JP2019059988A - Film deposition apparatus and film deposition method - Google Patents

Abstract

An object of the present invention is to provide a technique capable of performing stable film formation with little change in film formation speed and film quality regardless of the consumption state of a target. A film forming apparatus includes a vacuum chamber, a magnetron cathode provided in the vacuum chamber and capable of setting a target, a high-frequency antenna, and a substrate facing a target in the vacuum chamber. A substrate holding unit 31 for holding the substrate, a gas supply unit for supplying a sputtering gas into the vacuum chamber, a cathode power supply 571 for supplying a predetermined cathode power to the magnetron cathode to generate magnetron plasma, and a high frequency power for the high frequency antenna. And a high-frequency power source 572 for generating inductively coupled plasma by supplying the inductively coupled plasma. The high-frequency power supply 572 controls the magnitude of the high-frequency power applied to the high-frequency antenna based on the measurement result of the physical quantity indicating the magnitude of the plasma density near the target surface. [Selection diagram] FIG.

Description

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

  In the technology of forming a thin film on the substrate surface by sputtering the target by plasma, the film forming speed is high and good film quality can be obtained. Therefore, the technology is high in the magnetic field formed by the magnetic circuit using permanent magnets. A magnetron cathode system for generating a plasma of high density is widely used. Among them, there are those in which an inductively coupled plasma generated by applying high frequency power to an antenna is used in combination with a magnetron plasma in order to increase the plasma density (see, for example, Patent Documents 1 and 2).

  In plasma sputtering technology, the magnitude of the current flowing to the cathode affects the deposition rate, while the magnitude of the cathode voltage affects the film quality, more specifically, the film density on the substrate. For this reason, the power supply for supplying power to the cathode needs to be configured so that the cathode current and the cathode voltage can be properly managed.

JP, 2009-062568, A WO 2010/023878 Specification

  If the target surface is consumed and the target thickness is reduced by continuously executing sputtering, the distance between the plasma generation space in the vicinity of the target surface and the magnetic circuit is reduced, so that the magnetic flux density on the target surface is reduced. growing. This increases the plasma density on the target surface and lowers the plasma impedance. As a result, when the power supply tries to maintain either the cathode current or the cathode voltage at an appropriate value, the other is separated from the appropriate value, which makes it difficult to manage both the current value and the voltage value at an appropriate value. It becomes.

  For this reason, in the prior art, there has been a problem that it is not possible to stably maintain both the deposition rate and the film quality against the situation where the target is exhausted 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 technology capable of performing stable film formation with less fluctuation of film forming speed and film quality regardless of the consumption state of the target.

  One aspect of the present invention is a film forming apparatus for forming 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. A high frequency antenna disposed near the target in the vacuum chamber, a substrate holding unit holding the substrate opposite to the target in the vacuum chamber, and supplying a sputtering gas into the vacuum chamber A gas supply unit; a cathode power supply for supplying a predetermined cathode power to the magnetron cathode to generate magnetron plasma; and a high frequency power supply for supplying high frequency power to the high frequency antenna to generate inductively coupled plasma; A power supply indicates the magnitude of plasma density near the target surface. Based on the measurement results of the physical quantity, controlling the magnitude of the high frequency power applied to the high frequency antenna.

  Further, one aspect of the present invention is a film forming method for forming a film on a substrate by plasma sputtering, and 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 disposing a substrate, a step of supplying a sputtering gas into the vacuum chamber, a power supply section supplies a predetermined cathode power to the magnetron cathode to generate a magnetron plasma, and a high frequency power is supplied to the high frequency antenna. Supplying the high frequency antenna to generate the inductively coupled plasma, and the high frequency power supplied to the high frequency antenna is measured by the power supply unit based on the measurement result of the physical quantity indicative of the size of the plasma density in the vicinity of the target surface. It is controlled.

  Hereinafter, the current flowing to 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 it is not possible to control both the cathode current and the cathode voltage to an appropriate value only by the cathode power supply due to the progress (erosion) of the target 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 an appropriate value. Specifically, it is as follows.

  When the target surface is consumed by the progress of sputtering, the magnetic flux intensifies on the target surface, and the plasma density in the vicinity of the target surface increases. This increases the amount of sputtering of the target, resulting in an increase in cathode current. In addition, since the plasma impedance is lowered by the increase of the plasma density, the cathode voltage for the same cathode current is lowered. As described above, it is difficult for the cathode power supply to maintain both of them at an appropriate value because the cathode current and the cathode voltage change in conjunction with the progress of the erosion of the target.

  Here, the high frequency antenna to which high frequency power is given 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 plasma density and controlling the magnitude of high frequency power given to the high frequency antenna based on the measurement result, the fluctuation of plasma density due to the exhaustion of the target can be calculated. It is possible to compensate by increasing or decreasing the high frequency power.

