JPH084039B2 - Plasma generation method and thin film deposition method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma generation method and a thin film deposition method used.

2. Description of the Related Art As an example of a plasma generator used in a conventional metal thin film deposition apparatus using microwaves, a plasma generation chamber and a sample chamber are provided, and a plasma extraction window with a target is provided between them to provide both chambers. A plasma deposition device capable of supplying gas is disclosed in Japanese Patent Application No. 57-156843.
-47728). According to this, low temperature deposition, which is an advantage of the electron cyclotron resonance (ECR) plasma deposition method, is possible, and metal and
Metal compounds and the like are characterized in that a high-quality film having a high adhesion strength can be deposited.

FIG. 4 shows a conventional example of the above plasma deposition apparatus. 1
Is a plasma generation chamber, and 2 is a sample chamber. Reference numeral 3 denotes a microwave introduction window, which uses quartz glass. The microwave is guided from the rectangular waveguide 4 to the plasma generation chamber 1 through the microwave introduction window 3. In the plasma generation chamber 1, a plasma extraction window 5 is provided so as to face the microwave introduction window 3, and the plasma is guided onto the sample table 8 on which the sample substrate 7 is installed. The sample chamber 2 is connected to the exhaust system 9. A magnetic coil 10 is provided on the outer circumference of the plasma chamber 1 so that the magnetic field generated by the magnetic coil 10 satisfies the condition of ECR resonance by microwaves in a part of the plasma generation chamber. As a gas introduction system, there are two systems, a first gas introduction system 12 for introducing a gas for plasma generation and a second gas introduction system 13 for introducing a raw material gas into the sample chamber 2. In addition, the plasma generation chamber 1
Cooled by passing through 14-15. Further, a target electrode 17 containing a sputtering material 16 is arranged so as to surround the plasma flow 6 and is connected to a sputtering power source 19.

Problems to be Solved by the Invention This metal thin film deposition apparatus using ECR plasma and sputtering is a thin film deposition method that makes use of the advantages of ECR plasma. However, in the case of a conductive thin film, the metal atoms sputtered from the sputtering target diffuse into the plasma chamber 1 and the metal thin film is deposited on the microwave introduction window 3 to hinder the propagation of microwaves and stabilize the microwave. The disadvantage is that discharge becomes impossible and the thin film cannot be deposited continuously.

Means for Solving the Problems The present invention provides a plasma generating chamber to which a magnetic field can be applied from the outside in order to solve the above problems, and a window portion having one end connected to the plasma generating chamber and introducing a microwave to the other end. A plasma generation method using a plasma generation device having: a coaxial waveguide having: a gas introduction unit that introduces a plasma generation gas into a plasma generation chamber; and an exhaust unit that evacuates the plasma generation chamber. The length l of the waveguide in the microwave introduction direction is the mean free path λ of the plasma generating gas.
(L> λ), and the difference t between the linear inner radius of the cylindrical outer conductor of the coaxial waveguide and the radius of the inner conductor is smaller than the mean free path λ of the plasma generating gas (t <λ). In this configuration, microwaves are introduced into the plasma generation chamber from the window portion through the coaxial waveguide to generate plasma.

Action No thin film is deposited on the microwave introduction window, and even in the case of conductive thin film deposition, microwave discharge (ECR discharge) continues stably, and thin film deposition can be performed easily.

EXAMPLES Example 1 Hereinafter, the present invention will be described in detail together with Examples.

FIG. 1 is a device configuration diagram of a plasma generator used in the plasma generating method of the present invention.

The microwave generated by the magnetron propagates through the rectangular waveguide (above upper surface is omitted), and is converted into the fundamental mode of the coaxial waveguide by the coaxial waveguide converter 101.
It is coupled to the coaxial waveguide 102 through a microwave introduction window 103 made of alumina ceramic or beryllia between the 101 and the coaxial waveguide 102. The microwave introduction window 103 vacuum-seals the space between the coaxial waveguide converter 101 and the coaxial waveguide 102. Further, the heat due to the microwave propagation loss in the coupling portion and the loss due to the impedance mismatch is absorbed by the cooling mechanism 104 using the cooling water. The microwave propagating through the coaxial waveguide 102 is guided to the plasma generation chamber 106 via the tapered portion 105. In the plasma generation chamber 106, the tip of the inner conductor 102a of the coaxial waveguide 102 extends linearly and plays a role as a microwave antenna source. Conventionally, when high-density plasma is generated in the plasma generation chamber,
There was a problem that the microwave propagated by the generated plasma was reflected and the efficiency was lowered, but in the present invention, this problem is solved by the method of carrying the microwave by mounting it on this antenna, and a large power to the plasma It is possible to supply.

A magnet coil 107a surrounds the plasma generation chamber 106, and the magnet coil 107a
It is installed so that it can generate a magnetic field of 75G. The magnet coil 107b is attached to the outer periphery of the taper portion 105, and the magnet current value is set so that the electric current in the opposite direction to the magnet coil 107a flows and the magnetic field strength in the coaxial waveguide and the taper portion is minimized. There is.

Here, the structure and dimensions of the coaxial waveguide, which is a feature of this device, will be described.

