JP2011231390A - Film forming method and film forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film forming method which can deposit sputter particles inside a hole or a groove when a thin film is formed on a substrate with the hole or the groove at a high aspect ratio by sputtering, and can attempt to enhance the film forming ability.SOLUTION: In the film forming method, a voltage is applied to a target 13 arranged inside a vacuum chamber 10, plasma is generated in space between the target and a substrate 2 arranged opposing to the target, and the sputter particles beaten out from the target by the plasma are deposited on the substrate, thereby forming a thin film on the substrate. A meshed intermediate electrode 18 is arranged between the target and the substrate so as to block the substrate when viewing from the target, and a pulse voltage of a minus potential is applied to the intermediate electrode.

Description

  The present invention relates to a film forming method and a film forming apparatus for forming a thin film on a substrate by sputtering.

  Consider a technique for forming a thin film by sputtering on a semiconductor substrate in which holes and grooves are formed. In normal sputtering, there are sputtered particles that are incident on the substrate at an angle, so the film thickness in the hole / structure is thinner than the substrate surface.

  In order to improve this, there is a method in which a bias voltage is applied to the substrate to draw the sputtered particles in the direction of the substrate, and the sputtered particles are vertically incident on the substrate to improve the film forming property in the hole / premises. However, when a high voltage is applied to the substrate, there is a risk that a device formed on the substrate may be damaged, and there is a limit to the bias voltage that can be applied.

  Further, as shown in FIG. 5, when sputter deposition is performed on a semiconductor substrate, a porous grid electrode 102 is provided between the target 100 and the substrate 101, and a DC negative voltage or an AC voltage is applied to the grid electrode to form sputtered particles. A method of accelerating positive ions in the grid direction has also been proposed (see, for example, Patent Document 1). Sputtered particles emitted from the target are ionized by the coil electrode 103, and a DC negative voltage or an AC voltage is applied to the grid electrode to accelerate the positive ions of the sputtered particles in the grid direction. Since the grid electrode is porous, most of the accelerated ions pass through the grid and are incident on the substrate in a direction nearly perpendicular to the substrate.

  According to this method, a negative voltage is applied to the grid electrode while the substrate is grounded. Therefore, after ions accelerated in the grid direction from the target pass through the grid, this time, the ions are attracted in the grid direction and decelerated. Since the velocity component parallel to the substrate is not affected by the grid, the velocity component in the lateral direction of ions cannot be ignored as the substrate approaches the substrate, and eventually the ions are incident on the substrate in an oblique direction. Therefore, it is considered that it does not contribute to the improvement of the film formability in the hole (that is, the possibility of forming a film having a uniform film thickness on the side wall and bottom surface of the hole).

JP-A-8-213320

The present invention has been devised in view of such a conventional situation, and when a thin film is formed by sputtering on a substrate in which holes and grooves having a high aspect ratio are formed, sputtered particles are formed inside the holes and grooves. The first object is to provide a film forming method capable of depositing the film and capable of improving the film forming property.
In addition, the present invention is provided with a means for inducing sputtered particles inside a high aspect ratio hole or groove when a thin film is formed by sputtering on a substrate on which a high aspect ratio hole or groove is formed. A second object is to provide a film forming apparatus having film properties.
In the present invention, “film formability” means the ability to form a thin film having a uniform film thickness inside the holes and grooves.

