Film formation method and film formation device for carbon-based film

Abstract

[Problem] To suppress the generation of defects in a carbon-based film while suppressing the generation of overhangs of the carbon-based film when selectively forming the carbon-based film on a top part of a pattern such as a trench or a hole. [Solution] According to the present invention, when a wafer having an opening is held in a chamber, and a carbon-based film is formed on the wafer by generating plasma from a film formation gas composed of only acetylene gas, argon gas, and hydrogen gas by using high-frequency power, the carbon-based film is selectively formed on a top part of the opening by repeating changes in at least one processing condition among a plurality of processing conditions that include the flow rate of the hydrogen gas, the flow rate of the acetylene gas, the total flow rate of the film formation gas, the high-frequency power, the temperature of a placement table on which the wafer is placed, and the internal pressure of the chamber.

Description

Carbon-based film formation method and film formation apparatus

[0001] The present disclosure relates to a method and apparatus for forming a carbon-based film.

[0002] In semiconductor devices, in order to realize wiring with more complex shapes or finer wiring, a technique is known in which a carbon-based film is selectively formed on the top of a pattern such as a trench or hole formed in a mask or a film to be etched. For example, in the technique described in Patent Document 1, a carbon-based film is formed on the top of a trench formed in a substrate made of silicon. Specifically, in the substrate, a flowable film which is an amorphous carbon polymer film is deposited mainly on the bottom of the trench, and then the flowable film at the bottom is exposed to nitrogen plasma to etch the flowable film at the bottom, and gaseous C ｘ N ｙ H ｚ At this time, the C ｘ N ｙ H ｚ C to the top of the trench where silicon is exposed rather than the sticking coefficient of the species. ｘ N ｙ H ｚ Because of the high adhesion coefficient of the species, C ｘ N ｙ H ｚ The species are selectively redeposited onto the top of the trench, resulting in the selective formation of a carbon-based film on the top of the trench.

[0003] Japanese Patent Application Laid-Open No. 2021-19199

[0004] The technology according to the present disclosure suppresses the occurrence of defects in the carbon-based film while suppressing the occurrence of overhangs in the carbon-based film when selectively depositing the carbon-based film on the top of a pattern such as a trench or hole.

[0005] One aspect of the technology disclosed herein is a method for forming a carbon-based film, comprising a film-forming step of placing a substrate having a pattern inside a processing chamber, and using high-frequency power to generate plasma from a film-forming gas consisting only of hydrocarbon gas, argon gas, and hydrogen gas, to form a carbon-based film on the substrate, wherein the film-forming step selectively forms the carbon-based film on a top portion of the pattern by repeatedly varying at least one of a plurality of processing conditions including a flow rate of the hydrogen gas, a flow rate of the hydrocarbon gas, a total flow rate of the film-forming gas, the high-frequency power, a temperature of a mounting table on which the substrate is placed, and an internal pressure of the processing chamber.

[0006] According to the technology disclosed herein, when a carbon-based film is selectively formed on the top of a pattern such as a trench or a hole, it is possible to suppress the occurrence of overhangs in the carbon-based film while also suppressing the occurrence of defects in the carbon-based film.

[0007] 1 is a cross-sectional view schematically showing the configuration of a film formation apparatus according to an embodiment of the technology disclosed herein. FIG. 2 is a partially enlarged cross-sectional view of a wafer to be subjected to a film formation process in the film formation apparatus of FIG. 1. FIG. 3 is a partially enlarged cross-sectional view of a wafer to be subjected to a film formation process in the film formation apparatus of FIG. 1. FIG. 4 is a partially enlarged cross-sectional view of a wafer to be subjected to a film formation process in the film formation apparatus of FIG. 1. FIG. 5 is a partially enlarged cross-sectional view of a wafer to be subjected to a film formation process in the film formation apparatus of FIG. 1. FIG. 6 is a diagram showing a simplified configuration of an evaluation apparatus. FIG. 7 is an enlarged partial plan view showing the film formation form of a carbon-based film when a film formation process is performed in the evaluation apparatus of FIG. 3. FIG. 8 is an enlarged partial plan view showing the film formation form of a carbon-based film when a film formation process is performed in the evaluation apparatus of FIG. 3. FIG. 9 is a diagram for explaining the mechanism by which cracks occur in a carbon-based film. FIG. 10 is a diagram for explaining the mechanism by which cracks occur in a carbon-based film. FIG. 11 is a diagram for explaining the mechanism by which cracks occur in a carbon-based film. FIG. 12 is a diagram for explaining the occurrence of cracks on the surface of a carbon-based film when the flow rate of hydrogen gas is changed. FIG. 13 is a diagram for explaining the occurrence of cracks on the surface of a carbon-based film when the flow rate of hydrogen gas is changed. 1 is a diagram for explaining the occurrence of cracks on the surface of a carbon-based film when the flow rate of hydrogen gas is changed. FIG. 1 is a diagram for explaining the mechanism by which cracks are less likely to occur in a carbon-based film as the flow rate of hydrogen gas decreases, while the diameter of each hole becomes smaller. FIG. 2 is a diagram for explaining the mechanism by which cracks are less likely to occur in a carbon-based film as the flow rate of hydrogen gas decreases, while the diameter of each hole becomes smaller. FIG. 3 is a sequence diagram for alternately performing low flow rate processing and high flow rate processing. FIG. 4 is a diagram showing the film formation form of a carbon-based film when the flow rate of hydrogen gas is changed to two different levels of values ​​during the film formation process. FIG. 5 is a diagram showing the film formation form of a carbon-based film when the flow rate of hydrogen gas is changed to two different levels of values ​​during the film formation process. FIG. 6 is a flowchart showing a method for forming a carbon-based film according to an embodiment of the technology disclosed herein. FIG. 7 is a process diagram for explaining pretreatment of a film formation process of a carbon-based film. FIG. 8 is a process diagram for explaining pretreatment of a film formation process of a carbon-based film. FIG. 9 is a diagram for explaining the difference in the occurrence of cracks on the surface of a carbon-based film depending on whether or not pretreatment is performed. FIG. 10 is a diagram for explaining the difference in the occurrence of cracks on the surface of a carbon-based film depending on whether or not pretreatment is performed.1 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when the total flow rate of deposition gas is varied; FIG. 2 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when the total flow rate of deposition gas is varied; FIG. 3 is a flowchart showing a method for depositing a carbon-based film according to a first modified example of an embodiment of the technology disclosed herein; FIG. 4 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when the flow rate of acetylene gas is varied; FIG. 5 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when the flow rate of acetylene gas is varied; FIG. 6 is a flowchart showing a method for depositing a carbon-based film according to a second modified example of an embodiment of the technology disclosed herein; FIG. 7 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when high frequency power is varied; FIG. 8 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when high frequency power is varied; FIG. 9 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when high frequency power is varied; FIG. 10 is a flowchart showing a method for depositing a carbon-based film according to a third modified example of an embodiment of the technology disclosed herein; FIG. 11 is an enlarged partial cross-sectional view showing the deposition form of a carbon-based film when the temperature of a mounting table is varied. 25 is an enlarged partial cross-sectional view showing the formation mode of a carbon-based film when the temperature of the mounting table is varied. FIG. 26 is a flowchart showing a method for forming a carbon-based film in accordance with a fourth modified example of an embodiment of the technology according to the present disclosure. FIG. 27 is an enlarged partial cross-sectional view showing the formation mode of a carbon-based film when the pressure inside the chamber is varied. FIG. 28 is an enlarged partial cross-sectional view showing the formation mode of a carbon-based film when the pressure inside the chamber is varied. FIG. 29 is an enlarged partial cross-sectional view showing the formation mode of a carbon-based film when the pressure inside the chamber is varied. FIG. 29 is a flowchart showing a method for forming a carbon-based film in accordance with a fifth modified example of an embodiment of the technology according to the present disclosure. FIG. 29 is a diagram showing the formation mode of a carbon-based film when a film formation process is performed using high-output radio frequency power. FIG. 29 is a diagram showing the formation mode of a carbon-based film when a film formation process is performed using high-output radio frequency power. FIG. 29 is a sequence diagram showing fluctuations in radio frequency power and fluctuations in the flow rate of hydrogen gas in a carbon-based film formation process when high-output radio frequency power is used. FIG. 29 is a diagram showing the formation mode of a carbon-based film when the film formation process shown in FIG. 24 is performed on a wafer from which an oxynitride film has been removed. 25 is a diagram showing the film formation form of a carbon-based film when the film formation process shown in FIG. 24 is performed on a wafer from which the oxynitride film has been removed.25A and 25B are diagrams showing the film formation form of a carbon-based film when the film formation process shown in Fig. 24 is performed on a wafer from which an oxynitride film has not been removed, and Fig. 25A and 25B are diagrams showing the film formation form of a carbon-based film when the film formation process shown in Fig. 24 is performed on a wafer from which an oxynitride film has not been removed.

[0008] An embodiment of the technology according to the present disclosure will be described below with reference to the drawings. Fig. 1 is a cross-sectional view showing a schematic configuration of a film formation apparatus according to the present embodiment. This film formation apparatus is a plasma-enhanced chemical vapor deposition (PECVD) apparatus that forms a film by generating plasma from a film formation gas.

[0009] 1, a film forming apparatus 100 includes a substantially cylindrical chamber 11 (processing chamber) that accommodates a wafer W (substrate), and as will be described later, plasma is generated from a film forming gas inside the chamber 11. The chamber 11 has a sidewall through which a transfer port 12 is provided for transferring the wafer W into and out of the chamber 11, and the transfer port 12 is opened and closed by a gate valve 13.

[0010] A substantially disk-shaped mounting table 14 is disposed inside the chamber 11, and a wafer W is mounted on the mounting table 14. An annular guide ring 15 is disposed on the outer edge of the mounting table 14 so as to surround the mounted wafer W. The mounting table 14 is supported by a cylindrical support member 16 that extends upward from the bottom of the chamber 11.

