Plasma purging method and plasma processing apparatus

Abstract

To provide a technology capable of effectively reducing metal contamination even when cleaning treatment is repeated multiple times.SOLUTION: A plasma purging method is performed after cleaning the interior of a processing vessel and before processing a substrate placed in the processing vessel. The plasma purging method includes the steps of (A) activating and supplying a first processing gas containing N2 into the processing vessel, and (B) activating and supplying a second processing gas containing H2 and O2 into the processing vessel. The plasma purging method repeatedly increases and decreases the pressure inside the processing vessel during each of the steps (A) and (B).SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a plasma purging method and a plasma processing apparatus. [Background technology]

[0002] Patent Document 1 discloses a plasma purging method in which nitrogen (N2) gas is activated and supplied to remove metal contamination from a processing vessel in order to reduce metal contamination compounds (such as aluminum fluoride: AlF3) generated during cleaning of the processing vessel. Furthermore, this plasma purging method aims to reduce metal contamination by activating and supplying hydrogen (H2) gas and oxygen (O2) gas to remove metal particles present in the internal components of the processing vessel through a reduction or oxidation reaction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-49557 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can sufficiently reduce metal contamination even when cleaning processes for a processing vessel are performed multiple times. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a plasma purging method that is performed after cleaning the inside of a processing vessel and before placing a substrate in the processing vessel and processing the substrate, the plasma purging method comprising: (A) activating and supplying a first processing gas containing N2 into the processing vessel; and (B) activating and supplying a second processing gas containing H2 and O2 into the processing vessel, wherein the pressure inside the processing vessel is repeatedly increased and decreased in each of the steps (A) and (B). [Effects of the Invention]

[0006] According to one aspect, metal contamination can be sufficiently reduced even when the cleaning process of the processing vessel is performed multiple times. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic vertical cross-sectional view showing an example of a plasma processing apparatus that performs a plasma purging method according to an embodiment. [Figure 2] FIG. 2 is a schematic plan view of the plasma processing apparatus of FIG. [Figure 3] 2 is a bottom view of a gas supply / exhaust unit provided in the plasma processing apparatus of FIG. 1. FIG. [Figure 4] 1 is a flowchart showing a process flow of a plasma purge method. [Figure 5] FIG. 1 is a diagram for explaining a mechanism by which metal contamination occurs. [Figure 6] 1A and 1B are diagrams for explaining the mechanism by which metal contamination is reduced. [Figure 7] 4 is a timing chart showing the change in pressure in a vacuum vessel over time in a plasma purging method. [Figure 8] FIG. 10 is a diagram showing the emission intensity distribution of plasma. [Figure 9] FIG. 10 is a diagram showing the change in Al contamination when a conventional plasma purging method is repeated, and the change in Al contamination when the plasma purging method according to the embodiment is performed. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] First, with reference to FIGS. 1 to 3, a plasma processing apparatus 1 for performing a plasma purging method according to an embodiment will be described. The plasma processing apparatus 1 is configured as a film formation apparatus that forms a desired film on a surface of a substrate by atomic layer deposition (ALD) or molecular layer deposition (MLD). The substrate is, for example, a semiconductor wafer (hereinafter referred to as "wafer W"). A recess pattern such as a trench or via may be formed on the surface of the wafer W. Note that the plasma processing apparatus 1 is not limited to a film formation apparatus and may be, for example, an etching apparatus or an ashing apparatus.

[0010] The plasma processing apparatus 1 includes a vacuum vessel (processing vessel) 11 that accommodates a wafer W therein and performs substrate processing under a reduced pressure vacuum atmosphere. The vacuum vessel 11 has a generally circular planar shape. The vacuum vessel 11 includes a vessel body 11A and a top plate 11B. The vessel body 11A forms the side walls and bottom. The vacuum vessel 11 airtightly seals the vessel body 11A and the top plate 11B via a sealing member such as an O-ring. The vessel body 11A and the top plate 11B are formed of, for example, aluminum (Al).

[0011] A rotary table 12 is provided inside the vacuum vessel 11. The rotary table 12 has a circular planar shape. The rotary table 12 is made of, for example, quartz. The rotary table 12 is supported at the center of its back surface by a support 12A and is installed horizontally. A rotation mechanism 13 is connected to the underside of the support 12A. The rotation mechanism 13 rotates the rotary table 12 around a vertical axis via the support 12A during film formation processing.

[0012] A plurality of (six) recesses 14 are provided on the upper surface of the turntable 12 along the circumferential direction (rotation direction) of the turntable 12. A wafer W is placed in each recess 14. In other words, the plurality of wafers W placed on the turntable 12 revolve as the turntable 12 rotates.

[0013] A plurality of heaters 15 are provided at the bottom of the vacuum chamber 11. The heaters 15 are arranged, for example, concentrically. The heaters 15 heat the wafer W placed on the turntable 12.

[0014] A transfer port 16 is formed in the side wall of the vacuum vessel 11 for loading and unloading the wafer W. The transfer port 16 of the vacuum vessel 11 is opened and closed by a gate valve (not shown). When the gate valve is open, the wafer W is loaded and unloaded into and from the vacuum vessel 11 by a transfer arm (not shown) provided outside, and when the gate valve is closed, the internal space is airtightly sealed.

[0015] The plasma processing apparatus 1 includes a gas supply / exhaust unit 2 that supplies a processing gas into a vacuum chamber 11 and exhausts the gas from the vacuum chamber 11 .

[0016] The gas supply and exhaust unit 2 has a gas discharge port and an exhaust port for supplying a silicon (Si)-containing gas during substrate processing (film formation processing) of each wafer W. The gas supply and exhaust unit 2 will be described below with reference to FIG. 3. In a plan view, the gas supply and exhaust unit 2 is formed in a fan shape that widens in the circumferential direction of the turntable 12 as it moves from the center of the turntable 12 toward the radially outer side. The lower surface of the gas supply and exhaust unit 2 is close to and faces the upper surface of the turntable 12.

[0017] The lower surface of the gas supply and exhaust unit 2 is provided with gas discharge ports 21, exhaust ports 22, and purge gas discharge ports 23. A large number of gas discharge ports 21 are arranged in a fan-shaped region 24 located inside the periphery of the lower surface of the gas supply and exhaust unit 2. During substrate processing, the gas discharge ports 21 discharge a silicon (Si)-containing gas, which is a raw material gas, downward in a shower-like manner to supply the gas to the entire surface of the wafer W. The silicon-containing gas is, for example, dichlorosilane (DCS) gas.

