Patent Application
20220098717
The present disclosure relates to a film forming apparatus and a film forming method.
A magnetoresistive element including a magnetic film and a metal oxide film is used for a magnetic device such as a magnetoresistive random access memory (MRAM), a hard disk drive (HDD), or the like. As a film forming apparatus for forming a metal oxide film, Patent Document 1 discloses an apparatus including a processing chamber, a holding part for holding a target object in the processing chamber, a metal target, and an introduction mechanism for supplying oxygen gas toward the holding part. In the film forming apparatus of Patent Document 1, after a metal film is deposited on the target object by sputtering the target, the oxygen gas is introduced to oxidize and crystallize the metal film. In this manner, since the deposition of the metal film and the oxidation and crystallization of the metal film are performed in one processing chamber, the metal oxide film can be formed quickly.
Patent Document 1: Japanese Patent Application Publication No. 2016-33244
The present disclosure provides a film forming apparatus and a film forming method capable of suppressing oxidation of a metal target in the case of performing deposition of a metal film and oxidation of the deposited metal film in the same processing chamber.
In accordance with an aspect of the present disclosure, there is provided a film forming apparatus for forming a metal oxide film on a substrate, comprising: a processing chamber; a substrate holder configured to hold a substrate in the processing chamber; a target electrode disposed above the substrate holder and configured to hold a target made of a metal and supply an electrical power from a power source to the target; an oxidizing gas introduction mechanism configured to supply an oxidizing gas to the substrate held by the substrate holder; and a gas supply unit configured to supply an inert gas to a target arrangement space where the target is disposed, wherein a constituent metal is discharged in the form of sputter particles from the target supplied with the electrical power through the target electrode, and deposited on the substrate as a metal film, and the metal film is oxidized by the oxidizing gas introduced by the oxidizing gas introduction mechanism, thereby forming a metal oxide film, and when the oxidizing gas is introduced, the gas supply unit supplies the inert gas to the target arrangement space so that a pressure in the target arrangement space is positive with respect to a pressure in a processing space where the substrate is disposed.
The present disclosure provides a film forming apparatus and a film forming method capable of suppressing oxidation of a metal target in the case of performing deposition of a metal film and oxidation of the deposited metal film in the same processing chamber.
Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.
First, a first embodiment will be described.
The film forming apparatus 1 includes a processing chamber 10, a substrate holder 20, target electrodes 30a and 30b, a gas supply part 40, an oxidizing gas introduction mechanism 50, a partition unit 60, and a controller 70.
The processing chamber 10 is made of, e.g., aluminum, and defines a processing chamber for processing the substrate W. The processing chamber 10 is connected to a ground potential. The processing chamber 10 includes a chamber main body 10a having an upper opening, and a lid 10b for closing the upper opening of the chamber main body 10a. The lid 10b has a truncated cone shape.
An exhaust port 11 is formed at a bottom portion of the processing chamber 10, and an exhaust device (ED) 12 is connected to the exhaust port 11. The exhaust device 12 includes a pressure control valve and a vacuum pump, and the inside of the processing chamber 10 is vacuum exhausted to a predetermined vacuum level by the exhaust device 12.
A loading/unloading port 13 for loading/unloading the substrate W into/from an adjacent transfer chamber (not shown) is formed on a sidewall of the processing chamber 10. The loading/unloading port 13 is opened and closed by a gate valve 14.
The substrate holder 20 has a substantially disc shape and is disposed near the bottom portion in the processing chamber 10 to hold the substrate W horizontally. In the present embodiment, the substrate holder 20 includes a base portion 21 and an electrostatic chuck 22. The base portion 21 is made of, e.g., aluminum. The electrostatic chuck 22 is made of a dielectric material and has an electrode 23 therein. The substrate W is electrostatically attracted to the surface of the electrostatic chuck 22 by an electrostatic force generated by applying a DC voltage from a DC power source (not shown) to the electrode 23. In the illustrated example, the electrostatic chuck 22 is a bipolar electrostatic chuck. However, the electrostatic chuck 22 may be a unipolar electrostatic chuck.
