Method for forming carbon film and film forming apparatus

Abstract

The present invention relates to a carbon film forming method and a carbon film forming apparatus. In a low-temperature CVD carbon film forming process using halogen as a catalyst, the influence of halogen is reduced, and the productivity and film quality of a carbon film are improved. The present invention is provided with: a process of supplying a carbon-containing gas and a halogen gas to a substrate, and depositing a carbon film on the substrate by chemical vapor deposition; and a process of supplying a gas that reacts with the halogen that constitutes the halogen gas, and reducing the halogen contained in the carbon film. The process of depositing the carbon film and the process of reducing the halogen are repeated as one cycle for a plurality of cycles.

Description

TECHNICAL FIELD

[0001] The present application relates to a carbon film forming method and a carbon film forming apparatus. BACKGROUND

[0002] Conventionally, a carbon film forming method and a carbon film forming apparatus are known in which a carbon film is formed on a substrate (for example, refer to Patent Document 1). In the above-described carbon film forming method, a hydrocarbon-based carbon source gas and a thermal decomposition temperature-lowering gas containing a halogen element are introduced into a processing chamber, and a carbon film is formed by a thermal CVD method using non-plasma.

[0003] PRIOR ART DOCUMENT

[0004] PATENT DOCUMENT

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-33186 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In a low-temperature CVD carbon film forming process using a halogen as a catalyst, the influence of the halogen is reduced, and the productivity and film quality of the carbon film are improved.

[0008] SOLUTION TO THE PROBLEM

[0009] To achieve the above object, a carbon film forming method according to an embodiment of the present application includes the following steps:

[0010] a step of supplying a carbon-containing gas and a halogen gas to a substrate and depositing a carbon film on the substrate by chemical vapor deposition; and

[0011] a step of supplying a gas that reacts with a halogen that constitutes the halogen gas to reduce the halogen contained in the carbon film,

[0012] the step of depositing the carbon film and the step of reducing the halogen are repeated as one cycle for a plurality of cycles.

[0013] EFFECT OF THE INVENTION

[0014] According to the present disclosure, the film formation rate and uniformity of a carbon film can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A cross-sectional view schematically showing an example of a carbon film forming apparatus that can implement the carbon film forming method according to the present application.

[0016] Figure 2 A flowchart showing a flow of the carbon film forming method according to an embodiment of the present application.

[0017] Figure 3A cross-sectional view of a process when a carbon film forming method of an embodiment of the present application is implemented.

[0018] Figure 4 A graph for explaining a reaction pattern when an amino silane-based seed layer is used as a seed layer and a reaction pattern when a boron-based thin film is used as a seed layer.

[0019] Figure 5 A schematic view for showing a state of a substrate after a low-temperature CVD process when a boron-based thin film is used as a base film is implemented.

[0020] Figure 6 A graph for showing results of investigating a relationship between an in-plane film thickness and a composition when a boron-based thin film is used as a base film by XPS.

[0021] Figure 7 A graph for showing a time sequence of an existing carbon film forming method.

[0022] Figure 8 A graph for showing an example of a time sequence of a carbon film forming method of an embodiment of the present disclosure.

[0023] Figure 9 A graph for explaining a mechanism of a halogen reaction gas supply process.

[0024] Figure 10 A graph for showing an example of a carbon film forming method of an embodiment of the present application.

[0025] Figure 11 A graph for showing results of implementing a comparative example and Examples 1 to 3.

[0026] Figure 12 A graph for showing implementation results of the comparative example, Example 2, Example 4, and Example 5.

[0027] Figure 13 A graph for showing implementation results of the comparative example, Example 2, Example 4, and Example 5 in terms of a C / Cl composition ratio.

[0028] Figure 14 A graph for summarizing results of Examples.

[0029] Explanation of Reference Numerals

[0030] 10 substrate

[0031] 20 silicon oxide film

[0032] 30 amorphous silicon film

[0033] 40 seed layer

[0034] 50 carbon film

[0035] 100 film forming apparatus

[0036] 107 exhaust device

[0037] 112 boat

[0038] 130 process gas supply mechanism

[0039] 131a carbon-containing gas supply source

[0040] 131b thermal decomposition temperature-lowering gas supply source

[0041] 131d seed gas supply source

[0042] 150 control unit

[0043] S processing chamber

[0044] W semiconductor wafer DETAILED DESCRIPTION

[0045] Hereinafter, a description will be given of a mode for carrying out the present application with reference to the accompanying drawings.

[0046] [Deposition apparatus]

[0047] Figure 1 A cross-sectional view schematically showing an example of a deposition apparatus of an embodiment of the present disclosure.

