JP3950494B2 - Method for producing titanium nitride thin film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a titanium nitride (TiN) thin film using a plasma CVD apparatus including a plasma generating electrode inside a processing chamber, and more particularly to a method of manufacturing a titanium nitride thin film having a (111) crystal orientation.
[0002]
[Prior art]
As an application of the titanium nitride thin film, there is a semiconductor integrated circuit. In this case, the titanium nitride thin film is formed between the metal wiring material of the semiconductor integrated circuit and the semiconductor or insulator, and thereby functions to prevent diffusion between the metal wiring material and the semiconductor or insulator. Also, it functions to improve the adhesion between the metal wiring material and the semiconductor or insulator.
[0003]
As a metal wiring material of a semiconductor integrated circuit, aluminum or an aluminum alloy (for example, Al-1% Si) is generally used. When aluminum or an aluminum alloy is used as a metal wiring material, there is a problem that the wiring is disconnected or short-circuited between adjacent wirings due to the phenomenon of electromigration or stress migration. Therefore, it is known that the resistance to electromigration is improved by setting the crystal orientation of the metal wiring material made of aluminum or aluminum alloy to (111). Note that the (111) crystal orientation thin film means that the (111) crystal lattice plane is parallel to the surface of the thin film.
[0004]
When aluminum or aluminum alloy with (111) crystal orientation is formed as a wiring material on a titanium nitride thin film as a base, the crystal orientation of aluminum or aluminum alloy is strongly influenced by the crystal orientation of the base titanium nitride thin film. Therefore, it is important to make the underlying titanium nitride thin film have a (111) crystal orientation.
[0005]
On the other hand, as the semiconductor integrated circuit is highly integrated and miniaturized, the wiring in the integrated circuit is becoming thinner. In particular, when forming a metal wiring for a contact used for electrical connection with a semiconductor, an insulating film is formed on the semiconductor in advance, a contact hole is formed in the insulating film by etching, and nitriding is performed on the bottom and side walls of the contact hole. A method is used in which a titanium thin film is formed and metal wiring is formed thereon. This titanium nitride thin film functions as a diffusion preventing film and an adhesion improving film.
[0006]
Typical methods for forming a titanium nitride thin film in the contact hole include a sputtering method and a CVD method. The sputtering method has a problem that a film is deposited in an overhang shape at the entrance of the contact hole, and a titanium nitride thin film cannot be sufficiently deposited on the bottom and side walls of the contact hole.
[0007]
In contrast, in the CVD method, in principle, a film is uniformly deposited on the bottom and side walls of the contact hole. Typical CVD methods include a thermal CVD method that promotes a chemical reaction with thermal energy and a plasma CVD method that activates a source gas with plasma to promote a chemical reaction.
[0008]
In order to obtain a titanium nitride thin film having a (111) crystal orientation using a thermal CVD method, the film forming temperature needs to be 600 ° C. to 700 ° C. or higher (reference: N. Yokoyama, K. Hideo and Y. Homma, J. Electrochem. Soc., Vol. 138 (1991), pp. 190-195). However, considering the current situation in which a low temperature during thin film deposition is required as semiconductor integrated circuits are highly integrated and miniaturized, such a high temperature film formation process is not preferable.
[0009]
Therefore, a plasma CVD method capable of forming a film at a low temperature as compared with the thermal CVD method has attracted attention. However, when a titanium nitride thin film is deposited by the conventional plasma CVD method, the main crystal orientation becomes (200), and there is a problem that it is difficult to obtain a (111) crystal orientation film at a substrate temperature of 450 ° C. or less (reference) References: Atsushi Kawashima, Takaaki Miyamoto, Shingo Kadomura, Junichi Aoyama, Proceedings of the 49th Symposium on Semiconductor and Integrated Circuit Technology (1995), pp.120-125).
[0010]
In addition, when producing a titanium nitride thin film by a sputtering method, a method for controlling the crystal orientation of the titanium nitride thin film by applying a bias power to the substrate to generate a negative bias voltage is known (reference). Literature: Makiko Kageyama, Keiichi Hashimoto and Hiroshi Onoda, IEEE / IRPS (1991), pp. 97-101). However, in this method, when the negative bias voltage applied to the substrate is increased, the crystal orientation of the obtained titanium nitride thin film is mainly (200), and the (111) crystal orientation cannot be obtained.
