JP3698680B2 - Deposition method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film forming method, and more particularly to a method for forming a hafnium compound thin film.
[0002]
[Prior art]
A thin film of a hafnium compound, particularly a hafnium nitride film, is a thin film having an extremely high dielectric constant, and has recently attracted attention as a high dielectric thin film, a magnetic thin film, or a refractory metal thin film of a semiconductor element.
[0003]
Reference numeral 110 in FIG. 6 shows an apparatus used for forming a conventional hafnium nitride film. This apparatus has a vacuum chamber 101. An evacuation system 171 is connected to the vacuum chamber 101, and the inside of the vacuum chamber 101 can be evacuated when the evacuation system 171 is activated.
[0004]
An electron beam evaporation source 190 is disposed at the bottom of the vacuum chamber 101. The electron beam evaporation source 190 includes a crucible 103 and a filament 150. The crucible 103 can arrange a hafnium vapor deposition material made of hafnium (Hf) inside. The arranged hafnium vapor deposition material is indicated by reference numeral 143 in FIG. The filament 150 is located in the vicinity of the crucible 103 and is connected to a power source 151 disposed outside the vacuum chamber 101. When the power source 151 is activated with the hafnium vapor deposition material 143 filled in the crucible 103, the filament 150 generates heat. The electrons are emitted, and the thermal electrons are accelerated by an accelerator (not shown) and then irradiated onto the hafnium vapor deposition material 143, whereby the hafnium vapor deposition material 143 is melted and vapor of the hafnium vapor deposition material 143 is generated. ing.
[0005]
A substrate holder 105 is disposed vertically above the crucible 103. The substrate holder 105 is configured to be able to hold the substrate surface in a state where the substrate surface is directed vertically downward. The substrate in this state is indicated by reference numeral 108. The substrate holder 105 is provided with a lamp heater 131. When the substrate heater 105 is held by the substrate 108 and the lamp heater 131 is energized to generate heat, the substrate holder 105 can be heated and the substrate 108 can be heated. It is configured as follows.
[0006]
A gas introduction nozzle 163 is arranged in the vicinity of the substrate holder 105. The gas introduction nozzle 163 is connected to the gas cylinder 161 via a valve 162 arranged outside the vacuum chamber 101. When the valve 162 is opened while the substrate holder 105 holds the substrate 108, the nitrogen in the gas cylinder 161 is opened. The gas can be supplied to the surface of the substrate 108.
[0007]
In order to form a hafnium nitride film using the vapor deposition apparatus 110, first, the substrate 108 is held by the substrate holder 105, and the vacuum exhaust system 171 is activated to evacuate the inside of the vacuum chamber 101. A heater 181 is wound around the wall surface of the vacuum chamber 101, and when the internal pressure of the vacuum chamber 101 becomes 1.3 × 10 ⁻⁴ Pa or less, the heater 181 is energized to heat the inside of the vacuum chamber 101. Then, water adsorbed on the inner wall surface of the vacuum chamber 101 is desorbed and exhausted. Thereafter, when the pressure inside the vacuum chamber 101 reaches 6.5 × 10 ⁻⁷ Pa or less, heating of the heater 181 is stopped.
[0008]
Next, the lamp heater 131 is activated to heat the substrate holder 105, and the substrate holder 105 is heated to about 800 ° C. to 1000 ° C. to raise the temperature of the substrate 108. Next, when the electron beam evaporation source 190 is activated to evaporate the hafnium vapor deposition material 143, the vapor rises upward, and the constituent particles of the vapor of the hafnium vapor deposition material reach the surface of the substrate 108 heated to a high temperature. To do. Then, the constituent particles of the vapor of the hafnium vapor deposition material are activated by heat.
[0009]
Nitrogen gas is supplied to the surface of the substrate 108 from the gas introduction nozzle 163, and the constituent particles of the activated hafnium vapor deposition material vapor react with the nitrogen gas, and a hafnium nitride thin film grows on the surface of the substrate 108. When the hafnium nitride thin film has a desired thickness, the operation of the electron beam evaporation source 190 is stopped and the introduction of nitrogen gas is stopped, and the film forming process is ended.
