Film formation method and film formation device

Abstract

[Problem] To selectively and vertically form a carbon-based film on the top of a pattern even when the substrate resides at low temperatures. [Solution] In the case of placing a pattern-bearing substrate in the interior of a processing chamber, supplying a film-forming gas into the interior of the processing chamber, and generating a plasma from the film-forming gas by high-frequency power to perform a film-forming process on the substrate, the film-forming gas contains a plurality of types of hydrocarbon gases and a rare gas, and, when the plurality of types of hydrocarbon gases are excited and converted into plasma, the active species generated from each hydrocarbon gas have different configurations.

Description

Film forming method and film forming apparatus

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

[0002] A known method for producing hydrogenated amorphous carbon thin films is a deposition method using plasma generated from a hydrocarbon gas. In this deposition method, after depressurizing the vacuum chamber of a CVD apparatus, a mixed gas consisting of ethylene (C2H4) gas and methane (CH4) gas, or ethylene gas and acetylene (C2H2) gas, diluted with an appropriate amount of hydrogen gas, is introduced into the vacuum chamber. Then, while a susceptor carrying a substrate is rotated inside the vacuum chamber, 13.56 MHz high-frequency power of 20 W to 300 W is applied from a high-frequency power source between the electrode and the susceptor. At this time, plasma is generated from the mixed gas, and a hydrogenated amorphous carbon thin film is deposited on the substrate (see, for example, Patent Document 1). However, the deposition method described in Patent Document 1 only forms a carbon-based film that completely covers the surface of the substrate.

[0003] Meanwhile, in the manufacture of three-dimensional NAND flash memories, a technique has been developed for increasing the effective thickness of a mask film formed on the surface of a substrate during the formation of deep trenches or deep holes by etching. As this technique, the present applicant has proposed a deposition method for selectively and vertically depositing an amorphous carbon-based film on the top of a pattern (e.g., the top of a trench) formed on the mask film. In this deposition method, acetylene (C2H2) gas is used as a hydrocarbon gas in the deposition gas, and hydrogen (H2) gas is further added to the deposition gas. The amorphous carbon-based film deposited on the top of the pattern by plasma generated from the acetylene gas is then etched by hydrogen radicals so that it grows vertically without overhanging the pattern. In particular, since etching by hydrogen radicals becomes stronger as the substrate temperature increases, a deposition method using a deposition gas containing acetylene gas and hydrogen gas is performed after the substrate temperature is raised to, for example, approximately 350°C.

[0004] Japanese Patent Application Publication No. 1-301506

[0005] The technique according to the present disclosure deposits a carbon-based film selectively and vertically on the top of a pattern even when the substrate is at a low temperature.

[0006] One aspect of the technology disclosed herein is a film formation method that includes placing a substrate having a pattern inside a processing chamber, supplying a film formation gas into the processing chamber, and generating plasma from the film formation gas using high-frequency power to perform a film formation process on the substrate, wherein the film formation gas contains multiple types of hydrocarbon gases and a rare gas, and when the multiple types of hydrocarbon gases are excited to become plasma, the compositions of active species generated from each of the hydrocarbon gases are different.

[0007] According to the technique of the present disclosure, even if the substrate is at a low temperature, a carbon-based film can be selectively and vertically formed on the top of a pattern.

[0008] 1 is a cross-sectional view schematically showing the configuration of a film forming apparatus according to an embodiment of the technology disclosed herein; FIG. 2 is a partially enlarged cross-sectional view showing the film formation form of a carbon-based film when the type of hydrocarbon gas contained in the film formation gas is changed; FIG. 3 is a partially enlarged cross-sectional view showing the film formation form of a carbon-based film when the type of hydrocarbon gas contained in the film formation gas is changed; FIG. 4 is a partially enlarged cross-sectional view showing the film formation form of a carbon-based film when the type of hydrocarbon gas contained in the film formation gas is changed; FIG. 5 is a partially enlarged cross-sectional view showing the film formation form of a carbon-based film when a film formation process is performed using a film formation gas containing ethylene gas and acetylene gas as the hydrocarbon gas; and FIG. 6 is a partially enlarged cross-sectional view showing the film formation form of a carbon-based film when a film formation process is performed using a film formation gas containing only ethylene gas as the hydrocarbon gas in a case where the aspect ratio of the trench is low.

