JPH062132A - Magnetron-discharge treating device - Google Patents

Abstract

PURPOSE:To easily control the amt. and kinetic energy of the charged particles reaching a body to be treated by freely setting the potential of the body. CONSTITUTION:This device is provided with the cathode 2 and anode 4 arranged in a vacuum vessel 1 and a holder 3 for holding a body S to be treated at a position away from the closed region enclosed by the line of magnetic force leaving a part of the cathode 2 and entering the other part of the cathode 2 along the anode 4 and the cathode 2 surface. A magnetron discharge is generated between the cathode 2 and anode 4 by a discharge power source 22 while keeping the cathode 2 at a specified negative potential with respect to the anode 4, and the amt. and energy of the charged particles reaching the body S are controlled by a holder power source 32 while keeping the holder at a specified potential.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing apparatus utilizing magnetron discharge, such as a magnetron sputtering apparatus, an etching apparatus, a surface reforming apparatus and the like.

[0002]

2. Description of the Related Art Magnetron discharge utilizing magnetron motion of electrons in an orthogonal electromagnetic field is widely used for various processes including surface treatment of semiconductor wafers.
FIG. 5 is a schematic diagram of a conventional magnetron discharge treatment device. The magnetron discharge treatment apparatus shown in FIG. 5 includes a vacuum container 1, a cathode 2 arranged inside the vacuum container 1, and a vacuum container 1 arranged inside the vacuum container 1 in the same manner.
The object holder 3 which can be held in a state of being opposed to the object 3, a power source 6 for setting an electric field between the cathode 2 and the object holder 3 to generate magnetron discharge, and the power source 6 A magnet 5 for generating a magnetic field, at least a portion of which is orthogonal to the electric field, and a shield 7 for preventing electric discharge at an unnecessary portion are provided. As shown in FIG. 5, the magnet 5 is composed of, for example, a columnar N pole arranged in the center and a ring-shaped S pole arranged so as to surround the N pole. And the line of magnetic force by this magnet 5 is
As shown in FIG. 5, an arc is drawn in the discharge space from the surface of the cathode 2. Then, the lines of magnetic force are orthogonal to the electric field between the cathode 2 and the object holder 3 which are parallel to each other at the top of the arc, and realize the magnetron discharge. In the above magnetron discharge treatment apparatus, for example, when performing magnetron sputtering, the target is placed on the surface of the cathode 2 facing the discharge space, and when performing etching or the like, a gas introduction system provided in the vacuum container 1 Reactive gas is introduced from 12.

[0003]

The magnetron discharge described above is suitable for high-speed processing because high-density plasma can be obtained, but the amount of charged particles flowing into the object to be processed and its kinetic energy are controlled. There was a problem that was generally difficult. In the conventional magnetron discharge, since the magnetron discharge is performed by the electric field between the cathode and the object holder as described above, the potential of the object depends on the required discharge intensity and the potential of the cathode. It was decided and could not be changed freely. Therefore, the potential of the object to be processed may be set to a predetermined negative potential to prevent the inflow of electrons or negative ions, or a predetermined amount of cations may be made to collide with the object to be used to utilize its energy. It was difficult. On the contrary, it was difficult to increase the inflow of electrons into the object to be processed for a specific purpose by setting the object to be processed to a predetermined positive potential.

The invention of the present application has been made in consideration of such problems, and enables the potential of the object to be processed to be freely set, whereby charged particles reaching the object to be processed are provided. The purpose is to make it easy to control the amount of energy and its kinetic energy. In the present application, “controlling” the charged particles that reach the object to be processed includes the case where the amount of the charged particles that reach the object is zero.