[0011] Furthermore, a lower electrode 17, a heater 18, and a coolant passage (not shown) are embedded inside the mounting table 14. The heater 18 generates heat by power supplied from a heater power supply 19, thereby heating the wafer W mounted on the mounting table 14, and the coolant passage circulates a coolant supplied from the outside, thereby cooling the wafer W mounted on the mounting table 14. Note that a heat transfer gas may be supplied between the mounting table 14 and the wafer W to improve the thermal conductivity between the mounting table 14 and the wafer W.

[0012] An upper electrode 20 is disposed on the ceiling of the chamber 11 so as to face the mounting table 14, and an insulating member 21 is disposed between the chamber 11 and the upper electrode 20. The upper electrode 20 includes a base member 22, a top plate 23, and an intermediate member 24. The base member 22, the top plate 23, and the intermediate member 24 are made of conductive materials, such as aluminum. The top plate 23, the intermediate member 24, and the base member 22 are disposed in this order from below, with the top plate 23 and the base member 22 separated by the substantially annular intermediate member 24 to form a gas diffusion space 25 therebetween. Note that the intermediate member 24 can be omitted. In this case, recesses are provided in the top plate 23 and the base member 22 to form the gas diffusion space 25. A gas inlet port 26 communicating with the gas diffusion space 25 from above is formed in the base member 22, while a plurality of gas holes 27 communicating the gas diffusion space 25 with the interior of the chamber 11 is formed in the top plate 23.

[0013] The film forming apparatus 100 also includes a gas supply unit 28, which is connected to a gas inlet port 26 via a gas pipe 29. The gas supply unit 28 has a gas source, a flow rate controller, and an on-off valve, and supplies a process gas for generating plasma, such as a film forming gas. The supplied film forming gas is introduced into the gas diffusion space 25 via the gas inlet port 26, and then diffused and introduced into the chamber 11 through each gas hole 27. This causes the upper electrode 20 to function as a shower head. A heat insulating member 30 is disposed on the upper electrode 20. In this embodiment, the film forming gas supplied by the gas supply unit 28 is a hydrocarbon gas (for example, acetylene (C ２ H ２ ) gas), argon (Ar) gas and hydrogen (H ２ By using this film formation gas, the film formation apparatus 100 generates hydrocarbon plasma from the film formation gas during the film formation process, and forms a carbon-based film using hydrocarbon ions and hydrocarbon radicals in the hydrocarbon plasma.

[0014] The film forming apparatus 100 further includes an exhaust device 31, which may be, for example, a turbomolecular pump or a dry pump, and which reduces the pressure inside the chamber 11 via an exhaust pipe 36 connected to the bottom of the chamber 11.

[0015] The film forming apparatus 100 further includes a high-frequency power supply 32, which is connected to the upper electrode 20 via a matching box 33. The matching box 33 matches the impedance of the load of the high-frequency power supply 32 to the output impedance of the high-frequency power supply 32. The high-frequency power supply 32 supplies high-frequency power having a frequency of 40 MHz to 460 MHz to the upper electrode 20.

[0016] Therefore, in the film forming apparatus 100, high-frequency power having a frequency of 40 MHz or higher is supplied to the upper electrode 20. Generally, when high-frequency power having a frequency of 40 MHz or higher is supplied to the upper electrode 20 to generate plasma, the generated plasma becomes a high-density plasma, and the electrical impedance of the plasma decreases. As a result, the maximum value of the high-frequency power supplied to the upper electrode 20 is lower than the maximum value when low-frequency power (frequency: 200 kHz to 13 MHz) is supplied to the upper electrode 20. In other words, when high-frequency power is supplied to the upper electrode 20, the plasma potential decreases, thereby decreasing the sheath voltage that contributes to the acceleration of ions in the plasma. Furthermore, the higher the frequency of the supplied high-frequency power, the faster the sheath vibrates, thereby reducing the ion's ability to follow the sheath voltage. As a result, the ion energy imparted from the plasma to the wafer W placed on the mounting table 14 is reduced.

[0017] The film forming apparatus 100 further includes a control unit 34, which controls each component of the film forming apparatus 100. The control unit 34 is a computer including a processor, a memory, an input device, a display device, a signal input / output interface, etc., and a control program and recipe data are stored in the memory of the control unit 34. When a film forming process is performed in the film forming apparatus 100, the processor of the control unit 34 executes the corresponding control program and controls each component of the film forming apparatus 100 in accordance with the recipe data.

[0018] Specifically, the control unit 34 controls the gas supply unit 28 and the exhaust device 31 to adjust the pressure inside the chamber 11, and controls the high-frequency power supply 32 to supply high-frequency power to the upper electrode 20. The control unit 34 also controls the gas supply unit 28 to diffuse and introduce the film formation gas into the chamber 11. At this time, an electric field generated by the high-frequency power supplied to the upper electrode 20 excites the film formation gas to generate plasma, and the film formation process is performed on the wafer W by this plasma.

[0019] The film forming apparatus 100 further includes an impedance circuit 35. The impedance circuit 35 is disposed in an electrical path 37 connecting the lower electrode 17 and ground. The impedance circuit 35 includes at least one of an inductor and a capacitor, and can change the impedance between the lower electrode 17 and ground by connecting them in series or in parallel. The inductor and capacitor included in the impedance circuit 35 may be either a fixed element or a variable element.

[0020] By changing this impedance, it is possible to weaken the electrical coupling between the upper electrode 20 and the lower electrode 17, thereby controlling to further reduce the high frequency current flowing through the lower electrode 17. As a result, it is possible to more precisely control the energy of ions incident on the wafer W.

[0021] 2A to 2D are enlarged cross-sectional views of a wafer W subjected to a film formation process in the film formation apparatus 100 of FIG. In this wafer W, an insulating film 39 is formed by alternately stacking multiple oxide films and multiple nitride films on the surface of a silicon substrate 38, and a hard mask layer 40 made of amorphous carbon is formed on the insulating film 39. An oxynitride (SiON) film 41, for example, is formed on the surface of the hard mask layer 40, and a pattern, for example, a hole-shaped opening 42, is formed in the hard mask layer 40 using the oxynitride film 41 as a mask. The opening 42 penetrates the hard mask layer 40, and the insulating film 39 is exposed at the bottom of the opening 42 ( FIG. 2A ).

[0022] In this wafer W, during the semiconductor device manufacturing process, deep holes 43 corresponding to the openings 42 are formed in the insulating film 39 by etching using the hard mask layer 40 as a mask. However, forming the deep holes 43 requires a long etching time, and prolonged etching may cause the hard mask layer 40 to disappear, making it impossible to continue etching. Therefore, in the film forming apparatus 100, a carbon-based film 44 is selectively formed on the tops of the openings 42 in the hard mask layer 40 (tops of the pattern) ( FIG. 2B ). This carbon-based film 44 functions as a mask, similar to the hard mask layer 40, during etching to form the deep holes 43. The reason for selectively forming the carbon-based film 44 on the tops of the openings 42 is described in the specification of Japanese Patent Application No. 2023-200333 filed by the present applicant.

[0023] After the carbon-based film 44 is formed, the wafer W is subjected to an etching process to form deep holes 43 corresponding to the openings 42 in the insulating film 39. At this time, the carbon-based film 44 and the oxynitride film 41 are removed by etching (FIG. 2C). Thereafter, the hard mask layer 40 is removed by ashing or the like (FIG. 2D).

[0024] The present applicant has used an evaluation apparatus 45 having a similar structure to the film formation apparatus 100 of Fig. 1 to perform a film formation process on a wafer W and confirmed the film formation state of a carbon-based film 44 on the wafer W. The configuration of the evaluation apparatus 45 is shown in a simplified form in Fig. 3, and the configuration other than that shown is the same as the configuration of the film formation apparatus 100.

[0025] In the evaluation device 45, a conductive ring member 46 is disposed inside the chamber 11 so as to surround the mounting table 14 (lower electrode 17), the ring member 46 is grounded via an impedance circuit 47, and the lower electrode 17 is grounded via an impedance circuit 35. In the evaluation device 45, the film formation distribution can be controlled by controlling the impedances of the impedance circuit 47 and the impedance circuit 35. For example, when high-frequency power having a frequency of 40 MHz or higher is supplied to the upper electrode 20, the evaluation device 45 can reduce the ion energy imparted to the wafer W placed on the mounting table 14 by controlling the impedances of the impedance circuit 47 and the impedance circuit 35. Therefore, the evaluation device 45 can reproduce the film formation process performed in the film formation apparatus 100 with reduced ion energy.

[0026] 4A and 4B are enlarged partial plan views showing the film formation form of a carbon-based film 44 when a film formation process is performed in an evaluation device 45. Fig. 4A is an enlarged partial plan view of a wafer W before the film formation process, and a hole 48 as an opening 42 formed in a hard mask layer 40 is indicated by a "●". In the enlarged partial plan views that follow, the hole 48 is indicated by a "●" as in Fig. 4A.

[0027] At this time, the applicant set the flow rates of acetylene gas, hydrogen gas, and argon gas in the deposition gas to 30 sccm, 30 sccm, and 1000 sccm, respectively. The pressure inside the chamber 11 was set to 1 Torr, and high-frequency power having a frequency of 40 MHz was supplied from the high-frequency power supply 32 to the upper electrode 20 to generate plasma from the deposition gas, thereby performing a deposition process on the wafer W. The temperature of the mounting table 14 was set to 400° C.

[0028] Thereafter, the wafer W was subjected to a film formation process for 60 minutes under the above-described processing conditions, and the surface of the carbon-based film 44 formed on the hard mask layer 40 and having a thickness of approximately 1 μm was observed. The applicant then confirmed that, as shown in FIG. 4B , seam-like cracks 49 had formed on the surface of the carbon-based film 44, connecting the holes 48. Here, the cracks 49 cannot function as a mask in etching, and therefore the applicant confirmed that, under the above-described processing conditions, a carbon-based film 44 was formed that was unsuitable as an etching mask for forming the deep holes 43.

[0029] The present applicant has inferred the mechanism described below as the reason why such cracks 49 occur. Figures 5A to 5C are diagrams for explaining the mechanism by which cracks 49 occur in the carbon-based film 44. Figures 5A to 5C show enlarged partial cross sections of the wafer W around a hole 48.

