Film forming method and film forming apparatus

Abstract

[Problem] To suppress the occurrence of a constriction in a first film when the first film is formed selectively and vertically on a top part of a pattern. [Solution] Disclosed is a film forming apparatus in which a wafer having a trench is housed in a chamber, plasma is generated from a film forming gas with use of high-frequency power so as to selectively and vertically form a carbon-based film on a top part of the trench, an insulating film that covers the resulting carbon-based film is formed, and a carbon-based film is vertically formed again after the insulating film is formed. The material that constitutes the carbon-based film is different from the material that constitutes the insulating film, or alternatively, the material that constitutes the insulating film is the same as the material that constitutes the carbon-based film.

Description

Film forming method and film forming apparatus

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

[0002] In 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 technique according to the present disclosure suppresses the occurrence of constrictions in the first film when the first film is selectively and vertically deposited on the top of a pattern.

[0005] One aspect of the technology disclosed herein is a film formation method in which a substrate having a pattern is placed inside a processing chamber, and plasma is generated from a film formation gas using high-frequency power to perform a film formation process on the substrate, the method comprising: a first film formation process in which a first film is selectively and vertically formed on the top of the pattern; a second film formation process in which a second film is formed to cover the formed first film; and a third film formation process in which, after the second film is formed, the first film is again vertically formed.

[0006] According to the technology of the present disclosure, when a first film is formed selectively and vertically on the top of a pattern, it is possible to suppress the occurrence of constrictions in the first film.

[0007] FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a film formation apparatus according to a first embodiment of the technology disclosed herein. FIG. 2 is a partially enlarged cross-sectional view of an example of a pattern formed on 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 an example of a pattern formed on a wafer to be subjected to a film formation process in the film formation apparatus of FIG. 1. FIG. 4 is a diagram showing an example of distribution states of activated hydrocarbon species and activated hydrogen species generated from plasma in a simulation model that reproduces the film formation process of a top vertically grown carbon-based film. FIG. 5 is a diagram showing distribution states of activated hydrocarbon species and activated hydrogen species generated from plasma in a simulation model that reproduces the film formation process of a top vertically grown carbon-based film. FIG. 6 is a partially enlarged cross-sectional view for explaining an example of a difference in the occurrence mode of necking in a top vertically grown carbon-based film depending on whether a protective film is present or not. FIG. 7 is a partially enlarged cross-sectional view for explaining an example of a difference in the occurrence mode of necking in a top vertically grown carbon-based film depending on whether a protective film is present or not. FIG. 8 is a partially enlarged cross-sectional view for explaining an example of a difference in the occurrence mode of necking in a top vertically grown carbon-based film depending on whether a protective film is present or not. 7 is a partially enlarged cross-sectional view illustrating an example of a difference in the occurrence mode of constriction in a top vertically grown carbon-based film due to a difference in the thickness of the insulating film used as a protective film. FIG. 8 is a partially enlarged cross-sectional view illustrating an example of a difference in the occurrence mode of constriction in a top vertically grown carbon-based film due to a difference in the thickness of the insulating film used as a protective film. FIG. 9 is a partially enlarged cross-sectional view illustrating an example of a difference in the occurrence mode of constriction in a top vertically grown carbon-based film due to a difference in the thickness of the insulating film used as a protective film. FIG. 10 is a partially enlarged cross-sectional view illustrating an example of a difference in the occurrence mode of constriction in a top vertically grown carbon-based film due to a difference in the thickness of the insulating film used as a protective film. FIG. 11 is a flowchart illustrating an example of a film deposition method according to a first embodiment. FIG. 12 is a partially enlarged cross-sectional view illustrating an example of an embodiment (example) of a top vertically grown carbon-based film deposited by the film deposition method of FIG. 6. FIG. 13 is a process diagram illustrating an example of a film deposition method according to a second embodiment of the technology according to the present disclosure. FIG. 14 is a process diagram illustrating an example of a film deposition method according to a second embodiment of the technology according to the present disclosure.10 is a process diagram illustrating an example of a film forming method according to a second embodiment of the technology disclosed herein;

[0008] An embodiment of the technology according to the present disclosure will be described below with reference to the drawings. First, a first embodiment of the technology according to the present disclosure will be described. FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a film formation apparatus according to the first embodiment of the technology according to the present disclosure. This film formation apparatus is a PECVD (Plasma-Enhanced Chemical Vapor Deposition) 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 and a heater 18 are embedded inside the mounting table 14. The heater 18 generates heat by power supplied from a heater power supply 19, thereby heating the placed wafer W. A coolant passage (not shown) may be embedded inside the mounting table 14 as needed. This coolant passage cools the placed wafer W by circulating a coolant supplied from the outside. Furthermore, in order to improve the thermal conductivity between the mounting table 14 and the wafer W, a heat transfer gas may be supplied between the mounting table 14 and the wafer W as needed.