[0011]
[Problems to be solved by the invention]
Eventually, with the conventional CVD method or sputtering method, it was difficult to produce a titanium nitride thin film having a (111) crystal orientation without increasing the substrate temperature during film formation.
[0012]
The present invention has been made in order to solve such problems, and an object of the present invention is to form titanium nitride having a (111) crystal orientation by plasma CVD without increasing the substrate temperature at the time of film formation. The purpose is to produce a thin film.
[0013]
[Means for Solving the Problems]
In the present invention, when a titanium nitride thin film is produced by the plasma CVD method, a plasma generating electrode having two terminals is arranged inside a processing chamber, and one terminal of the plasma generating electrode is connected to a high frequency power supply source. The other terminal is grounded through a capacitor to generate plasma in the processing chamber. A high frequency bias power is applied to the substrate. Thereby, a titanium nitride thin film having a (111) crystal orientation can be deposited on the substrate. The obtained titanium nitride thin film has a low resistivity and a low chlorine content, and has a good film quality. This titanium nitride thin film can be used as a diffusion prevention film and an adhesion film for metal wiring of a semiconductor integrated circuit. For example, when an aluminum alloy is deposited as a metal wiring on a (111) crystal oriented titanium nitride thin film, this aluminum alloy also becomes (111) crystal orientation, and various migration resistances are improved.
[0014]
The high frequency bias power applied to the substrate is about 100 to 3000 W. When the high frequency bias power is about 100 W or less, the (111) orientation of the titanium nitride thin film is hardly observed. Strictly speaking, it has been observed that the value of the high-frequency bias power at which the (111) orientation of the titanium nitride thin film starts to become dominant varies somewhat depending on the high-frequency power applied to the plasma generating electrode. Considering this point, the lower limit value of the high frequency bias power is set to “about” 100 W. On the other hand, if the high frequency bias power is set to 3000 W or more, the absolute value of the negative bias voltage generated in the substrate becomes too large, and damage to the substrate due to positive ions in the plasma increases, which is not preferable. Preferably, the high frequency bias power is set to 300 to 1000 W. In this range, the (111) orientation is sufficiently enhanced and the damage to the substrate is relatively small.
[0015]
The capacitance of the capacitor connected to the other terminal of the plasma generating electrode is suitably 100 pF to 10 μF. If the capacity is too small, the discharge tends to become unstable. On the other hand, if the capacitance is too large, the capacitor becomes too large when using a ceramic capacitor with good high frequency characteristics, which is not practical.
[0016]
The processing chamber is normally grounded, but the processing chamber may be floated from the ground in a direct current manner. That is, a capacitor may be inserted between the processing chamber and the ground, and in that case, the capacitance of the capacitor may be controlled to adjust the potential of the processing chamber.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a configuration diagram of an example of a plasma CVD apparatus used in the present invention, and a portion of a processing chamber shows a front sectional view. A substrate holder 25 and a plasma generating electrode 61 are arranged inside the processing chamber 20 that can be maintained in a vacuum. A bias power supply source 90 is connected to the substrate holder 25, and power is supplied to the plasma generating electrode 61. Source 50 and ground coupling mechanism 80 are connected. Further, the gas introduction mechanism 10 and the exhaust mechanism 30 are connected to the processing chamber 20.
[0018]
First, the gas introduction mechanism 10 will be described. FIG. 2 is a configuration diagram of the gas introduction mechanism 10. The gas introduction mechanism 10 can use four kinds of gases. The titanium tetrachloride container 1a is a thermostatic tank that heats titanium tetrachloride in a liquid state at a normal temperature and pressure to a predetermined temperature. The titanium tetrachloride vaporized in the thermostatic tank is supplied with a flow controller 12a and a valve 13a. It is introduced into the processing chamber 20 via. The hydrogen gas container 1b, the nitrogen gas container 1c, and the argon gas container 1d are in the form of high-pressure gas cylinders, and the gas contained therein is decompressed by the decompression valves 11b, 11c, and 11d, respectively, and the flow rate controllers 12b, 12c. , 12d, the flow rate is controlled, and the valves 13b, 13c, 13d are opened and introduced into the processing chamber 20. The outlet of the gas introduction mechanism 10 opens near the center of the plasma generating electrode 61. The valves 13a, 13b, 13c, and 13d are opened when each gas is introduced. When the inside of the processing chamber 20 is made into the atmosphere, the valves 13a, 13b are used to prevent the gases from being contaminated with the atmosphere. , 13c, 13d are closed.
