JPH06101051A - Electron cyclotron resonance plasma cvd device - Google Patents

Abstract

PURPOSE:To generate a plasma current excellent in uniformity and to form a large-area uniform thin film at low cost by supplying a microwave to the plasma producing antenna consisting of the parallel wires connected to a microwave coaxial tube. CONSTITUTION:A microwave from a microwave oscillator 100 is supplied to a plasma producing antenna 113 through a directional coupler 104, a pole antenna 109 and coaxial tubes 110 and 112. As a result, plasma is produced in a plasma producing chamber 204 provided with a magnetic coil 214 and introduced into a reaction vessel 208 to form a thin film on a sample 210 in the vessel. In this electron cyclotron resonance plasam CVD device, the antenna 113 is formed with two wires bent in parallel. One wire is connected to the core wire of the coaxial tube 112 and another to the outer tube. One or both ends of these two wires are short-circuited.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a-Si, SiO ₂ , S
Chemical Vapor Deposition (Chemical Vapor) for forming silicon thin films such as i ₃ N ₄ and diamond thin films
Deposition, hereinafter referred to as CVD), Al ₂
Electron cyclotron resonance (Electror resonance) used for forming a metal compound film such as O ₃ and a sputter type film such as a silicon-based thin film, and etching a thin film such as Al and W
on Cyclotron Resonance (hereinafter referred to as ECR) plasma CVD apparatus.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional ECR plasma CVD apparatus. A case where a silicon nitride film is formed by this apparatus will be described as an example.

2.45 GHz microwave generated by a magnetron (microwave oscillator) (not shown)
Is an isolator, directional coupler, microwave power meter,
The light is propagated by the waveguide through a matching device (none of which is shown) and the like, and is introduced into the cavity chamber 2.

A ball antenna is installed in the cavity 2 and microwaves are propagated from the coaxial tube 3, the coaxial connector 4 and the coaxial tube 5 to the slitted metal plate 6 from this. The metal plate 6 with slits is arranged along the axial direction of the device. The slit metal plate 6 is made of Al,
It is made of a material such as Cu or SUS304. When microwaves are supplied to the metal plate 6 with slits through the coaxial tube 5 in this way, standing waves are generated on the slits of the metal plate 6 with slits, and plasma is generated.

The plasma generation chamber 7 communicates with a reaction container 12 through a plasma drawing window 8. This reaction vessel 12
Is evacuated by a vacuum pump (not shown) to a predetermined degree of vacuum necessary for thin film formation, for example, 10 ⁻⁴ Torr. Further, to the reaction container 12, N ₂ gas is supplied from the first gas supply pipe 9 via the plasma generation chamber 7, and SiH ₄ gas is supplied from the second gas supply pipe 10 via the annular stainless steel pipe 11, respectively. To be done.

A cooling pipe 15 is wound around the outer periphery of the plasma generation chamber 7 and the plasma generation chamber 7 is cooled by introducing and flowing cooling water 16. A magnetic coil 17 is arranged so as to surround the plasma generation chamber 7, and a magnetic field having a magnetic flux density of 875 Gauss is generated so as to cause electron cyclotron resonance with the supplied microwave of 2.45 GHz. The sample 13 is the reaction container 12
It is placed on the sample table 14 which is arranged in a position facing the plasma extraction window 8 inside.

In the electron cyclotron resonance, when the charge and mass of an electron are represented by e and m and the magnetic flux density is represented by B, the frequency fce of the cyclotron motion of the electron is fce = (1 / 2π) eB / m = 2. It occurs when the condition of 45 GHz is satisfied. As a result, a strong plasma flow 18 is formed in the plasma generation chamber 7, and the plasma flow 18 passes through the plasma extraction window 8 and the reaction container 12
Will be introduced in. And N used as a reaction gas
₂ and SiH ₄ gas are dissociated by the plasma flow 18, and a thin film of Si ₃ N ₄ is deposited on the surface of the sample 13.

When this ECR plasma CVD apparatus is used, plasma having a high activity can be obtained at a low gas pressure as compared with the case of using a normal CVD apparatus, and therefore, due to the impact effect of ions and electrons, high quality plasma is obtained at room temperature. It has features such as the ability to form thin films.

