Carbon film forming method and film forming apparatus

Abstract

To improve the productivity and film quality of a carbon film by reducing the effects of halogen, in a low temperature CVD carbon film deposition process using halogen as a catalyst.SOLUTION: A carbon film deposition method includes the steps of: supplying a carbon-containing gas and a halogen gas to a substrate to deposit a carbon film on the substrate by using chemical vapor deposition; and supplying a gas that reacts with halogens constituting the halogen gas to reduce the halogens contained in the carbon film. A cycle including the step of depositing the carbon film and the step of reducing the halogens is repeated a plurality of times.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for forming a carbon film. [Background technology]

[0002] Conventionally, a carbon film forming method and a carbon film forming apparatus for forming a carbon film on a substrate have been known (for example, see Patent Document 1). In the carbon film forming method, a hydrocarbon carbon source gas and a pyrolysis temperature lowering gas containing a halogen element are introduced into the processing chamber, and a carbon film is formed by a non-plasma thermal CVD method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-33186 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a low-temperature CVD carbon film formation process using halogen as a catalyst, the effect of halogen is reduced to improve the productivity and film quality of the carbon film. [Means for solving the problem]

[0005] In order to achieve the above object, a method for forming a carbon film according to one aspect of the present invention includes a step of supplying a boron-containing gas to form a boron-based seed layer on a substrate, and a step of supplying a carbon-containing gas and a halogen gas to the substrate and depositing the boron-based seed layer on the substrate by chemical vapor deposition. Rika a step of depositing a carbon film; and a step of supplying a gas that reacts with the halogen constituting the halogen gas to reduce the halogen contained in the carbon film, After the step of forming the boron-based seed layer on the substrate is performed, the step of forming the boron-based seed layer is omitted. The step of depositing the carbon film and the step of reducing the halogen constitute one cycle, and the cycles are repeated multiple times. Effect of the Invention

[0006] According to the present disclosure, it is possible to improve the deposition rate and uniformity of the carbon film. [Brief description of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view that illustrates an example of a film formation apparatus capable of carrying out a film formation method of the present invention. [Diagram 2] FIG. 2 is a flow diagram showing a flow of a carbon film forming method according to an embodiment of the present invention. [Diagram 3] 1A to 1C are cross-sectional views showing steps in carrying out a carbon film forming method according to an embodiment of the present invention. [Figure 4] FIG. 13 is a diagram for explaining a comparison between a reaction model in the case where an aminosilane-based seed layer is used as the seed layer and a reaction model in the case where a boron-based thin film is used as the seed layer. [Diagram 5] FIG. 1 is a model diagram showing the state of a substrate after a low-temperature CVD process is performed when a boron-based thin film is used as an undercoat film. [Figure 6] FIG. 13 is a diagram showing the results of an XPS study of the relationship between the in-plane film thickness and the composition when a boron-based thin film is used as an undercoat film. [Figure 7] FIG. 1 is a diagram showing a sequence of a conventional method for forming a carbon film. [Figure 8] 1 is a diagram showing an example of a sequence of a carbon film forming method according to an embodiment of the present disclosure. [Figure 9] FIG. 4 is a diagram for explaining the mechanism of a halogen reactive gas supplying step. [Figure 10] 1A to 1C are diagrams showing examples of a carbon film forming method according to an embodiment of the present invention; [Figure 11] FIG. 1 is a diagram showing the results of carrying out a comparative example and examples 1 to 3. [Figure 12] FIG. 1 shows the results of a comparative example, an embodiment 2, an embodiment 4, and an embodiment 5. [Figure 13]FIG. 1 is a diagram showing the results of a comparative example, an embodiment 2, an embodiment 4, and an embodiment 5 in terms of a C / Cl composition ratio. [Figure 14] FIG. 1 is a diagram showing the results of the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] [Film forming equipment] FIG. 1 is a cross-sectional view that illustrates a schematic example of a film forming apparatus according to an embodiment of the present disclosure.

[0010] 1, the film forming apparatus 100 is configured as a vertical batch-type film forming apparatus, and includes a cylindrical outer wall 101 with a ceiling, and a cylindrical inner wall 102 provided inside the outer wall 101. The outer wall 101 and the inner wall 102 are made of, for example, quartz, and the area inside the inner wall 102 forms a processing chamber S in which a plurality of semiconductor wafers (hereinafter simply referred to as wafers) W, which are objects to be processed, are processed at once.