[0019]
Next, returning to FIG. 1, the structure of the substrate holder 25 will be described. The substrate 21 is placed on the substrate holder 25. Inside the substrate holder 25 are a heater 26 and a thermocouple 27. The temperature of the substrate holder 25 is measured by a thermocouple 27, and electric power is supplied to the heater 26 by a substrate temperature adjusting device (not shown) to control the temperature of the substrate 21. This substrate temperature control apparatus uses a PID control method, but a fuzzy circuit may be used together, PI control, or simple ON-OFF control may be employed as necessary.
[0020]
Next, the exhaust mechanism 30 will be described. The roughing pump 31 is an oil rotary pump (exhaust speed is 650 liters per minute) and is connected to the processing chamber 20 via a roughing valve 32. When the cleanliness of the processing chamber 20 is very important, an oil-free pump can be used as the roughing pump 31, and a dry pump may be used to improve maintainability. The main pump 35 is connected to the processing chamber 20 via a variable orifice 34 and a main valve 33, and an auxiliary pump 36 is connected to the subsequent stage. The main pump 35 is a composite turbo molecular pump (the exhaust speed is 1300 liters per second), and an oil diffusion pump can be used if the cleanliness in the processing chamber 20 is not so important. The auxiliary pump 36 is an oil rotary pump (the exhaust speed is 1180 liters per minute), and a dry pump or the like may be used similarly to the roughing pump 31.
[0021]
In order to exhaust the processing chamber 20 from the atmospheric pressure, first, the roughing valve 32 is opened and the processing chamber 20 is exhausted by the roughing pump 31. After the pressure inside the processing chamber 20 is evacuated to a predetermined pressure (about 100 Pa in this embodiment depending on the exhaust system), the roughing valve 32 is closed, the main valve 33 is opened, and the main pump 35 further lowers the pressure. Exhaust to pressure range. Based on the processing chamber pressure measured by the vacuum gauge, the variable orifice 34 can be opened and closed to adjust the pressure in the processing chamber 20 to a predetermined value. In order to obtain a stable plasma with good reproducibility, it is effective to use the variable orifice 34.
[0022]
Next, a mechanism for applying bias power to the substrate will be described. The substrate holder 25 is connected to a high frequency power source 92 for bias through an impedance matching circuit 91. The impedance matching circuit 91 and the bias high-frequency power source 92 constitute a bias power supply source 90. The alternating power induced by the high frequency bias power source 92 is impedance-adjusted by the impedance matching circuit 91 and supplied to the base holder 25 so that the bias voltage of the base 21 is adjusted. Around the substrate holder 25 is a shield plate 93 connected to the processing chamber 20, and the substrate holder 25 is electrically insulated from the processing chamber 20 by an insulator 94. The frequency of the high frequency power supply 92 for bias needs to be at least 500 Hz different from the frequency of the high frequency power supply 52 for generating plasma. Otherwise, the two high frequencies interfere with each other and a stable plasma cannot be obtained. In this embodiment, the frequency of the high frequency power source 52 for generating plasma is 13.560 MHz, and the frequency of the high frequency power source 92 for bias is 13.562 MHz.
[0023]
Next, the magnetic field generation mechanism will be described. Around the processing chamber 20, many permanent magnets 121 elongated in the vertical direction are arranged. 5 is a cross-sectional view taken along line 5-5 of FIG. 1 and shows a horizontal cross section of the processing chamber 20. The 24 permanent magnets 121 are arranged at equal intervals around the processing chamber 20, and adjacent permanent magnets 121 have opposite polarities. That is, the north and south poles are alternately arranged toward the inside of the processing chamber 20. Due to the action of these permanent magnets 121, a multicusp magnetic field 122 is formed in the vicinity of the inner wall surface of the processing chamber 20. Note that the shape and number of permanent magnets are not limited to this, and other configurations may be employed as long as N poles and S poles are alternately arranged toward the inside of the processing chamber 20.