The rectangular waveguide with TE ₁₀ as the fundamental mode is set to have an impedance of 50Ω. In order to perform impedance matching of the coaxial waveguide, it is necessary to set the impedance Zo of the coaxial waveguide to 50Ω. From the following equation, Zo = √ (μ / ε) ln (b / a) 2π a: inner conductor Outer radius b: It is expressed by the inner radius of the outer conductor, and if back-calculated, it is necessary that b / a = 2.3. In this embodiment, in order to keep the value of ba (t in FIG. 1) sufficiently small, it was designed to be b: 1.76 cm a: 0.77 cm. The length 1 of the coaxial waveguide is 50 cm. First
For example, when Ar is introduced at 30 sccm from the gas introduction system 113, the pressure reaches 0.3 mTorr. At this time, the mean free path of the atom is λ = 2.33 × 10 ⁻²⁶ T / pδ ² T: absolute temperature p: pressure δ ² : atomic cross section T = 300 ° K p = 0.3 mTorr δ ² = 1.34 × 10 ^-19 Is calculated as λ = 0.17 m. In addition, the first gas introduction system 113
When a metal compound gas diluted with Ar or the like is flowed, the average free path of the atoms can be estimated to be about 10 cm even if Ar atoms are replaced with metal atoms in the above calculation. Further, the adhesion coefficient of gas on the wall surface at room temperature is close to 1, and metal atoms lose their kinetic energy by one collision with the wall surface and are easily adsorbed. The coaxial waveguide 10 of FIG.
In the dimension of 2, the vertical length l (50 cm) is larger than 10 cm which is the mean free path λ of the vacuum system gas (l
> Λ), the inner radius of the outer conductor 102b of the coaxial waveguide and the inner conductor 102a
And the difference t (1.01 cm) is enough from λ of the mean free path of gas
By satisfying that it is as small as 10 cm (t <λ), the metal atom that has penetrated into the coaxial waveguide tube collides with a certain atom before it reaches the microwave introduction window 103 and is scattered in the lateral direction so that it is coaxial. No deposition is performed on the microwave introduction window 103 because it is deposited inside the waveguide.

The metal thin film deposited in the coaxial tube is the first gas introduction system.
113 Etching gas (eg Cl ₂ , SiCl)
_If periodic maintenance is performed by ( ₄ etc.), it is possible to remove deposits adhering to the inside of the coaxial waveguide and the wall surface of the vacuum chamber, and prevent generation of dust.

Further, the inner radius of the outer conductor 102b of the coaxial waveguide and the inner conductor 102a
Is smaller than λ of the mean free path of the gas (t
<Λ) satisfies the condition that no electric discharge occurs in the coaxial waveguide. In the coaxial waveguide, only microwave TEM waves propagate, the electric field direction coincides from the center to the outer circumference, and the electrons are accelerated in the radial direction. The magnetic field in the coaxial waveguide is minimized by the magnet coil of 107b, so that electrons do not draw a circular orbit. The mean free path of electrons is about four times that of atoms, and the vacuum degree is about 40 cm. Therefore, the electrons collide with the atoms in the coaxial waveguide and cannot cause the subsequent ionization, so that no discharge occurs in the coaxial waveguide. Since no electric discharge is generated in the coaxial waveguide, microwave power can be efficiently introduced into the plasma chamber, and the undissociated metal compound is not dissociated in the coaxial waveguide. As described above, a plasma generator using microwaves can be configured, plasma can be generated only at a predetermined place, and even if conductive metal atoms are present in the plasma, a metal thin film is not present in the microwave introduction window. It is not deposited, the plasma discharge is stable, and it can be used as a large-area, large-capacity metal ion source.

Example 2 FIG. 2 shows a thin film deposition apparatus used in a thin film deposition method using the above plasma generator.

The side of the plasma generation chamber 106 where the coaxial waveguide 102 is not connected is opened, and the sample chamber 108 is opened through the plasma extraction window 109.
Connect. The substrate table 110a placed in the sample chamber 108 is placed so as to face the plasma generation chamber 106. Further, the substrate 110b can be held on the substrate table 110a, and the substrate can be loaded as necessary.
There is a substrate heating heater 111 that can raise the temperature to 300 ° C. Sample room
An exhaust system 112 connected to 108 can evacuate the system to 10 ^-6 Torr.

The first gas inlet system connected to the tapered portion 105
There is a gas introduction system 113 and a second gas introduction system 114 introduced into the sample chamber 108, and the first gas introduction system 113 has gas Ar, N ₂ , O ₂ , H ₂ , Etc. are washed away. The gas outlet 114a of the second gas introduction system 114 has a ring shape, and the gas is ejected from a plurality of small holes provided in the ring. As the gas, a silane-based gas and a metal compound-based gas (for example, TMA [trimethylaluminum], WF ₆ ) are flown.

