JPH1060641A - Inclined target type magnetron sputtering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable film formation at a high speed in which high energy sputtering particles from targets and recoil gas are utilized by symmetrically arranging a pair of targets and allowing them to incline to a substrate. SOLUTION: A pair of two targets 1 and 2 are symmetrically arranged, and inclined at a variable angle to a substrate 3 around the rotary shaft 11 of a target holder 8. Furthermore, magnets 5 and 6 are arranged by the targets 1 and 2, and the magnet 6 at the inside is preferably made shorter than the magnet 5 at the outside to improve the plasma density above the targets 1 and 2. Moreover, both sides of the target is preferably provided with an electrically floated metallic board 7 to smoothen the movement of electrons between the targets. Furthermore, a collimator 26 is preferably arranged at the front face of the substrate 3. By executing a magnetron sputtering process by this device, low energy sputtering particles 22 are regulated, and high energy sputtering particles 23 and recoil gas ions 24 are uniformly utilized, by which the formation of dense film with uniform thickness is attained at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of various semiconductor devices, the formation of corrosion-resistant and wear-resistant films on mechanical parts, and the like.
The present invention relates to a thin film forming apparatus used for forming a decorative film on a craft, a building material, and the like.

[0002]

2. Description of the Related Art The sputtering method has a great feature that vaporized atoms can be directly produced from a solid.
Polar sputtering and magnetron sputtering are the mainstream. Among them, magnetron sputtering, in which the plasma density is increased by combining an electric field and a magnetic field, is widely used as a high-speed sputtering apparatus having a high sputtering rate. However, there is a great difference between the quality of the films produced by these sputtering methods, and a sputtering method operating in a high vacuum, such as an ion beam sputtering method, is effective in obtaining a dense and excellent adhesion film. However, such a method has a high production cost due to the complexity of the apparatus and the film forming speed.

[0003] In addition, various targets can be used as targets for sputtering. In particular, it is known that an insulator target has a low film formation rate and requires a long time for film formation. If the input power is increased to increase the sputtering rate, there is a danger that the target itself will crack due to thermal expansion and thermal conduction of the insulating target. As a technology to solve this, reactive sputtering, which uses a metal material with excellent thermal conductivity for the target and introduces a gas that reacts with the metal as part of the introduced gas to perform sputtering, has also been devised, In order to obtain a good reaction, a large amount of gas is introduced, and as a result, the film formation conditions at a high gas pressure result, and the sputtered particles collide with the gas in the apparatus and the energy is reduced. No excellent film has been obtained. In that case, due to the gas pressure, a reaction occurs on the target surface, an insulator is formed on the surface of the conductive metal target, and the charge-up occurs, so that the sputtering phenomenon does not occur. Therefore, DC sputtering using a DC power supply is impossible, and RF sputtering using a high-frequency power supply is used. However, in order to form a film on a large area at a high speed, a method using simple DC sputtering is more cost effective than an RF sputtering in which impedance matching is difficult.

In the magnetron sputtering method widely used at present, a planar magnetron sputtering apparatus is used to increase a processing area. However, since a magnet for generating a magnetic field is provided at a rear portion of the target, erosion of the portion is small. Inefficient target use. As a solution to this, improvements have been made to move the internal magnets to achieve a more uniform erosion, but this is not essentially a satisfactory solution.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention realizes sputtering using high-energy sputter particles and a recoil gas and achieves high-speed sputtering as compared with the conventional sputtering method. It is an object of the present invention to provide a film forming apparatus characterized by simple film formation.

[0006]

In order to achieve the above object, the present invention provides a method for arranging targets symmetrically and tilting them with respect to a substrate so that high energy sputtered particles from the target can be eliminated. It is characterized by forming a high-speed film using a recoil gas.

Further, in order to utilize high-energy particles for film formation, sputtered particles struck from a target and a recoil gas reflected by the target reach the substrate without colliding with the gas inside the vacuum chamber. It is necessary to do so, and for that purpose, a discharge in a high vacuum is indispensable. Therefore,
In the present invention, a magnet is arranged beside the target, electrons are confined by a strong magnetic field and electrically floated beside the target, and a smooth electron trajectory is secured by reflection of electrons using a floating potential, thereby achieving high density. Thus, uniform erosion and operation in a high vacuum are enabled by forming uniform plasma.