[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 plasma from the film formation gas to generate hydrocarbon active species in the film formation process, and an amorphous carbon-based film is formed by hydrocarbon ions and hydrocarbon radicals in the hydrocarbon active species.

[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, the film formation gas is excited and turned into plasma by an electric field generated by the high-frequency power supplied to the upper electrode 20, generating activated species, which then perform a film formation process on the wafer W.

[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] In the film formation apparatus 100, when a film formation gas is converted into plasma to generate activated species and a film formation process is performed on the wafer W, an amorphous carbon-based film can be grown selectively and vertically on the top of a pattern formed on the wafer W, for example, a groove-shaped trench. The reason why an amorphous carbon-based film can be grown selectively and vertically on the top of a trench is described in the specification of Japanese Patent Application No. 2023-200333 filed by the present applicant. Furthermore, in the film formation apparatus 100, this carbon-based film is formed by a single film formation process step of simply converting the film formation gas into plasma.

[0022] An amorphous carbon-based film selectively and vertically grown on the top of such a pattern (hereinafter referred to as a "top-vertically grown carbon-based film") can be used as an additional hard mask. For example, in the manufacture of a three-dimensional NAND flash memory, when forming deep trenches or deep holes by etching, the top-vertically grown carbon-based film functions as an additional hard mask to an already formed hard mask. Therefore, there is a demand for thicker top-vertically grown carbon-based films, and for example, there is a demand for realizing top-vertically grown carbon-based films with a thickness of approximately 1000 nm. Therefore, the present applicant has used the film formation apparatus 100 to form a relatively thick top-vertically grown carbon-based film on the top of a pattern formed on a wafer W.

[0023] 2A and 2B are partially enlarged cross-sectional views of an example of a pattern formed on 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 on the surface of a substrate 38 made of silicon, and a hard mask layer 40 made of amorphous carbon is formed on the insulating film 39. A pattern, for example, a groove-shaped trench 41, is formed in the hard mask layer 40. The trench 41 penetrates the hard mask layer 40, and the insulating film 39 is exposed at the bottom of the trench 41 ( FIG. 2A ).

[0024] The applicant first formed a top vertically grown carbon-based film 42 having a thickness of about 200 nm on the top of the trench 41. At this time, the top vertically grown carbon-based film 42 was neither bulged nor constricted (FIG. 2A).

[0025] Next, the applicant formed a top vertically grown carbon-based film 42 with a thickness of approximately 400 nm on the top of the trench 41. At this time, the applicant confirmed that necking occurred in the top vertically grown carbon-based film 42 near the boundary between the hard mask layer 40 and the top vertically grown carbon-based film 42 ( FIG. 2B ). When etching is performed using the top vertically grown carbon-based film 42 as an additional hard mask, if such necking occurs, the top vertically grown carbon-based film 42 may be consumed in an unexpected manner during etching, and the desired shape may not be transferred to the layer to be etched. Therefore, when forming the top vertically grown carbon-based film 42 on the top of the trench 41, it is necessary to suppress the occurrence of necking in the top vertically grown carbon-based film 42.

[0026] In order to find the cause of the occurrence of the constriction in the top vertically grown carbon-based film 42, the applicant created a simulation model that reproduces the film formation process of the top vertically grown carbon-based film 42. Furthermore, the applicant used the model to simulate the film formation process when the top vertically grown carbon-based film 42 has different thicknesses, and confirmed the film formation form of the top vertically grown carbon-based film 42.

[0027] When the top vertically grown carbon-based film 42 is formed, hydrocarbon ions and hydrocarbon radicals in activated hydrocarbon species generated from acetylene gas contained in the film-forming gas form the carbon-based film. Meanwhile, hydrogen radicals in activated hydrogen species generated from hydrogen gas contained in the film-forming gas etch the carbon-based film. Therefore, the applicant confirmed the distribution of activated hydrocarbon species and activated hydrogen species in the film-forming process of the top vertically grown carbon-based film 42 using a simulation model.

[0028] 3A and 3B are diagrams showing an example of the distribution of activated hydrocarbon species and activated hydrogen species generated from plasma in a simulation model that reproduces the film formation process of the top vertically grown carbon-based film 42. In the figures, activated hydrocarbon species are indicated by "○" and activated hydrogen species are indicated by "●". Furthermore, inside the trench 41, activated hydrocarbon species and activated hydrogen species are actually present all the way down to the bottom of the trench. However, for ease of understanding, FIG. 3 shows the distribution of activated hydrocarbon species and activated hydrogen species from the top of the trench 41 to the vicinity of the boundary between the hard mask layer 40 and the top vertically grown carbon-based film 42. Hereinafter, the "boundary between the hard mask layer 40 and the top vertically grown carbon-based film 42" will simply be referred to as the "boundary of the carbon-based film."

