JP2015056529A - Film forming method and film forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an aluminum oxide film at a high film forming speed while stabilizing an oxidation degree.SOLUTION: A film forming method comprises the steps of: generating high frequency induction coupling plasma by supplying high-frequency power to a high-frequency antenna under a mixed atmosphere of a sputtering gas and a reactive gas of oxygen and forming an aluminum oxide film on a substrate by generating magnetron plasma by applying sputter voltage to a target by constant voltage control of a sputtering power supply (film forming step); and supplying the reactive gas during the film forming step (gas supply step). The gas supply step supplies the reactive gas so that reactive sputtering is performed in a transition state. The film forming step performs first film forming processing and second film forming step. First film forming processing forms an aluminum oxide film on the substrate under a plurality of plasma generation conditions. Second film forming processing further forms an aluminum oxide film at least one film forming speed faster than the film forming speed of first film forming processing.

Description

  The present invention relates to a technique for forming an aluminum oxide film on a substrate.

In recent years, with the demand for higher efficiency of solar cells, an effective passivation film on the p-type silicon surface has been demanded. For the silicon wafer p-type surface, SiNx and SiO ₂ having a positive charge are not appropriate in terms of field effect, and ideally a film having a negative charge is required. It is known that aluminum oxide (Al ₂ O ₃ ) is suitable as the passivation film having negative charges.

For example, Patent Document 1 describes a technique for forming a thin film (passivation film) of aluminum oxide (Al ₂ O ₃ ) on the back surface of a p-type silicon substrate using an ALD method (atomic layer deposition method). .

  In addition, the formation of an aluminum oxide film by magnetron sputtering has been studied. The magnetron sputtering method is widely put into practical use in the field of manufacturing semiconductors, liquid crystal display devices, magnetic recording devices, optical thin films and the like as one of thin film forming methods. In the magnetron sputtering method, a high-frequency magnetron sputtering method (Patent Document 2) in which a compound thin film is formed by using a compound target such as an oxide, nitride, or fluoride and using a high-frequency power source as a sputtering power source, or a metal target is used. There is a reactive DC magnetron sputtering method (Patent Document 3) in which a direct current power source is used as a sputtering power source and a reactive gas is introduced to form a thin film of metal oxide, nitride, fluoride or the like.

JP 2012-39088 A JP 2004-31493 A JP-A-8-232064

  However, since the ALD method is often extremely slow in film formation, the method of generating an aluminum oxide film by the method of Patent Document 1 is not suitable for mass production.

  In addition, it is difficult to increase the deposition rate even by the methods of Patent Documents 2 and 3 because the hardness of aluminum oxide is very high and the target surface is covered with aluminum oxide.

  In addition, in order to form an aluminum oxide film having a high passivation effect on the p-type Si surface in the sputtering method, oxidation of the aluminum oxide film to be formed is performed so as to have an oxidation degree when reactive sputtering is performed in a transition state. It is necessary to control the degree with a high degree of accuracy. However, when an aluminum oxide film is formed by the methods disclosed in Patent Documents 2 and 3, generally, control for driving the sputtering power source in a constant power mode (constant power control of the sputtering power source) is performed. For this reason, it is alternately repeated that aluminum is excessively oxidized or insufficiently oxidized, and the degree of oxidation of the formed aluminum oxide film is not stable.

  The present invention has been made to solve these problems, and an object of the present invention is to provide a technique capable of depositing aluminum oxide at a high deposition rate while stabilizing the degree of oxidation in reactive sputtering.

  In order to solve the above problems, a film forming method according to a first aspect is a film forming method of forming an aluminum oxide film on a substrate by reactive sputtering, wherein a sputtering gas and oxygen to which the substrate is exposed An aluminum target provided on a magnetron cathode for generating a high-frequency inductively coupled plasma by supplying high-frequency power to a high-frequency antenna composed of a conductor having less than one turn in a mixed atmosphere with a reactive gas, and forming a static magnetic field Sputtering voltage including negative voltage is applied by constant voltage control of the sputtering power source, magnetron plasma is generated by the static magnetic field, the aluminum target is sputtered, and an aluminum oxide film is formed on the substrate facing the aluminum target The film forming step and the reaction during the film forming step. A gas supply step for supplying a reactive gas into the mixed atmosphere, and the gas supply step flows to a magnetron cathode provided with an aluminum target facing the substrate so that reactive sputtering is performed in a transition state. The reactive gas is supplied while controlling the supply amount during the film forming step based on a sputtering current value, and the film forming step has at least one of generation conditions of high frequency inductively coupled plasma and magnetron plasma. In order to generate high frequency inductively coupled plasma and magnetron plasma under a plurality of mutually different plasma generation conditions, supply of high frequency power to the high frequency antenna in the mixed atmosphere and sputter voltage to the aluminum target facing the substrate The aluminum oxide film is formed by applying A first film forming process for forming an aluminum oxide film on the substrate that is not formed, and at least one film forming speed higher than a film forming speed in the first film forming process after the first film forming process, And a second film forming process for further forming an aluminum oxide film on the aluminum oxide film formed on the substrate.

  The film formation method according to the second aspect is the film formation method according to the first aspect, wherein the at least one film formation rate is a plurality of film formation rates that increase stepwise or continuously.

  A film forming method according to a third aspect is the film forming method according to the first or second aspect, wherein the gas supply step includes a sputtering current value flowing through a magnetron cathode provided with an aluminum target facing the substrate. Is a step of controlling the supply amount of the reactive gas into the mixed atmosphere so that each target current value is sequentially set, and each target current value changes in each of the plurality of plasma generation conditions. Each sputtering current value when reactive sputtering is performed in a state.

  A film formation method according to a fourth aspect is the film formation method according to any one of the first to third aspects, wherein the second film formation process is performed at a voltage higher than a sputtering voltage in the first film formation process. In this process, a sputtering voltage having a high negative voltage value is applied to the aluminum target facing the substrate.

  A film forming method according to a fifth aspect is the film forming method according to any one of the first to fourth aspects, wherein the sputtering voltage in the first film forming process is a negative voltage or a negative voltage and a positive voltage. The second film forming process is a process of applying a sputtering voltage having a frequency higher than the sputtering voltage in the first film forming process to the aluminum target facing the substrate.

  A film forming method according to a sixth aspect is the film forming method according to any one of the first to fifth aspects, wherein the first film forming process is performed using a negative voltage or a negative voltage and a positive voltage. The DC pulse is applied as a sputtering voltage to the aluminum target facing the substrate, and the second film forming process has a higher rate of positive voltage application time in the pulse period than the first film forming process. In this process, a direct current pulse composed of a negative voltage and a positive voltage is applied as a sputtering voltage to an aluminum target facing the substrate.

  A film forming method according to a seventh aspect is the film forming method according to any one of the first to sixth aspects, wherein the second film forming process is a high frequency supplied in the first film forming process. This is a process of supplying high-frequency power larger than power to the high-frequency antenna in the mixed atmosphere where the substrate is exposed.

  A film formation method according to an eighth aspect is the film formation method according to any one of the first to seventh aspects, wherein the at least one film formation rate is a plurality of steps that increase stepwise or continuously. The second film formation process is a sputtering voltage applied to the aluminum target facing the substrate only with respect to the film formation speed applied to the second and subsequent films among the plurality of film formation speeds. Is a process for changing the plasma generation condition by increasing the absolute value of.

  A film forming apparatus according to a ninth aspect is a film forming apparatus that forms an aluminum oxide film on a substrate by reactive sputtering, and includes an aluminum target and is provided in each of a plurality of processing spaces to form a static magnetic field. Each magnetron cathode, each high-frequency antenna provided in each of the plurality of processing spaces and made of a conductor having less than one turn, and a gas supply for supplying a sputtering gas and a reactive gas of oxygen to each of the plurality of processing spaces A gas supply amount control unit that controls a supply amount of the reactive gas to the plurality of processing spaces by the gas supply unit, and a processing path that sequentially faces each aluminum target of the plurality of processing spaces. Each of the plurality of processing spaces so that high-frequency inductively coupled plasma is generated in the plurality of processing spaces. A negative voltage is applied to each aluminum target such that magnetron plasma is generated in the plurality of processing spaces by each high-frequency power source that supplies high-frequency power to the frequency antenna and a static magnetic field formed by each magnetron cathode of the plurality of processing spaces. Each sputtering power source for applying a sputtering voltage including constant voltage control, and each high frequency power source so that a generation condition of at least one of the high frequency inductively coupled plasma and the magnetron plasma is different among the plurality of processing spaces. And each sputtering power source supply high frequency power to each high frequency antenna and apply a sputtering voltage to each aluminum target, and reactive sputtering is performed in a transition state in the plurality of processing spaces. The gas supply amount control unit is connected to each magnetron cathode. On the substrate on which the aluminum oxide film is not formed by sputtering each aluminum target in a state where the supply amount of the reactive gas to the plurality of processing spaces is controlled based on the sputtering current value A first film forming process for forming an aluminum oxide film on the substrate, and after the first film forming process, the film is formed on the substrate at at least one film forming speed higher than the film forming speed in the first film forming process. And a second film formation process for further forming an aluminum oxide film on the aluminum oxide film.

  A film forming apparatus according to a tenth aspect is a film forming apparatus that forms an aluminum oxide film on a substrate by reactive sputtering, and includes a magnetron cathode that is provided in a processing space with an aluminum target and forms a static magnetic field; A high-frequency antenna provided in the processing space and comprising a conductor having a number of turns of less than one turn, a gas supply unit for supplying a reactive gas of sputtering gas and oxygen to the processing space, and the processing space by the gas supply unit A gas supply amount control unit for controlling the supply amount of the reactive gas, a high frequency power source for supplying high frequency power to the high frequency antenna so that high frequency inductively coupled plasma is generated in the processing space, and the high frequency power source A high frequency power control unit that controls high frequency power to be generated and a static magnetic field formed by the magnetron cathode in the processing space. A sputtering power source for applying a sputtering voltage including a negative voltage to the aluminum target by constant voltage control so as to generate a magnetron plasma, and a sputtering voltage controller for controlling a sputtering voltage applied by the sputtering power source, The high-frequency inductively coupled plasma and the magnetron plasma are generated under a plurality of plasma generation conditions in which at least one of the high-frequency inductively coupled plasma and the magnetron plasma is temporally different from each other. The sputtering voltage control unit controls the high frequency power supplied to the high frequency antenna and the sputtering voltage applied to the magnetron cathode, and the gas supply amount control unit performs the reactive sputtering in a transition state. Sputter current value flowing in the magnetron cathode An aluminum oxide film is formed on the substrate on which the aluminum oxide film is not formed by sputtering the aluminum target in a state where the supply amount of the reactive gas supplied to the processing space is controlled based on On the aluminum oxide film formed on the substrate at a film forming speed higher than the film forming speed in the first film forming process after the first film forming process and the first film forming process. Further, a second film formation process for forming an aluminum oxide film is performed.

  In the invention according to any of the first to tenth aspects, the reactive gas is based on the sputtering current value so that the sputtering voltage is controlled at a constant voltage by the sputtering power source and the reactive sputtering is performed in the transition state. The supply amount is controlled during film formation. When the sputtering voltage is controlled at a constant voltage by a sputtering power source, the higher the degree of oxidation of the aluminum target surface, that is, the greater the amount of reactive gas, the greater the sputtering current value and the oxidation of the formed aluminum oxide film. The degree will be higher. Therefore, the oxidation degree of the aluminum oxide film can be stabilized at a desired value while performing reactive sputtering in the transition state. Further, a first film formation process for forming an aluminum oxide film on a substrate on which an aluminum oxide film is not formed, and at least one film formation speed higher than the film formation speed in the first film formation process after the first film formation process. Since the second film formation process for forming an aluminum oxide film on the aluminum oxide film formed on the substrate is performed at a film speed, the aluminum oxide film is formed as compared with the case where the film is formed at a constant film formation speed. The film formation rate can be increased. That is, according to the present invention, aluminum oxide can be deposited at a high deposition rate while stabilizing the degree of oxidation.

