JPH01212758A - Thin film forming device and microwave introducing method - Google Patents

Abstract

PURPOSE:To form a high-quality thin film on a low-temp. substrate at a high speed with high efficiency by connecting a microwave vacuum waveguide to a high magnetic flux density part of a plasma-forming chamber provided with a magnetic field diverting toward a substrate holder and executing sputtering. CONSTITUTION:The microwaves from the vacuum waveguide 10 are introduced into the plasma-forming chamber 11 as a cavity resonator to resonate the microwaves and gas is introduced from a gas introducing port 11A into the chamber to form the plasma. Two pieces of asymmetric electromagnets 8, 8 are disposed on the outside circumference of such plasma-forming chamber 11 to generate the magnetic field diverging toward a substrate holder 14 of a sample chamber 9 coupled thereto. The other end part of the above-mentioned vacuum waveguide 10 having an introducing window 6 at one end is connected to the plasma-forming chamber 11 in the part where the magnetic flux density is higher than the resonance magnetic flux density of the microwaves. The high-density plasma 3 is thereby generated in the gas of the low pressure and is introduced into the sample chamber 9. A cylindrical target 12 provided in the inlet part is sputtered at this time to efficiently and continuously form the high-quality thin film on the substrate 2 on the substrate holder 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to an apparatus for forming thin films of various materials on a substrate. The present invention relates to a novel thin film forming apparatus for forming thin films continuously and stably for a long period of time with high speed and efficiency.

[Prior Art] Conventionally, so-called sputtering apparatuses that form films by sputtering a target as a thin film forming element in plasma have been widely used in various fields for forming thin films of various materials.

Among these, the most common is a normal two-pole (RF, dC) sputtering apparatus in which a target 1 and a substrate 2 face each other as shown in FIG. This apparatus consists of a vacuum chamber 4 having a target 1 and a substrate 2 to which a thin film is attached, a gas introduction system and an exhaust system (not shown), and generates plasma inside the vacuum chamber 4.

[Problem to be solved by the invention] When trying to increase the film deposition rate using conventional sputtering equipment,
Although it is necessary to maintain the plasma at high density, the first O
In the sputtering equipment shown in the figure, the higher the plasma density, the more rapidly the applied voltage rises, and the substrate is therefore rapidly heated by the impact of high-energy particles or high-speed electrons in the plasma. The resulting film crystal itself is also damaged. For this reason, high-speed sputter deposition can only be applied to specific heat-resistant substrates, film materials, and film compositions.

Furthermore, in film formation using conventional sputtering equipment, gas and particles in the plasma are not sufficiently ionized.
Since most of the sputtered neutral particles as film deposition elements enter the substrate as neutral particles, their activity is insufficient from the viewpoint of reactivity. Therefore, in order to obtain some oxides and thermal nonequilibrium substances, a high substrate temperature of about 500 to 800° C. is required. Moreover, most of the power input to the plasma is consumed as thermal energy, and the ratio of power used for plasma formation (main part) to the input power is low, resulting in low power efficiency.

Further, in conventional sputtering equipment, a discharge cannot be stably formed at a low gas pressure of 1 O -3 Torr or less, and a large amount of impurities are incorporated into the film.

In order to eliminate the above-mentioned drawbacks of the conventional sputtering apparatus, the apparatus shown in FIG.
(See Publication No. 67). This device introduces microwaves into a plasma generation chamber 11 through a microwave guide tube 7 and a microwave introduction window 6, forms a magnetic field inside the plasma generation chamber 11 with an electromagnet 8, and generates microwave discharge in the magnetic field. A thin film is formed on the substrate 2 by sputtering the cylindrical target 12 using the generated plasma 3. This device has the following excellent features as a thin film forming device. That is, (1) Film formation can be performed at high speed without damaging the film or substrate or causing rapid temperature rise.

(2) Particle energy can be controlled over a wide range.

(3) Particle energy dispersion is small.

(4) The plasma has a high ionization rate and is active.

(5) Low gas pressure discharge is possible.

However, in this thin film forming apparatus, when a conductive film such as metal is formed, the film also adheres to the microwave introduction window and becomes conductive, so the microwave is reflected and plasma is generated continuously for a long time. I couldn't.

