JP2002053950A - Method and apparatus for depositing film on insulating substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film deposition method by which a metallic film can be deposited with high adhesion by ion plating on an organic substrate composed of insulator, such as printed wiring board. SOLUTION: The film deposition method is performed by using an ion plating apparatus which has a vacuum vessel 11, a pressure gradient type plasma beam generator 13 attached to the vacuum vessel, a main hearth 30 containing an vaporizable material and arranged in the vacuum vessel, and an auxiliary anode 31 consisting of an annular permanent magnet and an electromagnet coil and located around the main hearth. A resin substrate 1 as an object of film deposition is located opposedly to the main hearth. A metallic material is used as the vaporizable material held in the main hearth. Ion plating is carried out while applying AC power to the resin substrate 1 by an AC power source 4 from the surface on the side opposite to the main-hearth-side surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for ion-plating a metal film with good adhesion to an organic substrate.

[0002]

2. Description of the Related Art In accordance with high integration of a printed circuit board, a printed pattern has been miniaturized, and a build-up circuit board in which a plurality of printed circuit boards are stacked has been adopted. When a build-up board is manufactured, a process of making a hole in a resin layer of a printed board and plating the hole with copper is required. Conventionally, from the viewpoint of productivity, a two-step process in which electroless plating (seed layer) is applied to a resin layer whose surface is roughened in advance, followed by electroplating has been adopted.
However, with the need for faster electronic circuits, the resin used for printed circuit boards is being replaced by low-permittivity ones in order to reduce stray capacitance, and surface roughness has also been reduced. With conventional electroless plating, it has become difficult to ensure the adhesion of the plating film.

[0003]

For this reason, it has been considered to perform ion plating in vacuum instead of electroless plating. However, since the resin layer of the printed circuit board is an insulator, a DC bias voltage can be applied. Therefore, the effect of improving the adhesion of the film formed by ion plating cannot be exhibited.

Referring to FIG. 3, an ion plating apparatus will be described. In FIG. 3, a pressure gradient type plasma beam generator 13 is mounted on a cylindrical portion 12 provided on a side wall of a vacuum vessel 11. The plasma beam generator 13 includes a glass tube 1 whose one end is closed by a cathode 14.
5 is provided. In the glass tube 15, a disk 16 made of LaB ₆ and a cylinder 18 made of molybdenum Mo containing a pipe 17 made of tantalum Ta are fixed to the cathode 14. The pipe 17 is for introducing the carrier gas 10 into the plasma beam generator 13.

The first and second intermediate electrodes 19, 2 are provided between the cylindrical portion 12 and the end of the glass tube 15 on the side opposite to the cathode 14.
0 are arranged concentrically. In the first intermediate electrode (first grid) 19, an annular permanent magnet 21 for converging the plasma beam is incorporated. Second intermediate electrode 2
An electromagnet coil 22 for converging the plasma beam is also built in 0 (second grid). The electromagnet coil 22 is supplied with power from a power supply 23.

[0006] Around the cylindrical portion 12 on which the plasma beam generator 13 is mounted, a steering coil 24 for guiding a plasma beam into the vacuum vessel 11 is provided. The steering coil 24 is excited by a power supply 25 for the steering coil. Between the cathode 14 and the first and second intermediate electrodes 19 and 20, there are respectively provided drooping resistors 26 and 2
7, a variable power supply type main power supply 28 is connected.

[0007] A main hearth 30 as an anode and an annular auxiliary anode 31 arranged around the main hearth 30 are provided at the bottom inside the vacuum vessel 11. The main hearth 30 is constituted by a cylindrical hearth main body, and has a concave portion into which the plasma beam from the plasma beam generator 13 enters. The through-hole of the hearth body contains an evaporating substance. Auxiliary anode 31
Is constituted by an annular container. In the annular container, an annular permanent magnet 35 made of ferrite or the like and an electromagnet coil 36 concentrically laminated therewith are accommodated. For both the main hearth 30 and the auxiliary anode 31, a conductive material having good thermal conductivity, for example, copper is used. The auxiliary anode 31 is attached to the main hearth 30 via an insulator. The main hearth 30 and the auxiliary anode 31 are connected via a resistor 48. The main hearth 30 is connected to the positive side of the main power supply 28. Therefore, the main hearth 30
Constitutes an anode from which the plasma beam is sucked into the plasma beam generator 13.