[0029] In the simulation model, when the thickness of the top vertically grown carbon-based film 42 was approximately 200 nm, hydrocarbon active species were uniformly present inside the trench 41 from the top of the trench 41 to the vicinity of the boundary of the carbon-based film ( FIG. 3A ). From this, it was inferred that the reason why no constriction occurred in the top vertically grown carbon-based film 42 with a thickness of approximately 200 nm is because the deposition of the carbon-based film was dominant over the etching of the carbon-based film in the range from the top of the trench 41 to the vicinity of the boundary of the carbon-based film.

[0030] Furthermore, when the thickness of the top vertically grown carbon-based film 42 was approximately 400 nm, the simulation model showed that inside the trench 41, the hydrocarbon activated species were concentrated near the upper part of the trench 41 and were hardly present near the boundary of the carbon-based film. On the other hand, the hydrogen activated species were present not only near the upper part of the trench 41 but also uniformly near the boundary of the carbon-based film ( FIG. 3B ). From this, it was inferred that the reason for the occurrence of the constriction in the top vertically grown carbon-based film 42 having a thickness of approximately 400 nm was that the etching of the carbon-based film was dominant over the deposition of the carbon-based film near the boundary of the carbon-based film, resulting in the top vertically grown carbon-based film 42 being scraped away.

[0031] 3B , when the trench 41 is deep, the hydrocarbon active species are concentrated near the upper portion of the trench 41. The present applicant has inferred the mechanism described below as the reason why the hydrocarbon active species are concentrated near the upper portion of the trench 41. That is, because the hydrocarbon active species have a higher sticking coefficient than the hydrogen active species, many of the hydrocarbon active species adhere to the hard mask layer 40 near the upper portion of the trench 41, and few of the hydrocarbon active species reach the vicinity of the carbon-based film deposition site. On the other hand, because the hydrogen active species have a lower sticking coefficient than the hydrocarbon active species, few of the hydrogen active species adhere to the hard mask layer 40 near the upper portion of the trench 41, and many of the hydrogen active species reach the vicinity of the carbon-based film deposition site.

[0032] From the above, the applicant has come to the knowledge that the difference between the distribution of hydrocarbon activated species and the distribution of hydrogen activated species inside trench 41 due to the difference in sticking coefficient becomes apparent as trench 41 becomes deeper, causing the top vertically grown carbon-based film 42 to become constricted.

[0033] Based on this finding, the applicant has considered protecting the top vertically grown carbon-based film 42 itself from etching by activated hydrogen species as a means for suppressing the occurrence of constriction in the top vertically grown carbon-based film 42. Specifically, the applicant has considered covering the top vertically grown carbon-based film 42 with a protective film having etching resistance before the trench 41 becomes deeper and etching of the carbon-based film becomes more dominant than deposition of the carbon-based film near the boundary of the carbon-based film.

[0034] Therefore, the present applicant used the film forming apparatus 100 to compare a case (Example) in which the top vertically grown carbon-based film 42 is covered with a protective film with a case (Comparative Example) in which the top vertically grown carbon-based film 42 is not covered with a protective film on the wafer W. Figures 4A to 4D are partially enlarged cross-sectional views for explaining an example of the difference in the occurrence mode of the constriction in the top vertically grown carbon-based film 42 depending on whether or not a protective film is present.

[0035] Specifically, as a comparative example, a top vertically grown carbon-based film 42 having a thickness of approximately 200 nm was first formed on the top of a trench 41, as shown in FIG. 4A. In this film formation process, the flow rates of acetylene gas, hydrogen gas, and argon gas in the film formation gas were set to 30 sccm, 30 sccm, and 1000 sccm, respectively. The pressure inside the chamber 11 was set to 1 Torr, and 500 W of high-frequency power was supplied to the upper electrode 20. Subsequent film formation processes were also performed under the same conditions.

[0036] Thereafter, without covering the top vertically grown carbon-based film 42 with a protective film, the film formation process was continued until the thickness of the top vertically grown carbon-based film 42 reached approximately 400 nm. At this time, as shown in FIG. 4B , a constriction occurred in the top vertically grown carbon-based film 42 near the boundary of the carbon-based film.