The present invention solves the above-mentioned conventional drawbacks, generates high-density plasma in a low-pressure gas, performs sputtering using the plasma, and sputters high-quality thin films while keeping the sample substrate at a low temperature. It is an object of the present invention to provide a method for efficiently introducing microwaves into a thin film forming apparatus and a plasma generating apparatus that can continuously form thin films with high speed and efficiency.

[Means for Solving the Problems] In order to achieve such an object, the thin I model forming apparatus of the present invention forms a cavity resonator in which the introduced microwave resonates, and generates plasma by introducing gas. a plasma generation chamber that is connected to the plasma generation chamber and has a substrate holder inside; and a 6n field that is provided around the outer periphery of the plasma generation chamber and that is parallel to the side surface of the plasma generation chamber and diffuses toward the substrate holder. It has two asymmetrical magnetic field generation means for generating a microwave, a microwave introduction window at one end, and is coupled to the plasma generation chamber at the other end or at a part of the magnetic flux density higher than the resonant magnetic flux density of the microwave. A cylindrical target is provided on the inner wall of the plasma generation chamber or near the boundary between the sample chamber and the plasma generation chamber.

The microwave introduction method of the present invention forms an asymmetrical magnetic field parallel to the side surface of the plasma generation chamber in a plasma generation chamber for introducing gas to generate plasma, so that the magnetic flux density distribution is higher than the resonance density of the microwave. Part of the plasma generation chamber is characterized by introducing microwaves into the plasma generation chamber.

[Function] The present invention generates high-density plasma with high activity, performs sputtering using the plasma, and maintains the test substrate at a low temperature so that the conductivity of the film material becomes an obstacle to film formation. Therefore, high-quality thin films can be continuously formed at high speed and with high efficiency. That is, the present invention generates and heats plasma using an electron cyclotron (ECR) in a magnetic field, performs sputtering using the high-density plasma, and extracts low-energy ions of several eV to several tens of eV, and Achieve both generation of highly active plasma using electron temperature. Moreover, since the vacuum waveguide is joined to the plasma generation chamber orthogonally to the direction of one bundle, the acceleration of the plasma toward the vacuum waveguide is suppressed, making it possible to use the vacuum waveguide. As a result, the reflection of microwaves due to the adhesion of the conductive material film to the microwave introduction window can be ignored.
It is also possible to continuously and stably form a film of a conductive material such as metal for a long period of time. Furthermore, by increasing the magnetic flux at the coupling part between the vacuum waveguide and the plasma generation chamber using, for example, two asymmetrical solenoid coils as a magnetic field generating means, reflection of the injected microwaves can be reduced and efficient plasma generation can be achieved. enable generation.

[Example] Examples will be described below based on the drawings.

FIG. 1 is a sectional view of an embodiment of the thin film forming apparatus of the present invention. A vacuum waveguide 10 is coupled to the plasma generation chamber 11,
Through the microwave introduction window 6, the microwave waveguide 7,
Further, microwaves are supplied from a microwave source connected to a microwave introducing mechanism such as a matching box, a microwave power meter, and an isolator (not shown). In this embodiment, a quartz glass plate is used for the microwave introduction window 6, which is arranged in a part that cannot be directly seen from the target installed in the plasma generation chamber 11. As a microwave source, for example, 2.45
It uses a GHz magnetron.

The plasma generation chamber 11 and the vacuum waveguide 10 are water-cooled to prevent temperature rise due to plasma generation. A sample chamber 9 is coupled to the plasma generation chamber 11 . Gas can be introduced into the plasma generation chamber 11 from the gas introduction port 11A,
Also, the exhaust system and plasma generation chamber 11 (not shown)
And the sample chamber 9 can be evacuated to high vacuum. Other gas inlets may be provided in the sample chamber 9. Inside the sample chamber 9, there is a substrate holder 1 that supports the substrate 2 in the direction of magnetic flux generated by a magnet 8, which will be described later.
4, and a shutter (not shown) is arranged above the substrate 2 so as to be able to shut off the plasma 3. It is preferable that the substrate holder 14 has a built-in heater for heating the substrate 2. Furthermore, it is preferable to apply a DC or AC voltage to the substrate 2 to bias the substrate during film formation and to perform sputter cleaning of the substrate.

