Method for forming dopant-containing film and reactive sputtering apparatus

Abstract

A method for forming a film of a metal compound that contains a metal dopant on a substrate (S) includes, for the purpose of controlling the dopant concentration in the film or the distribution thereof: a step for simultaneously performing a first step (P1) in which the metal compound is sputtered to form a film on the substrate in a metal mode in which the flow rate of a reaction gas is less than a predetermined value, and a second step (P2) in which the metal dopant is sputtered to form a film on the substrate in a reaction mode in which the flow rate of the reaction gas is equal to or greater than the predetermined value; and a fourth step (P4) in which the supply of the reaction gas to the substrate is continued for a predetermined time period after the completion of the film formation in the first step , which occurs either simultaneously with the completion of the second step or after a predetermined time has elapsed after the completion of the second step.

Description

Method for forming dopant-containing film and reactive sputtering apparatus

[0001] The present invention relates to a method for forming a film containing a dopant and a reactive sputtering apparatus.

[0002] A metal oxide film containing a dopant can be formed by, for example, preparing a target material containing the dopant and then performing a reactive sputtering method using this target (Patent Document 1).

[0003] JP 2023-75686 A

[0004] However, the above-mentioned conventional techniques use a target material containing a dopant, and therefore, if the dopant distribution in the target material is non-uniform, the dopant concentration distribution in the resulting film will also be non-uniform. Even if the dopant distribution in the target material is uniform, it is extremely difficult to control the dopant concentration in the target film and the dopant distribution in the deposition direction. Furthermore, when changing the dopant amount, it is necessary to prepare or obtain a new target material and replace it.

[0005] The problem to be solved by the present invention is to provide a method for forming a dopant-containing film and a reactive sputtering apparatus that can control the dopant concentration or distribution in the film.

[0006] The present invention solves the above-mentioned problems by providing a film formation method for forming a film of a metal compound containing a metal dopant on a substrate, the film formation method including a first step of sputtering the metal compound on the substrate in a metallic mode with a flow rate of a reactive gas less than a predetermined value, and a second step of sputtering the metal dopant on the substrate in a reactive mode with a flow rate of the reactive gas equal to or greater than the predetermined value, in parallel.

[0007] In the above invention, after starting the film formation in the first process, the film formation in the second process may be started simultaneously with or after a predetermined time has elapsed since the start of the film formation in the first process, the film formation in the first process and the film formation in the second process may be performed in parallel, the film formation in the second process may be terminated, and the film formation in the first process may be terminated simultaneously with or after a predetermined time has elapsed, and the supply of the reactive gas to the substrate may be continued for a predetermined time.

[0008] The present invention also provides a film formation chamber into which a substrate on which a film is to be formed is placed, a pressure reducer for reducing the pressure in the film formation chamber to a predetermined pressure, a discharge gas introducer for introducing a discharge gas into the film formation chamber, a first sputtering electrode on which a first target serving as a main film formation material is attached and which is disposed so as to face the substrate, a first chimney for covering a first space in front of the first target and the first sputtering electrode by a first shutter which can be opened and closed, a second sputtering electrode on which a second target serving as a dopant for the main film formation material is attached and which is disposed so as to face the substrate, a second chimney for covering a second space in front of the second target and the second sputtering electrode by a second shutter which can be opened and closed, a discharge gas introducer for introducing a discharge gas into the film formation chamber, a reactive gas introducer for introducing a reactive gas into the film formation chamber via the second space and the second shutter, a DC power supply for supplying power to the first sputtering electrode and the second sputtering electrode, The above problem is solved by a reactive sputtering apparatus comprising: a square wave controller that controls the square waves applied from the DC power supply to each of the first sputtering electrode and the second sputtering electrode; a shutter opening / closing controller that controls the opening and closing of each of the first shutter and the second shutter; a gas introduction controller that controls each of the discharge gas introducer and the reactive gas introducer; and an overall controller that overall controls the square wave controller, the shutter opening / closing controller, and the gas introduction controller.

[0009] The present invention also solves the above-mentioned problems by a film formation method using the above-mentioned reactive sputtering apparatus to form a film on a substrate, the film containing the main film formation material as a main component and the dopant, comprising at least the following steps: a first step of introducing a discharge gas into the film formation chamber and the reactive gas into the second space, applying a DC voltage from the DC power supply to each of the first sputtering electrode and the second sputtering electrode, closing the second shutter and opening the first shutter, and forming an ultra-thin film of the first target on the substrate; a second step of opening the second shutter under the conditions of the first step and forming an ultra-thin film of the first target and an ultra-thin film of the second target on the substrate in parallel; and a third step of closing the second shutter under the conditions of the second step and forming an ultra-thin film of the first target on the substrate.

[0010] In the above invention, the rectangular wave controller may include: a first pulse wave conversion switch connected between the DC power supply and the first sputtering electrode, converting the DC voltage applied to the first sputtering electrode into a pulse wave voltage; and a second pulse wave conversion switch connected between the DC power supply and the second sputtering electrode, converting the DC voltage applied to the second sputtering electrode into a pulse wave voltage; and the overall controller may include a programmable oscillator having programmable pulse control signal patterns corresponding to a first sputtering target power to be supplied to the first sputtering electrode, a second sputtering target power to be supplied to the second sputtering electrode, target opening and closing timings of the first shutter and the second shutter, and introduction timings of the discharge gas and the reactive gas to be introduced into the film formation chamber, and controlling the first pulse wave conversion switch, the second pulse wave conversion switch, the shutter opening and closing controller, and the gas introduction controller in accordance with the programmed pulse control signal patterns.