[0030] For example, it is assumed that defects, such as microcracks 50, occur on the surface of the oxynitride film 41 before the carbon-based film 44 is formed (FIG. 2A).

[0031] At this time, when the carbon-based film 44 grows anisotropically (vertically in the drawing) at the tops of the holes 48 (pattern) during the film formation process, the carbon-based film 44 grows while maintaining the depressions of the microcracks 50 in the oxynitride film 41. Therefore, during the formation of the carbon-based film 44, cracks 49 appear on the surface of the carbon-based film 44 so as to correspond to the microcracks 50 (FIG. 5B). Then, as the carbon-based film 44 grows, the cracks 49 also grow and eventually connect the holes 48 (FIG. 5C).

[0032] Therefore, in order to confirm under what processing conditions cracks 49 occur (grow), the applicant performed a film formation process on wafers W in evaluation device 45 while changing the flow rate of hydrogen gas in the film formation gas, and observed the surface of the carbon-based film 44 formed.

[0033] In this case, the applicant set the flow rate of acetylene gas in the film formation gas to 30 sccm, the flow rate of argon gas to 300 sccm, and then changed the flow rate of hydrogen gas. Then, the pressure inside the chamber 11 was set to 1 Torr, and high-frequency power having a frequency of 40 MHz was supplied from the high-frequency power supply 32 to the upper electrode 20 to generate plasma from the film formation gas and perform a film formation process on the wafer W. The temperature of the mounting table 14 was set to 400° C.

[0034] 6A to 6C are diagrams illustrating the occurrence of cracks 49 on the surface of the carbon-based film 44 when the flow rate of hydrogen gas is changed. Fig. 6A shows the case where the flow rate of hydrogen gas is 12 sccm, Fig. 6B shows the case where the flow rate of hydrogen gas is 14 sccm, and Fig. 6C shows the case where the flow rate of hydrogen gas is 16 sccm.

[0035] 6A to 6C, it was confirmed that the smaller the flow rate of hydrogen gas, the less likely cracks 49 would occur on the surface of the carbon-based film 44. However, it was also confirmed that the smaller the flow rate of hydrogen gas, the smaller the diameter of each hole 48 in the carbon-based film 44 (the holes tend to be filled).

[0036] The present applicant has inferred the mechanism described below as the reason why cracks 49 are less likely to occur as the flow rate of hydrogen gas decreases, while the diameter of each hole 48 becomes smaller. Figures 7A and 7B are diagrams for explaining the mechanism by which cracks 49 are less likely to occur as the flow rate of hydrogen gas decreases in the carbon-based film 44, while the diameter of each hole 48 becomes smaller. Figures 7A and 7B also show enlarged partial cross sections of the wafer W around the hole 48.

[0037] For example, when the flow rate of hydrogen gas is reduced, the carbon-based film 44 grows not only anisotropically but also isotropically, filling the microcracks 50 in the oxynitride film 41, and as the carbon-based film 44 grows, the depressions of the microcracks 50 in the oxynitride film 41 are no longer maintained. As a result, cracks 49 are less likely to occur on the surface of the carbon-based film 44. However, at the top of the hole 48 (pattern), the carbon-based film 44 does not grow only vertically but also grows isotropically, so that the carbon-based film 44 overhangs toward the hole 48, resulting in a smaller diameter of the hole 48 (FIG. 7A).

[0038] On the other hand, when the flow rate of hydrogen gas increases, anisotropic growth of the carbon-based film 44 takes precedence, and the carbon-based film 44 grows while maintaining the depressions of the microcracks 50 in the oxynitride film 41, resulting in cracks 49 on the surface of the carbon-based film 44. However, since it becomes difficult for the carbon-based film 44 to grow isotropically at the top of the hole 48, the carbon-based film 44 does not overhang toward the hole 48, and as a result, the diameter of the hole 48 does not become smaller ( FIG. 7B ).

[0039] Furthermore, the applicant has inferred the mechanism described below as the reason why, when the flow rate of hydrogen gas decreases, the carbon-based film 44 grows not only anisotropically but also isotropically, while, when the flow rate of hydrogen gas increases, the anisotropic growth of the carbon-based film 44 prevails.

[0040] The film formation gas generates not only hydrocarbon plasma but also hydrogen plasma, and the hydrogen radicals contained in the hydrogen plasma isotropically etch the carbon-based film 44. Therefore, when the flow rate of hydrogen gas increases and the hydrogen radicals increase, the carbon-based film 44 is isotropically etched, and the isotropic growth of the carbon-based film 44 is hindered, resulting in anisotropic growth of the carbon-based film 44 being prioritized. On the other hand, when the flow rate of hydrogen gas decreases and the hydrogen radicals decrease, the carbon-based film 44 is less likely to be isotropically etched, and the isotropic growth of the carbon-based film 44 is not hindered. As a result, the carbon-based film 44 grows not only anisotropically but also isotropically.

[0041] That is, it was found that, when the flow rate of hydrogen gas in the film formation gas is reduced, the carbon-based film 44 overhangs, but the occurrence of cracks 49 in the carbon-based film 44 can be suppressed. Also, it was found that, when the flow rate of hydrogen gas in the film formation gas is increased, it becomes more difficult to suppress the occurrence of cracks 49 in the carbon-based film 44, but the occurrence of overhangs in the carbon-based film 44 can be suppressed.

[0042] Therefore, the present applicant has investigated how to simultaneously suppress the occurrence of overhangs in the carbon-based film 44 and the occurrence of cracks 49 in the carbon-based film 44 by increasing or decreasing the flow rate of hydrogen gas during the film formation process. Specifically, in the evaluation device 45, the film formation process was performed on the wafer W while varying the flow rate of hydrogen gas between two different levels.

[0043] The applicant set the internal pressure of the chamber 11 to 1 Torr and the temperature of the mounting table 14 to 380°C. The high-frequency power supply 32 supplied 500 W of high-frequency power with a frequency of 40 MHz to the upper electrode 20, generating plasma from the film-forming gas to perform a film-forming process on the wafer W. The flow rates of the acetylene gas and argon gas in the film-forming gas were set to 30 sccm, 1000 sccm, and two levels of hydrogen gas flow rates: a low flow rate of 20 sccm and a high flow rate of 24 sccm. The film-forming process with a low hydrogen gas flow rate (hereinafter referred to as the "low-flow process") and a high hydrogen gas flow rate (hereinafter referred to as the "high-flow process") were each continued for two minutes. As shown in FIG. 8 , the low-flow process and the high-flow process were alternately repeated eight times. The applicant then confirmed the morphology of the carbon-based film 44 formed.

[0044] 9A and 9B are diagrams showing the film formation form of the carbon-based film 44 when the flow rate of hydrogen gas is changed to two different levels during the film formation process, where FIG. 9A is an enlarged partial plan view of the film formation form of the carbon-based film 44, and FIG. 9B is an enlarged partial cross-sectional view of the film formation form of the carbon-based film 44.

[0045] As shown in Figures 9A and 9B, it was confirmed that when the flow rate of hydrogen gas was varied to two different levels during the film formation process, the occurrence of cracks 49 in the carbon-based film 44 was suppressed, and the occurrence of overhangs in the carbon-based film 44 was also suppressed.

[0046] The applicant also performed a film formation process on a wafer W by setting the hydrogen gas flow rates in the low-flow process and the high-flow process to different flow rates. Specifically, the pressure inside the chamber 11 was set to 1 Torr, and the temperature of the mounting table 14 was set to 350°C. Furthermore, a high-frequency power of 500 W with a frequency of 40 MHz was supplied from the high-frequency power supply 32 to the upper electrode 20, generating plasma from the film formation gas to perform a film formation process on the wafer W. The flow rates of acetylene gas and argon gas in the film formation gas were set to 30 sccm and 1000 sccm, respectively. The hydrogen gas flow rate in the low-flow process was set to 20 sccm, and the hydrogen gas flow rate in the high-flow process was set to 40 sccm. The low-flow process and the high-flow process were alternately repeated eight times, each lasting for two minutes. Results similar to those shown in FIGS. 9A and 9B were also obtained.

[0047] From these confirmation results, it was considered that even if the flow rate of hydrogen gas was reduced and the carbon-based film 44 overhangs slightly, a subsequent increase in the flow rate of hydrogen gas increases the number of hydrogen radicals, which causes the carbon-based film 44 to be isotropically etched, thereby eliminating the overhang of the carbon-based film 44. In this case, as described above, anisotropic growth of the carbon-based film 44 takes precedence. Furthermore, even if the flow rate of hydrogen gas increases and cracks 49 occur slightly in the carbon-based film 44, a subsequent decrease in the flow rate of hydrogen gas causes the carbon-based film 44 to grow not only anisotropically but also isotropically, thereby filling the cracks 49.

[0048] That is, the inventors have found that by repeating conditions for suppressing the occurrence of overhangs and conditions for filling microcracks 50 during the formation of the carbon-based film 44, it is possible to simultaneously suppress the occurrence of cracks 49 in the carbon-based film 44 and the occurrence of overhangs in the carbon-based film 44.

[0049] The technology of the present disclosure is based on this finding. In the following description, the conditions under which the occurrence of overhangs is suppressed and the anisotropic growth of the carbon-based film 44 is prioritized are referred to as "conditions for suppressing overhang occurrence." Furthermore, the conditions under which the microcracks 50 are filled are conditions under which the carbon-based film 44 grows not only anisotropically but also isotropically, and as a result, these conditions also promote the occurrence of overhangs, and therefore are referred to as "conditions for promoting overhang occurrence."

[0050] Furthermore, from the viewpoint of both suppressing the occurrence of cracks 49 in the carbon-based film 44 and suppressing the occurrence of overhangs in the carbon-based film 44, it is considered preferable to more effectively eliminate the overhangs in the carbon-based film 44 and more reliably fill the microcracks 50. That is, under the overhang-suppressing condition, it is preferable that the hydrogen radicals are increased, and under the overhang-promoting condition, it is preferable that the carbon-based film 44 grows more isotropically. Therefore, it is preferable that the difference in the flow rate of hydrogen gas between the overhang-suppressing condition and the overhang-promoting condition is large. In other words, based on the above-mentioned confirmation results, the ratio of the hydrogen gas flow rate (24 sccm) under the overhang-suppressing condition to the hydrogen gas flow rate (20 sccm) under the overhang-promoting condition is preferably 1.2 or more.

