Method and apparatus for forming boron nitride film

Abstract

The invention provides a boron nitride film forming method and a boron nitride film forming apparatus. The boron nitride film forming method and the boron nitride film forming apparatus can form a hexagonal boron nitride film having good adhesion and flatness and good film quality. In the method for forming a boron nitride film, a sequence including a step of supplying plasma and a raw material gas containing a borazine-based compound to a substrate disposed in a chamber, and then a step of supplying plasma to the substrate without supplying the raw material gas is performed a plurality of times. All or a part of the plurality of sequences further include a step of supplying plasma without supplying the raw material gas and then supplying plasma of a gas that does not include hydrogen to the substrate. In the step of supplying a raw material gas containing a borazine compound and a plasma and the step of supplying the plasma without supplying the raw material gas, the plasma containing a gas containing hydrogen is used as the plasma.

Description

Technical Field

[0001] The present disclosure relates to a method and an apparatus for forming a boron nitride film. Background Art

[0002] As a method for forming a boron nitride (BN) film, for example, the methods described in Patent Documents 1 to 3 are known.

[0003] Patent Document 1 describes the following technique: generating a plasma of a boron-containing gas and nitrogen, and forming a hexagonal BN (h-BN) film on the surface of a substrate by plasma CVD using the plasma diffused from the plasma generation region. Patent Document 2 describes the following method: forming a conformal BN film through a process including a CVD step and an exposure step, in which at least a part of the deposition using the boron-containing gas is performed in a non-plasma manner in the CVD step, and in which the deposited boron-containing film is exposed to a plasma containing N in the exposure step. Patent Document 3 describes the following method, which includes the following steps: forming a film having a borazane ring skeleton and containing boron and nitrogen on a substrate by intermittently performing a step of supplying a borazane-based gas containing a ligand to the substrate and a step of supplying a ligand-detaching gas for detaching the ligand to the substrate while maintaining the borazane ring skeleton in the borazane-based gas in a holding ring. Further, in Patent Document 3, NH 3 gas is used as the ligand-detaching gas, and a plasma of N 2 gas, which is an inert gas, is used during film formation.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-147826

[0007] Patent Document 2: U.S. Patent No. 8288292

[0008] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2016-63007 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] The present disclosure provides a method and an apparatus for forming a hexagonal boron nitride film that can form a film having good adhesion and flatness and good film quality.

[0011] Solutions to the Problems

[0012] In the method for forming a boron nitride film according to one embodiment of the present disclosure, a sequence including a step of supplying a raw material gas containing a borazine compound and plasma to a substrate disposed in a chamber and then a step of supplying the plasma without supplying the raw material gas to the substrate is repeated multiple times. All or a part of the multiple sequences further includes a step of supplying plasma of a gas not containing hydrogen to the substrate after the step of supplying the plasma without supplying the raw material gas. As the step of supplying the raw material gas containing the borazine compound and plasma, a step of supplying the raw material gas and plasma of a gas containing hydrogen to the substrate is performed. As the step of supplying the plasma without supplying the raw material gas, a step of supplying the plasma containing hydrogen without supplying the raw material gas is performed.

[0013] Effects of the Invention

[0014] According to the present disclosure, there are provided a method and an apparatus for forming a boron nitride film capable of forming a hexagonal boron nitride film having good adhesion and flatness and good film quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a timing chart showing an example of a method for forming a BN film according to one embodiment.

[0016] Figure 2 is a timing chart showing another example of a method for forming a BN film according to one embodiment.

[0017] Figure 3 is a timing chart showing still another example of a method for forming a BN film according to one embodiment.

[0018] Figure 4 is a diagram for explaining the mechanism of modification by plasma of a gas not containing H in step ST5.

[0019] Figure 5 is a diagram for explaining the film formation sequences of Samples 1 to 5 used in an experiment for confirming improvement in the film quality of a BN film according to one embodiment.

[0020] Figure 6 is a diagram obtained by measuring the absorbance in the wavenumber region of a peak containing h-BN (1380 cm -1 ) by FT-IR for Samples 1 to 5.

[0021] Figure 7 is a diagram obtained by measuring by FT-IR for Samples 1 to 5 a peak containing NH x (3300 cm -1 to 3500 cm -1A graph obtained from the absorbance in the wavenumber region of ().

[0022] Figure 8 It is a graph obtained by FT-IR measurement of the absorbance in the wavenumber region containing the BOH peak (around 3200 cm) for Samples 1 to 5. -1 A graph obtained from the absorbance in the wavenumber region of ().

[0023] Figure 9 It is a graph showing the film composition and B / N ratio of the BN films of Samples 1 to 5.

[0024] Figure 10 It is a graph showing the k value and leakage current of Samples 1 to 5.

[0025] Figure 11 It is a graph showing 3 the relationship between the N plasma modification time and the film density after NH 2 plasma.

[0026] Figure 12 It is a cross-sectional view showing an example of a film-forming apparatus. Detailed Embodiments

[0027] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0028] <Cause and Outline>

[0029] First, the cause and outline will be described.

[0030] The BN film is an insulating film having excellent properties, and its application to various uses is being discussed. In particular, the BN film is attracting attention as a low dielectric constant insulating film (Low-k insulating film) capable of achieving a k value of 3 or less. As the BN film, the hexagonal BN (h-BN) film having a lateral orientation has good wet etching resistance and dry etching resistance.

[0031] In the above Patent Document 1, the formation of the h-BN film is described, but the film-forming method is CVD, and the film-forming property, adhesion, and film quality may not be sufficient. In addition, in Patent Document 2, it is described that a conformal BN film is obtained by treating with a plasma containing N after the CVD step. In this CVD step, at least a part of the boron-containing gas deposited is carried out without plasma, but Patent Document 2 does not include the viewpoint of obtaining an h-BN film having good adhesion, flatness, and good film quality. The film-forming method described in Patent Document 3 focuses on the film-forming rate of the BN film, and still does not include the viewpoint of obtaining an h-BN film having good adhesion, flatness, and good film quality.