[0011] The present invention also solves the above-mentioned problems by a film formation method using the above-mentioned reactive sputtering apparatus to form a film on a substrate, the film containing the main film formation material as a main component and the dopant, the film formation method comprising at least the following steps: a first step of introducing a discharge gas into the film formation chamber and the reactive gas into the second space, applying a pulse voltage from the DC power supply to the first sputtering electrode, stopping the application of the pulse voltage to the second sputtering electrode, and opening the first shutter and the second shutter to form an ultra-thin film of the first target on the substrate; a second step of applying a pulse voltage to the second sputtering electrode under the conditions of the first step to form an ultra-thin film of the first target and an ultra-thin film of the second target on the substrate in parallel; and a third step of stopping the application of the pulse voltage to the second sputtering electrode under the conditions of the second step to form an ultra-thin film of the first target on the substrate.

[0012] The present invention also solves the above-mentioned problems by a film formation method using the above-mentioned reactive sputtering apparatus to form a film on a substrate, the film containing the main film formation material as a main component and the dopant, the film formation method comprising at least the following steps: a first step of introducing a discharge gas into the film formation chamber and the reactive gas into the second space, applying a pulse voltage from the DC power supply to the first sputtering electrode, stopping the application of the Ars voltage to the second sputtering electrode, and opening the first shutter and the second shutter to form an ultra-thin film of the first target on the substrate; a second step of applying a pulse voltage to the second sputtering electrode under the conditions of the first step to simultaneously form an ultra-thin film of the first target and an ultra-thin film of the second target on the substrate; and a third step of stopping the application of the pulse voltage to the second sputtering electrode under the conditions of the second step to form an ultra-thin film of the first target on the substrate.

[0013] In the above invention, after the third step, there may be at least a fourth step of closing the first shutter or stopping the application of the pulse voltage to the first sputtering electrode under the conditions of the third step, and reacting the film formed on the substrate.

[0014] In the above invention, the first step, the second step, and the third step, or the first step, the second step, the third step, and the fourth step may be repeated until a predetermined film thickness is reached.

[0015] In the above invention, the content of the dopant is preferably more than 0 atomic % and not more than 15 atomic %, more preferably more than 0 atomic % and not more than 10 atomic %, and most preferably more than 0 atomic % and not more than 5 atomic %, relative to the film containing the main film-forming material as a main component.

[0016] According to the present invention, it is possible to provide a method for forming a dopant-containing film and a reactive sputtering apparatus that are capable of controlling the dopant concentration or distribution in the film.

[0017] 1 is a block diagram showing an embodiment of a reactive sputtering apparatus according to the present invention. FIG. 2 is an enlarged view showing a first sputtering electrode and a second sputtering electrode of FIG. 1. FIG. 3 is a graph showing a characteristic profile of a target deposition rate versus a reactive gas flow rate under predetermined reactive sputtering conditions. FIG. 4 is a time chart showing an embodiment of a film deposition method using a reactive sputtering apparatus according to the present invention. FIG. 5 is a time chart showing another embodiment of a film deposition method using a reactive sputtering apparatus according to the present invention. FIG. 6 is a time chart showing yet another embodiment of a film deposition method using a reactive sputtering apparatus according to the present invention. FIG. 7 is a cross-sectional view showing a thin film obtained in the process (first step) of the film deposition method shown in FIG. 4. FIG. 8 is a cross-sectional view showing a thin film obtained in the process (second step) of the film deposition method shown in FIG. 4. FIG. 9 is a cross-sectional view showing a thin film obtained in the process (third step) of the film deposition method shown in FIG. 4.

[0018] <<Reactive Sputtering Apparatus>> An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a block diagram showing one embodiment of a reactive sputtering apparatus according to the present invention. The reactive sputtering apparatus 1 of this embodiment includes a film formation chamber 11 that forms a substantially sealed space. The film formation chamber 11 is provided with a substrate holder 12 that holds a substrate S, which is an object to be film-formed (a film-formed object), and a first sputtering electrode 18 and a second sputtering electrode 19 that face the substrate S.

[0019] The substrate holder 12 is formed, for example, in a flat plate shape and is provided in the film formation chamber 11. A substrate S to be subjected to film formation is placed on its upper surface. If the substrate S needs to be heated during film formation, the substrate holder 12 may be provided with a heater for heating the substrate S. Although not shown in FIG. 1 , in order to automate the film formation process, a load lock chamber may be connected to one side wall of the film formation chamber 11 via a gate valve. The gate valve may be opened to load the substrate S from the load lock chamber using a loading mechanism, and the substrate S may be placed on the upper surface of the substrate holder 12. After film formation, the substrate S may be transported from the substrate holder 12 to the load lock chamber using the loading mechanism. The reactive sputtering apparatus 1 of this embodiment is a so-called single-wafer reactive sputtering apparatus that performs sputter film formation on a single substrate S. However, the reactive sputtering apparatus 1 according to the present invention is not limited to the single-wafer type, and multiple substrates S may be simultaneously loaded into the film formation chamber 11 and processed. In addition, the substrate holder 12 in this example may be equipped with a rotation mechanism and a lifting mechanism to improve the uniformity of the film formation quality (film thickness and composition ratio) on the substrate S, and a transport and lifting mechanism to improve the operability when moving the substrate S in and out of the load lock chamber.