[0037] Next, as an example, first, a top vertically grown carbon-based film 42 having a thickness of about 200 nm was formed on the top of the trench 41. Thereafter, as shown in FIG. 4C , the top vertically grown carbon-based film 42 and the hard mask layer 40 were covered with a protective film thinner than the top vertically grown carbon-based film 42, for example, a silicon oxide (SiO ２ ) was deposited in the film deposition apparatus 100 by atomic layer deposition (ALD). Then, deposition of the top vertically grown carbon-based film 42 was started again, and the film deposition process was continued until the top vertically grown carbon-based film 42 reached a thickness of approximately 400 nm. At this time, as shown in FIG. 4D , no constrictions were generated in the top vertically grown carbon-based film 42, even near the boundary of the carbon-based film.

[0038] From the above, the applicant has found that if the top vertically grown carbon-based film 42 that has been grown to a certain thickness is covered with a thin insulating film 43, no constriction will occur in the top vertically grown carbon-based film 42 during subsequent deposition of the top vertically grown carbon-based film 42. In other words, the applicant has found that if the top vertically grown carbon-based film 42 is covered with a thin insulating film 43, the top vertically grown carbon-based film 42 will not be eroded by activated hydrogen species. The technology of the present disclosure is based on this finding.

[0039] The applicant also used the film formation apparatus 100 to confirm the thickness of the insulating film 43 required to suppress the occurrence of constriction in the top vertically grown carbon-based film 42 on the wafer W. At this time, after the top vertically grown carbon-based film 42 was once formed to a thickness of about 300 nm on the top of the trench 41, the top vertically grown carbon-based film 42 and the hard mask layer 40 were covered with the insulating film 43. Then, formation of the top vertically grown carbon-based film 42 was started again, and the film formation process was continued until the thickness of the top vertically grown carbon-based film 42 reached about 600 nm.

[0040] The applicant first formed a top vertically grown carbon-based film 42 with a thickness of about 300 nm on the top of the trench 41, and then checked the shape of the top vertically grown carbon-based film 42 to confirm that no constriction had occurred in the top vertically grown carbon-based film 42. In other words, it was confirmed that hydrocarbon active species were present evenly even about 300 nm below the upper opening of the trench 41, and that the formation of the carbon-based film was dominant over the etching of the carbon-based film.

[0041] 5A to 5D are enlarged partial cross-sectional views illustrating an example of differences in the form of constriction occurring in the top vertically grown carbon-based film 42 due to differences in the thickness of the insulating film 43 serving as a protective film. Note that in order to emphasize the form of the top vertically grown carbon-based film 42, the insulating film 43 is not shown in FIG.

[0042] Specifically, first, as Comparative Example 1, the film formation process was performed twice to form a top vertically grown carbon-based film 42 having a thickness of about 600 nm without covering the top vertically grown carbon-based film 42 with the insulating film 43. In this case, as shown in FIG. 5A , a relatively large constriction occurred in the top vertically grown carbon-based film 42 near the boundary of the carbon-based film.

[0043] Next, in Comparative Example 2, the top vertically grown carbon-based film 42 formed in the first film formation process to a thickness of approximately 300 nm was covered with an insulating film 43 to a thickness of approximately 0.4 nm. Thereafter, a second film formation process was performed to form a top vertically grown carbon-based film 42 to a thickness of approximately 600 nm. In this case, too, as shown in FIG. 5B , constrictions occurred in the top vertically grown carbon-based film 42 near the boundary of the carbon-based film. However, the constrictions in Comparative Example 2 were slightly smaller than those in Comparative Example 1.

[0044] Next, in Comparative Example 3, the top vertically grown carbon-based film 42 formed in the first film formation process to a thickness of approximately 300 nm was covered with an insulating film 43 to a thickness of approximately 1.0 nm. Thereafter, a second film formation process was performed to form a top vertically grown carbon-based film 42 to a thickness of approximately 600 nm. In this case, too, as shown in FIG. 5C , constrictions occurred in the top vertically grown carbon-based film 42 near the boundary of the carbon-based film. However, the constrictions in Comparative Example 3 were slightly smaller than those in Comparative Example 2.

[0045] Finally, in Example 1, the top vertically grown carbon-based film 42 having a thickness of about 300 nm formed by the first film formation process was covered with an insulating film 43 having a thickness of about 2.0 nm. Thereafter, a second film formation process was performed to form the top vertically grown carbon-based film 42 having a thickness of about 600 nm. At this time, as shown in FIG. 5D , no constriction occurred in the top vertically grown carbon-based film 42 near the boundary of the carbon-based film.

[0046] From the above, the applicant has found that if the thickness of the insulating film 43 covering the top vertically grown carbon-based film 42 is at least 2.0 nm or more, the occurrence of constriction in the top vertically grown carbon-based film 42 can be suppressed.

