Film formation method and film formation device

Abstract

A film formation method according to the present disclosure for forming, on a substrate, a film formed of gallium, zinc, and oxygen comprises: a pre-treatment step for heating the substrate to a first temperature in a first treatment container in which a vacuum atmosphere is formed; a step for conveying, through a conveying path in which a vacuum atmosphere is formed, the substrate from the inside of the first treatment container to the inside of a second treatment container in which a vacuum atmosphere is formed; a step for placing the substrate on a placement surface of a stage provided in the second treatment container in which the placement surface on which the substrate is placed is set to a second temperature lower than the first temperature; and, in order to form the film in which crystallization has occurred, a step for performing sputtering to form a film on the substrate while the temperature thereof is being lowered on the placement surface until before reaching the second temperature.

Description

Film forming method and film forming apparatus

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

[0002] In manufacturing a semiconductor device, a metal-containing film is formed on a substrate such as a semiconductor wafer (hereinafter referred to as a wafer) by sputtering. Patent Document 1 describes that the substrate is heated to 350°C to remove moisture, then transported into a chamber for sputtering, where an IGZO film is formed as the metal-containing film, and the film is analyzed after formation. It also describes that the temperature of the substrate during film formation is the temperature of the heating chuck on which the substrate is placed, and that film formation was performed at a temperature set within a range of 20°C to 375°C.

[0003] US2021 / 0164091A1 (paragraphs 0129-0134)

[0004] The present disclosure provides a technology that enables a film composed of gallium, zinc, and oxygen to be formed on a substrate in a highly convenient manner.

[0005] The film formation method disclosed herein is a film formation method for forming a film composed of gallium, zinc, and oxygen on a substrate, the film formation method comprising: a pretreatment step of heating the substrate to a first temperature in a first processing vessel in which a vacuum atmosphere is formed; a step of transporting the substrate from the first processing vessel to the second processing vessel in which a vacuum atmosphere is formed via a transport path in which a vacuum atmosphere is formed; a step of placing the substrate on the mounting surface of a stage provided in the second processing vessel, the mounting surface for placing the substrate being set to a second temperature lower than the first temperature; and a step of performing film formation by sputtering on the substrate while the temperature is decreasing on the mounting surface and before the second temperature is reached, in order to form a crystallized film.

[0006] The present disclosure enables a film composed of gallium, zinc, and oxygen to be formed on a substrate in a highly convenient manner.

[0007] 1 is a cross-sectional plan view of an embodiment of a film formation apparatus according to the present disclosure; FIG. 2 is a longitudinal side view of a load lock module provided in the film formation apparatus; FIG. 3 is a longitudinal side view of a sputtering processing module provided in the film formation apparatus; FIG. 4 is a flow diagram showing processing steps performed in the film formation apparatus; FIG. 5 is a graph showing the results of an evaluation test for a comparative example; FIG. 6 is a graph showing the results of an evaluation test for the present technology regarding the pressure during film formation; FIG. 7 is a graph showing the results of an evaluation test for the present technology regarding the pressure during film formation; FIG. 8 is a graph showing the relationship between the pressure during film formation and the peak of an acquired waveform; FIG. 9 is a graph showing the results of an evaluation test for the present technology regarding the partial pressure of oxygen during film formation; FIG. 10 is a graph showing the results of an evaluation test for the present technology regarding the partial pressure of oxygen during film formation; FIG. 11 is a graph showing the results of an evaluation test for the present technology regarding the change in temperature of pre-treatment heating; FIG. 12 is a graph showing the results of an evaluation test for the present technology regarding the change in temperature of pre-treatment heating.

[0008] [Configuration of Film Forming Apparatus] A film forming apparatus 1, which is one embodiment of the film forming apparatus of the present disclosure, will be described with reference to the plan view of FIG. 1 . The film forming apparatus 1 forms an IGZO film (indium gallium zinc oxide film), which is an oxide semiconductor film composed of indium (In), gallium (Ga), zinc (Zn), and oxygen (O), on a substrate, a wafer W, by sputtering. The film forming apparatus 1 performs a heat treatment on the wafer W before it is transferred into a processing chamber for film formation. During film formation, the IGZO film described above is crystallized due to the residual heat of the wafer W generated by this heat treatment. In the following description, the heat treatment performed on the substrate outside the processing chamber where sputtering is performed may be referred to as pre-treatment heating.

[0009] The film forming apparatus 1 includes an atmospheric transfer module 2 called an Equipment Front End Module (EFEM), two load lock modules 3, a vacuum transfer module 4, and processing modules 5A to 5C, with the atmospheric transfer module 2, load lock module 3, and vacuum transfer module 4 arranged in this order from front to rear. The load lock module may be hereinafter referred to as an LLM.

[0010] The vacuum transfer module 4 is roughly hexagonal in plan view. LLMs 3 and any of the processing modules 5A to 5C are arranged adjacent to five of the sides of this hexagon via gate valves G. LLMs 3 are provided side by side on the left and right behind the atmospheric transfer module 2, and the sides of the hexagon to which no modules are connected are sandwiched between these LLMs 3 and are positioned facing the atmospheric transfer module 2.

[0011] The processing modules 5A, 5B, and 5C are arranged in this order from right to left behind the LLM 3. However, in this embodiment, the processing modules 5B and 5C are not used, and their use will be described in other embodiments. In Figure 1, the left-right direction is represented as the X direction, and the front-rear direction is represented as the Y direction.

[0012] A gate valve G is also interposed between the atmospheric transfer module 2 and each LLM 3. Each gate valve G provided in the film formation apparatus 1 is closed except when necessary for transferring wafers W between modules, and the atmospheres between the modules are separated by closing this gate valve G. More specifically, each module constituting the film formation apparatus 1 has a housing or processing container with a transfer port for wafers W formed in its sidewall, and opening and closing this transfer port by the gate valve switches between a state in which wafers W can be transferred between modules and a state in which wafers W cannot be transferred between modules and the atmospheres are separated.