[0024]
The permanent magnet 121 was formed by combining lanthanum-based rare earth magnets (size: 25.4 mm × 6.3 mm × 12.8 mm). Although the magnetic flux density on the surface of this magnet is 1600 gauss, a magnet in the range of about 400 to 2200 gauss is effective. If the magnetic flux density is too small, the plasma confinement effect is weakened, and the uniformity of the surface treatment at the periphery of the substrate is poor. When the magnetic flux density is too large, the plasma is too far away from the inner wall of the processing chamber, and the region where the uniformity of the plasma is maintained becomes smaller than the inner diameter of the processing chamber. It is desirable that the magnetic pole spacing be within 150 mm. If the magnetic poles are too far apart, the magnetic flux density at the center between the magnetic poles will be reduced, and the plasma confinement effect will be reduced. In this embodiment, the magnetic pole spacing is 24 mm.
[0025]
When such a multicusp magnetic field 122 is used, the plasma does not diffuse to the vicinity of the inner wall surface of the processing chamber 20 due to the effect of confining the plasma by the magnetic field, and a uniform high-density plasma can be maintained. When this multicusp magnetic field and a bias power supply source are used in combination, a large current ion can be made to uniformly flow into the surface of a large substrate.
[0026]
Next, a plasma generator will be described. The plasma generator is for generating plasma inside the processing chamber 20, and includes a power supply source 50, a plasma generation electrode 61, and a ground coupling mechanism 80 in FIG. 1. The plasma generating electrode 61 is substantially a one-turn coil, and includes a pair of introduction terminals 62 and 63 that penetrate the wall of the processing chamber 20. The plasma generating electrode 61 faces the base 21. FIG. 3 is a plan view of the plasma generating electrode 61. The plasma generating electrode 61 is formed by bending a metal pipe into an approximately circular shape. The diameter is about 140 mm. Introducing terminals 62 and 63 are formed so as to be perpendicular to the annular portion. Since the metal pipe is exposed as it is in the processing chamber, the surface of the plasma generating electrode 61 is a conductor. This electrode can be cooled by flowing cooling water into the metal pipe. However, it can be air-cooled as necessary, and in the case of low power, it does not need to be cooled.
[0027]
Next, a cooling mechanism for the plasma generating electrode will be described. In this embodiment, the introduction terminals 62 and 63 and the plasma generating electrode 61 are hollow, and cooling water can be passed through the inside. The introduction terminals 62 and 63 are connected to a fluororesin water flow tube. The supply side tube is supplied with water at a pressure of about 5 kg per square centimeter, and the discharge side tube has a pressure close to atmospheric pressure. It is said. The cooling water temperature at the supply port is about 15 ° C., and the flow rate of water flowing inside the plasma generating electrode 61 is about 3 liters per minute. As the cooling medium, water is most excellent from the viewpoints of large specific heat, availability, small viscosity, and the like, but other mediums may be used. When air cooling or nitrogen gas cooling is employed, the flow rate should be increased. Nitrogen gas cooling does not contain moisture, so that moisture corrosion of the electrode can be prevented.
[0028]
Since the plasma generating electrode is in direct contact with the plasma, the surface may be etched by the plasma. According to experiments, when the plasma generating electrode is water-cooled, this etching can be suppressed and the life of the plasma generating electrode can be extended. When not cooled by water, the rate of decrease in the diameter of the plasma generating electrode was 0.1 mm per hour, but when cooled by water, it was 0.01 mm per hour. When the plasma generating electrode is etched, it may be mixed into the film on the substrate and become an impurity. However, the amount of etching can be reduced by cooling with water.