  Thereby, in the cathode power supplied from the cathode power supply to the magnetron cathode, it is possible to maintain the current value and the voltage value 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 any one of the current flowing to the magnetron cathode, the voltage of the magnetron cathode, and the plasma emission intensity near the target surface. As described above, since the cathode current and the cathode voltage fluctuate with the progress of the erosion of the target, it is possible to detect the fluctuation of the plasma density by measuring at least one of them. Also, by directly measuring the plasma emission intensity in the vicinity of the target surface, it is of course possible to directly detect the fluctuation of the plasma density.

  As described above, according to the present invention, the fluctuation of the magnetron plasma density caused by the increase of the magnetic flux density due to the exhaustion of the target can be suppressed by the increase or decrease of the power supplied to the high frequency antenna which generates the inductively coupled plasma. . As a result, both the current and voltage supplied to the magnetron cathode can be maintained at appropriate values, and film formation can be performed continuously with stable film formation speed and film quality.

FIG. 1 is a side view and a top view showing a schematic configuration of an embodiment of a film forming apparatus according to the present invention. It is a perspective view which shows arrangement | positioning of the main structures inside the film-forming apparatus. It is a block diagram which shows the electric constitution of the film-forming apparatus. It is a figure which shows the operation | movement of a sputter | spatter 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 supply, and the control input which a high frequency power supply can employ | adopt. It is a flowchart which shows the example of the output control processing in a high frequency electric-power. It is a figure which illustrates the effect of this output control processing. It is a figure which illustrates the case where cathode current is made into constant current control, and cathode voltage is made into control input. It is a figure which shows the modification of a sputter | spatter source.

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

  The film forming apparatus 1 is an apparatus for forming a film on the surface of a 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 or nickel or a metal oxide film such as aluminum oxide on one surface of a glass substrate as a substrate S or a resin flat plate, sheet or film. It is possible to apply the device 1. However, the material of the substrate and the film is not limited to this and is optional. Although a case where film formation is performed on a rectangular or sheet-like substrate S will be described as an example here, the substrate S may have an arbitrary shape.

  The substrate S is transported in the film forming apparatus 1 by a frame-shaped tray T having an opening at the central portion, with the peripheral portion thereof being held and most of the portion including the central portion of the lower surface opened downward. . By doing so, stable transportation can be performed in a state in which the substrate S is thin or large and flexible and easily bent. In the following description, a structure in which the tray T and the substrate S are integrated as the tray T supports the substrate S is referred to as a workpiece Wk to be processed by the film forming apparatus 1. The transport mode of the substrate S is not limited to this and is optional. For example, the substrate S may be transported alone, or may be transported in a state in which the upper surface is held by suction. Further, the substrate is not limited to the horizontal posture, and may be transported, for example, in a state in which the main surface is substantially vertical. In this case, the transport direction of the substrate may be either horizontal or vertical.

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

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

  The shutter 11 is controlled to open and close by a shutter open / close control unit 92 provided in the control unit 90. In the open state of the shutter 11, the work Wk can be carried in and out, while in the closed state of the shutter 11, the inside of the vacuum chamber 10 is airtight. The vacuum pump 12 and the pressure sensor 13 are connected to an 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 pressure. The atmosphere control unit 93 can set the atmospheric pressure in the vacuum chamber 10 in the film forming operation described later, that is, the film forming pressure in accordance with a control command from the CPU 91.

  The transport mechanism 30 has a function of transporting the workpiece Wk along a substantially horizontal transport path. Specifically, the transport mechanism 30 contacts the lower surface of the tray T that holds the substrate S to rotate the transport rollers 31 and the plurality of transport rollers 31 that support the workpiece Wk in the processing chamber 10. And a transport driver 32 for moving Wk in the X direction. The conveyance drive unit 32 is controlled by a conveyance control unit 94 provided in the control unit 90. The transport mechanism 30 configured in this manner transports the substrate S in the X direction while holding the substrate S in the horizontal posture in the vacuum chamber 10. The movement of the substrate S by the transport mechanism 30 may be a reciprocating movement as shown by a dotted arrow in FIG. 1 and may be either one of (+ X) direction or (−X) direction.

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

  The sputtering cathode 51 includes a backing plate 511 formed in a plate shape of a conductive material such as, for example, a copper plate. On the top surface of the backing plate 511, a target 512 formed in a flat plate shape (planar shape) of a film forming material for the substrate S is mounted. The periphery of the target 512 is surrounded by an anode shield 513. That is, the anode shield 513 has a frame shape in which an opening equal to the planar size of the target 512 is provided on the upper surface, covers the periphery of the target 512, and the upper surface of the target 512 on the lower surface of the substrate S via the opening. I will make you face. In addition, in the top view of FIG. 1 and FIG. 2, in order to clarify the internal structure of the sputter | spatter source 50, only the chimney 55 is shown with the dashed-two dotted line.

