Film forming method and system

Abstract

The present invention relates to a film forming method and system. [Subject] A technique for forming a thin film with a low impurity concentration is provided. [Solution] A film forming method according to one embodiment of the present invention forms a thin film by performing a plurality of cycles including the following steps: a step of supplying a raw material gas to a substrate; a step of supplying a reaction gas that reacts with the raw material gas to the substrate; and a step of treating the substrate with deuterium plasma.

Description

Technical Field

[0001] The present disclosure relates to film forming methods and systems. Background Art

[0002] A technique is disclosed in which a high-stress silicon nitride film is formed at a low temperature by introducing hydrogen plasma during an atomic layer deposition (ALD: Atomic Layer Deposition) cycle (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-278497 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] The present disclosure provides a technology capable of forming a thin film with a low impurity concentration.

[0008] Solutions for solving problems

[0009] A film forming method according to one embodiment of the present disclosure forms a thin film by performing a plurality of cycles including the steps of supplying a raw material gas to a substrate; supplying a reaction gas that reacts with the raw material gas to the substrate; and treating the substrate with deuterium plasma.

[0010] Effects of the Invention

[0011] According to the present disclosure, a thin film with a low impurity concentration can be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flowchart which shows the film formation method of 1st Embodiment.

[0013] Figure 2 It is a flowchart which shows the film formation method of 2nd Embodiment.

[0014] Figure 3 It is a flowchart which shows the film formation method of 3rd Embodiment.

[0015] Figure 4 It is a flowchart which shows the film formation method of 4th Embodiment.

[0016] Figure 5 This is a diagram showing the calculation results of the activation energy of H removal.

[0017] Figure 6 This is a diagram showing the calculation results of the activation energy of Cl departure.

[0018] Figure 7 A diagram showing an example of surface reaction when a silicon nitride film is exposed to D2 plasma and / or H2 plasma.

[0019] Figure 8 It is a cross-sectional view showing an example of a film formation apparatus capable of carrying out the film formation methods according to the first to fourth embodiments.

[0020] Fig. 9 For illustration Figure 8 A diagram of a processing container of a film-forming apparatus.

[0021] Fig.10 It is a diagram showing the calculation results of the mole fraction of each particle contained in H2 plasma and D2 plasma based on simulation.

[0022] Fig.11 It is a diagram showing the simulation results of the gas temperature dependency of D / H.

[0023] Fig.12 It is a graph showing the simulation results of the pressure dependence of D / H.

[0024] Fig.13 It is a diagram showing the simulation results of the gas flow rate dependency of D / H.

[0025] Description of Reference Numerals

[0026] 60 Control Unit

[0027] 100 vertical heat treatment device

[0028] W Wafer DETAILED DESCRIPTION

[0029] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the attached drawings. In all the attached drawings, the same or corresponding components or parts are denoted by the same or corresponding reference numerals, and repeated descriptions are omitted.

[0030] [Film formation method]

[0031] A film forming method according to one embodiment is a method for forming a thin film by atomic layer deposition (ALD: AtoMic Layer Deposition), and includes a step of introducing deuterium (D2) plasma in an ALD cycle. According to the film forming method according to one embodiment, a thin film with a low impurity concentration can be formed. Hereinafter, as an example of a film forming method according to one embodiment, a method for forming a silicon nitride film is described. However, the thin film formed by the film forming method according to one embodiment is not limited to a silicon nitride film, and may be, for example, a silicon oxide film, a metal nitride film, or a metal oxide film.

[0032] (First embodiment)

[0033] Figure 1 Flowchart showing the film forming method of the first embodiment. In the present embodiment, the film forming method includes the following steps: step S11 of supplying raw material gas, step S12 of performing purging, step S13 of performing treatment with heavy hydrogen plasma, step S14 of performing purging, step S15 of supplying reaction gas, and step S16 of performing purging. In addition, in the present embodiment, a plurality of cycles including steps S11 to S16 are performed. In addition, in the present embodiment, step S13 of performing treatment with heavy hydrogen plasma is performed after step S11 of supplying raw material gas and before step S15 of supplying reaction gas. Each step is described below.

[0034] In the step S11 of supplying the raw material gas, the raw material gas is supplied to the substrate contained in the processing container, so that the raw material gas is adsorbed on the substrate. In the present embodiment, the raw material gas may be dichlorosilane (DCS) gas. However, the raw material gas is not limited thereto. For example, when forming a silicon nitride film or a silicon oxide film, various silicon raw material gases may be used as the raw material gas. In addition, when forming a metal nitride film or a metal oxide film, various metal raw material gases may be used as the raw material gas.

[0035] The purging step S12 is performed after the raw material gas supplying step S11. In the purging step S12, the raw material gas remaining in the processing container is removed. In the present embodiment, the purging step S12 includes the following steps: supplying an inert gas such as nitrogen (N2) gas, argon (Ar) gas, etc. into the processing container. In addition, the purging step S12 may include the step of exhausting and evacuating the processing container without supplying gas into the processing container.

