Method for forming film

Abstract

To provide a technique capable of controlling the concentration of nickel in a silicon film.SOLUTION: A method for forming a film according to one embodiment of the present disclosure includes: preparing a substrate having an amorphous silicon film on the surface; modifying the surface state of the amorphous silicon film; and supplying a nickel source gas to the amorphous silicon film after the modifying step, and diffusing nickel into the amorphous silicon film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a film formation method. [Background technology]

[0002] A technique is known in which an amorphous silicon film is modified into a polycrystalline silicon film by adsorbing nickel particles onto the surface of the amorphous silicon film and then annealing the film (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-60908 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can control the nickel concentration in a silicon film. [Means for solving the problem]

[0005] A film formation method according to one aspect of the present disclosure includes the steps of preparing a substrate having an amorphous silicon film on its surface, modifying the surface state of the amorphous silicon film, and, after the modifying step, supplying a nickel source gas to the amorphous silicon film to diffuse nickel into the amorphous silicon film. [Effects of the Invention]

[0006] According to the present disclosure, the nickel concentration in the silicon film can be controlled. [Brief explanation of the drawings]

[0007] [Figure 1] 2 is a flowchart illustrating a film forming method according to an embodiment. [Figure 2] 1A to 1C are cross-sectional views illustrating a film forming method according to an embodiment. [Figure 3] FIG. 10 is a diagram showing the results of a thermodynamic calculation analysis of a surface reaction in a diffusion process. [Figure 4] FIG. 1 is a schematic diagram showing an example of a surface reaction in a diffusion step. [Figure 5] FIG. 10 is a schematic diagram showing another example of a surface reaction in the diffusion step. [Figure 6] 1 is a cross-sectional view showing a film forming apparatus according to an embodiment. [Figure 7] FIG. 10 is a diagram showing an example of a comparison result of nickel concentration in an amorphous silicon film. [Figure 8] FIG. 10 is a diagram showing an example of the temperature dependence of the nickel concentration in an amorphous silicon film. [Figure 9] FIG. 10 is a diagram showing another example of the temperature dependence of the nickel concentration in an amorphous silicon film. 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 FIGS. 1 to 5. The following description will be given taking as an example a case where a polycrystalline silicon film is formed on a substrate. The polycrystalline silicon film can be used as a channel silicon film of a 3D NAND flash memory, for example. FIG. 1 is a flowchart showing the film forming method according to an embodiment. FIG. 2 is a cross-sectional view showing the film forming method according to an embodiment.

[0010] As shown in FIG. 1, the film forming method according to the embodiment includes a preparation step S1, a surface state changing step S2, a diffusion step S3, and a crystallization step S4.

[0011] In the preparation step S1, as shown in FIG. 2(a), a substrate 101 is prepared. The substrate 101 is, for example, a silicon wafer. An oxide film 102 and an amorphous silicon film 103 may be formed on the substrate 101 in this order. The oxide film 102 is, for example, a silicon oxide film. The amorphous silicon film 103 can be formed by, for example, chemical vapor deposition (CVD) using a silicon-containing gas. The silicon-containing gas is, for example, diisopropylaminosilane (DIPAS), disilane, monosilane, or a combination thereof.

[0012] The surface condition changing step S2 is performed after the preparation step S1. In the surface condition changing step S2, the surface condition of the amorphous silicon film 103 is changed. The surface condition changing step S2 may include adjusting the ratio of Si—OH groups to Si—H groups on the surface of the amorphous silicon film 103. As shown in FIG. 2(b), the surface condition changing step S2 may include adjusting the ratio of Si—OH groups to Si—H groups by supplying a treatment liquid to the amorphous silicon film 103. When the treatment liquid is APM (a mixture of ammonia, hydrogen peroxide, and water), the ratio of Si—OH groups to Si—H groups can be increased. When the treatment liquid is DHF (dilute hydrofluoric acid), the ratio of Si—OH groups to Si—H groups can be decreased. In the surface condition changing step S2, APM may be supplied after DHF is supplied to the amorphous silicon film 103.

