METHOD FOR FORMING FILM AND APPARATUS FOR FORMING FILM

Abstract

To provide a technology of forming a film of a crystal structure containing strontium and titanium on a titanium nitride film.SOLUTION: An amorphous structure film is formed on a titanium nitride film formed on an upper surface of a substrate, the amorphous film containing strontium and oxygen with a content ratio of titanium to strontium at an atomic number level of 0 or more and less than 1.0. Then the substrate with the amorphous structure film formed thereon is heated to a temperature of 500°C or more to obtain a crystal structure film that includes titanium diffused from the titanium nitride film and contains strontium, titanium and oxygen.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Further improvements in capacitor performance are required for insulating films that constitute semiconductor devices, such as dynamic random access memories (DRAMs). Therefore, there is a growing need for ultra-high-k films, for example, with a relative dielectric constant of approximately 80 to 100, as insulating film materials. Crystals of complex oxides containing strontium (Sr) and titanium (Ti) (hereinafter, also referred to as "STO") are known as candidates for ultra-high-k films.

[0003] For example, Patent Document 1 describes a technique in which a first Sr—Ti—O based film of 10 nm or less formed on a Ru film is annealed to crystallize it, and then a second Sr—Ti—O based film is formed and crystallized by annealing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2009 / 104621 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique for forming a film with a crystalline structure containing strontium, titanium, and oxygen on a titanium nitride film. [Means for solving the problem]

[0006] The present disclosure provides a method for forming a film having a crystalline structure containing strontium, titanium, and oxygen on a substrate, the method comprising: forming an amorphous film containing strontium and oxygen on the upper surface of the titanium nitride film formed on the surface of the substrate, the titanium content being adjusted so that the ratio of titanium to strontium based on the atomic number is a value within the range of 0 or more and less than 1.0; and a step of heating the substrate on which the amorphous structure film has been formed at a temperature of 500° C. or higher to obtain a crystalline structure film containing titanium diffused from the titanium nitride film and containing strontium, titanium, and oxygen. fruit, In the step of forming the film, the amorphous structure film is formed to a thickness within a range of 5 nm or more and 10 nm or less; In the step of obtaining a film having a crystalline structure, the film having an amorphous structure is converted into a film having a crystalline structure, forming an amorphous upper layer film containing strontium, titanium, and oxygen on the upper surface of the crystalline film after the step of obtaining the crystalline film; Then, the substrate on which the upper layer film has been formed is heated at a temperature of 500°C or higher to convert the upper layer film into a film having a crystalline structure containing the strontium, titanium, and oxygen. It is a method. [Effects of the Invention]

[0007] According to the present disclosure, a film having a crystalline structure containing strontium, titanium, and oxygen can be formed on a titanium nitride film. [Brief explanation of the drawings]

[0008] [Figure 1] 1A to 1C are schematic diagrams illustrating a method for forming an STO film having a crystalline structure according to the first embodiment. [Figure 2] FIG. 2 is a plan view of a film forming apparatus for forming the STO film. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 1 is a diagram illustrating an example of a film formation sequence. [Figure 6] 5A to 5C are schematic diagrams showing a method for forming an STO film having a crystalline structure according to the second embodiment. [Figure 7] 10A to 10C are schematic diagrams showing a method for forming an STO film having a crystalline structure according to a third embodiment. [Figure 8] FIG. 1 is a first diffraction spectrum diagram showing the analysis results of the STO films according to the examples and the comparative examples by XRD. [Figure 9]1 is a graph showing a stacked structure of the STO film. [Figure 10] FIG. 10 is a second diffraction spectrum diagram showing the analysis results of the STO films according to the examples and comparative examples by XRD. [Figure 11] 1 is a first electron microscope photograph of the surface of an STO film according to an example and a comparative example. [Figure 12] 10 is a second electron microscope photograph of the surface of the STO film according to the example and the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment First, a method for forming an STO film having a crystalline structure (hereinafter also referred to as a "crystalline STO film") according to the present disclosure will be described with reference to FIG. 1(a) and 1(b) show a schematic diagram of a laminated structure of films formed on a semiconductor wafer (hereinafter referred to as "wafer") W, which is a substrate, during the process of forming, for example, a DRAM. Note that structures such as trenches and via holes formed in the wafer W are omitted from FIGS. 1, 6, and 7.

[0010] 1(a), a wafer W on which a crystalline STO film is to be formed has a silicon oxide film (SiO film) 82 as an underlayer film laminated on the upper surface of a main body of a silicon wafer 81, and a titanium nitride film (TiN film) 83 for making contact with the silicon wafer 81 through trenches and via holes (not shown). A crystalline STO film 85, which is an ultra high-k film, is formed on the upper surface of this TiN film 83.

[0011] Here, a known method for obtaining the crystalline STO film 85 is to form an amorphous STO film (hereinafter also referred to as "amorphous STO film") on a wafer W to be formed, and then convert the wafer W into a crystalline STO film by heat treating (annealing) the wafer W.

[0012] On the other hand, the inventors of the present disclosure have found that, unlike ordinary metals, a crystalline STO film may not be formed even if an amorphous STO film is formed on the upper surface of the TiN film 83 and then heat treatment is performed, as will be shown in experimental results in Examples described later. In this case, a possible method is to laminate an amorphous STO film on the upper surface of the amorphous STO film after the heat treatment and then perform heat treatment to obtain a crystalline STO film in the region not in contact with the TiN film 83. However, it has been found that even if a crystalline STO film is obtained by this method, irregularities called blisters may be formed on the surface of the crystalline STO film.

