Film Forming Apparatus and Film Forming Method

Abstract

To form a metal oxide film having a high refractive index at a high film deposition rate.SOLUTION: A film deposition apparatus for forming a metal oxide film on a substrate includes: a substrate support part for supporting the substrate; a heating mechanism for heating the substrate supported by the substrate support part; a treatment vessel having the substrate support part provided in the inside; a holder for holding a metal material target in the treatment vessel and connected to a power supply; a gas supply part constituted to be able to supply oxygen gas into the treatment vessel; and a control part. The control part controls the heating mechanism, the power supply, and the gas supply part so as to alternately and repeatedly perform (A) a step of forming a predetermined film on the substrate by reactive sputtering in a metal mode in the treatment vessel and (B) a step of reacting the predetermined film with the oxygen gas in the treatment vessel to form a target metal oxide film.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a film forming apparatus and a film forming method.

Background Art

[0002] Patent Document 1 discloses that metallic titanium is used as a target, a mixed gas of argon and oxygen is used as a gas to be introduced into a sputtering apparatus, the gas pressure of the introduced gas is set higher than 10 Torr, and anatase-type titanium oxide film is formed by reactive sputtering using the mixed gas plasma.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology according to the present disclosure forms a desired metal oxide film at a high film formation rate.

Means for Solving the Problems

[0005] One aspect of the present disclosure is a film forming apparatus for forming a metal oxide film on a substrate, including a substrate support portion that supports the substrate, a heating mechanism that heats the substrate supported by the substrate support portion, a processing container provided inside the substrate support portion, a holder that holds a target of a metal material and is connected to a power source, and a gas supply portion configured to supply oxygen gas into the processing container, A magnet unit provided at a position on the back side of the holder and outside the processing container, and a moving mechanism that swings the magnet unit along the back surface of the holder a control unit, wherein the control unit (A) By the swinging of the magnet unit forms a predetermined film on the substrate by reactive sputtering in a metal mode, Inside the processing container and (B) alternately repeats a step of reacting the predetermined film with oxygen gas in the processing container to form a target metal oxide film, and controls the heating mechanism, the power source、 The gas supply unit And the moving mechanism is controlled.

Advantages of the Invention

[0006] According to the present disclosure, a desired metal oxide film can be formed at a high film formation rate.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0008] In the manufacturing process of semiconductor devices and the like, a film formation process for forming a desired film such as a metal oxide film is performed on a substrate such as a semiconductor wafer (hereinafter referred to as "wafer"). Reactive sputtering may be used for the film formation process. For example, when forming a titanium oxide film as a metal oxide film by reactive sputtering, metal particles emitted from the target react with oxygen gas as a reactive gas to form a titanium oxide film on the substrate.

[0009] By the way, the characteristics of the titanium oxide film formed, particularly the refractive index, differ depending on the supply flow rate of oxygen gas during reactive sputtering. Specifically, as shown in FIG. 1, when reactive sputtering is performed in a reaction mode with a large supply flow rate of oxygen gas (also referred to as the poisoning mode), a titanium oxide film with a high refractive index can be obtained compared to when it is performed in a metal mode with a small supply flow rate of oxygen gas (also referred to as the metal mode). However, in the reaction mode, although a titanium oxide film with a high refractive index can be obtained as described above, the film formation rate is lower than that in the metal mode, and it is required to increase the film formation rate for mass production and the like. This is the same for other metal oxide films.

[0010] Therefore, the technology according to the present disclosure forms a metal oxide film with a high refractive index at a high film formation rate.

[0011] Hereinafter, the film forming apparatus and the film forming method according to the present embodiment will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0012] <Film forming apparatus> FIG. 2 is a longitudinal sectional view showing an outline of the configuration of a film forming apparatus 1 according to the present embodiment.

[0013] The film forming apparatus 1 in FIG. 2 forms a metal oxide film on a wafer W as a substrate. The metal oxide film formed by the film forming apparatus 1 is, for example, a titanium dioxide (TiO2) film, a silicon dioxide (SiO2) film, or a TiSiO X film. Hereinafter, the film forming apparatus 1 will be described by taking the example of forming a TiO2 film.