[0047] Fig. 6 is a flowchart showing an example of a film formation method according to this embodiment. The film formation method of Fig. 6 is realized by the processor of the control unit 34 executing a corresponding control program. In the film formation method according to this embodiment, the formation of the top vertically grown carbon-based film 42 and the formation of the insulating film 43 are performed alternately, and the formation of the top vertically grown carbon-based film 42 is performed at least twice.

[0048] First, in the film formation apparatus 100, a wafer W having a plurality of trenches 41 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 of only acetylene gas (first gas), argon gas, and hydrogen gas (second gas) into the chamber 11 is started, and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. This converts the film formation gas into plasma, generating hydrocarbon activated species and hydrogen activated species, and a film formation process is performed on the wafer W. At this time, the formation of a carbon-based film by the hydrocarbon activated species (first activated species) is dominant over the etching of the carbon-based film by the hydrogen activated species (second activated species). As a result, a top-vertically grown carbon-based film 42 (first film) is vertically formed on the top of the trench 41 (step S61) (first film formation process). Then, when the thickness of the top vertically grown carbon-based film 42 formed vertically on the top of the trench 41 reaches 300 nm, the film formation process is temporarily interrupted, and the inside of the chamber 11 is purged by the exhaust device 31 .

[0049] Next, with the wafer W placed on the mounting table 14 inside the chamber 11, a silicon-containing gas and an oxygen-containing gas are alternately introduced into the chamber 11 to generate plasma from each gas. Then, an insulating film 43 (second film) is formed by ALD so as to cover the hard mask layer 40 and the top vertically grown carbon-based film 42 (step S62) (second film formation process). Step S62 is stopped when the thickness of the formed insulating film 43 reaches at least 2 nm, and the inside of the chamber 11 is purged by the exhaust device 31.

[0050] Next, while the wafer W is still placed on the mounting table 14 inside the chamber 11, the supply of film-forming gas into the chamber 11 is again started, and high-frequency power with a frequency of 40 MHz is supplied to the upper electrode 20 to perform a film forming process on the wafer W. At this time, the formation of a carbon-based film by the activated hydrocarbon species prevails over the etching of the carbon-based film by the activated hydrogen species in the upper part of the trench 41. As a result, a new vertically grown top carbon-based film 42 is vertically formed on the already formed top vertically grown carbon-based film 42 (step S63) (third film forming process). Meanwhile, near the boundary of the carbon-based film, the top vertically grown carbon-based film 42 is protected by the insulating film 43, and etching of the top vertically grown carbon-based film 42 by the activated hydrogen species is suppressed. As a result, no constriction occurs in the top vertically grown carbon-based film 42. Then, when the thickness of the top vertically grown carbon-based film 42 formed again reaches 300 nm, the film formation process is temporarily interrupted, and the inside of the chamber 11 is purged by the exhaust device 31 .

[0051] Next, it is determined whether the number of times the top vertically grown carbon-based film 42 has been formed has reached a specified number of times required to obtain the required thickness of the top vertically grown carbon-based film 42 (step S64). If the number of times the top vertically grown carbon-based film 42 has been formed has not reached the specified number of times, the process returns to step S62, and steps S62 and S63 are repeated. On the other hand, if the number of times the top vertically grown carbon-based film 42 has been formed has reached the specified number of times, the process ends.

[0052] 6, the film formation process is temporarily interrupted when the thickness of the vertically grown top carbon-based film 42 reaches 300 nm. As described above, the formation of the carbon-based film is superior to the etching of the carbon-based film even about 300 nm below the upper opening of the trench 41. Therefore, when the film formation process is temporarily interrupted, no constriction occurs in the top vertically grown carbon-based film 42.

[0053] Thereafter, when step S63 is repeated, the top vertically grown carbon-based film 42 formed at an early stage moves further downward relative to the trench 41 from the upper opening of the trench 41. However, since the top vertically grown carbon-based film 42 is covered with the insulating film 43 each time it is formed, it is not eroded by activated hydrogen species unevenly distributed below the trench 41.

[0054] As a result, in the film forming method of FIG. 6, it is possible to suppress the occurrence of constrictions in the top vertically grown carbon-based film 42.

[0055] 6, the film formation process is temporarily interrupted when the thickness of the vertically grown top carbon-based film 42 reaches 300 nm, but the film formation process may also be temporarily interrupted when the thickness of the vertically grown top carbon-based film 42 reaches 200 nm. In this case, the distance from the upper opening of the trench 41 to the boundary of the carbon-based film becomes shorter, so that even hydrocarbon active species with a high sticking coefficient can easily reach the vicinity of the boundary of the carbon-based film, making the formation of the carbon-based film more reliably advantageous over etching of the carbon-based film.

