JP4126901B2 - Cathodic arc deposition system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cathodic arc film forming apparatus used for forming a thin film using cathodic arc discharge, and particularly for forming a carbon film formed on a magnetic head of a magnetic recording / reproducing apparatus.
[0002]
[Prior art]
In a magnetic head and a magnetic disk of a magnetic recording / reproducing apparatus, a backbone thin film is generally used as a protective film. In recent years, a ta-C (tetrahedral amorphous carbon) film forming technique using a cathodic arc discharge called FCVA (Filtered Cathodic Vacuum Arc) method is being used as a method for forming a protective film for a magnetic head. In a film forming apparatus using cathodic arc discharge, arc discharge is generated with respect to a graphite target provided on the cathode to generate plasma containing carbon ions. A carbon film is formed on the substrate by depositing carbon ions in the generated plasma on the substrate.
[0003]
The generated plasma contains electrically neutral particles in addition to carbon ions and electrons. These particles are mainly clusters of carbon atoms, and are generated not only by being discharged from the target by arc discharge but also by combining ions in a high-density plasma. If the particles are mixed when carbon ions are deposited on the substrate, the film quality deteriorates. Therefore, the following measures are adopted to reduce the particles.
[0004]
The first method is a method of trapping particles with a trap by bending the path of the plasma beam while transferring the plasma beam to the substrate using a magnetic field. In the second method, the generation of particles during plasma transfer is suppressed by lowering the plasma density by elongating the plasma transport path or the like to form a low density plasma.
[0005]
[Problems to be solved by the invention]
However, in the first method described above, particles emitted by arc discharge can be removed, but since particles are generated in the path from the trap portion to the substrate, the particle reduction effect is not sufficient. There wasn't. Further, the second method has a problem that the film formation rate is lowered because the plasma density is low.
[0006]
An object of the present invention is to provide a cathodic arc film forming apparatus capable of reducing particles incident on a substrate while preventing a decrease in film forming rate.
[0007]
[Means for Solving the Problems]
The embodiment of the invention will be described in association with FIG.
(1) The cathodic arc film forming apparatus according to the first aspect of the present invention includes a plasma beam generating apparatus 1 that generates a plasma beam including target ions by cathodic arc discharge, a chamber 4 in which a substrate 41 is loaded, and a plasma beam generating apparatus. The apparatus is applied to a cathodic arc film forming apparatus including a plasma transfer apparatus 2 that guides the plasma beam B generated by the apparatus 1 to a substrate 41 in the chamber 4. The plasma transfer apparatus 2 is generated by the plasma beam generation apparatus 1. A bent duct 20 into which the generated plasma beam B is incident, and a magnetic coil that forms an axial magnetic field along the axis of the bent duct 20 and bends the traveling path of the plasma beam B along the axis of the bent duct 20 21, disposed between the substrate 41 and the plasma transfer device 2, and having a shielding portion and an opening 44 a. The shielding plate 44, the connection duct 43 that connects the plasma transfer device 2 and the chamber 4 so that the plasma beam B emitted from the plasma transfer device 2 enters the shielding portion of the shielding plate 44, and the plasma transfer device 2 emits the plasma beam B. The above-mentioned object is achieved by including the deflecting device 3 that deflects the target ions C contained in the plasma beam B, which is incident on the substrate 41 through the opening 44a.
(2) The invention of claim 2 is the cathodic arc film forming apparatus according to claim 1, wherein a bias power source 22 for applying a bias voltage to the bent duct 20 is provided.
(4) A third aspect of the present invention is the cathodic arc film forming apparatus according to the first or second aspect, wherein the deflecting device 3 deflects the target ions C and the target ions C to the entire area of the substrate 41. And cathodic arc film forming apparatus.
[0008]
In the section of means for solving the above problems, the drawings of the embodiments of the invention are used for easy understanding of the present invention. However, the present invention is not limited to the embodiments of the invention. Absent.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a cathodic arc film forming apparatus according to the present invention, and shows a schematic configuration of the film forming apparatus. As shown in FIG. 1, the film forming apparatus includes a plasma generation unit 1, a plasma transfer unit 2, a scanning device 3, a film forming chamber 4, and a control device 5 that controls the entire apparatus.
[0010]
The plasma generation unit 1 includes a cathode unit 10 on which a target 11 is mounted, an anode chamber 12 to which the cathode unit 10 is fixed, and a trigger 14 for creating a trigger for arc discharge. For example, when forming a carbon film, carbon graphite is used as the target 11. In the following, description will be given taking carbon film formation as an example.
