Film forming method and film forming apparatus

Abstract

Disclosed is a film forming method which includes: (a) a step for providing a substrate in a chamber; and (b) a step for forming a hexagonal boron nitride film on the surface of a base substrate that is included in the substrate by supplying a starting material gas, which contains a compound having a B-N bond, and a hydrogen plasma chemical species or an ammonia plasma chemical species generated from a processing gas that contains a hydrogen gas or an ammonia gas to the substrate. The step (b) forms a hexagonal boron nitride film which contains hexagonal boron nitride crystals oriented in a direction that is generally perpendicular to the surface of the base substrate.

Description

Film Formation Method and Film Formation Apparatus

[0001] Exemplary embodiments of the present disclosure relate to a method for forming a boron nitride film and a film formation apparatus. ３ 0> A method of forming a boron nitride film on the surface of a substrate by supplying a boron-containing gas and a nitrogen-containing gas to the substrate is known (see, for example, Patent Documents 1 to 3 below). For example, in the method of Patent Document 1, diborane gas and ammonia gas are introduced into a film formation chamber, plasma is generated in the film formation chamber, and the diborane gas and the ammonia gas are reacted to form a boron nitride film.

[0003] Japanese Patent Application Laid-Open No. 2006-237478, Japanese Patent Application Laid-Open No. 2019-503326, Japanese Patent Application Laid-Open No. 2010-40883

[0004] The present disclosure provides a technique for forming a boron nitride film having a high thermal conductivity in a direction perpendicular to the surface of a substrate.

[0005] In one exemplary embodiment, a film formation method is provided. The film formation method includes: (a) providing a substrate in a chamber; and (b) supplying to the substrate a raw material gas containing a compound having a B-N bond and a hydrogen plasma species or an ammonia plasma species generated from a processing gas containing hydrogen gas or ammonia gas, and forming a hexagonal boron nitride film on the surface of a base substrate contained in the substrate. In (b), the hexagonal boron nitride film including hexagonal boron nitride crystals oriented substantially perpendicular to the surface of the base substrate is formed.

[0006] According to one exemplary embodiment, a boron nitride film having a high thermal conductivity in a direction perpendicular to the surface of a substrate can be formed.

[0007] This is a timing chart showing a method for depositing a boron nitride film according to the first embodiment. Figure 2(a) is a partially enlarged cross-sectional view of an example substrate, and Figure 2(b) is a partially enlarged cross-sectional view of an example substrate having a hexagonal boron nitride film. This figure shows an example in which hexagonal boron nitride crystals are oriented perpendicular to the surface of the underlying substrate. This figure shows an example of an FT-IR apparatus for detecting the perpendicular orientation in a hexagonal boron nitride film. This is a graph showing an example of an absorption spectrum. This is a graph showing an example of the relationship between the peak intensity ratio and the thermal conductivity in the direction perpendicular to the surface. This is a graph showing an example of the peak intensity ratio when the duration of the process for modifying the hexagonal boron nitride film is changed. This is a timing chart showing a method for depositing a boron nitride film according to the second embodiment. This is a timing chart showing a method for depositing a boron nitride film according to the third embodiment. This is a timing chart showing a method for depositing a boron nitride film according to the fourth embodiment. This is a timing chart showing another example of a method for depositing a boron nitride film according to the fourth embodiment. This is a timing chart showing yet another example of a method for depositing a boron nitride film according to the fourth embodiment. This is a graph showing an example of the atomic content and the ratio of boron atoms to nitrogen atoms constituting the hexagonal boron nitride film in each of the comparative example, the method shown in Figure 10, and the method shown in Figure 12. This is a graph showing an example of the absorption spectrum in each of the comparative example, the method shown in Figure 10, and the method shown in Figure 12. This is a graph showing an example of measuring the thermal conductivity in the vertical direction of the hexagonal boron nitride film in each of the comparative example, the method shown in Figure 10, and the method shown in Figure 12. This is a graph showing an example of the atomic content and the ratio of boron atoms to nitrogen atoms constituting the deposited hexagonal boron nitride film in each of the cases where the compound having a B-N bond is TMB and TDMAB. This is a table showing an example of the results of the film deposition rate, peak ratio, and the thermal conductivity in the vertical direction of the hexagonal boron nitride film F1. This is a diagram showing the configuration of a film deposition apparatus according to one exemplary embodiment.

[0008] Various exemplary embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0009] <Method for Deposition of Boron Nitride Film According to the First Embodiment> First, the method for depositing a boron nitride film according to the first embodiment will be described with reference to Figures 1 and 2(a) to 2(b). Figure 1 is a timing chart showing the method for depositing a boron nitride film according to the first embodiment. In Figure 1, the states in which various gases are supplied and the states in which high-frequency (RF) power is supplied are shown by solid lines with arrows in the film deposition method according to the first embodiment (hereinafter referred to as "Method MT1"). Figure 2(a) is a partially enlarged cross-sectional view of an example substrate, and Figure 2(b) is a partially enlarged cross-sectional view of an example substrate having a hexagonal boron nitride film.

[0010] Method MT1 is performed using a film deposition apparatus such as the film deposition apparatus 100 described later. Method MT1 is performed to form a boron nitride film on a base substrate UR included in the substrate W as shown in Figure 2(a). Before the boron nitride film is formed on the base substrate UR, the substrate W may consist only of the base substrate UR. The base substrate UR in the state shown in Figure 2(a) may be a semiconductor substrate or may be formed from silicon. As shown in Figure 1, Method MT1 includes steps ST1 to ST4. Steps ST1 to ST4 may be performed in order.

[0011] (Step ST1) In Step ST1, the substrate W shown in Figure 2(a) is provided into the chamber of a film deposition apparatus (for example, the film deposition apparatus 100 described later).

[0012] (Step ST2) In step ST2, a raw material gas containing a compound having a B-N bond and hydrogen plasma chemical species or ammonia plasma chemical species generated from a processing gas containing hydrogen gas or ammonia gas are supplied to the substrate UR. The B-N bond is a chemical bond between boron and nitrogen. As shown in Figure 2(b), a hexagonal boron nitride film (hBN film) F1 is formed on the surface URa of the substrate UR by the supply of hydrogen plasma chemical species or ammonia plasma chemical species.

[0013] Hexagonal boron nitride is a material having a hexagonal crystal system. The compound containing B-N bonds in the source gas may be a borazine compound. A borazine compound is a compound having a borazine ring as its basic framework, containing three alternately bonded B (boron atoms) and three N (nitrogen atoms). In this disclosure, unless otherwise specified, a boron nitride film will be described as a hexagonal boron nitride film F1.

[0014] In one embodiment, the borazine compound contained in the raw material gas is a borazine represented by the following formula (1), namely cyclotriborazane (B ３ H ６ N ３ ) is also acceptable.

[0015] The borazine compound may be an organic borazine compound in which some or all of the hydrogen atoms of borazine are substituted with an organic ligand. The organic borazine compound may be an alkylborazine compound containing an alkyl group as the organic ligand. The alkylborazine compound may be N,N',N''-trimethylborazine (TMB) having the structure shown in formula (2) below.

[0016] The alkylborazine compound may contain TMB, N,N',N''-triethylborazine, N,N',N''-tripropylborazine, N,N',N''-triisopropylborazine, B,B',B''-trimethylborazine, B,B',B''-triethylborazine, B,B',B''-tripropylborazine, B,B',B''-triisopropylborazine, or B,B',B''-triethyl-N,N',N''-trimethylborazine, or one or more of these.

[0017] In one embodiment, the compound having a B-N bond contained in the source gas may be a triaminoborane compound. A triaminoborane compound is a compound having a basic skeleton in which three N (nitrogen atoms) are bonded to one B (boron atom). The triaminoborane compound may also be a triaminoborane that does not have the cyclic skeleton shown in the following formula (3).

[0018] The triaminoborane compound may be an organic triaminoborane compound in which some or all of the hydrogen atoms of triaminoborane are substituted with an organic ligand. The organic triaminoborane compound may be a trisalkylaminoborane compound containing an alkyl group as the organic ligand. The trisalkylaminoborane compound may be tris(dimethylamino)borane (TDMAB) having the structure shown in the following formula (4).