[0056] Furthermore, although the thickness of the top vertically grown carbon-based film 42 is less than 400 nm, the film formation process may be temporarily interrupted when the thickness reaches approximately 400 nm. In this case, the number of times step S63 needs to be performed to obtain a thick top vertically grown carbon-based film 42 can be reduced, thereby improving throughput.

[0057] 7 is a partially enlarged cross-sectional view showing one embodiment (one example) of a top vertically grown carbon-based film 42 formed by the film formation method of FIG. 6. In the embodiment shown in FIG. 7, steps S62 and S63 were repeated twice. In this embodiment, a top vertically grown carbon-based film 42 having a thickness of approximately 900 nm was obtained, but no constriction occurred in the top vertically grown carbon-based film 42. Furthermore, because step S63 was repeated twice, three top vertically grown carbon-based films 42 are stacked overall, and the bottom and middle top vertically grown carbon-based films 42 are covered with insulating films 43. Furthermore, insulating films 43 are interposed between each top vertically grown carbon-based film 42.

[0058] The thickness of the insulating film 43 formed in step S62 is at least 2 nm. However, a thicker insulating film 43 is preferable from the viewpoint of protecting the top vertically grown carbon-based film 42. However, the insulating film 43 covers not only the top vertically grown carbon-based film 42 but also the hard mask layer 40 and the insulating film 39 exposed at the bottom of the trench 41. If the insulating film 43 covering the insulating film 39 is thick, etching of the insulating film 39 may be hindered when etching the insulating film 39 using the hard mask layer 40 or the top vertically grown carbon-based film 42 as a hard mask (hereinafter referred to as "next etching"). Furthermore, if the insulating film 43 covering the hard mask layer 40 (or the top vertically grown carbon-based film 42) is thick, the width of the trench 41 will be narrowed. Therefore, the thickness of the insulating film 43 is at least 2 nm, but preferably as close to 2 nm as possible.

[0059] Next, a second embodiment of the technology according to the present disclosure will be described. The second embodiment differs from the first embodiment in that the insulating film 43 is etched back each time the insulating film 43 is formed and that the insulating film 43 is completely removed at the end. Note that, in the following, a description of the same processing contents and configuration as the first embodiment will be omitted, and only the processing contents and configuration that are different from the first embodiment will be described.

[0060] 8A to 8E are process diagrams showing an example of a film formation method according to a second embodiment of the technology disclosed herein, and Fig. 9 is a flowchart showing an example of the film formation method according to this embodiment. The film formation method of Fig. 8 is also realized by the processor of the control unit 34 executing a corresponding control program. Furthermore, in the film formation method according to this embodiment, the top vertically grown carbon-based film 42 is also formed at least twice.

[0061] First, steps S61 and S62 are performed to vertically form a top vertically grown carbon-based film 42 on the top of the trench 41 (FIG. 8A), and then the top vertically grown carbon-based film 42 and the like are covered with an insulating film 43 (FIG. 8B).

[0062] Next, after purging the inside of the chamber 11 by the exhaust device 31, a processing gas for etch-back is introduced into the chamber 11 while the wafer W is placed on the mounting table 14 inside the chamber 11, and plasma is generated from each gas. The processing gas for etch-back is, for example, nitrogen trifluoride (NF ３ The etching by the plasma generated from the etching-back process gas includes a fluorinated carbon (CF)-based gas. Because etching by the plasma generated from this etch-back process gas is highly anisotropic, the insulating film 43 covering the top of the top vertically grown carbon-based film 42 is selectively removed (etched back) (step S91) ( FIG. 8C ) (film removal step). Step S91 is stopped after the insulating film 43 is removed and the top of the top vertically grown carbon-based film 42 is exposed, and the inside of the chamber 11 is purged by the exhaust device 31.

[0063] Next, step S63 is executed to vertically deposit another top vertically grown carbon-based film 42 on the already deposited top vertically grown carbon-based film 42 ( FIG. 8D ). Then, when the thickness of the newly deposited top vertically grown carbon-based film 42 reaches 300 nm, the film deposition process is temporarily interrupted and the inside of the chamber 11 is purged by the exhaust device 31.

[0064] Next, it is determined whether the number of times the top vertically grown carbon-based film 42 has been formed has reached a specified number of times necessary to obtain the required thickness of the top vertically grown carbon-based film 42 (step S64). If the number of times the top vertically grown carbon-based film 42 has been formed has not reached the specified number of times, the process returns to step S62, and steps S62, S91, and S63 are repeated. On the other hand, if the number of times the top vertically grown carbon-based film 42 has been formed has reached the specified number of times, the process proceeds to step S92.