  The lower portion of the backing plate 511 is covered by a box-shaped housing 514. The housing 514 is fixed to the bottom of the vacuum chamber 10. A magnet unit 515 is provided in a 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 from the cooling mechanism 58 described later to the space around it.

  A magnet unit 515 disposed below the backing plate 511 includes a yoke 515a and a plurality of magnets provided on the yoke 515a, ie, a central magnet 515b and a peripheral magnet 515c provided to surround the central magnet 515b. . The yoke 515a is a flat member formed of a magnetic material such as magnetically 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 disposed on a center line along the longitudinal direction (Y direction) of the upper surface of the yoke 515a. In addition, an annular (endless) peripheral magnet 515c is provided at the outer edge of the upper surface of the yoke 515a so as to surround the center magnet 515b. The central magnet 515 b and the peripheral magnet 515 c are, for example, permanent magnets. The polarities of the central magnet 515 b and the peripheral magnet 515 c on the side facing the lower surface of the backing plate 511 are different from each other. Therefore, a static magnetic field is formed around the target 512 by the magnet unit 515. As described above, the backing cathode plate 511, the magnet unit 515, the housing 514, and the like on which the target 512 is mounted together constitute a magnetron cathode.

  A pair of inductive coupling antennas 52 and 53 are provided to project from the bottom of the vacuum chamber 10 so as to sandwich the sputtering cathode 51 in the vacuum chamber 10. The inductive coupling antennas 52, 53 are also referred to as LIA (Low Inductance Antenna: registered trademark of EMD, Inc.), and as shown in FIG. For example, it has a structure in which the surface of 531 is covered with dielectrics 522, 532 such as quartz. The conductors 521 and 531 extend in the Y direction through the bottom of the vacuum chamber 10 with the U-shape upside down. A plurality of conductors 521 and 531 are arranged 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 covered with the dielectrics 522 and 532 prevents the conductors 521 and 531 from being exposed to plasma. This prevents the component elements of the conductors 521 and 531 from being mixed in the film on the substrate S. Further, as described later, inductively coupled plasma is generated by the high frequency current applied to the conductors 521 and 531, and it becomes possible to suppress abnormal discharge such as arc discharge and generate stable plasma.

  The conductors 521 and 531 of the inductive coupling antennas 52 and 53 configured in this way can be viewed as a loop antenna in which the X direction is the winding axis direction and the number of turns is less than one. Therefore, the inductance is low. By arranging a plurality of such small antennas in a direction orthogonal to the winding axis direction, it is possible to form an induction magnetic field for plasma generation described later in a wide range while suppressing an increase in inductance. is there. In addition, by arranging a pair of antenna arrays each consisting of a plurality of antennas arranged in the Y direction in parallel and spaced apart in the X direction, a strong uniform induction magnetic field can be generated in the space sandwiched by both antenna arrays. .

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

  An optical probe 59 made of, for example, an optical fiber is disposed at a position facing the surface of the target 512 in the chimney 55, and a part of plasma emission generated in a space in the chimney 55 is incident on the optical probe 59. The optical probe 59 is connected to a spectrometer (not shown), and the output signal of the spectrometer 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, the plasma intensity is measured by measuring the light intensity of a spectral component inherent to a substance with respect to film-forming particles that fly from the target 512 by sputtering, atoms or molecules excited in plasma, or ions (for example, argon atoms). The concentration of the substance in space is detected. Thereby, the plasma density in the plasma space can be determined.

  FIG. 4 shows the operation of the sputter source. An appropriate voltage is applied from the power supply unit 57 between the sputtering cathode 51 and the inductive coupling antennas 52 and 53. Specifically, the backing plate 511 of the sputtering cathode 51 is connected to the cathode power supply 571 provided in the power supply unit 57, and the cathode power supply 571 provides the backing plate 511 with an appropriate negative potential with respect to the ground potential. As a voltage output from the cathode power supply 571, a direct current, a direct current pulse, a sine wave alternating current, a square wave alternating current, a square wave alternating current pulse, and those on which some of them are superimposed can be used. However, in the following description, the term “cathode voltage” refers to the voltage at the negative direct current or negative alternating current component of various waveforms output from the cathode power supply 571. On the other hand, high frequency power supplies 572 provided in the power supply unit 57 are connected to the inductive coupling antennas 52 and 53 through matching circuits 575 and 576, respectively, and appropriate high frequency power is applied from the high frequency power supplies 572.

