JP6942015B2 - Film formation equipment and film formation method - Google Patents

Description

The present invention relates to a technique for forming a film on a substrate surface using a plasma sputtering technique.

In the technique of forming a thin film on the surface of a substrate by sputtering a target with plasma, the film formation speed is high and good film quality can be obtained. Therefore, it is high in a magnetic field formed by a magnetic circuit using a permanent magnet. The magnetron cathode method, which generates plasma of density, is widely used. Among them, inductively coupled plasma generated by applying high-frequency power to the antenna in order to further increase the plasma density is used in combination with magnetron plasma (see, for example, Patent Documents 1 and 2).

In the plasma sputtering technique, the magnitude of the current flowing through the cathode affects the film formation rate, while the magnitude of the cathode voltage affects the film quality, more specifically, the film density in the substrate. Therefore, the power supply that supplies power to the cathode needs to be configured so that the cathode current and the cathode voltage can be appropriately managed.

JP-A-2009-062568 International Publication No. 2010/023878

When the target surface is consumed and the target thickness becomes smaller due to continuous sputtering, the distance between the plasma generation space near the target surface and the magnetic circuit becomes smaller, so that the magnetic flux density on the target surface becomes smaller. growing. As a result, the plasma density on the target surface becomes high, and the plasma impedance decreases. As a result, when the power supply tries to maintain either the cathode current or the cathode voltage at an appropriate value, the other one deviates from the appropriate value, and it is difficult to manage both the current value and the voltage value at an appropriate value. It becomes.

Therefore, in the conventional technique, there remains a problem that both the film formation rate and the film quality cannot be stably maintained in a situation where the target is consumed by sputtering.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of performing stable film formation with little fluctuation in film formation rate and film quality regardless of the consumption state of the target.

One aspect of the present invention is a film forming apparatus that forms a film on a substrate by plasma sputtering, and in order to achieve the above object, a vacuum chamber and a magnetron cathode provided in the vacuum chamber and capable of installing a target can be installed. A high-frequency antenna arranged in the vicinity of the target in the vacuum chamber, a substrate holding portion for holding the substrate facing the target in the vacuum chamber, and a sputter gas being supplied into the vacuum chamber. A gas supply unit, a cathode power source that supplies a predetermined cathode power to the magnetron cathode to generate magnetron plasma, and a high-frequency power source that supplies high-frequency power to the high-frequency antenna to generate inductively coupled plasma are provided. The power supply controls the magnitude of the high-frequency power applied to the high-frequency antenna based on the measurement result of a physical quantity that indicates the magnitude of the plasma density in the vicinity of the target surface. Here, the voltage applied to the magnetron cathode by the cathode power source is controlled by a constant voltage or the power applied to the magnetron cathode is controlled by a constant voltage, and the physical quantity is the current flowing through the magnetron cathode or plasma emission in the vicinity of the target surface. Can be strength. Further, the current flowing through the magnetron cathode by the cathode power supply is controlled by a constant current, or the power applied to the magnetron cathode is controlled by a constant power, and the physical quantity can be the voltage of the magnetron cathode.

Further, one aspect of the present invention is a film forming method in which a film is formed on a substrate by plasma sputtering, and in order to achieve the above object, a magnetron cathode having a target in a vacuum chamber, a high frequency antenna, and the above. A step of arranging the substrate, a step of supplying sputter gas into the vacuum chamber, and a power supply unit supplying a predetermined cathode power to the magnetron cathode to generate magnetron plasma and applying high frequency power to the high frequency antenna. The target is a ferromagnetic material, and the high-frequency power applied to the high-frequency antenna is a physical quantity that indicates the magnitude of the plasma density in the vicinity of the target surface. It is controlled by the power supply unit based on the measurement result of any one of the current flowing through the magnetron cathode, the voltage of the magnetron cathode, and the plasma emission intensity in the vicinity of the target surface, and is reduced with time .

Hereinafter, the current flowing through the cathode is referred to as "cathode current", and the voltage applied to the cathode is referred to as "cathode voltage". In the invention configured as described above, there is a problem that both the cathode current and the cathode voltage cannot be controlled to appropriate values only by the cathode power supply due to the progress of target consumption (erosion) due to sputtering. In view of the above, by adjusting the high-frequency power supplied to the high-frequency antenna, it is possible to control both of them to appropriate values. Specifically, it is as follows.

When the target surface is consumed due to the progress of sputtering, the magnetic flux increases on the target surface, so that the plasma density in the vicinity of the target surface increases. This increases the amount of spatter on the target, resulting in an increase in cathode current. Further, as the plasma density increases, the plasma impedance decreases, so that the cathode voltage for the same cathode current decreases. The fact that the cathode current and the cathode voltage change in tandem with the progress of erosion of the target makes it difficult for the cathode power supply to maintain both of them at appropriate values.

Here, the high-frequency antenna to which high-frequency power is applied generates inductively coupled plasma, and acts to increase the plasma density by superimposing the inductively coupled plasma on the plasma generated by the magnetron plasma. Therefore, it is possible to increase or decrease the plasma density on the target surface by increasing or decreasing the high frequency power. From this, by measuring some physical quantity that indicates the fluctuation of the plasma density and controlling the magnitude of the high-frequency power applied to the high-frequency antenna based on the measurement result, the fluctuation of the plasma density due to the consumption of the target can be determined. Compensation can be achieved by increasing or decreasing the high-frequency power.

As a result, it is possible to maintain both the current value and the voltage value of the cathode power applied from the cathode power supply to the magnetron cathode at appropriate values. As a result, film formation can be continuously performed while maintaining a constant film formation rate and film quality.

The physical quantity to be measured is preferably one of the current flowing through the magnetron cathode, the voltage of the magnetron cathode, and the plasma emission intensity near the target surface. Since the cathode current and the cathode voltage fluctuate as the target erosion progresses as described above, it is possible to detect the fluctuation of the plasma density by measuring at least one of them. Further, of course, it is possible to directly detect the fluctuation of the plasma density by directly measuring the plasma emission intensity in the vicinity of the target surface.

As described above, according to the present invention, fluctuations in magnetron plasma density caused by an increase in magnetic flux density due to wear of the target can be suppressed by increasing or decreasing the power supplied to the high-frequency antenna that generates inductively coupled plasma. .. As a result, both the current and the voltage supplied to the magnetron cathode can be maintained at appropriate values, and the film formation rate and the film quality can be stabilized to continuously perform the film formation.