[0065] In step S92, the wafer W is unloaded from the chamber 11, and in another substrate processing apparatus, the wafer W is subjected to, for example, high-temperature heating etching (thermal etching) using a fluorine-based gas or wet etching using hydrofluoric acid. At this time, the insulating film 43 covering the hard mask layer 40 and the top vertically grown carbon-based film 42 is removed ( FIG. 8E ). Then, after no insulating film 43 remains inside the trench 41, the processing is terminated.

[0066] However, if an insulating film 43 is interposed between the top vertically grown carbon-based films 42, the top vertically grown carbon-based films 42 are removed and the insulating film 43 is exposed during the next etching process. When the insulating film 43, which is made of a different material from the top vertically grown carbon-based films 42, is exposed in this way, the wear rate of the hard mask changes, and more of the hard mask may remain after the next etching process is completed. If more of the hard mask remains than necessary, it takes time to remove the hard mask, which may reduce throughput.

[0067] 8 , the insulating film 43 covering the top of the top vertically grown carbon-based film 42 is selectively removed, and then another top vertically grown carbon-based film 42 is vertically grown again, so that the insulating film 43 does not intervene between the top vertically grown carbon-based films 42. Furthermore, the insulating film 43 covering the top vertically grown carbon-based film 42 is finally removed, so that no insulating film 43 remains inside the trench 41. Therefore, no more hard mask than necessary remains after the next etching step is completed, and the next etching step is not affected by charging of the insulating film 43. As a result, a decrease in throughput can be avoided in the next etching step, and trenches and holes of desired shapes can be formed.

[0068] 8, similarly to the film formation method of FIG. 6, it is possible to suppress the occurrence of constrictions in the top vertically grown carbon-based film 42.

[0069] 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.

[0070] For example, in the first embodiment, the insulating film 43 covering the hard mask layer 40 and the top vertically grown carbon-based film 42 is not removed, but as in the second embodiment, the insulating film 43 may be removed so that the insulating film 43 does not remain inside the trench 41.

[0071] Although the above-described embodiments use an insulating film made of silicon oxide as the protective film, other insulating films, such as an insulating film made of silicon nitride (SiN), may be used as long as they are resistant to activated hydrogen species. Furthermore, films other than insulating films that are resistant to activated hydrogen species may also be used as the protective film. For example, a carbon film with high etching resistance, such as diamond-like carbon (DLC), or a carbon-containing film with similar high etching resistance may be used as the protective film. In particular, since the carbon film has almost the same composition as the top vertically grown carbon-based film 42, it is not charged by plasma, eliminating the need to remove the protective film to avoid the effects of charging in the subsequent etching process. This improves throughput. Furthermore, when a carbon film is used, coating with a thin carbon film by ALD or the like may be frequently repeated during the growth of the top vertically grown carbon-based film 42. This allows the top vertically grown carbon-based film 42 to be grown while filling and repairing any small defects in the top vertically grown carbon-based film 42 caused by activated hydrogen species. However, when an insulating film other than that made of silicon oxide is used, it is preferable that the protective film be removable by thermal etching or wet etching.

[0072] The above-mentioned constriction may occur regardless of the active species used when a carbon-based film is selectively and vertically deposited on the top of a pattern using an active species with a high sticking coefficient that contributes to film formation and an active species with a low sticking coefficient that contributes to etching. Therefore, the film deposition methods shown in FIGS. 6 and 9 can be applied even when the film selectively and vertically deposited on the top of a pattern is a film other than an amorphous carbon-based film. For example, even when the film selectively and vertically deposited on the top of a pattern is made of tungsten carbide, the film deposition methods shown in FIGS. 6 and 9 can suppress the occurrence of constriction in the film. Furthermore, the film deposition methods shown in FIGS. 6 and 9 can be applied when other hydrogen compound gases are used instead of acetylene gas as the deposition gas. For example, the film deposition methods shown in FIGS. 6 and 9 can be applied when a film is selectively and vertically deposited on the top of a pattern using silane gas, a silicon hydrogen compound gas, or borane gas, a boron hydrogen compound gas.

[0073] The protective film may also have an adsorption inhibitory effect on the amorphous carbon-based film. This prevents the carbon-based film from adhering to the protective film when the top vertically grown carbon-based film 42 is again vertically formed in step S63, for example, so that the carbon-based film can be preferentially formed on the top of the trench 41. Furthermore, since the carbon-based film does not adhere to the protective film, narrowing of the width of the trench 41 can be prevented.

