JP2001011621A - Magnetron sputtering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron sputtering device by which the intrusion of discharge gas atoms into a film is reduced, and the obtainment of the formation of film of high quality is made possible. SOLUTION: This magnetron sputtering device is provided with a film forming chamber 1 in which a substrate 3 in which a thin film is formed on the inside and a target 5 to be the base material of the thin film are arranged, and discharge gas for obtaining ions for sputtering has been introduced, a magnet part 7 forming the desired magnetron magnetic field on the surface of the target 5 and a power source device 8 executing the intermittent feed and control of pulse electric power to the target 5. In this case, the pulse period of the pulse electric power is set in such a manner that the arrival time of sputtering particles emitted from the target 5 and the arrival time of discharge gas atoms made electrically neutral after the infiltration into the target 5 and sprung out by the collision of the ions at the substrate 3 are made different.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetron sputtering apparatus, and more particularly, to a pulse power type magnetron sputtering apparatus for forming a thin film by a magnetron sputtering method.

[0002]

2. Description of the Related Art A magnetron sputtering apparatus is one of thin film forming apparatuses widely used in the field of manufacturing electronic components such as semiconductors, liquid crystal display elements, magnetic heads and magnetic disks. Although there are various forms, the basic structure and operation principle are generally as follows.

A target called a target, which is a lump of a base material to be formed into a thin film, is arranged in a vacuum vessel, and a tunnel-like magnetic field is formed on the surface of the target by a permanent magnet or the like. Next, a discharge gas for ion generation is introduced into the vacuum vessel, and the target is set at a negative potential and the vacuum vessel is set at a positive potential to generate plasma by discharge on the target surface. Generally, an inert gas such as argon is often used as a discharge gas for generating ions. The ionized discharge gas contains positively charged ions. When the positive ions collide with the negative potential target, kinetic energy is given to atoms near the target surface. If the energy is greater than the bond energy between the atoms, the bond is broken and released into space. The released atoms are deposited as a thin film on the substrate, and a film is formed. Further, when ions collide with the target, secondary electrons are emitted from the target, and the secondary electrons are accelerated and released into space because the target has a negative potential. Here, the electric field is formed in a sheath region generated between the plasma and the target. The direction of movement of the secondary electrons is defined by the magnetic field of the target surface, and stays on the target surface for a long time. Therefore, the probability of collision and ionization with the discharge gas near the target surface increases. The ions generated by the ionization are accelerated toward the target. By repeating such a cycle, discharge is maintained and sputtering is maintained. The voltage applied to the target is often a DC voltage, but a technique of making the voltage applied to the target into a pulse shape for the purpose of suppressing abnormal discharge has been proposed. The basic mechanism for generating sputtering is the same for both DC voltage and pulse voltage. For example, when using a conductive substance such as a metal as the target,
When the gas pressure is adjusted to about 0.3 to 1 Pa and a DC voltage or a pulse voltage of about -200 to -1000 V is applied to the target, plasma is generated and a thin film is formed.

[0004] Like a magnetron sputtering apparatus, the physical properties of a thin film formed in a vacuum vessel are generally different from those of a lump in a target. One of the causes may be the penetration of high-energy particles into the film. This is because ions collide with the target, are combined with electrons, are neutralized, remain on the target surface or in the target, regain energy by newly flying ions, and enter the substrate side. Particles in which ions are neutralized in this manner do not necessarily bind to the target, and thus lose little energy when being released from the target. Therefore, it reaches the substrate side, that is, the film at a high speed while maintaining a large kinetic energy.

[0005] In some cases, ions that collide with the target bounce back into the space. However, there is an electric field called a sheath region between the target and the plasma. It doesn't matter.

An example of a pulse power supply is disclosed in
No. 98755 and an example of a sputtering method using a pulse is disclosed in, for example, JP-A No. 8-115076.

[0007]

As described above, in the conventional magnetron sputtering apparatus, after the discharge gas is ionized and sputtered on the target, the discharge gas remains in the target, and is further sputtered by ions that collide later. Released with the particles. Therefore, a thin film is formed in a state where sputtered particles and discharge gas atoms are mixed on the substrate surface. From the viewpoint of film quality, those other than sputtered particles are impurities, and the incorporation of discharge gas atoms is one of the causes of film quality deterioration, and a sputtering apparatus capable of reducing the incorporation of discharge gas atoms into the film. Was desired.

Conventionally, as a power supply for applying a voltage to the target, a DC power supply, a high-frequency power supply, a pulse power supply, and the like have been used. Of these, the use of the pulse power supply is mainly for the purpose of suppressing abnormal discharge. No consideration was given to mixing of discharge gas atoms into the film. In addition, for DC power supply and high frequency power supply,
No consideration was given to mixing of the discharge gas into the film.

[0009] The object of the present invention, in view of the above problems,
An object of the present invention is to provide a magnetron sputtering apparatus in which the mixing of discharge gas atoms into a film is reduced.