[0013] The diffusion step S3 is performed after the surface condition modification step S2. In the diffusion step S3, as shown in FIG. 2(c), a nickel source gas is supplied to the substrate 101 to diffuse nickel (Ni) into the amorphous silicon film 103. This results in the formation of an amorphous silicon film with nickel diffused therein (hereinafter referred to as a "nickel-containing amorphous silicon film 103a"). The nickel source gas can be generated, for example, by vaporizing a liquid nickel source. Examples of the liquid nickel source include (EtCp)Ni[Ni(C2H5C5H4)2], NiPF3[Ni(PF3)4], CpAllylNi[(C3H5)(C5H5)Ni], or Ni(CO)4. The nickel source gas can be generated, for example, by sublimating a solid nickel source. Examples of the solid nickel source include (MeCp)Ni[Ni(CH3C5H4)2]. For example, when (EtCp)Ni is used as the nickel source material, the substrate temperature is 150°C or higher and 300°C or lower. In the diffusion step S3, the amount of nickel diffused into the nickel-containing amorphous silicon film 103a can be adjusted by controlling the supply flow rate of the nickel source gas. The diffusion step S3 is performed, for example, consecutively in the same processing chamber as the preparation step S1. The diffusion step S3 may also be performed in a processing chamber different from that in which the preparation step S1 is performed.

[0014] 3 to 5, the surface reaction of the amorphous silicon film 103 in the diffusion step S3 will be described. The surface reaction of the amorphous silicon film 103 in the diffusion step S3 is considered to proceed as follows.

[0015] Figure 3 shows the results of a thermodynamic calculation of the surface reaction in the diffusion step S3. In Figure 3, the horizontal axis represents temperature [°C], and the vertical axis represents the change in Gibbs free energy ΔG [kcal]. In Figure 3, the solid line represents the change in Gibbs free energy of the reaction that produces Si-Ni groups from Si-OH groups and nickel source gas, and the dashed line represents the change in Gibbs free energy of the reaction that produces Si-Ni groups from Si-H groups and nickel source gas.

[0016] As shown in Figure 3, the Gibbs free energy change in the reaction of forming Si-Ni groups from Si-OH groups and nickel source gas and the Gibbs free energy change in the reaction of forming Si-Ni groups from Si-H groups and nickel source gas are both negative values. Furthermore, the absolute value of the Gibbs free energy change in the reaction of forming Si-Ni groups from Si-OH groups and nickel source gas is larger than the absolute value of the Gibbs free energy change in the reaction of forming Si-Ni groups from Si-H groups and nickel source gas. From these results, it can be said that the reaction of forming Si-Ni groups from Si-OH groups and nickel source gas proceeds more easily than the reaction of forming Si-Ni groups from Si-H groups and nickel source gas.

[0017] FIG. 4 is a schematic diagram showing an example of a surface reaction in the diffusion step S3. FIG. 4 shows the surface reaction in the diffusion step S3 when APM is used as the processing liquid in the surface state changing step S2. FIG. 4(a) is a diagram showing the surface state of the amorphous silicon film 103 before the diffusion step S3 is performed. FIG. 4(b) is a diagram showing the surface state of the amorphous silicon film 103 after a first hour has elapsed since the start of the diffusion step S3. FIG. 4(c) is a diagram showing the surface state of the amorphous silicon film 103 after a second hour has elapsed since the start of the diffusion step S3. The second hour is longer than the first hour.