The plasma generation chamber 11 adopts a circular cavity resonance mode TE113 as a condition for the microwave cavity resonator, and uses a cylindrical shape with a diameter of 20 cm and a height of 20 cm on the inside to increase the electric field strength of the microwave. , to increase the efficiency of microwave discharge. the lower end of the plasma generation chamber 11;
That is, a hole with a diameter of 10 cm is provided on the surface leading to the substrate portion, and this surface also serves as a reflection surface for microwaves, and the plasma generation chamber 11 acts as a cavity resonator.

Magnets 8 consisting of two asymmetric solenoids or a combination of at least two solenoids are provided at both ends of the outer periphery of the plasma generation chamber 11, thereby generating a magnetic field within the plasma generation chamber. At that time, the conditions for electron cyclotron resonance (ECR) using microwaves are determined to be established inside the plasma generation chamber 11. For example, for microwaves with a frequency of 2.45 GHz, the ECR condition is a magnetic flux density of 875 G, so the magnet 8 is designed so that the magnetic flux density of 875 G is realized inside the plasma generation chamber 11.

A cylindrical target 12 is installed in the sample chamber 9 on the inner side surface of the plasma generation chamber 11 or at the exit of the plasma generation chamber 11 so as to surround the plasma 3 .

As shown in FIG. 2, the target 12 is removably fixed to a water-coolable metal support 12A.
A negative voltage is applied from the power supply 13 via 2A.

What about vacuum waveguide 10? iff, inserted from the asymmetric part of the magnet and coupled to the plasma generation chamber. Moreover, the magnetic flux density of the coupling portion is determined to be larger than the magnetic flux density of the ECR condition. As is clear from the change in the reflectance of microwaves introduced perpendicular to the magnetic flux with respect to the magnetic flux density shown in Figure 3, the microwaves are strongly reflected near the ECR condition and the microwave introduction efficiency decreases. This is to prevent it. In addition, in this case, it is better to set the magnetic field distribution so that the magnetic field distribution inside the plasma generation chamber does not become a diffuse magnetic field gradient compared to the sample chamber side exit of the plasma generation chamber, which will accelerate the plasma toward the substrate. done effectively.

FIG. 4 shows t in the actual hN example of the present invention shown in FIG.
An example of the magnetic field strength distribution in the n east direction is shown.

In this case, a yoke or a permanent magnet may be placed on the upper surface of the plasma generation chamber in order to control the magnetic flux density distribution within the plasma generation chamber. FIGS. 5A and 5B respectively show 16 actual examples in which the yoke 15 is disposed on the upper surface of the plasma generation chamber and the magnetic flux density distribution inside the plasma generation chamber.

This yoke arrangement not only controls the magnetic field gradient, but also has the advantage that less magnet current is required to obtain the required magnetic flux density. For example, 875G
Normally, a magnet current of +8 A is required to obtain a magnetic flux density of 8.
58 was enough.

FIG. 6 shows an overview of the plasma generation state when the vacuum waveguide is connected in a direction parallel to the magnetic flux 5, and FIG. 7 shows an overview of the plasma generation state in the thin film forming apparatus of the invention. 1st
The same reference numerals as in the figure indicate the same parts. According to the invention, plasma intrusion into the vacuum waveguide is significantly less than in the conventional example.

Here, the parameters for generating plasma include the gas pressure in the plasma generation chamber, the power of the microwave, the power input to the target, the gradient of the magnetic field, the asymmetry of the magnets, and the distance between the magnets. For example, for microwaves with a frequency of 2.456) Iz, the magnetic flux density at the part where the vacuum waveguide is coupled to the plasma generation chamber is equal to 1.1 as described above.
It is sufficient that the magnetic flux density of 875 G or more, which is the condition of 875 G or more, and the magnetic flux density of 875 G that is the 1B condition for both of them is achieved in any part of the plasma generation chamber, and the magnetic flux density is gradually lowered in the direction of the substrate. Mirror field gradients, where there is a field minimum down to the substrate, or cusp field gradients, where there is a point of zero field in between, have been achieved.

