JPH0974265A - Manufacture of wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the adhesion of a Ti thin film layer to a photo resist layer to obtain a high-accuracy wiring pattern by a method wherein a plating is applied to an exposed base thin film layer and the photoresist layer is removed to remove the Ti thin film layer and the base thin film layer, which are positioned under the lower part of the photoresist layer. SOLUTION: A polyimide precursor is cured on the whole surface of an alumina substrate 1 containing Al2 O3 to form as a polyimide resin layer 2 and a base thin film layer 3 for a Cr thin film 3a and a Pd thin film 3b and moreover, a Ti thin film layer 4 are subjected to sputtering in order on the layer 2. A novolak resin photoresist 5 is applied on the layer 4 and the layer 5 is exposed and is dried to provide apertures in a wiring pattern. After that, the layer 4 is removed and the layer 3 having the thin film 3b on its upper surface is made to expose. Then, the substrate is cleaned, subsequently an electrolytic Au plated film is formed on wiring pattern parts 6. Moreover, the left photoresist layer 5 and the thin film layers 4 and 3, which are positioned under the lower part of the layer 5, are respectively removed with an etching liquid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing a wiring board. The wiring board manufactured by this method can be suitably used for a high-density multilayer board, a thermal printer head, and the like.

[0002]

2. Description of the Related Art It is known to form a fine conductor wiring by a photolithography technique and a thin film technique using a photoresist in order to make a wiring board have a high density and a multilayer structure.

For example, in Japanese Patent Publication No. 1-39236, a thin film is provided on an insulating substrate, a photoresist is applied, a pattern is formed through exposure and development, a noble metal is plated, and then the photoresist is removed. Furthermore, a method for producing a high-density multilayer substrate by etching away the thin film other than the plated portion is described. This method discloses a basic technique of forming a wiring pattern with a thin film, and only inorganic materials such as glass and ceramics are exemplified as the base material.

After that, various improvements were made so that an organic material such as polyimide can be applied as a base material. In JP-A-1-120094, C was sequentially formed on an insulating substrate.
forming a thin film of r, Ti, Cu or Au and Cr,
Wiring is performed by applying a photoresist, forming a pattern through exposure and development, etching Cr in the portion where the photoresist does not exist, and plating a thin film of Cu or Au with a low resistance metal such as Cu or Au. A method of manufacturing a substrate has been proposed. In this method, Cr, which has good adhesiveness to a photoresist or polyimide, is formed on the upper and lower sides to prevent the plating solution from penetrating into the gap between the thin film and the resin, and a thin film of Cu or Au that is easy to plate is interposed in the middle. In this way, the adhesion between the plating film and the thin film is improved, and further, Ti is interposed as a shielding layer so that the Cr etching solution does not permeate to the lower Cr thin film.

In any of these cases, two types of photoresists, positive type and negative type, can be applied. The positive type is one in which the portion irradiated with ultraviolet rays is soluble and is generally made of a novolac resin. The negative type is one in which the portion irradiated with ultraviolet rays is insoluble and is generally composed of cyclized polyisoprene. As for the pattern accuracy, the positive type is originally better, but an appropriate one is selected depending on the relationship between the conductor material or insulating material to be combined and the etching solution.

[0006]

SUMMARY OF THE INVENTION
The method described in Japanese Patent Publication No. 39236 only discloses a basic technique of forming a wiring pattern with a thin film, and does not consider the adhesiveness between the thin film, the photoresist to be finally removed, and the adhesiveness. In fact, among the thin films composed of the first layer of Ti or W and the second layer of Pd or Pt exemplified in the publication, the second layer forming the upper surface and the photoresist have essentially poor adhesion. Further, when such a thin film is formed on a base material such as polyimide which is close to a mirror surface, the surface of the thin film is also a flat surface close to the mirror surface, so that the adhesiveness between the photoresist and the thin film directly below it is even worse. If the adhesiveness is poor, a gap is created between the photoresist and the thin film, and the plating solution penetrates into the gap, and a highly accurate wiring pattern cannot be obtained.