[0019] Hydrogen plasma species are species contained in hydrogen plasma and may include hydrogen ions and hydrogen radicals. Ammonia plasma species are species contained in ammonia plasma and may include ammonia ions and ammonia radicals. Plasma species used in method MT1, such as hydrogen plasma species or ammonia plasma species, can be supplied to the substrate W in the chamber from plasma generated inside or outside the chamber. The plasma may be an RF plasma obtained by exciting a gas using RF (radio frequency) power. Examples of RF plasmas include capacitively coupled plasma (CCP), inductively coupled plasma (ICP), helicon wave plasma, and electron cyclotron resonance (ECR) plasma.

[0020] In one embodiment, the processing gas may further contain a noble gas in addition to hydrogen gas or ammonia gas. The noble gas may include argon gas. The processing gas may further contain nitrogen gas. In step ST2, argon plasma species and nitrogen plasma species are generated from the processing gas, and these plasma species may be supplied to the substrate UR together with hydrogen plasma species or ammonia plasma species.

[0021] In step ST2, a hexagonal boron nitride film F1 is formed, which includes hexagonal boron nitride crystals F11 oriented substantially perpendicular to the surface URa of the substrate UR. The hexagonal boron nitride film F1 may contain hexagonal boron nitride crystals F11. Figure 3 shows an example in which the hexagonal boron nitride crystals F11 are oriented perpendicular to the surface URa of the substrate UR. The state in which the hexagonal boron nitride crystals F11 are oriented perpendicular to the surface URa means, in other words, that the c-axis of the hexagonal boron nitride film F1 is parallel to the surface URa. The substantially perpendicular direction includes the case in which the orientation direction of the hexagonal boron nitride crystals F11 is perpendicular to the surface URa, as shown in Figure 3. However, the substantially perpendicular direction may also include the following cases. For example, the orientation direction of the hexagonal boron nitride crystal F11 may be deviated from the direction perpendicular to the surface URa (the direction in which the angle with respect to the surface URa is 90°). As an example, the angle between the orientation direction of the hexagonal boron nitride crystal F11 and the surface URa may be between 45° and 90°. Alternatively, the hexagonal boron nitride film F1 may contain hexagonal boron nitride crystal F11 whose orientation direction is deviated from the direction perpendicular to the surface URa.

[0022] The hexagonal boron nitride film F1 has high thermal conductivity in the orientation direction of the hexagonal boron nitride crystals F11. As shown in Figure 3, when the hexagonal boron nitride crystals F11 are oriented perpendicular to the surface URa, the thermal conductivity of the hexagonal boron nitride film F1 is high in the direction perpendicular to the surface URa. For example, the hexagonal boron nitride film F1 in the state shown in Figure 3 has higher thermal conductivity in the direction perpendicular to the surface URa compared to a hexagonal boron nitride film in which the hexagonal boron nitride crystals are oriented parallel to the surface URa. The state of being oriented parallel to the surface URa is, for example, a state in which the c-axis of the hexagonal boron nitride film F1 is perpendicular to the surface URa. Therefore, according to method MT1, a boron nitride film having high thermal conductivity in the direction perpendicular to the surface URa can be formed.

[0023] The orientation of the hexagonal boron nitride film F1 towards the approximately perpendicular direction can be changed by the flow rate ratio of the gases contained in the processing gas. In step ST2, the flow rate ratio of hydrogen gas or ammonia gas to the noble gas may be adjusted so that the orientation of the hexagonal boron nitride film F1 towards the approximately perpendicular direction is increased. Note that an increased orientation towards the approximately perpendicular direction means, for example, that the orientation direction of the multiple hexagonal boron nitride crystals F11 approaches the direction perpendicular to the surface URa. As an example, the flow rate of hydrogen gas or ammonia gas in the processing gas may be less than the flow rate of the noble gas in the processing gas. In this case, the flow rate ratio of hydrogen gas or ammonia gas to the total flow rate of hydrogen gas or ammonia gas and the noble gas combined may be 10% or more, or 30% or more.

[0024] (Step ST3) Step ST3 is a step to modify the hexagonal boron nitride film F1 after step ST2. Step ST3 includes stopping the supply of raw material gas to the substrate W and supplying hydrogen plasma species or ammonia plasma species to the substrate W. In step ST3, hydrogen plasma species or ammonia plasma species can be supplied to the substrate W in the chamber from plasma generated inside or outside the chamber, continuing from step ST2. In step ST3, the processing gas may be supplied into the chamber continuing from step ST2. In step ST3, the hexagonal boron nitride film F1 formed in step ST2 can react further with hydrogen plasma species, thereby further increasing the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction. Furthermore, in step ST3, carbon-containing substances in the hexagonal boron nitride film F1 can be removed, and the film quality of the hexagonal boron nitride film F1 can be improved. Furthermore, although the supply of raw material gas is stopped in process ST3, the formation of the hexagonal boron nitride film F1 can proceed due to the remaining raw material gas.

[0025] The orientation of the hexagonal boron nitride film F1 in the substantially perpendicular direction may change depending on the duration of step ST3. In step ST3, the duration of step ST3 may be adjusted so that the orientation of the hexagonal boron nitride film F1 in the substantially perpendicular direction is increased. The duration of step ST3 may be longer than the duration of step ST2. In this case, the longer time for the hexagonal boron nitride film F1 formed in step ST2 to react with hydrogen plasma species or ammonia plasma species in step ST3 may further increase the orientation of the hexagonal boron nitride film F1 in the substantially perpendicular direction. The duration of step ST3 may be 4 seconds or more, 10 seconds or more, or 16 seconds or more. The duration of step ST2 may be 2 seconds.

[0026] In step ST3, similar to step ST2, the flow rate ratio of hydrogen gas or ammonia gas to the noble gas may be adjusted so that the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction is increased. For example, the flow rate of hydrogen gas or ammonia gas is smaller than the flow rate of the noble gas. In this case, the flow rate ratio of hydrogen gas or ammonia gas to the total flow rate of hydrogen gas or ammonia gas and the noble gas combined may be 10% or more, or 30% or more.

[0027] In step ST3, for example, the hexagonal boron nitride film F1 formed in step ST2 reacts further with hydrogen plasma species or ammonia plasma species in step ST3, thereby further enhancing the orientation of the hexagonal boron nitride film in the substantially perpendicular direction. Furthermore, since carbon-containing materials are removed from the hexagonal boron nitride film in step ST3, the film quality of the hexagonal boron nitride film can be improved.

[0028] (Step ST4) In step ST4, the chamber of the film deposition apparatus is purged. In step ST4, a purge gas may be supplied into the chamber of the film deposition apparatus. In step ST4, the gas remaining in the chamber in step ST3 may be exhausted by the purge gas. In this case, since impurities in the chamber are discharged by purging, the film quality in the hexagonal boron nitride film F1 can be further improved. The purge gas may be an inert gas. The inert gas may be a noble gas such as argon gas.

[0029] Method MT1 may further include a step of repeating a cycle including steps ST2 to ST4. In this case, the thickness of the hexagonal boron nitride film F1 can be increased while ensuring high thermal conductivity of the hexagonal boron nitride film F1 in the direction perpendicular to the surface URa of the substrate UR. In the example in Figure 1, the cycle including steps ST2 to ST4 is executed x times. x is an integer of 1 or more. Note that step ST4 does not have to be executed repeatedly. In this case, Method MT1 may further include a step of alternately repeating steps ST2 and ST3.

[0030] In method MT1, either step ST3 or step ST4 is not necessarily required to be performed. If step ST3 is not performed, the orientation of the hexagonal boron nitride film F1 in a substantially perpendicular direction can be ensured by performing only step ST2. In this case, the duration of step ST3 is 0 seconds.

[0031] The following are examples of various conditions in Method MT1. In Method MT1, the temperature of the mounting stage on which the substrate W is placed may be 200°C or higher. The pressure inside the chamber may be 199.98 Pa or higher and 319.97 Pa or lower. The RF (radio frequency) power used to generate plasma from the processing gas may be 300 W or higher. The duration of step ST2 may be 2.8 seconds or less. In step ST2, the flow rate of the raw material gas may be 33 sccm or less. If the duration of step ST2 is less than 3 seconds or the flow rate of the raw material gas is less than 30 sccm, the orientation in the substantially vertical direction and the crystallinity of the hexagonal boron nitride film F1 may be higher.