It is a side view and the top view which shows the schematic structure of one Embodiment of the film forming apparatus which concerns on this invention. It is a perspective view which shows the arrangement of the main composition inside a film forming apparatus. It is a block diagram which shows the electrical structure of a film forming apparatus. It is a figure which shows the operation of a sputter source. It is a flowchart which shows the film-forming process by this film-forming apparatus. It is a figure which shows the relationship between the control system of a cathode power source, and the control input which can be adopted by a high frequency power source. It is a flowchart which shows the example of the output control processing in a high frequency power supply. It is a figure which illustrates the effect of this output control processing. It is a figure which illustrates the case where the cathode current is constant current control, and the cathode voltage is a control input. It is a figure which shows the modification of the sputter source.

FIG. 1 is a side view and a top view showing a schematic configuration of an embodiment of the film forming apparatus according to the present invention. FIG. 2 is a perspective view showing the arrangement of the main configurations inside the film forming apparatus. FIG. 3 is a block diagram showing an electrical configuration of the film forming apparatus. In order to show the directions in the following description in a unified manner, the XYZ orthogonal coordinate axes are set as shown in FIG. The XY plane represents the horizontal plane. Further, the Z axis represents the vertical axis, and more specifically, the (−Z) direction represents the vertical downward direction.

The film forming apparatus 1 is an apparatus for forming a film on the surface of the substrate S to be processed by plasma sputtering. For example, this film formation is for the purpose of forming a metal film such as titanium, chromium, nickel, or a metal oxide film such as aluminum oxide on one surface of a glass substrate as the substrate S, a flat plate made of resin, a sheet, a film, or the like. It is possible to apply the device 1. However, the material of the substrate and the film is not limited to this and is arbitrary. Although the case where the film is formed on the rectangular or single-wafer-shaped substrate S will be described here as an example, the substrate S may have an arbitrary shape.

The substrate S is conveyed in the film forming apparatus 1 in a state where most of the substrate S including the central portion of the lower surface is opened downward while the peripheral portion thereof is held by the frame-shaped tray T having an opening in the central portion. .. By doing so, even a thin or large-sized substrate S that is easily bent can be stably conveyed in a state of being maintained in a horizontal posture. In the following description, a structure in which the tray T and the substrate S are integrated by supporting the substrate S is referred to as a work Wk which is a processing target of the film forming apparatus 1. The transport mode of the substrate S is not limited to this, and is arbitrary. For example, the substrate S may be transported by itself, or may be transported with the upper surface adsorbed and held, for example. Further, the substrate is not limited to the horizontal posture, and may be conveyed, for example, in a state where the main surface is substantially vertical. In this case, the transport direction of the substrate may be either the horizontal direction or the vertical direction.

The film forming apparatus 1 includes a vacuum chamber 10, a conveying mechanism 30 for conveying the work Wk, a sputtering source 50, and a control unit 90 that controls the entire film forming apparatus 1. The vacuum chamber 10 is a hollow box-shaped member having a substantially rectangular parallelepiped outer shape, and is arranged so that the upper surface of the bottom plate is in a horizontal posture. The vacuum chamber 10 is composed mainly of a metal such as stainless steel or aluminum, but a transparent window made of, for example, quartz glass may be partially provided in order to make the inside of the chamber visible.

As shown in FIG. 3, the vacuum chamber 10 includes a shutter 11 that opens and closes between the internal space SP of the vacuum chamber 10 and an external space or a processing space in another processing chamber, and a vacuum chamber 10 for depressurizing the inside of the vacuum chamber 10. The vacuum pump 12 and the pressure sensor 13 for measuring the pressure pressure in the internal space SP of the vacuum chamber 10 are provided. Although not described in FIG. 1, the shutter 11 is provided on one or both of the (−X) side end and the (+ X) side end of the vacuum chamber 10.

The shutter 11 is opened / closed controlled by the shutter opening / closing control unit 92 provided in the control unit 90. The work Wk can be carried in and out when the shutter 11 is open, while the inside of the vacuum chamber 10 is airtight when the shutter 11 is closed. Further, the vacuum pump 12 and the pressure sensor 13 are connected to the atmosphere control unit 93 provided in the control unit 90. The atmosphere control unit 93 controls the vacuum pump 12 based on the pressure measurement result in the vacuum chamber 10 by the pressure sensor 13 to control the internal space SP of the vacuum chamber 10 to a predetermined atmospheric pressure. The atmosphere control unit 93 can set the air pressure in the vacuum chamber 10, that is, the film formation pressure in the film formation operation described later, in response to a control command from the CPU 91.

The transport mechanism 30 has a function of transporting the work Wk along a substantially horizontal transport path. Specifically, the transfer mechanism 30 rotates a plurality of transfer rollers 31 that support the work Wk in the processing chamber 10 by contacting the lower surface of the tray T that holds the substrate S, and the transfer rollers 31 to rotate the work. It is provided with a transport drive unit 32 that moves Wk in the X direction. The transport drive unit 32 is controlled by the transport control unit 94 provided in the control unit 90. The transport mechanism 30 configured in this way transports the substrate S while holding it in the horizontal posture in the vacuum chamber 10 to move the substrate S in the X direction. The movement of the substrate S by the transport mechanism 30 may be a reciprocating movement as shown by a dotted line arrow in FIG. 1, or may be one direction of either the (+ X) direction or the (−X) direction.

A sputtering source 50 is provided below the substrate S that is conveyed in the vacuum chamber 10 by the transfer mechanism 30. The sputter source 50 includes a sputter cathode 51, a pair of inductive coupling antennas 52 and 53 provided so as to sandwich the sputter cathode 51 from the X direction, and a sputter gas supply nozzle 54 that supplies sputter gas around the sputter cathode 51. , 54 and. Further, a chimney 55 formed in a box shape by a metal plate is provided so as to cover the periphery of the sputter cathode 51, the inductive coupling antennas 52 and 53, and the sputter gas supply nozzles 54 and 54.