[0013] The atmospheric transfer module 2 includes a rectangular parallelepiped housing 21 with its longitudinal direction in the X direction, and the interior of the housing 21 is kept at atmospheric pressure. A transfer mechanism 22 is provided within the housing 21, and the transfer mechanism 22 is configured, for example, as an articulated arm that can move left and right. The atmospheric transfer module 2 also includes, for example, three load ports 23 arranged side by side on the left and right, for transferring wafers W between a transfer container C storing wafers W and the film forming apparatus 1. Each load port 23 includes a loading platform 24 for the transfer container C provided on the front side of the housing 21, a transfer port provided in the side wall of the housing 21 facing the transfer container C on the loading platform 24, and a door 25 for opening and closing the transfer port. The transfer container C is, for example, a FOUP (Front Opening Unified Pod) configured to store multiple wafers W, and the transfer mechanism 22 transfers wafers W between the transfer container C and the LLM 3.

[0014] 2, which is a longitudinal side view, the LLM 3 will be described. One of the two LLMs 3 is used to transfer the wafer W from the atmospheric transfer module 2 to the vacuum transfer module 4, and the other is used to transfer the wafer W from the atmospheric transfer module 2 to the vacuum transfer module 4. In this LLM 3, the wafer W is subjected to the pre-processing heating described above.

[0015] The LLM 3 includes a housing 31. The housing 31 is formed with a transfer port for the wafer W described above. Two transfer ports are provided: one for the atmospheric transfer module 2 and one for the vacuum transfer module 4, but only one of them is shown in FIG. 2 as a transfer port 32. A stage 33 for placing the wafer W is provided within the housing 31. Although not shown, three protruding and retractable pins are provided on the top surface of the stage 33. The wafer W is transferred between the stage 33 and the transfer mechanism 22 of the atmospheric transfer module 2 and a transfer mechanism 43 of the vacuum transfer module 4 (described later) via these pins.

[0016] An exhaust port 34 and an air inlet 35 are open inside the housing 31. An exhaust mechanism 36 and a gas supply mechanism 37 are connected to the housing 31. The exhaust mechanism 36 is equipped with a valve and a vacuum pump, and can switch between a state in which exhaust from the exhaust port 34 is performed and a state in which exhaust is stopped. The exhaust by the exhaust mechanism 36 can create a vacuum pressure inside the housing 31.

[0017] The gas supply mechanism 37 includes an inert gas supply source and a valve, and can switch between a state in which the inert gas is supplied into the housing 31 via the gas inlet 35 and a state in which the supply is stopped. In order to enable the wafer W to be transferred between the vacuum transfer module 4 and the atmospheric transfer module 2, the pressure inside the housing 31 can be changed between atmospheric pressure and a predetermined vacuum pressure by exhausting or supplying the inert gas into the housing 31 while the gate valves G connected to the housing 31 are closed.

[0018] The ceiling of the housing 31 is configured as a window 38 that allows light to pass through. A light irradiation unit 39 for pre-heating is provided at the top of the housing 31. This light irradiation unit 39 includes a plurality of light sources 30, e.g., LEDs. Light emitted downward from each light source 30 (indicated by dashed arrows in the figure) is irradiated through the window 38 onto the wafer W placed on the stage 33, heating the wafer W. Light irradiation from the light sources 30 can be switched on and off as desired. The intensity of the light irradiated from the light sources 30 is adjustable, allowing the wafer W to be heated to a desired first temperature, e.g., 150°C to 450°C. The light irradiation onto the wafer W is performed during the process of reducing the pressure inside the housing 31 from atmospheric pressure to a predetermined vacuum pressure by exhausting air from the exhaust port 34. Since the wafer W is heated as described above, the housing 31 of the LLM 3 is a processing vessel for processing the wafer W therein, and corresponds to a first processing vessel. The light irradiation unit 39 corresponds to a heating mechanism.

[0019] [Configuration of Vacuum Transfer Module] Returning to Figure 1, the vacuum transfer module 4 will be described. The vacuum transfer module 4 includes a housing 41, which is generally hexagonal in plan view as described above. The interior of the housing 41 is formed as a transfer path 42 for the wafer W. This transfer path 42 is evacuated by an exhaust mechanism (not shown), so that a vacuum atmosphere of a predetermined pressure is always maintained while the film forming apparatus 1 is in operation. A transfer mechanism 43, which is an articulated arm, is provided within the housing 41.

[0020] The transfer mechanism 43 transfers the wafer W between the LLM 3 and the processing modules 5A to 5C adjacent to the vacuum transfer module 4 via the gate valve G. Since the vacuum transfer module 4 has a vacuum atmosphere, the surroundings of the wafer W are maintained in a vacuum atmosphere during transfer between these modules.

[0021] [Configuration of Sputtering Processing Module] Next, the processing module 5A will be described with reference to the vertical cross-sectional side view of FIG. 3. This processing module 5A is a module that forms the above-mentioned IGZO film on the wafer W by sputtering, more specifically, magnetron sputtering. The processing module 5A includes a metal processing vessel 51, which is grounded. An exhaust mechanism 52 is connected to the processing vessel 51, which is the second processing vessel, and exhaust is performed through an exhaust port 53 formed in the bottom wall of the processing vessel 51. This maintains the interior of the processing vessel 51 at a predetermined vacuum pressure. More specifically, for example, during film formation on the wafer W, a pressure of 6.0×10 －３ The pressure in the processing vessel 51 is maintained at a pressure of 1000 psi (0.8 Torr) or less. The exhaust mechanism 52, like the exhaust mechanism 36 of the LLM 3, is configured to include a valve and a vacuum pump so as to be able to adjust the amount of exhaust in the processing vessel 51, thereby creating a vacuum atmosphere at a desired pressure inside the processing vessel 51. The processing vessel 51 is also formed with a transfer port 54 for the wafer W, which is opened and closed by the gate valve G as described above.