The electromagnet coil 36 in the auxiliary anode 31 forms an electromagnet and is supplied with power from a coil power supply 38. In this case, the direction of the center-side magnetic field in the excited electromagnet coil 36 is configured to be the same as the center-side magnetic field generated by the permanent magnet 35. The coil power supply 38 is a variable power supply, and can change the current supplied to the electromagnet coil 36 by changing the voltage.

The main hearth 3 is also provided inside the vacuum vessel 11.
A substrate holder 42 for holding the substrate 41 is provided on the upper part of the “0”. The substrate holder 42 is electrically insulated and supported by the vacuum vessel 11. A bias power supply 45 is connected between the vacuum vessel 11 and the substrate holder 42. As a result, the substrate holder 42 is biased to a negative potential with respect to the vacuum vessel 11 connected to the zero potential. The auxiliary anode 31 is connected to the positive side of the main power supply 28 via a hearth switch 46. To the main power supply 28, a drooping resistor 29 and an auxiliary discharge power supply 47 are connected in parallel via a switch S1.

In this ion plating apparatus, a discharge is generated between the cathode of the plasma beam generator 13 and the main hearth 30 in the vacuum vessel 11, thereby generating a plasma beam (not shown). This plasma beam is guided by a magnetic field determined by the steering coil 24 and the permanent magnet 35 in the auxiliary anode 31 so that the main hearth 30
To reach. The evaporating substance contained in the main hearth 30 is heated by the plasma beam and evaporates. The evaporated particles are ionized by the plasma beam and adhere to the surface of the substrate 41 to which the negative voltage has been applied, thereby forming a film.

The ion plating apparatus itself is disclosed in Japanese Patent Application Laid-Open No. Hei 8-232060,
Various aspects of the polarities of the permanent magnet 35 and the electromagnet coil 36 and the flight distribution of the evaporating particles in Example 1 have been studied.

According to such an ion plating apparatus, a copper film can be formed on an insulating substrate, but the adhesion of the copper film to the substrate is insufficient. It is difficult to satisfy the required adhesiveness.

An object of the present invention is to provide a film forming method and a film forming apparatus capable of ion-plating a metal film with good adhesion to an organic substrate made of an insulator such as a printed circuit board.

[0014]

According to the present invention, there is provided a vacuum vessel, a pressure gradient type plasma beam generating source mounted on the vacuum vessel, and a vapor chamber disposed in the vacuum vessel. In a film forming method using an ion plating apparatus provided with an anode and an auxiliary anode composed of an annular permanent magnet and an electromagnet coil around the anode, an insulator substrate for film formation is arranged to face the anode. A metal material is used as an evaporating substance contained in the anode, and the insulating substrate is subjected to ion plating while applying AC power from a surface opposite to the surface on the anode side. A method for forming a film on an insulating substrate is provided.

According to the present invention, there is also provided a vacuum vessel, a pressure gradient type plasma beam generating source attached to the vacuum vessel, an anode disposed in the vacuum vessel and containing an evaporating substance, In an ion plating apparatus provided with an auxiliary anode composed of a ring-shaped permanent magnet and an electromagnet coil around the periphery, an insulating substrate for film formation is covered with an insulating cover except for a surface facing the anode. A metal material as an evaporating substance is accommodated in the anode, a bias electrode plate is provided on the surface of the insulator substrate opposite to the surface on the anode side, and the bias electrode plate has an alternating current. Since the power supply is connected, ion plating is performed while applying AC power to the insulator substrate, thereby providing an apparatus for forming a film on the insulator substrate.