The sputtered cathode 51 includes a backing plate 511 formed in a plate shape by a conductive material such as a copper plate. A target 512 formed in a flat plate shape (planar shape) by a film forming material on the substrate S is mounted on the upper surface of the backing plate 511. The target 512 is surrounded by the anode shield 513. That is, the anode shield 513 has a frame shape in which an opening equivalent to the plane size of the target 512 is provided on the upper surface thereof, covers the periphery of the target 512, and makes the upper surface of the target 512 on the lower surface of the substrate S through the opening. Let me face you. In addition, in the top view of FIG. 1 and FIG. 2, only the outer shape of the chimney 55 is shown by a chain double-dashed line in order to clarify the internal structure of the sputter source 50.

The lower part of the backing plate 511 is covered with a box-shaped housing 514. The housing 514 is fixed to the bottom surface of the vacuum chamber 10. A magnet unit 515 is provided in the space between the lower surface of the backing plate 511 and the housing 514, and a fluid as a refrigerant, for example, cooling water is supplied to the voids around the magnet unit 515 from a cooling mechanism 58 described later.

The magnet unit 515 arranged at the bottom of the backing plate 511 includes a yoke 515a and a plurality of magnets provided on the yoke 515a, that is, a central magnet 515b and peripheral magnets 515c provided so as to surround the central magnet 515b. .. The yoke 515a is a flat plate-like member formed of a magnetic material such as permeable steel and extended in the Y direction. The yoke 515a is fixed to the housing 514 by a fixing member (not shown).

A central magnet 515b extending in the Y direction is arranged on the center line of the upper surface of the yoke 515a along the longitudinal direction (Y direction). Further, an annular (endless) peripheral magnet 515c surrounding the periphery of the central magnet 515b is provided on the outer edge of the upper surface of the yoke 515a. The central magnet 515b and the peripheral magnet 515c are, for example, permanent magnets. The polarities of the central magnet 515b and the peripheral magnet 515c on the side facing the lower surface of the backing plate 511 are different from each other. Therefore, the magnet unit 515 forms a static magnetic field around the target 512. In this way, the backing cathode plate 511 equipped with the target 512, the magnet unit 515, the housing 514, and the like integrally form the magnetron cathode.

A pair of inductively coupled antennas 52, 53 are provided so as to sandwich the sputtering cathode 51 in the vacuum chamber 10 so as to project from the bottom surface of the vacuum chamber 10. The inductively coupled antennas 52 and 53 are also called LIA (Low Inductance Antenna: a registered trademark of EMD Co., Ltd.), and as shown in FIG. 2, conductors 521 and formed in a substantially U shape. The surface of 531 has a structure in which the surface is coated with a dielectric material such as quartz 522,532. The conductors 521 and 531 are extended in the Y direction through the bottom surface of the vacuum chamber 10 in a state where the U-shape is turned upside down. A plurality of conductors 521 and 531 are arranged side by side at different positions in the Y direction. The dielectric 522 may be provided independently so as to individually cover each of the plurality of conductors 521, or may be provided so as to collectively cover the plurality of conductors 521. The same applies to the dielectric 532.

The structure in which the surfaces of the conductors 521 and 531 are coated with the dielectric 522 and 532 prevents the conductors 521 and 531 from being exposed to plasma. As a result, the constituent elements of the conductors 521 and 531 are prevented from being mixed into the film on the substrate S. Further, as will be described later, inductively coupled plasma is generated by the high frequency current applied to the conductors 521 and 531, and it is possible to suppress abnormal discharge such as arc discharge and generate stable plasma.

Each of the conductors 521 and 531 of the inductively coupled antennas 52 and 53 configured in this way can be regarded as a loop antenna having the X direction as the winding axis direction and the number of windings being less than 1. Therefore, it has a low inductance. By arranging a plurality of such small antennas side by side in a direction orthogonal to the winding axis direction, it is possible to form an induced magnetic field for plasma generation, which will be described later, in a wide range while suppressing an increase in inductance. be. Further, by arranging a pair of antenna trains each consisting of a plurality of antennas arranged in the Y direction in parallel with each other separated in the X direction, a strong and uniform induced magnetic field can be generated in the space sandwiched between the two antenna trains. ..

A sputter gas (for example, an inert gas) is introduced from the gas supply unit 56 into the space around the sputter cathode 51 sandwiched between the inductive coupling antennas 52 and 53. Specifically, a pair of nozzles 54 and 54 connected to the gas supply unit 56 are provided on the bottom surface of the vacuum chamber 10 so as to sandwich the sputtering cathode 51 from the X direction. The gas supply unit 56 supplies an inert gas as a sputter gas, for example, argon gas or xenon gas, to the nozzles 54 and 54 in response to a control command from the film forming process control unit 95. The sputter gas is discharged from the nozzles 54 and 54 toward the periphery of the sputter cathode 51. The gas supply unit 56 preferably has a flow rate adjusting function for automatically controlling the flow rate of the sputtered gas, and may be provided with, for example, a mass flow controller.

An optical probe 59 made of, for example, an optical fiber is arranged in the chimney 55 so as to face the surface of the target 512, and a part of the plasma emission generated in the space inside the chimney 55 is incident on the optical probe 59. The optical probe 59 is connected to a spectroscope (not shown), and the output signal of the spectroscope is input to the control unit 90.

The control unit 90 measures the plasma emission intensity in the plasma space by the plasma emission method (PEM) based on the output signal of the spectroscope. Specifically, by measuring the light intensity of a substance-specific spectral component of film-formed particles flying from the target 512 by sputtering, atoms or molecules excited in the plasma, ions, etc. (for example, argon atom), the plasma Detect the concentration of the substance in space. Thereby, the plasma density in the plasma space can be obtained.

FIG. 4 is a diagram showing the operation of the spatter source. An appropriate voltage is applied from the power supply unit 57 between the sputtering cathode 51 and the inductively coupled antennas 52 and 53. Specifically, the backing plate 511 of the sputtered cathode 51 is connected to the cathode power supply 571 provided in the power supply unit 57, and an appropriate negative potential with respect to the ground potential is given to the backing plate 511 from the cathode power supply 571. As the voltage output by the cathode power supply 571, a DC, DC pulse, sine wave AC, square wave AC, square wave AC pulse, or a voltage obtained by superimposing some of them can be used. However, in the following description, the term "cathode voltage" refers to the voltage in the negative direct current or negative alternating current components of various waveforms output from the cathode power supply 571. On the other hand, the inductively coupled antennas 52 and 53 are connected to the high frequency power supply 572 provided in the power supply unit 57 via matching circuits 575 and 576, respectively, and an appropriate high frequency power is applied from the high frequency power supply 572.