[0029]
FIG. 4 is a perspective view in which a part of an insulating ring provided between the introduction terminal of the plasma generating electrode and the processing chamber is cut. The insulating ring 71 is made of quartz glass which is an electrically insulating material. A vacuum seal is formed between the insulating ring 71 and the plasma generating electrode introduction terminals 62 and 63 and between the insulating ring 71 and the processing chamber 20. The insulating ring 71 has a circular through-hole 73 formed in the center of a disc 72, and three annular projections 74 are formed on one side of the disc 72 (side exposed to the processing chamber space). It is formed concentrically. Two annular grooves 79 are formed between the annular protrusions 74. The opening of the groove 79 is in a plane perpendicular to the axis of the through hole 73, and the depth direction of the groove 79 is parallel to the axis of the through hole 73. These protrusions 74 and grooves 79 are all concentric with the through hole 73. A cylindrical introduction terminal 62 (see FIG. 1) of a plasma generating electrode is inserted into the through hole 73. Each of the three annular protrusions 74 has a height of 50 mm and a wall thickness of 1 mm. Therefore, the depth of the groove 79 is also 50 mm. The width of the groove 79 (the interval between adjacent protrusions 74) is 1 mm. The entire surface of the annular projection 74 and the surface of the disk 72 exposed to the processing chamber (the upper surface in FIG. 4) are roughened by blasting. This roughening makes it difficult for the film attached to the insulating ring 71 to peel off, and prevents dust contamination in the processing chamber due to film peeling. This will be described in detail. In the insulating ring 71, there is a possibility that a film adheres to a portion other than the inside of the groove 79. For example, the top surface of the protrusion 74, the outer peripheral surface of the outermost protrusion 74, A film may adhere to the outer disk surface. If these portions are roughened, the film attached to these portions is difficult to peel off.
[0030]
Returning to FIG. 1, one introduction terminal 62 of the plasma generating electrode 61 is connected to the high-frequency power source 52 via the impedance matching circuit 51. The impedance matching circuit 51 and the high frequency power source 52 constitute a power supply source 50. The frequency of the high frequency power supply 52 is 13.56 MHz, and the rated output is 3 kW. However, the frequency is not limited to this, and the order of kHz, 60 MHz, or 100 MHz may be used, and the usable range is about 10 kHz to 1000 MHz. If the upper limit of this range is exceeded, the conductor cannot be used as a wiring material, and if it falls below the lower limit, it will not be transmitted as radio waves. Further, the output waveform may be not only a sine wave but also a waveform obtained by subjecting it to a predetermined deformation. As the impedance matching circuit 51, a pie-type circuit is used, but other types such as a T-type circuit may be used. The alternating power induced by the high frequency power source 52 is impedance-adjusted by the impedance matching circuit 51 and supplied to the plasma generating electrode 61.
[0031]
Next, the ground coupling mechanism 80 will be described. The ground coupling mechanism 80 is provided between the introduction terminal 63 of the plasma generating electrode 61 and the ground potential, and includes a capacitor 81. By this capacitor 81, one end of the plasma generating electrode 61 is DC-isolated from the ground. The capacitance of the capacitor 81 of this embodiment is about 500 pF. However, it is not limited to this capacity, and a capacity of about 100 pF to 10 μF can be used depending on processing conditions. In contrast, the stray capacitance between the plasma generating electrode 61 and the processing chamber 20 is about several pF. As the capacitor 81, a ceramic capacitor having excellent high frequency characteristics and voltage resistance is suitable.
[0032]
When plasma is generated in the processing chamber, a DC bias voltage is induced in the plasma generation electrode 61 due to the presence of the capacitor 81 of the ground coupling mechanism 80. FIG. 9 is a graph showing the relationship between the capacitance of the capacitor 81 and the bias voltage induced in the plasma generating electrode 61. As can be seen from this graph, the absolute value of the DC bias voltage changes according to the capacitance of the capacitor. Therefore, it is possible to set the DC bias voltage of the plasma generating electrode to an arbitrary value by changing the capacitance of the capacitor. In the case where the plasma generating electrode is sputtered, the absolute value of the DC bias voltage is reduced by reducing the capacitance of the capacitor, and sputtering of the plasma generating electrode can be suppressed. Therefore, when the variable capacitor 81a is used as the ground coupling mechanism 80a as shown in FIG. 8, the capacitance change of the capacitor is simplified, and the control of the DC bias voltage of the plasma generating electrode is facilitated. In addition, if the DC bias component of the plasma generating electrode is monitored, the DC bias component remains constant even if the plasma processing conditions change slightly due to an increase in the number of batch processing when the plasma processing is performed in batch processing. The capacitance of the capacitor can be controlled so that
[0033]
By the way, the effect of the above-mentioned sputtering can be used conversely. For example, when a film is deposited on the substrate, the film may be deposited on the plasma generating electrode. In such a case, the capacitance of the capacitor is increased appropriately so that only the deposited film on the plasma generating electrode is deposited. Capacitor capacity can be searched for such that the plasma generating electrode itself is not sputtered.