[0011] The outer wall 101 and the inner wall 102 are separated from each other in the horizontal direction with an annular space 104 between them, and their lower ends are joined to a base material 105. The upper end of the inner wall 102 is separated from the ceiling of the outer wall 101, so that the upper part of the processing chamber S is in communication with the annular space 104. The annular space 104 in communication with the upper part of the processing chamber S serves as an exhaust path. The gas supplied to and diffused in the chamber S flows from below the processing chamber S to above the processing chamber S and is sucked into the annular space 104. An exhaust pipe 106 is connected to, for example, the lower end of the annular space 104, and the exhaust pipe 106 is connected to an exhaust device 107. The exhaust device 107 is configured to include a vacuum pump and the like, and exhausts the processing chamber S and adjusts the internal pressure of the processing chamber S to a pressure appropriate for processing.

[0012] A heating device 108 is provided outside the outer wall 101 so as to surround the periphery of the processing chamber S. The heating device 108 adjusts the temperature inside the processing chamber S to a temperature appropriate for processing, and heats a plurality of wafers W at once.

[0013] The lower part of the processing chamber S is in communication with an opening 109 provided in the base material 105. A manifold 110 formed in a cylindrical shape from, for example, stainless steel is connected to the opening 109 via a seal member 111 such as an O-ring. The lower end of the manifold 110 is opened, and a boat 112 is inserted into the processing chamber S through this opening. The boat 112 is made of, for example, quartz, and has a plurality of support columns 113. The support columns 113 are formed with grooves (not shown), and the grooves support a plurality of substrates to be processed at once. This allows the boat 112 to mount a plurality of substrates to be processed, for example, 50 to 150 wafers W, in multiple stages. By inserting the boat 112 on which the plurality of wafers W are mounted into the processing chamber S, the processing chamber S can accommodate a plurality of wafers W.

[0014] The boat 112 is placed on a table 115 via a thermal insulation tube 114 made of quartz. The table 115 is supported on a rotating shaft 117 that penetrates a lid 116 made of, for example, stainless steel. The lid 116 opens and closes an opening at the lower end of the manifold 110. A magnetic fluid seal 118, for example, is provided at the penetration part of the lid 116, and rotatably supports the rotating shaft 117 while sealing it airtight. In addition, a seal member 119 made of, for example, an O-ring is interposed between the peripheral part of the lid 116 and the lower end of the manifold 110, and maintains the sealing property of the inside of the processing chamber S. The rotating shaft 117 is attached to the tip of an arm 120 supported by a lifting mechanism (not shown) such as a boat elevator. As a result, the wafer boat 112 and the lid 116 are vertically raised and lowered together to be inserted into and removed from the processing chamber S.

[0015] The film forming apparatus 100 includes a process gas supply mechanism 130 inside the process chamber S for supplying gas used in the process.

[0016] The process gas supply mechanism 130 of this embodiment includes a hydrocarbon carbon source gas supply source 131a, a pyrolysis temperature drop gas supply source 131b, and an inert gas supply source 131c. d , and a seed gas source 131 e Contains:

[0017] The carbon-containing gas supply source 131a is connected to a gas supply port 134a via a mass flow controller (MFC) 132a and an on-off valve 133a. Similarly, the pyrolysis temperature drop gas supply source 131b is connected to a gas supply port 134b via a mass flow controller (MFC) 132b and an on-off valve 133b. d Flow Controller (MFC) 132 d and shutoff valve 133 d via gas supply port 134 d 131 is connected to a seed gas supply source e Flow Controller (MFC) 132 e and shutoff valve 133 e via gas supply port 134 e The gas supply ports 134a to 134 e are provided to penetrate the side wall of the manifold 110 in the horizontal direction, and diffuse the supplied gas toward the inside of the processing chamber S located above the manifold 110.

[0018] The carbon-containing gas supplied from the carbon-containing gas supply source 131a is a gas for forming a carbon film by low-pressure CVD, and various gases can be used as long as they contain carbon, for example, a hydrocarbon-based carbon source gas can be used.

[0019] Examples of hydrocarbon carbon source gases include: C n H 2n+2 C m H 2m C m H 2m-2 (where n is a natural number of 1 or more, and m is a natural number of 2 or more).

[0020] In addition, examples of the hydrocarbon carbon source gas include Benzene gas (C 6 H 6 ) may be included.