[0014] The film forming apparatus 1 includes a processing chamber 10. The processing chamber 10 is configured to be depressurized and houses a wafer W. For example, it is formed of aluminum and is connected to the ground potential. An exhaust device 11 for depressurizing the space K1 in the processing chamber 10 is connected to the bottom of the processing chamber 10. The exhaust device 11 has a vacuum pump (not shown) or the like and is connected to the processing chamber 10 via, for example, an APC valve 12.

[0015] Also, a wafer transfer port 13 is formed in a side wall on one side (the positive X direction side in the figure) of the processing chamber 10, and a gate valve 13a for opening and closing the transfer port 13 is provided at the transfer port 13.

[0016] A mounting table 14 as a substrate support part is provided in the processing chamber 10. The mounting table 14 supports the wafer W placed thereon. Specifically, the wafer W is horizontally placed on the mounting table 14 so as to face a processing space K2 defined by a shield part 30 described later. The mounting table 14 has an electrostatic chuck 14a, a heater 14b as a heating mechanism, and a base part 14c.

[0017] The electrostatic chuck 14a has, for example, a dielectric film and an electrode provided as an inner layer of the dielectric film, and is provided on the base part 14c. A DC power supply (not shown) is connected to the electrode of the electrostatic chuck 14a. The wafer W placed on the electrostatic chuck 14a is adsorbed and held by the electrostatic chuck 14a by an electrostatic adsorption force generated by applying a DC voltage from the DC power supply to the electrode.

[0018] The heater 14b heats the wafer W supported by the mounting table 14. The heater 14b heats the wafer W supported by the mounting table (specifically, the electrostatic chuck 14a) by heating the mounting table 14 (specifically, the electrostatic chuck 14a). For example, a resistance heating type heater can be used for the heater 14b. Also, the heater 14b is provided, for example, on the electrostatic chuck 14a.

[0019] The base portion 14c is formed in a disc shape using, for example, aluminum. Depending on the type of the heater 14b or the like, the heater 14b may be provided on the base portion 14c.

[0020] Note that the mounting table 14 may be provided with a cooling mechanism for cooling the wafer W placed on the mounting table 14.

[0021] Furthermore, the mounting table 14 is connected to a rotation / movement mechanism 15. The rotation / movement mechanism 15 has, for example, a support shaft 15a and a drive unit 15b. The support shaft 15a extends in the vertical direction so as to penetrate the bottom wall of the processing container 10. A sealing member SL1 is provided between the support shaft 15a and the bottom wall of the processing container 10. The sealing member SL1 is a member that seals the space between the bottom wall of the processing container 10 and the support shaft 15a so that the support shaft 15a can rotate and move up and down, and is, for example, a magnetic fluid seal. The upper end of the support shaft 15a is connected to the center of the lower surface of the mounting table 14, and the lower end is connected to the drive unit 15b. The drive unit 15b has a drive source such as a motor, for example, and generates a driving force for rotating and moving the support shaft 15a up and down. As the support shaft 15a rotates about its axis AX1, the mounting table 14 rotates about the axis AX1, and as the support shaft 15a moves up and down, the mounting table 14 moves up and down.

[0022] Above the mounting table 14, a holder 20a made of a conductive material that holds a target 20 made of a metal material is provided. The holder 20a holds the target 20 so that the target 20 is positioned within the processing container 10. This holder 20a is attached to the ceiling portion of the processing container 10. A through-hole is formed at the attachment position of the holder 20a in the processing container 10. Further, an insulating member 10a is provided on the inner wall surface of the processing container 10 so as to surround the through-hole. The holder 20a is attached to the processing container 10 via the insulating member 10a so as to close the through-hole.

[0023] The holder 20a holds the target 20 in the front so that the target 20 faces the mounting table 14. The target 20 is made of a metal which is a constituent element of the metal oxide film to be formed. The target 20 in this example is made of titanium (Ti) which is a constituent element of the TiO2 film. Also, a power supply 21 is connected to the holder 20a, and a negative DC voltage is applied from the power supply 21. Instead of the negative DC voltage, an AC voltage may be applied.

