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

Abstract

[Problem] To suppress the generation of constrictions of a carbon-based film while suppressing the generation of overhangs of the carbon-based film when selectively forming the carbon-based film on a top part of a pattern. [Solution] According to the present invention, when a wafer W having a trench is held in a chamber of a film formation device, and a carbon-based film is selectively formed on a top part of the trench by generating plasma from a film formation gas composed of only acetylene gas, argon gas, and hydrogen gas by using high-frequency power, film formation processing under overhang generation suppression conditions and film formation processing under constriction generation suppression conditions are executed once each, and the addition rate of the hydrogen gas in the film formation gas under the overhang generation suppression conditions is higher than the addition rate of the hydrogen gas in the film formation gas under the constriction generation suppression conditions.

Description

Carbon-based film formation method and film formation apparatus

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

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

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

[0004] The technology according to the present disclosure suppresses the occurrence of overhangs in the carbon-based film and also suppresses the occurrence of constrictions in the carbon-based film when selectively depositing the carbon-based film on the top of a pattern.

[0005] One aspect of the technology disclosed herein is a method for forming a carbon-based film, comprising a film formation process in which a substrate having a pattern is placed inside a processing chamber, and a plasma is generated from a film formation gas containing at least a hydrocarbon gas and a hydrogen gas using high-frequency power to form a carbon-based film on the substrate, the film formation process including a first film formation process and a second film formation process, and the addition rate of the hydrogen gas in the film formation gas in the first film formation process is higher than the addition rate of the hydrogen gas in the film formation gas in the second film formation process.

[0006] According to the technology disclosed herein, when a carbon-based film is selectively formed on the top of a pattern, it is possible to suppress the occurrence of overhangs in the carbon-based film and also suppress the occurrence of constrictions in the carbon-based film.

[0007] 1 is a cross-sectional view schematically illustrating an example of the configuration of a film formation apparatus according to an embodiment of the technology disclosed herein. FIG. 2 is a diagram simply illustrating an example of the configuration of an evaluation apparatus. FIG. 3 is a partially enlarged cross-sectional view showing an example of a wafer to be subjected to a film formation process in the evaluation apparatus of FIG. 2. FIG. 4 is a partially enlarged cross-sectional view showing an example of a wafer to which a film formation process has been performed in the evaluation apparatus of FIG. 2. FIG. 5 is a partially enlarged cross-sectional view showing an example of a wafer when the addition rate of hydrogen gas in the film formation gas is changed when each wafer is subjected to a film formation process in the evaluation apparatus of FIG. 2. FIG. 6 is a partially enlarged cross-sectional view showing an example of a wafer when the addition rate of hydrogen gas in the film formation gas is changed when each wafer is subjected to a film formation process in the evaluation apparatus of FIG. 2. FIG. 7 is a partially enlarged cross-sectional view showing an example of a wafer when the addition rate of hydrogen gas in the film formation gas is changed when each wafer is subjected to a film formation process in the evaluation apparatus of FIG. 2. FIG. 8 is a partially enlarged cross-sectional view showing an example of a wafer when the addition rate of hydrogen gas in the film formation gas is changed when each wafer is subjected to a film formation process in the evaluation apparatus of FIG. 2. 6A and 6B are enlarged cross-sectional views showing an example of a wafer when the addition rate of hydrogen gas in the film formation gas is changed when a film formation process is performed on each wafer in the evaluation apparatus of FIG. 2. FIG. 6B is a flow chart showing an example of a carbon-based film formation method according to the present embodiment. FIG. 6C is a flow chart showing an example of a carbon-based film formation method according to the present embodiment. FIG. 6D is a flow chart showing an example of a carbon-based film formation method according to the present embodiment. FIG. 6E is a flow chart showing an example of a carbon-based film formation method according to the present embodiment. FIG. 6F is a flow chart showing an example of a carbon-based film formation method according to the present embodiment. FIG. 6G is a flow chart showing an example of a carbon-based film formation method according to the present embodiment. FIG. 6H is a flow chart showing an example of a carbon-based film formation method according to the present embodiment.3 is a partially enlarged cross-sectional view showing an example of a wafer when the temperature of the mounting table is changed when a film formation process is performed on each wafer in the evaluation apparatus of FIG. 2. FIG. 4 is a flowchart showing a modified example of the carbon-based film formation method according to the present embodiment. FIG. 5 is a flowchart showing a modified example of the carbon-based film formation method according to the present embodiment. FIG. 6 is a process diagram showing an example of selectively forming a carbon-based film on the top of a metal protrusion as a wiring layer protruding from an interlayer insulating film. FIG. 7 is a process diagram showing an example of selectively forming a carbon-based film on the top of a metal protrusion as a wiring layer protruding from an interlayer insulating film. FIG. 8 is a process diagram showing an example of selectively forming a carbon-based film on the top of a metal protrusion as a wiring layer protruding from an interlayer insulating film. FIG. 9 is a process diagram showing an example of selectively forming a carbon-based film on the top of a metal protrusion as a wiring layer protruding from an interlayer insulating film. FIG. 10 is a process diagram showing an example of selectively forming a carbon-based film on the top of a metal protrusion as a wiring layer protruding from an interlayer insulating film.

