Patent Application
20190161853
The present invention relates to a method for forming a tungsten film.
In manufacturing Large Scale Integration (LSI) technology, tungsten is widely used in a gate electrode of a MOSFET (Metal Oxide Silicon Field Effect Transistor), contact between a source and a drain, a word line of a memory, and the like. In a multi-layer wiring process, copper wiring is mainly used. However, copper is insufficient in heat resistance and easily diffuses, so tungsten is used in regions requiring heat resistance, regions where electrical characteristics may deteriorate due to diffusion of copper, and the like.
A physical vapor deposition (PVD) method has been used for a tungsten film forming process. However, in a region that requires high step coverage, it may be difficult for the PVD method to achieve high step coverage. Therefore, film formation has been performed using a chemical vapor deposition (CVD) method capable of achieving high step coverage.
In a tungsten film (CVD-tungsten film) forming method using the CVD method, for example, a tungsten hexafluoride (WF6) gas as a source gas and H2 gas as a reducing gas are generally used to cause a reaction of WF6+3H2→W+6HF on a semiconductor wafer as a target substrate (see, e.g., Japanese Patent Application Publication Nos. 2003-193233 and 2004-273764).
In Japanese Patent Application Publication Nos. 2003-193233 and 2004-273764, before the main film formation of the tungsten film by the above reaction, a nucleation process is performed so that the tungsten film can be uniformly formed. At this time, an atomic layer deposition (ALD) method, in which a source gas and a reducing gas, e.g., SiH4 gas or B2H6 gas having a reducing power greater than that of H2 gas, are sequentially supplied with purging interposed therebetween, is employed to form a dense film.
Due to the recent progress of the miniaturization of semiconductor devices, the ALD method is also used for the main film formation of tungsten film (main tungsten film) to achieve higher step coverage.
However, in the case of forming the main tungsten film by a CVD method or an ALD method using tungsten hexafluoride (WF6) and H2 gas as a reducing gas, the formed tungsten film may not have sufficiently low resistance. Therefore, it is required to reliably make the formed tungsten film with sufficiently low resistance.
In view of the above, the present invention provides a tungsten film forming method capable of forming a tungsten film having low resistance.
In accordance with a first aspect of the present invention, there is provided a tungsten film forming method for forming a tungsten film on a surface of a substrate, the method comprising: disposing a substrate having an amorphous layer on a surface thereof in a processing chamber under a depressurized atmosphere; heating the substrate in the processing chamber; and forming a main tungsten film on the amorphous layer by supplying into the processing chamber WF6 gas as a tungsten source gas and H2 gas as a reducing gas.
In accordance with a second aspect of the present invention, there is provided a tungsten film forming method for forming a tungsten film on a surface of a substrate, the method comprising: disposing a substrate in a processing chamber under a depressurized atmosphere; heating the substrate in the processing chamber; forming an initial tungsten film that is an amorphous layer on the surface of the substrate by sequentially supplying into the processing chamber WF6 gas as a tungsten source gas and a reducing gas with purging of the processing chamber interposed therebetween; and forming a main tungsten film on the initial tungsten film by supplying into the processing chamber WF6 gas as a tungsten source gas and H2 gas as a reducing gas.
In the second aspect, the initial tungsten film may be formed by using B2H6 gas as the reducing gas. Further, the initial tungsten film may also be formed by using a gaseous mixture of B2H6 gas and SiH4 gas, or a gaseous mixture of B2H6 gas, SiH4 gas and H2 gas as the reducing gas.
In the second aspect, the tungsten film forming method may further comprise, before the forming the initial tungsten film that is the amorphous layer, performing an initiation process for facilitating the formation of the initial tungsten film that is the amorphous layer.
In accordance with a third aspect of the present invention, there is provided a tungsten film forming method for forming a tungsten film on a surface of a substrate, the method comprising: disposing a substrate in a processing chamber under a depressurized atmosphere; heating the substrate in the processing chamber; forming an initial tungsten film that is a crystalline layer on the surface of the substrate by sequentially supplying WF6 gas as a tungsten source gas and a reducing gas into the processing chamber with purging of the processing chamber interposed therebetween; forming an amorphous layer on the initial tungsten film; and forming a main tungsten film on the amorphous layer by supplying WF6 gas as a tungsten source gas and H2 gas as a reducing gas into the processing chamber.