[0009] In recent years, with the further miniaturization of wiring and the like in semiconductor devices, it has become necessary to form trenches with widths of several nanometers to several tens of nanometers in mask films. To meet this demand, patterns are formed in mask films using extreme ultraviolet (EUV) light with a wavelength of 13.5 nm. Chemically amplified resists are used as the material for such mask films, but the heat resistance temperature of chemically amplified resists is low, for example, around 200° C.

[0010] However, etching of carbon-based films by hydrogen radicals becomes considerably weaker at temperatures below 200° C., making it difficult to shape the carbon-based film deposited on the top of the pattern. As a result, even when hydrogen gas is added, the carbon-based film grows while overhanging so as to block the trench, and in the subsequent etching of the base film covered by the mask film, the shape of the pattern formed on the mask film may not be reflected in the base film.

[0011] In contrast, the technology according to the present disclosure controls the shape of the carbon-based film by using a film-forming gas containing multiple types of hydrocarbon gases without adding hydrogen gas to the film-forming gas.

[0012] 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 an embodiment of the technology according to the present disclosure. The film formation apparatus is a capacitively coupled plasma processing apparatus that generates plasma from a film formation gas to form a film.

[0013] 1, a film forming apparatus 10 includes a substantially cylindrical metallic chamber 11 (processing chamber), which is grounded. A wafer W (substrate) is accommodated inside the chamber 11, and a mounting table 12 on which the wafer W is placed is also arranged.

[0014] The mounting table 12 is made of an insulator and includes a grounded lower electrode (not shown). The mounting table 12 may be made of metal and function as the lower electrode. A heater and a coolant passage (neither of which is shown) are embedded within the mounting table 12. The heater generates heat using externally supplied power to heat the mounted wafer W, and the coolant passage circulates an externally supplied coolant to cool the mounted wafer W. A heat transfer gas may be supplied between the mounting table 12 and the wafer W to improve heat transfer between the mounting table 12 and the wafer W. The mounting table 12 has a plurality of lift pins (not shown) inserted therein that can be protruded and retracted from its upper surface. The lift pins are raised and lowered by a lift mechanism (not shown) to transfer the wafer W to and from the mounting table 12.

[0015] An opening is formed in the top of the chamber 11, and a shower head 13 is fitted into the opening via an insulating member 14 so as to face the mounting table 12. The shower head 13 is made of a cylindrical metal member and functions as an upper electrode. Alternatively, only a portion of the shower head 13 may be made of metal, and the metal portion may function as the upper electrode. The shower head 13 includes a shower body 15 having an opening at its bottom and a shower plate 16 arranged to close the opening of the shower body 15. The internal space between them functions as a gas diffusion space. The shower plate 16 also has multiple gas discharge holes 17 that penetrate the shower plate 16 in the thickness direction. The shower head 13 also has gas inlet holes 18, through which a film formation gas supplied from a gas supply unit 19 (described later) is introduced into the gas diffusion space. The film formation gas introduced into the gas diffusion space is then diffused and discharged from each gas outlet hole 17 into a space S between the shower head 13 and the mounting table 12 inside the chamber 11 (hereinafter referred to as the "processing space").

[0016] The film forming apparatus 10 further includes a gas supply unit 19. The gas supply unit 19 supplies a plurality of gases, such as a film forming gas and a purge gas. The gas supply unit 19 has a plurality of gas sources, flow rate controllers, and on-off valves, and adjusts the flow rate of each gas depending on the process. In this embodiment, a mixed gas containing a hydrocarbon gas and a rare gas is used as the film forming gas supplied by the gas supply unit 19.

[0017] A high frequency power supply 21 is connected to the shower head 13 via a power supply line 20. The high frequency power supply 21 applies a high frequency voltage having a frequency of 100 kHz to 220 MHz, for example, 450 kHz, to the shower head 13.

[0018] A matching box 22 is connected downstream of the high frequency power supply 21 on the power feed line 20. The matching box 22 matches the load impedance to the internal (or output) impedance of the high frequency power supply 21. Furthermore, a circuit for limiting the applied voltage, such as a clamp circuit 23, is provided downstream of the matching box 22 on the power feed line 20 between the high frequency power supply 21 and the shower head 13.