[0032] Therefore, in one embodiment of the present disclosure, on the premise that a sequence including a step of supplying a raw material gas containing a borazine compound and plasma to a substrate disposed in a chamber and then a step of supplying plasma to the substrate without supplying the raw material gas is repeated multiple times to form a BN film, the following necessary conditions are added. That is, all or a part of the multiple sequences further include a step of supplying plasma of a gas not containing hydrogen after the step of supplying plasma to the substrate without supplying the raw material gas, and in the step of supplying the raw material gas and plasma and the subsequent step of supplying plasma, plasma containing a hydrogen-containing gas is used as the plasma.

[0033] By using plasma containing a hydrogen-containing gas as the plasma supplied together with the raw material gas containing a borazine compound and the plasma subsequently supplied without supplying the raw material gas, an h-BN film with good adhesion of the film to the substrate and flatness of the film surface can be obtained. In addition, by supplying plasma of a gas not containing hydrogen after the step of supplying plasma to the substrate without supplying the raw material gas, hydrogen in the film can be removed to improve the film quality.

[0034] <Specific Embodiment>

[0035] Regarding the method for forming a BN film according to this embodiment, as described above, with the substrate disposed in the chamber of the film forming apparatus, a sequence including a step of supplying a raw material gas containing a borazine compound and plasma to the substrate and then a step of supplying plasma to the substrate without supplying the raw material gas is repeated multiple times. Moreover, all or a part of the multiple sequences further include a step of subjecting the substrate to a modification treatment by supplying plasma of a gas not containing hydrogen after the step of supplying plasma to the substrate without supplying the raw material gas, and in the above steps of supplying the raw material gas and plasma and supplying plasma without supplying the raw material gas, plasma containing a hydrogen-containing gas is used as the plasma.

[0036] Figure 1 It is a timing chart showing an example of the sequence of the method for forming a BN film according to one embodiment. Figure 1 The sequence is composed of step ST1, step ST2, step ST3, step ST4, step ST5, and step ST6.

[0037] The substrate is not particularly limited, but as an example, it can be a semiconductor substrate. As the semiconductor substrate, for example, a semiconductor substrate composed only of a substrate made of a semiconductor such as Si or a semiconductor substrate having a desired film formed on a substrate made of a semiconductor can be used.

[0038] In step ST1, the inside of the chamber is purged by supplying a purge gas to the chamber in which the substrate is disposed. At this time, it is also possible to flow the source gas through the exhaust line and fill the filling tank with the source gas to prepare for the supply of the source gas. As the purge gas, an inert gas can be used, and noble gases such as Ar gas and He gas can preferably be used. In addition, the plasma gas described later can also be supplied simultaneously.

[0039] In step ST2, a plasma of a source gas (source gas) containing a borazine-based compound and a gas containing hydrogen (H) is supplied to the substrate in the chamber. Thereby, the source gas is adsorbed on the substrate, and the source gas is activated by the plasma to promote the adsorption of the source gas. In Figure 1 , an example is shown in which NH 3 gas is supplied as the gas containing H and is turned into plasma by high-frequency (RF) power.

[0040] The borazine-based compound used as the source gas is a compound having a borazine (B 3 H 6 N 3 ) shown by the following formula (1) as the basis. That is, the borazine-based compound is a compound having a borazine ring in which 3 Bs and 3 Ns are alternately bonded to form the basic skeleton of borazine. For example, it can be an organic borazine compound obtained by substituting a part or all of the H of borazine with an organic substituent. As the organic borazine compound, an alkyl borazine compound obtained by using an alkyl group as the organic substituent can be used. For example, trimethylborazine (TMB) having the structure shown by the following formula (2) can be used. The source gas containing the borazine-based compound functions as the B source and N source of the BN film.

[0041]

Chemical formula 1

[0042]

[0043] The plasma of the gas containing H only needs to be supplied to the substrate. It can be generated in the chamber or can be a remote plasma in which the plasma generated in other places is introduced into the chamber. The method for generating the plasma is not particularly limited, and capacitively coupled plasma obtained by applying high-frequency (RF) power to parallel plate electrodes to form a high-frequency electric field in the processing space where the substrate is disposed can be used. Other plasmas such as inductively coupled plasma and microwave plasma can also be used.

[0044] As the plasma of the gas containing H, it can be, for example, H 2a plasma of a gas containing only H like a gas, but a plasma of a gas containing H and N can also be used, for example, a plasma of ammonia (NH 3 ) gas (also called NH 3 plasma). Additionally, it can also be a gas containing NH 3 gas (for example, NH 3 +N 2 gas) plasma. When using a plasma of a gas containing H and N, N in the plasma also functions as an N source for the BN film. The plasma is preferably set to an energy such that the basic skeleton of the source gas is not damaged when forming the h-BN film.

[0045] In step ST3, after step ST2, the supply of the source gas is stopped, and only a plasma containing H is supplied. Thereby, the adsorption of the source gas is promoted, and the reaction of the source gas adsorbed on the substrate to h-BN is promoted. Step ST3 is carried out continuously after step ST2. The plasma containing H at this time uses the same plasma as in step ST2.

[0046] By using a plasma of a gas containing H, such as a plasma containing NH 3 , as the plasma in step ST2 and step ST3 to form the h-BN film and contain H groups or NH x groups in the film, discontinuous parts are generated in the borazine ring structure of h-BN in the plane of the film, and the stress difference with the substrate is alleviated. Thereby, the adhesion of the BN film to the substrate and the flatness of the surface of the BN film become good.