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

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

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

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

[0012] An upper electrode 20 is disposed on the ceiling of the chamber 11 so as to face the mounting table 14, and an insulating member 21 is disposed between the chamber 11 and the upper electrode 20. The upper electrode 20 includes a base member 22, a top plate 23, and an intermediate member 24. The base member 22, the top plate 23, and the intermediate member 24 are made of conductive materials, such as aluminum. The top plate 23, the intermediate member 24, and the base member 22 are disposed in this order from below, and the top plate 23 and the base member 22 are separated by the substantially annular intermediate member 24 to form a gas diffusion space 25 therebetween. A gas introduction 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 allows 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 acetylene (C ２ H ２ ) gas (hydrocarbon gas), inert gas argon (Ar) gas and hydrogen (H ２By using this film formation gas, the film formation apparatus 100 generates hydrocarbon plasma from the film formation gas during the film formation process, and forms a carbon-based film using hydrocarbon ions and hydrocarbon radicals in the hydrocarbon plasma.

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

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

[0016] 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 is reduced. 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, and the sheath voltage that contributes to the acceleration of ions in the plasma decreases. 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 maximum value of the ion energy imparted from the plasma to the wafer W placed on the mounting table 14 is controlled to, for example, 200 eV or less.

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

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

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

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

[0021] The present applicant has used an evaluation apparatus 38 having a similar structure to the film formation apparatus 100 of Fig. 1 to perform a film formation process on a wafer W and confirmed the film formation state of a carbon-based film 45 on the wafer W. The configuration of the evaluation apparatus 38 is shown in a simplified form in Fig. 2, and the configuration other than that shown is the same as the configuration of the film formation apparatus 100.

[0022] As shown in FIG. 2 , in the evaluation device 38, a conductive ring member 39 is disposed inside the chamber 11 to surround the mounting table 14 (lower electrode 17). The ring member 39 is directly grounded, while the lower electrode 17 is grounded via an impedance circuit 35. The impedance circuit 35 applies a high impedance to the electrical path 37. Therefore, the impedance of the electrical path 37 is higher than the impedance of another electrical path 40 connecting the ring member 39 to ground. As a result, similar to the film formation apparatus 100, the maximum value of ion energy imparted to the wafer W placed on the mounting table 14 is controlled to, for example, 200 eV or less. Therefore, in the evaluation device 38, even if low-frequency power having a frequency of 450 kHz is supplied to the upper electrode 20, the ion energy imparted to the wafer W can be reduced, and the evaluation device 38 can reproduce the film formation process performed in the film formation apparatus 100.

[0023] 3 is a partially enlarged cross-sectional view showing an example of a wafer W to be subjected to a film forming process in the evaluation device 38 shown in FIG. 2. As shown in FIG. 3, the wafer W has a silicon oxide (SiO ２ A silicon oxide layer 42 is formed on the silicon oxide layer 42, and a silicon layer 43 is formed on the silicon layer 42. A pattern, for example, a groove-shaped trench 44 is formed in the silicon layer 43. The trench 44 penetrates the silicon layer 43, and the silicon oxide layer 42 is exposed at the bottom of the trench 44.

[0024] The applicant performed a film formation process on the wafer W shown in FIG. 3 in the evaluation apparatus 38 using a film formation gas consisting solely of acetylene gas, argon gas, and hydrogen gas. The applicant set the flow rates of acetylene gas, argon gas, and hydrogen gas in the film formation gas to 11 sccm, 330 sccm, and 45 sccm, respectively. The pressure inside the chamber 11 was set to 470 mTorr, and low-frequency power of 450 kHz was supplied from the high-frequency power supply 32 to the upper electrode 20 at 300 W to generate plasma from the film formation gas. The temperature of the mounting table 14 was set to 320° C.

[0025] By such a film formation process, the carbon-based film 45 is selectively formed on the top of the trench 44 in the wafer W. The reason why the carbon-based film 45 is selectively formed on the top of the trench 44 is described in the specification of Japanese Patent Application No. 2023-200333 filed by the present applicant.

[0026] 4 is a partially enlarged cross-sectional view showing an example of a wafer W subjected to a film formation process in the evaluation apparatus 38 shown in FIG. 4 . As shown in FIG. 4 , although a carbon-based film 45 is selectively formed on the top of the trench 44, necking of the carbon-based film 45 was observed near the boundary between the silicon layer 43 and the carbon-based film 45. Here, if such necking occurs during etching using the carbon-based film 45 as a mask film, the carbon-based film 45 may be consumed in an unexpected manner during etching, potentially preventing the desired shape from being transferred to the layer to be etched. Therefore, when selectively forming the carbon-based film 45 on the top of the trench 44, it is necessary to suppress the occurrence of necking of the carbon-based film 45.