[0019] The clamp circuit 23 has a capacitor 24 provided downstream of the matching device 22, and a ground circuit 26 branching off from the power supply line 20 downstream of the capacitor 24 and grounded via a diode 25. The capacitor 24 has a capacitance sufficient to reduce the impedance seen from the high frequency power supply 21.

[0020] When the high frequency power supply 21 outputs a positive voltage, the clamp circuit 23 passes a high frequency current through the diode 25 and flows it to the ground side, due to the storage function of the capacitor 24 and the rectification function of the diode 25 in the ground circuit 26. At this time, the high frequency power output by the high frequency power supply 21 is stored in the capacitor 24. This suppresses the positive voltage of the high frequency voltage applied to the shower head 13. On the other hand, when the high frequency power supply 21 outputs a negative voltage, the diode 25 does not pass the high frequency current, so the high frequency current does not flow to the ground side via the ground circuit 26. At this time, the power output by the high frequency power supply 21 and the power stored in the capacitor 24 are supplied to the shower head 13.

[0021] Although the film forming apparatus 10 is provided with the clamp circuit 23 as a circuit for suppressing the positive voltage of the high-frequency voltage, other types of circuits capable of suppressing the positive voltage of the high-frequency voltage may be provided instead of the clamp circuit 23. Furthermore, in the clamp circuit 23, the high-frequency power output by the high-frequency power supply 21 may be stored by a blocking capacitor of the matching device 22 instead of the capacitor 24. In this case, the need to provide the capacitor 24 in the clamp circuit 23 can be eliminated.

[0022] In a capacitively coupled plasma processing apparatus, when the lower electrode is grounded, the plasma potential is highly dependent on the potential of the upper electrode. In the film forming apparatus 10, the clamp circuit 23 suppresses the positive voltage, preventing the voltage of the upper electrode from fluctuating significantly toward the positive side. This allows the film forming apparatus 10 to reduce the plasma potential. Furthermore, ions in the plasma are accelerated by the sheath voltage and flow toward the wafer W. However, when the plasma potential is reduced, the absolute value of the sheath voltage (the difference between the plasma potential and the potential of the wafer W (mounting table 12)) generated in the processing space S decreases, and the ions are not accelerated as much. As a result, in the film forming apparatus 10, the ion energy imparted from the plasma to the wafer W mounted on the mounting table 12 is reduced.

[0023] Furthermore, in the film forming apparatus 10, an exhaust port 27 is provided at the bottom of the chamber 11, and an exhaust device 29 is connected to the exhaust port 27 via an exhaust pipe 28. The exhaust device 29 has an automatic pressure control valve and a vacuum pump, and evacuates the inside of the chamber 11 to reduce the pressure and maintain the inside of the chamber 11 at a desired vacuum level. In addition, a load / unload port (not shown) for loading / unloading the wafer W is provided on the sidewall of the chamber 11, and this load / unload port is opened and closed by a gate valve (not shown).

[0024] Furthermore, the film forming apparatus 10 includes a control unit 30, which controls the operation of each component of the film forming apparatus 10. The control unit 30 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 30. When a film forming process is performed in the film forming apparatus 10, the processor of the control unit 30 executes the corresponding control program and controls the operation of each component of the film forming apparatus 10 in accordance with the recipe data.

[0025] Specifically, the control unit 30 controls the gas supply unit 19 and the exhaust device 29 to adjust the pressure inside the chamber 11, and controls the high-frequency power supply 21 to apply a high-frequency voltage to the shower head 13. The control unit 30 also controls the gas supply unit 19 to diffuse and introduce the film formation gas into the chamber 11. At this time, the high-frequency voltage applied to the shower head 13 generates an electric field in the processing space S, which excites the film formation gas into plasma and generates activated species. The activated species perform a film formation process on the wafer W.

[0026] Incidentally, when forming a top vertically grown carbon-based film on the top of a pattern formed on a mask film made of chemically amplified resist, the temperature of the wafer W needs to be maintained at 200° C. or less because the heat resistance temperature of the chemically amplified resist is about 200° C. Therefore, the applicant used the film forming apparatus 10 to confirm the film formation form of the carbon-based film when the type of hydrocarbon gas contained in the film formation gas was changed while maintaining the temperature of the wafer W (specifically, the temperature of the mounting table 12) at 200° C.