[0048] As shown in FIG. 1, the deposition apparatus 100 is configured as a vertical batch-type deposition apparatus, which includes a top-having cylindrical outer wall 101 and a cylindrical inner wall 102 provided inside the outer wall 101. The outer wall 101 and the inner wall 102 are, for example, made of quartz, and an inner side region of the inner wall 102 becomes a processing chamber S in which a plurality of semiconductor wafers (hereinafter, simply referred to as wafers) W as processed bodies are processed at the same time. Figure 1 The outer wall 101 and the inner wall 102 are spaced apart from each other in the horizontal direction with a ring-shaped space 104 therebetween, and are joined to a base material 105 at lower end portions thereof. An upper end portion of the inner wall 102 is spaced apart from a top portion of the outer wall 101 so that an upper side of the processing chamber S communicates with the ring-shaped space 104. The ring-shaped space 104 that communicates with the upper side of the processing chamber S becomes an exhaust passage. A gas supplied to the processing chamber S and diffused flows from a lower side of the processing chamber S to an upper side thereof, and is drawn to the ring-shaped space 104. An exhaust pipe 106 is connected to the ring-shaped space 104, for example, at a lower end portion thereof, and the exhaust pipe 106 is connected to an exhaust device 107. The exhaust device 107 includes a vacuum pump or the like, and is configured to exhaust the processing chamber S and to adjust the pressure in the inside of the processing chamber S to a pressure suitable for processing.

[0049] The outer wall 101 and the inner wall 102 are spaced apart from each other in the horizontal direction with a ring-shaped space 104 therebetween, and are joined to a base material 105 at lower end portions thereof. An upper end portion of the inner wall 102 is spaced apart from a top portion of the outer wall 101 so that an upper side of the processing chamber S communicates with the ring-shaped space 104. The ring-shaped space 104 that communicates with the upper side of the processing chamber S becomes an exhaust passage. A gas supplied to the processing chamber S and diffused flows from a lower side of the processing chamber S to an upper side thereof, and is drawn to the ring-shaped space 104. An exhaust pipe 106 is connected to the ring-shaped space 104, for example, at a lower end portion thereof, and the exhaust pipe 106 is connected to an exhaust device 107. The exhaust device 107 includes a vacuum pump or the like, and is configured to exhaust the processing chamber S and to adjust the pressure in the inside of the processing chamber S to a pressure suitable for processing.

[0050] A heating device 108 is provided on the outside of the outer wall 101 in a manner so as to surround the periphery of the processing chamber S. The heating device 108 is adjusted in a manner so as to make the temperature of the inside of the processing chamber S a temperature suitable for processing, and simultaneously heats a plurality of wafers W.

[0051] The lower portion of the processing chamber S communicates with an opening 109 provided in the base material 105. A manifold 110 shaped in a cylindrical form, for example, of stainless steel is connected to the opening 109 by means of an O-ring or the like sealing member 111. The lower end portion of the manifold 110 becomes an opening, and a boat 112 is inserted into the inside of the processing chamber S by means of this opening. The boat 112 is, for example, of quartz, and has a plurality of supports 113. A groove, not shown, is formed in the supports 113, and a plurality of substrates to be processed are temporarily supported by this groove. Thus, the boat 112 can hold a plurality of, for example, 50 to 150, wafers W as substrates to be processed in a plurality of stages. By inserting the boat 112 on which a plurality of wafers W are placed into the inside of the processing chamber S, a plurality of wafers W can be accommodated in the inside of the processing chamber S.

[0052] The boat 112 is placed on a stage 115 by means of a heat insulating cylinder 114 of quartz. The stage 115 is supported on a rotating shaft 117, for example, which penetrates a lid portion 116 of stainless steel. The lid portion 116 opens and closes the opening of the lower end portion of the manifold 110. A magnetic fluid seal 118, for example, is provided in the penetrating portion of the lid portion 116, and rotatably supports the rotating shaft 117 in airtight fashion. Further, between the peripheral portion of the lid portion 116 and the lower end portion of the manifold 110, a sealing member 119 formed of an O-ring, for example, is interposed, and serves to maintain the airtightness of the inside of the processing chamber S. The rotating shaft 117 is mounted at the front end of an arm 120, which is supported by a lifting mechanism (not shown), such as a boat elevator. Thus, the boat 112 and the lid portion 116 or the like are integrally lifted in the vertical direction, and are inserted into or extracted from the processing chamber S.

[0053] The film formation device 100 has a processing gas supply mechanism 130 which supplies a gas used in processing to the inside of the processing chamber S.

[0054] The processing gas supply mechanism 130 of the present example includes a hydrocarbon-based carbon source gas supply source 131a, a pyrolysis temperature lowering gas supply source 131b, an inactive gas supply source 131c, and a seed gas supply source 131d.

[0055] A carbon-containing gas supply source 131a is connected to a gas supply port 134a via a flow controller (MFC) 132a and an on / off valve 133a. Similarly, a pyrolysis temperature-reducing gas supply source 131b is connected to a gas supply port 134b via a flow controller (MFC) 132b and an on / off valve 133b, an inactive gas supply source 131c is connected to a gas supply port 134c via a flow controller (MFC) 132c and an on / off valve 133c, and a seed gas supply source 131d is connected to a gas supply port 134d via a flow controller (MFC) 132d and an on / off valve 133d. Gas supply ports 134a to 134d are respectively arranged to penetrate the sidewall of the manifold 110 in a horizontal direction, so that the supplied gas diffuses toward the interior of the processing chamber S located above the manifold 110.

[0056] The carbon-containing gas supplied by the carbon-containing gas supply source 131a is the gas used for forming a carbon film by low-pressure CVD. As long as it contains carbon, various gases can be used, such as hydrocarbon-based carbon source gases.