[0021] Molecular formula C n H 2n+2 Examples of the hydrocarbon represented by the formula: Methane gas (CH 4 ) Ethane gas (C 2 H 6 ) Propane gas (C 3 H 8 ) Butane gas (C 4 H 10 (including other isomers) Pentane gas (C 5 H 12 (including other isomers) Some examples include:

[0022] Molecular formula C m H 2m Examples of the hydrocarbon represented by the formula: Ethylene gas (C 2 H 4 ) Propylene gas (C 3 H 6 (including other isomers) Butylene gas (C 4 H 8 (including other isomers) Pentane gas (C 5 H 10 (including other isomers) Some examples include:

[0023] Molecular formula C m H 2m-2 Examples of the hydrocarbon represented by the formula: Acetylene gas (C2 H 2 ) Propyne gas (C 3 H 4 (including other isomers) Butadiene gas (C 4 H 6 (including other isomers) Isoprene gas (C 5 H 8 (including other isomers) Some examples include:

[0024] A gas containing a halogen element is used as the pyrolysis temperature lowering gas supplied from the pyrolysis temperature lowering gas supply source 131b. The gas containing a halogen element has a catalytic function to lower the pyrolysis temperature of the hydrocarbon carbon source gas and to lower the deposition temperature of the carbon film by the thermal CVD method.

[0025] Halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Gases containing halogen elements are available in the form of elemental halogens, i.e. elemental fluorine (F 2 ) gas, elemental chlorine (Cl 2 ) gas, elemental bromine (Br 2 ) gas, and elemental iodine (I 2 ) gas or a compound containing these, the halogen element alone has the advantage that heat is not required for thermal decomposition and it is highly effective in lowering the thermal decomposition temperature of the hydrocarbon carbon source gas. Among the above halogen elements, fluorine is highly reactive and may impair the surface roughness and flatness of the carbon film to be formed. For this reason, chlorine, bromine, and iodine are preferred as halogen elements, except for fluorine. Of these, chlorine is preferred from the viewpoint of ease of handling.

[0026] The gas supplied from the halogen reactive gas supply source 131c is an element that reacts with halogen, and is NH 3 , H 2 , N 2These gases have the property of reacting with halogens and vaporizing, and can react with halogens on or in the carbon film to remove halogens from the surface or in the carbon film. Among these, the gas with the highest reactivity with halogens in the low-temperature CVd process is NH 3 and NH 3 It is preferable to use ammonia as the halogen reaction gas. However, the halogen reaction gas is not limited to ammonia. For example, in the case of a process at a higher temperature, H 2 and / or N 2 may be used.

[0027] The inert gas supplied from the inert gas supply source 131d is used as a purge gas or a dilution gas. 2 Gas such as argon gas or a rare gas such as Ar gas can be used.

[0028] The seed gas supplied from the seed gas supply source 131e is for forming a seed layer on the underlayer to improve adhesion between the underlayer and the carbon film 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 stoichiometric or boron-rich boron nitride is preferable.

[0029] A gas containing boron is used as the seed gas. The boron-containing gas used as the seed gas is diborane (B 2 H 6 ) gas, and boron trichloride (BCl 3 ) gas can be used. 2 H 6 If the boron-based thin film is boron nitride, a nitriding gas is used in addition to the boron-containing gas. The nitriding gas is ammonia (NH 3) gas can be suitably used. Other examples of the nitriding gas that can be used include organic amine gas and hydrazine gas. When using nitriding gas, it is preferable to provide a separate nitriding gas supply source and supply the nitriding gas into the processing chamber S from a separate gas supply port via a separate mass flow controller (MFC) and an on-off valve.

[0030] The film forming apparatus 100 has a control unit 150. The control unit 150 includes a process controller 151 formed of, for example, a microprocessor (computer), and the process controller 151 controls each component of the film forming apparatus 100. A user interface 152 and a storage unit 153 are connected to the process controller 151.

[0031] The user interface 152 includes an input section including a touch panel display and a keyboard for an operator to input commands to manage the film forming apparatus 100, and a display section including a display that visualizes and displays the operating status of the film forming apparatus 100.

[0032] The storage unit 153 stores so-called process recipes, which include control programs for implementing various processes executed in the film forming apparatus 100 under the control of the process controller 151, and programs for causing each component of the film forming apparatus 100 to execute processes according to processing conditions. The process recipes are stored in a storage medium in the storage unit 153. The storage medium may be a hard disk or a semiconductor memory, or may be a portable medium such as a CD-ROM, a DVD, or a flash memory. The process recipes may also be appropriately transmitted from another apparatus, for example, via a dedicated line.

[0033] The process recipe is read out from the storage unit 153 as required, for example, in response to an instruction from an operator via a user interface 152, and the process controller 151 causes the film forming apparatus 100 to perform processing in accordance with the read process recipe.

[0034] <Method of forming carbon film> Next, an embodiment of a carbon film forming method of the present invention, which is carried out by the film forming apparatus of FIG. 1, will be described.

[0035] FIG. 2 is a flow diagram showing the flow of a carbon film forming method according to one embodiment of the present invention, and FIG. 3 is a cross-sectional view showing the steps in the method.