[0027] 2A to 2C are partially enlarged cross-sectional views showing the formation of carbon-based films when the type of hydrocarbon gas contained in the film formation gas is changed. In FIGS. 2A to 2C, a mask film 32 made of, for example, a chemically amplified resist is formed on the surface of a substrate 31 made of, for example, silicon (Si) on a wafer W. A pattern, for example, a groove-shaped trench 33, is formed in the mask film 32. The trench 33 penetrates the mask film 32, and the substrate 31 is exposed at the bottom of the trench 33 ( FIGS. 2A to 2C ). In this embodiment, the top of the mask film 32 between two adjacent trenches 33 will be referred to as the "top of the trench 33" hereinafter.

[0028] First, the applicant performed a film formation process on a wafer W in the film formation apparatus 10 using a film formation gas containing only acetylene gas as a hydrocarbon gas (hereinafter referred to as "when acetylene gas is used"). The film formation gas contained argon (Ar) gas as a rare gas in addition to acetylene gas. In this case, the carbon-based film 34 was not formed selectively and vertically on the top of the trench 33, but was formed so as to overhang toward the trench 33, thereby blocking the trench 33. Furthermore, a carbon-based film 34 having a certain thickness (e.g., a thickness of about 7.6 nm) was also formed on the bottom of the trench 33, and the carbon-based film 34 was also formed on the side surfaces of the trench 33 ( FIG. 2A ).

[0029] Next, the applicant performed a film formation process on the wafer W in the film formation apparatus 10 using a film formation gas containing only ethylene gas as the hydrocarbon gas and only argon gas as the rare gas (hereinafter referred to as "when ethylene gas is used"). At this time, a vertically tapered carbon-based film 34 was selectively formed on the top of the trench 33. Note that although a small amount (e.g., a thickness of about 1.7 nm) of the carbon-based film 34 was formed on the bottom of the trench 33, the carbon-based film 34 was not formed on the side surface of the trench 33 ( FIG. 2B ).

[0030] Furthermore, the applicant performed a film formation process on a wafer W in the film formation apparatus 10 using a film formation gas containing only propylene (C3H6) gas as the hydrocarbon gas and only argon gas as the rare gas (hereinafter referred to as "when propylene gas was used"). At this time, a carbon-based film 34 was formed on the top of the trench 33, but the carbon-based film 34 did not block the trench 33. In addition, a thick carbon-based film 34 (e.g., about 10.3 nm thick) was formed on the bottom of the trench 33, and a carbon-based film 34 having a certain thickness (e.g., about 4.3 nm thick) was also formed on the side surface of the trench 33 (FIG. 2C).

[0031] As shown in FIGS. 2A to 2C, it was found that the deposition pattern of the carbon-based film 34 differed depending on the type of hydrocarbon gas. For example, when acetylene gas or propylene gas was used, the carbon-based film 34 was deposited not only on the top of the trench 33 but also on the bottom and side surfaces of the trench 33. This indicates that acetylene gas and propylene gas exhibit conformal properties when depositing the carbon-based film 34. On the other hand, when ethylene gas was used, the carbon-based film 34 was hardly deposited on the bottom or side surfaces of the trench 33, and was selectively deposited only on the top surface of the trench 33. This indicates that ethylene gas exhibits non-conformal properties when depositing the carbon-based film 34. Furthermore, the deposition amount was greatest when acetylene gas was used and least when ethylene gas was used.

[0032] Therefore, in order to find out the reason why the deposition form of the carbon-based film 34 differs depending on the type of hydrocarbon gas, the chemical species generated when each deposition gas is converted into plasma were confirmed using Chemkin, a simulation software from ANSYS.

[0033] First, when acetylene gas was used, it was confirmed that many carbon-based active species such as C and C2 and hydrocarbon-based active species with a low hydrogen element ratio were generated. Also, when ethylene gas was used, it was confirmed that many H2 active species (hydrogen radicals) and hydrocarbon-based active species were generated. Furthermore, when propylene gas was used, it was confirmed that many hydrocarbon-based active species with a high hydrogen element ratio were generated.

[0034] The results of this simulation revealed that the composition of active species generated from the deposition gas changes when the type of hydrocarbon gas is changed. Furthermore, the applicant has inferred the mechanism explained below as to why the composition of active species generated varies depending on the type of hydrocarbon gas.