On the other hand, the above-mentioned Japanese Patent Laid-Open No. 1-1 has improved adhesion.
According to the method described in Japanese Patent Publication No. 20094, the novolac resin is corroded with respect to the etching solution of Cr containing potassium ferricyanide or potassium hydroxide, and as described above, a positive resist having originally good pattern accuracy can be applied. Can not.

Therefore, an object of the present invention is to improve the adhesion between the thin film layer and the photoresist layer, thereby eliminating the penetration of the plating solution and providing a method of manufacturing a wiring board having a high pattern accuracy. is there.

[0009]

In order to achieve the object, a method of manufacturing a wiring board according to the present invention is characterized in that a Ti film is formed on a base material, at least an upper surface of which is made of a material that can be plated. A step of forming a thin film layer, a step of applying a photoresist on the thin film layer, and a step of exposing and developing the thin film layer of Ti by providing an opening portion of a predetermined pattern in the photoresist layer through an exposure and development step. A step of removing the Ti thin film by etching to expose the underlying thin film layer; a step of plating the exposed underlying thin film layer; a step of removing the photoresist layer; and a step below the photoresist layer. A step of removing the Ti thin film layer and the underlying thin film layer which are located.

[0010]

According to the above method, a Ti thin film layer is formed on a base thin film layer made of a material that can be plated, a photoresist is applied on the Ti thin film layer, and an exposure and development process is performed to form a predetermined thickness on the photoresist layer. The opening of the pattern is exposed to expose the Ti thin film layer, the exposed Ti thin film is removed by etching, the underlying thin film layer is exposed, the exposed underlying thin film layer is plated, and the photoresist is applied. The layer is removed, and the Ti thin film layer and the underlying thin film layer located under the photoresist layer are removed. At this time, since the Ti etching solution is an acidic aqueous solution containing nitric acid and hydrofluoric acid unlike the Cr etching solution, it does not corrode not only the negative photoresist but also the positive photoresist. Therefore, the high accuracy of the wiring pattern before etching is maintained. In addition, since the adhesion between the Ti thin film and the photoresist is good, the plating solution does not sink when plating is performed thereafter. Therefore, highly accurate fine wiring can be obtained. Ti
The thickness of the thin film is usually 1 nm to 500 nm, preferably 1 nm.
It is 0 nm to 100 nm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a base material, an organic material such as a polyimide resin can be applied in addition to a ceramic material, and the latter is preferable for fine wiring. In addition, a silicon wafer is also applicable. In any case, the film structure of the present invention is excellent in adhesion to a flat substrate whose surface is close to a mirror surface, and is effective for such a substrate.

The base thin film layer may be made of a material whose upper surface can be plated. Examples of the material that can be plated include Au, Cu, and Pd. On the other hand, the lower surface is not particularly limited, but if the lower surface is made of Cr, Cr adheres to both organic materials such as polyimide and inorganic materials such as ceramics, making it easy to select a base material. And is preferable. Further, as the underlying thin film layer, C
It is also preferable to select at least one of u, Au, Pd and Ni. Since these can be plated, conductors necessary for wiring can be plated on the upper surface, and since they are materials that can be electroless plated, they can be adhered to a base material such as ceramics by electroless plating. Is. As the photoresist, not only a negative type but also a positive type made of a novolac resin can be applied, which is preferable for a high precision pattern.

[0013]

【Example】

-Embodiment 1- A first embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 6A is a cross-sectional view showing, in the order of steps, a wiring board manufactured according to the first embodiment of the manufacturing method of the present invention. In this example,
The base material is polyimide.