[0013] The reason why a crystalline STO film cannot be obtained even after heat treatment is not clear. Regarding this point, the inventors speculated that a high titanium content near the interface between the TiN film 83 and the amorphous STO film creates conditions that make it difficult for STO crystals to grow.

[0014] 1(a), in the method for forming a crystalline STO film according to the first embodiment, a strontium oxide film (SrO film) 84 is formed on the surface of a TiN film 83 without adding titanium (a process for forming an amorphous STO film). Thereafter, the wafer W on which the SrO film 84 has been formed is heat-treated, and titanium is diffused from the TiN film 83 into the SrO film 84 to obtain a crystalline STO film 85 (a process for obtaining a crystalline STO film, FIG. 1(b)).

[0015] For example, when a crystalline STO film 85 having a thickness in the range of 1 nm to 5 nm is to be obtained, it is preferable to form the SrO film 84 having a thickness in the range of 2 nm to 10 nm. The heat treatment is carried out in an inert gas atmosphere such as argon (Ar) gas or nitrogen (N2) gas at a temperature within a range of 500 to 700°C, for example, 630°C, for a period within a range of 5 minutes to 1 hour, for example, 1 hour.

[0016] Hereinafter, the configuration of an apparatus (film forming apparatus 1) for performing the above-mentioned process and forming the crystalline STO film 85 will be described with reference to FIGS. The film forming apparatus 1 is configured as, for example, a multi-chamber vacuum processing apparatus. As shown in Fig. 2, the film forming apparatus 1 includes an atmospheric pressure transfer chamber 22 in which an atmospheric pressure atmosphere is maintained using, for example, Ar gas. A load port 21 is installed in front of the atmospheric pressure transfer chamber 22 to transfer the wafer W to, for example, a carrier C accommodating the wafer W. A door 27 is installed on the front wall of the atmospheric pressure transfer chamber 22 and is opened when the wafer W is transferred to or from the carrier C. A transfer arm 25 for transferring the wafer W is also installed inside the atmospheric pressure transfer chamber 22. An alignment chamber 26 for adjusting the orientation and eccentricity of the wafer W is also installed on the left wall of the atmospheric pressure transfer chamber 22 as viewed from the load port 21 side.

[0017] A load lock chamber 23 is connected to the wall of the atmospheric pressure transfer chamber 22 on the opposite side of the load port 21. The load lock chamber 23 has a function of switching the internal atmosphere between an atmospheric pressure atmosphere and a vacuum atmosphere while accommodating a wafer W. As viewed from the atmospheric pressure transfer chamber 22 side, for example, two load lock chambers 23 are arranged side by side on the left and right. As viewed from the atmospheric pressure transfer chamber 22, a vacuum transfer chamber 24 is arranged at the rear of these load lock chambers 23. The atmospheric pressure transfer chamber 22 and the vacuum transfer chamber 24 are connected to each load lock chamber 23 via a gate valve 29.

[0018] Connected to the vacuum transfer chamber 24 are a film formation module (film formation section) 101 that forms an SrO film 84 on the upper surface of a TiN film 83 formed on the wafer W, and a heat treatment module (heat treatment section) 102 that performs heat treatment on the wafer W after the SrO film 84 has been formed, to form a crystalline STO film 85 at the interface between the TiN film 83 and the SrO film 84. In this example, two film formation modules 101 and two heat treatment modules 102 are connected to the vacuum transfer chamber 24. A transfer arm 28 is provided in the vacuum transfer chamber 24, and this transfer arm 28 transfers the wafer W between each of the load lock chambers 23, the film formation module 101, and the heat treatment module 102.

[0019] Next, a configuration example of a film formation module 101 for forming an SrO film 84 on the upper surface side of a TiN film 83 by ALD (Atomic Layer Deposition), which is an atomic layer deposition method, will be described (FIG. 3). For convenience of explanation, the film formation module 101 shown in FIG. 3 is configured so that it can also form an Sr-rich STO film 86 and an STO upper layer film 87 described in the second and third embodiments. The formation of the SrO film 84 differs from the formation of the Sr-rich STO film 86 or the STO upper layer film 87 in that the Ti raw material gas supply unit 62 for supplying titanium (Ti) raw material gas is omitted or the Ti raw material gas supply unit 62 is not used. In the following explanation, the configuration of the film formation module 101 will be described, including the Ti raw material gas supply unit 62.

[0020] The film forming module 101 includes a processing chamber 30 for accommodating a wafer W, and a loading / unloading port 31 that can be opened and closed by the gate valve 29 described above is formed on the side of the processing chamber 30.

[0021] An exhaust duct 32, for example, having a circular shape, is disposed at the upper part of the sidewall of the processing vessel 30. Furthermore, a top plate 33 is provided on the upper surface of the exhaust duct 32 so as to close the upper opening of the processing vessel 30. The processing vessel 30 is connected to a vacuum exhaust unit 35, which is, for example, a vacuum pump, via a vacuum exhaust path 34 connected to an exhaust port 331 of the exhaust duct 32. An APC (Auto Pressure Controller) valve 36, which adjusts the pressure inside the processing vessel 30, is disposed in the vacuum exhaust path 34.