It is a schematic diagram which shows schematic structure of the film-forming unit which implement | achieves the film forming method which concerns on embodiment which forms an aluminum oxide film. It is a schematic diagram which shows schematic structure of the film-forming unit of FIG. It is a schematic diagram which shows schematic structure of the sputtering source of FIG. It is a side view which shows the example of a high frequency antenna. It is a schematic diagram for demonstrating the film-forming process in case assistance of plasma generation is made. It is a figure which shows typically the difference in the film-forming speed by the presence or absence of the assistance of plasma generation. It is a figure which shows typically the relationship between oxygen amount and a sputtering current value. It is an example of the time diagram of the film | membrane formation method which forms the aluminum oxide film which concerns on embodiment. It is an example of the time diagram of the film | membrane formation method which forms the aluminum oxide film which concerns on embodiment. It is a figure which shows the flow of the process performed in the film-forming unit of FIG. It is a figure which shows the flow of the process performed with respect to a board | substrate. It is a schematic diagram which shows schematic structure of the film-forming unit which concerns on a modification. It is a schematic diagram which shows schematic structure of the sputtering source of FIG. It is an example of the time diagram of the film | membrane formation method which forms the aluminum oxide film which concerns on a modification. It is an example of the time diagram of the film | membrane formation method which forms the aluminum oxide film which concerns on a modification. It is a figure which shows the flow of the process performed in the film-forming unit of FIG. It is a figure which shows the flow of the process performed in the film-forming unit of FIG.

<About the embodiment>
Hereinafter, embodiments will be described with reference to the drawings. The following embodiment is an example embodying the present invention, and is not an example of limiting the technical scope of the present invention. In the drawings, the size and number of each part may be exaggerated or simplified for easy understanding. Also, some drawings are provided with XYZ orthogonal coordinate axes to describe directions. The direction of the Z axis in this coordinate axis indicates the direction of the vertical line, and the XY plane is a horizontal plane.

<1. Overall configuration>
The overall configuration of the film forming apparatus 100 will be described with reference to FIG. FIG. 1 is a diagram schematically showing a schematic configuration of a film forming apparatus 100 that realizes a film forming method according to an embodiment for forming an aluminum oxide film. In FIG. 1 and FIGS. 2 and 12 referred later, the inside of the chamber is seen through the side wall of the chamber.

  In the film forming apparatus 100, the p-type doped layer on the substrate 9 (specifically, for example, the back surface of the p-type silicon substrate when the light incident surface of the solar cell is used as the front surface or the surface of the n-type silicon substrate). ) Is formed with an aluminum oxide film. The substrate 9 is disposed on the upper surface of the plate-like carrier 90. Specifically, the carrier 90 has, for example, a plurality of substrates 9 on which a target surface on which an aluminum oxide film is to be formed (here, the back surface of the substrate 9 (the surface opposite to the light incident surface)) is the carrier 90. It arrange | positions at the matrix form in the state which turned to the other side, and is fixed with respect to the carrier 90 (refer FIG. 2).

  The film forming apparatus 100 includes, for example, a plurality of processing chambers (specifically, a heating chamber 120, a formation chamber) between a pair of lock chambers (specifically, a load lock chamber 110 and an unload lock chamber 150). The film chamber 130 and the cooling chamber 140) are connected in a line.

  The load lock chamber 110 and the unload lock chamber 150 are chambers constituting the load lock chamber, and are provided to keep the processing chambers 120, 130, and 140 in a vacuum (that is, not open to the atmosphere). The load lock chamber 110 constitutes a load lock chamber for carrying the unprocessed substrate 9 into the heating chamber 120, and the unload lock chamber 150 is a load lock for carrying out the processed substrate 9 from the cooling chamber 140. Configure the chamber.

  The internal space of the heating chamber 120 forms a processing space for heating the substrate 9. That is, inside the heating chamber 120, heaters 121 are disposed on the upper side and the lower side of a transfer path L, which will be described later, and the heater 121 heats the substrate 9 transferred in the heating chamber 120. .

  The film forming chamber 130 and each element disposed therein constitute a film forming unit 1 that forms an aluminum oxide film on the substrate 9. The film forming unit 1 will be described in detail later.

  The internal space of the cooling chamber 140 forms a processing space for cooling the substrate 9. Specifically, a cooling plate 141 is disposed inside the cooling chamber 140 on each of an upper side and a lower side of a transfer path L described later, and the cooling plate 141 is transferred in the cooling chamber 140. The substrate 9 is cooled.

  A gate 160 is disposed between both ends of each lock chamber 110 and 150 and between each processing chamber 120, 130 and 140. The gate 160 can be switched between a state where it is connected to the adjacent chamber (open state) and a state where the adjacent chamber is shut off and sealed (closed state).

  Further, a high vacuum exhaust system 170 is connected to each of the chambers 110, 120, 130, 140, 150, so that the internal space of each of the chambers 110, 120, 130, 140, 150 can be decompressed to a vacuum state. ing.

  Within the group of chambers 110, 120, 130, 140, 150, horizontal transport paths (also referred to as “processing paths”) that penetrate the chambers 110, 120, 130, 140, 150 along their connecting directions. ) L is defined. The film forming apparatus 100 includes a transport unit 180 that transports the carrier 90 (that is, the carrier 90 on which the plurality of substrates 9 are disposed) along the transport path L. Specifically, the transport unit 180 sandwiches the transport path L from the horizontal direction (Y direction in the illustrated example) perpendicular to the transport path L, for example, inside each chamber 110, 120, 130, 140, 150. A pair of conveying rollers 181 arranged to face each other and a drive unit (not shown) that rotates and synchronizes them are configured. In other words, each of the chambers 110, 120, 130, 140, 150 includes the transport unit 180. A plurality of pairs of the transport rollers 181 are provided along the extending direction of the transport path L (X direction in the illustrated example). In this configuration, each carrier roller 181 rotates while abutting from the lower side in the vicinity of the edge of the carrier 90 (± Y side edge), so that the carrier 90 is set in a predetermined direction along the carrier path L ( In the illustrated example, the sheet is conveyed in the + X direction (arrow AR180).

  In the film forming apparatus 100, the load lock chamber 110, the heating chamber 120, the film forming chamber 130, the cooling chamber 140, and the unload lock chamber 150 are arranged from the upstream side (−X side) in the transport direction of the carrier 90. Arranged in order. Then, the substrate 9 disposed on the carrier 90 is subjected to processing determined in each chamber while passing through each chamber in the order of arrangement. That is, the substrate 9 carried into the film forming apparatus 100 via the load lock chamber 110 is first carried into the heating chamber 120 and subjected to heat treatment there. The substrate 9 after the heat treatment is subsequently carried into the film formation chamber 130 where film formation is performed. The substrate 9 after the film formation process is subsequently carried into the cooling chamber 140 where the cooling process is performed. The substrate 9 after the cooling process is unloaded from the film forming apparatus 100 through the unload lock chamber 150. However, the heat treatment and the cooling treatment are not necessarily essential and may be omitted depending on the process design.

  Each component included in the film forming apparatus 100 is electrically connected to a control unit 190 included in the film forming unit 1, and each component is controlled by the control unit 190. Specifically, the control unit 190 includes, for example, a CPU that performs various arithmetic processes, a ROM that stores programs, a RAM that serves as a work area for arithmetic processes, a hard disk that stores programs and various data files, a LAN, and the like. A data communication unit having a data communication function is connected to each other by a bus line or the like, and is configured by a general computer. The control unit 190 is connected to an input unit composed of a display for performing various displays, a keyboard, a mouse, and the like. In the film forming apparatus 100, a predetermined process is performed on the substrate 9 under the control of the control unit 190.

<2. Deposition unit 1>
<2-1. Overall configuration>
The overall configuration of the film forming unit 1 will be described with reference to FIG. FIG. 2 is a schematic diagram showing the overall configuration of the film forming unit 1.

  The film forming unit (“film forming apparatus”) 1 is a processing unit that forms an aluminum oxide film on the substrate 9 by reactive sputtering. Specifically, the film forming unit 1 includes a film forming chamber 130, a plurality of (in the illustrated example, four) sputter sources 10 disposed therein, and a transfer unit 180. The transport unit 180 transports the substrate 9 that sequentially faces each target 8 (described later) in each processing space V (described later) along the processing path L. The plurality of sputter sources 10 are arranged in a line along an axis (X axis) parallel to the transport path L (see FIG. 1) of the carrier 90.

  The film forming unit 1 further includes chimneys 20 that are cylindrical shielding members disposed so as to surround each sputter source 10. Each chimney 20 functions as a shield that limits the scattering range of the plasma generated by each sputter source 10 and the sputtered particles sputtered from the target. Each processing space V is a space partitioned by each chimney 20 and surrounding each sputtering source 10.

  That is, the internal space of the film forming chamber 130 is divided into a plurality (four in this case) of processing spaces V by a plurality of chimneys 20, and one sputter source 10 is provided in each of the plurality of processing spaces V. It is arranged one by one. In addition, the film forming unit 1 includes a heater 40 that heats the substrate 9 transported in the film forming chamber 130. The heater 40 is disposed on the upper side of the transport path L, for example.

Further, the film forming unit 1 includes a gas supply unit 50 that supplies a plasma generation gas to each processing space V. The film forming unit 1 forms a film of aluminum oxide, which is an oxide of aluminum, on the substrate 9 by reactive sputtering. For this reason, the gas supply unit 50 supplies each processing space V with a sputtering gas such as argon gas or xenon gas, which is an inert gas, and a reactive gas of oxygen (O ₂ ) as a plasma generation gas. The gas supply unit 50 includes a sputtering gas supply unit 51 that supplies a sputtering gas to each processing space V, and a reactive gas supply unit 52 that supplies a reactive gas to each processing space V.

  Specifically, the sputtering gas supply unit 51 includes, for example, an argon supply source 511 that is an argon gas supply source and an argon supply pipe 512. The argon supply pipe 512 has one end connected to the argon supply source 511, the other end branched into four, and each branch end communicating with each processing space V (specifically, each sputter source 10). Are connected to the respective discharge ports 16 (see FIG. 3). In addition, each supply valve 513 is provided in each of the four paths that are branched from the argon supply pipe 512. Each supply valve 513 adjusts the amount of argon supplied to each processing space V under the control of the control unit 190. Each supply valve 513 is preferably a valve that can automatically adjust the flow rate of the gas flowing through the pipe, and specifically includes, for example, a mass flow controller.

  Specifically, the reactive gas supply unit 52 includes, for example, an oxygen supply source 521 that is a supply source of oxygen gas as a reactive gas, and an oxygen supply pipe 522. One end of the oxygen supply pipe 522 is connected to the oxygen supply source 521, the other end is branched into four, and each branch end is connected to each discharge port 16 communicating with each processing space V. In addition, each supply valve 523 is provided in each of the four paths along which the oxygen supply pipe 522 branches. Each supply valve 523 adjusts the amount of oxygen supplied to each processing space V under the control of the control unit 190. More specifically, the control unit 190 monitors the sputtering current value supplied from the ammeter 164 of the sputtering power source 12 and controls the supply valve 523 based on the sputtering current value, thereby the reactive gas supply unit 52. The amount of reactive gas introduced into the film forming chamber 130 is controlled. That is, the control unit 190 also operates as a gas supply amount control unit that controls the supply amount of the reactive gas to each processing space V by the gas supply unit 50. Each supply valve 523 is preferably a valve that can automatically adjust the flow rate of the gas flowing through the pipe, and specifically includes, for example, a mass flow controller.

<2-2. Sputter source 10>
Next, the sputtering source 10 will be described with reference to FIGS. FIG. 3 is a diagram schematically showing the configuration of the sputter source 10. FIG. 4 is a side view showing an example of a high-frequency antenna.

  The sputter source 10 includes a base plate 11, a magnet (“magnetron sputtering magnet”) 13, an anode 14, a sputtering power source (“sputter power source”) 12, an inductively coupled plasma generator 15, and a high frequency power source 153. Is provided. A target 8 is held on the base plate 11 by a target holding unit (not shown). The base plate 11 and the magnet 13 are also referred to as a “magnetron cathode”. The magnetron cathode forms a static magnetic field near the surface of the target 8. In addition, the sputter source 10 further includes a mechanism (not shown) for cooling the target 8, the base plate 11, the high frequency antenna 151 of the inductively coupled plasma generating unit 15, and the like.

  Each sputtering source 10 provided in the film forming unit 1 has the same configuration. However, as will be described later, between each processing space V, at least one of the high-frequency power source 153 and the sputtering power source 12 is adjusted to supply a different high-frequency power or apply a different sputtering voltage. Has been.

  The base plate 11 is provided on the cylindrical side wall 18 so as to close the upper opening of the cylindrical side wall 18 standing on the bottom of the film forming chamber 130. The base plate 11 is in contact with the target 8 from below the target 8. The side wall 18 and the base plate 11 are conductors.