[0051] The hydrocarbon ions in the hydrocarbon plasma, which are the main cause of the formation of the carbon-based film 44, are highly anisotropic and adhere anisotropically (vertically in the figure) to the top of the opening 42. On the other hand, the hydrocarbon radicals in the hydrocarbon plasma are highly isotropic and adhere isotropically (from all directions) to the top of the opening 42.

[0052] The sticking probability of hydrocarbon ions is not significantly affected by the ambient temperature near the wafer W, but the sticking probability of hydrocarbon radicals increases as the ambient temperature near the wafer W decreases. Therefore, if the temperature of the mounting table 14 is low and the ambient temperature near the wafer W is also low, the amount of hydrocarbon radicals adhering to the top of the opening 42 increases unnecessarily, which may cause the carbon-based film 44 to grow excessively isotropically and significantly overhang toward the hole 48. Therefore, it is preferable to raise the temperature of the mounting table 14 to a certain degree during the formation of the carbon-based film 44; specifically, it is preferable to set the temperature of the mounting table 14 to a temperature higher than 200° C.

[0053] 10 is a flowchart showing a method for forming a carbon-based film according to an embodiment of the technology disclosed herein. The process of FIG. 10 is realized by the processor of the control unit 34 executing a corresponding control program.

[0054] First, in the film formation apparatus 100, a wafer W having a plurality of holes 48 formed in a hard mask layer 40 is loaded into the chamber 11 of the film formation apparatus 100, and the wafer W is placed on the mounting table 14. Next, supply of a film formation gas consisting only of acetylene gas, argon gas, and hydrogen gas into the chamber 11 begins (step S101), and high-frequency power with a frequency of 40 MHz is supplied to the upper electrode 20. At this time, the film formation gas is excited by an electric field generated between the upper electrode 20 and the mounting table 14, and becomes high-density plasma. Then, a carbon-based film 44 is formed on the top of the opening 42 by hydrocarbon plasma (mainly hydrocarbon ions) contained in the high-density plasma.

[0055] Next, while generating high density plasma from the film-forming gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions that promote overhang formation with a reduced flow rate of hydrogen gas (step S102).

[0056] Next, while generating high density plasma from the film-forming gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions for suppressing overhang generation with an increased flow rate of hydrogen gas (step S103).

[0057] Thereafter, it is determined whether the number of times the processes in steps S102 and S103 have been executed exceeds a specified number (step S104).

[0058] If the number of times that the processes of steps S102 and S103 are performed does not exceed the specified number, the process returns to step S102. On the other hand, if the number of times that the processes of steps S102 and S103 are performed exceeds the specified number, the supply of the film forming gas into the chamber 11 is stopped (step S105), the supply of high frequency power to the upper electrode 20 is stopped, and the process ends.

[0059] The specified number of times and the duration of the process in step S102 and the process in step S103 are set based on the results of previous experiments, and the specified number of times increases as the desired carbon-based film 44 becomes thicker.

[0060] According to this embodiment, when selectively depositing the carbon-based film 44 on the top of the opening 42, the process conditions are repeatedly changed between overhang-promoting conditions and overhang-suppressing conditions. As a result, even if the carbon-based film 44 overhangs slightly during the deposition process under the overhang-promoting conditions, the carbon-based film 44 is isotropically etched during the subsequent deposition process under the overhang-suppressing conditions, thereby eliminating the overhang of the carbon-based film 44. Furthermore, even if cracks 49 occur slightly in the carbon-based film 44 during the deposition process under the overhang-suppressing conditions, the carbon-based film 44 grows isotropically during the subsequent deposition process under the overhang-promoting conditions, thereby filling the cracks 49. As a result, the occurrence of overhangs in the carbon-based film 44 can be suppressed while also suppressing the occurrence of defects such as cracks 49 in the carbon-based film 44. In particular, by repeating the film formation process under the overhang formation promoting conditions, cracks 49 that occur in the carbon-based film 44 during the formation of the carbon-based film 44 can be filled by the film formation process under the overhang formation promoting conditions after the occurrence of the cracks 49. This makes it possible to more reliably suppress the occurrence of defects such as cracks 49 in the carbon-based film 44.

[0061] In the process of FIG. 10 described above, the duration of the film formation process (step S102) under the overhang formation promoting condition is the same as the duration of the film formation process (step S103) under the overhang formation suppressing condition. However, the duration of step S102 and the duration of step S103 do not have to be the same. For example, if priority is given to suppressing the occurrence of cracks 49, the duration of step S102 is set longer than the duration of step S103. Furthermore, if priority is given to suppressing the occurrence of overhangs in the carbon-based film 44, the duration of step S103 is set longer than the duration of step S102.

[0062] In this embodiment, the occurrence of cracks 49 is suppressed by performing the film formation process (step S102) under conditions that promote the occurrence of overhangs. However, the occurrence of cracks 49 may be more reliably suppressed by performing a pretreatment prior to the film formation process of the carbon-based film 44.

[0063] 11A and 11B are process diagrams illustrating the pretreatment of the carbon-based film 44 deposition process. As described above, cracks 49 in the carbon-based film 44 are caused by defects such as microcracks 50 in the oxynitride film 41. Furthermore, if microprotrusions 52 are present in the oxynitride film 41, the carbon-based film 44 may grow while maintaining the convex shape of the microprotrusions 52, potentially causing protrusions on the surface of the carbon-based film 44. Therefore, in the pretreatment shown in FIGS. 11A and 11B , defects in the oxynitride film 41 are removed before the carbon-based film 44 deposition process is performed. Specifically, a wafer W ( FIG. 11A ) having microcracks 50 and microprotrusions 52 in the oxynitride film 41 is subjected to dry etching using plasma or wet etching using a chemical solution, thereby removing the oxynitride film 41 together with the microcracks 50 and microprotrusions 52. This exposes the hard mask layer 40, the surface of which is not roughened ( FIG. 11B ).

[0064] 12A and 12B are diagrams for explaining the difference in the occurrence of cracks 49 on the surface of the carbon-based film 44 depending on whether or not pretreatment is performed. Note that the processing conditions were not changed in the film formation process of the carbon-based film 44 at this time.

[0065] 11A and 11B , when the carbon-based film 44 was formed on the wafer W, it was confirmed that cracks 49 occurred on the surface of the carbon-based film 44, as shown in Fig. 12A . On the other hand, when the carbon-based film 44 was formed on the wafer W after the pretreatments shown in Fig. 11A and 11B , it was confirmed that the occurrence of cracks 49 on the surface of the carbon-based film 44 was suppressed, as shown in Fig. 12B . That is, it was found that by performing the pretreatment of removing the oxynitride film 41 on the wafer W, the occurrence of cracks 49 can be more reliably suppressed when the treatment shown in Fig. 10 is performed.

[0066] In the above-described embodiment, the overhang formation promoting condition and the overhang formation suppressing condition are realized by varying the flow rate of hydrogen gas in the film formation gas. However, the process conditions that are varied to realize the overhang formation promoting condition and the overhang formation suppressing condition are not limited to the hydrogen gas flow rate. Below, we will explain the process conditions other than the hydrogen gas flow rate that are used to realize the overhang formation promoting condition and the overhang formation suppressing condition.

[0067] First, the applicant confirmed the film formation state of the carbon-based film 44 when the total flow rate of the film formation gas was varied. The applicant used a wafer W having an oxide layer 53 formed on the surface of a silicon substrate 38, with a plurality of trench-shaped openings 54 formed as a pattern in the oxide layer 53, and performed a film formation process on the wafer W by generating plasma from the film formation gas in the evaluation device 45. At this time, the applicant first set the total flow rate of the film formation gas to a predetermined flow rate and performed the film formation process on the wafer W. Thereafter, the applicant increased the total flow rate of the film formation gas to 1.2 times the predetermined flow rate and performed the film formation process on the wafer W.

[0068] 13A and 13B are enlarged partial cross-sectional views showing the formation of the carbon-based film 44 when the total flow rate of the film formation gas is varied. When the total flow rate of the film formation gas is set to a predetermined flow rate, the carbon-based film 44 is formed on the top of the opening 54 (pattern) without overhanging toward the opening 54 (FIG. 13A). On the other hand, when the total flow rate of the film formation gas is set to 1.2 times the predetermined flow rate, the carbon-based film 44 is formed on the top of the opening 54 with overhanging toward the opening 54 (FIG. 13B).

[0069] Here, it is believed that the reason why the carbon-based film 44 overhangs toward the opening 54 is because the isotropic growth of the carbon-based film 44 is strong. Also, it is believed that the reason why the carbon-based film 44 does not overhang is because the isotropic growth of the carbon-based film 44 is weak. Therefore, from the above-mentioned film formation mode, it is believed that an increase in the total flow rate of the film formation gas corresponds to a condition that promotes the occurrence of overhang, and at this time, the isotropic growth of the carbon-based film 44 becomes strong, and the occurrence of cracks 49 in the carbon-based film 44 is suppressed. Also, it is believed that a decrease in the total flow rate of the film formation gas corresponds to a condition that suppresses the occurrence of overhang, and at this time, the isotropic growth of the carbon-based film 44 becomes weak, and it is believed that it becomes difficult to suppress the occurrence of cracks 49 in the carbon-based film 44.

[0070] It is believed that this phenomenon occurred because, by varying the total flow rate of the film-forming gas, the balance between the hydrocarbon plasma that contributes to the formation of the carbon-based film 44 and the hydrogen plasma that contributes to the etching of the carbon-based film 44 changed, resulting in a change in the growth form of the carbon-based film 44.

[0071] In this way, it was found that by varying the total flow rate of the deposition gas between two different levels, it was possible to realize conditions that promote overhang formation and conditions that suppress overhang formation. Therefore, it was thought that by varying the total flow rate of the deposition gas, it was possible to simultaneously suppress the formation of overhangs in the carbon-based film 44 and the formation of cracks 49 in the carbon-based film 44. The process shown in FIG. 14 below is based on this finding.