[0022] A mounting table 4 that horizontally supports a wafer W is provided inside the processing vessel 30. A heater 41 for heating the wafer W is embedded in the mounting table 4. The mounting table 4 is connected to a lifting mechanism 44 via support posts 43 and can be raised and lowered by the lifting mechanism 44. In FIG. 3, the mounting table 4 that has been moved to a transfer position for the wafer W is shown by a dashed line. In the figure, reference numeral 45 denotes support pins for transferring the wafer W, and the support pins 45 can be raised and lowered by a lifting mechanism 46. Reference numeral 42 denotes through holes for the support pins 45, and reference numerals 47 and 48 denote bellows that expand and contract in accordance with the lifting and lowering movements of the mounting table 4 and the support pins 45, respectively.

[0023] The film formation module 101 is provided with a shower head 5 facing the mounting table 4 to supply a processing gas into the processing chamber 30. The shower head 5 has a gas diffusion space 51 therein, and its lower surface is configured as a shower plate 52 with a large number of gas discharge holes 53 formed therein. A gas supply system 6 is connected to the gas diffusion space 51 via a gas introduction hole 54.

[0024] The gas supply system 6 includes an Sr raw material gas supply unit 61 for supplying strontium (Sr) raw material gas toward the processing vessel 30, a Ti raw material gas supply unit 62 for supplying Ti raw material gas, and an oxidation gas supply unit 63 for supplying an oxidation gas that oxidizes the Sr raw material and the Ti raw material.

[0025] The Sr raw material supplied from the Sr raw material gas supply unit 61 is a compound containing strontium, such as Sr(Me5Cp)2 (bispentamethylcyclopentadienylstrontium) or Sr(THD)2 (strontium bistetramethylheptanedionato).The Ti raw material supplied from the Ti raw material gas supply unit 62 is a compound containing titanium, such as Ti(Me5Cp)(MeO)3 (pentamethylcyclopentadienyltitanium trimethoxide) or Ti(Me5Cp)(NMe2)3 (methylcyclopentadienyltrisdimethylaminotitanium). In this example, highly reactive ozone (O3) gas is used as the oxidizing gas. Note that, for example, a remote plasma obtained by ionizing oxygen gas may be supplied as the oxidizing gas.

[0026] The Sr raw material gas supply unit 61 includes a gas supply source 64 for supplying a strontium (Sr) raw material gas and a gas supply path 641. The Sr raw material gas supply source 64 has a function of vaporizing or sublimating the Sr raw material described above by bringing it into contact with a carrier gas and supplying it as a raw material gas. For example, the strontium gas supply path 641 is provided with, in order from the upstream side, a flow rate regulator 642, a storage tank 643, and a valve V1.

[0027] The Ti raw material gas supply unit 62 includes a gas supply source 65 for supplying a Ti raw material gas and a gas supply path 651. The Ti raw material gas supply source 65 has a function of vaporizing or sublimating the Ti raw material described above by bringing it into contact with a carrier gas and supplying it as a raw material gas. For example, the titanium gas supply path 651 is provided with, in order from the upstream side, a flow rate adjuster 652, a storage tank 653, and a valve V2.

[0028] The oxidizing gas supply unit 63 includes an O gas supply source 66 for supplying the oxidizing gas and a gas supply path 661. For example, the O gas supply path 661 is provided with, in order from the upstream side, a flow rate regulator 662, a storage tank 663, and a valve V3.

[0029] These Sr source gas, Ti source gas, and O3 are temporarily stored in storage tanks 643, 653, and 663, respectively, and are pressurized to a predetermined pressure before being supplied to the film formation module 101. The supply and stop of each gas from the storage tanks 643, 653, and 663 to the film formation module 101 is controlled by opening and closing valves V1, V2, and V3.

[0030] Furthermore, the gas supply system 6 includes an inert gas supply unit that supplies an inert gas, such as Ar gas, to the film formation module 101. The inert gas supply unit in this example includes Ar gas supply sources 67, 68, and 69 and Ar gas supply paths 671, 681, and 691.

[0031] In this example, the Ar gas supplied from Ar gas supply source 67 of Sr raw material gas supply unit 61 is a purge gas for the Sr raw material gas. This Ar gas supply source 67 is connected via Ar gas supply path 671 to the downstream side of valve V1 provided on the above-mentioned Sr raw material gas supply path 641. Furthermore, the Ar gas supplied from Ar gas supply source 68 of Ti raw material gas supply unit 62 is a purge gas for the Ti raw material gas. This Ar gas supply source 68 is connected via Ar gas supply path 681 to the downstream side of valve V2 provided on Ti raw material gas supply path 651.

[0032] Furthermore, the Ar gas supplied from the Ar gas supply source 69 of the oxidizing gas supply unit 63 is a purge gas for the oxidizing gas. The Ar gas supply source 69 is connected via an Ar gas supply path 691 to the downstream side of a valve V3 provided in the O gas supply path 661. In FIG. 3, reference numerals 672, 682, and 692 each indicate a flow rate adjusting unit, and reference numerals V4, V5, and V6 each indicate a valve.

[0033] When an SrO film 84 (or a Sr-rich STO film 86 described later) is formed on the upper surface of a TiN film 83 using the film formation module 101 shown in FIG. 3, the Sr raw material gas supply unit 61 corresponds to the first raw material gas supply unit, and the Ti raw material gas supply unit 62 corresponds to the second raw material gas supply unit.

[0034] Next, the configuration of the heat treatment module 102 will be described with reference to Fig. 4. In Fig. 4, components having the same functions as those in the film formation module 101 described with reference to Fig. 3 are denoted by the same reference numerals as those used in Fig. 3, and duplicated descriptions may be omitted.