In order to smoothly change the electron trajectory at the end of the target to a pair of targets, a magnetic field generated by making the magnet inside the target shorter than the outside magnet and a floating potential caused by a metal plate arranged at the end of the target. , The electrons are reflected, the movement of the trajectory of the electrons between the targets is smoothly performed, and the operation in a high vacuum is enabled.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sputtering apparatus of the present invention was designed based on the result of detailed analysis of a sputtering phenomenon using Monte Carlo simulation. The analysis results are shown below, typically using an example in which an iron target is vertically irradiated with argon ions accelerated at 1200 V. FIG. 4 shows the angles taken in this simulation. The angle 25 is 0 degree with respect to the target surface, and 9 degrees above the target.
The axis was set to 0 degrees.

FIG. 5 shows the energy angle distribution of sputtered particles. At an angle of 90 degrees parallel to the substrate, the average energy of the sputtered particles is about 20 eV,
At an angle of 45 degrees at a place inclined at an angle of 45 degrees, it is as high as 80 eV. Further, in this case, as shown in FIG. 6, the recoil argon, which is a recoil gas, has an average energy of 55 eV at an angle of 90 degrees, and 70 eV at a position of 45 degrees inclined at 45 degrees, as shown in FIG. It grows slowly. However, there is not as significant a difference as the energy of sputtered particles.

Next, the angle dependence of each particle was examined. The distribution of sputtered particles showed a regular distribution, and the recoil argon was
The distribution was more gradual. Therefore, the number of recoil argon for one sputtered particle showed a tendency as shown in FIG. At an angle of 90 degrees at a position parallel to the target, the angle is 0.02, but at a position of 45 degrees inclined 45 degrees, 0.08, and at a further inclined angle of 20 degrees,
There is an argon bombardment of 0.3 or more than 10 times the position parallel to the normal target. Therefore, as the angle of inclination from the target is increased, a film can be formed using the impact effect of high energy sputtered particles and recoil argon.

[0014] As shown in FIG. 4, the outline of the sputtering phenomenon occurring in the target is as shown in FIG. In some parts, high energy sputtered particles 22
Is released. The ions 20 accelerated to cause the sputtering phenomenon are reflected on the target, become recoil gas ions 23 having relatively high energy, and take a gentle regular distribution as compared with sputtered particles, and reach the substrate. Therefore, by changing the inclination of the substrate with respect to the target, the energy of the sputtered particles and the impact effect of the recoil gas can be controlled.

This tendency is reproduced by reproducing the above conditions using the ion beam sputtering method and examining the angle dependence of the substrate. As a result, as the inclination of the substrate increases, the quality of the sputtered film changes greatly, It shows the same properties as the quality of the film formed by the energy sputtered particles, and its effect starts to appear at 20 degrees with respect to the position parallel to the target.
The maximum effect was obtained at ~ 50 degrees. Since the film formation speed is significantly reduced when the film formation speed is inclined at 75 degrees or more, the inclination effect is effective in the range of about 20 degrees to 75 degrees from the relation of the film formation rate.

Hereinafter, the operation of the sputtering apparatus having this structure will be described. The sputtering device of the present invention is different from a normal sputtering device in that the target surface is not parallel to the substrate but is inclined. By the above operation, a film is formed by sputter particles having energy several times larger than that of ordinary sputter particles. Further, since the number of recoil gases per unit of sputtered particles is several times larger, a strong gas impact effect can be obtained.

This indicates that when reactive sputtering is considered, the number of substrate impacts of the reactive gas introduced to even react with sputtered particles increases, so that stronger reactive sputtering can be performed. . The recoil gas is
The energy of the gas in the vacuum apparatus is substantially different from the energy close to room temperature, has a high energy of several tens to 100 eV, is larger than the reaction energy of ordinary substances, and the chemical reaction easily proceeds. Therefore, good reactive sputtering can be performed.

Specifically, in consideration of an element which becomes a reactive sputter, an oxide, a nitride and the like can be mentioned. In this case, as the reactive gas, there are gases such as oxygen, nitrogen and ammonia containing these elements, but all of them are often lighter than the sputtering gas such as argon, so that the target gas is necessarily higher than the sputtering gas. As a result, the number of recoil gases reflected by the substrate increases, so that the chance of a reaction occurring on the substrate increases, and excellent reactive sputtering can be performed.