The ECR plasma is not limited to the formation of a silicon nitride (Si ₃ N ₄ ) film, but silicon (Si)
It can also be applied to formation of films, silicon oxide (SiO ₂ ) films, molybdenum silicide (MoSi ₂ ) films, etching, and the like.

[0010]

Problems to be Solved by the Invention FIGS. 6 (a) and 6 (b)
The structure of a metal plate with a slit used in a conventional ECR plasma CVD apparatus and the electric field intensity distribution around the metal plate are shown in FIG. As shown in FIG. 6B, as the distance from the metal plate 6 with slits increases, the electric field strength around it increases sharply. In the conventional ECR plasma CVD apparatus, the metal plate 6 with slits extends along the axial direction of the apparatus.
That is, they are arranged in the radial direction of the apparatus and perpendicular to the sample 13. Therefore, the radial distribution of the electric field strength is not uniform, and the distribution of the generated plasma is not uniform.
Therefore, the conventional apparatus cannot form a uniform thin film and is difficult to use for actual film formation.

In order to improve this point, it is conceivable to dispose the slitted metal plate 6 in the plasma generation chamber 7 so as to face the sample 13. But in this case,
The flow of the gas introduced from the gas introduction pipe 9, for example N ₂ gas, is significantly hindered. As a result, it becomes difficult to realize a uniform gas flow, which is most important when forming a uniform thin film over a large area. Moreover, since the direction of the generated strong plasma flow 18 is along the axial direction of the device, the plasma flow 18 collides violently with the slit metal plate 6. As a result, the metal of the constituent element is sputtered out from the metal plate 6 and is ejected, and this is mixed as an impurity in the thin film deposited on the sample 13, so that it is difficult to form a high quality thin film.

Further, as shown in FIG. 6 (a), since the metal plate 6 with slits used in the conventional apparatus is one plate in which grooves having a uniform width are processed, its fabrication is It was difficult and costly.

The present invention provides a low-cost electron cyclotron resonance plasma CVD apparatus capable of generating a plasma flow having excellent uniformity, capable of forming a thin film having a uniform thickness on a large-area substrate. With the goal.

[0014]

The electron cyclotron resonance plasma CVD apparatus of the present invention includes a microwave oscillator, a directional coupler, a ball antenna, a coaxial tube, a plasma generating antenna, a plasma generating chamber, a reaction vessel, and a magnetic coil. In an electron cyclotron resonance plasma CVD apparatus having a plasma generation antenna that generates plasma by supplying microwaves to the plasma generation antenna, the plasma generation antenna is formed by two wires that are bent in a plane and arranged in parallel with each other. One of the wire rods is connected to the core wire of the coaxial pipe, the other wire rod is connected to the outer pipe portion of the coaxial pipe, and one end or both ends of the two wire rods are short-circuited. It is a thing.

[0015]

Function: Electron cyclotron resonance plasma CV of the present invention
The plasma generation antenna used in the D device will be described in more detail.

2 which constitutes this plasma generating antenna
The length of the wire of the book is an integral multiple of half the wavelength of the microwave used (about 6 cm in the case of the microwave of 2.45 GHz) so that a standing wave is generated when the microwave is propagated. Is set to. These two wires are bent in a plane and arranged in parallel with each other at a constant interval of about 2 mm. The shape of the two wire rods bent in a plane is not particularly limited.

Of the two wire rods forming the plasma generating antenna, one wire rod is connected to the core wire of the coaxial pipe, and the other wire rod is connected to the outer pipe portion of the coaxial pipe. Short both ends. Microwaves are supplied to the plasma generating antenna as follows. That is, when only one end of the two wires is short-circuited, the microwave is supplied from the other end. On the other hand, when both ends of the two wires are short-circuited, the microwave is supplied at an arbitrary point where the distance from the one end is an integral multiple of the half wavelength of the microwave.

In the present invention, the plasma generating antenna is arranged so as to face the sample. Since this plasma generating antenna is composed of two wires, the flow of the reaction gas is not obstructed even if such an arrangement is adopted.

In the electron cyclotron resonance plasma CVD apparatus of the present invention, since the plasma generating antenna having the above-mentioned structure is used, the plasma having excellent uniformity is obtained as compared with the metal plate with the slit used in the conventional apparatus. It is possible to generate a flow and to reduce the mixing of impurities into the generated film. Therefore, a high-quality thin film having a uniform thickness can be formed on a large-area substrate. Further, the plasma generation antenna used in the device of the present invention is easier to manufacture than the metal plate with slit used in the conventional device.