[0018] As shown in FIG. 4( a), when APM is supplied to the amorphous silicon film 103, the ratio of Si—OH groups to Si—H groups increases on the surface of the amorphous silicon film 103. As described above, the reaction that generates Si—Ni groups from Si—OH groups and nickel source gas proceeds more easily than the reaction that generates Si—Ni groups from Si—H groups and nickel source gas. Therefore, as shown in FIG. 4( b), when nickel source gas is supplied to the amorphous silicon film 103, many Si—Ni groups are generated on the surface of the amorphous silicon film 103. If the supply of nickel source gas to the amorphous silicon film 103 continues, the nickel adsorbed on the surface of the amorphous silicon film 103 diffuses into the amorphous silicon film 103, and the nickel concentration in the amorphous silicon film 103 increases, as shown in FIG. 4( c).

[0019] Fig. 5 is a schematic diagram showing another example of the surface reaction in the diffusion step S3. Fig. 5 shows the surface reaction in the diffusion step S3 when DHF is used as the treatment liquid in the surface state changing step S2. Fig. 5(a) is a diagram showing the surface state of the amorphous silicon film 103 before the diffusion step S3 is performed. Fig. 5(b) is a diagram showing the surface state of the amorphous silicon film 103 after a first hour has elapsed since the start of the diffusion step S3. Fig. 5(c) is a diagram showing the surface state of the amorphous silicon film 103 after a second hour has elapsed since the start of the diffusion step S3.

[0020] As shown in FIG. 5( a), when DHF is supplied to the amorphous silicon film 103, the ratio of Si—OH groups to Si—H groups decreases on the surface of the amorphous silicon film 103. As described above, the reaction that generates Si—Ni groups from Si—H groups and nickel source gas proceeds more slowly than the reaction that generates Si—Ni groups from Si—OH groups and nickel source gas. Therefore, as shown in FIG. 5( b), even if nickel source gas is supplied to the amorphous silicon film 103, Si—Ni groups are unlikely to be generated on the surface of the amorphous silicon film 103. Even if the supply of nickel source gas to the amorphous silicon film 103 continues, nickel is unlikely to diffuse into the amorphous silicon film 103, as shown in FIG. 5( c), and therefore the nickel concentration in the amorphous silicon film 103 decreases.

[0021] The crystallization step S4 is performed after the diffusion step S3. In the crystallization step S4, as shown in FIG. 2(d), the nickel-containing amorphous silicon film 103a is crystallized by metal-induced lateral crystallization (MILC) to form a polycrystalline silicon film 105. In this case, the polycrystalline silicon film 105 can be formed by MILC using a low concentration of nickel. In the crystallization step S4, for example, the substrate 101 is heated to a first temperature, and the nickel-containing amorphous silicon film 103a is crystallized by MILC using nickel diffused into the nickel-containing amorphous silicon film 103a as nuclei to form the polycrystalline silicon film 105. The first temperature is, for example, 500°C or higher and 600°C or lower. The crystallization step S4 is performed, for example, under an inert gas atmosphere at atmospheric pressure. The crystallization step S4 may also be performed under reduced pressure. The crystallization step S4 is performed, for example, continuously in the same processing chamber as the diffusion step S3. The crystallization step S4 may be performed in a processing chamber different from that for the diffusion step S3. After the crystallization step S4, a step of removing nickel remaining on the surface of or within the polycrystalline silicon film 105 by, for example, gettering may be performed.

[0022] In this manner, the polycrystalline silicon film 105 can be formed on the substrate 101.

[0023] As described above, according to the film forming method of the embodiment, after the surface condition of the amorphous silicon film 103 is changed in the surface condition changing step S2, nickel is diffused into the amorphous silicon film 103 in the diffusion step S3. In this case, the ease with which the surface reaction proceeds in the diffusion step S3 changes, so that the nickel concentration in the amorphous silicon film 103 can be controlled.