According to a first aspect of the present invention, a voltage is applied to a target disposed in a vacuum vessel, and plasma is generated in a space between the target and a substrate disposed opposite to the target. In the film forming method for forming a thin film on the substrate by depositing sputtered particles knocked out of the target by the plasma on the substrate, the target is viewed from the target. A mesh-shaped intermediate electrode is arranged so as to block the substrate, and a pulse voltage having a negative potential is applied to the intermediate electrode.
A film forming method according to a second aspect of the present invention is the film forming method according to the first aspect, wherein the sputtered particles are uniformly directed toward the substrate according to the surface profile of the substrate by passing the intermediate electrode. It is characterized by that.
The film forming method according to claim 3 of the present invention is the film forming method according to claim 1 or 2, wherein the sputtered particles are ionized using a pulse power source, and the pulse voltage of the pulse power source and the pulse voltage applied to the mesh electrode are used. Are synchronized with each other.
According to a fourth aspect of the present invention, there is provided a film forming apparatus comprising: a vacuum vessel; a gas supply unit that supplies a process gas into the vacuum vessel; an exhaust unit that exhausts the gas in the vacuum vessel; A target placed on the substrate, a substrate stage disposed opposite to the target in the vacuum vessel and holding the substrate, a voltage is applied to the target, and plasma is generated in a space between the target and the substrate stage. Between the target and the substrate, a mesh-shaped intermediate electrode disposed so as to shield the substrate when viewed from the target, and a pulse voltage having a negative potential applied to the intermediate electrode. And a pulse power source to be applied.
According to a fifth aspect of the present invention, the film forming apparatus according to the fourth aspect further includes an ionization mechanism that ionizes sputtered particles knocked out of the target by the plasma.

  In the film forming method of the present invention, a mesh-like intermediate electrode is arranged between the target and the substrate so as to shield the substrate when viewed from the target, and a negative potential pulse voltage is applied to the intermediate electrode. Therefore, it becomes possible to cause the sputtered particles having a charge to enter the substrate perpendicularly by the pulse voltage. Accordingly, in the present invention, it is possible to deposit sputtered particles inside the holes and grooves having a high aspect ratio, and it is possible to provide a film forming method with improved film formability.

  In the film forming apparatus of the present invention, a mesh-like intermediate electrode disposed between the target and the substrate so as to shield the substrate when viewed from the target, and a pulse voltage having a negative potential applied to the intermediate electrode are applied. It is possible to cause the sputtered particles to be perpendicularly incident on the substrate by the pulse voltage applied to the intermediate electrode, and to induce the sputtered particles inside the high aspect ratio holes and grooves. Can do. Accordingly, in the present invention, it is possible to provide a film forming apparatus in which sputtered particles can be deposited inside the holes and grooves having a high aspect ratio, and the film forming property is improved.

The figure which shows the example of 1 structure of the film-forming apparatus which concerns on this invention. The figure which shows the other structural example of the film-forming apparatus which concerns on this invention. The figure which illustrates typically the behavior of a sputtered particle in this invention. The figure which shows a mode that sputtered particles are deposited inside the hole and groove | channel of a high aspect ratio. The figure which shows the example of 1 structure of the conventional film-forming apparatus.

  Hereinafter, preferred embodiments of a film forming method and a film forming apparatus of the present invention will be described.

FIG. 1 is a diagram schematically showing a configuration example of a film forming apparatus according to the present invention.
The film forming apparatus 1 of the present invention includes a vacuum vessel 10, a gas supply unit 11 that supplies a process gas into the vacuum vessel 10, an exhaust unit 12 that exhausts the gas in the vacuum vessel 10, and the vacuum vessel 10. A target 13 disposed in the substrate, a substrate stage 14 disposed opposite to the target 13 in the vacuum vessel 10 and holding the substrate 2, a voltage is applied to the target 13, and the target 13 and the substrate A voltage application means 15 for generating plasma in a space between the stage 14 and a mesh-like element disposed between the target 13 and the substrate 2 so as to shield the substrate 2 when viewed from the target 13. It is characterized by comprising at least an intermediate electrode 18 and a pulse power source 19 for applying a negative potential pulse voltage to the intermediate electrode 18.

In the film forming apparatus 1 of the present invention, a mesh-like intermediate electrode 18 disposed between the target 13 and the substrate 2 so as to shield the substrate 2 when viewed from the target 13, and the intermediate electrode 18 minus the intermediate electrode 18. Since the pulse power supply 19 for applying the pulse voltage of the potential and the wiring 20 for electrically connecting the two (the intermediate electrode 18 and the pulse power supply 19) are provided, the pulse voltage applied to the intermediate electrode 18 It becomes possible to make the sputtered particles 3 enter the substrate 2 perpendicularly. At that time, an ionization source 21 is disposed in the vicinity of the target 13, and a DC power source 22 is electrically connected to the ionization source 21 via a wiring 23.
Thus, according to the present invention, when forming a film on the substrate 2 in which holes and grooves having a high aspect ratio are formed, the sputtered particles are induced inside the holes and grooves, and the sputtered particles 3 are deposited inside the holes and grooves. Can do. As a result, the film formability can be improved. That is, it is possible to form a film having a uniform film thickness on the side wall and bottom surface of the hole.

