JPH03200394A - Formation of through hole - Google Patents

Abstract

PURPOSE:To improve reliability of continuity and to reduce cost by previously forming an insulator film which is not eroded by etchant in a through hole, and then etching a conductor film to pattern it. CONSTITUTION:Conductor films 2A are formed on the inner wall of a through lower hole 10A and both the front and rear surfaces of a ceramic board 1, and insulator films 6 of SiO2 or the like are formed to cover the inner wall of the hole 10A and the surface of the film 2A of a land of the peripheral edge. The entire surface of the board 1 including the inner wall of the hole 10A is coated with photoresist 3A, exposed, and developed to form a photoresist pattern 3. Then, the bare film 2A is removed by etching, land and desired pattern of the inner wall and the peripheral edge of the hole 10A remain, the pattern 3 is peeled, and a through hole 10 is provided. Thus, reliability of continuity is improved, and cost can be reduced.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method of manufacturing a ceramic circuit board, and in particular, to a method of forming a through hole in a thin film, and aims to provide a through hole with high conductivity reliability and low cost. After forming a conductive film on the inner wall of the pilot hole and both the front and back surfaces of the ceramic substrate, the inner wall of the pilot hole and the land portion of the conductor film are coated with an insulating film, and then the conductor film is coated with an insulating film by photolithography. Through-holes are provided by patterning the conductor film.

[Industrial application field]

The present invention relates to a method of manufacturing a ceramic circuit board,
In particular, it relates to a method for forming through holes in thin films.

In recent years, circuit board devices such as hybrid ICs have formed thin film circuits on both the front and back sides of ceramic substrates such as alumina, resulting in finer patterns, and connecting both sides through through holes to achieve high-speed signals. We are trying to increase the density and increase the density.

[Conventional technology]

Conventionally, through holes were provided in a ceramic substrate as shown in FIG.

First, as shown in FIG. 3(a), a through-hole pilot hole 10A with a desired inner diameter is bored at a desired location on a ceramic substrate l made of alumina or the like by laser processing, ultrasonic processing, etc., and then a conductive metal is formed. A conductive film 2A made of a thin film is formed on both the front and back surfaces of the ceramic substrate l and on the inner wall of the prepared through hole 10A by vapor deposition, sputtering, or the like.

Then, by using a spin cord means or the like, the through-hole pilot hole 10 is
A photoresist 3 is applied to the entire surface of the conductive film 2A including the inner wall of A.
Apply A.

Next, as shown in FIG. 3(b), using a desired photomask, the photoresist 3A is exposed, developed, and patterned to form a photoresist that covers only the inner wall of the through-hole pilot hole 10A, the land, and the surface of the desired pattern. Let's use pattern 3.

Then, as shown in FIG. 3(C), etching is performed to leave the inner wall of the through-hole pilot hole 10A, the land portion at the periphery of the through-hole pilot hole 10A, and a desired pattern. A conductor pattern 2 is provided.

Although not shown, after the through holes 10 are formed, the unnecessary photoresist pattern 3 on the conductive film is peeled off.

[Problem to be solved by the invention]

However, due to the sharp edges of the through-hole preparation hole 10A, it is difficult for the photoresist to adhere to it, as shown in FIG. 3(b).

Therefore, when patterning the conductor film, the etching solution corrodes the conductor film at the edges of the through holes, causing partial corrosion, resulting in the formation of defective portions K.

On the other hand, there is also a method in which the edges of the prepared through-holes are shaved to create a tapered surface to improve the adhesion of photoresist.

However, it is difficult to form the edge of the prepared through-hole into a tapered surface with high precision, and the resulting through-hole may be expensive.

The present invention was created in view of these points, and an object of the present invention is to provide a through hole with high reliability of conduction and low cost.

Then, the photoresist pattern 3 is further peeled off.
A through hole 10 shall be provided.

[Means to solve the problem]

In order to achieve the above object, the present invention forms a conductive film 2A on the inner wall of the through-hole pilot hole 10A and on both the front and back surfaces of the ceramic substrate 1.

Then, S
An insulator film 6 such as iO□ is formed and covered.

Then, photoresist is applied and formed on the entire surface of the ceramic substrate 1, including the inner wall of the prepared through hole 10A, and exposed to light.
After development, the photoresist is patterned to form a photoresist pattern 3 as shown in FIG. 1(a).

Then, as shown in FIG. 1(b), the exposed conductor film portion is removed, leaving the inner wall of the pilot hole 10A, the land portion at the periphery of the pilot hole 10A, and the desired pattern. Etching [Operation] According to the method of the present invention, the through-hole prepared hole 10A is formed.

The edges and land portions of the conductive film 2A are covered with an insulating film 6.