[0035] That is, acetylene gas contains a triple bond of carbon atoms, and the bond between carbon atoms and hydrogen atoms is easily dissociated, so a large amount of carbon-based active species is produced. Also, since acetylene gas originally has a low atomic ratio of hydrogen to carbon, the atomic ratio of hydrogen in the resulting hydrocarbon-based active species is also low. Although ethylene gas contains a double bond of carbon atoms, it originally has a high atomic ratio of hydrogen to carbon, so a large amount of hydrogen radicals and hydrocarbon-based active species are produced. In propylene gas, methyl (CH3) groups are bonded to carbon atoms, so the methyl groups are easily dissociated, and the atomic ratio of hydrogen in the resulting hydrocarbon-based active species is high.

[0036] Incidentally, the higher the hydrogen element ratio of hydrocarbon-based active species, the lower the sticking coefficient with respect to carbon. When hydrocarbon-based active species with a low sticking coefficient enter the trench 33, a small amount of them adhere near the opening of the trench 33 (i.e., the top), and a relatively large amount of hydrocarbon-based active species reach the bottom of the trench 33. As a result, the carbon-based film 34 is formed not only on the top of the trench 33 but also on the bottom and side surfaces of the trench 33. On the other hand, the lower the hydrogen element ratio of hydrocarbon-based active species, the higher the sticking coefficient with respect to carbon. When hydrocarbon-based active species with a high sticking coefficient enter the trench 33, most of them adhere near the opening (top) of the trench 33. Furthermore, because the sticking coefficient of carbon-based active species is very high, most of the carbon-based active species also adhere near the opening (top) of the trench 33 when they enter the trench 33.

[0037] When acetylene gas is used, as described above, many carbon-based active species and hydrocarbon-based active species with a low hydrogen element ratio are generated. However, because the sticking coefficients of these active species are high, many of these active species adhere near the opening (top) of the trench 33. Furthermore, because the carbon-based film 34 generated from the hydrocarbon-based active species with a low hydrogen element ratio has a high film density, even if hydrogen radicals are generated, etching by these hydrogen radicals is unlikely to proceed. As a result, the carbon-based film 34 is formed so as to overhang toward the trench 33, thereby blocking the trench 33. Furthermore, because the sticking coefficients of the active species generated from acetylene gas are high, these active species that do not adhere near the opening of the trench 33 but enter the interior of the trench 33 adhere to the bottom and side surfaces of the trench 33, and the carbon-based film 34 is formed on the bottom and side surfaces of the trench 33 as well. In this way, acetylene gas is a hydrocarbon gas that exhibits conformality during film formation, since it deposits the carbon-based film 34 not only on the top of the trench 33 but also on the bottom and side surfaces of the trench 33 .

[0038] Furthermore, when ethylene gas is used, as described above, hydrocarbon-based active species are generated. However, since most of the hydrocarbon-based active species are stable acetylene active species, a large amount of hydrocarbon-based active species do not adhere to the mask film 32. Furthermore, since a large amount of hydrogen radicals are generated simultaneously with the hydrocarbon-based active species, the carbon-based film 34 adhered to the bottom and side surfaces of the trench 33 is etched by the hydrogen radicals. As a result, almost no carbon-based film 34 is formed on the bottom and side surfaces of the trench 33, and the carbon-based film 34 is selectively and vertically formed mainly on the top surface of the trench 33. Furthermore, the carbon-based film 34 formed on the top surface of the trench 33 is also etched by the hydrogen radicals, resulting in a tapered shape. Thus, ethylene gas is a hydrocarbon gas that exhibits non-conformity during film formation because it does not form a carbon-based film 34 on the bottom and side surfaces of the trench 33, but forms the carbon-based film 34 mainly on the top surface of the trench 33.

[0039] Furthermore, when propylene gas is used, as described above, many hydrocarbon-based active species with a high elemental ratio of hydrogen are generated, but because the sticking coefficient of these hydrocarbon-based active species is low, these hydrocarbon-based active species adhere not only to the top of trench 33 but also to the bottom and side surfaces of trench 33. As a result, carbon-based film 34 is formed not only on the top of trench 33 but also on the bottom and side surfaces of trench 33. In this way, propylene gas forms carbon-based film 34 not only on the top of trench 33 but also on the bottom and side surfaces of trench 33, and therefore corresponds to a hydrocarbon gas that exhibits conformality during film formation.