[0057] As a source gas for hydrocarbons, examples include: [List of gases would be inserted here]

[0058] C n H 2n+2

[0059] C m H 2m

[0060] C m H 2m-2

[0061] The gaseous hydrocarbon with at least one molecular formula (where n is a natural number greater than or equal to 1 and m is a natural number greater than or equal to 2).

[0062] In addition, as a hydrocarbon-based carbon source gas, it can also contain

[0063] Benzene gas (C6H6).

[0064] As the molecular formula C n H 2n+2 Examples of hydrocarbons shown include:

[0065] Methane gas (CH4)

[0066] Ethane gas (C2H6)

[0067] Propane gas (C3H8)

[0068] Butane gas (C4H) 10 (Also includes other isomers)

[0069] Pentane gas (C5H) 12: also including other isomers)

[0070] and the like.

[0071] As the hydrocarbon represented by the molecular formula C m H 2m As the hydrocarbon represented by the molecular formula C

[0072] Ethylene gas (C2H4)

[0073] Propylene gas (C3H6: also including other isomers)

[0074] Butylene gas (C4H8: also including other isomers)

[0075] Pentene gas (C5H 10 : also including other isomers)

[0076] and the like.

[0077] As the hydrocarbon represented by the molecular formula C m H 2m-2 As the hydrocarbon represented by the molecular formula C

[0078] Acetylene gas (C2H2)

[0079] Propyne gas (C3H4: also including other isomers)

[0080] Butadiene gas (C4H6: also including other isomers)

[0081] Isoprene gas (C5H8: also including other isomers)

[0082] and the like.

[0083] As the thermal decomposition temperature gas supplied from the thermal decomposition temperature gas supply source 131b, a gas containing a halogen element is used. The gas containing a halogen element has the following function of lowering the thermal decomposition temperature of the hydrocarbon-based carbon source gas and lowering the film formation temperature of the carbon film based on the thermal CVD method, according to its catalytic function.

[0084] Among the halogen elements, fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) are contained. The gas containing a halogen element can be a halogen element simple substance, that is, simple fluorine (F2) gas, simple chlorine (Cl2) gas, simple bromine (Br2) gas, and simple iodine (I2) gas, or a compound containing them, but the halogen element simple substance has the following advantages: no heat for thermal decomposition is required, and the effect of lowering the thermal decomposition temperature of the hydrocarbon-based carbon source gas is high. Furthermore, among the above halogen elements, fluorine has high reactivity, and there is a possibility of damaging the surface roughness and flatness of the carbon film formed. Therefore, as the halogen element, chlorine, bromine, and iodine other than fluorine are preferable. Among these, from the viewpoint of operability, chlorine is preferable.

[0085] The gas supplied from the halogen reactive gas supply source 131c contains NH3, H2, N2, etc. of an element that reacts with halogen. That is, these gases have the property of reacting with halogen to be vaporized, and are gases that can react with halogen on the surface of the carbon film or in the film to remove halogen on the surface of the carbon film or in the carbon film. Of these, NH3 has the highest reactivity with halogen in the process of low-temperature CVD, and NH3 is preferably used as the halogen reactive gas. However, the halogen reactive gas is not limited to ammonia, and, for example, H2 and / or N2 can be used in the case of a higher-temperature process.

[0086] The non-reactive gas supplied from the non-reactive gas supply source 131d is used as a purge gas, a dilution gas. As the non-reactive gas, for example, N2 gas, Ar gas, or the like can be used.

[0087] The seed gas supplied from the seed gas supply source 131e is used to form a seed layer for improving adhesion between the substrate and the carbon film on the substrate prior to the formation of the carbon film. A boron-based thin film is used as the seed layer. As the boron-based thin film, boron or boron-rich boron nitride of stoichiometric composition is preferable.

[0088] As the seed gas, a gas containing a boron-containing gas is used. As the boron-containing gas used as the seed gas, a borane-based gas typified by diborane (B2H6) gas, boron trichloride (BC13) gas can be used. Of these, B2H6 gas is suitable. In the case of a boron-based thin film being boron nitride, a nitriding gas is used in addition to the boron-containing gas. As the nitriding gas, ammonia (NH3) gas can be suitably used. In addition to the nitriding gas, an organic amine gas, a hydrazine gas can be used. In the case of using a nitriding gas, a nitriding gas supply source is preferably provided separately, and the nitriding gas is supplied into the processing chamber S from a separate gas supply port by means of a separate flow rate controller (MFC) and an on-off valve.

[0089] The film formation apparatus 100 has a control section 150. The control section 150 has, for example, a process controller 151 including a microprocessor (computer), and the process controller 151 performs control of each of the constituent sections of the film formation apparatus 100. The process controller 151 is connected to a user interface 152 and a storage section 153.

[0090] The user interface 152 has an input section including a touch panel display, a keyboard, or the like for inputting an operation of an operator for managing the film formation apparatus 100, and a display section including a display for visualizing the operation of the film formation apparatus 100 and displaying the same.