[0011]
The cathode unit 10 is connected to the negative terminal of the arc power source (constant current source) 13, while the trigger chamber 14 and the anode chamber 12 connected to the positive terminal of the arc power source 13 are each grounded and become ground potential. ing. The trigger 14 is rotationally driven by a drive unit 15 such as a step motor with the shaft 140 as a rotational axis. The angle of the trigger 14 is detected by an angle sensor (not shown).
[0012]
The cathode portion 10 and the anode chamber 12 are electrically insulated by the insulating member 6. A magnetic coil 16 for forming an axial magnetic field in the anode chamber 12 is provided on the outer periphery of the anode chamber 12, and an excitation current is supplied from a power source 17. Although not shown, the cathode unit 10 is provided with cooling means such as a water cooling jacket.
[0013]
The plasma transfer unit 2 includes a bent duct 20 and a magnetic coil 21 provided around the duct 20. Excitation current is also supplied from the power source 17 to the magnetic coil 21. The plasma transfer unit 2 and the anode chamber 12 are fixed to each other via an insulating material 23, and both are electrically insulated. A positive bias voltage is applied to the duct 20 by a bias power source 22.
[0014]
A substrate stage 42 is provided in the film forming chamber 4, and a substrate 41 that is a film formation target is mounted on the substrate stage 42. The substrate stage 42 rotates the substrate 41 in its plane as indicated by an arrow R. In addition, a shielding plate 44 having an opening 44a is disposed in front of the substrate 41 (right side in the drawing). The film forming chamber 4 and the plasma transfer unit 2 are connected by a tilt duct 43, and the two flanges 43a and 43b of the tilt duct 43 form an angle θ with each other. The tilt angle θ is set to about 2.5 to 10 (deg), although there is a balance with a deflectable angle of the scanning device 3 to be described later, and preferably 5.5 (deg).
[0015]
The tilt duct 43 and the plasma transfer unit 2 are fixed via an insulating member 40 and are electrically insulated from each other. A scanning device 3 is provided around the tilt duct 43 and scans the carbon ions C in the plasma beam B in the yz direction. The scanning device 3 includes, for example, a pair of C-shaped magnetic cores (not shown). The magnetic pole of one magnetic core is arranged up and down in the figure with the tilt duct 43 in between, and the magnetic pole of the other magnetic core is arranged in the y direction perpendicular to the paper surface with the tilt duct 43 in between. A solenoid coil (not shown) is wound around the magnetic core of the scanning device 3, and an excitation current is supplied to the solenoid coil by a power supply 31.
[0016]
2A and 2B are diagrams illustrating an example of the shape of the duct 20, where FIG. 2A is a plan view viewed from the z direction in FIG. 1, FIG. 2B is a view taken along the arrow A <b> 1 in FIG. FIG. The duct 20 is a double vent type duct having three straight pipe portions 201, 203, 205 and two bent portions 202, 204. That is, the plasma beam incident from the flange 206 provided on the straight pipe portion 201 is bent at the bent portions 202 and 204, respectively, and is angled with respect to the horizontal direction from the flange 207 provided on the straight pipe portion 205. Exit.
[0017]
Next, an outline of the film forming operation will be described. When generating arc discharge, the trigger 14 that has been retracted to the position indicated by the broken line in FIG. The potential difference between the cathode 10 and the anode chamber 12 is set to several tens to several hundreds volts by the arc power supply 13, and when the trigger tip 14 a provided at the tip of the trigger 14 contacts the surface of the target 11, arc discharge occurs. To do.
[0018]
When arc discharge occurs, plasma is generated, and this plasma contains target ions (positive ions) emitted from the target 11. When the target 11 is graphite, plasma containing carbon ions is generated by arc discharge. At this time, in addition to carbon ions, clusters composed of many carbon atoms called macro particles are released from the graphite target 11.
[0019]
The control device 5 constantly monitors the state of the arc power supply 13, and if the occurrence of arc discharge is detected, sends a command to the drive unit 15 to lift the trigger 14 from the surface of the target 11. At this time, the angular position of the trigger 14 when arc discharge occurs is detected by the angle sensor described above, and the detected angular position is stored in a storage unit (not shown) provided in the control device 5. After the arc discharge occurs, the discharge state becomes weaker as time passes. Therefore, the trigger 14 is moved again to the stored position by the drive unit 15 so that stable arc discharge is maintained.