In a magnetron sputtering apparatus, the voltage and current characteristics applied to the cathode are determined by the pressure of the introduced gas.
Controlling the energy of the sputtered particles is difficult. However, in the present configuration, the operability in a high vacuum has a large range, and by changing the inclination angle,
The energy of the sputtered particles can be controlled, and a wide range of film quality can be controlled. For example, if particles with too high energy do not provide the desired film quality or if residual stress due to substrate impact is too large,
By making the inclination angle close to parallel, it is possible to keep the inclination small.

In general, the angle dependence of sputtered particles is almost a regular distribution, and depending on the sputter conditions, the center is concave.
Since it is known that an under-regular distribution is exhibited, it is possible to control so that the film forming rate is maximized. Also, by arranging two targets in pairs, many of the sputtered particles that do not go in the direction of the substrate adhere to another target, where they are re-sputtered and directed toward the substrate on which a thin film is to be formed. Is released to form a film. This operation is repeated until the sputtered particles reach the substrate, and a film using the target can be formed efficiently.

When a configuration in which two targets are arranged as a pair and a substrate is made as large as possible, in addition to a high energy component emitted from a low angle of the target,
Many low energy components also reach the substrate. Therefore, a plate with a thickness between the target and the substrate is arranged in a grid so that only sputtered particles perpendicular to the substrate can reach, and sputtered particles and recoil argon within a certain angle range pass through it. By installing a collimator that can control the energy of the sputtered particles from the target and the recoil gas by blocking the low-energy particles, the sputtered particles and the recoil with the optimal energy for film formation are achieved. Film formation using gas is also possible. In order to utilize this phenomenon, it is indispensable to perform discharge in a high vacuum in which sputtered particles do not cause gas collision.

A magnet is arranged beside the target to form a strong magnetic field on the target surface. In addition, a metal plate is arranged beside the target so that secondary electrons generated by the sputtering phenomenon do not go to other than the target surface, and the metal plate is electrically floated to have an electron reflection function. In order to smoothly move electrons between the pair of target ends, a radial magnetic field distribution is formed at the target end to change the electron trajectory at the target end, and a metal plate is arranged at the target end. It electrically floats and has an electron reflection function, so that electron orbits form a closed loop in a pair of targets, and electrons necessary for ionization of gas are confined on the target.

With these configurations, the present invention has the following features regarding erosion. In normal magnetron sputtering, due to the structure of placing a magnet under the target,
There is no magnetic field component parallel to the target above the magnet. For this reason, the plasma density in that portion is low, the sputtering efficiency is poor, and the erosion is not uniform on the surface. In this configuration, the part is not on the target due to the structure, only the horizontal component is present on the entire surface of the target, and the magnet part has the electron reflection function using the magnetic field generation and floating potential, so that the uniform plasma density on the target surface Is formed, the target erosion becomes uniform, and the target utilization efficiency is excellent.

By using a pair of paired targets, a part of the low-energy sputtered particles emitted from one side of the substrate in a direction perpendicular to the target is cut off by the paired targets. It is possible to use only high-energy sputtered particles for film formation by optimizing their positions. Since the configuration of the present invention uses a rectangular target, it can theoretically be extended in the horizontal direction, and a large-area film can be formed.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of one embodiment, and FIG. 2 is a schematic view of a target, a magnet, a floating potential metal plate, and an electron trajectory viewed from above. FIG. 3 is an oblique view of the device. FIG. 8 is a schematic view of a collimator portion for equalizing the energies of sputtered particles and recoil gas. In this film forming apparatus, a target portion for performing sputtering is described. This portion is maintained at a predetermined degree of vacuum by a vacuum exhaust device, and a predetermined amount of gas for forming plasma is introduced.

The targets 1 and 2 are arranged as targets, and the targets are rotated about a target holder rotating shaft 11 with respect to the substrate to direct high-energy sputtered particles and recoil gas onto the substrate. Install it in an inclined state. The substrate 3 is attached to a substrate holder 4. In order to enable sputtering in the magnetron mode, magnets 5 and 6 having different magnetic poles are arranged beside the targets 1 and 2 and magnetic fields 17 and 18 are applied horizontally to the target surface. The magnetic field is looped by the same target holder 7. An electrically floating metal plate 7 is arranged between the side of the target and the magnets 5 and 6, or the electrically conductive magnets 5 and 6 are electrically insulated and floated. Since a negative voltage is applied to the targets 1 and 2 as a sputtering voltage, the insulating sheet 1
At 0, it is insulated from the target holder 8. The targets 1 and 2 are water-cooled from the back through a water-cooling pipe 9 in order to suppress a temperature rise due to sputtering.