  The sputtering power source 12 applies a sputtering voltage including a negative voltage (“cathode applied voltage”, “bias voltage”) to the base plate 11 via the side wall 18. More specifically, a negative voltage, a pulsed voltage composed of a negative voltage and a positive voltage (also referred to as “DC pulse voltage” or “DC pulse”), or an AC sputtering voltage is applied as the sputtering voltage. The When a sputtering voltage is applied to the base plate 11 (and thus the target 8), an electric field for magnetron plasma is generated between the target 8 and the substrate 9 held by the carrier 90. When an electric field for magnetron plasma is generated, plasma of a plasma generation gas (“magnetron plasma”) is generated on the surface portion of the target 8 in the processing space V by the static magnetic field formed by the magnet 13. That is, the sputtering power source 12 applies a sputtering voltage including a negative voltage to the target 8 by constant voltage control so that magnetron plasma is generated in the processing space V by a static magnetic field formed by the magnetron cathode in the processing space V.

  The sputtering power supply 12 is driven in a constant voltage mode. That is, the sputtering power source 12 controls the sputtering voltage at a constant voltage. Thereby, as a sputtering voltage, for example, when a DC pulse composed of two kinds of voltages of −190 V and +19 V is supplied, each voltage of −190 V and +19 V does not vary even if the sputtering current value varies. By stabilizing the oxidation degree (“oxidation rate”, “oxidation state”) of the surface of the aluminum target 8 during the aluminum oxide film formation process, a high-quality passivation film can be formed. And if constant voltage control is performed, the oxidation degree of the aluminum oxide formed into a film easily can be stabilized compared with the case where constant power control is performed. Further, the sputtering current value ("bias current value") flowing through the magnetron cathode is detected by an ammeter 164 provided in the sputtering power supply 12 and supplied to the control unit 190, and processed by the control unit 190 during film formation. This is used to control the supply amount of the reactive gas supplied to the space V.

  The magnet 13 is disposed below the base plate 11. The magnet 13 is a magnetron sputtering magnet, and the magnet 13 is formed of a permanent magnet, for example, and forms a static magnetic field (magnetron magnetic field) near the surface of the target 8. By forming this static magnetic field, the magnetron plasma is confined near the surface of the target 8. In other words, the magnet 13 forms a static magnetic field (magnetron magnetic field) in a region including the surface of the target 8 placed on the base plate 11 so that plasma on the surface portion of the target 8 can be formed. The way the plasma spreads on the surface portion of the target 8 varies depending on the partial pressure of the plasma generation gas introduced into the film forming chamber 130, the magnetron magnetic field generated by the magnetron sputtering magnet 13, the intensity of the voltage applied to the target, and the like.

  As the target 8, an aluminum target formed of an aluminum (monometallic aluminum) material is used. The target 8 is held in a horizontal posture on the upper surface (the surface on the + Z side) of the base plate 11 by a target holding portion (not shown) and the base plate 11. The position where the target 8 is held is a position facing the transport path L of the carrier 90 at a predetermined distance. An opening 21 is provided on the upper surface of the chimney 20 so that the substrate 9 can face the target 8. That is, the target 8 and the substrate 9 (that is, the substrate 9 disposed on the carrier 90 transported along the transport path L) are opposed to each other with a predetermined distance while the postures thereof are parallel to each other. Is done. However, the target 8 is held facing the processing space V partitioned by the chimney 20 in the film forming chamber 130 while being insulated from the film forming chamber 130. Thereby, the substrate 9 is exposed to a mixed atmosphere of the sputtering gas introduced into the processing space V and the reactive gas of oxygen.

  Here, since the inductively coupled plasma generator 15 described later supports plasma generation by the magnetron cathode, the maximum horizontal magnetic flux density formed by the magnet 13 on the surface of the target 8 is 20 mT to 50 mT (millitesla). Even with a relatively low magnetic flux density, sufficient plasma can be generated by the plasma assist by the inductively coupled plasma generator 15.

  The anode 14 is disposed on the side of the base plate 11 and the cylindrical side wall 18 on which the base plate 11 is provided with a space therebetween (that is, in a non-contact state with the base plate 11 and the side wall 18). . The upper portion of the anode 14 is bent in a direction approaching the target 8 to reach an end portion, and this end portion is disposed close to the side surface of the target 8 in a non-contact state.

  The inductively coupled plasma generator 15 supports plasma generation by the magnetron cathode. The inductively coupled plasma generating unit 15 includes two linear high frequency antennas (also referred to as “inductively coupled antennas”) 151 that are inductively coupled high frequency antennas. A pair of dielectric antenna fixing blocks 182 projecting into the processing space V so as to sandwich the anode 14 are provided on the bottom of the film forming chamber 130 on the side of the anode 14. Each high frequency antenna 151 of the inductively coupled plasma generating unit 15 is inserted and fixed to a pair of antenna fixing blocks 182 so as to stand one by one before and after the anode 14 along the transport path L. ing.

  For example, as shown in FIG. 4, the high-frequency antenna 151 is formed by bending a metal pipe-like conductor into a U shape, and the bottom of the film formation chamber 130 with the “U” shape turned upside down. And projecting into the processing space V. A part on the upper end side of the high-frequency antenna 151 penetrates the antenna fixing block 182 and protrudes into the processing space V. The protruding portion of the high-frequency antenna 151 is covered with a dielectric protective pipe 411 made of quartz or the like. A lower end portion of the high frequency antenna 151, that is, both end portions of the high frequency antenna 151 pass through the bottom portion of the film forming chamber 130 and protrude downward.

  In order to increase the plasma density in the vicinity of the surface of the target 8, the position in the height direction of the high-frequency antenna 151 is adjusted so that the bottom of the “U” shape is several centimeters higher than the top surface of the target 8. However, the high-frequency antenna 151 is fixed in the film formation chamber 130 while being insulated from the film formation chamber 130. In addition, the arrangement | positioning aspect of the high frequency antenna 151 can be variously changed.

  One end of the high-frequency antenna 151 is connected to the high-frequency power source 153 via the matching circuit 152. The other end of the high frequency antenna 151 is grounded. The high frequency power supply 153 supplies high frequency power to the high frequency antenna 151 provided in the processing space V so that high frequency inductively coupled plasma is generated in the processing space V.

  In this configuration, when high frequency power (specifically, for example, 13.56 MHz high frequency power) is supplied from the high frequency power supply 153 to the high frequency antenna 151, an electric field (high frequency induction electric field) is generated around the high frequency antenna 151, Inductively coupled plasma (ICP) (also referred to as “high frequency inductively coupled plasma”) of sputtering gas and reactive gas is generated in the processing space V. The generated high-frequency inductively coupled plasma is confined to the surface portion of the target 8 by the static magnetic field formed by the magnet 13 in the vicinity of the target 8 together with the magnetron plasma.

  In the film forming unit 1, a high frequency power source 153 and a sputtering power source 12 are provided in each of the plurality of processing spaces V. Each high frequency power supply 153 supplies high frequency power to each high frequency antenna 151 so that at least one of the generation conditions of the high frequency inductively coupled plasma and the magnetron plasma is different among the plurality of processing spaces V, and Each sputtering power source 12 applies a sputtering voltage to each target 8.

  As described above, the high-frequency antenna 151 has a U shape. Such a U-shaped high-frequency antenna 151 corresponds to an inductively coupled antenna having less than one turn, and has a lower inductance than an inductively coupled antenna having one or more turns, so that a high-frequency voltage generated at both ends of the high-frequency antenna 151 is generated. The high frequency fluctuation of the plasma potential accompanying the electrostatic coupling to the generated plasma is suppressed. For this reason, excessive electron loss accompanying the plasma potential fluctuation to the ground potential is reduced, and the plasma potential can be suppressed particularly low. This enables a thin film formation process with low ion damage on the substrate. As the shape of the high-frequency antenna 151, for example, an arc shape may be employed. The number of turns of the high-frequency antenna 151 is less than one turn. In order to prevent the occurrence of standing waves, the length of the high frequency antenna 151 is preferably set to a length equal to or less than ¼ of the wavelength of the power supplied by the high frequency power supply 153. One end of the high frequency antenna 151 is supplied with high frequency power, and the other end is grounded. Thereby, inductively coupled plasma is generated. If such a high-frequency antenna 151 is employed, the antenna voltage can be lowered because the antenna inductance is low as compared with the method of generating inductively coupled plasma using a coiled (spiral) antenna, so that plasma is reduced. Damage can be suppressed. Further, by reducing the antenna length to ¼ or less of the wavelength of the high frequency, it is possible to suppress the sputtering unevenness (nonuniformity) due to the plasma unevenness due to the influence of the standing wave. Further, since the antenna can be accommodated in the processing space V, the sputtering efficiency can be improved. Further, the number of high-frequency antennas 151 is increased in accordance with the substrate size to be deposited, and the sputtering rate can be improved even when the substrate size is large by increasing the target size.

  In the film forming unit 1, discharge ports 16 are formed in association with the respective sputtering sources 10. Specifically, the discharge port 16 is formed between each high frequency antenna 151 and the target 8, for example. As described above, the gas supply unit 50 is connected to the discharge port 16, and the gas supplied from the gas supply unit 50 to the discharge port 16 is supplied to the processing space in which the sputtering source 10 is disposed. . But the formation position of the discharge outlet 16 does not necessarily need to be between the high frequency antenna 151 and the target 8. However, the discharge port 16 is preferably provided at a position corresponding to each of the two high-frequency antennas 151.

  As described above, the film forming unit 1 introduces the sputtering gas and the oxygen reactive gas into each processing space V divided by each chimney 20 in the film forming chamber 130. Each sputtering source 10 provided corresponding to each processing space V sputters the target 8 by generating a mixed plasma of magnetron plasma and high frequency inductively coupled plasma on the surface portion of the target 8. Thereby, an aluminum oxide film is formed in a two-dimensional region on the substrate 9 facing the target 8.

  More specifically, the film forming unit 1 includes the high-frequency power sources 153 and the sputtering power sources 12 so that the generation conditions of at least one of high-frequency inductively coupled plasma and magnetron plasma differ among the plurality of processing spaces V. Supplies high-frequency power to each high-frequency antenna 151 and applies a sputtering voltage to each target 8. Then, the film forming unit 1 moves to the plurality of processing spaces V based on the sputtering current value that the control unit 190 flows to each magnetron cathode so that reactive sputtering is performed in the transition state (transition mode) in the plurality of processing spaces V. Each target 8 is sputtered while the supply amount of the reactive gas is controlled. Thereby, the film forming unit 1 performs the first film forming process for forming the aluminum oxide film on the substrate 9 on which the aluminum oxide film is not formed. The film forming unit 1 further oxidizes the aluminum oxide film formed on the substrate 9 after the first film forming process at at least one film forming speed higher than the film forming speed in the first film forming process. A second film forming process for forming an aluminum film is performed. The first film forming process and the second film forming process will be described later.

<3. About aluminum oxide film formation process>
FIG. 5 illustrates a phenomenon that is expected to occur more in the film formation process when the film formation method for forming the aluminum oxide film according to the embodiment supports plasma generation by high frequency inductively coupled plasma. It is a schematic diagram for doing. FIG. 6 is a diagram schematically showing a difference in film formation rate between the case where there is support for plasma generation by high-frequency inductively coupled plasma and the case where there is no support in the film formation method for forming an aluminum oxide film according to the embodiment. is there. A graph G1 in FIG. 6 shows the relationship between the film formation rate of aluminum oxide (Al ₂ O ₃ ) by the usual reactive magnetron sputtering and the amount of oxygen (when the plasma generation by the high frequency inductively coupled plasma is not supported). . Graphs G2 and G3 show the relationship between the deposition rate and the oxygen amount by the film forming method for forming the aluminum oxide film according to the present embodiment, which is supported for plasma generation by high frequency inductively coupled plasma. The graph G2 corresponds to the case where a negative voltage is applied as the sputtering voltage, and the graph G3 corresponds to the case where a direct current pulse consisting of a negative voltage and a positive voltage or an alternating current is applied as the sputtering voltage.

<3-1. About increasing film deposition speed>
In the process of film formation of aluminum oxide (Al ₂ O ₃ ) by the usual reactive magnetron sputtering (when plasma generation is not supported by high-frequency inductively coupled plasma), when the oxygen partial pressure in the processing space V increases, The oxidation reaction on the surface of the target 8 is promoted. When the oxygen partial pressure is further increased, the surface is almost covered with stoichiometric aluminum oxide (Al ₂ O ₃ ). Since the stoichiometric aluminum oxide has a high hardness, the sputter yield decreases, and as a result, the film formation rate decreases (region including the point SP1 on the right side of the broken line L1 in the graph G1 in FIG. 6).