[0074] Furthermore, a sacrificial layer may be used instead of the protective film. In this case, when the top vertically grown carbon-based film 42 is again vertically formed, the sacrificial layer is more actively etched by activated hydrogen species than the top vertically grown carbon-based film 42. As a result, etching of the top vertically grown carbon-based film 42 can be suppressed, and thus the occurrence of constriction in the top vertically grown carbon-based film 42 can be suppressed.

[0075] In addition, in each of the above-described embodiments, the underlying layer of the top vertically grown carbon-based film 42 is the hard mask layer 40 made of amorphous carbon, but the underlying layer of the top vertically grown carbon-based film 42 is not limited to this. For example, the underlying layer of the top vertically grown carbon-based film 42 may be silicon as a base material, a mask made of an oxynitride film, an insulating layer in which a plurality of oxide films and a plurality of nitride films are alternately stacked, a single layer of oxide film, a single layer of nitride film, or a wiring layer made of metal.

[0076] 6 and 9 are applied when the top vertically grown carbon-based film 42 is formed vertically on the top of the trench 41. However, the film formation methods of Fig. 6 and 9 may also be applied when the top vertically grown carbon-based film 42 is formed vertically on the top of a hole as a pattern.

[0077] 6 and 9 is not limited to the film formation apparatus 100 shown in Fig. 1. Any film formation apparatus capable of reducing the energy of ions incident on the wafer W can perform the film formation methods shown in Fig. 6 and 9.

[0078] This application claims priority based on Japanese Patent Application No. 2024-051536, filed on March 27, 2024, the entire contents of which are incorporated herein by reference.

[0079] W wafer 11 chamber 41 trench 42 top vertically grown carbon-based film 43 insulating film 100 film formation apparatus

Claims

1. A film formation method in which a substrate having a pattern is placed inside a processing chamber, and a plasma is generated from a film formation gas using high frequency power to perform a film formation process on the substrate, the film formation method comprising: a first film formation process in which a first film is selectively and vertically formed on the top of the pattern; a second film formation process in which a second film is formed to cover the first film that has been formed; and a third film formation process in which, after the second film has been formed, the first film is again vertically formed.

2. The film forming method according to claim 1, wherein the material constituting the first film is different from the material constituting the second film.

3. The film forming method according to claim 1, wherein the material constituting the first film and the material constituting the second film are both carbon-based materials.

4. The film forming method according to claim 2 or 3, wherein the second film forming step and the third film forming step are repeatedly performed.

5. The film forming method according to claim 2 or 3, wherein the second film is thinner than the first film.

6. The film forming method according to claim 2 or 3, wherein the first film is formed in a single step of generating plasma from the film forming gas.

7. The film formation method according to claim 2 or 3, wherein in the first film formation process and the third film formation process, first active species generated from a first gas contained in the film formation gas form the first film, and second active species generated from a second gas contained in the film formation gas etch the first film.

8. The film forming method according to claim 7, wherein the second film has etching resistance to the second active species.

9. The film forming method according to claim 7, wherein the first gas is a hydrocarbon gas.

10. The film forming method according to claim 7, wherein the second gas is hydrogen gas.

11. A film forming method according to claim 2 or 3, further comprising a film removal step of removing at least the second film covering the top of the first film, the film removal step being carried out between the second film forming step and the third film forming step.

12. The film forming method according to claim 2 or 3, wherein the first film is an amorphous carbon-based film, and the second film is an insulating film.

13. The film forming method according to claim 12, wherein the insulating film is made of silicon oxide.

14. A film formation method for placing a substrate having a pattern inside a processing chamber, generating plasma from a film formation gas using high-frequency power, and performing a film formation process on the substrate, the film formation method comprising: a first film formation process for selectively and vertically forming a first film on a top of the pattern; a second film formation process for forming a second film covering the first film formed; and a third film formation process for vertically forming the first film again after the second film has been formed, wherein in the first film formation process and the third film formation process, first active species generated from a first gas contained in the film formation gas form the first film, and second active species generated from a second gas contained in the film formation gas etch the first film, and the sticking coefficient of the second active species is lower than the sticking coefficient of the first active species.

15. The film forming method according to claim 14, wherein the second film has etching resistance to the second activated species.

16. 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 to perform a film formation process on the substrate, the film formation apparatus further comprising a control unit that executes a first film formation process of selectively and vertically forming a first film on the top of the pattern, a second film formation process of forming a second film to cover the formed first film, and a third film formation process of vertically forming the first film again after the second film has been formed.

17. The film forming apparatus according to claim 16, wherein the first film and the second film are made of different materials.

18. The film forming apparatus according to claim 16, wherein the material constituting the first film and the material constituting the second film are both carbon-based materials.

19. The film forming apparatus according to claim 17 or 18, wherein the first film forming process, the second film forming process, and the third film forming process are performed inside the same processing chamber.

Images