Film forming method and processing apparatus

Abstract

To provide a technique that can improve the filling characteristics of a boron nitride film in a recess.SOLUTION: A deposition method according to an aspect of the present disclosure includes the steps of preparing a substrate having a recess, supplying a first gas containing a boron-containing gas and a nitrogen-containing gas to the substrate, and forming a boron nitride film in the recess, and supplying a second gas containing a nitrogen-containing gas but not a boron-containing gas to the substrate and heat-treating the boron nitride film.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a film forming method and a processing apparatus. [Background technology]

[0002] A technique is known in which a film is filled into recesses formed on the surface of a substrate by alternately repeating a film formation step and an etching step (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-33230 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can improve the filling characteristics of a boron nitride film in a recess. [Means for solving the problem]

[0005] A film forming method according to one aspect of the present disclosure includes the steps of: preparing a substrate having a recess; supplying a first gas containing a boron-containing gas and a nitrogen-containing gas to the substrate to form a boron nitride film in the recess; and supplying a second gas containing a nitrogen-containing gas but not a boron-containing gas to the substrate to heat-treat the boron nitride film. death , In the step of forming the boron nitride film, a gap is formed in the recess, and in the step of heat-treating the boron nitride film, the volume of the boron nitride film increases, thereby filling the gap with the boron nitride film. . [Effects of the Invention]

[0006] According to the present disclosure, the embedding characteristics of a boron nitride film in recesses can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flowchart illustrating a film forming method according to an embodiment. [Figure 2] 1 is a cross-sectional view illustrating a film forming method according to an embodiment; [Figure 3] Schematic diagram showing a processing apparatus according to an embodiment. [Figure 4] Graph showing the rate of change in film thickness of a boron nitride film before and after heat treatment [Figure 5] Graph showing the B / N ratio of boron nitride film before and after heat treatment [Figure 6] Graph showing the surface roughness (RMS) of boron nitride films before and after heat treatment DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the accompanying drawings, the same or corresponding reference numerals are used to designate the same or corresponding members or components, and redundant descriptions will be omitted.

[0009] [Film formation method] A film forming method according to an embodiment will be described with reference to Figures 1 and 2. As shown in Figure 1, the film forming method according to the embodiment includes a preparation step S10, a boron nitride film forming step S20, and a heat treatment step S30.

[0010] In the preparation step S10, as shown in FIG. 2(a), a substrate 101 having a recess 102 on its surface is prepared. The substrate 101 may be a semiconductor substrate such as a silicon substrate. The recess 102 may be a trench or a hole. An insulating film such as a silicon oxide film or a silicon nitride film may be formed on the surface of the recess 102.

[0011] The boron nitride film forming step S20 is performed after the preparation step S10. In the boron nitride film forming step S20, as shown in FIG. 2(b), a first gas containing a boron-containing gas and a nitrogen-containing gas is supplied to the substrate 101, and a boron nitride film 103 is formed in the recess 102. In the boron nitride film forming step S20, a boron-rich boron nitride film 103 is formed. The boron-rich boron nitride film 103 refers to a boron nitride film 103 in which room for nitridation remains. The boron-rich boron nitride film 103 contains boron with dangling bonds in the film. When the boron nitride film 103 is formed in the recess 102, gaps 104 may be formed in the recess 102. The gaps 104 may be, for example, voids or seams.

[0012] The boron nitride film forming step S20 may include maintaining the substrate 101 at a first temperature. The first temperature is preferably 300°C or lower. In this case, a boron nitride film 103 containing a large amount of boron with dangling bonds in the film can be formed. In addition, a boron nitride film 103 with small surface roughness can be easily formed. The first temperature is more preferably 235°C or lower. In this case, a boron nitride film 103 containing a particularly large amount of boron with dangling bonds in the film can be formed.

[0013] An example of the boron-containing gas contained in the first gas is diborane (B2H6) gas. An example of the nitrogen-containing gas contained in the first gas is ammonia (NH3) gas. The method for forming the boron nitride film 103 is not particularly limited. For example, the boron nitride film 103 can be formed by atomic layer deposition (ALD) or chemical vapor deposition (CVD). The first gas may contain a gas other than the boron-containing gas and the nitrogen-containing gas, such as an inert gas. Examples of the inert gas include nitrogen (N2) gas and argon (Ar) gas.