[0020] A first target T1 made of, for example, a main film forming material is attached to the tip of the first sputtering electrode 18, and a second target T2 made of a dopant for the main film forming material is attached to the tip of the second sputtering electrode 19. Note that the first target T1 made of the main film forming material may be attached to the second sputtering electrode 19, and the second target T2 made of a dopant may be attached to the first sputtering electrode 18. In addition, in the reactive sputtering apparatus 1 of this embodiment, two sputtering electrodes 18, 19 are provided for one surface of the substrate S, but the reactive sputtering apparatus according to the present invention is not limited to only two sputtering electrodes 18, 19, and three or more sputtering electrodes may be provided for one surface of the substrate S to correspond to different dopant species.

[0021] In this embodiment, a material that accounts for 85 atomic % or more (preferably 90 atomic % or more, and more preferably 95 atomic % or more) of the constituent materials of the target thin film is referred to as a "main film-forming material," and a material that contains an amount of 15 atomic % or less (preferably 10 atomic % or less, and more preferably 5 atomic % or less) of this main film-forming material is referred to as a "dopant."

[0022] When multiple sputtering electrodes are provided facing the substrate S, the surfaces of all targets are not parallel to the surface of the substrate S. However, in consideration of ease of film formation control, it is preferable to provide each sputtering electrode at an equal distance from the central axis of the substrate S. For example, in the two sputtering electrodes, first sputtering electrode 18 and second sputtering electrode 19 shown in Fig. 1, the central axis C1 of first sputtering electrode 18 and the central axis C2 of second sputtering electrode 19 are directed toward the center O of the substrate S, and are provided so that the angles θ1 and θ2 formed by them are equal.

[0023] 2 is an enlarged view showing the first sputtering electrode 18 and the second sputtering electrode 19 according to this embodiment. The reactive sputtering apparatus 1 of this embodiment includes a first chimney 181 and a second chimney 191. The first chimney 181 is provided to cover a first space 183 in front of the first sputtering electrode 18 on which the first target T1 is attached, in an openable and closable manner by a first shutter 182. Similarly, the second chimney 191 is provided to cover a second space 193 in front of the second sputtering electrode 19 on which the second target T2 is attached, in an openable and closable manner by a second shutter 192.

[0024] The first chimney 181 is a cylindrical member with both ends open that covers the first space 183 between the first target T1 and the first shutter 182 from the side. The first shutter 182 is provided near the tip of the first chimney 181 and can be opened and closed by an actuator (not shown). The first shutter 182 is driven to a closed position (shown by a solid line in FIG. 2 ) facing the first target T1 to block the flying material, and to an open position (shown by a two-dot chain line in FIG. 2 ) retracted from the front of the first target T1 to allow the flying material. The actuator that drives the opening and closing of the first shutter 182 is controlled by a control signal from the programmable oscillator 24 via the shutter opening and closing controller 17. This chimney is designed to maintain plasma in the first space 183 even when the first shutter 182 is closed.

[0025] The second chimney 191 is a cylindrical member with both ends open that covers the second space 193 between the second target T2 and the second shutter 192 from the side. The second shutter 192 is provided near the tip of the second chimney 191 and can be opened and closed by an actuator (not shown). The second shutter 192 is driven to a closed position (shown by a solid line in FIG. 2 ) facing the second target T2 to block the flying material, and to an open position (shown by a two-dot chain line in FIG. 2 ) retracted from the front of the second target T2 to allow the flying material. The actuator that drives the second shutter 192 to open and close is controlled by a control signal from the programmable oscillator 24 via the shutter opening / closing controller 17. This chimney is designed to maintain plasma in the second space 193 even when the second shutter 192 is closed.

[0026] As will be described in detail later, a first space 183 in front of the first target T1, which is partitioned by the first chimney 181 and the first shutter 182, is supplied with a discharge gas from the discharge gas introducer 15, and a second space 193 in front of the second target T2, which is partitioned by the second chimney 191 and the second shutter 192, is supplied with a discharge gas from the discharge gas introducer 15 and a reactive gas from the reactive gas introducer 16. By introducing a discharge gas and a reactive gas into the second space 193 in front of the second target T2, the partial pressure of the reactive gas can be set to a relatively high state.

[0027] The first shutter 182 and the second shutter 192 do not hermetically close the first space 183 and the second space 193, respectively, but rather block the flying of material from the first target T1 and the second target T2. Therefore, even if the first shutter 182 and the second shutter 192 are closed, a predetermined amount of the discharge gas or reaction gas supplied to the first space 183 and the second space 193 will leak toward the substrate S.

[0028] Returning to Fig. 1, the reactive sputtering apparatus 1 of this embodiment includes a DC power supply 20 that supplies power to the first sputtering electrode 18 and the second sputtering electrode 19. The DC power supply 20 applies a DC pulse voltage of 1 kV or less to the target to cause discharge, which causes a portion of the discharge gas (e.g., argon gas) to emit electrons and become positive ions, which collide with the target and knock out the target atoms, which are then deposited on the substrate S in the extension direction of the target. It is desirable that the DC power supply 20 of this embodiment be a power supply that can automatically switch between power control (CP), voltage control (CV), and current (CC).