[0047] In step ST2 and step ST3, the temperature can be 200°C to 400°C. The lower the temperature, the more difficult it is to form h-BN. Additionally, the pressure can be 4 Torr or more. However, when the pressure is 12 Torr or more, the film formation rate (GPC: Growth per Cycle) tends to become too low. Additionally, the time of step ST2 (film formation time) can be 2 seconds or less. When it exceeds 2 seconds, the amorphous BN component tends to increase. The time of step ST3 (plasma time) can be 4 seconds or more. When it is 4 seconds or more, there is a tendency to promote the formation of the lateral orientation of h-BN. The RF power of the plasma in step ST2 and step ST3 can be 100 W or more. The lower the power, the more the film quality tends to decline.

[0048] In step ST4, a purge gas is supplied into the chamber to purge the gas remaining in the chamber after step ST3. As the purge gas, an inert gas can be used, and noble gases such as Ar gas and He gas can preferably be used. In step ST4, as Figure 1As shown, a gas not containing H (e.g., N 2 gas) that can be used in the subsequent step ST5 can also be supplied.

[0049] In step ST5, a plasma of a gas not containing H is supplied to the substrate for modification treatment. Similar to the H-containing plasma in step ST2 and step ST3, as long as the plasma of the gas not containing H is supplied to the substrate, it can be generated in the chamber or can be a remote plasma in which the plasma generated at other places is introduced into the chamber. Regarding the method of generating the plasma, similar to the plasma of the H-containing gas, it is not particularly limited, and capacitively coupled plasma, inductively coupled plasma, microwave plasma, etc. can be used. The plasma of the gas not containing H can be, for example, a plasma of N 2 gas (also called N 2 plasma), or can be a plasma of a noble gas such as Ar gas. In addition, it can also be a plasma containing both N 2 gas and noble gas. Through the modification treatment using the plasma not containing H in step ST5, the film quality of the BN film can be improved by reducing H in the film, etc.

[0050] In step ST5, the temperature can be the same as in step ST2 and step ST3, which is 200°C to 400°C. In addition, the pressure can be 6 Torr or more. In addition, the time (modification treatment time) of step ST5 can be 1 second or more. The RF power of the plasma in step ST5 can be 400 W or more.

[0051] In step ST6, a purge gas is supplied into the chamber to purge the gas remaining in the chamber after step ST5. As the purge gas, an inert gas can be used, and noble gases such as Ar gas and He gas can be preferably used.

[0052] A thin unit film of h-BN is formed through the sequence of steps ST1 to ST6 as described above. Moreover, by performing multiple sequences including the sequence composed of steps ST1 to ST6, an h-BN film with a desired film thickness is formed.

[0053] In addition, instead of the sequence of steps ST1 to ST6, as Figure 2 shown, a sequence with a pre-plasma step (step ST7) of performing plasma treatment on the substrate before step ST2 is added. This step ST7 is used to make the surface smoothness of the formed BN film better. The pre-plasma step of step ST7 can be performed in the same manner as step ST3.

[0054] In addition, as Figure 3As shown, it may also be a sequence that replaces step ST1 with a pre-gas supply step (step ST8) of supplying a cyclic borazane-based compound gas to the substrate before step ST2. The pre-gas supply step of step ST8 is performed by supplying the same cyclic borazane-based compound gas as in step ST2 without using plasma. The pre-gas supply step of this step ST8 is used to improve the step-coverage of the formed BN film. In step ST8, a purge gas such as a noble gas may also be supplied together with the cyclic borazane-based compound gas. Additionally, a plasma gas may also be supplied.

[0055] In the present embodiment, in Figures 1 to 3 any of the sequences, it includes step ST2 of supplying a raw material gas and a plasma containing H, followed by step ST3 of supplying only the plasma containing H, and step ST5 of supplying a plasma without H for modification treatment. Through step ST2 and step ST3, an h-BN film with good film adhesion and flatness can be formed, but since the film contains H, the film quality deteriorates. Therefore, in step ST5, modification treatment is performed with a plasma of a gas without H to improve the film quality.

[0056] Hereinafter, a detailed description will be given.

[0057] In the present embodiment, by supplying a raw material gas containing a cyclic borazane-based compound to the substrate, the cyclic borazane-based compound is adsorbed on the substrate, and the ligand is removed while maintaining the cyclic borazane skeleton of the cyclic borazane-based compound, thereby forming a two-dimensional structured h-BN film. At this time, by supplying plasma in addition to the raw material gas, the cyclic borazane-based compound is activated to promote the adsorption and reaction of the raw material gas. Additionally, by subsequently supplying only the plasma, the reaction is further promoted. Therefore, an h-BN film can be formed at a high film formation rate (GPC).

[0058] At this time, by using a gas containing H as the gas for generating plasma, an H group or NH x group is included in the film through the plasma of the gas containing H, thereby generating discontinuous portions in the cyclic borazane ring structure of h-BN in the plane of the film, alleviating the stress difference from the substrate, and thus, compared with the case of using a gas without H as the gas for generating plasma, the adhesion of the film to the substrate and the flatness of the film surface become good. At this time, by using a gas containing H and N, such as NH 3 gas, as the plasma of the gas containing H, N in the plasma also functions as an N source for the BN film, and additionally, the adhesion of the film and the flatness of the film surface can be made better.

[0059] However, it was found that since the plasma in steps ST2 and ST3 contains H, film quality problems such as an increase in H in the film, an increase in the B / N ratio of the BN film caused thereby, and a decrease in oxidation resistance occur.

[0060] In response to this discovery, by performing a modification treatment using the plasma of the gas not containing H in step ST5, H and H-containing groups are detached from the gas phase and the borazine-based compound in the film. As the film is modified, H in the film decreases, the film quality improves, and the lateral orientation also improves.

[0061] Refer to Figure 4 to explain the mechanism of film modification at this time.

[0062] Here, TMB is used as the borazine-based compound in step ST2, and NH 3 plasma is used as the plasma of the gas containing H in steps ST2 and ST3, and N 2 plasma is used as the plasma of the gas not containing H in step ST5 as an example for explanation.