In any of the above-described film forming method and film forming apparatus, the AC power is applied immediately before or at the start of film formation, and after the film formation is started, the AC power is controlled. .

In any of the above-described film forming method and film forming apparatus, when the resin substrate is a printed circuit board,
By using copper as the evaporating substance, a copper film can be formed on the printed circuit board.

Further, copper may be further plated on the copper film formed by the above film forming method by electroplating.

[0019]

According to the present invention, a flat resin substrate (insulator) is provided.
By applying a bias voltage using AC power, a seed layer of a metal film such as copper can be formed on the resin substrate with good adhesion.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an embodiment of the present invention will be described for a case where a copper film is formed on a resin substrate. FIG. 1 shows a schematic configuration of an ion plating apparatus for carrying out the present invention, but is substantially the same as the ion plating apparatus shown in FIG. Therefore, the same parts as those in FIG. 3 are given the same numbers.

An auxiliary anode 31 containing a pressure gradient type plasma beam generator 13, an annular permanent magnet and an electromagnet coil
In the ion plating apparatus having a (plasma beam controller), the main hearth 30 contains copper as an evaporating substance. The flat resin substrate 1 is placed above the main hearth 30 so that the surface other than the surface on which the film is to be formed is covered with the insulating cover 2. A bias electrode plate 3 for applying a bias is provided on the entire back surface (upper surface) of the resin substrate 1 and connected to an AC power supply 4. Between the AC power supply 4 and the bias electrode plate 3, a capacitor in a matching circuit or another capacitor is provided so that the bias electrode plate 3 does not fall to the ground in a DC manner. In FIG. 1, the details of the matching circuit are not shown, and only the capacitor 5 is shown.

The operation of the present ion plating apparatus will be described. Plasma is formed between the pressure gradient type plasma beam generator 13 and the main hearth 30. The resin substrate 1 is arranged facing the plasma, and the AC power is applied from the back side as described above. AC power is resin substrate 1
The negative self-bias potential is generated on the surface of the resin substrate 1 as shown in FIG. This is due to the difference in capacitance between the sheaths on the surface of the bias electrode plate 3 when a high frequency is applied to the plasma, and a phenomenon in which a potential is generated which is inversely proportional to the fourth power of the area ratio of the bias electrode plate 3 Derived from

In the case of this apparatus, since the area of the resin substrate 1 is smaller than the inner area of the vacuum vessel 11, a high self-bias potential is generated on the resin substrate 1 side. Due to this self-bias potential, positive ions are attracted to the surface of the resin substrate 1 during the application of AC power.

In the film forming process, first, the pressure gradient type plasma beam generator 13 and the main hearth 30 (or the auxiliary anode 3
1) to generate plasma, and apply AC power to remove water adhering to the surface of the resin substrate 1. The application of AC power is performed immediately before the start of film formation or at the start of film formation.

Next, the output of the plasma beam generator 13 is increased, and copper in the main hearth 30 is dissolved and evaporated to perform ion plating. Here, it is necessary to keep applying AC power to the bias electrode plate 3 at least at the initial stage of film formation, which is important for adhesion. After the film is formed to some extent, control such as adjusting the power of the AC power or stopping the application may be performed. During the application of the AC power, the copper ions are accelerated by the self-bias and bombard the surface of the resin substrate 1. At this time, if the self-bias voltage is too high, film formation is hindered and the resin substrate 1 is damaged. At an appropriate bias voltage, the part where the adhesion is insufficient at the time of film formation is etched, and only the part with good adhesion that is strongly bonded to the base remains and the film grows, so that a film with extremely good adhesion is obtained. Can be

As an example of the test results, adhesion was 300 g / cm in peel strength when a film was formed without applying a bias by AC power and electroplated. On the other hand, when the film was formed without applying heat to the substrate and applying a bias of a high frequency AC power of 1.5 W and 100 W from the AC power supply 4, the peel strength after electroplating was improved to 900 g / cm. Was done. Further, the conventional electroless plating method could only obtain a peel strength lower than 300 g / cm.

