam introducing tube portion 41 with respect to the plasma generating chamber 1 for setting the degree of vacuum individually for the electron beam introducing tube portion 41 side and the plasma generating chamber 1. . Orifice 51 is 3
The electron beam introducing tube portion 41 side and the plasma generating chamber 1 may be configured by a plate body having a through hole of about mm.
Secure a differential pressure of 1 digit (Torr).

The plasma generating chamber 1 is exhausted by another exhaust pump (not shown), and this exhaust pump may be a turbo molecular pump having an exhaust speed of about 1800 liter / sec.

An electron beam generator 53 is arranged at the other end of the electron beam linear conduit 45. Electron beam generator 5
3 has a needle-shaped two-pole filament 59 made of tungsten, which is electrically insulated and supported by a support 57 by an insulator 55, and the needle-shaped two-pole filament 59 is energized by a heating power source 61, Electrons are generated by heating the needle-shaped bipolar filament 59. At the tip of the needle of the needle-shaped bipolar filament 59, a ring-shaped lead electrode 63 is provided so as to surround the needle. The extraction electrode 63 is connected to the electron beam linear conduit 4 by the insulator 65.
5 and the support 57 are electrically insulated and supported, and a high voltage of, for example, about 10 KV is applied between the high-voltage power supply 67 and the needle-shaped bipolar filament 59.

An accelerating electrode 71 is provided by an insulator 69 at the connecting portion between the electron beam introducing tube portion 41 and the electron beam linear conduit 45. The potential of the acceleration electrode 71 is the power source 73
Is higher than the extraction electrode 63, and the acceleration electrode 71 is kept at a predetermined potential with respect to the plasma generation container 3 by the power supply 75. The accelerating electrode 71 may also have the function of restricting the orifice 51, and in this case, the orifice 51 can be omitted.

Solenoid coils 77 and 79 are arranged around the accelerating electrode 71 and around the electron beam linear conduit 45, respectively. The solenoid coils 77 and 79 generate a magnetic field in the beam transmission direction to converge the electron beam, and may be a quadrupole lens or an electrostatic lens.

On the other side of the plasma generating container 3, a sampling tube portion 81 is provided on the same axis as the electron beam introducing tube portion 41.
Is provided. The sampling tube portion 81 penetrates the bobbin center space of the electromagnetic coil 23 and extends in the same direction as the electron beam introducing tube portion 41, and the tip thereof is the end plate 8.
Closed by 3. A Faraday cup 85 for measuring the electron beam current is provided in the sampling tube portion 81.
Is connected to the Faraday cup 85. An ammeter 87 capable of measuring a current in microamperes is connected to the Faraday cup 85. The ammeter 87 has one terminal connected to the Faraday cup 85 and the other terminal connected to the power supply 11 to have the same potential as the plasma generation container 3.

Next, the operation of the above-described plasma CVD apparatus will be described by taking the case of forming a SiO ₂ film on the wafer W as an example.

First, the plasma generating chamber 1, the film forming chamber 5, the electron beam introducing pipe portion 41, the electron beam linear conduit 45, and the sampling pipe portion 81 are evacuated to about 10 ^-7 Torr by an exhaust pump 47 or the like.

Next, the electron injection device 43 is operated, and the amount of the electron beam is measured by the Faraday cup 85. Specifically, the needle-shaped bipolar filament 59 is energized by the heating power source 61 to heat the needle-shaped bipolar filament 59. By this heating, thermoelectrons are emitted from the needle-shaped bipolar filament 59, and the electrons extracted by the extraction electrode 63 are converted into a beam having energy in the same direction as the direction of the mirror magnetic field formed in the area A. Then, it goes to the acceleration electrode 71 and is accelerated by the acceleration electrode 71.
When the applied voltage (acceleration voltage) to the acceleration electrode 71 is 10 KV, an electron beam of several μamperes can be obtained.
The electron beam is focused by the solenoid coils 77 and 79.

This electron beam is an electron beam having energy in the same direction as the direction of the mirror magnetic field formed in the area A, passes through the through hole of the orifice 51 without being deflected, and is in the plasma generating chamber 1. to go into. As a result, electrons are injected into the plasma generation chamber 1.

Then, the amount of current passed through the solenoid type coils 77 and 79 and the voltages of the heating power source 61 and the power sources 73 and 75 are adjusted so that the electron beam amount measured by the Faraday cup 85 becomes the maximum value. This adjustment does not energize the electromagnetic coils 23 and 25, and the plasma generation chamber 1
It is performed without supplying microwaves or gas.

After the above-mentioned adjustment is completed, O ₂ gas is supplied into the plasma generation chamber 1 through the gas introduction pipe 27,
The supply of the cooling water to the cooling water passage 13 and the supply of the reaction gas to the film forming chamber 5 through the gas introduction pipe 37 are started. The flow rate of this cooling water may be about several liters / minute. The supply of the reaction gas through the gas introduction pipe 37 may be performed from an annular nozzle for the purpose of making the molecular weight of the gas falling on the wafer W uniform.

Next, the electromagnetic coils 23 and 25 are energized in the same direction, and the electromagnetic coils 23 and 25 form a mirror magnetic field having a magnetic flux density of 875 Gauss in the region A in the plasma generation chamber 1. The direction of this mirror magnetic field is, as shown by the arrow in FIG. 1, a direction orthogonal to the direction of propagation of microwaves by the waveguide 21.