[0024] In the above embodiment, the polycrystalline silicon film 105 is formed on the substrate 101, but the present disclosure is not limited thereto. For example, the film formation method of the present disclosure can also be applied to a case where recesses such as holes and trenches are formed on the surface of the substrate 101 and the polycrystalline silicon film 105 is formed on the inner surface of the recesses. In this case, nickel is diffused into the amorphous silicon film 103 using a nickel source gas, thereby reducing the variation in the amount of nickel diffused in the depth direction of the recesses. This allows the formation of a polycrystalline silicon film 105 with small variation in grain size in the depth direction of the recesses.

[0025] [Film forming equipment] An example of a film formation apparatus 1 capable of performing the preparation step S1, the diffusion step S3, and the crystallization step S4 of the film formation method according to the embodiment will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing the film formation apparatus 1 according to the embodiment.

[0026] The film forming apparatus 1 includes a processing chamber 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, and a control unit 90.

[0027] The processing vessel 10 has a double-tube structure consisting of a cylindrical inner tube 11 and a ceiling-equipped outer tube 12 concentrically placed outside the inner tube 11. The inner tube 11 and the outer tube 12 are made of, for example, quartz. The processing vessel 10 is configured to be able to accommodate a boat 16.

[0028] A storage section 13 is formed on one side of the inner pipe 11 along its longitudinal direction (vertical direction). The storage section 13 is an area within a protrusion 14 formed by protruding part of the side wall of the inner pipe 11 outward. The storage section 13 stores supply pipes 31a and 32a, which will be described later.

[0029] 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. The flange 18 supports the lower end of the outer tube 12. A seal member 19, such as an O-ring, is provided between the flange 18 and the lower end of the outer tube 12.

[0030] An annular support member 20 is provided on the inner wall of the upper part of the manifold 17. The support member 20 supports the lower end of the inner tube 11. An exhaust port 21 is provided on the side wall of the upper part of the manifold 17 above the support member 20. A lid member 22 is airtightly attached to the opening at the lower end of the manifold 17 via a sealing member 23 such as an O-ring. The lid member 22 is made of, for example, stainless steel.

[0031] A rotating shaft 25 is provided through the center of the lid 22 via a magnetic fluid seal 24. The lower end of the rotating shaft 25 is rotatably supported by an arm 26A of an elevating mechanism 26 consisting of a boat elevator. A rotating plate 27 is provided at the upper end of the rotating shaft 25. The boat 16 is placed on the rotating plate 27 via a quartz heat-insulating tube 28.

[0032] Boat 16 holds a plurality of (e.g., 25 to 200) substrates W substantially horizontally with vertical spacing between them. The substrates W are, for example, semiconductor wafers. Boat 16 rotates integrally with rotation shaft 25. Boat 16 moves up and down integrally with lid 22 as arm 26A moves up and down, and is inserted into and removed from processing vessel 10.

[0033] The gas supply unit 30 is configured to be able to introduce various gases into the inner tube 11. The various gases include gases used in the film formation method according to the embodiment. The gas supply unit 30 includes a silicon raw material supply unit 31 and a nickel raw material supply unit 32.

[0034] The silicon source supply unit 31 includes a supply pipe 31a inside the processing vessel 10 and a supply path 31b outside the processing vessel 10. A silicon source 31c, a mass flow controller 31d, and an on-off valve 31e are installed on the supply path 31b, in this order from upstream to downstream in the gas flow direction. The on-off valve 31e controls the supply timing of the silicon-containing gas from the silicon source 31c, and the mass flow controller 31d adjusts the flow rate to a predetermined value. The silicon-containing gas flows from the supply path 31b into the supply pipe 31a and is then discharged from the supply pipe 31a into the processing vessel 10.

[0035] The nickel raw material supply unit 32 includes a supply pipe 32a inside the processing vessel 10 and a supply path 32b outside the processing vessel 10. A raw material tank 32c, a control valve 32d, and an on-off valve 32e are provided on the supply path 32b, in this order from upstream to downstream in the gas flow direction. The raw material tank 32c contains the nickel raw material. The nickel raw material is a raw material that is liquid at room temperature or a raw material that is solid at room temperature. A heater 32f is provided around the raw material tank 32c. The heater 32f heats the nickel raw material in the raw material tank 32c. As a result, the liquid nickel raw material is vaporized or the solid nickel raw material is sublimated, generating a nickel raw material gas.

