JP2001024087A - Method for formation of bump, wiring board prepared thereby and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesion between a wiring part and a bump part by etching half a metallic layer of a blind via hole bottom part after removing organic substance residue and forming a bump by an electrical plating method thereafter. SOLUTION: Laser beam is cast from a polyimide film side of a packaging film base material consisting of a polyimide film and a copper foil, a blind via hole part is shaped, pulse laser is cast on organic substance residue attaching to a side wall of a blind via hole and a bottom thereof and the residue is removed completely. After a copper layer exposed in a blind via hole bottom is etched by iron chloride solution and an about 1 μm-deep recess is formed, copper is precipitated by an electrical plating method inside a blind hole, and a bump is prepared. As a result, bump formation by electrical plating can be performed also for a high density wiring board which requires a fine blind via hole, and a highly reliable high density wiring board can be obtained at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer wiring board, and more particularly to a method for manufacturing a multilayer wiring board having blind via holes.

[0002]

2. Description of the Related Art In recent years, the wiring patterns of IC packages have been increasing in density as electronic devices have become denser and smaller. One of these is a laminated wiring board. Generally, a blind via hole is provided in such a laminated wiring board for conduction.

In general, when a laminated wiring board is manufactured using a laminated film including an insulating film containing an organic substance and a metal layer, a laser beam is used, particularly when minute blind via holes are made in the substrate. One of the major factors is that the diameter of the laser beam can be easily changed by optical means. Another major factor is that the laser beam is blocked by the metal layer forming the wiring and unnecessary damage to the wiring portion is avoided.

[0004] In a hole formed by opening with a laser beam,
The exposed wiring portion is used as a cathode to be electroplated and filled with metal to form a metal protrusion, which is used as a bump. The bump is used for bonding to an external circuit board or a semiconductor element.

[0005] When holes are formed in a laminated film using a laser beam, a residue of an organic substance may remain in the holes, and good holes may not be obtained. It is known that re-irradiation of the laser beam is effective.

However, as the diameter of the blind via hole becomes smaller, the adhesion between the metal layer forming the wiring and the bump raised by plating is reduced, and there is a problem that the reliability becomes unreliable. Densification,
There is a problem that it cannot cope with high integration.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a method of forming a bump in which the adhesion between a wiring portion and a bump portion is not reduced even when the diameter of a blind via hole is reduced. As an issue.

[0008]

According to a first aspect of the present invention for solving the above-mentioned problems, a laminated via film comprising an organic film and a metal layer is irradiated with a laser beam to form a blind via hole reaching the metal layer in the organic film. Then, irradiating the blind via hole with laser light of a different wavelength, removing the organic substance residue in the blind via hole, filling the metal layer in the blind via hole by electroplating, and forming a bump, the organic substance residue is removed. After the removal, the metal layer at the bottom of the blind via hole is half-etched, and thereafter, a bump is formed by electroplating.

The second invention is a wiring board having the bumps of the first invention, and the third invention is a semiconductor device using the wiring board.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to forming a bump by electroplating, the metal layer exposed at the bottom of a blind via hole functioning as a cathode is half-etched to roughen or slightly depress the surface. Thereby, the adhesion between the bumps to be formed and the metal layer is improved.

Hereinafter, the present invention will be further described with reference to the drawings. 1 to 6 are diagrams schematically illustrating processing steps according to an embodiment of the present invention in the order of steps. Here, as a substrate to be processed, a film substrate for mounting composed of a polyimide film 1 having a thickness of 30 μm and a copper foil 2 having a thickness of 18 μm was used.

FIG. 1 is a view in which a laser beam is irradiated from the polyimide film side of the substrate. In this example, the laser irradiation was performed while blowing nitrogen gas at a rate of 10 liters / minute onto the irradiation unit. In this step, the wavelength is 515n.
m pulse oscillation argon laser was used.

FIG. 2 is a view showing a cross section of the blind via hole portion opened in FIG. In this example, the via hole had a bottom of 40 μm and a top of 70 μm. An organic substance residue having a thickness of about 30 μm was adhered to the side wall and the bottom of the blind via hole.

FIG. 3 is a view showing that an organic residue in a blind via hole is irradiated with a pulsed laser beam composed of the second harmonic of a QswYAG laser to completely remove a decomposition residue.

FIG. 4 is a view showing a cross section of the blind via hole after removing the organic substance residue. Even when observed by an electron microscope, no residue is observed and the copper layer at the bottom of the blind via hole is completely removed. It was confirmed that it was exposed.

FIG. 5 shows that the copper layer exposed at the bottom of the blind via hole is etched with an iron chloride solution to about 1 μm.
FIG. 4 is a cross-sectional view of the blind via hole portion, in which a dent having a depth of is formed. When the depth of the depression is increased, the variation in the depth direction increases, and the smoothness of the copper surface is lost.

FIG. 6 is a sectional view of a bump portion formed by depositing copper by copper electroplating in a blind via hole completed as shown in FIG. In this example, copper bumps could be formed in all the blind via holes in a uniform shape with good reproducibility.

In this way, the adhesion strength between the obtained bump and the metal layer constituting the wiring is increased, and a wiring board with bumps which is much more reliable than that obtained by the conventional method can be obtained.

[0019]

Next, the present invention will be further described with reference to examples. (Conventional Example, Examples 1 to 5) A copper polyimide substrate having a width of 70 mm and a length of 100 m in which a copper layer having a thickness of 18 μm was provided on a polyimide film having a thickness of 30 μm and having device holes, and a copper foil surface of the substrate was used. Is coated with a commercially available photosensitive resist (manufactured by Tokyo Ohka, product name: PMER), exposed using a mask having a desired wiring pattern, developed, and the exposed copper foil is etched using an iron chloride solution. Next, the remaining resist layer was removed to form a wiring portion.