[0034]
FIG. 10 shows still another example of the ground coupling mechanism. In the ground coupling mechanism 80b, a DC power source 82 is connected between the introduction terminal 63 of the plasma generating electrode 61 and the variable capacitor 81a via an inductor 83. Thereby, the potential of the plasma generating electrode 61 can be more positively controlled.
[0035]
By the way, in FIG. 1, when the introduction terminal 63 of the plasma generating electrode is directly grounded without passing through the capacitor 81, the plasma in the processing chamber becomes a discharge having strong capacitive coupling, and the entire space of the processing chamber is further exhausted. It extends to the space of the mechanism 30. As a result, the electron density of the plasma is lowered. On the other hand, when grounded via the capacitor 81, the plasma is localized in the central portion of the processing chamber, and the electron density of the plasma is increased. As a specific example, when plasma is generated by introducing argon gas into the processing chamber, setting the pressure to 6 mTorr, and applying power to the plasma generating electrode to 2 kW, the electron density of the plasma is “10” per cubic centimeter. Reached 11th power.
[0036]
Next, a first embodiment for producing a titanium nitride thin film using the plasma CVD apparatus of FIG. 1 will be described. 1 and 2, titanium tetrachloride supplied from the container 1a is 20 milliliters per minute, hydrogen gas from the container 1b is 200 milliliters per minute, nitrogen gas from the container 1c is 20 milliliters per minute, and from the container 1d. Argon gas was flowed at a flow rate of 35 milliliters per minute. The pressure in the processing chamber 20 was set to 1.3 Pa, and the temperature of the substrate 21 was set to 450 ° C. The power supplied from the high frequency power source 52 to the plasma generating electrode 61 was 3.0 kW, and the power supplied from the bias high frequency power source 92 to the substrate holder 25 was 300 W. The capacity of the capacitor 81 was 500 pF.
[0037]
Under such conditions, when a thin film was deposited on an 8-inch silicon wafer with (100) crystal orientation, a film mainly composed of titanium nitride was deposited at a deposition rate of about 60 nm per minute. The in-plane film thickness distribution of this film was ± 10% or less. Further, when a film was embedded in a hole having a hole diameter of 0.45 μm and a depth of 1 μm, a titanium nitride thin film could be formed with good coverage on the bottom and side walls of the hole. When the crystal orientation of the deposited titanium nitride thin film was examined by X-ray diffraction, the main peak was of (111) orientation. Further, when the resistivity of the film was measured by the four-probe method, a low value of 36 μΩcm was obtained, and the chlorine content in the film was also as small as about 0.1 atomic%, and a very good quality titanium nitride thin film was obtained. Obtained.
[0038]
FIG. 6 is a graph of an X-ray diffraction pattern showing the crystal orientation of the titanium nitride thin film prepared under the above-described conditions (high-frequency power supplied to the plasma generating electrode is 3 kW). The horizontal axis is the diffraction angle (2θ) by X-ray diffraction, and the vertical axis is the diffraction intensity. This graph shows the change of the diffraction pattern when the high frequency power applied to the substrate holder is changed. As can be seen from this graph, when a DC bias power of 120 W is applied to the base holder to make the bias voltage positive, and when the bias power is 0 W, the diffraction peak of (200) and the diffraction of (111) There is almost no difference in diffraction intensity between the peaks. On the other hand, when the high-frequency bias power is set to 100 W (the substrate has a negative bias voltage), the intensity of the diffraction peak of (111) becomes slightly larger. When the high-frequency bias power is set to 200 W, the intensity of the (111) diffraction peak is further increased. When the high frequency bias power is set to 300 W, the intensity of the (111) peak further increases and the intensity of the (200) peak significantly decreases. When the high frequency bias power is set to 700 W, the intensity of the (111) peak becomes very large, and the (200) peak is hardly observed. Thus, as the high frequency bias power applied to the substrate holder increases, the obtained titanium nitride thin film is strongly oriented to (111). In FIG. 6, the observed (111) peak is slightly shifted to the lower angle side with respect to the known (111) peak diffraction angle of titanium nitride because of the influence of the film stress ( 111) is presumed to be slightly larger than the standard value.