The voltage waveforms output from each of the cathode power supply 571 and the high frequency power supply 57 2 are set by a control command from the film formation process control unit 95 of the control unit 90. Further, a current measuring unit 573 is inserted in the middle of the wiring from the cathode power supply 572 to the backing plate 511, and the current measuring unit 573 measures the current flowing through the wiring, that is, the cathode current. The detection output of the current measuring unit 573 is input to the cathode power supply 571 and the high frequency power supply 572. Further, a voltage measuring unit 574 is provided between the wiring and the device ground, and the cathode voltage, more specifically, the DC voltage of the backing plate 511 with respect to the ground potential is measured. The detection output of the voltage measuring unit 574 is also input to the cathode power supply 571 and the high frequency power supply 572.

The cathode power supply 571 controls the output power based on the value of the cathode current measured by the current measuring unit 573 and the value of the cathode voltage measured by the voltage measuring unit 574. As the control method, constant current control that keeps the cathode current value constant, constant voltage control that keeps the cathode voltage value constant, and constant power control that keeps the product of the cathode current and the cathode voltage constant can be selected. Is.

On the other hand, in addition to the outputs from the current measuring unit 573 and the voltage measuring unit 574, the high frequency power supply 57 2 receives the detection output from the optical probe 59 for measuring the plasma emission intensity. Although it is described in FIG. 4 that the optical probe 59 and the high frequency power supply 572 are directly connected for the purpose of explaining the principle, in reality, it is based on the signal given from the optical probe 59 via the spectroscope. A value corresponding to the magnitude of the plasma density detected by the control unit 90 is given from the control unit 90 to the high frequency power supply 572. The mode of output control by the high frequency power supply 572 will be described later.

When high-frequency power (for example, high-frequency power with a frequency of 13.56 MHz) is supplied from the high-frequency power source 572 to the inductively coupled antennas 52 and 53, a high-frequency induced magnetic field is generated in the surrounding space of the inductively coupled antennas 52 and 53, and plasma of sputter gas is generated. More specifically, a mixed plasma of a magnetron plasma and an inductively coupled plasma (ICP) is generated. The sputtered cathode 51 including the target 512 and the magnet unit 515 and the inductively coupled antennas 52 and 53 both extend long along the Y direction perpendicular to the paper surface of FIG. Therefore, the plasma space PL in which plasma is generated also becomes a space region having a shape elongated in the Y direction along the surface of the sputtering cathode 51.

The cations contained in the plasma thus generated in the plasma space PL (indicated by white circles in the figure) collide with the sputtered cathode 51 to which a negative potential is applied. As a result, the surface of the target 512 is sputtered, and fine particles of the target material flying from the target 512 adhere to the lower surface of the substrate S as film-forming particles (indicated by black circles in the figure). As a result, a film is formed on the surface (lower surface) of the substrate S. Specifically, a film is formed by plasma sputtering on a band-shaped region along the Y direction of the lower surface of the substrate S, and the substrate S is scanned in a direction parallel to the main surface and orthogonal to the Y direction, that is, in the X direction. By moving, film formation is performed two-dimensionally over the entire film formation target area.

By providing the chimney 55 so as to cover the plasma space PL, it is possible to prevent the plasma particles generated in the plasma space PL and the film-formed particles sputtered from the plasma particles from scattering into the vacuum chamber 10 and from the surface of the target 512. The flying direction of the film-formed particles flying by sputtering is limited to the direction toward the substrate S. Therefore, the target material can be efficiently contributed to the film formation. By supplying the cooling water from the cooling mechanism 58 to the sputtering cathode 51, the temperature rise of the target 512 exposed to the plasma is suppressed.

As shown in FIG. 3, in addition to the above, the control unit 90 includes a CPU (Central Processing Unit) 91 that performs various arithmetic processes, a memory and storage 96 that stores programs and various data executed by the CPU 91, an external device, and a user. It is equipped with an interface 97 and the like for exchanging information between the two. For example, a general-purpose computer device can be used as the control unit 90. Each functional block such as the shutter open / close control unit 92, the atmosphere control unit 93, the transfer control unit 94, and the film formation process control unit 95 provided in the control unit 90 is realized by dedicated hardware. It may also be realized on software executed by the CPU 91.

FIG. 5 is a flowchart showing a film forming process by this film forming apparatus. This process is realized by causing each part of the film forming apparatus 1 to perform a predetermined operation based on a control program prepared in advance by the control unit 90. The exhaust in the vacuum chamber 10 is started prior to the work Wk including the substrate S to be formed into the film forming apparatus 1 (step S101).

The lighting of the plasma is started in a state where the inside of the vacuum chamber 10 is controlled to a predetermined atmospheric pressure (step S102). Specifically, the sputter gas is discharged from the nozzle 54 into the vacuum chamber 10 at a predetermined flow rate. Then, when the power supply unit 57 applies a predetermined voltage to each of the sputtering cathode 51 and the inductively coupled antennas 52 and 53, a mixed plasma of magnetron plasma and inductively coupled plasma is generated in the vacuum chamber 10.

In this way, the shutter 11 is opened with the plasma lit in the vacuum chamber 10 in advance, and the work Wk is received in the vacuum chamber 10 (step S103). In order to stabilize the lighting state of the plasma, it is desirable that the work Wk is carried in from another vacuum chamber (not shown) maintained in a vacuum state similar to that of the vacuum chamber 10. The same applies when the work is carried out after the film forming process. The shutter for receiving the work Wk before the film forming process and the shutter for discharging the work Wk after the film forming process may be different.

When the work Wk is carried into the vacuum chamber 10, the transfer mechanism 30 scans and moves the work Wk in the X direction (step S104). As a result, a film having a composition containing the target material is formed on the lower surface of the substrate S in the work Wk. A reactive gas (for example, oxygen gas) may be further supplied to the plasma space PL to form a film (for example, a metal oxide film) containing the component of the target 512 and the component of the reactive gas.