[0018] The sectorial region 24 is divided into three zones 24A, 24B, and 24C extending from the center of the turntable 12 toward the outside in the radial direction of the turntable 12. The gas supply and exhaust unit 2 has a plurality of gas flow paths (shown) that are separated from one another so that a silicon-containing gas can be independently supplied to each of the gas discharge ports 21 provided in the zones 24A, 24B, and 24C. Each gas flow path is connected to a silicon-containing gas supply source (not shown) via a gas supply device including a valve and a mass flow controller.

[0019] The exhaust port 22 and the purge gas outlet port 23 are annularly opened on the periphery of the lower surface of the gas supply and exhaust unit 2 so as to surround the fan-shaped region 24 and face the upper surface of the turntable 12. The purge gas outlet port 23 is located outside the exhaust port 22. The region on the turntable 12 inside the exhaust port 22 forms a first processing region R1 (see FIG. 2) where a silicon-containing gas is supplied to the surface of the wafer W. An exhaust device (not shown) is connected to the exhaust port 22, and a purge gas supply source is connected to the purge gas outlet port 23. The purge gas is, for example, argon (Ar) gas.

[0020] During the film formation process, the plasma processing apparatus 1 simultaneously discharges a silicon-containing gas from the gas discharge port 21, exhausts the gas from the exhaust port 22, and discharges a purge gas from the purge gas discharge port 23. As a result, the silicon-containing gas and purge gas discharged onto the turntable 12 travel from the upper surface of the turntable 12 toward the exhaust port 22 and are exhausted from the exhaust port 22. By discharging and exhausting the purge gas in this manner, the first processing region R1 is isolated from the external atmosphere, and the silicon-containing gas can be supplied only to the first processing region R1. In other words, mixing of the silicon-containing gas supplied to the first processing region R1 with the gases and activated species of the gases supplied to the outside of the first processing region R1 by the plasma generation units 3A to 3C (described later) can be suppressed.

[0021] 2, the gas supply and exhaust unit 2 includes a second processing region R2, a third processing region R3, and a fourth processing region R4, arranged in this order along the rotation direction of the turntable 12. The gas supply and exhaust unit 2 for the second to fourth processing regions R2 to R4 is made up of plasma generation units (activation sections) 3A to 3C that can activate gas in each region. The plasma generation units 3A to 3C are each configured in the same way. The following describes the plasma generation unit 3C shown in FIG. 1 as a representative example.

[0022] The plasma generation unit 3C generates plasma by supplying a plasma generation gas onto the turntable 12 and supplying microwaves to the plasma generation gas. The plasma generation unit 3C includes an antenna 31 for supplying microwaves.

[0023] The antenna 31 includes a dielectric plate 32 and a metallic waveguide 33. In a plan view, the dielectric plate 32 is formed in a generally fan-like shape that widens radially outward from the center of the turntable 12. A generally fan-shaped through-hole is provided in the top plate 11B of the vacuum vessel 11 to correspond to the shape of the dielectric plate 32. The inner peripheral surface of the lower end of the through-hole protrudes slightly toward the center of the through-hole to form a support portion 34. The dielectric plate 32 closes the through-hole from above and is provided facing the turntable 12, with the outer peripheral edge of the dielectric plate 32 supported by the support portion 34. The waveguide 33 is provided on the dielectric plate 32. The waveguide 33 has an internal space 35 extending above the top plate 11B. A slot plate 36 is provided on the upper surface of the dielectric plate 32 so as to be in contact with the dielectric plate 32. The slot plate 36 forms the lower portion of the waveguide 33. The slot plate 36 has multiple slot holes 36A. The end of the waveguide 33 on the central side of the turntable 12 is closed, and a microwave generator 37 is connected to the end on the peripheral side of the turntable 12. The microwave generator 37 supplies microwaves of, for example, 2.45 GHz to the waveguide 33.

[0024] 2, the second processing region R2 includes a gas injector 41 downstream in the rotation direction of the turntable 12. The gas injector 41 is connected to a hydrogen (H2) gas supply source 41a and a nitrogen (N2) gas supply source 41b via a pipe 41p. The gas injector 41 ejects hydrogen gas and nitrogen gas toward the upstream side in the rotation direction of the turntable 12. By supplying hydrogen gas, H bonds to dangling bonds in the SiO2 film, thereby modifying the film to a denser one.

[0025] The third processing region R3 includes a gas injector 42 on the upstream side in the rotation direction of the turntable 12. The gas injector 42 is connected to a hydrogen gas supply source 42a and a nitrogen gas supply source 42b via a pipe 42p. The gas injector 42 injects hydrogen gas and nitrogen gas toward the downstream side in the rotation direction of the turntable 12.

[0026] The fourth processing region R4 includes a gas injector 43 on the downstream side in the rotation direction of the turntable 12. The gas injector 43 is connected to a hydrogen gas supply source 43a and a nitrogen gas supply source 43b via a pipe 43p. The gas injector 43 discharges hydrogen gas and nitrogen gas toward the upstream side in the rotation direction of the turntable 12. The second processing region R2 to the fourth processing region R4 may be connected to another gas supply source, for example, an argon gas supply source.

[0027] The gas injectors 41 to 43 are, for example, formed of a long, thin tubular body with a closed tip. The gas injectors 41 to 43 are each fixed to the side wall of the vacuum vessel 11 and extend horizontally from the side wall toward the central region of the vacuum vessel 11. The gas injectors 41 to 43 are each disposed so as to intersect with the region through which the wafer W on the turntable 12 passes. The gas injectors 41 to 43 have a plurality of discharge ports 40 along the extending direction. For example, each discharge port 40 is formed in the gas injectors 41 to 43 so as to overlap with the region through which the wafer W on the turntable 12 passes.

[0028] 2, gas injector 41 is provided below an area adjacent to the downstream side of plasma generation unit 3A in the rotational direction, but may be provided, for example, below plasma generation unit 3A. Gas injector 42 is provided below an area adjacent to the upstream side of plasma generation unit 3B in the rotational direction, but may be provided, for example, below plasma generation unit 3B. Gas injector 43 is provided below an area adjacent to the downstream side of plasma generation unit 3C in the rotational direction, but may be provided, for example, below plasma generation unit 3C.