[0014] The heat treatment step S30 is performed after the boron nitride film formation step S20. In the heat treatment step S30, a second gas containing no boron-containing gas but a nitrogen-containing gas is supplied to the substrate 101, and the boron nitride film 103 is heat-treated. As a result, dangling boron bonds bond with nitrogen in the nitrogen-containing gas contained in the second gas and are nitrided. This causes the volume of the boron nitride film 103 to increase and expand. As a result, the gaps 104 are filled with the boron nitride film 103, and the gaps 104 disappear. In other words, the filling characteristics of the boron nitride film 103 in the recesses 102 can be improved. In FIG. 2(c), the portion of the boron nitride film 103 before its volume increase is indicated by reference numeral 103a, and the expanded portion is indicated by reference numeral 103b. Furthermore, since the number of dangling boron bonds is reduced, the film quality of the boron nitride film 103 is improved.

[0015] The heat treatment step S30 may include maintaining the substrate 101 at a second temperature. The second temperature is higher than the first temperature. The second temperature is preferably 550°C or higher. In this case, bonding between dangling bonds of boron and nitrogen of the nitrogen-containing gas is promoted.

[0016] The heat treatment step S30 may include exposing the substrate 101 to plasma generated from the second gas. In this case, the dangling bonds of boron are bonded with nitrogen in the nitrogen-containing gas and nitrided at a lower temperature than when plasma is not used. For example, the heat treatment step S30 can be performed at the same temperature as the boron nitride film formation step S20.

[0017] The heat treatment step S30 may be performed in the same processing chamber as the boron nitride film forming step S20, or may be performed in a processing chamber different from the boron nitride film forming step S20.

[0018] The nitrogen-containing gas contained in the second gas may be, for example, ammonia gas. The second gas may also contain another gas, such as an inert gas, other than the nitrogen-containing gas. Examples of the inert gas include nitrogen gas and argon gas.

[0019] As a result of the above, the boron nitride film 103 can be embedded in the recess 102.

[0020] According to the film forming method of the embodiment, first, in the boron nitride film forming step S20, a first gas containing a boron-containing gas and a nitrogen-containing gas is supplied to the substrate 101, and the boron nitride film 103 is formed in the recess 102. Next, in the heat treatment step S30, a second gas containing a nitrogen-containing gas but not a boron-containing gas is supplied to the substrate 101, and the boron nitride film 103 is heat-treated. As a result, boron atoms having dangling bonds in the boron nitride film 103 formed in the boron nitride film forming step S20 are nitrided by bonding with nitrogen in the nitrogen-containing gas contained in the second gas supplied in the heat treatment step S30. This causes the volume of the boron nitride film 103 to increase and expand. As a result, the gap 104 is filled with the boron nitride film 103, and the gap 104 disappears. In other words, the filling characteristics of the boron nitride film 103 in the recess 102 can be improved. Furthermore, since the number of dangling bonds of boron is reduced, the film quality of the boron nitride film 103 is improved.

[0021] In the above embodiment, the boron nitride film forming step S20 and the heat treatment step S30 are each performed once, but this is not limiting. For example, the boron nitride film forming step S20 and the heat treatment step S30 may be repeated multiple times to fill the recesses 102. In this case, the boron nitride film 103 is nitrided each time a relatively thin boron nitride film 103 is formed, so dangling boron bonds are less likely to remain. This improves the film quality of the boron nitride film 103.

[0022] [Processing device] An example of a processing apparatus capable of performing the film forming method according to the embodiment will be described with reference to Fig. 3. As shown in Fig. 3, the processing apparatus 1 is a batch-type apparatus that processes a plurality of substrates W at once. The substrates W are, for example, semiconductor wafers.

[0023] The processing apparatus 1 includes a processing vessel 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, and a control unit 90.