[0072] 14 is a flowchart showing a carbon-based film forming method according to a first modified example of an embodiment of the technology disclosed herein. The process of FIG. 14 is also realized by the processor of the control unit 34 executing a corresponding control program.

[0073] First, in the film formation apparatus 100, the wafer W having the plurality of openings 54 formed in the hard mask layer 40 is placed on the mounting table 14. Next, the supply of the film formation gas into the chamber 11 is started (step S141), and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, high-density plasma is generated from the film formation gas, and a carbon-based film 44 is formed on the top of the openings 54 by hydrocarbon plasma contained in the high-density plasma.

[0074] Next, while generating high density plasma from the deposition gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions that promote overhang generation with the total flow rate of the deposition gas increased (step S142).

[0075] Next, while generating high density plasma from the deposition gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions for suppressing overhang generation in which the total flow rate of the deposition gas is reduced (step S143).

[0076] Thereafter, it is determined whether the number of times the processes in steps S142 and S143 have been executed exceeds a specified number (step S144).

[0077] If the number of times that the processes of steps S142 and S143 are performed does not exceed the specified number of times, the process returns to step S142. On the other hand, if the number of times that the processes of steps S142 and S143 are performed exceeds the specified number of times, the supply of the film forming gas into the chamber 11 is stopped (step S145), the supply of high frequency power to the upper electrode 20 is stopped, and the process ends.

[0078] The specified number of times and the duration of the processing of step S142 and the processing of step S143 are set based on the results of prior experiments, etc., as in the processing of FIG. 10, and the specified number of times becomes larger particularly as the desired carbon-based film 44 becomes thicker.

[0079] Furthermore, since it is preferable to more effectively eliminate the overhang of the carbon-based film 44 and more reliably suppress the occurrence of cracks 49, it is considered preferable that the overhang-suppressing conditions and the overhang-promoting conditions are as far apart as possible. In other words, it is considered preferable that the difference between the total flow rates of the film-forming gas under the overhang-suppressing conditions and the overhang-promoting conditions is large. In other words, from the confirmation results shown in Figures 13A and 13B, it is considered preferable that the ratio of the total flow rate of the film-forming gas under the overhang-promoting conditions to the total flow rate of the film-forming gas under the overhang-suppressing conditions be 1.2 times or more.

[0080] Next, the applicant confirmed the film formation state of the carbon-based film 44 when the flow rate of the acetylene gas was varied. The applicant used the same wafer W as in the first modified example, and performed a film formation process on the wafer W by generating plasma from the film formation gas in the evaluation device 45. At this time, the applicant first set the flow rate of the acetylene gas to a predetermined flow rate and performed the film formation process on the wafer W. Thereafter, the applicant increased the flow rate of the acetylene gas to 1.5 times the predetermined flow rate and performed the film formation process on the wafer W.

[0081] 15A and 15B are enlarged partial cross-sectional views showing the formation of the carbon-based film 44 when the flow rate of the acetylene gas was varied. When the flow rate of the acetylene gas was set to a predetermined flow rate, the carbon-based film 44 was formed on the top of the opening 54 (pattern) without overhanging toward the opening 54 (FIG. 15A). On the other hand, when the flow rate of the acetylene gas was set to 1.5 times the predetermined flow rate, the carbon-based film 44 was formed on the top of the opening 54 with overhanging toward the opening 54 (FIG. 15B).

[0082] From the above-described film formation mode, it was considered that an increase in the flow rate of acetylene gas corresponds to a condition for promoting the occurrence of overhang, in which case the isotropic growth of the carbon-based film 44 becomes stronger, and the occurrence of cracks 49 in the carbon-based film 44 is suppressed. In addition, it was considered that a decrease in the flow rate of acetylene gas corresponds to a condition for suppressing the occurrence of overhang, in which case the isotropic growth of the carbon-based film 44 becomes weaker, and the occurrence of cracks 49 in the carbon-based film 44 is difficult to suppress.

[0083] It is believed that this phenomenon occurred because, as in the first modified example, the balance between hydrocarbon plasma and hydrogen plasma was changed by varying the flow rate of acetylene gas, which changed the growth form of the carbon-based film 44.

[0084] In this way, it was found that by varying the flow rate of acetylene gas between two different levels, it was possible to realize conditions for promoting overhang formation and conditions for suppressing overhang formation. Therefore, it was thought that by varying the flow rate of acetylene gas, it was possible to simultaneously suppress the formation of overhangs in the carbon-based film 44 and the formation of cracks 49 in the carbon-based film 44. The process shown in FIG. 16 below is based on this finding.

[0085] 16 is a flowchart showing a carbon-based film forming method according to a second modified example of an embodiment of the technology disclosed herein. The process of FIG. 16 is also realized by the processor of the control unit 34 executing a corresponding control program.

[0086] First, in the film formation apparatus 100, the wafer W having the openings 54 formed in the hard mask layer 40 is placed on the mounting table 14. Next, the supply of the film formation gas into the chamber 11 is started (step S161), and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, high-density plasma is generated from the film formation gas, and a carbon-based film 44 is formed on the top of the openings 54 by hydrocarbon plasma contained in the high-density plasma.

[0087] Next, while generating high density plasma from the deposition gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions that promote overhang formation by increasing the flow rate of acetylene gas (step S162).

[0088] Next, while generating high density plasma from the film-forming gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions for suppressing overhang generation with a reduced flow rate of acetylene gas (step S163).

[0089] Thereafter, it is determined whether the number of times the processes in steps S162 and S163 have been executed exceeds a specified number (step S164).

[0090] If the number of times that the processes of steps S162 and S163 are performed does not exceed the specified number of times, the process returns to step S162. On the other hand, if the number of times that the processes of steps S162 and S163 are performed exceeds the specified number of times, the supply of the film forming gas into the chamber 11 is stopped (step S165), the supply of high frequency power to the upper electrode 20 is stopped, and the process ends.

[0091] The specified number of times and the duration of the processing of step S162 and the processing of step S163 are set based on the results of prior experiments, etc., as in the processing of FIG. 10, and the specified number of times becomes larger particularly as the desired carbon-based film 44 becomes thicker.

[0092] Also, in the second modified example, it is considered that the greater the difference between the overhang generation suppression conditions and the overhang generation promotion conditions, the more effectively the overhang of the carbon-based film 44 is eliminated and the more reliably the occurrence of cracks 49 is suppressed. Therefore, it is preferable that the difference in the flow rate of acetylene gas between the overhang generation suppression conditions and the overhang generation promotion conditions is large. Furthermore, from the confirmation results shown in Figures 15A and 15B, it is considered that the ratio of the flow rate of acetylene gas under the overhang generation promotion conditions to the flow rate of acetylene gas under the overhang generation suppression conditions is preferably 1.5 times or more.

[0093] Next, the applicant confirmed the film formation state of the carbon-based film 44 when the high-frequency power was varied. The applicant used the same wafer W as in the first modified example, and performed a film formation process on the wafer W by generating plasma from the film formation gas in the evaluation device 45. At this time, the applicant first performed the film formation process on the wafer W by setting the high-frequency power to 100 W. Thereafter, the applicant performed the film formation process on the wafer W by setting the high-frequency power to 125 W. Furthermore, the applicant performed the film formation process on the wafer W by setting the high-frequency power to 150 W.

[0094] 17A to 17C are enlarged partial cross-sectional views showing the deposition state of the carbon-based film 44 when the high-frequency power is varied. Fig. 17A shows the case where the high-frequency power is set to 100 W, Fig. 17B shows the case where the high-frequency power is set to 125 W, and Fig. 17C shows the case where the high-frequency power is set to 150 W.

[0095] 17A to 17C, it was confirmed that when the high frequency power was reduced, the carbon-based film 44 was formed on the top of the opening 54 (pattern), but the carbon-based film 44 slightly overhangs toward the opening 54, narrowing the opening 54. It was also confirmed that when the high frequency power was increased, the carbon-based film 44 was formed on the top of the opening 54, but the carbon-based film 44 did not overhang toward the opening 54.

[0096] From the above-described film formation mode, it was considered that a decrease in the radio frequency power corresponds to a condition that promotes the occurrence of overhangs, and at this time, the isotropic growth of the carbon-based film 44 becomes stronger, and the occurrence of cracks 49 in the carbon-based film 44 is suppressed. On the other hand, it was considered that an increase in the radio frequency power corresponds to a condition that suppresses the occurrence of overhangs, and at this time, the isotropic growth of the carbon-based film 44 becomes weaker, and it becomes more difficult to suppress the occurrence of cracks 49 in the carbon-based film 44.

[0097] This phenomenon is believed to occur because, as the high frequency power increases, the excitation of hydrogen gas is promoted, more hydrogen plasma is generated, and isotropic etching of the carbon-based film 44 by hydrogen radicals progresses.

[0098] In this way, it was found that by varying the high-frequency power between at least two different levels, it was possible to realize conditions that promote overhang formation and conditions that suppress overhang formation. Therefore, it was thought that by varying the high-frequency power, it was possible to simultaneously suppress the formation of overhangs in the carbon-based film 44 and the formation of cracks 49 in the carbon-based film 44. The process shown in FIG. 18 below is based on this finding.

[0099] 18 is a flowchart showing a method for forming a carbon-based film according to a third modified example of an embodiment of the technology disclosed herein. The process of FIG. 18 is also realized by the processor of the control unit 34 executing a corresponding control program.

[0100] First, in the film formation apparatus 100, the wafer W having the openings 54 formed in the hard mask layer 40 is placed on the mounting table 14. Next, the supply of the film formation gas into the chamber 11 is started (step S181), and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, high-density plasma is generated from the film formation gas, and a carbon-based film 44 is formed on the top of the openings 54 by hydrocarbon plasma contained in the high-density plasma.

[0101] Next, while generating high density plasma from the deposition gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions that promote overhang generation with a reduced high frequency power (for example, reduced to 100 W) (step S182).

[0102] Next, while generating high-density plasma from the deposition gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions for suppressing overhang generation by increasing the high-frequency power (for example, increasing it to 150 W) (step S183).

[0103] Thereafter, it is determined whether the number of times the processes in steps S182 and S183 have been executed exceeds a specified number (step S184).