[0036] First, as shown in FIG. 3(a), a plurality of wafers W, for example 50 to 150 wafers W each having a silicon oxide film 20 formed on a silicon substrate 10 having a predetermined structure (not shown) formed on the upper portion thereof and an amorphous silicon film 30 formed thereon, are loaded onto a wafer boat 112, and the wafer boat 112 is inserted from below into a processing chamber S in a film forming apparatus 100 to load 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 116 to make the processing chamber S into an airtight space. In this state, the processing chamber S is evacuated to maintain a predetermined reduced pressure atmosphere, and the power supplied to the heating device 108 is controlled to raise the wafer temperature and maintain it at the process temperature, and the wafer boat 112 is rotated.

[0037] In this state, first, a gas containing a boron-containing gas is supplied as a seed gas from the seed gas supply source 131e and adsorbed onto the wafer surface (the surface of the underlying amorphous silicon film 3), thereby forming a seed layer 4 for improving adhesion (step 20, FIG. 3(b)).

[0038] In step 2, diborane (B 2 H 6 ) gas, and boron trichloride (BCl 3 ) gas is used to form a boron-based thin film as the seed layer 40.

[0039] As the boron-based thin film, a boron film made of simple boron, or a stoichiometric or boron-rich boron nitride film can be suitably used. In the case of a boron film, the film can be formed by thermal decomposition using only the above-mentioned boron-containing gas as the gas containing boron. On the other hand, in the case of a boron nitride film, in addition to the above-mentioned boron-containing gas, ammonia (NH 3 Nitriding gases such as nitriding gas, organic amine gas, and hydrazine gas are used. 2 H 6 The nitriding gas is preferably NH 3 Gas is preferred.

[0040] The temperature of the wafer W during the formation of the seed layer 40 in step 20 is preferably 200 to 300° C. from the viewpoint of enabling film formation and having good controllability.

[0041] After the seed layer 40 is formed in step 2, the processing chamber S is purged, and a carbon film 50 is formed by non-plasma-assisted thermal CVD (step 30, FIG. 3(c)).

[0042] In the carbon film formation process by thermal CVD in step 3, a hydrocarbon-based carbon source gas containing a hydrocarbon, such as a C 4 H 6 The gas is supplied to the processing chamber S, and a halogen-containing gas, for example, Cl, is supplied as a pyrolysis temperature lowering gas from the pyrolysis temperature lowering gas supply source 131b. 2 Gas is supplied, and the hydrocarbon carbon source gas is heated to a predetermined temperature lower than its thermal decomposition temperature to be thermally decomposed, and a carbon film 50 is formed on the surface of the wafer W by thermal CVD.

[0043] In this way, by using the pyrolysis temperature lowering gas when forming a carbon film, the pyrolysis temperature of the hydrocarbon carbon source gas is lowered by its catalytic effect, and the carbon film is formed at a temperature lower than the pyrolysis temperature of the carbon source gas. In other words, the temperature of 650°C or higher, which was conventionally required for forming a carbon film in a thermal CVD method using a hydrocarbon carbon source gas, can be lowered to a lower temperature, and film formation at a low temperature of about 300°C is also possible.

[0044] In addition, Cl is a halogen-containing gas that constitutes the pyrolysis temperature drop gas. 2 By using this gas, hydrogen (H) can be extracted from a hydrocarbon carbon source gas (CxHy), for example, ethylene gas (C2H4), to decompose the ethylene gas. That is, when forming a carbon film, a halogen element such as chlorine (Cl) extracts H from the surface layer and is exhausted as, for example, HCl. As a result, H is eliminated to generate dangling bonds, which contribute to film formation. In addition, by using a seed layer adsorbed with an aminosilane gas between the base and the carbon film, the adhesion between the base and the carbon film is improved.

[0045] However, when using a silicon film as the base, even if an aminosilane gas is adsorbed as a seed layer, adhesion deteriorates to such an extent that even a thin carbon film with a thickness of about 10 nm can cause film peeling when the film formation temperature is about 350°C or higher.

[0046] In other words, when Cl2 gas is used as the pyrolysis temperature reduction gas, Cl is highly reactive and, depending on the underlying material, even if an aminosilane-based seed layer is present, Cl is likely to terminate dangling bonds as shown in Figure 4(a), which reduces the number of dangling bond activation sites that serve as carbon adsorption sites, inhibiting C adsorption, thereby causing a deterioration in adhesion even with a thin film thickness of about 10 nm.