[0024] Furthermore, a magnet unit 22 is provided at a position on the back side of the holder 20a and outside the processing container 10. The magnet unit 22 forms a magnetic field that leaks to the front side of the target 20 held by the holder 20a.

[0025] The magnet unit 22 is connected to a moving mechanism 23. The moving mechanism 23 swings the magnet unit 22 in the depth direction of the apparatus (Y direction in FIG. 2) along the back surface of the holder 20a. For example, it has a rail 23a extending along the depth direction of the apparatus (Y direction in FIG. 2) and a drive unit 23b including a motor or the like. Due to the driving force generated by the drive unit 23b, the magnet unit 22 moves along the rail 23a in the depth direction of the apparatus (Y direction in FIG. 2). More specifically, due to the driving force generated by the drive unit 23b, the magnet unit 22 moves so as to reciprocate between one end (negative side end in the Y direction in FIG. 2) and the other end (positive side end in the Y direction in FIG. 2) of the target 20 in the depth direction of the apparatus. The drive unit 23b is controlled by a control unit U described later. By swinging the magnet unit 22 by the moving mechanism 23, it becomes possible to utilize substantially the entire target 20.

[0026] Furthermore, the film forming apparatus 1 has a shield portion 30 that forms a processing space K2 in the processing container 10. The shield portion 30 is provided in the processing container 10.

[0027] The shield portion 30 has a first shield member 31 and a second shield member 32. The first shield member 31 and the second shield member 32 are formed of, for example, aluminum.

[0028] The first shield member 31 is a pot-shaped member with an open top, and has a hole 31a on the bottom surface for exposing the processing space K2 to the wafer W placed on the mounting table 14. The first shield member 31 is supported in the processing container 10 via a support member (not shown), for example.

[0029] The second shield member 32 is a lid member that closes the opening at the top of the first shield member 31, and is formed such that the central portion in plan view protrudes upward. The second shield member 32 has an opening 32a. Through the opening 32a, sputter particles from the target 20 held by the holder 20a are supplied to the processing space K2.

[0030] Further, the second shield member 32 is configured to be rotatable about a central axis passing through the center in a top view. By rotating the second shield member 32, the opening 32a of the second shield member 32 can be opposed to the target 20 held by the holder 20a, or a portion where the opening 32a of the second shield member 32 is not formed can be opposed to the target 20.

[0031] Furthermore, the film forming apparatus 1 includes a gas supply unit 40 that supplies gas into the processing container 10. The gas supply unit 40 supplies an inert gas such as argon (Ar) gas or krypton (Kr) gas, which is a sputtering gas, into the processing container 10. In addition, the gas supply unit 40 supplies oxygen (O2) gas into the processing container 10.

[0032] The gas supply unit 40 has, for example, gas sources 41, 42, flow controllers 43, 44 such as mass flow controllers, and a gas introduction unit 45. The gas source 41 stores an inert gas such as the above-mentioned Ar gas. The gas source 42 stores O2 gas. The gas sources 41, 42 are each connected to the gas introduction unit 45 via the flow controllers 43, 44. The gas introduction unit 45 is a member that introduces the gas from the gas sources 41, 42 into the processing container 10.

[0033] As shown in FIG. 2, the film forming apparatus 1 further includes a control unit U. The control unit U is constituted by a computer including, for example, a CPU, a memory, etc., and has a program storage unit (not shown). In the program storage unit, a program for controlling the heater 14b, the power supply 21, the gas supply unit 40, etc., to realize a film forming process described later in the film forming apparatus 1 is stored. Note that the above program may be recorded on a computer-readable storage medium and installed from the storage medium into the control unit U. The above storage medium may be temporary or non-temporary. Further, part or all of the program may be realized by dedicated hardware (circuit board).

[0034] <Film forming process> Next, an example of the film forming process using the film forming apparatus 1 will be described with reference to FIGS. 3 and 4. FIGS. 3 and 4 are diagrams showing the state inside the processing container 10 during the film forming process. Note that the following processes are performed under the control of the control unit U.