In the third aspect, the initial tungsten film may be formed by using SiH4 gas as the reducing gas. Further, a gas containing a material of the amorphous layer may be a gaseous mixture of B2H6 gas and H2 gas, or a gaseous mixture of B2H6 gas, H2 gas and WF6 gas, and the amorphous layer may be an amorphous boron film or an amorphous tungsten film.
In the third aspect, the tungsten film forming method of claim 15 may further comprise, before the forming the initial tungsten film, performing an initiation process for facilitating the formation of the initial tungsten film on the surface of the substrate. The initiation process may be performed on the surface of the substrate by supplying SiH4 gas, or a gaseous mixture of SiH4 gas and H2 gas, or B2H6 gas, or a gaseous mixture of B2H6 gas and H2 gas.
In accordance with a fourth aspect of the present invention, there is provided a tungsten film forming method for forming a tungsten film on a surface of a substrate, the method comprising: disposing a substrate in a processing chamber under a depressurized atmosphere; heating the substrate in the processing chamber; forming an amorphous layer on the surface of the substrate; and forming a main tungsten film on the amorphous layer by supplying WF6 gas as a tungsten source gas and H2 gas as a reducing gas into the processing chamber.
In the fourth aspect, a gas for forming the amorphous layer may be SiH4 gas or B2H6 gas, or a gaseous mixture thereof, and the amorphous layer may be an amorphous silicon film or an amorphous boron film.
In the first to the fourth aspect, the substrate may have a TiN film on the surface thereof.
In accordance with a fifth aspect of the present invention, there is provided a tungsten film forming method for forming a tungsten film on a surface of a substrate, the method comprising: preparing a substrate; forming an amorphous layer on the surface of the substrate; heating the substrate in a processing chamber under a depressurized atmosphere; and forming a main tungsten film on the amorphous layer by supplying WF6 gas as a tungsten source gas and H2 gas as a reducing gas into the processing chamber.
In the fifth aspect, the tungsten film forming method may further comprise, before the forming the main tungsten film, performing an initiation process for facilitating the formation of the main tungsten film on the amorphous layer formed on the surface of the substrate. The forming the amorphous layer on the substrate and the forming the main tungsten film are performed in-situ. The substrate may have a TiSiN film on the surface thereof. The initiation process may be performed on the surface of the substrate by supplying SiH4 gas, or a gaseous mixture of SiH4 gas and H2 gas, or B2H6 gas, or a gaseous mixture of B2H6 gas and H2 gas.
In the first to the fifth aspect, the substrate may be heated is to a temperature of 300° C. to 500° C., particularly, a temperature of 350° C. to 450° C.
In the first to the fifth aspect, the main tungsten film may be formed by sequentially supplying WF6 gas as the tungsten source gas and H2 gas as the reducing gas into the processing chamber with purging of the processing chamber interposed therebetween.
In accordance with a sixth aspect of the present invention, there is provided a storage medium storing a program that is executed on a computer to control a film forming apparatus, wherein the program, when executed on the computer, controls the film forming apparatus to perform the tungsten film forming method of any one of the first to the fifth aspect.
In accordance with the present invention, by forming the main tungsten film on the amorphous layer, the number of nuclei of tungsten can be reduced and, thus, the crystal grain size can be increased. Further, the resistance of the tungsten film can be lowered.
As a result of extensive studies to achieve the above-mentioned objects, the present inventors have found that crystal grains of a main tungsten film can be increased by forming the main tungsten film on an amorphous film and the low resistance of the tungsten film can be achieved, and have conceived the present invention.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
<Example of Film Forming Apparatus>
As shown in
The chamber 1 is made of a metal such as aluminum or the like and has a substantially cylindrical shape. A loading/unloading port 11 for loading/unloading the wafer W is formed at the sidewall of the chamber 1. The loading/unloading port 11 can be opened and closed by a gate valve 12. An annular gas exhaust duct 13 having a rectangular cross section is provided on the main body of the chamber 1. A slit 13a is formed along the inner peripheral surface of the gas exhaust duct 13. A gas exhaust port 13b is formed at the outer wall of the gas exhaust duct 13. A ceiling plate 14 is provided on the upper surface of the gas exhaust duct 13 to block the upper opening of the chamber 1. A gap between the ceiling plate 14 and the gas exhaust duct 13 is hermetically sealed by a sealing ring 15.