[0020]

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

FIG. 1 is a schematic configuration diagram showing an electron cyclotron resonance plasma CVD apparatus according to an embodiment of the present invention. In FIG. 1, the microwave of 2.45 GHz generated by the microwave oscillator 100 is the isolator 10
1, waveguide 102, directional coupler 104, waveguide 10
2. Propagated to the cavity 108 through the stub tuner 107. The isolator 101 has a function of preventing the microwave oscillator 100 from being damaged by the generated reflected wave of the microwave. A microwave power meter 105 is connected to the directional coupler 104 provided in the middle of the waveguide 102. The stub tuner 107 has a function of adjusting the impedance of microwaves.

When the microwave is propagated to the cavity 108, a TE ₁₀ mode microwave standing wave is generated in the cavity 108. That is, considering the strength of the electric field, the amplitude is zero on the inner wall of the cavity 108, and the distribution is close to the Gaussian mode, which takes the maximum in the central portion.

A ball antenna 109 is installed in the cavity 108 at a portion where the electric field strength distribution is substantially uniform. Microwaves propagate from the ball antenna 109 to the plasma generation antenna 113 in the plasma generation chamber 204 via the coaxial tube 110, the coaxial connector 111, and the coaxial tube 112. This plasma generation antenna 113
Are held in the plasma generation chamber 204 via an insulating member. Here, the coaxial tube 110 and the coaxial connector 111
Also, the length and mounting direction of the coaxial waveguide 112 are important for propagating the microwave energy without attenuating it, and adversely affect the plasma density and its distribution in the plasma generating antenna 113 which is not set to the optimum condition. give. In this embodiment, the ball antenna 109 to the coaxial tube 1
The distance to the end of 12 is set to a half wavelength of the microwave or less, that is, about 6 cm or less.

The plasma generation chamber 204 has a plasma extraction window 2
09 to communicate with the reaction container 208. The reaction container 208 is evacuated to a predetermined vacuum degree necessary for the reaction, for example, 10 ⁻³ to 10 ⁻⁸ Torr, by an exhaust device (not shown). Further, in the reaction container 208, for example, N ₂ gas is supplied from the first gas supply pipe 205 via the plasma generation chamber 204, and the annular stainless steel pipe 2 is supplied from the second gas supply pipe 206.
For example, SiH ₄ gas is supplied via 07.

A cooling pipe 2 is provided around the plasma generating chamber 204.
12 is wound, and the plasma generation chamber 204 is cooled by introducing and flowing the cooling water 213. In addition, a magnetic coil 214 is arranged so as to surround the plasma generation chamber 204 and is supplied with 2.45 GHz.
A magnetic field having a magnetic flux density of 875 Gauss is generated so as to cause electron cyclotron resonance with the microwave. The sample 210 is placed on the sample table 211 arranged in the reaction vessel 208 at a position facing the plasma extraction window 209.

FIG. 2 shows a schematic shape of the plasma generating antenna 113 used in this embodiment. The plasma generating antenna 113 is composed of two wires having a length that is an integral multiple of a half wavelength of the microwave. The two wires forming the plasma generating antenna 113 are bent in a U shape in a plan view, arranged in parallel with each other at a constant interval of about 2 mm, and short-circuited at both ends. The straight line portion in the x-axis direction is sufficiently shorter than the straight line portion in the y-axis direction. In addition, the length obtained by adding one linear portion in each of the x-axis direction and the y-axis direction is about one wavelength of the microwave. Of these two wires, one is connected to the core wire of the coaxial tube 112, and the other is connected to the outer tube portion of the coaxial tube 112. The connecting position is set to a position of about half the length of each wire as shown. Also, the plasma generation antenna 113
Are arranged on the surface of the magnetic flux density of 875 Gauss generated by the magnetic coil 214, that is, so as to face the sample 210.

In the apparatus of the present invention, when microwaves are supplied to the plasma generating antenna 113 via the coaxial tube 112, a standing wave is generated between the two wires. In this case, the directions of the electric fields in the y-axis direction are the same. As a result,
As shown in FIG. 3, the electric field strength distribution along the plasma generating antenna 113 becomes substantially uniform. Since the plasma intensity distribution depends on the electric field intensity distribution, a uniform thin film can be formed on the sample 210.