[0091] The storage section 153 stores a so-called process recipe program including a control program for implementing various processes performed in the film formation apparatus 100 under the control of the process controller 151, and a program for causing each constituent section of the film formation apparatus 100 to perform a process in accordance with a processing condition. The process recipe program is stored in a storage medium in the storage section 153. The storage medium can be a hard disk, a semiconductor memory, or a mobile medium such as a CD-ROM, a DVD, or a flash memory. Alternatively, the process recipe program can be transmitted from another apparatus via a dedicated line, as appropriate.

[0092] The process recipe program is read from the storage section 153 under the instruction of an operator from the user interface 152, as appropriate, and the process controller 151 causes the film formation apparatus 100 to perform a process in accordance with the read process recipe program.

[0093] <Method for forming carbon film> Next, an embodiment of the method for forming a carbon film of the present application, which is performed by the film formation apparatus shown in

[0094] Figure 1 Next, an embodiment of the method for forming a carbon film of the present application, which is performed by the film formation apparatus shown in

[0095] Figure 2 A flowchart showing the flow of the method for forming a carbon film of the embodiment of the present application, and Figure 3 A process cross-sectional view at this time.

[0096] First, for example, a plurality of wafers W, for example, 50 to 150, each of which is formed with a silicon film 20 on a silicon substrate 10 formed with a prescribed structure (not shown) at the upper portion, and further formed with an amorphous silicon film 30, as shown in (a) of FIG. 1, are mounted on a boat 112, and the boat 112 is inserted into a processing chamber S in the film formation apparatus 100 from the lower side, thereby carrying the plurality of wafers W into the processing chamber S (step 10). Then, the lower end opening of the manifold 110 is closed with a lid section 116, thereby forming a sealed space in the processing chamber S. In this state, the processing chamber S is evacuated, and the wafer temperature is raised by controlling the supply of electric power to the heating device 108 while maintaining a prescribed reduced pressure atmosphere, and a state in which the boat 112 is rotated is formed. Figure 3 In this state, initially, a gas containing a boron-containing gas as a seed gas is supplied from a seed gas supply source 131e to be adsorbed to the wafer surface (the surface of the amorphous silicon film 3 as a base), thereby forming a seed layer 4 for improving adhesion (step 20, (b) of FIG. 1).

[0097] Figure 3

[0098] ​​In Step 2, the boron-containing gas supplied from the self-seed gas supply source 131e is a borane-based gas typified by diborane (B2H6) gas, boron trichloride (BC13) gas, and the like, and forms a boron film as the seed layer 40.

[0099] As the boron film, a boron film formed of boron element, or a boron-nitrogen film that is stoichiometrically composed or boron-rich can be suitably used. In the case of the boron film, as the gas containing the boron-containing gas, only the above-described boron-containing gas can be used to form a film by pyrolysis. On the other hand, in the case of the boron-nitrogen film, as the gas containing the boron-containing gas, a nitrogenizing gas such as ammonia (NH3) gas, an organic amine gas, a hydrazine gas, or the like is used in addition to the above-described boron-containing gas. As the boron-containing gas, B2H6gas is preferred, and as the nitrogenizing gas, NH3gas is preferred.

[0100] From the viewpoint of being able to form a film and having good controllability, the temperature of the wafer W at the time of forming the seed layer 40 in Step 2 is preferably 200 to 300°C.

[0101] After the seed layer 40 is formed in Step 2, the inside of the processing chamber S is purged, and film formation processing of the carbon film 50 is performed by thermal CVD without using plasma assistance (Step 3, Figure 3 (c) of FIG. 1).

[0102] In the film formation processing of the carbon film based on thermal CVD in Step 3, a hydrocarbon-based carbon source gas containing a hydrocarbon, such as C4H6gas, is supplied as a carbon-containing gas from the hydrocarbon-based carbon source gas supply source 131a to the processing chamber S, and a halogen-containing gas, such as Cl2gas, is supplied as a pyrolysis temperature-lowering gas from the pyrolysis temperature-lowering gas supply source 131b, the hydrocarbon-based carbon source gas is heated to a prescribed temperature lower than the pyrolysis temperature thereof, pyrolysis is performed, and a carbon film 50 is formed on the surface of the wafer W by thermal CVD.

[0103] Thus, by using the pyrolysis temperature-lowering gas at the time of carbon film formation, the pyrolysis temperature of the hydrocarbon-based carbon source gas is lowered in accordance with the catalytic effect thereof, and a carbon film is formed at a temperature lower than the pyrolysis temperature of the carbon source gas. That is, the temperature of 650°C or higher required for carbon film formation in the conventional thermal CVD method using a hydrocarbon-based carbon source gas can be lowered to a much lower temperature, and carbon film formation can be performed at a low temperature of about 300°C or lower.

[0104] Furthermore, by using Cl2 gas as a halogen-containing gas constituting the gas that lowers the pyrolysis temperature, hydrogen (H) can be extracted from hydrocarbon carbon source gases (CxHy), such as ethylene gas (C2H4), causing the ethylene gas to decompose. That is, during carbon film formation, halogen elements such as chlorine (Cl) attract H from the surface, for example, being degassed as HCl. Therefore, H leaves and dangling bonds are formed, which are beneficial for film formation. In addition, by using a product formed by adsorbing aminosilane-based gases as a seed layer between the substrate and the carbon film, the adhesion between the substrate and the carbon film can be improved.