FIG. 2 is a diagram schematically showing another configuration example of the film forming apparatus according to the present invention.
The film forming apparatus in FIG. 2 differs from the film forming apparatus in FIG. 1 in the number of necessary power supplies. The other structure is the same as FIG. 1 and FIG. That is, in the film forming apparatus of FIG. 2, the pulse power source 19 connected to the intermediate electrode 18 is also connected in parallel to the ionization source 21 and functions as a DC power source. Thus, according to the film forming apparatus of FIG. 2, the number of necessary power supplies can be halved, so that it is possible to reduce power consumption and simultaneously save space.

The vacuum vessel 10 is a highly airtight vessel formed of iron, stainless steel, aluminum or the like that maintains a predetermined degree of vacuum for performing sputtering, and is grounded.
A gas supply means 11 for supplying a process gas for film formation and an exhaust means 12 for exhausting the gas in the vacuum container 10 are attached to the vacuum container 10.
As the process gas supplied into the vacuum vessel 10 by the gas supply means 11, argon (Ar) or a mixed gas of argon (Ar) and oxygen (O ₂ ) can be used.
The evacuation unit 12 evacuates the gas in the vacuum container 10 in order to make the inside of the vacuum container 10 have a predetermined degree of vacuum and to maintain this predetermined degree of vacuum during film formation.

Although the material of the target 13 is not specifically limited, For example, Ti, Cu, Cr etc. are mentioned. Further, the size of the target 13 is not particularly limited, but for example, the surface area is about 750 cm ² (circular shape with a diameter of 310 mm).

  The substrate stage 14 is disposed to face the target 13 in the vacuum vessel 10. The substrate 2 that is the object to be processed is held on the substrate stage 14. In the film forming apparatus 1, the target 13 and the substrate 2 are disposed so as to be substantially parallel. The distance between the target 13 and the substrate 2 is not particularly limited, but is about 10 cm, for example.

The voltage application unit 15 includes a sputtering electrode 16 and a high-frequency power source 17 connected to the sputtering electrode 16.
The sputter electrode 16 is disposed above the inside of the vacuum vessel 10 and holds a target 13 having a composition corresponding to the composition of a thin film such as a piezoelectric film formed on the surface thereof, and is connected to a high frequency power source 17. Has been. The sputter electrode 16 is discharged by applying high-frequency power (negative high-frequency) from the high-frequency power source 17, and gas such as Ar introduced into the vacuum chamber 10 is turned into plasma to generate positive ions such as Ar ions.

  The high-frequency power source 17 is for supplying a high-frequency power (negative high-frequency) for turning the gas such as Ar introduced into the vacuum vessel 10 into plasma to the sputter electrode 16, and one end of the high-frequency power source 17 is sputtered. The other end is connected to the electrode 16 and grounded. The sputter application power of the voltage application means 15 is not particularly limited. For example, the frequency of the high frequency power supply 17 is 13.56 MHz and the output is 1.5 kW to 3.0 kW.

  The positive ions generated in this way sputter the target 13. In this way, the constituent elements of the target 13 sputtered (struck out) by the positive ions are released from the target 13 and are neutralized or ionized on the substrate 2 held on the substrate stage 14. Vapor deposited.

In the film forming apparatus 1 of the present invention, a mesh-like intermediate electrode 18 disposed between the target 13 and the substrate 2 so as to shield the substrate 2 when viewed from the target 13, and the intermediate electrode 18 and a pulse power source 19 for applying a negative potential pulse voltage.
The intermediate electrode 18 is preferably made of a nonmagnetic material, for example, stainless steel.