  The voltage waveform output from each of the cathode power supply 571 and the high frequency power supply 572 is set by a control command from the film formation process control unit 95 of the control unit 90. Further, a current measurement unit 573 is interposed in the middle of the wiring from the cathode power supply 572 to the backing plate 511, and the current measurement unit 573 measures the current flowing through the wiring, that is, the cathode current. The detection output of the current measurement unit 573 is input to the cathode power supply 571 and the high frequency power supply 572. Further, a voltage measurement 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 measurement 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 measurement unit 573 and the value of the cathode voltage measured by the voltage measurement unit 574. As a control method, it is possible to select constant current control to keep the value of cathode current constant, constant voltage control to keep the value of cathode voltage constant, and constant power control to keep the product of cathode current and cathode voltage constant. It is.

  On the other hand, in addition to the outputs from the current measurement unit 573 and the voltage measurement unit 574, the detection output from the optical probe 59 for measuring the plasma emission intensity is input to the high frequency power supply 572. Although FIG. 4 shows that the optical probe 59 and the high frequency power supply 572 are directly connected for the purpose of principle explanation, in fact, based on the signal given from the optical probe 59 through 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 aspect of output control by the high frequency power supply 572 will be described later.

  A high frequency induction magnetic field is generated in the space around the inductive coupling antennas 52 and 53 by supplying a high frequency power (for example, a high frequency power of 13.56 MHz) to the inductive coupling antennas 52 and 53 from the high frequency power supply 572 to generate plasma of sputtering gas. More specifically, a mixed plasma of a magnetron plasma and an inductively coupled plasma (ICP) is generated. Both the sputtering cathode 51 including the target 512 and the magnet unit 515 and the inductive coupling antennas 52 and 53 extend along the Y direction perpendicular to the paper surface of FIG. Therefore, the plasma space PL generated by the plasma is also a space region having a shape elongated in the Y direction along the surface of the sputtering cathode 51.

  Thus, positive ions (indicated by white circles in the figure) contained in the plasma generated in the plasma space PL collide with the sputtering cathode 51 given a negative potential. As a result, the surface of the target 512 is sputtered, and the particles of the fine 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, film formation is performed on the front surface (lower surface) of the substrate S. Specifically, film formation by plasma sputtering is performed on a band-like region along the Y direction in the lower surface of the substrate S, and the substrate S is scanned in the direction parallel to the main surface and orthogonal to the Y direction, that is, the X direction By being moved, film formation is two-dimensionally performed on the entire film formation target region.

  By providing the chimney 55 so as to cover the plasma space PL, it is suppressed that the plasma particles generated in the plasma space PL and the film-forming particles generated by being sputtered into the vacuum chamber 10 scatter from the surface of the target 512. The flight direction of the film-forming particles that has been blown by sputtering is restricted in the direction toward the substrate S. Therefore, the target material can be efficiently contributed to the film formation. By supplying cooling water from the cooling mechanism 58 to the sputter cathode 51, the temperature rise of the target 512 exposed to plasma is suppressed.

  As shown in FIG. 3, in addition to the above, the control unit 90 includes a central processing unit (CPU) 91 that performs various arithmetic processing, a memory and storage 96 that store programs executed by the CPU 91 and various data, external devices and users. Interface 97 and the like that are responsible for exchanging information between the two. For example, a general purpose computer device can be used as the control unit 90. The respective functional blocks such as the shutter open / close control unit 92, the atmosphere control unit 93, the transport control unit 94 and the film forming process control unit 95 provided in the control unit 90 are realized by dedicated hardware. And may be realized on software executed by the CPU 91.

  FIG. 5 is a flowchart showing the film forming process by this film forming apparatus. This process is realized by causing each unit of the film forming apparatus 1 to perform a predetermined operation based on a control program prepared in advance by the control unit 90. Prior to the work Wk including the substrate S which is a film formation target being carried into the film forming apparatus 1, the evacuation in the vacuum chamber 10 is started (step S101).

  With the inside of the vacuum chamber 10 controlled to a predetermined pressure, lighting of the plasma is started (step S102). Specifically, the sputtering gas is discharged from the nozzle 54 into the vacuum chamber 10 at a predetermined flow rate. Then, the power supply unit 57 applies a predetermined voltage to each of the sputtering cathode 51 and the inductive coupling antennas 52 and 53 to generate mixed plasma of magnetron plasma and inductive coupling plasma in the vacuum chamber 10.