[0024] The processing vessel 10 can have its interior depressurized. The processing vessel 10 accommodates a substrate W therein. The processing vessel 10 has a cylindrical inner tube 11 with a ceiling and an open lower end, and a cylindrical outer tube 12 with a ceiling and an open lower end that covers the outside of the inner tube 11. The inner tube 11 and the outer tube 12 are made of a heat-resistant material such as quartz, and are arranged coaxially to form a double-tube structure.

[0025] The ceiling of the inner pipe 11 is, for example, flat. A storage section 13 for storing a gas nozzle is formed on one side of the inner pipe 11 along its longitudinal direction (vertical direction). For example, a part of the side wall of the inner pipe 11 protrudes outward to form a convex section 14, and the inside of the convex section 14 is formed as the storage section 13.

[0026] A rectangular opening 15 is formed in the side wall of the inner tube 11 opposite the housing portion 13 along its longitudinal direction (vertical direction).

[0027] The opening 15 is a gas exhaust port formed so as to be able to exhaust gas from the inner tube 11. The length of the opening 15 is the same as the length of the boat 16, or is formed so as to extend in the vertical direction longer than the length of the boat 16.

[0028] The lower end of the processing vessel 10 is supported by a cylindrical manifold 17 made of, for example, stainless steel. A flange 18 is formed at the upper end of the manifold 17, and the lower end of the outer tube 12 is placed on the flange 18 to support it. A seal member 19 such as an O-ring is interposed between the flange 18 and the lower end of the outer tube 12 to keep the inside of the outer tube 12 airtight.

[0029] An annular support 20 is provided on the inner wall of the upper portion of the manifold 17, and the lower end of the inner tube 11 is placed and supported on the support 20. A lid 21 is airtightly attached to the opening at the lower end of the manifold 17 via a sealing member 22 such as an O-ring, so as to airtightly close the opening at the lower end of the processing vessel 10, i.e., the opening of the manifold 17. The lid 21 is made of, for example, stainless steel.

[0030] A rotating shaft 24 that rotatably supports the boat 16 via a magnetic fluid seal 23 penetrates the center of the lid 21. A lower portion of the rotating shaft 24 is rotatably supported by an arm 25A of an elevating mechanism 25 that is a boat elevator.

[0031] A rotating plate 26 is provided at the upper end of the rotating shaft 24, and the boat 16 holding the substrates W is placed on the rotating plate 26 via a quartz heat retention stand 27. Therefore, by raising and lowering the lifting mechanism 25, the lid 21 and the boat 16 move up and down as a unit, allowing the boat 16 to be inserted into and removed from the processing vessel 10. The boat 16 can be accommodated in the processing vessel 10, and holds a plurality of substrates W (e.g., 50 to 150 substrates) approximately horizontally with spacing between them in the vertical direction.

[0032] The gas supply unit 30 is configured to be able to introduce various process gases used in the above-described film formation method into the process vessel 10. The gas supply unit 30 includes a boron-containing gas supply unit 31 and a nitrogen-containing gas supply unit 32.

[0033] The boron-containing gas supply unit 31 includes a boron-containing gas supply pipe 31a inside the processing vessel 10 and a boron-containing gas supply path 31b outside the processing vessel 10. The boron-containing gas supply path 31b is provided with a boron-containing gas source 31c, a mass flow controller 31d, and a boron-containing gas valve 31e, arranged in this order from upstream to downstream in the gas flow direction. The boron-containing gas from the boron-containing gas source 31c is supplied with a supply timing controlled by the boron-containing gas valve 31e and a predetermined flow rate controlled by the mass flow controller 31d. The boron-containing gas flows from the boron-containing gas supply path 31b into the boron-containing gas supply pipe 31a and is then discharged from the boron-containing gas supply pipe 31a into the processing vessel 10.

[0034] The nitrogen-containing gas supply unit 32 includes a nitrogen-containing gas supply pipe 32a inside the processing vessel 10 and a nitrogen-containing gas supply path 32b outside the processing vessel 10. The nitrogen-containing gas supply path 32b is provided with, in this order from upstream to downstream in the gas flow direction, a nitrogen-containing gas source 32c, a mass flow controller 32d, and a nitrogen-containing gas valve 32e. The nitrogen-containing gas from the nitrogen-containing gas source 32c is supplied at a predetermined flow rate controlled by the nitrogen-containing gas valve 32e and controlled by the mass flow controller 32d. The nitrogen-containing gas flows from the nitrogen-containing gas supply path 32b into the nitrogen-containing gas supply pipe 32a and is then discharged from the nitrogen-containing gas supply pipe 32a into the processing vessel 10.