Further, a heater 24 is disposed in the substrate holder 20. The heater 24 has, e.g., a heating resistance element, and emits heat by an electrical power supplied from a heater power source (not shown) to heat the substrate W. The heater 24 is used as a first heater for oxidizing the metal film deposited on the surface of the substrate W. When the metal is Mg, the heater 24 heats the substrate W to a temperature within a range of 50° C. to 300° C. In
The substrate holder 20 is connected to a driving unit 25. The driving unit 25 has a driving device (DD) 26 and a support shaft 27. The driving device 26 is disposed below the processing chamber 10. The support shaft 27 extends from the driving device 26 penetrating through the bottom wall of the processing chamber 10, and the tip end thereof is connected to the center of the bottom surface of the substrate holder 20. The driving device 26 rotates and vertically moves up and down the substrate holder 20 via the support shaft 27. The space between the support shaft 27 and the bottom wall of the processing chamber 10 is sealed by a sealing member 28. By providing the sealing member 28, the support shaft 27 can rotate and vertically move while maintaining the vacuum state of the processing chamber 10. The sealing member 28 may be, e.g., a magnetic fluid seal.
The target electrodes 30a and 30b are respectively electrically connected to targets 31a and 31b disposed above the substrate holder 20 and hold the targets 31a and 31b. The target electrodes 30a and 30b are respectively attached on inclined surfaces of the lid 10b of the processing chamber 10 via insulating members 32a and 32b, obliquely with respect to the substrate W. The targets 31a and 31b are made of a metal forming a metal film to be deposited, and the material thereof is appropriately selected depending on the type of a metal oxide film to be formed. For example, the targets 31a and 31b are made of Mg, Al, or the like. Although the number of the targets is two in this example, the number of the targets is not limited thereto and may be one or more, e.g., four.
Power sources 33a and 33b are connected to the target electrodes 30a and 30b, respectively. In this example, the power sources 33a and 33b are DC power sources. However, the power sources 33a and 33b may be AC power sources. The power from the power sources 33a and 33b is supplied to the targets 31a and 31b through the target electrodes 30a and 30b, respectively. Cathode magnets 34a and 34b are disposed on the sides of the target electrodes 30a and 30b opposite to the sides where the targets 31a and 31b are disposed, respectively. Magnet driving units (MDU) 35a and 35b are connected to the cathode magnets 34a and 34b, respectively. Ring-shaped members 36a and 36b for restricting the emission direction of sputter particles are disposed at outer peripheral portions of the surfaces of the targets 31a and 31b, respectively. The ring-shaped members 36a and 36b are grounded.
In the present embodiment, the gas supply unit 40 includes a gas supply source 41, a gas supply line 42 extending from the gas supply source 41, a flow rate controller (FRC) 43, such as a mass flow controller, disposed in the gas supply pipe 42, and a gas introducing member 44. An inert gas, e.g., a noble gas such as Ar, He, Ne, Kr, He, or the like is supplied as a gas to be excited in the processing chamber 10 from the gas supply source 41 into the processing chamber 10 through the gas supply line 42 and the gas introducing member 44.
The gas supply unit 40 is used as a sputtering gas supply mechanism, and also functions an oxygen gas arrival suppression mechanism for suppressing an oxidizing gas to be described later from reaching the targets 31a and 31b.
When the gas supply unit 40 functions as the sputtering gas supply mechanism, the gas from the gas supply unit 40 is supplied as a sputtering gas into the processing chamber 10 when a metal film is deposited by sputtering. The supplied gas is excited by applying a voltage from the power sources 33a and 33b to the targets 31a and 31b through the target electrodes 30a and 30b, respectively, thereby generating plasma. On the other hand, when the cathode magnets 34a and 34b are driven by the magnet driving units 35a and 35b, respectively, a magnetic field is generated around the targets 31a and 31b, so that the plasma is concentrated near the targets 31a and 31b. Then, positive ions in the plasma collide with the targets 31a and 31b, so that the constituent metals are released as sputter particles from the targets 31a and 31b and deposited on the substrate W.
A voltage may be applied from both of the power sources 33a and 33b so that sputter particles can be emitted from both the targets 31a and 31b, or may be applied to only one of the targets 31a and 31b so that sputter particles can be emitted.
The case where the gas supply unit 40 functions as the oxidizing gas arrival suppression mechanism will be described later in detail.