  Thus, in a state where the plasma is turned on in advance in the vacuum chamber 10, the shutter 11 is opened, and the workpiece 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 workpiece Wk be carried in from another vacuum chamber (not shown) kept at the same degree of vacuum as the vacuum chamber 10. The same applies to the time of unloading the workpiece after the film forming process. Note that the shutter for receiving the workpiece Wk before the film forming process may be different from the shutter for discharging the workpiece Wk after the film forming process.

  When the workpiece Wk is carried into the vacuum chamber 10, the transport mechanism 30 scans and moves the workpiece Wk in the X direction (step S104). As a result, a film having a composition including the target material is formed on the lower surface of the substrate S in the workpiece 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) including the component of the target 512 and the component of the reactive gas.

  As the transport mechanism 30 scans and moves the workpiece Wk, it is possible to change the landing position of the film forming particles on the lower surface of the substrate S and perform film formation on the entire substrate S. By continuing such scanning movement of the workpiece 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 film-formed workpiece Wk 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, receives 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), end processing is executed to shift each part of the apparatus to a state in which the operation can be ended (step S108), and the series of operations is ended.

  Next, output control of the high frequency power supply 572 will be described. In the film forming apparatus 1, mixed plasma of magnetron plasma and inductively coupled plasma is generated in the vicinity of the target 512, thereby sputtering the surface of the target to form a film on the substrate S. Here, when the surface of the target 512 is consumed by sputtering 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 Becomes higher. As a result, the plasma density in the vicinity of the surface of the target 512 is increased, and the amount of sputtering of the target 512 is increased.

  An increase in the amount of sputtering leads to an increase in the deposition rate, but the plasma impedance tends to decrease as the plasma density increases, so the cathode voltage tends to decrease for the same cathode current. The cathode voltage is a factor affecting the film quality, particularly the film density, and an increase in plasma density results in the improvement of the deposition rate but the decrease of the film quality.

  In particular, when the target 512 is formed of a ferromagnetic material such as metallic nickel, for example, the magnetic shielding effect by the target 512 becomes weaker as the thickness decreases. For this reason, the magnetic flux density in the vicinity of 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 the film quality in continuous film formation, it is required that variation in both the cathode current and the cathode voltage be small during the film formation process. Although this problem is solved if the magnet unit 515 is moved away by the reduction of the target thickness, the equipment cost significantly increases to realize the mechanism and control for moving the heavy and large magnet unit with excellent positional accuracy. Is inevitable.

  As described above, the cathode power supply 571 can take various control methods of constant power control, constant current control and constant voltage control, but both can stably maintain both the cathode current and the cathode voltage. It is not a thing. The cathode current and the cathode voltage are related to each other through the plasma impedance, and the cathode current and the cathode voltage are controlled by the cathode power supply 571 in response to the decrease of the plasma impedance with the increase of the plasma density. If one of the two is to be set to the proper value, the other will be separated from the proper value.

  Therefore, in this embodiment, the plasma density is stabilized by changing the high frequency power applied to the inductive coupling antennas 52 and 53. Specifically, the physical quantity changing with the fluctuation of plasma density in the plasma space PL is measured, and the plasma density is stabilized by 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 sputtering cathode 51 are maintained at appropriate values.

  Examples of physical quantities indicative of plasma density include the magnitude of the cathode current, the magnitude of the cathode voltage, and the plasma emission intensity. As described above, when the plasma density increases, the amount of sputtering of the target 512 increases, and thus the cathode current also increases. That is, the increase of the cathode current under the constant power control of the cathode power supply 571 means that the plasma density is rising. In addition, if the plasma impedance decreases due to the increase of plasma density, the cathode voltage decreases. That is, a decrease in cathode voltage under constant power control of the cathode power supply 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. Furthermore, it is also possible to measure the film thickness of the substrate S on which the film formation has been performed and estimate the plasma density indirectly from the film thickness. In particular, if the film thickness can be measured in real time during film formation, it is possible to use the measured film thickness as a physical quantity to be an index of plasma density for control of high frequency power.

  In this embodiment, the high frequency power supply 572 controls the output power with an appropriate physical quantity among them as a control input. More specifically, the output power of the high frequency power supply 572 is controlled such that the measured value of the physical quantity to be control-input satisfies the 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 the power supply from the cathode power supply 571 to the sputter 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, a “o” mark indicates that the physical quantity is used as a control input of the high frequency power supply 572 in line with the output control of the cathode power supply 571, that is, appropriately usable as a control input. On the other hand, the “-” mark indicates that the control of the high frequency power supply 572 whose control input is the physical quantity and the output control of the cathode power supply 571 do not match.

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

  Since the output of the cathode power source 571 is constant current controlled, the cathode current and the plasma density are managed at appropriate values. Therefore, even if these physical quantities are used as the control input of the high frequency power supply 572, the cathode voltage can not be maintained properly.

