Method for forming film and film formation device

Abstract

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

Description

[Technical Field]

[0001] The present disclosure relates to a film formation method and a film formation apparatus. [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 techniques that can increase the nickel concentration in silicon films. [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; and simultaneously supplying a nickel source gas and a hydrogen 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 increased. [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] 1 is a cross-sectional view showing a film forming apparatus according to an embodiment. [Figure 4] FIG. 10 is a diagram showing an example of the dependency of the nickel concentration in an amorphous silicon film on the hydrogen gas flow rate. 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. 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. Figure 1 is a flowchart showing the film forming method according to an embodiment. Figure 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. The surface condition changing step S2 may be omitted.

[0013] The diffusion step S3 is performed after the surface condition changing step S2. In the diffusion step S3, 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 in which nickel has diffused (hereinafter referred to as a "nickel-containing amorphous silicon film 103a"). At this time, as shown in FIG. 2(c), a nickel source gas and a hydrogen gas are simultaneously supplied to the substrate 101. This increases the nickel concentration in the amorphous silicon film 103. This is thought to be because the hydrogen gas promotes the decomposition of the nickel source gas. The flow rate of the hydrogen gas may be greater than the flow rate of the nickel source gas. In this case, the decomposition of the nickel source gas is more likely to be promoted. The flow rate ratio of the nickel source gas to the hydrogen gas is, for example, 1:40 to 1:80.

[0014] The nickel source gas can be generated, for example, by vaporizing a liquid nickel source or sublimating a solid nickel source. The nickel source may be an organic nickel source. The liquid nickel source may be, for example, (EtCp)Ni[Ni(C2H5C5H4)2] or CpAllylNi[(C3H5)(C5H5)Ni]. The solid nickel source may be, for example, (MeCp)Ni[Ni(CH3C5H4)2]. For example, when (EtCp)Ni is used as the nickel source, the substrate temperature is 150°C or higher and 300°C or lower. The diffusion step S3 is performed, for example, consecutively in the same processing vessel as the preparation step S1. The diffusion step S3 may also be performed in a processing vessel different from the preparation step S1.

[0015] 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.

[0016] In this manner, the polycrystalline silicon film 105 can be formed on the substrate 101.

[0017] As described above, according to the film forming method of the embodiment, in the diffusion step S3, nickel source gas and hydrogen gas are simultaneously supplied to the substrate 101, thereby diffusing nickel into the amorphous silicon film 103. In this case, the nickel concentration in the amorphous silicon film 103 can be increased.

[0018] 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.

[0019] 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.

[0020] [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. 3. Fig. 3 is a cross-sectional view showing the film formation apparatus 1 according to the embodiment.

[0021] 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.

[0022] 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.

[0023] 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, 32a, and 33a, which will be described later.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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, a nickel raw material supply unit 32, and a hydrogen gas supply unit 33.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] The hydrogen gas supply unit 33 includes a supply pipe 33a inside the processing vessel 10 and a supply path 33b outside the processing vessel 10. A hydrogen gas source 33c, a mass flow controller 33d, and an on-off valve 33e are installed on the supply path 33b, in this order from upstream to downstream in the gas flow direction. The supply timing of hydrogen gas from the hydrogen gas source 33c is controlled by the on-off valve 33e, and the flow rate is adjusted to a predetermined value by the mass flow controller 33d. The hydrogen gas flows from the supply path 33b into the supply pipe 33a and is discharged from the supply pipe 33a into the processing vessel 10.

[0034] The supply pipes 31a, 32a, and 33a are fixed to the manifold 17. The supply pipes 31a, 32a, and 33a are made of, for example, quartz. The supply pipes 31a, 32a, and 33a 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, and 33a are arranged side by side along the circumferential direction of the inner pipe 11 and are formed at the same height.