[0010]
In the conventional film forming method, the hafnium vapor deposition material 143 is evaporated using the electron beam vapor deposition source 190. Since the constituent particles of the hafnium vapor generated by this evaporation were electrically neutral, the nitriding reaction of hafnium did not proceed even if nitrogen gas was simply flowed over the surface of the substrate 105. Therefore, the substrate holder 105 must be heated to a temperature of 800 ° C. to 1000 ° C., the temperature of the substrate 108 is raised to a high temperature, and hafnium adhering to the surface of the substrate 108 must be activated by heat to cause a nitriding reaction.
[0011]
Therefore, a material that can withstand high temperatures is required as the material of the substrate 108. Further, since the electron beam evaporation source 190 emits a large amount of heat, the temperature of the inner wall of the vacuum chamber 101 becomes high, and oxygen that cannot be desorbed by the inner wall of the vacuum chamber 101, hydrogen generated by decomposition of water, and the like There is a problem that it adheres to the surface of the hafnium film and is mixed as an impurity.
[0012]
[Problems to be solved by the invention]
The present invention was created to solve the above-mentioned disadvantages of the prior art. The purpose of the present invention is to form a hafnium compound thin film without heating to a high temperature and to mix impurities in the thin film. The purpose is to provide technology to prevent such a situation.
[0013]
[Means for Solving the Problems]
The present invention was created based on the above knowledge, and the invention according to claim 1 is a film forming method, wherein a gas introduction nozzle for introducing a raw material gas is disposed in a vacuum chamber, and the gas A substrate is disposed in the vicinity of the introduction nozzle, a hafnium vapor deposition material is disposed on the substrate center axis perpendicular to the substrate surface through the approximate center of the substrate, and the source gas is introduced to the vicinity of the substrate surface by the gas introduction nozzle. And when a positive charge is emitted from a side surface of the hafnium vapor deposition material in a direction parallel to the substrate surface, a magnetic field that applies a force toward the substrate to the positive charge is formed around the substrate central axis. Discharging at least charged particles of a constituent material of the hafnium vapor deposition material from the hafnium vapor deposition material, moving the charged particles in the direction of the substrate, and reacting with the source gas; The surface, forming a thin film made of the reaction product.
[0014]
In the film forming method of the present invention, an anode electrode and a trigger electrode are arranged in the vicinity of the hafnium vapor deposition material in a vacuum atmosphere, and a negative voltage with respect to the anode electrode is applied to the hafnium vapor deposition material. When a trigger discharge is generated between the electrode and the trigger electrode, a part of the hafnium vapor deposition material is melted by the trigger discharge and the constituent particles of the vapor deposition material are released, and the pressure between the vapor deposition material and the anode electrode is increased, resulting in hafnium. The withstand voltage between the vapor deposition material and the anode electrode decreases, and arc discharge occurs between the hafnium vapor deposition material and the anode electrode.
[0015]
At this time, when the arc current flowing by the arc discharge is caused to flow in a direction parallel to the substrate center axis and away from the substrate, a magnetic field is formed around the substrate center axis by the arc current. The direction of the magnetic field is a direction in which the right screw is rotated so that the right screw advances when the direction in which the arc current flows is defined as the moving direction of the right screw.
[0016]
The magnetic field and the arc current flowing in the direction away from the substrate in parallel with the substrate central axis are the positive charge and electrons emitted from the hafnium vapor deposition material to the positive charge and electrons along the substrate central axis. It exerts a Lorentz force toward the direction toward the surface, and the movement direction of positive charges and electrons is bent toward the substrate. In particular, since electrons have a small mass and a small radius of curvature to deflect, the traveling direction is bent toward the substrate. The positive charge is attracted to the bent electrons by the Coulomb force and bent.