[0104] If the number of times that the processes of steps S182 and S183 are performed does not exceed the specified number of times, the process returns to step S182. On the other hand, if the number of times that the processes of steps S182 and S183 are performed exceeds the specified number of times, the supply of the film forming gas into the chamber 11 is stopped (step S185), the supply of high frequency power to the upper electrode 20 is stopped, and the process ends.

[0105] The specified number of times and the duration of the processing of step S182 and the processing of step S183 are set based on the results of prior experiments, as in the processing of FIG. 10, and the specified number of times becomes larger as the desired carbon-based film 44 becomes thicker.

[0106] Furthermore, in the third modified example, it is believed that the greater the difference between the overhang generation suppression condition and the overhang generation promotion condition, the more effectively the overhang in the carbon-based film 44 is eliminated and the more reliably the occurrence of cracks 49 is suppressed. Therefore, it is preferable that the difference in the high-frequency power between the overhang generation suppression condition and the overhang generation promotion condition is large. Furthermore, from the confirmation results shown in Figures 17A to 17C, it is believed that the ratio of the high-frequency power (e.g., 150 W) under the overhang generation suppression condition to the high-frequency power (e.g., 100 W) under the overhang generation promotion condition is preferably 1.5 or more.

[0107] Next, the applicant confirmed the film formation state of the carbon-based film 44 when the temperature of the mounting table 14 was varied. The applicant used the same wafer W as in the first modified example, and performed a film formation process on the wafer W by generating plasma from the film formation gas in the evaluation device 45. At this time, the applicant first set the temperature of the mounting table 14 to 300°C and performed the film formation process on the wafer W. Thereafter, the applicant set the temperature of the mounting table 14 to 360°C and performed the film formation process on the wafer W.

[0108] 19A and 19B are enlarged partial cross-sectional views showing the formation of the carbon-based film 44 when the temperature of the mounting table 14 is varied. When the temperature of the mounting table 14 is set to 300°C, it was confirmed that the carbon-based film 44 grows isotropically on the top of the opening 54 (pattern) and overhangs toward the opening 54, thereby blocking the opening 54 (FIG. 19A). On the other hand, when the temperature of the mounting table 14 is set to 360°C, it was confirmed that the carbon-based film 44 is formed on the top of the opening 54, but does not overhang toward the opening 54 (FIG. 19B).

[0109] From the above-described film formation mode, it was considered that a decrease in the temperature of the mounting table 14 corresponds to a condition that promotes the occurrence of an overhang, and at this time, the isotropic growth of the carbon-based film 44 becomes stronger, and the occurrence of cracks 49 in the carbon-based film 44 is suppressed. On the other hand, it was considered that an increase in the temperature of the mounting table 14 corresponds to a condition that suppresses the occurrence of an overhang, and at this time, the isotropic growth of the carbon-based film 44 becomes weaker, and the occurrence of cracks 49 in the carbon-based film 44 is difficult to suppress.

[0110] This phenomenon is thought to occur because, as the temperature of the mounting table 14 rises, the ambient temperature in the vicinity of the wafer W also rises, and at this time, the etching power of the hydrogen radicals increases, and the isotropic etching of the carbon-based film 44 by the hydrogen radicals progresses. It is also thought that this is because, as the temperature of the mounting table 14 rises, the ambient temperature in the vicinity of the wafer W also rises, and the probability of adhesion of highly isotropic hydrocarbon radicals decreases.

[0111] In this way, it was found that by varying the temperature of the mounting table 14 between two different levels, it is possible to achieve conditions that promote overhang formation and conditions that suppress overhang formation. Therefore, it was thought that varying the temperature of the mounting table 14 can simultaneously suppress the formation of overhangs in the carbon-based film 44 and the formation of cracks 49 in the carbon-based film 44. The process shown in FIG. 20 below is based on this finding.

[0112] 20 is a flowchart showing a carbon-based film forming method according to a fourth modified example of an embodiment of the technology disclosed herein. The process of FIG. 20 is also realized by the processor of the control unit 34 executing a corresponding control program.

[0113] First, in the film formation apparatus 100, the wafer W having the openings 54 formed in the hard mask layer 40 is placed on the mounting table 14. Next, the supply of the film formation gas into the chamber 11 is started (step S201), and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, high-density plasma is generated from the film formation gas, and a carbon-based film 44 is formed on the top of the openings 54 by hydrocarbon plasma contained in the high-density plasma.

[0114] Next, while generating high density plasma from the film-forming gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions that promote overhang formation, in which the temperature of the mounting table 14 is lowered (step S202).

[0115] Next, while generating high-density plasma from the film-forming gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions for suppressing overhang generation, in which the temperature of the mounting table 14 is increased (step S203).

[0116] Thereafter, it is determined whether the number of times the processes in steps S202 and S203 have been executed exceeds a specified number (step S204).

[0117] If the number of times that the processes of steps S202 and S203 are performed does not exceed the specified number, the process returns to step S202. On the other hand, if the number of times that the processes of steps S202 and S203 are performed exceeds the specified number, the supply of the film forming gas into the chamber 11 is stopped (step S205), the supply of high frequency power to the upper electrode 20 is stopped, and the process ends.

[0118] The specified number of times and the duration of the processing of step S202 and the processing of step S203 are set based on the results of prior experiments, as in the processing of FIG. 10, and the specified number of times increases particularly as the desired carbon-based film 44 becomes thicker.

[0119] Also, in the fourth modification, it is considered that the greater the difference between the overhang-suppressing condition and the overhang-promoting condition, the more effectively the overhang of the carbon-based film 44 is eliminated and the more reliably the occurrence of cracks 49 is suppressed. Therefore, it is preferable that the difference in temperature of the mounting table 14 between the overhang-suppressing condition and the overhang-promoting condition is large. Furthermore, based on the confirmation results shown in FIGS. 19A and 19B , it is considered that the ratio of the temperature of the mounting table 14 under the overhang-suppressing condition (e.g., 360° C.) to the temperature of the mounting table 14 under the overhang-promoting condition (e.g., 300° C.) is preferably 1.2 or more.

[0120] Next, the applicant confirmed the film formation state of the carbon-based film 44 when the pressure inside the chamber 11 was varied. The applicant used a wafer W similar to that in the first modified example, and performed a film formation process on the wafer W by generating plasma from the film formation gas in the evaluation device 45. At this time, the applicant first performed the film formation process on the wafer W by setting the pressure inside the chamber 11 to 1 Torr. Thereafter, the applicant performed the film formation process on the wafer W by setting the pressure inside the chamber 11 to 1.1 Torr. Furthermore, the applicant performed the film formation process on the wafer W by setting the pressure inside the chamber 11 to 1.2 Torr.

[0121] 21A to 21C are enlarged partial cross-sectional views showing the deposition state of the carbon-based film 44 when the pressure inside the chamber 11 is varied. Fig. 21A shows the case where the pressure inside the chamber 11 is set to 1 Torr, Fig. 21B shows the case where the pressure inside the chamber 11 is set to 1.1 Torr, and Fig. 21C shows the case where the pressure inside the chamber 11 is set to 1.2 Torr.

[0122] 21A to 21C, it was confirmed that when the pressure inside the chamber 11 was reduced, the carbon-based film 44 was formed on the top of the opening 54 (pattern), but the carbon-based film 44 overhangs toward the opening 54, narrowing the opening 54. It was also confirmed that when the pressure inside the chamber 11 was increased, the carbon-based film 44 was formed on the top of the opening 54, but the carbon-based film 44 did not overhang toward the opening 54.

[0123] From the above-described film formation mode, it was considered that a decrease in the pressure inside the chamber 11 corresponds to a condition that promotes the occurrence of overhang, and at this time, the isotropic growth of the carbon-based film 44 becomes stronger, and the occurrence of cracks 49 in the carbon-based film 44 is suppressed. Also, it was considered that an increase in the pressure inside the chamber 11 corresponds to a condition that suppresses the occurrence of overhang, and at this time, the isotropic growth of the carbon-based film 44 becomes weaker, and the occurrence of cracks 49 in the carbon-based film 44 is difficult to suppress.

[0124] This phenomenon is thought to occur because the density of the hydrogen plasma generated from the hydrogen gas increases as the pressure inside the chamber 11 increases, and the isotropic etching of the carbon-based film 44 by the hydrogen radicals progresses.

[0125] In this way, it was found that conditions for promoting overhang formation and conditions for suppressing overhang formation can be realized by varying the pressure inside the chamber 11 between at least two different levels. Therefore, it was thought that by varying the pressure inside the chamber 11, it is possible to simultaneously suppress the formation of overhangs in the carbon-based film 44 and the formation of cracks 49 in the carbon-based film 44. The process shown in FIG. 22 below is based on this finding.

[0126] 22 is a flowchart showing a carbon-based film forming method according to a fifth modified example of an embodiment of the technology disclosed herein. The process of FIG. 22 is also realized by the processor of the control unit 34 executing a corresponding control program.

[0127] First, in the film formation apparatus 100, the wafer W having the openings 54 formed in the hard mask layer 40 is placed on the mounting table 14. Next, the supply of the film formation gas into the chamber 11 is started (step S221), and the pressure inside the chamber 11 having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, high-density plasma is generated from the film formation gas, and a carbon-based film 44 is formed on the top of the openings 54 by hydrocarbon plasma contained in the high-density plasma.

[0128] Next, while generating high-density plasma from the deposition gas, deposition of the carbon-based film 44 is continued for a certain period of time under conditions that promote overhang generation by reducing the pressure inside the chamber 11 (for example, to 1 Torr) (step S222).

[0129] Next, while generating high-density plasma from the deposition gas, the pressure inside the chamber 11 is increased (for example, increased to 1.2 Torr) and deposition of the carbon-based film 44 is continued for a certain period of time under conditions that suppress overhang generation (step S223).

[0130] Thereafter, it is determined whether the number of times the processes in steps S222 and S223 have been executed exceeds a specified number (step S224).

