JPH06177051A - Cvd device - Google Patents

Abstract

PURPOSE:To reduce ion damage effectively and to form a film widely and uniformly by laying out a CVD device so that the strength of the magnetic field directly above a substrate is high and is reduced away from the substrate and then controlling it so that the influence due to collision of a charged particle can be avoided for a film-formed object directly above the substrate. CONSTITUTION:Electromagnets 41a and 41b for increasing the strength of the magnetic field directly above a substrate and for decreasing it away from the substrate are laid out to reduce the speed of an ion moving toward the substrate in the direction of the substrate. Since the speed of the ion entering the substrate differs due to operation pressure, optimum conditions are set by changing the current flowing to the electromagnets 41a and 41b and the position of a substrate 5. Normally, the strength of the magnetic field near the surface of the substrate is approximately 0.2-3.0 KGauss. By using the electromagnets 41a and 41b in a pair, the direction of the magnetic field near the substrate can be aligned nearly vertically for the substrate, thus obtaining uniform crystallizability over a wide area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to plasma CVD (Ch
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical vapor deposition apparatus, and more particularly to a CVD apparatus capable of performing plasma processing on a large area with less damage by ions.

[0002]

2. Description of the Related Art Plasma CVD is used for forming a diamond thin film and an amorphous Si thin film.

As a plasma generation source in plasma processing such as plasma CVD or plasma etching, for example, magnetic field microwave plasma generation as disclosed in JP-A-64-65843, particularly electron
Examples thereof include plasma generating means using cyclotron resonance (ECR), plasma generating means using high frequency induction heating, direct current plasma, and the like. Among these, since a high-density plasma can be obtained and the processing speed is high, a method using a magnetic field microwave such as ECR is attracting attention.

The ECR plasma generator is a device for accelerating electrons resonantly by the interaction of an electric field and a magnetic field and turning the gas into plasma by collision of the electrons. There is also known a method of extracting desired ions from the plasma thus generated by a control electrode for extracting ions (Japanese Patent Laid-Open No. 60-103099).

Plasma CVD is a method of forming a film by depositing ionizing / dissociating species such as ions and radicals in the plasma thus generated on a substrate. Also, as disclosed in Japanese Patent Laid-Open No. 64-65843,
Electrons are extracted from this plasma, the extracted electrons are made to collide with the raw material gas into plasma, and the generated ions,
Radicals can also be deposited on the substrate.

By the way, when performing plasma CVD, damage to deposits and substrates by ions becomes a problem.
As a method of avoiding this, there is a method of applying a positive bias voltage to the substrate, but if the area of the substrate is increased, the substrate potential (V
The application of s) also increases the plasma potential (Vp), so that the Vs-Vf potential cannot be effectively controlled to be positive, and as a result, ion damage cannot be avoided.

In fact, plasma CVD of diamond usually requires operating pressures of 10 to 10 ² Torr,
It is said that it is difficult to form a diamond thin film below 0 ^-2 Torr. The reason for this is considered to be destruction of the diamond structure due to ion damage. In order to avoid this, the pressure may be raised to increase the frequency of collision between particles in plasma. However, in the high-pressure discharge of 10 to 10 ² Torr, the generated plasma is localized, which makes it impossible to perform plasma treatment on a large area.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma CVD apparatus capable of effectively reducing ion damage and forming a film over a large area and uniformly.

[0009]

These objects are achieved by the present invention described in (1) to (5) below.

(1) In a CVD apparatus using plasma generated by applying electromagnetic energy, the magnetic field strength directly above the substrate is high, and the magnetic field strength is arranged so as to decrease as the distance from the substrate increases, and charged particles are directed toward the substrate. A CVD apparatus having a magnetic circuit that is controlled so that the speed is sufficiently reduced and the influence of collision of charged particles on a film-formed product on the substrate can be avoided.

(2) The CVD apparatus according to the above 1, wherein the plasma generating means is an electron cyclotron resonance type plasma generating means.