[0047] In contrast, in this embodiment, since a boron-based thin film is used as the seed layer 40, the adhesion is unlikely to deteriorate due to the difference in reactivity with the underlying silicon film. That is, by using a boron-based thin film as the seed layer 4, the reactivity with Cl is suppressed, and as shown in FIG. 4(b), Cl is unlikely to terminate the dangling bond. Therefore, the dangling bond activation site that becomes the adsorption site of carbon is unlikely to decrease, and the adhesion of the carbon film is unlikely to deteriorate due to the adsorption inhibition. Therefore, a carbon film with good adhesion can be formed regardless of the underlying film. In addition, damage caused by Cl is also suppressed by the seed layer made of a boron-based thin film. From the viewpoint of obtaining such an 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.

[0048] However, it has become clear that even when such a process is carried out using a boron-based thin film as an undercoat, chlorine remains in the carbon layer, and Cl termination impedes the growth of the carbon film.

[0049] Fig. 5 is a model diagram showing the state of the substrate after a low-temperature CVD process is performed when a boron-based thin film is used as the underlayer. Although the use of a boron-based thin film as the underlayer tends to suppress Cl termination more than when a silicon film is used as the underlayer, it is believed that Cl termination still remains.

[0050] FIG. 6 shows the results of an XPS (X-ray photoelectron spectroscopy) study of the relationship between the in-plane film thickness and the composition when a boron-based thin film is used as an undercoat film.

[0051] Fig. 6(a) is a diagram showing the Cl composition, and Fig. 6(b) is a diagram showing the carbon film thickness. Fig. 6(c) is a diagram showing the carbon composition, and Fig. 6(d) is a diagram showing the C / Cl ratio. In Figs. 6(a) to (d), the center of the wafer W is shown as zero, and the edge is shown as 150 mm.

[0052] As shown in Figures 6(a) and 6(b), the carbon film thickness is thicker at the edge than at the center, and the chlorine composition is higher at the center and lower at the edge. As shown in Figure 6(c), the carbon composition is higher at the center and lower at the edge. As shown in Figure 6(d), the C / Cl ratio is higher at the edge and lower at the center.

[0053] These results suggest that the thickness of the carbon film is low in the central area where the chlorine content is high, and high in the edge areas where the chlorine content is low. In other words, it is believed that the presence of chlorine hinders the growth of the carbon film.

[0054] FIG. 7 is a diagram showing a sequence of a conventional carbon film forming method. As shown in FIG. 7, in the conventional carbon film forming method, a carbon-containing gas (C 4 H 6 ) and halogen gas (Cl 2 ) will continue to be supplied.

[0055] 8 is a diagram showing an example of a sequence of a carbon film forming method according to an embodiment of the present disclosure. As shown in FIG. 8, in the film forming method according to an embodiment of the present disclosure, after a carbon-containing gas and a halogen gas are supplied, the supply is temporarily stopped, and a gas that reacts with the halogen and vaporizes is supplied. In FIG. 8, C 4 H 6 is supplied, and halogen gas is used as Cl 2 Ammonia (NH) is supplied as a gas that reacts with halogen gas. 3 8 is provided. Note that the times shown in FIG. 8 are merely examples and are not intended to be limiting. They are intended to be displayed to show an example of the time ratio.

[0056] Ammonia reacts with the Cl terminus to form NH 4 It becomes Cl, and the Cl termination can be removed. Therefore, it is supplied as a reaction gas for removing Cl. In addition, ammonia can also react with halogens other than Cl, such as F, Br, and I, so it can be used as a gas for halogen reactions even when halogen gases other than chlorine are used.

[0057] Others, H 2 , N 2 However, in low-temperature CVD processes below 300°C, ammonia is the most reactive with halogens and can effectively remove halogens.

[0058] In addition, before and after the supply of ammonia, an exhaust / purge process may be performed. This is to remove the C 4 H 6 and Cl 2 or NH 3 This is a process provided to remove the above-mentioned, but is not essential and may be provided as necessary.

[0059] The exhaust process is a process for increasing the amount of exhaust by increasing the opening of an exhaust valve, and the purge process is a process for supplying an inert gas to the wafer W. Either the exhaust process or the purge process may be performed, or both may be performed.

[0060] The inert gas is N 2 Gases such as Ar, He, etc. may be used. For example, N 2 may be used as a purge gas.

[0061] The exhaust / purge process is intended to smoothly switch the gas in the processing chamber S. For example, it is possible to supply ammonia immediately after the low-temperature CVD process, or to supply a carbon-containing gas and a halogen gas immediately after supplying ammonia.

[0062] It is advisable to supply ammonia multiple times for short periods, which will be described later.