[0005]

In order to achieve the above object, a magnetron discharge treatment apparatus of the present invention comprises a vacuum container, a cathode arranged inside the vacuum container, an inside of the vacuum container or a vacuum container. An anode that is provided as a part of the vacuum vessel and a magnetron discharge is performed between the cathode and the cathode, and is located inside the vacuum container at a position where a predetermined process can be performed by utilizing the discharge between the cathode and the anode. A target object holder for holding a target object, a discharge power source for setting a predetermined electric field between a cathode and an anode to perform magnetron discharge, and a magnetic field at least a part of which is orthogonal to the electric field generated by the discharge power source. A magnetron discharge treatment apparatus comprising a magnet for generating, wherein the object holder is surrounded by magnetic field lines that come out of a part of the cathode, come into contact with the anode and enter the other part of the cathode, and the surface of the cathode. Closure At a position away from those that retain the target object. In the magnetron discharge device having the above configuration, the magnetron discharge is performed by the electric field between the anode and the cathode. The electrons generated by the discharge are trapped in the lines of magnetic force, are confined in the closed region, and flow into the anode. Since the object holder does not participate in the formation of the magnetron discharge, it can be kept at a free potential as long as it does not disturb the discharge between the cathode and the anode more than the limit.

[0006]

EXAMPLES Examples of the present invention will be described below. Figure 1
1 is a schematic diagram of a magnetron discharge treatment apparatus according to an embodiment of the present invention. The magnetron discharge device shown in FIG.
And a cathode 2 disposed inside the vacuum container 1, and a target object holder that is also disposed inside the vacuum container 1 and can hold the target object S in a state of facing the cathode 2. 3, an anode 4 provided inside the vacuum container for performing magnetron discharge with a cathode, a discharge power source 22 for setting a predetermined electric field between the cathode 2 and the anode 4, and an object holder 3, a holder power supply 32 for keeping 3 at a predetermined potential, a magnet 5 for generating a magnetic field at least partially orthogonal to the electric field generated by the discharge power supply 22, an exhaust system 11 for exhausting the inside of the vacuum container 1, and a vacuum. It is mainly composed of a gas introduction system 12 for introducing a predetermined gas into the container 1.

The magnetron discharge treatment apparatus shown in FIG.
As an example, an example in the case of being configured as a sputtering device is shown. That is, the flat target 20 is arranged on the surface of the cathode 2 facing the discharge space. Cathode 2
The structures of the magnet 5 and the magnet 5 are almost the same as those used in a typical flat plate magnetron discharge. However, the magnet 5
5 is different from the conventional one shown in FIG. 5 in that it is composed only of a cylindrical central magnet 51 arranged on the yoke.
The ring-shaped member surrounding 1 is a non-magnetized pole piece 52 formed of a metal such as iron. Therefore, the lines of magnetic force emitted from the central magnet 51 draw a large arc as shown in FIG. 1 and reach the side surface portion of the magnetic pole piece 52 and the like. Cathode 2
Is a cylindrical shape having a central magnet 51 and a magnetic pole piece 52 housed therein, and the target 20 described above is fixed to the upper opening of the vacuum magnet 1 via a cathode conducting tube 21 fixed to the bottom plate. Is connected to the discharging power source 22. still,
An insulating material 1 is provided between the cathode conduit 21 and the wall of the vacuum container 1.
0 is interposed.

An object holder 3 for holding an object S to be processed
Also has a structure similar to that of the normal object holder 3 used in the sputtering apparatus, and holds the object S at a position facing the discharge space by a holding mechanism (not shown).
The object holder 3 is connected to a holder power source 32 outside the vacuum container 1 by a holder conducting tube 31 and is held at a predetermined potential.

Next, the structure of the anode 4, which is one of the features of this embodiment, will be described. The anode 4 used in this embodiment has a short cylindrical shape, and surrounds the space between the cathode 2 and the object holder 3 as shown in FIG. It is located inside. This anode 4
Is connected to an anode power source 42 outside the vacuum container 1 by an anode conduction tube 41 and is held at a ground potential or a predetermined positive potential. The anode conducting tube 41 also serves as a mechanical holding means for the anode 4 inside the vacuum container 1, and several anode conducting tubes 41 are radially arranged at equal intervals to hold the anode 4. . The insulating material 10 is also interposed between the anode conducting tube 41 and the wall of the vacuum container 1.
Further, the anode 4 has a hollow inside and is cooled by the supply of a refrigerant. Then, the anode conducting tube 41 also serves to introduce the refrigerant into the anode 4,
Refrigerant supplied from a cooling system (not shown) is introduced into the anode 4 through the anode conduit 41 to cool the anode 4.
Such a cooling structure is the same for the cathode conducting tube 21 and the holder conducting tube 31.

