JPH11233902A - Ceramic board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic board having a proper insulating property between conductive patterns, even if fine conductive patterns are formed on the board surface by a plating method. SOLUTION: In case fine conductive patterns having a distance of 50 μm between the conductive patterns are formed, an insulating property between the conductive patterns 20 can be prevented from becoming improper by forming a gap 12 at a roughened region 11 between the conductive patterns 20, even if conductive particles which have penetrated the roughened region during a non-electrolytic plating step remain at the roughened region between the conductive patterns during a soft etching step. Accordingly, even if fine conductive patterns are formed on the board surface by the plating method, a ceramic board having a proper insulating property between the conductive patterns can be obtained. Additionally the gap 12 is formed by the laser irradiation beam of a YAG laser, therefore the required roughened region between the conductive patterns can easily and accurately be eliminated by choking a spot diameter of the laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic substrate and a method of manufacturing the same, and more particularly, to a ceramic substrate having a plurality of conductor patterns on a substrate surface and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, electronic devices have become more and more sophisticated, compact, and high-density, and semiconductor devices mounted on them have become multi-pin and multi-chip.
Along with this, wire bonding, TAB (Tape Automated) has been
The flip-chip method is more often used than the Bonding method. The flip chip method is a method in which a solder bump is further formed on a pad formed on one surface of an LSI, and the solder bump is connected to a substrate-side electrode pad. In the flip chip method, the connection length can be shortened, the electric characteristics can be improved, and many pads can be formed without using a narrow pitch.
It has such advantages that the ratio of the SI area to the package area can be increased and the mounting thickness can be reduced.

With the increase in the density of such electronic devices, a technique for forming a conductor pattern such as a fine wiring having a line width of 100 μm or less or an electrode pad having a diameter of 100 μm or less on a ceramic substrate is required. It has become to. In addition, the operating frequency of semiconductor devices has been increasing, and it has become necessary to improve the conductivity of conductive wiring in order to reduce propagation delay during high-speed operation. In addition, as a material of the ceramic substrate main body, alumina which satisfies the substrate characteristics such as mechanical strength and electrical insulation and is inexpensive to manufacture is mainly used.

Hereinafter, a method for forming a conductor pattern on a ceramic substrate will be described. Conventionally, a method for forming a conductor pattern on a ceramic substrate has been a thin film method, a thick film method,
It is roughly divided into plating method and the like. The thin film method is a method of forming a conductive metal layer having a thickness on the order of several μm on a ceramic substrate by vapor deposition, sputtering, ion plating, or the like. However, there are problems that the adhesion between the conductor pattern formed by the thin film method and the ceramic substrate body is low, the number of steps is large as compared with other methods, and the thin film forming apparatus is expensive.

The thick film method uses a conductive paste in which conductive particles are dispersed in an organic vehicle containing a liquid component such as a solvent, and discharges the conductive paste from a mesh screen with a squeegee onto a ceramic substrate body. In this method, a conductor pattern is formed on a ceramic substrate by printing a predetermined pattern and then firing the pattern. In the thick film method, a conductor pattern having sufficient adhesion strength to the ceramic substrate body can be formed at low cost. However, when the above-mentioned conductor paste is printed on the ceramic substrate body, the liquid component in the conductor paste is not absorbed into the inside of the ceramic substrate body, so that the printed liquid component in the conductor paste spreads in the horizontal direction and oozes. Occurs, and it is difficult to form a conductor pattern having a width or a distance between conductor patterns of 100 μm or less as designed.

[0006] The plating method is a method of forming a conductor pattern on a ceramic substrate by an electrochemical method in a solution. The plating method has an advantage that a fine wiring with high precision can be formed since a photolithography method using a photoresist can be used.

[0007]

However, the above plating method has a problem that the adhesion between the formed conductor pattern and the ceramic substrate body is low.
Therefore, in order to improve the adhesion between the conductor pattern and the ceramic substrate body, the surface of the ceramic substrate body is roughened to form a roughened area, and a thin conductor layer is provided on the roughened area by electroless plating. There is known a method in which a thick conductor layer is provided on the thin conductor layer by electrolytic plating, and then the conductor layer is eroded by soft etching or etching to form a conductor pattern on the substrate surface.