[0029] The reactive sputtering apparatus 1 of this embodiment also includes a first pulse wave conversion switch 22 and a second pulse wave conversion switch 23 connected in parallel between the DC power supply 20 and the first sputtering electrode 18 and the second sputtering electrode 19. The first pulse wave conversion switch 22 and the second pulse wave conversion switch 23 convert the DC voltage applied to the first sputtering electrode 18 and the second sputtering electrode 19 into a pulse wave voltage, respectively.

[0030] That is, in this embodiment, a first pulse-wave conversion switch 22 is provided on the power supply line between the DC power supply 20 and the first sputtering electrode 18, and a second pulse-wave conversion switch 23 is provided on the power supply line between the DC power supply 20 and the second sputtering electrode 19. These first pulse-wave conversion switch 22 and second pulse-wave conversion switch 23 are connected in parallel to the DC power supply 20, and therefore the same voltage as that of the DC power supply 20 is applied to each of them. However, when controlling the power of the DC power supply 20, the applied voltage may differ depending on the type of target. These first pulse-wave conversion switch 22 and second pulse-wave conversion switch 23 are formed of switching elements that convert the DC voltage from the DC power supply 20 into a pulse-wave voltage, and switching elements that can withstand high voltages of several kV, such as MOSFETs, IGBTs, and SiC power transistors, may be used. It is noted that different DC power supplies 20 may be provided for the first sputtering electrode 18 and the second sputtering electrode 19, and the DC voltages may be controlled individually.

[0031] The reactive sputtering apparatus 1 of this embodiment includes a programmable oscillator 24. The programmable oscillator 24 of this embodiment is a device that can program the sputtering pulse control signals (sputtering target power including frequency, duty ratio, and phase angle) to be supplied to each of the first sputtering electrode 18 and the second sputtering electrode 19, the pulse control signal pattern corresponding to the opening and closing timing of the first shutter 182 and the second shutter 192, the pulse control signal pattern corresponding to the target introduction timing of the discharge gas introducer 15 and the reactive gas introducer 16, and the number of repetitions, and controls the first pulse wave conversion switch 22 and the second pulse wave conversion switch 23, as well as the shutter opening and closing controller 17 and the gas introduction controller 27 according to the pulse control signal pattern.

[0032] The first pulse wave conversion switch 22 and the second pulse wave conversion switch 23 are independently controlled while maintaining synchronization by a programmable oscillator 24. That is, the programmable oscillator 24 outputs ON / OFF patterns of pulse control signals to be supplied to the first sputtering electrode 18 and the second sputtering electrode 19 to the first pulse wave conversion switch 22 and the second pulse wave conversion switch 23, respectively, and supplies pulsed power to the first sputtering electrode 18 and the second sputtering electrode 19. When the output is ON, a sputtering voltage (negative potential) from the DC power supply 20 is applied. When the output is OFF, a bias (fixed positive potential) is applied from a separate power supply, which attracts electrons to the target and prevents abnormal discharge due to charge-up of the target.

[0033] The reactive sputtering apparatus 1 of this embodiment includes a pressure reducer 13 that reduces the pressure in the film formation chamber 11 to a predetermined pressure, and a conductance valve 14 that also serves as a gate valve (main valve) that controls the pressure in the film formation chamber 11 reduced by the pressure reducer 13. Note that a conductance valve and another gate valve (main valve) may be provided in this order from the film formation chamber 11 side in the piping between the film formation chamber 11 and the pressure reducer 13.

[0034] The pressure reducer 13 includes an exhaust port, an exhaust pipe, and an exhaust pump (vacuum pump) for adjusting the pressure in the film formation chamber 11 to a level suitable for sputtering during sputtering. To remove residual gas from the film formation chamber 11, the film formation chamber 11 is evacuated to a predetermined high vacuum pressure, thereby preparing for sputtering. In sputtering, a discharge gas from a discharge gas introducer 15 and a reactive gas from a reactive gas introducer 16 are introduced into the film formation chamber 11, and the conductance valve 14, which also serves as a gate valve, is operated to set the film formation chamber 11 to a predetermined pressure, for example, a reduced pressure (vacuum) atmosphere of several mPa to several tens of Pa.

[0035] The gate valve (main valve) is a valve that opens or closes, and the conductance valve is a valve whose opening is variable to adjust the exhaust speed. After film formation is completed, the conductance valve 14, which also serves as a gate valve, is closed, and a leak valve (not shown) provided in the film formation chamber 11 is opened to the atmosphere, thereby returning the film formation chamber 11 to normal pressure. The film formation chamber 11 is opened to the atmosphere by the leak valve provided in the film formation chamber 11. It is desirable to keep the pressure reducer 13 reduced. This is because stopping the pressure reducer 13 and opening it to the atmosphere may result in contamination of the pressure reducer 13 with water or dust contained in the atmosphere.

[0036] As shown in FIG. 1 , the reactive sputtering apparatus 1 of this embodiment includes a discharge gas introducer 15 for introducing a discharge gas into the film formation chamber 11, and a reactive gas introducer 16 for introducing a reactive gas into the film formation chamber 11.