Since the spatial position of the anode 4 is important in this embodiment, it will be described in detail below. As described in the section of the conventional technique, a number of arc-shaped magnetic lines of force are emitted from the surface of the cathode 2 toward the target object holder 3. A necessary condition regarding the spatial position of the anode 4 is that the magnetic field lines 54 contacting the anode 4 are not in contact with the object S to be processed among these magnetic field lines. That is, in FIG. 1, when the anode 4 is not provided, the tangential magnetic field lines 5 of the object to be processed are the same as in FIG.
3 forms a closed region, and electrons are trapped between the surface of the cathode 2 and the tangential magnetic force line 53 of the object to be processed. However, when the anode 4 is arranged at the above-mentioned position, the magnetic field lines contacting the anode 4 (hereinafter,
Electrons are trapped between the anode tangential magnetic field line 54 and the surface of the cathode 2, and the closed region is limited to this region.
That is, the object S to be processed is held at a position away from the closed region. In this example, the target 20 is arranged as a part of the cathode 2, and the surface of the target 20 actually forms a closed region.

When the anode 4 is arranged at such a position, the magnetron discharge is formed exclusively between the anode 4 and the cathode 2, and the object holder 3 is not actively involved in the formation of the magnetron discharge. As a result, the potential of the object holder 3 can be kept at a free potential as long as it does not disturb the discharge between the cathode 2 and the anode 4. Incidentally, as such an anode 4, not only a cylindrical one surrounding the discharge space but also various other structures can be adopted. For example, as shown by a two-dot chain line in FIG. 1, a small flat plate-shaped anode 4 may be arranged between the cathode 2 and the object S to be processed. In this case as well, the magnetic field lines 54 that come out of a part of the cathode 2 and come into contact with the anode 4 are in a positional relationship such that they do not come into contact with the object S to be processed, and the above-mentioned effect is obtained.

On the other hand, the anode power source 42 connected to the anode 4 can keep the anode 4 at a predetermined positive potential with respect to the cathode 2. In the case where the magnetron discharge is sufficiently achieved only by the negative potential applied by the discharge power source 22 described above, the anode 4 need only be held at the ground potential. However, there may be a case where the anode 4 is kept at a predetermined positive potential to increase the potential difference between the anode 4 and the object to be processed S for a specific purpose such as enhancing the effect of collecting electrons or negative ions.

The structures of the exhaust system 11 and the gas introduction system 12 are as follows.
Since well-known ones can be used, detailed description will be omitted. As the exhaust system 11, a system using a diffusion pump, a rotary pump, or the like can be adopted, and the inside of the vacuum container 1 is exhausted to a predetermined degree of vacuum according to the necessity of the process.
The gas introduction system 12 is composed of a tank containing a gas such as Ar and a variable conductance valve.

Next, the operation of the magnetron discharge treatment apparatus of this embodiment having the above construction will be described. Continuing,
The operation when performing the sputtering process will be described. The object S to be processed (specifically, a semiconductor wafer or the like) is carried into the inside of the vacuum container 1 through a carry-in port (not shown), and is held in the object holder 3 in advance. First, the exhaust system 11 operates to exhaust the inside of the vacuum container 1 to a predetermined degree of vacuum, and then the conductance valve of the gas introduction system 12 opens to introduce the gas into the vacuum container 1. The opening amount of the conductance valve is adjusted so that the inside of the vacuum container 1 is maintained at a predetermined degree of vacuum necessary for processing. Then, the discharge power supply 22 or the anode power supply 42 operates to generate an electric field between the cathode 2 and the anode 4, and the magnetron discharge operates. At that time, the current flowing through the anode 4 or the cathode 2 is monitored to control the output voltage of the power supply, and the discharge intensity is maintained at a predetermined value. Target 2 with ionized gas by magnetron discharge
0 is sputtered, and the material of the sputtered target 20 floats in the discharge space, reaches the object S to be processed, and is deposited.
The film thickness on the surface of the object S to be processed is monitored by a film thickness meter (not shown), and when the film thickness reaches a predetermined value, the process ends.