[0036] The nickel source material supply unit 32 has a carrier gas pipe 32g inserted into the source material tank 32c from above. The carrier gas pipe 32g is provided with a carrier gas source 32h, an on-off valve 32i, and an adjustment valve 32j, in this order from upstream to downstream in the gas flow direction. Thus, the carrier gas from the carrier gas source 32h is supplied into the source material tank 32c with the supply timing controlled by the on-off valve 32i and the flow rate adjusted to a predetermined value by the adjustment valve 32j. The carrier gas, together with the nickel source material gas in the source material tank 32c, is supplied into the supply pipe 32a from the supply path 32b with the supply timing controlled by the on-off valve 32e and the flow rate adjusted to a predetermined value by the adjustment valve 32d. The nickel source material gas and carrier gas that have flowed into the supply pipe 32a are discharged into the processing vessel 10 from the supply pipe 32a.

[0037] A bypass path 32k may be provided that connects the upstream side of the on-off valve 32i in the carrier gas pipe 32g to the downstream side of the on-off valve 32e in the supply path 32b. A bypass valve 32l may be provided in the bypass path 32k.

[0038] The supply pipes 31a, 32a are fixed to the manifold 17. The supply pipes 31a, 32a are made of, for example, quartz. The supply pipes 31a, 32a extend linearly in the vertical direction near the inner pipe 11, and then bend in an L-shape within the manifold 17 and extend horizontally, thereby penetrating the manifold 17. The supply pipes 31a, 32a are arranged side by side along the circumferential direction of the inner pipe 11 and are formed at the same height.

[0039] A plurality of gas holes 31p, 32p are provided in the supply pipes 31a, 32a at portions thereof located within the inner pipe 11. The gas holes 31p, 32p are formed at predetermined intervals along the extension direction of the respective supply pipes 31a, 32a. The gas holes 31p, 32p discharge gas in the horizontal direction. The interval between the gas holes 31p, 32p is set to be the same as the interval between the substrates W held in the boat 16, for example. The height positions of the gas holes 31p, 32p are set at the midpoint between the vertically adjacent substrates W. In this case, the gas holes 31p, 32p can efficiently supply gas to the opposing surfaces of the adjacent substrates W.

[0040] The gas supply unit 30 may mix multiple types of gases and discharge the mixed gas from one supply pipe. For example, the supply pipes 31a and 32a may be configured to be able to discharge an inert gas. The supply pipes 31a and 32a may have different shapes and arrangements. The gas supply unit 30 may further include a supply pipe that supplies another gas in addition to the silicon-containing gas and the nickel raw material gas.

[0041] The exhaust unit 40 includes an exhaust passage 41, a pressure adjustment valve 42, and a vacuum pump 43. The exhaust passage 41 is connected to the exhaust port 21. The pressure adjustment valve 42 and the vacuum pump 43 are provided midway along the exhaust passage 41. The vacuum pump 43 is provided downstream of the pressure adjustment valve 42 in the gas flow direction. The exhaust flow rate of the gas inside the processing chamber 10 is controlled by the pressure adjustment valve 42, and the gas is discharged to the outside of the processing chamber 10 by the vacuum pump 43.

[0042] The heating part 50 has a cylindrical shape and is provided around the outer tube 12. The heating part 50 heats each substrate W in the processing chamber 10. The heating part 50 includes, for example, a heater.

[0043] The control unit 90 is an electronic circuit such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc. The control unit 90 executes various control operations described in this specification by executing instruction codes stored in a memory or by being a circuit designed for a specific application.

[0044] [Operation of the Film Forming Apparatus] The operation of the film forming apparatus 1 when performing the diffusion step S3 and the crystallization step S4 of the film forming method according to the embodiment will be described.