[0063] First, by supplying NH 3 plasma to TMB in the gas phase and the film of the structure (a) generated in step ST2 in step ST3, due to the action of NH x * and H* in the plasma, CH 3 and H are detached from TMB in the gas phase and the film, becoming the structure shown in (b). Then, by supplying N 2 plasma to the structure shown in (b) in step ST5, due to the action of N* in the plasma, H and NH x are detached from the structure shown in (b) or replaced by N:, becoming the structure shown in (c). The structure shown in (c) has an adsorption site for TMB, and the adsorption of TMB is promoted by supplying TMB in the next step. As a result, H in the film of the BN film decreases, and the film quality improves. In addition, the lateral orientation also improves. Regarding the film quality, specifically, an increase in oxidation resistance, achievement of a BN ratio close to the stoichiometric composition, reduction of the k value and leakage current, and increase in film density are observed.

[0064] Describe the experiments that confirmed these.

[0065] Here, like Figure 5 (a) of, TMB + N 2 plasma (TMB + pN 2 ), N 2 plasma (pN 2) The sample obtained by forming a BN film on a substrate by repeating the sequence of purging (PRG) many times was designated as Sample 1. Additionally, as in Figure 5 (b) of 3 plasma (TMB + pNH 3 ), NH 3 plasma (pNH 3 ), the sample obtained by forming a BN film on a substrate by repeating the sequence of purging (PRG) many times was designated as Sample 2. And, as in Figure 5 (c) of 3 plasma (TMB + pNH 3 ), NH 3 plasma (pNH 3 ), purging (PRG), N 2 plasma modification (pN 2 ), the sample obtained by forming a BN film on a substrate by repeating the sequence of purging (PRG) many times was designated as Samples 3 - 5. Samples 3 - 5 are samples obtained by varying the time of N 2 plasma modification. It was set to 1 second for Sample 3, 4 seconds for Sample 4, and 16 seconds for Sample 5. As other conditions, temperature: 400 °C, pressure: 8 Torr, the time of TMB + pN 2 and TMB + pNH 3 was set to 2 seconds, and the time of pN 2 and pNH 3 was set to 4 seconds (only 16 seconds for Sample 5).

[0066] Figure 6 is a graph obtained by measuring the absorbance in the wavenumber region containing the peak of h - BN (1380 cm -1 ) for Samples 1 - 5 by FT - IR. As shown in Figure 6 , the peak of h - BN was also observed in Sample 1 and Sample 2, but an increase in the h - BN peak was observed due to N 2 plasma modification. By lengthening the time of N 2 plasma modification, the degree of increase in the h - BN peak became larger. That is, it was confirmed that the lateral orientation of h - BN was improved by N 2 plasma modification.

[0067] Figure 7 is a graph obtained by measuring the absorbance in the wavenumber region containing the peak of NH x (3300 cm -1 -3500 cm -1 ) for Samples 1 - 5 by FT - IR. As can be seen from Figure 7 , it is known that NH was used during film formation.3 The sample 2 obtained by using plasma and the sample 1 obtained by using N 2 plasma, the peak height of NH x is higher, and the amount of H in the film is more. It can be seen that, in contrast, after NH 3 plasma, for samples 3 - 5 obtained by N 2 plasma modification compared with sample 2, the peak of NH x decreases, and by prolonging the modification time, the peak of NH x decreases more. Thus, it was confirmed that the H in the film was reduced by N 2 plasma modification.

[0068] Figure 8 is a graph obtained by measuring the absorbance in the wavenumber region containing the peak of BOH (around 3200 cm -1 ) by FT - IR for samples 1 - 5. As Figure 8 shown, the peak of BOH was observed in sample 2 obtained by using NH 3 plasma during film formation, but the peak of BOH was hardly observed in sample 1 obtained by using N 2 plasma. That is, it is considered that BOH derived from atmospheric oxidation was formed due to the presence of NH 3 in sample 2. In contrast, for samples 3 - 5 obtained by N 3 plasma modification after NH 2 plasma compared with sample 2, BOH decreased.

[0069] Figure 9 is a graph showing the film composition and B / N ratio of the BN films of samples 1 - 5. The fewer impurities such as oxygen in the BN film and the closer the B / N ratio is to 1, the more preferable. However, as Figure 9 shown, in sample 2 obtained by using NH 3 plasma, the oxygen content is as high as 5 at%, and the B / N ratio is also as high as 1.15, rich in B. This is considered to be because BOH was generated in sample 2, the bond of the BN ring was cut off by it, and N was detached. In contrast, for samples 3 - 5 obtained by N 3 plasma modification after NH 2 plasma, the oxygen content decreased, and the B / N ratio was improved to 1.06 - 1.09. Especially for the oxygen content, in sample 5 where the N 2 plasma modification was carried out for 16 seconds, it decreased to 1 at%.

[0070] According to Figure 8 and Figure 9 results, it was confirmed that in the case of using NH 3In sample 2 obtained by plasma, the formation of BOH was observed but the oxidation resistance was insufficient. Therefore, the oxygen content in the film was high and the B / N ratio was also high. However, by performing N 2 plasma modification, the oxidation resistance was improved, the oxygen content in the film decreased, and the B / N ratio also became good.

[0071] Figure 10 It is a graph showing the k values and leakage currents of samples 1 to 5. As shown in this graph, in sample 2 obtained by using NH 3 plasma, the k value was 3.0, higher than that of sample 1, and the leakage current value was 4.7E-08 A / cm 2 , which was at the same level as the leakage current value of sample 1. In contrast, in sample 4 obtained by performing N 3 plasma modification after NH 2 plasma, the k value was 2.6 and the leakage current value was 2.4E-08 A / cm 2 , both of which decreased.

[0072] Figure 11 It is a graph showing the relationship between the N 3 plasma modification time after NH 2 plasma and the film density. The value of the N 2 plasma modification time of 0 seconds was the value of sample 2 without N 2 plasma modification. As Figure 11 shown, the film density in the case of not performing N 2 plasma modification was 1.85 g / cm 3 , but by performing 4 seconds of N 2 plasma modification, the film density increased to 2.15 g / cm 3 .