[0035] The boron-containing gas supply unit 31 and the nitrogen-containing gas supply unit 32 may each include an inert gas supply path (not shown) for introducing an inert gas into the boron-containing gas supply pipe 31 a and the nitrogen-containing gas supply pipe 32 a, respectively. The inert gas supply path may be provided with an inert gas source, a mass flow controller, and an inert gas valve, all of which are not shown, in this order from the upstream side to the downstream side in the gas flow direction.

[0036] Each gas supply pipe (boron-containing gas supply pipe 31a, nitrogen-containing gas supply pipe 32a) is made of, for example, quartz. Each gas supply pipe is fixed to manifold 17. Each gas supply pipe extends linearly in the vertical direction near inner pipe 11, and then bends in an L-shape within manifold 17 and extends horizontally, thereby penetrating manifold 17. Each gas supply pipe is arranged side by side along the circumferential direction of inner pipe 11 and is formed at the same height as each other.

[0037] A plurality of boron-containing gas discharge ports 31f are provided in the boron-containing gas supply pipe 31a at a position located in the inner pipe 11. A plurality of nitrogen-containing gas discharge ports 32f are provided in the nitrogen-containing gas supply pipe 32a at a position located in the inner pipe 11. The discharge ports (boron-containing gas discharge ports 31f, nitrogen-containing gas discharge ports 32f) are formed at predetermined intervals along the extension direction of the respective gas supply pipes. Each discharge port discharges gas in the horizontal direction. The interval between each discharge port is set to be the same as the interval between the substrates W held in the boat 16, for example. The height position of each discharge port is set to be the midpoint between vertically adjacent substrates W. This allows each discharge port to efficiently supply gas to the opposing surfaces between adjacent substrates W.

[0038] The gas supply unit 30 may mix multiple types of gases and discharge the mixed gas from one supply pipe. The gas supply pipes (boron-containing gas supply pipe 31a, nitrogen-containing gas supply pipe 32a) may have different shapes and arrangements. The gas supply unit 30 may be configured to supply other gases in addition to the boron-containing gas, nitrogen-containing gas, and inert gas.

[0039] The exhaust unit 40 exhausts gas that is discharged from the inner tube 11 through the opening 15 and then discharged from the exhaust port 41 via the space P1 between the inner tube 11 and the outer tube 12. The exhaust port 41 is formed on the side wall of the upper part of the manifold 17, above the support unit 20. An exhaust passage 42 is connected to the exhaust port 41. A pressure adjustment valve 43 and a vacuum pump 44 are provided in the exhaust passage 42, in this order from upstream to downstream in the gas flow direction. The exhaust unit 40 operates the pressure adjustment valve 43 and the vacuum pump 44 based on the operation of the control unit 90, and adjusts the pressure inside the processing vessel 10 using the pressure adjustment valve 43 while using the vacuum pump 44 to suck out gas inside the processing vessel 10.

[0040] The heating unit 50 has a cylindrical heater 51 that surrounds the outer tube 12 on the radially outer side of the outer tube 12. The heater 51 heats the entire periphery of the processing vessel 10, thereby heating each substrate W accommodated in the processing vessel 10.

[0041] The control unit 90 may be a computer having one or more processors 91, memory 92, an input / output interface (not shown), and electronic circuits. The processor 91 is one or a combination of a CPU, an ASIC, an FPGA, a circuit made up of multiple discrete semiconductors, etc. The memory 92 includes volatile memory and non-volatile memory (e.g., a compact disc, a DVD, a hard disk, a flash memory, etc.) and stores a program for operating the processing apparatus 1 and a recipe for the process conditions for substrate processing. The processor 91 executes the program and recipe stored in the memory 92 to control each component of the processing apparatus 1 and perform the aforementioned film formation method.

[0042] [Operation of the Processing Device] The operation of the processing apparatus 1 when carrying out the film forming method according to the embodiment will be described.