[0029] A gas injector 44 is provided at the upstream end of the fourth processing region R4. The gas injector 44 is connected to an oxygen (O2) gas supply source 44a via a pipe 44p. The gas injector 44 is configured as a long, thin tubular body with a closed tip. The gas injector 44 is fixed to the side wall of the vacuum vessel 11 and extends horizontally from the side wall toward the central region of the vacuum vessel 11. The gas injector 44 has a gas outlet (not shown) at its tip. This outlet discharges oxygen gas from the central region of the vacuum vessel 11 radially outward. The gas injector 44 may also be connected to another gas supply source (e.g., an argon gas supply source).

[0030] In the second to fourth processing regions R2 to R4, the microwaves supplied to the waveguide 33 pass through the slot holes 36A of the slot plate 36 to reach the dielectric plate 32, and are supplied to the gases, such as hydrogen gas, nitrogen gas, and oxygen gas, discharged below the dielectric plate 32. As a result, plasma is formed limitedly in the second to fourth processing regions R2 to R4 below the dielectric plate 32.

[0031] 2, a gas injector 45 is provided between the second processing region R2 and the third processing region R3. The gas injector 45 is configured as a long, thin tube with an open tip. The gas injector 45 is fixed to the side wall of the vacuum vessel 11 and protrudes slightly from the side wall toward the central region of the vacuum vessel 11. The gas injector 45 discharges various gases from the opening at the tip toward the center of the vacuum vessel 11.

[0032] The gas injector 45 is connected to, for example, a nitrogen trifluoride (NF3) gas supply source 45a, a nitrogen gas supply source 45b, and an oxygen gas supply source 45c via a pipe 45p. A remote plasma source 46 is provided midway along the pipe 45p. The remote plasma source 46 activates, by plasma, various gases introduced into the gas injector 45 from the respective supply sources via the pipe 45p. This allows the gas injector 45 to discharge the activated gases into the vacuum chamber 11.

[0033] For example, in substrate processing, the gas injector 45 discharges oxygen gas into the vacuum chamber 11. In the plasma processing apparatus 1, the oxygen gas may be activated before being discharged from the gas injector 45, or the oxygen gas may be discharged from the gas injector 45 without being activated.

[0034] Furthermore, for example, in a cleaning process inside the vacuum chamber 11, the gas injector 45 injects a fluorine-containing gas such as nitrogen trifluoride gas into the vacuum chamber 11. The plasma processing apparatus 1 may activate the nitrogen trifluoride gas before injecting it from the gas injector 45, or may inactivate the nitrogen trifluoride gas before injecting it from the gas injector 45. The cleaning process is performed when repeated substrate processing (film formation process) causes a large amount of oxide films to accumulate on the surface of the turntable 12 or inside the vacuum chamber 11, and it is determined that these oxide films should be removed.

[0035] Furthermore, for example, in a method for plasma purging the inside of the vacuum chamber 11, the gas injector 45 discharges nitrogen gas and oxygen gas into the vacuum chamber 11 at an appropriate timing. In the plasma processing apparatus 1, the nitrogen gas may be activated before being discharged from the gas injector 45, or the nitrogen gas may be discharged from the gas injector 45 without being activated. This cleaning process and the plasma purging method will be described in detail later.

[0036] The vacuum chamber 11 includes a separation region D between the third processing region R3 and the fourth processing region R4. The ceiling surface of the separation region D is lower than the ceiling surfaces of the third processing region R3 and the fourth processing region R4. In a plan view, the separation region D is formed in a fan shape that widens in the circumferential direction of the turntable 12 as it moves from the center of the turntable 12 toward the radially outward direction. The lower surface of the separation region D faces the upper surface of the turntable 12 in a position sufficiently close to the upper surface. The distance between the lower surface of the separation region D and the upper surface of the turntable 12 is set to, for example, 3 mm to prevent gas from entering below the separation region D.

[0037] Furthermore, a first exhaust port 51, a second exhaust port 52, and a third exhaust port 53 are opened at positions outside the turntable 12 facing the upstream end of the second processing region R2, the downstream end of the third processing region R3, and the upstream end of the fourth processing region R4, respectively. The first to third exhaust ports 51 to 53 exhaust gases from the second to fourth processing regions R2 to R4, respectively.

[0038] As shown in FIG. 1, the third exhaust port 53 is formed in an area outside the turntable 12 in the vessel body 11A of the vacuum vessel 11. The third exhaust port 53 is located below the turntable 12 and is connected to an exhaust device 54 via an exhaust flow path 531. As shown in FIG. 2, the first exhaust port 51 and the second exhaust port 52 are configured similarly to the third exhaust port 53 and are connected to an exhaust device 54 of the gas supply and exhaust unit 2 via exhaust flow paths 511 and 521, respectively. Each exhaust flow path 511, 521, and 531 is provided with an exhaust rate adjustment unit (not shown). Each exhaust rate adjustment unit can, for example, individually adjust the exhaust rate from the first to third exhaust ports 51 to 53 by the exhaust device 54. The exhaust rates from the first to third exhaust ports 51 to 53 may be adjusted by a common exhaust rate adjustment unit. In this way, in the second to fourth processing regions R2 to R4, the gases discharged from the gas injectors 41 to 43 are exhausted from the first to third exhaust ports 51 to 53, and a vacuum atmosphere of a pressure corresponding to the amount of exhaust is formed in the vacuum vessel 11.

[0039] As shown in FIG. 1, the plasma processing apparatus 1 includes a control unit 70 that controls various components. The control unit 70 may be a computer having a processor, memory, input / output interface, communication interface, etc. (not shown). The processor is one or a combination of a CPU, GPU, ASIC, FPGA, and circuits made up of multiple discrete semiconductors, and executes programs stored in memory. The memory includes a main storage device made up of semiconductor memory, etc., and an auxiliary storage device made up of disks, drives, semiconductor memory (flash memory), etc. The memory sends control signals to each component of the plasma processing apparatus 1 to control its operation, and stores programs, recipes, etc. for executing substrate processing (film formation processing) of wafers W and cleaning processing including a plasma purging method.