[0073] According to Figures 9 to 11 the results, it was confirmed that by performing N 3 plasma modification after film formation using NH 2 plasma, the k value and the leakage current value decreased, the film density increased, and N 2 plasma modification had an effect of improving the film quality.

[0074] In addition, it can be that all sequences include the step ST2 of supplying a raw material gas and a plasma containing H as shown in the sequence of Figures 1 to 3 , the subsequent step ST3 of only supplying a plasma containing H, and the step ST5 of supplying a plasma not containing H for modification treatment. It can also be that a part of the sequence is composed of these steps. In this case, as long as other sequences include at least the following processes: supplying a raw material gas containing a borazine compound and a plasma to the substrate; and then supplying a plasma to the substrate without supplying the raw material gas.

[0075] For example, the modification treatment using a plasma that does not contain H in step ST5 does not need to be performed throughout the entire sequence of steps ST2 and ST3. That is, for example, it can also be performed periodically in such a way that it is performed once in a specified number of times (for example, 2 to 10 times) in the sequence of steps ST2 and ST3.

[0076] In addition, for a part of multiple sequences, the plasma containing H in steps ST2 and ST3, such as NH 3 plasma, can be replaced with a plasma that does not contain H, such as N 2 plasma. There may also be no plasma modification treatment in this sequence. For example, it can be such that, for the sequence of Figure 1 (or the sequence of Figure 2 ), the sequence of Figure 3 ), in the initial stage of film formation where high tightness and flatness are particularly required, a sequence using a plasma that does not contain H (such as N 2 plasma) is used for the film body formation stage. At this time, for example, instead of replacing all with N 3 plasma in the film body formation stage after the sequence using NH 2 plasma in the initial stage of film formation, a migration period composed of multiple sequences is set between them, and from the initial stage of film formation to the film body formation stage, the frequency of N 2 plasma relative to NH 3 plasma is gradually increased. In addition, it can also be set that during the migration period, a part of the NH 3 gas as the plasma gas is replaced with N 2 gas, and from the initial stage of film formation to the film body formation stage, the ratio of N 2 gas is gradually increased, and it is transferred to N 2 plasma.

[0077] <Film formation apparatus>

[0078] Next, an example of a film formation apparatus capable of implementing the film formation method applicable to the above BN film will be described.

[0079] Figure 12 It is a cross-sectional view showing an example of the film formation apparatus.

[0080] The film formation apparatus 100 includes a chamber 1, a stage 2, a shower head 3, an exhaust unit 4, a gas supply mechanism 5, a plasma generation unit 6, and a control unit 7, and forms a BN film on a substrate W. The substrate W is not particularly limited, and for example, it can be a semiconductor substrate such as a Si substrate.

[0081] The chamber 1 is made of a metal such as aluminum and has a substantially cylindrical shape. An inlet / outlet 11 for loading / unloading the substrate W is formed in the side wall of the chamber 1, and the inlet / outlet 11 can be opened and closed by a gate valve 12. A circular exhaust duct 13 with a rectangular cross-section is provided on the main body of the chamber 1. In the exhaust duct 13, a slit 13a is formed along the inner peripheral surface. In addition, 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 so as to block the upper opening of the chamber 1. The top wall 14 and the exhaust duct 13 are hermetically sealed by a sealing ring 15.

[0082] The mounting table 2 horizontally mounts the substrate W, has a circular plate shape corresponding to the size of the substrate W, and is supported by a support member 23. The mounting table 2 is made of a ceramic material such as aluminum nitride (AlN), a metal material such as aluminum, or a nickel-based alloy, and a heater 21 for heating the substrate W is embedded inside the mounting table 2. A cover member 22 is provided on the mounting table 2 so as to cover the side surface.

[0083] 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 the lower end of the support member 23 is connected to the mounting table lifting mechanism 24. The mounting table 2 can be lifted and lowered via the support member 23 by the mounting table lifting mechanism 24 between the processing position indicated by the solid line and the transfer position indicated by the one-dot chain line below where the substrate can be transferred. In addition, a flange portion 25 is installed at a position below the chamber 1 of the support member 23, and a bellows 26 is provided between the bottom surface of the chamber 1 and the flange portion 25. The bellows 26 divides the atmosphere inside the chamber 1 from the outside air, and the bellows 26 expands and contracts as the mounting table 2 moves up and down.

[0084] Near the bottom surface of the chamber 1, three (only two are shown) substrate support pins 27 are provided so as to protrude upward from the lifting plate 27a. The substrate support pins 27 can be lifted and lowered via the lifting plate 27a by a substrate support pin lifting mechanism 28 provided below the chamber 1, and can penetrate through a through hole 2a provided in the mounting table 2 at the transfer position and protrude and retract relative to the upper surface of the mounting table 2. By lifting and lowering the substrate support pins 27 in this way, the substrate W is transferred between the substrate transfer 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.

[0085] The showerhead 3 supplies a processing gas into the chamber 1 in a shower-like manner. The showerhead 3 is arranged to face the mounting table 2 and has approximately the same diameter as the mounting table 2. The showerhead 3 has a shower main body portion 31 fixed to the top wall 14 of the chamber 1 and a shower plate 32 connected to the lower part of the shower main body portion 31. A gas diffusion space 33 is formed between the shower main body portion 31 and the shower plate 32, and a gas introduction hole 36 is connected to the gas diffusion space 33. The gas introduction hole 36 is provided to penetrate the center of the main body portion 31 and the top wall 14 of the chamber 1. Gas ejection holes 34 are formed in the shower plate 32. In a state where the mounting table 2 is in the processing position, a processing space S is formed between the shower plate 32 and the mounting table 2.

[0086] 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 by the exhaust mechanism 43 of the exhaust unit 4 through the exhaust pipe 41 from the exhaust duct 13.