[0036] The step S13 of treating with deuterium plasma is performed after the step S12 of purging. However, the step S12 of purging may be omitted, and the step S13 of treating with deuterium plasma may be performed after the step S11 of supplying the raw material gas. In the step S13 of treating with deuterium plasma, deuterium plasma is generated, and the substrate contained in the processing container is treated with the deuterium plasma. In the present embodiment, the step S13 of treating with deuterium plasma includes the following steps: the deuterium gas is plasma-formed in the processing container to be activated and exposed to the substrate. At this time, an inactive gas such as N2 gas and Ar gas may be simultaneously supplied into the processing container.

[0037] The purging step S14 is performed after the step S13 of treating with deuterium plasma. In the purging step S14, the raw material gas and deuterium gas remaining in the processing container are removed. In the present embodiment, the purging step S14 includes the following steps: supplying an inert gas such as N2 gas and Ar gas into the processing container. In addition, the purging step S14 may include the step of exhausting and evacuating the processing container without supplying gas into the processing container.

[0038] The step S15 of supplying the reaction gas is performed after the step S14 of performing the purge. However, the step S14 of performing the purge can be omitted, and the step S15 of supplying the reaction gas can be performed after the step S13 of performing the treatment with the heavy hydrogen plasma. In the step S15 of supplying the reaction gas, the reaction gas is supplied to the substrate accommodated in the processing container, thereby generating a reaction product of the raw material gas adsorbed on the substrate and the reaction gas. In the present embodiment, in the step S15 of supplying the reaction gas, the raw material gas and the reaction gas are reacted by thermally decomposing the reaction gas or by activating the reaction gas by plasma. In addition, in the present embodiment, the reaction gas can be ammonia (NH3) gas. However, the reaction gas is not limited thereto. For example, in the case of forming a silicon nitride film or a metal nitride film, various nitriding gases can be used as the reaction gas. In addition, in the case of forming a silicon oxide film or a metal oxide film, various oxidizing gases can be used as the reaction gas.

[0039] The purging step S16 is performed after the reaction gas supplying step S15. In the purging step S16, the reaction gas remaining in the processing container is removed. In the present embodiment, the purging step S16 includes the following steps: supplying an inert gas such as N2 gas and Ar gas into the processing container. In addition, the purging step S16 may also include the step of exhausting and evacuating the processing container without supplying gas into the processing container.

[0040] Step S17 is performed after step S16 in which purging is performed. In step S17, it is determined whether the cycle including steps S11 to S16 has been performed a predetermined number of times. The predetermined number of times can be predetermined according to the film thickness of the thin film to be formed. When the cycle including steps S11 to S16 reaches the predetermined number of times, the process is terminated. On the other hand, when the cycle including steps S11 to S16 does not reach the predetermined number of times, the process returns to step S11.

[0041] By performing the above steps S11 to S17 , a silicon nitride film can be formed on the substrate.

[0042] According to the film forming method of this embodiment, after the step S11 of supplying the raw material gas, the step S13 of treating with the deuterium plasma is performed. Thus, the impurities such as hydrogen (H) and chlorine (Cl) contained in the raw material gas adsorbed on the substrate surface can be removed by the particles such as deuterium radicals contained in the deuterium plasma. Therefore, a high-quality film with a low impurity concentration can be formed.

[0043] In addition, according to the film forming method of the present embodiment, after the step S11 of supplying the raw material gas, the step S13 of treating with deuterium plasma is performed, so that the hydrogen (H) terminal in the film can be replaced with a deuterium (D) terminal formed by deuterium having a stronger bonding force than hydrogen. In addition, the dangling bond can be terminated with deuterium. Therefore, after the film is formed, it is possible to prevent the unterminated state caused by the departure generated in the subsequent steps. In addition, the deuterium radical has a longer lifespan than the hydrogen radical, so it is easy to spread throughout the entire surface of the substrate. Therefore, the uniformity of the film quality in the surface of the substrate is improved.

[0044] (Second embodiment)

[0045] Figure 2 1 is a flowchart showing a film forming method of the second embodiment. The film forming method of this embodiment is different from the film forming method of the first embodiment in that it includes a step S21 of treating with hydrogen plasma after the step S11 of supplying the raw material gas and before the step S13 of treating with deuterium plasma. It should be noted that other aspects are the same as those of the film forming method of the first embodiment. The following description will focus on the aspects that are different from the film forming method of the first embodiment.

[0046] The step S21 of treating with hydrogen plasma is performed after the step S12 of purging. However, the step S12 of purging may be omitted, and the step S21 of treating with hydrogen plasma may be performed after the step S11 of supplying the raw material gas. In the step S21 of treating with hydrogen plasma, hydrogen plasma is generated, and the substrate contained in the processing container is treated with hydrogen plasma. In the present embodiment, the step S21 of treating with hydrogen plasma includes the following steps: hydrogen gas is plasma-formed and activated in the processing container and exposed to the substrate. At this time, inactive gases such as N2 gas and Ar gas may also be supplied into the processing container at the same time. It should be noted that the step of purging may be performed after the step S21 of treating with hydrogen plasma and before the step S13 of treating with deuterium plasma.