  The mesh shape of the intermediate electrode 18 is not particularly limited and may be anything as long as the sputtered particles 3 can pass therethrough. The larger the mesh opening, the better the transmittance of the sputtered particles 3, but if the mesh opening is too large, the electric field near the intermediate electrode 18 becomes non-uniform. If the mesh opening is too small, the sputtered particles 3 adhere and accumulate, and clogging is likely to occur. For example, the mesh opening is set to about 1 cm square or less.

The intermediate electrode 18 is installed in a space between the target 13 and the substrate 2 so as to block the substrate 2 when viewed from the target 13.
Although the position where the intermediate electrode 18 is disposed is not particularly limited, the sputtered particles 3 collide with the atoms of the discharge gas while flying from the mesh electrode to the substrate 2, and therefore, between the intermediate electrode 18 and the substrate 2. If the distance is long, the sputtered particles 3 are decelerated. For example, the mean free path at a pressure of 1 Pa is about 1 cm. A position close to the substrate between the target 13 and the substrate 2, for example, about 1 cm from the substrate 2 is preferable.

The vacuum vessel 10 and the substrate stage 14 are grounded, and a pulse power source 19 is connected to the intermediate electrode 18 so that a negative voltage can be applied in a pulse manner.
The pulse applied voltage of the pulse power source 19 is not particularly limited, but is set to about 100 to 1000 V, for example. When the pulse application voltage is 200 V, the speed of the sputtered particles 3 in the vertical direction of the substrate is about 10 times that in the parallel direction. However, if the voltage is increased too much, a discharge occurs between the intermediate electrode 18 and the substrate 2.

For example, when the pressure is 1 Pa, the separation distance between the target 13 and the substrate 2 is 10 cm, the separation distance between the intermediate electrode 18 and the substrate 2 is 1 cm, and the applied voltage to the intermediate electrode 18 is 200 V, respectively. The time for the target to fly from the target 13 to the substrate 2 is about 100 μs.
Further, the pulse frequency of the pulse power source 19 is not particularly limited, but is a rectangular wave of 5 to 10 kHz, for example. If the pulse frequency is too short, ions will be pushed back before reaching the substrate 2.

  The film forming apparatus 1 of the present invention preferably further includes an ionization mechanism that ionizes the sputtered particles 3 struck out from the target 13 by the plasma. The ionization mechanism includes an ionization source 21, a DC power supply 22, and a wiring 23 that connects the ionization source 21 and the DC power supply 22. A current is supplied from a DC power source 22 to the ionization source 21 (for example, a filament) and heated to emit thermoelectrons. Between the target 13 and the substrate 2, the thermal electrons emitted from the ionization source 21 collide with the sputtered particles 3 and the sputter discharge process gas particles to ionize the sputtered particles 3. As a result, the number of sputtered particles 3 having an electric charge increases, so that the number of sputtered particles 3 accelerated in the vertical direction by the mesh electrode increases, and the film can be efficiently formed inside the holes and grooves having a high aspect ratio.

Next, a film forming method for forming a thin film on the substrate 2 using such a film forming apparatus 1 will be described.
In the film forming method of the present invention, a voltage is applied to the target 13 disposed in the vacuum vessel 10 to generate plasma in a space between the target 13 and the substrate 2 disposed to face the target 13. In the film forming method of forming a film on the substrate 2 by depositing the sputtered particles 3 struck out from the target 13 by the plasma on the substrate 2, the target 13 is disposed between the substrate 2 and the substrate 2. A mesh-like intermediate electrode 18 is disposed so as to block the substrate 2 when viewed from the target 13, and a pulse voltage having a negative potential is applied to the intermediate electrode 18.

  In the film forming method of the present invention, a mesh-like intermediate electrode 18 is disposed between the target 13 and the substrate 2 so as to shield the substrate 2 when viewed from the target 13, and the intermediate electrode 18 has a negative potential. Since the pulse voltage is applied, it becomes possible to cause the sputtered particles 3 having electric charges to enter the substrate 2 perpendicularly by the pulse voltage. Thus, in the present invention, when forming a film on the substrate 2 in which holes and grooves having a high aspect ratio are formed, the sputtered particles 3 can be deposited inside the holes and grooves. As a result, the film formability can be improved. That is, it is possible to form a film having a uniform film thickness on the side wall and bottom surface of the hole.