[0043] First, the control unit 90 controls the lifting mechanism 25 to load the boat 16 holding the substrates W into the processing vessel 10, and then airtightly closes and seals the opening at the bottom of the processing vessel 10 with the lid 21. Each substrate W is a substrate 101 having a recess 102 on its surface.

[0044] Next, the control unit 90 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to perform the boron nitride film formation process S20. Specifically, first, the control unit 90 controls the exhaust unit 40 to reduce the pressure inside the processing chamber 10 to a predetermined value, and controls the heating unit 50 to adjust and maintain the substrate temperature at a predetermined value. The predetermined value is, for example, 300°C or lower. Next, the control unit 90 controls the gas supply unit 30 to supply a first gas containing a boron-containing gas and a nitrogen-containing gas into the processing chamber 10. As a result, a boron-rich boron nitride film 103 is formed in the recess 102.

[0045] Next, the control unit 90 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to perform the heat treatment process S30. Specifically, the control unit 90 first controls the exhaust unit 40 to reduce the pressure inside the processing chamber 10 to a predetermined level, and then controls the heating unit 50 to adjust and maintain the substrate temperature at a predetermined level. The predetermined level is, for example, 550°C or higher. Next, the control unit 90 controls the gas supply unit 30 to supply a second gas containing no boron-containing gas but a nitrogen-containing gas into the processing chamber 10. As a result, dangling bonds of boron are bonded with nitrogen in the nitrogen-containing gas contained in the second gas and nitrided. This causes the volume of the boron nitride film 103 to increase and expand. As a result, the gaps 104 are filled with the boron nitride film 103, and the gaps 104 disappear. In other words, the filling characteristics of the boron nitride film 103 in the recesses 102 can be improved. Furthermore, since the number of dangling bonds of boron is reduced, the film quality of the boron nitride film 103 is improved.

[0046] Next, the control unit 90 increases the pressure inside the processing vessel 10 to atmospheric pressure and decreases the temperature inside the processing vessel 10 to the unloading temperature, and then controls the lifting mechanism 25 to unload the boat 16 from the processing vessel 10.

[0047] As described above, the boron nitride film 103 can be embedded in the recess 102 in the processing apparatus 1 by the film forming method according to the embodiment.

[0048] [Experimental results] First, experiments A and B conducted to confirm that the volume of the boron nitride film increases due to the heat treatment step S30 in the film forming method according to the embodiment will be described.

[0049] In experiment A, first, the boron nitride film formation step S20 was performed in the processing apparatus 1 described above under condition A1 below, and a boron nitride film was formed on a silicon substrate. Next, the film thickness of the formed boron nitride film (before heat treatment) was measured using a spectroscopic ellipsometer. Next, the heat treatment step S30 was performed in the processing apparatus 1 described above under condition A2 below, and the boron nitride film was subjected to heat treatment. Next, the film thickness of the boron nitride film after heat treatment was measured using a spectroscopic ellipsometer. In addition, the film thickness change rate of the boron nitride film before and after heat treatment was calculated. The film thickness change rate was calculated using the following formula.

[0050] Film thickness change rate = (film thickness after heat treatment - film thickness before heat treatment) / film thickness before heat treatment

[0051] (Condition A1) Film formation method: CVD First gas: boron-containing gas + nitrogen-containing gas + inert gas Boron-containing gas: Diborane gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 235℃ (Condition A2) Second gas: Nitrogen-containing gas + inert gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 600℃

[0052] In experiment B, first, the boron nitride film formation step S20 was performed in the processing apparatus 1 described above under the condition B1 shown below, and a boron nitride film was formed on a silicon substrate. Next, the film thickness of the formed boron nitride film (before heat treatment) was measured using a spectroscopic ellipsometer. Next, the heat treatment step S30 was performed in the processing apparatus 1 described above under the condition B2 shown below, and the boron nitride film was subjected to heat treatment. Next, the film thickness of the boron nitride film after heat treatment was measured using a spectroscopic ellipsometer. In addition, the film thickness change rate of the boron nitride film before and after heat treatment was calculated. The film thickness change rate was calculated using the following formula.