  When the cathode power supply 571 performs constant voltage control, that is, controls the output such that the cathode voltage is constant, the high frequency power supply 572 can determine the high frequency output 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 such 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, an increase in cathode current and plasma density can be suppressed. That is, both the cathode current and the cathode voltage can be maintained at target values. Since the cathode voltage is controlled at a constant voltage, even this control input does not correspond to the control corresponding to the variation of the cathode current.

  When the cathode power supply 571 controls the output such that constant power control is performed, that is, the product of the cathode current and the cathode voltage is constant, the individual values of the cathode current and the cathode voltage may be unstable, Stabilization by adjusting the high frequency output of the power supply 572 makes the other stable. That is, any measured value of the cathode current and the cathode voltage can be used as a control input of the high frequency power supply 572.

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

  FIG. 7 is a flowchart showing an example of output control processing with a high frequency power supply. Here, the control operation of the high frequency power supply 572 is exemplified in the case where the cathode power supply 571 is performing constant voltage control and the cathode current is used as a control input. However, even in the case where the control method of the cathode power supply 571 and the physical quantity to be the control input with the high frequency power supply 572 are different, the processing flow can be created in the same way. For example, a controller (not shown) built in the high frequency power supply 572 may execute this process, and 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. It may be realized by giving an output instruction to the power supply 571.

  The high frequency voltage and current set in advance are outputted from the high frequency power source 572 and the application to the inductive coupling antennas 52 and 53 is started (step S201). Then, the value of the cathode current measured by the current measurement unit 573 interposed between the cathode power supply 571 and the sputtering cathode 51 is acquired (step S202). If the current value exceeds a predetermined target value (YES in step S203), the voltage and current applied to inductive coupling antennas 52 and 53 are reduced by a magnitude according to the excess (step S204). ). On the other hand, when the current value does not reach the target value (YES in step S205), the voltage and current applied to inductive coupling 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. Thereafter, the acquisition of the cathode current value and the adjustment of the high frequency power output associated therewith are continuously performed.

  By such processing, the cathode current flowing from the cathode power source 571 to the sputtering cathode 51 is maintained at a constant value. Since the cathode voltage is controlled at a constant voltage by the cathode power supply 571, as a result, both the cathode current and the cathode voltage are maintained constant, and the power injected into the sputter 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, it is assumed that the cathode current changes from the target value It to the current value Ia in a state where constant voltage control is performed so that the cathode voltage becomes the target value Vt. As shown in the lower graph of FIG. 8, the high frequency power supply 572 is configured such that the high frequency power output decreases as the cathode current increases. When the increase of 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. Thus, the cathode current is maintained at the target value It. The same can be done when emitting plasma intensity is used as a control input.

  FIG. 9 is a diagram illustrating a case where the cathode current is constant current controlled and the cathode voltage is a control input. In this case, as shown in the lower graph of FIG. 9, the high frequency power supply 572 is configured such that the higher the cathode voltage, the larger the high frequency power output. Therefore, as shown in the upper graph of FIG. 9, when the cathode voltage decreases 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 a decrease in cathode voltage under constant current control is caused by a decrease in plasma impedance due to an increase in plasma density, it is possible to recover the cathode voltage by reducing the high frequency power to reduce the plasma density. Thus, the cathode voltage is maintained at the target value Vt.

  In FIGS. 8 and 9, although it is illustrated that the high frequency power changes linearly with respect to the control input for principle explanation, they may have a non-linear relationship. Also, when the cathode power supply 571 performs constant power control of the output, the relationship between the current and the voltage in the upper graphs of FIGS. 8 and 9 is represented by a parabola, but even in that case The other is also uniquely determined by adjusting the output of the high frequency power and stabilizing one of the cathode current and the cathode voltage according to the principle similar to 8 or FIG.

  Also, although in FIG. 8 and FIG. 9 the target values It and Vt of the cathode voltage and the cathode current are respectively made unique values, as shown by attaching symbols ΔI and ΔV to the figure, as target ranges having a certain width It may be defined.

  Further, the case where the cathode current changes in the direction of increasing the constant current control (FIG. 8) and the case where the cathode voltage changes in the direction of decreasing the constant current control (FIG. 9) are described as examples. In any of these cases, the high frequency power is changed in the direction to be reduced. The reason for giving such an example is as follows.

  When considering the fluctuation of plasma density due to the erosion of the target 512, the thickness of the target 512 changes only in the decreasing direction, so the magnetic flux on the surface of the target 512 becomes irreversibly strong as the sputtering progresses. For this reason, the progress of erosion acts to increase the plasma density. From this, it is only necessary to control the high frequency power to suppress the increase of the plasma density.