[0037] 1 , the discharge gas introducer 15 includes a discharge gas cylinder 151, a regulator, a gate valve, a gas pipe, a flow rate adjuster 152, and, if necessary, a pump, for supplying a discharge gas (a gas that forms a plasma state in the sputtering process and generates ions that collide with the target) to a first space 183 formed in a first chimney 181 of the film formation chamber 11. The discharge gas introducer 15 also includes a branch gas pipe and a flow rate adjuster 153 for supplying the discharge gas from the discharge gas cylinder 151 to a second space 193 covered by a second chimney 191 of the film formation chamber 11. The discharge gas is not particularly limited, but an inert gas such as argon gas is used, for example.

[0038] 1, the reactive gas introducer 16 includes a reactive gas cylinder 161, a regulator, a gate valve, a gas pipe, a flow rate adjuster 162, and a pump as needed, for supplying a reactive gas to the second space 193 covered by the second chimney 191 of the film formation chamber 11. The type of reactive gas is not particularly limited, and when sputtering a metal oxide film or a metal nitride film as a film formation material, oxygen gas or nitrogen gas is used as the reactive gas. Note that, if needed, multiple reactive gas introduction systems may be installed for oxygen gas and nitrogen gas.

[0039] The supply / stop of discharge gas from the discharge gas cylinder 151 to the first space 183 (ON / OFF of discharge gas supply), the supply / stop of discharge gas from the discharge gas cylinder 151 to the second space 193 (ON / OFF of discharge gas supply), and the supply / stop of reactive gas from the reactive gas cylinder 161 to the second space 193 (ON / OFF of reactive gas supply) are controlled by a gas introduction controller 27. The programmable oscillator 24 controls the gas introduction controller 27 in accordance with a pulse control signal pattern corresponding to the target introduction timing of the discharge gas introducer 15 and the reactive gas introducer 16.

[0040] The apparatus controller 25 shown in FIG. 1 controls the pressure reducer 13 and the conductance valve 14 based on a control signal from the film formation controller 26 .

[0041] <<Film Forming Method Using Reactive Sputtering Apparatus>> By using the reactive sputtering apparatus 1 of this embodiment, for example, hafnium oxide (HfO ２ A composite metal compound-doped film can be formed by doping a thin film mainly composed of ZnO (ZnO), ZnS (ZnO), and ZnO (ZnO) with 15 atomic % or less, preferably 10 atomic % or less, and more preferably 5 atomic % or less of zirconium (Zr). In this case, the dopant zirconium can be doped uniformly throughout the film, or alternatively, the doping concentration of zirconium can be varied across the film thickness.

[0042] FIG. 3 is a graph showing the characteristic profile of the film formation rate (deposition amount per unit time) versus the flow rate of a predetermined type of reactive gas, such as oxygen gas, nitrogen gas, or other gas, under predetermined reactive sputtering conditions. The range where the reactive gas flow rate is relatively low is called the metallic mode, the range where the reactive gas flow rate is relatively high is called the reactive mode (also called the oxidation mode when oxygen is used as the reactive gas), and the region between these is called the transition mode. Regarding the film formation rate versus the reactive gas flow rate, the film formation rate is high in the metallic mode as the reactive gas flow rate increases from 0 to the transition mode, but changes rapidly near the transition mode range, and the film formation rate decreases in the reactive mode where the reactive gas flow rate is high. Although the slope of the profile varies slightly depending on the metal species of the target, the general trend is common to metal sputtering. That is, the film formation rate is slow in the reactive mode and fast in the metallic mode.

[0043] In particular, when the first chimney 181 is used as in the reactive sputtering apparatus 1 of this embodiment, the partial pressure of the reactive gas is relatively low near the first target T1 in the first space 183, where only the discharge gas is introduced, so the effect of the reactive gas flow rate is relatively small, and the metallic mode region is extended as shown in Figure 3. In contrast, when the second chimney 191 is used, the partial pressure of the reactive gas can be relatively high near the second target T2 in the second space 193, where the discharge gas and the reactive gas are introduced, so that a mode change from metallic mode to reactive mode occurs even with a relatively low reactive gas flow rate, as shown in Figure 3. As a result, even in the same deposition chamber 11, there is a range in which metallic mode sputtering of the first target T1 and reactive mode sputtering of the second target T2 coexist at an appropriate gas flow rate.

[0044] In the film formation method of this embodiment, when a voltage is applied to two sputtering electrodes 18, 19 to which two types of targets T1, T2 are respectively attached to perform sputtering, the film portion that will become the main component is formed in a metal mode by lowering the partial pressure of the reactive gas, and the film portion that will become the dopant is formed in a reaction mode by raising the partial pressure of the reactive gas. By simultaneously performing these two sputtering processes, the film portion that will become the main component is formed in a short time by high-speed film formation, while the film portion that will become the dopant is formed in a small proportion by low-speed film formation, making it possible to control the dopant concentration uniformly or variably in the deposition direction.

[0045] 4 is a time chart showing an embodiment of a film formation method using the reactive sputtering apparatus 1 according to the present invention, showing one period (one cycle) which is a unit of the film formation process. The figure shows a pulse control signal pattern (the vertical axis of the figure indicates ON / OFF or OPEN / CLOSE, and the horizontal axis indicates time) programmed in the programmable oscillator 24, and from the top to bottom, shows the pulse (ON / OFF) applied to the first sputtering electrode 18, the pulse (OPEN / CLOSE) applied to the first shutter 182, the pulse (ON / OFF) applied to the second sputtering electrode 19, the pulse (OPEN / CLOSE) applied to the second shutter 192, the introduction of reactive gas (ON / OFF), and the introduction of discharge gas (ON / OFF). The film formation method shown in FIG. 4 uses, for example, hafnium Hf (or hafnium oxide HfO ) as the first target T1. ２ ) and can be applied to the case where zirconium Zr is selected as the second target T2 and oxygen is selected as the reactive gas to form a composite metal compound doped film of hafnium oxide containing a trace amount of zirconium.