[0063] After the carbon film formation is completed, the processing chamber S is evacuated by the exhaust device 107, and the inert gas supply source 131 is d For example, N is used as a purge gas for the processing chamber S.2 Gas is supplied to purge the processing chamber S, and then the processing chamber S is returned to atmospheric pressure, after which the wafer boat 112 is lowered and the wafers W are unloaded.

[0064] 9A and 9B are diagrams for explaining the mechanism of the halogen reactive gas supply step. Fig. 9A is a diagram showing a state in which hydrogen termination and chlorine termination are provided on the surface of the seed layer 40 in addition to dangling bond active sites, which are adsorption sites for a carbon-containing gas. That is, it is a diagram showing the state of the substrate before the carbon film is formed.

[0065] FIG. 9(b) is a diagram showing the surface state of the substrate in the carbon film deposition process. As shown in FIG. 9(b), in the low-temperature CVD process, carbon-containing gas C 4 H 6 In addition, chlorine is also supplied as a catalyst, so chlorine remains in the carbon film. Therefore, in addition to dangling bond active sites, hydrogen and chlorine are terminated on the surface of the carbon film 50. The remaining chlorine inhibits the growth of the carbon film 50, as described in FIG. 6.

[0066] 9(c) is a diagram showing an example of a halogen reactive gas supplying process. In the halogen reactive gas supplying process, a gas capable of reacting with halogen to be vaporized is supplied to the wafer W. The gas capable of reacting with halogen to be vaporized is, for example, ammonia gas, and ammonia reacts with chlorine termination to produce NH 4 The chlorine becomes Cl and vaporizes, and the chlorine in the carbon film 50 is removed. In this way, the Cl termination is removed, and the H termination increases. This can contribute to improving the quality and productivity of the carbon film 50. The reaction formula for the removal of chlorine is expressed as formula (1). This makes it possible to form an adsorption site for the carbon-containing gas while removing chlorine and hydrogen from the chlorine termination and hydrogen termination.

[0067] Cl+H+NH 3 →NH 4 Cl (1) In this way, according to the method for forming a carbon film according to this embodiment, the chlorine concentration in the carbon film 50 can be reduced, and the film formation rate and quality of the carbon film 50 can be improved.

[0068] [Example] The carbon film forming method according to this embodiment shown in Fig. 8 was carried out by setting various times and repetition numbers of the carbon film deposition step and the chlorine reaction gas supply step. Examples will be described below.

[0069] FIG. 10 is a diagram showing an example of the carbon film forming method according to the present embodiment. 4 H 6 and Cl 2 The halogen reactant gas supply step uses Cl as the chlorine reactant gas. 2 was used.

[0070] As shown in Figure 10, 4 H 6 and Cl 2 As a comparative example, a process in which ammonia was not supplied was performed to form a carbon film.

[0071] In Example 1, the carbon film formation time was 10 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition step and the halogen reaction gas supply step were performed in two cycles. The total process time was 30 minutes, and the total time for the carbon film deposition step was 20 minutes.

[0072] In Example 2, the carbon film deposition time was 10 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition step and the halogen reaction gas supply step were performed in five cycles. The total process time was 75 minutes, and the total time for the carbon film deposition step was 50 minutes.

[0073] In Example 3, the carbon film formation time was 10 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition step and the halogen reaction gas supply step were performed in eight cycles. The total process time was 120 minutes, and the total time for the carbon film deposition step was 80 minutes.

[0074] In Example 4, the carbon film formation time was 5 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition step and the halogen reaction gas supply step were performed 10 cycles. The total process time was 150 minutes, and the total time for the carbon film deposition step was 50 minutes.

[0075] In Example 5, the carbon film formation time was 2.5 minutes, the ammonia supply time was 5 minutes, and the carbon film deposition step and the halogen reaction gas supply step were performed 20 cycles. The total process time was 150 minutes, and the total time for the carbon film deposition step was 50 minutes.

[0076] Fig. 11 is a diagram showing the results of carrying out the comparative example and examples 1 to 3. In Fig. 11, Ref indicates the comparative example, 2cyc indicates example 1, 5cyc indicates example 2, and 8cyc indicates example 3. The horizontal axis indicates the radial position [mm] when the center of the wafer W is set to zero, and the vertical axis indicates the film thickness [Å].

[0077] 11, the carbon film thickness of Example 3 is the highest, and the carbon film thickness is equivalent to that of Comparative Example and Example 2. The carbon film deposition process of Comparative Example is an 80-minute process, whereas the carbon film deposition process of Example 2 is a 50-minute process, so that the time for forming the carbon film is reduced to 5 / 8, and the film formation rate is 1.6 (= 8 / 5) times.