  In other words, when focusing on the response to erosion of the target 512, the high frequency power supplied to the inductive coupling antennas 52 and 53 is relatively large at the initial stage when the consumption of the target 512 is small, and the supplied power It is only necessary to control the output from the high frequency power source 572 so as to decrease gradually. Therefore, for example, a configuration in which the high frequency power output is gradually reduced based on a preset schedule may be considered. However, from the viewpoint of control stability, output control using a physical quantity indicating a change in plasma density as a control input as described above is more effective.

  Further, the output control processing of the present embodiment illustrated in FIG. 7 has processing contents that can cope with both the increase and the decrease of 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 erosion of the target, and film deposition can be continuously performed with stable film deposition rate and film quality.

  As described above, in this embodiment, in the plasma sputtering deposition apparatus 1 using the magnetron as the plasma generation source, high frequency power to generate inductively coupled plasma by being applied to the inductive coupling antennas 52 and 53 which are high frequency antennas. The size of is controlled based on the measurement result of the physical quantity which 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 exhaustion of the target is suppressed by the adjustment of the high frequency power. Therefore, film formation can be performed while maintaining both the cathode current and the cathode voltage supplied from the cathode power supply 571 to the sputtering cathode 51 at appropriate values.

  The cathode current is a factor that affects the deposition rate, and the cathode voltage affects the film quality (more specifically, the film density) of the film to be deposited. By performing film formation in a state where these are appropriately controlled, it is possible to continuously perform stable film formation while suppressing fluctuations in the film formation rate and the film quality. Therefore, a film with 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 efficiently used. 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 sputtering cathode 51 provided with the magnet unit 515 functions as the “magnetron cathode” of the present invention. Further, the transport mechanism 30, in particular, the transport roller 31, functions as the "substrate holding portion" in the present invention. Further, both of the inductive coupling antennas 52 and 53 function as the "high frequency antenna" of the present invention. Further, in the inductive coupling 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 can be made other than the above without departing from the scope of the invention. For example, in the above-described embodiment, two sets of inductive coupling antennas 52 and 53 are disposed across the set of sputtering cathodes 51 in the vacuum chamber 10. However, the arrangement of the sputtering cathode and the inductive coupling antenna in the sputtering source is not limited to this, and, for example, the following arrangement is also possible.

  FIG. 10 is a view showing a modification of the sputter source. Here, only the arrangement of the sputtering cathode and the inductive coupling antenna among the components constituting the film forming apparatus is shown, but the other components included in the above embodiment are also appropriately arranged. In the modified example shown in FIG. 10A, two sets of sputtering cathodes 612 and 613 are disposed to sandwich one set of inductive coupling antenna 611. Further, in the modified example shown in FIG. 10B, two sets of inductive coupling antennas 623 and 624 are arranged with the sputtering cathodes 621 and 622 arranged two by two in a row. Further, in the modification shown in FIG. 10C, two sets of sputtering cathodes 631, 632 and three sets of inductive coupling antennas 633, 634, 635 are alternately arranged.

  With these configurations as well, the inductive coupling plasma is generated around the sputtering cathode by the RF power supply to the inductive coupling antenna and the cathode power supply to the sputtering cathode, thereby realizing the sputtering of the target and the film formation on the substrate. .

  Further, in the above embodiment, a planar cathode in which a target is formed in a flat plate shape is used as a sputtering cathode, and the target is fixed in a vacuum chamber. In conventional magnetron plasma sputtering deposition, the local consumption of the target due to the uneven distribution of horizontal magnetic flux parallel to the target surface degrades the utilization efficiency of the target. In order to solve this problem and uniformly use the target, a rotary cathode system is also used, in which the target and the magnetic circuit are moved relative to each other by forming the target in a cylindrical shape and rotating it.

  Even in such a rotary cathode type film forming apparatus, the problem of the increase in magnetic flux density due to the decrease in target thickness still remains. Therefore, by applying the same high frequency power control as that of the above embodiment, it is possible to perform more stable film deposition 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 may be possible. That is, the film thickness may be 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 current measurement unit 573 and the voltage measurement unit 574 for measuring the cathode current and the cathode voltage are provided in the power supply unit 57. However, if the cathode power supply 571 incorporates these measurement functions for output control and it is possible to take out the measurement results to the outside, this measurement function should be used as a current and voltage measurement unit. It is also good.

  As described above, as the specific embodiment has been illustrated and described, in the present invention, the physical quantities used for controlling the high frequency power include, for example, the current flowing to 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 These are all physical quantities that change due to fluctuations in plasma density, and control of high-frequency power based on the measurement results makes it possible to suppress fluctuations in plasma density.