Next, in order to form a blind via hole at a desired position from the polyimide side, nitrogen gas is blown onto the irradiation part at a rate of 10 liter / minute, and a wavelength of 515 nm is applied.
m pulsed argon laser and then Qsw
A pulsed laser beam composed of the second harmonic of a YAG laser was applied. The irradiation time of each laser beam is 0.1 to 0.3 msec per blind via hole.

Thus, 2160 per pattern
Blind via holes were made. When the insides of all the blind via holes were observed with an electron microscope for the ten patterns, no organic substance residue was found in any of the blind via holes, and it was confirmed that the copper layer at the bottom of the blind via holes was completely exposed.

Incidentally, the bottom of the blind via hole had a diameter of 40 μm, and the top had an inverted truncated cone having a diameter of 70 μm.

Next, this is immersed in an iron chloride solution to form a copper layer having a depth of 0 (conventional example), 0.5 (example 1), 0.8 (example 2), 0.9 (example 2). 3), 3.5 (Example 4), 1
0.7 (Example 5) A depression of each μm was prepared, and electroplated with copper to prepare a bump.

Next, the polyimide film was removed by etching, leaving only the bumps and the wiring portions. In this state, the bumps were sheared, and the adhesion between the bumps and the wiring portions was checked.
The results obtained are shown in Table 1.

Table 1 Blind via hole shear strength Remarks Depth of depression in copper wiring portion 0 μm 14.8 gf Conventional example 0.5 μm 30.9 gf Example 1 0.8 μm 39.4 gf Example 2 0.9 μm 38.8 gf Example 3 3.5 μm 40.4 gf Example 4 10.7 μm 37.0 gf Example 5 From these results, it is possible to form a very small depression in the copper layer and then to perform electroplating to form a bump. It was possible to obtain a bump having a bonding strength of about 2.5 times that of the bump prepared in the above.

When the depth of the recess provided in the copper layer at the bottom of the blind via hole is increased to 10 μm, the cross section of the blind via hole becomes an uneven depth as shown in FIG.
Control by subsequent electroplating becomes difficult.

(Embodiments 6 and 7) Tape BGA in the same manner as in Embodiment 1 except that the depth of the depression of the copper wiring portion was set to 0.8 (Example 6) and 3.5 (Example 7) μm. 100 TAB tapes are prepared, and semiconductor chips are mounted on them.
Zero semiconductor devices were produced. Each of the 100 semiconductor devices was bonded to an external circuit board, and the electrical characteristics were measured.

Next, when the semiconductor device was peeled off, none of them peeled off at the joint surface between the bump and the external circuit board, and no peeling was found at the boundary between the bump and the circuit surface inside the semiconductor device.

[0029]

As described above, according to the present invention, the adhesion between the conventional metal layer at the bottom of the blind via hole and the bump formed by the plating method can be increased by about 2.5 times. As a result, it is possible to form bumps by electrolytic plating even on a high-density wiring board that requires fine blind via holes, for which it has not been possible to obtain an adhesion force until now. Can be obtained at low cost. Also, even when a semiconductor device or the like having a semiconductor chip mounted on a higher density wiring board obtained by using the present invention is mounted on a circuit board, electrical failure due to insufficient adhesion of the bump portion is greatly reduced, and reliability is improved. A high semiconductor device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a processing step of an embodiment of the present invention in the order of steps, and is a view in which laser light is irradiated from a polyimide film side of a substrate.

FIG. 2 is a schematic view showing a processing step of the embodiment of the present invention in the order of steps, and is a view showing a cross section of a blind via hole portion opened in FIG. 1;

FIG. 3 is a schematic diagram showing the processing steps of the embodiment of the present invention in the order of steps, and shows an organic residue in a blind via hole;
FIG. 5 is a diagram showing that a pulsed laser beam composed of a second harmonic of a QswYAG laser is irradiated to completely remove decomposition residues.

FIG. 4 is a schematic view showing the processing steps of the embodiment of the present invention in the order of steps, and is a view showing a cross section of a blind via hole portion after removing an organic substance residue.

FIG. 5 is a schematic view showing the processing steps of the embodiment of the present invention in the order of steps, wherein the copper layer exposed at the bottom of the blind via hole is etched with an iron chloride solution to form a depression, It is sectional drawing.

FIG. 6 is a schematic view showing the processing steps of the embodiment of the present invention in the order of steps, and is a cross-sectional view of a bump portion formed by depositing copper by a copper electroplating method in a blind via hole completed as shown in FIG. It is.

FIG. 7: 10.7 μm of copper substrate at the bottom of blind via hole
It is a figure which shows the cross-sectional shape of a bump part at the time of m etching.

Claims (4)

[Claims] 1. A laminated film comprising an organic film and a metal layer is irradiated with a laser beam to form a blind via hole reaching the metal layer on the organic film, and then the blind via hole is irradiated with a laser beam having a different wavelength to form a blind via hole. In the method of removing the organic substance residue in the inside, filling the metal layer in the blind via hole by electroplating and forming a bump, after removing the organic substance residue, half-etching the metal layer at the bottom of the blind via hole, and then Forming a bump on the substrate by electroplating. 2. The method according to claim 1, wherein the depth of the depression of the metal layer formed by half etching is 0.5 to 10 μm. 3. A wiring board having bumps formed by the method according to claim 1. 4. A semiconductor device using the wiring board according to claim 3.