A polyimide precursor is spin-coated on the entire surface of an alumina substrate 1 having an Al ₂ O ₃ content of 92% by weight, prebaked at a temperature of 80 ° C., and subsequently 350 ° C. in a nitrogen atmosphere.
To cure the polyimide precursor to form a polyimide resin layer 2, on which a 25 nm thick Cr thin film 3a and a thickness of 3 are formed.
A base thin film layer 3 made of a Pd thin film 3b having a thickness of 00 nm and a Ti thin film layer 4 having a thickness of 100 nm were sequentially sputtered (FIG. 1 (a)). AZ-4620 novolac resin photoresist 5 manufactured by Hoechst Co., Ltd. is applied thereon to a thickness of 10 μm, exposed, immersed in a developing solution and dried to give a width of 25 μm.
An opening 6 having a wiring pattern of μm and a pitch of 50 μm was provided (FIG. 1 (b)). The Ti thin film layer 4 is exposed on the bottom surface of the opening 6.

After that, the wiring pattern portion (opening) 6
Of the Ti thin film layer 4 is removed by an etching solution (mixed solution of nitric acid and hydrofluoric acid), and the underlying thin film layer 3 having the Pd thin film 3b on the upper surface is removed.
Was exposed (Fig. 1 (c)). Next, the substrate was washed, and subsequently, the substrate was immersed in an Au plating solution to energize the underlying thin film layer 3 to form an electrolytic Au plated film 7 having a thickness of 5 μm on the exposed wiring pattern portion 6 of the underlying thin film layer 3. (Fig. 1
(d)). Further, the remaining photoresist layer 5 and the Ti thin film layer 4 and the underlying thin film layer 3 located therebelow were removed by respective etching solutions to manufacture a wiring board (FIG. 1 (e)). According to the present embodiment, the thin films 3a and 3b of Cr and Pd are used as the bases on the polyimide resin layer 2 to form A.
This means that u-plated wiring has been formed.

When the surface of the obtained wiring board was observed with a magnifying glass, not only a short circuit between wirings but also no bleeding occurred. Since the adhesion between the Ti thin film layer 4 and the photoresist layer 5 is high, the Au plating solution does not penetrate between the two, and even if the Ti thin film layer 4 is removed by etching,
This is because the photoresist, which is a novolac resin, is not attacked, so that the wiring pattern is not bleed.

In the above embodiments, the polyimide resin is used as the base material and the thin film layer and the photoresist layer are formed on the base material. However, other organic resins such as epoxy resin and BCB resin are also used. Obviously, may be used as a substrate. In addition, alumina, mullite,
A substrate made of an inorganic material such as AlN, glass ceramic, or glass may be used as the base material.

In the above embodiment, C is used as the underlying thin film layer.
Although a thin film composed of an r thin film and a Pd thin film was used, a material having high adhesion to the base material (for example, Mo, Z
r, Ti, Ti-Mo, etc.) may be used. Furthermore, Cu, Au, or the like may be used instead of Pd as long as the upper surface can be plated. Further, the base thin film layer is shown to be composed of two layers of Cr / Pd in the above embodiment, but if the upper surface is composed of Pd, Cu, Au or the like which can be plated, two or more layers are formed. The layers may be stacked, or conversely, a single layer of Pd or the like may be used as long as the adhesion to the base material is obtained.

-Comparative Example 1-A Cr thin film was formed in place of the Ti thin film layer 4, and this Cr thin film was formed.
Potassium ferricyanide 10 as thin film etching solution
An attempt was made to manufacture a wiring board under the same conditions as in Example 1 except for using%. When the unnecessary Cr thin film after forming the wiring pattern was removed with an etching solution, the photoresist melted and the wiring pattern collapsed. . Therefore, the subsequent plating became impossible. This is because the novolac resin dissolves in alkali.

-Comparative Example 2-This example is a method of directly coating a photoresist without forming the Ti thin film layer 4 or the Cr thin film shown in Comparative Example 1 on a thin film that can be plated. That is, a wiring board was manufactured under the same conditions as those of the above-described example except that the formation of the Ti thin film layer 4 and the immersion of Ti in the etching solution were omitted.