[0022] A stage 55, which is circular in plan view and on which a wafer W is placed, is provided within the processing vessel 51. The upper side of the stage 55 is configured as an electrostatic chuck 56. The upper surface of the electrostatic chuck 56 is configured as a mounting surface 55A on which the wafer W is horizontally placed, and the wafer W is placed so that its center is aligned with the center of the mounting surface 55A, and the placed wafer W is attracted to the mounting surface 55A.

[0023] The lower side of the stage 55 is configured as a base body 57, and is provided with a flow path (not shown) through which a fluid whose temperature is regulated by, for example, a chiller flows. Heat exchange caused by the flow of this fluid causes the temperature of the mounting surface 55A of the electrostatic chuck 56 to be kept at room temperature. Specifically, room temperature here refers to a temperature within a range of 20°C to 30°C. Therefore, the second temperature, which is the temperature of the mounting surface 55A, is set to be lower than the first temperature, which is the heating temperature of the wafer W in the LLM3.

[0024] Due to such settings, as will be described in detail later in the description of the processing steps by the film forming apparatus 1, a wafer W at a temperature higher than room temperature is placed on the mounting surface 55A of the stage 55. The temperature of the wafer W placed on the mounting surface 55A is then lowered to room temperature, but film formation by sputtering on the wafer W begins before the temperature of the wafer W reaches room temperature. Note that, in addition to the second temperature, the temperature of the mounting surface 55A increases when the wafer W is placed on it, but the second temperature is the temperature before the wafer W is placed on it, i.e., before the temperature increases.

[0025] Similar to the stage 33 of the LLM 3, the stage 55 also has three retractable pins on its upper surface (i.e., the mounting surface 55A), and the wafer W can be transferred between the transfer mechanism 43 of the vacuum transfer module 4 and the electrostatic chuck 56 via these pins. The pins are also omitted from FIG. 3 . The lower surface of the stage 55 is connected via a support 58 to a drive mechanism 59 provided outside the processing vessel 51. The drive mechanism 59 allows the stage 55 to rotate around a central axis aligned in the vertical direction of the stage 55. In the figure, reference numeral 50 denotes a seal member provided between the processing vessel 51 and the support 58, which keeps the interior of the processing vessel 51 airtight.

[0026] The ceiling of the processing vessel 51 forms a sloped portion that descends from the center of the stage 55 toward the periphery, and this sloped portion has, for example, four through-holes formed in the circumferential direction in a plan view. A plate-shaped target holder 62 is supported by an annular insulating member 61 provided along the edge of each through-hole and is provided to close the through-hole. As will be described later, the target holder 62 is configured as a cathode. A rectangular plate-shaped target 63 made of a metal material is provided by being stacked on each target holder 62 from below and supported by the target holder 62. Therefore, in this example, four target holders 62 and four targets 63 are provided, and two of them are shown in the figure.

[0027] If these target holders 62 and the targets 63 below them are considered as one set, the four sets are located at the same height and are arranged in a rotationally symmetrical positional relationship around the rotation axis of the wafer W on the stage 55 in a plan view. The main surface (lower surface) of each target 63 is inclined with respect to the horizontal and vertical planes and is arranged to face the stage 55. A TS distance H1, which is the vertical distance between the center of the main surface of this target 63 and the mounting surface 55A of the stage 55, is, for example, 200 mm to 300 mm.

[0028] Each target 63 contains In, Ga, Zn, and O (oxygen), and the concentration of each element in the target 63 is adjusted so that the IGZO film formed on the wafer W has a desired concentration of In, Ga, and Zn. Note that "containing In, Ga, Zn, and O" here means that they are included as constituent components, not as unavoidable impurities. Specifically, for example, the ratio of element concentrations in the target 63 is In:Ga:Zn=1:1:2. Each target holder 62 is connected to a power supply 64, and a negative DC voltage of, for example, 325 W to 1300 W is applied from the power supply 64 to sputter the target 63.

[0029] A magnet unit 65 is provided on the back side (upper surface side) of each target holder 62, outside the processing vessel 51. The magnet unit 65 is composed of a plurality of magnets arranged in a predetermined direction, and forms a leaking magnetic field on the front side (lower surface side) of the target 63 held by the lower target holder 62. In order to prevent local erosion of the target 63, the magnet unit 65 is moved back and forth linearly along the back surface of the target holder 62 by a moving mechanism 66 during sputtering of the target 63. The target holder 62, the target 63, the power supply 64, and the magnet unit 65 constitute a sputtering mechanism.

[0030] Furthermore, a gas inlet 67 is opened in the processing vessel 51, and gas is supplied from a gas supply mechanism 68 into the processing vessel 51 through the gas inlet 67. This gas is an inert gas for sputtering, or a mixed gas of the inert gas and an oxidizing gas for oxidizing In, Ga, and Zn. Specifically, the inert gas is, for example, argon (Ar) gas, and the oxidizing gas is, for example, oxygen (O ２ The gas supply mechanism 68 includes a supply source of Ar gas, an O ２ The chamber is equipped with a gas supply source, valves for switching on and off the supply of each gas into the processing vessel 51, and flow rate adjusting units such as mass flow controllers for adjusting the supply flow rate of each gas downstream of the flow path.

[0031] The ratio of the flow rate of the oxygen gas to the total flow rate of the Ar gas and the oxygen gas supplied from the gas supply port 67 is, for example, 0% to 20%. ２ Since only gas is supplied, setting the flow rates of each gas in this manner means that the partial pressure of oxygen gas is set to 0% to 20% of the total pressure inside the processing vessel 51. The flow rate of the Ar gas is, for example, 40 sccm to 800 sccm.