[0046] 4, at time t1, the gas introduction controller 27 is controlled to introduce a discharge gas such as an inert gas into the film formation chamber 11 via the first space 183 and the second space 193, and to introduce a reactive gas such as oxygen gas into the second space 193. The pulses applied to the first sputtering electrode 18 and the second sputtering electrode 19 are turned off, and the first shutter 182 and the second shutter 192 remain closed.

[0047] At the following time t2, the introduction of the discharge gas and reactive gas continues, while the second shutter 192 remains closed. The pulses applied to the first sputtering electrode 18, on which the target T1 (e.g., hafnium) is mounted, and the second sputtering electrode 19, on which the target T2 (e.g., zirconium Zr) is mounted, are turned on. At the same time, the first shutter 182 is opened. This initiates the metal-mode sputtering process of the target T1 (e.g., hafnium). FIG. 7A is a cross-sectional view showing the thin film obtained in steps t2-t3 of the film-forming method of FIG. 4. This metal-mode sputtering process forms an ultra-thin hafnium film F1 on the surface of the substrate S, with an atomic-level thickness corresponding to the time t2-t3. The steps t2-t5, which perform metal-mode sputtering of the main film-forming material (a metal compound such as hafnium oxide) of the desired composite metal compound-doped film, are also referred to as the first step P1.

[0048] At the following time t3, the introduction of the discharge gas and reactive gas continues, and the pulses applied to the first sputtering electrode 18 on which the target T1 (e.g., hafnium) is mounted and the second sputtering electrode 19 on which the target T2 (e.g., zirconium Zr) is mounted continue to be ON. The first shutter 182 remains open, and the second shutter 192 is opened. From time t1 to t3, reactive gas is introduced into the second space 193 of the second chimney 191, and the partial pressure of the reactive gas is relatively high. Therefore, from time t3 when the second shutter 192 is opened, sputtering processing in a reactive mode of the target T2 (e.g., zirconium Zr) can be performed. Note that the process t3 to t4 in which a dopant (metal dopant such as zirconium) for the main film-forming material of the desired composite metal compound doped film is sputtered in a reactive mode is also referred to as the second process P2.

[0049] Between times t3 and t4, the sputtering process of target T1 (e.g., hafnium) in the metal mode continues, so that the sputtering process of target T1 (e.g., hafnium) in the metal mode and the sputtering process of target T2 (e.g., zirconium Zr) in the reactive mode are performed simultaneously. Figure 7B is a cross-sectional view showing a thin film obtained during steps t3 to t4 of the film formation method of Figure 4. By the sputtering process of target T1 (e.g., hafnium) in the metal mode and the sputtering process of target T2 (e.g., zirconium Zr) in the reactive mode, a mixed ultra-thin film F2 of hafnium Hf and zirconium Zr having an atomic-level thickness corresponding to the time t3 to t4 is formed on the surface of the ultra-thin hafnium film F1 formed on the surface of substrate S. At the same time, oxygen gas introduced into second space 193 is introduced into substrate S, so that the ultra-thin hafnium film F1 and the mixed ultra-thin hafnium and zirconium film F2 are oxidized by the oxygen gas.

[0050] At the following time t4, the introduction of the discharge gas and reactive gas continues, and the pulses applied to the first sputtering electrode 18 on which the target T1 (e.g., hafnium) is mounted and the second sputtering electrode 19 on which the target T2 (e.g., zirconium Zr) is mounted remain ON. The first shutter 182 remains open, while the second shutter 192 closes. This allows only the sputtering process of the target T1 (e.g., hafnium) in the metal mode to continue. FIG. 7C is a cross-sectional view showing the thin film obtained in steps t4 to t5 of the film-forming method of FIG. 4 . An ultra-thin film F3 of hafnium Hf with an atomic-level thickness corresponding to times t4 to t5 is formed on the surface of the ultra-thin film F2 of hafnium Hf and zirconium Zr. Note that the steps t4 to t5, which follow the second step and involve sputtering the main film-forming material (a metal compound such as hafnium oxide) of the desired composite metal compound-doped film in the metal mode, are also referred to as the third step P3. The third process P3 is also part of the first process P1.

[0051] At the following time t5, the introduction of the discharge gas and reactive gas continues, and the pulses applied to the first sputtering electrode 18 on which the target T1 (e.g., hafnium) is mounted and the second sputtering electrode 19 on which the target T2 (e.g., zirconium Zr) is mounted continue to be ON. The first shutter 182 is closed while the second shutter 192 remains closed. This also ends the sputtering process in the metal mode for the target T1 (e.g., hafnium). However, as described above, even when the second shutter 192 is closed, a portion of the discharge gas and reactive gas supplied to the second space 193 is configured to leak a predetermined amount toward the substrate S. Therefore, the oxidation reaction of the ultra-thin hafnium film F1 and the ultra-thin zirconium Zr film F2 by oxygen gas continues between times t5 and t6. Note that the processes t5 and t6, which are performed after the third process P3 and involve introducing reactive gas and reacting the film formed on the substrate S, are also referred to as the fourth process P4.

