JPH05145238A - Thin film formation of ceramic substrate - Google Patents

Abstract

PURPOSE:To bring formed pads and collective layers surely in continuity through conductor vias by firmly connecting a conductor via formed by plating to the top face of a collective layer and by bringing a conductor film coating the top face of an insulating layer serving as an interlayer insulating film in continuity to a conductor via exposed from the top face of the insulating layer. CONSTITUTION:The top face of a collective layer 1-1 of a substrate 1 is plated by a coat with a plating resist film 12 having a via lower hole 12-1, thereby making a conductor via 13 of constant level project out of the top face of the collective layer 1-1. After the resist film 12 is removed, photosensitive polyimide is applied; when the whole surface of a polyimide film 14' is etched by dryetching or the like, an insulating layer 14 is formed with exposure of a conductor via 13. Since coating the whole surface of this insulating layer 14 with a conductor film 15' enables a coat of the conductor film 15' of continuity to the conductor via 13, this conductor film 15' is wetetched or the like to form a pad 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film on a ceramic substrate which is widely used in the construction of various electronic devices.

Recently, as highly integrated electronic components are mounted at high density on a printed circuit board unit mounted on various electronic devices, a circuit board on which the electronic components are mounted is a ceramic substrate (hereinafter referred to as substrate). (Hereinafter abbreviated as "), a multi-layered structure in which a via conductor for interlayer connection and a fine pad for joining electronic components are respectively formed at high density is laminated.

Therefore, a method of forming a via hole in which a conductive via is formed in an interlayer insulating layer in which a liquid polyimide resin is applied to a ceramic substrate is as follows. Although a pilot hole is formed, incomplete penetration of the via pilot hole occurs during the development of the polyimide resin, resulting in poor electrical continuity with the pad of the interlayer insulating layer. Therefore, the collective layer of the ceramic substrate and the interlayer insulating layer are formed. There is a need for a new method for forming a thin film on a ceramic substrate, which ensures reliable conduction with a pad formed on the substrate.

[0004]

2. Description of the Related Art A method of forming a thin film on a ceramic substrate, which has been widely used in the past, will be described with reference to FIG.

(A) is a thick-film substrate 1 having a fine collective layer 1-1 formed on the surface thereof, and a photosensitive liquid polyimide resin is applied to the upper surface of the substrate 1 and the collective layer 1-1. Then, the thin insulating first layer 2 is formed.

In (b), a mask for forming a primary via hole (not shown) is brought into close contact with the upper surface of the insulating first layer 2 for exposure, and it is immersed in a dedicated developing solution for irradiation with ultrasonic waves or the like. By doing so, the primary via hole 2-1 is formed in the insulating first layer 2 and the temporary baking is performed.

(C) is a thin film insulation by applying a photosensitive liquid polyimide resin similar to (a) to the upper surface of the insulating first layer 2 in which the primary via hole 2-1 is formed. The state in which the second layer 3 is formed.

In (d), the upper surface of the insulating second layer 3 is exposed by using a mask for forming a secondary via (not shown), immersed in a dedicated developer again, and irradiated with ultrasonic waves or the like. A state in which a stepped via pilot hole 3-1 is formed and then hard baking is performed.

(E) is a conductive via 4 formed by filling the stepped via lower hole 3-1 with a conductive metal such as copper by cathode sputtering or the like, and then conducting with the conductive via 4 by electroless copper plating. Formed conductive film 5'on the entire surface of the insulating second layer 3, a thin coating of resist is applied on the upper surface of the conductive film 5 ', and the conductive film 5'is formed to the same size as the pad to be formed by exposure. The state where the coated resist film 6 is formed.

(F) is a state in which the conductor film 5'exposed from the resist film 6 is dissolved and removed by wet etching to form the pad 5 on the upper surface of the second insulating layer 3. A thin film is formed on the surface of the ceramic substrate by the process of.

[0011]

The problem with the conventional thin film forming method described above is that a photosensitive liquid polyimide resin is applied to the surface of the substrate 1 as shown in FIGS. 2 (a) to 2 (d). The via formation hole 3-1 is formed by a developing method in which the via formation part is exposed to light, and this is immersed in a dedicated developer to irradiate with ultrasonic waves, but as shown in FIG. Due to various factors such as the condition and baking, the polyimide resin remains and there is a portion where the via hole 3-1 for exposing the collective layer 1-1 formed on the substrate 1 is not formed.

Therefore, the electrical connection between the second insulating layer 3 and the pad 5 formed on the upper surface of the second insulating layer 3 is lost.
It is repaired by performing re-treatment of exposure and development, but if the collective layer 1-1 is not exposed even after performing this re-treatment, the substrate 1 is discarded as a defect and the thin film formation cost rises. There is a problem of doing.

In view of the above problems, it is an object of the present invention to provide a new method for forming a thin film on a ceramic substrate, which can form a pad on the surface of an insulating layer that is surely electrically connected to the collective layer.