The susceptor 2 is formed in a disc shape having a size corresponding to that of the wafer W, and is supported by a support member 23. The susceptor 2 is made of ceramic material such as aluminum nitride (AlN) or the like, or metal such as aluminum, a nickel-based alloy or the like. A heater 21 for heating the wafer W is embedded in the susceptor 2. The heater 21 is configured to generate heat by power supplied from a heater power supply (not shown). The temperature of the wafer W is controlled to a predetermined level by controlling the output of the heater 21 by a temperature signal of a thermocouple (not shown) provided near a wafer mounting surface on the upper surface of the susceptor 2.
A cover member 22 made of ceramic such as alumina or the like is provided at the susceptor 2 to cover the outer peripheral region of the wafer mounting surface and the side surface of the susceptor 2.
The support member 23 supporting the susceptor 2 extends downward from a center of a bottom surface of the susceptor 2 to a position below the chamber 1 while penetrating through a hole formed in a bottom portion of the chamber 1. The lower end of the support member 23 is connected to an elevating mechanism 24. The susceptor 2 can be raised and lowered by the elevating mechanism 24 between a processing position shown in
Three wafer supporting pins 27 (only two being shown) are provided near the bottom surface of the chamber 1 to protrude upward from an elevating plate 27a. The wafer supporting pins 27 can be lifted and lowered through the elevating plate 27a by an elevating mechanism 28 provided below the chamber 1. Further, the wafer supporting pins 27 can protrude beyond and retract below the top surface of the susceptor 2 while being inserted into through-holes 2a formed in the susceptor 2 positioned at the transfer position. By lifting and lowering the wafer support pins 27, the wafer W is transferred between a wafer transfer mechanism (not shown) and the susceptor 2.
The shower head 3 is made of metal and is provided to face the susceptor 2. The shower head 3 has substantially the same diameter as that of the susceptor 2. The shower head 3 has a main body 31 fixed to the ceiling plate 14 of the chamber 1, and a shower plate 32 connected to the bottom of the main body 31. A gas diffusion space 33 is formed between the main body 31 and the shower plate 32. A gas inlet hole 36 penetrating through the center portions of the main body 31 and the ceiling plate 14 of the chamber 1 is connected to the gas diffusion space 33. An annular protrusion 34 protruding downward is formed at the peripheral portion of the shower plate 32. Gas injection holes 35 are formed on the flat surface of the shower plate 32 inward of the annular protrusion 34.
In a state where the susceptor 2 is located at the processing position, a processing space 37 is formed between the shower plate 32 and the susceptor 2. In that state, the annular protrusion 34 and the top surface of the cover member 22 of the susceptor 2 become close to each other to form an annular gap 38.
The gas exhaust unit 4 includes a gas exhaust line 41 connected to the gas exhaust port 13b of the gas exhaust duct 13, and a gas exhaust mechanism 42 connected to the gas exhaust line 41 and having a vacuum pump, a pressure control valve and the like. During the processing, the gas in the chamber 1 reaches the gas exhaust duct 13 through the slit 13a and is exhausted from the gas exhaust duct 13 through the gas exhaust line 41 by the gas exhaust mechanism 42 of the gas exhaust unit 4.
The processing gas supply unit 5 includes: a WF6 gas supply source 51 for supplying WF6 gas as a tungsten source gas; an H2 gas supply source 52 for supplying H2 gas as a reducing gas; an SiH4 gas supply source 53 for supplying SiH4 gas; a B2H6 gas supply source 54 for supplying B2H6 gas; and a first and a second N2 gas supply source 55 and 56 for supplying N2 gas as a purge gas. The processing gas supply unit 5 further includes: a WF6 gas supply line 61 extending from the WF6 gas supply source 51; an H2 gas supply line 62 extending from the H2 gas supply source 52; an SiH4 gas supply line 63 extending from the SiH4 gas supply source 53; a B2H6 gas supply line 64 extending from the B2H6 gas supply source 54; a first N2 gas supply line 64 extending from the first N2 gas supply source 55 and configured to supply N2 gas to the WF6 gas supply line 61; and a second N2 gas supply line 66 extending from the second N2 gas supply source 56 and configured to supply N2 gas to the H2 gas supply line 62.