[0052] At the next time t6, one cycle of the film formation method of this embodiment ends, and this cycle is repeated multiple times until the desired film thickness is obtained. Thus, from time t2 to time t5 of one cycle, sputtering processing is performed in the metal mode with the first target T1, resulting in a relatively high film formation rate and highly productive metal film formation with the first target T1. Meanwhile, from time t3 to time t4 of one cycle, sputtering processing in the metal mode with the first target T1 and sputtering processing in the reactive mode (e.g., oxidation mode) with the second target T2 are simultaneously performed.

[0053] The reactive gas introduced into the second space 193 is expected to be radicalized by the electric field of the second sputtering electrode 19, and the ultra-thin film of the first target T1 formed on the substrate S will react with the radicalized reactive gas. For example, in the case where hafnium is used as the first target T1 and oxygen gas is used as the reactive gas, the ultra-thin film of hafnium Hf deposited on the substrate S in the metal mode from time t2 to t5 will react with the oxygen gas O introduced in the reactive mode at time t3. ２ Hafnium oxide (HfO) is oxidized by ２At the same time, zirconium oxide ZrO ２ This cycle is then repeated until the target film thickness is reached. As a result, a method for forming a dopant-containing film and a reactive sputtering apparatus are provided that allow for control of the dopant concentration or distribution in the film.

[0054] In particular, at time t1, reactive gas is introduced into the second space 193 of the second chimney 191 before starting sputtering processing using the second target T2, so that the second target T2 is exposed to a reactive gas atmosphere, and sputtering processing in reactive mode can be performed from the start of the next time t3.

[0055] FIG. 5 is a time chart showing another embodiment of a film formation method using the reactive sputtering apparatus 1 according to the present invention, showing one period (one cycle) as a unit of the film formation process. The film formation method of the embodiment shown in FIG. 5 differs from the film formation method of the embodiment shown in FIG. 4 in the pulse applied to the second sputtering electrode 19 and the opening / closing signal of the second shutter 192, but the other control steps are the same. That is, in the film formation method of the embodiment shown in FIG. 4, the pulse applied to the second sputtering electrode 19 is always ON and controlled by opening / closing the second shutter 192 during the sputtering process of the second target T2. In contrast, in the film formation method of the embodiment shown in FIG. 5, the second shutter 192 is always open and controlled by ON / OFF control of the pulse applied to the second sputtering electrode 19 during the sputtering process of the second target T2. The film formation method of this embodiment also produces the composite metal compound-doped films shown in FIGS. 7A to 7C .

[0056] FIG. 6 is a time chart illustrating yet another embodiment of a film formation method using the reactive sputtering apparatus 1 according to the present invention, showing one period (one cycle) as a unit of the film formation process. The film formation method of the embodiment shown in FIG. 6 differs from the film formation method of the embodiment shown in FIG. 5 in the pulse applied to the first sputtering electrode 18 and the opening / closing signal of the first shutter 182, but the other control steps are the same. That is, in the film formation method of the embodiment shown in FIG. 5, the pulse applied to the first sputtering electrode 18 is always ON and controlled by opening / closing the first shutter 182 during the sputtering process of the first target T1. In contrast, in the film formation method of the embodiment shown in FIG. 6, the first shutter 182 is always open and controlled by ON / OFF control of the pulse applied to the first sputtering electrode 18 during the sputtering process of the first target T1. The film formation method of this embodiment also produces the composite metal compound-doped films shown in FIGS. 7A to 7C .

[0057] 4 to 6, the timing for starting the second step P2 is not limited to time t3 shown in the figures, but may be simultaneous with the start of the first step P1 (t2). Also, in FIGS. 4 to 6, the timing for ending the second step P2 is not limited to time t4 shown in the figures, but may be simultaneous with the end of the first step P1 (t5). Also, in FIGS. 4 to 6, the fourth step P4 is not an essential step, and may be omitted.

[0058] 1... reactive sputtering apparatus 11... film formation chamber 12... substrate holder 13... pressure reducer 14... gate valve / conductance valve 15... discharge gas introducer 151... discharge gas cylinder 152, 153... flow rate regulator 16... reactive gas introducer 161... reactive gas cylinder 162... flow rate regulator 17... shutter opening / closing controller 18... first sputtering electrode 181... first chimney 182... first shutter 183... first space 19... second sputtering electrode 191... second chimney 192... second shutter 193... second space 20... DC power supply 22... first pulse wave conversion switch 23... second pulse wave conversion switch 24... programmable oscillator 25... apparatus controller 26... film formation controller 27... gas introduction controller T1... first target T2... second target S...Substrate

Claims

1. A method for forming a film of a metal compound containing a metal dopant on a substrate, the method comprising the steps of: a first step of sputtering the metal compound on the substrate in a metallic mode with a flow rate of a reactive gas less than a predetermined value; and a second step of sputtering the metal dopant on the substrate in a reactive mode with a flow rate of the reactive gas equal to or greater than the predetermined value.

2. A film formation method according to claim 1, wherein after starting the film formation in the first step, the film formation in the second step is started simultaneously with the start of the film formation in the first step or after a predetermined time has elapsed, the film formation in the first step and the film formation in the second step are carried out in parallel, the film formation in the second step is terminated, and the film formation in the first step is terminated simultaneously with this or after a predetermined time has elapsed, and then the supply of the reactive gas to the substrate is continued for a predetermined time.