[0040] Here, in the manufacture of a three-dimensional NAND flash memory, it is considered that the effective thickness of the mask film 32 is increased by the carbon-based film 34 in order to form a deep trench or the like. At this time, if the trench 33 is blocked or the carbon-based film 34 is formed on the bottom or sidewall of the trench 33, the shape of the trench 33 cannot be accurately reflected in the layer to be etched. Therefore, in order to increase the effective thickness of the mask film 32 by the carbon-based film 34, it is considered preferable to use ethylene gas, which exhibits non-conformity during film formation, as the hydrocarbon gas in the film formation gas.

[0041] However, when ethylene gas is used, the amount of carbon-based film 34 formed is small due to the effects of etching by hydrogen radicals and the effects of active species of acetylene generated from the ethylene gas, and the carbon-based film 34 has a tapered shape. Therefore, even if the film-forming gas contains only ethylene gas as the hydrocarbon gas, it is difficult to impart a sufficient thickness of the carbon-based film 34 to the mask film 32 for forming a deep trench or the like.

[0042] Therefore, the present applicant investigated the possibility of imparting a sufficient thickness to the mask film 32 by including ethylene gas and a gas other than ethylene gas as the hydrocarbon gas in the film formation gas, thereby suppressing the effects of etching by hydrogen radicals and the effects of activated acetylene species. Specifically, the inventors investigated the inclusion of not only ethylene gas but also acetylene gas as the hydrocarbon gas in the film formation gas, and performed a film formation process using this film formation gas in the film formation apparatus 10. Note that, during this process, the temperature of the wafer W (specifically, the temperature of the mounting table 12) was maintained at 200° C., and the flow rates of acetylene gas, ethylene gas, and argon gas in the film formation gas were set to 3 / 15 / 150 (all in sccm). Furthermore, a 450 kHz radio frequency voltage was applied to the shower head 13 at an output of 100 W, and the pressure inside the chamber 11 was set to 2 Torr.

[0043] FIG. 3 is a partially enlarged cross-sectional view showing the formation of a carbon-based film when a film formation process was performed using a film formation gas containing ethylene gas and acetylene gas as the hydrocarbon gas. As shown in FIG. 3 , a carbon-based film 34 was selectively and vertically formed on the top of the trench 33, but the carbon-based film 34 did not exhibit a tapered shape, as occurs when ethylene gas is used. Furthermore, the amount of film formed was sufficient to impart a sufficient thickness to the mask film 32. Specifically, the thickness of the carbon-based film 34 at the top of the trench 33 was approximately 54.9 nm, which was approximately the same as the thickness (approximately 53.2 nm) of the carbon-based film 34 at the top of the trench 33 when acetylene gas was used. Furthermore, while the carbon-based film 34 was not formed on the sidewall of the trench 33, a carbon-based film 34 having a certain thickness (e.g., approximately 4.6 nm) was formed on the bottom of the trench 33. However, the amount of the carbon-based film 34 formed on the bottom was sufficient to be removed by anisotropic etching as post-etching performed after the film formation process, for example, etching using plasma generated from oxygen (O) gas.

[0044] The mechanism by which the carbon-based film 34 shown in FIG. 3 is formed is as follows. That is, many of the carbon-based active species and hydrocarbon-based active species with a low hydrogen elemental ratio generated from acetylene gas adhere to the vicinity of the opening of the trench 33, thereby increasing the amount of carbon-based film 34 formed by the hydrocarbon-based active species generated from ethylene gas. Meanwhile, hydrogen radicals generated from ethylene gas moderately etch the carbon-based film 34 formed on the top of the trench 33, preventing the carbon-based film 34 from overhanging toward the trench 33. Furthermore, even if the carbon-based active species and hydrocarbon-based active species with a low hydrogen elemental ratio generated from acetylene gas enter the interior of the trench 33 and adhere to the bottom or side surfaces of the trench 33, they are etched by the hydrogen radicals generated from the ethylene gas. As a result, a non-tapered carbon-based film 34 is selectively and vertically formed on the top of the trench 33.