[0047] According to the film forming method of this embodiment, similarly to the film forming method of the first embodiment, after the step S11 of supplying the source gas, the step S13 of treating with deuterium plasma is performed. Thus, the same effects as those of the film forming method of the first embodiment can be achieved.

[0048] (Third embodiment)

[0049] Figure 3 1 is a flowchart showing a film forming method of the third embodiment. The film forming method of this embodiment is different from the film forming method of the first embodiment in that it includes a step S31 of treating with hydrogen plasma after the step S13 of treating with deuterium plasma and before the step S15 of supplying a reaction gas. It should be noted that other aspects are the same as those of the film forming method of the first embodiment. The following description will focus on the aspects that are different from the film forming method of the first embodiment.

[0050] The step S31 of treating with hydrogen plasma is performed after the step S13 of treating with deuterium plasma. In the step S31 of treating with hydrogen plasma, hydrogen plasma is generated, and the substrate contained in the processing container is treated with hydrogen plasma. In the present embodiment, the step S31 of treating with hydrogen plasma includes the following steps: hydrogen gas is plasma-formed in the processing container to be activated and exposed to the substrate. At this time, inactive gases such as N2 gas and Ar gas can be supplied to the processing container at the same time. It should be noted that the step of purging can be performed after the step S13 of treating with deuterium plasma and before the step S31 of treating with hydrogen plasma.

[0051] According to the film forming method of this embodiment, similarly to the film forming method of the first embodiment, the step S13 of treating with deuterium plasma is performed after the step S11 of supplying the raw material gas. Thus, the same effects as those of the film forming method of the first embodiment can be achieved.

[0052] (Fourth embodiment)

[0053] Figure 4 1 is a flowchart showing a film forming method of the fourth embodiment. The film forming method of this embodiment is different from the film forming method of the first embodiment in that it includes a step S41 of treating with deuterium plasma after the step S15 of supplying the reaction gas and before the step S11 of supplying the raw material gas. It should be noted that other aspects are the same as those of the film forming method of the first embodiment. The following description will focus on the aspects that are different from the first embodiment.

[0054] The step S41 of treating with deuterium plasma is performed after the step S16 of purging. However, the step S16 of purging can be omitted, and the step S41 of treating with deuterium plasma can be performed after the step S15 of supplying the reaction gas. In the step S41 of treating with deuterium plasma, deuterium plasma is generated, and the substrate accommodated in the processing container is treated with deuterium plasma. In the present embodiment, the step S41 of treating with deuterium plasma includes the following steps: the deuterium gas is plasma-formed in the processing container to be activated and exposed to the substrate. At this time, an inactive gas such as N2 gas and Ar gas can be simultaneously supplied into the processing container. It should be noted that in the present embodiment, the step S41 of treating with deuterium plasma is not purged, but the step S41 of treating with deuterium plasma can also be purged.

[0055] According to the film forming method of this embodiment, similarly to the film forming method of the first embodiment, the step S13 of treating with deuterium plasma is performed after the step S11 of supplying the raw material gas. Thus, the same effects as those of the film forming method of the first embodiment can be achieved.

[0056] As mentioned above, the film formation methods according to the first embodiment to the fourth embodiment have been described. However, two or more of the film formation methods according to the first embodiment to the fourth embodiment may be combined and performed.

[0057] 〔mechanism〕

[0058] The mechanism by which a thin film with a low impurity concentration can be formed by the film formation method of the above-mentioned embodiment will be described.

[0059] First, the activation energy of H bonded to Si leaving SiNH2ClH2 when H radical (H*) and D radical (D*) are supplied to SiNH2ClH2 is calculated by the B3LYP method as a functional using the software GaUssian09. It should be noted that 6-311+g(2d, p) is used as a basis set.

[0060] Figure 5 This is a diagram showing the calculated results of the activation energy of H removal. Figure 5 As shown in (a), when D radicals are supplied to SiNH2ClH2, the activation energy of H bonded to Si leaving SiNH2ClH2 is 0.0336 eV. Figure 5As shown in (b), when H radicals are supplied to SiNH2ClH2, the activation energy of H bonded to Si leaving SiNH2ClH2 is 0.0422 eV. From these results, it can be said that by supplying D radicals to SiNH2ClH2, H bonded to Si can be separated at a lower energy than when H radicals are supplied.

[0061] Next, the activation energy of the departure of Cl bonded to Si from SiNH2ClH2 when H radicals and D radicals are supplied to SiNH2ClH2 is calculated by the B3LYP method as a functional using the software GaUssian09. It should be noted that 6-311+g(2d, p) is used as a basis set.