Therefore, as shown in FIG. 1(a), even if the photoresist does not adhere sufficiently to the edge of the through hole, since this area is covered with the insulating film 6, the conductive film can be etched. be prevented from being done. That is, the reliability of conduction of the through hole is improved.

In addition, an insulating film can be easily formed using the lift-off method, which is known as another patterning method, without special processing the edge of the prepared through-hole, so the resulting through-hole has a low It's cost.

〔Example〕

The present invention will be specifically explained below with reference to FIG. Note that the same reference numerals indicate the same objects throughout the figures.

The through hole forming method of the present invention is as follows.

■ Formation of a conductor film (see Figure 2 (a)) A through-hole pilot hole 10A with a desired inner diameter is bored at a desired location on a ceramic substrate l made of alumina or the like by laser processing, ultrasonic processing, etc., and then Conductive metal is deposited, sputtered, etc. on both the front and back sides of the ceramic substrate l, and through-hole pilot hole 1.
A conductor film 2A made of a thin film is formed on the inner wall of 0A.

■ Application and formation of lift-off resist (see Fig. 2 (b)) Screen print the lift-off resist 5 made of an insulator on the entire front and back surfaces of the ceramic substrate l, excluding the through-hole pilot hole 10A and the land portion around its periphery. and apply
Then pre-bake.

■ Formation of an insulator film (see Figure 2 (C)) An insulator such as SiOz is deposited on the inner wall of the lower through hole 10A,
An insulating film 6 is formed on the entire surface of the land and lift-off resist 5.

■ Patterning of the insulator film (see FIG. 2(d)) By immersing the ceramic substrate l in a solvent and dissolving the lift-off resist 5, the insulator film 6 on the surface of the lift-off resist 5 is removed. The insulator film 6 on the inner wall portion and the land portion of the through-hole prepared hole 10A is left.

■ Application of photoresist (see Fig. 2 (e)) Conductive film 2A formed on the inner wall of the pilot hole, the entire surface of the insulating film 6 at the land portion, and both the front and back surfaces of the ceramic substrate 1
A photoresist 3A is coated on the entire surface using a spin code means or the like, and then prebaked.

■ Patterning of photoresist (see Figure 2)) Using a desired photomask, expose and develop the photoresist 3A and pattern it to form a photoresist pattern that covers only the inner wall of the through-hole pilot hole 10A, the land, and the surface of the desired pattern. Set it to 3.

■ Etching of the conductor film (Fig. 2 (see chain)) The ceramic substrate 1 on which the photoresist pattern 3 has been formed is immersed in an etching solution to remove the exposed part of the conductor film 2A.
A conductive film covered with photoresist pattern 3 is left.

That is, a through hole 10 (the inner wall of the pilot hole 10A of the through hole and a land portion around the periphery of the pilot hole 10A of the through hole) and a desired conductor pattern 2 are provided.

■ Peel off the photoresist (see Figure 2 (h)), then
The ceramic substrate l is dipped in a solvent to form through holes 10.
．． Then, the unnecessary photoresist pattern 3 on the conductor pattern 2 is removed.

As described above, according to the method of the present invention, when etching the conductor film, the through-hole prepared hole 10A and its edge are etched.

The conductive film at the land portion is covered with an insulating film 6.

Therefore, even if the photoresist is not sufficiently attached to the edge portion of the through hole, etching of the conductive film is prevented.

〔Effect of the invention〕

As explained above, the present invention is a through hole forming method in which an insulating film that will not be attacked by an etching solution is formed in advance in the through hole portion, and then a conductive film is etched and patterned. Since the conductor film at the edge of the hole is not corroded, the reliability of the conduction of the resulting through-hole is high.

On the other hand, the edge of the pilot hole of the through-hole should not be specially processed (
Since the insulating film is formed by the lift-off method, which is widely known as a patterning method, the resulting through-holes are low in cost.

[Brief explanation of drawings]

(a) and (b) in Fig. 1 are diagrams showing the principle of the present invention, and (a), (b), (C1, (d), (e) in Fig. 2)
, ge>, (g), (h) are diagrams showing the steps of the method of the present invention, and (a), (b), (C) of FIG. 3 are diagrams showing the conventional method. In the figure, l is a ceramic substrate, 2 is a conductor pattern, 2A is a conductor film, 31! 3A is a photoresist pattern, 5 is a foot-off resist, 6 is an insulator film, 10 is a through hole, and 10A is a through hole pilot hole. ? Sadakinota's process and nail T diagram! Lock -52C; Figure F12 (2 of 2)

Claims (1)

[Scope of Claims] After forming a conductor film (2A) on the inner wall of the through-hole prepared hole (10A) and on both the front and back surfaces of the ceramic substrate (1), the through-hole prepared hole (10A) of the conductor film (2A) is ) is coated with an insulating film (6), and then the conductor film (2A) is patterned by photolithography to provide a through hole (10). Formation method.