[0131] If the number of times that the processes of steps S222 and S223 are executed does not exceed the specified number of times, the process returns to step S222. On the other hand, if the number of times that the processes of steps S222 and S223 are executed exceeds the specified number of times, the supply of the film forming gas into the chamber 11 is stopped (step S225), the supply of the pressure inside the chamber 11 to the upper electrode 20 is stopped, and this process ends.

[0132] The specified number of times and the duration of the processing of step S222 and the processing of step S223 are set based on the results of prior experiments, etc., as in the processing of FIG. 10, and the specified number of times becomes larger particularly as the desired carbon-based film 44 becomes thicker.

[0133] Also, in the fifth modification, it is believed that the greater the difference between the overhang generation suppression condition and the overhang generation promotion condition, the more effectively the overhang in the carbon-based film 44 is eliminated and the more reliably the occurrence of cracks 49 is suppressed. Therefore, it is preferable that the difference in the internal pressure of chamber 11 under the overhang generation suppression condition and the overhang generation promotion condition be large. Furthermore, from the confirmation results shown in Figures 21A to 21C, it is believed that the ratio of the internal pressure of chamber 11 under the overhang generation suppression condition (e.g., 1.2 Torr) to the internal pressure of chamber 11 under the overhang generation promotion condition (e.g., 1 Torr) is preferably 1.2 or more.

[0134] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the present disclosure.

[0135] In the above-described embodiment and its modifications, the flow rate of hydrogen gas, the flow rate of acetylene gas, the total flow rate of film formation gas, the radio-frequency power, the temperature of the mounting table 14, or the pressure inside the chamber 11 was varied during the film formation process of the carbon-based film 44. However, the process conditions that can be varied to achieve the overhang formation promoting condition or the overhang formation suppressing condition are not limited to these. For example, the impedance between the lower electrode 17 and ground may be varied by the impedance circuit 35. In this case, it is believed that the energy of hydrocarbon ions incident on the wafer W can be changed, thereby changing the growth morphology of the carbon-based film 44. In other words, it is believed that the overhang formation promoting condition or the overhang formation suppressing condition can be achieved by varying the impedance between the lower electrode 17 and ground.

[0136] Furthermore, the base layer on which the carbon-based film 44 is formed is not limited to a mask made of an oxynitride film, an insulating film in which a plurality of oxide films and a plurality of nitride films are alternately stacked, or a single layer of oxide film, but may also be a single layer of nitride film or a wiring layer made of metal. Note that the pattern formed in the base layer on which the carbon-based film 44 is formed may be either a hole or a trench.

[0137] Furthermore, in the above-described embodiment and its variations, only one process condition is varied to achieve the overhang formation promoting condition or the overhang formation suppressing condition. However, the overhang formation promoting condition or the overhang formation suppressing condition may be achieved by varying two or more process conditions in a coordinated manner. For example, the hydrogen gas flow rate and the temperature of the mounting table 14 may be varied in a coordinated manner, the total flow rate of the film formation gas and the high-frequency power may be varied in a coordinated manner, or the acetylene gas flow rate and the pressure inside the chamber 11 may be varied in a coordinated manner.

[0138] Incidentally, in order to improve the throughput during the deposition of the carbon-based film 44, it is preferable to increase the deposition rate of the carbon-based film 44. Therefore, the present applicant has investigated further increasing the high frequency power (increasing the output) during the deposition of the carbon-based film 44, with the aim of improving the deposition rate of the carbon-based film 44.

[0139] 23A and 23B are diagrams showing the film formation form of a carbon-based film 44 when a film formation process is performed using high-output high-frequency power, where FIG. 23A is an enlarged partial plan view of a wafer W after the film formation process has been performed, and FIG. 23B is an enlarged partial cross-sectional view of a wafer W after the film formation process has been performed.

[0140] At this time, the applicant set the flow rate of acetylene gas in the film formation gas to 30 sccm, the flow rate of hydrogen gas to 32 sccm, and the output of 40 MHz high frequency power supplied from the high frequency power supply 32 to the upper electrode 20 to 600 W. Then, plasma was generated from the film formation gas to perform a film formation process on the wafer W to form the carbon-based film 44. Note that, in the wafer W used here, the oxynitride film 41 had been removed prior to the formation of the carbon-based film 44.

[0141] The applicant confirmed that increasing the output of high-frequency power improved the deposition rate of the carbon-based film 44. However, at the same time, as shown in Fig. 23A, it was confirmed that several seam-like, crack-like defects 55 connecting the holes 48 occurred on the surface of the carbon-based film 44. Furthermore, as shown in Fig. 23B, it was confirmed that although the occurrence of overhangs in the carbon-based film 44 was suppressed, constrictions occurred in the carbon-based film 44 near the boundary with the hard mask layer 40.

[0142] The following mechanism has been inferred as the reason why defects 55 and constrictions are more likely to occur when the radio frequency power output is increased. Specifically, increasing the radio frequency power output promotes the excitation of acetylene gas, generating many hydrocarbon ions and hydrocarbon radicals. This also promotes the excitation of hydrogen gas contained in the film-forming gas, generating many hydrogen radicals. If more hydrogen radicals are generated than necessary, the isotropic etching of the carbon-based film 44 by the hydrogen radicals becomes stronger, inhibiting the isotropic growth of the carbon-based film 44. As a result, the anisotropic growth of the carbon-based film 44 is accelerated by the increase in hydrocarbon ions. As a result, the carbon-based film 44 grows anisotropically faster than the isotropic growth of the carbon-based film 44 can fill the microdefects on the surface of the hard mask layer 40, accentuating the microdefects and eventually forming defects 55. Furthermore, when the isotropic etching of the carbonaceous film 44 becomes stronger due to an increase in hydrogen radicals, the carbonaceous film 44 does not form an overhang, but rather is largely etched away, causing a constriction in the carbonaceous film 44 .

[0143] Therefore, in order to appropriately reduce the amount of hydrogen radicals generated when the high-frequency power output is increased, the applicant considered reducing the flow rate of hydrogen gas, which is the source of hydrogen radicals, when the high-frequency power output is increased.

[0144] Furthermore, in the technology of the present disclosure, in order to simultaneously suppress the occurrence of overhang in the carbon-based film 44 and the occurrence of cracks 49 in the carbon-based film 44, the film formation process is performed on the wafer W while varying the high frequency power as in the process of Fig. 18. Here, when the high frequency power varies from high output to low output, the carbon-based film 44 tends to grow isotropically, and as a result, the carbon-based film 44 tends to overhang.

[0145] However, when the excitation of hydrogen gas is slowed and the number of hydrogen radicals is reduced due to a reduction in the output of high frequency power, the isotropic etching of the carbon-based film 44 is weakened, which may cause excessive overhang growth of the carbon-based film 44 and reduce the effective opening diameter of the hole 48. To address this, it is necessary to prevent the reduction in hydrogen radicals and ensure a certain degree of isotropic etching power for the carbon-based film 44, thereby suppressing the excessive growth of the overhang of the carbon-based film 44.

[0146] Therefore, in order to appropriately increase the amount of hydrogen radicals generated when the high frequency power output is reduced, the applicant considered increasing the flow rate of hydrogen gas, which is the source of hydrogen radicals, when the high frequency power output is reduced.

[0147] That is, assuming that high-output radio frequency power is used, when the radio frequency power is varied between high and low output to form the carbon-based film 44, the flow rate of the hydrogen gas is reduced when the radio frequency power is increased in output, and the flow rate of the hydrogen gas is increased when the radio frequency power is decreased in output.

[0148] 24 is a sequence diagram showing fluctuations in high-frequency power and fluctuations in the flow rate of hydrogen gas during the film formation process of a carbon-based film 44 when high-output high-frequency power is used. In the film formation process shown in FIG. 24 , the applicant set the internal pressure of the chamber 11 to 500 mTorr, the temperature of the mounting table 14 to 360° C., and supplied 40 MHz high-frequency power from the high-frequency power supply 32 to the upper electrode 20.

[0149] The radio frequency power (one of the two processing conditions) was varied between two levels: a high output of 600 W (one of the two levels) and a low output of 300 W (the other of the two levels). The flow rate of the hydrogen gas (the other of the two processing conditions) was varied between two levels: a low flow rate of 10 sccm (one of the two levels) and a high flow rate of 100 sccm (the other of the two levels).

[0150] At this time, the flow rate of the hydrogen gas was changed to a low flow rate in conjunction with the change in the high frequency power output, and the flow rate of the hydrogen gas was changed to a low flow rate in conjunction with the change in the high frequency power output, thereby generating plasma from the film formation gas and forming a carbon-based film 44 on the wafer W. Film formation using high-output high frequency power and film formation using low-output high frequency power were alternately repeated five times each.

[0151] Note that the "linkage" in the film formation process shown in FIG. 24 is not limited to the case where the fluctuations in the high frequency power and the fluctuations in the hydrogen gas flow rate occur simultaneously (synchronized). Specifically, it is sufficient that the period during which the high frequency power is fluctuated and maintained at a high output overlaps at least a portion of the period during which the hydrogen gas flow rate is fluctuated and maintained at a low flow rate. Furthermore, it is sufficient that the period during which the high frequency power is fluctuated and maintained at a low output overlaps at least a portion of the period during which the hydrogen gas flow rate is fluctuated and maintained at a high flow rate. However, the shift between the period during which the high frequency power is maintained and the period during which the hydrogen gas flow rate is maintained at a low flow rate must be limited to an extent that does not promote the enhancement of micro-defects associated with the increase in the high frequency power output. Furthermore, the shift between the period during which the low frequency power is maintained and the period during which the hydrogen gas flow rate is maintained at a high flow rate must be limited to an extent that does not promote the excessive growth of overhangs in the carbon-based film 44 associated with the decrease in the high frequency power output.

[0152] 24, the period during which the high-frequency power is maintained at a high output is preferably set longer than the period during which the high-frequency power is maintained at a low output, since the purpose of the film formation process shown in FIG. 24 is to improve the film formation rate of the carbon-based film 44. For example, the period during which the high-frequency power is maintained at a low output is set to 1 second, while the period during which the high-frequency power is maintained at a high output is set to 2 seconds.