[0062] Figure 6 This is a diagram showing the calculated results of the activation energy of Cl removal. Figure 6 As shown in (a), when D radicals are supplied to SiNH2ClH2, the activation energy of the Cl bonded to Si leaving SiNH2ClH2 is 0.630 eV. Figure 5 As shown in (b), when H radicals are supplied to SiNH2ClH2, the activation energy of the departure of Cl bonded to Si from SiNH2ClH2 is 0.653 eV. From these results, it can be said that by supplying D radicals to SiNH2ClH2, Cl bonded to Si can be departed at a lower energy than when H radicals are supplied. It should be noted that the departure of Cl is shown as an example, but the same effect can be expected in other halogen elements such as F, Br, and I.

[0063] Next, a surface reaction occurring on the surface of the silicon nitride film when the silicon nitride film is exposed to D 2 plasma and / or H 2 plasma will be described. Figure 7 A diagram showing an example of surface reaction when a silicon nitride film is exposed to D2 plasma and / or H2 plasma.

[0064] Figure 7 (a) shows an example of the surface reaction when the silicon nitride film is exposed to H2 plasma only. Figure 7 As shown in (a), when the silicon nitride film is exposed to H2 plasma alone, H and Cl are captured from the surface of the silicon nitride film by H radicals contained in the H2 plasma in the initial stage. At this time, H is basically not adsorbed to the dangling bonds. In the later stage, H and Cl are further captured from the surface of the silicon nitride film by H radicals contained in the H2 plasma, but H adsorption to the dangling bonds may also occur.

[0065] Figure 7 (b) shows an example of the surface reaction when the silicon nitride film is exposed to D2 plasma only. Figure 7As shown in (b), when the silicon nitride film is exposed to D2 plasma only, H and Cl are captured from the surface of the silicon nitride film by the D radicals contained in the D2 plasma in the initial stage. At this time, the activation energy of the departure of H and Cl from SiNH2ClH2 based on the D radicals is less than the activation energy of the departure of H and Cl from SiNH2ClH2 based on the H radicals. Therefore, when the silicon nitride film is exposed to D2 plasma, H and Cl are captured from the surface of the silicon nitride film compared to the case where the silicon nitride film is exposed to H2 plasma. In addition, H is basically not adsorbed on the dangling bonds. In the later stage, H and Cl are further captured from the surface of the silicon nitride film by the D radicals contained in the D2 plasma, but adsorption of D on the dangling bonds can also occur. In this way, by exposing the silicon nitride film only to D2 plasma, more H and Cl can be removed than when the silicon nitride film is exposed to H2 plasma only.

[0066] Figure 7 (c) shows an example of the surface reaction when the silicon nitride film is exposed to H2 plasma and then to D2 plasma. Figure 7 As shown in (c), when the silicon nitride film is exposed to H2 plasma and then to D2 plasma, H and Cl are captured from the surface of the silicon nitride film by H radicals contained in the H2 plasma in the initial stage. At this time, H is hardly adsorbed on the dangling bonds. In the later stage, H and Cl are captured from the surface of the silicon nitride film by D radicals contained in the D2 plasma. At this time, the activation energy of the departure of H and Cl from SiNH2ClH2 based on the D radical is lower than the activation energy of the departure of H and Cl from SiNH2ClH2 based on the H radical. Therefore, when the silicon nitride film is exposed to D2 plasma, H and Cl are captured from the surface of the silicon nitride film compared with the case where the silicon nitride film is exposed to H2 plasma. In addition, in the later stage, the adsorption of D to the dangling bonds may also occur, but in the initial stage, the amount of H and Cl that leave is small (the number of dangling bonds is small) compared with the case where the silicon nitride film is exposed to D2 plasma. Therefore, compared with the case where the silicon nitride film is exposed to only D2 plasma, the adsorption amount of D is small. As a result, a silicon nitride film having a particularly low concentration of impurities such as H, D, and Cl can be formed.

[0067] Figure 7 (d) shows an example of the surface reaction when the silicon nitride film is exposed to D2 plasma and then to H2 plasma. Figure 7As shown in (d), when the silicon nitride film is exposed to D2 plasma and then to H2 plasma, in the initial stage, when the silicon nitride film is exposed to D2 plasma, H and Cl are captured from the surface of the silicon nitride film by the D radicals contained in the D2 plasma. At this time, the activation energy of the departure of H and Cl from SiNH2ClH2 based on the D radicals is lower than the activation energy of the departure of H and Cl from SiNH2ClH2 based on the H radicals. Therefore, when the silicon nitride film is exposed to D2 plasma, H and Cl are captured from the surface of the silicon nitride film compared to when the silicon nitride film is exposed to H2 plasma. In addition, H is hardly adsorbed on the dangling bonds. In the later stage, H and Cl are further captured from the surface of the silicon nitride film by the H radicals contained in the H2 plasma, but adsorption of H on the dangling bonds may also occur. In this way, by exposing the silicon nitride film to D 2 plasma and then to H 2 plasma, more H and Cl can be removed than when the silicon nitride film is exposed to only H 2 plasma.