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

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

  Alternatively, the cathode power supply can be configured to perform constant current control of the current flowing to the magnetron cathode or constant power control of the power applied to the magnetron cathode, and the high frequency power supply to control high frequency power using 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 voltage of the magnetron cathode are maintained at appropriate values.

  Furthermore, the cathode power supply can be configured to perform constant voltage control of the voltage applied to the magnetron cathode or constant power control of the power applied to the magnetron cathode, and the high frequency power supply to control the high frequency power using the plasma emission intensity as a physical quantity. According to such a configuration, the fluctuation of 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 to the magnetron cathode is stabilized, and as a result, both the current and voltage of the magnetron cathode are maintained at appropriate values.

  Also, 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 falls within a predetermined appropriate range, both voltage and current of the magnetron cathode are maintained within the appropriate range as a result of the above control. It is possible to

  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, the magnetic shielding also weakens. For this reason, the fluctuation of the magnetic flux density on the target surface is larger than in the case where the target is a nonmagnetic 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 stabilization effect of 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 thickness of the target due to sputtering appears to be irreversibly smaller. In order to suppress an increase in plasma density due to this, the high frequency power is preferably controlled to decrease with time. By doing this, it becomes possible to stabilize the plasma density regardless of the thickness change of the target and perform stable film formation.

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

1 film deposition apparatus 10 vacuum chamber 31 transport roller (substrate holding unit)
51 Sputtering 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 572 High frequency power supply 573 Current measurement unit 574 Voltage measurement unit S Substrate

Claims (11)

In a film forming apparatus for forming a film on a substrate by plasma sputtering,
A vacuum chamber,
A magnetron cathode provided in the vacuum chamber and capable of installing a target;
A high frequency antenna disposed in the vacuum chamber near the target;
A substrate holding unit for holding the substrate opposite to the target in the vacuum chamber;
A gas supply unit for supplying a sputtering gas into the vacuum chamber;
A cathode power supply for supplying a predetermined cathode power to the magnetron cathode to generate a magnetron plasma;
A high frequency power supply for supplying high frequency power to the high frequency antenna to generate inductively coupled plasma;
The high-frequency power supply controls the magnitude of the high-frequency power to be given to the high-frequency antenna based on a measurement result of a physical quantity indicating a magnitude of plasma density in the vicinity of the surface of the target.   The film forming apparatus according to claim 1, wherein the physical quantity is any one of a current flowing to the magnetron cathode, a voltage of the magnetron cathode, and a plasma emission intensity in the vicinity of the surface of the target.   The film forming apparatus according to claim 1, wherein the high frequency antenna has a structure in which a linear conductor having a number of turns of less than one turn is covered with a dielectric layer. The cathode power supply performs constant voltage control of a voltage applied to the magnetron cathode or constant power control of power applied to the magnetron cathode,
The film forming apparatus according to any one of claims 1 to 3, wherein the high frequency power supply controls the high frequency power with the current flowing to the magnetron cathode as the physical quantity. The cathode power supply performs constant current control of current flowing to the magnetron cathode, or constant power control of power supplied to the magnetron cathode,
The film forming apparatus according to any one of claims 1 to 3, wherein the high frequency power supply controls the high frequency power with the voltage of the magnetron cathode as the physical quantity. The cathode power supply performs constant voltage control of a voltage applied to the magnetron cathode or constant power control of power applied to the magnetron cathode,
The film forming apparatus according to any one of claims 1 to 3, wherein the high frequency power supply controls the high frequency power with the plasma emission intensity as the physical quantity.   The film forming apparatus according to any one of claims 4 to 6, wherein the high frequency power source controls the high frequency power so that the measured value falls within a predetermined proper range. In a film forming method for forming a film on a substrate by plasma sputtering,
Placing a magnetron cathode having a target, a radio frequency antenna and the substrate in a vacuum chamber;
Supplying a sputtering gas into the vacuum chamber;
Supplying a predetermined cathode power from the power supply unit to the magnetron cathode to generate a magnetron plasma, and supplying a high frequency power to the high frequency antenna to generate an inductively coupled plasma;
The film forming method, wherein the high frequency power supplied to the high frequency antenna is controlled by the power supply unit based on a measurement result of a physical quantity indicating a magnitude of plasma density in the vicinity of the target surface.   The film forming method according to claim 8, wherein the physical quantity is any one of a current flowing to the magnetron cathode, a voltage of the magnetron cathode, and a plasma emission intensity in the vicinity of the surface of the target.   The film forming method according to claim 8, wherein the target is a ferromagnetic material.   The film forming method according to any one of claims 8 to 10, wherein the high frequency power supplied to the high frequency antenna is reduced with time.

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