[0035] (S1: Loading) First, the wafer W is loaded into the processing container 10. Specifically, the gate valve 13a is opened, and a transfer mechanism (not shown) holding the wafer W is inserted into the processing container 10 through the transfer port 13 from a transfer chamber (not shown) in a vacuum atmosphere adjacent to the processing container 10 whose pressure has been adjusted to a desired pressure by the exhaust device 11. Then, the wafer W is transferred above the mounting table 14 heated to a predetermined temperature by the heater 14b. Next, the wafer W is transferred onto the raised support pins (not shown), and then the transfer mechanism is withdrawn from the processing container 10, and the gate valve 13a is closed. At the same time, the support pins are lowered, the wafer W is placed on the mounting table 14, and is adsorbed and held by the electrostatic adsorption force of the electrostatic chuck 14a. Further, the mounting table 14 is raised, and the wafer W moves directly below the hole 31a of the shield portion 30.

[0036] (S2: Formation of a predetermined film) Next, a predetermined film is formed on the wafer W by reactive sputtering in a metal mode within the processing vessel 10. Specifically, the predetermined film is a metal oxide film, i.e., a titanium monoxide (TiO) film, which contains a higher proportion of metal (specifically Ti) than the TiO2 film, which is the titanium oxide film intended to be formed.

[0037] In this step, for example, as shown in FIG. 3, Ar gas and O2 gas, which are sputtering gases, are supplied from the gas supply unit 40 (see FIG. 2) into the processing space K2 of the processing vessel 10. The flow rate of the Ar gas is, for example, 20 sccm to 80 sccm. Also, the flow rate of the O2 gas is a flow rate determined based on the results of tests etc. conducted in advance, at which reactive sputtering in a metal mode is performed, and is, for example, 1 sccm to 40 sccm. Note that when the range of the flow rate (i.e., partial pressure) of the Ar gas is made higher (or wider) than the above, the range of the flow rate (i.e., partial pressure) of the O2 gas is set higher (or wider) than the above. In this step, together with the supply of the Ar gas and O2 gas, power is supplied from the power supply 21 to the target 20, and the magnet unit 22 is moved by the moving mechanism 23 so as to repeatedly reciprocate, i.e., oscillate, along the depth direction of the apparatus (Y direction in FIG. 2) above the target 20. Due to the power from the power supply 21, the Ar gas in the processing vessel 10 is ionized, and the electrons generated by the ionization drift due to the magnetic field (i.e., leakage magnetic field) formed by the magnet unit 22 in front of the target 20, generating a high-density plasma. The surface of the target 20 is sputtered by the Ar ions generated in this plasma, and sputtered particles of Ti are released. The sputtered particles of Ti released from the target 20 react with the O2 gas, and a titanium oxide film is formed on the surface of the wafer W on the stage 14 heated to a predetermined temperature by the heater 14b. At this time, since the flow rate of the O2 gas is a flow rate at which film formation by reactive sputtering in a metal mode is performed as described above, the titanium oxide generated by the reaction of the sputtered particles of Ti and the O2 gas is TiO, in which the proportion of Ti metal is higher than that of the target titanium oxide TiO2, and a TiO film is formed on the wafer W.

[0038] This process is performed, for example, over a period of 2 to 10 seconds. On the wafer W, a TiO film with an atomic-level thickness, specifically, a TiO film with a thickness of 1 to 4×10 -10 m is formed on the wafer W. Also, the temperature of the mounting table 14 in this process is 80°C or higher.

[0039] In this specification, the reaction mode and the metal mode are as follows. The reaction mode is a mode in which, when forming a metal oxide film on the wafer W by reactive sputtering, a metal oxide film close to stoichiometry is formed, and the atoms of O2 gas adhere to the surface of the target 20, resulting in a slow film formation rate. On the other hand, the metal mode is a mode in which, when forming a metal oxide film on the wafer W by reactive sputtering, a film with a large proportion of metal contained in the film is formed, and the atoms of O2 gas do not adhere to the surface of the target 20, leaving the target metal exposed and resulting in a fast film formation rate.

[0040] (S3: Formation of the target titanium oxide film) Following step S2, in the processing container 10, the above-mentioned predetermined film reacts with O2 gas to form the target titanium oxide film to be formed. The target titanium oxide film is a TiO2 film as described above, and more specifically, a TiO2 film with an anatase-type crystal structure.