(3) The CVD apparatus according to 1 or 2 above, wherein the direction of the magnetic field vector near the substrate is orthogonal to the substrate surface.

(4) The CVD apparatus according to 1 or 2 above, wherein a component of a magnetic field vector near the substrate in a direction perpendicular to the substrate surface is directed from the substrate surface toward the plasma side.

(5) The CVD apparatus according to 1 or 2 above, wherein the magnetic circuit is formed by a mirror type magnetic field.

Here, the electromagnetic energy referred to in the first invention means microwaves, high frequencies, direct current, and the like.

[0016]

[Operation and effect] When the strength of the magnetic field (B) decreases as the distance from the substrate increases, the ions (mass; M) moving toward the substrate increase in velocity with the increase in the magnetic field (v ₁ ) Increases.

[0017] This is because the magnetic moments of the first adiabatic invariant of the following formula (mu) and total kinetic energy of the ions (Mv ^2/2) are stored.

[0018] ^{_{μ = Mv 1 2 / 2B Mv}} 2/2 = M (v 1 2 + v 2 2) / 2 rate for this reason, parallel ion and magnetic field vector (v ₂₎
Decreases. From this fact, the magnetic field strength and distribution directly above the substrate can be appropriately controlled depending on the film forming conditions to reduce the velocity of ions incident on the substrate in the substrate vertical direction, and as a result, the ion damage is reduced.

In plasma CVD, when a film is formed on the order of 0.1 Torr, the ionized raw material gas forms secondary ions in the plasma, and ions and radicals of polyatomic molecules different from the raw material gas are generated. It becomes difficult to control the reactive species by gas. Further, among these secondary ions, reaction active species that inhibit the film formation reaction also exist, the crystal structure is lowered, and the film contains a large amount of impurities.

On the other hand, when the pressure is set to 10 ^-2 Torr or less, most of the ion species generated by the plasma are primary ions, and the above-mentioned adverse effects are eliminated. However, in low pressure discharge, the mean free path of ions is long, Since the collisions with neutral species in the plasma are small, the ions are not decelerated, which causes a problem of ion damage of the film. For example, in a material such as a diamond thin film that is difficult to form at a vacuum of 10 ^-2 Torr or less, the cause may be damage to the film due to fast ions, but by applying the above magnetic circuit to the device, Ion damage can be avoided at 10 ^-2 Torr or less, and it is possible to form a diamond thin film having high purity and a large area.

As described above, particularly in CVD in a vacuum of 10 ^-2 Torr or less, it is difficult to form diamond, Si, etc.
It was found to be effective for forming a film of C, c-BN and the like.

[0022]

Specific Structure The specific structure of the present invention will be described in detail below. 1 to 3 will be described. In Figure 1,
A preferred embodiment of the invention is shown.

In FIG. 1, a CVD processing apparatus 1 has a plasma generating chamber 2 in a processing chamber 4, and a raw material gas inlet 3 is provided in communication with the plasma generating chamber 2. A waveguide 21 connected to a microwave power source (not shown) is provided in the plasma generation chamber 2 through a microwave introduction window 22, and a Helmholtz magnet is provided on the outer periphery of the plasma generation chamber 2 as a magnet. Type electromagnets 23a, 23b are provided,
These constitute an electron cyclotron resonance (hereinafter referred to as ECR) type magnetic field microwave plasma generation means. A vacuum exhaust port is provided in the processing chamber 4 so that a predetermined operating pressure can be achieved, and the substrate holder 6 is movably provided.
It can be installed at a predetermined position in the processing chamber 4 while being heated to a predetermined substrate temperature.

In the plasma generation chamber 2, microwaves are introduced through the microwave introduction window 22, and at the same time, a magnetic field that preferably satisfies the ECR condition is applied to the insides of the plasma generation chambers by the electromagnets 23a and 23b. Therefore, the electrons in the plasma generation chamber 2 are accelerated by the magnetic field and the electric field of the microwave and collide with the raw material gas particles to generate plasma.