[0035] As shown in FIG. 4, the heat treatment module 102 includes a processing vessel 30, a mounting table 4a on which a wafer W to be processed is placed, and a shower head 5 provided on the ceiling surface side of the processing vessel 30 so as to face the mounting table 4a.

[0036] In this embodiment, the mounting table 4a is fixedly disposed on the bottom plate of the processing chamber 30. A wafer W having an SrO film 84 formed thereon in the film formation module 101 is placed on the mounting table 4a. A plurality of support pins (not shown) configured to be able to move up and down are provided inside the mounting table 4a, and the wafer W is transferred by projecting and retracting these support pins from the upper surface of the mounting table 4a.

[0037] A heater 41 is provided inside the mounting table 4a to heat the wafer W to a temperature within a range of 500 to 700° C., for example, to 630° C. A plurality of exhaust ports 331 for exhausting the inside of the processing chamber 30 are formed in the bottom plate around the mounting table 4a.

[0038] An inert gas supply unit 60 is connected to the shower head 5 to supply Ar gas, which is an example of an inert gas, to the processing chamber 30. The inert gas supply unit 60 includes an Ar inert gas supply source 600 and a gas supply path 601. For example, a flow rate regulator 602 and a valve V7 are provided in the Ar gas supply path 601 in this order from the upstream side.

[0039] The film forming apparatus 1 having the above-described configuration includes a control unit 100 as shown in FIG. 2. The control unit 100 is configured with a computer including a storage unit, a memory, and a CPU that stores a program. The program contains instructions (steps) for outputting control signals from the control unit 100 to each unit of the film forming apparatus 1 and executing the formation of the SrO film 84 on the wafer W and the subsequent heat treatment. The program is stored in a storage unit of the computer, such as a flexible disk, compact disk, hard disk, MO (magneto-optical disk), or nonvolatile memory, and is read from the storage unit and installed in the control unit 100.

[0040] The operation of the film forming apparatus 1 having the above-described configuration will be described. First, a carrier C containing a plurality of wafers W is transferred to the load port 21 of the film forming apparatus 1. An SiO film 82, as shown in the schematic diagram of FIG. 1(a), is formed on the upper surface of each wafer W. The wafer W is removed from the carrier C by the transfer arm 25, and transferred into the alignment chamber 26 via the atmospheric pressure transfer chamber 22. After alignment, the wafer W is transferred into the vacuum transfer chamber 24 via the load lock chamber 23.

[0041] Next, the wafer W is transferred by the transfer arm 28 to the film formation module 101, where an SrO film 84 is formed by the ALD method. The wafer W transferred into the processing chamber 30 is placed on the mounting table 4, and heating of the wafer W is initiated by raising the temperature of the heater 41 to a temperature within a range of 250 to 400°C. Simultaneously with this heating operation, Ar gas is supplied into the processing chamber 30 from Ar gas supply sources 67, 68, and 69 at preset flow rates. Then, the vacuum exhaust unit 35 evacuates the processing chamber 30, and the opening of the valve 36 is adjusted so that the interior of the processing chamber 30 reaches a target pressure.

[0042] Next, a step of forming an SrO film 84 is performed based on the film formation sequence of Fig. 5. When forming the SrO film 84, only the cycle of steps 1 to 4 (first cycle) shown in Fig. 5 is performed. On the other hand, the cycle of steps 5 to 8 (second cycle) is not performed. First, valve V1 is opened to supply Sr raw material gas, and Ar gas is supplied from Ar gas supply sources 67, 68, and 69 at preset flow rates (step 1). By this process, the Sr raw material is adsorbed onto the entire surface of wafer W.

[0043] Next, the valve V1 is closed to stop the supply of the Sr source gas, while continuing to supply Ar gas from the Ar gas supply sources 67, 68, and 69. In this manner, purging with Ar gas is performed to remove the Sr source gas remaining in the processing vessel 30 (Step 2).

[0044] Next, while continuing to supply Ar gas from Ar gas supply sources 67, 68, and 69, valve V3 is opened to supply O3, an oxidizing gas. This process causes the Sr raw material adsorbed on wafer W to react with O3, forming a thin film of SrO (step 3). Note that when the Sr raw material is composed of an organometallic compound, as in the example of the Sr raw material described above, the thin film of SrO may contain a component containing carbon (e.g., SrCO3). Subsequently, valve V3 is closed to stop the supply of O3, while Ar gas is continuously supplied from Ar gas supply sources 67, 68, and 69 to perform purging with Ar gas and remove O3 remaining in processing vessel 30 (step 4).

[0045] Thus, in the process of forming the SrO film 84, the Sr source gas and the oxidizing gas are alternately supplied while supplying Ar gas, which is an inert gas, into the processing chamber 30, and steps 1 to 4 are repeated a set number of times to form the SrO film 84 with a desired thickness. The thickness of the SrO film 84 can be, for example, 10 nm, which is within the range of 2 nm to 10 nm.

[0046] After the formation of the SrO film 84 is completed, the wafer W is unloaded from the film-forming module 101 and loaded into the heat treatment module 102, where a step of obtaining a crystalline STO film 85 is carried out. That is, after the wafer W is placed on the mounting table 4a of the film forming module 101, the gate valve 29 is closed, and while the processing chamber 30 is being evacuated, Ar gas is supplied from the inert gas supply unit 60 to adjust the pressure inside the processing chamber 30 to a preset level. In addition, power is supplied to the heater 41 from a power supply unit (not shown), and the wafer W on the mounting table 4a is heated to a temperature within a range of 500 to 700°C, for example, to 630°C.