[0020]
An axial magnetic field is formed in the anode chamber 12 by the magnetic coil 16. Therefore, the plasma generated by the arc discharge, that is, the plasma containing carbon ions and electrons emitted from the target 11 is focused by this axial magnetic field and guided to the duct 20 of the plasma transfer unit 2. Also in the plasma transfer unit 2, an axial magnetic field along the axis of the duct 20 is formed by the magnetic coil 21 provided around the duct 20, and the plasma is transferred to the film forming chamber 4 along this magnetic field. .
[0021]
The plasma beam B includes carbon ions C, particles P, and the like. The plasma density of the plasma beam B decreases from the center of the plasma cross section to the periphery, and the region indicated by the symbol B in FIG. 1 represents a range of a predetermined density or higher. FIG. 3 qualitatively shows the distribution shape L1 of the carbon ions C and the distribution shape L2 of the particles P. Although the density of the particles P is much smaller than the density of the carbon ions C, the distribution shape is shown on the assumption that both have the same density for easy comparison.
[0022]
Since the carbon ions C are charged, they repel each other, and the distribution shape L2 is broader than the distribution shape L2 of the particles P. Therefore, a positive bias voltage is applied to the duct 20 to form a radial electric field in the duct 20 so that it is unevenly distributed in the center of the duct. At this time, the distribution shape L1 of the carbon ions C changes like the distribution shape L10, and high-density plasma is obtained.
[0023]
By the way, since the particle P is electrically neutral, when the plasma beam is bent at the bent portions 202 and 204 (see FIG. 2) of the duct 20, the particle P goes straight and is trapped by the duct 20. Thus, the particles P can be removed from the beam B by making the transfer path of the plasma beam B curved. However, since the particles P are also generated in the plasma beam B, the particles P are included in the plasma beam B emitted from the duct 20.
[0024]
An AC magnetic field is applied to the plasma beam B incident from the duct 20 into the tilt duct 43 by the scanning device 3. As a result, the traveling direction of the carbon ions C is bent by the magnetic field, and for example, the beam B1 containing the carbon ions C is separated from the beam B as shown in FIG. FIG. 1 shows the moment when the carbon ions C are deflected in the negative z-axis direction, and the beam B1 is irradiated onto the substrate 41 through the opening 44a formed in the shielding plate 44. On the other hand, the beam B goes straight and is blocked by the shielding plate 44, and does not reach the substrate 41 side.
[0025]
4 is a view of the shielding plate 44 as seen from the plus direction of the x axis in FIG. The circular opening 44 a is formed eccentrically in the z-axis minus direction from the center O of the substrate 41. On the other hand, since the duct 20 is connected to the film forming chamber 4 via the tilt duct 43 as shown in FIG. 1, the beam B containing particles is shielded above the center O (a region where the z position is positive). It does not collide with the plate 44 and enter the opening 44a. As shown in FIG. 4, since the region between the center and the lower edge of the substrate 41 can be seen through the opening 44a, when the beam B1 of the carbon ion C is scanned in the z-axis direction, the center 0 and the edge are detected. The carbon ion C is irradiated to the area to include. Since the substrate 41 is rotated about the center O, the carbon ions C are uniformly deposited on the entire surface of the substrate 41 by the scanning motion and the rotational motion.
[0026]
FIG. 5 is a diagram for explaining a film forming method of a conventional cathodic arc film forming apparatus, and shows how to guide the plasma beam B to the substrate 41. The plasma beam B bent by the magnetic coil 21 is emitted from the duct 20 and applied to the substrate 41 in the film forming chamber. The plasma beam B is scanned by the scanning device 51 so that the entire region of the substrate 41 is irradiated with the plasma beam B. As described above, the particles P in the plasma beam B are removed by the path being bent in the duct 20, but the particles P are also incident on the substrate 41 from the vicinity of the duct exit facing the substrate surface. Generated. The particles P are incident on the substrate 41 together with the carbon ions C, and the film quality is deteriorated.
[0027]
On the other hand, in the film forming apparatus of the present embodiment, the carbon ions C deflected and separated from the plasma beam B immediately before the substrate 41 are irradiated onto the substrate 41 as described above. Therefore, the particles P formed in the vicinity of the outlet of the duct 20 is captured by the straight to the shield plate 4 4 as the beam B, and not incident on the substrate 41. As a result, as described below, the number of particles P incident on the substrate 41 could be reduced as compared with the conventional case.