In the magnetron discharge treatment apparatus having the above operation, in the discharge space, electrons emitted from the cathode 2 due to a strong electric field, electrons generated by ionization of gas molecules, and further electrons emitted from the target 20 during sputtering. And so on. These electrons are pulled by the anode 4 by the electric field between the cathode 2 and the anode 4 and are captured by the magnetic field generated by the magnet 5, and move by Lorentz force. The movement of electrons in the orthogonal electromagnetic field is described in, for example, "Applied Physics" Vol. 41, No. 5, page 451. In this way, the electrons captured in the magnetic field in the discharge space gradually approach the anode 4 while moving by the Lorentz force, and finally flow into the anode 4. still,
Although it is the state of the discharge space, it may not be in the plasma state. According to a recent study by the inventors of the present application, in the case of a flat magnetron discharge with a high electric field and a high magnetic field,
It has been confirmed that in a high vacuum of 10 ^-1 Pa or less, the state of the discharge space changes from a plasma state to a state in which negative space charges are dominant (“Vacuum”, Vol. 35, No. 2, 70 to 7).
Page 5).

Next, the object holder 3 in this embodiment
The handling of the potential will be described below. The potential of the object holder 3 is appropriately changed to control the charged particles reaching the object S to be processed. The control of the charged particles is roughly classified into (1) when the amount or energy of the charged particles reaching the object to be processed is controlled to be zero, and (2) when a predetermined amount or energy of cations reaches. In the case of controlling, (3) it is divided into three cases of controlling so that electrons or negative ions of a predetermined amount or energy reach. In the following description, the control of (1) will be described in detail.

In the conventional apparatus shown in FIG. 5, as is clear from the above description, magnetic force lines 53 contacting the object S to be processed (hereinafter referred to as tangential magnetic force lines of the object to be processed) 53 become magnetic field lines forming a closed region. , The electron is the tangential magnetic field line 5 of the object to be processed
In the vicinity where 3 is in contact with the processing object S, the processing object S
Most often flows into. Such a local inflow of electrons into the object S to be processed generally causes damage to the object S to be processed. For example, when a thin film for Al wiring is formed by the magnetron sputtering method, a portion such as a MOS element formed in advance may be damaged by inflowing electrons, which may cause a circuit failure. Such damage to the object S to be processed is not limited to electrons, but is also caused by collision of negative ions generated from the cathode 2 or the like with the object S to be processed. For example, in the case of forming a conductive optical thin film such as ITO, which has been attracting attention recently, a material that generates negative ions such as oxygen is often used as a target,
Negative ions emitted from the target may be attracted to the ground potential of the object S to be processed, reach the object S to be processed, and may collide with or flow into the object S to be processed. In this case, the object S to be processed may be damaged by the collision of the negative ions, or the negative ions may be mixed in the thin film to affect the conductivity.

When the apparatus of this embodiment is used, a closed region is formed by the tangential magnetic field lines 54 of the anode as described above, and the electrons exclusively flow into the anode 4, so that they reach the object S to be processed and damage the object S to be processed. There is nothing to do. Even in this case, if the potential of the object S to be processed is higher than the potential of the cathode 2 due to the ground potential or the like, there is an electric field between the cathode 2 and the object S to be processed. The electrons reaching the top of the anode tangential magnetic field lines 54 may reach the object S to be processed by the electric field. Therefore, in the present embodiment, the object holder 3
Is held at a predetermined negative potential by the holder power supply 32. As a result, it is possible to prevent the electrons from reaching the processing target S through the closed region. When the potential of the object holder 3 is set to the same potential as the negative potential of the cathode 2, there is no electric field between the object holder 3 and the cathode 2, which is most effective. However, if the negative potential is set too deep, there is a possibility that gas molecules, which are cations, may collide with or be mixed with the object S to be processed, and thus caution is required.

Examples of the case (2) in which a predetermined amount of cations are controlled to reach include the case of sputtering a tantalum film. "Basics of Thin Film Making" (1977
, Nikkan Kogyo Shimbun Co., Ltd., pp. 170-173, forming a tantalum film while ion bombarding improves the resistance of the formed film. Therefore, a high-quality tantalum film can be obtained by using the apparatus of the present application to hold the object holder 3 at a predetermined negative potential and perform thin film formation while colliding positive ions of a predetermined amount or energy.