[0047] By forming the SrO film 84 on the upper surface side of the TiN film 83, titanium diffuses from the TiN film 83 side to the SrO film 84 side due to the difference in titanium concentration. The diffusion of titanium is promoted by heating the wafer W. On the other hand, even if titanium moves to the SrO film 84 side due to diffusion, the titanium concentration is lower than that of a conventional amorphous STO film, and may not be so high as to prevent crystallization of the region containing strontium, titanium, and oxygen.

[0048] Therefore, by performing a heat treatment on the wafer W having the SrO film 84 formed on the TiN film 83, crystallization can be promoted in the region where titanium has diffused toward the SrO film 84 at the interface between the TiN film 83 and the SrO film 84. As a result, a crystalline STO film 85 can be obtained as shown in FIG.

[0049] For example, to obtain a crystalline STO film 85 having a thickness in the range of 1 nm to 5 nm at the aforementioned heating temperature, the heat treatment is performed for a treatment time in the range of 5 minutes to 1 hour. Note that the SrO film 84 remaining on the upper surface of the crystalline STO film 85 may be removed by etching or CMP (Chemical Mechanical Polishing) after the wafer W is removed from the film forming apparatus 1.

[0050] After the wafer W has been heat-treated for a preset time in the heat treatment module 102, the wafer W is removed from the heat treatment module 102 and transported through the vacuum transfer chamber 24, the load lock chamber 23, and the atmospheric pressure transfer chamber 22 in the opposite direction to the route taken when the wafer W was loaded, and the processed wafer W is then placed back into the original carrier C.

[0051] According to the film forming apparatus 1 of the present disclosure, a titanium-free SrO film 84 is formed on the upper surface of the TiN film 83, and then a heat treatment is performed on the wafer W. As a result, an excessive increase in the titanium content at the interface between the TiN film 83 and the SrO film 84 is suppressed, and a crystalline STO film 85 can be formed on the upper surface of the TiN film 83, where it has been difficult to crystallize an amorphous STO film in the past.

[0052] 1(a) and 1(b), the film formed on the upper surface of the TiN film 83 to obtain the crystalline STO film 85 is not limited to the titanium-free SrO film 84. For example, it may be a strontium (Sr)-rich STO film in which the titanium content (based on the atomic number) relative to strontium is relatively low. The structure of the Sr-rich STO film will be exemplified in the second embodiment described below.

[0053] <Second embodiment> 6 is a schematic diagram showing a method for forming a crystalline STO film 85 according to the second embodiment. In the second embodiment, an SrO film 84a (or an Sr-rich STO film 86) is formed to a thickness in the range of 5 nm to 10 nm, which is close to the thickness of the crystalline STO film 85 formed on the upper surface of the TiN film 83. Then, the entire SrO film 84a (or the Sr-rich STO film 86) is converted into the crystalline STO film 85 by heat treatment, which is different from the first embodiment in that the interface region of the SrO film 84 with the TiN film 83 is crystallized.

[0054] The SrO film 84a shown in FIG. 6(a-1) is formed by the same method as in the first embodiment, except that the SrO film 84a has a thickness in the range of 5 nm to 10 nm, as compared with the SrO film 84 shown in FIG. 1(a) (for example, a thickness of 2 nm to 10 nm). Furthermore, as long as the time required for the heat treatment to be performed is sufficient to convert the entire SrO film 84a into the crystalline STO film 85, there is no change in the heat treatment method from the first embodiment.

[0055] If the thickness of the titanium diffused from the TiN film 83 is within a range that allows it to be distributed throughout the entire SrO film 84a in the thickness direction, the entire SrO film 84a can be converted into a crystalline STO film 85 by the same mechanism as in the example described in the first embodiment.

[0056] Furthermore, the film that can be converted into the crystalline STO film 85 by heat treatment is not limited to the titanium-free SrO film 84. Fig. 6(a-2) shows an example in which an Sr-rich STO film 86 having a relatively low titanium to strontium content is formed on the upper surface side of a TiN film 83. The Sr-rich STO film 86 is formed so that the atomic ratio of titanium to strontium is greater than 0 and less than 1.0, preferably greater than 0 and 0.7 or less. The thickness range of the Sr-rich STO film 86 is the same as that of the SrO film 84a described above.

[0057] The Sr-rich STO film 86 can be formed by performing all of steps 1 to 8 of the film formation sequence shown in FIG. 5 using the film formation module 101 (provided with the Ti raw material gas supply unit 62) described with reference to FIG. 3.

[0058] That is, to form the Sr-rich STO film 86, the cycle of steps 1 to 4 described above is performed to form a thin SrO film. Next, the cycle of supplying a Ti source gas, adsorbing the Ti source onto the wafer W (step 5), stopping the supply of the Ti source gas, purging the processing chamber 30 (step 6), supplying an oxidizing gas (O) (step 7), stopping the supply of the Ti source gas, and purging the processing chamber 30 (step 8) is performed to form a thin TiO film. The cycle of steps 1 to 4 (first cycle) and the cycle of steps 5 to 8 (second cycle) are then alternately repeated multiple times. This allows the Sr-rich STO film 86 to have a desired thickness. In FIG. 5, the number of times the first cycle and the second cycle are alternately repeated is indicated as "Z."