The oxidizing gas introduction mechanism 50 includes a head portion 51, a moving mechanism 52, and an oxidizing gas supply unit 57. The head portion 51 has a substantially disc shape. The moving mechanism 52 has a driving device (DD) 53 and a support shaft 54. The driving device 53 is disposed below the processing chamber 10. The support shaft 54 extends from the driving device 53 penetrating through the bottom wall of the processing chamber 10, and the tip end thereof is connected to the bottom portion of a connection portion 55. The connection portion 55 is coupled to the head portion 51.
The space between the support shaft 54 and the bottom wall of the processing chamber 10 is sealed by a sealing member 54a. The sealing member 54a may be, e.g., a magnetic fluid seal. When the driving device 53 rotates the support shaft 54, the head portion 51 can be moved between an oxidation treatment position in a processing space S directly above the substrate holder 20 and a retreat position distant from the processing space S indicated by dashed lines in the drawing.
A circular gas diffusion space 51a and a plurality of gas injection holes 51b that extend downward from the gas diffusion space 51a and are opened are formed in the head portion 51. A gas line 56 is formed in the support shaft 54 and the connection portion 55, and one end of the gas line 56 is connected to the gas diffusion space 51a. The other end of the gas line 56 is disposed below the processing chamber 10 and connected to the oxidizing gas supply unit 57. The oxidizing gas supply unit 57 includes a gas supply source 58, a gas supply line 59 extending from the gas supply source 58 and connected to the gas line 56, and a flow rate controller (FRC) 59a such as a mass flow controller, disposed in the gas supply line 9. The oxidizing gas, e.g., an oxygen gas (O2 gas), is supplied from the gas supply source 58. When the substrate holder 20 is located at the oxidation treatment position, the oxidizing gas is supplied to the substrate W held by the substrate holder 20 through the gas supply line 59, the gas line 56, the gas diffusion space 51a, and the gas injection holes 51b.
The head portion 51 is provided with a heater 51c. Various heating methods such as resistance heating, lamp heating, induction heating, and microwave heating are applicable for the heater 51c. The heater 51c emits heat by an electrical power supplied from a heater power source (not shown). The heater 51c is used as a second heater for crystallizing the metal oxide film formed on the substrate. When the metal is Mg, the heater 51c heats the substrate W to a temperature within a range of 250° C. to 400° C. The heater 51c may also be used to heat the oxidizing gas in the case of supplying the oxidizing gas (e.g., O2 gas) from the head portion 51. Accordingly, it is possible to further reduce the time required for the metal oxidation.
The partition unit 60 functions as a shielding member for shielding the targets 31a and 31b, and partitions the space in which the targets 31a and 31b are arranged (target arrangement space) and the processing space S in which the substrate is disposed. The partition unit 60 has a first partition plate 61 and a second partition plate 62 disposed below the first partition plate 61. Both of the first partition plate 61 and the second partition plate 62 have a truncated cone shape corresponding to the shape of the lid portion 10b of the processing chamber 10 and overlap with each other in a vertical direction. The first partition plate 61 and the second partition plate 62 have openings having sizes corresponding to those of the targets 31a and 31b, respectively. Further, the first partition plate 61 and the second partition plate 62 can be rotated independently by the rotation mechanism (RM) 63. The first partition plate 61 and the second partition plate 62 can be rotated to an open state in which the openings are located at positions corresponding to the targets 31a and 31b and to a closed state (partition state) in which the openings are located at positions that do not correspond to the targets 31a and 31b. When the first partition plate 61 and the second partition plate 62 are in the open state, the centers of the targets 31a and 31b coincide with the centers of the openings. When the first partition plate 61 and the second partition plate 62 are in the open state, the shielding by the partition unit 60 is released and a metal film can be deposited by sputtering. On the other hand, when the first partition plate 61 and the second partition plate 62 are in the closed state, the target arrangement space and the processing space S are partitioned.
The second partition plate 62 is closed when the targets 31a and 31b are sputter-cleaned by opening the first partition plate 61, and is shielded so that the sputter particles are not emitted to the processing space during the sputter-cleaning of the target targets 31a and 31b.