[0039]
FIG. 13 relates to the graph of FIG. 6, in the region where the high frequency bias power is relatively small, the diffraction intensity “I (100)” of the (111) peak with respect to the diffraction intensity “I (200)” of the (200) peak. The ratio (hereinafter referred to as the diffraction intensity ratio) is measured by changing the high frequency bias power. When the bias power was 0 W, it was observed that the diffraction intensity ratio was slightly less than 1. That is, the diffraction intensity of the (200) peak is slightly higher than the diffraction intensity of the (111) peak. When the bias power is 100 W, the diffraction intensity ratio clearly exceeds 1, and the (111) orientation is dominant. When the bias power is 200 W, the diffraction intensity ratio further increases. From this graph, it can be seen that the high frequency bias power for the substrate should be 100 W or more under the condition that 3 kW of high frequency power is applied to the plasma generating electrode in order to make the (111) orientation predominate even slightly. Note that when the high frequency power applied to the plasma generating electrode is changed to 2 kW, the high frequency bias power at which the (111) orientation starts to prevail changes (shifts to the lower bias power side than in the case of FIG. 6). That is, the lower limit value of the high-frequency bias power that the (111) orientation starts to become dominant varies depending on the value of the high-frequency power applied to the plasma generating electrode. Although there is such a variation, the (111) orientation becomes predominant when the high-frequency bias power is set to 100 W or more.
[0040]
Next, a second embodiment will be described. In this second embodiment, the temperature of the substrate was set at a lower temperature of 350 ° C. The other conditions are the same as the film forming conditions in the first embodiment. In this case, the deposition rate, in-plane film thickness distribution, hole coverage, and (111) orientation were the same as those of the titanium nitride thin film obtained in the first example. The resistivity of the film was about 40 μΩcm, and the chlorine content in the film was about 0.2 atomic%. Thus, a good titanium nitride thin film was obtained even when the substrate temperature was lowered to 350 ° C.
[0041]
In FIG. 1, the material of the plasma generating electrode 61 is titanium. This titanium is one of the constituent elements of the deposited film (titanium nitride). Therefore, even if the plasma generating electrode is sputtered and titanium is mixed into the thin film, it does not become a contaminant of the titanium nitride thin film.
[0042]
As shown in FIG. 5, when a multicusp magnetic field is formed in the vicinity of the inner wall surface of the processing chamber, relatively uniform plasma can be maintained at the center of the processing chamber that is about 5 cm or more away from the inner wall surface of the processing chamber. In order to form a large substrate with good uniformity (thickness distribution, film quality distribution, and uniformity of bottom coverage), it is very useful to form this multicusp magnetic field. In particular, when used in combination with a substrate bias power supply source, a good bottom coverage can be obtained with good uniformity and a further effect can be obtained. By forming this multicusp magnetic field, the thickness distribution of the titanium nitride thin film is improved.
[0043]
In the example of the apparatus shown in FIG. 1, the plasma generating electrode 61 is a one-turn coil, but may be formed in another shape. FIG. 11A shows an example in which the plasma generating electrode has a two-turn coil shape. Furthermore, you may make 3 turns or more. FIG. 11B shows an example in which the plasma generating electrode is spirally wound in a horizontal plane. The plasma generating electrode in FIG. 11C is an example of a single rectangular flat plate, and FIG. 11D is an example of a single circular flat plate. Further, the plasma generating electrode in FIG. 12A is an example of a single bar extending linearly. The plasma generating electrode in FIG. 12B is an example in which three rod-shaped electrodes are arranged in parallel in a horizontal plane, and the plasma generating electrode in FIG. 12C is a sample in which three rod-shaped electrodes are arranged in parallel in a vertical plane. Is an example. Each of the electrode examples shown in FIGS. 11 and 12 includes two terminals, one terminal is connected to a high-frequency power source, and the other end is grounded via a capacitor. In either case, the two terminals are located near both ends of the plasma generating electrode. Further, these plasma generating electrodes and their two terminals can be cooled by passing cooling water through them.