A schematic diagram surrounded by broken line frames 601 to 603 (FIG. 5) is a film formation method for forming an aluminum oxide film according to the embodiment, that is, plasma generation is supported by high frequency inductively coupled plasma generated by the high frequency antenna 151. 4 shows a part of the film formation process of aluminum oxide (Al ₂ O ₃ ), which is predicted to occur during reactive magnetron sputtering. In this case as well, the above-described generation process in normal reactive magnetron sputtering is also expected to occur.

According to the film forming method for forming an aluminum oxide film according to the present embodiment, in which plasma generation is supported by high frequency inductively coupled plasma, a DC pulse consisting of a negative DC voltage, a negative voltage and a positive voltage as a sputtering voltage. Regardless of whether a voltage or an alternating voltage is applied, the density of the magnetron plasma can be sufficiently increased. Furthermore, radicals in the processing space V are much more than ions. Then, oxygen radicals positively act on the surface of the substrate 74 to be formed, thereby promoting the production of stoichiometric aluminum oxide (Al ₂ O ₃ ) on the surface of the substrate 74. As described above, as a result of promoting the oxidation of the surface of the substrate 74 by oxygen radicals (schematic diagram in the broken line frame 602), the sputtering condition with a low oxygen addition amount can be selected on the target surface, so that the stoichiometric oxidation degree can be selected. Sputtering in the state of aluminum oxide having a lower oxidation degree, that is, non-stoichiometric aluminum oxide (AlO) is promoted, and the target surface is softened (schematic diagram in broken line frame 601). In other words, the target surface becomes soft aluminum oxide with a low degree of oxidation, and the sputtering yield increases, while AlO particles sputtered from the target are increased on the surface of the film formation target substrate or between the substrate and the target by the increased oxygen radicals. It changes into stoichiometric aluminum oxide (Al ₂ O ₃ ) in the vacuum space, and is formed on the substrate (schematic diagram in a broken line frame 602). Therefore, the deposition rate of aluminum oxide on the surface of the substrate to be deposited is increased compared to normal reactive magnetron sputtering that does not support plasma generation by high frequency inductively coupled plasma, and the deposition rate according to the amount of oxygen added The rate of change will be moderate. Furthermore, since the hysteresis characteristic in the transition region as shown in graph G1 seen in normal reactive magnetron sputtering without plasma support by high frequency inductively coupled plasma is relaxed, the controllability of the oxidation degree of the aluminum oxide film to be formed is This dramatically improves (a region between the broken line L2 and the broken line L3 including the point SP2 in the graph G2 in FIG. 6 and a region between the broken line L3 and the broken line L4 including the point SP3 in the graph G3).

  Note that, according to the film forming method for forming an aluminum oxide film according to this embodiment in which a DC pulse voltage or an AC voltage is applied as the sputtering voltage, a voltage composed of a negative voltage and a positive voltage is applied to the target. In addition to the effect of applying a negative DC voltage, softening due to a chemical reaction on the target surface is further promoted by oxygen radicals on the target surface in accordance with the effect of attracting electrons to the target surface (scheme in the broken line frame 603) Fig.), Non-stoichiometric AlO sputtering from the target surface is further promoted. As a result, the sputtering yield of the target can be further increased, and the formation of an oxide film on the target can be suppressed. Therefore, according to the film forming method for forming the aluminum oxide film according to this embodiment in which a DC pulse voltage or an AC voltage is applied as the sputtering voltage, there is support for plasma generation by high frequency inductively coupled plasma, and the sputtering voltage The film formation speed can be further increased as compared with the film formation method for forming the aluminum oxide film according to the present embodiment to which a negative DC voltage is applied (corresponding to the fastest film formation speed in the graph G3 in FIG. 6). (A region between the broken line L3 and the broken line L4 including the point SP3).

<3-2. Stabilization of oxidation degree by constant voltage control>
In each sputtering source 10, the sputtering voltage is controlled at a constant voltage by a sputtering power source in the magnetron plasma generation process. Further, the control unit 190 monitors the sputtering current value supplied from the ammeter 164 of the sputtering power source 12 and controls the supply valve 523 so that the monitored sputtering current value becomes the target current value, thereby forming the film. A reactive gas (more precisely, for example, 5% pure oxygen gas or 5% pure oxygen gas and inert gas such as Ar) supplied into the processing space V from the reactive gas supply unit 52 during the processing. The amount of introduction of the diluted mixed gas with the gas) is controlled. Specifically, based on the difference value obtained by subtracting the target current value from the detected sputtering current value, if the sign of the difference is positive, the amount of reactive gas introduced is reduced according to the difference value, and the difference If the sign of is negative, processing for increasing the amount of reactive gas introduced is performed according to the difference value. The control unit 190 obtains the value of the introduction amount to be adjusted by referring to, for example, an arithmetic expression stored in advance in the hard disk of the control unit 190, a table representing a correspondence relationship, or the like.

  The value of the sputtering current flowing through the magnetron cathode is a value corresponding to the total amount of the argon ion flux, which is the flow rate of argon ions colliding with the target 8, and the amount of secondary electrons emitted when the target 8 is sputtered. . Here, the higher the negative voltage value of the sputtering voltage, the higher the concentration of magnetron plasma, and the argon ions collide with the target 8 at a high speed, so that the argon ion flux increases according to the sputtering voltage. Further, the higher the degree of oxidation of the surface of the target 8, that is, the greater the amount of oxygen in the processing space V, the more secondary electrons are emitted when the target 8 is sputtered.

  Accordingly, when the sputtering voltage is controlled at a constant voltage by the sputtering power source, that is, when the sputtering power source 12 is driven in the constant voltage mode, the argon ion flux is constant, so that the oxidation degree of the surface of the target 8 is higher. That is, as the amount of reactive gas in the processing space V increases, the sputtering current value increases. And the oxidation degree of the aluminum oxide formed on the board | substrate 9 also becomes high. When the sputtering voltage is controlled at a constant voltage by a sputtering power source, the degree of oxidation of the aluminum oxide film formed on the substrate 9 is stable and balanced according to the amount of oxygen in the processing space V, that is, the amount of reactive gas. Try to settle to the point.

  Therefore, by introducing the reactive gas into the processing space V so that the sputtering current value becomes the target current value while controlling the sputtering voltage at a constant voltage by the sputtering power source, for example, the moisture adsorbed on the substrate 9 or the like. Regardless of disturbance factors such as reactive gas generated due to this, the degree of oxidation of the aluminum oxide film formed on the substrate 9 can be stabilized.

  As a result, the target current value is set to the sputtering current value when the target 8 is sputtered in the transition state, and the sputtering voltage is controlled at a constant voltage by the sputtering power source, so that the sputtering current value becomes the target current value. By controlling the amount of oxygen supplied to the processing space V, aluminum oxide can be deposited at a high deposition rate while stabilizing the degree of oxidation.

Here, in the graph G2 of FIG. 6, when the oxygen amount is in the right region from the broken line L3, stoichiometric aluminum oxide (Al ₂ O ₃ ) is generated on the surface of the substrate 9, and the oxygen in the left region from the broken line L3 is generated. In quantity, non-stoichiometric aluminum oxide (AlO) is produced. Then, the oxidation degree of aluminum oxide formed on the surface of the substrate 9 is, for example, stoichiometric aluminum oxide and stoichiometric oxidation as in the film forming condition at point SP2 in the vicinity of the broken line L3 in FIG. It has been found that an aluminum oxide film that exhibits a high passivation effect is formed when the oxidation degree is near the boundary of the respective oxidation degree with aluminum oxide having a lower oxidation degree than aluminum.

  For this reason, in the film forming unit 1, when a passivation film is formed on the substrate 9, the target current value referred to in the control of the introduction amount of the reactive gas is preferably the aluminum oxide film to be formed. Is set to a sputtering current value when the degree of oxidation becomes a degree of oxidation near the boundary between the degree of oxidation of stoichiometric aluminum oxide and aluminum oxide having a lower degree of oxidation than stoichiometric aluminum oxide. In this case, the oxidation degree of aluminum oxide corresponding to the target current value in the sputter source 10 is an oxidation degree at which the passivation effect of aluminum oxide is increased and an oxidation degree at a high film formation rate. Therefore, an aluminum oxide film that exhibits a high passivation effect suitable for the back surface passivation film of the p-type silicon substrate can be formed at a high film formation rate while stabilizing the oxidation degree with good controllability.

<3-3. Voltage and target current value for constant voltage control>
FIG. 7 is a diagram schematically showing the relationship between the oxygen amount and the sputtering current value by graphs G5 and G6, respectively. Graph G5 shows the relationship between the amount of oxygen and the sputtering current value when the sputtering voltage is controlled to a DC voltage of -200V by the sputtering power supply, and graph G6 shows the relationship between the sputtering voltage and the DC voltage of -300V by the sputtering power supply. The relationship between the amount of oxygen and the sputtering current value when constant voltage control is performed is shown.

  Since the argon ion flux increases as the negative voltage value of the sputtering voltage increases, the negative voltage value of the sputtering voltage increases as shown in the graphs G5 and G6 when the amount of oxygen supplied to the processing space V is zero. As the sputtering current value increases.

Further, as the argon flux increases, more oxygen is required to form the aluminum oxide film. For this reason, as shown in the graphs G5 and G6, as the negative voltage value of the sputtering voltage increases, the rate of increase of the sputtering current value with respect to the increase amount of oxygen becomes gentle. Here, points P1 and P2 are points where the oxidation degrees of aluminum oxide formed on the substrate 9 are equal to each other, and reactive sputtering is performed in a transition state. At point P1, the sputtering current value is I ₂₀₀ when the oxygen amount is O ₂₀₀ , and at point P2, the sputtering current value is I ₃₀₀ when the oxygen amount is O ₃₀₀ . Thus, in order to keep the degree of oxidation of the formed aluminum oxide constant, it is necessary to increase the target current value of the sputtering current as the negative voltage value of the sputtering voltage increases. In addition, even when a DC pulse voltage consisting of a negative voltage and a positive voltage or an AC voltage is applied as the sputtering voltage, the relationship between the oxygen amount and the sputtering current is the case where the above-described negative DC voltage is applied. It is the same.

  As described above, in the film forming unit 1, each target current value of the sputtering current in each processing space V is set to each sputtering current value at which reactive sputtering is performed in the transition state under the plasma generation conditions in each processing space V. Is done. Then, the control unit 190 is in a mixed atmosphere of a sputtering gas and a reactive gas so that the sputtering current value flowing through each magnetron cathode provided with each target 8 facing the substrate 9 sequentially becomes each target current value. The amount of reactive gas supplied to the is controlled. That is, the control unit 190 controls the supply amount of the reactive gas to each processing space V so that the sputter current value flowing through the magnetron cathode of each processing space V becomes each target current value for each processing space V. To do. This enables reactive sputtering in the transition mode regardless of the sputtering voltage, which is one of the plasma generation conditions, that is, regardless of the deposition rate.

<3-4. Changes in film formation and plasma generation conditions>
In the film forming unit 1, parameters that can efficiently change the generation conditions of the high frequency inductively coupled plasma and the magnetron plasma include, for example, the frequency of the DC pulse (sputtering voltage), the inversion time of the DC pulse (sputtering voltage), and the high frequency antenna. Four parameters of the value of the high-frequency power supplied to 151 and the absolute value of the sputtering voltage can be spatially changed independently.

  When the absolute value of the sputtering voltage increases, as described above, the density of the magnetron plasma increases and the velocity of argon ions that collide with the target 8 increases. The film formation rate of the aluminum oxide film formed at the same time increases.

  When the frequency of the DC pulse as the sputtering voltage increases, the time until the positive charge charged on the surface of the target 8 is reduced (so-called refresh is performed) by applying a positive voltage to the target 8 in a short cycle. Since it is shortened, the deposition rate of the aluminum oxide film increases.

  When the pulse inversion (positive voltage) time of the DC pulse as the sputtering voltage is increased and the pulse duty ratio of the negative voltage is decreased, the time for the positive charge charged on the surface of the target 8 to be refreshed is increased. As in the case of increasing, the deposition rate of the aluminum oxide film increases.

  Further, when the high-frequency power supplied to the high-frequency antenna 151 is increased, the density of the high-frequency inductively coupled plasma is increased and plasma assist is further performed, so that the deposition rate of the aluminum oxide film is increased.