[0068] 〔Film forming device〕

[0069] The film forming apparatus capable of implementing the above-mentioned film forming method is described by taking an intermittent vertical heat treatment apparatus that performs heat treatment on multiple substrates at the same time as an example. However, the film forming apparatus is not limited to an intermittent apparatus, and may be, for example, a single-sheet apparatus that processes each substrate. In addition, it may be a semi-intermittent apparatus. The semi-intermittent apparatus is as follows: multiple substrates arranged around the rotation center line of the turntable are rotated together with the turntable, and sequentially pass through multiple areas to which different gases are supplied.

[0070] Figure 8 It is a cross-sectional view showing an example of a film formation apparatus capable of carrying out the film formation methods according to the first to fourth embodiments. Fig. 9 For illustration Figure 8 A diagram of a processing container of a film-forming apparatus.

[0071] The vertical heat treatment apparatus 100 has a cylindrical processing container 1 with an open bottom and a top. The entire processing container 1 is formed of, for example, quartz. A top plate 2 formed of quartz is provided near the top end of the processing container 1 to seal the area below the top plate 2. A cylindrical metal manifold 3 is connected to the opening at the bottom end of the processing container 1 via a sealing member 4 such as an O-ring.

[0072] The manifold 3 supports the lower end of the processing container 1, and a wafer boat 5 is inserted into the processing container 1 from the bottom of the manifold 3. The wafer boat 5 carries multiple (e.g., 25 to 150) semiconductor wafers (hereinafter referred to as "wafers W") as substrates in multiple stages. In this way, multiple wafers W are stored approximately horizontally with intervals in the vertical direction in the processing container 1. The wafer boat 5 is made of, for example, quartz. The wafer boat 5 has three rods 6 (see Figure 2 ), a plurality of wafers W are supported by grooves (not shown) formed in the rod 6.

[0073] The wafer boat 5 is placed on a table 8 via a heat-insulating tube 7 made of quartz. The table 8 is supported by a rotating shaft 10 that passes through a cover 9 made of metal (stainless steel) that opens and closes the opening at the lower end of the manifold 3 .

[0074] A magnetic fluid seal 11 is provided in the through-portion of the rotating shaft 10 to hermetically seal the rotating shaft 10 and rotatably support the rotating shaft 10. A sealing member 12 is provided between the peripheral portion of the cover 9 and the lower end of the manifold 3 to maintain airtightness in the processing chamber 1.

[0075] The rotating shaft 10 is installed at the front end of an arm 13 supported by a lifting mechanism (not shown) such as a boat elevator, for example, and the wafer boat 5 is raised and lowered as a whole with the cover 9, and inserted and pulled out of the processing container 1. It should be noted that by fixing and setting the stage 8 to the cover 9 side, the wafer W can be processed without rotating the wafer boat 5.

[0076] Furthermore, the vertical heat treatment apparatus 100 includes a gas supply unit 20 for supplying gases such as a processing gas and a purge gas into the processing container 1 .

[0077] The gas supply unit 20 includes gas supply pipes 21, 22, 23, and 24. The gas supply pipes 21, 22, and 23 are formed of, for example, quartz, penetrate the side wall of the manifold 3 inward, bend upward, and extend vertically. In the vertical portions of the gas supply pipes 21, 22, and 23, a plurality of gas holes 21a, 22a, and 23a are formed at predetermined intervals over the length in the up-down direction corresponding to the wafer support range of the wafer boat 5. Each gas hole 21a, 22a, and 23a discharges gas in the horizontal direction. The gas supply pipe 24 is formed of, for example, quartz, and is formed of a short quartz pipe provided to penetrate the side wall of the manifold 3.

[0078] The vertical portion of the gas supply pipe 21 is disposed in the processing container 1. In the gas supply pipe 21, a gas containing a film-forming raw material (hereinafter referred to as "raw gas") is supplied from a raw gas supply source by means of a gas pipe. A flow controller and a switch valve are provided on the gas pipe. Thus, the raw gas from the raw gas supply source is supplied to the processing container 1 by means of the gas pipe and the gas supply pipe 21. As the raw gas, for example, silicon (Si) compounds containing chlorine (Cl) such as dichlorosilane (DCS; SiH2Cl2), monochlorosilane (MCS; SiH3Cl), trichlorosilane (TCS; SiHCl3), silicon tetrachloride (STC; SiCl4), and hexachlorodisilane (HCD; Si2Cl6) can be used. In addition, for example, silicon (Si) compounds containing iodine (I) such as diiodosilane (DIS; SiH2I2) and triiodosilane (TIS; SiHI3), or silicon (Si) compounds containing bromine (Br) such as dibromosilane (DBS; SiH2Br2) and tribromosilane (TBS; SiHBr3) can be used.