[0027] In order to confirm the effect of the hydrogen gas addition rate in the film formation gas on the film formation form of the carbon-based film 45, the applicant performed film formation processing on multiple wafers W in the evaluation device 38 while changing the hydrogen gas addition rate, and confirmed the film formation form of the carbon-based film 45 on each wafer W.

[0028] 5A to 5F are enlarged partial cross-sectional views showing examples of wafers W when the addition rate of hydrogen gas in the film formation gas is changed when the film formation process is performed on each wafer W in the evaluation apparatus 38 of FIG. 2. At this time, the film formation process was performed on each wafer W under the same conditions as the film formation process performed on the wafer W of FIG. 4, except for the addition rate of hydrogen gas.

[0029] FIG. 5A shows the formation of the carbon-based film 45 when the hydrogen gas flow rate is set to 8 sccm (addition rate: 2.3%), FIG. 5B shows the formation of the carbon-based film 45 when the hydrogen gas flow rate is set to 13 sccm (addition rate: 3.7%), FIG. 5C shows the formation of the carbon-based film 45 when the hydrogen gas flow rate is set to 18 sccm (addition rate: 5.0%), FIG. 5D shows the formation of the carbon-based film 45 when the hydrogen gas flow rate is set to 20 sccm (addition rate: 5.5%), FIG. 5E shows the formation of the carbon-based film 45 when the hydrogen gas flow rate is set to 40 sccm (addition rate: 10.5%), and FIG. 5F shows the formation of the carbon-based film 45 when the hydrogen gas flow rate is set to 45 sccm (addition rate: 11.7%).

[0030] 5A to 5F, when the flow rate of hydrogen gas was 40 sccm or more, constriction occurred in the carbon-based film 45. However, when the flow rate of hydrogen gas was 20 sccm, constriction hardly occurred in the carbon-based film 45, and when the flow rate of hydrogen gas was 18 sccm or less, constriction did not occur in the carbon-based film 45.

[0031] On the other hand, when the flow rate of hydrogen gas was 20 sccm or less, an overhang occurred, which is a phenomenon in which the carbon-based film 45 grows laterally so as to block the trench 44. In particular, when the flow rate of hydrogen gas was 13 sccm or less, the carbon-based film 45 also adhered to the bottom and sidewalls of the trench 44. However, when the flow rate of hydrogen gas was 40 sccm or more, the overhang of the carbon-based film 45 did not occur, and the carbon-based film 45 did not adhere to the bottom and sidewalls of the trench 44.

[0032] Therefore, it has been found that, when the flow rate of hydrogen gas is reduced to lower the additive rate of hydrogen gas in the deposition gas, the occurrence of constriction in the carbon-based film 45 can be suppressed, but there is a risk of overhanging in the carbon-based film 45. It has also been found that, when the flow rate of hydrogen gas is increased to raise the additive rate of hydrogen gas in the deposition gas, the occurrence of overhanging in the carbon-based film 45 can be suppressed, but there is a risk of constriction in the carbon-based film 45. The applicant has inferred the mechanism described below as the reason why the occurrence of constriction and overhanging in the carbon-based film 45 is affected by the flow rate of hydrogen gas.

[0033] The deposition gas generates not only hydrocarbon plasma but also hydrogen plasma, and the hydrogen radicals contained in the hydrogen plasma etch the carbon-based film 45 isotropically. When the flow rate of hydrogen gas is reduced, the carbon-based film 45 is less likely to be isotropically etched. Therefore, the isotropic growth of the carbon-based film 45 is not inhibited. Therefore, the carbon-based film 45 grows not only anisotropically (upward in FIGS. 5A to 5F ) but also isotropically (laterally in FIGS. 5A to 5F ), resulting in overhangs. Furthermore, although the constriction of the carbon-based film 45 is thought to occur when the carbon-based film 45 is scraped from the lateral direction in the figures, when the carbon-based film 45 is less likely to be isotropically etched, the carbon-based film 45 is not scraped from the lateral direction in the figures. Therefore, when the flow rate of hydrogen gas is reduced, overhangs of the carbon-based film 45 are more likely to occur, but the occurrence of constrictions of the carbon-based film 45 is suppressed.

[0034] On the other hand, when the flow rate of hydrogen gas increases and the number of hydrogen radicals increases, isotropic etching of the carbon-based film 45 becomes dominant, inhibiting isotropic growth of the carbon-based film 45, causing the carbon-based film 45 to grow primarily anisotropically (upward in FIGS. 5A to 5F). When isotropic etching of the carbon-based film 45 becomes dominant, the carbon-based film 45 is removed laterally in the figures. Therefore, when the flow rate of hydrogen gas increases, the occurrence of overhangs in the carbon-based film 45 is suppressed, but constrictions in the carbon-based film 45 become more likely to occur.