  Therefore, in the film forming unit 1, each high frequency power source 153 and each sputtering power source 12 have different generation conditions so that at least one of the high frequency inductively coupled plasma and the magnetron plasma is generated between the plurality of processing spaces V. The high frequency power is supplied to the high frequency antenna 151 and the sputtering voltage is applied to each target 8. The sputtering voltage applied to each target 8 is controlled at a constant voltage by the sputtering power supply 12. Further, the control unit 190 controls the supply amount of the reactive gas to each processing space V based on the sputtering current value flowing to each magnetron cathode so that reactive sputtering is performed in a transition state in the plurality of processing spaces V.

  In this state, the film forming unit 1 transports the substrate 9 while sputtering each target 8 in each processing space V. First, in the processing space V on the most upstream side, an aluminum oxide film is not formed. A first film forming process for forming an aluminum oxide film on the film 9 is performed. The film forming unit 1 is further formed on the substrate 9 after the first film forming process in each of the other processing spaces V at at least one film forming speed higher than the film forming speed in the first film forming process. A second film forming process for forming an aluminum oxide film on the aluminum oxide film is performed.

  During the first and second film forming processes, the sputtering voltage is controlled at a constant voltage by the sputtering power source, and the reactive gas is supplied based on the sputtering current value so that the reactive sputtering is performed in the transition state. While being controlled, the gas is supplied into the mixed atmosphere of the sputtering gas and the reactive gas in each processing space V. When the sputtering voltage is controlled at a constant voltage, the higher the degree of oxidation of the aluminum target surface, that is, the greater the amount of reactive gas, the higher the sputtering current value and the higher the degree of oxidation of the formed aluminum oxide film. Become. Therefore, the oxidation degree of the aluminum oxide film can be stabilized to the oxidation degree when reactive sputtering is performed in the transition state. Further, a first film formation process for forming an aluminum oxide film on a substrate on which an aluminum oxide film is not formed, and at least one film formation speed higher than the film formation speed in the first film formation process after the first film formation process. Since the second film formation process for forming an aluminum oxide film on the aluminum oxide film formed on the substrate is performed at a film speed, the aluminum oxide film is formed as compared with the case where the film is formed at a constant film formation speed. The film formation rate can be increased. That is, according to the film forming unit 1, aluminum oxide can be formed at a high film formation rate while stabilizing the degree of oxidation.

  8 and 9 are examples of time diagrams of the film forming method for forming the aluminum oxide film according to the embodiment. More specifically, in FIG. 8, the film forming unit 1 includes nine processing spaces V in which at least one of the plasma generation conditions of the high frequency inductively coupled plasma and the magnetron plasma is spatially different from each other. Shows a time diagram of a film forming method in the case where an aluminum oxide film is sequentially formed on the substrate 9 while passing through each processing space V. FIG. 9 shows a time diagram in the same manner as FIG. 8 when the film forming unit 1 includes seven processing spaces V in which plasma generation conditions are spatially different from each other.

  8 and 9, the sputtering voltage applied to the magnetron cathode is a negative DC voltage (note that the negative DC voltage is a negative voltage with a frequency of 0 KHz and a positive voltage with an inversion time of 0 seconds. DC pulse, that is, only a negative voltage DC voltage) and negative and positive DC pulses are applied. 8 and 9, in order from the top, the frequency of the DC pulse (sputtering voltage), the inversion time of the DC pulse (sputtering voltage), the value of the high-frequency power supplied to the high-frequency antenna 151, the negative voltage value of the sputtering voltage, Seven time diagrams of the flow rate of oxygen supplied to the processing space V, the measured value of the sputtering current, and the target current value of the sputtering current are shown. The inversion time of the DC pulse (sputtering voltage) is the application time of the positive voltage in the pulse period.

  Further, in each of the seven time diagrams of FIG. 8 (FIG. 9), the substrate 9 is moved from the upstream side to the downstream side of the transport path L in each period a1 to a9 (b1 to b7) of the horizontal time axis. Each time required for the substrate 9 to pass through each opening 21 of each chimney 20 in the process of sequentially passing through the seven (7) processing spaces V is shown. The time display indicated by numerals indicates the accumulated time when the substrate 9 passes over each opening 21 of each chimney 20 that divides each processing space V, and the substrate 9 corresponds to each opening. The period of passing through the portion between 21 is not shown. The difference in length in each period is caused by the difference in length along the transport path L of each opening 21 in each processing space V. Each length of each opening 21 is set so that an aluminum oxide film having a predetermined thickness is sequentially formed for each processing space V in each required time for the substrate 9 to pass through each opening 21. Has been.

  In the example of FIG. 8, first, a DC voltage of −200 V is applied as a sputtering voltage to the magnetron cathode provided with the target 8 facing the substrate 9 in the most upstream processing space V in which the first film forming process is performed. (Period a1). In the period a1, the frequency of the DC pulse is 0 KHz, and the inversion time of the DC pulse is 0 usec. The high frequency power is 400 W.

  If the absolute value of the sputtering voltage is too large, the passivation ability of the formed aluminum oxide film is impaired. However, when a DC voltage of about −200 V (for example, −200 V to −150 V) may be applied as the sputtering voltage, An aluminum oxide film that suitably exhibits passivation ability can be formed. Further, in order for the aluminum oxide film to exhibit passivation ability, the film thickness may be about 10 nm or more.

  In each of the second and subsequent processing spaces, the second film forming process is sequentially performed. In the second processing space V, the frequency of the DC pulse is set to 10 KHz and the inversion time of the DC pulse is set. 5 usec. (Period a2). Further, in the next processing space V, the high-frequency power is set to 500 W (period a3), and in the next processing space V, the frequency of the DC pulse is set to 20 KHz (period a4). In the next processing space V, the inversion time of the DC pulse is 10 usec. (Period a5), and in the next processing space V, the high frequency power is set to 600 W (period a6). Further, in the next processing space V, the negative voltage value of the sputtering voltage is set to 250 V (period a7), and in the further next processing space V, the negative voltage sputtering voltage value is set to 300 V (period a8). Finally, in the most downstream processing space V, the frequency of the direct current pulse is set to 50 KHz (period a9).

  In the example of FIG. 9, first, a sputtering voltage is applied to the magnetron cathode provided with the target 8 facing the substrate 9 in the most upstream processing space V where the first film forming process is performed, as in the period a1 of FIG. As a result, a DC voltage of −200 V is applied (period b1). The other parameters are set in the same manner as the parameters in FIG.

  In each of the second and subsequent processing spaces, the second film forming process is sequentially performed. In the second processing space V, the high-frequency power is set to 500 W (period b2), and in the next processing space V. The negative sputtering voltage value is set to 250 V (period b3). Further, in the next processing space V, the frequency of the DC pulse is set to 10 KHz, and the inversion time of the DC pulse is 10 usec. And high frequency power is set to 600 W (period b4). Further, in the next processing space V, the frequency of the DC pulse is set to 20 KHz (period b5), and in the next processing space V, the frequency of the DC pulse is increased to 50 KHz (period b6). In the final processing space V, the negative sputtering voltage value is set to 300 V (period b7).

  In FIG. 8 (FIG. 9), the target current value of the sputtering current in the period a1 (b1) is 2 A, and 4 A in the period a9 (b7). And each target electric current value about each processing space V is set so that it may become high little by little over periods a1-a9 (b1-b7). Each target current value is set to each sputtering current value at which reactive sputtering is performed in a transition state under the plasma generation conditions in each processing space V (each period). Then, the control unit 190 sequentially converts each sputtering current flowing through each magnetron cathode in each processing space V, that is, each sputtering current value flowing through each magnetron cathode provided with each target 8 facing the substrate 9, into each target current value. Thus, the supply amount of the reactive gas into the mixed atmosphere of the sputtering gas and the reactive gas is controlled. By this control, the supply amount of oxygen reactive gas is increased in each processing space V as the downstream processing space V is so that the measured value of each sputtering current becomes each target current value. Are being supplied as.

  The target current value in the period a1 (b1) is that the oxidation degree of aluminum oxide formed on the substrate 9 is stoichiometric aluminum oxide and aluminum oxide having an oxidation degree lower than that of stoichiometric aluminum oxide, respectively. The sputtering current value is set when the oxidation degree is near the boundary of the oxidation degree. This degree of oxidation is also the degree of oxidation in which reactive sputtering is performed in the transition state. In each period after the period a2 (b2), reactive sputtering is performed in the transition state, and the degree of oxidation of the aluminum oxide film to be formed is maintained with respect to the previous period. Or each target electric current value is set so that it may become a higher oxidation degree.

  Even in the process of the period a1 (b1), that is, in the first film formation process, even if a DC pulse having a negative voltage and a positive voltage, for example, a DC pulse of 5 KHz or less, or an AC of 5 KHz or less is applied to the target 8 as a sputtering voltage. As compared with the case where a negative DC voltage is applied, the passivation effect of the formed aluminum oxide film is not significantly impaired. Furthermore, the effect of refreshing the positive charge charged on the target 8 can also be obtained. Therefore, in the first film forming process, even if a DC pulse having a negative voltage and a positive voltage, for example, a DC pulse of 5 KHz or less, or an AC of 5 KHz or less is applied to the target 8 as a sputtering voltage, the usefulness of the present invention is improved. There is no loss.

  As shown in FIGS. 8 and 9, the second and subsequent periods in which the second film forming process is performed are more than the first periods in which the first film forming process is performed (that is, the periods a <b> 1 and b <b> 1). The parameters for determining the plasma generation conditions are set so that the film forming speed is increased. This shortens the time required to complete the film forming process compared to the case where the film forming speed in the first period (that is, the periods a1 and b1) in which the first film forming process is performed is maintained in other periods. Is done.

  Further, in the examples of FIGS. 8 and 9, plasma is generated in each of the second and subsequent processing spaces V, that is, in each of the second and subsequent plural periods so that the film formation rate is higher than that in the previous period. Parameters that determine the conditions are set. Thereby, in the second film formation process, the film formation is sequentially performed at a plurality of film formation speeds higher than the film formation speed in the first film formation process. Furthermore, the plurality of film formation speeds in the second film formation process increase stepwise as the processing space V is located on the downstream side, that is, as the time period is later. Note that supply of high-frequency power or application of a sputtering voltage may be performed so that the plurality of film formation rates continuously increase.

  As described above, in the second film formation process, in the case where the film formation is performed at a plurality of film formation speeds higher than the film formation speed in the first film formation process, the film formation speed is gradually increased in the second film formation process. It is possible to adopt a plasma generation condition in which the damage is increased, that is, a plasma generation condition in which damage to the substrate 9 is gradually increased. Therefore, an aluminum oxide film for protecting the aluminum oxide film on the aluminum oxide film is reduced by the second film forming process while reducing damage to the aluminum oxide film having a high passivation effect formed in the first film forming process. Further, it can be formed. Further, in this case, the damage applied to the aluminum oxide film is increased, so that the damage given to the aluminum oxide film can be reduced.

  The film forming unit 1 includes two processing spaces V, the first film forming process is performed in the upstream processing space V, and the downstream processing space V is faster than the film forming speed of the first film forming process. The second film formation process for forming the aluminum oxide film at a single high film formation speed may be performed.

  As shown in FIGS. 8 and 9, the second film forming process is performed by applying a sputtering voltage having a negative voltage value higher than the sputtering voltage in the first film forming process to the target 8 facing the substrate 9. obtain. The second film formation process can also be performed by applying a sputtering voltage having a frequency higher than the sputtering voltage in the first film formation process to the target 8 facing the substrate 9. In addition, the second film forming process is performed by sputtering a negative DC voltage applied in the first film forming process, that is, a DC pulse having a higher positive voltage application time ratio in the pulse period than a sputtering voltage to which no positive voltage is applied. It can also be performed by applying a voltage to the target 8 facing the substrate 9. In the second film formation process, high-frequency power larger than the high-frequency power supplied in the first film formation process is applied to the high-frequency antenna 151 in the mixed atmosphere of the sputtering gas and the reactive gas to which the substrate 9 is exposed. It can also be done by feeding.

  In the examples shown in FIGS. 8 and 9, the negative voltage value of the sputtering voltage applied to the target 8 is increased only in the period a3 (b3) and thereafter. As described above, the film formation is performed at the plurality of film formation speeds in the second film formation process, and the substrate is formed only in the film formation process corresponding to the film formation speed applied to the second or later of the plurality of film formation speeds. The negative voltage value of the sputtering voltage applied to the target 8 opposed to 9 may be increased. Here, when the negative voltage value of the sputtering voltage is increased, the frequency of the direct current pulse (sputtering voltage), the inversion time of the direct current pulse (sputtering voltage), and the high frequency power are usually increased. Efficient film formation speed. For this reason, if the negative voltage value of the sputtering voltage is increased only in the film forming process corresponding to the film forming speed applied after the second of the plurality of film forming speeds in the second film forming process, Rapid increase can be suppressed.