A negative voltage (several hundreds to several thousand volts) is applied to the targets 1 and 2 to cause discharge. In this state, in the portion of the sheath 12 on the target surface, the electrons are pushed back to the plasma 13 on the sheath mainly by the electric field, but inside the plasma, the electrons are perpendicular to the magnetic field by the horizontal magnetic field formed by the magnets 5 and 6. A cyclotron motion 16 is caused in the direction. However, because of the disturbance of the magnetic field and the electric field inside the plasma, not all of the electrons move along the orbit 16, so the metal plate 7 that is electrically floated between the side of the target and the magnets 5 and 6 is arranged. Alternatively, the magnets 5 and 6 are electrically floated to form an equilibrium potential of the plasma. Since the potential is closer to the ground than the potential of the plasma, the potential is positive when viewed from the electrons in the plasma. Then, reflection of the electrons occurs, and as a result, the electrons in the plasma rotate while drawing a loop on the trajectory 16.

On the other hand, in the target end region 19 where the electron trajectory changes rapidly, the length of the magnet 6 is made shorter than the length of the magnet 5, and the magnetic field distribution is changed from 18 so that the electron trajectory draws an arc. Change as 17 And
In order to provide a function of reflecting electrons at both ends of the target, electrically floating metal plates 14 and 15 are arranged, and electrons that cannot be completely rotated by Lorentz force due to a magnetic field are transferred onto a pair of targets by the force of the floating electric field. Lead. As a result, the electrons generated on the target rotate on the trajectory 16 without escaping to other parts, collide efficiently with the gas existing on the trajectory, and form plasma. Positive ions in the plasma bombard the target, generating sputtered particles. The high-energy sputtered particles 23 and the recoil gas 2
4 reaches the substrate 3 and a film is formed. The sputtered particles that have landed on the pair of targets are re-sputtered there and partly reach the substrate.

Since two rectangular targets are used, due to their structure, in addition to the high energy components emitted from the middle and low angles of the target, many low energy components in the direction perpendicular to the target reach the substrate. Therefore, in order to form a film with uniform energy as much as possible, a plate having a thickness between the target and the substrate is arranged in a grid 27 so that only sputtered particles perpendicular to the substrate can be reached. The collimator 26 is arranged so that only sputtered particles and recoil argon within a certain angle range can pass through the hollow portion 28 of the target, and has a structure in which the low-energy component 22 in the direction perpendicular to the target is cut off. The energy of the sputtered particles and the recoil gas is made uniform, and the film is formed only by the sputter particles 23 and the recoil gas 24 having the optimum energy for the film formation. The thickness and interval of the collimator are determined geometrically so as to block the component 22 perpendicular to the target from the positional relationship between the target and the substrate.

In the present invention, since the trajectory of the electron is divided into a region 20 that only moves straight and a region 19 that transitions to a paired target, the straight region 20 can be extended theoretically. Large-area film formation suitable for production lines is possible. Further, it is possible to form a large-area film by repeating this apparatus periodically.

[0029]

Since the present invention is configured as described above, it has the following effects. When the sputtered ions are bombarded perpendicularly to the target, the distribution of the sputtered particles shows a regular distribution, but the energy of the sputtered particles becomes higher according to the inclination angle. Since the recoil gas has a more gradual distribution than the regular distribution of sputter particles, the arrival ratio of sputter particles and recoil gas particles at an inclined location is significantly higher than when the target is parallel to the target used in normal sputtering. It is large and its energy is as high as tens of eV. Therefore, by inclining the target, a high-energy sputtered particle and a recoil gas ion bombardment effect can be used, and a dense thin film can be formed and a film having excellent adhesion can be formed.