[0035] The technology of the present disclosure is based on this finding. In the following description, a condition under which an overhang in the carbon-based film 45 is likely to occur but the occurrence of a constriction in the carbon-based film 45 is suppressed is referred to as a "constriction occurrence suppression condition." Furthermore, a condition under which a constriction in the carbon-based film 45 is likely to occur but the occurrence of an overhang in the carbon-based film 45 is suppressed is referred to as an "overhang occurrence suppression condition." In this embodiment, by combining the constriction occurrence suppression condition and the overhang occurrence suppression condition, the occurrence of an overhang in the carbon-based film 45 is suppressed while also suppressing the occurrence of a constriction in the carbon-based film 45.

[0036] As described above, when the hydrogen gas addition rate in the deposition gas is changed, the condition where the hydrogen gas addition rate is set to 10.5% or more (hydrogen gas flow rate of 40 sccm) corresponds to the condition for suppressing overhang generation, and the condition where the hydrogen gas addition rate is set to 5.5% or less (hydrogen gas flow rate of 20 sccm) corresponds to the condition for suppressing constriction generation.

[0037] 6A and 6B are flowcharts showing an example of a carbon-based film deposition method according to this embodiment. The carbon-based film deposition method (deposition process) of FIGS. 6A and 6B is realized by the processor of the control unit 34 executing a corresponding control program. In the carbon-based film deposition method according to this embodiment, a deposition process under the overhang generation suppression condition and a deposition process under the constriction generation suppression condition are each performed once. Here, a carbon-based film deposition method in which a deposition process under the overhang generation suppression condition is performed first will be described ( FIG. 6A ).

[0038] First, in the film formation apparatus 100, a wafer W having a plurality of trenches 44 formed in a silicon layer 43 is loaded into the chamber 11 of the film formation apparatus 100, and the wafer W is placed on the mounting table 14. Next, as shown in FIG. 6A , supply of a film formation gas consisting only of acetylene gas, argon gas, and hydrogen gas into the chamber 11 begins (step S61), and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, the film formation gas is excited by an electric field generated between the upper electrode 20 and the mounting table 14, and becomes high-density plasma. Hydrocarbon plasma (mainly hydrocarbon ions) contained in this high-density plasma causes a carbon-based film 45 to begin to be formed on the top of the trenches 44.

[0039] When the carbon-based film 45 is formed, the film formation process is first performed under conditions for suppressing overhang generation by increasing the hydrogen gas content in the film formation gas (step S62) (first film formation step). At this time, the hydrogen gas content is set to, for example, 10.5% or more.

[0040] After the film formation process is performed for a predetermined time under the overhang suppression condition, the film formation process is performed under the constriction suppression condition by reducing the hydrogen gas addition rate in the film formation gas (step S63) (second film formation process). At this time, the hydrogen gas addition rate is set to, for example, 5.5% or less.

[0041] Next, after the film formation process is performed for a predetermined time under the conditions for suppressing the occurrence of constrictions, the supply of the film formation gas is stopped (step S64), and the process ends. Note that in both steps S62 and S63, the temperature of the mounting table 14 is kept constant during the film formation process.

[0042] In this film formation method, a constriction occurs in the carbon-based film 45 formed on the top of the trench 44 due to the film formation process under the overhang generation suppression conditions. However, the carbon-based film 45 grows isotropically in the subsequent film formation process under the constriction generation suppression conditions, thereby eliminating the constriction in the carbon-based film 45. Furthermore, in the film formation process under the constriction generation suppression conditions, the carbon-based film 45 grows isotropically in the constriction in the carbon-based film 45, so the carbon-based film 45 does not grow to the extent that it blocks the trench 44. Therefore, an overhang in the carbon-based film 45 does not occur. In other words, in the film formation method of FIG. 6A , when the carbon-based film 45 is selectively formed on the top of the trench 44, the occurrence of an overhang in the carbon-based film 45 can be suppressed while the occurrence of a constriction in the carbon-based film 45 can be suppressed.

[0043] Next, a carbon-based film deposition method in which a deposition process is first performed under conditions for suppressing the occurrence of constrictions will be described ( FIG. 6B ). As shown in FIG. 6B , step S61 is first performed, and when the carbon-based film 45 is deposited, the deposition process is performed under conditions for suppressing the occurrence of constrictions by initially lowering the hydrogen gas addition rate in the deposition gas (step S65) (second deposition step). At this time, the hydrogen gas addition rate is set to, for example, 5.5% or less.

[0044] After the film formation process is performed for a predetermined time under the constriction suppression condition, the film formation process is performed under the overhang suppression condition by increasing the hydrogen gas addition rate in the film formation gas (step S66) (first film formation step). At this time, the hydrogen gas addition rate is set to, for example, 10.5% or more.

[0045] Next, after the film formation process is performed for a predetermined time under the overhang suppression conditions, the supply of the film formation gas is stopped (step S64), and the process ends. Note that in both steps S65 and S66, the temperature of the mounting table 14 is kept constant during the film formation process.