The formation of the above conductor pattern is conventionally performed by a semi-additive method or a subtractive method as a method for introducing photolithography using a photoresist. In the semi-additive method, a roughened region is formed on the surface of a ceramic substrate body, a thin conductor layer is provided on the roughened region by electroless plating, a photoresist layer is formed on the thin conductor layer, and then photolithography is performed. A concave portion is formed in the above-mentioned photoresist layer in the form of a conductor pattern by the above-mentioned method, a thick conductor layer is provided by electrolytic plating on the thin conductor layer of the concave portion, and the photoresist layer is removed. A method of forming a conductor pattern on the substrate surface by erosion is employed. Fine wiring can be accurately formed by the semi-additive method.

In the subtract method, a roughened region is formed on the surface of a ceramic substrate body, a thin conductor layer is provided on the roughened region by electroless plating, and a thick conductor layer is formed on the thin conductor layer by electrolytic plating. After forming a photoresist layer on this thick conductor layer, a conductor pattern is formed on the above-mentioned photoresist layer by a photolithography method, and after etching the thin conductor layer and the thick conductor layer by etching, the photoresist is formed. In this method, a conductor pattern is formed on the substrate surface by removing the layer. Although the precision of the fine wiring is inferior to that of the semi-additive method by the subtract method, the number of steps is relatively small and the manufacturing cost can be relatively low.

However, when the distance between the formed conductor patterns is as fine as 100 μm or less, the conductive particles which have entered the roughened region in the step of providing a thin conductor layer by electroless plating on the roughened region are soft-etched. Alternatively, there is a problem in that it remains in a roughened region between conductor patterns in an etching step, and insulation between conductor patterns deteriorates.

The present invention has been made to solve such a problem, and a ceramic substrate having good insulation between the conductor patterns even if a fine conductor pattern is formed on the substrate surface by a plating method. The purpose is to provide.

[0012]

According to the ceramic substrate according to the first aspect of the present invention, the plurality of conductor patterns formed on the substrate surface include a thin conductor layer provided by electroless plating and a thin conductor layer formed on the thin conductor layer. And a thick conductor layer provided by electrolytic plating, a roughened region is formed at the interface with the conductor pattern of the ceramic substrate body, and a groove is formed in the roughened region between the conductor patterns. For this reason, even if the conductive particles that have penetrated into the roughened region in the step of providing a thin conductor layer by electroless plating on the roughened region remain in the roughened region between the conductor patterns in the soft etching or etching process, The grooves formed in the roughened regions between the patterns can prevent the insulation between the conductor patterns from deteriorating. Therefore, even if a fine conductor pattern is formed on the substrate surface by plating, a ceramic substrate having good insulation between the conductor patterns can be obtained.

The depth of the groove is preferably a distance approximately equal to the thickness of the roughened region. If the depth of the groove is too deep, the mechanical strength of the ceramic substrate body may be deteriorated. Also,
If the depth of the groove is too shallow, the effect of preventing the deterioration of the insulation between the conductor patterns may be reduced. According to the ceramic substrate according to the second aspect of the present invention, since the groove is formed in the roughened region where the distance between the conductor patterns is 100 μm or less, it is possible to reliably prevent the insulation between the conductor patterns from deteriorating. Can be. Therefore, even if a fine conductor pattern is formed on the substrate surface by a plating method, a ceramic substrate having better insulation between the conductor patterns can be obtained.

According to the method of manufacturing a ceramic substrate according to the third aspect of the present invention, the surface of the ceramic substrate body is roughened to form a roughened region, and a thin conductor layer is provided on the roughened region by electroless plating. By providing a thick conductor layer on the thin conductor layer by electrolytic plating and eroding the thin conductor layer by soft etching, or by eroding the thin conductor layer and the thick conductor layer by etching, a plurality of conductor patterns are formed on the substrate surface. Is formed, and a groove is formed in a roughened region between the conductor patterns. For this reason, even if the conductive particles that have penetrated into the roughened region in the step of providing a thin conductor layer by electroless plating on the roughened region remain in the roughened region between the conductor patterns in the soft etching or etching process, By forming the groove in the roughened region between the patterns, it is possible to prevent the insulation between the conductor patterns from being deteriorated. Therefore, even if a fine conductor pattern is formed on the substrate surface by plating, a ceramic substrate having good insulation between the conductor patterns can be obtained.