[0032] The film forming apparatus 1 also includes a control unit 10, which is a computer (see FIG. 1). The control unit 10 includes a program, a memory, and a CPU. The program contains instructions (each step) for processing and transporting the wafer W, and the program is stored on a storage medium such as a compact disc, a hard disk, a magneto-optical disc, or a DVD, and is installed in the control unit 10. The control unit 10 outputs control signals to each part of the film forming apparatus 1 according to the program, thereby controlling the operation of each part.

[0033] The operations of the film forming apparatus 1 controlled by such control signals include the transfer of wafers W between modules by the movement of each transfer mechanism and the raising and lowering of stage pins, the opening and closing of gate valve G, changes in the pressure inside the housing 31 by supplying and exhausting gas in LLM3, light irradiation and its intensity in LLM3 (i.e., the heating temperature of wafers W in pre-processing), the rotation of stage 55 in processing module 5A, the supply of gas from air inlet 67, the pressure inside processing vessel 51, and switching between performing and stopping sputtering by turning on and off the power supply 64.

[0034] [Processing Steps in Film Forming Apparatus 1] The processing steps for a wafer W in the film forming apparatus 1 will be described with reference to the flowchart of FIG. 4 . First, the transfer mechanism 22 of the atmospheric transfer module 2 removes the wafer W from the transfer container C (step S1). The wafer W is then transferred into the housing 31, which is under atmospheric pressure in one of the two LLMs 3, and placed on the stage 33 within the housing 31. The pressure within the housing 31 is evacuated to reduce the pressure. While the pressure is decreasing, the light irradiation unit 39 irradiates the stage 33 with light, thereby performing pre-heating (step S2). Therefore, while the pressure within the housing 31 decreases, the temperature of the wafer W increases. This temperature increase vaporizes and removes foreign matter, such as moisture, adhering to the wafer W, and the temperature of the wafer W reaches the first temperature, for example, in the range of 150°C to 450°C.

[0035] Thereafter, when the interior of the housing 31 reaches a predetermined vacuum pressure and the temperature of the wafer W reaches the first temperature, the light irradiation is stopped, and the transfer mechanism 43 of the vacuum transfer module 4 receives the wafer W and transfers it toward the processing module 5A. During this transfer to the processing module 5A, the wafer W is surrounded by a vacuum atmosphere, so heat radiation from the wafer W is suppressed. Therefore, the wafer W is transferred into the processing chamber 51 of the processing module 5A in a state where the temperature drop is relatively suppressed, and is placed on the stage 55, the mounting surface 55A of which is set to a second temperature within the room temperature range. As described above, because residual heat of the wafer W is utilized for film formation, the temperature difference between the wafer W and the upper surface of the stage 55 at the time of placement is relatively large, e.g., 100°C or more. Heat radiation from the wafer W continues even after placement on the stage 55, and the temperature of the wafer W continues to drop.

[0036] Then, Ar gas or Ar gas and O ２ The mixed gas with the gas is supplied, and the pressure inside the processing vessel 51 is increased to the previously mentioned 6.0×10 －３ The pressure in the processing vessel 51 is adjusted to a predetermined pressure of 0.2 Torr (0.8 Pa) or less. ２ The gas pressure (partial pressure) is set to 20% or less. Meanwhile, rotation of stage 55 and reciprocating movement of magnet unit 65 are started. Then, power supply 64 is turned on to start magnetron sputtering. That is, formation of an IGZO film on the surface of wafer W is started, and the film thickness of the IGZO film increases (step S3).

[0037] Therefore, magnetron sputtering is initiated before the wafer W reaches room temperature, which is the set temperature of the upper surface of the stage 55. The IGZO film formed on the wafer W is crystallized by receiving energy from the residual heat of the wafer W. Even during this film formation, the temperature of the wafer W continues to decrease because the temperature of the upper surface of the stage 55 is lower than the temperature of the wafer W when heated in the LLM 3. In other words, the state in which film formation continues on the wafer W while its temperature is decreasing.

[0038] Then, when the thickness of the IGZO film on the surface of the wafer W reaches a predetermined thickness, the power supply 64 is turned off, thereby stopping the film formation process, and the supply of gas from the gas inlet 67, the rotation of the stage 55, and the reciprocating movement of the magnet unit 65 are stopped. The wafer W on which the film has been formed as described above is transferred by the transfer mechanism 43 into the other of the two LLMs 3, the housing 31, which is set to a vacuum atmosphere. When the pressure inside the housing 31 returns to atmospheric pressure, the wafer W is returned by the transfer mechanism 22 to the transfer container C. Note that, when the power supply 64 of the processing module 5A is turned off and sputtering of the target 63 is stopped (i.e., film formation on the wafer W is stopped) as described above, the temperature of the wafer W may have completely dropped to the same temperature as the upper surface of the stage 55, or the temperature of the wafer W may not have completely dropped and may still be dropping.

[0039] [Matters related to crystallized IGZO film] An IGZO film is used, for example, as a channel between the source and drain of an FeFET (Ferroelectric Field Effect Transistor). In this case, better characteristics can be obtained by using a crystallized IGZO film than by using amorphous IGZO (hereinafter referred to as a-IGZO). Specifically, both the field effect mobility and stability can be increased. High stability means that the electrical characteristics fluctuate little with heat or stress.

[0040] Crystallized IGZO includes spinel and CAAC (Co-Axis-Aligned-Crystalline), with spinel being more crystallized than CAAC. CAAC has a higher field effect mobility and spinel has a higher stability. However, when CAAC and spinel are mixed in a film, it is not possible to sufficiently increase the field effect mobility or stability. Therefore, it is necessary to form an IGZO film of either CAAC or spinel to suppress this mixing.

[0041] [Regarding the Film Formation Method of the Comparative Example] When forming a crystallized IGZO film on a substrate by sputtering, a method different from the film formation method in the film formation apparatus 1 has been used so far. Specifically, in this film formation method (hereinafter referred to as the film formation method of the comparative example), the pre-treatment heating described as being performed in the LLM 3 is not performed, and the film is formed by heating the substrate to a relatively high temperature in a processing chamber where sputtering is performed. Various variations of this film formation method of the comparative example have been shown so far, but there have been concerns. These are exemplified below.