In order to effectively realize the target tilting effect, two rectangular targets are used in pairs, and it is easy to extend the length of the targets in principle. Large area film formation is possible. The confinement of electrons by a strong horizontal magnetic field and a floating potential on the target surface enables discharge at 0.1 mTorr or less, which is one order of magnitude lower than the normal magnetron sputtering operating voltage of 1 mTorr. In a normal sputtering device, the discharge characteristics are such that the current is substantially constant even when the voltage is changed. You cannot choose any voltage. However,
When discharge is possible in a high vacuum, discharge can be performed at a high sputtering voltage, and high-energy sputtered particles and recoil gas ions can be generated. Also,
At the degree of vacuum in this region, the mean free path of the sputtered particles also extends to several meters, which is much larger than several tens of cm of a normal sputtering device, and the high-energy particles can reach the substrate directly without collision in the middle. it can. Actually, when a film is formed, the distance between the target and the substrate is often several tens of cm, and without the mean free path near 1 m, it is difficult to use those high-energy sputter particles in the film formation. It is.

Operating in a high vacuum means that the ionization efficiency of the introduced gas in the vicinity of the target is good, and the film formation rate per unit input power naturally increases.
Energy efficiency also increases. In addition, the plasma density and temperature in the vicinity of the target are increased, and there are many particles with high reactivity, so that reactive sputtering using a DC power source can be easily performed. Depending on the type of target, the distribution may show a collapsed, under-regular distribution from a regular distribution. When it is desired to give priority to the film formation speed over the film quality, the film formation rate can be increased by inclining at 20 to 30 degrees.

[Brief description of the drawings]

FIG. 1 is a sectional view of an inclined target type magnetron sputtering apparatus.

FIG. 2 is a top view of a tilted target type magnetron sputtering apparatus.

FIG. 3 is a bird's-eye view of an inclined target type magnetron sputtering apparatus.

FIG. 4 is a schematic diagram of a sputtering phenomenon.

FIG. 5 is an energy angle distribution chart of sputtered particles.

FIG. 6 is an energy angle distribution diagram of recoil argon.

FIG. 7 is an angular distribution diagram of the number (arrival ratio) of recoil argon per unit sputtered particle.

FIG. 8 is a schematic top view of a collimator inserted between a target and a substrate.

DESCRIPTION OF SYMBOLS 1, 2 Target 3 Substrate 4 Substrate holder 5 Magnet 6 Magnet 7 Metal plate 8 Target holder 9 Water cooling pipe 10 Insulation sheet 11 Target holder rotation axis 12 Plasma sheath 13 Plasma 14, 15 Metal plate 16 Electron orbit 17 Target The direction of the magnetic field on the edge 18 The direction of the magnetic field on the target 19 The electron transition region between the pair of targets 20 The central region of the target 21 Ions for causing a sputtering phenomenon 22 Low energy sputtered particles 23 High energy sputtered particles 24 Recoil gas ions 25 Incident angle 26 Collimator 27 Plate forming collimator 28 Cavity created by collimator

Claims (6)

[Claims] 1. By providing a pair of targets symmetrically and having a function of tilting them with respect to a substrate, high-speed formation using high-energy sputter particles and recoil gas from the targets is achieved. Film forming apparatus characterized by film 2. The film forming apparatus according to claim 1, wherein a magnet is arranged beside the target to confine the plasma in the apparatus. 3. The apparatus according to claim 1, further comprising: a metal plate electrically floated beside the target, providing a function of reflecting electrons using the floating potential, and limiting the electrons to an upper portion of the target to improve the plasma density. The film forming apparatus according to claim 1, 4. The apparatus of claim 1, wherein the inner target magnet is shorter than the outer magnet to form a continuously changing magnetic field distribution between the target ends, thereby providing a target between the target ends in a pair. 2. The film forming apparatus according to claim 1, wherein the movement of the electron trajectory is smoothed and the plasma density is improved. 5. The apparatus according to claim 1, wherein an electrically floating metal plate is arranged at both ends of the target, and the floating potential is used to reflect the electrons, thereby smoothly moving the electron trajectory between the pair of targets. 2. The film forming apparatus according to claim 1, wherein the plasma density is improved. 6. In the apparatus, a plate having a thickness between the target and the substrate is arranged in a lattice shape so that only sputtered particles perpendicular to the substrate can reach the substrate, and a plate having a thickness within a certain angle range. 2. The film forming apparatus according to claim 1, wherein a collimator that allows passage of sputtered particles and recoil argon is provided to equalize the energy of the sputtered particles from the target and the energy of the recoil gas.