[0040] The plasma processing apparatus 1 is basically configured as described above. Next, the substrate processing and cleaning processing of each wafer W will be described with reference to FIGS.

[0041] The control unit 70 of the plasma processing apparatus 1 controls the substrate processing and cleaning processing by causing a processor to execute a program stored in a memory. In the substrate processing and cleaning processing, the control unit 70 performs steps S101 to S108 shown in FIG.

[0042] In order to perform substrate processing, the plasma processing apparatus 1 opens the transfer port 16 of the vacuum chamber 11, and works in cooperation with the transfer arm to transfer the wafers W into the vacuum chamber 11, and sequentially places the wafers W in each recess 14 of the turntable 12 (step S101).

[0043] When wafers W are placed in all of the recesses 14 of the turntable 12, the plasma processing apparatus 1 closes the transfer port 16 of the vacuum chamber 11 and starts substrate processing (step S102).

[0044] For example, the plasma processing apparatus 1 operates the gas supply / exhaust unit 2 to supply appropriate gases and exhaust gases, thereby reducing the pressure inside the vacuum chamber 11 to a vacuum atmosphere. At this time, the plasma processing apparatus 1 controls each gas supply device based on the supply timing and flow rate of each gas in the recipe, and controls the gas exhaust rate of the exhaust device 54 based on the pressure in the recipe to adjust the pressure inside the vacuum chamber 11 to a target pressure. The plasma processing apparatus 1 also controls the rotation mechanism 13 based on the target rotation speed in the recipe to rotate the turntable 12. Furthermore, the plasma processing apparatus 1 controls the heater 15 based on the target temperature in the recipe to adjust the temperature of each wafer W. The plasma processing apparatus 1 then generates plasma in the gas inside the vacuum chamber 11 by supplying microwaves to the gas in the plasma generation units 3A to 3C.

[0045] Each wafer W rotated by the turntable 12 in the vacuum chamber 11 is supplied with a source gas as it passes through the first processing region R1, causing the source gas to adhere to the surface. Furthermore, each wafer W undergoes oxidation, modification, etc. of the source gas adhering to the surface in the second processing region R2 to the fourth processing region R4. By continuing the above substrate processing for a set period, the plasma processing apparatus 1 can deposit a film having a desired thickness on the surface of each wafer W.

[0046] After the substrate processing, the plasma processing apparatus 1 opens the transfer port 16 of the vacuum chamber 11 and unloads each wafer W placed in each recess 14 of the turntable 12 in cooperation with the transfer arm (step S103).

[0047] After the substrate processing, the control unit 70 determines whether or not to perform a cleaning process on the vacuum container 11 (step S104). For example, the control unit 70 counts the total period or number of substrate processing operations, and determines whether to perform a cleaning process when the total period or number of operations reaches a preset threshold value or more. If the cleaning process is to be performed (step S104: YES), the control unit 70 proceeds to step S105, whereas if the cleaning process is not to be performed (step S104: NO), the control unit 70 ends the current substrate processing operation. Furthermore, when performing the next substrate processing operation, the plasma processing apparatus 1 repeats the above steps S101 to S103 again.

[0048] In step S105, the plasma processing apparatus 1 performs a cleaning process to remove films that have adhered to each component in the vacuum chamber 11 during substrate processing. For example, the plasma processing apparatus 1 discharges nitrogen trifluoride gas from the gas injector 45 into the vacuum chamber 11 to dry-clean the interior of the vacuum chamber 11. The plasma processing apparatus 1 continues this cleaning process for a set period of time to remove films that have adhered to each component. The plasma processing apparatus 1 may perform the cleaning process without placing a wafer W in each recess 14, or may perform the cleaning process with a dummy wafer or the like placed in each recess 14.

[0049] Here, in the plasma processing apparatus 1, performing a cleaning process tends to generate (adhere to or become detached from) metal contaminants on components and the like within the vacuum chamber 11. Examples of such metal contaminants include metal particles such as aluminum fluoride (AlF3) or aluminum (Al). For example, as shown in FIGS. 5(a) and 6(a), the plasma P1 generated during the cleaning process etches Al, the material of the chamber body 11A and the top plate 11B, to generate aluminum fluoride, which then adheres to the underside of the top plate 11B. Furthermore, if a substrate process (film formation process) is performed after the cleaning process, as shown in FIG. 5(b), the plasma P2 generated during the substrate process causes aluminum to detach from the underside of the top plate 11B and adhere to the wafer W as particles.

[0050] Therefore, the plasma processing apparatus 1 performs the plasma purging method after the cleaning process and before the substrate processing is performed on the wafer W (before the wafer W is loaded into the vacuum chamber 11). In other words, the plasma purging method from step S106 onwards is performed in a state where the wafer W is not placed in each recess 14 of the turntable 12.

[0051] In the plasma purging method, the plasma processing apparatus 1 first performs a nitrogen plasma purging process (step S106: (A)). In the nitrogen plasma purging process, a first process gas containing nitrogen (N2) gas is supplied into the vacuum chamber 11 from the gas injectors 41-43, 45. The flow rate of the nitrogen gas is, for example, about 200 sccm to 250 sccm. At this time, the plasma processing apparatus 1 decomposes and activates the nitrogen gas by supplying microwaves to the nitrogen gas from the plasma generation units 3A-3C. The output of the microwave generator 37 in this case is, for example, about 2.5 kW. Furthermore, the plasma processing apparatus 1 sets the temperature of the heater 15 to, for example, 550°C.

[0052] As shown in FIG. 6(b), the activated nitrogen gas (nitrogen plasma) in the nitrogen plasma purge process sputters aluminum fluoride, a metal contaminant generated during the cleaning process. That is, the aluminum fluoride is detached from the underside of the top plate 11B by the sputtering effect and is discharged from the inside of the vacuum chamber 11 under the suction of the exhaust device 54. By performing the nitrogen plasma purge process in this manner, the plasma processing apparatus 1 can remove metal contaminants that cause particles during the film formation process. As shown in FIG. 6(c), the plasma processing apparatus 1 suppresses the detachment of aluminum from the underside of the top plate 11B by the plasma P2 formed during substrate processing after the cleaning process, thereby preventing particles from adhering to the wafer W.