[0042] When forming an IGZO film of CAAC using the comparative film formation method, the oxygen partial pressure in the sputtering chamber is sometimes relatively high, for example, approximately 100%, to enhance crystallization. However, such an excessively high oxygen partial pressure results in an excessively low partial pressure of the inert gas used in sputtering, making it difficult to produce ions (sputter ions) of the inert gas. This necessitates the application of a high voltage to the target to ensure the necessary amount of sputter ions. Furthermore, the small number of sputter ions produced results in a longer film formation time. In other words, the comparative film formation method raises concerns about significant limitations on the equipment configuration and reduced throughput.

[0043] Furthermore, when forming an IGZO film of CAAC using the film formation method of the comparative example, the substrate may be annealed at a high temperature after film formation to enhance crystallization. In the explanation of the film formation apparatus 1, an example of film formation on a wafer W as the substrate was described, but there are cases where film formation is required on substrates other than wafer W. Such substrates include substrates with relatively low heat resistance, such as organic substrates. In other words, there is a concern that the film formation method of the comparative example may limit the substrates on which the film can be formed.

[0044] As will be shown in detail later in the evaluation test, a spinel IGZO film with reduced CAAC contamination can be formed by forming a seed layer on the substrate in advance and then forming a film on this seed layer using the film formation method of the comparative example. However, because the substrate needs to be heated to a high temperature to form this seed layer, there is a concern that the substrates on which the film can be formed may be limited, as in the case of forming a CAAC IGZO film.

[0045] [Evaluation Test] For the above reasons, there has been a demand for forming an IGZO film of a selected one of CAAC and Spinel on a substrate without heating the substrate to an excessively high temperature, suppressing the oxygen partial pressure during film formation, and suppressing the mixing of crystal structures. The film formation method using the above-mentioned film formation apparatus 1 described in FIG. 4 can meet each of the above requirements. The evaluation test that provides the basis for this will be described below.

[0046] Evaluation Tests 1 and 2 In Evaluation Tests 1 and 2, the film formation method of the comparative example described above was performed using the processing module 5A to form an IGZO film on a wafer W, and evaluation was performed. Specifically, in Evaluation Test 1, when forming an IGZO film on a plurality of wafers W, the temperature of the mounting surface 55A of the stage 55 (i.e., the temperature of the wafer W) was set to a different temperature for each wafer W. The temperature of this wafer W was set to a temperature within a range of 25°C to 350°C. After film formation, the surface of each wafer W was analyzed by X-ray diffraction (XRD).

[0047] In Evaluation Test 2, a wafer W having a thin layer of GZO formed on its surface as a seed layer was transferred to processing module 5A, and an IGZO film was formed thereon. The temperature of the wafer W during the formation of the IGZO film was set to 200°C. After the film formation, the surface of the wafer W was analyzed by XRD. Note that this seed layer was not formed on each wafer W in Evaluation Test 1 described above. In addition, in Comparative Test 2, the surface of the wafer W on which the seed layer was formed was analyzed by XRD. That is, in Comparative Test 2, an XRD analysis was performed on a wafer W on which no IGZO film was formed.

[0048] Figure 5 is a graph showing the results of Evaluation Tests 1 and 2 and Comparative Test 2. In each of the graphs showing the results of XRD in Figure 5 and subsequent figures, the horizontal axis represents 2θ (unit: degrees) and the vertical axis represents intensity (unitless), where θ is the angle of incidence of the X-rays. Regarding the waveforms in the graphs, specific peaks indicating the presence of a crystalline structure are indicated by numbers in parentheses corresponding to the peaks.

[0049] 5 shows graphs in the upper, middle, and lower rows, with the upper and middle graphs showing the results of Evaluation Test 1 and the lower graph showing the results of Evaluation Test 2 and Comparative Test 2. The horizontal axes of the graphs in each row are aligned with each other. That is, in each graph, the same horizontal position indicates the same 2θ value.

[0050] Looking at the waveform of the graph for Evaluation Test 1 in the upper part, when the temperature of the wafer W during film formation is in the range of 350°C to 200°C, the higher the temperature, the larger the peak representing CAAC and the smaller the peak representing Spinel. As the temperature decreases, the peak representing CAAC becomes smaller and the peak representing Spinel becomes larger. In other words, within this temperature range, the closer to 350°C, the more CAAC is contained, and the closer to 200°C, the more Spinel is contained. However, even at temperatures at or near 350°C, the peak representing Spinel is observed, and even at 200°C and temperatures slightly higher than 200°C, the peak representing CAAC is observed. In other words, at 350°C to 200°C, a crystal structure in which Spinel and CAAC are mixed is formed.

[0051] As shown in the middle graph, when the temperature of the wafer W during film formation is in the range of lower than 200° C., the Spinel peak becomes smaller as the temperature decreases, and both the CAAC peak and the Spinel peak are relatively small at or near 25° C. Therefore, when the temperature of the wafer W during film formation is in the range of 25° C. or higher and lower than 200° C., the result is that the degree of crystallization of the IGZO film is low.

[0052] Furthermore, looking at the graph for Evaluation Test 2 in the lower part, the peak representing Spinel is relatively large, and no peak representing CAAC is observed. However, when forming the seed layer of GZO described above, it is necessary to heat the wafer W to 700°C for film formation. Therefore, from the viewpoint of suppressing the mixing of crystal structures, the film formation method for forming the seed layer in Evaluation Test 2 is preferable, but film formation at a lower temperature is required.