[0105] However, when using a silicon film as a substrate, even if aminosilane-based gases are adsorbed as a seed layer, the adhesion of a relatively thin carbon film with a thickness of about 10 nm will deteriorate to the point of causing film peeling when the film formation temperature is above 350°C.

[0106] That is, when Cl2 gas is used as the gas to lower the pyrolysis temperature, due to the high reactivity of Cl, depending on the substrate material, even if an aminosilane seed layer is present, it will still be as... Figure 4 As shown in (a), Cl is more likely to terminate dangling bonds, thereby reducing the number of dangling bond activation sites that become adsorption sites for carbon, resulting in C adsorption hindrance. Therefore, even a relatively thin film thickness of about 10 nm causes a deterioration in adhesion.

[0107] In contrast, this embodiment uses a boron-based thin film as the seed layer 40. Therefore, due to the difference in reactivity with the silicon film of the substrate, deterioration of adhesion is less likely to occur. That is, by using a boron-based thin film as the seed layer 4, reactivity with Cl can be suppressed, such as... Figure 4 As shown in (b), Cl becomes less likely to terminate dangling bonds. Therefore, the number of dangling bond activation sites that become adsorption sites for carbon is less likely to decrease, and the deterioration of the carbon film's adhesion due to adsorption hindrance is less likely to occur. Therefore, regardless of the substrate, a carbon film with good adhesion can be formed. Furthermore, by utilizing a seed layer formed from a boron-based thin film, damage caused by Cl can also be suppressed. From the viewpoint of obtaining this effect, the thickness of the boron-based thin film constituting the seed layer 40 is preferably in the range of 0.5 to 3.0 nm.

[0108] However, it is known that even when implementing this process of using boron-based thin films as the substrate film, chlorine remains in the carbon film, and the Cl termini hinder the growth of the carbon film.

[0109] Figure 5 This is a schematic diagram illustrating the state of a substrate after a low-temperature CVD process when using a boron-based thin film as the substrate. It is believed that, compared to using a silicon film as the substrate, although there is a tendency for Cl-terminals to be suppressed when using a boron-based thin film as the substrate, Cl-terminals still remain.

[0110] Figure 6 FIG. 1 is a graph showing the results of investigating the relationship between the in-plane film thickness and the composition when a boron-based film is used as a base film using XPS (X-ray photoelectron spectroscopy).

[0111] Figure 6 (a) of FIG. 1 is a graph showing the Cl composition, Figure 6 (b) of FIG. 1 is a graph showing the carbon film thickness. Figure 6 (c) of FIG. 1 is a graph showing the carbon composition, Figure 6 (d) of FIG. 1 is a graph showing the C / Cl ratio. Note that, Figure 6 In (a) to (d) of FIG. 1, zero indicates the center of the wafer W, and 150 mm indicates the edge.

[0112] As shown in (a) and (b) of FIG. 1, in the carbon film thickness, the edge is thicker than the center portion, and in the Cl composition, the center side is higher and the edge side is lower. Further, as shown in (c) of FIG. 1, in the carbon composition, the center side is higher and the edge side is lower. Further, as shown in (d) of FIG. 1, in the C / Cl ratio, the edge side is higher and the center side is lower. Figure 6 Figure 6 Figure 6

[0113] From these results, it was found that the carbon film thickness is low in the center portion where the Cl composition is high, and the carbon film thickness is high in the edge portion where the Cl composition is low. That is, it is considered that the presence of Cl hinders the growth of the carbon film.

[0114] Figure 7 FIG. 2 is a graph showing the time series of a film formation method of a conventional carbon film. As shown in (a) of FIG. 2, in the film formation method of the conventional carbon film, a carbon-containing gas (C4H6) and a halogen gas (Cl2) are continuously supplied. Figure 7

[0115] FIG. 3 is a graph showing an example of the time series of a film formation method of a carbon film of an embodiment of the present disclosure. As shown in (a) of FIG. 3, in the film formation method of the embodiment of the present disclosure, after a carbon-containing gas and a halogen gas are supplied, the supply of the carbon-containing gas and the halogen gas is temporarily stopped, and a gas that is gasified by reacting with the halogen gas is supplied. Figure 8 In (a) of FIG. 3, C4H6 is supplied as the carbon-containing gas, and Cl2 is supplied as the halogen gas. Further, NH3 is supplied as the gas that reacts with the halogen gas. Note that, Figure 8 The times shown in (a) of FIG. 3 are merely examples, and are not intended to be limited thereto. They are intended to be shown for the purpose of showing an example of the time ratio. Figure 8 Figure 8

[0116] ​​​​​The ammonia reacts with the Cl-terminated end to become NH4Cl, and the Cl-terminated end can be removed. Thus, the ammonia is supplied as a reaction gas for Cl removal. Note that the ammonia can also react with halogens other than Cl, i.e., F, Br, and I. In the case where a halogen gas other than chlorine is used, the ammonia can also be used as a gas for the halogen reaction.

[0117] Further, H2and N2may also be used as a gas for reaction with halogens. However, the reactivity of ammonia with halogens is the highest in a low-temperature CVD process at 3000C or lower, and halogens can be effectively removed.