3. A film formation chamber into which a substrate to be film-formed is placed; a pressure reducer for reducing the pressure in the film formation chamber to a predetermined level; a discharge gas introducer for introducing a discharge gas into the film formation chamber; a first sputtering electrode on which a first target serving as a main film formation material is mounted and which is disposed so as to face the substrate; a first chimney for covering a first space in front of the first target and the first sputtering electrode by a first shutter that can be opened and closed; a second sputtering electrode on which a second target serving as a dopant for the main film formation material is mounted and which is disposed so as to face the substrate; a second chimney for covering a second space in front of the second target and the second sputtering electrode by a second shutter that can be opened and closed; a discharge gas introducer for introducing a discharge gas into the first space and the film formation chamber; a reactive gas introducer for introducing a reactive gas into the film formation chamber via the second space; a DC power supply for supplying power to the first sputtering electrode and the second sputtering electrode; a shutter opening / closing controller that controls the opening and closing of the first shutter and the second shutter, respectively; a gas introduction controller that controls the discharge gas introducer and the reactive gas introducer, respectively; and an overall controller that controls the electrode voltage controller, the shutter opening / closing controller, and the gas introduction controller in an overall manner.

4. The reactive sputtering apparatus according to claim 3, wherein the electrode voltage controller includes: a first pulse wave conversion switch connected between the DC power supply and the first sputtering electrode, for converting the DC voltage applied to the first sputtering electrode into a pulse wave voltage; and a second pulse wave conversion switch connected between the DC power supply and the second sputtering electrode, for converting the DC voltage applied to the second sputtering electrode into a pulse wave voltage; and the overall controller includes a programmable oscillator in which pulse control signal patterns can be programmed according to a first sputtering target power to be supplied to the first sputtering electrode, a second sputtering target power to be supplied to the second sputtering electrode, target opening and closing timings of the first shutter and the second shutter, and target introduction timings of the discharge gas and the reactive gas to be introduced into the film formation chamber, and which controls the first pulse wave conversion switch, the second pulse wave conversion switch, the shutter opening and closing controller, and the gas introduction controller in accordance with the programmed pulse control signal pattern.

5. A film formation method for forming a film on a substrate, the film containing the main film formation material as a main component and the dopant, using the reactive sputtering apparatus described in claim 3 or 4, comprising at least the following steps: a first step of introducing a discharge gas into the film formation chamber and the reactive gas into the second space, applying a pulse voltage from the DC power supply to each of the first sputtering electrode and the second sputtering electrode, closing the second shutter and opening the first shutter, and forming an ultra-thin film of the first target on the substrate; a second step of opening the second shutter under the conditions of the first step and simultaneously forming an ultra-thin film of the first target and an ultra-thin film of the second target on the substrate; and a third step of closing the second shutter under the conditions of the second step and forming an ultra-thin film of the first target on the substrate.

6. A film formation method for forming a film on a substrate, the film containing the main film formation material as a main component and the dopant, using the reactive sputtering apparatus described in claim 3 or 4, comprising at least the following steps: a first step of introducing a discharge gas into the film formation chamber and the reactive gas into the second space, applying a pulse voltage from the DC power supply to the first sputtering electrode, stopping the application of the DC voltage to the second sputtering electrode, opening the first shutter and the second shutter, and forming an ultra-thin film of the first target on the substrate; a second step of applying a pulse voltage to the second sputtering electrode under the conditions of the first step, and simultaneously forming an ultra-thin film of the first target and an ultra-thin film of the second target on the substrate; and a third step of stopping the application of the DC voltage to the second sputtering electrode under the conditions of the second step, and forming an ultra-thin film of the first target on the substrate.

7. A film formation method for forming a film on a substrate, the film containing the main film formation material as a main component and the dopant, using the reactive sputtering apparatus described in claim 3 or 4, comprising at least the following steps: a first step of introducing a discharge gas into the film formation chamber and the reactive gas into the second space, applying a pulse voltage from the DC power supply to the first sputtering electrode, stopping the application of the DC voltage to the second sputtering electrode, opening the first shutter and the second shutter, and forming an ultra-thin film of the first target on the substrate; a second step of applying a pulse voltage to the second sputtering electrode under the conditions of the first step, and simultaneously forming an ultra-thin film of the first target and an ultra-thin film of the second target on the substrate; and a third step of stopping the application of the DC voltage to the second sputtering electrode under the conditions of the second step, and forming an ultra-thin film of the first target on the substrate.

8. A film forming method according to claim 5 or 6, comprising at least a fourth step, after the third step, of closing the first shutter under the conditions of the third step and reacting the film formed on the substrate.

9. A film forming method according to claim 7, comprising at least a fourth step, after the third step, of stopping the application of a pulse voltage to the first sputtering electrode under the conditions of the third step and reacting the film formed on the substrate.

10. A film forming method according to any one of claims 5 to 7, wherein the first step, the second step, and the third step are repeated until a predetermined film thickness is achieved.

11. The film forming method according to claim 8 or 9, wherein the first step, the second step, the third step and the fourth step are repeated until a predetermined film thickness is achieved.

12. A film forming method according to any one of claims 5 to 11, wherein the film composed mainly of the main film forming material contains the dopant in an amount of more than 0 atomic % and not more than 5 atomic %.

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