A voltage is applied to the target 13 disposed in the vacuum vessel 10 to generate plasma in a space between the target 13 and the substrate 2 disposed to face the target 13. The sputtered particles 3 struck out are deposited on the substrate 2.
First, the sputtering target 13 is mounted and held in the vacuum vessel 10, and the thin film is formed on the substrate stage 14 that is spaced apart from the target 13 in the vacuum vessel 10. Wear and hold.
Thereafter, the inside of the vacuum vessel 10 is evacuated by the exhaust unit 12 until a predetermined degree of vacuum is maintained, and a plasma gas such as argon gas (Ar) is supplied by the gas supply unit 11 while maintaining the predetermined degree of vacuum. The pressure in the vacuum vessel 10 is not particularly limited, but is set to 1 Pa, for example.

Then, a high frequency (negative high frequency power) is applied to the sputter electrode 16 by the voltage applying means 15 to discharge the sputter electrode 16 to plasmaize a gas such as Ar introduced into the vacuum vessel 10, and so on. Of positive ions.
The positive ions thus formed sputter the target 13, and the sputtered particles 3 made of the constituent elements of the sputtered target 13 are released from the target 13 and are neutral or ionized. It vapor-deposits on the board | substrate 2 hold | maintained at the substrate stage 14 arrange | positioned oppositely, and film-forming is started.

In particular, in the present invention, a mesh-like intermediate electrode 18 is disposed between the target 13 and the substrate 2 so as to shield the substrate 2 when viewed from the target 13, and a pulse voltage having a negative potential is applied to the intermediate electrode 18. Is applied.
For the sake of simplicity, first consider the case where the ionized sputtered particles 3 exist only in the vicinity of the target 13. The sputtered particle 3 ions are accelerated in a direction perpendicular to the substrate 2 while a negative voltage is applied to the mesh-shaped intermediate electrode 18 [see FIG. Here, if the intermediate electrode 18 is dropped to the ground potential immediately after the ions have passed through the intermediate electrode 18, the ions are not subjected to force and go straight at the same speed [see FIG. 3 (b)]. Therefore, the sputtered particle 3 ions can be incident on the substrate 2 in the vertical direction. Thereby, the sputtered particles 3 can be deposited inside the holes and grooves having a high aspect ratio, and the film formability can be improved.

  FIG. 4 is a diagram schematically showing how sputtered particles are deposited inside high aspect ratio holes and grooves. 4 (a) and 4 (b) show the case of a conventional film forming apparatus, and FIGS. 4 (c) and 4 (d) show the case of the film forming apparatus of the present invention. In particular, FIGS. 4 (a) and 4 (c) show how the sputtered particles fly to the substrate (before deposition), and FIGS. 4 (b) and 4 (d) show that the film was formed on the substrate. Each state (after deposition) is shown.

  In the conventional film forming method and film forming apparatus, as shown in FIG. 4A, the sputtered particles 3a, 3b, 3c (3) form different angles with respect to the holes and grooves 4 provided in the substrate 2. To fly. Therefore, the sputter particles 3a, 3b, 3c (3) are biased in the sticking probability with respect to the inner bottom surface 4a (4), the inner side surface 4b (4) of the hole or groove, and the surface 2a of the substrate. As a result, as shown in FIG. 4B, the film grows thick on the surface 2a of the substrate, and on the inner side surface 4b (4) of the hole or groove, the film becomes thinner toward the back, and the inner bottom surface of the hole or groove. 4a (4) tended to form the thinnest film.