<4. Operation of Deposition Unit 1>
Next, the operation of the film forming unit 1 will be described with reference to FIG. 10 in addition to FIGS. FIG. 10 is a diagram showing a flow of processing executed in the film forming unit 1. The operations described below are executed under the control of the control unit 190.

  When the carrier 90 in which the substrate 9 (that is, the substrate 9 subjected to the heat treatment in the heating chamber 120) is disposed in the film formation chamber 130, the gate 160 on the entrance side of the film formation chamber 130 is closed. (Step S1). Note that the inside of the chamber 130 is kept at a high vacuum by a high vacuum exhaust system 170.

  Subsequently, the gas supply unit 50 supplies argon, which is a sputtering gas, and oxygen, which is a reactive gas, to each processing space V (step S2).

  Further, in each of the sputter sources 10, for example, as illustrated in FIGS. 8 and 9, high-frequency power is supplied from the high-frequency power source 153 to the high-frequency antenna 151, and the sputter power source 12 sputters onto the base plate 11. A voltage is applied (step S3). Then, plasma (high frequency inductively coupled plasma) is generated by a high frequency induction electric field around the high frequency antenna 151 (so-called plasma assist). Further, when a sputtering voltage is applied to the base plate 11, high-density plasma is generated near the target 8. These two types of plasma are confined to the surface portion of the target 8 by a static magnetic field formed by the magnet 13 in the vicinity of the target 8. Then, argon ions in the plasma atmosphere collide with the target 8, and aluminum oxide that is not stoichiometric is ejected from the surface of the target 8 (so-called reactive sputtering).

  Further, in order to supplement the reactive gas of consumed oxygen by the reactive sputtering and maintain the state in which the target 8 is sputtered in the transition mode (transition state), as illustrated in FIGS. Control of the supply amount of the reactive gas to the processing space V is started (step S4). In this supply process, during the film forming process, that is, in parallel with the film forming process, based on the sputtering current value flowing in the magnetron cathode of each processing space V so that the reactive sputtering of the target 8 is performed in the transition state. Thus, the reactive gas is supplied to each processing space V while its supply amount is controlled.

  On the other hand, the transport unit 180 transports the carrier 90 on which the substrate 9 is disposed along the transport path L (that is, along the arrangement direction of the plurality of processing spaces V) at a constant speed (step S5). ). The substrate 9 disposed in the carrier 90 sequentially passes through each processing space V along the transport path L, and is subjected to film forming processing in order in each processing space. However, in the case where the substrate 9 is a p-type silicon substrate, the substrate 90 is disposed on the carrier 90 with the back surface when the light incident surface is the front surface facing away from the carrier 90. 90 is transported in such a posture that the surface on which the substrate 9 is disposed is directed to each sputtering source 10. That is, the substrate 9 held by the carrier 90 is transported in each processing space in such a posture that the back surface thereof faces the target 8 of each sputtering source 10.

  In other words, in this film forming process, high frequency power is supplied to the high frequency antenna 151 and high frequency inductively coupled plasma is generated in a mixed atmosphere of the sputtering gas to which the substrate 9 is exposed and an oxygen reactive gas. At the same time, a sputtering voltage including a negative voltage is applied to the target 8 provided on the magnetron cathode forming the static magnetic field by constant voltage control, and magnetron plasma is generated by the static magnetic field. Then, the target 8 is sputtered (reactive sputtering) by the generated high frequency inductively coupled plasma and magnetron plasma, and an aluminum oxide film is formed on the substrate 9 facing the target 8.

  More specifically, in this film forming process, high-frequency inductively coupled plasma and magnetron plasma are generated under a plurality of plasma generating conditions in which at least one of high-frequency inductively coupled plasma and magnetron plasma is spatially different from each other. In each processing space V, high-frequency power is supplied to the high-frequency antenna 151 in a mixed atmosphere of a sputtering gas and a reactive gas, and a sputtering voltage is applied to the target 8 facing the substrate 9 in each processing space V. .

  Processing executed on the substrate 9 transported in the film forming chamber 130 will be described with reference to FIG. FIG. 11 is a diagram showing a flow of processing performed on the substrate 9 transported in the film forming chamber 130.

  Each processing space V is supplied with a sputtering gas and a reactive gas of oxygen, and the target 8 is sputtered with ions (argon ions) of the sputtering gas in the plasma atmosphere while being plasma-assisted. Then, reactive sputtering proceeds in each processing space V, and an aluminum oxide film is formed by reactive sputtering on the substrate 9 disposed opposite to the target 8, that is, on the back surface of the substrate 9. That is, an aluminum oxide film is formed on the back surface of the substrate 9 while the substrate 9 held by the carrier 90 passes through each processing space V from the upstream side to the downstream side along the transfer path L. .

  More specifically, the substrate 9 first passes along the transport path L through the processing space V on the most upstream side of the transport path L among the processing spaces V. And the 1st film-forming process which forms an aluminum oxide film on the board | substrate 9 in which the aluminum oxide film is not formed is performed (step S101).

  Then, after the first film formation process is performed on the substrate 9, the film formation speed in the first film formation process when the substrate 9 passes through each of the second and subsequent process spaces among the process spaces V. A second film formation process is performed in which an aluminum oxide film is further formed on the aluminum oxide film formed on the substrate 9 at at least one film formation speed higher than that (step S102).

  The substrate 9 that exits the processing space V on the most downstream side of the transfer path L among the processing spaces V (that is, the substrate 9 on which the aluminum oxide film is formed on the back surface) is the gate 160 on the outlet side of the film forming chamber 130. Is released from the film forming chamber 130. As described above, the substrate 9 carried out of the film forming chamber 130 is subsequently carried into the cooling chamber 140 where it is subjected to a cooling process as necessary.

  Further, since damage on the surface of the silicon substrate 9 can be recovered to some extent by heat treatment (annealing) after film formation, annealing is performed at, for example, around 450 ° C. (400 ° C. to 500 ° C.) after the formation of the aluminum oxide film. May be implemented.

<5. Modification>
<When 5-1.1 sputter sources 10 are provided>
In the above embodiment, the film forming unit 1 is configured to include the plurality of sputter sources 10, but the film forming unit may be configured to include, for example, one sputter source 10s. FIG. 12 schematically shows a schematic configuration of a film forming unit 1s including one sputter source 10s. FIG. 13 schematically shows a schematic configuration of the sputter source 10s of FIG.

  The film forming chamber 130s provided in the film forming unit 1s forms one processing space Vs partitioned by the chimney 20 in its internal space, and one sputter source 10s is arranged in the processing space Vs. The film forming unit 1s has the same configuration as the film forming unit 1 according to the above-described embodiment except that the film forming unit 1s includes one sputter source 10s and a control unit 190s. Also in the drawing, the same reference numerals are given to portions having the same configuration and function as those of the above-described embodiment, and description of the portions is omitted. Note that the film forming unit 1 s also includes a transport unit 180 as in the film forming unit 1. The film forming unit 1 forms a film on the substrate 9 while transferring the substrate 9 over the plurality of processing spaces V by the transfer unit 180, whereas the film forming unit 1 in the film forming unit 1 uses the target 8 in the processing space Vs. The film forming process is performed on the substrate 9 in a state where the transfer unit 180 is stopped so as to face the substrate 9.

  Similarly to the gas supply unit 50 according to the above-described embodiment, the gas supply unit 50s that supplies gas to the processing space Vs is a sputtering gas supply unit 51s that supplies sputtering gas (for example, argon) to the processing space Vs. And a reactive gas supply part 52s for supplying a reactive gas of oxygen to the processing space Vs. The sputter gas supply unit 51 s is provided in correspondence with the argon supply source 511, one end connected to the argon supply source 511, and the other end communicating with the processing space Vs (specifically, the sputter source 10 s. And an argon supply pipe 512 connected to the discharge port 16). A supply valve 513 s is provided in the middle of the argon supply pipe 512. The supply valve 513s adjusts the amount of argon supplied to the processing space Vs under the control of the control unit 190s. The reactive gas supply unit 52s includes an oxygen supply source 521, and an oxygen supply pipe 522 having one end connected to the oxygen supply source 521 and the other end connected to the discharge port 16 communicating with the processing space Vs. A supply valve 523 s is provided in the middle of the oxygen supply pipe 522. The supply valve 523s adjusts the amount of oxygen supplied to the processing space Vs under the control of the control unit 190s.

  The sputter source 10 s is configured in the same manner as the sputter source 10 except that it includes a high-frequency power source 153 s and a sputtering power source 12 s instead of the high-frequency power source 153 and the sputtering power source 12 of the sputter source 10. The high-frequency power supply 153s is configured to be able to change the high-frequency power supplied to the high-frequency antenna 151 under the control of the control unit 190s. The high-frequency power is supplied to the high-frequency antenna 151 so that high-frequency inductively coupled plasma is generated in the processing space Vs. Supply. The sputtering power supply 12 s is configured to be able to change the sputtering voltage applied to the target 8 under the control of the control unit 190 s, so that the magnetron plasma is generated in the processing space Vs by the static magnetic field formed by the magnetron cathode. A sputtering voltage including a negative voltage is applied to 8 by constant voltage control.

  The control unit 190s includes the same components as those of the control unit 190 according to the embodiment. In addition to having the same functions as the control unit 190, the control unit 190s is electrically connected to the high-frequency power source 153s and the sputtering power source 12s. These controls are further performed. Similarly to the control unit 190, the control unit 190s also operates as a gas supply amount control unit that controls the supply amount of the reactive gas to the processing space Vs by the gas supply unit 50s. The control unit 190 s also operates as a high-frequency power control unit that controls the high-frequency power supplied from the high-frequency power source 153 s to the high-frequency antenna 151, and the sputtering voltage control that controls the sputtering voltage that the sputtering power source 12 s applies to the target 8. Also works as a part.

  More specifically, the control unit 190s generates the high frequency inductively coupled plasma and the magnetron plasma under a plurality of plasma generating conditions on time axes in which at least one of the high frequency inductively coupled plasma and the magnetron plasma is generated. Thus, the high frequency power supplied to the high frequency antenna 151 and the sputtering voltage applied to the magnetron cathode are controlled. In addition, the control unit 190s may react with oxygen reactive gas (more accurately, supplied to the processing space Vs based on the sputtering current value flowing in the magnetron cathode during the film forming process so that reactive sputtering is performed in the transition state. For example, a 5% pure oxygen gas or a diluted mixed gas of 5% pure oxygen gas and an inert gas such as Ar is desirable). Then, the film forming unit 1s sputters the target 8 in this state. As a result, the film forming unit 1s performs the first film forming process for forming the aluminum oxide film on the substrate 9 on which the aluminum oxide film is not formed, and in the first film forming process after the first film forming process. A second film forming process for forming an aluminum oxide film on the aluminum oxide film formed on the substrate 9 is performed at at least one film forming speed higher than the film forming speed.

<5-2. Changes in film formation and plasma generation conditions>
In the film forming unit 1s, for example, the frequency of the direct current pulse (sputtering voltage), the direct current pulse (sputtering voltage), and the like can be used as parameters that can efficiently change the generation conditions of the high frequency inductively coupled plasma and the magnetron plasma. Voltage) inversion time, the value of the high-frequency power supplied to the high-frequency antenna 151, and the absolute value of the sputtering voltage can be independently changed over time.

  In the film forming unit 1s, the high frequency power source 153s and the sputtering power source 12s are under the control of the control unit 190s so that the high frequency inductively coupled plasma and the magnetron plasma are generated under a plurality of plasma generation conditions that are temporally different from each other. Then, the high frequency power is supplied to the high frequency antenna 151 and the sputtering voltage is applied to the target 8. Between the plurality of plasma generation conditions, at least one of the generation conditions of the high frequency inductively coupled plasma and the magnetron plasma is temporally different. The sputtering voltage applied to the target 8 is controlled at a constant voltage by a sputtering power source 12s. In addition, the control unit 190s controls the supply amount of the reactive gas to the processing space Vs based on the sputtering current value flowing to the magnetron cathode so that the reactive sputtering is performed in the transition state in the processing space Vs.