[0053] In the plasma purging method, the plasma processing apparatus 1 then performs a hydrogen / oxygen plasma purging process (step S107: (B)). In the hydrogen / oxygen plasma purging process, the plasma processing apparatus 1 supplies hydrogen radicals and oxygen radicals into the vacuum chamber 11. Specifically, the plasma processing apparatus 1 supplies hydrogen gas from the gas injectors 41 to 43 into the vacuum chamber 11, and supplies oxygen gas from the gas injectors 44 and 45 into the vacuum chamber 11. The flow rate of the hydrogen gas is, for example, about 4 slm. The flow rate of the oxygen gas is, for example, about 6 slm. At this time, the plasma processing apparatus 1 supplies microwaves to the hydrogen gas and oxygen gas from the plasma generation units 3A to 3C, thereby decomposing and activating the hydrogen gas and oxygen gas and generating hydrogen radicals and oxygen radicals. The output of the microwave generator 37 in this case is, for example, about 3.0 kW. Furthermore, the plasma processing apparatus 1 sets the temperature of the heater 15 to, for example, 550°C.

[0054] During the hydrogen / oxygen plasma purge process, various reactions occur due to the generation of hydrogen radicals H*, which function as reducing agents, and oxygen radicals O*, which function as oxidizing agents. Metal elements of components in the vacuum chamber 11 are extracted by the reduction reaction of the reducing agent or the oxidation reaction of the oxidizing agent. In other words, the hydrogen radicals H* and oxygen radicals O* can remove not only metal particles present on the surface of the components but also metal particles that are free from the components and present slightly inside the surface through reduction or oxidation reactions. While such reduction and oxidation reactions are not necessarily effective for all metal elements, the vacuum chamber 11 contains a wide variety of metal element particles, and among these, there are bound to be metal elements for which reduction or oxidation reactions are effective. By supplying hydrogen radicals H* and oxygen radicals O*, the plasma processing apparatus 1 can suppress metal contamination of metal elements for which supply of reducing agents and oxidizing agents is effective.

[0055] After the nitrogen plasma purge process (step S106) and the hydrogen / oxygen plasma purge process (step S107) are performed in this order, the control unit 70 determines whether to end the plasma purge method (step S108). For example, the control unit 70 stores a target number of times to repeat steps S106 and S107 in advance in a recipe or the like, and if the target number of times has not been reached (step S108: NO), the control unit 70 returns to step S106 and repeats the same processing flow thereafter. On the other hand, if the number of times steps S106 and S107 have been repeated reaches the target number of times (step S108: YES), the control unit 70 ends the plasma purge method.

[0056] As described above, according to the plasma purging method, by performing the nitrogen plasma purging step and the hydrogen / oxygen plasma purging step, it is possible to significantly reduce metal contaminants inside the vacuum vessel 11. However, in the past, as the number of cleaning processes increased, the metal contaminants remaining on the vessel body 11A and the top plate 11B tended to gradually increase. Therefore, in the plasma purging method according to the embodiment, the pressure inside the vacuum vessel 11 is changed in the nitrogen plasma purging step and the hydrogen / oxygen plasma purging step, thereby varying the emission distribution of the plasma formed inside the vacuum vessel 11. The operation and effect of changing this pressure will be described below with reference to FIG. 7.

[0057] In each of the nitrogen plasma purge step and the hydrogen / oxygen plasma purge step, the control unit 70 varies the amount of gas exhausted by the exhaust device 54 (or the exhaust amount adjustment unit) to vary the pressure.

[0058] Specifically, the nitrogen plasma purge process includes a nitrogen pressure amplitude step and a nitrogen pressure constant step. For example, the control unit 70 performs the nitrogen pressure amplitude step and the nitrogen pressure constant step in this order in one nitrogen plasma purge process.

[0059] In the nitrogen pressure amplitude step, the control unit 70 sets upper and lower limit values for the pressure for the nitrogen pressure amplitude step, and increases or decreases the pressure in the vacuum vessel 11 within the range between the set upper and lower limit values. Based on parameters stored in a recipe or the like, the control unit 70 sets the upper limit value for the pressure for the nitrogen pressure amplitude step to 1.0 Torr (133 Pa) and the lower limit value to 0.4 Torr (53 Pa), for example.

[0060] In the nitrogen pressure amplitude step, the control unit 70 changes the exhaust rate of the exhaust device 54 while maintaining a constant supply of nitrogen gas, thereby oscillating the pressure in the vacuum vessel 11 between the set upper and lower limit values. At this time, the control unit 70 commands (transmits) the target exhaust rate in stages to the exhaust device 54. As a result, the pressure in the vacuum vessel 11 increases or decreases in stages in accordance with the gradual change in the gas exhaust rate.

[0061] Then, in the nitrogen pressure amplitude step, the control unit 70 repeats the amplitude of the pressure in the vacuum vessel 11 multiple times over a target period. This target period can be set arbitrarily by the user, for example, to 90 minutes. Note that, although the increase and decrease in the pressure in the vacuum vessel 11 is repeated three times over the target period in FIG. 7, the number of times this pressure oscillation occurs is not limited and may be, for example, four or more times. After performing the nitrogen pressure amplitude step over the target period, the control unit 70 proceeds to the next nitrogen pressure constant step.

[0062] In the nitrogen pressure constant step, the control unit 70 maintains the pressure in the vacuum vessel 11 constant by maintaining the supply rate of nitrogen gas and the exhaust rate of the exhaust device 54 constant. The pressure in the vacuum vessel 11 in this nitrogen pressure constant step is preferably greater than the upper limit of the pressure in the nitrogen pressure amplitude step. For example, the control unit 70 sets the pressure in the vacuum vessel 11 to 2.3 Torr (307 Pa) based on parameters stored in a recipe or the like. The control unit 70 also continues the nitrogen pressure constant step for its target period. The target period of the nitrogen pressure constant step can be set shorter than the nitrogen pressure amplitude step, for example, to 30 minutes. After completing this pressure constant step for the target period, the control unit 70 stops the supply of nitrogen gas and reduces the pressure in the vacuum vessel 11, thereby ending the nitrogen plasma purge process.

[0063] The next hydrogen / oxygen plasma purge step, like the nitrogen plasma purge step, also has a hydrogen / oxygen pressure amplitude step and a hydrogen / oxygen pressure constant step. For example, the control unit 70 performs the hydrogen / oxygen pressure amplitude step and the hydrogen / oxygen pressure constant step in this order in one hydrogen / oxygen plasma purge step.