[0087] The gas supply mechanism 5 supplies a gas for film formation to the showerhead 3, and supplies a source gas containing a borazine compound, a plasma gas containing H, a plasma gas for modification treatment not containing H, and a purge gas. As described above, TMB is shown here as the borazine compound, NH 3 gas is used as the plasma gas containing H, and N 2 gas is used as the plasma gas for modification treatment not containing H, and Ar gas is used as the purge gas. However, as described above, the borazine compound, the plasma gas containing H, the plasma gas for modification treatment not containing H, and the purge gas are not limited to these.

[0088] The gas supply mechanism 5 has a TMB gas supply source 51 that supplies TMB gas as the source gas, an NH 3 gas supply source 52 that supplies NH 3 gas as the gas containing H for generating the plasma for film formation, and an N 2 gas supply source 53 that supplies N 2 gas as the gas not containing H for generating the plasma for modification. In addition, it has a first Ar gas supply source 54, a second Ar gas supply source 55, and a third Ar gas supply source 56 that supply Ar gas as the purge gas.

[0089] The TMB gas supply source 51 is connected to one end of the TMB gas line 57. In the TMB gas line 57, a valve 57a, a filling tank 57b, and a flow rate adjustment unit 57c are successively clamped from the downstream side. NH3 The gas supply source 52 is connected to one end of the NH 3 gas line 58. In the NH 3 gas line 58, a valve 58a, a filling tank 58b, and a flow rate adjusting section 58c are successively interposed from the downstream side. N 2 The gas supply source 53 is connected to N 2 gas line 59. In the N 2 gas line 59, a valve 59a, a filling tank 59b, and a flow rate adjusting section 59c are successively interposed from the downstream side. The TMB gas line 57, the NH 3 gas line 58, and the N 2 gas line 59 are connected to one end of a common line 63, and the other end of the common line 63 is connected to the gas introduction hole 36 of the spray head 3.

[0090] The first Ar gas supply source 54 is connected to one end of the first Ar gas line 60. In the first Ar gas line 60, a valve 60a and a flow rate adjusting section 60c are successively interposed from the downstream side. The other end of the first Ar gas line 60 is connected to a position on the TMB gas line 57 downstream of the valve 57a. The second Ar gas supply source 55 is connected to one end of the second Ar gas line 61. In the second Ar gas line 61, a valve 61a and a flow rate adjusting section 61c are successively interposed from the downstream side. The other end of the second Ar gas line 61 is connected to a position on the NH 3 gas line 58 downstream of the valve 58a. The third Ar gas supply source 56 is connected to one end of the third Ar gas line 62. In the third Ar gas line 62, a valve 62a and a flow rate adjusting section 62c are successively interposed from the downstream side. The other end of the third Ar gas line 62 is connected to a position on the N 2 gas line 59 downstream of the valve 59a. During the film formation process, the valves 60a, 61a, and 62a are always open, and Ar gas as a purge gas is always supplied into the chamber 1 from the first Ar gas line 60, the second Ar gas line 61, and the third gas line 62 through the TMB gas line 57, the NH 3 gas line 58, and the N 2 gas line 59.

[0091] The valves 57a, 58a, and 59a are configured as high-speed on-off valves that rapidly open and close the corresponding gas lines. The valves 60a, 61a, and 62a can be ordinary on-off valves.

[0092] The filling tanks 57b, 58b, and 59b are respectively used to temporarily store the TMB gas, NH 3 gas, and N 2 gas before supplying the TMB gas, NH 3 gas, and N 2Gas. By storing gas in the filling tanks 57b, 58b, and 59b, the filling tanks 57b, 58b, and 59b are set to a state where the pressure is boosted to a specified pressure. Thereafter, each gas can be ejected into the chamber 1 by opening the valves 57a, 58a, and 59a. Thus, a large flow rate of gas can be stably supplied to the chamber 1.

[0093] The flow rate adjustment units 57c, 58c, 59c, 60c, 61c, and 62c are constituted by, for example, mass flow controllers, and adjust and control the flow rate of the gas flowing in the respective corresponding gas lines.

[0094] The plasma generation unit 6 has a power supply line 65 connected to the shower main body 31 of the shower head 3, and a matcher 66 and a high-frequency (RF) power supply 67 connected to the power supply line 65. By supplying high-frequency (RF) power from the RF power supply 67 to the shower head 3, a high-frequency (RF) electric field is formed in the processing space S between the shower head 3 and the stage 2, and capacitive coupling plasma is generated by this RF electric field. In addition, when the stage 2 is formed of a ceramic material, an electrode is buried in the stage 2, and an RF electric field is formed between the shower head 3 and the electrode.

[0095] The control unit 7 is constituted by a computer, and has a main control unit having a CPU, an input device, an output device, a display device, and a storage device (storage medium). The main control unit controls the structural parts of the film forming apparatus 100, such as valves, flow rate adjustment units, automatic pressure control valves, heaters, and lifting mechanisms. Parameters of various processes executed by the film forming apparatus 100 are stored in the storage device. In addition, the storage device has a storage medium that stores a program for controlling the processes executed by the film forming apparatus 100, that is, a processing process. The main control unit calls a specified processing process stored in the storage medium, and based on this processing process, causes the film forming apparatus 100 to execute a specified action.

[0096] In the film forming apparatus 100 configured as described above, first, the gate valve 12 is opened, and a substrate W is carried into the chamber 1 via the carry-in / carry-out port 11 by a transfer device (not shown), and is placed on the stage 2. The transfer device is retracted, and the stage 2 is raised to the processing position. Then, the gate valve 12 is closed, the inside of the chamber 1 is evacuated, and the temperature of the stage 2 (substrate temperature) is heated and controlled to a desired temperature by the heater 21.

[0097] In this state, the actual film forming process is started.