  In this state, the film forming unit 1s first performs the first film forming process for forming the aluminum oxide film on the substrate 9 on which the aluminum oxide film is not formed by sputtering the target 8 in the processing space Vs. The film forming unit 1s further includes, after the first film forming process, the aluminum oxide formed on the substrate 9 in the processing space Vs at at least one film forming speed higher than the film forming speed in the first film forming process. A second film forming process for further forming an aluminum oxide film on the film is performed.

  During the first and second film forming processes, the sputtering voltage is controlled at a constant voltage by the sputtering power source, and the reactive gas is supplied based on the sputtering current value so that reactive sputtering is performed in the transition state. While being controlled, the gas is supplied into the mixed atmosphere of the sputtering gas and the reactive gas in the processing space Vs. Thereby, the oxidation degree of the aluminum oxide film can be stabilized to the oxidation degree when reactive sputtering is performed in the transition state. Further, a first film formation process for forming an aluminum oxide film on a substrate on which an aluminum oxide film is not formed, and at least one film formation speed higher than the film formation speed in the first film formation process after the first film formation process. Since the second film formation process for forming an aluminum oxide film on the aluminum oxide film formed on the substrate is performed at a film speed, the aluminum oxide film is formed as compared with the case where the film is formed at a constant film formation speed. The film formation rate can be increased. That is, according to the film forming unit 1s, aluminum oxide can be formed at a high film formation rate while stabilizing the degree of oxidation.

  FIG. 14 and FIG. 15 are examples of time diagrams of the method of forming the aluminum oxide film by the film forming unit 1s. More specifically, FIG. 14 shows a time diagram when the aluminum oxide films are sequentially formed on the substrate 9 in the processing space Vs under the plasma generation conditions where the film forming units 1s are different in time from each other. It is shown. The plasma generation conditions of at least one of the high frequency inductively coupled plasma and the magnetron plasma are different among the nine plasma generation conditions. FIG. 15 shows a time diagram in the case where the film forming unit 1s performs the film forming process under seven plasma generation conditions that are different from each other in time, as in FIG.

  In the example of FIGS. 14 and 15, as in FIGS. 8 and 9, a negative DC voltage and a negative and positive DC pulse are applied as the sputtering voltage applied to the magnetron cathode. FIGS. 14 and 15 show the seven time diagrams shown in FIGS. 8 and 9 in the same display order as FIGS. 8 and 9.

  Further, in each of the seven time diagrams of FIG. 14 (FIG. 15), each of the periods a1 to a9 (b1 to b7) on the horizontal time axis has nine (seven) substrates 9 in the processing space Vs. In the plasma generation conditions, each film formation time is formed sequentially in time. The time display indicated by numerals indicates the accumulated time of each film formation time. Each film formation time is set so that aluminum oxide films having respective film thicknesses set in advance under nine (seven) plasma generation conditions are formed in time sequence. That is, the control unit 190s changes the plasma generation conditions in time sequence based on the film formation times so that aluminum oxide films having respective preset thicknesses are formed in time sequence in each plasma generation condition. To do.

  FIG. 14 (FIG. 15) is displayed by the above-described display method. As a result, in FIG. 14 (FIG. 15), the frequency of the DC pulse (sputtering voltage), the inversion time of the DC pulse (sputtering voltage), and the high-frequency antenna 151 The four parameters, the value of the high-frequency power supplied to and the absolute value of the sputtering voltage, are set to the same value on the time axis at the same timing as in FIG. Periods a1 to a9 (b1 to b7) in FIG. 14 (FIG. 15) are periods of the same length as the periods a1 to a9 (b1 to b7) in FIG. 8 (FIG. 9).

  Further, the respective target current values of the sputtering current in the periods a1 to a9 (b1 to b7) shown in FIG. 14 (FIG. 15) are the respective targets in the periods a1 to a9 (b1 to b7) in FIG. It is the same as the current value. As a result, the supply amount of the reactive gas into the mixed atmosphere of the sputtering gas and the reactive gas in each period of FIG. 14 (FIG. 15) is the supply amount of the reactive gas in each period of FIG. 8 (FIG. 9). The same supply amount is set. Due to the supply of the reactive gas, the measured value of the sputtering current in each period of FIG. 14 (FIG. 15) is substantially the same as the measured value of each period of FIG. 8 (FIG. 9). More strictly, in FIG. 8 (FIG. 9), the measured value of the sputtering current changes stepwise to the same value as the target current value at the same timing as the target current value, but in FIG. 14 (FIG. 15), The measured sputtering current value continuously increases during the whole period or a part of the front side. Here, in the film forming unit 1 according to the embodiment, the plasma generation conditions in each processing space V are constantly set to the respective plasma generation conditions set in advance for each processing space V. On the other hand, in the film forming unit 1s, the plasma generation conditions in one processing space Vs, the target current value of the sputtering current, and the supply amount of the reactive gas are in accordance with the time table that defines these values and the change timing. It is changed in time sequence. Furthermore, there is a time difference from when the supply amount of the reactive gas of oxygen is changed according to the target current value of the sputtering current until the change of the supply amount of the reactive gas is actually reflected in the sputtering current value. These cause the continuous increase in the measured sputtering current value described above.

  As described above with reference to FIGS. 14 and 15, also in the film forming process by the film forming unit 1 s, an aluminum oxide film can be formed on the substrate 9 according to the same time diagram as the film forming unit 1. Therefore, the film forming process by the film forming unit 1s can obtain the same effects as the film forming process by the film forming unit 1 and can be similarly modified.

  Specifically, as shown in FIGS. 14 and 15, in each of the second and subsequent periods in which the second film formation process is performed, the first period in which the first film formation process is performed (that is, the period a1). , B1), parameters for determining the plasma generation conditions are set so that the film forming rate is increased. This shortens the time required to complete the film forming process compared to the case where the film forming speed in the first period (that is, the periods a1 and b1) in which the first film forming process is performed is maintained in other periods. Is done.

  Further, in the examples of FIGS. 14 and 15, the deposition rate is increased in each of the second and subsequent plasma generation conditions (deposition conditions), that is, in each of the second and subsequent periods. Are set with parameters for determining the plasma generation conditions. Thereby, in the second film formation process, the film formation is performed in time sequence at a plurality of film formation speeds higher than the film formation speed in the first film formation process. Further, the plurality of film forming speeds in the second film forming process increase stepwise in time sequence. Note that supply of high-frequency power or application of a sputtering voltage may be performed so that the plurality of film formation speeds continuously increase in time sequence. The film forming unit 1s first performs the first film forming process, and then forms the aluminum oxide film at one film forming speed higher than the film forming speed of the first film forming process. May be performed.

  As shown in FIGS. 14 and 15, the second film forming process is performed by applying a sputtering voltage having a negative voltage value higher than the sputtering voltage in the first film forming process to the target 8 facing the substrate 9. obtain. The second film formation process can also be performed by applying a sputtering voltage having a frequency higher than the sputtering voltage in the first film formation process to the target 8 facing the substrate 9. In addition, the second film forming process is performed by sputtering a negative DC voltage applied in the first film forming process, that is, a DC pulse having a higher positive voltage application time ratio in the pulse period than a sputtering voltage to which no positive voltage is applied. It can also be performed by applying a voltage to the target 8 facing the substrate 9. In the second film formation process, high-frequency power larger than the high-frequency power supplied in the first film formation process is applied to the high-frequency antenna 151 in the mixed atmosphere of the sputtering gas and the reactive gas to which the substrate 9 is exposed. It can also be done by feeding.

  In the examples shown in FIGS. 14 and 15, the absolute value of the sputtering voltage applied to the target 8 increases only after the period a3 (b3). As described above, the film formation is performed at the plurality of film formation speeds in the second film formation process, and the substrate is formed only in the film formation process corresponding to the film formation speed applied to the second or later of the plurality of film formation speeds. The absolute value of the sputtering voltage applied to the target 8 facing 9 may be increased.

<5-3. Operation of Deposition Unit 1s>
The operation of the film forming unit 1s will be described with reference to FIGS. 11, 16, and 17 in addition to FIGS. 16 and 17 are diagrams showing a flow of processing executed in the film forming unit 1s. FIG. 11 is a diagram showing the flow of processing performed on the substrate 9 as described above. The operation described below is executed under the control of the control unit 190s.

  When the carrier 90 in which the substrate 9 (that is, the substrate 9 subjected to the heat treatment in the heating chamber 120) is disposed in the film formation chamber 130, the transport unit 180 performs a predetermined process on the carrier 90. The carrier 90 is moved to a position (specifically, a position where the substrate 9 held by the carrier 90 is disposed so as to face the target 8 of the sputtering source 10s), and the carrier 90 is stationary at the processing position. Hold (step S11). That is, in the film forming unit 1 according to the above-described embodiment, the substrate 9 has been subjected to a series of film forming processes from the sputter sources 10 one after another while moving relative to the plurality of sputter sources 10. On the other hand, in the film forming unit 1s according to the modification, the substrate 9 is subjected to a series of film forming processes from the sputter source 10s while being stationary with respect to one sputter source 10s.

  On the other hand, when the carrier 90 on which the substrate 9 is disposed is carried into the film forming chamber 130, the gate 160 on the entrance side of the film forming chamber 130 is closed (step S12). Note that the inside of the chamber 130 is kept at a high vacuum by a high vacuum exhaust system 170. Either step S11 or step S12 may be performed first, or may be performed in parallel.

  Subsequently, the gas supply unit 50 starts supplying the sputtering gas and the reactive gas of oxygen to the processing space Vs so as to have a predetermined gas partial pressure (step S13).

  Furthermore, in the sputter source 10s, for example, as shown in the examples of FIGS. 14 and 15, the high-frequency power for the first film formation process is supplied from the high-frequency power source 153 to the high-frequency antenna 151 to cause a high-frequency current to flow. A sputtering voltage for the first film forming process is applied from 12 to the base plate 11 (step S14).

  Further, based on the sputtering current value supplied from the ammeter 164 of the sputtering power source 12s, for example, as shown in FIGS. 14 and 15, the reactive gas supply amount is controlled (supply for the first film forming process). Quantity control) is started (step S15).

  At this stage, a sputtering gas and a reactive gas of oxygen are supplied to the processing space Vs, and the target 8 is sputtered by ions (argon ions) of the sputtering gas in the plasma atmosphere in a state where plasma assist is performed. Is done. Then, reactive sputtering proceeds in the processing space Vs, and a first film forming process for forming an aluminum oxide film on the substrate 9 on which the aluminum oxide film is not formed is performed (step S101).

  When a predetermined time for forming an aluminum oxide film having a predetermined film thickness (for example, 10 nm) elapses after the process of step S14, for example, a high-frequency power source as in the examples of FIGS. A high-frequency power for the second film formation process is supplied from 153 s to the high-frequency antenna 151 to cause a high-frequency current to flow, and a sputtering voltage for the second film formation process is applied to the base plate 11 from the power source 12 s for sputtering (step) S16).

  Further, based on the sputtering current value supplied from the ammeter 164 of the sputtering power supply 12s, for example, as shown in FIGS. 14 and 15, the reactive gas supply amount is controlled (supply for the second film forming process). Quantity control) is started (step S17).

  Then, a second formation film is further formed on the aluminum oxide film formed on the substrate 9 by the first film formation process at at least one film formation speed higher than the film formation speed in the first film formation process. Film processing is performed (step S102).

  When a predetermined time for forming an aluminum oxide film having a predetermined film thickness (for example, 30 nm to 100 nm) elapses after the processing of step S16, the sputtering power source 12s stops applying the sputtering voltage. The high frequency power supply 153s stops supplying high frequency power (step S18).

  The gas supply unit 50 s stops the supply of the reactive gas of oxygen to the processing space Vs (Step S 19), the gate 160 is released, and the carrier 90 on which the substrate 9 is disposed is formed by the transport unit 180. It is carried out from the chamber 130 (step S20).

  In the film forming unit 1 according to the above-described embodiment, a plurality of sputter sources 10 are arranged in one film forming chamber 130. However, each sputter source is housed in an individual chamber, and It is good also as a structure which connects each chamber via a vacuum path | route. In this case, the internal space of each of the plurality of chambers connected via the vacuum path forms one processing space.

  Further, the chamber configuration of the film forming apparatus 100 according to the above-described embodiment is not limited to the one exemplified above. For example, a further processing chamber may be added to the film forming apparatus, and for example, at least one of the heating chamber 120 and the cooling chamber 140 may be omitted.