When the surface of the obtained wiring board was observed with a magnifying glass, bleeding occurred at the edge of the wiring and short-circuiting occurred between adjacent wirings. It is considered that this is because the adhesiveness between the photoresist and the Pd thin film is low, and thus the plating solution sunk into the gap between the two.

Second Embodiment A second embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 6A is a sectional view showing a wiring board manufactured according to the second embodiment of the manufacturing method of the present invention in the order of steps. In this example,
The base material is alumina, which also serves as the substrate material.

A base thin film layer 1 consisting of a Cr thin film 13a having a thickness of 50 nm and a Pd thin film 13b having a thickness of 500 nm is formed on the entire surface of an alumina substrate 11 having an Al ₂ O ₃ content of 92% by weight.
3. Then, a Ti thin film layer 14 having a thickness of 100 nm was sequentially sputtered (FIG. 2 (a)). AZ manufactured by Hoechst
-4620 Novolac resin photoresist 15 was applied to a thickness of 10 μm, exposed, immersed in a developing solution, and dried to provide an opening 16 of a wiring pattern having a width of 25 μm and a pitch of 50 μm (FIG. 2 (b)). . The Ti thin film layer 14 is exposed on the bottom surface of the opening 16.

After that, the wiring pattern portion (opening) 1
The Ti thin film layer 4 of No. 6 was removed with an etching solution (mixed solution of nitric acid and hydrofluoric acid) to expose the underlying thin film layer 13 having the Pd thin film 13b on the upper surface (FIG. 2 (c)). Then, the substrate was washed, and subsequently, the substrate was immersed in an Au plating solution to energize the underlying thin film layer 13 to form an electrolytic Au plating film 17 having a thickness of 5 μm on the exposed wiring pattern portion 16 of the underlying thin film layer 3. (Fig. 2 (d)). Furthermore, the remaining photoresist layer 15, the Ti thin film layer 14 and the underlying thin film layer 1 located thereunder
By removing 3 with each etchant,
A wiring board was manufactured (Fig. 2 (e)). According to this embodiment,
Cr and Pd thin films 13a, 13 on the alumina substrate 11
This means that the Au-plated wiring was formed using b as the base.

When the surface of the obtained wiring board was observed with a magnifying glass, no bleeding occurred as well as a short circuit between the wirings. Since the adhesion between the Ti thin film layer 14 and the photoresist layer 15 is high, Au plating does not penetrate between them, and even if the Ti thin film layer 14 is removed by etching, the photoresist which is a novolac resin can be removed. This is because there is no bleeding, and therefore no bleeding occurs in the wiring pattern.

Further, according to the first and the present examples, when the base thin film layer has the lower surface made of Cr, the base material may be the polyimide resin as in the first embodiment or the ceramic as in the present example. It is clear that the underlying thin film layer adheres to the substrate.

Third Embodiment A third embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 6A is a sectional view showing a wiring board manufactured according to a third embodiment of the manufacturing method of the present invention in the order of steps. Also in this example,
The base material is alumina, which also serves as the substrate material.

On the entire surface of the alumina substrate 21 having an Al ₂ O ₃ content of 92% by weight, a 500 nm thick underlying thin film layer 23 of Cu is electrolessly plated, and a 100 nm thick Ti thin film layer 24 is formed thereon. It was sputtered (FIG. 3 (a)). AZ-4620 novolac resin photoresist 25 manufactured by Hoechst Co., Ltd. is applied thereon to a thickness of 10 μm, exposed to light, dipped in a developing solution and dried to give a width of 25 μm and a pitch of 5
An opening 26 having a wiring pattern of 0 μm is provided (see FIG. 3).
(b)). The Ti thin film layer 24 is exposed on the bottom surface of the opening 26.