An example of actually forming a silicon nitride thin film using the apparatus of the present invention will be described. The degree of vacuum in the reaction container 208 is set to about 5.0 × 10 ⁻⁷ Torr by an exhaust device (not shown in FIG. 1) and the internal impurity gas is sufficiently exhausted.
To N ₂ at 500 cc / min, second gas supply pipe 20
SiH ₄ gas was supplied from No. 6 at 50 cc / min. The pressure inside the reaction container 208 after the gas supply is 2 × 10 ⁻⁴ Torr.
Set to. Further, the cooling water 213 was introduced into the cooling pipe 212 to sufficiently cool the plasma generation chamber 204. In this state, a plasma flow was generated to form a silicon nitride film on the sample.

In the apparatus of the present invention, the plasma electron density is 2
The value was × 10 ^-11 cm ^-3 , which was significantly larger than that of the conventional device. The deposition rate of the silicon nitride film was 8 Å / sec. Further, a thin film having a substantially uniform film thickness could be formed within a diameter range of 300 mm. Further, when the obtained silicon nitride film was analyzed, the refractive index was 1.9.
.About.2.0, and the Si / N ratio in the film was 1.32. Further, the metal impurities contained inside are 1 × 10 ¹⁴ atom /
It was cc.

Although the plasma generating antenna shown in FIG. 2 is used in the above embodiment, if the requirements of the present invention are satisfied, a plasma generating antenna having a star shape as shown in FIG. 4 is used. You may. Similarly, it has been confirmed that even an antenna having a curved portion can generate plasma. Further, by arranging a plurality of such antennas in the plasma generation chamber, it is possible to obtain plasma with higher density and higher uniformity. Furthermore, by using the apparatus of the present invention, not only the silicon nitride thin film but also various kinds of thin films can be formed by changing the type of gas used.

[0031]

As described above in detail, when the electron cyclotron resonance plasma CVD apparatus of the present invention is used, a plasma flow excellent in uniformity can be generated, and a thin film having a uniform thickness can be formed on a large area substrate. Can be formed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an electron cyclotron resonance plasma CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a plasma generation antenna used in the electron cyclotron resonance plasma CVD apparatus.

FIG. 3 is a view showing an electric field strength distribution generated around a microwave when the microwave is supplied to the plasma generating antenna.

FIG. 4 is a plan view of another plasma generation antenna used in the electron cyclotron resonance plasma CVD apparatus.

FIG. 5: Conventional electron cyclotron resonance plasma CVD
The schematic block diagram which shows an apparatus.

FIG. 6A is a plan view of a metal plate with a slit used in a conventional electron cyclotron resonance plasma CVD apparatus;
(B) is a figure which shows the electric field strength distribution which arises in the periphery when a microwave is supplied to the metal plate with a slit.

[Explanation of symbols]

100 ... Microwave oscillator, 101 ... Isolator, 1
02 ... Waveguide, 104 ... Directional coupler, 105 ... Microwave power meter, 107 ... Stub tuner, 108 ... Cavity chamber, 109 ... Ball antenna, 110 ... Coaxial tube, 111
... coaxial connector, 112 ... coaxial tube, 113 ... plasma generation antenna, 204 ... plasma generation chamber, 205 ... first
Gas supply pipe, 206 ... Second gas supply pipe, 207 ... Annular stainless steel pipe, 208 ... Reaction container, 209 ... Plasma extraction window, 210 ... Sample, 211 ... Sample stand, 212 ... Cooling pipe, 213 ... Cooling water, 214 ... Magnetic coil.

Claims (1)

[Claims] 1. A microwave oscillator, a directional coupler, a ball antenna, a coaxial tube, a plasma generation antenna, a plasma generation chamber, a reaction vessel, and a magnetic coil, and by supplying microwaves to the plasma generation antenna. Electron cyclotron resonance plasma CVD for generating plasma
In the apparatus, the plasma generating antenna is composed of two wire rods that are bent in a plane and arranged in parallel with each other, one wire rod is connected to a core wire of the coaxial pipe, and the other wire rod is connected to the coaxial pipe. An electron cyclotron resonance plasma CVD apparatus, characterized in that it is connected to an outer tube portion and one end or both ends of the above-mentioned two wires are short-circuited.