[0041] In this process, for example, the supply of Ar gas from the gas supply unit 40 into the processing space K2 of the processing container 10, the power supply from the power supply 21 to the target 20, and the oscillation of the magnet unit 22 are stopped. On the other hand, as shown in FIG. 4, the supply of O2 gas from the gas supply unit 40 into the processing space K2 of the processing container 10 and the heating of the mounting table 14 by the heater 14b are continued. For example, the flow rate of O2 gas and the temperature of the mounting table 14 are common in step S2 and step S3. The TiO film formed on the wafer W on the mounting table 14 is in an activated state due to the heat from the heated mounting table 14. Therefore, when the TiO film is exposed to O2 gas in the processing space K2, it reacts with the O2 gas to form a TiO2 film.

[0042] This step is performed, for example, over 5 to 10 seconds.

[0043] The above step S2 and step S3 are alternately repeated until a TiO2 film of a desired thickness is formed on the wafer W. For example, the above step S3 and step S3 are repeated 350 to 750 cycles (times), and a film of about 100 nm is formed in a total time of 5000 to 10000 seconds. In steps S2 and S3, the mounting table 14 on which the wafer W is placed may be rotated. Further, in step S3, following step S2, the opening of the second shield member 32 may be kept in a state facing the target 20 held by the holder 20a.

[0044] (Unloading) Thereafter, the wafer W is unloaded from the processing container 10. Specifically, the wafer W is unloaded outside the processing container 10 by an operation reverse to that at the time of loading. Then, it returns to the above-described loading step, and the next wafer W to be film-formed is processed in the same manner.

[0045] <Main effects of this embodiment> As described above, in the film-forming method according to this embodiment, (a) a step of forming a predetermined film on the wafer W by reactive sputtering in a metal mode; (b) a step of reacting the predetermined film with O2 gas to form a target titanium oxide film, that is, a TiO2 film; are alternately repeated. Thereby, a TiO2 film of a desired thickness is formed. The predetermined film formed on the wafer W in the metal mode in the above step (a) is a film with a higher metal ratio than the TiO2 film formed in the reaction mode (for example, a TiO film) and has a low refractive index. However, the film formation rate in the metal mode in the above step (a) is 20 times or more higher than the film formation rate in the reaction mode (see Figure 1). And the TiO film formed in the above step (a) is converted into a TiO2 film by the above step (b) performed thereafter. Also, the time required for the above step (b) is about the same as the time required for the above step (a). Therefore, when forming a TiO2 film in the above step (a) and the above step (b), compared with the case of forming a TiO2 film in the reaction mode, the time required to form a TiO2 film of the same thickness can be shortened. Therefore, by repeating the above step (a) and the above step (b), a TiO2 film with a high refractive index and a desired thickness can be formed at a high film formation rate.

[0046] Note that, different from this embodiment, in the method of forming a Ti film with a thickness equivalent to the final target film thickness of the TiO2 film at once and oxidizing it in an oxidation furnace to form a TiO2 film with the target film thickness, it is necessary to set the temperature in the oxidation furnace to 500 °C or higher, for example. In the method according to this embodiment, a TiO2 film can be formed in a low-temperature process such as 250 °C compared with the method using the above oxidation furnace.

[0047] Figure 5 is a diagram showing the refractive index (for light with a wavelength of 520) of the TiO2 film actually formed by the film formation method according to the above-described embodiment and the film formation rate at that time. The main conditions when forming this TiO2 film are as follows. Power to the target 20 during the above step (a): DC power 500 W Inert gas during the above step (a): Ar gas Temperature of the mounting table 14: 250 °C Ar gas flow rate during the above step (a): 30 sccm O2 gas flow rate: 20 sccm Thickness of the TiO film in one cycle: 2 - 4 Å Time of the above step (b): 5 - 10 seconds Number of cycles (number of repetitions): 350 Final film thickness of the TiO2 film: 100 nm

[0048] As is clear from FIG. 5, the refractive index of the TiO2 film formed by the film formation method according to the present embodiment was as high as 2.5 or more, which was comparable to the TiO2 film formed by reactive sputtering in the reaction mode shown in FIG. 1. Further, as shown in FIG. 1, the film formation rate of the TiO2 film having a refractive index of about 2.6 by reactive sputtering in the reaction mode was about 0.02 Å / s. On the other hand, the film formation rate of the TiO2 film by the film formation method according to the present embodiment was about 0.12 Å / s to 0.2 Å / s, which was 5 to 10 times or more faster than the film formation rate by reactive sputtering in the reaction mode.