FIG. i and FIG. 98 show other embodiments of the present invention, and FIGS. 8B and 9B show the distribution of the magnetic field in each embodiment. As shown in the embodiment of FIG. 8A, the magnetic field gradient can be controlled by installing an auxiliary electromagnet 16 around the substrate or on the outer periphery of the sample chamber, and controlling it by the value of the current flowing there. Furthermore, as shown in FIG. 9A, even when a yoke 15 for magnetic field gradient control is installed, the magnetic field gradient can be similarly controlled using the auxiliary electromagnet 16.

Cylindrical target 1 facing the generated high-density plasma
By applying a negative voltage to 2, ions in the high-density plasma are efficiently drawn into the cylindrical target 12 to cause sputtering. At this time, most of the sputtered particles, which are mostly neutral, are also scattered toward the substrate. Ions are also generated.

Electrons with higher mobility leak out in the direction of the magnetic flux at the plasma edge, leaving positive ions behind in the plasma, and this charge separation inevitably induces an electric field. This electric field becomes an electric field that accelerates positive ions in the plasma toward the substrate. In reality, it is impossible for electrons and ions to behave independently, as this would violate the neutrality of the plasma, and equilibrium occurs when the potential difference between the substrate surface and the plasma is equal to the average energy of the electrons, and this electric field becomes It acts as a decelerating electric field for electrons and an accelerating electric field for ions, and takes the form of so-called ambipolar diffusion in which the amount of emission of both species is approximately the same. As a result, by extracting ions with a relatively low energy of several eV to several tens of eV, a thin film can be formed using the target material as a raw material.

The above-mentioned magnetic field gradient directly affects the energy of the ions, and the ion energy can be easily controlled by controlling the magnetic field gradient.

At this time, more efficient sputtering can be achieved by arranging appropriate yokes and permanent magnets on the back side of the target and in the vertical direction so that magnetic flux flows appropriately over the target surface, and by using magnetron discharge.

In addition, since the plasma is active, not only can a discharge be stably formed even at lower gas pressures on the order of 10-5 Torr, but active plasma can also be formed even at relatively high gas pressures, where active species play an important role in thin film formation. As a result, thin films with good crystallinity can be formed even at low substrate temperatures.

When forming a conductive material film, if the microwave introduction window becomes foggy, plasma cannot be generated for a long time. Therefore, the first idea is to install the microwave introduction window 6 away from the plasma generation chamber 11 and use the vacuum waveguide 10 to prevent the microwave introduction window 6 from becoming cloudy due to the adhesion of the conductive material film. When vacuum waveguides are simply connected in the magnetic flux direction, the magnetic flux density of the ECR condition is satisfied inside the vacuum waveguide lO, and plasma is generated there, so that the microwave power is transferred to the plasma generation chamber 11. The plasma is not effectively injected into the plasma, resulting in non-uniform plasma generation.

At the same time, since a divergent magnetic field is formed from the vacuum waveguide 10 in the microwave introduction direction, the plasma is accelerated not only in the direction of the substrate but also in the microwave introduction direction. On the other hand, if the vacuum waveguide lO is connected perpendicular to the magnetic flux, the plasma will not be accelerated in the direction perpendicular to the magnetic flux, so the plasma will be accelerated in the microwave introduction direction. There isn't. On the other hand, among the particles sputtered from the cylindrical target 12 installed in the plasma generation chamber 11, neutral particles that are not ionized are not affected by the magnetic field or electric field and fly almost straight from the target. Therefore, by installing the microwave introduction window 6 in a position where it cannot be directly seen from the target, it is possible to prevent the microwave introduction window 6 from becoming cloudy due to sputtered particles. In this way, it is possible to continuously and stably form a film of any material for a long time without fogging the microwave introduction window, regardless of the conductivity of the formed film or its thickness. is possible.

Next, the results of forming a film using the apparatus of the present invention will be explained. After evacuating the sample chamber 9 to a vacuum level of 5 x 10-' Torr, Ar gas was introduced at a flow rate of 5 cc/min to raise the gas pressure in the plasma generation chamber to 5 x 10-'Torr.
The microwave power is 100 to 500 W as rr, and the power immersed in the cylindrical An target 13 is 30 to 600 W.
Films were formed in a divergent magnetic field gradient. At this time, the film was formed at room temperature without heating the sample stage. As a result, 5 to 1
At a deposition rate of 100 n/min, <1111 M could be continuously and stably and efficiently deposited for a long period of time.