[0078] Therefore, it can be seen that in Example 1, in which the carbon film deposition process time is only 20 minutes, the film thickness is lower than in the comparative example, whereas in Example 2, in which the carbon film deposition process time is only 50 minutes, the film thickness is equivalent to that of the comparative example, and in Example 3, in which the carbon film deposition process time is 80 minutes, the same as the comparative example, the film formation rate is significantly higher than that of the comparative example.

[0079] As described above, FIG. 11 shows that the carbon film formation rate can be significantly improved by increasing the number of cycles in which the carbon film deposition step and the halogen reactive gas supply step are repeated.

[0080] Fig. 12 is a diagram showing the results of carrying out the comparative example, Example 2, Example 4, and Example 5. Fig. 12(a) shows the carbon film thickness at the position of the radial coordinate of the wafer W, with the horizontal axis showing the position in the radial coordinate of the wafer W and the vertical axis showing the film thickness of the carbon film. The time for one carbon film deposition process in Example 2 was 10 minutes, the time for one carbon film deposition process in Example 4 was 5 minutes, and the time for one carbon film deposition process in Example 5 was 2.5 minutes, and the total time for each carbon film deposition process was 50 minutes, so that the influence of one carbon film formation time can be examined.

[0081] As shown in FIG. 12(a), Example 5, which has the shortest film formation time per run, has the largest film thickness, followed by Example 4, which has the second shortest film formation time per run, then the comparative example, and Example 2, which has the longest film formation time per run, has the smallest film thickness.

[0082] In addition, the film formation time in the comparative example was 80 minutes, and the film formation time in examples 2, 4, and 5 was 50 minutes. Therefore, even though the film thickness in example 2 was smaller than that in the comparative example, the film formation rate in example 2 was not slower than that in the comparative example.

[0083] Comparing Examples 2, 4, and 5, it is shown that, when the total film formation time is the same, it is more effective to shorten the film formation time per step and increase the number of cycles. Therefore, according to Fig. 12(a), it is shown that a process in which the time per step of the carbon film deposition step and the halogen reaction gas supply step is shortened and the number of steps is increased is more effective than a process in which the number of cycles is small and the process time per step is long.

[0084] Fig. 12(b) is a diagram in which the results of Fig. 12(a) have been normalized for each example so that the film thickness at the center is 1. This makes it possible to know the uniformity of the film thickness.

[0085] 12(b), the film thickness in Example 5 is the most uniform from the center to the periphery of the wafer W. In Example 4, the variation in the periphery is larger than in Example 5, but smaller than the variation in Example 2. Moreover, the variation in Example 2 is smaller than the comparative example.

[0086] Therefore, FIG. 12(b) shows that a deposition pattern in which the deposition time per cycle is short and the number of cycles is large is excellent not only in deposition rate but also in film thickness uniformity.

[0087] 13 is a diagram showing the results of Comparative Example, Example 2, Example 4, and Example 5 in terms of C / Cl composition ratio. Fig. 13(a) is a diagram showing the results of Comparative Example, Example 2, Example 4, and Example 5 in terms of C / Cl composition ratio with the horizontal axis representing the radial coordinate of the wafer W.

[0088] 13(a) shows a similar tendency to that of FIG. 12(a), with the C / Cl composition ratio increasing in the order of Example 5, Example 4, Comparative Example, and Example 2, but it can be seen that the difference in the C / Cl composition ratios of Examples 5, 4, and 2 is more significant than that of Example 2. In other words, it can be seen that when a film formation process with a large number of cycles is performed, the carbon concentration increases and the Cl concentration decreases, thereby increasing the purity of the carbon film.

[0089] FIG. 13(b) is a diagram showing the C / Cl composition ratio normalized by setting the C / Cl composition ratio at the center of the wafer W to 1 and the results of each experiment.

[0090] FIG. 13(b) also shows that the C / Cl composition ratio is more uniform in the example with a larger number of cycles than in the example with a smaller number of cycles, similar to FIG. 12(b). 3 It can be seen that when the SiO 2 film is supplied, the in-plane variation in the inhibition of carbon adsorption due to Cl termination is eliminated, improving the uniformity of the carbon film.

[0091] Fig. 14 is a diagram showing the results of the examples. In Fig. 14, the details of the carbon film formation process and the results of the film formation rate and the in-plane uniformity are shown for the comparative example, example 2, example 4, and example 5.

[0092] 12 and 13, the carbon film deposition step in the comparative example took 80 minutes, and in Examples 2, 4, and 5, took 50 minutes. 3 The annealing time was set to 5 minutes for all the samples, and the number of cycles was set to 5, 10, and 20, respectively.