[0044]
FIG. 7 is a block diagram showing the main part of another example of the plasma CVD apparatus used in the present invention. In this example, the solenoid coil 130 is disposed above the plasma generating electrode 61. The other configuration is the same as that of the apparatus shown in FIG. The magnetic field lines 131 generated by the solenoid coil 130 diverge through the vicinity of the center of the plasma generating electrode 61 in the shape of a one-turn coil. Due to the action of the magnetic force lines 131, higher density plasma can be generated in the processing chamber 20. In addition, in this apparatus example, discharge can be easily started.
[0045]
As a combination of source gases, argon gas can be omitted from the above-described embodiments. For example, a titanium nitride thin film can be similarly produced by flowing titanium tetrachloride at a flow rate of 30 ml / min, hydrogen gas at 300 ml / min, and nitrogen gas at a flow rate of 60 ml / min.
[0046]
【The invention's effect】
According to the present invention, when a titanium nitride thin film is produced by plasma CVD, high-frequency power is supplied to one of two terminals of a plasma generating electrode in the processing chamber and the other terminal is grounded via a capacitor. To the substrate. Within the range of about 100W to 3000W By applying a high frequency bias power, a titanium nitride thin film having a (111) crystal orientation can be deposited on the substrate. This titanium nitride thin film has a good film quality with a low resistivity and a low chlorine content, and can be used as a diffusion preventing film and an adhesion film for metal wiring of a semiconductor integrated circuit.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an example of a plasma CVD apparatus for carrying out the method of the present invention.
FIG. 2 is a configuration diagram of a gas introduction mechanism.
FIG. 3 is a plan view of a plasma generating electrode.
FIG. 4 is a perspective view in which a part of the insulating ring is cut.
5 is a cross-sectional view taken along line 5-5 of FIG.
FIG. 6 is a graph of an X-ray diffraction pattern showing the substrate bias power dependence of the crystal orientation of a titanium nitride thin film.
FIG. 7 is a block diagram showing the main part of another example of the plasma CVD apparatus used in the present invention.
FIG. 8 is a configuration diagram showing a modified example of the ground coupling mechanism.
FIG. 9 is a graph showing the relationship between the capacitance of a capacitor and the DC bias voltage of a plasma generating electrode.
FIG. 10 is a configuration diagram showing another modification of the ground coupling mechanism.
FIG. 11 is a perspective view showing a modified example of the plasma generating electrode.
FIG. 12 is a perspective view showing another modified example of the plasma generating electrode.
FIG. 13 is a graph showing the high frequency bias power dependency of the diffraction intensity ratio of a titanium nitride thin film.
[Explanation of symbols]
10 Gas introduction mechanism
20 treatment room
21 Base
25 Base holder
30 Exhaust mechanism
50 Power supply source
52 High frequency power supply
61 Plasma generating electrode
62, 63 Introduction terminal
80 Ground coupling mechanism
81 capacitors
90 Bias power supply
92 High frequency power supply for bias

Claims (3)

In a method for producing a titanium nitride thin film in which a raw material gas is introduced into a processing chamber and a titanium nitride thin film is deposited on a substrate in the processing chamber by plasma CVD, a plasma generating electrode having two terminals is disposed inside the processing chamber. Then, one terminal of the plasma generating electrode is connected to a high-frequency power supply source, and the other terminal is grounded via a capacitor to generate plasma inside the processing chamber, and about 100 W to 3000 W on the substrate. A titanium nitride thin film having a (111) crystal orientation is deposited on the substrate by applying a high frequency bias power within a range of The RF bias power The method of claim 1, wherein in the range of 300W～1000W. In a method for producing a titanium nitride thin film in which a raw material gas is introduced into a processing chamber and a titanium nitride thin film is deposited on a substrate in the processing chamber by plasma CVD, a plasma generating electrode having two terminals is arranged inside the processing chamber. Then, one terminal of the plasma generating electrode is connected to a high-frequency power supply source, and the other terminal is grounded via a capacitor having a capacitance of 100 pF to 10 μF to generate plasma inside the processing chamber. A method for producing a titanium nitride thin film, comprising applying a high frequency bias power to the substrate to deposit a titanium nitride thin film having a (111) crystal orientation on the substrate.

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