[0053] Film thickness change rate = (film thickness after heat treatment - film thickness before heat treatment) / film thickness before heat treatment

[0054] (Condition B1) Film formation method: CVD First gas: boron-containing gas + nitrogen-containing gas + inert gas Boron-containing gas: Diborane gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 300℃ (Condition B2) Second gas: Nitrogen-containing gas + inert gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 700℃

[0055] Figure 4 shows the change in thickness of boron nitride films before and after heat treatment. In Figure 4, the bar graph on the left shows the change in thickness [%] before and after heat treatment of the boron nitride film formed in Experiment A, and the bar graph on the right shows the change in thickness [%] before and after heat treatment of the boron nitride film formed in Experiment B.

[0056] As shown in Figure 4, the thickness change rate of the boron nitride film formed in Experiment A was 24.3%, and the thickness change rate of the boron nitride film formed in Experiment B was 12.8%. These results show that the volume of the boron nitride film can be increased by performing the boron nitride film formation step S20 and the heat treatment step S30 in this order. Furthermore, the thickness change rate of the boron nitride film in Experiment A was greater than that in Experiment B. These results show that by setting the substrate temperature at 235°C in the boron nitride film formation step S20, the thickness change rate of the boron nitride film can be increased compared to setting the substrate temperature at 300°C.

[0057] Next, experiments C and D will be described, which were conducted to confirm the influence of differences in substrate temperature in the boron nitride film formation step S20 in the film formation method according to the embodiment on the degree of progress of nitridation of boron contained in the boron nitride film.

[0058] In Experiment C, first, a boron nitride film was formed on a silicon substrate by performing the boron nitride film formation step S20 in the processing apparatus 1 described above under the following condition C1. The composition of the formed boron nitride film (before heat treatment) was then measured by X-ray photoelectron spectroscopy (XPS). The heat treatment step S30 was then performed in the processing apparatus 1 described above under the following condition C2, and the boron nitride film was subjected to heat treatment. The composition of the heat-treated boron nitride film was then measured by XPS. The ratio of the boron concentration to the nitrogen concentration in the boron nitride film (hereinafter referred to as the "B / N ratio") was also calculated before and after the heat treatment.

[0059] (Condition C1) Film formation method: CVD First gas: boron-containing gas + nitrogen-containing gas + inert gas Boron-containing gas: Diborane gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 300℃ (Condition C2) Second gas: Nitrogen-containing gas + inert gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 700℃

[0060] In experiment D, first, a boron nitride film formation step S20 was performed in the processing apparatus 1 described above under condition D1 below, and a boron nitride film was formed on a silicon substrate. The composition of the formed boron nitride film (before heat treatment) was then measured by XPS. Next, a heat treatment step S30 was performed in the processing apparatus 1 described above under condition D2 below, and the boron nitride film was subjected to heat treatment. The composition of the boron nitride film after heat treatment was then measured by XPS. The B / N ratio of the boron nitride film was also calculated before and after heat treatment.

[0061] (Condition D1) Film formation method: CVD First gas: boron-containing gas + nitrogen-containing gas + inert gas Boron-containing gas: Diborane gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 550℃ (Condition D2) Second gas: Nitrogen-containing gas + inert gas Nitrogen-containing gas: Ammonia gas Inert gas: Nitrogen gas Substrate temperature: 700℃

[0062] Fig. 5 shows the B / N ratio of the boron nitride film before and after heat treatment. In Fig. 5, the bar graph on the left shows the B / N ratio of the boron nitride film formed in Experiment C before and after heat treatment, and the bar graph on the right shows the B / N ratio of the boron nitride film formed in Experiment D before and after heat treatment.

[0063] As shown in FIG. 5, the B / N ratio of the boron nitride film formed in Experiment C was 4.4 before the heat treatment and 1.2 after the heat treatment. The B / N ratio of the boron nitride film formed in Experiment D was 1.9 before the heat treatment and 1.3 after the heat treatment. These results indicate that performing the boron nitride film formation step S20 and the heat treatment step S30 in this order can nitride the boron in the boron nitride film. Furthermore, the rate of change in the B / N ratio of the boron nitride film before and after the heat treatment was greater in Experiment C than in Experiment D. These results indicate that setting the substrate temperature at 300°C in the boron nitride film formation step S20 can increase the rate of change in the B / N ratio of the boron nitride film compared to setting the substrate temperature at 550°C.