[0046] In this film formation method, film formation processing under conditions for suppressing the occurrence of constrictions causes overhangs in the carbon-based film 45 formed on the top of the trench 44. However, in the subsequent film formation processing under conditions for suppressing the occurrence of overhangs, isotropic etching of the carbon-based film 45 becomes dominant, and the carbon-based film 45 is removed laterally, thereby eliminating the overhangs in the carbon-based film 45.

[0047] Furthermore, in the film formation process under the overhang generation suppression conditions, the isotropic etching of the carbon-based film 45 removes the overhang of the carbon-based film 45, and therefore the isotropic etching of the carbon-based film 45 does not proceed to the extent that a constriction occurs in the carbon-based film 45. Therefore, no constriction occurs in the carbon-based film 45. In other words, even in the film formation method of FIG. 6B , when the carbon-based film 45 is selectively formed on the top of the trench 44, the occurrence of an overhang in the carbon-based film 45 can be suppressed while the occurrence of a constriction in the carbon-based film 45 can be suppressed.

[0048] The allocation between the execution time of the film formation process under the overhang generation suppression condition and the execution time of the film formation process under the constriction generation suppression condition varies depending on what is prioritized in the carbon-based film 45. For example, if priority is given to reliably suppressing the occurrence of overhangs even if some constriction is tolerated, the execution time of the film formation process under the overhang generation suppression condition is made longer than the execution time of the film formation process under the constriction generation suppression condition. Also, for example, if priority is given to reliably suppressing the occurrence of constrictions even if some overhangs are tolerated, the execution time of the film formation process under the constriction generation suppression condition is made longer than the execution time of the film formation process under the overhang generation suppression condition.

[0049] Fig. 7 is a partially enlarged cross-sectional view showing an example of a wafer W when the carbon-based film deposition method of Fig. 6A and Fig. 6B is performed. When the carbon-based film 45 is selectively deposited on the top of the trench 44 by the carbon-based film deposition method of Fig. 6A and Fig. 6B, it was confirmed that no overhang or constriction occurs in the carbon-based film 45, as shown in Fig. 7.

[0050] In either case where the film formation process was first performed under the overhang generation suppression conditions or where the film formation process was first performed under the constriction generation suppression conditions, the carbon-based film 45 did not adhere to the bottom or side walls of the trench 44.

[0051] The applicant has inferred the reason for this when a film formation process is first performed under the overhang generation suppression conditions, as explained below. That is, in the process first performed under the overhang generation suppression conditions, the carbon-based film 45 grows mainly upward. Then, in the process subsequently performed under the constriction generation suppression conditions, the carbon-based film 45 grown upward shields the trench 44 from the hydrocarbon plasma that attempts to enter the trench 44 obliquely. As a result, almost no hydrocarbon plasma enters the trench 44, and the carbon-based film 45 does not adhere to the bottom or sidewalls of the trench 44.

[0052] The present applicant has also inferred the mechanism described below when a film formation process is first performed under the constriction generation suppression conditions. That is, in the process performed first under the constriction generation suppression conditions, hydrocarbon plasma enters trench 44, causing carbon-based film 45 to adhere to the bottom and sidewalls of trench 44. However, in the process performed subsequently under the constriction generation suppression conditions, isotropic etching by hydrogen radicals removes carbon-based film 45 from the bottom and sidewalls of trench 44, and ultimately, carbon-based film 45 does not adhere to the bottom and sidewalls of trench 44.

[0053] 6A and 6B, the conditions for suppressing overhangs and constrictions are achieved by changing the hydrogen gas addition rate (flow rate of hydrogen gas) in the film formation gas. However, the conditions for suppressing overhangs and constrictions may also be achieved by changing other conditions.

[0054] In this regard, in order to confirm the effect of the temperature of the mounting table 14 on the film formation form of the carbon-based film 45, the applicant performed a film formation process on multiple wafers W in the evaluation device 38 while changing the temperature of the mounting table 14, and confirmed the film formation form of the carbon-based film 45 on each wafer W.

[0055] 8A to 8F are enlarged partial cross-sectional views showing an example of the wafer W when the temperature of the mounting table 14 is changed during film formation processing on each wafer W in the evaluation device 38 of Fig. 2. At this time, the film formation processing on each wafer W was performed under the same conditions as those for the wafer W of Fig. 4, except for the temperature of the mounting table 14 and the flow rate of hydrogen gas.

[0056] 8A shows the formation of the carbon-based film 45 when the temperature of the mounting table 14 is set to 400° C. and the flow rate of hydrogen gas is set to 8 sccm (addition rate: 2.3%). FIG. 8B shows the formation of the carbon-based film 45 when the temperature of the mounting table 14 is set to 370° C. and the flow rate of hydrogen gas is set to 8 sccm. FIG. 8C shows the formation of the carbon-based film 45 when the temperature of the mounting table 14 is set to 370° C. and the flow rate of hydrogen gas is set to 15 sccm (addition rate: 4.2%). FIG. 8D shows the formation of the carbon-based film 45 when the temperature of the mounting table 14 is set to 320° C. and the flow rate of hydrogen gas is set to 20 sccm (addition rate: 5.5%). 8E shows the state of the carbon-based film 45 formed when the temperature of the mounting table 14 is set to 320° C. and the flow rate of hydrogen gas is set to 40 sccm (addition rate: 10.5%). Fig. 8F shows the state of the carbon-based film 45 formed when the temperature of the mounting table 14 is set to 320° C. and the flow rate of hydrogen gas is set to 45 sccm (addition rate: 11.7%).