[0017]
When the hafnium vapor deposition material is evaporated in a state where such a magnetic field is generated, the vapor generated by the evaporation contains positively charged particles, negatively charged particles, and electrically neutral particles. The positively charged particles, the negatively charged particles, and the neutral particles are released into the above-described magnetic field.
[0018]
As described above, a negative voltage is applied to the hafnium vapor deposition material with respect to the anode electrode, and the positively charged charged particles move to the hafnium vapor deposition material. receive. On the other hand, the negatively charged charged particles move to the anode electrode in the opposite direction to the positively charged charged particles, and receive a force in a direction approaching the substrate like the positively charged charged particles.
[0019]
Accordingly, both the positively charged particles and the negatively charged particles receive a Lorentz force directed toward the opening of the anode electrode, and the moving direction is bent by the force, approaching the substrate, and moving toward the substrate.
[0020]
When neutral particles contained in the vapor of the vapor deposition material are released from the hafnium vapor deposition material, unlike the charged particles, they do not receive the Lorentz force due to the magnetic field, so the moving direction does not bend in the substrate direction and cannot reach the substrate surface. . Also, even if the huge particles contained in the vapor are uncharged or have a charge, the mass is extremely large compared to the amount of charge, so the amount of bending due to the Lorentz force is small, adheres to the anode electrode, and adheres to the substrate surface. Is not reachable. Therefore, only charged particles of the hafnium vapor deposition material, which are active particles, can reach the substrate surface.
[0021]
When charged particles of the hafnium vapor deposition material reach the substrate surface, the charged particles of the hafnium vapor deposition material are active, so they combine with the constituent materials of the source gas, and a hafnium compound thin film grows on the substrate surface without heating the substrate as in the past To do. For this reason, unlike the conventional case, the inside of the vacuum chamber is not heated to a high temperature, so oxygen or water on the inner wall of the vacuum chamber heated to a high temperature is not desorbed and mixed into the thin film as impurities, and the high-purity hafnium compound A thin film can be formed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Reference numeral 10 in FIG. 1 shows a vapor deposition apparatus used in a film forming method according to an embodiment of the present invention. The vapor deposition apparatus 10 has a vacuum chamber 1. An evacuation system 71 is connected to the vacuum chamber 1, and the interior of the vacuum chamber 1 can be evacuated when the evacuation system 71 is activated.
[0023]
A substrate holder 5 is disposed on the ceiling side inside the vacuum chamber 1. The substrate holder 5 is configured to hold the substrate with the substrate surface directed vertically downward. Reference numeral 8 in FIG. 1 indicates the substrate in that state.
[0024]
A gas introduction nozzle 63 is arranged in the vicinity of the substrate holder 5. The gas introduction nozzle 63 is connected to the gas cylinder 61 via a valve 62 disposed outside the vacuum chamber 1. When the valve 62 is opened while the substrate holder 5 holds the substrate, the nitrogen in the gas cylinder 61 is opened. The gas can be supplied to the substrate surface.
[0025]
A coaxial vacuum arc vapor deposition source 3 is disposed vertically below the substrate holder 5. The coaxial vacuum arc vapor deposition source 3 has a cylindrical anode electrode 30 and a hafnium vapor deposition material 43 made of hafnium.
[0026]
The anode electrode 30 is arranged such that its central axis coincides with the substrate central axis extending in the direction perpendicular to the surface of the substrate 8 through the center of the substrate 8. The anode electrode opening 30a faces vertically upward. Reference numeral 8b in FIG. 1 shows these coincident central axes, which will be simply referred to as a substrate central axis 8b hereinafter.
The hafnium vapor deposition material 43 is provided inside the anode electrode 30, and is disposed on the substrate center axis 8 b in a non-contact state with the anode electrode 30.
[0027]
A schematic cross-sectional view of the coaxial vacuum arc deposition source 3 is shown in FIG. A trigger electrode 42 is arranged in the vicinity of the hafnium vapor deposition material 43. The trigger electrode 42 and the hafnium vapor deposition material 43 are in a non-contact state and insulated from each other. Here, the trigger electrode 42 and the hafnium vapor deposition material 43 are insulated from each other by the insulating member 41.