[0028]
When the ta-C film was formed by conventional low density plasma, the film formation rate was about 0.1 (Å / sec). On the other hand, since the film forming apparatus of this embodiment uses high-density plasma, a high film forming rate of 0.4 (Å / sec) can be obtained. Further, regarding the particles, in the case of a film forming apparatus using a bubble vent type trap (duct 20), the number of particles was 0.3 (μm) or more and 10 (pieces / cm ² ) or more. In the film forming apparatus of the form, it was possible to reduce to 1 to 2 (pieces / cm ² ).
[0029]
Thus, in this embodiment, not only particles generated during arc generation but also particles generated during high-density plasma transfer can be removed with high probability. As a result, it is possible to form a high purity carbon film with very little particle contamination at a high film formation rate. Note that the film formation apparatus of this embodiment can be applied not only to the formation of a carbon film but also to the formation of various thin films.
[0030]
In the embodiment described above, the AC magnetic field is formed by the scanning device 3 to deflect the carbon ions C. However, the carbon ions C may be deflected by using a permanent magnet or by forming an electric field. The duct 20 is a double vent type, but a single vent type duct may be used.
[0031]
In FIG. 1, since the substrate 41 is disposed perpendicular to the x-axis, the beam B1 enters the substrate 41 almost perpendicularly. On the other hand, when the substrate 41 is disposed at an angle α with respect to the beam B1 as shown in FIG. 6, the migration of the carbon atoms deposited because the beam B is obliquely incident on the substrate surface promotes the residual stress. A small carbon film is formed. For example, when the stress is 2.4 (GPa) at normal incidence, the stress is reduced to 1.4 (GPa) when incident at an angle α = 45 (deg).
[0032]
In the correspondence between the embodiment described above and the elements of the claims, the plasma generator 1 constitutes a plasma beam generator, the shielding plate 44 constitutes a trap, and the scanning device 3 constitutes a deflection device. Moreover, the part in which the opening 44a of the shielding board 44 is not formed comprises a shielding part.
[0033]
【The invention's effect】
As described above, according to the present invention, target ions deflected and separated from the plasma beam are incident on the substrate, and the plasma beam including particles is not captured by the trap and incident on the substrate. Therefore, a film with very little particle contamination is formed on the substrate. In addition, since it is not necessary to lower the plasma density in order to reduce particles, it is possible to avoid a decrease in film formation rate.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a cathodic arc film forming apparatus according to the present invention, and shows a schematic configuration of the film forming apparatus.
2A and 2B are diagrams showing an example of the shape of a duct 20; FIG. 2A is a plan view seen from the z direction in FIG. 1, FIG. 2B is a view taken along the arrow A1 in FIG. FIG.
3 is a diagram showing a distribution shape L1 of carbon ions C and a distribution shape L2 of particles P. FIG.
4 is a view of the shielding plate 44 as seen from the x-axis plus direction of FIG.
FIG. 5 is a diagram for explaining a film forming method of a conventional cathodic arc film forming apparatus, and shows how to guide a plasma beam B to a substrate 41;
FIG. 6 is a diagram showing a relationship between the substrate 41 and the beam B1 when the substrate 41 is disposed at an angle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma generating part 2 Plasma transfer part 3, 51 Scanning apparatus 4, 50 Film formation chamber 5 Control apparatus 11 Target 12, 16 Magnetic coil 20 Duct 22 Bias power supply 41 Substrate 42 Substrate stage 43 Tilt duct 44 Shielding plate 44a Opening C Carbon ion P particle

Claims (3)

A plasma beam generator for generating a plasma beam containing target ions by cathodic arc discharge;
A chamber loaded with a substrate;
In a cathodic arc film forming apparatus comprising a plasma transfer device for guiding a plasma beam generated by the plasma beam generating device to a substrate in the chamber,
The plasma transfer device forms a bent duct into which the plasma beam generated by the plasma beam generator is incident, and an axial magnetic field along the axis of the bent duct, and the travel path of the plasma beam is bent. A magnetic coil that bends along the axis of the duct;
A shielding plate disposed between the substrate and the plasma transfer device and having a shielding part and an opening;
A connection duct connecting the plasma transfer device and the chamber so that a plasma beam emitted from the plasma transfer device is incident on a shielding portion of the shielding plate;
A cathodic arc film forming apparatus comprising: a deflecting device for deflecting the target ions contained in a plasma beam emitted from the plasma transfer device and causing the target ions to enter the substrate through the opening. 2. The cathodic arc film forming apparatus according to claim 1 , further comprising a bias power source for applying a bias voltage to the bent duct. In the cathodic arc film-forming apparatus according to claim 1 or 2 ,
The deflecting apparatus deflects the target ions and scans the target ions over the entire irradiation region of the substrate.

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