[0045] First, the control unit 90 controls the lifting mechanism 26 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 22. Each substrate W is, for example, a substrate 101 after the surface condition changing step S2 has been performed. The surface condition changing step S2 is performed, for example, in a coating apparatus provided separately from the film forming apparatus 1.

[0046] Next, the control unit 90 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to perform the diffusion step S3. Specifically, first, the control unit 90 controls the exhaust unit 40 to reduce the pressure inside the processing chamber 10 to a predetermined level, and controls the heating unit 50 to adjust and maintain the temperature of the substrate W at a predetermined level. Next, the control unit 90 controls the gas supply unit 30 to supply a nickel source gas into the processing chamber 10. As a result, nickel diffuses into the amorphous silicon film 103, and a nickel-containing amorphous silicon film 103a is formed.

[0047] Next, the control unit 90 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to perform the crystallization step S4. Specifically, the control unit 90 first controls the gas supply unit 30 to supply an inert gas into the processing vessel 10, controls the exhaust unit 40 to adjust the pressure inside the processing vessel 10 to a predetermined value, and controls the heating unit 50 to adjust and maintain the temperature of the substrate W at a predetermined value. As a result, the nickel-containing amorphous silicon film 103a is crystallized by metal-induced lateral crystallization, and a polycrystalline silicon film 105 is formed.

[0048] 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 26 to unload the boat 16 from the processing vessel 10.

[0049] [Experimental results] (Experiment 1) In Experiment 1, the nickel concentration in the amorphous silicon film was measured after performing the preparation step S1, the surface condition modification step S2, and the diffusion step S3 in this order in the film formation apparatus 1. In the surface condition modification step S2, one of the following conditions was set: no treatment liquid was supplied to the amorphous silicon film (hereinafter also referred to as "uncleaned"); DHF and APM were supplied to the amorphous silicon film in this order (hereinafter also referred to as "APM"); or DHF was supplied to the amorphous silicon film (hereinafter also referred to as "DHF"). In the diffusion step S3, the substrate temperature was set to 250°C, and the flow rate of the nickel source gas was set to 5 sccm. The nickel concentration was measured by total reflection X-ray fluorescence (TXRF) analysis.

[0050] Fig. 7 shows an example of the comparison results of nickel concentrations in amorphous silicon films. In Fig. 7, the nickel concentrations in the amorphous silicon films in "APM" and "DHF" are shown as relative values, with the nickel concentration in the "uncleaned" amorphous silicon film set to 1.

[0051] As shown in Figure 7, the nickel concentration in the amorphous silicon film was higher with "APM" than with "uncleaned," and lower with "DHF" than with "uncleaned." These results show that supplying DHF and APM to the amorphous silicon film in that order increases the nickel concentration in the amorphous silicon film, and supplying DHF to the amorphous silicon film decreases the nickel concentration in the amorphous silicon film. In other words, it was shown that the nickel concentration in the amorphous silicon film can be controlled by diffusing nickel into the amorphous silicon film after changing the surface condition of the amorphous silicon film.

[0052] (Experiment 2) In Experiment 2, similar to Experiment 1, the nickel concentration in the amorphous silicon film was measured after performing the preparation step S1, the surface condition modification step S2, and the diffusion step S3 in this order in the film formation apparatus 1. In Experiment 2, when the surface condition modification step S2 was performed under the condition that DHF and APM were supplied to the amorphous silicon film in this order, the effect of the temperature when nickel was diffused into the amorphous silicon film in the diffusion step S3 on the nickel concentration in the amorphous silicon film was evaluated.

[0053] Fig. 8 is a graph showing an example of the temperature dependence of the nickel concentration in an amorphous silicon film, where the horizontal axis represents the temperature [°C] when nickel is diffused into the amorphous silicon film, and the vertical axis represents the nickel concentration in the amorphous silicon film in logarithm.