[0093] Under these conditions, the deposition rate improves as the number of cycles increases, with the comparative example being 0.38 nm / min, the example 2 being 0.56 nm / min, the example 4 being 0.74 nm / min, and the example 5 being 0.90 nm / min. Also, the in-plane uniformity improves as the number of cycles increases, with the comparative example being 4.6, the example 2 being 4.3, the example 4 being 2.8, and the example 5 being 1.6.

[0094] In this way, a carbon film formation process is performed using a halogen gas as the carbon-containing gas, and then a halogen removal process is performed using a gas that reacts with a halogen and vaporizes, such as ammonia, and the cycle of the carbon film formation process and the halogen removal process is made short and frequent, thereby making it possible to improve the film formation rate and uniformity.

[0095] It is optional whether or not to provide the vacuum / purge step in FIG. 8, and the carbon-containing gas is also optional, but a hydrocarbon gas is preferable. In addition to chlorine, fluorine, iodine, bromine, etc. can be used as the halogen gas. Furthermore, in addition to ammonia, hydrogen and nitrogen can also be used as the halogen reaction gas that reacts with the halogen gas. However, in a low-temperature CVD process at 400° C. or less, it is preferable to use ammonia from the viewpoint of reactivity. In a high-temperature CVD process at 500° C. to 800° C., hydrogen and nitrogen can also be used as the halogen reaction gas.

[0096] Although the preferred embodiments and examples of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments and examples, and various modifications and substitutions can be made to the above-described embodiments and examples without departing from the scope of the present disclosure. [Explanation of symbols]

[0097] 10 Substrate 20 Silicon oxide film 30 Amorphous silicon film 40 Seed Layer 50 Carbon Film 100 Film deposition equipment 107 Exhaust system 112 Wafer Boat 130 Processing gas supply mechanism 131a Carbon-containing gas source 131b Pyrolysis temperature drop gas supply source 131 e Seed Gas Source 150 Control section S Processing Room W Semiconductor wafer

Claims

1. providing a boron-containing gas to form a boron-based seed layer on the substrate; supplying a carbon-containing gas and a halogen gas to a substrate and depositing a carbon film by chemical vapor deposition; supplying a gas that reacts with the halogen constituting the halogen gas to reduce the halogen contained in the carbon film; A carbon film forming method in which, after performing the step of forming the boron-based seed layer on a substrate, a step of depositing the carbon film while omitting the step of forming the boron-based seed layer and a step of reducing the halogen constitute one cycle, and the carbon film forming method repeats the cycle multiple times.

2. 2. The method for forming a carbon film according to claim 1, wherein the gas which reacts with the halogen gas is ammonia gas.

3. 3. The method for forming a carbon film according to claim 1, wherein the number of cycles is five or more.

4. 4. The method for forming a carbon film according to claim 1, wherein the step of depositing a carbon film on the substrate and the step of reducing the halogen are carried out at a temperature of 400° C. or less.

5. 5. The method for forming a carbon film according to claim 1, wherein the halogen gas is any one of chlorine gas, fluorine gas, bromine gas, and iodine gas.

6. 6. The method for forming a carbon film according to claim 1, wherein the carbon-containing gas is a hydrocarbon gas.

7. The hydrocarbon gas is ４ H ６ 7. The method for forming a carbon film according to claim 6, wherein the gas is a gas.

8. The method for forming a carbon film according to any one of claims 1 to 7, further comprising a step of supplying a purge gas to the substrate 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.

9. 9. The method for forming a carbon film according to claim 8, wherein the purge gas is an inert gas.

10. 10. The method for forming a carbon film according to claim 9, wherein the inert gas is nitrogen gas.

11. 11. The carbon film forming method according to claim 8, wherein the step of supplying the purge gas is performed while evacuating a processing chamber in which the substrate is placed.

12. A processing chamber; a substrate holder provided in the processing chamber; a process gas supply unit that supplies a boron-containing gas, a carbon-containing gas, and a halogen gas to the substrate held by the substrate holder; a halogen reactive gas supply unit for supplying a gas that reacts with the halogen constituting the halogen gas; A control unit, The control unit is supplying the boron-containing gas to form a boron-based seed layer on the substrate; supplying the carbon-containing gas and the halogen gas to the substrate and depositing a carbon film by chemical vapor deposition; supplying a gas that reacts with the halogen constituting the halogen gas to reduce the halogen contained in the carbon film; A film forming apparatus which repeats a cycle including a step of depositing the carbon film (without the step of forming the boron-based seed layer) and a step of reducing the halogen multiple times after performing the step of forming the boron-based seed layer on the substrate.

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