JPH0240233B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a multilayer wiring board used in general electronic equipment.

(Prior Art) A multilayer wiring board electrically connects wiring circuit conductors formed on both the front and back surfaces of each insulating board by making through holes conductive. Various methods have been practiced in the past. Generally, a polyimide layer is formed on the lower conductor wiring layer (hereinafter abbreviated as lower layer wiring), the through hole portion is etched later, and then the upper conductor wiring layer (hereinafter abbreviated as upper layer wiring) is formed. By doing so, conduction between the upper and lower layers is obtained via the through hole. In some cases, a method is also available in which a thin film is formed over the entire surface of polyimide with through holes formed, selective plating is performed on the through holes, and the through holes are filled with a conductor, and then upper layer wiring is formed. It is being

(Problems to be Solved by the Invention) When through-holes are conventionally formed by chemical etching, defects such as over-etching and under-etching are likely to occur, and a thin oxide barrier layer is formed on the lower wiring of the through-hole. This may cause high resistance in the remaining upper and lower layer interconnects, and when upper layer interconnects are formed in the stepped portion caused by the through hole, defects such as disconnections are likely to occur at the side walls and opening corners of the through hole. In addition, since the process of forming a new thin film over the entire surface and filling the inside of the through hole with plating is complicated, it is desirable to simplify the process.

(Means for Solving the Invention) The present invention has been made in view of the above-mentioned circumstances, and is a method of providing through holes in an insulator and then connecting upper and lower layer wiring by plating the through holes or the like. Instead, a conductor pillar is first formed to connect the upper and lower layer wiring, and then a through hole is formed in the insulator, resulting in a structure in which the through hole is filled with a conductor. be. That is, without removing the entire thin film and resist used when forming the lower layer wiring by selective plating, a resist for selective plating of conductor pillars is further formed on top of it, conductor pillars are formed by selective plating, and then the conductor pillars are formed by selective plating. After removing the resist and unnecessary thin film, an insulating layer of polyimide or glass ceramics is provided, this surface is polished to make it flat, the top surface of the conductor pillar is exposed by etching, and selective plating is applied on top of this. To provide a method for manufacturing a multilayer wiring board by filling the top of a conductor column with a conductor column, forming an upper layer wiring, connecting the lower layer wiring and the upper layer wiring by the conductor column, and sequentially repeating the above operations. It is.

(Function) As described above, the thin film for selective electrolytic plating of lower layer wiring can be used as is for electrolytic plating of conductor columns, and the complicated chemical etching process can be replaced with selective plating and polishing, thereby simplifying the manufacturing process. In addition, even if the insulating layer is thick, the thickness that requires chemical etching is reduced by the height of the conductor pillars, making etching easier, and the upper opening diameter of the tapered cross section can be kept small, allowing for small diameter and small pitch. Through holes can be formed. Furthermore, since most of the through-hole is filled with a conductor, the connection resistance is reduced, and the reliability of the connection is high because there is no step or only a small step in the through-hole when forming the upper layer wiring.

(Example) FIG. 1 shows an example of the method for manufacturing a multilayer wiring board according to the present invention. In FIG.
As shown in Figure 2, a photoresist 3 with a line width of 20 ~
A resist pattern of 50 μm and a pitch of 50 to 100 μm was formed, and the lower layer wiring 4 was selectively plated to a thickness of 8 μm by electrolytic Cu plating as shown in FIG. 1. A resist pattern for through-holes with a diameter of 20 to 50 μm is formed using photoresist 5 made by E, and conductor columns 6 with a height of 20 μm are formed by electrolytic copper plating as shown in FIG.
As shown in FIG. 1, photoresist 3, photoresist 5 and Cu-Cr
Unnecessary non-patterned parts of the thin film 2 are removed, and polyimide varnish is coated on the entire surface to a thickness of 20 μm from the end face of the conductor column so that the conductor column 6 is buried as shown in FIG. form. Next, as shown in FIG. 1, the surface of the polyimide insulating layer 7 is polished to make it flat. Next, Figure 1 9
As shown in FIG. 1, a thin aluminum film 11 is formed by sputtering on the surface of the flattened polyimide insulating layer 7 as a mask for plasma etching.
As shown in FIG. 1, a resist pattern for through holes with a diameter of 20 to 50 μm is formed using photoresist 12 using photolithography, and then, as shown in FIG. do. Subsequently, as shown in FIG. 12, the photoresist 12 and the polyimide insulating layer 7 are O ₂ plasma etched to expose the top surface of the conductor column 6, and then, as shown in FIG.
As shown in the figure, the aluminum thin film 11 is removed, the above-mentioned wiring Cu-Cr thin film 8 is formed on the polyimide insulating layer 7 and the conductor pillars 6 by sputtering, and then the upper layer wiring 1 is formed.
0 is formed, and the above steps are repeated to obtain a multilayer wiring board.

Note that when glass ceramics is used instead of the polyimide insulating layer 7, the surface is polished after drying.
After that, it is fired to expose the top surface of the conductor column.

(Effects of the invention) When conventional through-hole formation is performed by chemical etching, defects such as over-etching and under-etching tend to occur, and a thin oxide barrier layer remains in the through-hole, causing high resistance in the wiring between the upper and lower layers. However, according to the manufacturing method of the present invention, most of the through holes are filled with conductor pillars, and polishing eliminates the steps. Problems such as these will be solved and reliability will be greatly improved.

Furthermore, if the insulating layer needs to be thin, instead of relatively complicated etching, a simple method of selectively plating the conductor pillars and polishing the surface of the insulating layer can be used to reduce the thickness by φ20 μm.
A multilayer structure with fine through holes of 20 μm can be obtained. In addition, when the required thickness of the insulating layer is large, etching in the conventional manufacturing method results in a tapered cross section, which is a problem, but in the manufacturing method of the present invention, if conventional chemical etching or plasma etching is used in combination, However, since the thickness to be etched is reduced by the height of the conductor pillar, etching becomes easier and the upper part can be made smaller without the cross section becoming tapered, making it possible to form through holes with large diameters and small pitches.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a board in main manufacturing steps for explaining a method of manufacturing a multilayer wiring board in an embodiment of the present invention. 1: Ceramic substrate, 4: Lower conductor wiring layer,
6: conductor pillar, 7: insulator, 10: upper conductor wiring layer.

Claims (1)

[Claims] 1. In a method for manufacturing a multilayer wiring board consisting of a plurality of conductor wiring layers and a polyimide or crystallized glass insulating layer located between the conductor wiring layers, the lower conductor wiring layer is selectively plated for each of the above-mentioned insulating layers. The lower conductor wiring layer and the conductor pillars are covered with the insulator, the surface is polished to make the surface flat, and the conductor pillars are formed by etching. The top surface of the column capital is exposed, and the upper part of the conductor column is filled with selective plating, and an upper conductor wiring layer is formed, and the lower conductor wiring layer and the upper conductor wiring layer are connected by the conductor column, and the above-mentioned 1. A method for manufacturing a multilayer wiring board, comprising repeating the above operations to obtain a multilayer wiring board.