[0054] As shown in Figure 8, the higher the temperature when diffusing nickel into the amorphous silicon film, the higher the nickel concentration in the amorphous silicon film. This result shows that the nickel concentration in the amorphous silicon film can be controlled by supplying DHF and APM to the amorphous silicon film in this order in the surface condition changing step S2 and adjusting the temperature when diffusing nickel into the amorphous silicon film in the diffusion step S3.

[0055] (Experiment 3) In Experiment 3, similarly to Experiment 1, the nickel concentration in the amorphous silicon film was measured after performing the preparation step S1, the surface condition changing step S2, and the diffusion step S3 in this order in the film forming apparatus 1. In Example 3, when the surface condition changing step S2 was performed under the condition that DHF was supplied to the amorphous silicon film, the influence of the temperature when nickel was diffused into the amorphous silicon film in the diffusion step S3 on the nickel concentration in the amorphous silicon film was evaluated.

[0056] 9 is a graph showing another example of the temperature dependence of the nickel concentration in an amorphous silicon film, where the horizontal axis represents the temperature [°C] when nickel is diffused into the amorphous silicon film, and the vertical axis represents the nickel concentration in the amorphous silicon film in logarithm.

[0057] As shown in Figure 9, the higher the temperature when diffusing nickel into the amorphous silicon film, the higher the nickel concentration in the amorphous silicon film. This result shows that the nickel concentration in the amorphous silicon film can be controlled by supplying DHF to the amorphous silicon film in the surface condition changing step S2 and adjusting the temperature when diffusing nickel into the amorphous silicon film in the diffusion step S3.

[0058] 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.

[0059] In the above embodiment, the film forming apparatus is a batch type apparatus that processes multiple substrates at once, but the present disclosure is not limited to this. For example, the film forming apparatus may be a single-wafer type apparatus that processes substrates one by one. [Explanation of symbols]

[0060] S1 Preparation process S2 Surface condition change process S3 Diffusion process

Claims

1. preparing a substrate having an amorphous silicon film on its surface; modifying the surface state of the amorphous silicon film; after the changing step, supplying a nickel source gas to the amorphous silicon film to diffuse nickel into the amorphous silicon film; The film forming method includes the steps of:

2. the modifying step includes adjusting a ratio of Si—OH groups to Si—H groups on the surface of the amorphous silicon film; The film forming method according to claim 1 .

3. the changing step includes adjusting the ratio by supplying a processing liquid to the amorphous silicon film. The film forming method according to claim 2 .

4. The treatment liquid contains APM, the step of changing includes increasing the ratio. The film forming method according to claim 3 .

5. The treatment liquid contains DHF, the step of changing includes lowering the ratio. The film forming method according to claim 3 .

6. a step of heating the amorphous silicon film and crystallizing the amorphous silicon film by metal-induced lateral crystallization using the nickel diffused in the amorphous silicon film as nuclei to form a polycrystalline silicon film; The film forming method according to claim 1 .

7. The diffusing step includes vaporizing a liquid nickel source material or sublimating a solid nickel source material to generate the nickel source gas. The film forming method according to claim 1 .

8. The nickel raw material is Ni(C ２ H ５ C ５ H ４ ) ２ , Ni(PF ３ ) ４ , (C ３ H ５ ) (C ５ H ５ )Ni, Ni(CO) ４ , or Ni(CH ３ C ５ H ４ ) ２ That is, The film forming method according to claim 7 .

9. a recess is formed on the surface of the substrate; the preparing step includes forming the amorphous silicon film on an inner surface of the recess; The film forming method according to claim 1 .

10. the preparing step includes forming the amorphous silicon film on the surface of the substrate in the same processing chamber as the diffusing step; The film forming method according to claim 1 .

11. the diffusing step and the polycrystalline silicon film forming step are performed in the same processing chamber. The film forming method according to claim 6.

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