  In contrast, in the film forming method and film forming apparatus of the present invention, as shown in FIG. 4C, all the sputtered particles 3x, 3y, 3z (3) are substantially perpendicular to the substrate 4. And then fly. Therefore, each sputtered particle 3x, 3y, 3z (3) has the same level of adhesion probability with respect to the inner bottom surface 4a (4), inner side surface 4b (4) of the hole or groove, and the surface 2a of the substrate. Become. As a result, as shown in FIG. 4D, a film having substantially the same level of thickness is formed without depending on the position of the substrate. That is, according to the present invention, the substrate surface 2a, the inner side surface 4b (4) of the hole or groove of the substrate, and the inner bottom surface 4a (4) of the hole or groove of the substrate have a more uniform thickness than before. The film can be formed stably.

  In other words, in the film forming apparatus according to the present invention, when the sputtered particles 3 are ionized using the pulse power source 19 in the vicinity of the target 13, the sputtered particle 3 ions are present only in the vicinity of the target 13 immediately after ionization. Therefore, it is preferable to synchronize the pulse voltage of the pulse power supply 19 and the pulse voltage applied to the mesh electrode at an appropriate timing. Thereby, the ionized sputtered particles 3 can be efficiently incident on the substrate 2, and the film forming property can be further improved.

  When using an ionization source that always performs ionization, ions receive an attractive force in the direction of the intermediate electrode 18 while a negative voltage is applied to the intermediate electrode 18, and force is applied while it is at ground potential. I do not receive it. Therefore, at the moment when a negative voltage is applied to the intermediate electrode 18, ions in the space between the target 13 and the intermediate electrode 18 are accelerated toward the substrate, while ions between the intermediate electrode 18 and the substrate 2 are accelerated to the substrate 2. Therefore, the efficiency is lower than the case where the sputtered particles 3 are ionized by pulses.

  In the present invention, it is preferable to guide the sputtered particles 3 uniformly toward the substrate 2 according to the surface profile of the substrate 2 by passing through the intermediate electrode 18. As a result, the number of sputtered particles 3 accelerated in the vertical direction by the mesh electrode is increased, and the film can be formed efficiently.

  The film forming method and film forming apparatus of the present invention have been described above. However, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.

  The present invention is widely applicable to a film forming method and a film forming apparatus for forming a film on a substrate by sputtering.

  DESCRIPTION OF SYMBOLS 1 Deposition apparatus, 2 Substrate, 3 Sputtered particle, 10 Vacuum container, 11 Gas supply means, 12 Exhaust means, 13 Target, 14 Substrate stage, 15 Voltage application means, 16 Sputter electrode, 17 High frequency power supply, 18 Intermediate electrode, 19 Pulse power supply, 20, 23 wiring, 21 ionization source, 22 DC power supply.

Claims (5)

A voltage is applied to a target disposed in a vacuum vessel, plasma is generated in a space between the target and a substrate disposed opposite to the target, and sputtered particles knocked out of the target by the plasma In a film forming method for forming a thin film on the substrate by depositing on the substrate,
A mesh-shaped intermediate electrode is arranged between the target and the substrate so as to shield the substrate when viewed from the target, and a negative potential pulse voltage is applied to the intermediate electrode. Membrane method.   2. The film forming method according to claim 1, wherein the sputtered particles are uniformly directed toward the substrate according to a surface profile of the substrate by passing the intermediate electrode.   The film forming method according to claim 1, wherein the sputtered particles are ionized using a pulse power source, and a pulse voltage of the pulse power source and a pulse voltage applied to the mesh electrode are synchronized. A vacuum vessel;
Gas supply means for supplying a process gas into the vacuum vessel;
An exhaust means for exhausting the gas in the vacuum vessel;
A target disposed in the vacuum vessel;
A substrate stage that is disposed opposite to the target in the vacuum vessel and holds the substrate;
Voltage applying means for applying a voltage to the target and generating plasma in a space between the target and the substrate stage;
A mesh-like intermediate electrode disposed between the target and the substrate so as to shield the substrate when viewed from the target;
And a pulse power supply for applying a negative pulse voltage to the intermediate electrode.   The film forming apparatus according to claim 4, further comprising an ionization mechanism that ionizes sputtered particles struck from the target by the plasma.

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