By scanning and moving the work Wk by the transport mechanism 30, it is possible to change the landing position of the film-formed particles on the lower surface of the substrate S to form a film on the entire substrate S. By continuing such scanning movement of the work Wk for a predetermined time (step S105), a film having a predetermined thickness is formed on the surface (lower surface) of the substrate S. The work Wk after the film formation on which the film is formed on the substrate S is discharged to the outside (step S106). Then, if there is a work Wk to be processed next (YES in step S107), the process returns to step S103, accepts a new work Wk, and executes the same film forming process as described above. If there is no work to be processed (NO in step S107), the termination process for shifting each part of the apparatus to a state in which the operation can be terminated is executed (step S108), and the series of operations is terminated.

Next, the output control of the high frequency power supply 572 will be described. In this film forming apparatus 1, a mixed plasma of magnetron plasma and inductively coupled plasma is generated in the vicinity of the target 512, and the surface of the target is sputtered to form a film on the substrate S. Here, when the surface of the target 512 is sputtered and its surface is consumed and the thickness of the target 512 is reduced, the distance between the surface of the target 512 and the magnet unit 515 is reduced, so that the magnetic flux density of the static magnetic field on the surface of the target 512 is reduced. Will be higher. As a result, the plasma density near the surface of the target 512 increases, and the amount of sputtering of the target 512 increases.

An increase in the amount of sputtering leads to an improvement in the film formation rate, but since the plasma impedance decreases as the plasma density increases, the cathode voltage tends to decrease for the same cathode current. Cathode voltage is a factor that affects film quality, especially film density, and an increase in plasma density results in an increase in film formation rate but a decrease in film quality.

In particular, when the target 512 is made of a ferromagnetic material such as metallic nickel, the magnetic shielding effect of the target 512 becomes weaker as its thickness decreases. Therefore, the magnetic flux density near the surface of the target 512 fluctuates greatly, and the plasma density also fluctuates.

In order to perform film formation while stably maintaining the film formation rate and film quality in continuous film formation, it is required that there is little fluctuation in both the cathode current and the cathode voltage during the film formation process. This problem can be solved by moving the magnet unit 515 away by the amount of reduction in the target thickness, but the equipment cost will increase significantly to realize the mechanism and control for moving the heavy and large magnet unit with excellent position accuracy. Is inevitable.

As described above, the cathode power supply 571 can adopt various control methods of constant power control, constant current control, and constant voltage control, and all of them can stably maintain both the cathode current and the cathode voltage. It's not a thing. This is because the cathode current and the cathode voltage are related to each other via the plasma impedance, and the cathode current and the cathode voltage are controlled by the cathode power supply 571 in response to the decrease in the plasma impedance due to the increase in the plasma density. This is because if one of the above values is set to an appropriate value, the other value deviates from the appropriate value.

Therefore, in this embodiment, the plasma density is stabilized by changing the high-frequency power applied to the inductively coupled antennas 52 and 53. Specifically, the plasma density is stabilized by measuring the physical quantity that changes with the fluctuation of the plasma density in the plasma space PL and controlling the magnitude of the high-frequency power output by the high-frequency power supply 572 based on the measurement result. As a result, both the cathode current and the cathode voltage supplied from the cathode power supply 571 to the sputtered cathode 51 are maintained at appropriate values.

Examples of the physical quantity that indicates the plasma density include the magnitude of the cathode current, the magnitude of the cathode voltage, and the plasma emission intensity. As described above, as the plasma density increases, the amount of sputtering of the target 512 increases, and therefore the cathode current also increases. That is, an increase in the cathode current under constant power control of the cathode power supply 571 means that the plasma density is increasing. Further, when the plasma impedance decreases due to the increase in plasma density, the cathode voltage decreases. That is, a decrease in the cathode voltage under constant power control of the cathode power source 571 indicates an increase in plasma density.

Further, as described above, it is possible to estimate the plasma density from the measurement result of the plasma emission intensity in the vicinity of the surface of the target 512. Further, it is also possible to actually measure the film thickness of the substrate S on which the film is formed and indirectly estimate the plasma density from the film thickness. In particular, if the film thickness can be measured in real time during film formation, the measured film thickness can be used for controlling high-frequency power as a physical quantity as an index of plasma density.

In this embodiment, the high-frequency power supply 572 controls the output power by using an appropriate physical quantity among them as a control input. More specifically, the output power of the high frequency power supply 572 is controlled so that the measured value of the physical quantity to be controlled and input satisfies a predetermined target value or target range. In particular, when the cathode current or the cathode voltage is used as the control input, the output power of the high frequency power supply 572 is determined based on the result of detecting the state of power supply from the cathode power supply 571 to the sputtered cathode 51.

FIG. 6 is a diagram showing the relationship between the control method of the cathode power supply and the control input that can be adopted by the high frequency power supply. In the figure, the “◯” mark indicates that the physical quantity used as the control input of the high frequency power supply 572 is consistent with the output control of the cathode power supply 571, that is, it can be appropriately used as the control input. On the other hand, the "-" mark indicates that the control of the high-frequency power supply 572 using the physical quantity as the control input and the output control of the cathode power supply 571 do not match.

When the cathode power supply 571 controls the output so that the cathode current is constant, that is, the cathode power supply 571 can determine the high frequency output by using the cathode voltage as a control input. In this case, the output of the high frequency power supply 572 is controlled so that the measured value of the cathode voltage becomes a target value (or within the target range, the same applies hereinafter). Since the cathode current is constantly controlled by the cathode power supply 571, both the cathode current and the cathode voltage are maintained at the target values as a result.

Since the output of the cathode power supply 571 is controlled by a constant current, the cathode current and the plasma density are controlled to appropriate values. Therefore, even if these physical quantities are used as control inputs for the high-frequency power supply 572, the cathode voltage cannot be maintained properly.

When the cathode power supply 571 controls the output by constant voltage control, that is, the output is controlled so that the cathode voltage becomes constant, the high frequency power supply 572 can determine the high frequency output by using the cathode current or the plasma emission intensity as a control input. In this case, the output of the high frequency power supply 572 is controlled so that the measured value of the cathode current or the plasma emission intensity becomes a target value. When the cathode voltage is controlled to be constant, the plasma density increases and the cathode current increases as the erosion of the target 512 progresses.