Further, the CVD processing apparatus 1 shown in FIG.
2 shows a capacitively coupled plasma CVD apparatus in which a high-frequency electrode 7 is arranged facing each other and a plasma is generated by applying electric power from a high-frequency power source 8 between the electrodes.

In addition to this, an inductively coupled plasma CVD apparatus in which a coil is arranged on the outer circumference of the reaction vessel and a high frequency is applied to the coil to generate plasma, and a direct current plasma CVD apparatus in which a DC voltage is applied to generate plasma and so on.

In conventional plasma CVD, film formation on the order of 0.1 Torr is because the ionized raw material gas forms secondary ions in the plasma, and ions and radicals of polyatomic molecules different from the raw material gas are generated. However, it becomes difficult to control the reactive species by the source gas. In addition, these secondary ions form reaction active species that inhibit the film formation reaction, and the crystal structure is lowered, or the film becomes a film containing a large amount of impurities.

On the other hand, the pressure is set to 10 in the conventional CVD apparatus.
^{When the} pressure is set to ^-2 torr or less, most of the ion species generated by plasma are primary ions, and the above-mentioned adverse effects are eliminated, but the average free path of the charged particles is long, so that damage to the film formation becomes a problem. That is, since the pressure is as low as 10 ^-2 Torr, collision between charged particles and neutral species such as source gas hardly occurs in plasma, and as a result, the charged particles reach the substrate surface without being decelerated. In particular, since the mass of ions is larger than that of electrons, the film-formed product is damaged (ion damage) and the crystallinity is lowered.

In order to solve such a problem, the present invention reduces the velocity of ions moving toward the substrate toward the substrate. Therefore, the strength of the magnetic field directly above the substrate is increased and the distance from the substrate is increased. Electromagnets 41a, 4 to reduce
1b is arranged. Generally, the velocity of the ions incident on the substrate varies depending on the operating pressure.
The optimum condition is set by changing the current flowing in b and the position of the substrate 5, but normally the magnetic field strength near the substrate surface is about 0.2 to 3.0 kGauss.

As shown in FIGS. 1 and 2, the electromagnets 41a,
By using one pair of 41b, the direction of the magnetic field in the vicinity of the substrate can be aligned substantially at right angles to the substrate, and uniform crystallinity can be obtained over a wide area. On the other hand, as shown in FIG. 3, one electromagnet may be used as long as the magnetic field strength in the vicinity of the substrate can be made sufficiently large.

4 and 5 show the calculation results of the magnetic field strength on the central axis in the apparatus of FIG. In the figure, the magnetic field on the left side is a magnetic field generated to generate ECR plasma, and the magnetic field on the right side is a magnetic field generated to reduce ion damage. 4 and 5, the direction of the generated magnetic field is ECR in order to reduce ion damage.
The case where the magnetic field is in the same direction (hereinafter referred to as a mirror magnetic field) and the case where the magnetic field is in the opposite direction are shown. As is clear from the figure, in any case, the ratio of the maximum magnetic field strength (Bmax) and the minimum magnetic field strength (Bmin) ((Bmax-Bmin) / Bni), which is an index of the effect of reducing ion damage.
It can be seen that n) can be large and is effective.

The plasma CVD to which the present invention is applied is not limited, and includes diamond, amorphous silicon, and S.
iC, carbon, SiNx, SiOx, etc., polycrystalline silicon, SiC, c-BN, etc., single crystalline silicon, S
The present invention is effective for any film formation of iC, c-BN, diamond or the like.

In forming these films, various conditions such as the substrate temperature are not particularly limited, and may be appropriately determined according to the purpose. The raw material gas used in these plasma CVD may be an ordinary reactive gas such as hydrocarbon and hydrogen used for diamond film formation, silane gas used for amorphous Si film formation, and is not particularly limited.

[0034]

EXAMPLES The present invention will be described in more detail with reference to specific examples.