[0059] The titanium to strontium content ratio in the Sr-rich STO film 86 is adjusted by changing the ratio between the number of times the first cycle is performed (denoted as "X" in FIG. 5) and the number of times the second cycle is performed (denoted as "Y" in FIG. 5).

[0060] Specifically, a preliminary experiment is conducted to change the ratio "X:Y" of these cycles, and the composition of the amorphous STO film obtained is analyzed (e.g., by secondary ion mass spectrometry, etc.).Then, the number of cycles X and Y corresponding to the desired titanium to strontium content ratio (based on the atomic number) within the range of greater than 0 and less than 1.0 are adopted as the film formation conditions for the actual Sr-rich STO film 86.

[0061] As with the SrO film 84a shown in FIG. 6(a-1), the Sr-rich STO film 86 formed by the above-described method can be entirely converted into a crystalline STO film 85 by heat treatment using the heat treatment module 102.

[0062] <Third embodiment> If a crystalline STO film 85 can be formed on the upper surface of the TiN film 83 by the method described in the first or second embodiment, it is possible to form a thicker crystalline STO film by utilizing this crystalline STO film 85 as a barrier for the TiN film 83. The third embodiment shown in Figures 7(a) to 7(d) shows an example in which a crystalline STO film is formed by this method.

[0063] 7(a) and (b) are re-drawings of Figures 6(a-1) and (b), respectively, and show an example in which an SrO film 84a is formed on the upper surface of a TiN film 83, and then heat treatment is performed to obtain a crystalline STO film 85. Next, an amorphous STO upper film 87 is formed on the upper surface of this crystalline STO film 85 (Figure 7(c)).

[0064] The STO upper layer film 87 can be formed using a film formation module 101 including the Ti source gas supply unit 62 described with reference to FIG. 3. The film formation module 101 that forms the STO upper layer film 87 corresponds to the upper layer film formation unit in this example. As the upper layer film formation unit, the film formation module 101 that is common to those that form the SrO film 84 according to the first embodiment, the SrO film 84a according to the second embodiment, and the Sr-rich STO film 86 may be used. Furthermore, a film formation module 101 different from the film formation modules 101 that form these films 84, 84a, and 86 may be connected to the vacuum transfer chamber 24.

[0065] The STO upper layer film 87 is formed to a thickness of 3 nm or more and 30 nm or less, which is thicker than the crystalline STO film 85. The STO upper layer film 87 can also have a titanium to strontium atomic ratio of 1.0 or more. Because the STO upper layer film 87 is not in direct contact with the TiN film 83, the strontium to titanium atomic ratio is not limited to the range of 0 to less than 1.0, and can be more freely adjusted. For example, if the range of the ratio close to 1.0 or 1.0 or more includes conditions for obtaining a crystalline STO film with a higher dielectric constant, a high-quality STO upper layer film 87 can be formed without being restricted by the requirement for forming the crystalline STO film 85 on the TiN film 83. In such a case, the STO upper layer film 87 preferably has a titanium to strontium atomic ratio of 0.8 to 1.2.

[0066] The STO upper layer film 87 formed by the above-described method can also be converted into a crystalline STO film 88 by heat treatment using a heat treatment module 102. As the upper layer film heat treatment section that performs the heat treatment on the STO upper layer film 87, the same heat treatment module 102 that performs the heat treatment on the SrO film 84 according to the first embodiment, or the SrO film 84a and Sr-rich STO film 86 according to the second embodiment may be used. Alternatively, a heat treatment module 102 separate from the heat treatment modules 102 that form these films 84, 84a, and 86 may be connected to the vacuum transfer chamber 24.

[0067] In the first to third embodiments described above, the film formation module 101 and the heat treatment module 102, which are single-wafer processing modules, are connected to a common vacuum transfer chamber 24. Meanwhile, the process of forming amorphous films (SrO films 84, 84a, and Sr-rich STO film 86) and the process of converting these films 84, 84a, and 86 into a crystalline STO film 85 by heat treatment are not limited to being performed in a common film formation apparatus 1. For example, the amorphous film formation and the heat treatment may be performed separately using a batch processing apparatus in which a boat holding a large number of wafers W is accommodated in a heating furnace. Regarding the heat treatment, the wafers W may be heated for a processing time shorter than the aforementioned five minutes using, for example, an RTA (Rapid Thermal Annealing) apparatus using infrared lamps. Alternatively, for forming an amorphous film, a semi-batch type film forming apparatus may be used in which a plurality of wafers W are placed on a rotary table, and the wafers W are revolved around a rotary shaft and passed through a plurality of processing spaces partitioned from one another to repeatedly perform the adsorption of source gases and the formation of thin films of SiO or TiO using oxidizing gases.

[0068] On the other hand, for example, another module, such as a module for forming a TiN film 83, may be connected to the vacuum transfer chamber 24 of the film forming apparatus 1 shown in Fig. 2. In this case, it becomes possible to form a laminated structure of multiple types of films on the wafer W in a common film forming apparatus 1.