The average energy of the ions at this time is 5eV to 30e
It changed to V.

The thin film forming apparatus of the present invention not only forms an Il film, but also
can be used for almost all thin film formations, and most reactive gases can be used as the introduced gases, thereby also realizing reactive sputtering.

In the above embodiments, the magnetic field necessary for ECR is obtained by an electromagnet, but it is clear that the same effect can be obtained by using various permanent magnets or by combining them.

[Effects of the Invention] As explained above, the present invention utilizes sputtering using microwave plasma generated by electron cyclotron resonance, accelerates plasma toward the substrate using a 6n field gradient, and performs sputtering in a low gas pressure. It realizes highly efficient low-temperature film formation, and realizes continuous and stable film formation for a long time regardless of the conductivity or thickness of the film. In addition, the particle energy can be freely controlled over a wide range from several eV to several tens of eV, and highly active plasma is used, so this equipment can be used to produce high-quality films with little damage at high speed and at low substrate temperatures. Can be continuously formed with high stability.

In addition, by making the magnetic flux density at the coupling portion between the vacuum waveguide and the plasma generation chamber higher than the resonance magnetic flux density, reflection of the injected microwave can be reduced and efficient plasma generation can be achieved.

The microwave introduction method of the present invention is not limited to sputtering equipment,
It is also effective for devices that do not have a target mechanism, such as CvIll polishing and etching devices.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of an embodiment of the thin film forming apparatus of the present invention, Figure 2 is a detailed cross-sectional view of a cylindrical target, and Figure 3 is a graph showing the relationship between the reflectance of microwaves incident perpendicular to the magnetic flux and the magnetic flux density. 4 is a diagram showing the magnetic field strength distribution in the magnetic flux direction in the embodiment of the thin film forming apparatus of the present invention shown in FIG. 1, and FIG. 5A is a cross-sectional view of another embodiment of the present invention. 5
Figure B is a diagram of the magnetic flux density distribution, Figure 6 is a schematic diagram of the plasma generation state when the vacuum waveguide is connected in the magnetic flux direction, and Figure 7 is a diagram of the plasma generation state in the thin film forming apparatus of the present invention. , Fig. 88 is a sectional view of another embodiment of the present invention, Fig. 8B is a magnetic flux density distribution diagram thereof, Fig. 9A is a sectional view of still another embodiment of the invention, and Fig. 9B is a sectional view of another embodiment of the present invention.
The figure is a magnetic flux density distribution diagram, FIG. 10 is a configuration diagram of a two-pole sputtering device, and FIG. 11 is a sectional view of a conventional thin film forming device. DESCRIPTION OF SYMBOLS 1... Target, 2... Substrate, 3... Plasma, 4... Vacuum chamber, 5... Magnetic flux, 6... Microwave introduction window, 7... Microwave waveguide, 8 ... Magnetic field generation electromagnet, 9... Sample chamber, 1O... Vacuum waveguide, 11... Plasma generation chamber, 12... Cylindrical target, 15... Yoke, 16... Auxiliary electromagnet.

Claims (1)

[Claims] 1) A plasma generation chamber that forms a cavity resonator in which the introduced microwave resonates and generates plasma by introducing gas, and a substrate holder that is coupled to the plasma generation chamber and has a substrate holder inside. a sample chamber having a sample chamber; two asymmetrical magnetic field generating means provided on the outer periphery of the plasma generation chamber for generating a magnetic field that is parallel to the side surface of the plasma generation chamber and diffused toward the substrate holder; a vacuum waveguide having a microwave introduction window at one end thereof, the other end of which is coupled to the plasma generation chamber at a portion having a magnetic flux density higher than the resonant magnetic flux density of the microwave; A thin film forming apparatus comprising: a cylindrical target provided near a boundary between a sample chamber and the plasma generation chamber. 2) The thin film forming apparatus according to claim 1, wherein the microwave introduction window is provided at a position that is not visible from the target. 3) A magnetic field parallel and asymmetrical to the side surface of the plasma generation chamber is formed in the plasma generation chamber for introducing gas to generate plasma, and the plasma is generated in a portion where the magnetic flux density distribution is higher than the microwave resonance density. A microwave introduction method characterized by introducing microwaves into a generation chamber.