The first N2 gas supply line 65 is branched to a first continuous N2 gas supply line 67 for constantly supplying N2 gas during the film formation using the ALD method and a first flush purge line 68 for supplying N2 gas only during the purge process. The second N2 gas supply line 66 is branched to a second continuous N2 gas supply line 69 for constantly supplying N2 gas during the film formation using the ALD method and a second flush purge line 70 for supplying N2 gas only during the purge process. The first continuous N2 gas supply line 67 and the first flush purge line 68 are connected to a first connection line 71. The first connection line 71 is connected to the WF6 gas supply line 61. The SiH4 gas supply line 63, the B2H6 gas supply line 64, the second continuous N2 gas supply line 69 and the second flush purge line 70 are connected to a second connection line 72. The second connection line 72 is connected to the H2 gas supply line 62. The WF6 gas supply line 61 and the H2 gas supply line 62 are joined with a joint line 73. The joint line 73 is connected to the above-described gas inlet hole 36.
The WF6 gas supply line 61, the H2 gas supply line 62, the SiH4 gas supply line 63, the B2H6 gas supply line 64, the first continuous N2 gas supply line 67, the first flush purge line 68, the second continuous N2 gas supply line 69 and the second flush purge line 70 are provided with opening/closing valves 74, 75, 76, 77, 78, 79, 80 and 81 for switching gases at the time of performing ALD, respectively. Mass flow controllers 84, 85, 86, 87, 88, 89, 90 and 91 as flow rate controllers are provided at the upstream sides of the opening/closing valves of the WF6 gas supply line 61, the H2 gas supply line 62, the SiH4 gas supply line 63, the B2H6 gas supply line 64, the first continuous N2 gas supply line 67, the first flush purge line 68, the second continuous N2 gas supply line 69 and the second flush purge line 70, respectively. The WF6 gas supply line 61, the H2 gas supply line 62, the SiH4 gas supply line 63 and the B2H6 gas supply line 64 are provided with buffer tanks 92, 93, 94 and 95, respectively, so that required gases can be supplied within a short period of time.
N2 gas is continuously supplied from the first continuous N2 gas supply line 67 and the second continuous N2 gas supply line 69 during the film formation of the tungsten film. N2 gas as a purge gas is supplied from the first flush purge line 68 and the second flush purge line 70 only during the purge process at the time of performing ALD. Instead of N2 gas, another inert gas such as Ar gas or the like may be used.
One end of a bypass line 101 is connected to the downstream side of the mass flow controller 84 in the WF6 gas supply line 61. The other end of the bypass line 101 is connected to the gas exhaust line 41. Opening/closing valves 102 and 103 are provided in the bypass line 101 at positions near the WF6 gas supply line 61 and the gas exhaust line 41, respectively. One end of the bypass line 104 is connected to the downstream side of the mass flow controller 86 in the SiH4 gas supply line 63. The other end of the bypass line 104 is connected to the gas exhaust line 41. Opening/closing valves 105 and 106 are provided in the bypass line 104 at positions near the SiH4 gas supply line 63 and the gas exhaust line 41, respectively. One ends of the bypass lines 107 and 109 are respectively connected to the downstream side of the mass flow controller 85 in the H2 gas supply line 62 and the downstream side of the mass flow controller 87 in the B2H6 gas supply line 64. The other ends of the bypass lines 107 and 109 are connected to the bypass line 104. WF6 gas, H2 gas, SiH4 gas, and B2H6 gas can bypass the chamber 1 through the respective bypass lines 101, 104, 107 and 109 to flow into the gas exhaust line 41.