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

[0070] (Experiment 1) Corresponding to the first embodiment, an SrO film 84 was formed on the upper surface of the TiN film 83 described with reference to FIG. 1, and the difference in film structure depending on whether or not heat treatment was performed was confirmed. A. Experimental Conditions Example 1: A 10-nm-thick TiN film 83 was formed on a wafer W, and a 10-nm-thick SrO film 84 was formed on the upper surface thereof by the ALD method based on steps 1 to 4 of FIG. 5. A cyclopentadienyl-based strontium compound was used as the Sr source, and the wafer W was heated to 350°C. Thereafter, the wafer W was heated to 600°C in an argon gas supply atmosphere (pressure 400 Pa (3 Torr)), and heat-treated for 1 hour. After the heat treatment, the wafer W was subjected to crystal structure analysis by XRD (X-ray diffraction) and cross-sectional observation by TEM (Transmission Electron Microscope). Comparative Example 1 After the SrO film 84 was formed, the same analysis as in Example 1 was carried out on a wafer W that had not been subjected to heat treatment.

[0071] B. Experimental Results The results of the XRD analysis for Example 1 and Comparative Example 1 are shown in Figure 8. The horizontal axis of Figure 8 represents the X-ray diffraction angle, and the vertical axis represents the detected X-ray intensity. Figure 9 also shows a stacked bar graph of the thickness of each layer in the stacked structure of the TiN film 83, SrO film 84, and crystalline STO film 85 based on the results of TEM observation.

[0072] 8, in Example 1, in which heat treatment was performed after the formation of the SrO film 84, X-ray diffraction peaks were confirmed at diffraction angles corresponding to the crystal planes of the crystalline STO. This suggests that a crystalline STO film 85 is formed by performing heat treatment on the wafer W after the SrO film 84 is formed on the upper surface of the TiN film 83. On the other hand, in Comparative Example 1, no diffraction peaks corresponding to the crystalline STO were confirmed.

[0073] 9, it was confirmed that in Example 1, a layer with a thickness of about 6 nm was formed between the TiN film 83 and the SrO film 84. This layer can be understood to correspond to the crystalline STO film 85, which showed a diffraction peak corresponding to the crystal plane of the crystalline STO in the XRD analysis. On the other hand, the TEM observation of Comparative Example 1 also showed that a thin layer of about 3.5 nm was formed between the TiN film 83 and the SrO film 84. However, considering that no diffraction peak corresponding to the crystal plane of crystalline STO was confirmed in the XRD analysis, this can be understood as a mixed amorphous layer of SrO and SiN formed during the deposition of the SrO film 84.

[0074] (Experiment 2) Corresponding to the second embodiment, the film type formed on the upper surface of the TiN film 83 described with reference to FIG. 6 was changed to confirm the difference in film structure after heat treatment. A. Experimental Conditions (Example 2-1) An SrO film 84a was formed under the same conditions as in Example 1, except that the thickness was set to 5 nm. Thereafter, the wafer W was heated to 630°C in an argon gas supply atmosphere (pressure 400 Pa (3 Torr)) and subjected to heat treatment for 1 hour. After the heat treatment, the wafer W was subjected to crystal structure analysis by XRD and surface observation by SEM (Scanning Electron Microscope). (Example 2-2) Instead of the SrO film 84a, an Sr-rich STO film 86 having a titanium to strontium ratio of 9.4 (first cycle execution count X:first cycle execution count Y=10:1) was formed by the ALD method based on cycles 1 to 8 of Fig. 5. This wafer W was subjected to the same analysis as in Example 2-1. Comparative Example 2-1: An amorphous STO film having a titanium to strontium ratio of 1.0 (first cycle execution count X:first cycle execution count Y=2:3) was formed by the same method as in Example 2-1. This wafer W was subjected to the same heat treatment and analysis as in Example 2-1.

[0075] B. Experimental Results The results of the XRD analysis for Examples 2-1 and 2-2 and Comparative Example 2-1 are shown in Figure 10. The horizontal and vertical axes in Figure 10 are the same as those in Figure 8. SEM photographs of the surfaces of the wafers W are shown in Figures 11(a) to 11(c).

[0076] 10, diffraction peaks corresponding to crystalline STO were confirmed in both Example 2-1, in which a 5-nm-thick SrO film 84a was formed, and Example 2-2, in which a 5-nm-thick Sr-rich STO film 86 was formed. The results of this XRD analysis show that these films 84a and 86 were converted into a crystalline STO film 85. On the other hand, in Comparative Example 2-1, which had a high titanium content, no diffraction peaks corresponding to crystalline STO were confirmed.

[0077] 11(a) and 11(b) show that the crystalline STO films 85 according to Examples 2-1 and 2-2, which were obtained by heat-treating the SrO film 84a and the Sr-rich STO film 86, respectively, had flat surfaces. On the other hand, according to FIG. 11(c), numerous protrusions called blisters were formed on the surface of the wafer W according to Comparative Example 2-2, which was obtained by heat-treating amorphous STO having a titanium to strontium ratio of 1.0. These blisters are caused by partial peeling of the amorphous STO film, and are undesirable because they can accelerate film peeling and cause deterioration of film properties, such as a decrease in the dielectric constant.