After that, the wiring pattern portion (opening) 2
The Ti thin film layer 4 of No. 6 was removed by an etching solution (mixed solution of nitric acid and hydrofluoric acid) to expose the underlying thin film layer 3 made of Cu (FIG. 3 (c)). Next, the substrate is washed, and subsequently, while being energized to the underlying thin film layer 23, the substrate is immersed in a Cu plating solution, a Ni plating solution, and an Au plating solution in this order, whereby
3 has a Cu film 27a with a thickness of 2 μm, a Ni film 27b with a thickness of 1 μm, and an A with a thickness of 2 μm.
A plating film 27 made of the u film 27c was formed (see FIG. 3).
(d)). Further, the remaining photoresist layer 25 and the Ti thin film layer 24 and the underlying thin film layer 23 located therebelow were removed by respective etching solutions to manufacture a wiring board (FIG. 3 (e)). According to this embodiment, Cu / Ni / A is formed on the alumina substrate 1 with a Cu plating film as a base.
This means that u3 layer plated wiring is formed.

When the surface of the obtained wiring board was observed with a magnifying glass, not only a short circuit between wirings but also no bleeding occurred. Since the adhesion between the Ti thin film layer 24 and the photoresist layer 25 is high, Cu plating solution, Ni plating solution and A
None of the u-plating liquid will sneak between the two,
Further, even if the Ti thin film layer 24 is removed by etching, it does not attack the photoresist which is a novolac resin, so that the wiring pattern does not have bleeding.

Further, in this example, since Cu which can be plated and at the same time can be electrolessly plated on the alumina substrate is used as the underlying thin film layer, the conductor required for wiring is plated on the upper surface with the Cu1 layer. Not only can it be done, but it is also in close contact with the substrate, and the film structure and process are simple.

[0032]

As described above, according to the manufacturing method of the present invention, it is possible to prevent the plating solution from penetrating between the thin film layer and the photoresist layer regardless of the type of the plating solution. As a result, it is possible to obtain a wiring board having a highly accurate wiring pattern formed of a positive resist as well as a negative resist, which contributes to high density multi-layering and miniaturization of the wiring board.

[Brief description of drawings]

1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment in the order of steps.

2A to 2D are cross-sectional views illustrating a manufacturing method according to a second embodiment in the order of steps.

FIG. 3 is a cross-sectional view illustrating the manufacturing method of the third embodiment in the order of steps.

[Explanation of symbols]

 1,11,21 Alumina substrate 2 Polyimide resin layer 3,13,23 Base thin film layer 4,14,24 Ti thin film layer 5,15,25 Photoresist layer 6,16,26 Opening part (wiring pattern part) 7,17 , 27 Au plating film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Kanamori No. 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Nihon Special Ceramics Co., Ltd. (72) Inventor Tomomi 14 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi No. 18 Nihon Special Ceramics Co., Ltd.

Claims (6)

[Claims] 1. A step of forming a Ti thin film layer on a base thin film layer formed on a base material and at least having an upper surface made of a material capable of being plated, a photoresist is applied thereon, and an exposure and development step is performed. A step of exposing the Ti thin film layer by providing an opening of a predetermined pattern in the photoresist layer, a step of removing the exposed Ti thin film by etching to expose the underlying thin film layer, and the exposed underlayer. A wiring comprising: a step of plating the thin film layer, a step of removing the photoresist layer, and a step of removing the Ti thin film layer and the underlying thin film layer located under the photoresist layer. Substrate manufacturing method. 2. The method for manufacturing a wiring board according to claim 1, wherein the base material is an organic material such as a polyimide resin. 3. The substrate is a ceramic material.
A method for manufacturing a wiring board according to. 4. The method for manufacturing a wiring board according to claim 1, wherein the underlying thin film layer has a lower surface made of Cr. 5. The base thin film layer is Cu, Au, Pd and N.
The method for manufacturing a wiring board according to claim 1, comprising at least one selected from i. 6. The method for manufacturing a wiring board according to claim 1, wherein the photoresist is a novolac resin.