[0028]
A cathode electrode 45 is provided in the anode electrode 30, and the hafnium vapor deposition material 43 is led out of the anode electrode 30 by the cathode electrode 45. Here, the cathode electrode 45 is formed in a rod shape and is disposed in parallel with the substrate center axis 8b.
[0029]
The vacuum chamber 1 is grounded. A trigger power source 46 and an arc power source 47 are disposed outside the vacuum chamber 1.
The trigger power supply 46 is connected to the trigger electrode 42 and the cathode electrode 45, and is configured such that a negative voltage can be applied to the trigger electrode 42 when the trigger power supply 46 is activated. On the other hand, the arc power source 47 is connected to the anode electrode 30 and the cathode electrode 45, and the anode electrode 30 is grounded. When the arc power source 47 is started, the cathode electrode 45 has a negative polarity with respect to the anode electrode 30 at the ground potential. In addition, a negative voltage higher than the voltage applied to the trigger electrode 42 can be applied.
[0030]
When forming a hafnium nitride thin film using the vapor deposition apparatus 10, the substrate 8 made of silicon is held by the substrate holder 5, and the inside of the vacuum chamber 1 is evacuated. When the pressure inside the anode electrode 30 reaches 6.5 × 10 ⁻⁷ Pa or less, nitrogen gas is supplied to the surface of the substrate 8 from the gas introduction nozzle 63 and a voltage is applied between the anode electrode 30 and the hafnium vapor deposition material 43. When a pulse voltage is applied to the trigger electrode 42, a trigger discharge is generated between the trigger electrode 42 and the side surface of the hafnium vapor deposition material 43. Due to this trigger discharge, a trigger current flows through the hafnium vapor deposition material 43. Code i ₁ of Figure 3 shows the trigger current, the trigger current i _1, the side surface of the hafnium deposition material 43 is evaporated, the constituent particles of hafnium deposition material 43 is released from its side, the anode electrode 30 inside The pressure increases.
[0031]
As a result, the withstand voltage between the anode electrode 30 and the hafnium vapor deposition material 43 decreases, and arc discharge occurs between the side surface of the hafnium vapor deposition material 43 and the anode electrode 30. When the arc current i ₂ flows from the inner peripheral surface of the anode electrode 30 toward the side surface of the hafnium vapor deposition material 43 by the arc discharge, the hafnium vapor deposition material 43 is melted and vapor is released from the side surface of the hafnium vapor deposition material 43. Since the arc current i ₂ is a large current of 1200 to 1400 A, the amount of steam released is larger than the steam released during the trigger discharge.
[0032]
The arc current i ₂ flows linearly in the rod-like cathode electrode 45 from the end on the hafnium vapor deposition material 43 side to the opposite end on the substrate center axis 8b in a direction away from the substrate 8. Due to the arc current i ₂ , a magnetic field is formed around the cathode electrode 45 so as to turn the right screw so that the right screw advances when the flow direction of the arc current i ₂ is the advancing direction of the right screw. The This magnetic field is indicated by reference numeral 20a in FIG. Since the arc current i ₂ flows in the same direction as the central axis of the cathode electrode 45 and in the same direction as the substrate central axis 8b, the magnetic field 20a is formed around the substrate central axis 8b.
[0033]
The large amount of vapor emitted by the arc current i ₂ contains charged particles of the hafnium vapor deposition material 43 and neutral particles of the electrically neutral hafnium vapor deposition material 43. particles, subjected to a force by a magnetic field 20a which is formed by an arc current i _2. The charged particles of the hafnium vapor deposition material 43 include positively charged particles and negatively charged particles. As described above, since a positive voltage is applied to the anode electrode 30 with respect to the cathode electrode 45, the positively charged particles and the negatively charged particles move toward the hafnium vapor deposition material 43, and the anode electrode On the other hand, the negatively charged charged particles move toward the anode electrode 30 in the opposite direction to the positively charged particles. Similarly to the positively charged particles, the negatively charged charged particles move to the anode electrode 30. Receives force in the opening direction.