[0064] In the hydrogen / oxygen pressure amplitude step, the control unit 70 sets upper and lower limit pressure values for the hydrogen / oxygen pressure amplitude step and increases or decreases the pressure in the vacuum vessel 11 within the set upper and lower limit values. The upper limit pressure value for the hydrogen / oxygen pressure amplitude step should be set to be equal to or greater than the upper limit pressure value for the nitrogen pressure amplitude step. Furthermore, the lower limit pressure value for the hydrogen / oxygen pressure amplitude step should be set to be equal to or greater than the lower limit pressure value for the nitrogen pressure amplitude step. For example, the control unit 70 sets the upper limit value to 3.0 Torr (400 Pa) and the lower limit value to 0.5 Torr (67 Pa). In other words, the pressure amplitude in the hydrogen / oxygen pressure amplitude step is greater than the pressure amplitude in the nitrogen pressure amplitude step.

[0065] In the hydrogen / oxygen pressure amplitude step, the control unit 70 changes the exhaust rate of the exhaust device 54 while maintaining the supply rates of hydrogen gas and oxygen gas constant, thereby oscillating the pressure in the vacuum vessel 11 to the set upper and lower limit values. The control unit 70 also commands (sends) the target exhaust rate in stages in the hydrogen / oxygen pressure amplitude step. As a result, the pressure in the vacuum vessel 11 increases or decreases in stages in accordance with the gradual change in the exhaust rate of the gases.

[0066] Then, in the hydrogen / oxygen pressure amplitude step, the control unit 70 repeats the amplitude of the pressure in the vacuum vessel 11 multiple times over a target period. For example, the target period can be set to 90 minutes. After performing the hydrogen / oxygen pressure amplitude step over the target period, the control unit 70 proceeds to the next hydrogen / oxygen pressure constant step.

[0067] During the hydrogen / oxygen pressure constant step, the control unit 70 maintains the pressure in the vacuum vessel 11 constant by maintaining the hydrogen gas supply rate, the oxygen gas supply rate, and the exhaust rate of the exhaust device 54 constant. The pressure in the vacuum vessel 11 during this hydrogen / oxygen pressure constant step is preferably greater than the upper limit of the pressure during the hydrogen / oxygen pressure amplitude step. For example, the control unit 70 sets the pressure in the vacuum vessel 11 to 4.4 Torr (587 Pa) based on parameters stored in a recipe or the like. The control unit 70 also continues the hydrogen / oxygen pressure constant step for its target period. The target period for this hydrogen / oxygen pressure constant step can be set shorter than the hydrogen / oxygen pressure amplitude step, for example, to 30 minutes. After completing this hydrogen / oxygen pressure constant step for the target period, the control unit 70 reduces the pressure in the vacuum vessel 11 to terminate the hydrogen / oxygen plasma purge process.

[0068] The sequence of the plasma purge method having the nitrogen pressure amplitude step and the hydrogen / oxygen pressure amplitude step can be summarized as follows.

[0069] In the plasma purging method, a nitrogen plasma purging process is started at time t1 after the cleaning process. With the start of the plasma purging process, the control unit 70 first executes a nitrogen pressure amplitude step. The plasma processing apparatus 1 supplies nitrogen gas into the vacuum chamber 11 and exhausts the gas in the vacuum chamber 11 using the exhaust device 54. The plasma processing apparatus 1 also supplies microwaves while supplying nitrogen gas, thereby generating nitrogen gas plasma in the vacuum chamber 11.

[0070] After time t1, the plasma processing apparatus 1 increases the pressure in the vacuum chamber 11 from the lower limit to the upper limit and oscillates the pressure from the upper limit to the lower limit. The plasma processing apparatus 1 repeats the oscillation of the pressure in the vacuum chamber 11 from time t1 to time t2 (the target period of the nitrogen pressure amplitude step).

[0071] At time t2, the plasma processing apparatus 1 ends the nitrogen pressure amplitude step and moves on to a nitrogen pressure constant step. In the nitrogen pressure constant step, the plasma processing apparatus 1 supplies nitrogen gas while exhausting the gas at a constant exhaust rate using the exhaust device 54. The plasma processing apparatus 1 also generates plasma in the nitrogen gas in the vacuum vessel 11, thereby performing plasma purging of the vacuum vessel 11, which has been kept at a constant high pressure. The plasma processing apparatus 1 then maintains the pressure in the vacuum vessel 11 constant from time t2 to time t3 (the target period of the nitrogen pressure constant step).

[0072] At time t3, the plasma processing apparatus 1 ends the nitrogen plasma purge process. At this time, the plasma processing apparatus 1 stops the supply of nitrogen gas to reduce the pressure inside the vacuum chamber 11.

[0073] Thereafter, at time t4, the plasma processing apparatus 1 starts a hydrogen / oxygen plasma purge process. With the start of the hydrogen / oxygen plasma purge process, the control unit 70 first executes a hydrogen / oxygen pressure amplitude step. The plasma processing apparatus 1 supplies hydrogen gas and oxygen gas into the vacuum chamber 11, and exhausts the gas from the vacuum chamber 11 using the exhaust device 54. The plasma processing apparatus 1 also supplies microwaves while supplying the hydrogen gas and oxygen gas, thereby generating a plasma of the hydrogen gas and oxygen gas within the vacuum chamber 11.

[0074] After time t4, the plasma processing apparatus 1 varies the exhaust rate of the gas while supplying hydrogen gas and oxygen gas to the vacuum chamber 11, thereby increasing the pressure in the vacuum chamber 11 from the lower limit to the upper limit and oscillating from the upper limit to the lower limit. Therefore, the pressure in the vacuum chamber 11 repeatedly oscillates from time t4 to time t5 (the target period of the hydrogen / oxygen pressure amplitude step).