[0032] <Indicators of Orientation in the Nearly Vertical Direction> Below, we will explain the peak intensity ratio of absorbance detected by FT-IR (Fourier transform infrared spectroscopy) as an indicator of orientation in the near-vertical direction in the hexagonal boron nitride film F1.

[0033] Figure 4 shows an example of an FT-IR apparatus 110 for detecting the orientation of a hexagonal boron nitride film F1 in the vertical direction. The FT-IR apparatus 110 includes a polarizer 111 and a detector 112. The substrate W having the hexagonal boron nitride film F1 to be measured is placed between the polarizer 111 and the detector 112. The substrate W rotates around a rotation axis A that is perpendicular to the incident direction of light L2. The polarizer 111 is, for example, a polarizing plate, which transmits only the p-polarization component of the polarization component of light L1 irradiated from a light source (not shown) and blocks the other components. The p-polarization component is the component perpendicular to both the optical axis (parallel to the incident direction of light L2) and the rotation axis A.

[0034] Light L2, which is the p-polarized component of light L1, is incident on the substrate W. The substrate W is positioned at an angle with respect to a direction perpendicular to the direction of incidence of light L2. For example, the substrate W is tilted 60° with respect to a direction perpendicular to the direction of incidence of light L2. As a result, light L2 is incident on the substrate W at an oblique angle. Light L2 transmitted through the substrate W may contain an LO mode (Longitudinal Optical mode) component and a TO mode (Transverse Optical mode) component. The LO mode component is the component in which the direction of vibration of light L2 is parallel to the propagation direction. The TO mode component is the component in which the direction of vibration of light L2 is perpendicular to the propagation direction. Light L2 transmitted through the substrate W is incident on the detector 112. The detector 112 is, for example, a photodiode and generates an electrical signal based on the intensity of the incident light L2. The electrical signal generated by the detector 112 is output to, for example, an analyzer (not shown). The analyzer generates an absorption spectrum from the input electrical signal.

[0035] Figure 5 is a graph showing an example of an absorbance spectrum generated by the analyzer. The horizontal axis of Figure 5 represents the wavenumber, and the vertical axis represents the normalized absorbance value. The absorbance spectrum in Figure 5 contains two absorbance peaks. 1380 cm⁻¹ －１ The peaks in the surrounding wavenumbers are the TO mode components, and they increase as the horizontal orientation of the hexagonal boron nitride film F1 increases. (1600 cm) －１ The peaks occurring in the vicinity of the wavenumber are the LO mode component peaks, and their size increases as the vertical orientation of the hexagonal boron nitride film F1 increases. The ratio of the peak intensity of the LO mode component to the peak intensity of the TO mode component, i.e., the peak intensity ratio, is an indicator of the approximately vertical orientation of the hexagonal boron nitride film F1, and the higher the approximately vertical orientation of the hexagonal boron nitride film F1, the larger the ratio.

[0036] Figure 6 shows a graph illustrating the relationship between the peak intensity ratio of a hexagonal boron nitride film and its thermal conductivity in the direction perpendicular to the surface URa. In the examples of Figures 6 and 7, hydrogen gas is used as the processing gas. Plot point P16 in Figure 6 shows the relationship between the peak intensity ratio and thermal conductivity obtained in method MT1, where trimethylborazine (TMB) is used as the compound having a B-N bond in the raw material gas, and the duration of step ST3 is 16 seconds. Plot point P4 in Figure 6 shows the relationship between the peak intensity ratio and thermal conductivity obtained in method MT1, where TMB is used as the compound having a B-N bond in the raw material gas, and the duration of step ST3 is 4 seconds. When plot points P16 and P4 were obtained, the flow rate ratio of hydrogen gas to the total flow rate of hydrogen gas and argon gas combined in the processing gas was, for example, 10%. Furthermore, the plotted point PB in Figure 6 shows the relationship between the peak intensity ratio and thermal conductivity obtained when tris(dimethylamino)borane (TDMAB) was used as the compound having a B-N bond in the source gas in method MT1. As shown in Figure 6, there is a strong correlation between the peak intensity ratio and thermal conductivity, and the relationship between the peak intensity ratio and thermal conductivity can be approximated by a linear function (y = 1.7x - 0.7813). According to this linear function, the peak intensity ratio of a hexagonal boron nitride film having the same thermal conductivity as the thermal oxide film of silicon (1.4) is estimated to be 1.3. Therefore, when a hexagonal boron nitride film has a peak intensity ratio of 1.3 or higher, it has a superior thermal conductivity in the direction perpendicular to the surface URa, which is higher than that of the thermal oxide film, and can be said to have high orientation in the perpendicular direction.

[0037] FIG. 7 is a graph showing an example of the peak intensity ratio when the duration of step ST3 in method MT1 is changed. In the processing gas used to obtain the peak intensity ratio shown in FIG. 7, the flow rate ratio of hydrogen gas to the total flow rate of hydrogen gas and argon gas combined was, for example, 10%. In the example of FIG. 7, it can be seen that even when the duration is 0 seconds, the peak intensity ratio exceeds the above-mentioned reference value of 1.3. That is, according to method MT1, even if step ST3 is not executed, it can be said that in the hexagonal boron nitride film F1, an orientation in a substantially vertical direction can be realized. Also, as the duration of step ST3 becomes longer, the peak intensity ratio becomes larger. That is, it was confirmed that the longer the duration of step ST3, the higher the orientation in the substantially vertical direction in the hexagonal boron nitride film F1.

[0038] <Film formation method of boron nitride according to the second embodiment> Next, a film formation method of a boron nitride film according to the second embodiment will be described. FIG. 8 is a timing chart showing the film formation method of the boron nitride film according to the second embodiment. In FIG. 8, the states in which various gases are supplied and the state in which high-frequency (RF) power is supplied in the film formation method according to the second embodiment (hereinafter referred to as "method MT2") are shown by solid lines or broken lines with arrows. Method MT2 is different from method MT1 in that it does not include step ST4 which is a purge step of the chamber, includes step ST5 before step ST2, and includes a step of repeating a cycle including steps ST5 to ST3.

[0039] (Step ST5) In step ST5, before step ST2, the raw material gas is stored in a filter tank provided between the chamber and the supply source of the raw material gas. In step ST2, the raw material gas stored in the filter tank is supplied to the substrate W. Step ST5 is, in other words, a step for preparing step ST2. In step ST5, a processing gas is supplied into the chamber of the film formation apparatus. In step ST5, the raw material gas may not be supplied into the chamber. In step ST5, RF power for generating plasma may be supplied.

[0040] By executing step ST5 before step ST2, a sufficient amount of raw material gas can be supplied to the substrate W in step ST2 while shortening the duration of step ST2. For this reason, the duration of step ST2 may be shorter than the duration of step ST5. Also, the duration of step ST5 may be shorter than the duration of step ST3. As an example, in method MT2, the duration of step ST5 is 2 seconds, the duration of step ST2 is 0.5 seconds, and the duration of step ST3 is 14 seconds. The duration of step ST5 is not limited to this and may be 16 seconds or less. Also, in method MT2, step ST3 is not necessarily executed. For example, even with only steps ST5 and ST2, it is possible to ensure orientation in the approximately perpendicular direction in the hexagonal boron nitride film F1. In this case, the duration of step ST3 is 0 seconds.

[0041] In method MT2, similar to method MT1, the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction may change depending on the flow rate ratio of the gases contained in the processing gas. However, in steps ST2 and ST3 of method MT2, the greater the flow rate ratio of hydrogen gas or ammonia gas to the noble gas, the greater the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction may become. Therefore, in steps ST2 and ST3 of method MT2, as an example, the flow rate of hydrogen gas or ammonia gas is greater than the flow rate of the noble gas. In steps ST2 and ST3 of method MT2, the flow rate ratio of hydrogen gas or ammonia gas to the total flow rate of hydrogen gas or ammonia gas and the noble gas combined may be 30% or more, or 70% or more.

[0042] In method MT2, the orientation of the hexagonal boron nitride film F1 in the substantially perpendicular direction may also change depending on the flow rate ratio of nitrogen gas to noble gas contained in the processing gas. In steps ST2 and ST3 of method MT2, the flow rate ratio of nitrogen gas to the total flow rate of hydrogen gas or ammonia gas, nitrogen gas, and noble gas may be 41% or less.