[0153] Then, after performing the film formation process shown in Fig. 24, the applicant confirmed the form of the formed carbon-based film 44. Figures 25A and 25B are views showing the form of the carbon-based film 44 formed when the wafer is subjected to the film formation process shown in Fig. 24, with Fig. 25A being an enlarged partial plan view of the wafer W after the film formation process, and Fig. 25B being an enlarged partial cross-sectional view of the wafer W after the film formation process. Note that, even in the wafer W used here, the oxynitride film 41 was removed prior to the formation of the carbon-based film 44.

[0154] 25A and 25B , the applicant confirmed that no crack-like defects 55 ( FIG. 23A ) connecting the holes 48 occurred on the surface of the carbon-based film 44. The applicant also confirmed that the occurrence of overhangs in the carbon-based film 44 was suppressed, and that no constrictions occurred in the carbon-based film 44 near the boundary with the hard mask layer 40. That is, it was found that by performing the film formation process shown in FIG. 24 , it was possible to achieve both an improvement in throughput due to an increase in the film formation rate of the carbon-based film 44 and suppression of the occurrence of defects 55 and constrictions in the carbon-based film 44.

[0155] Incidentally, the oxynitride film 41 of the wafer W is used as a mask for forming a pattern on the hard mask layer 40. Therefore, when the hard mask layer 40 is etched, the oxynitride film 41 is attacked by an etchant or the like, and the surface shape is distorted. Specifically, the cross-sectional shape of the oxynitride film 41 exhibits a shape with a chipped shoulder (see FIG. 26B ). Such a deformation of the surface shape can cause defects, so it is expected that a large number of defects 55 will occur if a simple film formation process of a carbon-based film 44 is performed on a wafer W from which the oxynitride film 41 has not been removed.

[0156] Therefore, when forming a carbon-based film 44 on a wafer W from which the oxynitride film 41 had not been removed, the applicant performed the film formation process shown in Fig. 24 and confirmed the form of the formed carbon-based film 44. Figures 26A and 26B are views showing the form of the carbon-based film 44 formed when the film formation process shown in Fig. 24 is performed on a wafer W from which the oxynitride film 41 had not been removed, with Fig. 26A being an enlarged partial plan view of the wafer W after the film formation process, and Fig. 26B being an enlarged partial cross-sectional view of the wafer W after the film formation process.

[0157] 25A and 25B , the applicant confirmed that no crack-like defects 55 connecting the holes 48 occurred on the surface of the carbon-based film 44. The applicant also confirmed that the occurrence of overhangs in the carbon-based film 44 was suppressed, and that no constrictions occurred in the carbon-based film 44 near the boundary with the hard mask layer 40. In other words, it was found that even if the oxynitride film 41 with a deformed surface remains, by performing the film formation process shown in FIG. 24 , it is possible to improve throughput by increasing the film formation rate of the carbon-based film 44, and to suppress the occurrence of defects 55 and constrictions in the carbon-based film 44.

[0158] In the above-described embodiment and its variations, each processing condition is varied between two different values ​​to achieve the overhang formation promoting condition and the overhang formation suppressing condition. However, each processing condition may be varied between three or more different values. For example, the hydrogen gas flow rate may be varied between three levels, i.e., 18 sccm, 25 sccm, and 32 sccm, and this variation may be repeated. Furthermore, for example, the high-frequency power may be varied between three levels, i.e., 100 W, 300 W, and 400 W, and this variation may be repeated. Furthermore, when two or more processing conditions are varied in conjunction with each other, each processing condition may be varied between three or more different values. In this case, when one processing condition is varied to one of the levels, the other processing condition is also varied to one of the levels in conjunction with each other.

[0159] In the above-described embodiment and its modified examples, when the film formation process under the overhang formation promoting condition and the film formation process under the overhang formation suppressing condition are repeated, the film formation process under the overhang formation promoting condition is performed first. However, the film formation process under the overhang formation suppressing condition may be performed first.

[0160] In the above-described film formation process, a hydrocarbon gas (acetylene gas) is used as the hydrogen compound gas contained in the film formation gas. However, other hydrogen compound gases, such as silane gas, which is a silicon hydrogen compound gas, or borane gas, which is a boron hydrogen compound gas, may be used instead of the hydrocarbon gas.

[0161] Furthermore, the film formation apparatus that performs the carbon-based film formation method according to the above-described embodiment and its modified examples is not limited to the film formation apparatus 100 of Fig. 1. Any film formation apparatus that can reduce the energy of ions incident on the wafer W can perform the carbon-based film formation method according to the above-described embodiment and its modified examples.

[0162] This application claims priority based on Japanese Patent Application No. 2024-028619 filed on February 28, 2024 and Japanese Patent Application No. 2024-110939 filed on July 10, 2024, the entire contents of which are incorporated herein by reference.

[0163] W wafer 11 chamber 14 mounting table 42, 54 opening 44 carbon-based film 48 hole 49 crack 100 film forming apparatus

Claims

1. A method for forming a carbon-based film, comprising: a film-forming process in which a substrate having a pattern is placed inside a processing chamber; and a plasma is generated from a film-forming gas consisting only of hydrocarbon gas, argon gas, and hydrogen gas using high-frequency power to form a carbon-based film on the substrate; wherein the film-forming process selectively forms the carbon-based film on the top of the pattern by repeatedly varying at least one of a plurality of processing conditions including the flow rate of the hydrogen gas, the flow rate of the hydrocarbon gas, the total flow rate of the film-forming gas, the high-frequency power, the temperature of a mounting table on which the substrate is placed, and the internal pressure of the processing chamber.

2. The carbon-based film deposition method according to claim 1, wherein in the film deposition step, the at least one processing condition is varied between two mutually different levels of values, and the variation is repeated.

3. The method for forming a carbon-based film according to claim 2, wherein, in the film formation process, when the at least one processing condition is one of the two levels of values, anisotropic growth of the carbon-based film is prioritized, and when the at least one processing condition is the other of the two levels of values, the carbon-based film grows not only anisotropically but also isotropically.

4. A method for forming a carbon-based film according to claim 3, wherein the time during which the carbon-based film grows not only anisotropically but also isotropically, and the time during which anisotropic growth of the carbon-based film is preferred, are adjusted according to the form of the carbon-based film to be formed.

5. The method for forming a carbon-based film according to claim 3, wherein, when the at least one processing condition is the flow rate of the hydrogen gas, the ratio of the flow rate of the hydrogen gas when the carbon-based film grows not only anisotropically but also isotropically to the flow rate of the hydrogen gas when anisotropic growth of the carbon-based film is preferred is 1.2 times or more.

6. The method for forming a carbon-based film according to claim 3, wherein, when the at least one process condition is the total flow rate of the film-forming gas, the ratio of the total flow rate of the film-forming gas when the carbon-based film grows not only anisotropically but also isotropically to the total flow rate of the film-forming gas when anisotropic growth of the carbon-based film is preferred is 1.2 times or more.

7. The method for forming a carbon-based film according to claim 3, wherein, when the at least one processing condition is the flow rate of the hydrocarbon gas, the ratio of the flow rate of the hydrocarbon gas when the carbon-based film grows not only anisotropically but also isotropically to the flow rate of the hydrocarbon gas when anisotropic growth of the carbon-based film is preferred is 1.5 times or more.

8. The method for forming a carbon-based film according to claim 3, wherein, when the at least one processing condition is the high-frequency power, the ratio of the high-frequency power when the carbon-based film grows not only anisotropically but also isotropically to the high-frequency power when anisotropic growth of the carbon-based film is preferred is 1.5 times or more.

9. The carbon-based film deposition method according to claim 1, wherein in the film deposition step, two of a plurality of processing conditions including the flow rate of the hydrogen gas, the flow rate of the hydrocarbon gas, the total flow rate of the film deposition gas, the high-frequency power, the temperature of the mounting table on which the substrate is placed, and the internal pressure of the processing chamber are repeatedly varied, and when the variation of the two processing conditions is repeated, each of the two processing conditions is varied to two mutually different levels of values, and the other of the two processing conditions is varied in conjunction with the variation of one of the two processing conditions.

10. A method for forming a carbon-based film according to claim 9, wherein, when the two processing conditions are repeatedly varied in the film formation process, a period during which one of the two processing conditions is maintained at one of the two level values ​​overlaps with at least a portion of a period during which the other of the two processing conditions is maintained at one of the two level values, and a period during which one of the two processing conditions is maintained at the other of the two level values ​​overlaps with at least a portion of a period during which the other of the two processing conditions is maintained at the other of the two level values.

11. The method for forming a carbon-based film according to claim 10, wherein, in the film formation step, when one of the two processing conditions is one of the two level values, anisotropic growth of the carbon-based film takes precedence, and when one of the two processing conditions is the other of the two level values, the carbon-based film grows not only anisotropically but also isotropically.

12. A method for forming a carbon-based film as described in claim 11, wherein one of the two processing conditions is the high-frequency power that fluctuates between two levels of values, high output and low output, and the other of the two processing conditions is the flow rate of the hydrogen gas that fluctuates between two levels of values, high flow rate and low flow rate, and the flow rate of the hydrogen gas fluctuates to the low flow rate in conjunction with the fluctuation of the high-frequency power to the high output, and the flow rate of the hydrogen gas fluctuates to the high flow rate in conjunction with the fluctuation of the high-frequency power to the low output.

13. The carbon-based film deposition method according to claim 12, wherein, in the film deposition process, when the high-frequency power and the flow rate of the hydrogen gas are repeatedly changed, the period during which the high-frequency power is maintained at the high output is longer than the period during which the high-frequency power is maintained at the low output.

14. A film formation apparatus comprising a processing chamber with a reduced pressure inside, which accommodates a substrate having a pattern inside the processing chamber and uses high-frequency power to generate plasma from a film formation gas consisting only of hydrocarbon gas, argon gas, and hydrogen gas to form a carbon-based film on the substrate, further comprising a control unit, which executes a film formation step of selectively forming the carbon-based film on the top of the pattern by repeatedly varying at least one of a plurality of processing conditions including the flow rate of the hydrogen gas, the flow rate of the hydrocarbon gas, the total flow rate of the film formation gas, the high-frequency power, the temperature of a mounting table on which the substrate is placed, and the internal pressure of the processing chamber.

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