[0098] In performing the above Figure 1In the case of the sequence shown in FIG. 1 , first, Ar gas as a purge gas is supplied from the first Ar gas supply source 54, the second Ar gas supply source 55, and the third Ar gas supply source 56 via the first Ar gas line 60, the second Ar gas line 61, and the third Ar gas line 62 and the shower head 3 to the processing space S, thereby performing purge in the chamber 1 in step ST1 (step ST1). At this time, NH 2 may also be supplied as a plasma gas. 3 Alternatively, the supply may be prepared by filling a filling tank with TMB gas as a raw material gas or by allowing the TMB gas to flow through an exhaust line.

[0099] Next, TMB gas and NH 3 Specifically, the Ar gas is continuously supplied, and the NH 3 The gas supply source 52 is supplied via NH 3 The gas line 58 and the shower head 3 supply NH 2 as plasma gas to the processing space S. 3 In the state of gas, RF power is supplied from the RF power supply 67 of the plasma generating unit 6 to the shower head 3. As a result, NH 3 In addition, TMB gas as a raw material gas is supplied from the TMB gas supply source 51 to the processing space S via the TMB gas line 57 and the shower head 3. Thus, the TMB gas and NH 3 Plasma, TMB gas is adsorbed on the substrate W, and the TMB gas in the gas phase neutralization film is NH 3 The adsorption of TMB gas is promoted by plasma activation.

[0100] After step ST2 is completed, continue to perform NH 3 In the state of plasma generation, the valve 57a is closed to stop the TMB gas, and only NH 3 Plasma (step ST3 ). Thus, the TMB gas in the film is further activated to promote the adsorption of the TMB gas and promote the reaction of the TMB gas to h-BN.

[0101] Next, the RF power from the RF power supply 67 is turned off, and the valve 58a is closed to stop the NH 3 The supply of gas is continued, and the chamber 1 is purged while Ar gas is continuously supplied (step ST4). At this time, the valve 59a may be opened to supply Ar gas from N 2 The gas supply source 53 is supplied via N 2 The gas line 59 and the shower head 3 also supply N2 as a plasma gas for the reforming process to the processing space S. 2 gas.

[0102] Next, by turning on the RF power from the RF power supply 67 and continuing the supply of N 2 gas, N is generated in the processing space S 2 plasma, and the modification treatment by N 2 plasma is performed (step ST5).

[0103] Next, turn off the RF power from the RF power supply 67, close the valve 59a to stop the supply of N 2 gas, and purge the inside of the chamber 1 in a state where Ar gas is continuously supplied (step ST6).

[0104] By repeating the sequence of steps ST1 to ST6 as described above for a desired number of cycles, an h-BN film with a desired film thickness is formed.

[0105] In addition, in the case where a pre-plasma step (step ST7) is performed before step ST2 as shown Figure 2 , step ST7 can be performed in the same manner as step ST3. Additionally, in the case where a pre-gas supply step (step ST8) is performed instead of step ST1 as shown Figure 3 , it is performed by supplying a borazine-based compound gas similar to that in step ST2 without using plasma.

[0106] Furthermore, as described above, it is not necessary to set multiple sequences as steps ST1 to ST6 (or Figure 2 、 Figure 3 sequence), and a sequence that does not perform the modification treatment using N 2 plasma can be included in a part, and a sequence of plasma during film formation and subsequent plasma using N 2 plasma can also be included in a part.

[0107] In this way, in the process of supplying TMB gas and plasma and the process of supplying plasma without supplying TMB gas, NH 3 plasma is used as the plasma. Therefore, the adhesion of the formed h-BN film and the flatness of the film surface are good. Additionally, through the subsequent modification treatment using N 2 plasma, H in the film is reduced, and an h-BN film with good film quality is obtained.

[0108] <Other Applications>

[0109] The above describes the embodiments, but it should be considered that all points of the embodiments disclosed herein are illustrative and not restrictive. The above embodiments can be omitted, replaced, and changed in various ways without departing from the appended claims and their gist.

[0110] For example, in the above-described embodiment, as a basic sequence, the following was exemplified: Figures 1 to 3 The sequence shown, including the supply of a borazine-based compound gas and a plasma containing H (step ST2), the supply of a plasma containing H (step ST3), purge (step ST4), modification treatment using a plasma not containing H (step ST5), and purge (step ST6). However, as a basic sequence, as long as it includes the steps of supplying a borazine-based compound gas and a plasma containing H to the substrate, the subsequent step of supplying a plasma containing H to the substrate, and the modification treatment using a plasma not containing H, it is not limited to these. In addition, as described above, it is not limited to the case where all of the multiple sequences are the above-described basic sequence. As long as it includes the steps of supplying a source gas containing a borazine-based compound gas and a plasma to the substrate, and the subsequent step of supplying a plasma to the substrate without supplying the source gas, a part of the sequence may also be different from the basic sequence.

[0111] In addition, regarding the film-forming apparatus, Figure 12 the apparatus shown is merely an example. As long as it is an apparatus capable of sequentially performing step ST2 of supplying a borazine-based compound gas and a plasma containing H to the substrate, step ST3 of supplying a plasma containing H, and step ST5 of modification treatment using a plasma not containing H, it is not particularly limited, and is not limited to a single-sheet type, and may also be a batch type. In addition, in Figure 12 the film-forming apparatus 100 shown, an example of generating capacitively coupled plasma between the showerhead 3 and the stage 2 by supplying RF power to the showerhead 3 is shown, but it is not limited thereto, and various plasmas such as inductively coupled plasma and microwave plasma can be used. Also, it may be a remote plasma that transports the plasma generated in other places to the substrate.

[0112] Description of Reference Numerals

[0113] 1: Chamber; 2: Stage; 3: Showerhead; 4: Exhaust section; 5: Gas supply mechanism; 6: Plasma generation unit; 7: Control unit; 51: TMB gas supply source; 52: NH 3 gas supply source; 53: N 2 gas supply source; 54, 55, 56: Ar gas supply source; 100: Film-forming apparatus; W: Substrate.