[0034]
Both the positively charged particles and the negatively charged particles receive a force F directed in the opening direction of the anode electrode 30, the movement direction is bent by the force F, and the inside of the vacuum chamber 1 is opened from the opening 30 a of the anode electrode 30. Is released. In particular, since the negative charge has a small mass, it is bent into the opening of the anode electrode 30. The positive charge is attracted to the negatively charged electron group by Coulomb force and bent to the anode opening. The charged particles are indicated by reference numeral 51 in FIG. The substrate 8 is positioned vertically above the opening 30a of the anode electrode, and the charged particles 51 move toward the substrate 8 and reach the surface of the substrate 8.
[0035]
Since the neutral particles 52 of the hafnium vapor deposition material 43 are electrically neutral and do not receive the force F due to the magnetic field, the moving direction is not bent in the direction of the opening 30a of the anode electrode. The inner surface of the substrate 8 does not reach the surface of the substrate 8. Therefore, only the charged particles 51 that are active particles reach the surface of the substrate 8. Since the charged particles 51 are active particles, they react with the nitrogen gas supplied to the surface of the substrate 8 to generate hafnium nitride, and a hafnium nitride thin film begins to grow on the surface of the substrate 8.
[0036]
As described above, according to the film forming method of the present invention, a hafnium nitride thin film can be formed without heating the surface of the substrate and activating the hafnium particles with heat, and the inside of the vacuum chamber 1 is kept at room temperature. A hafnium nitride thin film can be formed even to the extent. Therefore, unlike the conventional case where the inside of the vacuum chamber is heated because the substrate and the vacuum chamber are heated, oxygen and water etc. on the inner wall of the vacuum chamber are not desorbed and mixed into the thin film as impurities. High hafnium nitride film can be obtained.
[0037]
The large amount of vapor described above includes a large particle 53 having a mass larger than the charge amount. However, the large particle 53 has a small amount of bending in the moving direction due to the force F, and as a result, the large particle 53. Adheres to the inner peripheral surface of the anode electrode 30 and does not reach the surface of the substrate 8. When the giant particles 53 reach the surface of the substrate 8, they become so-called droplets and are mixed into the growing thin film, and the film quality of the thin film deteriorates. However, the giant particles 53 do not reach the substrate surface, so the substrate 8 A hafnium nitride thin film having excellent crystallinity can be formed on the surface.
[0038]
Since the arc current i ₂ is a large current, the arc power supply 47 is consumed so much that the arc discharge automatically stops when the output voltage of the arc power supply 47 decreases to such an extent that the arc discharge cannot be maintained. The amount of the charged particles 51 emitted by one trigger discharge is determined by the power supply capability of the arc power supply 47. Therefore, by repeatedly generating the trigger discharge as many times as necessary, a hafnium nitride thin film having a desired film thickness is formed on the substrate 8. A film can be formed on the surface. When the hafnium nitride thin film having a desired thickness is formed, the operation of the trigger power source 46 and the arc power source 47 is stopped and the introduction of the nitrogen gas is stopped to finish the film forming process.
[0039]
The inventors of the present invention formed a hafnium nitride thin film on the sample substrate by the above-described film forming method while changing the film forming conditions in order to investigate favorable film forming conditions of the hafnium nitride thin film. FIG. 4 is a graph showing the dependence of hafnium nitridation on the N ₂ partial pressure in the vacuum chamber. In FIG. 4, the horizontal axis represents the N ₂ partial pressure in the vacuum chamber, and the vertical axis represents the molecular density of hafnium nitride. The internal pressure before the start of film formation is 1 × 10 ⁻⁹ Torr. As shown in FIG. 4, the higher the N ₂ partial pressure, the higher the molecular density of hafnium nitride. The N ₂ partial pressure is 1 × 10 ⁻⁶ Torr and the molecular density of hafnium nitride is about 25%. It can be seen that the molecular density is increased to about 40% at 5 × 10 ⁻³ Torr.