[0118] Note that the exhaust / sweeping process can also be performed before and after the ammonia is supplied. This is a process for removing C4H6and Cl2or NH3existing in the processing chamber S, and is not essential, and can be provided as needed.

[0119] Note that the exhaust process is a process for increasing the opening of a valve for exhaust and increasing the exhaust amount, and the sweeping process is a process for supplying an inactive gas to the wafer W. Either one of the exhaust process and the sweeping process can be performed, or both can be performed.

[0120] The inactive gas can use N2, Ar, He, or the like. For example, N2can be used as a sweeping gas.

[0121] The exhaust / sweeping process is performed in order to smoothly perform switching of the gas in the processing chamber S, and for example, the ammonia can be supplied immediately after the low-temperature CVD process, or the carbon-containing gas and the halogen gas can be supplied immediately after the ammonia is supplied.

[0122] Note that the supply of ammonia can be performed a plurality of times for a short period, and this will be described later.

[0123] Further, after the deposition of the carbon film is completed, the processing chamber S is exhausted by the exhaust device 107, and N2gas as a sweeping gas is supplied from the inactive gas supply source 131c to the processing chamber S, the processing chamber S is swept, and then the processing chamber S is returned to the atmospheric pressure, the wafer boat 112 is lowered, and the wafer W is carried out.

[0124] Figure 9 Fig. 2 is a diagram for explaining the mechanism of the halogen reaction gas supply process. Figure 9 (a) of Fig. 2 is a diagram showing the dangling bond active site as an adsorption site of the carbon-containing gas and the hydrogen-terminated end and the chlorine-terminated end provided on the seed layer 40. That is, a diagram showing the state of the substrate before the deposition of the carbon film.

[0125] Figure 9 (b) of Fig. 2 is a diagram showing the surface state of the substrate in the carbon film deposition process. As shown in (b) of Fig. 2, the carbon-containing gas is supplied to the substrate, and the carbon-containing gas is adsorbed on the dangling bond active site on the surface of the substrate. Figure 9As shown in (b), in the low-temperature CVD process, chlorine is supplied as a catalyst in addition to C4H6 as the carbon-containing gas, and thus, chlorine remains in the carbon film. As a result, on the surface of the carbon film 50, in addition to the dangling bond active sites, hydrogen and chlorine terminals remain. The remaining chlorine reacts with the dangling bond active sites as shown in (c) and (d), and thus, the growth of the carbon film 50 is hindered. Figure 6

[0126] Figure 9 (c) is a view showing an example of a halogen reaction gas supply process. In the halogen reaction gas supply process, a gas that can be vaporized by reacting with a halogen is supplied to the wafer W. The gas that can be vaporized by reacting with a halogen is, for example, ammonia gas. The ammonia reacts with the chlorine terminal to become NH4CI and is vaporized, and the chlorine in the carbon film 50 is removed. Thus, by removing the Cl terminal, the H terminal is increased. As a result, the quality improvement and the productivity improvement of the carbon film 50 can be facilitated. Note that the reaction formula of chlorine removal is shown in formula (1). As a result, chlorine and hydrogen can be removed from the chlorine terminal and the hydrogen terminal, and an adsorption site of the carbon-containing gas is formed.

[0127] Cl + H + NH3→ NH4CI (1)

[0128] Thus, according to the carbon film formation method of the present embodiment, the chlorine concentration in the carbon film 50 can be reduced, and the film formation rate and the quality of the carbon film 50 can be improved.

[0129] [Embodiment]

[0130] The carbon film formation method of the present embodiment shown in (a) was implemented by setting the time and the number of repetitions of the carbon film deposition process and the chlorine reaction gas supply process, respectively. Figure 8 The embodiment will be described below.

[0131] Figure 10 (a) is a view showing an example of a carbon film formation method of the present embodiment. In the carbon film deposition process, C4H6 and Cl2 are used, and in the halogen reaction gas supply process, Cl2 is used.

[0132] As shown in (b), C4H6 and Cl2 were supplied to form the carbon film for 80 minutes, and a process in which ammonia was not supplied was implemented as a comparative example. Figure 10 In Example 1, the carbon film formation time was set to 10 minutes, the ammonia supply time was set to 5 minutes, and the carbon film deposition process and the halogen reaction gas supply process were repeated twice. The total process time was 30 minutes, and the total time of the carbon film deposition process was 20 minutes.

[0133]

[0134] ​​In Example 2, the carbon film formation time was 10 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition process and the halogen reaction gas supply process were performed for 5 cycles. The total process time was 75 minutes, and the total time for the carbon film deposition process was 50 minutes.

[0135] In Example 3, the carbon film formation time was 10 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition process and the halogen reaction gas supply process were performed for 8 cycles. The total process time was 120 minutes, and the total time for the carbon film deposition process was 80 minutes.

[0136] In Example 4, the carbon film formation time was 5 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition process and halogen reaction gas supply process were performed for 10 cycles. The total process time was 150 minutes, and the total time for the carbon film deposition process was 50 minutes.

[0137] In Example 5, the carbon film formation time was 2.5 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition process and halogen reaction gas supply process were performed for 20 cycles. The total process time was 150 minutes, and the total time for the carbon film deposition process was 50 minutes.