[0078] (Experiment 3) In accordance with the third embodiment, the type of film formed on the lower surface side of the STO upper layer film 87 described with reference to FIG. 7 was changed to confirm the difference in film structure after heat treatment. A. Experimental Conditions Example 3-1: An STO upper layer film 87 having a thickness of 20 nm and a titanium to strontium content ratio of 1.0 was formed on the upper surface of a crystalline STO film 85 formed by the method described in Example 2-2. The method for forming the STO upper layer film 87 was the same as in Comparative Example 2-1. After the STO upper layer film 87 was formed, the wafer W was heated to 630°C in an argon gas supply atmosphere (pressure 400 Pa (3 Torr)) and subjected to a heat treatment for 1 hour. The surface of the wafer W after the heat treatment was observed by SEM. Comparative Example 3-1 An amorphous STO film having a titanium to strontium ratio of 1.0 formed by the method described in Comparative Example 2-1 was heat-treated, and then an STO upper layer film 87 was formed on the upper surface thereof. The STO upper layer film 87 was then formed and heat-treated under the same conditions as in Example 3-1, except that the STO upper layer film 87 was then formed on the upper surface thereof. The surface was then observed by SEM.

[0079] B. Experimental Results 12(a) and 12(b) show SEM photographs of Example 3-1 and Comparative Example 3-1, respectively. In both experimental results, it was confirmed by XRD analysis that a crystalline STO film 88 was formed after the heat treatment of the STO upper layer film 87. 12(a), it can be confirmed that when an STO upper layer film 87 is formed on the upper surface of the flat crystalline STO film 85 shown in Fig. 11(b), the surface of the crystalline STO film 88 after the heat treatment is also flat. On the other hand, according to the result shown in Fig. 12(b), it was found that when an STO upper layer film 87 is formed on the surface of the film having blisters shown in Fig. 11(c), blisters are also formed on the surface of the crystalline STO film 88 after the heat treatment. [Explanation of symbols]

[0080] W wafer 1 Film deposition equipment 101 Deposition module 102 Heat Treatment Module 83 TiN film 84 SrO film 85 Crystalline STO film

Claims

1. A method for forming a film having a crystalline structure containing strontium, titanium, and oxygen on a substrate, comprising: forming an amorphous film containing strontium and oxygen on the upper surface of the titanium nitride film formed on the surface of the substrate, the titanium content being adjusted so that the ratio of the titanium to the strontium content based on the atomic number is a value within the range of 0 or more and less than 1.0; heating the substrate on which the amorphous film has been formed at a temperature of 500° C. or higher to obtain a crystalline film containing titanium diffused from the titanium nitride film and containing strontium, titanium, and oxygen; In the step of forming the film, the amorphous structure film is formed to a thickness in the range of 5 nm or more and 10 nm or less; In the step of obtaining a film having a crystalline structure, the film having an amorphous structure is converted into a film having a crystalline structure, forming an amorphous upper layer film containing strontium, titanium, and oxygen on the upper surface of the crystalline film after the step of obtaining the crystalline film; Then, the substrate on which the upper layer film has been formed is heated at a temperature of 500°C or higher to convert the upper layer film into a film having a crystalline structure containing the strontium, titanium, and oxygen.

2. The method according to claim 1 , wherein the amorphous upper film is formed to a thickness of 3 nm or more.

3. 3. The method according to claim 1, wherein the upper layer film having an amorphous structure has a titanium to strontium atomic ratio of 0.8 to 1.

2.

4. An apparatus for forming a film having a crystalline structure containing strontium, titanium, and oxygen on a substrate, comprising: a film forming unit that forms an amorphous film on the upper surface of the titanium nitride film formed on the surface of the substrate, the film containing strontium and oxygen, and the titanium content adjusted so that the atomic ratio of titanium to strontium is within a range of 0 or more and less than 1.0; a heat treatment unit that heats the substrate on which the amorphous structure film has been formed at a temperature of 500° C. or higher to obtain a crystalline structure film containing titanium diffused from the titanium nitride film and containing strontium, titanium, and oxygen, In the heat treatment section, the amorphous film having a thickness in the range of 5 nm or more and 10 nm or less is formed, In the heat treatment section, the amorphous film is converted into the crystalline film by the heat treatment, an upper layer film forming unit that forms an amorphous upper layer film containing strontium, titanium, and oxygen on an upper surface of the crystalline film after the heat treatment in the heat treatment unit; and an upper layer film heat treatment section that heats the substrate on which the upper layer film has been formed at a temperature of 500°C or higher to convert the upper layer film into a film with a crystalline structure containing the strontium, titanium, and oxygen.

5. The film forming unit a processing vessel that accommodates the substrate on which the titanium nitride film is formed; a first source gas supply unit that supplies a strontium source gas containing strontium to the processing vessel; a second source gas supply unit that supplies a titanium source gas containing titanium to the processing vessel; an oxidation gas supply unit that supplies an oxidation gas that oxidizes the strontium source and the titanium source to the processing vessel, The device further comprises a control unit, the control unit is configured to output a control signal for repeatedly performing a first cycle including a step of supplying the strontium source gas from the first gas supply unit to the substrate in the processing vessel to cause the strontium source to be adsorbed onto the substrate, and then supplying an oxidation gas from the oxidation gas supply unit to the substrate to oxidize the strontium source; and a second cycle including a step of supplying the titanium source gas from the second gas supply unit to cause the titanium source to be adsorbed onto the substrate, and then supplying the oxidation gas from the oxidation gas supply unit to the substrate to oxidize the titanium source; The apparatus according to claim 4 , wherein the content ratio of the amorphous structure in the film is adjusted by a ratio of the number of times the first cycle and the second cycle are performed.

6. The apparatus according to claim 4 , wherein the upper layer film has a thickness of 3 nm or more in the upper layer film forming section.

7. 7. The device according to claim 4, wherein the upper film of the amorphous structure has a titanium to strontium atomic ratio of 0.8 to 1.2.

Images