[0057] 8A to 8F, as the temperature of the mounting table 14 increases, the carbon-based film 45 adheres more easily to the bottom and sidewalls of the trench 44, but constriction of the carbon-based film 45 is less likely to occur. On the other hand, as the temperature of the mounting table 14 decreases, the carbon-based film 45 adheres more easily to the bottom and sidewalls of the trench 44, but constriction of the carbon-based film 45 is more likely to occur. Therefore, an increase in the temperature of the mounting table 14 corresponds to the condition for suppressing constriction. Furthermore, as the temperature of the mounting table 14 decreases, the carbon-based film 45 is scraped off the bottom and sidewalls of the trench 44, and therefore, a decrease in the temperature of the mounting table 14 is considered to correspond to the condition for suppressing overhang occurrence.

[0058] 9A and 9B are flowcharts showing a modified example of the carbon-based film deposition method according to the present embodiment. The carbon-based film deposition method of FIG. 9A and FIG. 9B is also realized by the processor of the control unit 34 executing a corresponding control program.

[0059] 9A and 9B, a film formation process under the overhang generation suppression condition and a film formation process under the constriction generation suppression condition are each performed once. Here, a description will be given of a modified carbon-based film formation method in which a film formation process under the overhang generation suppression condition is first performed (FIG. 9A).

[0060] 9A , first, in the film formation apparatus 100, a wafer W having a plurality of trenches 44 formed in a silicon layer 43 is loaded into the chamber 11 of the film formation apparatus 100, and the wafer W is placed on the mounting table 14. Next, supply of a film formation gas consisting only of acetylene gas, argon gas, and hydrogen gas into the chamber 11 begins (step S61), and high-frequency power having a frequency of 40 MHz is supplied to the upper electrode 20. At this time, a carbon-based film 45 begins to be formed on the top of the trenches 44.

[0061] When the carbon-based film 45 is formed, the temperature of the mounting table 14 is first lowered to perform the film forming process under the condition for suppressing the occurrence of overhangs (step S91). At this time, the temperature of the mounting table 14 is set to 320°C.

[0062] After the film formation process is performed for a predetermined time under the overhang suppression condition, the temperature of the mounting table 14 is increased and the film formation process is performed under the constriction suppression condition (step S92). At this time, the temperature of the mounting table 14 is set to 370° C. or higher.

[0063] Next, after the film formation process is performed for a predetermined time under the conditions for suppressing the occurrence of constriction, the supply of the film formation gas is stopped (step S64), and the process ends. Note that in both steps S91 and S92, it is preferable to keep the flow rate of the hydrogen gas constant during the film formation process.

[0064] Even with this film formation method, a film formation process under the overhang generation suppression conditions causes a constriction in the carbon-based film 45 formed on the top of the trench 44, but a subsequent film formation process under the constriction generation suppression conditions eliminates the constriction in the carbon-based film 45. Furthermore, in the film formation process under the constriction generation suppression conditions, the carbon-based film 45 grows in the constriction in the carbon-based film 45, so the carbon-based film 45 does not grow to the extent that it blocks the trench 44. Therefore, an overhang in the carbon-based film 45 does not occur. In other words, in the modified film formation method of FIG. 9A , when the carbon-based film 45 is selectively formed on the top of the trench 44, it is possible to suppress the occurrence of an overhang in the carbon-based film 45 while also suppressing the occurrence of a constriction in the carbon-based film 45.

[0065] Next, a modified example of the carbon-based film deposition method in which the deposition process is first performed under the constriction suppression condition will be described ( FIG. 9B ). In this case, as shown in FIG. 9B , step S61 is first performed, and when the carbon-based film 45 is deposited, the temperature of the mounting table 14 in the deposition gas is first increased to perform the deposition process under the constriction suppression condition ( step S93 ). In this case, the temperature of the mounting table 14 is set to 370° C. or higher.

[0066] After the film formation process is performed for a predetermined time under the constriction suppression condition, the temperature of the mounting table 14 is lowered and the film formation process is performed under the overhang suppression condition (step S94). At this time, the temperature of the mounting table 14 is set to 320° C.

[0067] Next, after the film formation process is performed for a predetermined time under the overhang suppression conditions, the supply of the film formation gas is stopped (step S64), and the process ends. Note that in both steps S93 and S94, it is preferable to keep the flow rate of the hydrogen gas constant during the film formation process.