The control unit 6 includes a process controller, a user interface, and a storage unit. The process controller has a microprocessor (computer) for controlling the respective components, specifically, the valve, the power supply, the heater, the pump and the like. The respective components of the film forming apparatus 100 are electrically connected to and controlled by the process controller. The user interface is connected to the process controller, and includes a keyboard through which an operator inputs commands to manage the respective components of the film forming apparatus 100, a display for visualizing and displaying operation states of the respective components of the film forming apparatus, and the like. The storage unit is also connected to the process controller, and stores a control program, i.e., a process recipe, for controlling the film forming apparatus 100 to perform a predetermined process based on processing conditions, various database and the like. The process recipe is stored in a storage medium (not shown) in the storage unit. The storage medium may be a hard disk, a CD-ROM, a DVD, a semiconductor memory, or the like. A recipe may be appropriately transmitted from another device, e.g., through a dedicated line. If necessary, a predetermined process recipe is read-out from the storage unit by an instruction from the user interface or the like and executed by the process controller. Accordingly, a desired process is performed in the film forming apparatus 100 under the control of the process controller.
<Film Forming Method>
Next, embodiments of the film forming method performed by the film forming apparatus 100 configured as described above will be described.
(First Embodiment of Film Forming Method)
First, a first embodiment of the film forming method will be described.
First, a wafer in which a TiN film 202 serving as a barrier layer is formed on an interlayer insulating film 201 made of SiO2 or the like as shown in
Next, an atmosphere in the chamber 1 is set to a predetermined depressurized atmosphere. The wafer W on the susceptor 2 is heated to a predetermined temperature by the heater 21 in the susceptor 2, and for example, SiH4 gas, or a gaeous mixture of SiH4 gas and H2 gas, or B2H6 gas, or a gaeous mixture of B2H6 gas and H2 gas is supplied onto the wafer surface to perform an initiation process for facilitating formation of an amorphous layer as shown in
Next, in a state where the heating temperature of the susceptor 2 is maintained, an initial tungsten film 204 serving as a base of a main tungsten film is formed by a method in which WF6 gas and a reducing gas (B2H6 gas, SiH4 gas or H2 gas) are sequentially supplied with purging of the chamber 1 interposed therebetween, e.g., an ALD method in which WF6 gas and a reducing gas are supplied multiple times with purging of the chamber 1 interposed therebetween, from the processing gas supply mechanism 5 into the chamber 1 (STEP 3,
In this specification, the term “amorphous” means no definite crystal structure. However, very fine crystals may partially exist. Specifically, when a diffraction peak showing crystallinity is not observed or slightly observed or a halo peak is observed in the X-ray diffraction spectrum (XRD), it is determined to be amorphous.
Next, in a state where the heating temperature of the susceptor 2 is maintained, a main tungsten film 205 is formed on the initial tungsten film 204 that is an amorphous layer (STEP 4,
By forming the main tungsten film 205 by the method in which gases are sequentially supplied such as the ALD method, a high step coverage can be obtained. Accordingly, satisfactory fillability can be obtained even in a fine recess having a high aspect ratio. The film thickness of the main tungsten film is appropriately set depending on the size of the recess or the like, and the number of repetitions of ALD or the like is set depending on the film thickness.
When the initial tungsten film is a crystalline layer as in the conventional case, the initial tungsten film has a columnar crystal structure by the influence of the TiN film having a columnar crystal structure. If the main tungsten film is formed on the initial tungsten film, the main tungsten film also has a columnar crystal structure by the influence of the initial tungsten film. It is known that a resistance value of a crystalline substance decreases as a crystal grain diameter increases and the number of grain boundaries decreases. However, the columnar crystals have vertical grain boundaries, and the resistance of the film is not sufficiently low due to the presence of the vertical grain boundaries.
On the other hand, in the present embodiment, by forming the initial tungsten film 204 that is an amorphous layer and then forming the main tungsten film 205 on the amorphous initial tungsten film 204, the crystal grain size of the main tungsten film 205 can be increased and the resistance can be reduced.
In other word, an amorphous structure does not have grain boundaries with high energy which correspond to nucleation sites in a polycrystalline structure. Therefore, nucleation is less likely to occur and the number of nuclei decreases. Accordingly, in the case of forming the main tungsten film 205 on the initial tungsten film 204 that is an amorphous layer, each crystal grain tends to be greater and the crystal grain diameter becomes greater compared to that in the conventional case. As a result, the low resistance can be achieved.