Further, as an example of (3) controlling so that a predetermined amount of electrons or negative ions arrive, there is, for example, sputtering of a superconducting thin film. Oxides are often used as the superconducting thin film material, but when forming a superconducting thin film by the sputtering method, the sputtered superconducting material decomposes while floating in the discharge space, and oxygen elements become ions. May be lost in the state of. In this case, when the object holder 3 is set to a predetermined negative potential using the device of the present application so that a predetermined amount of oxygen ions reach the object S to be treated,
Since a thin film can be formed while supplementing the lost oxygen element, a high-quality superconducting thin film can be formed.

2 and 3 are diagrams showing the results of experiments for confirming the effect of controlling charged particles in the apparatus of FIG. In both figures, the horizontal axis represents the potential of the object holder and the vertical axis represents the current. Then, It is a cathode current, and Is is a current of the object holder (hereinafter, holder current). First,
In the experiment shown in FIG. 2, the potential of the target object holder 3 was changed in the range of +4 to -7 kV under the condition that the pressure during discharge was 10 ^-2 Pa and the cathode voltage was -6 kV. Was measured. The anode 4 was kept at the ground potential.
In the experiment shown in FIG. 3, the pressure was 2 × 10 ⁻¹ Pa.
Other conditions were measured under the same conditions as in FIG.

In FIG. 2, the potential of the object holder 3 is -3.
The holder current is zero near kV. Therefore, it is understood that when the control for reducing the charged particles flowing into the object to be processed to zero under this condition, the potential of the object holder 3 is set to about -3 kV. Further, in FIG. 3, -1
The holder current is zero in the vicinity of kV, and it can be seen that under this condition, the potential should be about -3 kV.
As a matter of course, the zero holder current means that the positive charge inflow amount and the negative charge inflow amount are the same as in the case where the amount of charged particles flowing into the object holder 3 is zero. The case is also included. The optimum potential of the object holder 3 may be experimentally obtained in advance as described above, or a control circuit may be provided in the holder power supply 32 so that the current flowing through the object holder 3 is zero. Various controls may be performed.
As is clear from this experiment, the holder power supply 32 may be not only direct current but also alternating current (including low frequency to ultra high frequency such as microwave). The cathode current It and the holder current Is
Is significantly different between FIG. 2 and FIG. In the case of FIG. 3 where the pressure is high, the discharge space is in the plasma state, while in the state of FIG. 2 where the pressure is low, the “negative space charge discharge” discussed in the above-mentioned “Vacuum” paper. It is considered that the cause is that the discharge space is changed to another foreign state such as ".

Next, the effect of uniformizing the processing obtained when the apparatus of this embodiment is applied to etching or the like will be described. When the magnetron discharge treatment apparatus of the above-mentioned embodiment is applied to etching or the like, the gas introduction system 12 supplies a reactive gas for generating excited active species such as CFCs to the vacuum vessel 1.
To be introduced inside. In this case, since the object S to be processed is arranged at a position away from the closed area where the electrons are confined as described above, local inflow of the electrons in the closed area to the object S to be processed is suppressed, and the object to be processed is suppressed. A non-uniform reaction on the surface of the body S is prevented. If the potential of the object holder 3 is adjusted by the holder power supply 32, the amount and energy of the charged particles reaching the object S can be controlled, so that the plasma generated by the magnetron discharge can be uniformly and optimally. The processing of the object to be processed S can be performed by utilizing it.
Since the above-described embodiment was applied to the sputtering apparatus, the object S to be processed is held in a state of facing the cathode 2. However, when applied to etching, surface modification, etc. You don't have to. It may be held at a position where it can be processed by utilizing plasma generated by electric discharge. Examples of surface modification include, for example, hardening treatment of stainless steel surface using nitrogen plasma.