[0045] The film formation method according to the present embodiment is based on this finding. Specifically, when performing a film formation process, the film formation gas contains ethylene gas, which exhibits non-conformal behavior during film formation, and acetylene gas, which exhibits conformal behavior during film formation. This appropriately balances the non-conformal and conformal properties of the multiple hydrocarbon gases, allowing a carbon-based film 34 to be selectively and vertically formed on the top of the trench 33 without tapering even when the wafer W is at a low temperature, e.g., 200° C. or lower. Furthermore, in this case, as shown in FIG. 3 , the carbon-based film 34 (carbon-containing residue) remains on the bottom of the trench 33. Therefore, after the film formation process, anisotropic etching is performed on the wafer W to remove the carbon-based film 34 from the bottom.

[0046] In the example shown in Figure 3, acetylene gas was used as the hydrocarbon gas that exhibits conformal properties during film formation. However, propylene gas, which exhibits conformal properties during film formation, may be used instead of acetylene gas. Incidentally, as shown in Figure 4, when the aspect ratio of the trench 33 is low and only ethylene gas is used as the hydrocarbon gas, a carbon-based film 34 having a certain thickness (e.g., approximately 3.6 nm) is selectively deposited on the top of the trench 33. Furthermore, the carbon-based film 34 is not formed on the bottom or side surfaces of the trench 33 (Figure 2B). However, even in this case, it is difficult to impart a sufficient thickness to the mask film 32 using the carbon-based film 34 to form a deep trench or the like.

[0047] Therefore, it is necessary to provide a sufficient thickness to the mask film 32 by including a hydrocarbon gas that deposits a greater amount of the carbon-based film 34 than ethylene gas. In the example shown in FIG. 3 , the depth of the trench 33 is approximately 95.6 nm, whereas in the example shown in FIG. 4 , the depth of the trench 33 is approximately 23.5 nm, making the trench 33 very shallow. Therefore, if acetylene gas, which deposits a greater amount of the carbon-based film 34, is included as the hydrocarbon gas, the trench 33 may be completely filled with the carbon-based film 34. Therefore, it is preferable to include propylene gas, which deposits a smaller amount of the carbon-based film 34 than acetylene gas, as the hydrocarbon gas in the deposition gas. This increases the amount of carbon-based film 34 deposited at the top of the trench 33 without completely filling the trench 33, thereby providing a sufficient thickness to the mask film 32. At this time, due to the propylene gas, a carbon-based film 34 having a certain thickness is also formed on the bottom and side surfaces of the trench 33, but this carbon-based film 34 is removed by subjecting the wafer W to anisotropic etching after the film formation process is performed.

[0048] Furthermore, as described above, ethylene gas, acetylene gas, and propylene gas have different compositions of activated species generated when they are converted into plasma. Therefore, the film formation method according to the present embodiment can be said to include, in the film formation process, multiple types of hydrocarbon gases that have different compositions of activated species generated when they are converted into plasma.

[0049] Furthermore, in this embodiment, a mask film made of a chemically amplified resist is used as the mask film 32. Therefore, the film formation method according to this embodiment is performed while maintaining the temperature of the wafer W (specifically, the temperature of the mounting table 12) at 200° C. or less. However, if a mask film having higher heat resistance than the chemically amplified resist is used as the mask film 32, the film formation method according to this embodiment may be performed while maintaining the temperature of the wafer W (specifically, the temperature of the mounting table 12) at a temperature higher than 200° C.

[0050] In the film formation method according to the present embodiment, the film formation gas includes not only a hydrocarbon gas that exhibits conformal behavior during film formation and a hydrocarbon gas that exhibits non-conformal behavior during film formation, but also a rare gas, for example, argon gas. Note that, hereinafter, a hydrocarbon gas that exhibits conformal behavior during film formation will be referred to as a "conformal hydrocarbon gas," and a hydrocarbon gas that exhibits non-conformal behavior during film formation will be referred to as a "non-conformal hydrocarbon gas."

[0051] 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.

[0052] In the above-described embodiment, acetylene gas or propylene gas is used as the conformal hydrocarbon gas, but the conformal hydrocarbon gas is not limited to these gases, and for example, methane (CH4) gas may also be used. Like propylene gas, methane gas has a methyl group, and therefore, like propylene gas, it allows the carbon-based film 34 to be formed not only on the top but also on the bottom and side surfaces of the trench 33 without blocking the trench 33. Therefore, it is mainly used as a substitute for propylene gas.