A shielding member 65 is disposed above the substrate holder 20 to extend from the outer end of the upper surface of the substrate holder 20 to the vicinity of the lower end of the partition unit 60. The shielding member 65 has a function of suppressing the oxidizing gas supplied from the oxidizing gas introduction mechanism 50 from being diffused toward the targets 31a and 31b.
The controller 70 is comprised of a computer and includes a main controller having a CPU for controlling individual components of the film forming apparatus 1, such as the power sources 33a and 33b, the exhaust device 12, the driving unit 25, the gas supply unit 40, the oxidizing gas introduction mechanism 50, the partition unit 60, and the like. The controller 70 further includes an input device such as a keyboard or a mouse, an output device, a display device, and a storage device. The main controller of the controller sets a storage medium in which a processing recipe is stored in the storage device, and causes the film forming apparatus 1 to perform a predetermined operation based on the processing recipe called from the storage medium.
Next, a film forming method of one embodiment that can be performed by the film forming apparatus according to the first embodiment configured as described above will be described with reference to the flowchart of
The film forming method of
First, prior to the execution of the film forming method, the gate valve 14 is opened, and the substrate W is loaded into the processing chamber 10 from the transfer chamber (not shown) adjacent to the processing chamber 10 by a transfer unit (not shown) and held by the substrate holder 20.
In step ST1, a metal film such as an Mg film, an Al film, or the like is deposited on the substrate W on the substrate holder 20 by sputtering. At this time, prior to the deposition of the metal film, the partition unit 60 is set to the open state in the film forming apparatus 1 as shown in
Specifically, the sputtering of step ST1 is performed as follows. First, an inert gas such as Ar gas is introduced into the processing chamber 10 from the gas supply unit 40 while adjusting a pressure in the processing chamber 10 to a predetermined pressure by the exhaust device 12. Next, plasma is generated by applying an electrical power from the power sources 33a and 33b to the targets 31a and 31b through the target electrodes 30a and 30b, respectively, and a magnetic field from the cathode magnets 34a and 34b is made to act. At this time, the cathode magnets 34a and 34b are driven by the magnet driving units 35a and 35b, respectively. Accordingly, the positive ions in the plasma collide with the targets 31a and 31b, and sputter particles P made of the constituent metals of the targets 31a and 31b are emitted from the targets 31a and 31b as shown in
In step ST2, an inert gas such as Ar, He, Ne, Kr, He or the like is supplied from the gas supply unit 40 to the target arrangement space in which the targets 31a and 31b are arranged, and a pressure in the target arrangement space is set to be positive compared to a pressure in the processing space S near the substrate W. At this time, the first partition plate 61 and the second partition plate 61 are rotated to set the partition unit 60 in the closed state.
In step ST3, an oxidizing gas, e.g., O2 gas, is supplied to the substrate W held by the substrate holder 20 while supplying an inert gas to the target arrangement space, and the metal film deposited on the substrate W is oxidized to form a metal oxide film. At this time, the head portion 51 of the oxidizing gas introduction mechanism 50 is moved to the oxidation treatment position directly above the substrate holder 20, and the oxidizing gas is supplied from the head portion 51 of the oxidizing gas introduction mechanism 50 to the substrate W. Further, the substrate W is heated by the heater 24 to a temperature of, e.g., 50° C. to 300° C. In step ST3, after the oxide film is formed, the substrate W may be heated to a temperature of, e.g., 250° C. to 400° C., by the heater 51c to crystallize the metal oxide film. The pressure in step ST3 is preferably within a range of 1×10−7 Torr to 2×10−2 Torr (1.3×10−5 Pa to 2.6 Pa).
In step ST4, the inert gas supplied in step ST2 and the oxidizing gas supplied in step ST3 are discharged from the processing chamber 10 by vacuum exhaustion.
By repeating steps ST1 to ST4 a predetermined number of times, a metal oxide film having a desired film thickness is formed.
If necessary, prior to the deposition of the metal film in step ST1, a voltage may be applied to the targets 31a and 31b to sputter-clean the targets 31a and 31b in a state the first partition plate 61 is set to the open state the second partition plate 62 is set to the closed state. In this way, natural oxide films on the surfaces of the targets 31a and 31b are removed. At this time, the sputter particles are deposited on the second partition plate 62. After the completion of the sputter cleaning, the partition plate 62 is set to the open state. Accordingly, the partition unit 60 is set to the open state, and the deposition of the metal film in step ST1 is performed.