[0075] At time t5, the plasma processing apparatus 1 ends the hydrogen / oxygen pressure amplitude step and moves on to a hydrogen / oxygen pressure constant step. During the hydrogen / oxygen pressure constant step, the plasma processing apparatus 1 supplies hydrogen gas and oxygen gas while exhausting the gas at a constant exhaust rate using the exhaust device 54. The plasma processing apparatus 1 also generates plasma in the hydrogen gas and oxygen gas in the vacuum chamber 11, thereby performing plasma purging of the vacuum chamber 11, which has been kept at a constant high pressure. The plasma processing apparatus 1 then maintains the pressure in the vacuum chamber 11 constant from time t5 to time t6 (the target period of the hydrogen / oxygen pressure constant step).

[0076] As described above, in the plasma purging method, the pressure inside the vacuum vessel 11 is increased and decreased while plasma of nitrogen gas, hydrogen gas, and oxygen gas is generated. This allows the plasma purging method to change the in-plane distribution of the plasma emission intensity in accordance with the change in pressure inside the vacuum vessel 11. In other words, the plasma of nitrogen gas, hydrogen gas, and oxygen gas spreads throughout the vacuum vessel 11, allowing it to act on metal contaminants adhering to each component of the vacuum vessel 11. As a result, it is possible to reduce the amount of metal contaminants remaining on each component of the vacuum vessel 11.

[0077] Below, the results of evaluating the emission intensity distribution when hydrogen gas plasma was generated inside the vacuum vessel 11 using an infrared camera installed outside the vacuum vessel 11 will be described with reference to Figure 8. The left diagram in Figure 8 shows the results when the pressure inside the vacuum vessel 11 was 1 Torr (133 Pa). The center diagram in Figure 8 shows the results when the pressure inside the vacuum vessel 11 was 2 Torr (267 Pa). The right diagram in Figure 8 shows the results when the pressure inside the vacuum vessel 11 was 5 Torr (667 Pa). Note that in Figure 8, the whiter the area, the stronger the plasma emission intensity, and the darker the area, the weaker the plasma emission intensity.

[0078] As shown in Figure 8, it can be seen that the distribution of the emission intensity of the hydrogen gas plasma changes when the pressure inside the vacuum vessel 11 is changed. Specifically, when the pressure inside the vacuum vessel 11 is low, the emission intensity of the plasma at the outer periphery of the vacuum vessel 11 is high, whereas when the pressure inside the vacuum vessel 11 is high, the emission intensity of the plasma at the center of the vacuum vessel 11 is high. Therefore, it can be said that by oscillating the pressure inside the vacuum vessel 11, the in-plane distribution of the emission intensity of the plasma can be changed.

[0079] Finally, the relationship between changing the pressure in the vacuum vessel 11 and suppressing metal contamination will be described with reference to Fig. 9. Fig. 9 shows the amount of aluminum contamination when a conventional plasma purging method is performed after a cleaning process, in which the pressure in the vacuum vessel 11 is not changed, and then a plasma purging method according to an embodiment is performed, in which the pressure in the vacuum vessel 11 is changed. The amount of aluminum contamination is the detected amount of aluminum mixed in the SiN film formed on the wafer W, and corresponds to an index indicating the amount of aluminum fluoride, a metal contamination substance, generated inside the vacuum vessel 11.

[0080] When the plasma purging method according to the reference example, which does not change the pressure in the vacuum vessel 11, is performed, aluminum contamination gradually increases with each repetition of the plasma purging method, as shown in the reference example in the graph. In the example, the vacuum vessel 11 with increased aluminum contamination was subjected to the plasma purging method according to the embodiment, which changes the pressure in the vacuum vessel 11, once (see the plasma purging method according to the embodiment in the graph). This single plasma purging method reduced the aluminum contamination that had increased in the reference example. In other words, it can be considered that the plasma purging method that changes the pressure in the vacuum vessel 11 effectively reduced the metal contaminants in the vacuum vessel 11, thereby lowering the amount of aluminum contamination. In other words, the plasma purging method according to the embodiment can reduce metal contaminants in the vacuum vessel 11, and the effect can be maintained even when the cleaning process is repeated multiple times.

[0081] The plasma purging method and plasma processing apparatus 1 according to the embodiment are not limited to the above-described embodiment and may take various modifications. For example, the plasma purging method is not limited to changing the pressure in the vacuum chamber 11 stepwise in the nitrogen pressure amplitude step or the hydrogen / oxygen pressure amplitude step, and may be configured to change the pressure linearly (continuously). Furthermore, for example, in the plasma purging method, the method for activating the nitrogen gas, hydrogen gas, and oxygen gas is not particularly limited, and may involve heating the gas without using plasma.

[0082] The plasma purge method may be configured to perform the nitrogen plasma purge step and the hydrogen / oxygen plasma purge step only once. Even in this case, metal contamination of the vacuum vessel 11 can be reduced by adjusting the target periods of the nitrogen pressure amplitude step and the hydrogen / oxygen pressure amplitude step. Also, the plasma purge method does not need to perform the nitrogen pressure constant step and the hydrogen / oxygen pressure constant step. This allows the implementation period of the plasma purge method to be shortened. Furthermore, the order of the nitrogen plasma purge step and the hydrogen / oxygen plasma purge step may be reversed in the plasma purge method.

[0083] The plasma processing apparatus 1 is not limited to the above configuration, and may be an apparatus in which the turntable 12 revolves while rotating (spinning) each wafer W placed on the turntable 12 for each recess 14. The plasma processing apparatus 1 may also be a single-wafer type apparatus in which wafers W are processed one by one, or conversely, a batch type apparatus in which a plurality of wafers W are lined up and processed.

[0084] The technical ideas and effects of the present disclosure explained in the above embodiments will be described below.

[0085] A first aspect of the present disclosure is a plasma purging method that is performed after cleaning the interior of a processing vessel (vacuum vessel 11) and before placing a substrate (wafer W) inside the processing vessel and processing the substrate, and includes the steps of (A) activating and supplying a first processing gas containing N2 into the processing vessel, and (B) activating and supplying a second processing gas containing H2 and O2 into the processing vessel, and repeatedly increasing and decreasing the pressure inside the processing vessel in each of steps (A) and (B).

[0086] As described above, the plasma purging method can remove metal contamination evenly by repeatedly increasing and decreasing the pressure inside the processing vessel (vacuum vessel 11), thereby changing the location inside the processing vessel where the metal contamination is removed. Therefore, the plasma purging method can effectively reduce metal contamination even when the cleaning process inside the processing vessel is repeated multiple times.