[0068] In this film formation method, an overhang occurs in the carbon-based film 45 formed on the top of the trench 44 due to the film formation process under conditions that suppress the occurrence of constrictions, but the overhang of the carbon-based film 45 is eliminated by the subsequent film formation process under conditions that suppress the occurrence of overhangs.

[0069] Furthermore, in the film formation process under the overhang generation suppression conditions, the overhang of the carbon-based film 45 is removed, and therefore the etching of the carbon-based film 45 does not proceed to the extent that a constriction occurs in the carbon-based film 45. Therefore, no constriction occurs in the carbon-based film 45. In other words, even in the modified film formation method of FIG. 9B , when the carbon-based film 45 is selectively formed on the top of the trench 44, the occurrence of an overhang of the carbon-based film 45 can be suppressed while the occurrence of a constriction in the carbon-based film 45 can be suppressed.

[0070] Under the conditions for suppressing the occurrence of constrictions, the temperature of the mounting table 14 is set to 370° C. or higher, but from the viewpoint of suppressing crystallization of the carbon-based film 45, it is preferable that the temperature of the mounting table 14 be set to 430° C. or lower.

[0071] 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.

[0072] For example, in the above-described embodiment, the overhang generation suppression condition and the constriction generation suppression condition are achieved by changing only one of the hydrogen gas addition rate or the temperature of the mounting table 14. However, the overhang generation suppression condition and the constriction generation suppression condition may be achieved by simultaneously changing both the hydrogen gas addition rate and the temperature of the mounting table 14. In this case, the overhang generation suppression condition involves increasing the hydrogen gas addition rate and decreasing the temperature of the mounting table 14, while the constriction generation suppression condition involves decreasing the hydrogen gas addition rate and increasing the temperature of the mounting table 14.

[0073] 6A and 6B and modifications of the carbon-based film deposition method shown in Figures 9A and 9B are applied when selectively depositing a carbon-based film 45 on the top of a trench 44. However, modifications of the carbon-based film deposition method shown in Figures 6A and 6B and modifications of the carbon-based film deposition method shown in Figures 9A and 9B may also be applied when selectively depositing a carbon-based film 45 on the top of a hole as a pattern.

[0074] Furthermore, in the above-described film formation process, a hydrocarbon gas (acetylene gas) is used as the hydrogen compound gas contained in the film formation gas, but other hydrogen compound gases, such as silane gas, which is a silicon hydrogen compound gas, or borane gas, which is a boron hydrogen compound gas, may be used instead of the hydrocarbon gas.

[0075] 6A and 6B and the modified examples of the carbon-based film forming method shown in Figures 9A and 9B are not limited to the film forming apparatus 100 shown in Figure 1. Any film forming apparatus that can reduce the energy of ions incident on the wafer W can implement the carbon-based film forming method shown in Figures 6A and 6B and the modified examples of the carbon-based film forming method shown in Figures 9A and 9B.

[0076] Furthermore, in the above-described embodiment, the carbon-based film 45 is formed on the silicon layer 43, but the underlying layer of the carbon-based film 45 is not limited to a silicon layer. For example, the underlying layer of the carbon-based film 45 may be 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 an oxide film, a single layer of a nitride film, or a wiring layer made of a metal.

[0077] 10A to 10F are process diagrams illustrating an example of selectively forming a carbon-based film 45 on the tops of metal protrusions that serve as wiring layers protruding from an interlayer insulating film. In Fig. 10A, first, on a wafer W, a metal is buried in each trench of an interlayer insulating film 46 having a plurality of trenches formed therein, to form a wiring layer 47. At this time, the upper surfaces of the interlayer insulating film 46 and the wiring layer 47 are planarized by CMP (Chemical Mechanical Polishing) or the like (Fig. 10A).

[0078] Next, the wafer W is subjected to ashing to selectively remove the interlayer insulating film 46, thereby forming a recessed shape in the interlayer insulating film 46. At this time, the wiring layer 47 protrudes relative to the interlayer insulating film 46, forming metal protrusions 47a (FIG. 10B).

[0079] Thereafter, in the film formation apparatus 100, the wafer W is placed inside the chamber 11 of the film formation apparatus 100, and the carbon-based film formation method of Figures 6A and 6B and the modified carbon-based film formation method of Figures 9A and 9B are performed. At this time, a carbon-based film 45 in which the occurrence of constrictions and overhangs is suppressed is selectively formed on the tops of the metal protrusions 47a of the wiring layer 47 (Figure 10C).

[0080] Next, an insulating film is formed on the wafer W to grow an interlayer insulating film 46 so as to fill the recessed shape. At this time, the upper surfaces of the interlayer insulating film 46 and the carbon-based film 45 are also planarized by CMP or the like (FIG. 10D).

[0081] Thereafter, the wafer W is subjected to ashing to completely remove the carbon-based film 45. At this time, the upper part of the interlayer insulating film 46 is also removed at the same time, but because the ashing rate of the carbon-based film 45 is higher than the ashing rate of the interlayer insulating film 46, a recessed shape is formed in the wiring layer 47 (FIG. 10E).