[0043] The method MT2 may further include a step of repeating a cycle including steps ST5 to ST3. In the example of FIG. 8, the cycle including steps ST5 to ST3 is executed x times. x is an integer of 1 or more.

[0044] The various conditions in the method MT2 are as follows, for example. In the method MT2, the temperature of the stage on which the substrate W is placed may be 200°C or higher. The pressure in the chamber may be 173.32 Pa or higher and 519.96 Pa or lower. The RF (radio frequency) power may be 300 W or higher. The duration of step ST2 may be 2.8 seconds or shorter. In step ST2, the flow rate of the source gas may be 305 sccm or lower.

[0045] <Method for Forming Boron Nitride Film According to Third Embodiment> Next, a method for forming a boron nitride film according to the third embodiment will be described. FIG. 9 is a timing chart showing the method for forming a boron nitride film according to the third embodiment. In FIG. 9, the states in which various gases are supplied and the state in which radio frequency (RF) power is supplied in the film formation method according to the third embodiment (hereinafter referred to as "method MT3") are shown by solid lines with arrows. The method MT3 is different from the method MT1 in that it does not include step ST3 which is a step of modifying the hexagonal boron nitride film F1, and in that it does not include step ST4 which is a purge step of the chamber.

[0046] In the method MT3, the supply of the source gas, the supply of the processing gas, and the supply of the RF power can be continuously executed in step ST2. Even in this case, the hexagonal boron nitride crystal F11 is oriented in a direction substantially perpendicular to the surface UR a of the underlying substrate UR. The thermal conductivity of the hexagonal boron nitride film F1 is high in the orientation direction of the hexagonal boron nitride crystal F11. Therefore, a boron nitride film having a high thermal conductivity in the direction perpendicular to the surface UR a can be formed.

[0047] In method MT3, similar to method MT1, the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction may change depending on the flow rate ratio of the gases contained in the processing gas. However, in step ST2 of method MT3, similar to method MT2, the greater the ratio of the flow rate of hydrogen gas or ammonia gas to the total flow rate of hydrogen gas or ammonia gas and the noble gas combined, the higher the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction may be. Therefore, in step ST2 of method MT3, as an example, the flow rate of hydrogen gas or ammonia gas is greater than the flow rate of the noble gas. In step ST2 of method MT3, the flow rate ratio of hydrogen gas or ammonia gas to the total flow rate of hydrogen gas or ammonia gas and the noble gas combined may be 30% or more, or 70% or more.

[0048] In method MT3, the orientation of the hexagonal boron nitride film F1 in the substantially perpendicular direction may also change depending on the flow rate ratio of nitrogen gas to noble gas contained in the processing gas. In step ST2 of method MT3, the flow rate ratio of nitrogen gas to the total flow rate of hydrogen gas or ammonia gas, nitrogen gas, and noble gas may be 41% or less.

[0049] The various conditions in method MT3 are as follows, for example. In method MT3, the temperature of the mounting stage on which the substrate W is placed may be 200°C or higher. The pressure inside the chamber may be 173.32 Pa or higher and 333.31 Pa or lower. The RF power may be 300 W or higher. When the RF power exceeds 200 W, the orientation in the approximately vertical direction of the hexagonal boron nitride film F1 tends to improve. In step ST2, the flow rate of the raw material gas may be 22 sccm or less.

[0050] <Method for Deposition of Boron Nitride Film According to the Fourth Embodiment> Next, a method for depositing a boron nitride film according to the fourth embodiment will be described. Figure 10 is a timing chart showing the method for depositing a boron nitride film according to the fourth embodiment. In Figure 10, the states in which various gases are supplied and the states in which high-frequency (RF) power is supplied are shown by solid lines with arrows. Method MT4 differs from Method MT1 in that it includes step ST6 after step ST4 and step ST7 after step ST6. Furthermore, Method MT4 differs from Method MT1 in that it includes a step in which the cycle including steps ST2 to ST7 is repeated x times, instead of a step in which the cycle including steps ST2 to ST4 is repeated.

[0051] (Step ST6) Step ST6 is a step in which the hexagonal boron nitride film is further modified after it has been modified in step ST3. In step ST6, the supply of raw material gas to the substrate W is stopped, and nitrogen plasma chemical species generated from the modified gas containing nitrogen gas are supplied to the substrate W. In step ST6, the supply of hydrogen gas or ammonia gas may be stopped. In step ST6, RF power may be supplied to generate the plasma.

[0052] The duration of process ST6 may be longer than the duration of process ST2. Alternatively, the duration of process ST6 may be the same as the duration of process ST3. For example, in method MT4, the duration of process ST2 is 2 seconds, the duration of process ST3 is 16 seconds, and the duration of process ST6 is 16 seconds. However, the duration of process ST6 is not limited to this and may be 16 seconds or less.

[0053] The reformed gas may further contain a noble gas. The noble gas may include argon gas. In step ST6, the orientation of the hexagonal boron nitride film F1 in the approximately vertical direction may change depending on the flow rate ratio of the gases contained in the reformed gas. For example, the larger the flow rate ratio of nitrogen gas to the noble gas, the higher the orientation of the hexagonal boron nitride film F1 in the approximately vertical direction may become. In step ST6, for example, the flow rate of nitrogen gas is greater than the flow rate of the noble gas.

[0054] In step ST6, the hexagonal boron nitride film F1 is further modified by nitrogen gas, which can increase the orientation in the approximately perpendicular direction and the crystallinity of the hexagonal boron nitride film F1. As a result, the thermal conductivity of the hexagonal boron nitride film F1 in the direction perpendicular to the surface URa of the substrate UR can be further increased. For example, in step ST6, impurities such as carbon-containing substances are removed from the hexagonal boron nitride film F1, and the ratio of nitrogen to boron in the hexagonal boron nitride film F1 becomes more uniform, which can increase the orientation in the approximately perpendicular direction. Alternatively, the supply of nitrogen gas in step ST6 can reduce the concentration of hydrogen gas in the processing gas, which can increase the orientation in the approximately perpendicular direction. Alternatively, if nitrogen vacancies are present in the hexagonal boron nitride film F1, nitrogen plasma chemical species generated by nitrogen gas may enter the vacancies, repairing defects in the hexagonal boron nitride film F1, thereby increasing the orientation in the approximately vertical direction.

[0055] (Step ST7) In step ST7, the chamber of the film deposition apparatus is purged, similar to step ST4. In step ST7, a purge gas may be supplied into the chamber of the film deposition apparatus. In step ST7, the purge gas may be used to exhaust any gas remaining in the chamber in step ST6.

[0056] Method MT4 may further include a step that repeats a cycle including steps ST2, ST3, and ST7. For example, Method MT4 may further include a step that repeats a cycle including steps ST2 to ST7. In the example in Figure 10, the cycle including steps ST2 to ST7 is executed x times. x is an integer of 1 or more.

[0057] Figure 11 is a timing chart showing method MT4A as another example of method MT4. Method MT4A differs from method MT4 in that it includes a process that repeats a cycle including processes ST2 to ST4. That is, in method MT4A, process ST6 is executed after the process that repeats a cycle including processes ST2 to ST4.

[0058] Furthermore, method MT4A differs from method MT4 in that it further includes a process that repeats a cycle including processes ST2 to ST4, and a process that repeats a cycle including processes ST6 and ST7. In the example in Figure 11, the cycle including processes ST2 to ST4 is executed x times, where x is an integer greater than or equal to 1. Furthermore, the process that repeats the cycle including processes ST2 to ST4 x times, and the cycle including processes ST6 and ST7 are executed y times, where y is an integer greater than or equal to 1, and may be greater than or less than x.

[0059] In method MT4A, as in method MT4, the hexagonal boron nitride film F1 is further modified by nitrogen gas by including step ST6. This can further improve the orientation of the hexagonal boron nitride film F1 in the approximately perpendicular direction and the crystallinity of the hexagonal boron nitride film F1.

[0060] Figure 12 is a timing chart showing method MT4B as yet another example of method MT4. Method MT4B differs from method MT4 in that the processing gas in steps ST2 and ST3 does not contain nitrogen gas. In method MT4B, nitrogen plasma species may not be generated in steps ST2 and ST3, and instead, plasma species of noble gases, and hydrogen plasma species or ammonia plasma species may be supplied to the substrate UR. In method MT4B, as in method MT4, by including step ST6, the hexagonal boron nitride film F1 is further modified by nitrogen gas, which can further increase the orientation in the substantially vertical direction and the crystallinity of the hexagonal boron nitride film F1.