A diamond thin film was formed using the CVD processing apparatus 1 as shown in FIG. That is, the substrate was set on the substrate holder 6 and brought into the state shown in FIG. Si (100) was used as the substrate. Then 1x in the system
Evacuate to 10 ^-5 Torr, raise the substrate temperature to 600 ° C,
Further evacuation was performed.

After the pressure reached 1 × 10 ^-6 Torr, the raw material gas was introduced through the raw material gas inlet 3.

The raw material gas is CH ₄ / H ₂ = 1/9 in volume ratio.
9, the flow rate CH _4: 1sccm, H _2: it is 99Sccm. After that, the reaction pressure 3 by the automatic pressure controller (APC).
It was set to × 10 ^-3 Torr.

The electromagnets 41a and 41b for reducing the ion damage were changed in current value so that the magnetic field strength was strong near the substrate surface shown in FIG. 4 and weakened as the distance from the substrate decreased. Under these conditions, Bm shown in the figure
Ratio of ax and Bmin ((Bmax-Bmin) / Bma
x) was adjusted to be ˜1. Of course, this value is appropriately adjusted according to the conditions such as the film-forming material and the pressure. In addition, the position of the substrate is Bma at which the magnetic field strength shows a maximum.
set to x.

Next, in the plasma generation chamber 2, 2.45 GHz,
A microwave of 500 W was applied to generate ECR plasma. At this time, the substrate temperature is kept at 600 ° C. by heating.

When the obtained film was analyzed by X-ray diffraction, Raman spectroscopic analysis and scanning electron microscope, uniform diamond could be formed on a 4-inch substrate.

For comparison with this, electromagnets 41a,
An experiment was carried out when the current of 41b was not applied,
Only a graphite film was obtained.

From the above results, the effect of the present invention is clear.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a preferred embodiment of a CVD apparatus of the present invention.

FIG. 2 is a configuration diagram showing a preferred embodiment of the CVD apparatus of the present invention.

FIG. 3 is a configuration diagram showing a preferred embodiment of the CVD apparatus of the present invention.

FIG. 4 is a calculation example of the magnetic field strength distribution on the central axis of the ion damage prevention magnet of the present invention. The figure shows the case where the direction of the magnetic field generated to reduce the ion damage is the same as the direction of the ECR magnetic field.

FIG. 5 is a calculation example of the magnetic field strength distribution on the central axis of the ion damage prevention magnet of the present invention. The figure shows the case where the direction of the magnetic field generated to reduce the ion damage is opposite to the direction of the ECR magnetic field.

[Explanation of symbols]

 1 CVD processing apparatus 2 Plasma generation chamber 21 Waveguide 22 Microwave introduction window 23a Electromagnet 23b Electromagnet 3 Raw material gas introduction port 4 Processing chamber 41 Electromagnet 41a Electromagnet 41b Electromagnet 5 Substrate 6 Substrate holder 7 High frequency electrode 8 High frequency power source

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Mikio Omori 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (5)

[Claims] 1. In a CVD apparatus using plasma generated by applying electromagnetic energy, the magnetic field intensity right above the substrate is high, and the magnetic field intensity is arranged so as to decrease with the distance from the substrate, and the velocity of charged particles in the substrate direction. C has a magnetic circuit for controlling so that the influence of the collision of the charged particles with the film-deposited material can be avoided immediately above the substrate.
VD device. 2. The CVD apparatus according to claim 1, wherein the plasma generating means is an electron cyclotron resonance type plasma generating means. 3. The CVD apparatus according to claim 1, wherein the direction of the magnetic field vector near the substrate is orthogonal to the surface of the substrate. 4. The CVD apparatus according to claim 1, wherein a component of a magnetic field vector near the substrate in a direction perpendicular to the substrate surface is directed from the substrate surface to the plasma side. 5. The CVD apparatus according to claim 1, wherein the magnetic circuit is formed by a mirror type magnetic field.