[0079] The vertical portion of the gas supply pipe 22 is disposed in the plasma generation space described later. In the gas supply pipe 22, nitriding gas is supplied from the nitriding gas supply source via a gas pipe. A flow controller and a switch valve are provided on the gas pipe. Thus, the nitriding gas from the nitriding gas supply source is supplied to the plasma generation space via the gas pipe and the gas supply pipe 22, is plasmatized in the plasma generation space, and is supplied to the processing container 1. As the nitriding gas, for example, organic hydrazine compounds such as ammonia (NH3), nitrogen (N2), dinitrogen (N2H2), hydrazine (N2H4), and monomethylhydrazine (CH3(NH)NH2) can be used.

[0080] The vertical portion of the gas supply pipe 23 is arranged in the plasma generation space described later. In the gas supply pipe 23, hydrogen (H2) gas is supplied from the hydrogen gas supply source by means of a gas pipe. In addition, in the gas supply pipe 23, deuterium (D2) gas is supplied from the deuterium gas supply source by means of a gas pipe. A flow controller and a switch valve are provided on the gas pipe. Thus, the H2 gas from the hydrogen gas supply source and the D2 gas from the deuterium gas supply source are supplied to the plasma generation space by means of the gas pipe and the gas supply pipe 23, are plasmatized in the plasma generation space, and are supplied to the processing container 1.

[0081] In the gas supply pipe 24, a purge gas is supplied from a purge gas supply source by means of a gas pipe. A flow controller and a switch valve are provided on the gas pipe. Thus, the purge gas from the purge gas supply source is supplied to the processing container 1 by means of the gas pipe and the gas supply pipe 24. As the purge gas, for example, an inert gas such as argon (Ar) or nitrogen (N2) can be used. It should be noted that the case where the purge gas is supplied from the purge gas supply source to the processing container 1 by means of the gas pipe and the gas supply pipe 24 is described, but it is not limited to this, and the purge gas can also be supplied from the gas supply pipes 21, 22, and 23.

[0082] A plasma generating mechanism 30 is formed at a portion of the side wall of the processing container 1. The plasma generating mechanism 30 converts the nitriding gas into plasma to generate active materials for nitridation. In addition, the plasma generating mechanism 30 converts the H2 gas into plasma to generate H radicals. In addition, the plasma generating mechanism 30 converts the D2 gas into plasma to generate D radicals.

[0083] The plasma generating mechanism 30 includes a plasma partition wall 32 , a pair of plasma electrodes 33 , a power supply line 34 , a high-frequency power source 35 , and an insulating protective cover 36 .

[0084] The plasma partition wall 32 is welded to the outer wall of the processing container 1 in an airtight manner. The plasma partition wall 32 is formed of quartz, for example. The plasma partition wall 32 has a concave cross-section and covers the opening 31 formed in the side wall of the processing container 1. The opening 31 is formed to be elongated in the vertical direction in such a manner that all wafers W supported by the wafer boat 5 can be covered in the vertical direction. In the inner space limited by the plasma partition wall 32 and connected to the processing container 1, that is, the plasma generation space, a gas supply pipe 22 for discharging nitriding gas and a gas supply pipe 23 for discharging H2 gas and D2 gas are arranged. It should be noted that the gas supply pipe 21 for discharging raw material gas is arranged at a position close to the wafer W along the inner wall of the processing container 1 outside the plasma generation space.

[0085] The pair of plasma electrodes 33 each has an elongated shape, and is disposed facing each other in the up-down direction on the outer surfaces of the walls on both sides of the plasma partition wall 32. A power supply line 34 is connected to the lower end of each plasma electrode 33.

[0086] The power supply line 34 electrically connects each plasma electrode 33 to the high frequency power supply 35. In the example shown in the figure, one end of the power supply line 34 is connected to the side of the short side of each plasma electrode 33, that is, the lower end, and the other end is connected to the high frequency power supply 35.

[0087] The high-frequency power supply 35 is connected to the lower end of each plasma electrode 33 via a power supply line 34, and supplies a high-frequency power of, for example, 13.56 MHz to the pair of plasma electrodes 33. Thus, high-frequency power is applied to the plasma generation space limited by the plasma partition wall 32. The nitriding gas discharged from the gas supply pipe 22 is plasmatized in the plasma generation space to which high-frequency power is applied, and the active material for nitridation generated thereby is supplied to the inside of the processing container 1 via the opening 31. In addition, the H2 gas and the D2 gas discharged from the gas supply pipe 23 are plasmatized in the plasma generation space to which high-frequency power is applied, and the H radicals and the D radicals generated thereby are supplied to the inside of the processing container 1 via the opening 31.

[0088] An insulating protective cover 36 is installed on the outer side of the plasma partition wall 32 in a manner covering the plasma partition wall 32. A refrigerant passage (not shown) is provided on the inner side of the insulating protective cover 36, and a refrigerant such as a cooled nitrogen (N2) gas flows in the refrigerant passage, thereby cooling the plasma electrode 33. In addition, a shield (not shown) may be provided between the plasma electrode 33 and the insulating protective cover 36 in a manner covering the plasma electrode 33. The shield is formed of a good conductor such as metal and is grounded.