[0053] Evaluation Test 3 Each evaluation test from Evaluation Test 3 onward is an evaluation test in which wafers W are processed using the film formation apparatus 1 described above in accordance with the flow explained in FIG. 4 and analyzed by XRD. That is, wafers W pre-heated outside the processing module 5A are transferred to the processing module 5A via the vacuum transfer module 4, and an IGZO film is formed on the wafers W and analyzed. In Evaluation Test 3, after the wafers W are pre-heated to 300°, the pressure inside the processing chamber 51 during film formation in the processing module 5A is set differently for each wafer W, and film formation processing is performed. The set pressures inside the processing chamber 51 are listed in ascending order of pressure: 5.0×10 －４ Torr (0.067Pa), 1.2×10 －３ Torr (0.16Pa), 2.5×10 －３ Torr (0.33Pa), 4.9×10 －３ Torr (0.65Pa), 6.0×10 －３ Torr (0.8 Pa). The tests performed in ascending order of set pressure are referred to as evaluation tests 3-1, 3-2, 3-3, 3-4, and 3-5. －４ Torr, and in evaluation test 3-2, the pressure was set to 2.5 × 10 －３ Torr.

[0054] Regarding the processing conditions other than the pressure in the processing vessel 51 in the evaluation tests 3-1 to 3-5, in the evaluation tests 3-1 to 3-5, the O ２The partial pressure of the gas was set to 10% of the total pressure in the processing vessel 51. In the evaluation tests 3-1 to 3-5, the flow rate of the Ar gas supplied into the processing vessel 51 was set in the range of 40 to 800 sccm, and the higher the pressure in the processing vessel 51, the larger the flow rate of the Ar gas. In the following description, the partial pressure of the O gas relative to the total pressure in the processing vessel 51 is set to 10% of the total pressure in the processing vessel 51. ２ The ratio of partial pressures of gases is simply O ２ It may be expressed as the partial pressure of the gas.

[0055] FIG. 6 shows the results of Evaluation Tests 3-1 to 3-3, and FIG. 7 shows the results of Evaluation Tests 3-4 to 3-5. Evaluation Test 3-1 exhibits a relatively large spinel peak, while the CAAC peak is extremely small. Evaluation Test 3-2 exhibits a spinel peak of similar intensity to Evaluation Test 3-1, but exhibits a CAAC peak that is larger than that of Evaluation Test 3-1. Evaluation Tests 3-3 to 3-5 exhibit an extremely small spinel peak, while the CAAC peak is relatively large. FIG. 8 is a graph showing the results of Evaluation Test 3 in a different manner from FIGS. 6 and 7 . The horizontal axis represents the pressure within the processing vessel 51 during film formation, and the vertical axis represents the peak intensities of the spinel and CAAC.

[0056] 6 to 8, the results of Evaluation Test 3 show that it is possible to switch between the formation of CAAC and the formation of Spinel by adjusting the pressure inside the processing vessel 51, and that it is possible to suppress the coexistence of these crystals. －３ It was possible to suppress the inclusion of crystals when forming an IGZO film at a pressure of 1.2×10 Torr (0.8 Pa) or less. －３ Torr, and －４ On the other hand, in order to form CAAC while suppressing the inclusion of crystals, it is more preferable to set the pressure to 1.2 × 10 Torr or less. －３ Torr, and －３It is clear that it is more preferable to set the pressure higher than Torr.

[0057] Evaluation Test 4: In evaluation test 4, after the wafer W was heated to 300° C. in the pre-heating, O 2 was measured during film formation in the processing module 5A. ２ The partial pressure of the gas was set differently for each wafer W to perform the film formation process, and the surface of the wafer W after film formation was analyzed by XPS. In this evaluation test 4, the combination of the pressure in the processing vessel 51 and the flow rate of Ar gas was changed depending on the wafer W. In the evaluation test 4, the pressure in the processing vessel 51 was set to 5.0×10 －４ The test in which the flow rates of Torr and Ar gas were set to 40 sccm was designated as evaluation test 4-1, and the pressure inside the processing vessel 51 was set to 2.5×10 －３ The test in which the flow rates of Torr and Ar gas were set to 275 sccm was designated as Evaluation Test 4-2. ２ The partial pressure of the gas was changed within a range of 0% to 20% in evaluation test 4-1, and within a range of 0% to 15% in evaluation test 4-2.

[0058] FIG. 9 shows the results of evaluation test 4-1, and FIG. 10 shows the results of evaluation test 4-2. For convenience of illustration, FIG. 10 shows the graph divided into two sections, upper and lower. In this graph divided into two sections, the values ​​on the horizontal axis are aligned as in the graph of FIG. 5. Looking at FIG. 9, it can be seen that O ２ The higher the partial pressure of the gas, the stronger the intensity of the spinel peak. ２ When the partial pressure of the gas is 20%, 15%, and 10%, the peak of the spinel appears particularly large. ２ No large peak indicating CAAC is observed when the gas partial pressure is 20%, 15%, 10%, or 0%.

[0059] Also, looking at FIG. ２ CAAC peaks were observed when the partial pressure of the gas was 15%, 10%, 3.5%, 2.5%, 1.5%, and 0%. ２ The higher the partial pressure of the gas, the stronger the CAAC peak. ２ When the partial pressure of the gas is 10% or more, the peak of CAAC is particularly large.２ No large peak indicating spinel is observed at any of the above gas partial pressures.

[0060] As described above, the results of evaluation test 4 show that O ２ It can be seen that the IGZO film can be crystallized so that the coexistence of spinel and CAAC is suppressed when the partial pressure of the gas is in the range of 0% to 20%. ２ It was confirmed that the partial pressure of the gas is preferably 10% or more.

[0061] As mentioned above, in each of the evaluation tests 4-1 and 4-2, ２ It was confirmed that the higher the partial pressure of the gas, the larger the peaks indicating spinel and CAAC, and the more the crystallization progressed. ２ It is believed that if the partial pressure of the gas is increased to more than 20%, the crystallization will proceed further. ２ If the partial pressure of the gas is 50% or less, the O ２ The problem of excessively high partial pressure of the gas is not significant, and this is considered preferable.