In this state, the waveguide 21 is moved to 2.45 GH.
The microwave of z is continuously introduced into the plasma generation chamber 1.

As a result, in the region A, the electron frequency due to the magnetic field of 875 Gauss and the electron frequency due to the microwave coincide with each other, and the electron cyclotron resonance phenomenon continuously occurs, and high-density plasma is generated there.

Since electrons are continuously injected into this region A by the incidence of an electron beam from the electron injection device 43, the amount of electrons that cause electron cyclotron resonance is increased, which results in a very high density. Plasma is generated. Along with this, the ionization efficiency and radical generation efficiency are also significantly improved.

In this case, since the incident direction of the electron beam with respect to the magnetic field in the region A is the same as the direction of the magnetic field, the electron beam receives the Lorentz force and goes straight without being deflected, and the electron beam converges. Therefore, the electron injection to the magnetic field by the electron beam is continuously and efficiently performed.

Ions and electrons in the plasma generated in the plasma generation chamber 1 are supplied into the film formation chamber 5 through the microwave shield plate 31 and the extraction electrode 33, and the ions and radicals extracted from the plasma are supplied. Reacts with the reaction gas in the film forming chamber 5 to form a SiO ₂ film on the wafer W.

In this case, a film forming rate of 2.5 μm / min was obtained. It was found that the film formation rate was 0.3 μm / min when electron injection was not performed in the same apparatus, and the film formation rate was increased to about 8 times by electron injection.

In the above embodiment, the electromagnetic coils 23 and 25
Although the mirror magnetic field is provided by energizing in the same direction, it is also possible to energize the electromagnetic coils 23 and 25 in opposite directions to provide the cup magnetic field. The direction of the magnetic field in this case is indicated by the arrow in FIG. Although the magnetic field generated by the electromagnetic coil 23 is in the right direction and the magnetic field generated by the electromagnetic coil 25 is in the left direction in FIG. 2, this may be the opposite direction as a whole.

In the case of using the Kaps magnetic field, it becomes possible to inject electrons into the plasma confined in the Kaps magnetic field, so that high density plasma generation is performed more effectively. In this case, the plasma density can be expected to be improved by about one digit as compared with the conventional one.

In the case of using the cup magnetic field, a film forming rate of 3.5 μm / min can be obtained under the same conditions as described above.
It was found that the film formation rate was increased about 11 times by electron injection.

In any case, the wafer W may be heated during the film forming process. In the above, the present invention has been described in detail with respect to specific embodiments, but the present invention is not limited to these, and various embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

[0057]

As can be understood from the above description, according to the electron injection type plasma generator of the present invention, the electromagnetic coil generates a magnetic field in the plasma generation chamber in the direction orthogonal to the microwave propagation direction. Electrons are continuously injected into the magnetic field in the form of an electron beam having energy in the same direction as the direction of the magnetic field by the electron injection means, and the amount of electrons in the magnetic field increases, so that the plasma generated in this magnetic field region The density is increased, and accordingly, the film formation rate in plasma CVD can be increased.

In this case, since the incident direction of the electron beam with respect to the magnetic field is the same as that of the magnetic field, the electron beam receives the Lorentz force and goes straight without being deflected, and the electron beam converges. Electron injection by electron beam to magnetic field causes electron beam incidence and ECR
The plasma is continuously and efficiently performed without being alternately generated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment in which an electron injection type plasma generator according to the present invention is applied as a plasma source of a plasma CVD apparatus.

FIG. 2 is a configuration diagram showing another embodiment in which the electron injection type plasma generator according to the present invention is applied as a plasma source of a plasma CVD apparatus.

FIG. 3 is a configuration diagram showing a conventional ECR plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation chamber 3 Plasma generation container 5 Film formation chamber 7 Film formation container 11 Power supply 21 Waveguide 23,25 Electromagnetic coil 27 Gas introduction pipe 35 Sample stage 37 Gas introduction pipe 41 Electron beam introduction pipe part 43 Electron injection device 45 Electron Beam linear conduit 47 Exhaust pump 53 Electron beam generator 59 Needle-shaped two-pole filament 63 Extraction electrode 71 Accelerating electrode 77,79 Solenoid coil 81 Sampling tube 85 Faraday cup

Claims (2)

[Claims] 1. An electron injection type plasma generator for generating a plasma by cyclotron resonance by injecting a microwave into a magnetic field, a microwave waveguide for introducing the microwave into the plasma generation chamber, and the microwave in the plasma generation chamber. An electromagnetic coil for generating a magnetic field in a direction orthogonal to the propagation direction of the magnetic field, and electron injection means for injecting electrons into the magnetic field in the form of an electron beam having energy in the same direction as the magnetic field. An electron injection type plasma generator characterized in that. 2. The electron injection means extends in a direction orthogonal to a microwave propagation direction and has an electron beam linear introduction passage means opened at the one end into the plasma generation chamber, and the electron beam linear introduction passage means. 2. An electron injection type plasma generator according to claim 1, further comprising: an electron beam generator disposed at the other end of the electron beam generator; and an acceleration electrode provided in the middle of the electron beam linear introduction passage means. .