[0053] Furthermore, in the above-described embodiment, the film forming gas contains one type of conformal hydrocarbon gas, but the film forming gas may contain a plurality of types of conformal hydrocarbon gas.

[0054] Furthermore, in the above-described embodiment, the film formation gas contains both a non-conformal hydrocarbon gas and a conformal hydrocarbon gas as hydrocarbon gases. That is, in the film formation process, the non-conformal hydrocarbon gas and the conformal hydrocarbon gas are simultaneously supplied into the chamber 11.

[0055] However, in the film formation process, a non-conformal hydrocarbon gas and a conformal hydrocarbon gas may be alternately supplied into the chamber 11. Also, in the film formation process, only a non-conformal hydrocarbon gas and a mixed gas of a non-conformal hydrocarbon gas and a conformal hydrocarbon gas may be alternately supplied into the chamber 11. Furthermore, in the film formation process, only a conformal hydrocarbon gas and a mixed gas of a non-conformal hydrocarbon gas and a conformal hydrocarbon gas may be alternately supplied into the chamber 11. Also, in the film formation process, the non-conformal hydrocarbon gas and the conformal hydrocarbon gas may be supplied into the chamber 11 while changing the mixture ratio.

[0056] This application claims priority based on Japanese Patent Application No. 2024-154849, filed on September 9, 2024, the entire contents of which are incorporated herein by reference.

[0057] W wafer 10 film forming apparatus 11 chamber 32 mask film 33 trench 34 carbon-based film

Claims

1. A film formation method comprising: placing a substrate having a pattern inside a processing chamber; supplying a film formation gas into the processing chamber; generating plasma from the film formation gas using high-frequency power to perform a film formation process on the substrate; the film formation gas containing multiple types of hydrocarbon gases and a rare gas; and when the multiple types of hydrocarbon gases are excited to become plasma, the compositions of active species generated from each of the hydrocarbon gases are different.

2. The film forming method according to claim 1, wherein the film forming gas contains a hydrocarbon gas that exhibits conformal behavior during film formation and a hydrocarbon gas that exhibits non-conformal behavior during film formation.

3. The film deposition method according to claim 2, wherein the hydrocarbon plasma generated from the hydrocarbon gas exhibiting non-conformity during the film deposition deposits a carbon-based film primarily on the top of the pattern.

4. The film formation method according to claim 2, wherein the hydrocarbon gas exhibiting non-conformity during film formation is ethylene (C2H4) gas, and the hydrocarbon gas exhibiting conformity during film formation is acetylene (C2H2) gas or propylene (C3H6) gas.

5. The film forming method according to claim 1, wherein the plurality of types of hydrocarbon gases are alternately supplied into the processing chamber.

6. The film forming method according to claim 1, wherein the temperature of the substrate is maintained at 200° C. or less when the film forming process is performed on the substrate.

7. The film forming method according to claim 6, wherein the pattern is formed on a mask film made of a chemically amplified resist.

8. The method of claim 1, further comprising the step of: subjecting the substrate to an anisotropic etching process to remove carbon-containing residues after the film deposition process.

9. The film forming method according to claim 1, wherein the rare gas is argon (Ar) gas.

10. A film formation method comprising: placing a substrate having a pattern inside a processing chamber; supplying a film formation gas into the processing chamber; generating plasma from the film formation gas using high-frequency power to perform a film formation process on the substrate; wherein the film formation gas includes ethylene gas, a hydrocarbon gas different from the ethylene gas, and a rare gas.

11. The film forming method according to claim 10, wherein the hydrocarbon gas other than ethylene gas is acetylene gas or propylene gas.

12. A film formation apparatus comprising a processing chamber with a reduced pressure inside, which accommodates a substrate having a pattern inside the processing chamber, supplies a film formation gas into the processing chamber, and generates plasma from the film formation gas using high-frequency power to perform a film formation process on the substrate, wherein the film formation gas contains multiple types of hydrocarbon gases and a rare gas, and when the multiple types of hydrocarbon gases are excited to become plasma, the compositions of active species generated from each of the hydrocarbon gases are different.

Images