[0061] The effects of methods MT4 and MT4B described above will be explained below in comparison with the comparative example, with reference to Figures 13 to 15. The method of the comparative example differs from method MT4B in that it does not include steps ST6 and ST7.

[0062] Figure 13 is a graph showing examples of the atomic content and the ratio of boron atoms to nitrogen atoms constituting the hexagonal boron nitride film F1 deposited by the comparative example, method MT4, and method MT4B, respectively. The graph illustrated in Figure 13 may be measured, for example, by X-ray photoelectron spectroscopy (XPS). As shown in Figure 13, the hexagonal boron nitride film F1 deposited by method MT4 and method MT4B has a reduced content of impurities such as carbon atoms compared to the hexagonal boron nitride film F1 deposited by the comparative example. In addition, the ratio of boron atoms to nitrogen atoms is closer to 1 in the hexagonal boron nitride film F1 deposited by method MT4 and method MT4B compared to the hexagonal boron nitride film F1 deposited by the comparative example. Since methods MT4 and MT4B include step ST6, it is assumed that the hexagonal boron nitride film F1 is further modified with nitrogen gas.

[0063] Figure 14 is a graph showing examples of absorbance spectra for the comparative example, method MT4, and method MT4B. The absorbance spectra illustrated in Figure 14 may be measured, for example, by an FT-IR apparatus 110 as shown in Figure 4. In Figure 14, as in Figure 5, the wavenumber is 1600 cm⁻¹. －１ The peaks that appear in the vicinity are peaks of the LO mode component, and they become larger as the vertical orientation of the hexagonal boron nitride film F1 increases. As shown in Figure 14, the peak of the hexagonal boron nitride film F1 deposited by method MT4B is larger than the peak of the hexagonal boron nitride film F1 deposited by the comparative example. Furthermore, the peak of the hexagonal boron nitride film F1 deposited by method MT4 is larger than the peak of the hexagonal boron nitride film F1 deposited by method MT4B. In method MT4, the processing gas in steps ST2 and ST3 contains nitrogen gas, and also includes step ST6, so it is assumed that the modification of the hexagonal boron nitride film F1 by nitrogen gas progressed more than in the other methods.

[0064] Figure 15 is a graph showing an example of measuring the thermal conductivity of a hexagonal boron nitride film F1 in the vertical direction for each of the comparative example, method MT4, and method MT4B. The graph illustrated in Figure 15 may be measured, for example, by the laser flash method. In this case, for example, a laser may be irradiated onto the hexagonal boron nitride film F1 and the thermal response from the irradiated surface or the back surface opposite the irradiated surface may be detected. As shown in Figure 15, the thermal conductivity of the hexagonal boron nitride film F1 deposited by method MT4B is greater than that of the hexagonal boron nitride film F1 deposited by the comparative example. Furthermore, the thermal conductivity of the hexagonal boron nitride film F1 deposited by method MT4 is greater than that of the hexagonal boron nitride film F1 deposited by method MT4B. The thermal conductivity is expected to increase in the order of the hexagonal boron nitride film F1 deposited by the comparative example, the hexagonal boron nitride film F1 deposited by method MT4B, and the hexagonal boron nitride film F1 deposited by method MT4, similar to the orientation of the hexagonal boron nitride film F1 in the vertical direction.

[0065] <Influence of raw material gas and processing gas on hexagonal boron nitride film> In step ST2 of methods MT1 to MT4B described above, if the compound having a B-N bond contained in the raw material gas is an alkylborazine compound and the processing gas contains nitrogen gas, the flow rate ratio of hydrogen gas or ammonia gas in the processing gas to nitrogen gas in the processing gas may be adjusted. This can increase the orientation of the hexagonal boron nitride film F1 in the substantially vertical direction. For example, the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate may be 1 or less. The ratio of the nitrogen gas flow rate to the hydrogen gas flow rate may be 0.5 or less, or 0.1 or more.

[0066] To increase the orientation of the hexagonal boron nitride film F1 in the nearly perpendicular direction, the compound having a B-N bond may be tris(dimethylamino)borane (TDMAB). Figure 16 is a graph showing an example of the atomic content and the ratio of boron atoms to nitrogen atoms constituting the deposited hexagonal boron nitride film F1 in the cases where the compound having a B-N bond is trimethylborazine (TMB) and TDMAB. In Figure 16, when the compound having a B-N bond is TDMAB, the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is changed to 1.0, 0.2, and 0.1. As shown in Figure 16, when the compound having a B-N bond is TDMAB and the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is 0.1, the ratio of boron atoms to nitrogen atoms is closer to 1 compared to when the compound having a B-N bond is TMB and the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is 0.1. As shown in equations (2) and (4), TDMAB contains more nitrogen atoms than TMB, so it is assumed that the ratio of boron atoms to nitrogen atoms is more likely to approach 1 compared to TMB.

[0067] As shown in Figure 16, when the compound having a B-N bond is a TDMAB, the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is 0.1 or 0.2, compared to when the ratio is 1.0, resulting in a ratio of boron atoms to nitrogen atoms that is closer to 1. Referring to Figure 17, the effect of the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate on the hexagonal boron nitride film F1 when the compound having a B-N bond is a TDMAB will be further explained. Figure 17 is a table showing an example of the results for the deposition rate, peak intensity ratio, and the thermal conductivity of the hexagonal boron nitride film F1 in the vertical direction. The compound having a B-N bond is a TDMAB, and the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is one of 1.0, 0.2, or 0.1. The unit of the deposition rate is, for example, angstroms per second. The peak intensity ratio is measured by an FT-IR apparatus 110 as shown in Figure 4. The peak intensity ratio is, for example, the ratio of the peak intensity of the LO mode component to the peak intensity of the TO mode component. Thermal conductivity may be measured, for example, by the laser flash method.

[0068] As shown in Figure 17, the film deposition rate is fastest when the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is 1.0. On the other hand, the thermal conductivity is highest when the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is 0.2. Therefore, to maximize the thermal conductivity, it is preferable that the ratio of the nitrogen gas flow rate to the hydrogen gas flow rate is 0.2.

[0069] <Film forming equipment>

[0070] The following describes a film deposition apparatus according to one exemplary embodiment with reference to Figure 18. Figure 18 is a diagram showing the configuration of a film deposition apparatus according to one exemplary embodiment. The film deposition apparatus 100 shown in Figure 18 is a film deposition apparatus that can be used in any of methods MT1 to MT4B. The film deposition apparatus 100 includes a chamber 1, a gas supply mechanism 5, a plasma generation unit 6, and a control unit 7. The film deposition apparatus 100 may further include a mounting table 2, a shower head 3, and an exhaust unit 4.

[0071] Chamber 1 is capable of housing a substrate W within its internal space. Chamber 1 is made of a metal such as aluminum and has a substantially cylindrical shape. An inlet / outlet 11 for loading and unloading the substrate W is formed in the side wall of Chamber 1, and the inlet / outlet 11 can be opened and closed by a gate valve 12. An annular exhaust duct 13 with a rectangular cross-section is provided on top of the main body of Chamber 1.

[0072] A slit 13a is formed along the inner circumference of the exhaust duct 13. An exhaust port 13b is formed on the outer wall of the exhaust duct 13. A top wall 14 is provided on the upper surface of the exhaust duct 13 to close the upper opening of the chamber 1. A sealing ring 15 is sandwiched between the top wall 14 and the exhaust duct 13 to ensure airtightness of the space inside the chamber 1.

[0073] The mounting base 2 is a base capable of supporting the substrate W placed on it in a horizontal position. It is a disc-shaped base sized to correspond to the substrate W and is supported by a support member 23. This mounting base 2 is made of a ceramic material such as aluminum nitride (AlN) or a metallic material such as aluminum or nickel-based alloy. A heater 21 for heating the substrate W is embedded inside the mounting base 2. A cover member 22 is provided on the mounting base 2 to cover its sides.