Next, another embodiment of the magnetron discharge device of the present invention will be described. FIG. 4 is a schematic view of another embodiment of the magnetron discharge treatment apparatus of the present invention. This example is different from the above-described embodiment in that a peripheral magnet 55 similar to the conventional one is used instead of the pole piece 52 and a strong magnetic field is used. In this example, as shown in FIG. 4, the magnetic lines of force are gathered at a position closer to the center of the vacuum container 1, so that the position of the anode 4 is located closer to the position of the center of the vacuum container 1 than in the case of FIG. There is a need to. Also, in this example, the cathode 2
Since a magnetic field line that wraps around the side of is generated, it is necessary to provide the shield 7 similar to the conventional one. If the gap between the side surface of the cathode 2 and the shield 7 is made sufficiently small, the electrons emitted from the cathode 2 immediately flow into the shield 7 without ionizing the discharge gas, so unnecessary discharge is prevented in this portion. It

In the magnetron discharge treatment apparatus of each of the embodiments described above, the anode 4 can be constructed by using a part of the vacuum container 1 and can also be used. In this case, since the vacuum container 1 can be made small, there is an advantage that the device is simplified. Further, as the power source 22 for discharge, a high frequency discharge is used in the case of sputtering a dielectric target or in the case where it is necessary to efficiently form plasma by an etching process or the like. Since a power supply that can switch or superimpose the DC power supply and the high-frequency power supply is commercially available, it is preferable to adopt such a power supply. In FIG. 1, the discharge power source 22, the holder power source 32, and the anode power source 42 are shown as separate power sources, but in an actual device, a circuit portion in a certain power source is used. There is also.

Further, in each of the above embodiments, the shape of the anode 4 is not limited to the ring shape as described above, and various shapes such as a rod shape and a spherical shape can be adopted. Further, in the case of processing in the liquid crystal substrate process, since a square object S is to be processed, it is preferable to adopt a square cathode provided with a square magnet. Further, although the permanent magnet is used as the magnet 5 in the above embodiment, an electromagnet may be used. Further, the magnet 5 can be located outside the vacuum vessel 1 or multiple magnets can be used to achieve the desired results. That is, as disclosed in FIGS. 4 and 6 of JP-A-2-254158, another magnet is arranged so as to face the cathode 2 or surround the space above the cathode 2. By doing so, a magnetic field having a distribution as shown in FIG. 1 can be easily obtained without weakening the magnetic field strength. Particularly in the case of FIG. 6 of the publication, the ring-shaped magnet 86 is attached to the anode 4 of the present application.
It is also possible to combine the roles of.

As described above, according to the magnetron discharge treatment apparatus of claim 1 of the present application, the potential of the holder of the object to be processed can be freely changed, so that the charged particles reaching the object to be processed can be changed. It can be controlled freely. Further, since the local inflow of electrons to the object to be processed is eliminated,
When applied to etching or the like, uniform processing can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetron discharge treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a result of an experiment for confirming a charged particle control effect in the apparatus of FIG.

FIG. 3 is a diagram showing a result of an experiment for confirming a charged particle control effect in the apparatus of FIG.

FIG. 4 is a schematic view of another embodiment of the magnetron discharge treatment apparatus of the present invention.

FIG. 5 is a schematic view of a conventional magnetron discharge treatment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 10 Insulating material 11 Exhaust system 12 Gas introduction system 2 Cathode 20 Target 21 Cathode conduction tube 22 Discharge power source 3 Processing object holder 31 Holder conduction tube 32 Holder power supply S Processing object 4 Anode 41 Anode conduction tube 42 Anode Power supply 5 magnet

Claims (1)

[Claims] 1. A vacuum container, a cathode arranged inside the vacuum container, an anode provided inside the vacuum container or as a part of the vacuum container, and magnetron discharges between the cathode and the vacuum container, and a vacuum. A target object holder, which is disposed inside the container and holds the target object at a position where a predetermined process can be performed by utilizing discharge between the cathode and the anode, and a predetermined value between the cathode and the anode. A discharge power source for setting a desired electric field to perform a magnetron discharge, and a magnet for generating a magnetic field at least a part of which is orthogonal to the electric field generated by the discharge power source. Is characterized in that it holds the object to be processed at a position apart from a closed region surrounded by the magnetic field lines that come out of a part of the cathode and come into contact with the anode and enter the other part of the cathode, and the surface of the cathode. Magnetro Discharge processing equipment.