Hereinafter, the test results that support the above conclusions will be described.
Here, a sample (sample A) was obtained by: setting a pressure in the chamber to 500 Pa and a wafer temperature to 450° C.; performing an initiation process on the TiN film for 60 sec by supplying SiH4 gas and H2 gas at 700 sccm and 500 sccm, respectively; forming an initial tungsten film with a film thickness of 2 nm by repeating a cycle of supplying WF6 gas at 300 sccm for 1 sec, performing a purge process for 5 sec, supplying SiH4 gas at 400 sccm for 1 sec and performing a purge process for 5 sec; and forming a main tungsten film with a film thickness of 19.8 nm by repeating a cycle of supplying WF6 gas at 100 sccm for 0.15 sec, performing a purge process for 0.2 sec, supplying H2 gas at 4500 sccm for 0.3 sec and performing a purge process for 0.3 sec. Also, a sample (sample B) was obtained by; setting the pressure and the temperature to the same conditions as those in the sample A; performing an initiation process on the TiN film by supplying B2H6 gas and H2 gas at 100 sccm and 500 sccm, respectively; forming an initial tungsten film with a film thickness of 2 nm by ALD by repeating a cycle of supplying WF6 gas at 300 sccm for 1 sec, performing a purge process for 5 sec, supplying B2H6 gas at 100 sccm for 1 sec and performing a purge process for 5 sec; and forming a main tungsten film with a film thickness of 15.9 nm under the same conditions as those in the sample A.
The resistivity of the sample A was 43.5 μΩ·cm and that of the sample B was 26.3 μΩ·cm. In other words, the resistivity of the sample B was lower than that of the sample A even though the main tungsten film was formed under the same conditions and the main tungsten film of the sample B was thinner than that of the sample A. This shows that the resistance can be reduced depending on the base of the main tungsten film.
Next, X-ray diffraction (XRD) was performed on the sample B having a low resistance in the case of performing processes up to the formation of the initial tungsten film and in the case of performing processes up to the formation of the main tungsten film. The results are shown in
Next, the crystal states of the sample A and the sample B were monitored by SEM.
The crystal states of the sample A and the sample B were monitored in detail by TEM.
From the above, it has been found that when the base of the main tungsten film is an amorphous layer, the crystal grains of the main tungsten film become greater and, thus, a tungsten film having a low resistance can be obtained.
The crystal grain diameter can be increased not only by forming the initial tungsten film 204 that is an amorphous layer but also by increasing the film formation temperature of the main tungsten film 205. In that case as well, a tungsten film having a low resistance can be obtained.
Next, specific examples of the present embodiment will be described.
In this example, as shown in
In the initiation process, B2H6 gas is used as the reducing gas so that the initial tungsten film can easily grow on the TiN film.
In the case of forming the initial tungsten film by the ALD method, the supply of WF6 gas as a tungsten source gas and the supply of B2H6 gas as a reducing gas are repeated multiple times with purging interposed therebetween, as shown in
In the case of forming the main tungsten film by the ALD method, the supply of WF6 gas as a tungsten source gas and the supply of H2 gas as a reducing gas are repeated multiple times with purging interposed therebetween as shown in
Hereinafter, preferable conditions of the respective steps in this example will be described.
1. Initiation Process
2. Initial Tungsten Film Formation
3. Main Tungsten Film Formation
In this example, as shown in
In this example, in the case of forming the initial tungsten film by the ALD method, the supply of WF6 gas as a film forming gas and the supply of a gaseous mixture of B2H6 gas and SiH4 gas or a gaseous mixture of B2H6 gas, SiH4 gas and H2 gas as a reducing gas are repeated multiple times with purging interposed therebetween as shown in
Hereinafter, preferable conditions of the respective steps in this example will be described. Since the conditions of the main tungsten film are the same as those in the first example, redundant description thereof will be omitted.
1. Initiation Process
2. Initial Tungsten Film Formation
(Second Embodiment of Film Forming Method)
Next, a second embodiment of the film forming method will be described.