[0074] The support member 23 that supports the mounting table 2 extends downward from the center of the bottom surface of the mounting table 2, through a hole formed in the bottom wall of the chamber 1, and downward from the chamber 1. The lower end of the support member 23 is connected to the mounting table lifting mechanism 24. The mounting table 2 can be raised and lowered between the processing position shown by the solid line and the transport position shown by the dashed line, via the support member 23 and the mounting table lifting mechanism 24. The transport position is lower than the processing position and is the position where the substrate is placed for transport.

[0075] Below the chamber 1, a flange portion 25 is attached to the support member 23. Between the bottom surface of the chamber 1 and the flange portion 25, a bellows 26 is provided that partitions the atmosphere inside the chamber 1 from the outside air and expands and contracts in accordance with the raising and lowering movement of the mounting platform 2.

[0076] Near the bottom of the chamber 1, three substrate support pins 27 (only two are shown) are provided so as to protrude upward from the lifting plate 27a. The substrate support pins 27 can be raised and lowered via the lifting plate 27a by a substrate support pin lifting mechanism 28 provided below the chamber 1, and can be inserted through holes 2a provided in the mounting table 2 at the transport position, allowing them to protrude and retract relative to the upper surface of the mounting table 2.

[0077] By raising and lowering the substrate support pins 27 in this manner, the substrate W is transferred between the substrate transport mechanism (not shown) and the mounting table 2. A bellows 28a is provided between the bottom surface of the chamber 1 and the substrate support pin lifting mechanism 28.

[0078] The shower head 3 supplies the processed gas into the chamber 1 in a shower-like manner. The shower head 3 is positioned opposite the mounting base 2 and has approximately the same diameter as the mounting base 2. The shower head 3 has a shower body 31 fixed to the top wall 14 of the chamber 1 and a shower plate 32 connected below the shower body 31.

[0079] A gas diffusion space 33 is formed between the shower body 31 and the shower plate 32. A gas inlet 36, which is provided to penetrate the shower body 31 and the center of the top wall 14 of the chamber 1, is connected to this gas diffusion space 33. A gas discharge hole 34 is formed in the shower plate 32. The gas discharge hole 34 extends downward from the gas diffusion space 33 and penetrates the shower plate 32. When the mounting base 2 is in the processing position, a processing space S is formed between the shower plate 32 and the mounting base 2.

[0080] The exhaust unit 4 includes an exhaust pipe 41 connected to the exhaust port 13b of the exhaust duct 13, an automatic pressure control (APC) valve 42 connected to the exhaust pipe 41, and an exhaust mechanism 43 having a vacuum pump. During processing, the gas in the chamber 1 reaches the exhaust duct 13 through the slit 13a, and is exhausted from the exhaust duct 13 through the exhaust pipe 41 by the exhaust mechanism 43 of the exhaust unit 4.

[0081] The gas supply mechanism (gas supply unit) 5 supplies the gas used for film formation to the shower head 3. That is, the gas supply mechanism 5 can supply the above-mentioned raw material gas, processing gas (for example, hydrogen gas, ammonia gas, noble gas, nitrogen gas), and purge gas to the processing space S in the chamber 1 via the shower head 3.

[0082] The gas supply mechanism 5 includes a raw material gas supply source 51, a hydrogen gas or ammonia gas supply source 52 from the processed gas, a noble gas supply source 53 from the processed gas, a nitrogen gas supply source 54 from the processed gas, and a purge gas supply source 55. Supply source 51 is connected to the gas inlet 36 via a flow regulator 51d, a fill tank 51c, and a valve 51b. Supply source 52 is connected to the gas inlet 36 via a flow regulator 52d, a fill tank 52c, and a valve 52b. Supply source 53 is connected to the gas inlet 36 via a flow regulator 53d, a fill tank 53c, and a valve 53b. Supply source 54 is connected to the gas inlet 36 via a flow regulator 54d, a fill tank 54c, and a valve 54b. Supply source 55 is connected to the gas inlet 36 via a flow regulator 55d and a valve 55b.

[0083] Valves 51b, 52b, 53b, and 54b may be configured as high-speed on / off valves that can be opened and closed at high speed. Valve 55b may be a normal on / off valve. During the execution of each of methods MT1 to MT4B, valve 55b may be kept open at all times, and purge gas may be continuously supplied into chamber 1.

[0084] Fill tanks 51c, 52c, 53c, and 54c are tanks for temporarily storing raw material gas, hydrogen gas or ammonia gas, noble gas, and nitrogen gas, respectively, before supplying them into chamber 1.

[0085] By storing the corresponding gas in fill tanks 51c, 52c, 53c, and 54c, a state can be created where the pressure inside each tank is increased to a predetermined pressure. After increasing the pressure inside each of fill tanks 51c, 52c, 53c, and 54c, the corresponding valves among valves 51b, 52b, 53b, and 54b are opened. This allows the corresponding gas to be discharged into chamber 1, making it possible to stably supply a large flow rate of gas to chamber 1.

[0086] Flow regulators 51d, 52d, 53d, 54d, and 55d are configured, for example, by a mass flow controller. Each of the flow regulators 51d, 52d, 53d, 54d, and 55d is configured to adjust the flow rate of the gas flowing in from upstream and to output the gas with the adjusted flow rate.

[0087] The plasma generation unit 6 includes a power supply line 61 connected to the shower body 31 of the shower head 3, and a matching unit 62 and an RF power supply 63 (high-frequency power supply) connected to the power supply line 61. When high-frequency (RF) power is supplied to the shower head 3 from the RF power supply 63, a high-frequency (RF) electric field is formed in the processing space S between the shower head 3 and the mounting base 2, and plasma is generated from the gas as a capacitively coupled plasma by this RF electric field. If the mounting base 2 is made of ceramic material, the RF electric field may be formed between the shower head 3 and electrodes embedded in the mounting base 2.

[0088] The control unit 7 is composed of a computer and includes a main control unit equipped with a CPU, an input device, an output device, a display device, and a storage device (storage medium). The main control unit controls the components of the film deposition apparatus 100, such as valves, flow regulators, automatic pressure control valves, heaters, and lifting mechanisms.

[0089] The memory device stores parameters for various processes performed by the film deposition apparatus 100. The memory device also has a storage medium that stores programs, i.e., processing recipes, for controlling the processes performed by the film deposition apparatus 100. The main control unit retrieves a predetermined processing recipe stored in the storage medium and, based on that processing recipe, causes the film deposition apparatus 100 to execute a predetermined operation.

[0090] The control unit 7 is configured to control various parts of the film deposition apparatus 100, such as the gas supply mechanism 5 and the plasma generation unit 6, while the substrate W is housed in the chamber 1, in order to execute a method selected from methods MT1 to MT4B.

[0091] When the film deposition apparatus 100 is used, in each step ST1 of methods MT1 to MT4B, the substrate W (see Figure 2(a)) is prepared in the chamber 1 of the film deposition apparatus 100. Specifically, the gate valve 12 is opened and the substrate W is loaded into the chamber 1. The substrate W is loaded via the loading port 11 by a transport device (not shown). The loaded substrate W is placed on the mounting table 2. Next, the transport device is moved out of the space inside the chamber 1 and the mounting table 2 is raised to the processing position. Then, the gate valve 12 is closed and the chamber 1 is evacuated. After that, the mounting table 2 is heated by the heater 21 and the temperature of the mounting table 2 (substrate temperature) is adjusted to the desired temperature. With the substrate W prepared in the chamber 1 of the film deposition apparatus 100 in this way, the film deposition process can be started.

[0092] In each step ST2 of methods MT1 to MT4B, the valve 51b is set to the open state and raw material gas is supplied from the supply source 51 to the processing space S via the shower head 3. Also in step ST2, the processing gas mentioned above is supplied from the gas supply mechanism 5 to the processing space S via the shower head 3. Specifically, in step ST2, the valve 52b is set to the open state and hydrogen gas or ammonia gas is supplied from the supply source 52 to the processing space S via the shower head 3. Furthermore, in step ST2, the valves 53b and 54b may be set to the open state and noble gas and nitrogen gas may be supplied from the supply sources 53 and 54 to the processing space S via the shower head 3. Also, in step ST2, RF power may be supplied from the RF power supply 63 of the plasma generation unit 6 to the shower head 3 and plasma may be generated from the gas in the processing space S. In step ST2, a hydrogen plasma chemical species or ammonia plasma chemical species generated from a raw material gas containing a compound having a B-N bond and a processing gas containing hydrogen gas or ammonia gas is supplied to the substrate UR, and a hexagonal boron nitride film (hBN film) is formed on the surface URa of the substrate UR. As a result, a hexagonal boron nitride film F1 is formed on the surface URa, as shown in Figure 2(b). In step ST2, a hexagonal boron nitride film F1 is formed, which contains hexagonal boron nitride crystals F11 oriented substantially perpendicular to the surface URa of the substrate UR.