In this embodiment, by introducing a metal compound from the second gas introduction system 114, it can be used as a plasma CVD apparatus for depositing a metal thin film. The actual first gas introduction system 113 from the H ₂ gas as an example of depositing a metal thin film, in passing the TMA from the second gas introduction system than 114, the H ₂ gas is dissociated or ionized by plasma efficiently microwaves, Generation chamber
A high density plasma is generated at 106 and drawn towards the deposition chamber 108. The extracted hydrogen radicals are stored in the deposition chamber 10
At 8, the Al-C and C-H bonds of TMA are dissociated by the H-abstraction reaction of H radicals, and an Al film of high purity can be uniformly formed on the substrate 110b.

As a plasma CVD technology for depositing a metal, as a reference example, T.Ito, T.Sugai and T.Nakamura, 1982 Symposium on VLSI Technology (Symp.on VL
SI Technology), Digest 2-2 (1982), but plasma that deposits metal thin films using microwaves.
The CVD device was developed for the first time, and it can be seen that it is extremely important for thin film deposition technology. Japanese Patent Application No. Sho 57-1568
It goes without saying that the advantage of the present invention can be utilized even if the metal supply source is a sputter target, as in Japanese Patent Laid-Open No. 59-47728. Furthermore, any thin metal film or conductive thin film can be deposited by supplying a compound gas or a target.

Embodiment 3 In the apparatus configuration shown in Embodiment 1, the antenna 103a is modified so as to have a shape shown in FIG. With this structure, energy can be supplied with high efficiency without reflecting microwaves to the inside of the plasma chamber 106. Also the plasma chamber
It is possible to generate the plasma at 106 uniformly over a large area. In addition, as a device to generate plasma uniformly over a large area, the Ligitano coil (G.Lisitano et al. The Rev. of
It goes without saying that Sci.Insrument Vol.39 No.3 1968) etc. can be used for the antenna.

EFFECTS OF THE INVENTION-It can be used as a high-density, large-area metal ion supply device using microwave discharge (ECR discharge).

-A metal thin film can be deposited using microwave discharge (ECR discharge). A sputtering target or a metal compound gas can be used as a metal supply source of the metal film.

・ Since microwave discharge (ECR discharge) is used, high plasma density is created in high-density ECR discharge, so high decomposition of metal compounds is performed, and high-speed deposition and high-purity deposition of metal thin films are possible.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the configuration of an embodiment of the plasma generator of the present invention, FIG. 2 is a conceptual diagram of the configuration of a thin film deposition apparatus using the same, and FIG. 3 is a structural diagram showing an improved antenna shape. , FIG. 4 is a conceptual diagram of a configuration of a conventional thin film deposition apparatus. 101 ... Coaxial waveguide converter, 102 ... Coaxial waveguide, 102a ...
… Inner conductor, 103 …… Microwave introduction window, 104 …… Cooling mechanism, 105 …… Taper part, 106 …… Plasma generation chamber, 107
a, 107b …… Magnet coil, 112 …… Exhaust system.

Claims (4)

[Claims] 1. A plasma generating chamber to which a magnetic field can be applied from the outside, a coaxial waveguide having one end connected to the plasma generating chamber and a window portion for introducing a microwave to the other end, and the plasma generating chamber A plasma generation method using a plasma generator having gas introduction means for introducing a plasma generation gas and exhaust means for evacuating the plasma generation chamber, wherein the microwave of the coaxial waveguide is introduced. The length l in the direction is larger than the mean free path λ of the plasma generating gas (l> λ), and the difference t between the linear inner radius of the cylindrical outer conductor of the coaxial waveguide and the radius of the inner conductor is the above-mentioned. The plasma is generated by introducing the microwave into the plasma generation chamber from the window through the coaxial waveguide in a state smaller than the mean free path λ of the plasma generation gas (t <λ). And the plastic Ma generation method. 2. An end portion of an inner conductor of a coaxial waveguide is extended and the extended portion of the inner conductor is used as a microwave linear antenna in the plasma generating chamber, or the shape is changed to form a spiral coil. The plasma generation method according to claim 1, wherein the plasma generation method is used. 3. A plasma generation chamber to which a magnetic field can be applied from the outside, a coaxial waveguide having one end connected to the plasma generation chamber and a window portion for introducing a microwave to the other end, and the plasma generation chamber Gas introducing means for introducing a plasma generating gas, and exhaust means for evacuating the plasma generating chamber,
A thin film deposition method using a thin film deposition apparatus having a sample chamber in which a substrate table can be placed in the plasma generation chamber, wherein the length l of the coaxial waveguide in the direction of introducing the microwave is The mean free path λ of the plasma generating gas
(1> λ), and the difference t between the linear inner radius of the cylindrical outer conductor of the coaxial waveguide and the radius of the inner conductor of the coaxial waveguide is smaller than the mean free path λ of the plasma generating gas (t <λ. ) State, the microwave is introduced into the plasma generation chamber from the window portion through the coaxial waveguide to generate plasma, and a thin film is deposited on a substrate grounded to the substrate table. Thin film deposition method. 4. An end portion of an inner conductor of a coaxial waveguide is extended, and an extended portion of the inner conductor is used as a microwave linear antenna in a plasma generation chamber, or the shape is changed to form a spiral coil. The thin film deposition method according to claim 3, wherein the thin film deposition method is used.