[0040]
Further, the inventors of the present invention formed a hafnium nitride thin film on the surface of the sample substrate, and examined the atomic density in the depth direction by Auger analysis. FIG. 5 shows the measurement results. The horizontal axis in FIG. 5 represents the sputtering time, which corresponds to the depth from the surface of the thin film. The vertical axis in FIG. 5 is the atomic density. The curve (A) in FIG. 5 corresponds to Hf, the curve (B) corresponds to N ₂ , the curve (C) corresponds to Si, the curve (D) corresponds to O, and the curve (E) corresponds to C. The sample substrate was made of Si, and the film was formed under the condition that the N ₂ partial pressure was 5 × 10 ⁻³ Torr.
[0041]
As shown in curves (A), (B), and (C), the atomic density of Hf and N ₂ is increased up to a depth at which Si as a substrate material starts to be detected (sputtering time: about 7 to 8 minutes). The ratio is almost constant. From this, it was confirmed that Hf was nitrided from the time when Hf began to adhere to the substrate surface.
[0042]
In the above-described embodiment, the hafnium vapor deposition material 43 is disposed on the substrate center axis 8b, and the substrate center axis 8b is configured to pass through the center of the substrate 8. However, the substrate center axis 8b is not necessarily the substrate 8. The substrate center axis 8b may pass near the center of the substrate 8, and the hafnium vapor deposition material 43 may be disposed on the substrate center axis 8b.
[0043]
In the above-described film forming method, the coaxial arc vapor deposition source 3 is used. However, in order to perform the film forming method of the present invention, the coaxial arc vapor deposition source is not necessarily required, and charged particles of hafnium are used as the substrate. Any device may be used as long as it can reach the surface.
[0044]
Further, the case of forming a thin film of hafnium nitride has been described. However, the film forming method of the present invention is not limited to the formation of a hafnium nitride thin film, and can be applied to the film formation of any hafnium compound. For example, hafnium oxide (HfO) It is also applicable to film formation of hafnium carbide (HfC) or the like.
[0045]
【The invention's effect】
A hafnium compound thin film can be formed at room temperature, and a hafnium compound thin film with high purity can be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a vapor deposition apparatus used in the film forming method of the present invention. FIG. 2 is a cross-sectional view showing a coaxial vacuum arc vapor deposition source used in the film forming method of the present invention. FIG. 4 is a graph illustrating the principle of a vacuum arc evaporation source. FIG. 4 is a graph showing the dependence of hafnium nitridation on the N ₂ partial pressure in a vacuum chamber in a film forming method according to an embodiment of the present invention. 6 is a graph showing the atomic density distribution in the depth direction of a hafnium nitride thin film formed by the film forming method according to one embodiment. FIG. 6 is a cross-sectional view illustrating a vapor deposition apparatus used in a conventional film forming method. Description】
DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 3 ... Coaxial type vacuum arc vapor deposition source 10 ... Deposition apparatus 20a ... Magnetic field 30 ... Anode electrode 30a ... Opening 41 ... Insulating member 42 ... Trigger electrode 43 ... Deposition material 45 ... Cathode electrode 51 …… Charged particle 52 …… Neutral particle 63 …… Gas introduction nozzle

Claims (1)

A gas introduction nozzle for introducing the raw material gas into the vacuum chamber is arranged,
A substrate is disposed in the vicinity of the gas introduction nozzle,
A hafnium vapor deposition material is disposed on the substrate center axis perpendicular to the substrate surface through the approximate center of the substrate,
The source gas is caused to flow near the substrate surface with the gas introduction nozzle,
When a positive charge is emitted from a side surface of the hafnium vapor deposition material in a direction parallel to the substrate surface, a magnetic field that applies a force toward the substrate to the positive charge is formed around the substrate central axis, and From the hafnium vapor deposition material, at least charged particles of the constituent material of the hafnium vapor deposition material are released,
A deposition method in which the charged particles are moved in the direction of the substrate and reacted with the source gas to form a thin film made of a reaction product on the substrate surface.

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