[0089] An exhaust port 40 for evacuating the processing container 1 is provided on the side wall portion of the processing container 1 opposite to the opening 31. The exhaust port 40 is formed slenderly up and down corresponding to the wafer boat 5. An exhaust mask component 41 formed in a U-shaped cross-section is installed in the portion of the processing container 1 corresponding to the exhaust port 40 so as to cover the exhaust port 40. The exhaust mask component 41 extends upward along the side wall of the processing container 1. At the lower part of the exhaust mask component 41, an exhaust pipe 42 for exhausting the processing container 1 through the exhaust port 40 is connected. The exhaust pipe 42 is connected to a pressure control valve 43 for controlling the pressure in the processing container 1 and an exhaust device 44 including a vacuum pump, etc., and the exhaust device 44 exhausts the processing container 1 through the exhaust pipe 42.

[0090] In addition, a cylindrical heating mechanism 50 for heating the processing container 1 and the wafers W therein is provided so as to surround the outer circumference of the processing container 1 .

[0091] In addition, the vertical heat treatment device 100 has a control unit 60. The control unit 60, for example, controls the operation of each part of the vertical heat treatment device 100. The control unit 60, for example, can be a computer or the like. In addition, the program of the computer that performs the operation of each part of the vertical heat treatment device 100 is stored in a storage medium. The storage medium can be, for example, a floppy disk, an optical disk, a hard disk, a flash memory, a DVD, etc.

[0092] An example of a method of forming a thin film on a wafer W by a film forming method according to an embodiment using the vertical heat treatment apparatus 100 will be described.

[0093] First, the control unit 60 controls the lifting mechanism (not shown) to move the wafer boat 5 holding a plurality of wafers W into the processing container 1 , and hermetically blocks and seals the lower opening of the processing container 1 with the cover 9 .

[0094] Then, the control unit 60 controls the gas supply unit 20, the plasma generation mechanism 30, the pressure control valve 43, the heating mechanism 50, etc. to perform any of the film forming methods of the first to fourth embodiments. Thus, a silicon nitride film with a low impurity concentration can be formed on the wafer W.

[0095] 〔Simulation results〕

[0096] The molar fraction of each particle contained in H2 plasma and D2 plasma was calculated using the PlasMa PSR (Perfectly Stirred Reactor) Model using the software ANSYS Chemkin-Pro 2019R2.

[0097] First, using the simulation condition A shown below, the mole fraction of each particle contained in the H 2 plasma and the D 2 plasma was calculated.

[0098] (Simulation condition A)

[0099] Volume of plasma generation space: 1.008×10 -5 m 3

[0100] Pressure of plasma generation space: 300mTorr (40Pa)

[0101] Gas temperature during plasma treatment: 550°C

[0102] Gas flow rate per unit plasma generation space: 50.85sccm

[0103] Plasma power per unit plasma generation space: 0.8474W

[0104] Fig.10 It is a diagram showing the calculation results of the mole fraction of each particle contained in H2 plasma and D2 plasma based on simulation. Fig.10 In the figure, from the left, they represent electrons (E), protonated molecules (H3 + 、D3 + ), molecular ions (H2 + 、D2 + ), ions (H+ , D + ), the calculation results of the molar fractions of free radicals (H, D) and molecules (H2, D2).

[0105] like Fig.10 As shown, it can be confirmed that the amount of D radicals contained in D2 plasma is about 1.7 times greater than the amount of H radicals contained in H2 plasma. From this result, it is believed that the introduction of D2 plasma in the ALD cycle can improve the modification effect of the film formed by the ALD cycle.

[0106] Next, regarding the simulation condition A, the ratio of D radical to H radical (D / H) was evaluated when the gas temperature was changed within the range of 300 to 700°C.

[0107] Fig.11 It is a diagram showing the simulation results of the gas temperature dependency of D / H. Fig.11 In the figure, the horizontal axis represents the gas temperature [° C.] during the plasma treatment, and the vertical axis represents D / H.

[0108] like Fig.11 As shown in the figure, it can be seen that even if the gas temperature during plasma treatment is any temperature of 300 to 700°C, D / H is greater than 1. From this result, it is believed that when the gas temperature during plasma treatment is 300 to 700°C, by using D2 plasma, the amount of radicals contained in the plasma increases compared to the case where H2 plasma is not used, and the effect of removing impurities on the film surface can be improved. In other words, it is believed that by using D2 plasma, a thin film with a low impurity concentration can be formed compared to the case where H2 plasma is used.

[0109] In addition, if Fig.11 As shown in the figure, it can be seen that D / H increases when the gas temperature during plasma treatment increases within the temperature range of 300 to 700° C. From this result, it is believed that the higher the gas temperature during plasma treatment, the more effective it is to remove impurities on the film surface by radicals contained in the plasma.