[0064] Next, experiments E and F will be described, which were conducted to confirm the influence of differences in substrate temperature in the boron nitride film forming step S20 in the film forming method according to the embodiment on the surface roughness of the boron nitride film.

[0065] In Experiment E, first, the boron nitride film formation step S20 was performed in the processing apparatus 1 described above under the condition C1 described above to form a boron nitride film on a silicon substrate. The surface shape of the formed boron nitride film (before heat treatment) was then measured using a scanning electron microscope (SEM) to calculate the surface roughness (RMS) of the boron nitride film. Next, the heat treatment step S30 was performed in the processing apparatus 1 described above under the condition C2 described above to subject the boron nitride film to heat treatment. The surface shape of the heat-treated boron nitride film was then measured using the SEM to calculate the surface roughness (RMS) of the boron nitride film.

[0066] In experiment F, first, the boron nitride film formation step S20 was performed in the processing apparatus 1 described above under the condition D1 described above to form a boron nitride film on a silicon substrate. The surface shape of the formed boron nitride film (before heat treatment) was measured using an SEM to calculate the surface roughness (RMS) of the boron nitride film. Next, the heat treatment step S30 was performed in the processing apparatus 1 described above under the condition D2 described above to subject the boron nitride film to heat treatment. Next, the surface shape of the heat-treated boron nitride film was measured using an SEM to calculate the surface roughness (RMS) of the boron nitride film.

[0067] Fig. 6 shows the surface roughness (RMS) of the boron nitride film before and after heat treatment. In Fig. 6, the bar graph on the left shows the RMS [nm] before and after heat treatment of the boron nitride film formed in Experiment E, and the bar graph on the right shows the RMS [nm] before and after heat treatment of the boron nitride film formed in Experiment F.

[0068] As shown in Figure 6, the RMS of the boron nitride film deposited in Experiment E was 0.26 before heat treatment and 0.64 after heat treatment. The RMS of the boron nitride film deposited in Experiment F was 2.34 before heat treatment and 2.56 after heat treatment. These results show that by setting the substrate temperature to 300°C in the boron nitride film deposition step S20, the surface roughness of the boron nitride film can be reduced more than when the substrate temperature is set to 550°C.

[0069] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0070] 101 Substrate 102 recess 103 Boron nitride film

Claims

1. providing a substrate having a recess; supplying a first gas containing a boron-containing gas and a nitrogen-containing gas to the substrate to form a boron nitride film in the recess; supplying a second gas containing no boron-containing gas but containing a nitrogen-containing gas to the substrate, and heat-treating the boron nitride film; and a gap is formed in the recess in the step of forming the boron nitride film, In the step of heat-treating the boron nitride film, the volume of the boron nitride film increases, and the gaps are filled with the boron nitride film. Film formation method.

2. the step of depositing the boron nitride film includes maintaining the substrate at a first temperature; the step of heat-treating the boron nitride film includes holding the substrate at a second temperature higher than the first temperature; The film forming method according to claim 1 .

3. the first temperature is 300°C or less; The second temperature is 550°C or higher. The film forming method according to claim 2 .

4. the step of heat-treating the boron nitride film includes exposing the substrate to plasma generated from the second gas. The film forming method according to claim 1 .

5. the boron-containing gas is diborane gas; The nitrogen-containing gas is ammonia gas. The film forming method according to claim 1 .

6. A processing apparatus including a processing vessel, a gas supply unit, and a control unit, The control unit placing a substrate having a recess in the processing chamber; supplying a first gas containing a boron-containing gas and a nitrogen-containing gas into the processing chamber to form a boron nitride film in the recess; supplying a second gas containing no boron-containing gas but containing a nitrogen-containing gas into the processing vessel, and heat-treating the boron nitride film; configured to control the gas supply to perform a gap is formed in the recess in the step of forming the boron nitride film, In the step of heat-treating the boron nitride film, the volume of the boron nitride film increases, and the gaps are filled with the boron nitride film. Processing equipment.

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