[0049] In addition, according to the tests conducted by the present inventors, the attenuation coefficient of the TiO2 film formed by the film formation method according to the present embodiment under the above conditions was as low as 0.00 or less. That is, according to the present embodiment, a TiO2 film having an anatase crystal structure that satisfies the optical characteristics of a transparent film, namely, a high refractive index and a low attenuation coefficient, can be formed on the wafer W at a productive film formation rate.

[0050] It should be considered that all the embodiments disclosed this time are illustrative in all respects and not restrictive. The above embodiments may be omitted, replaced, or changed in various forms without departing from the scope and gist of the appended claims.

Explanation of Reference Numerals

[0051] 1 Film formation apparatus 10 Processing container 14 Mounting table 14b Heater 20 Target 20a Holder 21 Power supply 40 Gas supply unit U Control unit W Wafer

Claims

1. A film forming apparatus for forming a metal oxide film on a substrate, comprising: a substrate support portion for supporting the substrate; a heating mechanism for heating the substrate supported by the substrate support portion; a processing container provided inside the substrate support portion; a holder for holding a target of a metal material and connected to a power source inside the processing container; a gas supply portion configured to supply oxygen gas into the processing container; a magnet unit provided at a position on the back side of the holder and outside the processing container; a moving mechanism for swinging the magnet unit along the back surface of the holder; a control unit, wherein the control unit (A) forms a predetermined film on the substrate in the processing container by reactive sputtering in a metal mode by swinging the magnet unit; and (B) forms a target metal oxide film by reacting the predetermined film with oxygen gas in the processing container, and controls the heating mechanism, the power source, the gas supply portion, and the moving mechanism to alternately repeat the above steps.

2. In step (A), power is supplied from the power source to the holder, and the substrate supported by the substrate support portion is heated by the heating mechanism. In step (B), the substrate supported by the substrate support portion is heated without supplying power from the power source to the holder. The film forming apparatus according to claim 1.

3. The film forming apparatus according to claim 1 or 2, wherein the predetermined film having a thickness of 2 to 4 Å is formed by one execution of step (A).

4. The film forming apparatus according to any one of claims 1 to 3, wherein the predetermined film is a metal oxide film containing a higher proportion of metal than the target metal oxide film.

5. The film forming apparatus according to any one of claims 1 to 4, wherein the target metal oxide film is a titanium dioxide film, a silicon dioxide film, or an oxide film containing both titanium and silicon.

6. The film forming apparatus according to claim 5, wherein the target metal oxide film is a titanium dioxide film having an anatase crystal structure.

7. A film forming method for forming a metal oxide film on a substrate, comprising: (a) forming a predetermined film on the substrate in the processing container by reactive sputtering in a metal mode by swinging a magnet unit provided at a position on the back side of a holder for holding a target of a metal material and outside the processing container; (b) a step of reacting the predetermined film with oxygen gas in the processing container to form a target metal oxide film; A film forming method in which the above steps are alternately repeated. **Claim 8** In the step (a), power is supplied to the holder and the substrate is heated. The film forming method according to claim 7, wherein in the step (b), the substrate is heated in a state where no power is supplied to the holder. **Claim 9** The method of forming a film according to claim 7 or 8, wherein the predetermined film having a thickness of 1 to 4 × 10 －１０ m is formed by the step (a) once. **Claim 10** The film forming method according to any one of claims 7 to 9, wherein the predetermined film is a metal oxide film containing a higher proportion of metal than the target metal oxide film. **Claim 11** The film forming method according to any one of claims 7 to 10, wherein the target metal oxide film is a titanium dioxide film, a silicon dioxide film, or an oxide film containing both titanium and silicon. **Claim 12** The film forming method according to claim 11, wherein the target metal oxide film is a titanium dioxide film having an anatase crystal structure.

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