In addition, in order to prevent oxidation of the thick conductor layer of the formed conductor pattern and to make the conductor pattern adhere to the ceramic substrate body due to the reaction between the thick conductor layer and the solder layer when solder is joined to the conductor pattern. In order to prevent the deterioration of the thickness and to secure the solder wettability to the thick conductor layer, the surface of the thick conductor layer may be plated with Ni, Au, or the like after the formation of the conductor pattern.

When a conductor pattern is formed on the substrate surface by the above method, the conductor particles constituting the thin conductor layer and the thick conductor layer include, for example, W, Mo, Ni, Au,
Metals such as Ag, Ag / Pd alloy, and Cu are used. In order to form a fine conductor pattern on the substrate surface, the conductor metal used for the thin conductor layer and the thick conductor layer preferably has as low an electric resistance as possible. Among the above metals, low resistance metals include Au, Ag, and Cu. However, Au is expensive, and Ag has problems such as easy migration in a humid atmosphere. Cu
Is most preferred.

As a method for forming the conductor pattern, a semi-additive method or a subtractive method using a photolithography technique using a photoresist can be employed. Further, when using the photolithography technique in the present invention, as the photoresist to be used, as long as it can be developed with alkali, even a negative type,
A positive type can also be used.

The ceramic substrate used in the present invention is not particularly limited as long as it can be used as a wiring substrate. Specific examples thereof include an alumina substrate, a mullite substrate, a low-temperature fired glass substrate, and an aluminum nitride substrate. And the like. Further, a substrate in which wiring and the like are formed inside a ceramic substrate may be used. According to the method of manufacturing a ceramic substrate according to claim 4 of the present invention, since the groove is formed in the roughened region where the distance between the conductor patterns is 100 μm or less, it is ensured that the insulation between the conductor patterns is deteriorated. Can be prevented. Therefore, even if a fine conductor pattern is formed on the substrate surface by a plating method, a ceramic substrate having better insulation between the conductor patterns can be obtained.

According to the method of manufacturing a ceramic substrate according to the fifth aspect of the present invention, since the groove is formed by irradiating a laser beam, the spot diameter of the laser beam is reduced by using, for example, a YAG laser or an excimer laser. In addition, a roughened area between desired conductor patterns can be easily and accurately removed. Therefore, even if a finer conductor pattern is formed on the substrate surface, a ceramic substrate having good insulation between the conductor patterns can be obtained.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. One embodiment in which the present invention is applied to a ceramic substrate made of alumina will be described with reference to FIGS. First, a method for manufacturing a ceramic substrate body made of alumina will be described.

(1) Magnesia, silica,
Calcined talc, sintering aids such as calcium carbonate, and a powder obtained by adding a small amount of a coloring agent such as titanium oxide, chromium oxide, and molybdenum oxide, a plasticizer such as dioxyl phthalate, a binder such as an acrylic resin and toluene, Solvents such as xylene and alcohols are added and sufficiently kneaded to obtain a viscosity of 2000 to 2000.
A slurry of 40,000 cps is prepared, and a green sheet made of alumina having a thickness of, for example, 1.0 mm is formed by a doctor blade method, and the alumina green sheet is fired at 1500 to 1600 ° C. in air to obtain an alumina ceramic substrate body. Is obtained.

Next, a method for forming a conductive pattern on the alumina substrate body obtained in the above (1) by plating will be described by taking a semi-additive method as an example. (2) In step S1 shown in FIG. 7, the surface of the alumina substrate body is roughened by dissolving the glass component of the surface layer of the alumina substrate body using, for example, an HF (hydrogen fluoride) aqueous solution or the like. A roughened region is formed.