In accordance with the present embodiment, since the deposition of the metal film and the oxidation treatment of the metal film can be performed in one processing chamber, the film formation of the metal oxide film can be performed quickly as in the technique of Patent Document 1.
However, in the technique of Patent Document 1, since the oxidation treatment is performed in the same processing chamber, the oxidizing gas (O2 gas) reaches the targets 31a and 31b during the oxidation treatment, and the surfaces of the targets 31a and 31b are naturally oxidized as shown in
When the natural oxide films are formed on the surfaces of the targets 31a and 31b, the sputtering rate decreases. In addition, a discharge voltage changes due to the surface oxidation, and arc discharge occurs between the natural oxide films and the surfaces of the targets 31a and 31b or between the natural oxide films and the inner wall of the processing chamber. Also, the thickness of the metal film changes. Accordingly, in the case of forming the metal oxide film on multiple substrates W, the thickness of the metal oxide film is reduced and it is difficult to stably manufacture an element having the same characteristics.
Conventionally, it is known that when a sputtering target contains impurities, the impurities are locally charged and, thus, arc occurs. Also in the present embodiment, it is considered that micro-arc occurs because an oxide portion is locally charged. In this case, it is known that by applying the voltage of a temporarily inverted pulse shape to the target (cathode), electrons are exposed on the target surface to remove the accumulated charges and the occurrence of arc is suppressed.
However, even if the occurrence of arc can be suppressed by the above method, that is not a fundamental solution because the natural oxidation of the target surface is not prevented.
Therefore, in the present embodiment, after the metal film is deposited, an inert gas is supplied from the gas supply unit 40 to the target arrangement space, and the pressure in the target arrangement space is set to be positive with respect to the pressure in the processing space S near the substrate W. Then, the oxidation treatment is performed. Accordingly, as shown in
Therefore, it is possible to suppress the oxidation of the surfaces of the targets 31a and 31b, and it is possible to suppress a decrease in the sputtering rate, a change in the discharge voltage, and the occurrence of arc discharge at the time of depositing the metal film by sputtering. In addition, the change in the thickness of the metal film is suppressed. Accordingly, it is possible to stably manufacture an element having the same characteristics.
Next, a test example related to the first embodiment will be described.
First, the effect of preventing the intrusion of O2 gas by supplying Ar gas as an inert gas during the oxidation treatment was checked. Here, the pressure change after the gas supply was monitored in the case of supplying only O2 gas at 1000 sccm, in the case of supplying each of O2 gas and Ar gas at 1000 sccm, and in the case of supplying only Ar gas at 1000 sccm. The result is shown in
As shown in
Next, the effect of supplying Ar gas together with O2 gas during the oxidation treatment was checked. Here, Mg was used as a target, and the sputtering was performed by igniting plasma under the conditions: supply power of 700 W, Ar gas flow rate of 400 sccm, and processing time of 4 sec. Thereafter, the oxidation treatment was performed. The oxidation treatment was performed under common conditions: O2 gas flow rate of 2000 sccm and processing time of 30 sec, and under two types of conditions: a case where Ar gas was not supplied during the oxidation treatment and a case where Ar gas was supplied at 1000 sccm. The pressure during the treatment was 2×10−2 Torr, and the temperature was room temperature. The treatment was repeated under the above conditions, and a discharge voltage at the time of ignition and the number of times of occurrence of micro-arc were monitored. The result is shown in
As shown in
Next, the second embodiment will be described.
The rotation/elevating mechanism 163 switches the partition unit 60 between the open state and the closed state, and vertically moves up and down the partition unit 60 close to or separated from the targets 31a and 31b. More specifically, the rotation/elevating mechanism 163 includes a rotation mechanism (RM) 164 having the same structure as that of the rotation mechanism 63 of
The rotation/elevating mechanism 163 can move the partition unit 60 close to the targets 31a and 31b. In other words, by raising the first partition plate 61 of the partition unit 60, the first partition plate 61 can be moved close to the targets 31a and 31b. By moving the partition unit 60 (the first partition plate 61) close to the targets 31a and 31b, the path through which the oxidizing gas reaches the targets 31a and 31b may be narrowed, and the oxidizing gas can be suppressed from reaching the targets 31a and 31b. Particularly, as shown in
Next, a film forming method according to one embodiment that can be performed by the film forming apparatus according to the second embodiment configured as described above will be described with reference to the flowchart of
The film forming method of
First, prior to the execution of the film forming method, the gate valve 14 is opened, and the substrate W is loaded into the processing chamber 10 from the transfer chamber (not shown) adjacent to the processing chamber 10 by a transfer unit (not shown) and held by the substrate holder 20.