[0093] When method MT2 is performed in the film deposition apparatus 100, in step ST5 preceding step ST2, the valve 51b is set to the closed state and the raw material gas is stored in the fill tank 51c. In step ST2, the raw material gas stored in the fill tank 51c is supplied to the substrate. In step ST5, similar to step ST2, the processing gas described above may be supplied from the gas supply mechanism 5 to the processing space S via the shower head 3. Also, in step ST5, similar to step ST2, RF power may be supplied from the RF power supply 63 of the plasma generation unit 6 to the shower head 3, and plasma may be generated from the gas in the processing space S.

[0094] Furthermore, when each of methods MT1, MT2, and MT4 to MT4B is performed in the film deposition apparatus 100, in step ST3, the state of valve 51b is set to the closed state to stop the supply of raw material gas to the substrate W. The states of valves 52b to 54b may be continuously set to the open state. As a result, in step ST3, hydrogen plasma chemical species or ammonia plasma chemical species can be supplied to the substrate W from the plasma generated in the chamber 1, continuing from step ST2. In step ST3, the hexagonal boron nitride film F1 formed on the underlayment substrate UR is modified.

[0095] Furthermore, when each of methods MT1 and MT4 to MT4B is performed in the film deposition apparatus 100, the chamber 1 is purged in step ST4. In step ST4, the valve 55b is set to the open state, and purge gas is supplied from the supply source 55 to the processing space S via the shower head 3. The gas in the chamber 1 is exhausted by the exhaust unit 4. Also in step ST4, the supply of RF power from the RF power supply 63 is stopped.

[0096] Furthermore, when each of methods MT4 to MT4B is performed in the film deposition apparatus 100, in step ST6, the valve 54b may be set to the open state and nitrogen gas may be supplied from the supply source 54 to the processing space S via the shower head 3. Also, in step ST6, the valve 53b may be set to the open state and noble gas may be supplied from the supply source 53 to the processing space S via the shower head 3.

[0097] Furthermore, when each of methods MT4 to MT4B is performed in the film deposition apparatus 100, in step ST7, the chamber 1 is purged, similar to step ST4.

[0098] Although various exemplary embodiments have been described above, the invention is not limited to the exemplary embodiments described above, and various additions, omissions, substitutions, and modifications may be made. Furthermore, it is possible to combine elements from different embodiments to form other embodiments.

[0099] Herein, various exemplary embodiments included in this disclosure are described in [E1] to [E32] below.

[0100] [E1] A film formation method comprising: (a) providing a substrate in a chamber; and (b) supplying a hydrogen plasma chemical species or an ammonia plasma chemical species generated from a raw material gas containing a compound having a B-N bond and a processing gas containing hydrogen gas or ammonia gas to the substrate to form a hexagonal boron nitride film on the surface of a base substrate contained in the substrate, wherein (b) forms the hexagonal boron nitride film containing hexagonal boron nitride crystals oriented substantially perpendicular to the surface of the base substrate.

[0101] [E2] (c) A step of modifying the hexagonal boron nitride film after (b), further comprising stopping the supply of the raw material gas to the substrate and supplying the hydrogen plasma chemical species or the ammonia plasma chemical species to the substrate, the method of forming a film according to [E1].

[0102] [E3] (d) The method for forming a film according to [E2], further comprising the step of alternately repeating (b) and (c).

[0103] [E4] (e) A step of further modifying the hexagonal boron nitride film after (c), further comprising stopping the supply of the raw material gas to the substrate and supplying nitrogen plasma chemical species generated from a modified gas containing nitrogen gas to the substrate, the method of forming a film according to [E2].

[0104] [E5] (f) The method for forming a film according to [E4], further comprising the step of repeating a cycle including (b), (c), and (e).

[0105] [E6] (g) A method for forming a film according to [E3], further comprising the step of modifying the hexagonal boron nitride film after (d), the step of stopping the supply of the raw material gas to the substrate and supplying nitrogen plasma chemical species generated from a modified gas containing nitrogen gas to the substrate.

[0106] [E7] (h) The method for forming a film according to [E6], further comprising the step of alternately repeating (d) and (g).

[0107] [E8] The film formation method according to any one of [E1] to [E7], wherein the processing gas further comprises a noble gas.

[0108] [E9] The film formation method according to any one of [E4] to [E7], wherein the reformed gas further comprises a noble gas.

[0109] [E10] The film formation method according to any one of [E1] to [E9], wherein the processing gas further comprises nitrogen gas.

[0110] [E11] The film formation method according to [E8], wherein the noble gas comprises argon gas.

[0111] [E12] The film formation method according to any one of [E1] to [E11], wherein the compound having the B-N bond is borazine.

[0112] [E13] The film formation method according to any one of [E1] to [E11], wherein the compound having a B-N bond is an alkylborazine compound containing an alkyl group.

[0113] [E14] The film formation method according to [E13], wherein the alkylborazine compound is trimethylborazine.

[0114] [E15] The film formation method according to any one of [E1] to [E11], wherein the compound having the B-N bond is triaminoborane.

[0115] [E16] The compound having a B-N bond is a trisalkylaminoborane compound containing an alkyl group, any one of [E1] to [E11] or the film formation method according to [E15].

[0116] [E17] The method for forming a film according to [E16], wherein the trisalkylaminoborane compound is tris(dimethylamino)borane.

[0117] [E18] The film formation method according to [E13], wherein the processing gas contains hydrogen gas and further contains nitrogen gas, and the ratio of nitrogen gas to hydrogen gas in the processing gas is 1 or less.

[0118] [E19] The film formation method according to any one of [E2] to [E7], wherein the processing gas further contains a noble gas, and in (b) and (c), the flow rate of the hydrogen gas or the ammonia gas is smaller than the flow rate of the noble gas.

[0119] [E20] The film formation method according to [E19], wherein the flow rate ratio of the hydrogen gas or ammonia gas to the total flow rate of the hydrogen gas or ammonia gas and the noble gas combined is 10% or more.

[0120] [E21] The film formation method according to any one of [E2] to [E7], wherein the duration of (c) is longer than the duration of (b).

[0121] [E22] The film formation method according to [E21], wherein the duration of (c) is 4 seconds or more.

[0122] [E23] The film formation method according to [E21], wherein the duration of (c) is 16 seconds or more.

[0123] [E24] The method for forming a film according to [E3], further comprising the step of purging the chamber after (c), wherein the cycle comprising (b), (c), and (i) is repeated.

[0124] [E25] (j) The method for forming a film according to any one of [E1] to [E24], further comprising the step of storing the raw material gas in a fill tank provided between the chamber and the source of the raw material gas, prior to (b), wherein the raw material gas stored in the fill tank is supplied to the substrate in (b).

[0125] [E26] A film deposition apparatus comprising: a chamber; a gas supply unit connected to the chamber; a plasma generation unit configured to generate plasma from the gas in the chamber; and a control unit, wherein the control unit controls the gas supply unit and the plasma generation unit to supply a raw material gas containing a compound having a B-N bond and a hydrogen plasma chemical species or ammonia plasma chemical species generated from a processing gas containing hydrogen gas or ammonia gas to a substrate in the chamber, thereby forming a hexagonal boron nitride film containing hexagonal boron nitride crystals oriented substantially perpendicular to the surface of a substrate contained in the substrate on the surface of the substrate.

[0126] [E27] The film deposition apparatus according to [E26], wherein the control unit is configured to control the gas supply unit and the plasma generation unit to stop the supply of the raw material gas to the substrate and to supply the hydrogen plasma chemical species or the ammonia plasma chemical species to the substrate to modify the hexagonal boron nitride film after forming the hexagonal boron nitride film on the surface of the substrate.