[0138] Figure 11 The figure shows the results of implementing comparative examples and Examples 1 to 3. Figure 11 In the diagram, Ref represents a comparative example, 2cyc represents Example 1, 5cyc represents Example 2, and 8cyc represents Example 3, respectively. Furthermore, the horizontal axis represents the radial position [mm] with the center of wafer W at zero, and the vertical axis represents the film thickness.

[0139] like Figure 11 As shown, the carbon film thickness in Example 3 is the highest, while the carbon film thickness in the comparative example is the same as that in Example 2. The comparative example uses a carbon film deposition process of 80 minutes, while Example 2 uses a carbon film deposition process of 50 minutes. Therefore, it can be seen that the time for forming a carbon film is reduced to 5 / 8, and the film formation rate becomes 1.6 (=8 / 5) times.

[0140] Therefore, in Example 1, where the carbon film deposition process takes only 20 minutes, the film thickness is reduced compared to the comparative example. However, in Example 2, where the carbon film deposition process takes only 50 minutes, it is the same as the comparative example. In Example 3, where the carbon film deposition process takes the same time as the comparative example (80 minutes), the film formation rate is significantly higher than that of the comparative example.

[0141] Thus, according to Figure 11 This indicates that increasing the number of cycles in the repeated carbon film deposition process and the halogen reaction gas supply process can significantly improve the carbon film formation rate.

[0142] Figure 12Figures illustrating the implementation results of comparative examples, Example 2, Example 4, and Example 5. Figure 12 In (a), the horizontal axis represents the position of the wafer W in the radius coordinate system, and the vertical axis represents the carbon film thickness at the position of the wafer W in the radius coordinate system. The carbon film deposition process in Example 2 takes 10 minutes per cycle, the carbon film deposition process in Example 4 takes 5 minutes per cycle, and the carbon film deposition process in Example 5 takes 2.5 minutes per cycle. The total time for the carbon film deposition process in all examples is 50 minutes. Therefore, the influence of the carbon film deposition time per cycle can be studied.

[0143] like Figure 12 As shown in (a), the film thickness of Example 5, which has the shortest film formation time per cycle, is the largest. The film thickness of Example 4, which has the shortest film formation time per cycle, is the second largest. The film thickness of the comparative examples is the largest. The film thickness of Example 2, which has the longest film formation time per cycle, becomes the smallest.

[0144] It should be noted that the film formation time of the comparative example was 80 minutes, while the film formation time of Examples 2, 4, and 5 was 50 minutes. Therefore, the film thickness of Example 2 was smaller than that of the comparative example, and the film formation rate of Example 2 was not slower than that of the comparative example.

[0145] Comparing Examples 2, 4, and 5, it is shown that, with the total film-forming time remaining the same, shortening the film-forming time per cycle and increasing the number of cycles is effective. Therefore, based on... Figure 12 (a) indicates that a process that shortens the time per cycle of the carbon film deposition process and the halogen reaction gas supply process and increases the number of cycles is more effective than a process with fewer cycles and longer time per cycle.

[0146] Figure 12 (b) is a method in which the film thickness becomes 1 with respect to the center. Figure 12 The result of (a) is a graph standardized from each embodiment. From this, the uniformity of the film thickness can be determined.

[0147] like Figure 12 As shown in (b), for the film thickness of Example 5, the film thickness is most uniform from the center to the periphery of wafer W. In Example 4, compared with Example 5, the fluctuation at the periphery is larger, but smaller than that of Example 2. In addition, the fluctuation of Example 2 is smaller than that of the comparative example.

[0148] Therefore, by Figure 12 (b) shows that the film formation mode with short film formation time and high number of cycles not only has excellent film formation rate, but also excellent film thickness uniformity.

[0149] Figure 13 The graph shows the implementation results of Comparative Example, Example 2, Example 4 and Example 5 with C / Cl composition ratio. Figure 13(a) is a graph showing the implementation results of Comparative Example, Example 2, Example 4 and Example 5 with the vertical axis being the C / Cl composition ratio and the horizontal axis being the radius coordinate of the wafer W.

[0150] It can be seen that, Figure 13 (a) shows the relationship with Figure 12 Similar to (a), the C / Cl ratio increases sequentially in the order of Example 5, Example 4, Comparative Example, and Example 2, but the difference in C / Cl ratio between Examples 5, 4, and 2 becomes more significant than that between Example 2. That is, it can be seen that if a film-forming process with a higher number of cycles is implemented, the carbon concentration improves, the Cl concentration decreases, and the purity of the carbon film increases.

[0151] Figure 13 (b) is a graph showing the C / Cl composition ratio obtained by standardizing the results of each implementation so that the C / Cl composition ratio at the center of wafer W is 1.

[0152] It can be seen that, Figure 13 (b) is also with Figure 12 In example (b), which involves a higher number of cycles, a more uniform C / Cl composition ratio was obtained compared to examples with a lower number of cycles. This indicates that when NH3 is supplied at smaller intervals, the in-plane fluctuations caused by the adsorption of carbon at the Cl-terminus disappear, improving the uniformity of the carbon film.

[0153] Figure 14 A diagram illustrating the results of the embodiments. Figure 14 In the comparative examples, Example 2, Example 4 and Example 5, the contents of the carbon film formation process and the implementation results of film formation rate and in-plane uniformity are shown.