By detecting such an increase and adjusting the high frequency output, it is possible to suppress an increase in the cathode current and the plasma density. That is, both the cathode current and the cathode voltage can be maintained at the target values. Since the cathode voltage is controlled by a constant voltage, even if this is used as a control input, the control does not correspond to the fluctuation of the cathode current.

When the cathode power supply 571 controls the output so that the product of the cathode current and the cathode voltage is constant, the individual values of the cathode current and the cathode voltage can be unstable, but one of them is high frequency. By stabilizing the power supply 572 by adjusting the high-frequency output, the other is also stable. That is, both the measured values of the cathode current and the cathode voltage can be used as the control input of the high frequency power supply 572.

Further, even when the plasma emission intensity is used as the control input, the cathode current is stabilized by performing high-frequency power control so that the plasma density indexed by the control input becomes constant. Therefore, the constant power control of the cathode power supply 571 is performed. The cathode voltage is also stable. Therefore, in this case, any of the cathode current, the cathode voltage, and the plasma emission intensity can be established as control inputs.

FIG. 7 is a flowchart showing an example of output control processing in a high frequency power supply. Here, the control operation of the high frequency power supply 572 when the cathode power supply 571 performs constant voltage control and the cathode current is used as the control input is illustrated. However, even when the control method of the cathode power supply 571 and the physical quantity of the control input are different from those of the high frequency power supply 571, the processing flow can be created in the same way. This process may be executed by, for example, a controller (not shown) built in the high frequency power supply 572, or the CPU 91 or the film forming process control unit 95 provided in the control unit 90 of the film forming apparatus 1 executes this process to perform the high frequency. It may be realized by giving an output instruction to the power source 571.

A preset high-frequency voltage and current are output from the high-frequency power supply 572, and application to the inductively coupled antennas 52 and 53 is started (step S201). Then, the value of the cathode current measured by the current measuring unit 573 inserted between the cathode power supply 571 and the sputtered cathode 51 is acquired (step S202). When the current value exceeds a predetermined target value (YES in step S203), the voltage and current applied to the inductively coupled antennas 52 and 53 are reduced by a magnitude corresponding to the excess (step S204). ). On the other hand, when the current value is less than the target value (YES in step S205), the voltage and current applied to the inductively coupled antennas 52 and 53 are increased by a magnitude corresponding to the shortage (step S206). .. If the cathode current matches the target value (NO in both steps S203 and S205), the current high frequency output is maintained. After that, the acquisition of the cathode current value and the adjustment of the high frequency power output associated therewith are continuously executed.

By such a process, the cathode current flowing from the cathode power source 571 to the sputtered cathode 51 is maintained at a constant value. Since the cathode voltage is controlled by the cathode power supply 571 at a constant voltage, as a result, both the cathode current and the cathode voltage are kept constant, and the electric power injected into the sputtered cathode 51 becomes constant. As a result, the film forming speed and the film quality of the film to be formed become stable.

FIG. 8 is a diagram illustrating the effect of this output control process. As shown in the graph on the upper side of FIG. 8, consider a case where the cathode current changes from the target value It to the current value Ia in a state where the cathode voltage is controlled by a constant voltage so as to be the target value Vt. As shown in the lower graph of FIG. 8, the high-frequency power supply 572 is configured so that the high-frequency power output decreases as the cathode current increases. When an increase in the cathode current from the target value It to the current value Ia is detected, the high frequency power supply 572 reduces the high frequency power output from the initial value Po to the value Pa. As a result, the plasma density in the plasma space PL decreases, and the cathode current changes in the direction of decreasing. In this way, the cathode current is maintained at the target value It. The same can be applied when the emission plasma intensity is used as the control input.

FIG. 9 is a diagram illustrating a case where the cathode current is controlled by a constant current and the cathode voltage is used as a control input. In this case, as shown in the graph on the lower side of FIG. 9, the high frequency power supply 572 is configured so that the higher the cathode voltage, the larger the high frequency power output. Therefore, as shown in the graph on the upper side of FIG. 9, when the cathode voltage drops from the target value Vt to the value Vb, the high frequency power output of the high frequency power supply 572 also decreases from the initial value Po to the value Pb. Since the decrease in the cathode voltage under constant current control is caused by the decrease in the plasma impedance due to the increase in the plasma density, it is possible to recover the cathode voltage by lowering the high frequency power and lowering the plasma density. In this way, the cathode voltage is maintained at the target value Vt.

In addition, in FIGS. 8 and 9, for the purpose of explaining the principle, the high frequency power is drawn so as to change linearly with respect to the control input, but these may have a non-linear relationship. Further, when the cathode power supply 571 controls the output with constant power, the relationship between the current and the voltage in the upper graphs of FIGS. 8 and 9 is represented by a parabolic line, but even in that case, the figure is shown. By adjusting the output of high-frequency power to stabilize one of the cathode current and the cathode voltage by the same principle as in 8 or 9, the other is uniquely determined.

Further, in FIGS. 8 and 9, the target values It and Vt of the cathode voltage and the cathode current are set to unique values, respectively. It may be defined.

Further, here, a case where the cathode current changes in the direction of increasing in the constant voltage control (FIG. 8) and a case in which the cathode voltage changes in the direction of decreasing in the constant current control (FIG. 9) have been described as examples. In each of these cases, the high frequency power will be changed in the direction of decreasing. The reason for giving such an example is as follows.

Considering the fluctuation of the plasma density due to the erosion of the target 512, the thickness of the target 512 changes only in the decreasing direction, so that the magnetic flux on the surface of the target 512 becomes irreversibly stronger as the sputtering progresses. Therefore, the progress of erosion acts in the direction of increasing the plasma density. From this, it is sufficient that the high frequency power is controlled so as to suppress the increase in the plasma density.

In other words, when focusing on the response to erosion of the target 512, the high-frequency power supplied to the inductively coupled antennas 52 and 53 is relatively large in the initial stage when the consumption of the target 512 is small, and the supplied power increases as the consumption progresses. It suffices if the output from the high frequency power supply 572 is controlled so as to gradually decrease. Therefore, for example, a configuration in which the high-frequency power output is gradually reduced based on a preset schedule can be considered. However, from the viewpoint of control stability, output control using a physical quantity that indicates a change in plasma density as a control input as described above is more effective.