[0127] [E28] The film deposition apparatus according to [E27], wherein the control unit controls the gas supply unit and the plasma generation unit to alternately repeat the process of forming the hexagonal boron nitride film on the surface of the substrate and modifying the hexagonal boron nitride film.

[0128] [E29] The film deposition apparatus according to [E27], wherein the control unit is configured to, after modifying the hexagonal boron nitride film, control the gas supply unit and the plasma generation unit to stop the supply of the raw material gas to the substrate, and to supply nitrogen plasma chemical species generated from the modified gas containing nitrogen gas to the substrate to further modify the hexagonal boron nitride film.

[0129] [E30] The film deposition apparatus according to [E29], wherein the control unit controls the gas supply unit and the plasma generation unit to repeat a cycle that includes forming the hexagonal boron nitride film on the surface of the substrate, modifying the hexagonal boron nitride film, and further modifying the hexagonal boron nitride film.

[0130] [E31] The film deposition apparatus according to [E28], wherein the control unit is configured to alternately repeat the process of forming the hexagonal boron nitride film and modifying the hexagonal boron nitride film, and then control the gas supply unit and the plasma generation unit to stop the supply of the raw material gas to the substrate, and to supply nitrogen plasma chemical species generated from the modified gas containing nitrogen gas to the substrate to further modify the hexagonal boron nitride film.

[0131] [E32] The film deposition apparatus according to [E31], wherein the control unit controls the gas supply unit and the plasma generation unit to alternately repeat the process of forming the hexagonal boron nitride film and modifying the hexagonal boron nitride film, and further modifying the hexagonal boron nitride film.

[0132] From the above description, it will be understood that the various embodiments of this disclosure are described herein for illustrative purposes and can be modified in various ways without departing from the scope and spirit of this disclosure. Accordingly, the various embodiments disclosed herein are not intended to limit the scope and spirit, and the true scope and spirit are shown by the appended claims.

[0133] 100...Film deposition apparatus, 1...Chamber, 5...Gas supply mechanism (gas supply unit), 6...Plasma generation unit, 7...Control unit, W...Substrate, UR...Underlayment substrate, URa...Surface, F1...Hexagonal boron nitride film, F11...Hexagonal boron nitride crystal.

Claims

1. A film formation method comprising: (a) providing a substrate in a chamber; and (b) supplying a hydrogen plasma chemical species or an ammonia plasma chemical species generated from a raw material gas containing a compound having a B-N bond and a processing gas containing hydrogen gas or ammonia gas to the substrate to form a hexagonal boron nitride film on the surface of a base substrate contained in the substrate, wherein (b) forms the hexagonal boron nitride film containing hexagonal boron nitride crystals oriented substantially perpendicular to the surface of the base substrate.

2. (c) A step of modifying the hexagonal boron nitride film after (b), further comprising stopping the supply of the raw material gas to the substrate and supplying the hydrogen plasma chemical species or the ammonia plasma chemical species to the substrate, the method for forming a film according to claim 1.

3. (d) The method for forming a film according to claim 2, further comprising the step of alternately repeating (b) and (c).

4. (e) A method for forming a film according to claim 2, further comprising a step of further modifying the hexagonal boron nitride film after (c), the step of stopping the supply of the raw material gas to the substrate and supplying nitrogen plasma chemical species generated from a modified gas containing nitrogen gas to the substrate.

5. (f) The method for forming a film according to claim 4, further comprising the step of repeating a cycle including (b), (c), and (e).

6. (g) A method for forming a film according to claim 3, further comprising the step of further modifying the hexagonal boron nitride film after (d), the step of stopping the supply of the raw material gas to the substrate and supplying nitrogen plasma chemical species generated from a modified gas containing nitrogen gas to the substrate.

7. (h) The method for forming a film according to claim 6, further comprising the step of alternately repeating (d) and (g).

8. The film formation method according to any one of claims 1 to 7, wherein the processing gas further comprises a noble gas.

9. The film formation method according to any one of claims 4 to 7, wherein the reformed gas further comprises a noble gas.

10. The film formation method according to any one of claims 1 to 7, wherein the processing gas further comprises nitrogen gas.

11. The film formation method according to claim 8, wherein the noble gas includes argon gas.

12. The film formation method according to any one of claims 1 to 7, wherein the compound having the B-N bond is borazine.

13. The film-forming method according to any one of claims 1 to 7, wherein the compound having a B-N bond is an alkylborazine compound containing an alkyl group.

14. The film formation method according to claim 13, wherein the alkylborazine compound is trimethylborazine.

15. The film formation method according to any one of claims 1 to 7, wherein the compound having the B-N bond is triaminoborane.

16. The film formation method according to any one of claims 1 to 7, wherein the compound having a B-N bond is a trisalkylaminoborane compound containing an alkyl group.

17. The method for forming a film according to claim 16, wherein the trisalkylaminoborane compound is tris(dimethylamino)borane.

18. The film formation method according to claim 13, wherein the processing gas contains hydrogen gas and further contains nitrogen gas, and the ratio of the nitrogen gas to the hydrogen gas in the processing gas is 1 or less.

19. The method for forming a film according to any one of claims 2 to 7, wherein the processing gas further contains a noble gas, and in (b) and (c), the flow rate of the hydrogen gas or the ammonia gas is less than the flow rate of the noble gas.

20. The film formation method according to claim 19, wherein the flow rate ratio of the hydrogen gas or ammonia gas to the total flow rate of the hydrogen gas or ammonia gas and the noble gas combined is 10% or more.

21. The film formation method according to any one of claims 2 to 7, wherein the duration of (c) is longer than the duration of (b).

22. The film formation method according to claim 21, wherein the duration of (c) is 4 seconds or more.

23. The film formation method according to claim 21, wherein the duration of (c) is 16 seconds or more.

24. The method for forming a film according to claim 3, further comprising the step of purging the chamber after (c), wherein the cycle comprising (b), (c), and (i) is repeated.

25. (j) The method for forming a film according to any one of claims 1 to 7, further comprising the step of storing the raw material gas in a fill tank provided between the chamber and the source of the raw material gas, prior to (b), wherein the raw material gas stored in the fill tank in (b) is supplied to the substrate.

26. A film deposition apparatus comprising: a chamber; a gas supply unit connected to the chamber; a plasma generation unit configured to generate plasma from the gas in the chamber; and a control unit, wherein the control unit controls the gas supply unit and the plasma generation unit to supply a raw material gas containing a compound having a B-N bond and a hydrogen plasma chemical species or ammonia plasma chemical species generated from a processing gas containing hydrogen gas or ammonia gas to a substrate in the chamber, thereby forming a hexagonal boron nitride film containing hexagonal boron nitride crystals oriented substantially perpendicular to the surface of a substrate contained in the substrate on the surface of the substrate.

27. The film deposition apparatus according to claim 26, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to stop the supply of the raw material gas to the substrate and to supply the hydrogen plasma chemical species or the ammonia plasma chemical species to the substrate to modify the hexagonal boron nitride film after the hexagonal boron nitride film has been formed on the surface of the substrate.

28. The film deposition apparatus according to claim 27, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to alternately repeat the process of forming the hexagonal boron nitride film on the surface of the substrate and modifying the hexagonal boron nitride film.

29. The film deposition apparatus according to claim 27, wherein the control unit is configured to, after modifying the hexagonal boron nitride film, control the gas supply unit and the plasma generation unit to stop the supply of the raw material gas to the substrate, and to supply nitrogen plasma chemical species generated from the modified gas containing nitrogen gas to the substrate to further modify the hexagonal boron nitride film.

30. The film deposition apparatus according to claim 29, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to repeat a cycle including forming the hexagonal boron nitride film on the surface of the substrate, modifying the hexagonal boron nitride film, and further modifying the hexagonal boron nitride film.

31. The film deposition apparatus according to claim 28, wherein the control unit is configured to alternately repeat the process of forming the hexagonal boron nitride film and modifying the hexagonal boron nitride film, and then control the gas supply unit and the plasma generation unit to stop the supply of the raw material gas to the substrate, and to supply nitrogen plasma chemical species generated from a modified gas containing nitrogen gas to the substrate to further modify the hexagonal boron nitride film.

32. The film deposition apparatus according to claim 31, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to alternately repeat the process of forming the hexagonal boron nitride film and modifying the hexagonal boron nitride film, and to further modify the hexagonal boron nitride film.

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