[0062] Evaluation Test 5: In Evaluation Test 5, the temperature during pre-heating (i.e., the first temperature) was set to a different temperature within the range of 150°C to 350°C for each wafer W, and then a film formation process was performed on each wafer W in the process module 5A. The surface of each wafer W after film formation was analyzed by XPS. ２ The partial pressure of the gas was set to 10%. In this evaluation test 5, the combination of the pressure inside the processing vessel 51 and the flow rate of the Ar gas supplied into the processing vessel 51 was also changed depending on the wafer W. In the evaluation test 5, the pressure inside the processing vessel 51 was set to 5.0×10 －４ The test in which the flow rates of Torr and Ar gas were set to 40 sccm was designated as evaluation test 5-1, and the pressure inside the processing vessel 51 was set to 2.5×10 －３ A test in which the flow rates of Torr and Ar gas were set to 275 sccm was designated as evaluation test 5-2.

[0063] FIG. 11 shows the results of Evaluation Test 5-1, and FIG. 12 shows the results of Evaluation Test 5-2. Regarding Evaluation Test 5-1, when the first temperature was 150°C, 200°C, 250°C, and 350°C, a relatively large peak of spinel was observed, but no large peak indicating CAAC was observed. The higher the first temperature, the larger the peak indicating spinel. Regarding Evaluation Test 5-2, when the first temperature was 150°C, 200°C, 250°C, and 350°C, a relatively large peak of CAAC was observed, but no large peak indicating spinel was observed. The higher the first temperature, the larger the peak indicating CAAC.

[0064] Evaluation Test 5 showed that it is possible to crystallize the IGZO film while suppressing the inclusion of crystals at a first temperature in the range of at least 150° C. or higher. It also showed that setting the first temperature to a higher temperature is preferable in terms of promoting crystallization.

[0065] Summarizing the results of Evaluation Tests 3 to 5, it was shown that when forming an IGZO film so as to suppress the intermixing of crystal structures using the film formation method of the present technology shown in the flow chart of FIG. 4 , it is possible to set the first temperature during pre-heating at 150°C or higher. Because the first temperature can be set lower than the temperature (700°C) required for forming the seed layer in Evaluation Test 2, and because the stage temperature in the processing vessel 51 can be room temperature as described above, it can be said that the film formation method of the present technology does not require the wafer W to be heated to an excessively high temperature. Furthermore, it was also shown that when forming an IGZO film so as to suppress the intermixing of crystal structures, it is possible to set the oxygen partial pressure in the processing vessel 51 to a relatively low oxygen partial pressure of 20% or less of the total pressure in the processing vessel 51. Therefore, the film formation method of the present technology can prevent the occurrence of the problems described in the description of the film formation method of the comparative example. Furthermore, the film formation method of the present technology allows for switching between forming a spinel film or a CAAC film by setting the pressure in the processing vessel 51 during film formation. From the above, it can be said that the film formation method of this technology is highly convenient.

[0066] [Additional Information Regarding the Configuration of the Sputtering Processing Module] In the processing module 5A, the number of target holders 62, targets 63, and magnet units 65 installed is not limited to four as in the example described above, and any number may be provided, for example, two of each. Furthermore, the power supply 64 is not limited to applying a DC voltage to the target holder 62, and may apply an AC voltage.

[0067] Furthermore, the ratio of the element concentrations of In, Ga, and Zn contained in the target 63 is not limited to the above example and can be any ratio depending on the IGZO film to be formed on the wafer W. Specific examples include ratios such as In:Ga:Zn = 1:1:1, 2:1:4, 1:2:1, or 2:1:1. Alternatively, the In ratio can be 0, such as In:Ga:Zn = 0:2:1. That is, a GZO film may be formed on the wafer W by providing a target 63 composed of elements other than In among In, Ga, Zn, and O in the processing module 5A. Like the IGZO film, this GZO film can also be formed on the wafer W in a crystallized state by pre-processing heating. In the above-described evaluation tests 3 to 5, an IGZO film having a thickness of 10 nm to 100 nm is formed on the wafer W. However, the thickness of the film to be formed is not limited to this range and can be set appropriately, and can be any size within the range of 10 nm to 1 μm, for example.

[0068] Although the mounting surface 55A of the stage 55 of the processing module 5A is set to room temperature (20°C to 30°C) before the wafer W is placed thereon, this is not limited to room temperature. For example, the temperature of the mounting surface 55A may be set to a temperature higher than 30°C or lower than 20°C. That is, it may be set to a temperature other than room temperature. However, setting the temperature at room temperature is preferable because it requires less energy to operate the apparatus, allowing for low-cost operation of the apparatus. To give a specific example, when a fluid is passed through the stage 55 as described above to bring the mounting surface 55A to room temperature, the temperature can be adjusted to the desired room temperature without excessive heating or cooling of the fluid. In other words, energy required for adjusting the temperature of the fluid is saved, allowing for low-cost operation of the apparatus as described above.

[0069] [Additional Information Regarding the Module Performing Pre-heating] As described above, the pre-heating is performed on the wafer W transferred from the atmospheric transfer module 2 to the vacuum transfer module 4, so the light irradiation unit 39 and the window 38 may be provided in only one of the two LLMs 3. Furthermore, the location where the pre-heating is performed is not limited to the LLM 3. For example, the pre-heating may be performed in the processing module 5B shown in FIG.

[0070] This processing module 5B has a configuration similar to that of the LLM 3, except that the pressure inside the housing 31 is maintained at a vacuum pressure rather than atmospheric pressure during operation of the apparatus. When pre-heating is performed in the processing module 5B instead of the LLM 3, the wafer W is taken out of the transfer container C and transferred to the LLM 3, and then transferred to the processing module 5B by the transfer mechanism 43 of the vacuum transfer module 4 for pre-heating. The wafer W is then transferred to the processing module 5A, where film formation processing is performed in the same manner as when pre-heating is performed in the LLM 3.