Further, the output control process of the present embodiment illustrated in FIG. 7 has a process content that can deal with both an increase and a decrease in the physical quantity used as the control input. Therefore, it is possible to cope with fluctuations in plasma density due to various causes different from the target erosion, and it is possible to continuously perform film formation with stable film formation rate and film quality.

As described above, in this embodiment, in the plasma sputtering film forming apparatus 1 using a magnetron as a plasma generation source, high-frequency power that is applied to the inductively coupled antennas 52 and 53, which are high-frequency antennas, to generate inductively coupled plasma. The size of is controlled based on the measurement result of the physical quantity that indicates the plasma density near the target surface. Therefore, the increase in plasma density caused by the increase in magnetic flux density due to the consumption of the target is suppressed by adjusting the high frequency power. Therefore, the film can be formed while maintaining both the cathode current and the cathode voltage supplied from the cathode power source 571 to the sputtered cathode 51 at appropriate values.

The cathode current is a factor that affects the film formation rate, and the cathode voltage is a factor that affects the film quality (more specifically, the film density) of the film to be filmed. By performing the film formation in a state in which these are properly controlled, it is possible to continuously perform a stable film formation while suppressing fluctuations in the film formation rate and the film quality. Therefore, a film having good film quality can be stably obtained. In addition to this, even if the thickness of the target changes, the film formation result is not affected, so that the target material can be used efficiently. As a result, the loss of the target material can be suppressed and the frequency of replacement of the target can be reduced, so that the film formation cost can also be reduced.

As described above, in the above embodiment, the sputtered cathode 51 including the magnet unit 515 functions as the "magnetron cathode" of the present invention. Further, the transport mechanism 30, particularly the transport roller 31, functions as the "board holding portion" of the present invention. Further, both the inductively coupled antennas 52 and 53 function as the "high frequency antenna" of the present invention. Further, in the inductively coupled antennas 52 and 53, the conductors 521 and 531 correspond to the "linear conductor" of the present invention, and the dielectrics 522 and 532 correspond to the "dielectric layer" of the present invention.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, two sets of inductively coupled antennas 52 and 53 are arranged in the vacuum chamber 10 with one set of sputtering cathodes 51 interposed therebetween. However, the arrangement of the sputtered cathode and the inductively coupled antenna in the sputter source is not limited to this, and for example, the following arrangement is also possible.

FIG. 10 is a diagram showing a modified example of the spatter source. Here, only the arrangement of the sputtering cathode and the inductively coupled antenna among the parts constituting the film forming apparatus is shown, but other configurations provided in the above embodiment are also appropriately arranged. In the modified example shown in FIG. 10A, two sets of sputter cathodes 612 and 613 are arranged so as to sandwich one set of inductively coupled antennas 611. Further, in the modified example shown in FIG. 10B, two sets of inductively coupled antennas 623 and 624 are arranged with two sets of sputter cathodes 621 and 622 arranged side by side. Further, in the modified example shown in FIG. 10 (c), two sets of sputter cathodes 631, 632 and three sets of inductively coupled antennas 633, 634, 635 are alternately arranged.

Even with these configurations, inductively coupled plasma is generated around the sputtered cathode by supplying high-frequency power to the inductively coupled antenna and supplying cathode power to the sputtered cathode, thereby realizing sputtering of the target and film formation on the substrate. ..

Further, in the above embodiment, a planar cathode having a target formed in a flat plate shape is used as the sputtering cathode, and the target is fixed in the vacuum chamber. In the conventional magnetron plasma sputtering film formation, the utilization efficiency of the target deteriorates due to the local consumption of the target due to the uneven distribution of the horizontal magnetic flux parallel to the target surface. In order to solve this problem and use the target evenly, a rotary cathode method is also used in which the target is formed into a cylindrical shape and rotated to move the target and the magnetic circuit relative to each other.

Even in such a rotary cathode type film forming apparatus, the problem of an increase in magnetic flux density due to a decrease in the target thickness still remains. Therefore, by applying the same high-frequency power control as in the above embodiment, it is possible to perform a more stable film formation with excellent film quality.

Further, in the above embodiment, the high frequency power output is controlled in real time based on the measurement result of the physical quantity indicating the plasma density, but instead of this, for example, the following can be performed. That is, the film thickness may be actually measured for each film formation on one substrate, and the output value of the high frequency power in the next film formation process may be determined based on this.

Further, in the above embodiment, the power supply unit 57 is provided with a current measuring unit 573 and a voltage measuring unit 574 for measuring the cathode current and the cathode voltage. However, if the cathode power supply 571 has these measuring functions built-in for output control and the measurement results can be taken out to the outside, this measuring function should be used as a current and voltage measuring unit. May be good.

As described above, as described by exemplifying specific embodiments, the physical quantities used for controlling high-frequency power in the present invention include, for example, the current flowing through the magnetron cathode, the voltage of the magnetron cathode, and the vicinity of the target surface. It may be any of the plasma emission intensities of. All of these are physical quantities that change due to fluctuations in plasma density, and by controlling high-frequency power based on the measurement results, fluctuations in plasma density can be suppressed.

Further, for example, the high-frequency antenna may have a structure in which a linear conductor having less than one turn is covered with a dielectric layer. A high-frequency antenna having such a structure has a low inductance and can inject a large amount of high-frequency power. Therefore, it is possible to stably generate high-density inductively coupled plasma.

Specifically, for example, the cathode power supply controls the voltage applied to the magnetron cathode by a constant voltage or controls the power applied to the magnetron cathode by a constant power, and the high frequency power supply controls the high frequency power by using the current flowing through the magnetron cathode as a physical quantity. can do. According to such a configuration, the current flowing through the magnetron cathode is stabilized, and as a result, both the current and the voltage of the magnetron cathode are maintained at appropriate values.

Alternatively, the cathode power supply may be configured to control the current flowing through the magnetron cathode with a constant current or to control the power applied to the magnetron cathode with a constant power, and the high frequency power supply may be configured to control the high frequency power with the voltage of the magnetron cathode as a physical quantity. According to such a configuration, the voltage applied to the magnetron cathode is stabilized, and as a result, both the current and the voltage of the magnetron cathode are maintained at appropriate values.