[0035] A plurality of gas holes 31p, 32p, and 33p are provided in the supply pipes 31a, 32a, and 33a at portions thereof located within the inner pipe 11. The gas holes 31p, 32p, and 33p are formed at predetermined intervals along the extension direction of the respective supply pipes 31a, 32a, and 33a. The gas holes 31p, 32p, and 33p discharge gas in the horizontal direction. The intervals between the gas holes 31p, 32p, and 33p are set to be the same as the intervals between the substrates W held in the boat 16, for example. The height positions of the gas holes 31p, 32p, and 33p are set at midpoints between vertically adjacent substrates W. In this case, the gas holes 31p, 32p, and 33p can efficiently supply gas to the opposing surfaces of the adjacent substrates W.

[0036] 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, 32a, and 33a may be configured to be able to discharge an inert gas. For example, instead of providing the supply pipe 33a, the supply pipe 31a or the supply pipe 32a may be configured to be able to discharge hydrogen gas. The supply pipes 31a, 32a, and 33a 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, nickel source gas, and hydrogen gas.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] [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.

[0041] 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.

[0042] 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 simultaneously supply a nickel source gas and a hydrogen 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.

[0043] 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.

[0044] 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.

[0045] [Experimental results] In the film formation apparatus 1, the preparation step S1, the surface condition modification step S2, and the diffusion step S3 were performed in this order, and then the nickel concentration in the amorphous silicon film was measured. In the surface condition modification step S2, DHF and APM were supplied to the amorphous silicon film in this order. 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 source gas used was a gas generated by vaporizing Ni(C2H5C5H4)2, a liquid nickel source. In the diffusion step S3, the flow rate of the hydrogen gas was set to 0 sccm, 100 sccm, 200 sccm, or 400 sccm. The nickel concentration was measured using total reflection X-ray fluorescence (TXRF) analysis.

[0046] Fig. 4 is a graph showing an example of the dependency of the nickel concentration in an amorphous silicon film on the hydrogen gas flow rate. Fig. 4 shows the nickel concentration in the amorphous silicon film when the hydrogen gas flow rate is 100 sccm, 200 sccm, and 400 sccm, expressed as a relative value, with the nickel concentration in the amorphous silicon film when the hydrogen gas flow rate is 0 sccm set to 1.

[0047] 4, when the hydrogen gas flow rates are 100 sccm, 200 sccm, and 400 sccm, the nickel concentration in the amorphous silicon film is 1.3 to 1.4 times higher than when the hydrogen gas flow rate is 0 sccm. In other words, when the nickel source gas and hydrogen gas are supplied simultaneously in the diffusion step S3, the nickel concentration in the amorphous silicon film is 1.3 to 1.4 times higher than when the nickel source gas is supplied without supplying hydrogen gas in the diffusion step S3. This result demonstrates that the nickel concentration in the amorphous silicon film can be increased by supplying the nickel source gas and hydrogen gas simultaneously in the diffusion step S3.

[0048] 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.

[0049] 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]

[0050] S1 Preparation process S3 Diffusion process

Claims

1. preparing a substrate having an amorphous silicon film on its surface; a step of simultaneously supplying a nickel source gas and a hydrogen gas to the amorphous silicon film to diffuse nickel into the amorphous silicon film; The film forming method includes the steps of:

2. the flow rate of the hydrogen gas is greater than the flow rate of the nickel source gas; The film forming method according to claim 1 .

3. 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 .

4. 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 .

5. The nickel raw material is an organic nickel raw material. The film forming method according to claim 4.

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

7. 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 .

8. 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 .

9. the diffusing step and the polycrystalline silicon film forming step are performed in the same processing chamber. The film forming method according to claim 3 .

10. a step of changing a surface state of the amorphous silicon film between the preparing step and the diffusing step; The film forming method according to claim 1 .

11. a processing vessel for accommodating a substrate; a gas supply unit that supplies a nickel source gas and a hydrogen gas into the processing vessel; A control unit; Equipped with The control unit preparing a substrate having an amorphous silicon film on its surface; simultaneously supplying the nickel source gas and the hydrogen gas to the amorphous silicon film to diffuse nickel into the amorphous silicon film; configured to: Film deposition equipment.

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