  Further, the configuration of each sputter source 10 is not limited to the above example. For example, the number of the high-frequency antennas 151 arranged in each sputter source 10 does not need to be two, and can be appropriately selected according to the size of the substrate 9 that is the object of film deposition, the size of the target 8, and the like. . Further, the sputtering gas is not necessarily argon, and may be, for example, xenon (Xe) gas.

  In addition, as described above, the film forming method according to the present invention includes a passivation film for a solar cell silicon substrate (particularly, a back surface passivation film for a p-type silicon substrate and a passivation film for a surface p-type doped layer on an n-type silicon substrate). Although suitable for production, the film formation method according to the present invention can be applied to the production of various other films. For example, it can be applied to the production of various barrier films, sealing films for organic EL displays, sealing films for solar cells, and the like.

  In any of the film forming unit 1 according to the present embodiment as described above and the film forming unit 1s according to the modification, the sputtering voltage is controlled at a constant voltage by the sputtering power source, and the reactive sputtering is performed in the transition state. In addition, the reactive gas is supplied during film formation while the supply amount is controlled based on the sputtering current value. When the sputtering voltage is controlled at a constant voltage, the higher the degree of oxidation of the surface of the target 8, that is, the greater the amount of reactive gas, the larger the sputtering current value and the degree of oxidation of the formed aluminum oxide film. Get higher. Therefore, the oxidation degree of the aluminum oxide film can be stabilized to the oxidation degree when reactive sputtering is performed in the transition state. Also, a first film formation process for forming an aluminum oxide film on the substrate 9 on which the aluminum oxide film is not formed, and at least one film formation speed higher than the film formation speed in the first film formation process after the first film formation process Since the second film forming process for forming an aluminum oxide film on the aluminum oxide film formed on the substrate 9 is performed at the film forming speed, the oxidation is performed as compared with the case where the film is formed at a constant film forming speed. The film formation rate of aluminum can be increased. That is, aluminum oxide can be deposited at a high deposition rate while stabilizing the oxidation degree. Further, if a structure in which a nitride film is formed as a protective film on the aluminum oxide film formed by the first film forming process is employed, the protective film can be easily formed, but a CVD apparatus is required. In the film forming unit 1 and the film forming unit 1s, the aluminum oxide film is further formed as a protective film by the second film forming process on the aluminum oxide film formed by the first film forming process. The device configuration is simplified.

  In addition, in any of the film forming unit 1 according to the present embodiment and the film forming unit 1s according to the modification as described above, the second film forming process has a plurality of speeds higher than the film forming speed in the first film forming process. The film is formed at the film forming speed. Thereby, in the second film forming process, it is possible to adopt a plasma generating condition in which the film forming speed is gradually increased according to the film thickness of the aluminum oxide film, that is, a plasma generating condition in which damage to the substrate 9 is gradually increased. . Therefore, it is possible to further form an aluminum oxide film for protecting the aluminum oxide film on the aluminum oxide film by the second film forming process while reducing damage to the aluminum oxide film formed in the first film forming process. it can.

  In addition, in any of the film forming unit 1 according to the present embodiment and the film forming unit 1s according to the modification described above, each target current value corresponding to each of the plurality of plasma generation conditions is set to the plurality of plasma generation conditions. Each sputtering current value is set when reactive sputtering is performed in the transition state. Then, into the mixed atmosphere of the sputtering gas and the reactive gas of oxygen in the processing space so that the sputtering current value flowing through the magnetron cathode provided with the target 8 facing the substrate 9 sequentially becomes each target current value, The reactive gas is supplied while the supply amount is controlled. This enables reactive sputtering in the transition mode regardless of the plasma generation conditions, that is, regardless of the deposition rate.

  In addition, the film forming unit 1 according to the present embodiment and the film forming unit 1s according to the modification described above form films at a plurality of film forming speeds in the second film forming process. Only in the film forming process at the film forming speed applied after the second of the plurality of film forming speeds, the absolute value of the sputtering voltage applied to the target 8 facing the substrate 9 is the same as in the previous film forming process. The absolute value of the sputtering voltage applied to the target 8 facing the substrate 9 is set so as to increase. When the absolute value of the sputtering voltage is increased, the film forming speed is usually increased as compared with the case where any of the frequency of the sputtering voltage, the inversion time of the sputtering voltage to the positive voltage, and the high frequency power is increased. Thereby, a rapid increase in damage to the formed aluminum oxide film can be suppressed.

  Although the invention has been shown and described in detail, the above description is illustrative in all aspects and not restrictive. Therefore, embodiments of the present invention can be modified or omitted as appropriate within the scope of the invention.

1,1s film forming unit (film forming equipment)
DESCRIPTION OF SYMBOLS 10 Sputter source 11 Base plate 12, 12 s Sputtering power source 13 Magnet 14 Anode 15 Inductive coupling type plasma generating unit 151 High frequency antenna 153, 153 s High frequency power source 16 Discharge port 20 Chimney 40 Heater 50, 50 s Gas supply unit 51 Sputter gas supply unit 52 Reactive gas supply unit 8 Target 9 Substrate 90 Carrier 100 Film forming device 130 Film forming chamber 170 High vacuum exhaust system 180 Transport unit 190, 190s Control unit L Transport path (processing path)
V, Vs processing space

Claims (10)

A film forming method of forming an aluminum oxide film on a substrate by reactive sputtering,
In a mixed atmosphere of sputtering gas and oxygen reactive gas to which the substrate is exposed, high-frequency inductively coupled plasma is generated by supplying high-frequency power to a high-frequency antenna composed of a conductor having less than one turn, and a static magnetic field is generated. Sputtering voltage including negative voltage is applied to the aluminum target provided on the magnetron cathode to be formed by constant voltage control of the sputtering power source to generate magnetron plasma by the static magnetic field to sputter the aluminum target and face the aluminum target A film forming step of forming an aluminum oxide film on the substrate;
A gas supply step of supplying the reactive gas into the mixed atmosphere during the film forming step;
With
The gas supply step includes
The reactive gas is supplied while controlling the supply amount during the film forming step based on the sputtering current value flowing through the magnetron cathode provided with the aluminum target facing the substrate so that reactive sputtering is performed in the transition state. Is a step to
The film forming step includes
The high frequency power to the high frequency antenna in the mixed atmosphere is generated so that the high frequency inductively coupled plasma and the magnetron plasma are generated under a plurality of plasma generating conditions in which at least one of the high frequency inductively coupled plasma and the magnetron plasma is different from each other. And applying a sputtering voltage to the aluminum target facing the substrate,
A first film forming process for forming an aluminum oxide film on the substrate on which the aluminum oxide film is not formed;
After the first film forming process, an aluminum oxide film is further formed on the aluminum oxide film formed on the substrate at at least one film forming speed higher than the film forming speed in the first film forming process. 2 film formation process;
A film forming method, which is a step of performing. The film forming method according to claim 1,
The film forming method, wherein the at least one film forming speed is a plurality of film forming speeds that increase stepwise or continuously. The film forming method according to claim 1 or 2,
The gas supply step includes
A step of controlling the supply amount of the reactive gas into the mixed atmosphere so that the sputtering current value flowing through the magnetron cathode provided with the aluminum target facing the substrate sequentially reaches each target current value,
Each of the target current values is a sputtering current value when reactive sputtering is performed in a transition state under each of the plurality of plasma generation conditions. A film forming method according to any one of claims 1 to 3, wherein
The second film forming process
A film forming method, which is a process of applying a sputtering voltage having a negative voltage value higher than a sputtering voltage in the first film forming process to an aluminum target facing the substrate. A film forming method according to any one of claims 1 to 4, wherein
The sputtering voltage in the first film forming process is a negative voltage or a direct current pulse composed of a negative voltage and a positive voltage,
The second film forming process
A film forming method, which is a process of applying a sputtering voltage having a frequency higher than a sputtering voltage in the first film forming process to an aluminum target facing the substrate. A film forming method according to any one of claims 1 to 5, comprising:
The first film forming process is a process of applying a negative voltage or a direct current pulse composed of a negative voltage and a positive voltage to the aluminum target facing the substrate as a sputtering voltage,
In the second film forming process, an aluminum target facing the substrate with a DC pulse consisting of a negative voltage and a positive voltage as a sputtering voltage, which has a higher rate of positive voltage application time in the pulse period than the first film forming process. A film forming method, which is a process applied to the film. A film forming method according to any one of claims 1 to 6, comprising:
The second film forming process
A film forming method, which is a process of supplying a high frequency power larger than the high frequency power supplied in the first film forming process to the high frequency antenna in the mixed atmosphere to which the substrate is exposed. A film forming method according to any one of claims 1 to 7,
The at least one deposition rate is a plurality of deposition rates that increase stepwise or continuously,
The second film forming process
The plasma generation condition is changed by increasing the absolute value of the sputtering voltage applied to the aluminum target facing the substrate only for the second and subsequent film forming speeds of the plurality of film forming speeds. A film forming method which is a treatment. A film forming apparatus for forming an aluminum oxide film on a substrate by reactive sputtering,
Each magnetron cathode provided with an aluminum target and provided in each of a plurality of processing spaces to form a static magnetic field;
Each high-frequency antenna provided in each of the plurality of processing spaces and made of a conductor having a number of turns of less than one turn,
A gas supply unit configured to supply a sputtering gas and a reactive gas of oxygen to each of the plurality of processing spaces;
A gas supply amount control unit for controlling the supply amount of the reactive gas to the plurality of processing spaces by the gas supply unit;
A transport unit that transports a substrate along a processing path that sequentially faces each aluminum target of the plurality of processing spaces;
Each high-frequency power source that supplies high-frequency power to each high-frequency antenna in the plurality of processing spaces so that high-frequency inductively coupled plasma is generated in the plurality of processing spaces
Each sputtering power source for applying a sputtering voltage including a negative voltage to each aluminum target by constant voltage control so that magnetron plasma is generated in the plurality of processing spaces by a static magnetic field formed by each magnetron cathode of the plurality of processing spaces. When,
With
Each high frequency power source and each sputter power source supply high frequency power to each high frequency antenna so that at least one of the generation conditions of high frequency inductively coupled plasma and magnetron plasma differs between the plurality of processing spaces. Applying a sputtering voltage to each of the aluminum targets, and the gas supply amount control unit based on a sputtering current value flowing to each of the magnetron cathodes so that reactive sputtering is performed in a transition state in the plurality of processing spaces. In the state where the supply amount of the reactive gas to the plurality of processing spaces is controlled, by sputtering each aluminum target,
A first film forming process for forming an aluminum oxide film on the substrate on which the aluminum oxide film is not formed;
After the first film forming process, an aluminum oxide film is further formed on the aluminum oxide film formed on the substrate at at least one film forming speed higher than the film forming speed in the first film forming process. 2. A film forming apparatus that performs a film forming process. A film forming apparatus for forming an aluminum oxide film on a substrate by reactive sputtering,
A magnetron cathode provided with an aluminum target in a processing space and forming a static magnetic field;
A high-frequency antenna provided in the processing space and comprising a conductor having a number of turns of less than one turn;
A gas supply unit for supplying a sputtering gas and a reactive gas of oxygen to the processing space;
A gas supply amount control unit for controlling a supply amount of the reactive gas to the processing space by the gas supply unit;
A high frequency power supply for supplying high frequency power to the high frequency antenna so that high frequency inductively coupled plasma is generated in the processing space;
A high frequency power control unit for controlling high frequency power supplied by the high frequency power source;
A sputtering power source for applying a sputtering voltage including a negative voltage to the aluminum target by constant voltage control so that a magnetron plasma is generated in the processing space by a static magnetic field formed by the magnetron cathode;
A sputtering voltage controller for controlling a sputtering voltage applied by the sputtering power source;
With
The high-frequency inductively coupled plasma and the magnetron plasma are generated under a plurality of plasma generation conditions in which at least one of the high-frequency inductively coupled plasma and the magnetron plasma is temporally different from each other. The sputtering voltage control unit controls the high frequency power supplied to the high frequency antenna and the sputtering voltage applied to the magnetron cathode, and the gas supply amount control unit performs the reactive sputtering in a transition state. Sputtering the aluminum target while controlling the supply amount of the reactive gas supplied to the processing space based on the value of the sputtering current flowing through the magnetron cathode,
A first film forming process for forming an aluminum oxide film on the substrate on which the aluminum oxide film is not formed;
After the first film forming process, an aluminum oxide film is further formed on the aluminum oxide film formed on the substrate at at least one film forming speed higher than the film forming speed in the first film forming process. 2. A film forming apparatus that performs a film forming process.

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