Although the embodiment of the present invention has been described with reference to the case where a copper film is formed on a resin substrate such as a printed circuit board, the target substrate in the present invention is not limited to the resin substrate but covers all the insulating substrates. However, the evaporation material is not limited to copper. After the copper film is formed by the film forming apparatus according to the present invention, copper may be further plated on the copper film by well-known electroplating.

[0028]

According to the present invention, a metal film can be ion-plated with good adhesion to an organic substrate made of an insulator such as a printed circuit board.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a film forming apparatus according to the present invention.

FIG. 2 is a waveform chart for explaining a self-bias voltage in the film forming apparatus of FIG.

FIG. 3 is a diagram showing a configuration of a general ion plating apparatus.

[Explanation of symbols]

 Reference Signs List 1 resin substrate 2 insulating cover 3 bias electrode plate 4 AC power supply 5 capacitor 10 carrier gas 11 vacuum vessel 13 plasma beam generator 14 cathode 19 first intermediate electrode 20 second intermediate electrode 21 annular permanent magnet 22 electromagnet coil 23, 25 Power supply 24 Steering coil 26, 27 Droop resistor 28 Main power supply 30 Main hearth 31 Auxiliary anode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshiyuki Sakami 5-2 Sokai-cho, Niihama-shi, Ehime F-term in Niihama Works, Sumitomo Heavy Industries, Ltd. 4K029 AA11 BA08 BD00 CA03 CA13 DD05 JA01

Claims (7)

[Claims] 1. A vacuum vessel, a pressure gradient plasma beam source attached to the vacuum vessel, an anode disposed in the vacuum vessel and containing an evaporating substance, and an annular ring around the anode. In a film forming method using an ion plating apparatus provided with an auxiliary anode composed of a permanent magnet and an electromagnet coil, an insulating substrate for film formation is arranged so as to face the anode, and as an evaporating substance contained in the anode. A method of forming a film on an insulator substrate, wherein a metal material is used and ion plating is performed on the insulator substrate while applying AC power from a surface opposite to the surface on the anode side. 2. The film forming method according to claim 1, wherein the AC power is applied immediately before or at the start of film formation.
A method for forming a film on an insulator substrate, wherein the AC power is controlled after the start of the film formation. 3. The insulating substrate according to claim 1, wherein said resin substrate is a printed circuit board, said evaporating substance is copper, and a copper film is formed on said printed circuit board. Film formation method. 4. A method for forming a film on an insulating substrate, further comprising plating copper on the copper film formed by the method of claim 3 by electroplating. 5. A vacuum vessel, a pressure-gradient plasma beam source mounted on the vacuum vessel, an anode disposed in the vacuum vessel and containing an evaporating substance, and an annular ring around the anode. In an ion plating apparatus provided with an auxiliary anode composed of a permanent magnet and an electromagnet coil, an insulating substrate for forming a film is disposed so as to be covered with an insulating cover except for a surface facing the anode, and the anode is provided. Contains a metal material as an evaporating substance, a bias electrode plate is provided on the surface of the insulator substrate opposite to the surface on the anode side, and an AC power supply is connected to the bias electrode plate. And performing ion plating while applying AC power to the insulator substrate. 6. The film forming apparatus according to claim 5, wherein the AC power is applied immediately before or at the start of film formation.
An apparatus for forming a film on an insulator substrate, wherein the apparatus controls the AC power after the start of the film formation. 7. The insulating substrate according to claim 5, wherein the resin substrate is a printed board, and the evaporating substance is copper, and a copper film is formed on the printed board. Film forming equipment.