[0010]

The present invention employs the following means in order to solve the above-mentioned problems.

A substrate on which a thin film is formed and a target serving as a base material of the thin film are arranged, and a vacuum vessel into which a discharge gas for obtaining ions for sputtering is introduced; In a magnetron sputtering apparatus including a magnet unit that forms a desired magnetron magnetic field, and a power supply unit that intermittently supplies pulse power to the target, a pulse cycle of the pulse power is
The sputtered particles emitted from the target and the discharge gas atoms that become electrically neutral after entering the target and are repelled by ion collisions have different arrival times when reaching the substrate. It is characterized by having been set.

A vacuum vessel into which a substrate on which a thin film is formed and a target serving as a base material of the thin film are arranged, and a discharge gas for obtaining ions for sputtering is introduced, and a surface of the target is provided. In a magnetron sputtering apparatus including a magnet unit that forms a desired magnetron magnetic field thereon and a power supply unit that intermittently supplies pulse power to the target, a pulse cycle of the pulse power is emitted from the target. Sputtered particles,
Becomes electrically neutral after penetrating into the target,
Discharge gas atoms repelled by ion collisions
It is characterized in that it is set so as to reach the substrate alternately.

[0013] In the magnetron sputtering apparatus according to any one of claims 1 to 2, an opening / closing operation can be performed between the substrate and the target at the same cycle as the pulse cycle. A shutter mechanism for blocking discharge gas atoms from reaching the substrate is provided.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an outline of a pulse power type magnetron sputtering apparatus according to the present embodiment.

In FIG. 1, reference numeral 1 denotes a film forming chamber;
Extraction chamber, 3 a substrate, 4 a guide, 5 a target using pure molybdenum as a material, 6 and 10 vacuum pumps, 7 a magnet assembly, 8 a pulse power supply, 9
Is a transfer robot, 11 is a mass flow controller, 12
Is an argon gas cylinder, 13 is a gate valve, and 14 is an interval L between the target and the substrate.

As shown in FIG. 1, the magnetron sputtering apparatus comprises a film forming chamber 1 and a charging / unloading chamber 2.
In the film forming chamber 1, argon is introduced as a discharge gas.

FIG. 2 is a diagram showing the pulse current waveform flowing to the target, the arrival timing of the argon gas atoms to the substrate, and the arrival timing of the sputtered particles to the substrate from the top, with the horizontal axis representing time.

In FIG. 1, reference numeral 21 denotes a target of 10 k.
Hz pulse current waveform when a pulse current of 2 Hz is applied, 2
2 represents the time required for the argon atoms to reach the substrate from the target, and 23 represents the time required for the sputtered particles to reach the substrate from the target.

Here, the period T of the pulse current is obtained from the following relational expression.

T / 2 = | L / V _Ar -L / V _Sp | V _Ar : average velocity of argon, V _Sp : average velocity of sputtered particles.

The period T of the pulse current depends on the distance between the target and the substrate, the material of the target, and the type of the discharge gas, and may be changed according to the combination thereof. As described above, basically, the difference between the flight time of the sputter particles as the target material and the flight time of the discharge gas may be selected to be one half of the pulse period.

Next, the processing in the magnetron sputtering apparatus will be described with reference to FIGS.

In FIG. 1, a film forming chamber 1 is connected to a vacuum pump 6
Then, the charging / discharging chamber 2 is evacuated by the vacuum pump 10. The substrate 3 is put into the loading / unloading chamber 2 from the atmosphere and evacuated. When a predetermined pressure is reached, the gate valve 13 is opened, and the transfer robot 9 transfers the substrate 3 from the loading / unloading chamber 2 to the film forming chamber 1. The substrate 3 is lifted by the guide 4 and the transfer robot 9 is
Return to the extraction room 2. After that, the gate valve 13 is closed,
While the flow rate of argon gas as a discharge gas is adjusted from the cylinder 12 by the mass flow controller 11,
It is introduced into the film forming chamber 1. The pressure in the film forming chamber 1 is controlled by a pump 6
Pumping speed, the flow rate of argon, the conductance which is the ease of gas flow, and the like. In this embodiment, the argon gas is supplied for 200 S in order to make the pressure 0.4 Pa.
CCM flowed. With the argon gas flowing, a voltage is applied to the target 5 by the pulse power supply 8. As a result, plasma is generated on the surface of the target 5, ions in the plasma collide with the target 5, and sputtering occurs.