In step ST11, the partition unit 60 is set to the open state. Specifically, the first and second partition plates 61 and 62 are set to the open state in which the openings 61a and 62a are located at positions corresponding to the targets 31a and 31b, respectively. In this state, the centers of the openings 61a and 62a coincide with the centers of the targets 31a and 31b. At this time, the head portion 51 of the oxidizing gas introduction mechanism 50 is located at the retreat position.
In step ST12, a metal film such as an Mg film or an Al film is deposited on the substrate W on the substrate holder 20 by sputtering. This step is performed in the same manner as that in step ST1 of the first embodiment.
In step ST13, the partition unit 60 is set to the closed state. Specifically, first, the second partition plate 62 is rotated to the closed state and, then, the first partition plate 61 is rotated to the closed state.
In step ST14, the partition unit 60 is raised to move close to the targets 31a and 31b. Specifically, by raising the first partition plate 61, the first partition plate 61 is moved close to the targets 31a and 31b. Preferably, as shown in
In step ST15, an oxidizing gas, e.g., O2 gas, is supplied to the substrate W, and the metal film deposited on the substrate W is oxidized to form a metal oxide film. At this time, the head portion 51 of the oxidizing gas introduction mechanism 50 is moved to the oxidation treatment position directly above the substrate holder 20, and the oxidizing gas is supplied from the head portion 51 of the oxidizing gas introduction mechanism 50 to the substrate W. The oxidation treatment of step ST15 is performed in the same manner as that in step ST3 of the first embodiment.
In step ST16, the oxidizing gas supplied in step ST3 is discharged from the processing chamber 10 by vacuum exhaustion.
By repeating steps ST11 to ST16 a predetermined number of times, a metal oxide film having a desired film thickness is formed.
In accordance with the present embodiment, the deposition of the metal film and the oxidation treatment of the metal film can be performed in one processing chamber, so that the formation of the metal oxide film can be performed quickly as in the technique of Patent Document 1. Further, since the partition unit 60 (first partition plate 61) is moved close to the targets 31a and 31b, the intrusion path of the oxidizing gas is narrowed, which makes it possible to suppress the oxidizing gas from reaching the targets 31a and 31b during the oxidation treatment. Particularly, when the first partition plate 61 is brought into close contact with the ring-shaped members 36a and 36b, the space surrounded by the targets 31a and 31b, the partition plate 61 and the ring-shaped members 36a and 36b becomes substantially closed. Accordingly, it is possible to more effectively suppress the oxidizing gas from reaching the surfaces of the targets 31a and 31b.
Therefore, it is possible to suppress the oxidation of the surfaces of the targets 31a and 31b, and also possible to suppress the decrease in the sputtering rate, the change in the discharge voltage, and the occurrence of arc discharge at the time of depositing the metal film by sputtering. In addition, the change in the thickness of the metal film is also suppressed. Accordingly, it is possible to stably manufacture an element having the same characteristics.
In the second embodiment, as shown in
Further, in the second embodiment, as shown in
As a mechanism for moving the partition unit 60 close to the targets 31a and 31b, the mechanism shown in
The embodiments of the present disclosure are illustrative in all respects and are not restrictive. The above-described embodiments can be embodied in various forms. Further, the above-described embodiments may be omitted, replaced, or changed in various forms without departing from the scope of the appended claims and the gist thereof.
For example, the sputtering method for forming a metal film described in the above embodiments is an example. Another sputtering method may be used, or sputter particles may be emitted by a method other than that of the present disclosure. Further, although the oxidizing gas is supplied to the substrate from the head portion disposed above the substrate in the above embodiments, the present disclosure is not limited thereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-021298 | Feb 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/036980 | 9/20/2019 | WO | 00 |