Further, the cathode power supply may be configured to control the voltage applied to the magnetron cathode at a constant voltage or the power applied to the magnetron cathode to be controlled at a constant power, and the high frequency power supply may be configured to control the high frequency power using the plasma emission intensity as a physical quantity. According to such a configuration, the fluctuation of the plasma density can be suppressed by increasing or decreasing the high frequency power according to the magnitude of the plasma emission intensity. As a result, the current flowing through the magnetron cathode is stabilized, and as a result, both the current and the voltage of the magnetron cathode are maintained at appropriate values.

Further, for example, if the high-frequency power supply is configured to control the high-frequency power so that the measured value of the physical quantity is within a predetermined appropriate range, both the voltage and the current of the magnetron cathode are maintained within the appropriate range as a result of the above control. It becomes possible to do.

Further, in the present invention, the target may be a ferromagnetic material. When the target is a ferromagnetic material, the target acts as a magnetic shield, but as the thickness of the target decreases, so does the magnetic shield. Therefore, the fluctuation of the magnetic flux density on the surface of the target becomes larger than that when the target is a non-magnetic material, and it becomes difficult to stabilize the plasma density by the cathode power supply. By applying the present invention to such a case, the effect of stabilizing the plasma density obtained becomes more remarkable.

Further, for example, in the control of the high frequency power according to the present invention, the control may be such that the high frequency power applied to the high frequency antenna is reduced with time. The change in the thickness of the target due to spatter appears in the direction of irreversibly decreasing. In order to suppress the increase in plasma density due to this, it is preferable that the high frequency power is controlled so as to decrease with time. By doing so, the plasma density can be stabilized regardless of the change in the thickness of the target, and stable film formation can be performed.

The present invention can be applied to all the techniques for forming a film on a substrate by plasma sputtering using a magnetron, and is particularly suitable for a plasma sputtering film forming technique using a mixed plasma of magnetron plasma and inductively coupled plasma. be.

1 Film forming equipment 10 Vacuum chamber 31 Conveying roller (board holding part)
51 Sputtered cathode (magnetron cathode)
52,53 Inductively coupled antenna (high frequency antenna)
56 Gas supply unit 57 Power supply unit 59 Optical probe 512 Target 515 Magnet unit 521,531 Conductor (linear conductor)
522,532 Dielectric (dielectric layer)
571 Cathode power supply 57 2 High frequency power supply 573 Current measurement unit 574 Voltage measurement unit S board

Claims (6)

In a film forming apparatus that forms a film on a substrate by plasma sputtering,
With a vacuum chamber
A magnetron cathode provided in the vacuum chamber and capable of placing a target,
A high-frequency antenna arranged in the vacuum chamber in the vicinity of the target,
A substrate holding portion that holds the substrate facing the target in the vacuum chamber,
A gas supply unit that supplies sputter gas into the vacuum chamber and
A cathode power supply that supplies a predetermined cathode power to the magnetron cathode to generate magnetron plasma, and
It is equipped with a high-frequency power supply that supplies high-frequency power to the high-frequency antenna to generate inductively coupled plasma.
The cathode power supply constantly controls the voltage applied to the magnetron cathode or controls the power applied to the magnetron cathode.
The high-frequency power supply controls the magnitude of the high-frequency power applied to the high-frequency antenna based on the measurement result of the current flowing through the magnetron cathode as a physical quantity that indicates the magnitude of the plasma density in the vicinity of the target surface. Membrane device. In a film forming apparatus that forms a film on a substrate by plasma sputtering,
With a vacuum chamber
A magnetron cathode provided in the vacuum chamber and capable of placing a target,
A high-frequency antenna arranged in the vacuum chamber in the vicinity of the target,
A substrate holding portion that holds the substrate facing the target in the vacuum chamber,
A gas supply unit that supplies sputter gas into the vacuum chamber and
A cathode power supply that supplies a predetermined cathode power to the magnetron cathode to generate magnetron plasma, and
It is equipped with a high-frequency power supply that supplies high-frequency power to the high-frequency antenna to generate inductively coupled plasma.
The cathode power supply constantly controls the current flowing through the magnetron cathode or constantly controls the power applied to the magnetron cathode.
The high-frequency power supply controls the magnitude of the high-frequency power applied to the high-frequency antenna based on the measurement result of the voltage of the magnetron cathode as a physical quantity that indicates the magnitude of the plasma density in the vicinity of the target surface. Device. In a film forming apparatus that forms a film on a substrate by plasma sputtering,
With a vacuum chamber
A magnetron cathode provided in the vacuum chamber and capable of placing a target,
A high-frequency antenna arranged in the vacuum chamber in the vicinity of the target,
A substrate holding portion that holds the substrate facing the target in the vacuum chamber,
A gas supply unit that supplies sputter gas into the vacuum chamber and
A cathode power supply that supplies a predetermined cathode power to the magnetron cathode to generate magnetron plasma, and
It is equipped with a high-frequency power supply that supplies high-frequency power to the high-frequency antenna to generate inductively coupled plasma.
The cathode power supply constantly controls the voltage applied to the magnetron cathode or controls the power applied to the magnetron cathode.
The high-frequency power supply determines the magnitude of the high-frequency power applied to the high-frequency antenna based on the measurement result of the plasma emission intensity near the target surface as a physical quantity that indicates the magnitude of the plasma density in the vicinity of the target surface. A film forming device to control. The film forming apparatus according to any one of claims 1 to 3, wherein the high-frequency antenna has a structure in which a linear conductor having less than one turn is coated with a dielectric layer. The film forming apparatus according to any one of claims 1 to 4 , wherein the high-frequency power source controls the high-frequency power so that the measured value is within a predetermined appropriate range. In a film forming method in which a film is formed on a substrate by plasma sputtering,
A process of arranging a magnetron cathode having a target, a high-frequency antenna, and the substrate in a vacuum chamber.
The process of supplying sputter gas into the vacuum chamber and
A step of supplying a predetermined cathode power to the magnetron cathode from the power supply unit to generate magnetron plasma and supplying high frequency power to the high frequency antenna to generate inductively coupled plasma is provided.
The target is a ferromagnetic material
The high-frequency power applied to the high-frequency antenna is a current flowing through the magnetron cathode as a physical quantity indicating the magnitude of plasma density near the target surface, a voltage of the magnetron cathode, and plasma emission near the target surface. It is controlled by the power supply unit based on the measurement result of any of the intensities, and is reduced over time.
Film formation method.

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