[0071] The pre-heating process is not limited to light irradiation. The process module 5C in FIG. 1 includes a process container 71, the interior of which is evacuated to a predetermined vacuum pressure, and a stage 72 disposed within the process container. The stage 72 may be equipped with a heating mechanism, such as a heater, to perform pre-heating on the wafer W placed on the upper surface. The stage 72 is configured to allow the wafer W to be transferred between its upper surface and the transfer mechanism 43 using pins, similar to the other stages. Instead of transferring the wafer W to the process module 5B, the wafer W may be transferred to the process module 5C, where it is subjected to pre-heating, and then transferred to the process module 5A for film formation.

[0072] However, when pre-heating is performed in the LLM 3, the wafer W can be heated by light irradiation from the light irradiation unit 39 while the pressure inside the housing 31 is reduced by exhausting, so there is no need to set a dedicated time for pre-heating. This is therefore preferable because it increases the throughput of the film forming apparatus 1. Note that the LLM 3 is not limited to being configured to perform pre-heating by the light irradiation unit 39, and may be configured to have a heater provided on the stage, as in the process module 5C, so that the wafer W placed on the upper surface of the stage is pre-heated.

[0073] [Film Formation Process According to Wafer W Lot] As described in Evaluation Test 3, the crystal structure of the IGZO film formed on the wafer W switches between spinel and CAAC depending on the pressure inside the processing vessel 51 during film formation. Therefore, the pressure inside the processing vessel 51 may be switched during film formation depending on the lot to which the wafer W belongs, so that an IGZO film having a desired crystal structure, either spinel or CAAC, is formed on the wafer W. This will be described in detail below. The wafers W are stored in a transfer container C by lot, and after one lot is transferred into the film formation apparatus 1 and processed, the next lot is transferred into the film formation apparatus 1 and processed. In addition, information specifying whether the IGZO film to be formed is spinel or CAAC, is transmitted from the host computer (high-level computer) to the control unit 10 of the film formation apparatus 1 for each lot.

[0074] The control unit 10 outputs a control signal based on the above information to adjust the pressure inside the processing chamber 51 of the module during film formation on the wafer W. If the information specifies the formation of an IGZO film of Spinel, the pressure is adjusted to 1.2×10 －３ Torr, more specifically, for example, 5.0×10 －４ If the information specifies the deposition of an IGZO film using CAAC, the pressure should be 1.2 × 10 －３ Torr, more specifically, for example, 2.5×10 －３ The pressure is set to be higher than Torr. In this way, the pressure according to the lot is set, and an IGZO film having a desired crystal structure, either Spinel or CAAC, may be formed for each lot. As described above, since Spinel and CAAC have different characteristics, it is preferable to select Spinel film formation or CAAC film formation in this way in order to achieve desired characteristics for semiconductor devices produced from wafers W.

[0075] While the above description has focused on wafers as the substrates to be processed, substrates processed by the film forming apparatus 1 include, in addition to wafers, substrates for manufacturing flat panel displays, substrates for manufacturing exposure masks used in photolithography, and dummy substrates processed for the purpose of testing or setting processing parameters in a substrate processing apparatus. Therefore, the IGZO film is not limited to being formed as a film constituting the FeFET described above. Furthermore, since the processing module 5A for forming the IGZO film only needs to be capable of performing film formation by sputtering, the movement direction of the magnet unit 65, the shape of the target, and the like are not limited to the examples described above.

[0076] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, modifications, and combinations may be made in the above-described embodiments without departing from the scope and spirit of the appended claims.

[0077] W: Semiconductor wafer 31: Housing 42: Transport path 51: Processing vessel 55: Stage 55A: Mounting surface

Claims

1. A film formation method for forming a film composed of gallium, zinc, and oxygen on a substrate, comprising: a pre-processing step of heating the substrate to a first temperature in a first processing vessel in which a vacuum atmosphere is formed; a step of transporting the substrate from the first processing vessel to the second processing vessel in which a vacuum atmosphere is formed via a transport path in which a vacuum atmosphere is formed; a step of placing the substrate on the mounting surface of a stage provided in the second processing vessel, the mounting surface for placing the substrate being set to a second temperature lower than the first temperature; and a step of performing film formation by sputtering on the substrate while the temperature is decreasing on the mounting surface and before it reaches the second temperature, in order to form a crystallized film.

2. The film forming method according to claim 1, wherein the film is an IGZO film composed of indium, gallium, zinc, and oxygen.

3. A film forming method according to claim 1, wherein the first processing vessel constitutes a load lock module for transporting the substrate between the transport path and a transport vessel storing the substrate, and the pre-processing step is a step of heating the substrate while the pressure inside the first processing vessel is decreasing.

4. A film forming method according to claim 1, wherein the first temperature is 150°C to 450°C.

5. A film forming method according to claim 4, wherein the second temperature is 20°C to 30°C.

6. A film forming method according to claim 1, wherein the pressure inside said second processing vessel during film formation by sputtering is 0.8 Pa or less.

7. A film forming method according to claim 6, wherein the ratio of the partial pressure of oxygen to the total pressure in said second processing vessel during said film formation by sputtering is 20% or less.

8. A film formation apparatus for forming a film composed of gallium, zinc, and oxygen on a substrate, comprising: a first processing vessel and a second processing vessel in which a vacuum atmosphere is formed; a transport path in which a vacuum atmosphere is formed and which transports the substrate from the first processing vessel to the second processing vessel; a heating mechanism for heating the substrate in the first processing vessel to a first temperature; a stage provided in the second processing vessel, the stage having a mounting surface for mounting the substrate at a second temperature lower than the first temperature; and a sputtering mechanism for performing sputtering on the substrate while the temperature is decreasing on the mounting surface and before the substrate reaches the second temperature, in order to form a crystallized film.

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