[0154] like Figure 12 , 13 As explained, the carbon film deposition process in the comparative example was 80 minutes, while that in Examples 2, 4, and 5 was 50 minutes. Furthermore, the NH3 annealing time in the halogen reaction gas supply process was set to 5 minutes for all cases, with the number of cycles set to 5, 10, and 20 cycles respectively.

[0155] Under the above conditions, the film formation rates were as follows: 0.38 nm / min for Comparative Example, 0.56 nm / min for Example 2, 0.74 nm / min for Example 4, and 0.90 nm / min for Example 5. The film formation rate improved with increasing cycle number. Furthermore, regarding in-plane uniformity, the rates were 4.6 for Comparative Example, 4.3 for Example 2, 2.8 for Example 4, and 1.6 for Example 5, and the in-plane uniformity also improved with increasing cycle number.

[0156] Thus, by using carbon-containing gas as the halogen gas for the carbon film formation process, and then using a gas such as ammonia that reacts with halogens to vaporize for the dehalogenation process, the film formation rate and uniformity can be improved by shortening the cycle of the carbon film formation process and the dehalogenation process and increasing the number of cycles.

[0157] It should be noted whether or not to set Figure 8 The vacuum / purging process is arbitrary, as is the carbon-containing gas, but hydrocarbon gases are preferred. In addition to chlorine, fluorine, iodine, and bromine can also be used as halogen gases. Furthermore, in addition to ammonia, hydrogen and nitrogen can be used as halogen reactants. However, in low-temperature CVD processes below 400°C, ammonia is preferred from a reactivity point of view. In high-temperature CVD processes between 500°C and 800°C, hydrogen and nitrogen can also be used as halogen reactants.

[0158] The preferred embodiments and examples of this disclosure have been described in detail above. However, this disclosure is not limited to the above-described embodiments and examples. Various modifications and substitutions can be made to the above-described embodiments and examples without departing from the scope of this disclosure.

Claims

1. A film forming method of a carbon film, comprising the steps of: forming a seed layer on a substrate by supplying a boron-containing gas; supplying a carbon-containing gas and a halogen gas to the substrate and depositing a carbon film on the seed layer by chemical vapor deposition; and supplying a gas that reacts with a halogen that constitutes the halogen gas to reduce the halogen contained in the carbon film. The gas that reacts with the halogen gas is ammonia gas. The number of cycles is five or more. The step of depositing a carbon film on the substrate and the step of reducing the halogen are performed at a temperature of 400°C or lower. After the seed layer is formed, the process of depositing the carbon film and the process of reducing the halogen are repeated as one cycle for a plurality of cycles, wherein The halogen gas is any one of chlorine gas, fluorine gas, bromine gas, and iodine gas.

2. The carbon film formation method according to claim 1, wherein The carbon-containing gas is a hydrocarbon gas.

3. The carbon film formation method according to claim 1 or 2, wherein, The hydrocarbon gas is C4H6 gas.

4. The carbon film formation method according to claim 1 or 2, wherein The step of supplying a purge gas to the substrate is provided between the step of depositing the carbon film and the step of reducing the halogen and between the step of reducing the halogen and the step of depositing the carbon film.

5. The carbon film formation method according to claim 1 or 2, wherein The purge gas is an inactive gas.

6. The carbon film formation method according to claim 1 or 2, wherein The inactive gas is nitrogen gas.

7. The carbon film forming method according to claim 6, wherein The step of supplying the purge gas is performed while performing vacuum exhaust in a processing chamber provided with the substrate.

8. The carbon film formation method according to claim 1 or 2, wherein 12. A film forming apparatus, comprising: a processing chamber; a substrate holding device provided in the processing chamber; a processing gas supply portion that supplies a carbon-containing gas and a halogen gas to the substrate holding device; and a halogen reaction gas supply portion that supplies a gas that reacts with a halogen that constitutes the halogen gas, wherein the film forming apparatus further comprises a control portion that performs the following steps: a step of forming a seed layer on a substrate by supplying a boron-containing gas; a step of supplying a carbon-containing gas and a halogen gas to the substrate and depositing a carbon film on the seed layer by chemical vapor deposition; and a step of supplying a gas that reacts with a halogen that constitutes the halogen gas to reduce the halogen contained in the carbon film.

9. The carbon film forming method according to claim 8, wherein The gas that reacts with the halogen gas is ammonia gas.

10. The carbon film forming method according to claim 9, wherein The number of cycles is five or more.

11. The carbon film formation method according to claim 9 or 10, wherein The step of depositing a carbon film on the substrate and the step of reducing the halogen are performed at a temperature of 400°C or lower. The halogen gas is any one of chlorine gas, fluorine gas, bromine gas, and iodine gas. The carbon-containing gas is a hydrocarbon gas. The hydrocarbon gas is C4H6 gas. The step of supplying a purge gas to the substrate is provided between the step of depositing the carbon film and the step of reducing the halogen and between the step of reducing the halogen and the step of depositing the carbon film. The purge gas is an inactive gas. The inactive gas is nitrogen gas. The step of supplying the purge gas is performed while performing vacuum exhaust in a processing chamber provided with the substrate. ​ ​ ​

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