Claims

1. A method for forming a boron nitride film, wherein: A sequence including a step of supplying a source gas containing a borazine-based compound and plasma to a substrate disposed in a chamber and a step of supplying the plasma to the substrate without supplying the source gas is performed multiple times, All or part of the multiple sequences also include a step of supplying plasma of a gas not containing hydrogen to the substrate after the step of supplying the plasma without supplying the raw material gas, a step of supplying the raw material gas and the plasma of a gas containing hydrogen to the substrate as a step of supplying the raw material gas and plasma containing the cycloborazine series compound, and a step of supplying the plasma of a gas containing hydrogen without supplying the raw material gas as a step of supplying the plasma without supplying the raw material gas.

2. The method for forming a boron nitride film according to claim 1, wherein: The sequence consists of the following steps: purging the chamber; then supplying the raw material gas and the plasma of the gas containing hydrogen to the substrate; then supplying the plasma of the gas containing hydrogen to the substrate without supplying the raw material gas; then purging the chamber; then supplying the plasma of the gas not containing hydrogen to the substrate; and purging the chamber.

3. The method for forming a boron nitride film according to claim 1, wherein: The sequence consists of the following steps: purging the chamber; then supplying a plasma of a gas containing hydrogen to the substrate; then supplying the raw material gas and the plasma of a gas containing hydrogen to the substrate; then supplying the plasma of a gas containing hydrogen to the substrate without supplying the raw material gas; then purging the chamber; then supplying the plasma of the gas not containing hydrogen to the substrate; and then purging the chamber.

4. The method for forming a boron nitride film according to claim 1, wherein: The sequence consists of the following steps: supplying the raw material gas to the substrate; then supplying the raw material gas and the plasma of the gas containing hydrogen to the substrate; then supplying the plasma of the gas containing hydrogen to the substrate without supplying the raw material gas; then purging the chamber; then supplying the plasma of the gas not containing hydrogen to the substrate; and then purging the chamber.

5. The method for forming a boron nitride film according to any one of claims 1 to 4, wherein: The borazine compound is an alkyl borazine compound.

6. The method for forming a boron nitride film according to claim 5, wherein: The borazine compound is trimethyl borazine.

7. The method for forming a boron nitride film according to any one of claims 1 to 4, wherein: The gas containing hydrogen contains hydrogen and nitrogen.

8. The method for forming a boron nitride film according to claim 7, wherein: The gas containing hydrogen is ammonia gas.

9. The method for forming a boron nitride film according to any one of claims 1 to 4, wherein: The gas not containing hydrogen is at least one of a rare gas and nitrogen.

10. The method for forming a boron nitride film according to any one of claims 1 to 4, wherein: The following sequence is implemented as a sequence of a part of the sequence of a plurality of times, the sequence comprising the steps of: supplying the plasma of the source gas and the gas containing hydrogen to the substrate; supplying the plasma of the gas containing hydrogen without supplying the source gas; and supplying the plasma of the gas not containing hydrogen to the substrate, The following sequence is implemented as a sequence of another part of the sequence that is repeated multiple times, and the sequence includes the following steps: supplying the plasma of the raw material gas and the gas containing hydrogen to the substrate; and supplying the plasma of the gas containing hydrogen without supplying the raw material gas, and the sequence does not include the step of supplying the plasma of the gas not containing hydrogen to the substrate.

11. The method for forming a boron nitride film according to claim 10, wherein: The step of periodically supplying plasma of a gas not containing hydrogen to the substrate is performed.

12. The method for forming a boron nitride film according to any one of claims 1 to 4, wherein: The following sequence is implemented as a sequence of a part of the sequence of a plurality of times, the sequence comprising the steps of: supplying the plasma of the source gas and the gas containing hydrogen to the substrate; supplying the plasma of the gas containing hydrogen without supplying the source gas; and supplying the plasma of the gas not containing hydrogen to the substrate, The following sequence is implemented as another part of the sequence repeated multiple times, and includes the steps of supplying the raw material gas and plasma of a gas not containing hydrogen to the substrate; and then supplying plasma of a gas not containing hydrogen to the substrate without supplying the raw material gas.

13. The method for forming a boron nitride film according to claim 12, wherein: The following sequence is implemented at the initial stage of film formation, the sequence comprising the following steps: supplying the source gas and the plasma of the gas containing hydrogen to the substrate; supplying the plasma of the gas containing hydrogen without supplying the source gas; and supplying the plasma of the gas not containing hydrogen to the substrate, In the film forming stage, the following sequence is implemented, the sequence including the steps of: supplying the source gas and plasma of a gas not containing hydrogen to the substrate; and then supplying plasma of a gas not containing hydrogen to the substrate without supplying the source gas.

14. The method for forming a boron nitride film according to claim 13, wherein: There is a migration period consisting of multiple sequences between the film formation initial stage and the film body film formation stage. During the migration period, the frequency of the plasma of the gas not containing hydrogen is gradually increased from the film formation initial stage to the film body film formation stage, or a part of the gas containing hydrogen is replaced with the gas not containing hydrogen from the film formation initial stage to the film body film formation stage to increase the ratio of the gas not containing hydrogen.

15. A boron nitride film forming device, comprising: a chamber that receives a substrate; a gas supply mechanism for supplying a raw material gas containing a borazine-based compound and a gas for generating plasma into the chamber; An exhaust mechanism for exhausting the chamber; a plasma generating unit for generating plasma; a heating mechanism that heats the substrate; and Control Department, in, The control unit performs a sequence including a step of supplying a source gas containing a borazine-based compound and plasma to a substrate disposed in a chamber and a step of supplying the plasma to the substrate without supplying the source gas a plurality of times. All or part of the multiple sequences also include a step of supplying plasma of a gas not containing hydrogen to the substrate after the step of supplying the plasma without supplying the raw material gas, a step of supplying the raw material gas and the plasma of a gas containing hydrogen to the substrate as a step of supplying the raw material gas and plasma containing the cycloborazine series compound, and a step of supplying the plasma of a gas containing hydrogen without supplying the raw material gas as a step of supplying the plasma without supplying the raw material gas.

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