The atomic mass of molybdenum, which is the material of the target 5, is 1.59 × 10 ⁻²⁵ kg, while the atomic mass of argon is 6.63 × 10 ⁻²⁶ kg. The average kinetic energy of molybdenum atoms sputtered by the target 5 and flying to the substrate 3 is 5 eV (electron volt).
Then, the distance (L) 14 between the target and the substrate is 0.2
m, the time 13 for molybdenum atoms as sputtered particles to reach the substrate 3 from the target 5 is 63 μs.
On the other hand, the neutralized argon remaining in the target 5 is sputtered to obtain a kinetic energy of about 50 eV.
In this case, the time 12 required for the argon atoms to reach the substrate 3 from the target 5 is 13 μs. Then, 50 μm, which is the arrival time difference between molybdenum atoms and argon atoms, is used.
a frequency at which s is a half cycle (T / 2) 11, that is,
In this embodiment, a pulse current of 10 kHz may be applied to the target 5.

As shown in FIG. 2, by appropriately selecting the pulse frequency of the pulse current applied to the target, many molybdenum atoms and argon atoms can reach the substrate 3 alternately. Argon atoms that can be reached can be reduced.

Here, when molybdenum atoms and argon atoms reach the substrate alternately, the proportion of argon atoms mixed into the substrate can be reduced as compared with the case where molybdenum atoms and argon atoms simultaneously reach the substrate. According to this, mixing of argon atoms into the substrate can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a diagram showing an outline of a magnetron sputtering apparatus according to this embodiment.

In FIG. 1, reference numeral 15 denotes a motor, and 16 denotes a shutter mechanism having an opening 17 and rotated by the motor 15 at a constant period. The other configuration is the same as the configuration of the same reference numeral shown in FIG.

This embodiment is different from the first embodiment in that
The difference is that a shutter mechanism for blocking the passage of argon atoms coming from the target is provided.

As shown in FIG. 3, the shutter 16 has an opening 17 and rotates or rotates at a high speed by the motor 15 to pass or block particles flying from the target 5. By setting the intermittent interval of the shutter 16 to be equal to one half of the pulse period, argon atoms can be blocked by the shutter 16.

According to the present embodiment, the amount of argon atoms reaching the substrate 3 can be greatly reduced as compared with the first embodiment, and the mixing of argon atoms into the substrate 3 can be greatly reduced. Can be.

A molybdenum film formed by the magnetron sputtering apparatus of each of the above embodiments and a molybdenum film formed by the same film forming apparatus at the same film forming rate using a conventional DC power supply. And the amount of argon atoms contained in both films was evaluated by secondary ion mass spectrometry, and a comparison was made. As a result, in the molybdenum film formed according to the first embodiment, the detected value of argon was reduced by the conventional method. In the molybdenum film formed according to the second embodiment, the detection value of argon can be reduced to one-fifth of the molybdenum film formed by the conventional method. We were able to.

[0034]

As described above, according to the present invention, the mixing of discharge gas atoms into the film can be greatly reduced, so that a high-purity film can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a pulse power type magnetron sputtering apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a pulse current waveform flowing to a target, a timing at which argon gas atoms reach a substrate, and a timing at which sputtered particles reach a substrate.

FIG. 3 is a diagram showing an outline of a pulse power type magnetron sputtering apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Film-forming chamber 2 Loading / unloading chamber 3 Substrate 4 Guide 5 Target, 6,10 Vacuum pump 7 Magnet assembly, 8 Pulse power supply 9 Transfer robot 11 Mass flow controller 12 Argon gas cylinder 13 Gate valve 14 Distance between target and substrate 15 Shutter rotation Motor 16 shutter 21 half cycle of pulse current (T / 2) 22 time required for argon atoms to reach substrate from target 23 time required for sputtered particles to reach substrate from target

Claims (3)

[Claims] 1. A vacuum vessel in which a substrate on which a thin film is formed and a target serving as a base material of the thin film are arranged, and a discharge gas for obtaining ions for sputtering is introduced, and a surface of the target. In a magnetron sputtering apparatus comprising a magnet unit for forming a desired magnetron magnetic field thereon and a power supply device for intermittently supplying pulse power to the target, a pulse cycle of the pulse power is emitted from the target. The sputtered particles and the discharge gas atoms that become electrically neutral after penetrating into the target and are repelled by the collision of ions are set to have different arrival times when reaching the substrate. Magnetron sputtering equipment. 2. A vacuum vessel in which a substrate on which a thin film is formed and a target which is a base material of the thin film are arranged, and a discharge gas for obtaining ions for sputtering is introduced, and a surface of the target. In a magnetron sputtering apparatus comprising a magnet unit for forming a desired magnetron magnetic field thereon and a power supply device for intermittently supplying pulse power to the target, a pulse cycle of the pulse power is emitted from the target. A magnetron sputtering apparatus, wherein sputtered particles and discharge gas atoms which become electrically neutral after entering the target and are repelled by ion collision reach the substrate alternately. 3. The substrate according to claim 1, wherein the substrate can be opened and closed between the substrate and the target at the same period as the pulse period, and the substrate of the discharge gas atoms can be opened and closed. A magnetron sputtering apparatus comprising a shutter mechanism for blocking the arrival at the magnetron.