(3) In step S2 shown in FIG. 7, as shown in FIG.
A Cu thin conductor layer 21 is formed thereon by, for example, electroless Cu plating.
Is provided. (4) In step S3 shown in FIG. 7, for example, by applying a photolithography technique using a positive type photoresist, ultraviolet rays are irradiated through a photomask designed to be exposed to a desired pattern shape, Thereafter, by performing a development process, a positive photoresist layer 30 having a concave portion 31 in a desired pattern shape is formed on the Cu thin conductor layer 21 as shown in FIG. By the above method, a positive photoresist layer 30 having a concave portion 31 having a diameter and an interval between adjacent ones of about 20 μm or more can be formed on the positive photoresist. Also,
By irradiating the positive photoresist with a laser beam using, for example, a YAG laser or an excimer laser, the diameter of the positive photoresist and the distance between adjacent ones are reduced to about one.
A positive photoresist layer having a recess of about 0 μm or more can be formed.

(5) In step S4 shown in FIG. 7, a Cu thick conductor layer 22 is provided on the Cu thin conductor layer 21 in the recess 31 by, for example, electrolytic Cu plating, as shown in FIG. (6) In step S5 shown in FIG. 7, as shown in FIG. 5, a photoresist is formed using an alkaline aqueous solution using an alkali metal hydroxide such as NaOH (sodium hydroxide) or KOH (potassium hydroxide). Dissolve the layers,
Make it disappear.

(7) In step S6 shown in FIG. 7, as shown in FIG. 6, the thin conductor layer 21 is formed by soft etching.
Erosion, the roughened region 1 of the alumina substrate body 10
A plurality of Cu conductor patterns 20 each having a thin conductor layer 21 and a thick conductor layer 22 are formed on the substrate 1. (8) In step S7 shown in FIG. 7, as shown in FIG. 1, for example, using a YAG laser, the roughened region 11 between the conductor patterns 20 having the thin conductor layer 21 and the thick conductor layer 22 is used.
The groove 12 is formed by irradiating the substrate with a laser beam. The depth of the groove 12 is preferably approximately the same as the thickness of the roughened region 11.

By the above steps (2) to (8), as shown in FIG. 1, the thin conductor layer 21 provided on the substrate surface by electroless plating, and the thin conductor layer 21 provided on the thin conductor layer 21 by electrolytic plating. Alumina substrate body 10 having a plurality of conductor patterns 20 having thick conductor layers 22, a roughened region 11 formed at an interface with conductor pattern 20, and a groove 12 formed in roughened region 11 between conductor patterns 20 Can be obtained. Here, the groove 12 is, as evidenced by the experimental results described below,
It is important that the conductor pattern 20 is formed in the roughened region 11 having a distance of 100 μm or less.

Finally, the wiring pattern on the alumina substrate is completed by plating Ni, Au, or the like on the surface of the thick conductor layer of the conductor pattern. Next, changing the width of the conductor pattern and the distance between the conductor patterns, the above (2) to
An experimental result of measuring a resistance value between the conductor patterns of the alumina substrate manufactured in the step (8) will be described. Table 1 shows the results. Table 2 shows the laser beam irradiation conditions in the above step (8).

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Table 1, in this embodiment, when the width of the conductor pattern and the distance between the conductor patterns are 50 μm or more, the resistance value is 10 ¹⁰ Ω or more, and an alumina substrate having good insulating properties is obtained. be able to. Next, by changing the width of the conductor pattern and the distance between the conductor patterns, a plurality of conductor patterns are formed on the substrate surface of the alumina substrate by the same steps as the steps (2) to (7) of this embodiment, and the conductors are formed. Table 1 shows the results of measuring the resistance value between the conductor patterns in the comparative example in which the groove was not formed in the roughened region between the patterns. As shown in Table 1, in the comparative example, the resistance value was 300 kΩ when the width of the conductor patterns and the distance between the conductor patterns were 80 μm, and 1 Ω when the width of the conductor patterns and the distance between the conductor patterns were 50 μm or more. is there. Therefore, it can be said that the insulation resistance of the alumina substrate having the width of the conductor pattern and the distance between the conductor patterns of 80 μm or less in the comparative example is not practically suitable.