[0087] In addition, the plasma purging method increases the pressure inside the processing vessel (vacuum vessel 11) in a stepwise manner, and decreases the pressure inside the processing vessel in a stepwise manner. This allows the plasma purging method to increase and decrease the pressure inside the processing vessel at an appropriate speed, and makes it possible to stably remove metal contaminants at each stepwise pressure.

[0088] Furthermore, the pressure amplitude in step (B) is larger than the pressure amplitude in step (A). As a result, the plasma purging method can cause a reduction reaction or an oxidation reaction over a wide range inside the processing vessel (vacuum vessel 11) during processing with the second processing gas, and can effectively remove metal particles present on various components.

[0089] Furthermore, in each of the steps (A) and (B), after repeatedly increasing and decreasing the pressure inside the processing vessel (vacuum vessel 11), a step of maintaining the pressure inside the processing vessel constant is performed. This allows the plasma purging method to perform sputtering, reduction reactions, and oxidation reactions even when the pressure inside the processing vessel is stabilized, thereby more effectively reducing metal contaminants.

[0090] Furthermore, the step of repeatedly increasing and decreasing the pressure inside the processing vessel (vacuum vessel 11) is performed for a longer period than the step of maintaining the pressure inside the processing vessel constant, which allows the plasma purging method to increase the amount of metal contaminants removed and shorten the period of time required for the plasma purging method.

[0091] Furthermore, the plasma purging method performs the steps (A) and (B) in this order, so that even if metal contaminants are generated inside the processing vessel (vacuum vessel 11) in the step (A), the plasma purging method can effectively remove them in the step (B).

[0092] Furthermore, the plasma purging method performs steps (A) and (B) multiple times, thereby enabling the plasma purging method to more reliably remove metal contaminants from inside the processing vessel.

[0093] The first process gas and the second process gas are activated by plasma. By using the first process gas and the second process gas activated by plasma in this manner, the plasma purge method can efficiently remove metal contaminants.

[0094] Furthermore, the microwave power for generating plasma in step (B) is greater than the microwave power for generating plasma in step (A), so that the plasma purging method can cause sufficient reduction and oxidation reactions inside the processing vessel (vacuum vessel 11).

[0095] A second aspect of the present disclosure is a plasma processing apparatus 1 including a processing vessel (vacuum vessel 11) for accommodating a substrate (wafer W) therein and performing substrate processing thereon, a gas supply and exhaust section (gas supply and exhaust unit 2) for supplying a first processing gas containing N2 and a second processing gas containing H2 and O2 into the processing vessel and exhausting the gas inside the processing vessel, an activation section for activating the first processing gas and the second processing gas, and a controller 70 for controlling the gas supply and exhaust section and the activation section, in which the controller 70 performs, after cleaning the inside of the processing vessel and before accommodating a substrate in the processing vessel and performing substrate processing thereon, the steps of (A) activating and supplying the first processing gas containing N2 into the processing vessel and (B) activating and supplying the second processing gas containing H2 and O2 into the processing vessel, and repeatedly increasing and decreasing the pressure inside the processing vessel during each of the steps (A) and (B). As a result, the plasma processing apparatus 1 can effectively suppress metal contamination even when the cleaning process is repeated multiple times.

[0096] The plasma purge method and plasma processing apparatus 1 according to the presently disclosed embodiments are illustrative in all respects and not restrictive. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features described in the above embodiments can be configured in other ways and can be combined within the scope of the appended claims.

[0097] The plasma processing apparatus of the present disclosure can be applied to any type of apparatus, including atomic layer deposition (ALD) apparatus, capacitively coupled plasma (CCP), inductively coupled plasma (ICP), radial line slot antenna (RLSA), electron cyclotron resonance plasma (ECR), and helicon wave plasma (HWP). [Explanation of symbols]

[0098] 1. Plasma processing equipment 2 Gas supply and exhaust unit 11 Vacuum container 70 Control Unit W wafer

Claims

1. 1. A plasma purging method performed after cleaning the inside of a processing vessel and before placing a substrate in the processing vessel and processing the substrate, comprising: (A) N is introduced into the processing vessel. ２ activating and supplying a first process gas containing the (B) H is introduced into the processing vessel. ２ and O ２ and activating and supplying a second process gas containing In each of the steps (A) and (B), the pressure inside the processing vessel is repeatedly increased and decreased. Plasma purge method.

2. In increasing the pressure inside the processing vessel, the pressure is increased stepwise; The pressure inside the processing vessel is decreased stepwise. The plasma purging method according to claim 1 .

3. The amplitude of the pressure in the step (B) is greater than the amplitude of the pressure in the step (A). The plasma purging method according to claim 2.

4. Each of the steps (A) and (B) includes a step of repeatedly increasing and decreasing the pressure inside the processing vessel, followed by a step of maintaining the pressure inside the processing vessel constant. The plasma purging method according to any one of claims 1 to 3.

5. the step of repeatedly increasing and decreasing the pressure inside the processing vessel is performed for a longer period of time than the step of maintaining the pressure inside the processing vessel constant; The plasma purging method according to claim 4.

6. The step (A) and the step (B) are carried out in this order. The plasma purging method according to any one of claims 1 to 3.

7. The step (A) and the step (B) are carried out multiple times. The plasma purging method according to any one of claims 1 to 3.

8. the first process gas and the second process gas are activated by plasma; The plasma purging method according to any one of claims 1 to 3.

9. The microwave power for generating the plasma in the step (B) is greater than the microwave power for generating the plasma in the step (A). The plasma purging method according to claim 8.

10. a processing vessel for accommodating a substrate therein and performing substrate processing; The inside of the processing vessel is filled with N ２ a first process gas comprising: ２ and O ２ a gas supply / exhaust unit that supplies a second process gas containing the compound and exhausts gas from the inside of the process vessel; an activation unit that activates the first process gas and the second process gas; a control unit that controls the gas supply and exhaust unit and the activation unit, The control unit After the inside of the processing vessel is cleaned and before a substrate is placed in the processing vessel and processed, (A) N is introduced into the processing vessel. ２ activating and supplying the first process gas containing the (B) H is introduced into the processing vessel. ２ and O ２ and activating and supplying the second process gas containing and in each of the steps (A) and (B), the pressure inside the processing vessel is repeatedly increased and decreased. Plasma processing equipment.

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