[0014]

According to the present invention, as shown in FIG. 1, a via hole 12 is formed on the upper surface of a substrate 1 and a collective layer 1-1.
-1 is coated with a resist film 12 for plating, and a conductive via 13 having a constant height is formed by plating on the collective layer 1-1.
Of the substrate 1, the collective layer 1-1 and the conductive via after the resist film 12 is removed by projecting the resist film 12 onto the upper surface of the substrate 1.
A photosensitive polyimide film 14 ′ that covers the upper surface of 13 is formed, and the entire surface of the polyimide film 14 ′ is dry-etched to form an insulating layer 14 that exposes the upper surface of the conductor via 13, and sputtering and electroless plating are performed. A conductive film 15 'which is electrically connected to the conductive via 13 is coated on the entire surface of the insulating layer 14 by plating, and the conductive film 15' is dissolved and removed by etching or the like to remove the insulating layer 14 '.
Pad 15 is formed on the upper surface of the.

[0015]

In the present invention, the conductive vias 13 having a constant height are formed by coating the plating resist film 12 having the via lower holes 12-1 on the upper surface of the collective layer 1-1 of the substrate 1 and plating. 1-1 is projected from the upper surface, and after removing the resist film 12, a photosensitive polyimide is applied and the entire surface of the polyimide film 14 'is etched by dry etching or the like to form an insulating layer 14 in which the conductor via 13 is exposed. When the entire surface of the insulating layer 14 is covered with the conductive film 15 ′, the conductive film 15 ′ is electrically connected to the conductive via 13.
Since the conductor film 15 'is coated with the conductive film 15' by forming the pad 15 by wet etching or the like, it is possible to form a thin film having a pad electrically connected to the collective layer 1-1.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the embodiments shown in the drawings. FIG. 1 is a side sectional view showing a method of forming a thin film on a ceramic substrate according to this embodiment in the order of steps, in which the same members as those in FIG. 2 are designated by the same reference numerals.

In the thin film forming method of the present invention, as shown in FIG. 1 (a), a thick film substrate 1 having a fine collective layer 1-1 formed on the surface thereof is used for the substrate 1 and the collective layer.
By coating a resist for plating on the upper surface of 1-1 and exposing this resist with a via hole forming mask (not shown), the collective layer 1-1 has a fine diameter, for example, 30
A state in which a resist film 12 for plating having a via hole 12-1 exposed to 130 μm is coated.

(B) shows a state in which a conductive via 13 having a height of 20 to 30 μm is formed on the upper surface of the collective layer 1-1 exposed from the resist film 12 by copper electrolytic plating. (c) shows that after the resist film 12 for plating is removed, a photosensitive liquid polyimide resin is applied in an amount of 20 to 30 μm to cover the upper surface of the substrate 1, the collective layer 1-1 and the conductor via 13. The state where the polyimide film 14 'is formed.

(D) shows that the entire surface of the polyimide film 14 'is removed by about 2 to 5 .mu.m by dry etching such as reactive-ion-etching (RIE) to remove the conductor vias.
A state in which an insulating layer 14 exposing the upper surface of 13 is formed.

In (e), a conductor film 15 'made of copper having a thickness of about 5 .mu.m is formed on the entire surface of the insulating layer 14 by cathode sputtering and electroless plating, and the conductor film 15' is formed on the upper surface of the conductor film 15 '. A state in which a resist film 16 covering the conductor film 15 ′ having the same size as the pad to be formed is formed by thinly applying a resist for plating and exposing it.

(F) shows a state where the pad 15 is formed on the upper surface of the insulating layer 14 by dissolving and removing the conductor film 15 ′ exposed from the resist film 16 by wet etching. A thin film is formed on the surface of the ceramic substrate by the process of.

As a result, the conductor via 13 formed by plating is firmly connected to the upper surface of the collective layer 1-1, and the conductor film 15 'coated on the upper surface of the insulating layer 14 serving as an interlayer insulating film is Since the conductive via 13 exposed from the upper surface of the insulating layer 14 is surely conducted, the pad 15 formed by wet etching and the collective layer 1-1 can easily form a thin film which is surely conducted through the conductive via 13. can do.

[0023]

As is apparent from the above description, according to the present invention, it is possible to easily form a thin film provided with a pad that surely conducts to the collective layer of the substrate by an extremely simple method. Therefore, it is possible to provide a method for forming a thin film of a ceramic substrate, which is expected to have a remarkable economic effect and an effect of improving reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in order of the steps, showing a method for forming a thin film on a ceramic substrate according to an embodiment of the present invention.

FIG. 2 is a sectional view in the order of steps, showing a conventional thin film forming method.

FIG. 3 is a side sectional view for explaining a problem.

[Explanation of symbols]

1 is a substrate, 1-1 is a collective layer 12, 16 is a resist film, 12-1 is a via hole, 13 is a conductive via, 14 is an insulating layer,
14 'is a polyimide film, 15 is a pad,
15 'is a conductor film,

Claims (1)

[Claims] 1. A plating method comprising: forming a resist film (12) for plating having a via pilot hole (12-1) on the upper surface of a ceramic substrate (1) and a collective layer (1-1) formed on the surface, and plating. The conductive via (13) with a certain height by the collective layer (1-1)
Of the substrate (1), after removing the resist film (12), a photosensitive polyimide film covering the upper surfaces of the collective layer (1-1) and the conductor via (13) is applied, The entire surface of the polyimide film is dry-etched to form an insulating layer (14) exposing the upper surface of the conductor via (13), and the entire surface of the insulating layer (14) is electrically connected to the conductor via (13). A method of forming a thin film on a ceramic substrate, characterized by forming a pad (15) by coating a conductor film and etching or the like.