[0082] Next, via holes 47b are formed by reforming the interlayer insulating film 46 and adding a portion of the wiring layer 47 (FIG. 10F). At this time, reforming the interlayer insulating film 46 ensures a sufficient separation distance L between the via holes 47b and the wiring layer 47 adjacent to the via holes 47b.

[0083] This application claims priority based on Japanese Patent Application No. 2024-028618, filed February 28, 2024, the entire contents of which are incorporated herein by reference.

[0084] W wafer 11 chamber 14 mounting table 32 high frequency power supply 44 trench 45 carbon-based film

Claims

1. A method for forming a carbon-based film, comprising a film-forming process in which a substrate having a pattern is placed inside a processing chamber, and a plasma is generated from a film-forming gas containing at least a hydrocarbon gas and a hydrogen gas using high-frequency power to form a carbon-based film on the substrate, the film-forming process comprising a first film-forming process and a second film-forming process, and the addition rate of the hydrogen gas in the film-forming gas in the first film-forming process is higher than the addition rate of the hydrogen gas in the film-forming gas in the second film-forming process.

2. The carbon-based film forming method according to claim 1, wherein in the film forming steps, the first film forming step is performed first, and then the second film forming step is performed.

3. The carbon-based film forming method according to claim 1, wherein in the film forming step, the second film forming step is performed first, and then the first film forming step is performed.

4. The carbon-based film forming method according to claim 1, wherein the hydrogen gas addition rate in the film forming gas in the first film forming step is 10.5% or more, and the hydrogen gas addition rate in the film forming gas in the second film forming step is 5.5% or less.

5. The carbon-based film deposition method according to claim 1, wherein in the film deposition step, the substrate is placed on a temperature-adjustable mounting table, and the temperature of the mounting table in the first film deposition step and the temperature of the mounting table in the second film deposition step are set to the same temperature.

6. The carbon-based film forming method according to claim 5, wherein the temperature of the stage in the first film forming step and the second film forming step is set to any temperature between 320°C and 430°C.

7. The method for forming a carbon-based film according to claim 1, wherein in the film forming step, the carbon-based film is selectively formed on the top of the pattern, in the first film forming step, overhangs in the formed carbon-based film are eliminated, and in the second film forming step, constrictions in the formed carbon-based film are eliminated.

8. The method for forming a carbon-based film according to claim 1, wherein the hydrocarbon gas is acetylene gas.

9. The method for forming a carbon-based film according to claim 1, wherein the film-forming gas further contains an inert gas.

10. The method for forming a carbon-based film according to claim 1, wherein the pattern is either a trench or a hole.

11. The carbon-based film deposition method according to claim 1, wherein in the film deposition step, the maximum value of the ion energy of the plasma is controlled to 200 eV or less.

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, and which uses high-frequency power to generate plasma from a film formation gas containing at least a hydrocarbon gas and a hydrogen gas to form a carbon-based film on the substrate, further comprising a control unit, which executes a film formation process including a first film formation process and a second film formation process, and wherein the addition rate of the hydrogen gas in the film formation gas in the first film formation process is higher than the addition rate of the hydrogen gas in the film formation gas in the second film formation process.

13. A method for depositing a carbon-based film, comprising a film-forming process in which a substrate having a pattern is placed inside a processing chamber and placed on a temperature-adjustable mounting table, and high-frequency power is used to generate plasma from a film-forming gas containing at least a hydrocarbon gas and a hydrogen gas, thereby depositing a carbon-based film on the substrate, wherein the film-forming process includes a first film-forming process and a second film-forming process, and the temperature of the mounting table in the first film-forming process is lower than the temperature of the mounting table in the second film-forming process.

14. The carbon-based film forming method according to claim 13, wherein in the film forming steps, the first film forming step is performed first, and then the second film forming step is performed.

15. The carbon-based film forming method according to claim 13, wherein in the film forming step, the second film forming step is performed first, and then the first film forming step is performed.

16. The carbon-based film forming method according to claim 13, wherein the temperature of the stage in the first film forming step is 320°C.

17. The carbon-based film forming method according to claim 13, wherein the temperature of the stage in the second film forming step is 370°C or higher and 430°C or lower.

18. The carbon-based film deposition method according to claim 13, wherein the flow rate of the hydrocarbon gas contained in the deposition gas is kept constant in the first deposition step and the second deposition step.

19. A film formation apparatus comprising a processing chamber with a reduced pressure inside and a temperature-adjustable mounting table disposed inside the processing chamber, wherein a substrate having a pattern is placed inside the processing chamber and mounted on the mounting table, and wherein high-frequency power is used to generate plasma from a film formation gas containing at least a hydrocarbon gas and a hydrogen gas, thereby forming a carbon-based film on the substrate, further comprising a control unit, wherein the control unit executes a film formation process including a first film formation process and a second film formation process, and wherein the temperature of the mounting table in the first film formation process is lower than the temperature of the mounting table in the second film formation process.

Images