[0110] Next, regarding the simulation condition A, D / H was evaluated when the pressure of the plasma generation space was changed within the range of 300 to 2100 mTorr (40 to 100 Pa).

[0111] Fig.12 It is a graph showing the simulation results of the pressure dependence of D / H. Fig.12 In FIG. 5 , the horizontal axis represents the pressure [mTorr] of the plasma generation space, and the vertical axis represents D / H.

[0112] like Fig.12As shown in the figure, it can be seen that even if the pressure of the plasma generation space is any pressure of 300 to 2100 mTorr, D / H is greater than 1. From this result, it is believed that when the pressure of the plasma generation space is 300 to 2100 mTorr, by using D2 plasma, the amount of radicals contained in the plasma increases compared to the case of using H2 plasma, and the effect of removing impurities on the film surface can be improved. In other words, it is believed that by using D2 plasma, a thin film with a low impurity concentration can be formed compared to the case of using H2 plasma.

[0113] In addition, if Fig.12 As shown in the figure, it can be seen that in the pressure range of 300 to 2100 mTorr, if the pressure of the plasma generation space is reduced, D / H becomes higher. From this result, it is believed that the effect of removing impurities on the film surface by radicals contained in the plasma can be further improved as the pressure of the plasma generation space is reduced.

[0114] Next, regarding the simulation condition A, D / H was evaluated when the gas flow rate per unit plasma generation space was changed within a range of 33.9 to 67.8 sccm.

[0115] Fig.13 It is a diagram showing the simulation results of the gas flow rate dependency of D / H. Fig.13 In the figure, the horizontal axis represents the gas flow rate [sccm] per unit plasma generation space, and the vertical axis represents D / H.

[0116] like Fig.13 As shown in the figure, it can be seen that even if the gas flow rate per unit plasma generation space is any gas flow rate of 33.9 to 67.8 sccm, D / H is greater than 1. From this result, it is believed that when the gas flow rate per unit plasma generation space is 33.9 to 67.8 sccm, by using D2 plasma, the amount of radicals contained in the plasma increases compared to the case of using H2 plasma, and the effect of removing impurities on the film surface can be improved. In other words, it is believed that by using D2 plasma, a thin film with a low impurity concentration can be formed compared to the case of using H2 plasma.

[0117] In addition, if Fig.13 As shown in the figure, it can be seen that within the flow rate range of 33.9 to 67.8 sccm, if the gas flow rate per unit plasma generation space is reduced, D / H becomes higher. From this result, it is believed that the smaller the gas flow rate per unit plasma generation space, the more effective it is to remove impurities on the film surface by radicals contained in the plasma.

[0118] The embodiments disclosed herein are illustrative in all aspects and should not be construed as limiting. The above embodiments may be omitted, replaced, or modified in various ways without departing from the appended claims and the gist thereof.

Claims

1. A film forming method, which forms a thin film by performing a plurality of cycles including the following steps: A process of supplying a raw material gas to a substrate; supplying a reaction gas that reacts with the raw material gas to the substrate; The step of treating the substrate with deuterium plasma; and The step of treating the substrate with hydrogen plasma is performed before or after the step of treating the substrate with deuterium plasma.

2. The film forming method according to claim 1, wherein The step of treating with deuterium plasma is performed after the step of supplying the raw material gas and before the step of supplying the reaction gas.

3. The film forming method according to claim 2, wherein: The step of treating with deuterium plasma is performed after the step of supplying the reaction gas and before the step of supplying the source gas.

4. The film forming method according to any one of claims 1 to 3, wherein In at least one of the step of treating with deuterium plasma and the step of treating with hydrogen plasma, an inert gas is supplied.

5. The film forming method according to any one of claims 1 to 3, wherein In the step of supplying the reaction gas, the reaction gas is thermally decomposed or activated by plasma, thereby causing the raw material gas to react with the reaction gas.

6. The film forming method according to any one of claims 1 to 3, wherein: The raw material gas is silicon raw material gas, The reaction gas is a nitriding gas.

7. The film forming method according to claim 6, wherein: The silicon raw material gas is a silicon compound containing a halogen element.

8. The film forming method according to claim 7, wherein: The halogen element is at least any one of Cl, I, and Br.

9. The film forming method according to claim 6, wherein: The silicon raw material gas includes dichlorosilane gas.

10. A system comprising a film forming device and a control unit, The control unit is configured to control the film forming device to form a thin film on the substrate by performing a plurality of cycles including the following steps: A process of supplying a raw material gas to a substrate; supplying a reaction gas that reacts with the raw material gas to the substrate; The step of treating the substrate with deuterium plasma; and The step of treating the substrate with hydrogen plasma is performed before or after the step of treating the substrate with deuterium plasma. 11 . A computer-readable storage medium storing a computer program which, when executed by a processor, implements the film-forming method according to claim 1 . 12 . A computer program product comprising a computer program, which, when executed by a processor, implements the film forming method according to claim 1 .

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