First, as in the first embodiment, a wafer on which a TiN film 202 serving as a barrier layer is formed on an interlayer insulating film 201 made of SiO2 or the like as shown in
Next, an atmosphere in the chamber 1 is set to a predetermined depressurized atmosphere. The wafer W on the susceptor 2 is heated to a predetermined temperature by the heater 21 in the susceptor 2, and gases, e.g., SiH4 gas, or a gaseous mixture of SiH4 gas and H2 gas, or B2H6 gas, or a gaseous mixture of B2H6 gas and H2 gas are supplied to perform an initiation process for allowing nuclei 203 to be adsorbed on the wafer surface as shown in
Next, an initial tungsten film 204a is formed by a method in which WF6 gas and a reducing gas (SiH4 gas or the like) are sequentially supplied with purging of the chamber 1 interposed therebetween, e.g., an ALD method in which WF6 gas and a reducing gas are supplied multiple times with purging of the chamber 1 interposed therebetween, from the processing gas supply mechanism 5 into the chamber 1 (STEP 13,
Next, an amorphous layer 206 is formed by allowing a gas containing a material for nucleation, e.g., a gas containing B2H6 gas, to be adsorbed on the surface of the initial tungsten film 204a (STEP 14,
Next, a main tungsten film 205 is formed on the amorphous layer 206 (STEP 15,
By forming the amorphous layer 206 prior to the formation of the main tungsten film 205, the main tungsten film 205 can be easily formed and, also, the number of nuclei of tungsten can be decreased. Accordingly, the crystal grain diameter can be increased, and the resistance of the tungsten film can be lowered.
Since the tungsten film 205 can be formed with high step coverage by the method in which gases are sequentially supplied such as the ALD method, satisfactory fillability can be obtained even in a fine recess having a high aspect ratio.
Next, a specific example of the present embodiment will be described.
In this example, as shown in
In the initiation process, SiH4 gas used as a reducing gas in forming the initial tungsten film is used as a nucleation gas so that the initial tungsten film can easily grow on the TiN film.
In the case of forming the initial tungsten film by the ALD method, the supply of WF6 gas as the tungsten source gas and the supply of SiH4 gas as the reducing gas are repeated multiple times with purging interposed therebetween. Accordingly, the initial tungsten film that is a crystalline layer is formed.
In the formation of the amorphous layer, a film of a material for nucleation is formed by performing a nucleation process similar to the initiation process on the surface of the initial tungsten film for a long period of time. By using B2H6 gas and H2 gas, B material for nucleation becomes an amorphous boron film.
Here, the amorphous boron film is formed using B2H6 gas by the following method.
The substrate is processed under the conditions:
Film forming temperature: 400° C., 450° C. and 500° C.
Film forming pressure: 500 Pa
Flow rate of B2H6 gas diluted with 5% H2 gas: 100 sccm
Flow rate of continuously supplied N2 gas: 6000 sccm
Processing time: 20 sec and 60 sec
B intensity of XRF was 0.8057 kcps and 0.8151 kcps under the respective conditions of 400° C. and 20 sec and 400° C. and 60 sec; 0.8074 kcps and 2.0388 kcps under the respective conditions of 450° C. and 20 sec and 450° C. and 60 sec; and 0.9271 kcps and 3.905 kcps under the respective conditions of 500° C. and 20 sec and 500° C. and 60 sec. Boron SEM film thicknesses equivalent to these intensities were substantially 0 nm under the conditions of 400° C. and 20 sec and 400° C. and 60 sec; substantially 0 nm under the condition of 450° C. and 20 sec; 6.9 nm under the condition of 450° C. and 60 sec; 0.4 nm under the condition of 500° C. and 20 sec; and 17.8 nm under the condition of 500° C. and 60 sec.
According to the XRD analysis of the crystallinity of the film formed under the condition of 450° C. and 60 sec, a broad peak was observed and the film was determined to be amorphous.
In the case of supplying B2H6 gas diluted with 5% H2 gas to the substrate under the above conditions, an amorphous boron film having a desired thickness can be obtained by controlling the temperature and the supply period of time.
Hereinafter, preferable conditions of the respective steps in this example will be described. The conditions of the initiation process are the same as those in the second example of the first embodiment, and the conditions of the main tungsten film formation are the same as those in the first example of the first embodiment. Therefore, redundant description thereof will be omitted.