As described above, in the comparative example, since no groove is formed in the roughened region between the conductor patterns, when a fine conductor pattern having a distance between the conductor patterns of 80 μm or less is formed, electroless plating is performed. The conductor particles that have entered the roughened region in the process remain in the roughened region between the conductor patterns in the soft etching process, and the insulation between the conductor patterns is deteriorated.

On the other hand, in the present embodiment, when a fine conductor pattern having a distance between conductor patterns of 50 μm is formed, the conductor particles that have entered the roughened region in the electroless plating step may become conductive in the soft etching step. By forming the groove 12 in the roughened area 11 between the conductor patterns 20 even if the groove 12 remains in the roughened area between the patterns,
It is possible to prevent the insulation between the conductor patterns 20 from deteriorating. Therefore, even if a fine conductor pattern is formed on the substrate surface by plating, an alumina substrate having good insulation between the conductor patterns can be obtained.

Further, in the present embodiment, since the groove 12 is formed by irradiating the laser beam of the YAG laser, the roughened area between the desired conductor patterns can be formed simply and accurately by narrowing the spot diameter of the laser beam. Can be removed well. Therefore, even if a finer conductive pattern is formed on the substrate surface, an alumina substrate having good insulation between the conductive patterns can be obtained. Note that the laser light irradiation is not limited to the YAG laser, and another laser light such as an excimer laser may be used.

In this embodiment, the conductor pattern is formed on the surface of the alumina substrate by the semi-additive method. However, in the present invention, the conductor pattern may be formed on the surface of the alumina substrate by the subtract method. Further, in the present invention, W, Mo, Ni,
A conductor pattern may be formed by providing a thin conductor layer and a thick conductor layer using a metal such as Au, Ag, and an Ag / Pd alloy.

In the present invention, the present invention is not limited to the alumina substrate but may be applied to any ceramic substrate such as an aluminum nitride substrate, a mullite substrate, and a low-temperature fired glass substrate. Further, the substrate may have a wiring or the like formed therein.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment in which the present invention is applied to an alumina substrate.

FIG. 2 is a schematic cross-sectional view for explaining a method of manufacturing an alumina substrate according to one embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view for explaining a method for manufacturing an alumina substrate according to one embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view for explaining a method of manufacturing an alumina substrate according to one embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view for explaining a method of manufacturing an alumina substrate according to one embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view for explaining a method for manufacturing an alumina substrate according to one embodiment of the present invention.

FIG. 7 is a flowchart for explaining a method of manufacturing an alumina substrate according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Alumina substrate main body (ceramic substrate main body) 11 Roughened area 12 Groove part 20 Conductor pattern 21 Thin conductor layer 22 Thick conductor layer 30 Photoresist layer 31 Depression 100 Alumina substrate (ceramic substrate)

Claims (5)

[Claims] 1. A plurality of conductor patterns each having a thin conductor layer provided on a substrate surface by electroless plating and a thick conductor layer provided on the thin conductor layer by electrolytic plating, and formed at an interface between the conductor patterns. A ceramic substrate body having a roughened region, and a groove formed in the roughened region between the conductor patterns. 2. The ceramic substrate according to claim 1, wherein the groove is formed in the roughened region where a distance between the conductor patterns is 100 μm or less. 3. A step of roughening the surface of the ceramic substrate body to form a roughened region, providing a thin conductor layer on the roughened region by electroless plating, and forming a thick conductor on the thin conductor layer by electrolytic plating. Providing a layer, and eroding the thin conductor layer by soft etching, or eroding the thin conductor layer and the thick conductor layer by etching, to form a plurality of conductor patterns on the substrate surface, Forming a groove in the roughened region between the conductive patterns. 4. The method according to claim 3, wherein the groove is formed in the roughened region where a distance between the conductor patterns is 100 μm or less. 5. The method according to claim 3, wherein the groove is formed by irradiating a laser beam.