1. Initial Tungsten Film Formation
2. Formation of Amorphous Layer
(Third Embodiment of Film Forming Method)
Next, a third embodiment of the film forming method will be described.
First, as in the first embodiment, a wafer on which a TiN film 202 serving as a barrier film is formed on an interlayer insulating film 201 made of SiO2 or the like as shown in
Next, an atmosphere in the chamber 1 is set to a predetermined depressurized atmosphere. The wafer W on the susceptor 2 is heated to a predetermined temperature by the heater 21 in the susceptor 2, and a gas containing SiH4 gas is supplied and adsorbed on the surface of the TiN film 202 to form an amorphous layer 207 (STEP 22,
Next, in a state where the heating temperature of the susceptor 2 is maintained, a main tungsten film 205 is formed on the amorphous layer 207 (STEP 23,
By forming the amorphous layer 207 prior to the formation of the main tungsten film 205, the main tungsten film 205 can be easily formed, and the number of nuclei of tungsten can be decreased. Accordingly, the crystal grain diameter can be increased, and the resistance of the tungsten film can be lowered.
Since the tungsten film 205 can be formed with high step coverage by the method in which gases are sequentially supplied, such as the ALD method or the like, satisfactory fillability can be obtained even in a fine recess having a high aspect ratio.
In addition, since the initial tungsten film is not required, the processing can be simplified.
Next, a specific example of the present embodiment will be described.
In this example, as shown in
In the formation of the amorphous layer, a film of a material for nucleation is formed by performing a nucleation process similar to the initiation process on the surface of the TiN film for a long period of time. By using SiH4 gas and H2 gas, Si material for nucleation becomes an amorphous silicon film.
Hereinafter, preferable conditions of the respective steps in this example will be described. Since the main tungsten film formation conditions are the same as those in the first example of the first embodiment, redundant description thereof will be omitted.
1. Amorphous Layer Formation
(Fourth Embodiment of Film Forming Method)
Next, a fourth embodiment of the film forming method will be described.
First, as shown in
Next, the wafer on which the TiSiN film 208 is formed is loaded into the chamber 1 and mounted on the susceptor 2. Then, an atmosphere in the chamber 1 is set to a predetermined depressurized atmosphere. Thereafter, as shown in
Next, the main tungsten film 205 is formed on the TiSiN film 208 that is an amorphous layer (STEP 33,
Since the TiSiN film 208 that is an amorphous layer is formed as a barrier layer of a base film, when the main tungsten film 205 is formed thereon, the number of nuclei of tungsten can be decreased. Accordingly, the crystal grain diameter can be increased, and the resistance of the tungsten film can be lowered.
Since the tungsten film 205 can be formed with high step coverage by the method in which gases are sequentially supplied, e.g., the ALD method or the like, satisfactory fillability can be obtained even in a fine recess having a high aspect ratio.
Further, since the main tungsten film 205 is formed on the base film that is an amorphous layer with the initiation process interposed therebetween, the initial tungsten film becomes unnecessary and the processing can be simplified.
As for the amorphous layer serving as the base of the main tungsten film 205, various films other than the TiSiN film can be used. For example, it is possible to use an amorphous molybdenum film formed by CVD or ALD using an organic molybdenum film as a raw material.
Next, a specific example of this embodiment will be described.
In this example, as shown in
Although the embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments and can be variously modified.
The above-described embodiments have described the example in which the main tungsten film is formed by the method in which gases are sequentially supplied such as the ALD method. However, the present invention can also be applied to the case in which the main tungsten film is formed by a CVD method.
Although the above-described embodiments have described the examples in which the base of the main tungsten film is an amorphous layer, the material of the amorphous layer is not limited thereto.
Although a semiconductor wafer has been described as an example of a target substrate, the semiconductor wafer may be silicon or may be a compound semiconductor such as GaAs, SiC, GaN, or the like. Further, the present invention can also be applied to a glass substrate used for FPD (Flat Panel Display) such as a liquid crystal display or the like, a ceramic substrate, or the like without being limited to a semiconductor wafer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-146089 | Jul 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/025251 | 7/11/2017 | WO | 00 |
